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4G mobile networks** + +Recommendation ITU-T G.1028.1 + +ITU-T + +![ITU logo: A globe with a red lightning bolt and the text 'ITU International Telecommunication Union'.](1d7527f4316cfe2d342b08d1653d1592_img.jpg) + +The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with a red lightning bolt striking across it. To the right of the globe, the text "ITU" is written in a bold, blue, sans-serif font. Below "ITU", the words "International Telecommunication Union" are written in a smaller, blue, sans-serif font. + +ITU logo: A globe with a red lightning bolt and the text 'ITU International Telecommunication Union'. + +## ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.1028.1 + +## End-to-end quality of service for video telephony over 4G mobile networks + +## Summary + +Recommendation ITU-T G.1028.1 provides guidelines concerning key aspects impacting end-to-end performance of carrier-grade (in opposition to over-the-top (OTT) approaches, which are outside of the scope of this Recommendation) conversational video services over long-term evolution (LTE) networks, also known as video-telephony over LTE (ViLTE), as defined by Global System for Mobile communications Association (GSMA). It identifies the preconditions for an optimally operating ViLTE network and provides remedial measures that operators can leverage to address the associated impact of quality of service (QoS) degradations in the LTE network. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.1028.1 | 2019-02-06 | 12 | 11.1002/1000/13831 | + +## Keywords + +LTE, QoS, quality of service, video, video telephony, ViLTE, 4G. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2019 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|-----------------------------------------------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 3 | +| 3.1 Terms defined elsewhere ..... | 3 | +| 3.2 Terms defined in this Recommendation..... | 3 | +| 4 Abbreviations and acronyms ..... | 3 | +| 5 Conventions ..... | 6 | +| 6 Brief introduction on video-telephony over LTE and assumptions..... | 6 | +| 7 ViLTE network architecture ..... | 7 | +| 8 QoS requirements for ViLTE – Segmented approach ..... | 8 | +| 8.1 Overview of QoS issues experienced by end-users..... | 8 | +| 8.2 User equipment (codec design and implementation) ..... | 9 | +| 8.3 E-UTRAN (Radio resource management) ..... | 10 | +| 8.4 Evolved packet core (QCI allocation and mobility management procedures) ..... | 11 | +| 8.5 IMS and IP transit core (call control and signalling) ..... | 11 | +| 9 Budget estimation and QoS parameterization ..... | 11 | +| 9.1 Relevant indicators ..... | 11 | +| 9.2 Impact assessment of relevant operating conditions on QoS parameters..... | 13 | +| 9.3 Quality targets ..... | 15 | +| 10 Diagnostic strategy for QoS degradations ..... | 16 | +| 10.1 QoS problem source-linked to availability of service ..... | 17 | +| 10.2 QoS problem source-linked to network performance ..... | 17 | +| 10.3 Tools and models for measurement and prediction of video quality ..... | 19 | +| Bibliography..... | 21 | + +## Introduction + +Mobile broadband operators, facing a competitive broadband market, are obliged to redefine their business models to enhance revenue-generating streams. This has necessitated a deployment shift to converged IP-based technology platforms and high-throughput access network technologies that deliver high-quality triple-play services (telephony, internet and video streaming) to consumers whose expectation for improved user experience continues to remain insatiable. In this perspective, video-telephony services over 4G networks (i.e., long-term evolution (LTE)) present an opportunity for operators to offer new value-added services to their customers and convince them to remain faithful. There still exists ongoing research work by academics, systems developers and standards organizations; all attempting to help fill the knowledge gap for successful commercial video-telephony over LTE (ViLTE) deployment worldwide. + +## Recommendation ITU-T G.1028.1 + +## End-to-end quality of service for video telephony over 4G mobile networks + +## 1 Scope + +This Recommendation covers end-to-end quality of service (QoS) requirements for video-telephony over long-term evolution (LTE) (ViLTE) network segments (see [b-GSMA IR.94]), budget allocation considerations for different service architecture scenarios, QoS parameterization for regulatory compliance, impact assessment of some relevant operating conditions on identified service parameters as well as a diagnostic strategy for QoS degradations in ViLTE. The intention of this Recommendation is to serve as a reference guide for LTE operators and regulators. + +This Recommendation is a complement to [ITU-T G.1028]. All voice-related aspects of ViLTE are exactly similar to those for voice over LTE (VoLTE), and therefore covered by [ITU-T G.1028], and thus, they are not repeated in this Recommendation. + +## 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.1011] Recommendation ITU-T G.1011 (2016), *Reference guide to quality of experience assessment methodologies*. +- [ITU-T G.1028] Recommendation ITU-T G.1028 (2016), *End-to-end quality of service for voice over 4G mobile networks*. +- [ITU-T G.1070] Recommendation ITU-T G.1070 (2018), *Opinion model for video-telephony applications*. +- [ITU-T G.1071] Recommendation ITU-T G.1071 (2016), *Opinion model for network planning of video and audio streaming applications*. +- [ITU-T H.264] Recommendation ITU-T H.264 (2017), *Advanced video coding for generic audiovisual services*. +- [ITU-T H.265] Recommendation ITU-T H.265 (2018), *High efficiency video coding*. +- [ITU-T J.144] Recommendation ITU-T J.144 (2004), *Objective perceptual video quality measurement techniques for digital cable television in the presence of a full reference*. +- [ITU-T J.246] Recommendation ITU-T J.246 (2008), *Perceptual visual quality measurement techniques for multimedia services over digital cable television networks in the presence of a reduced bandwidth reference*. +- [ITU-T J.247] Recommendation ITU-T J.247 (2008), *Objective perceptual multimedia video quality measurement in the presence of a full reference*. +- [ITU-T J.249] Recommendation ITU-T J.249 (2010), *Perceptual video quality measurement techniques for digital cable television in the presence of a reduced reference*. + +- [ITU-T J.341] Recommendation ITU-T J.341 (2016), *Objective perceptual multimedia video quality measurement of HDTV for digital cable television in the presence of a full reference.* +- [ITU-T J.342] Recommendation ITU-T J.342 (2011), *Objective multimedia video quality measurement of HDTV for digital cable television in the presence of a reduced reference signal.* +- [ITU-T J.343.1] Recommendation ITU-T J.343.1 (2014), *Hybrid-NRe objective perceptual video quality measurement for HDTV and multimedia IP-based video services in the presence of encrypted bitstream data.* +- [ITU-T J.343.2] Recommendation ITU-T J.343.2 (2014), *Hybrid-NR objective perceptual video quality measurement for HDTV and multimedia IP-based video services in the presence of non-encrypted bitstream data.* +- [ITU-T J.343.3] Recommendation ITU-T J.343.3 (2014), *Hybrid-RRe objective perceptual video quality measurement for HDTV and multimedia IP-based video services in the presence of a reduced reference signal and encrypted bitstream data.* +- [ITU-T J.343.4] Recommendation ITU-T J.343.4 (2014), *Hybrid-RR objective perceptual video quality measurement for HDTV and multimedia IP-based video services in the presence of a reduced reference signal and non-encrypted bitstream data.* +- [ITU-T J.343.5] Recommendation ITU-T J.343.5 (2014), *Hybrid-FRe objective perceptual video quality measurement for HDTV and multimedia IP-based video services in the presence of a full reference signal and encrypted bitstream data.* +- [ITU-T J.343.6] Recommendation ITU-T J.343.6 (2014), *Hybrid-FR objective perceptual video quality measurement for HDTV and multimedia IP-based video services in the presence of a full reference signal and non-encrypted bitstream data.* +- [ITU-T P.863] Recommendation ITU-T P.863 (2018), *Perceptual objective listening quality prediction.* +- [ITU-T P.1201] Recommendation ITU-T P.1201 (2012), *Parametric non-intrusive assessment of audiovisual media streaming quality.* +- [ITU-T P.1201.1] Recommendation ITU-T P.1201.1 (2012), *Parametric non-intrusive assessment of audiovisual media streaming quality – Lower resolution application area.* +- [ITU-T P.1201.2] Recommendation ITU-T P.1201.2 (2012), *Parametric non-intrusive assessment of audiovisual media streaming quality – Higher resolution application area.* +- [ITU-T P.1202.1] Recommendation ITU-T P.1202.1 (2012), *Parametric non-intrusive bitstream assessment of video media streaming quality – Lower resolution application area.* +- [ITU-T P.1202.2] Recommendation ITU-T P.1202.2 (2013), *Parametric non-intrusive bitstream assessment of video media streaming quality – Higher resolution application area.* +- [ETSI TS 122 105] ETSI TS 122 105 v15.0.0 (2018-07), *Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); LTE; Services and service capabilities (3GPP TS 22.105 version 15.0.0 Release 15).* +- [ETSI TS 123 203] ETSI TS 123 203 v15.4.0 (2018-09), *Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System* + +*(UMTS); LTE; Policy and charging control architecture (3GPP TS 23.203 version 15.4.0 Release 15).* + +[ETSI TS 126 114] ETSI TS 126 114 v15.4.0 (2018-10), *Universal Mobile Telecommunications System (UMTS); LTE; IP Multimedia Subsystem (IMS); Multimedia telephony; Media handling and interaction (3GPP TS 26.114 version 15.4.0 Release 15).* + +## **3 Definitions** + +### **3.1 Terms defined elsewhere** + +None. + +### **3.2 Terms defined in this Recommendation** + +None. + +## **4 Abbreviations and acronyms** + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|---------|-------------------------------------------| +| 3G | Third Generation of radio access network | +| 4G | Fourth Generation of radio access network | +| AEC | Acoustic Echo Control | +| AGC | Automatic Gain Control | +| AMR-WB | Adaptive Multi-Rate Wideband | +| AS | Application Server | +| ATCF | Access Transfer Control Function | +| ATGW | Access Transfer Gateway | +| BE | Best Effort | +| BGCF | Border Gateway Control Function | +| BSC | Base Station Controller | +| BTS | Base Transceiver Station | +| CIF | Common Intermediate Format | +| CS | Circuit Switched | +| CSFB | Circuit Switched Fallback | +| DL | Downlink | +| DRB | Data Radio Bearer | +| DRX | Discontinuous Reception | +| DSCP | Differentiated Services Code Point | +| DTMF | Dual-Tone Multi-Frequency | +| EF | Expedited Forwarding | +| eMSC | Enhanced MSC | +| e-NodeB | Enhanced Node B | +| EPC | Evolved Packet Core | + +| | | +|---------|-----------------------------------------------| +| E-UTRAN | Evolved UMTS Terrestrial Radio Access Network | +| GBR | Guaranteed Bit Rate | +| GERAN | GSM/Edge Radio Access Network | +| GPRS | General Packet Radio Service | +| GSM | Global System for Mobile Communications | +| GSMA | GSM Association | +| GTP | GPRS Tunnelling Protocol | +| GW | Gateway | +| HARQ | Hybrid Automatic-Repeat-Request | +| HD | High Definition | +| HSS | Home Subscriber Server | +| HVGA | Half Video Graphics Array | +| IBCF | Interconnection Border Control Function | +| I-CSCF | Interrogating Call Session Control Function | +| IMS | IP Multimedia Subsystem | +| LTE | Long-Term Evolution | +| MBR | Maximum Bit Rate | +| MGCF | Media Gateway Controller Function | +| MGW | Media Gateway | +| M-LWDF | Modified Largest Weighted Delay First | +| MME | Mobility Management Entity | +| MOS | Mean Opinion Score | +| MOS-LQ | Mean Opinion Score – Listening Quality | +| MRFC | Multimedia Resource Function Controller | +| MRFP | Multimedia Resource Function Processor | +| MSC | Mobile Switching Centre | +| MSCS | MSC Server | +| MTSI | Multimedia Telephony Service for IMS | +| NB | Narrowband | +| NGN | Next Generation Network | +| NR | Noise Reduction | +| OFDMA | Orthogonal Frequency-Division Multiple Access | +| OT | Third Operator | +| OTT | Over-The-Top | +| PCC | Policy and Charging Control | +| PCEF | Policy and Charging Enforcement Function | +| PCRF | Policy and Charging Rule Function | + +| | | +|--------|-------------------------------------------| +| P-CSCF | Proxy Call Session Control Function | +| PDA | Personal Digital Assistant | +| PDCP | Packet Data Convergence Protocol | +| PDD | Post Dialling Delay | +| PF | Proportionality Fair | +| P-GW | Packet Data Network Gateway | +| PLF | Packet Loss Fair | +| PSTN | Public Switched Telephone Network | +| QCI | QoS Class Identifier | +| QCIF | Quarter Common Intermediate Format | +| QoS | Quality of Service | +| QVGA | Quarter Video Graphics Array | +| RACH | Random Access Channel | +| RLC | Radio Link Control | +| RNC | Radio Network Controller | +| RoHC | Robust Header Compression | +| RRC | Radio Resource Control | +| RSRP | Reference Signal Received Power | +| RTCP | Real-time Transport Control Protocol | +| RTP | Real-time Transport Protocol | +| S-CSCF | Serving Call Session Control Function | +| SD | Standard Definition | +| SDP | Session Description Protocol | +| S-GW | Serving Gateway | +| SIP | Session Initiation Protocol | +| SRB | Signalling Radio Bearer | +| SRVCC | Single Radio Voice Call Continuity | +| TAS | Telephony Application Server | +| TrGW | Trunking Gateway | +| TTI | Transmission Time Interval | +| UDP | User Datagram Protocol | +| UE | User Equipment | +| UL | Uplink | +| UMTS | Universal Mobile Telecommunication System | +| UTRAN | UMTS Terrestrial Radio Access Network | +| ViLTE | Video-telephony over LTE | +| VGA | Video Graphics Array | + +| | | +|-------|-----------------| +| VoLTE | Voice over LTE | +| VT | Video Telephony | +| WB | Wideband | + +## 5 Conventions + +None. + +## 6 Brief introduction on video-telephony over LTE and assumptions + +This Recommendation considers some key assumptions in respect of the IP multimedia subsystem (IMS) profile for video as defined by the Global System for Mobile communications Association (GSMA) in [b-GSMA IR.94] and the multimedia telephony service for IMS (MTSI) media handling procedures (video part only) defined by 3GPP in [ETSI TS 126 114]. + +- To deploy ViLTE, VoLTE is required as a prerequisite. Voice aspects and network service architecture of ViLTE are adequately addressed in [ITU-T G.1028]; +- To support a video call, the user equipment (UE) transmits its video capability to the LTE network. The video call request encapsulates the video media with real-time transport protocol (RTP) on user datagram protocol (UDP) (RTP/UDP); +- RTP is the media protocol for the transmission of realtime audio or video streams. Different than VoLTE, packet data network gateway (P-GW) and serving gateway (S-GW) establish two bearers for a video call: one for voice and one for video; +- ViLTE uses the mandatory ITU-T H.264 codecs or preferably the optional (ITU-T H.265 Main tier level 3.1 codecs) to encode and decode the video stream with trade-off consideration for the optimization of both the bit rate and video signal quality; +- The ITU-T H.264/ITU-T H.265 codec delivers superior quality as compared to the low bit ITU-T H.263 codec that is used in third generation (3G) conversational video calls; +- Video resolution and coding rate is likely to adapt, during a call, to network conditions such as a reduction in downlink bandwidth. The real-time transport control protocol (RTCP) is used for the communication of capacities between the UE and the IMS entities inside the network during a call, thus triggering adaptation; +- ViLTE uses the same control plane protocol as VoLTE, namely session initiation protocol (SIP); +- The IMS core network along with the applicable application server (AS) performs the call control; +- ViLTE video calls are allocated appropriate quality of service (QoS) to differentiate and prioritize such delay and jitter sensitive conversational traffic from other streaming video traffic that is not as delay or jitter sensitive; +- The mechanism used is called QoS class identifier (QCI). The ViLTE bearer traffic is typically allocated QCI-2, and the SIP-based IMS signalling QCI-5; +- During ViLTE sessions, video capable devices often ensure lip-synchronization across audio and video components, a phenomenon that is characterized by the sending of timing information to each other; +- Call handling in ViLTE provides communicating devices with options to turn off video at any time during the call and continue with voice only; +- Conversational video calling services may be carried out in either simplex or duplex mode; + +- Video streams can be changed from one mode to another by the sending of a re-INVITE request with a session description protocol (SDP) offer using appropriate media descriptors (e.g., sendrecv, sendonly, recvonly). + +**Table 1 – Standardized QCI characteristics for use in ViLTE [ETSI TS 123 203]** + +| QCI | Resource type | Priority level | Packet delay budget | Packet error rate | Service type | +|-----|---------------------------|----------------|---------------------|-------------------|---------------------------------------| +| 1 | Guaranteed bit rate (GBR) | 2 | 100 ms | 1/100 | Conversational voice | +| 2 | | 4 | 150 ms | 1/1000 | Conversational video (live streaming) | +| 5 | Non-GBR | 1 | 100 ms | 1/1000000 | IMS signalling | + +## 7 ViLTE network architecture + +The network architecture for ViLTE is similar to the one for VoLTE (see [ITU-T G.1028]). + +Figure 1 (taken from [ITU-T G.1028]) shows the overall network architecture for ViLTE services. + +![Overall network architecture for ViLTE services diagram showing Device, Radio access, Mobile core, and Mobile IMS layers with various network elements like LTE-UU, eNodeB, S-GW, P-GW, MME, HSS, and IMS components.](ddc7460821484f1ae2835c67955c554c_img.jpg) + +The diagram illustrates the overall network architecture for ViLTE services, organized into four main layers: Device, Radio access, Mobile core, and Mobile IMS. + +- Device:** Contains the LTE-UU (User Equipment) with protocol stacks (RLC, UM, AM, PDCP, DRB, SRB2, SRB1, SRB0). It connects to the Radio access via RRC and SIP/SDP. +- Radio access:** Includes eNodeB (connected to LTE-UU), NodeB (connected to RNC), and BTS (connected to BSC/RNC). It also shows GERAN (GPRS) and UTRAN (UMTS) access networks. +- Mobile core:** Features the MME (Mobility Management Entity), S-GW (Serving Gateway), P-GW (PDN Gateway), HSS (Home Subscriber Server), and SPR (Service Profile Repository). It handles data bearers (Dedicated bearer, Default bearer) and signaling (S1-MME, S11, S5, S6a, S12). +- Mobile IMS:** Contains the SRVCC (Single Radio Voice Call Continuity) and AT&T (AT&T) components, including ATCF, ATGW, SCC-AS, ASs, TAS, voicemail, MRFP, and MRFC. It also shows connections to the PSTN, Broadband IMS, and OT (Over The Top) services via IBCF, TrGW, MGCF, and MGW. + +Other network elements shown include the PCRF (PDN Gateway Control and Policy Function), AF (Application Function), and various interfaces like SGi, S12, and Sh. + +Overall network architecture for ViLTE services diagram showing Device, Radio access, Mobile core, and Mobile IMS layers with various network elements like LTE-UU, eNodeB, S-GW, P-GW, MME, HSS, and IMS components. + +G.1028.1(19)\_F01 + +**Figure 1 – Overall network architecture for ViLTE services** + +## 8 QoS requirements for ViLTE – Segmented approach + +### 8.1 Overview of QoS issues experienced by end-users + +ViLTE is a relatively new service, and not enough data is available yet to understand global QoS perceived by customers and how big the weight of the different dimensions of QoS is. However, An analogy can be made with existing services for which consolidated data are available. + +The main families of QoS parameters for conversational services are known from telephony. These are service accessibility, audio/video quality (part of service integrity including audio quality, video quality, and relations between simultaneous audio/video signals such as lip synchronization) and service continuity. A detailed list of the most relevant metrics pertaining to each QoS family is provided in clause 9.1. + +Furthermore, ViLTE shares several characteristics with other services available over the same access technology, such as VoLTE [ITU-T G.1028] and video streaming over LTE (for video aspects). Concerning this last point: + +- The intrinsic quality of video rendering, highly correlated with video coding technology and bit rate, video size, resolution (and their adequation with screen size) and video frame rate; +- The occurrence of network (core or access) congestion, resulting in several visible artefacts (depending on decoding and buffering strategies at receiving side) like image freezing (similarly to re-buffering events in video streaming), pixelation, blocks, ghosting, etc.; +- A combination of the two last elements, bandwidth limitation or jitter buffer, that can be compensated by video coding bitrate adaptation, yielding potential visible quality degradations. + +However, ViLTE is also characterized by the differences of media handling applied to voice and video, since the service profile for ViLTE, as defined in [b-GSMA IR.94], is based on QCI (see Table 1). + +Thus, in case of network congestion or in the event a ViLTE terminal is at the edge of radio coverage, voice will be given a priority over video. A mechanism like transmission time interval (TTI) bundling, allowing retransmission of voice packets to ensure they are not lost, and thus limiting the bandwidth for other packets, amplifies this priority. TTI bundling actually defines the final threshold for ViLTE coverage beyond which only 64 kbit/s video can run with non-acceptable quality using ITU-T H.264 "Baseline". By reducing the video bit rate, coverage is improved but by only 4 dB gain with half the bit rate, as illustrated in Figure 2 below. In the most severe situations, depending on the strategy defined by service provider, end users will face either a communication reduced to its voice component or a call drop. + +![Figure 2: Video bit rate versus coverage. A diagram showing three rows of quality levels (Video 768 kbps, Video 384 kbps, Voice 24 kbps) across a pathloss range from 128 dB to 142 dB. The diagram is divided into three quality zones: 'Good video quality' (green), 'Degraded video quality' (yellow), and 'Not acceptable degraded video quality' (red). A 'Coverage gap' is indicated between 132 dB and 142 dB. The x-axis is labeled 'Pathloss (dB)' with markers at 128, 132, and 142. Vertical dashed lines at 128 dB and 132 dB separate the zones. For Video 768 kbps, the 'Not acceptable' zone starts at 132 dB. For Video 384 kbps, it starts at 132 dB. For Voice 24 kbps, the 'Not acceptable' zone starts at 142 dB.](71ab4df17511d75261da8d462d643b1a_img.jpg) + +Figure 2: Video bit rate versus coverage. A diagram showing three rows of quality levels (Video 768 kbps, Video 384 kbps, Voice 24 kbps) across a pathloss range from 128 dB to 142 dB. The diagram is divided into three quality zones: 'Good video quality' (green), 'Degraded video quality' (yellow), and 'Not acceptable degraded video quality' (red). A 'Coverage gap' is indicated between 132 dB and 142 dB. The x-axis is labeled 'Pathloss (dB)' with markers at 128, 132, and 142. Vertical dashed lines at 128 dB and 132 dB separate the zones. For Video 768 kbps, the 'Not acceptable' zone starts at 132 dB. For Video 384 kbps, it starts at 132 dB. For Voice 24 kbps, the 'Not acceptable' zone starts at 142 dB. + +G.1028.1(19)\_F02 + +**Figure 2 – Video bit rate versus coverage** + +Another element of consideration is how different overall ViLTE service quality, as experienced by users, can be when issues are related to audio only or to video only. It is known from user tests that customers are more sensitive to voice impairments than to video impairments during audio-video conversations. This generally results in better overall judgments when impairments affect video signal and to a lesser degree voice signal. + +### **8.2 User equipment (codec design and implementation)** + +ITU-T H.264 constrained high profile level 1.2, as specified in clause 5.2.2 of [ETSI TS 126 114], is mandatory in UE. However, for backward compatibility, it is required that UE also supports constrained baseline profile level 3.1 of the same release. Support for ITU-T H.265 Main profile, Main tier, level 3.1 is also recommended. + +Also, as part of procedures, in clause 2.2.2 of [b-GSMA IR.94], the UE and the network must be able to establish a video call directly during session establishment or by adding video to a voice session by sending SIP (re-) INVITE request with an SDP offer that contains both voice and video media descriptors. To ensure optimum QoS delivery it is imperative to adjust the maximum bit rate (MBR) of the video signal to levels far below the configuration settings of level 3.1 of [ITU-T H.264] and fine-tuned to the transmission capabilities of the network. + +It is recommended to align codec implementations for ViLTE so that codecs can be used in use cases taken as assumptions for the development of relevant parametric models proposed in [ITU-T G.1070] and [ITU-T P.1202.1]. Suffice to indicate that ITU-T H.264/ITU-T H.265 codec resolution, frame rate and encoding bit rate constitute key dependencies as far as maximum user perceived quality of the ViLTE service is concerned. Manufacturers of terminal devices (mobile phones and personal digital assistants (PDAs)) that support video telephony over the LTE network can find interesting guidance in the Table 2 assumptions, whereas codec design requirements should consider the coefficient derivation functions cited in Appendix I of [ITU-T G.1070]. + +**Table 2 – Assumptions about monitor characteristics** + +| Monitor specifications | Nominal values | +|------------------------|----------------| +| Diagonal length (Note) | 2-10 inches | +| Dot pitch | < 0.30 | +| Colour temperature | 6500 K | +| Bit depth | 8 bits/colour | + +**Table 2 – Assumptions about monitor characteristics** + +| Monitor specifications | Nominal values | +|---------------------------------------------------------|---------------------------| +| Refresh rate | $\geq 60$ Hz | +| Brightness | 100-300 cd/m 2 | +| NOTE – Diagonal length means the image size of monitor. | | + +The end-to-end delay that a ViLTE video packet experiences may fluctuate from packet to packet. This variation in end-to-end delay is referred to as delay jitter. Delay jitter is a crucial problem for ViLTE because the receiving terminal (UE) must receive/decode/display frames in realtime and at a constant rate, any late frames resulting from the delay jitter can produce annoying artefacts in the reconstructed video e.g., jerks in the video. + +This problem is typically addressed by including a playout buffer at the receiver. While the playout buffer can compensate for the delay jitter, it can potentially introduce additional delay. Video jitter buffer management for guaranteed QoS in video channels requires placing a cap on the jitter buffer latency (delay threshold), probing the jitter buffer state and doing away with excess video packets from the jitter buffer. In the case of an overflow a latency exceeded message is sent to notify the application that there may be enough delay in the jitter buffer to affect media synchronization and this is addressed by purging the jitter buffer. + +### 8.3 E-UTRAN (Radio resource management) + +Within the evolved-UMTS terrestrial radio access network (E-UTRAN) segment of the ViLTE architecture model, it is the responsibility of the enhanced Node B (e-NodeB) to ensure the provisioning of the necessary QoS conditions for a dedicated (video) bearer over the radio interface, taking into consideration such key determinants as the QCI and the priority levels. + +One very key requirement in QoS provisioning at the radio-interface level is the type of scheduling strategy that must be administered on the e-NodeB as part of the radio resource management functions for a multi-user orthogonal frequency-division multiple access (OFDMA)-based mobile system. A good and efficient scheduling algorithm is required to demonstrate the desired performance levels in accordance with tolerable limits specified in [ETSI TS 123 203] for video telephony traffic. The priority and packet delay budget, and to some extent the acceptable packet loss rate from the QCI label, is required to determine the radio link control (RLC) mode configuration and how the scheduler in the medium access control (MAC) handles packets sent over the bearer. + +It is thus recommended to RAN equipment vendors and systems operators a scheduling strategy that overcomes some of the limits of traditional benchmark scheduling algorithms (e.g., packet loss fair (PLF), modified largest weighted delay first (M-LWDF) or proportionality fair (PF)) in terms of throughput, packet loss and fairness among others. An LTE network operating a radio cell coverage, reference signal received power (RSRP) level, of less than -105 dBm is required to guarantee basic rule of thumb on admission controls based on the appropriate QCI from the user equipment. + +An IMS session request for a video call (originating or terminating) in E-UTRAN requires that one dedicated bearer resource for voice and another dedicated bearer resource for video as specified in [b-GSMA IR.94] is created by authorizing the flows utilizing dynamic policy and charging control (PCC). The network must initiate the creation of dedicated bearer resources to transport the voice and video media. The dedicated bearer for conversational video stream may be a GBR or a non-GBR bearer. If a GBR bearer is used it must utilize the standardized QCI value of two (2) and have the associated characteristics as provided in [ETSI TS 123 203]. In the case of IMS termination of a session using conversational media, dedicated bearer resources must be deleted by withdrawing the authorization of the flows. The network must initiate the deletion of the bearer resources. + +### 8.4 Evolved packet core (QCI allocation and mobility management procedures) + +Evolved packet core (EPC) provides support to the QoS classification (between the policy and charging enforcement function (PCEF) and the ViLTE client), as defined in clause 5 of [ETSI TS 122 105] and clause 6.1.7 of [ETSI TS 123 203]. The mobility management entity (MME) provides tracking area updates to mobile UEs. + +When a UE attaches with the network, a mutual authentication of the UE and the network is performed between the UE and the MME/home subscriber server (HSS). This authentication function also establishes security keys that are used for encryption of the bearers. Signalling overhead due to excessive tracking area (TA) updates must be managed in such a way as to guarantee reduced delays during the video calling session setup. + +The S-GW supports transport level QoS through marking IP packets with appropriate Diffserv code points based on the parameters associated with the corresponding bearer. The P-GW is the point of interconnect to external IP networks through the SGi interface. It also has a key role in supporting QoS for end-user IP services. + +A good hierarchical design is required to provide for seamless coordination of control-plane signalling during mobility with the two (2) major QoS preconditions being minimization of interruption in QoS during handover as well as improved support for interoperability among mobility protocols (IP/IPv6). + +### 8.5 IMS and IP transit core (call control and signalling) + +The IMS core supports ViLTE client registration and authentication. Video over IP (VoIP) session setup and release is enabled by the IMS and requires SIP signalling operating at an assigned QCI-5 as well as a realtime transfer of voice and video RTP flow as at QCI-1 and QCI-2, respectively (see Table 1). + +To fulfil these requirements, and in the context of a capacity-constrained network, the Diffserv (differentiated services code point (DSCP)) approach may be used to ensure efficient bandwidth allocation and scheduling among several traffic applications including video telephony. + +An LTE operator providing triple-play service offerings (voice, video, data) can adapt to the varying traffic requirements on their network by creating a traffic class group for each of the service types. + +## 9 Budget estimation and QoS parameterization + +### 9.1 Relevant indicators + +There are two categories of indicators to consider when assessing the quality of ViLTE services: + +- 1) Session setup and continuity; +- 2) Integrity of the content. + +In the first category, the target is to assess which level of quality a user can access and use the service over an entire ViLTE session. The recommended metrics are given in Table 3 below. + +**Table 3 – QoS parameters for session setup and continuity** + +| Name | Definition | +|-------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Video telephony (VT) service availability | End-to-end service availability in terms of capacity to establish a call, as well as its audio and video components, from, and to, a ViLTE customer.
An attempted ViLTE call resulting in a voice-only session is considered as failed. | + +**Table 3 – QoS parameters for session setup and continuity** + +| Name | Definition | +|-------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Video component availability | The availability of the video component if it is requested to be added to an existing VoLTE call. | +| VT setup time (post dialling delay (PDD)) | Time interval (in seconds) between the end of dialling by a caller and the reception back of the appropriate ringing tone, in case of a successful ViLTE call. | +| Components setup time | Time interval (in seconds) between the reception of a ringing tone and the beginning of the corresponding audio and video sessions, in case of a successful ViLTE call, or the time it takes to add the video component after request from a VoLTE call.
Narrowband (NB): this metric does not consider whether or not the relevant QCI has been assigned to each flow (QCI-1 for voice, QCI-2 for video). | +| VT service interruption time | Time interval (in seconds) during which the session is paused (at least one medium, audio or video, is missing) before the session starts again. | +| VT cut-off ratio | The possibility to use the service and/or its audio and video components until the user requests to release the call.
A ViLTE call with an undesired release of the video component, but the audio component still working, is considered as dropped. | + +The second category concerns video quality (audio quality is considered in [ITU-T G.1028]), with two complementary points of view: global quality (expressed in terms of mean opinion score (MOS)) and detection and characterization of artefacts. The recommended metrics are given in Table 4 below. + +**Table 4 – QoS parameters video quality measurements** + +| Name | Definition | +|---------------------------|-------------------------------------------------------------------------------------------------------------------------------------| +| Video quality (MOS) | Provides an objective view on the quality of the video signal as perceived by the VT customer | +| Detection of freezing |
  • number and rate of detections
  • cumulative duration of all detected events
| +| Detection of blurriness |
  • number and rate of detections
  • cumulative duration of all detected events
| +| Detection of pixelization |
  • number and rate of detections
  • cumulative duration of all detected events
| + +Guidance is given in clause 10.3 on video quality measurement methods. + +- **Freezing:** for reliable transmission freezing is the only distortion caused by transmission problems, in ViLTE it is just one in between others (and a minor one). In principle, it happens only if the (short) buffer runs empty. Based on current knowledge, the player decodes and plays-out what it gets, regardless of how destroyed the packets are. But it is a question of time that players apply other strategies as error concealment or freezing until the next I-frame is received for full synchronization. +- **Blurriness:** caused by low resolution along with compression. Depending on the markets, the native image resolution is usually limited at 240p or 360p (quite blurry on a high definition (HD) phone display). Even if standards allow higher resolutions and also adaptive bit rates. Detection of 'blocks' in case of a 240p I-frame is considered as blurriness. + +- **Pixelization:** what can be seen in case of transmission errors is the full set of image distortions caused by wrong updates (erroneous intra-frames). These are false-colour macro-blocks appearing and moving around, wrongly moved macro-blocks in general, freezing part of the image, luminance information that does not fit to the chrominance and more. The effect of 'error propagation' also needs to be considered: one erroneous intra-frame destroys an image, so that, even if all following intra-frames are received without error, the update information is applied to a destroyed image. + +### 9.2 Impact assessment of relevant operating conditions on QoS parameters + +Below are feedbacks provided from laboratory or field tests concerning the influence of operating conditions on the various dimensions of QoS for ViLTE. This clause is to be completed in further revisions. + +- Codec resolution vs. video quality + +![Line graph showing Note (Y-axis, 1.0 to 5.0) versus Resolution (X-axis, 176x144 to 1280x720) for different Framerates (10, 12, 15, 20, 25 fps). The graph shows that video quality increases with resolution and framerate. The background is shaded green for Note values above 4.0 and orange for values between 3.0 and 4.0.](3468bcffa38de23cef94bfb460ccb301_img.jpg) + +| Resolution | Framerate 10 fps | Framerate 12 fps | Framerate 15 fps | Framerate 20 fps | Framerate 25 fps | +|------------|------------------|------------------|------------------|------------------|------------------| +| 176x144 | ~1.9 | ~2.0 | ~2.1 | ~2.2 | ~2.3 | +| 320x240 | ~2.8 | ~2.9 | ~3.0 | ~3.1 | ~3.2 | +| 352x288 | ~2.9 | ~3.1 | ~3.3 | ~3.4 | ~3.5 | +| 640x360 | ~3.0 | ~3.5 | ~3.8 | ~4.0 | ~4.2 | +| 640x480 | ~3.2 | ~3.6 | ~3.9 | ~4.0 | ~4.1 | +| 704x576 | ~3.2 | ~3.7 | ~3.8 | ~4.1 | ~4.2 | +| 960x540 | ~3.5 | ~3.7 | ~4.0 | ~4.2 | ~4.5 | +| 1280x720 | ~3.5 | ~3.8 | ~4.1 | ~4.3 | ~4.5 | + +Line graph showing Note (Y-axis, 1.0 to 5.0) versus Resolution (X-axis, 176x144 to 1280x720) for different Framerates (10, 12, 15, 20, 25 fps). The graph shows that video quality increases with resolution and framerate. The background is shaded green for Note values above 4.0 and orange for values between 3.0 and 4.0. + +G.1028.1(19)\_F03 + +**Figure 3 – Codec resolution versus video quality** + +Results from subjective tests show that video graphics array (VGA) (320×240) at 15 fps can only provide a medium quality user experience (MOS ≈ 3.0). A good quality (MOS ≈ 4) requires a minimum resolution of (640×360) at 15 fps. VGA (640×480) is however, the widely-supported resolution for achieving this quality level. + +- Encoding bitrate vs. video quality + +![Figure 4: Bit rate versus video quality. The figure consists of three line graphs for resolutions 320x240, 640x480, and 1280x720. Each graph plots Mean Opinion Score (MOS) on the y-axis (1.0 to 5.0) against bit rate on the x-axis. Three data series are shown: 10 fps (blue solid line with circles), 15 fps (red dashed line with squares), and 25 fps (green dotted line with diamonds). Shaded regions indicate quality levels: green for MOS ≥ 4.0 and red for MOS < 4.0. The 25 fps series generally achieves higher MOS than the others at the same bit rate, while the 10 fps series achieves lower MOS.](3102c32204f998dba666e1e915d5babf_img.jpg) + +Figure 4: Bit rate versus video quality. The figure consists of three line graphs for resolutions 320x240, 640x480, and 1280x720. Each graph plots Mean Opinion Score (MOS) on the y-axis (1.0 to 5.0) against bit rate on the x-axis. Three data series are shown: 10 fps (blue solid line with circles), 15 fps (red dashed line with squares), and 25 fps (green dotted line with diamonds). Shaded regions indicate quality levels: green for MOS ≥ 4.0 and red for MOS < 4.0. The 25 fps series generally achieves higher MOS than the others at the same bit rate, while the 10 fps series achieves lower MOS. + +G.1028.1(19)\_F04 + +**Figure 4 – Bit rate versus video quality** + +It can be inferred from subjective test results that the optimal operating range for good video MOS using ITU-T H.264 baseline level 3.1 is a VGA resolution with frame rate of 15 fps to 30 fps and a bit rate of 384 kbit/s to 768 kbit/s. Thus, 384 kbit/s is the minimum bit rate to ensure a quite good quality experience (approx. 3.5 MOS) whereas a very good video quality ( $\geq 4.0$ MOS) requires a bit rate up to 768 kbit/s. A better codec will, however, not solve all capacity/coverage issues – rate adaptation is needed. Devices must be capable to detect transmission conditions (at receiver and sender side) and adapt bit rate/frame rate and resolution accordingly. + +– Video bit rate vs. capacity + +Dedicated bearer for ViLTE (with QCI-2) provides a GBR. The radio scheduler gives more radio resources to this bearer to ensure the GBR at cell edge. With a GBR at 768 kbit/s, a single ViLTE call consumes 20% of the radio resources in uplink (UL) (10 MHz bandwidth); thus, the overall data performance in the cell is impacted. + +**Table 5 – Video bit rate versus capacity** + +| %rRadio resource allocation per ViLTE terminal | | Cell-centre | Mid cell | ViLTE cell edge | +|------------------------------------------------|------------|-------------|----------|-----------------| +| 10 MHz | 384 kbit/s | 2.0% | 8.0% | 12% | +| | 768 kbit/s | 3.2% | 2.0% | 20.6% | +| 20 MHz | 384 kbit/s | 1.0% | 4.0% | 6.0% | +| | 768 kbit/s | 1.6% | 5.5% | 10.3% | + +To ensure ViLTE quality of experience (QoE) without affecting other user's throughput, practical best-fit measures would have to be taken. The use of GBR = MBR is actually not suitable for operation with rate adaptation. The possible options for maximum video quality are: + +- Use of QCI-2 with GBR < MBR; or +- Use of a non-GBR QCI (6 or 7) with scheduling priority + cell based min bit rate + ViWifi whenever possible. + +In summary, to ensure a more optimal ViLTE performance there is the need for efficient codecs to reduce the video bit rate, adapt the video bit rate to transmission condition with rate adaptation and possibly consider other QCI options than 2. + +- Jitter buffer performance vs. video quality; +- RTP packet loss vs. setup time (PDD); +- Tracking area update vs. setup time; +- Coverage/interference vs. service availability and call cut-off ratio; +- Handover vs. service interruption time. + +### 9.3 Quality targets + +This clause is for further study. Table 6 below will be completed once feedback from field deployments are available. + +**Table 6 – Quality budget allocation** + +| Network segment | LTE-LTE
(intra) | | LTE-LTE
(with interconnection) | | LTE-LTE
(with roaming) | | +|---------------------|--------------------|-------------|-----------------------------------|-------------|---------------------------|-------------| +| | Indicator A | Indicator B | Indicator A | Indicator B | Indicator A | Indicator B | +| UE | | | | | | | +| E-UTRAN | | | | | | | +| EPC | | | | | | | +| IMS/AS | | | | | | | +| Total budget | | | | | | | +| | Indicator C | Indicator D | Indicator C | Indicator D | Indicator C | Indicator D | +| UE | | | | | | | +| E-UTRAN | | | | | | | +| EPC | | | | | | | +| IMS/AS | | | | | | | +| Total budget | | | | | | | +| | Indicator E | Indicator F | Indicator E | Indicator F | Indicator E | Indicator F | +| UE | | | | | | | +| E-UTRAN | | | | | | | +| EPC | | | | | | | + +**Table 6 – Quality budget allocation** + +| Network segment | LTE-LTE
(intra) | | LTE-LTE
(with interconnection) | | LTE-LTE
(with roaming) | | +|---------------------|--------------------|-------------|-----------------------------------|-------------|---------------------------|-------------| +| | Indicator G | Indicator H | Indicator G | Indicator H | Indicator G | Indicator H | +| IMS/AS | | | | | | | +| Total budget | | | | | | | +| | | | | | | | +| UE | | | | | | | +| E-UTRAN | | | | | | | +| EPC | | | | | | | +| IMS/AS | | | | | | | +| Total budget | | | | | | | + +## 10 Diagnostic strategy for QoS degradations + +This clause explains the various video-centric degradations that can be encountered on a mobile LTE network. Main elements of the mobile network are depicted to show the signalling and media elements as well as the connections with public switched telephone network (PSTN) or mobile platforms. + +![Diagram illustrating sources of potential audiovisual impairments in ViLTE. It shows a network architecture with UE, eNodeB, EPC (MME, SGW, PGW), HSS, IMS (AS/SCC-AS, P-CSCF, I/S-CSCF), and IP Core network. Various impairments are listed in boxes connected to these elements.](09955ff8214ffb6947951fc0f60eb6ab_img.jpg) + +The diagram illustrates the network architecture for ViLTE and identifies potential sources of audiovisual impairments. The architecture includes: + +- UE (User Equipment):** Two mobile devices connected to eNodeB via S1c. Impairments: Echo, Noise, Low/high audio level, Device acoustic, White call, Chopped conversation, Encoding/decoding issues. +- eNodeB:** Two base stations connected to the EPC via S1u. Impairments: Call drop, Handover latency, Radio degradation (BER/FER). +- EPC (Evolved Packet Core):** Contains MME, SGW, and PGW. Impairments: IP packet loss, Network delay variation (Jitter), IP desequencement, Link failure, Availability of basic call service and Supplementary services, Identification failure (Sim card, ...). +- HSS (Home Subscriber Server):** Connected to MME via S6a. Impairments: Availability, DTMF not recognized, Encoding/decoding issues. +- IMS (IP Multimedia Subsystem):** Contains AS/SCC-AS, P-CSCF, and I/S-CSCF. Impairments: Availability, DTMF not recognized, Encoding/decoding issues. +- IP Core network:** Connected to PGW via SGi and to IMS via AGW/CBGF. Impairments: Availability, DTMF not recognized, Encoding/decoding issues. + +A central box indicates that frozen image, pixelization, blockiness, back to only voice, E2E delay, availability of calls, and PDD are generated by all elements. The diagram is labeled G.1028.1(18)\_F05. + +Diagram illustrating sources of potential audiovisual impairments in ViLTE. It shows a network architecture with UE, eNodeB, EPC (MME, SGW, PGW), HSS, IMS (AS/SCC-AS, P-CSCF, I/S-CSCF), and IP Core network. Various impairments are listed in boxes connected to these elements. + +**Figure 5 – Sources of potential audiovisual impairments in ViLTE** + +In order to have a point of comparison in terms of QoS delivered, a reference call is taken whose ideal characteristics are: + +- Fourth generation (4G)-4G call with end-to-end codecs (adaptive multi-rate wideband (AMR-WB) for audio, ITU-T H.264/ITU-T H.265 for video) and associated video features (frame rate, ITU-T H.264/ITU-T H.265 profile, video orientation) correctly negotiated; +- No degradation on EPC (no IP loss, no load, etc.); +- No degradation on E-UTRAN (no radio degradation, no congestion, etc.); +- Wideband audio compliant devices, both on 4G, with excellent acoustic, voice quality enhancement algorithms (noise reduction (NR), acoustic echo control (AEC) and automatic gain control (AGC)), electronic; +- Quiet environment on both ends; +- All services are available (e.g., call transfer, dual-tone multi-frequency (DTMF)). + +Below are the main possible technical reasons, which generate the encountered degradations. Separation is done according to the impact assessment due to the customer. + +### 10.1 QoS problem source-linked to availability of service + +**Table 7 – Degradations related to availability of the service and their potential causes** + +| Kind of degradation | Possible reasons | Location | +|-----------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------| +| UE identification failure |
  • • problem with MME, HSS or policy and charging rule function (PCRF)
| EPC | +| Unavailability of basic call |
  • • error in scheduling
  • • radio resource control (RRC) connection setup failure (reception of RRC connection reject, or expiry of timer T300, no RRC connection setup complete sent after reception of RRC connection setup)
| EUTRAN | +| |
  • • not available due to load (S-GW or P-GW)
  • • failed negotiation (e.g., allocation of QCI, codec)
  • • reception of several SIP error codes (e.g., 401 = Unauthorized, 405 = Method Not Allowed)
  • • reception of SIP CANCEL from IMS
  • • TD internal timer expired, causing a "SessionSetupFailureTimeout"
| EPC | +| Unavailability of video component |
  • • failed negotiation (e.g., allocation of QCI, codec, resolution)
| EPC/Terminal | +| PDD |
  • • load
  • • interworking between systems
  • • circuit switched (CS) fallback at call setup
| All | +| Link failure |
  • • bad negotiation between two pieces of equipment of the network during call establishment (bad codec management)
| EUTRAN/EPC | +| White call |
  • • terminal is not able to code or decode speech while the signalling is OK for the communication
| Terminal | + +### 10.2 QoS problem source-linked to network performance + +In this sub-section, QoS degradations, which are linked to network performance, are depicted. In concrete terms, these degradations, specific to network mainly lead to video degradation from the customer's perspective. + +**Table 8 – Degradations related to network performance and their potential causes** + +| Kind of degradation | Possible reasons | Location | +|---------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------| +| Frozen image |
  • no reception of video frame
  • network congestion (several causes: traffic load, distance from cell center causing activation of TTI bundling, for instance)
  • jitter buffers not adapted to actual jitter amount
| All | +| Blurriness |
  • no reception of infra video frame
  • recovery strategy of decoder in terminal
| All | +| Blockiness / Pixelization |
  • no reception of infra video frame
  • recovery strategy of decoder in terminal
| All | +| Encoding/Decoding issues | | Terminal/
eUTRAN | +| E2E delay (latency) |
  • network load
  • media handling (packet construction, jitter buffer management)
  • speech processing in terminals
  • random access channel (RACH) upon receiving handover command
  • RACH/contention procedure
  • additional RACH attempts
  • dynamic scheduling, link adaptation
  • radio link failure/re-establishment during handover (possibly different cell)
| All | +| Bad (lip) synchronization between voice and video |
  • network congestion associated with differentiated QoS (QCI)
  • different jitter buffer size and behavior
  • decoding time
| All | +| RTCP/IP packet loss |
  • network congestion (several causes: traffic load, distance from cell center causing activation of TTI bundling, for instance)
  • jitter buffers not adapted to actual jitter amount or packet size (can depend on use of robust header compression (RoHC) or not)
| EPC /
Terminal | +| RTP/IP desequencing |
  • new route after a problem such as congestion
| EPC | +| Network delay variation (Jitter) |
  • network congestion.
  • jitter buffers not adapted
| EPC /
Terminal | +| Radio degradations |
  • limit of the cell coverage
  • interference
  • area not well covered (e.g., obstacle)
  • bad radio optimization.
  • radio loss profile
  • bad radio scheduling
  • no or bad use of hybrid automatic-repeat-request (HARQ)
  • mechanisms
  • etc.
| eUTRAN | + +**Table 8 – Degradations related to network performance and their potential causes** + +| Kind of degradation | Possible reasons | Location | +|----------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------| +| Handover latency |
  • latency due to new route after handover or single radio voice call continuity (SRVCC)
| EPC / CS network | +| Call drop |
  • terminal bug, bad covered area, handover/SRVCC failures due to cells neighborhood problem, etc.
    RRC connection drop (at reception of RRC connection Re-establishment reject, or expiry of timer T301 or in case RRC connection release is received before new RRC connection setup attempt)
| Terminal/
eUTRAN | +| |
  • link failure: system failure, bad re-negotiation between two equipments of the network during call
  • reception of SIP status code 500 (server internal error)
  • no RTP packet received during a period longer than "SessionDropTimeout" TD internal timer
  • no SIP 200 OK on BYE is received within the time measured by "SessionHangupTimeout" TD internal timer
| EPC | +| Back to voice-only communication |
  • network congestion (several causes: traffic load, distance from cell center causing activation of TTI bundling)
  • strategy of service provided and/or device maker
| | + +### 10.3 Tools and models for measurement and prediction of video quality + +This clause is a complement for video to clause 10.3.2 of [ITU-T G.1028] where an overview of tools and models for voice quality is provided. + +A global view of all standard quality assessment methods is given in Table 10.3 of [ITU-T G.1011] and shows a detailed application scope of each model in terms of supported resolutions and codecs. + +Following the taxonomy provided there, the potential methods are: + +- Media layer models: all models for video media streaming quality assessment: + - full reference: [ITU-T J.144] (standard definition (SD)), [ITU-T J.247] (quarter common intermediate format (QCIF), common intermediate format (CIF), VGA), [ITU-T J.341] (HD); + - reduced reference: [ITU-T J.249] (SD), [ITU-T J.246] (QCIF, CIF, VGA), [ITU-T J.342] (HD); + - no reference: none. +- Packet layer models: + - models for planning purposes: [ITU-T G.1070] (dedicated tool for video telephony, including also an audio quality module), [ITU-T G.1071] (for video streaming, SD, HD); + - models for monitoring purposes (no reference) on UDP for video media streaming quality assessment: [ITU-T P.1201.1] (QCIF, quarter video graphics array (QVGA), half video graphics array (HVGA)), [ITU-T P.1201.2] (SD, HD), [ITU-T P.1201] Amd. 2, App. III (HVGA, HD (1080i50, 1080p24, 1080i60, 1080p30)). +- Bitstream layer models (no reference) on UDP for audiovisual media streaming quality assessment: + - [ITU-T P.1202.1] (QCIF, QVGA, HVGA), [ITU-T P.1202.2] (SD, HD). +- Hybrid models: all models for video media streaming quality assessment: + +- full reference: [ITU-T J.343.5] (HD, encrypted bitstream), [ITU-T J.343.6] (HD, not encrypted bitstream); +- reduced reference: [ITU-T J.343.3] (HD, encrypted bitstream), [ITU-T J.343.4] (HD, not encrypted bitstream); +- no reference: [ITU-T J.343.1] (HD, encrypted bitstream), [ITU-T J.343.2] (HD, not encrypted bitstream). + +With the exception of [ITU-T G.1070], all these methods have been developed for an application on video or audiovisual streaming services, not for video telephony. Because of the relatively good similarity between contents of both types of services, their application for the evaluation of quality of video telephony services may be envisaged, though it need to be understood that it would require some hard validation work. + +Indeed, implementation of these methods raises some important concerns: + +- Rating the impairments of video quality based on (encrypted) bitstreams is rather complicated. A bitstream method can give some metrics, how it would look like in a general statistical view under assumption of medium players and encoding strategies, but the accuracy and the relevance of the measurement results must be considered with highest caution; +- Full reference methods require the possibility to inject a reference video or audiovisual content at the applicative level inside UEs instead of the content provided by the camera. This feature is currently not supported on almost all models of mobile devices; +- The video player strategy of mobile devices to deal with errors and to minimize their visibility is varying between devices. Models must be calibrated before they can be applied on a given model of device. + +## Bibliography + +[b-GSMA IR.94] GSMA IR.94 v 11.0 (2016), *IMS Profile for Conversational Video Service*. + + + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.103-199812-I_PDF-E/raw.md b/marked/G/T-REC-G.103-199812-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..a65f2e82e0f444b84eccfa82899d3ce24d117ae2 --- /dev/null +++ b/marked/G/T-REC-G.103-199812-I_PDF-E/raw.md @@ -0,0 +1,719 @@ + + +![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.103** + +(12/98) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +International telephone connections and circuits – General +definitions + +--- + +# **Hypothetical reference connections** + +ITU-T Recommendation G.103 + +(Previously CCITT Recommendations) + +--- + +## ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| General definitions | G.100–G.109 | +| General Recommendations on the transmission quality for an entire international telephone connection | G.110–G.119 | +| General characteristics of national systems forming part of international connections | G.120–G.129 | +| General characteristics of the 4-wire chain formed by the international circuits and national extension circuits | G.130–G.139 | +| General characteristics of the 4-wire chain of international circuits; international transit | G.140–G.149 | +| General characteristics of international telephone circuits and national extension circuits | G.150–G.159 | +| Apparatus associated with long-distance telephone circuits | G.160–G.169 | +| Transmission plan aspects of special circuits and connections using the international telephone connection network | G.170–G.179 | +| Protection and restoration of transmission systems | G.180–G.189 | +| Software tools for transmission systems | G.190–G.199 | +| INTERNATIONAL ANALOGUE CARRIER SYSTEM | | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TRANSMISSION SYSTEMS | | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | + +*For further details, please refer to ITU-T List of Recommendations.* + +# **HYPOTHETICAL REFERENCE CONNECTIONS** + +## **Summary** + +This Recommendation was revised to introduce Integrated Services Digital Network and Integrated Digital Network Hypothetical Reference Connections, and also to allow for the introduction of ATM Technology into the PSTN. This Recommendation provides a number of Hypothetical Reference Connections that can be used to perform transmission impairment studies. + +## **Source** + +ITU-T Recommendation G.103 was revised by ITU-T Study Group 12 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 3rd of December 1998. + +## FOREWORD + +ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation the term *recognized operating agency (ROA)* includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms *Administration*, *ROA* and *public correspondence* are defined in the *Constitution of the ITU (Geneva, 1992)*. + +## INTELLECTUAL PROPERTY RIGHTS + +The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 1999 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +## CONTENTS + +| | Page | +|--------------------------------------------------------------------------------------------------------------------------------------|------| +| 1 Scope ..... | 1 | +| 2 Purpose ..... | 1 | +| 3 References ..... | 1 | +| 4 Composition of hypothetical reference connections ..... | 2 | +| 5 Number of modulation and demodulation equipments ..... | 12 | +| 6 Developments arising from the ongoing introduction of PCM digital processes ..... | 12 | +| Annex A – An explanation of how hypothetical reference connections can be drawn
assuming all send switching levels are 0 dBr..... | 13 | + + + +# **HYPOTHETICAL REFERENCE CONNECTIONS** + +*(Mar del Plata, 1968; amended at Geneva, 1972, 1976 and 1980; +at Malaga-Torremolinos, 1984; revised in 1998)* + +## **1 Scope** + +This Recommendation provides a number of Hypothetical Reference Connections. In particular, connections involving hybrid, i.e. analogue/digital networks, and wholly digital networks are addressed. The ongoing transitional problems associated with the conversion of hybrid networks to wholly digital networks are addressed in clause 6. + +## **2 Purpose** + +A hypothetical reference connection for transmission impairment studies is a model in which the impairments contributed by circuits and exchanges are described. + +Such a model may be used by an Administration: + +- to examine the effect on transmission quality of possible changes of routing structure, noise allocations, signal processing impairments and transmission losses in national networks; and +- to test national planning rules for prima facie compliance with any statistical impairment criteria which may be recommended by the ITU-T for national systems. + +For these purposes, several models are desirable. In each model, the international circuits and exchanges are assumed to be digital. The one wholly digital hypothetical reference connection and the five hybrid reference connections described below should encompass most of the studies required to be undertaken. + +Hypothetical reference connections are *not* to be regarded as recommending particular values of loss or noise or other impairments, although the various values quoted are in many cases recommended values. Hypothetical reference connections are not intended to be used for the design of transmission systems. + +## **3 References** + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- [1] *Transmission planning of switched telephone networks*, ITU, Geneva, 1976. +- [2] CCITT Recommendation E.171 (1988), *International telephone routing plan*. +- [3] ITU-T Recommendation G.101 (1996), *The transmission plan*. +- [4] ITU-T Recommendation G.111 (1993), *Loudness Ratings (LRs) in an international connection*. + +- [5] ITU-T Recommendation G.113 (1996), *Transmission impairments*. +- [6] ITU-T Recommendation G.114 (1996), *One-way transmission time*. +- [7] ITU-T Recommendation G.120 (1998), *Transmission characteristics of national networks*. +- [8] ITU-T Recommendation G.121 (1993), *Loudness Ratings (LRs) of national systems*. +- [9] CCITT Recommendation G.726 (1990), *40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM)*. +- [10] ITU-T Recommendation M.60 (1993), *Maintenance terminology and definitions*. +- [11] ITU-T Recommendation P.310 (1996), *Transmission characteristics for telephone-band (300 – 3400 Hz) digital telephones*. + +## 4 Composition of hypothetical reference connections + +4.1 The composition of the various connections is defined in Figures 1, 2, 3, 4, 5 and 6. + +*Figure 1* – The longest wholly digital Integrated Services Digital Network (ISDN) international connection with the maximum number of international and national circuits expected to occur in practice. + +*Figure 2* – The longest Integrated Digital Network (IDN) international connection comprising the maximum number of international and national circuits expected to occur in practice. + +*Figure 3* – An integrated digital network international connection comprising the maximum number of international circuits and the least number of national circuits expected to occur in practice. + +*Figure 4* – An international connection comprising the maximum number of digital international circuits and the least number of analogue national circuits expected to occur in practice. + +*Figure 5* – An international connection of moderate length (i.e. not longer than 2000 km) comprising the most frequent number of international and analogue national circuits. In such a connection, the noise contribution of the national systems would be expected to predominate. + +*Figure 6* – The longest international connection with the maximum number of digital international and analogue national circuits expected to occur in practice. In such a connection, the noise contribution of the national systems would be expected to predominate. The attenuation distortion, group delay, and group-delay distortion would also be higher than for the IDN case. Such connections are expected to be extremely rare. + +4.2 *General remarks applicable to Figures 1, 2, 3, 4, 5 and 6.* + +4.2.1 The hypothetical reference connections show the international circuits connected together at 0 dBr and 0 dBr virtual switching points, as they are digital switching points interconnected by digital facilities, instead of –3.5 dBr and –4 dBr points, the values normally assigned to analogue ISC switches. This was felt to be more directly useful to those who might have to use the reference connections in their studies. + +It might be felt that it is somewhat inconsistent that the hypothetical reference connections do not use "conventional" analogue ISC –3.5/–4 dBr virtual switching points. However, if the reference connections are drawn using that convention, the noise power figures appearing on the diagram can no longer be the familiar ones that appear elsewhere in other Recommendations. Annex A gives further explanations. + +4.2.2 The nomenclature is based on the international routing plan recommended in Recommendation E.171, i.e. ISC = International Switching Centre. + +**4.2.3** In each case, only one direction of transmission is shown. + +**4.2.4** The design objectives for the mean noise powers are indicated according to current national recommendations. For long-distance national analogue carrier circuits they are proportional to length, the appropriate noise power rate, 4 pW/km or 1 pW/km, being used according to whether the basic hypothetical reference circuit is one 2500 km long or 7500 km long. + +**4.2.5** The abbreviation pW0p stands for picowatts psophometric referred to a point of zero relative level. In the case of analogue exchange noise, the point referred to is considered to be in the circuit immediately downstream, of the exchange. The noise powers for circuits are referred to points of zero relative level in the circuits themselves and not to some point on the connection. + +**4.2.6** This Recommendation was prepared using the assumption that Plesiochronous Digital Hierarchy/Synchronous Digital Hierarchy (PDH/SDH) technology and ATM digital technology may be used in the PSTN. + +**4.2.7** It is recommended that the E-Model be used to evaluate the transmission performance of specific configurations, especially when speech compression technology, e.g. G.726 compliant Digital Circuit Multiplication Equipment (DCME), is used. + +![Figure 1/G.103 - The longest ISDN international connection likely to occur in practice](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg) + +The diagram shows a symmetrical vertical path of a digital telephone connection. It starts at a 'Digital telephone' at the top, goes through a series of exchanges (LE, PC, SC, TC, QC, ISC), crosses an international boundary through multiple ISCs, and then descends through a mirrored set of exchanges (ISC, QC, TC, SC, PC, LE) to another 'Digital telephone' at the bottom. + +**Vertical Segments:** + - Top National segment: 1750 km + - International segment: 24 000 km + - Bottom National segment: 1750 km + +**Technical Specifications (Top to Bottom):** + - 8 dB (SLR) + - 8 dB (Note 1) + - 100 pWp (400 pW0p) (Note 2) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - 2 dB (Note 6) + - 0 pW0p (Note 7) + - 2 dB (RLR) + +Figure 1/G.103 - The longest ISDN international connection likely to occur in practice + +*Legend for Figures 1, 2, 3, 4, 5 and 6* + +| | | | | | | +|-----|---------------------------|-----|--------------------------------|-------|----------| +| SLR | Sending Loudness Rating | SC | Secondary Centre | —— | Analogue | +| RLR | Receiving Loudness Rating | TC | Tertiary Centre | - - - | Digital | +| LE | Local Exchange | QC | Quaternary Centre | | | +| PC | Primary Centre | ISC | International Switching Centre | | | + +**Figure 1/G.103 – The longest ISDN international connection likely to occur in practice** + +4 Recommendation G.103 (12/98) + +![Diagram of the longest IDN international connection likely to occur in practice. It shows a vertical chain of network elements between two analogue telephones. The chain includes line elements (LE), switching centres (SC), tandem centres (TC), quality centres (QC), and international switching centres (ISC). Various loss and noise parameters are specified for each element and section. On the left, three vertical arrows indicate distances: 1750 km for the top national section, 24 000 km for the international section, and 1750 km for the bottom national section. Loss parameters include 10.5 dB (SLR) at the top, -1 dB (RLR) at the bottom, and 10 dB at 1600 Hz for unloaded line plants at both ends. Noise parameters include 100 pWp (500 pWp), 0 dB (T Pad), 0 pW0p, and 0 dB, sigma = 0 dB for various components.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg) + +Analogue telephone + +10 dB at 1600 Hz. Root-f law for unloaded line plant + +10.5 dB (SLR) + +1750 km + +100 pWp (500 pWp), (Note 8) + +0 dB (T Pad) (Note 9) + +LE \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +SC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +TC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +QC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +ISC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +ISC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +ISC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +ISC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +ISC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +QC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +TC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +SC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +PC \* + +0 pW0p (Note 3) + +0 pW0p (Note 4) + +0 dB, $\sigma = 0$ dB (Note 5) + +LE \* + +0 pW0p (Note 3) + +7 dB (R Pad) (Note 10) + +10 dB at 1600 Hz. Root-f law for unloaded line plant + +100 pWp (500 pWp) (Note 8) + +-1 dB (RLR) + +1750 km + +24 000 km + +International + +National + +T1208870-98 + +Analogue telephone + +Diagram of the longest IDN international connection likely to occur in practice. It shows a vertical chain of network elements between two analogue telephones. The chain includes line elements (LE), switching centres (SC), tandem centres (TC), quality centres (QC), and international switching centres (ISC). Various loss and noise parameters are specified for each element and section. On the left, three vertical arrows indicate distances: 1750 km for the top national section, 24 000 km for the international section, and 1750 km for the bottom national section. Loss parameters include 10.5 dB (SLR) at the top, -1 dB (RLR) at the bottom, and 10 dB at 1600 Hz for unloaded line plants at both ends. Noise parameters include 100 pWp (500 pWp), 0 dB (T Pad), 0 pW0p, and 0 dB, sigma = 0 dB for various components. + +Figure 2/G.103 – The longest IDN international connection likely to occur in practice + +![Figure 3/G.103 – An example of an IDN international connection of 4 international circuits between subscribers situated near the terminal ISCs](d4af765160d04ecef538e5066006dc77_img.jpg) + +The diagram shows a vertical signal path between two analogue sets. + Top section (National): + - Analogue set + - 3 dB at 1600 Hz. Root-f law for unloaded line plant + - 4 dB (SLR) + - 100 pWp (500 pWp) (Note 8) + - 0 dB (T Pad) (Note 9) + - LE (Local Exchange) with 0 pW0p (Note 3) + Middle section (International): + - A series of ISCs (International Switching Centers) connected by circuits. + - Each ISC/circuit segment has annotations: + - 0 pW0p (Note 4) + - 0 dB, σ = 0 dB (Note 5) + - 0 pW0p (Note 3) + - This pattern repeats for 4 international circuits. + Bottom section (National): + - LE (Local Exchange) with 0 pW0p (Note 3) + - 7 dB (R Pad) (Note 10) + - 3 dB at 1600 Hz. Root-f law for unloaded line plant + - -4.5 dB (RLR) + - 100 pWp (500 pWp) (Note 8) + - Analogue telephone + - T1208880-98 + +Figure 3/G.103 – An example of an IDN international connection of 4 international circuits between subscribers situated near the terminal ISCs + +**Figure 3/G.103 – An example of an IDN international connection of 4 international circuits +between subscribers situated near the terminal ISCs** + +6          **Recommendation G.103 (12/98)** + +![Diagram of a hybrid international connection showing signal levels and reference points between two analogue telephones across national and international segments.](af7916c89a458fdab6c3f443217388ae_img.jpg) + +The diagram illustrates a hybrid international connection between two analogue telephones, showing signal levels and reference points across different network segments. + +**Top Segment (National):** + +- Starts with an **Analogue telephone** connected to a line with a loss of **3 dB at 1600 Hz. Root-f law for unloaded line plant**. +- A reference point **4 dB (SLR)** is indicated. +- The signal passes through a series of components: + - A point marked with a dot (●) with a reference of **100 pWp (500 pWp) (Note 8)**. + - A line element **LE** marked with an 'X' with a reference of **100 pWp (200 pWp) (Note 11)**. + - A point marked with a dot (●) with a reference of **0 dB (Note 12)**. + - An **ISC** (Interchange Switching Centre) marked with an 'X' with a reference of **0 pW0p (Note 3)**. + +**International Segment:** + +- The signal continues through a series of components: + - A point marked with a dot (●) with a reference of **0 pW0p (Note 4)**. + - A point marked with a dot (●) with a reference of **0 dB, $\sigma = 0$ dB (Note 5)**. + - An **ISC** marked with an 'X' with a reference of **0 pW0p (Note 3)**. + - A point marked with a dot (●) with a reference of **0 pW0p (Note 4)**. + - A point marked with a dot (●) with a reference of **0 dB, $\sigma = 0$ dB (Note 5)**. + - An **ISC** marked with an 'X' with a reference of **0 pW0p (Note 3)**. + - A point marked with a dot (●) with a reference of **0 pW0p (Note 4)**. + - A point marked with a dot (●) with a reference of **0 dB, $\sigma = 0$ dB (Note 5)**. + - An **ISC** marked with an 'X' with a reference of **0 pW0p (Note 3)**. + - A point marked with a dot (●) with a reference of **0 pW0p (Note 4)**. + - A point marked with a dot (●) with a reference of **0 dB, $\sigma = 0$ dB (Note 5)**. + - An **ISC** marked with an 'X' with a reference of **0 pW0p (Note 3)**. + - A point marked with a dot (●) with a reference of **4 dB (Notes 12 and 13)**. + - A point marked with a dot (●) with a reference of **0 pW0p (Notes 3 and 14)**. + - A point marked with a dot (●) with a reference of **0 dB (Notes 12 and 14)**. + - A line element **LE** marked with an 'X' with a reference of **100 pWp (200 pWp) (Note 11)**. + +**Bottom Segment (National):** + +- The signal passes through a line with a loss of **3 dB at 1600 Hz. Root-f law for unloaded plant line**. +- A reference point **- 4.5 dB (RLR)** is indicated. +- The signal ends at another **Analogue telephone**. +- A final reference point is marked with a dot (●) with a reference of **100 pWp (500 pWp) (Note 8)**. + +The diagram is labeled **T1208890-98** at the bottom. + +Diagram of a hybrid international connection showing signal levels and reference points between two analogue telephones across national and international segments. + +**Figure 4/G.103 – An example of a hybrid international connection of 4 international circuits between subscribers situated near the terminal ISCs** + +![Diagram of a hybrid international connection of moderate length with only one international circuit. The diagram shows a vertical line representing the connection path between two analogue telephones. The path is divided into three main segments: National (top), International (middle), and National (bottom). The top National segment is labeled 'National' and '≤ 500 km'. It includes a 4 dB (SLR) loss at the top, followed by an analogue telephone, a 3 dB at 1600 Hz. Root-f law for unloaded line plant, a 100 pWp (500 pWp) (Note 8) point, an LE X point with a 100 pWp (200 pWp) (Note 11) point, a Zero or 500 pW0p (Note 15); see Note 16 for maximum value and length point, a 5.5 dB, σ = 0 or 3 dB, σ = 1 (Note 17) point, and a PC X point with a 100 pW0p (200 pW0p) (Note 11) point. The International segment is labeled 'International' and '1000 km'. It includes a 500 pW0p (2000 pW0p) (Note 18) point, a 0.5 dB, σ = 1; length 2500 km (Note 13) point, an ISC X point with a 0 pW0p (Note 3) point, a 0 pW0p (Note 4) point, a 0 dB, σ = 0 dB (Note 5) point, another ISC X point with a 0 pW0p (Note 3) point, and a 500 pW0p (2000 pW0p) (Note 17) point. The bottom National segment is labeled 'National' and '≤ 500 km'. It includes a 0.5 dB, σ = 1 point, a 14 dB point, a PC X point with a 100 pW0p (2000 pW0p) (Note 11) point, a Zero or 500 pW0p (Note 18); for maximum value and length see Note 15 point, a 5.5 dB, σ = 0 or 3 dB, σ = 1 (Note 17) point, an LE X point with a 100 pWp (200 pW0p) (Note 11) point, a 3 dB at 1600 Hz. Root-f law for unloaded line plant point, a 100 pWp (500 pWp) (Note 8) point, and finally an analogue telephone at the bottom. A -4.5 dB (RLR) loss is indicated at the bottom. The diagram is labeled T1208900-98 at the bottom left.](4801720824e4b5e2361a5564f91cfb70_img.jpg) + +National + ≤ 500 km + 4 dB (SLR) + Analogue telephone + 3 dB at 1600 Hz. Root-f law for unloaded line plant + 100 pWp (500 pWp) (Note 8) + LE X 100 pWp (200 pWp) (Note 11) + Zero or 500 pW0p (Note 15); see Note 16 for maximum value and length + 5.5 dB, $\sigma = 0$ or 3 dB, $\sigma = 1$ (Note 17) + PC X 100 pW0p (200 pW0p) (Note 11) + 500 pW0p (2000 pW0p) (Note 18) + 0.5 dB, $\sigma = 1$ ; length 2500 km (Note 13) + ISC X 0 pW0p (Note 3) + 0 pW0p (Note 4) + 0 dB, $\sigma = 0$ dB (Note 5) + ISC X 0 pW0p (Note 3) + 500 pW0p (2000 pW0p) (Note 17) + 0.5 dB, $\sigma = 1$ + 14 dB (Note 13) + PC X 100 pW0p (2000 pW0p) (Note 11) + Zero or 500 pW0p (Note 18); for maximum value and length see Note 15 + 5.5 dB, $\sigma = 0$ or 3 dB, $\sigma = 1$ (Note 17) + LE X 100 pWp (200 pW0p) (Note 11) + 3 dB at 1600 Hz. Root-f law for unloaded line plant + 100 pWp (500 pWp) (Note 8) + Analogue telephone + -4.5 dB (RLR) + T1208900-98 + +Diagram of a hybrid international connection of moderate length with only one international circuit. The diagram shows a vertical line representing the connection path between two analogue telephones. The path is divided into three main segments: National (top), International (middle), and National (bottom). The top National segment is labeled 'National' and '≤ 500 km'. It includes a 4 dB (SLR) loss at the top, followed by an analogue telephone, a 3 dB at 1600 Hz. Root-f law for unloaded line plant, a 100 pWp (500 pWp) (Note 8) point, an LE X point with a 100 pWp (200 pWp) (Note 11) point, a Zero or 500 pW0p (Note 15); see Note 16 for maximum value and length point, a 5.5 dB, σ = 0 or 3 dB, σ = 1 (Note 17) point, and a PC X point with a 100 pW0p (200 pW0p) (Note 11) point. The International segment is labeled 'International' and '1000 km'. It includes a 500 pW0p (2000 pW0p) (Note 18) point, a 0.5 dB, σ = 1; length 2500 km (Note 13) point, an ISC X point with a 0 pW0p (Note 3) point, a 0 pW0p (Note 4) point, a 0 dB, σ = 0 dB (Note 5) point, another ISC X point with a 0 pW0p (Note 3) point, and a 500 pW0p (2000 pW0p) (Note 17) point. The bottom National segment is labeled 'National' and '≤ 500 km'. It includes a 0.5 dB, σ = 1 point, a 14 dB point, a PC X point with a 100 pW0p (2000 pW0p) (Note 11) point, a Zero or 500 pW0p (Note 18); for maximum value and length see Note 15 point, a 5.5 dB, σ = 0 or 3 dB, σ = 1 (Note 17) point, an LE X point with a 100 pWp (200 pW0p) (Note 11) point, a 3 dB at 1600 Hz. Root-f law for unloaded line plant point, a 100 pWp (500 pWp) (Note 8) point, and finally an analogue telephone at the bottom. A -4.5 dB (RLR) loss is indicated at the bottom. The diagram is labeled T1208900-98 at the bottom left. + +**Figure 5/G.103 – An example of a hybrid international connection of moderate length with only one international circuit** + +![Diagram of the longest hybrid international connection likely to occur in practice, showing signal levels and noise limits across National and International segments.](33ed1f9b27c7c21c797aa928b0f06851_img.jpg) + +The diagram illustrates a hybrid international connection between two analogue telephones, divided into three main segments: National (top), International (middle), and National (bottom). + +- Top National Segment (1750 km):** + - Starts at an **Analogue telephone**. + - Signal level: **10.5 dB (SLR)**. + - Line plant: **10 dB at 1600 Hz. Root-f law for unloaded line plant**. + - Equipment and limits: + - LE**: 100 pWp (500 pWp) (Note 8); 100 pWp (200 pW0p) (Note 11); Zero or 500 pW0p (Note 1); see Note 16 for maximum value and length. + - PC**: 5.5 dB, $\sigma = 0$ or 3 dB, $\sigma = 1$ (Note 17); 100 pW0p (200 pW0p) (Note 11). + - SC**: 500 pW0p (2000 pW0p) (Note 16); 0 dB, $\sigma = 1$ (Note 20); 100 pW0p (200 pW0p) (Note 11). + - TC**: (1000 pW0p); 0 dB, $\sigma = 1$ (Note 21); length 250 km; 100 pW0p (200 pW0p) (Note 11); (1000 pW0p). + - QC**: 0 dB, $\sigma = 1$ (Note 20); length 250 km; 100 pW0p (200 pW0p) (Note 11); (2000 pW0p) (Note 21). + - A bracket on the right indicates: **See Note 19 for an alternative arrangement**. +- International Segment (24 000 km):** + - Starts at **ISC**. + - Signal level: **0 dB, $\sigma = 1$ (Note 21); length 500 km**. + - Equipment and limits: + - ISC**: 0 pW0p (Note 3); 0 pW0p (Note 4); 0 dB, $\sigma = 0$ dB; (Note 5); 0 pW0p (Note 3); 0 pW0p (Note 4); 0 dB, $\sigma = 0$ dB; (Note 5); 0 pW0p (Note 3); 0 pW0p (Note 4). + - ISC**: 0 dB, $\sigma = 0$ dB; (Note 5); 0 pW0p (Note 3); 0 pW0p (Note 4); 0 dB, $\sigma = 0$ dB; (Note 5); 0 pW0p (Note 3); (2000 pW0p) (Note 20). + - QC**: 0.5 dB, $\sigma = 1$ dB; length 4500 km; 100 pW0p (200 pW0p) (Note 11); (1000 pW0p). + - TC**: 0.5 dB, $\sigma = 1$ (Note 20) length 250 km; 100 pW0p (200 pW0p) (Note 11); (1000 pW0p). + - SC**: 0 dB, $\sigma = 1$ ; (Note 20); length 250 km; 100 pW0p (200 pW0p) (Note 11); 500 pW0p (2000 pW0p); (Note 18). + - ISC**: 0 dB, $\sigma = 1$ (Note 20); 7 dB, $\sigma = 0$ ; (Note 20). + - A bracket on the right indicates: **See Note 19 for an alternative arrangement**. +- Bottom National Segment (1750 km):** + - Starts at **PC**. + - Equipment and limits: + - PC**: 100 pW0p (200 pW0p) (Note 11); Zero or 500 pW0p (Note 15); (Note 16) for maximum value and length. + - LE**: 5.5 dB, $\sigma = 0$ or 3 dB, $\sigma = 1$ (Note 17); 100 pW0p (200 pW0p) (Note 11). + - Line plant: **10 dB at 1600 Hz. Root-f law for unloaded line plant**. + - Ends at **Analogue telephone** with signal level: **100 pW0p (500 pW0p) (Note 8)**. + - Signal level: **- 1 dB (RLR)**. + +T1208910-98 + +Diagram of the longest hybrid international connection likely to occur in practice, showing signal levels and noise limits across National and International segments. + +**Figure 6/G.103 – The longest hybrid international connection likely to occur in practice** + +## NOTES to Figures 1, 2, 3, 4, 5 and 6 + +NOTE 1 – A value of 8 dB was selected for the SLR of the digital telephone set to be consistent with Recommendation P.310. + +NOTE 2 – A nominal value of noise of 100 pW0p (–70 dBm) was selected as a typical value for the noise generated by a digital telephone set. A value of 400 pW0p (–64 dBm0p) was selected as the maximum noise generated by the transmit section of a digital telephone set to be consistent with Recommendation P.310. + +NOTE 3 – The noise contribution of a digital switch is assumed to be 0 pW0p. + +NOTE 4 – The noise contribution of a digital trunk is assumed to be 0 pW0p. + +NOTE 5 – The loss associated with a digital circuit is assumed to be 0 dB, $\sigma = 0$ . + +NOTE 6 – A value of 2 dB was selected for the RLR of the digital telephone set to be consistent with Recommendation P.310. + +NOTE 7 – The noise contribution of a digital access and a digital telephone set receiver is assumed to be 0 pW0p. + +NOTE 8 – The average value of 100 pWp for subscriber line noise is considered to be typical and is used by at least one Administration as an objective for maximum noise at the receiver. The maximum planning value should never exceed 500 pWp. + +NOTE 9 – This is the T pad and a value of 0 dB was arbitrarily selected. The value of the T pad will depend upon the national transmission plan. Table C.1/G.121 provides values of T and R pads for various countries. + +NOTE 10 – This is the R pad and a value of 7 dB was arbitrarily selected. The value of the R pad will depend upon the national transmission plan. Table C.1/G.121 provides values of T and R pads for various countries. + +NOTE 11 – The value of 200 pW0p as the design objective for the maximum noise power in a national 4-wire automatic exchange was taken from clause 3/G.123, which is no longer in force. The same value, i.e. an absolute noise power of 200 pWp, has been assumed for national 2-wire exchanges. No assumption has been made concerning the position of any national zero relative level point. + +NOTE 12 – The value of this pad will depend upon the national transmission plan. + +NOTE 13 – Both countries are assumed to have the $2 + 0.5 + 0.5 + 0.5$ dB type of plan. The nominal value of the 4 dB pad in the receiving direction at the switching centre includes the loss of the terminating unit (see General Remark, 4.2.12). + +NOTE 14 – The local exchange and primary centre are assumed to be both co-sited with the ISC. + +NOTE 15 – The noise power level may be taken as negligible if the circuit is provided on physical line plant. A mean value of 500 pW0p is appropriate if the circuit is provided on a *FDM or TDM* short-distance carrier system. + +NOTE 16 – For FDM or TDM short-distance carrier circuits not exceeding about 250 km, the maximum value of noise power may be taken to be 1000 pW0p. + +NOTE 17 – For circuits on physical line plant, the LR may be taken to have a nominal maximum value of 6 dB with $\sigma = 0$ . This value was arrived at in the following way: Recommendation G.121 gives a 97% limit on 20 dB Sending Loudness Rating (SLR) referred to a point of –3.5 dBr on the international circuit at the IC. Referring this to a zero relative level point at the input to the chain of national and international circuits (i.e. to the primary centre) gives 16.5 dB. Reference [1] indicates that a 10.5 dB Sending Loudness Rating (SLR) is typical for maximum local lines, thus leaving 6 dB for the circuit from the local exchange to the primary centre, switching losses being included (see General Remark, 4.2.12). + +For FDM or TDM short-distance carrier circuits which are 2-wire switched at the primary centre, the nominal value of the circuit loss may be taken as 3 dB with $\sigma = 1$ . This circuit may for instance be provided on a PCM system using either 7-bit encoding ( $\mu = 100$ or $A = 87.6$ ) or 8-bit encoding ( $\mu = 225$ or $A = 87.6$ ). Only 8-bit coding is recommended by the ITU-T. + +NOTE 18 – The maximum planning value of 2000 pW0p provides for a circuit length of about 500 km with some margin. + +NOTE 19 – The following arrangements may be encountered if 4-wire switching (space-division or time-division) is used at the primary centre. Clearly in principle the terminating set may be at any point between the 2-wire switch and the 4-wire switch, although in practice it is ordinarily associated with one or the other. + +![Two diagrams, (a) and (b), showing network configurations. Diagram (a) shows a line with an LE (Local Exchange) pad on the left, a central node, and a PC (Primary Centre) pad on the right. Diagram (b) shows a similar line but with the LE pad on the left connected to a node that has a branch to the left. Both diagrams have a dashed line extending from the left and right. The label 'T1210900-99' is present in diagram (b).](2cde062fd82833415971a8bd1a2cafab_img.jpg) + +Two diagrams, (a) and (b), showing network configurations. Diagram (a) shows a line with an LE (Local Exchange) pad on the left, a central node, and a PC (Primary Centre) pad on the right. Diagram (b) shows a similar line but with the LE pad on the left connected to a node that has a branch to the left. Both diagrams have a dashed line extending from the left and right. The label 'T1210900-99' is present in diagram (b). + +If arrangement b) is adopted, then the minimum loss *a-t-b* (called for in accordance with Recommendation G.122) must still be assured, irrespective of whether the national transmission plan uses the $3.5 + 0 + 0 + 0$ or $2.5 + 0.5 + 0.5 + 0.5$ basis, since there could now be an extra circuit in the 4-wire chain. Where an additional 0.5 dB is needed, this could in principle either be introduced by changing the loss of the tertiary centre/ISC circuit from 0 to 0.5 dB, or by allocating it to the PC/LE circuits. Such arrangements may be encountered at either end of the connection. + +NOTE 20 – Both countries are assumed to have the $3.5 + 0 + 0 + 0$ dB type of plan. The nominal value of the pad in the receiving direction at the primary centre includes the loss of the terminating unit (see General Remark, 4.2.12). + +NOTE 21 – The noise value corresponds to a design objective of 4 pW0p/km for the most adverse noise power during the busy hour. + +**4.2.8** The pad symbols represent the nominal loss of the particular channel or circuit and the relative position of the noise generator. The pad also indicates that if the noise is to be referred to the receiving end of a circuit, it must be modified by the power ratio corresponding to the loss of the pad. + +If it is required to refer the noise powers to some particular point on the connection (for example, the receiving local exchange or the point of zero relative level on the first international circuit), then the rule to be applied is as follows: + +If a noise power level at a point *A* is to be referred to a point *B* downstream of its position, it is obtained by augmenting the level at point *B* by the sum of the losses that is imagined to be traversed from *A* to *B*. If it is to be referred to a point *C* upstream of its position, it is obtained by diminishing the level at point *C* by the sum of all the losses that is imagined to be traversed from *A* to *C*. + +**4.2.9** The nominal terminal loss of the connection [i.e. the normal overall loss less the sum of the transit losses (via net losses) of the individual circuits] is shown as one pad associated with the extreme right-hand circuit in the 4-wire chain. This artifice enables the noise powers to be indicated as if they were injected at zero relative level points on the individual circuits as explained in Annex A. + +**4.2.10** Information concerning the distributions of attenuation distortion and group-delay distortion for analogue circuits and exchanges is to be found in Annex A/G.113. + +Recommendation G.114 gives information concerning group delay. + +**4.2.11** The standard deviation of transmission loss of circuits is in accord with the objectives of clause 10/G.120. + +**4.2.12** "Circuit" in these reference connections is defined in the sense of Recommendation M.60 as the whole of the line and the equipment proper to the line; it extends from the switches of one exchange to the switches of the next. In this way, switching and exchange cabling losses are included in the values of transmission loss assigned to the circuits, together with the loss (or gain) introduced by the transmission system. If it is required to separately distinguish exchange losses, an additional pad symbol of appropriate value may be used. + +It should also be noted that, according to this convention, the 3.5 dB loss ordinarily assigned to a terminating set does not figure explicitly in 2-wire/4-wire circuits; its value is also included in the loss assigned to the circuit. + +## **5 Number of modulation and demodulation equipments** + +For the study of transmission performance, the longest international connection expected to occur (see Figure 6) may be considered to have the following arrangement of modulator/demodulator pairs in the 4-wire chain. See Table 1. + +**Table 1/G.103 – Number of maximum modulator/demodulator pairs in a wholly analogue national 4-wire chain and wholly digital international 4-wire chain** + +| | Eight national circuits | Circuits between ISCs | Total | +|------------|--------------------------------|------------------------------|--------------| +| Channel | 8 | 0 | 8 | +| Group | 12 | 0 | 12 | +| Supergroup | 16 | 0 | 16 | + +Of the 12 channel modulator/demodulator pairs, a maximum of three may be of the special type which provide more than 12 telephone circuits per group. + +## **6 Developments arising from the ongoing introduction of PCM digital processes** + +The worldwide telephone network is undergoing a transition from what is largely a hybrid network to a wholly digital network. Looking farther into the future, this transition is expected to continue and result in a network that would be predominantly wholly digital. Background on this transitional process is given in clause 4/G.101. + +With reference to the hypothetical reference connections of Figures 1, 2, 3, 4, 5 and 6, the configurations used concerning numbers of circuits and numbers of exchanges should also be appropriate for network conditions in the mixed analogue/digital period. However, for transmission studies pertaining to mixed analogue/digital and wholly digital connections, account must also be taken of all unintegrated digital processes that might be present. Such unintegrated digital processes could have an important effect on overall transmission performance particularly with regard to such parameters as quantizing distortion (Recommendation G.113) and transmission delay. + +Where the worldwide network becomes all-digital, many of the transmission impairments that were present in the mixed analogue/digital period, due to the incorporation of unintegrated digital processes, would be eliminated. However, certain processes might remain which could introduce transmission penalties. These are the processes which operate on the basis of recoding the bit stream as is done, for example, in the case of digital pads or speech compression. Although the accumulated transmission impairments introduced by such processes may be well within recommended limits, the + +resulting loss of bit integrity could be an important disadvantage. This is particularly true in the case of services requiring the preservation of bit integrity on an end-to-end basis. Consequently, processes of this type should be avoided where possible, or appropriate arrangements made to circumvent them, where services requiring bit integrity are to be carried over the affected connections. + +## ANNEX A + +### An explanation of how hypothetical reference connections can be drawn assuming all send switching levels are 0 dBr + +**A.1** Consider the connection shown in Figure A.1 in which 3 circuits with losses of 1 dB, 6 dB and 2 dB are connected together by exchanges with actual send switching levels of -2, +1 and -3 dBr. + +![Figure A.1/G.103 – Connection with various send switching levels. The diagram shows a horizontal line representing a connection path. From left to right: a source symbol (circle with a vertical line), a segment labeled '8 dB (SLR)', an exchange symbol 'E1' with an arrow pointing up labeled '-2', a loss symbol '1' (two vertical bars), an exchange symbol 'E2' with an arrow pointing up labeled '+1', a loss symbol '6', an exchange symbol 'E3' with an arrow pointing up labeled '-3', a loss symbol '2', an exchange symbol 'E4', and a destination symbol (square with a vertical line). The text 'T1210910-99' is at the bottom right.](10781f43062bf3e9601a1e086710556c_img.jpg) + +Figure A.1/G.103 – Connection with various send switching levels. The diagram shows a horizontal line representing a connection path. From left to right: a source symbol (circle with a vertical line), a segment labeled '8 dB (SLR)', an exchange symbol 'E1' with an arrow pointing up labeled '-2', a loss symbol '1' (two vertical bars), an exchange symbol 'E2' with an arrow pointing up labeled '+1', a loss symbol '6', an exchange symbol 'E3' with an arrow pointing up labeled '-3', a loss symbol '2', an exchange symbol 'E4', and a destination symbol (square with a vertical line). The text 'T1210910-99' is at the bottom right. + +Figure A.1/G.103 – Connection with various send switching levels + +**A.2** We assume that noise powers of these circuits are $N_1$ , $N_2$ and $N_3$ pW0p respectively. Figure A.2 shows these noise powers entering their circuits via appropriately valued pads chosen to take cognizance of the switching level concerned and dispense with the arrow symbols. + +![Figure A.2/G.103 – The noise powers added. This diagram is similar to Figure A.1 but replaces the switching level arrows with noise power inputs. At exchange E1, a vertical line labeled '2' points down to noise power N1. At exchange E2, a vertical line labeled '-1' points down to noise power N2. At exchange E3, a vertical line labeled '3' points down to noise power N3. The text 'pW0p' is at the bottom right. The text 'T1210920-99' is also present.](12de9b926df0384ec07702671827c9cd_img.jpg) + +Figure A.2/G.103 – The noise powers added. This diagram is similar to Figure A.1 but replaces the switching level arrows with noise power inputs. At exchange E1, a vertical line labeled '2' points down to noise power N1. At exchange E2, a vertical line labeled '-1' points down to noise power N2. At exchange E3, a vertical line labeled '3' points down to noise power N3. The text 'pW0p' is at the bottom right. The text 'T1210920-99' is also present. + +Figure A.2/G.103 – The noise powers added + +**A.3** We note that $N_1$ traverses a total of 11 dB to reach $E_4$ , $N_2$ a total of 7 dB, and $N_3$ a total of 5 dB. Also the difference between the accumulated Sending Loudness Rating (SLR) at each exchange and the corresponding circuit noise level is 6 dB (for $N_1$ ), 10 dB (for $N_2$ ) and 12 dB (for $N_3$ ). Hence, we may redraw the connection reallocating the losses as shown in Figure A.3 in which all send switching levels are 0 dBr and all the other conditions are met as well. + +![Diagram of a transmission line showing switching levels and noise components. A horizontal line represents the transmission path, starting with a circle on the left and ending with a rectangle on the right. A bracket at the top left indicates a '6 dB (SLR)' range. Along the line, there are three switch points marked with 'x' and solid dots. Upward arrows from below point to these dots, labeled E1 + N1, E2 + N2, and E3 + N3. Between the switch points are vertical tick marks with numbers: '4' between the first and second switch points, '2' between the second and third, and '5' after the third. The label 'pW0p' is near the end of the line. The text 'T1210930-99' is in the bottom right corner of the diagram area.](b6671cfafda3820aafe9a24fa7a4d8c7_img.jpg) + +Diagram of a transmission line showing switching levels and noise components. A horizontal line represents the transmission path, starting with a circle on the left and ending with a rectangle on the right. A bracket at the top left indicates a '6 dB (SLR)' range. Along the line, there are three switch points marked with 'x' and solid dots. Upward arrows from below point to these dots, labeled E1 + N1, E2 + N2, and E3 + N3. Between the switch points are vertical tick marks with numbers: '4' between the first and second switch points, '2' between the second and third, and '5' after the third. The label 'pW0p' is near the end of the line. The text 'T1210930-99' is in the bottom right corner of the diagram area. + +**Figure A.3/G.103 – All send switching levels are 0 dBr** + +**A.4** Since the relative level of the immediate downstream circuit at each switch point is now arranged to be 0 dBr, the exchange noise powers can be added as is done in the hypothetical reference connections in Recommendation G.103. + +## ITU-T RECOMMENDATIONS SERIES + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of the ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data 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It features a blue globe with a red lightning bolt striking across it. To the right of the globe, the text "ITU" is written in a bold, blue, sans-serif font. Below "ITU", the words "International Telecommunication Union" are written in a smaller, blue, sans-serif font. + +ITU logo: A globe with a red lightning bolt and the text 'ITU International Telecommunication Union'. + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.1031 + +# QoE factors in web-browsing + +## Summary + +Recommendation ITU-T G.1031 describes the framework for an opinion model for web-browsing quality of experience (QoE). User perceived quality for web-browsing is dependent on various influence factors (IF) that are related to user, context and system. This Recommendation addresses the latter two influence factors (context and system) and provides an overview of them. At the perceptual level, it defines the relevant events that the user perceives while accessing a web page and contrasts them with the events taking place at the application level and at the network level. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.1031 | 2014-02-13 | 12 | 11.1002/1000/12123 | + +## Keywords + +Modeling, page-view cycle, perceptual events, web-browsing session, web-QoE. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2014 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|-----------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 1 | +| 3.1 Terms defined elsewhere ..... | 1 | +| 3.2 Terms defined in this Recommendation..... | 1 | +| 4 Abbreviations and acronyms ..... | 1 | +| 5 Conventions ..... | 2 | +| 6 Factors influencing web-QoE ..... | 2 | +| 6.1 Context influence factors..... | 2 | +| 6.2 System influence factors..... | 3 | +| 7 Perceptual dimension..... | 4 | +| 8 Use cases of a web-QoE opinion model ..... | 4 | +| Bibliography..... | 6 | + + + +# Recommendation ITU-T G.1031 + +## QoE factors in web-browsing + +# 1 Scope + +This Recommendation describes the framework for an opinion model for web-browsing QoE. This Recommendation aims to provide: + +- guidance in the development of an opinion model +- an overview of key influence factors (IF) +- a starting point for performance assessment and KPI definitions. + +This Recommendation introduces a taxonomy of influence factors and related model parameters, as well as a definition of QoE relevant perceptual events. + +# 2 References + +This Recommendation does not use any normative references. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +None. + +## 3.2 Terms defined in this Recommendation + +This Recommendation defines the following terms: + +**3.2.1 element:** Visual content of a webpage, which is displayed to the user on the rendered webpage, e.g., text, pictures, widgets, videos, etc. + +**3.2.2 first element:** A character or a picture for example. + +**3.2.3 object:** A HTTP object that is used for processing and rendering the webpage and is referenced by the page mark-up or script. An object however is not necessarily visible on the fully rendered page (see the definition for element). + +**3.2.4 visible portion:** The part of the requested web page that is visible to the user. + +**3.2.5 web-browsing session:** A web-browsing session is an interactive information exchange between a user and one or more websites over a limited period of time, mediated via a web-browsing application. The starting point of such a session is the first page request initiated by the user, which is followed by a number of request-response interactions between the user and the webhost(s), resulting in a series of page views [b-Egger1]. A web session is typically terminated when the user exits the browsing application or stops the browsing activity for a certain period of time. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +CPU Central Processing Unit + +HTML Hyper Text Mark-up Language + +IF Influence Factor + +OS Operating System + +| | | +|-----|-----------------------| +| PLT | Page Load Time | +| QoE | Quality of Experience | +| RTT | Round Trip Time | + +# 5 Conventions + +This Recommendation uses the following notation: + +| | | +|-------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| t0: | The moment in time when the user requests a new web page (typically by clicking or pressing enter "Enter" after having typed the URL of the web page in the browser's address bar). | +| tSBr: | The moment in time when a change in the status bar happens (usually a progress bar becomes visible at this moment). | +| tSgB: | The moment in time when the previously viewed web page vanishes and the content of the requested page has not yet started to render. | +| tPrs: | The moment in time when the first element of the requested page appears on the screen, independent of the type of element. | +| tPPLT: | The moment in time when from the point of view of the user the page is sufficiently rendered such that he can access the information he is looking for. | +| tVSrc: | The moment of time when the visible portion of the web page (as determined by screen or browser windows size) is fully rendered 1 . | +| tIHRs: | The moment in time when the initial HTTP request is sent by the browser. | +| tBHPr: | The moment in time when the first HTML element is received (see [b-W3schools]). | +| tHP: | The moment in time when the HTML page is processed by the browser (can only be observed at application level). | +| tPLT_1: | The moment of time when all objects of the page are downloaded from the server at the browser's device. | +| tPLT_2: | The moment of time when the page is completely rendered and displayed by the browser. | + +# 6 Factors influencing web-QoE + +Typically, QoE influence factors (IFs) are grouped according to the following three main categories: + +- User influence factors +- Context influence factors +- System influence factors + +User influence factors are outside of the scope of this Recommendation. Context influence factors are discussed in clause 6.1. System influence factors are discussed in clause 6.2. + +## 6.1 Context influence factors + +The context in which a web page is accessed can have a critical influence on the user behaviour and his QoE. The range of context influence factors spans: + +- Location: Cafeteria, office, home + +--- + +1 It should be noted that there can be further rendering activity outside of the visible screen area. + +- Interactivity: High level interactivity vs. low level interactivity +- Task type: business, entertainment, etc. +- Task urgency: urgent vs. casual (without time constraints). + +## 6.2 System influence factors + +The range of system influence factors spans the following content, network and client related IFs: + +- Server-related influence factors (see clause 6.2.1) +- Content-related influence factors (see clause 6.2.2) +- Delivery network influence factors (see clause 6.2.3) +- Client influence factors (see clause 6.2.4) + +In order to better understand the position of these IFs in the delivery chain, a typical Web-QoE delivery chain is depicted in Figure 1. + +![Figure 1 – Delivery chain for a typical webpage. The diagram shows a flow from left to right: 'Perceived quality' (User icon) connected to a 'Device' (laptop icon), which is connected to an 'Access network' box, then a 'Core network' box, then an 'Internet' cloud, and finally a 'Server + content' box (server icon) leading to 'Produced quality'. A small label 'G.1031(14)_F01' is at the bottom right.](367926125450c2bc3f4bdca9d59a62ba_img.jpg) + +``` + +graph LR + User((User)) -- Perceived quality --> Device[laptop icon] + Device --> Access[Access network] + Access --> Core[Core network] + Core --> Internet((Internet)) + Internet --> Server[Server + content] + Server -- Produced quality --> End[ ] + style End fill:none,stroke:none + +``` + +Figure 1 – Delivery chain for a typical webpage. The diagram shows a flow from left to right: 'Perceived quality' (User icon) connected to a 'Device' (laptop icon), which is connected to an 'Access network' box, then a 'Core network' box, then an 'Internet' cloud, and finally a 'Server + content' box (server icon) leading to 'Produced quality'. A small label 'G.1031(14)\_F01' is at the bottom right. + +**Figure 1 – Delivery chain for a typical webpage** + +### 6.2.1 Server-related influence factors + +- Response time (determined by CPU, OS, memory, software, etc.) +- Capacity of the link(s) connecting the server(s) and the Internet. + +### 6.2.2 Content-related influence factors + +These factors go beyond the established notion of content as used in QoE. This is because in Web QoE, content is typically constituted by a mix of different element types such as text, pictures, audio files and videos. In addition, the HTML mark-up of the webpage (and related scripts) strongly determines the actual loading behaviour of the page according to its internal structure and the utilized objects such as: + +- Number of objects +- Type of objects +- Size of objects +- Order of objects +- Number of elements +- Type of elements +- Size of elements +- Element appearance on the screen (determined by the order of the objects as well as by the rendering strategy of the browser, see [b-Strohmeier]). + +### 6.2.3 Delivery network influence factors + +- Network contribution to transaction time (see [b-ITU-T G.1040]) +- Available capacity (see [b-ITU-T Y.1540]) +- Caching along the delivery network: The caching elements lower perceived server response time as they shorten client-to-server requests and therefore lower the RTT. + +### 6.2.4 Client influence factors + +- Resource (webpage) loading procedure +- Processing power and other processes demanding processing power +- Browser implementation +- TCP/IP stack and configuration +- Operating system. + +All of these IF's impact the user perceived performance of the web page display when requested by the user. + +# 7 Perceptual dimension + +When the end user requests a page by means of entering a dedicated web address or clicking on a link on an already loaded web page, the download of content from a web server is initiated. This requested content (typically a base HTML page that references additional elements like images and scripts) is progressively fetched and rendered by the browser. During this process the user encounters several observable events as depicted in Figure 2. + +![Figure 2: Perceptual events in a web page view cycle from the end-user point of view. The diagram shows two horizontal timelines. The top timeline, labeled 'User perception', has a black line with an arrow pointing right, labeled 'Time'. It has tick marks at t0, tSBr, tSGB, tPRs, tPPLT, and tSVrc. The bottom timeline, labeled 'Application and network', has a blue line with tick marks at tIHRs, tBHPr, tHp, tTPLT_1, and tTPLT_2. The tick marks on the two timelines are vertically aligned. A small label 'G.1031(14)_F02' is at the bottom right of the diagram.](b8661c6c54f72ecc7ff6cb05e47b2891_img.jpg) + +G.1031(14)\_F02 + +Figure 2: Perceptual events in a web page view cycle from the end-user point of view. The diagram shows two horizontal timelines. The top timeline, labeled 'User perception', has a black line with an arrow pointing right, labeled 'Time'. It has tick marks at t0, tSBr, tSGB, tPRs, tPPLT, and tSVrc. The bottom timeline, labeled 'Application and network', has a blue line with tick marks at tIHRs, tBHPr, tHp, tTPLT\_1, and tTPLT\_2. The tick marks on the two timelines are vertically aligned. A small label 'G.1031(14)\_F02' is at the bottom right of the diagram. + +**Figure 2 – Perceptual events in a web page view cycle from the end-user point of view** + +Note that in this figure the application and network timeline (in blue) displays related technical events at the application or network levels. Note also that in this figure the distance between the perceptual events is shown as being equal, but this is not necessarily the case in real-world browser implementations. + +This description differentiates between perceived page load time (PLT) $t_{PPLT}$ and technical page load time $t_{TPLT\_1}$ (or $t_{TPLT\_2}$ depending on the actual measurement procedure). This differentiation is important since ultimately, for the user QoE, only the perceived PLT $t_{PPLT}$ matters. This distinguishes this description from related work described in Annex A of [b-ITU-T G.1030], where only the technical PLT $t_{TPLT}$ is used as a basis for QoE estimation. This difference is essential, since $t_{PPLT}$ can be considerably shorter than $t_{TPLT}$ and depends on several technical and non-technical influence factors such as user task, web page design, number of elements, etc. This is shown in [b- Egger2] where the presented empirical data from subjective tests quantifies the differences between these two points in time. + +NOTE – In a regular web-browsing session the end user encounters several sets of such page view event sequences. + +# 8 Use cases of a web-QoE opinion model + +A perceptual opinion model for Web-QoE can be used in the following use cases: + +- Network dimensioning, including: + - Network planning + +- Traffic management solutions design and optimization +- Online/offline measurement of Web-QoE based on network and application logs or probes +- Performance testing (of elements in the delivery chain). + +## Bibliography + +- [b-ITU-T G.1030] Recommendation ITU-T G.1030 (2014), *Estimating end-to-end performance in IP networks for data applications*. +- [b-ITU-T G.1040] Recommendation ITU-T G.1040 (2006), *Network contribution to transaction time*. +- [b-ITU-T Y.1540] Recommendation ITU-T Y.1540 (2011), *Internet protocol data communication service – IP packet transfer and availability performance parameters*. +- [b-Egger1] Egger, *et al.*, "Waiting times in quality of experience for web based services," In Proc. of 2012 Fourth International Workshop on Quality of Multimedia Experience (QoMEX), pp. 86, 96, 5-7 July 2012. +- [b-Egger2] Egger, *et al.*, "Time is bandwidth"? Narrowing the gap between subjective time perception and Quality of Experience, "In Proc. of 2012 IEEE International Conference on Communications (ICC), pp. 1325, 1330, 10-15 June 2012. +- [b-W3schools] W3schools (2013, November 25). *HTML head elements*. +<[http://www.w3schools.com/html/html\\_head.asp](http://www.w3schools.com/html/html_head.asp)> +- [b-Strohmeier] Strohmeier, *et al.*, (2012), *Toward task-dependent evaluation of Web-QoE: Free exploration vs. "Who Ate What?"*, In: Proc. QoEMC at GLOBECOM 2012, pp. 1309, 1313, 3-7 Dec. 2012. + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|---------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Terminals and subjective and objective assessment methods | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects and next-generation networks | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.1033-201910-I_PDF-E/raw.md b/marked/G/T-REC-G.1033-201910-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..578366486fcc10a52182f3540dde35ef125605fc --- /dev/null +++ b/marked/G/T-REC-G.1033-201910-I_PDF-E/raw.md @@ -0,0 +1,880 @@ + + +International Telecommunication Union + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.1033** + +(10/2019) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Multimedia Quality of Service and performance – Generic +and user-related aspects + +--- + +**Quality of service and quality of experience +aspects of digital financial services** + +Recommendation ITU-T G.1033 + +ITU-T + +![ITU logo](1d7527f4316cfe2d342b08d1653d1592_img.jpg) + +The logo of the International Telecommunication Union (ITU) features a stylized globe with a red lightning bolt striking through it, symbolizing global connectivity and telecommunications. To the right of the globe, the text "International Telecommunication Union" is written in a blue, sans-serif font. + +ITU logo + +International +Telecommunication +Union + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.1033 + +# Quality of service and quality of experience aspects of digital financial services + +## Summary + +Recommendation ITU-T G.1033 highlights important aspects related to quality of service (QoS) and quality of experience (QoE) that require consideration in the context of digital financial services (DFSs). + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.1033 | 2019-10-14 | 12 | 11.1002/1000/14065 | + +## Keywords + +Digital financial service, QoE, QoS + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2019 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +# Table of Contents + +| | | Page | +|--------------|---------------------------------------------------------|------| +| 1 | Scope ..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions ..... | 1 | +| 3.1 | Terms defined elsewhere ..... | 1 | +| 3.2 | Terms defined in this Recommendation..... | 1 | +| 4 | Abbreviations and acronyms ..... | 1 | +| 5 | Conventions ..... | 2 | +| 6 | Problem statements ..... | 2 | +| 6.1 | Different use cases..... | 3 | +| 6.2 | Legal entities ..... | 3 | +| 6.3 | Mobile network QoS affecting all services ..... | 4 | +| 6.4 | Possible solutions ..... | 5 | +| 7 | Conclusions ..... | 5 | +| 7.1 | Conclusions for service category 1 ..... | 5 | +| 7.2 | Conclusions for service category 2..... | 6 | +| 7.3 | Conclusions related to digital financial services ..... | 6 | +| 8 | Future considerations: Top-level view ..... | 6 | +| 8.1 | Use cases and related top-level KPI ..... | 7 | +| 8.2 | Technological components of DFSs..... | 8 | +| 8.3 | Stakeholders ..... | 9 | +| 8.4 | QoS monitoring ..... | 10 | +| Annex A | – Underlying functionalities of DFS applications ..... | 12 | +| A.1 | Service category 1 (feature phone)..... | 12 | +| A.2 | Service category 2 (smartphone)..... | 14 | +| Appendix I | – Considerations related to the fitness for DFSs..... | 16 | +| Appendix II | – Is DFS a "popular service"?..... | 19 | +| II.1 | Relationship between QoS and QoE..... | 19 | +| II.2 | Services, applications or "popular services" ..... | 21 | +| II.3 | Is a DFS a "popular service"?..... | 21 | +| Bibliography | ..... | 23 | + + + +# Recommendation ITU-T G.1033 + +## Quality of service and quality of experience aspects of digital financial services + +# 1 Scope + +This Recommendation highlights important aspects related to quality of service (QoS) and quality of experience (QoE) which shall be considered in the context of digital financial services (DFSs). + +NOTE – This Recommendation builds upon the discussions in the (now closed) DFS Focus Group and on [b-ITU-T DFS TR]. The continuation of work on QoS and QoE aspects is undertaken by the Financial Inclusion Global Initiative (FIGI) [b-FIGI 2019a], [b-FIGI 2019b], [b-FIGI 2019c]. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +[ITU-T E.811] Recommendation ITU-T E.811 (2017), *Quality measurement in major events*. + +[ETSI TS 103 296] ETSI TS 103 296 V1.1.1 (2016), *Speech and multimedia transmission quality (STQ); Requirements for emotion detectors used for telecommunication measurement applications; Detectors for written text and spoken speech*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +None. + +## 3.2 Terms defined in this Recommendation + +None. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|------|-----------------------------------------| +| 2G | second Generation | +| 3G | third Generation | +| CPU | Central Processing Unit | +| DFS | Digital Financial Service | +| DTMF | Dual Tone Multi Frequency | +| E2E | End-to-End | +| FEC | Forward Error Correction | +| GSM | Global System for Mobile communications | +| HLR | Home Location Register | + +| | | +|-------|--------------------------------------------| +| HTML | Hypertext Markup Language | +| HTTP | Hypertext Transfer Protocol | +| HTTPS | Hypertext Transfer Protocol Secure | +| IP | Internet Protocol | +| IPTV | IP Television | +| IVR | Interactive Voice Response | +| KPI | Key Performance Indicator | +| KQI | Key Quality Indicator | +| MMS | Multimedia Messaging Service | +| MOS | Mean Opinion Score | +| OTT | Over The Top | +| P2P | Person to Person | +| QoE | Quality of Experience | +| QoS | Quality of Service | +| QoSE | QoS Experienced | +| QoSP | QoS Perceived | +| RTP | Real-Time Protocol | +| SIP | Session Initiation Protocol | +| SLA | Service Level Agreement | +| SMS | Short Message Service | +| SMSC | Short Message Service Centre | +| SSL | Secure Sockets Layer | +| TCP | Transmission Control Protocol | +| TLS | Transport Layer Security | +| UMTS | Universal Mobile Telecommunications System | +| USSD | Unstructured Supplementary Service Data | +| VoIP | Voice over IP | +| VoLTE | Voice over Long-Term Evolution | +| WAP | Wireless Application Protocol | +| WML | Wireless Markup Language | +| XML | extensible Markup Language | + +# 5 Conventions + +None. + +# 6 Problem statements + +QoS and QoE aspects depend in particular on the use case under consideration and related aspects like environment and detailed macro parameters. + +## 6.1 Different use cases + +Use cases of DFSs can be easily categorized and analysed when applying the hierarchy concept depicted in Figure 1. + +![Figure 1: Hierarchy of use cases, types, and macroscopic parameters. The diagram shows a three-level hierarchy. The top level, 'Main use case', contains 'P2P money transfer'. The second level, 'Type/environment', branches into 'National, same DFS operator', 'Interoperability: national; different DFS operators', and 'Interoperability, international'. The third level, 'Macro parameter', branches from 'National, same DFS operator' into 'Smartphone based' and 'Feature phone based'.](562f471e8153729557e6a4ee6343c32c_img.jpg) + +``` +graph TD; A[P2P money transfer] --> B[National, same DFS operator]; A --> C[Interoperability: national; different DFS operators]; A --> D[Interoperability, international]; B --> E[Smartphone based]; B --> F[Feature phone based]; +``` + +G.1033(19)\_F01 + +Figure 1: Hierarchy of use cases, types, and macroscopic parameters. The diagram shows a three-level hierarchy. The top level, 'Main use case', contains 'P2P money transfer'. The second level, 'Type/environment', branches into 'National, same DFS operator', 'Interoperability: national; different DFS operators', and 'Interoperability, international'. The third level, 'Macro parameter', branches from 'National, same DFS operator' into 'Smartphone based' and 'Feature phone based'. + +**Figure 1 – Hierarchy of use cases, types, and macroscopic parameters** + +Other main use cases are, for example, transfers between a mobile device and a bank account, or bulk transfers such as payment of wages by an employer. The hierarchy also allows the introduction of higher-level classifications (transfer types), e.g., one-to-one, one-to-many, many-to-one + +NOTE – The use case hierarchy shown in Figure 1 displays some variants that are for further study. + +QoS aspects of DFSs need to be assessed for two different service categories that are, with reference to Figure 1, macroscopic parameters of a main use case, namely person to person (P2P) money transfers. + +- 1) In service category 1, the targeted group of users is limited to the use of (cheap) basic feature phones. This excludes for example browser-based DFS solutions. +- 2) In service category 2, the additional QoS aspects are assessed when the minimum requirements to the phones used for DFSs are raised and basic smartphone functionality can be assumed. + +## 6.2 Legal entities + +It is important to accept that in reality the provision of a service offer ("service") is – as a general rule – independent of the physical operation of a telecommunication network. + +Whereas for most service offers there is – beside the general legal framework – no specific regulation, DFS "services" are under the close control of banking sector regulators, whereas operators of telecommunication networks are under the control of telecom sector regulators. + +Therefore, legal aspects (from a QoS perspective) need to assess two different legal cases: + +- 1) in legal case A, the provider of a DFS "service" and the operator of a physical telecommunication network are two distinct and different legal entities; +- 2) in legal case B, the provider of a DFS "service" and the operator of a physical telecommunication network are the same and identical legal entity. + +NOTE – This Recommendation is without prejudice regarding actual legal actions or situations or conclusions or any combination thereof. + +## 6.3 Mobile network QoS affecting all services + +Figure 2 (adapted from [b-ITU-T E.804] and [b-ETSI TS 102 250-2]) shows a model for QoS parameters. This model has four layers, each of which provides the necessary precondition for the next layer, i.e., that a property belonging to layer $N$ needs the presence of the properties of layer $N - 1$ . + +The first layer is network availability, which determines QoS from the viewpoint of the service provider than the service user. The second layer is network access. From the service user's point of view, this is the basic requirement for all the other QoS aspects and parameters. The third layer contains the other three QoS aspects: service access, service integrity and service retainability. The different services are located in the fourth layer; the performance of these services is characterized by service specific QoS key performance indicators (KPIs). + +The first three layers (with green highlights) are common to all mobile services or applications. + +They are characterized typically by the following parameters (KPIs): + +- network availability; +- network accessibility; +- service accessibility; +- service integrity; +- service retainability. + +In cases where the KPIs in layers 1, 2 and 3 are not maintained at a stable high level, it is useless to attempt to assess the QoS of any kind of service, because prerequisite conditions are not met and the relevance of QoS figures received will be close to zero. + +![Figure 2 – Model for quality of service parameters. A hierarchical diagram showing four layers of QoS parameters. Layer 1 (Network availability) is at the top. Layer 2 (Network accessibility) is below it, with sub-categories 'Circuit switched' and 'Packet switched'. Layer 3 (Service accessibility, Service integrity, Service retainability) is below Layer 2. Layer 4 (various services) is at the bottom, with sub-categories 'E-mail', 'File transfer', 'MMS', 'Mobile broadcast', 'Ping', 'PoC', 'SMS', 'Streaming', 'Telephony', 'Video telephony', 'Web browsing', and 'DFS'. The first three layers are highlighted in green, and the fourth layer is highlighted in yellow. The DFS box is highlighted in orange.](c2fc2621e8206d24427b56bcb2398fc0_img.jpg) + +The diagram illustrates a four-layer model for quality of service (QoS) parameters. Layer 1 (Network availability) is at the top. Layer 2 (Network accessibility) is below it, with sub-categories 'Circuit switched' and 'Packet switched'. Layer 3 (Service accessibility, Service integrity, Service retainability) is below Layer 2. Layer 4 (various services) is at the bottom, with sub-categories 'E-mail', 'File transfer', 'MMS', 'Mobile broadcast', 'Ping', 'PoC', 'SMS', 'Streaming', 'Telephony', 'Video telephony', 'Web browsing', and 'DFS'. The first three layers are highlighted in green, and the fourth layer is highlighted in yellow. The DFS box is highlighted in orange. + +G.1033(19)\_F02 + +Figure 2 – Model for quality of service parameters. A hierarchical diagram showing four layers of QoS parameters. Layer 1 (Network availability) is at the top. Layer 2 (Network accessibility) is below it, with sub-categories 'Circuit switched' and 'Packet switched'. Layer 3 (Service accessibility, Service integrity, Service retainability) is below Layer 2. Layer 4 (various services) is at the bottom, with sub-categories 'E-mail', 'File transfer', 'MMS', 'Mobile broadcast', 'Ping', 'PoC', 'SMS', 'Streaming', 'Telephony', 'Video telephony', 'Web browsing', and 'DFS'. The first three layers are highlighted in green, and the fourth layer is highlighted in yellow. The DFS box is highlighted in orange. + +Figure 2 – Model for quality of service parameters + +Persisting problems with the KPIs for layers 1, 2 and 3 of a mobile network need to be resolved by the stakeholder in the interest of any mobile service and are therefore clearly out of scope of QoS-for-DFS-considerations. + +NOTE – Figure 2 requires an update. First of all, layers 1 to 3 describe actually a kind of "pyramid of needs", i.e., before starting to think about service integrity (e.g., call drop rate in telephony), the service needs to be accessible first. Also, the "service" picture needs an overhaul. The "circuit/packet switched" division is legacy from 2G or 3G. Some of the "services" in layer 4 actually depend on each other or belong to different groups. There are "carrier services" such as the basic Internet protocol (IP), and also combined services using one or more such carrier services, e.g., the multimedia messaging service (MMS) that relies on the short message service (SMS) (which is actually an end user-related service as well) for notification, and uses packet data to actually transfer data. A "service" with the same effect for end users, e.g., some kind of over the top (OTT) chat with attached files, uses only basic packet data. In any case, there is no longer any real "technology dependency". If an operator decides to suppress Skype, or prioritizes certain video streaming, this is not the result of some fundamental ability or inability, but just the effect of some "traffic shaping" elements. + +## 6.4 Possible solutions + +DFSs are realized through utilization of basic services provided by a network. Assuming that the reliability of DFSs has to be very high, there are two basic ways to ensure this reliability. + +- Network centric: The QoS level for basic services provided by the network is sufficiently high to create the required reliability. +- User centric: Robust E2E protocols on UE- and DFS-related infrastructure ensure the reliability of the actual service, even in the presence of deficiencies in the underlying functionality. + +Such robustness can be described by key criteria for DFSs. Topmost is, for each transaction, a clear indication whether it was successful, which needs to be consistent for both sides. Assume a transaction is composed of a number of steps, each step being the exchange of a data token. If the transfer of a data token has no clear "lost" criterion, but can take, in principle, indefinite time, a time-out needs to create a defined situation. The essential property of robustness is that, if a data token now arrives after its time-out, the protocol needs to ensure that this token is not causing any action any more. + +With respect to practical aspects of DFS implementations, this poses some fundamental differences. When the main goal is to introduce DFSs in the near future, it needs to operate with the existing installed base of end user devices. This will automatically limit the spectrum of applicable methods to those which can be supported by those devices. A possible drawback of this approach is that if a technology has been deployed and is widely used, it will – as long as it is working without major problems – be difficult to replace, even if the new technology is superior. This may be less an issue with respect to end user devices as the penetration of smartphones continues to increase strongly due to their manifold advantages. It may be that these retaining factors are more on the side of infrastructure, as introduction of new technologies requires new investment that may, at least in the first years of usage, not be balanced by similar new opportunities to generate additional revenue. + +# 7 Conclusions + +The following conclusions are, with respect to clause 6, based on the assumption that necessary DFS performance is achieved by ensuring a sufficiently high performance of the basic services used to implement DFSs. The case of using a robust E2E protocol is not treated here. + +## 7.1 Conclusions for service category 1 + +Four different techniques are discussed in Annex B, which might be used in conjunction with DFS offers for service category 1. + +- SMS is a store and forward service. Even if the share of short transfer times may be high in typical cases, it cannot – without modifications – be used reliably for real-time transactions. +- Dual tone multi-frequency (DTMF) has limited transfer capabilities and will most probably only be used to complement one of the other techniques. +- Interactive voice response (IVR) typically requires reasonably high listening quality, which might pose a problem with feature phones in environments with higher levels of background noise. +- Unstructured supplementary service data (USSD) is a true real-time technique. However, the message transfers which could be used for DFSs are not standardized. + +## 7.2 Conclusions for service category 2 + +Seven different techniques are discussed in Annex A, which might be used in conjunction with DFS offers for service category 2. As per availability on smartphones, solutions based on the hypertext transfer protocol secure (HTTPS) appear to be the optimal carrier technology for DFSs. + +## 7.3 Conclusions related to digital financial services + +It is of importance for any further work in the field of QoS/QoE for DFSs to get access to more detailed information, such as descriptions of the various DFS offers to see on a technical level, which underlying services in the network are used and which are the technical parameters associated with them, e.g., timer values, timeout events and number of interactions involved in a single financial transaction. Doing so carries potential for improving the quality of standards development and testing, which has been an on-going need. + +Therefore, it is suggested that telecom regulators collect such information prior to the issue of licenses in order to make their own judgement of the quality of the planned DFS offering. + +Such information should be submitted by regulators to ITU-T Study Group 12, where the experts could start categorizing the different approaches and provide comments and guidance on such implementations. If possible, the information on the DFSs should be summarized in a flowchart. + +There are even more issues remaining currently open, which will need further discussion. + +- Mobile operators have increasing problems with the huge amount of data traffic in their networks. Therefore, if high-speed fixed networks are available, there is a massive trend to use so-called "Wi-Fi offloading", where data traffic is redirected via Wi-Fi accesses to the internet backbone core. The consequences for DFSs seem to be quite unexplored, as yet. +- The text displayed in the course of DFS interactions or the accentuation in spoken dialogue systems may be loaded with emotion, which could affect the user experience of the service (QoE). Emotion detectors could be used to minimize any negative impact from this text and speech material. Currently, requirements for emotion detectors in telecommunications have been published in [ETSI TS 103 296]. +- A serious problem (mostly for regulators) are effects that cannot easily be allocated to one of the stakeholders in the DFS process. A prominent example is so-called early timeouts in DFSs, which anyone outside the DFS provider would interpret as dropped- calls, i.e., blame the network or blame the terminal or blame the user – in reality it turns out just to be a badly designed flow-of-actions: users still reading instructions on their screens before initiating the next step of a transaction are hit by an invisible timer's timeout action. + +# 8 Future considerations: Top-level view + +This clause deals with an end-to-end (E2E) model of DFSs. It focuses on the essence for user-related functionality of DFSs by providing a top-level view of (selected) DFS use cases. + +The term "transaction" is used to describe a single instance of a complete use case from a customer point of view, in accordance with the usage of this term in other fields of QoS standardization. It is noted that in this case, the term is also part of the common expression "financial transaction". + +The use cases described serve as examples to explain the underlying framework. The underlying model can, however, be easily applied to other use cases that are identified to be relevant in the DFS context. + +From the use cases, quality metrics are derived. The key point of the model is that it is, on its topmost level, "technology agnostic". The actual implementation may be in manifold ways, with specific technical characteristics, strengths and weaknesses; these come in at lower levels of the model. The technology agnostic top level makes sure that no "technology-related" allowances are made (such as "discounts" for known technical weaknesses of particular implementations). Also, the model makes sure that new technical developments in realizing DFSs do not disrupt existing QoS metrics. + +The underlying general principle of the QoS metrics proposed is also to provide the smallest possible number of KPIs, with each KPI having a clearly defined relation to user perception. This shall avoid the situation, observed in some KPI sets, where individual KPIs overlap in meaning, which can lead to unclear or even contradictory results. + +An actual DFS implementation uses different network- related "services" or functionality. The relevant clause shows how the use case related top-level view – and its KPIs – can be mapped to this technological level of currently existing "carrier services" with appropriate (mostly already existing) KPIs. + +The principle of having a small number of strong KPIs does not exclude additional KPIs with diagnostic or administrative functions. + +It is recognized that there are several stakeholders with different interests. The relevant clause – which is also to be seen as an expandable illustration of the underlying concept – describes this view in more detail. + +The fact that different stakeholders have different interests also leads to the conclusion that not all KPIs are of equal importance to all stakeholders. This aspect can provide guidance when it comes to the provision of a legal or regulatory framework to enable or support emergence of DFSs. + +Clause 8.4 considers how practical monitoring of DFS service performance could be implemented. It differentiates between test and measurement in the introduction phase, and continuous quality monitoring in the operational phase of DFSs. + +## **8.1 Use cases and related top-level KPI** + +### **8.1.1 Transfer of money from A to B** + +Basic flow of activities: + +Party A decides to transfer amount $X$ from its account to the account of B. Key interests of this transfers are: + +- 1) the transfer is made with a clear indication of success or failure on both sides within a reasonable time span; +- 2) the success rate of a money transfer needs to be high; +- 3) the duration of a transaction is reasonably short; +- 4) if the transaction fails, the situation needs to be completely reversed within a reasonably short time span (i.e., no money "lost in limbo"); +- 5) the transaction leads to a stable and correct end state for all participants in a reasonably short time span (i.e., all accounts are "up to date" as fast as possible); + +- 6) there are no losses or duplications of money during the transaction (i.e., money not deducted from A's account but appearing in B's account). + +NOTE – Not all of these conditions are of equal importance to all stakeholders, e.g., the absence of "money duplications" may not be of interest to end users. + +A further differentiation of the use case may come from the question whether some kind of proof for the transaction is created, and if yes, in which way. This may be a crucial element if money is paid to clear debts, e.g., an electricity bill. This may involve data transmission to a possible third party to send such a proof, or access to appropriate services to produce this. + +From these requirements, the following E2E KPIs can be derived: + +- money transfer completion rate; +- money transfer completion time; +- money transfer false positive rate; +- money transfer false negative rate; +- money transfer failed transaction resolution rate; +- money transfer account stabilization success rate; +- money transfer account stabilization time; +- money transfer loss rate; +- money transfer duplication rate. + +NOTE – These KPIs and their technical basis are currently not standardized and therefore cannot be assessed in a comparative manner. + +This list clearly contains elements that are not primarily related to mobile network behaviour or performance; they also relate to the performance of underlying banking processes and implementations. So, the list can probably be reduced to elements that are assumed to be primarily linked to mobile networks. + +There is, however, a connection. If, for example, a connection loss occurs during a transaction consisting of a number of roundtrips estimated to complete a DFS transaction, this may have different results depending on a particular implementation of such banking processes. Therefore, it is assumed that the robustness and stability of such processes against failures which are typical to specific basic services of mobile networks will also have an effect on the overall QoS of DFSs. + +### 8.1.2 Other use cases + +This is for further study. + +## 8.2 Technological components of DFSs + +As outlined in other parts of this Recommendation, there are some services and functionalities within existing mobile networks that can be used – with a further selection by available features of mobile devices – to realize DFSs. + +From the concept of a "pyramid of needs" and assessment of the E2E KPIs for DFSs, a clear hierarchy of quality requirements can be derived. + +The topmost requirement will be the integrity of a transaction. Integrity in DFSs is the clear and reliable assessment, whether a transaction has been successful or not. This is seen as even more important than the overall success rate of an implementation. If a transaction is erroneously assessed as being successful or failed, the objective damage (e.g., to a person's financial condition) will be larger than a case where a transaction has to be repeated due to a detected failure. The same applies to a transaction that is erroneously assessed as unsuccessful, which would result in duplicate transfer due to a repetition of the process. + +From a QoE point of view, the situation can be more complex. Assuming there are two implementations: one of them being stable and robust in the sense of low (ideally zero) probability of false positives or negatives, but slow; the other one faster, but more sensitive to such errors. Unless the false-assessment error is quite large, it is likely that in the customer perception, the latter will appear as the "better" one. It follows that in this area, consideration beyond mere competition according to market rules is needed. + +An E2E approach needs to be taken because the overall robustness of a particular implementation depends on several factors. + +Assume that there are two alternatives, one of them requiring a number, $N_1$ , of roundtrips, each having a time duration of $T_1$ , and a success rate per roundtrip of $S_1$ ; the other is characterized likewise by $N_2$ , $T_2$ and $S_2$ . Clearly, there are several interactions with typical network properties. For instance, if the transaction is performed while the actor is moving (e.g., in a public transport vehicle or as a passenger in a car), the change of network conditions during a transaction influences the overall success rate. This links the time scale of motion-related impairments to transaction characteristics. If the typical overall duration of a DFS transaction ( $T_1*N_1$ and $T_2*N_2$ ) is above the typical time during which network properties show degradations, the probability of failure increases. In a more general view, the overall success rate of a DFS transaction can be expressed as $S_1^{N_1}$ and $S_2^{N_2}$ . So even if an individual success rate per roundtrip of a specific implementation (where the motion profile can be factored in) is lower, the resulting E2E success rate may be higher if the number of roundtrips in this implementation is sufficiently smaller. + +The same linkage between characteristics includes the times involved. For instance, if a transaction fails (in a "proper" way, i.e., with correct assessment of the result), the negative impact on QoE will presumably be smaller if this result is obtained in a shorter period of time, as a follow-up try can be started and completed faster. + +## 8.3 Stakeholders + +This clause is not meant to be a complete analysis of stakeholder structure and their requirements. The point is that different stakeholder types exist, and that their concerns and main interests differ. This will have an impact on the relative weighting of particular QoS metrics and therefore on definition of QoE. + +### *End customers* + +The main interest of end customers will be to have access to DFSs at low cost (which also means without the need to spend more on new mobile devices) and with a high degree of reliability, as financial losses due to service failures will be felt relatively strongly, in particular in low-income segments. It is assumed that transaction speed considerations are (as long as transaction times are within certain reasonable limits) of less importance. + +### *Businesses* + +Assuming the same basic need for reliable and affordable transactions, larger enterprises at least will have an interest in DFS technologies that allow for efficient processing of recurring or larger scale transfers. It is further assumed that there may be interest in technologies that can be deployed on fixed-network equipment (i.e., personal computers) without excessive cost. This will in turn affect market acceptance of solutions with different ways of interfacing. An example is access to certain gateways or other network-based functions like a short message service centre (SMSC). + +### *Network operators* + +As network operators are, usually, subject to regulation, relevant factors actually can be separated into two categories. The first category contains general technical and commercial requirements, such as cost of operation of a particular technology in relation to profits that can be generated. The second category may include cost of non-compliance with legal or regulatory requirements, in terms of + +service level agreements (SLAs), or linkages between, for example, licenses and obligations to provide certain services or service properties. + +### ***DFS operators*** + +Although DFS operators are not identical to network operators, they will basically be subject to similar conditions to them, with perhaps other governmental entities responsible for setting and enforcing the rules under which they operate. Commercially, their market power will probably be large enough to impose quality standards (SLAs) or other market forces to service providers (network operators). + +### ***Governments/Regulators*** + +Assuming that the main objective of governments is economic development, their task is to find a balance between carrot and stick, i.e., a level of rules and regulations that enables technical evolution, while leaving DFS operators enough room to run a profitable service, and making sure that costs of DFS services are in an affordable range. For this stakeholder group, it is assumed that the main objectives are stable, reliable services in combination with a technology that gives the target segment of the population a sufficiently barrier-free access to DFSs. + +Furthermore, there are different ways in which each of these stakeholder groups has influence on other stakeholders, for instance in rewarding or sanctioning market offerings or more general decisions. The crucial point to be made here is that beyond the directly visible first-order effects, second-order interactions exist that do not necessarily have to be weaker, but may work in a "cybernetic" way, i.e., with longer time constants, but with likewise or even stronger effects than first-order dependencies. + +## **8.4 QoS monitoring** + +In order to secure the necessary quality level of DFSs, appropriate regulatory guidance and comprehensive performance targets need to be established. Basically, it would be possible to refer to basic performance measurements of respective carrier services (such as SMS, telephony (for DTMF or IVR) or packet data. Due to the nature of services implementation this will, however, be a surrogate with considerable risk of predicting actual DFS performance incorrectly. + +It is therefore – owing to the importance of DFS – assumed that a better way of monitoring needs to be established. This monitoring should – while being fully aware of practical issues in definition and implementation – use actual use cases, i.e., actual money transfer. + +The monitoring is proposed to have multiple forms that cover all stages of the technical life cycle of any DFS implementation. + +### ***Assessment and roll-out phase:*** + +E2E performance measurements as professionally done by dedicated systems, e.g., under control of regulatory authorities. + +### ***Operational phase:*** + +Regular E2E performance measurements as professionally done by dedicated systems, e.g., under control of regulatory authorities. + +### ***"Test panel" performance measurements, integrated into selected end user devices/apps:*** + +For this kind of measurement, a group of end users, selected to be representative for the general usership, would be recruited and equipped with specially designed DFS clients. This group would, along with doing their "real life" DFS usage, also file additional reports. These reports would then allow responsible entities to constantly assess the performance of DFSs in the field. + +### ***"Crowd-sourced" performance measurements, integrated into end user devices/apps:*** + +This would be a simple and non-intrusive way to obtain information on DFS performance on a broad scale. Professional systems used would be equipped with functionality to not only measure E2E performance, but also collect diagnostic information allowing to track root causes for poor performance or malfunction of services. + +Using real use cases creates additional cost. This cost needs to be assessed against the benefits of obtaining real instead of surrogate data that only can estimate actual service performance. Moreover, it is possible, with a little additional effort in planning and implementation, to design processes that optimize additional cost, such as re-transferring money that has been moved by a DFS. + +It is therefore proposed to add appropriate concepts to a DFS implementation strategy. To increase the effectiveness of such concepts, it is recommended that a pilot phase be designed to give insight into practical aspects and provide information to optimize respective operations. + +# Annex A + +## Underlying functionalities of DFS applications + +(This annex forms an integral part of this Recommendation.) + +### A.1 Service category 1 (feature phone) + +This clause focuses on DFS applications that can be run using simple mobile feature phones (low-end mobile phones that are limited in capabilities in contrast to modern smartphones, see clause 6.1). Therefore it is assumed in the following that financial services requiring file transfer protocol, hypertext transfer protocol (HTTP) or browser-based transactions can be safely excluded from the discussion in this clause. + +**Table A.1 – Summary of technologies for service category 1** + +| Technique | Main features | Disadvantages | Advantages | +|-------------|----------------------------------------------------------------------------------|-------------------------------------------|------------------------------------------| +| SMS | Store-and-forward alphanumerical messages | Not real-time | Globally available
Interconnection ok | +| IVR | Interaction with user by artificial or recorded voice, voice recognition or DTMF | Requires good speech quality transmission | Real-time | +| DTMF | Simple keypad operation | Limited character set | Real-time | +| USSD | Alphanumerical messages | Requires USSD Gateways | Real-time | + +#### A.1.1 Short message service + +The SMS is used to send text messages to and from mobile phones, fax machines or IP addresses. The messages can typically be up to 160 characters in length, though some services use 5-bit mode, which supports 224 characters. SMS was originally created for phones that use the global system for mobile communications (GSM), but now all major mobile phone systems support it. Once a message is sent, it is received by an SMSC, which must then get it to the appropriate mobile device. + +To do this, the SMSC sends an SMS request to the home location register (HLR) to find the roaming customer. Once the HLR receives the request, it will respond to the SMSC with the subscriber's status: + +- 1) inactive or active; +- 2) where subscriber is roaming. + +If the response is "inactive", then the SMSC will hold on to the message for a period of time. When the subscriber accesses his device, the HLR sends an SMS notification to the SMSC, and the SMSC will attempt delivery. + +The SMSC transfers the message in a short message delivery point to point format to the serving system. The system pages the device, and if it responds, the message gets delivered. + +The SMSC receives verification that the message was received by the end user, then categorizes the message as "sent" and will not attempt to send again. + +SMS falls into the group of the so-called store-and-forward services and is normally being transported in the background class according to [b-ETSI TS 123 107]. As a consequence, parameters like SMS delivery time or SMS response time depend very much on the traffic load of the mobile network and cannot be guaranteed. + +#### **A.1.2 Interactive voice response** + +IVR is a technology that allows a computer to interact with human users through the use of voice and DTMF tone input via a keypad. + +In telecommunications, IVR allows customers to interact with a company's host system via a telephone keypad or by speech recognition, after which they can service their own enquiries by following the IVR dialogue. IVR systems can respond with pre-recorded or dynamically generated audio to further direct users on how to proceed. IVR applications can be used to control almost any function where the interface can be broken down into a series of simple interactions. + +#### **A.1.3 Dual tone multi-frequency signalling** + +The DTMF system uses a set of eight audio frequencies transmitted in pairs to represent 16 signals, represented by the 10 digits, the letters A to D, and the symbols # and \* as described in [b-ITU-T Q.23]. Detailed requirements for DTMF are specified in [b-ETSI ES 201 235-1], [b-ETSI ES 201 235-2], [b-ETSI ES 201 235-3] and [b-ETSI ES 201 235-4]. As the signals are audible tones in the voice frequency range, they can be transmitted like speech signals. Originally used to dial the number of the remote terminal, it became a common method to transmit small amounts of data. + +In packet based networks, there are three common ways of sending DTMF: + +- session initiation protocol (SIP) INFO packets as described in [b-IETF RFC 2976]; +- as specially marked events in the real-time protocol (RTP) stream – as described in [b-IETF RFC 2833]; +- inband as normal audio tones in the RTP stream with no special coding or markers. + +For mobile networks [b-ETSI TS 123 014] describes how DTMF signals are supported. A message-based signalling system is used across the air interface. Inband transmission is not possible. + +That means that in mobile communication, the originating mobile terminal directly creates relevant messages when the keys are pressed by the user during a call. + +#### **A.1.4 Unstructured supplementary service data – both push and pull services** + +USSD is a protocol used by mobile terminals to communicate with the network of the mobile operator. + +USSD messages are up to 182 alphanumeric characters in length. USSD messages create a real-time connection during a USSD session. The connection remains open, allowing a two-way exchange of a sequence of data. This makes USSD more responsive than services that use SMS. + +Messages sent over USSD are not standardized: + +Normally, USSD is used in the format \*nnn# as part of configuring the phone on the network. In order to transfer text messages via USSD to another mobile network, a special USSD gateway is required, which mobile operators do not normally provide. + +USSD is sometimes used in conjunction with SMS. The user sends a request to the network via USSD, and the network replies within the same USSD session with an acknowledgement of receipt. + +Subsequently, one or more mobile terminated SMS messages communicate the status or results of the initial request. In such cases, SMS is used to "push" a reply or updates to the handset when the network is ready to send them. In contrast, USSD is used for command-and-control only. + +USSD is generally associated with real-time or instant messaging services. There is no store-and-forward capability, as is typical of other short-message protocols like SMS. + +USSD is specified in [b-ETSI TS 100 625], [b-ETSI TS 100 549] and in [b-ETSI EN 300 957]. USSD modes are: + +- mobile-initiated: USSD/ PULL or USSD/P2P. + +When the user dials a code from mobile terminal + +- network-initiated: USSD/ PUSH or USSD/A2P. + +When the user receives a push message from the network: + +USSD can be used, e.g., for prepaid call-back service, mobile-money services, location-based content services, menu-based information services and as part of configuring the phone on the network. + +### A.2 Service category 2 (smartphone) + +In addition to service category 1, the underlying techniques listed in Table A.2 can be taken into account. Even basic smart phones (see clause 6.1) will provide services based on these techniques. + +**Table A.2 – Summary of technologies for service category 2** + +| Technique | Main features | Disadvantages | Advantages | +|--------------|----------------------------------------------------------------------------------|-------------------------------------------|-----------------------------------------------------------| +| SMS | Store-and-forward alphanumerical messages | Not real-time | Globally available
Interconnection ok | +| IVR | Interaction with user by artificial or recorded voice, voice recognition or DTMF | Requires good speech quality transmission | Real-time | +| DTMF | Simple keypad operation | Limited character set | Real-time | +| USSD | Alphanumerical messages | Requires USSD Gateways | Real-time | +| WAP | Simple web browser | Limited set of functions | Available on some phones even if they do not support HTTP | +| HTTP | Standard web browser | Unsecure | Internet-like access | +| HTTPS | Safe web browser | Complex | Encrypted, not even subject to traffic shaping | + +#### A.2.1 Wireless application protocol + +The WAP is a technical standard for accessing information over a mobile wireless network. A WAP browser is a web browser for mobile devices such as mobile phones that use the protocol. + +WAPs that use displays and access the Internet run what are called micro browsers – browsers with small file sizes that can accommodate the low memory constraints of hand-held devices and the low-bandwidth constraints of a wireless hand-held network. + +Although WAP supports hypertext markup language (HTML) and extensible markup language (XML), the wireless markup language (WML; an XML application) is specifically devised for small screens and one-hand navigation without a keyboard. WML is scalable from two- line text displays + +up through graphic screens found on items such as smart phones and communicators. WAP also supports WMLScript, which is similar to JavaScript, but makes minimal demands on memory and central processing unit (CPU) power, because it does not contain many of the functions found in other scripting languages that are unnecessary in this context. + +#### **A.2.2 Hypertext transfer protocol** + +The HTTP is an application protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the world wide web. Hypertext is structured text that uses logical links (hyperlinks) between nodes containing text. HTTP is the protocol to exchange or transfer hypertext. + +HTTP functions as a request-response protocol in the client-server computing model. A web browser, for example, may be the client and an application running on a computer hosting a web site may be the server. The client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content or performs other functions on behalf of the client returns a response message to the client. The response contains completion status information about the request and may also contain requested content in its message body. + +#### **A.2.3 Hypertext transfer protocol secure** + +HTTPS (also called HTTP over transport layer security (TLS), HTTP over a secure sockets layer (SSL), and HTTP Secure) is a protocol for secure communication over a computer network that is widely used on the Internet. HTTPS consists of communication over HTTP within a connection encrypted by TLS or its predecessor, SSL. The main motivation for HTTPS is authentication of websites visited and protection of the privacy and integrity of the exchanged data. + +In its popular deployment on the internet, HTTPS provides authentication of the website and associated web server with which the user is communicating, which protects against man-in-the-middle attacks. Additionally, it provides bidirectional encryption of communications between a client and server, which protects against eavesdropping and tampering with or forging the contents of the communication. + +# Appendix I + +## Considerations related to the fitness for DFSs + +(This appendix does not form an integral part of this Recommendation.) + +A successful introduction of DFSs via a mobile network requires fitness of the whole environment used, which is + +- fitness of the mobile network, to provide a minimum level of availability and accessibility; +- fitness of the mobile network to provide the services required for realization of DFSs; +- fitness of mobile devices used, to support the basic services used to realize DFSs; +- fitness of the DFS service itself to provide useable interfaces; +- fitness of users to successfully use DFSs – this may include the necessary skills to operate DFSs on phones as well as basic understanding of properties of DFSs in general, to protect users against exploitation of insufficient knowledge, see [b-FIGI 2019c]; +- fitness of the general society and the governmental institutions for DFSs. + +Figures I.1 to I.5 are decision diagrams meant to facilitate discussion between stakeholders in different regions or countries. Figures I.1 to I.5 do not contain any numbers or specific target values. This is by intention, because target values acceptable for all stakeholders will vary from region to region and from country to country. + +The term "major events" used in Figures I.1 to I.5 refers to [ITU-T E.811], aiming at QoS in mobile networks during major events, as for example, major sports events. + +![Decision diagram for fitness of a mobile network for DFSs](90ddf538ef276510e2b631f7b96654e6_img.jpg) + +The diagram illustrates four categories of network fitness for DFSs, each represented by a colored circle and a corresponding vertical bar: + +- INSUFFICIENT (Red Circle):** Unstable radio connections, Service interruptions, Handover problems. +- CRITICAL (Purple Circle):** Stable radio conditions, Core network congestion, Coverage problems in some areas. +- GOOD (Green Circle):** Radio network operation well, No congestions or dropouts, Fit for DFS (highlighted in a green box). +- MAJOR EVENTS (Blue Circle):** Possible overload of radio network, Possible congestions, DFS may be affected. + +G.1033(19)\_FI.1 + +Decision diagram for fitness of a mobile network for DFSs + +Figure I.1 – Decision diagram for fitness of a mobile network for DFSs + +![Decision diagram for fitness of mobile terminals for DFSs. It consists of four vertical bars: INSUFFICIENT (SMS), CRITICAL (USSD, HTTP), GOOD (HTTPS, Data protection, Fit for DFS), and MAJOR EVENTS (TBD).](c914f51f4427bc672dd0526cfc90ebe9_img.jpg) + +This diagram illustrates the fitness of mobile terminals for DFSs across four categories: + +- INSUFFICIENT:** SMS +- CRITICAL:** USSD, HTTP +- GOOD:** HTTPS, Data protection, Fit for DFS +- MAJOR EVENTS:** TBD + +G.1033(19)\_FI.2 + +Decision diagram for fitness of mobile terminals for DFSs. It consists of four vertical bars: INSUFFICIENT (SMS), CRITICAL (USSD, HTTP), GOOD (HTTPS, Data protection, Fit for DFS), and MAJOR EVENTS (TBD). + +Figure I.2 – Decision diagram for fitness of mobile terminals for DFSs + +![Decision diagram for fitness of mobile network services for DFSs. It consists of four vertical bars: INSUFFICIENT (No proof of concept), CRITICAL (High session drop rate, Large delay fluctuations, Process not under control), GOOD (Stable 24/7/365 provision, Low volatility of KPIs, Fit for DFS), and MAJOR EVENTS (Capable of increase in number of transactions?).](d734a6ea1b381280f043fcf70391b6db_img.jpg) + +This diagram illustrates the fitness of mobile network services for DFSs across four categories: + +- INSUFFICIENT:** No proof of concept +- CRITICAL:** High session drop rate, Large delay fluctuations, Process not under control +- GOOD:** Stable 24/7/365 provision, Low volatility of KPIs, Fit for DFS +- MAJOR EVENTS:** Capable of increase in number of transactions? + +G.1033(19)\_FI.3 + +Decision diagram for fitness of mobile network services for DFSs. It consists of four vertical bars: INSUFFICIENT (No proof of concept), CRITICAL (High session drop rate, Large delay fluctuations, Process not under control), GOOD (Stable 24/7/365 provision, Low volatility of KPIs, Fit for DFS), and MAJOR EVENTS (Capable of increase in number of transactions?). + +Figure I.3 – Decision diagram for fitness of mobile network services for DFSs + +![Decision diagram for fitness of mobile users for DFSs. It consists of four vertical bars: INSUFFICIENT (High illiteracy), CRITICAL (Low technical understanding), GOOD (Ability to access situations correctly w/respect to success/failure, Ability to report deficiencies in services, Fit for DFS), and MAJOR EVENTS (User may be distracted).](844077b3034f0030b404207db0ad76b4_img.jpg) + +This diagram illustrates the fitness of mobile users for DFSs across four categories: + +- INSUFFICIENT:** High illiteracy +- CRITICAL:** Low technical understanding +- GOOD:** Ability to access situations correctly w/respect to success/failure, Ability to report deficiencies in services, Fit for DFS +- MAJOR EVENTS:** User may be distracted + +G.1033(19)\_FI.4 + +Decision diagram for fitness of mobile users for DFSs. It consists of four vertical bars: INSUFFICIENT (High illiteracy), CRITICAL (Low technical understanding), GOOD (Ability to access situations correctly w/respect to success/failure, Ability to report deficiencies in services, Fit for DFS), and MAJOR EVENTS (User may be distracted). + +Figure I.4 – Decision diagram for fitness of mobile users for DFSs + +![Decision diagram for fitness of a society/government for DFSs. The diagram consists of four vertical bars representing different levels of fitness: INSUFFICIENT, CRITICAL, GOOD, and MAJOR EVENTS. The INSUFFICIENT bar shows 'No regulatory framework'. The CRITICAL bar shows 'Lack of effective sanctioning mechanisms', 'Lack of cost transparency', and 'Monopolistic structures'. The GOOD bar shows 'Functioning mechanisms to identity, report and sanction criminal misuse', 'Market mechanisms sanction exploitation or over pricing', and a green box labeled 'Fit for DFS'. The MAJOR EVENTS bar shows 'TBD'.](c5452f95f3b28f1bfe29e84fbc2e1267_img.jpg) + +| INSUFFICIENT | CRITICAL | GOOD | MAJOR EVENTS | +|-------------------------|--------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------|--------------| +| No regulatory framework | Lack of effective sanctioning mechanisms
Lack of cost transparency
Monopolistic structures | Functioning mechanisms to identity, report and sanction criminal misuse
Market mechanisms sanction exploitation or over pricing
Fit for DFS | TBD | + +Decision diagram for fitness of a society/government for DFSs. The diagram consists of four vertical bars representing different levels of fitness: INSUFFICIENT, CRITICAL, GOOD, and MAJOR EVENTS. The INSUFFICIENT bar shows 'No regulatory framework'. The CRITICAL bar shows 'Lack of effective sanctioning mechanisms', 'Lack of cost transparency', and 'Monopolistic structures'. The GOOD bar shows 'Functioning mechanisms to identity, report and sanction criminal misuse', 'Market mechanisms sanction exploitation or over pricing', and a green box labeled 'Fit for DFS'. The MAJOR EVENTS bar shows 'TBD'. + +G.1033(19)\_FI.5 + +**Figure I.5 – Decision diagram for fitness of a society/government for DFSs** + +It is important for any further work in the field of QoS/QoE for DFSs to get access to more detailed information, such as descriptions of the various DFS offers to see on a technical level, which underlying services in the network are used and which are the technical parameters associated with them, e.g., timer values, timeout events, number of interactions involved in a single financial transaction. + +Therefore, it is suggested that telecom regulators collect such information prior to the issue of licences in order to make their own judgement of the quality of the planned DFS offering. + +Such flowchart information should be submitted by regulators to ITU-T SG12, where the experts could start categorizing the different approaches, and provide comments and guidance on such implementations. + +There are even more issues remaining currently open, which will need further discussions: + +- Mobile operators have increasing problems with the huge amount of data traffic in their networks. Therefore, if high speed fixed networks are available, there is a massive trend to use so-called "WiFi offloading", where data traffic is redirected via Wi-Fi accesses to the internet backbone core. The consequences for DFS seem to be quite unexplored, as yet. +- The text displayed in the course of DFS interactions or the accentuation in spoken dialogue systems may be loaded with emotions, which could affect the users' experience of the service (QoE). Emotion detectors could be used to minimize any negative impact from this text and speech material. Requirements for emotion detectors in telecommunications are provided in [ETSI TS 103 296]. +- A serious problem (mostly for regulators) are effects that cannot easily be allocated to one of the stakeholders in the DFS process. A prominent example is so-called early timeouts in DFSs, which anyone outside the DFS provider would interpret as dropped- calls, i.e., blame the network or blame the terminal or blame the user – in reality it turns out just to be a badly designed flow-of-actions: users still reading instructions on their screens before initiating the next step of a transaction are hit by an invisible timer's timeout action. + +Because the field of DFSs and its related QoS and QoE aspects is both of high importance and quite complex, capacity building is essential. + +# Appendix II + +## Is DFS a "popular service"? + +(This appendix does not form an integral part of this Recommendation.) + +## II.1 Relationship between QoS and QoE + +In addition to the term QoS, the term QoE is often used nowadays to stress the purely subjective nature of quality assessments in telecommunications and their focus on the user's perspective of the overall value of the service provided. + +The increased significance of the term QoE is related to the fact that in the past the term QoS was used mostly for only technical concepts focused on networks and network elements. The definition of QoS, however, does include the degree of satisfaction of a user with a service. Thus, non-technical aspects are included, like e.g., the user's environment, expectations, the nature of the content and its importance. However, most service providers used QoS only in relation to the actual user-service interaction to cross-check whether user requirements were met by the service implementation of a provider (as perceived by the user). Therefore, there was a strong focus on the actual network performance and its immediate influence on user perceivable aspects, while additional subjective and not directly related service aspects were omitted. + +QoE is defined in [b-ITU-T P.10] as the degree of delight or annoyance of the user of an application or service. It includes the complete E2E system effects (client, terminal, network, services infrastructure, etc.) and may be influenced by user expectations and context. Hence, QoE is measured subjectively by the end user and may differ from one user to another. However, it is often estimated by a combination of objective measurements and metrics describing subjective elements. + +NOTE – The definition of QoE and, in particular, the dividing line between QoS and QoE is, however, quite fuzzy, and up to today it does not appear that a globally accepted definition exists. For example, [b-ITU-T E.800] does not use the term QoE at all; instead, it uses a four-viewpoint model (similar to the one in [b-ITU-T G.1000]) with terminology, like QoS experienced (QoSE) or QoS perceived (QoSP). + +For working purposes, preferably the use of QoS can be limited to things that can be measured by machines or technical means (including, for example, speech quality metrics, like [b-ITU-T P.863], which already contain some perceptual considerations), and QoE should be used for items further down a "processing chain" where some kind of assessment has been applied. This assessment can be, for instance, some kind of usually nonlinear (clipping) function expressing limits where service quality is either "unacceptable" anyway, or so good that a further improvement will not have any practical consequences. It is important to note that such limits will be strongly dependent on previous experience, i.e., will vary between regions or countries, and will also vary with time as people get accustomed to improvements. Therefore, the issue of "typical values" or "threshold values" is characteristic for the QoE domain. + +Objective measurements deal with quantities that can usually be determined by technical measurements, such as information loss and delay. Subjective elements are components of human perception that may include emotions, linguistic background, attitude, motivation, etc., which determine the overall acceptability of the service by the end user. An important part of subjectivity is expectations that usually are formed by previous experience of users for the same or similar types of service. + +Figure II.1 shows factors contributing to QoE. These factors are organized as those related to QoS and those that can be classified as human components. QoE for voice and video is often measured via carefully controlled subjective tests, where voice or video samples are played to viewers who are asked to rate them on a scale. The ratings assigned to each case are averaged together to yield the mean opinion score (MOS). + +QoS is defined in [b-ITU-T E.800] as the totality of characteristics of a telecommunications service that bear on its ability to satisfy stated and implied needs of the user of the service.. In general, QoS is measured in an objective way. + +In telecommunications, QoS is usually a measure of performance of services delivered by networks. QoS mechanisms include any mechanism that contributes to improvement of the overall performance of the system and hence to improving the end user experience. QoS mechanisms can be implemented at different levels. + +Example – At the network level, QoS mechanisms include traffic management mechanisms, such as buffering and scheduling employed to differentiate between traffic belonging to different applications. Other QoS mechanisms at levels other than transport include loss concealment, application forward error correction (FEC), etc. + +QoS parameters are used to describe the QoS observed. Similar to the QoS mechanisms, QoS parameters can be defined at different layers. Figure II.1 shows the factors that have an influence on QoS and QoE. + +![A hierarchical diagram showing the factors influencing Quality of Experience (QoE). QoE is at the top, branching into 'Objective' and 'Subjective' categories. 'Objective' leads to 'Quality of service', which further branches into 'Service factors', 'Transport factors', and 'Application factors'. 'Subjective' leads to 'Human components', which branches into 'Emotions', 'Service billing', and 'Experience'. A dashed line connects 'Emotions' and 'Service billing'. The diagram is labeled G.1033(19)_FII.1 at the bottom right.](58f4167687de8d7339594e5f6fbe0bc6_img.jpg) + +``` +graph TD; QoE[QoE] -- Objective --> QoS[Quality of service]; QoE -- Subjective --> HC[Human components]; QoS --> SF[Service factors]; QoS --> TF[Transport factors]; QoS --> AF[Application factors]; HC --> E[Emotions]; HC --> SB[Service billing]; HC --> EX[Experience]; E -.-> SB; +``` + +A hierarchical diagram showing the factors influencing Quality of Experience (QoE). QoE is at the top, branching into 'Objective' and 'Subjective' categories. 'Objective' leads to 'Quality of service', which further branches into 'Service factors', 'Transport factors', and 'Application factors'. 'Subjective' leads to 'Human components', which branches into 'Emotions', 'Service billing', and 'Experience'. A dashed line connects 'Emotions' and 'Service billing'. The diagram is labeled G.1033(19)\_FII.1 at the bottom right. + +**Figure II.1 – Factors that have an influence on QoS and QoE** + +In general, there is a correlation between the subjective QoE as measured by the MOS and various objective parameters of QoS. + +Typically, there will be multiple service level performance (QoS) metrics that impact overall QoE. + +The relation between QoE and service performance (QoS) metrics is typically derived empirically. + +Having identified the QoE/QoS relationship, it can be used in two ways: + +- 1) given a QoS measurement, the expected QoE for a user can be predicted; +- 2) given a target QoE, the net required service layer performance can be deduced. + +– These prediction and deduction steps are built on assumptions and approximations. + +Due to the complexity of services and the many factors that have an influence on QoS/QoE, there is no close one-to-one relationship that would allow statements like "If the bandwidth is increased by 200 kbit/s, then the rating by the user will rise by 0.5 points". + +To ensure that the appropriate service quality is delivered, QoE targets should be established for each service and be included early on in system design and engineering processes where they are translated into objective service level performance metrics. + +QoE is an important factor in services that are successful in the marketplace and is a key differentiator with respect to competing service offerings. Subscribers to network services do not care how service quality is achieved. What matters to them is how well a service meets their expectations (e.g., in terms of price, effectiveness, operability, availability, and ease of use). + +### II.2 Services, applications or "popular services" + +Within the formal standardization community, the term "service" was always understood as a functionality for which all aspects are standardized (i.e., standardized service); the concept behind this was that globally all networks would (be able and willing to) offer exactly the same – fully interoperable, harmonized service. + +However, over time the terminology got corrupted in a sense that service today stands for any application. For example, the Internet Engineering Task Force (IETF) refers to their standards which basically describe network functionalities as services. + +Under end user aspects, "service" is used for any application offered in the networks; this makes it very difficult to standardize assessment methods and target values or requirements for related KPIs. + +Therefore, if we speak about services, today, we can distinguish multiple dimensions: + +| | | | | | +|----|---------------------------------|-----|----|--------------------------------| +| a) | applications with global reach | vs. | b) | locally limited applications | +| c) | specifically named applications | vs. | d) | application class denominators | + +Typical examples for each dimension are: + +- a) Netflix or YouTube; +- b) eGovernment application in country xyz; +- c) Netflix or YouTube; +- d) video streaming, IP television (IPTV). + +Since services in all these dimensions are not standardized in their functionality *a priori*, the communities involved in assessing QoS and QoE for them have focused on what are called "popular services". The underlying concept is to provide assessment methods and targets for such services that are used frequently by a huge number of users. + +- Looking first at dimension a) with the examples given above, these are truly "popular services" – however, the underlying technical aspects, such as carrier services, may change from time to time. +- For dimension b), the main obstacle is the limitation itself. It is highly probable that there will not be any international standard to measure the QoS or QoE of exactly one of those specific services. +- Dimension c) requires close cooperation between the stakeholder providing these services and standardization experts. +- Appropriate handling of dimension d) requires the standardization of new E2E mechanisms. Otherwise, existing carrier services will be confronted with more stringent targets for existing services. + +## II.3 Is a DFS a "popular service"? + +*A DFS is popular, yes – but DFS is only a class denominator.* + +NOTE 1 – At the time work on mobile QoS started (about 10 years ago), the experts considered "service" as something that has a direct impact on the customer's perception. Typical examples are telephony or web browsing. A "service" in this view is understood as something connected to an E2E use case. However, many E2E use cases relate to "carrier services", such as some types of packet data functionality having their own QoS metrics (KPIs). + +In this context, a DFS can be considered as a classical example of such a user-related service, which can be realized in several ways, using "carrier services" such as SMS or packet data functionality of networks. + +A DFS is not alone in this "top level service" view. Today's telephony is a prominent example. End users basically do not care if the function they are looking for (being able to orally communicate with another) is realized using legacy GSM or the universal mobile telecommunications system (UMTS), voice over long-term evolution (VoLTE) or some OTT voice over IP (VoIP) technology. Their quality assessment is based on universal metrics such as setup time, call drop rate or speech quality, which are exactly those metrics which are at the core of documents such as [b-ITU-T E.804] or [b-ETSI TS 102 250]. + +The sometimes very detailed KPI definitions in these documents arise due to a "diagnostic" approach, but this is by no means "the golden rule". Future developments will attempt to reveal true "end customer" related key quality indicators (KQIs). + +An additional example for this may be web browsing using HTTPS instead of HTTP. For the user, nothing seems to have changed, so top-level QoS KPIs to assess user perception are the same – however, the networks are treating HTTPS and HTTP traffic in many cases differently, which will lead to a difference in usage of such KPIs for diagnostic purposes. + +If a technical assessment is desired of the expected top-level QoS of a particular DFS offering using a carrier service point of view, knowledge is needed of the technical flow of data and signalization. This information is not normally available from service providers' websites or brochures. + +NOTE 2 – Strictly speaking this is true for most other services offered by network operators. First of all, operators typically do not commit themselves (at least not towards end customers) to strict performance targets; in the case of mobile networks, this is perfectly understandable as the local conditions vary in a wide range (e.g., from rooftop to cellar of a house even in the same geographical spot). Then, with networks going even more towards "content sensitive" behaviour for the sake of resource optimization, the performance cannot safely be predicted from just some general "bit pipe" properties, measured using simple E2E services, such as web browsing. However, a DFS can be – as will be shown later – made subject to objective measurement quite easily. + +Ideally, this must be dealt with when licences are negotiated between regulators and potential DFS service providers. + +NOTE 3 – This is well known and understood for other services, e.g., video streaming: + +When YouTube first became popular, it was based on transmission control protocol (TCP) streaming; with this information KPIs could be defined in standards, QoS could be assessed and QoE could be predicted. Today, for good reasons, the same service by the same entity is rendered as adaptive streaming using HTTPS. Consequently, new standards have been written with new KPIs in order to assess QoS for the "same service". + +Strictly speaking, the KPIs with respect to video quality are still the same; only the methods have changed (or were forced to change). Most importantly, KPI definitions using "low level" technical events as those from the IP level no longer work if encrypted connections such as HTTPS are used. + +If it is possible to identify categories of different DFS offerings, it can be concluded, which of such categories constitute "popular services" (i.e., which are widespread and used by many customers) and a more selective look into KPI definitions could be initiated. + +# Bibliography + +- [b-ITU-T E.800] Recommendation ITU-T E.800 (2008), *Definitions of terms related to quality of service*. +- [b-ITU-T E.804] Recommendation ITU-T E.804 (2014), *Quality of service aspects for popular services in mobile networks*. +- [b-ITU-T G.1000] Recommendation ITU-T G.1000 (2001), *Communications quality of service: A framework and definitions*. +- [b-ITU-T P.10] Recommendation ITU-T P.10/G.100 (11/2017), *Vocabulary for performance, quality of service and quality of experience*. +- [b-ITU-T P.863] Recommendation ITU-T P.863 (2018), *Perceptual objective listening quality prediction*. +- [b-ITU-T Q.23] Recommendation ITU-T Q.23 (1988), *Technical features of push-button telephone sets*. +- [b-ITU-T DFS TR] ITU-T Focus Group Digital Financial Services: Technical Report (2016), *QoS and QoE aspects of digital financial services*. Available [viewed 2019-11-07] at: [https://www.itu.int/en/ITU-T/focusgroups/dfs/Documents/09\\_2016/FGDFSQoSReport.pdf](https://www.itu.int/en/ITU-T/focusgroups/dfs/Documents/09_2016/FGDFSQoSReport.pdf) +- [b-ITU FIGI 2019a] ITU Financial Inclusion Global Initiative, Security, Infrastructure and Trust Working Group (SIT WG) (2019a), *Methodology for measurement of QoS KPIs for DFS*. Available [viewed 2019-11-07] at: [https://www.itu.int/en/ITU-T/extcoop/figisymposium/Documents/ITU\\_SIT\\_WG\\_Methodology%20for%20measurement%20of%20QoS%20KPIs%20for%20DFS.pdf](https://www.itu.int/en/ITU-T/extcoop/figisymposium/Documents/ITU_SIT_WG_Methodology%20for%20measurement%20of%20QoS%20KPIs%20for%20DFS.pdf) +- [b- ITU FIGI 2019b] ITU Financial Inclusion Global Initiative, Security, Infrastructure and Trust Working Group (SIT WG) (2019b), *Report on the DFS pilot measurement campaign conducted in Ghana* Available [viewed 2019-11-07] at: [Pilot measurement of QoS KPIs for DFS in Ghana](#) +- [b-ITU FIGI 2019c] ITU Financial Inclusion Global Initiative, Security, Infrastructure and Trust Working Group (SIT WG) (2019c), *DFS consumer competency framework*. Available [2019-11-15] at: +- [b-ETSI EN 300 957] ETSI EN 300 957 V7.0.1 (2000-01), *Digital cellular telecommunications system (Phase 2+); Unstructured Supplementary Service Data (USSD); Stage 3 (GSM 04.90 version 7.0.1 Release 1998)*. +- [b-ETSI ES 201 235-1] ETSI ES 201 235-1 V1.1.1 (2000-09), *Specification of dual tone multi-frequency (DTMF) transmitters and receivers; Part 1: General*. +- [b-ETSI ES 201 235-2] ETSI ES 201 235-2 V1.2.1 (2002-05), *Access and terminals (AT); Specification of dual-tone multi-frequency (DTMF) transmitters and receivers; Part 2: Transmitters*. +- [b-ETSI ES 201 235-3] ETSI ES 201 235-3 V1.3.1 (2006-03), *Access and terminals (AT); Specification of dual-tone multi-frequency (DTMF) transmitters and receivers; Part 3: Receivers*. +- [b-ETSI ES 201 235-4] ETSI ES 201 235-4 V1.3.1 (2006-03), *Access and terminals (AT); Specification of dual-tone multi-frequency (DTMF) transmitters and* + +*receivers; Part 4: Transmitters and receivers for use in terminal equipment for end-to-end signalling.* + +- [b-ETSI TS 100 549] ETSI TS 100 549 V7.0.0 (1999-08), *Digital cellular telecommunications system (Phase 2+); Unstructured supplementary service data (USSD) – Stage 2 (GSM 03.90 version 7.0.0 release 1998).* +- [b-ETSI TS 100 625] ETSI TS 100 625 V7.0.0 (1999-08), *Digital cellular telecommunications system (Phase 2+); Unstructured supplementary service data (USSD) – Stage 1 (GSM 02.90 version 7.0.0 Release 1998).* +- [b-ETSI TS 102 250] ETSI TS 102 250 series, *Speech and multimedia transmission quality (STQ); QoS aspects for popular services in mobile networks [8 parts].* +- [b-ETSI TS 102 250-2] ETSI TS 102 250-2 V2.4.1 (2015-05), *Speech and multimedia transmission quality (STQ); QoS aspects for popular services in mobile networks; Part 2: Definition of quality of service parameters and their computation.* +- [b-ETSI TS 123 014] ETSI TS 123 014 V15.0.0 (2018-06), *Digital cellular telecommunications system (Phase 2+) (GSM); Universal mobile telecommunications system (UMTS); Support of dual tone multi-frequency (DTMF) signalling (3GPP TS 23.014 version 15.0.0 Release 15).* +- [b-ETSI TS 123 107] ETSI TS 123 107 V15.0.0 (2018-06), *Digital cellular telecommunications system (Phase 2+) (GSM); Universal mobile telecommunications system (UMTS); LTE; Quality of service (QoS) concept and architecture (3GPP TS 23.107 version 15.0.0 Release 15).* +- [b-IETF RFC 2833] IETF RFC 2833 (2000), *RTP payload for DTMF digits, telephony tones and telephony signals.* +- [b-IETF RFC 2976] IETF RFC 2976 (2000), *The SIP INFO method.* + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.1035-202111-I_PDF-E/raw.md b/marked/G/T-REC-G.1035-202111-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..4e73ddc70b918dac798b824565750fb8ded82c07 --- /dev/null +++ b/marked/G/T-REC-G.1035-202111-I_PDF-E/raw.md @@ -0,0 +1,638 @@ + + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.1035** + +(11/2021) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Multimedia Quality of Service and performance – Generic +and user-related aspects + +# --- **Influencing factors on quality of experience for virtual reality services** + +Recommendation ITU-T G.1035 + +## ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## Recommendation ITU-T G.1035 + +# Influencing factors on quality of experience for virtual reality services + +## Summary + +Recommendation ITU-T G.1035 classifies virtual reality (VR) services and identifies the key quality of experience (QoE) factors of VR. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.1035 | 2020-05-29 | 12 | 11.1002/1000/14274 | +| 2.0 | ITU-T G.1035 | 2021-11-29 | 12 | 11.1002/1000/14826 | + +## Keywords + +Cybersickness, presence, quality of experience, QoE, simulator sickness, virtual reality, VR. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at . + +© ITU 2022 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|-------------------------------------------------------|------| +| 1 Scope ..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 1 | +| 3.1 Terms defined elsewhere ..... | 1 | +| 3.2 Terms defined in this Recommendation..... | 2 | +| 4 Abbreviations and acronyms ..... | 2 | +| 5 Conventions ..... | 3 | +| 6 Virtual reality overview ..... | 3 | +| 6.1 Devices ..... | 3 | +| 6.2 Content ..... | 3 | +| 6.3 Platform ..... | 3 | +| 6.4 Services..... | 4 | +| 7 Virtual reality QoE influencing factors ..... | 4 | +| 7.1 Human influencing factors ..... | 5 | +| 7.2 System influencing factors ..... | 7 | +| 7.3 Context influencing factors ..... | 12 | +| Appendix I – Virtual reality services use cases ..... | 14 | +| I.1 Use scenario..... | 14 | +| Appendix II – Tile-based streaming..... | 16 | +| Bibliography..... | 17 | + + + +# Influencing factors on quality of experience for virtual reality services + +# 1 Scope + +This Recommendation categorizes and summarizes the factors affecting the user-perceived experience of a virtual reality (VR) service, with the intention of helping to identify the methodologies for assessing VR quality. VR quality of experience (QoE) assessment methodologies are left for further study. Since VR technologies are still evolving, this Recommendation mainly addresses omnidirectional video services, while leaving others, e.g., point-cloud or volumetric video types, for further study. + +VR is a new type of media which is different from traditional video and audio. It generates realistic images, sounds and other sensations that replicate a real environment and simulate a user's physical presence in this environment by enabling the user to interact with this space and any objects depicted therein using specialized display screens or projectors and other devices. These multisensory experiences, which can include sight, hearing and, less commonly, touch and smell, are well coordinated and synchronized through the user's interaction and feedback. A person using VR equipment is typically able to "look around" the artificial world, move about within it and interact with features or items that are depicted on a screen or in goggles as in the real world. + +In order to understand whether QoE or user-perceived performance of the VR service is good enough or not, benchmarking is critical. Benchmarking aims to measure user-perceived performance or QoE in the VR environment. Compared with traditional video and audio, the multisensory experience in VR imposes a new set of requirements for QoE assessment. The challenge is to characterize VR's real-life immersive video, spatial audio and interactivity. Prior to being able to benchmark the QoE, it is important to address the requirements and basic factors that are relevant for assessing the VR quality for different VR services. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +None. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined elsewhere: + +**3.1.1 frame rate** [b-ITU-T H.262]: The rate at which frames are output from the decoding process. + +**3.1.2 quality of experience (QoE)** [b-ITU-T P.10]: The degree of delight or annoyance of the user of an application or service. + +**3.1.3 QoE influencing factors** [b-ITU-T P.10]: Include the type and characteristics of the application or service, context of use, the user's expectations with respect to the application or service + +and their fulfilment, the user's cultural background, socio-economic issues, psychological profiles, emotional state of the user, and other factors whose number will likely expand with further research. + +## 3.2 Terms defined in this Recommendation + +This Recommendation defines the following terms: + +**3.2.1 cybersickness or simulator sickness:** A physiological condition arising when exposed to a virtual reality environment. + +NOTE – Definition based on combined information in [b-Kennedy] and [b-Stanney]. + +**3.2.2 degree of freedom (DoF):** Represents the ways an object can move within a space, which is a key element in helping create an immersive environment for a user. + +**3.2.3 immersion:** A psychological state characterized by perceiving oneself to be enveloped by, included in and interacting with an environment that provides a continuous stream of stimuli and experiences. + +NOTE – Definition based on [b-Witmer]. + +**3.2.4 motion-to-photon latency:** The time it takes between the user moving their head and this motion being reflected on the screen of the head-mounted display (HMD). + +NOTE – Definition based on [b-Brandenburg]. + +**3.2.5 presence:** The subjective experience of being in one place or environment, when one is physically situated in another place or environment. + +NOTE – Definition based on [b-Witmer]. + +**3.2.6 refresh rate:** The frequency at which a display updates its image, expressed in hertz. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|------|----------------------------------| +| 2D | Two Dimensional | +| 3D | Three Dimensional | +| AR | Augmented Reality | +| DoF | Degree of Freedom | +| FoV | Field of View | +| GPU | Graphic Processing Unit | +| HD | High Definition | +| HMD | Head-Mounted Display | +| HRTF | Head-Related Transfer Function | +| MPEG | Moving Picture Experts Group | +| MR | Mixed Reality | +| PPD | Pixel Per Degree | +| PPI | Pixel Per Inch | +| SSQ | Simulator Sickness Questionnaire | +| UHD | Ultra High Definition | +| VR | Virtual Reality | + +VoD Video on Demand + +VVC Versatile Video Coding + +# 5 Conventions + +Within the scope of this Recommendation, a person interacting with a VR head-mounted display (HMD) is referred to as a user, viewer or player, all with equivalent inference. + +# 6 Virtual reality overview + +Virtual reality (VR) is a technology that uses game engines (e.g., Unity) to create artificial environments that enable people to interact in six degrees of freedom (DoF). VR generates realistic images, sounds and other sensations that emulate a real environment or create a synthetic one. VR services aim to provide users with high levels of immersion and presence wherein users may feel detached from their physical, real-world surroundings. This is different from augmented reality (AR) or mixed reality (MR), which enhance user experiences by adding virtual components such as digital images, graphics or sensations as a new layer of interaction with the real world. + +## 6.1 Devices + +A VR display device is usually a typical head-mounted display (HMD) with two goggle-size miniature screens – one per eye. These displays focus and reshape the picture for each eye and can create a stereoscopic three-dimensional (3D) image by angling the two dimensional (2D) images to mimic how human eyes see the world. + +To achieve an immersive experience, head tracking or eye tracking are used in HMDs to create the correct camera angle and perspective so as to attain a natural viewing experience. In addition, tracking may include capturing of the movements of any other body parts. + +Depending on the VR service and DoF permitted for the users, audio hardware needs to take into account headphone or loudspeaker audio reproduction. The headphones may be standalone or integrated into the HMD, both of which allow open and closed acoustic design. When using standalone headphones, additional hardware such as a soundcard or wireless technology may also be involved. + +## 6.2 Content + +There are two types of content to consider when constructing a virtual environment for the VR experience. + +The first consideration is synthetic, which is completely invented from geometric primitives and simulated physics. This is common in VR games and VR social services. Synthetic representations of individuals, called avatars, enable users to interact and can provide a level of anonymity in some contexts. + +The second consideration is captured using 360° cameras. For example, 360°/omnidirectional images and videos are captured to allow users to explore the scene in $360^\circ \times 180^\circ$ from a given viewpoint in a VR system, which could be seen as an extension of traditional video streaming applications. + +## 6.3 Platform + +When using online VR applications, VR contents are stored in servers, streamed by requests and rendered locally in user's devices. Local rendering requires high-performance terminal devices to provide an acceptable user experience. + +Cloud VR [b-GSMA AR/VR] is a new cloud computing technology, where VR content is stored and rendered in the server. Therefore, video and audio outputs are coded, compressed and transmitted to + +user terminals. Servers in cloud VR are required to be as close as possible to end-users to reduce the influence introduced on QoE by the additional network processing time. + +## 6.4 Services + +VR services can be classified into two types: weak-interaction VR and strong-interaction VR [b-Huawei VR]. + +Weak-interaction VR services mainly comprise but are not limited to 360° video, VR theatre and VR live broadcast. In this kind of VR services, users can explore the scene by turning their head; however, they do not interact with the objects present in the scene. For example, touching the entities in the virtual world is not possible. + +Strong-interaction VR services include VR games, VR home fitness, VR social networking, etc. Users can interact with these virtual environments through interactive entities (e.g., controllers) in addition to HMD head tracking. + +Appendix I provides information for some typical VR services. + +# 7 Virtual reality QoE influencing factors + +QoE influencing factor categories are illustrated in Figure 1. (See also [b-Reiter].) + +![A hierarchical diagram showing 'Virtual reality influencing factors' at the top, branching into three categories: 'Human', 'System', and 'Context'. 'Human' includes Vision and hearing, Simulator sickness, Immersion, Expectations and expertise, Demographic background, and Emotions. 'System' includes Content, Media/coding, Network transmission, and Hardware. 'Context' includes Physical, Temporal, Social, and Task. The label G.1035(20)_F01 is at the bottom right.](54fabc351eda5228d2fa28cd9ba07971_img.jpg) + +``` +graph TD; A[Virtual reality influencing factors] --> B[Human]; A --> C[System]; A --> D[Context]; B --> B1[Vision and hearing]; B --> B2[Simulator sickness]; B --> B3[Immersion]; B --> B4[Expectations and expertise]; B --> B5[Demographic background]; B --> B6[Emotions]; C --> C1[Content]; C --> C2[Media/coding]; C --> C3[Network transmission]; C --> C4[Hardware]; D --> D1[Physical]; D --> D2[Temporal]; D --> D3[Social]; D --> D4[Task]; +``` + +G.1035(20)\_F01 + +A hierarchical diagram showing 'Virtual reality influencing factors' at the top, branching into three categories: 'Human', 'System', and 'Context'. 'Human' includes Vision and hearing, Simulator sickness, Immersion, Expectations and expertise, Demographic background, and Emotions. 'System' includes Content, Media/coding, Network transmission, and Hardware. 'Context' includes Physical, Temporal, Social, and Task. The label G.1035(20)\_F01 is at the bottom right. + +**Figure 1 – Virtual reality QoE influencing factor categories** + +Furthermore, influencing factors can occur on different levels of magnitude (micro vs. macro), behaviour (static vs. dynamic), and patterns of occurrence (rhythmic vs. random), either independently or as usual mixtures of all three levels [b-Reiter]. That is because this is not a binary state; all factors can be static or dynamic, but the time-frequency of changes can determine whether a factor is dynamic or static. + +## 7.1 Human influencing factors + +### 7.1.1 Vision and hearing + +Visual abnormalities such as longsightedness, shortsightedness, astigmatism and chromatic aberration may occur in the human eye. Each eye may also be affected differently. Such vision problems may negatively affect the user experience. When vision problems can be corrected by lenses, having the user wear their normal glasses may be a solution, although this may be uncomfortable for the user. + +Hearing impairments may result in attenuated hearing over the full audible frequency range or at specific frequencies. An impairment may also occur asymmetrically in only the left or the right ear, which has consequences on spatial hearing. Loss of sensitivity at high frequencies is a normal age-related hearing impairment, but different types of impairments are present in populations of all ages. Often, individuals are not aware of having a hearing impairment as they develop over time and the auditory system adapts to the lowered sensitivity. + +It is important to consider that each individual hears differently, and that audio reproduction has to take this into account in order to provide a good experience. Head-related transfer functions (HRTFs) describe the individual filtering process that occurs when sound travels from a point in space to the two ears. HRTFs depend on the shape of the pinna and ear canal, and the size and shape of the head and upper torso. They vary individually and to achieve perfect binaural reproduction the HRTFs should be individually measured and applied in the audio rendering process. In practice, generalized HRTFs are often used, resulting in possible degradation in sound localization. + +### 7.1.2 Simulator sickness + +Cybersickness is also known as simulator sickness, VR sickness or visually induced motion sickness and is triggered only by visual stimuli. This undesirable phenomenon is caused by the sensory conflict arising between the visual and vestibular system. While watching 360° videos in an HMD, a user may experience symptoms of simulator sickness such as fatigue, sweating, vertigo or nausea [b-Kennedy]. The most popular questionnaire for assessing simulator sickness is the simulator sickness questionnaire (SSQ), published in 1993. + +Simulator sickness is an important factor that affects QoE for 360°/VR videos [b-Singla-1]. There are different factors such as resolution, audio, time, field of view (FoV), the orientation of users, HMD, player, type of video sequences, etc., by which simulator sickness scores can be affected. (These and other factors are discussed in clause 7.2.) When considering QoE, the video sequences that are noted to lead to the highest simulator sickness scores also lead to the lowest QoE scores. Inversely, those video sequences that have the lowest simulator sickness scores also have the highest QoE scores. These observations indicate that simulator sickness interacts with QoE when 360° videos are watched in HMDs [b-Singla-1]. + +Apart from technical factors, there are individual factors such as age, gender, postural stability, etc., contextual factors such as duration of task, orientation of users, etc. and co-variate constructs such as QoE, presence and exploration behaviour that can impact the severity of simulator sickness. The symptoms of simulator sickness can be reduced but cannot be eliminated for every user. If everything is performed correctly and the needs of the user are met, then the symptoms of simulator sickness will become motion sickness [b-Kopyt]. + +Simulator sickness can also be caused by vergence-accommodation conflict. This symptom occurs when the brain receives mismatching information between a focusing distance and the distance to the virtual object [b-George]. Vergence-accommodation conflict can cause eye strain, fatigue, focusing problems, etc. + +### 7.1.3 Immersion + +The tendency to experience immersion and the level of expertise in using VR systems vary individually. People who tend to be more immersed in a virtual environment may not notice small impairments in reproduction. How immersion affects VR QoE is for further study. Relevant investigations are continuing in ITU-T. + +### 7.1.4 Expectations and expertise + +The attitude towards VR creates varying contexts for experiencing it. Some people may dislike a VR experience regardless of its technical quality based on their beliefs and fears of using such systems. The level of expertise in using VR systems may affect how capable the users are in using the systems to achieve a certain goal, which in turn affects the QoE. Some users may be awed by the novel experience, while more experienced users can focus on the task at hand. + +The influence of a subject's internal reference, provided by their interactions and experiences in the real world, will also influence the QoE of a VR service. + +### 7.1.5 Demographic background + +Demographic data is a statistical representation of variables such as age and gender, as well as socio-economic information such as employment, education, income, race, marital status and others. When it comes to VR services in general, depending on the demographic background, users could have different experiences and performances. Solutions for VR services in a number of areas (from gaming over telemeeting, e-learning and sports) have been researched in order to determine which user attributes have a considerable influence on the experience. + +Demographic factors such as age is a user factor that influences one's preference for VR technology. When it comes to how likely individuals are to interact with technology in general [b-Franke], younger participants had a higher affinity for technology, including a comparable inclination for VR services [b-Kojic-1]. Also, gender is another influencing factor where significant differences in technological affinity were reported [b-Franke], in particular for VR [b-Kojic-2]. Further on, there is a gender gap reported while exploring presence in VR services. Significant differences were identified on presence subscales (considering the binary gender scale) [b-Felnhofer], where men reported a different feeling presence than women for VR services. + +### 7.1.6 Emotions + +The increasing availability of VR equipment and advances in technology have inspired its use in a variety of research sectors, including human emotional states and responses to VR services. At the level of human emotional states, the effect of moods and emotions on QoE has been researched [b-Felnhofer]; although both have a relatively brief duration, moods typically last longer (varying from hours to days) than emotions (ranging from seconds to minutes) [b-Reiter]. Overall, emotions can have an impact on QoE in general including for VR services in the same way as a stimulus that triggers (among other things) an emotional response in the recipient; secondly, a stimulus may generate an emotional response in the recipient as a result of its meaning [b-Schleicher]. + +Studies have shown that content and interaction possibilities with VR environments can change arousal and valence levels. Further on, for example, the possibility to interact with the virtual environment can impact various quality and emotion related parameter such as involvement and spatial presence [b-Voigt-Antons-2]. Furthermore, when implementing the most immersive presentation method (such as head-mounted display), 360° video stimuli might be used to evoke the intended emotional reactions in participants with a greater sense of presence [b-Voigt-Antons-1]. + +## 7.2 System influencing factors + +### 7.2.1 Content related factors + +VR content is crucial for the user's experience and has additional requirements when compared with traditional multimedia content. In addition to the requirements for good quality of video and audio, VR content also requires stitching, special effects, stereoscopic 3D and composition. To ensure an immersive experience, it is important that the VR content is generated at a good quality and then delivered as perfectly as possible. This clause lists the aspects related to VR content which will influence the quality of a VR service. + +#### 7.2.1.1 Spatial audio + +Spatial audio involves the use of spatial audio reproduction techniques that are loudspeaker- or headphone-based such as multiloudspeaker stereophonic approaches, generalizations such as vector-base amplitude panning, sound-field synthesis (higher-order ambisonics, wave-field-synthesis), headphone-based binaural, or combinations thereof. By using spatial audio, virtual sound sources can be created at any point within the 3D space. Sound reproduction for VR is most often done via headphones, but loudspeaker setups are also possible especially in three DoF and six DoF scenarios. In addition to the direct sound, spatial audio can further include the auditory spatial impression of the room acoustics (e.g., early reflections and reverberation), perceptually plausible acoustic effects of sound sources being occluded by structures in the VR world (e.g., attenuation and diffraction), and sound radiation patterns of individual audio objects. Spatial audio is an important aspect for creating the illusion of immersion for VR services. QoE-related aspects are, in particular, the perceived coloration and spaciousness (including features such as source width, envelopment, locatedness) of the (virtual) sources, as well as additional artefacts due to coding or other types of processing. + +#### 7.2.1.2 Spatial depth (3D) + +It also is possible to playout stereoscopic video content, addressing human binocular vision, which is based on the depth-dependent disparity stemming from the two slightly different views presented to the two eyes. This allows humans to judge distance and have a perception of depth. To avoid crosstalk effects, the left view of the content has to be displayed only to the left eye and the right view of the content has to be displayed only to the right eye (see [b-Woods]). In the system design of most HMD systems, which are commonly used for playing out VR content, both views are already separated from each other. + +Encoding the stereoscopic representation with a low bitrate has to be avoided as it decreases the perceived quality even more than using non-stereoscopic content with the same bitrate. The quality advantage of the 3D over the 2D representation is only slightly visible for higher bitrates. Thus, a relatively high bitrate should be used for encoding to assure that the advantage of stereoscopic over non-stereoscopic omnidirectional video content becomes visible. It has to be mentioned that this is strongly dependent on the general stereoscopic quality of the video content. Simulator sickness scores and how a stereoscopic representation influences the VR QoE are for further study. + +Note that this factor is not mandatory in VR. Many VR services use 2D content while still allowing people to feel immersed due to the rendered omnidirectional scenes. + +#### 7.2.1.3 Spatiotemporal complexity + +Spatial perceptual information indicates the complexity of a video picture. With some high complexity content, the viewer may be distracted, while with less complexity content, the subject may be more focused on the main objects. Temporal perceptual information indicates the amount of changing of the video picture. Different spatial and temporal complexity video sequences require a different amount of bandwidth. For example, sequences with higher spatial and temporal information generally require higher bandwidth. + +Spatiotemporal complexity is a content feature which may affect VR QoE. For example, if the VR content has high temporal values, it may produce a high amount of simulator sickness which may affect QoE [b-Singla-1]. + +### 7.2.2 Media/codec related factors + +#### 7.2.2.1 Compression + +Video/audio codecs are used to compress original scene data from raw format so that they can be saved offline or streamed via a network, saving bandwidth and resources. Various codecs have been developed in the industry and are widely used for traditional media coding and these codecs may be used for VR media. However, some codecs are unsuitable for certain scene representations. + +#### 7.2.2.2 Video + +Traditional video codecs (e.g., [b-ITU-T H.264], [b-ITU-T H.265], VP8, VP9) may also be used for VR content, but may not be suitable for certain spatial representations (e.g., point-clouds). + +These different codec technologies are based on different compression implementations, and each can cause different information loss when the encoder compresses the raw data, and the decoder renders it back for display. This results in different perceived quality of the experience and decoding speed. + +A common shortcoming for traditional video codecs being used in VR is that the compression rate is still too low. This means that the bandwidth consumption is still a big problem for streaming the VR content when dealing with full VR streaming. New video coding technologies in progress such as versatile video coding (VVC) will significantly improve the transport quality for VR content in the industry. + +In order to save bandwidth and network resources for 360°/VR videos, many streaming service providers propose to transmit only pixels in the users' FoV in high resolution, and the remaining pixels in minimal quality resolution. This technique is called viewport-adaptive or tile-based streaming of omnidirectional video. The tile-based adaptive streaming architecture is shown in Figure 2. The two main strategies of tile-based streaming are described in Appendix II. + +![Figure 2: Tile-based adaptive streaming – behaviour dependent. A block diagram showing the flow from a 360-degree video source with a highlighted 'View-port' rectangle, through 'Encoding', 'CDN', 'IP-network', and 'Player' blocks. The Player block connects to a 3D diagram of a human head with three rotational axes labeled: 'roll' (red circular arrow), 'pitch' (green circular arrow), and 'yaw' (blue circular arrow).](c036e2540a94b31357ceb0002f0cacab_img.jpg) + +``` + + graph LR + A[360 Video with View-port] --> B[Encoding] + B --> C[CDN] + C --. IP-network .--> D[Player] + D --> E[User Head: Roll, Pitch, Yaw] + +``` + +G.1035(20)\_F02 + +Figure 2: Tile-based adaptive streaming – behaviour dependent. A block diagram showing the flow from a 360-degree video source with a highlighted 'View-port' rectangle, through 'Encoding', 'CDN', 'IP-network', and 'Player' blocks. The Player block connects to a 3D diagram of a human head with three rotational axes labeled: 'roll' (red circular arrow), 'pitch' (green circular arrow), and 'yaw' (blue circular arrow). + +**Figure 2 – Tile-based adaptive streaming – behaviour dependent** + +#### 7.2.2.3 Audio + +For non-interactive three DoF and six DoF VR scenes, requirements on audio metadata are typically consistent with current 3D audio content. Where a categorical number of static positions can be authored, additional data for user head rotation should be incorporated to render a spatial auditory scene consistent with listener movements. For interactive and six DoF VR services where an infinite number of source and listener positions are available, translating user movements and geometric data of the auditory environment is essential for setting the requirements for an audio codec. Direct sound, early reflections and late reverberation should be accounted for and be coherent with all sound sources and listener(s) movements as they may influence the QoE. + +The production of audio content for VR may also feature various approaches such as channel-based, object-based or ambisonics. These may be recorded via multichannel microphones or single microphones, with both techniques requiring various formatting in order to implement and deliver immersive audio. An audio codec would need to be adaptive in the input data stream of content, as seen in the current moving picture experts group (MPEG) H-series codec for three DoF scenes, along with a consistent input stream of user actions. + +#### **7.2.2.4 Storage and transport** + +In 2016, a new approach was released to encode 360° videos with a pyramid geometry, which saves almost 80% of the bitrate [b-Kuzyakov]. In pyramid projection, the base of the pyramid is always available in the full resolution and the sides of the pyramid decrease gradually in quality until all the sides meet at a point. When a user changes the viewing direction, it is decided which stream should be fetched based on the network condition and the orientation of the user. + +Besides that, other technologies (e.g., tile-based streaming) are also used in VR to reduce bandwidth and resource consumption. MPEG has now developed a standard called omnidirectional media format [b-ISO/IEC 23090-2] which intends to standardize the storage and transmission of VR content, mainly for 360° videos. There are multiple media profiles supported, one of which divides the entire 360° video into independently coded tiles that the HMD has to recompile into the image from the tiles required according to the user's viewing directions. + +#### **7.2.2.5 Bitrate** + +Bitrate is the number of audio or video bits that are conveyed or processed per unit of time. Bitrate serves as a more general indicator of quality. Higher resolution, higher frame rates and lower compression usually lead to an increased bitrate under the same encoding environment. + +#### **7.2.2.6 Resolution** + +Video resolution represents the number of distinct pixels contained in the video content that can be displayed in each dimension. Resolution of a video should be compatible with the resolution of the display device, otherwise the video resolution might have to be reduced or cannot even be displayed. + +Higher resolution for VR is required as compared with 2D video in order to have similar visual quality because pixels are spread in a 360° viewing sphere around the viewer. Depending upon the field of view of the HMD, a viewer sees around 25% of the total pixels. For example, if a 4K video is shown to a user in an HMD, it would appear as if the user were watching a 1K video. In order to provide a 4K experience to the viewers, 16K video should be displayed. + +#### **7.2.2.7 Frame rate** + +Frame rate indicates the frequency at which consecutive images, called frames, are displayed. For improving the QoE, the frame rate of the VR content should be exactly the same as the refresh rate of the HMD's display. Playing back the content in a frame rate not matching the panel's refresh rate leads to artefacts such as frame fluctuation, frame drops and frame manipulation using black frame insertion. These artefacts mostly lead to jerkiness, which leads to a lower QoE [b-Hofmeyer]. + +The frame rate in VR services has higher requirements than normal 2D video services because jerkiness in the motion may lead to simulator sickness in the VR environment. Frame rate is even more demanding for VR gaming applications where scenes are rendered by a graphic processing unit (GPU) instead of those created by video cameras. + +In the area of 360° videos, applying motion interpolation to contents with a lower frame rate than the HMD's display refresh rate is a suitable method for increasing the QoE. This especially applies to videos with a higher amount of motion. (See [b-Hofmeyer] and [b-Fremerey].) + +#### **7.2.2.8 Audio sample rate** + +The sample rate is the number of samples of audio carried per second, measured in hertz (Hz). In VR services, this factor has no difference from the traditional streaming services. + +#### **7.2.2.9 Coding delay** + +As the codec standards only describe the algorithmic decoding procedure and profile features, there are still many options in selecting coding modes and parameters when designing a system. VR related applications typically require low and even extremely low delay. Therefore, how to effectively reduce the coding delay which contributes to the final end to end delay should be considered. Extremely low coding delays will also satisfy the need to synchronize audio and video presentation. + +Perceptual thresholds exist for television (TV) broadcasting (e.g., [b-ITU-T J.248]), but VR brings new challenges due to the immersive experience and sensorimotor coupling in six DoF where additionally synchronizing the rendered content with self-movement is essential. Perceptual thresholds in six DoF scenarios are topics for future study. + +### **7.2.3 Network/transmission related factors** + +Network/transmission related factors only exist in online VR services. + +#### **7.2.3.1 Delay** + +In VR environments, stringent latency requirements are of utmost importance for providing a pleasant immersive VR experience. Delay includes queuing delay, over-the-air delay and buffering delay. Delay is usually the main reason for high motion-to-photon latency leading to simulator sickness (see clause 7.1.2). It is also the cause of presentation quality degradation, e.g., long initial loading delay and stalling. Some VR services may offload computing tasks, such as rendering capability, to remote cloud servers to significantly relieve the computing burden from the user's HMDs, which is at the expense of incurring additional communication delay. + +The influence of resolution, bandwidth and network round-trip delay on QoE aspects of tile-based streaming of 360° videos was studied in [b-Singla-2]. These experimental results showed that lowering delay by up to 50 ms has a minimal effect on QoE ratings. The video quality degrades significantly for higher values (>100 ms) of delay. The effect of network delay on the simulator sickness scores cannot be seen. This may be explained by the fact that the background is always visible in the low resolution and always moves consistently with head motion [b-Singla-2]. + +#### **7.2.3.2 Bandwidth** + +Immersive experience with VR streaming application requires a lot of data. If the required bandwidth is not guaranteed for specific VR applications, the quality of the content will be degraded during network transmission. That is, congestion can cause long delays and packet loss which can then degrade the perceived immersive QoE of the VR system. + +#### **7.2.3.3 Loss** + +The impact of packet loss on the VR experience depends on the method of transmission. In reliable transmission protocols, packet loss incurs packet retransmissions which increase the overall delay. With unreliable transmission, packet loss may result in the loss of parts of frames or entire frames and thus degrade audiovisual quality, which may be presented as phenomena such as video freezing and tiling artefacts. + +### **7.2.4 Hardware related** + +Hardware plays an important role in creating an immersive experience for users. VR hardware comprises HMDs, headphones, haptic feedback devices, input controllers and tracking systems with various possibilities to bring real-world objects into the VR domain. + +#### **7.2.4.1 Head-mounted display** + +Unlike traditional terminal devices, HMD wearing comfort may also greatly impact the final VR QoE. To improve this, it is important to consider device weight, size, heat dissipation, resolution, refresh rate, etc. + +#### **7.2.4.2 Headphones** + +The frequency response of headphones, when used, is a factor that affects QoE. Neutral headphones or headphones whose frequency response have been compensated may be able to better convey the spatial audio experience of the listener. Additionally, the ability to block outside noise may be of importance for VR, with closed headphones or in-ear headphones being best suited for this. However, the use of such headphones that entirely block outside noise may cause the user to feel disoriented in their real environment and may be a safety hazard. + +#### **7.2.4.3 Decoder performance** + +The decoder capability has an impact on the overall resolution of the video to be transmitted and decoded in the display device, whether high definition (HD) or ultra high definition (UHD), and thus decides the final resolution of the video that could be displayed to the user. In addition, codec support, e.g., [b-ITU-T H.264] or [b-ITU-T H.265], is also important since different codecs have different decoding performances. + +The codecs supported by the decoder should be compatible with the encoder; otherwise, the content may not be displayed correctly. + +The number of decoders determines the number of streams the device is capable of decoding, e.g., if streams are separately encoded when tiled streaming is applied. + +Compared with those implemented in software, decoders implemented in hardware have much faster performance when decoding the same content, which contribute less delay to VR media processing and lead to a better QoE. + +Some decoders may also have some error correction mechanisms that are capable of fixing errors that may occur during transport or encoding. This can also increase the QoE of the final VR experience. + +#### **7.2.4.4 Head tracking** + +To enable interaction between users and the environment, it is important to obtain the positions and motion information of users. This is usually done, for example, by the inertial measurement unit implemented inside the HMD. Typical devices use combinations of accelerometers, gyroscopes and sometimes magnetometers to track objects' motions. + +There are two tracking technologies that are used thus far: outside-in and inside-out. Outside-in tracking indicates that the headset and accessories rely on some external devices, e.g., a lighthouse sensor or computer display. It has more accuracy and better latency than an inside-out unit but is limited by the environment. Inside-out tracking does not rely on external devices. It uses the HMD sensor to determine how the position is changing in relation to the external environment. + +Low head-tracking latency and back tracking accuracy are certainly important attributes to provide a smooth change of view for the user, while long head-tracking latency induces discomfort and loss of immersive experience. + +#### **7.2.4.5 Field of view** + +FoV is the extent of the observable environment at any given time. With a wider FoV, a user is more likely to feel at-the-scene in the experience. FoV is the solid angle that is visible by a human through the HMD lenses. When it comes to VR FoV, the limiting factor is the lenses, not the pupils. To get a better FoV, the user can either move closer to the lenses, as is the case with VR HMD lenses, or increase the size of the lenses [b-VR Lens Lab]. + +While a wide FoV can increase immersion, it can also more easily cause simulator sickness to certain individuals. This is mainly because some people are sensitive to the flickers or movements of images, and also because the large visual input brought from large FoV may cause conflicts with the vestibular and proprioceptive systems. + +Therefore, FoV is an important parameter that helps evaluate to what extent a VR device could create an immersive experience. + +#### **7.2.4.6 Display resolution** + +Display resolution is a basic attribute of the screen that indicates the pixels per inch that a screen supports. An appropriate screen resolution, relative to the resolution of viewpoint shown in the HMD, would provide the best and most comfortable experience. + +Pixel per degree (PPD) is a core technology specification that is better suited for measuring the pixel density of a VR near-eye display rather than the more traditional pixel per inch (PPI) value. Typically, the higher the PPD, the better of the image quality will be. A lower PPD may result in the screen-door effect. + +#### **7.2.4.7 Refresh rate** + +The refresh rate is the number of times per second that a display grabs a new image from the GPU. A lower refresh rate can contribute to increased processing latency and lead to VR sickness, i.e., viewing glitches on the screen. + +## **7.3 Context influencing factors** + +Context influencing factors are related to the setting or situational property which influences a user's environment in terms of direct influences on the signals presented to the user (audio, video, etc.), the goals connected to a certain system usage and the impact on the user's expectations. + +### **7.3.1 Physical context** + +Physical context factors are related to the environment where a user is experiencing the VR services. Background noises may affect the user's experience. In addition, the experience of the user may differ depending on whether the HMD device is wireless or connected to a stationary processing device, e.g., a PC, which could restrict movement and the possibilities to explore a VR scene. Room lighting may not affect users' experience as much when using HMDs as compared with traditional video environments since the devices are close to their eyes. The ambient temperature of the room in which the user is engaged with the VR service affects the QoE. Normally, the room temperature is set to a typical room temperature to which the user is accustomed, so that they will feel comfortable enough not to get distracted. However, in some cases, the room temperature can be modulated to approximate the virtual world in order to achieve the best immersive experience. For example, if a user is immersed in a VR skiing scene, they may have a better sense of 'being there' when the room temperature is cold enough to make them feel as if they are in the real world, as simulated in the VR scene. + +The amount of sunlight entering the environment can also affect VR QoE. Only a low amount or ideally no direct sunlight should enter the environment. The infrared light could influence the performance of the HMD's tracking system, which could lead to picture outages and other errors. + +Furthermore, the respective safety features of the provided HMD system (such as virtual walls or a pass-through mode using cameras) should be activated to avoid any collisions of the VR user with their physical environment. Ideally, a second person who is not participating in the VR services should pay attention to the physical actions of the user consuming the VR service. + +### **7.3.2 Temporal context** + +Temporal context factors include the frequency and duration of use. A VR device may not be able to support long usage periods. Over time, simulator sickness symptoms such as dizziness, loss of spatial + +awareness, nausea and eye soreness typically become worse as the duration of use increases. These effects will greatly reduce the QoE. + +### **7.3.3 Social context** + +Social context factors include considerations such as VR content popularity and how VR services are consumed (i.e., alone or in a group). A user may be affected by the interaction with a group of other people, e.g., their family, friends or even strangers. For example, co-located co-viewing or co-playing may increase a user's overall satisfaction with a program. This may also hold true for VR services, especially for social VR, in which people use a virtual reality platform to form synthetic societies which contain avatars connected to real people to simulate the physical world. To what extent this factor affects the overall QoE of VR services requires further investigation. + +### **7.3.4 Task context** + +VR experience depends on the goals of the user of the VR service. These factors are called task context factors. For example, if the task is formal, the participants may pay specific attention to some aspects of perceived influence, while they may ignore such experience when doing a relatively casual task. Additionally, the QoE for streaming-type VR, e.g., 360° VR, would be quite different from gaming VR or social VR. For the former, users may have less tolerance towards video impairments. For the latter, users may have less tolerance towards bad interaction experience. + +# Appendix I + +## Virtual reality services use cases + +(This appendix does not form an integral part of this Recommendation.) + +Generally, VR applications can be divided into two types, online and offline: + +- Online VR: VR applications of this type work either partially or primarily through the Internet or another computer network. In this case, VR content is streamed from a server at the time when the user is using it. Obviously, any network delay occurring in this type of VR application may affect the experience of users. However, it can save the local storage of VR terminal devices and expand the range of content that the user can experience. +- Offline VR: VR applications of this type work offline. To do this, users need to download the VR content completely to their devices in advance. While running these applications there are usually no network delay issues and no requirement for network bandwidth. However, the content that the user can experience is limited by the capacity of a local storage device. Offline VR services are not in the study scope of this Recommendation. + +## I.1 Use scenario + +There are many different types of VR services. Five types are listed in this clause. + +### I.1.1 Live + +Live VR is broadcast in real time, as events happen, in the present. The difference between the traditional live program and live VR is that live VR is panoramic and interactive. Live VR can provide an immersive experience of attending the live event at the event venue. The live 360° VR described in [b-ITU-T H.430.3] is a service of this type, which constructs 360° panoramic view in real time via multiple cameras feeds from the site. Users can observe the live event with proper VR HMDs that constantly process and stitch multiple images to project the real world. + +Live VR services require extremely stringent delay so that users can smoothly change the viewpoints when watching it. Live VR services also require UHD resolutions to make users feel as if they are in the real venue. The bandwidth consumption issue is very challenging when a massive number of users consume the live VR service at the same time. Interaction is also an important issue, although in 360° VR, only a few actions can be taken, for example, turning your head around. + +### I.1.2 Video on demand + +Video on demand (VoD) VR services allow users to select and experience the content at any preferable time of their choice rather than a specific broadcast time. Live and VoD VR share the same experience. The only difference is that the content of VoD VR is prepared in advance rather than in real time. The typical usage could be that some applications offered by some major over the top (OTT) providers allow users to watch the entire environment in every scene. + +VoD VR services have the same requirements as live VR for delay issues and video resolutions. The bandwidth consumption is relatively smaller than live VR as viewers can consume the same content at different times. + +Many VR applications in different industries can be seen as VoD VR services. For example, some applications present a user with a cinematic experience with HMD at home and some applications use VR for education, but they are all basically VoD VR services. + +### I.1.3 Gaming + +VR gaming services allow a user to experience being in a 3D virtual entertainment environment through an avatar and interact with the environment during the game. VR gaming services may + +require more devices other than an HMD. One example is a data glove with small sensors that can capture the movements made by the user, which are then interpreted by computers and trigger a variety of responses within that space. + +VR game services require extremely sensitive interaction to reach the best experience. Also, the immersive experience of "being there" where "there" is not equivalent to the position of one's own body but the place the VR content suggests is what a VR game seeks. Other aspects of gaming discussed in [b-ITU-T G.1032] should also be considered. + +### **I.1.4 Social** + +VR social is a service that allows users of the VR platform to form synthetic societies which contain avatars connected to real people to simulate the physical world. A typical example would be the Facebook of VR which provides new social VR features for Oculus Rift. Users can create a custom avatar based on photos from their profile and spend time with other people in a virtual space. + +Like a VR game, VR social also requires extremely sensitive interaction so that users feel as if they are in a real world. Non-synchronized movement of these synthetic avatars with actual human motion will result in a very bad experience for users of the services. + +### **I.1.5 Shopping** + +In addition to the VR services listed in this clause, there are other applications which may be promising in the future when using VR devices. For example, VR shopping could allow users to purchase items through a VR headset by virtually transporting themselves to international retail outlets, enabling them to experience the entire shopping experience from finding products to payment. VR shopping is similar to VR VoD, which records the content in advance, but requires more interaction and less data consumption than VoD streaming VR. + +# Appendix II + +## Tile-based streaming + +(This appendix does not form an integral part of this Recommendation.) + +In tile-based streaming, only the field of view is transmitted in the highest quality and rest of the video is transmitted in lower quality. Based on the client, this can be divided mainly into two categories: + +- 1) Full delivery basic: In this method, the base layer is always available in the low resolution and high-resolution tiles are only available for the current field of view/viewport. When a user changes the viewing direction, the player software finds which of the tiles are in current viewport and fetch those tiles from the network [b-Brandenburg]. +- 2) Full delivery advanced: In this method, the tiles that belongs to the user's viewport are sent in higher quality. In addition, the user head motion is continuously predicted to find where the user's viewport will be in future. These corresponding tiles are requested in a higher quality at the time when it is expected that the user will move into a specific direction [b-Mario]. + +# Bibliography + +- [b-ITU-T G.1032] Recommendation ITU-T G.1032 (2017), *Influence factors on gaming quality of experience*. +- [b-ITU-T H.262] Recommendation ITU-T H.262 (2012), *Information technology – Generic coding of moving pictures and associated audio information: Video*. +- [b-ITU-T H.264] Recommendation ITU-T H.264 (2019), *Advanced video coding for generic audiovisual services*. +- [b-ITU-T H.265] Recommendation ITU-T H.265 (2021), *High efficiency video coding*. +- [b-ITU-T H.430.3] Recommendation ITU-T H.430.3 (2018), *Service scenario of immersive live experience (ILE)*. +- [b-ITU-T J.248] Recommendation ITU-T J.248 (2008), *Requirements for operational monitoring of video-to-audio delay in the distribution of television programs*. +- [b-ITU-T P.10] Recommendation ITU-T P.10/G.100 (2017), *Vocabulary for performance, quality of service and quality of experience*. +- [b-ISO/IEC 23090-2] ISO/IEC 23090-2 (2019), *Information technology – Coded representation of immersive media – Part 2: Omnidirectional media format*. +- [b-Brandenburg] R. van Brandenburg, R. Koenen, and D. Szytkman (2017). *CDN optimization for VR streaming*. +<> +- [b-Felnhofer] Felnhofer, A., et al. (2012), *Is virtual reality made for men only? Exploring gender differences in the sense of presence*. Proceedings of the International Society on Presence Research, pp. 103–112. +- [b-Franke] Franke, T., Attig, C., and Wessel, D. (2019), *A personal resource for technology interaction: development and validation of the affinity for technology interaction (ATI) scale*. International Journal of Human–Computer Interaction Vol. 35, No. 6, 456–467. +<> +- [b-Fremerey] Fremerey, S., Hofmeyer, F., et al. (2019). *Impact of Various Motion Interpolation Algorithms on 360° Video QoE*. 11th International Conference on Quality of Multimedia Experience (QoMEX 2019), IEEE Signal Processing Society. +- [b-George] Koulieris, G., Bui, B., et al. (2017). *Accommodation and comfort in head-mounted displays*. ACM Transactions on Graphics, Vol. 36, No. 4, Article 87, July. +<> +- [b-GSMA AR/VR] GSMA (2019). *Cloud AR/VR Streaming: Accelerate mass adoption and improve quality of experience of AR/VR using 5G and edge cloud*. GSMA Mobile World Congress, booklet. +<> +- [b-Hofmeyer] Hofmeyer, F., Fremerey, S., et al. (2019). *Impacts of internal HMD playback processing on subjective quality perception*. Society for Imaging Science and Technology, International Symposium on Electronic Imaging 2019, pp. 219-1-291-7. +<> + +- [b-Huawei VR] iLab (2019). *Cloud VR – Service Quality Monitoring White Paper*. Huawei iLab. +<[https://www.huawei.com/minisite/static/Cloud\\_VR\\_Service\\_QM\\_WhitePaper.pdf](https://www.huawei.com/minisite/static/Cloud_VR_Service_QM_WhitePaper.pdf)> +- [b-Kennedy] Kennedy, R. S., Lane, N. E., et al. (1993). *Simulator sickness questionnaire: An enhanced method of quantifying simulator sickness*. The International Journal of Aviation Psychology, Vol. 3, No. 3, pp. 203–220. +<[https://www.tandfonline.com/doi/abs/10.1207/s15327108ijap0303\\_3](https://www.tandfonline.com/doi/abs/10.1207/s15327108ijap0303_3)> +- [b-Kojic-1] Kojic, Tanja, et al (2010), *Influence of UI complexity and positioning on user experience during VR exergames*. Eleventh International Conference on Quality of Multimedia Experience (QoMEX). IEEE. +<> +- [b-Kojic-2] Kojić, Tanja, et al (2020), *Exploring visualisations for financial statements in virtual reality*. IEEE International Conference on Artificial Intelligence and Virtual Reality (AIVR). IEEE. +<> +- [b-Kopyt] Koyt, A., Narkiewicz, J. (2013). *Technical factors influencing simulator sickness*. Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika Vol. 85 [288], No. 4 (2013), pp. 455–467. +- [b-Kuzyakov] Kuzyakov, E., Pio, D. (2016). *Next-generation video encoding techniques for 360 video and VR*. Blogpost, January. +<> +- [b-Mario] Graf, M., Timmerer, C., Mueller, C. (2017). *Towards bandwidth efficient adaptive streaming of omnidirectional video over http: Design, implementation, and evaluation*. Proceedings of the 8th ACM on Multimedia Systems Conference. pp. 261–271. +<> +- [b-Reiter] Reiter, U., et al. (2014). *Factors Influencing Quality of Experience*. Quality of Experience. T-Labs Series in Telecommunication Services. Springer, Cham, Switzerland. pp. 55–72. +<[https://doi.org/10.1007/978-3-319-02681-7\\_4](https://doi.org/10.1007/978-3-319-02681-7_4)> +- [b-Schleicher] Schleicher, R., and Antons, J.-N. (2014) *Evoking emotions and evaluating emotional impact*. Quality of Experience. Springer, Cham, Switzerland. 121–132. +<[https://doi.org/10.1007/978-3-319-02681-7\\_9](https://doi.org/10.1007/978-3-319-02681-7_9)> +- [b-Singla-1] Singla, A., Fremerey, S., et al. (2017). *Measuring and comparing QoE and simulator sickness of omnidirectional videos in different head mounted displays*. 9th International Conference on Quality of Multimedia Experience (QoMEX 2017). pp. 1–6. +<> +- [b-Singla-2] Singla, A., Göring, S., et al. (2019). *Subjective quality evaluation of tile-based streaming for omnidirectional videos*. Proceedings of the 10th ACM Multimedia Systems Conference (MMSys '19). Association for Computing Machinery, New York, NY, USA. pp. 232–242. +<> +- [b-Stanney] Stanney, K. M., Kennedy, R. S., Drexler, J. M. (1997). *Cybersickness is Not Simulator Sickness*. Proceedings of the Human Factors and Ergonomics Society Annual Meeting. Vol. 41, No. 2. pp. 1138–1142. + +- [b-Voigt-Antons-1] Voigt-Antons, Jan-Niklas, et al. (2020), *Comparing emotional states induced by 360° videos via head-mounted display and computer screen*. Twelfth International Conference on Quality of Multimedia Experience (QoMEX). IEEE. +<> +- [b-Voigt-Antons-2] Voigt-Antons, Jan-Niklas, et al (2021), *Don't Worry be Happy - Using virtual environments to induce emotional states measured by subjective scales and heart rate parameters*. IEEE Virtual Reality and 3D User Interfaces (VR). IEEE. +<> +- [b-VR Lens Lab] VR Lens Lab (2016). *Field of View for Virtual Reality Headsets Explained*. Website. +<> +- [b-Witmer] Witmer, B. G., Singer, M. J. (1998). *Measuring Presence in Virtual Environments: A Presence Questionnaire*. +- [b-Woods] Woods, A. (2010). *Understanding crosstalk in stereoscopic displays*. Keynote Presentation at the Three-Dimensional Systems and Applications Conference, Tokyo, Japan. + + + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and 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CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.1070 + +# Opinion model for video-telephony applications + +## Summary + +Recommendation ITU-T G.1070 proposes an algorithm that estimates videophone quality for quality of experience (QoE)/quality of service (QoS) planners. This model can be used by QoE/QoS planners to help ensure that users will be satisfied with end-to-end service quality. The model provides estimates of multimedia quality that take interactivity into account and it allows planners to avoid under-engineering. + +The application of this Recommendation is limited to QoE/QoS planning. Other applications such as quality benchmarking and monitoring are outside the scope of this Recommendation. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.1070 | 2007-04-22 | 12 | 11.1002/1000/9050 | +| 1.1 | ITU-T G.1070 (2007) Amd. 1 | 2009-11-12 | 12 | 11.1002/1000/9187 | +| 2.0 | ITU-T G.1070 | 2012-07-14 | 12 | 11.1002/1000/11683 | +| 3.0 | ITU-T G.1070 | 2018-06-13 | 12 | 11.1002/1000/13622 | + +## Keywords + +MOS, multimedia, opinion model, QoE, QoS, quality planning, subjective quality, video telephony. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2018 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +# Table of Contents + +| | | Page | +|---------|-----------------------------------------------------------------------------------------------------------------------------------------------|------| +| 1 | Scope..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions ..... | 2 | +| 3.1 | Terms defined elsewhere ..... | 2 | +| 3.2 | Terms defined in this Recommendation..... | 2 | +| 4 | Abbreviations and acronyms ..... | 4 | +| 5 | Conventions ..... | 5 | +| 6 | Application ..... | 5 | +| 7 | Framework..... | 5 | +| 8 | Model assumptions ..... | 8 | +| 8.1 | Speech-related assumptions..... | 8 | +| 8.2 | Video-related assumptions ..... | 8 | +| 8.3 | Task-related assumptions ..... | 9 | +| 9 | Model inputs ..... | 9 | +| 9.1 | Speech quality parameters ..... | 9 | +| 9.2 | Video quality parameters..... | 10 | +| 10 | Model outputs ..... | 11 | +| 11 | Model description ..... | 11 | +| 11.1 | Speech quality estimation function for narrowband speech..... | 11 | +| 11.2 | Speech quality estimation function for wideband speech ..... | 12 | +| 11.3 | Video quality estimation function ..... | 13 | +| 11.4 | Multimedia quality integration function..... | 14 | +| 12 | Accuracy of model..... | 14 | +| Annex A | – Methodology for deriving the coefficients in the video quality estimation function with respect to coding and packet-loss degradation ..... | 17 | +| A.1 | Methodology for deriving coefficients $v_1, v_2, \dots$ , and $v_7$ ..... | 17 | +| A.2 | Methodology for deriving coefficients $v_8, v_9, \dots$ , and $v_{12}$ ..... | 18 | +| Annex B | – Coefficients in the video quality estimation function with respect to coding and packet-loss degradation..... | 20 | +| B.1 | Coefficients for small and medium screen ..... | 20 | +| B.2 | Coefficients for small screen (with screen size of 6 inches) ..... | 21 | +| B.3 | Coefficients for large screen (with screen size of 65 inches)..... | 21 | +| Annex C | – Coefficients in the multimedia quality integration function..... | 23 | +| | Bibliography..... | 24 | + + + +# Recommendation ITU-T G.1070 + +# Opinion model for video-telephony applications + +# 1 Scope + +This Recommendation describes a computational model for point-to-point interactive videophone applications over IP networks that is useful as a quality of experience (QoE)/ quality of service (QoS) planning tool for assessing the combined effects of variations in several video and speech parameters that affect the QoE. This model can be used by QoE/QoS planners to help ensure that users will be satisfied with end-to-end service quality. Actually, they want to avoid under-engineering. Network, application and terminal quality parameters of high importance to QoE/QoS planners are incorporated into this model. + +The model provided in this Recommendation needs to be a flexible tool capable of providing feedback on individual qualities as well as overall quality. + +This Recommendation is very different from [ITU-T J.148] in terms of input parameters. In this Recommendation, multimedia quality is calculated by using network, application and terminal equipment parameters, whereas in [ITU-T J.148], the calculation is done by using speech and video signals. + +This Recommendation assumes videophone applications using dedicated videophone terminals, desktop PCs, laptop PCs, personal digital assistants (PDAs) and mobile phones. The speech bandwidth is limited to the telephone band (300-3400 Hz). + +The application of this Recommendation is limited to QoE/QoS planning. Other applications such as quality benchmarking and monitoring are outside the scope of this Recommendation. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.107] Recommendation ITU-T G.107 (2015), *The E-model: a computational model for use in transmission planning*. +- [ITU-T G.107.1] Recommendation ITU-T G.107.1 (2015), *Wideband E-model*. +- [ITU-T G.113] Recommendation ITU-T G.113 (2007), *Transmission impairments due to speech processing*. +- [ITU-T G.122] Recommendation ITU-T G.122 (1993), *Influence of national systems on stability and talker echo in international connections*. +- [ITU-T G.711] Recommendation ITU-T G.711 (1988), *Pulse code modulation (PCM) of voice frequencies*. +- [ITU-T J.144] Recommendation ITU-T J.144 (2004), *Objective perceptual video quality measurement techniques for digital cable television in the presence of a full reference*. + +- [ITU-T J.148] Recommendation ITU-T J.148 (2003), *Requirements for an objective perceptual multimedia quality model.* +- [ITU-T P.79] Recommendation ITU-T P.79 (2007), *Calculation of loudness ratings.* +- [ITU-T P.561] Recommendation ITU-T P.561 (2002), *In-service non-intrusive measurement device – Voice service measurements.* +- [ITU-T P.562] Recommendation ITU-T P.562 (2004), *Analysis and interpretation of INMD voice-service measurements.* +- [ITU-T P.563] Recommendation ITU-T P.563 (2004), *Single-ended method for objective speech quality assessment in narrow-band telephony applications.* +- [ITU-T P.564] Recommendation ITU-T P.564 (2007), *Conformance testing for voice over IP transmission quality assessment models.* +- [ITU-T P.800] Recommendation ITU-T P.800 (1996), *Methods for subjective determination of transmission quality.* +- [ITU-T P.833] Recommendation ITU-T P.833 (2001), *Methodology for derivation of equipment impairment factors from subjective listening-only tests.* +- [ITU-T P.834] Recommendation ITU-T P.834 (2002), *Methodology for the derivation of equipment impairment factors from instrumental models.* +- [ITU-T P.862] Recommendation ITU-T P.862 (2001), *Perceptual evaluation of speech quality (PESQ): An objective method for end-to-end speech quality assessment of narrow-band telephone networks and speech codecs.* +- [ITU-T P.862.1] Recommendation ITU-T P.862.1 (2003), *Mapping function for transforming P.862 raw result scores to MOS-LQO.* +- [ITU-T P.862.2] Recommendation ITU-T P.862.2 (2007), *Wideband extension to Recommendation P.862 for the assessment of wideband telephone networks and speech codecs.* +- [ITU-T P.910] Recommendation ITU-T P.910 (2008), *Subjective video quality assessment methods for multimedia applications.* +- [ITU-T P.911] Recommendation ITU-T P.911 (1998), *Subjective audiovisual quality assessment methods for multimedia applications.* +- [ITU-T P.920] Recommendation ITU-T P.920 (2000), *Interactive test methods for audiovisual communications.* +- [ITU-R BS.1387-1] Recommendation ITU-R BS.1387-1 (2001), *Method for objective measurements of perceived audio quality.* + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +None. + +## 3.2 Terms defined in this Recommendation + +This Recommendation defines the following terms shown in Table 1: + +**Table 1 – List of definitions** + +| Name | Description | Unit | +|-----------------|---------------------------------------------------------------------------------------------------------------------------------|--------| +| $AD$ | Absolute audio-visual delay | – | +| $b_n$ | Video bit rate ( $n = 1, 2, \dots, N$ ) | kbit/s | +| $Bpl_s$ | Speech packet-loss robustness | – | +| $Br_V$ | Video bit rate | kbit/s | +| $D_{bnfm}$ | Degree of video quality robustness against packet loss ( $n = 1, 2, \dots, N$ , $m = 1, 2, \dots, M$ ) | – | +| $D_{FrV}$ | Degree of video quality robustness due to frame rate reduction | – | +| $D_n$ | Degree of video quality robustness due to frame rate reduction ( $n = 1, 2, \dots, N$ ) | – | +| $D_{PplV}$ | Degree of video quality robustness against packet loss | – | +| $f_m$ | Frame rate ( $m = 1, 2, \dots, M$ ) | fps | +| $Fr_V$ | Video frame rate | fps | +| $I_{coding}$ | Objective measurement of basic video quality accounting for coding distortion | – | +| $I_{dd}$ | Degradation caused by pure delay in [ITU-T G.107] | – | +| $I_{dd, WB}$ | Degradation caused by pure delay in [ITU-T G.107.1] | – | +| $I_{dte}$ | Degradation caused by talker echo in a narrowband context | – | +| $I_{dte, WB}$ | Degradation caused by talker echo in a wideband context | – | +| $I_{e-eff}$ | Degradation caused by speech coding and packet loss in a narrowband context | – | +| $I_{e-eff, WB}$ | Degradation caused by speech coding and packet loss in a wideband context | – | +| $I_{es}$ | Speech coding distortion in a narrowband context | – | +| $I_{es, WB}$ | Speech coding distortion in a wideband context | – | +| $I_n$ | Objective measurement of maximum video quality at each bit rate ( $n = 1, 2, \dots, N$ ) | – | +| $I_{ofr}$ | Objective measurement of maximum video quality at each bit rate | – | +| $MM_q$ | Objective measurement of multimedia quality accounting for the influence of speech and video quality and speech and video delay | – | +| $MM_{sv}$ | Audio-visual quality | – | +| $MM_T$ | Audio-visual delay impairment factor | – | +| $MS$ | Audio-visual media synchronization | – | +| $Ofr$ | Optimal frame rate that maximizes video quality at each bit rate | – | +| $O_n$ | Optimal frame rate ( $n = 1, 2, \dots, N$ ) | – | +| $Ppl_s$ | Speech packet-loss rate | % | +| $Ppl_V$ | Video packet-loss rate | % | +| $Q$ | Speech quality index | – | +| $R$ | Transmission rating factor | – | +| $S_q$ | Objective measurement of speech quality | – | + +**Table 1 – List of definitions** + +| Name | Description | Unit | +|--------------------|-----------------------------------------------------------------------------------|------| +| $S_q(V_q)$ | Objective measurement of speech quality accounting for influence of video quality | – | +| $TELR$ | Talker echo loudness rating in a narrowband context | dB | +| $TELR, WB$ | Talker echo loudness rating in a wideband context | dB | +| $T_s$ | Speech delay | ms | +| $T_v$ | Video delay | ms | +| $V_q$ | Objective measurement of video quality | – | +| $V_q(S_q)$ | Objective measurement of video quality accounting for influence of speech quality | – | +| $V_{qs}$ | Subjective video quality | | +| $V_{qs}(b_n, f_m)$ | Subjective video quality under conditions of $b_n$ and $f_m$ | – | + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|-------|-------------------------------------------------| +| ACR | Absolute Category Rating | +| AEC | Acoustic Echo Canceller | +| BP | Baseline Profile | +| CIF | Common Intermediate Format (352 × 288 pixels) | +| CT | Codec Type | +| ERL | Echo Return Loss | +| HP | High Profile | +| KFI | Key Frame Interval | +| LSA | Least Square Approximation | +| MOS | Mean Opinion Score | +| PDA | Personal Digital Assistant | +| QCIF | Quarter CIF (176 × 144 pixels) | +| QQVGA | Quarter Quarter VGA (160 × 120 pixels) | +| QVGA | Quarter Video Graphics Array (320 × 240 pixels) | +| RLR | Receiving Loudness Rating | +| SLR | Sending Loudness Rating | +| VDS | Video Display Size | +| VF | Video Format | +| VGA | Video Graphics Array (640 × 480 pixels) | + +# 5 Conventions + +In this Recommendation, "subjective quality" refers to the mean opinion score (MOS) obtained in absolute category rating (ACR) tests as defined in [ITU-T P.800], [ITU-T P.910], [ITU-T P.911] and [ITU-T P.920], depending on the media under evaluation and evaluation context such as one-way listening/viewing and two-way interactive communication. + +# 6 Application + +The application of this Recommendation is limited to QoE/QoS planning. Other applications such as quality benchmarking and monitoring are outside the scope of this Recommendation. Table 2 gives an overview of various Recommendations related to objective quality assessment methods and their intended applications, the media types they apply to, and the subjective quality aspects that are taken into account. + +**Table 2 – Relationship of ITU-T G.1070 to other ITU Recommendations for objective quality assessment** + +| Media | Estimated subjective quality | Application | | | +|---------------------------|-------------------------------------|----------------------------------------------------------------------------------------|-----------------------------------------------------|--------------------------------------------------------------------| +| | | Benchmarking/
Intrusive monitoring | Non-intrusive
monitoring | Network planning | +| Speech | One way
(listening quality) | [ITU-T P.862]/
[ITU-T P.862.1]
(telephone band)
[ITU-T P.862.2]
(wideband) | [ITU-T P.563],
[ITU-T P.564]
(telephone band) | [ITU-T G.107]
(telephone band)
[ITU-T G.107.1]
(wideband) | +| | Two way
(conversational quality) | FFS (telephone-band) | | | +| Audio | One way
(listening quality) | [ITU-R BS.1387-1] | | | +| Video | One way
(viewing quality) | [ITU-T J.144]
(cable TV)
FFS (multimedia) | FFS (cable TV)
FFS (multimedia) | | +| Speech/Audio
and Video | One way | [ITU-T J.148] (multimedia) | | FFS (video streaming) | +| | Two way | | | [ITU-T G.1070]
(videophone) | +| Data | One way | FFS (web browsing) | | [ITU-T G.1030]
Annex A (web browsing) | + +NOTE – FFS stands for "for further study" + +# 7 Framework + +The framework of the opinion model treated in this Recommendation is illustrated in Figure 1. Its input parameters are video and speech quality parameters that are considered important in QoE/QoS planning. The model consists of three functions: video quality estimation, speech quality estimation + +and multimedia quality integration functions. The degradation caused by pure delay is considered only in the multimedia quality integration function. + +This Recommendation provides basic formulae for the above functions. The outputs from the model are multimedia quality ( $MM_q$ ), video quality influenced by speech quality ( $V_q(S_q)$ ), and speech quality influenced by video quality ( $S_q(V_q)$ ). + +The model assumes some specific evaluation conditions for terminals, environments, and evaluation contexts, and quality estimation under other evaluation conditions is currently under study. In this sense, these are the limitations of the current Recommendation. + +It should be noted that the effects of a codec on subjective quality are dependent on its implementation. In particular, the quality of a video codec cannot be estimated based simply on the information about the coding technology (e.g., MPEG-4) used in the system under test, although specifying the implementation of a speech codec based on the standard (e.g., [ITU-T G.711]) employed in the system under test is relatively easy. For example, there are a number of different implementations for MPEG-4 codecs due to variations in coding-parameter settings and decoder characteristics. Therefore, the coefficients of video and speech quality estimation functions in this Recommendation were determined by referring to tables prepared in advance for each video and speech codec. A coefficient database for video is illustrated in Figure 2. Such tables can be constructed by using the methodology provided in Annex A for video and by using [ITU-T P.833] or [ITU-T P.834] for speech. + +![Framework of a multimedia communication quality assessment model diagram showing inputs for video and speech quality estimation leading to a multimedia quality integration function.](af7916c89a458fdab6c3f443217388ae_img.jpg) + +The diagram illustrates the framework of a multimedia communication quality assessment model. It consists of several input blocks on the left and a processing pipeline on the right. + +**Inputs:** + +- Video-related assumptions:** Terminal type, Terminal characteristics (Monitor size, Monitor resolution, Ambient illuminance). +- Common assumptions:** Conversational task, Packet-loss pattern. +- Speech-related assumptions:** Terminal factors (Loudness rating etc.), Environmental factors (Ambient noise), Network factors (Packet-loss pattern). + +**Video Quality Path:** + +- Video quality parameters:** End-to-end delay, Video codec (Codec type, Video format, Key frame interval, Video display size), Bit rate, Frame rate, Packet-loss rate. +- These parameters are input to the **Video quality estimation function**. +- The function also interacts with a **Coefficient database**. +- The output is **Video-alone quality $V_q$** . + +**Speech Quality Path:** + +- Speech quality parameters:** End-to-end delay, Speech codec (Codec type, Bit rate), Packet-loss rate, TELR. +- These parameters are input to the **Speech quality estimation function**. +- The function also interacts with a **Coefficient database**. +- The output is **Speech-alone quality $S_q$** . + +**Multimedia Quality Integration:** + +- The **Multimedia quality integration function** receives **Video-alone quality $V_q$** , **Speech-alone quality $S_q$** , and **End-to-end delay** (from both paths) as inputs. +- It produces three outputs: **Video quality $V_q(S_q)$** , **Multimedia quality $MM_q$** , and **Speech quality $S_q(V_q)$** . + +G.1070(18)\_F01 + +Framework of a multimedia communication quality assessment model diagram showing inputs for video and speech quality estimation leading to a multimedia quality integration function. + +Figure 1 – Framework of a multimedia communication quality assessment model + +![Diagram illustrating the determination of coefficients for video quality estimation. On the left, a box titled 'Video quality parameters' lists: End-to-end delay, Video codec (with sub-parameters: Codec type, Video format, Key frame interval, Video display size), Bit rate, Frame rate, and Packet-loss rate. An arrow points from this box to a green box labeled 'Video quality estimation function', which outputs 'Vq'. A dashed 'look-up' arrow points from the 'Video quality estimation function' to a 'Coefficient database' (represented as a cylinder). The database contains multiple coefficient tables. 'Coefficient table X' is for 'Codec type: Product X based on ITU-T H.263'. 'Coefficient table B' is for 'Codec type: Product A based on MPEG4, Video format: QVGA, Key frame interval: 1 s, Video display size: 4.2 inch', with coefficients: coef. #1 = 0.123, coef. #2 = 0.456, ..., coef. #N = 0.999. An orange box on the left notes that these tables are 'Predetermined coefficient tables constructed by applying the method provided in Annex A'. The diagram is labeled 'G.1070(18)_F02' at the bottom right.](4801720824e4b5e2361a5564f91cfb70_img.jpg) + +Diagram illustrating the determination of coefficients for video quality estimation. On the left, a box titled 'Video quality parameters' lists: End-to-end delay, Video codec (with sub-parameters: Codec type, Video format, Key frame interval, Video display size), Bit rate, Frame rate, and Packet-loss rate. An arrow points from this box to a green box labeled 'Video quality estimation function', which outputs 'Vq'. A dashed 'look-up' arrow points from the 'Video quality estimation function' to a 'Coefficient database' (represented as a cylinder). The database contains multiple coefficient tables. 'Coefficient table X' is for 'Codec type: Product X based on ITU-T H.263'. 'Coefficient table B' is for 'Codec type: Product A based on MPEG4, Video format: QVGA, Key frame interval: 1 s, Video display size: 4.2 inch', with coefficients: coef. #1 = 0.123, coef. #2 = 0.456, ..., coef. #N = 0.999. An orange box on the left notes that these tables are 'Predetermined coefficient tables constructed by applying the method provided in Annex A'. The diagram is labeled 'G.1070(18)\_F02' at the bottom right. + +**Figure 2 – Determination of coefficients that depend on codec implementation** + +# 8 Model assumptions + +This clause describes conditions that the model assumes for terminals, environments, and evaluation contexts. + +## 8.1 Speech-related assumptions + +### 8.1.1 Terminal factors + +The model assumes the use of a handset as the interface for the voice path. We recognize that in many cases the interface will be a hands-free or headset unit; further work is needed to include these in the ITU-T G.107 and ITU-T G.107.1 models, before they can be included as options for the multimedia model. This means that one needs to be very careful when evaluating a mobile terminal, which usually has a hands-free function. + +If a noise canceller and/or an automatic gain controller is applied, it is assumed that the device works without causing any additional degradation of speech signals. + +### 8.1.2 Environmental factors + +The assumed ambient noise is Hoth noise at 35 dB(A). Although other ambient noise conditions can be assumed to exist, especially in mobile applications, dealing with such conditions is for further study. + +## 8.2 Video-related assumptions + +### 8.2.1 Terminal factors + +The model estimates video quality which has been evaluated by using a monitor whose specifications are listed in Table 3. Although this Recommendation treats video-telephony services using dedicated + +videophone terminals, desktop PCs, laptop PCs, PDAs and mobile phones, the effects of terminal characteristics with specifications other than those shown in Table 3 are still under study. + +NOTE – Specifications of monitors used in most PDAs and mobile phones are lower than those in Table 3. Thus, the model's predictions are often more sensitive than the users' opinions. Table 3 suggests nominal values, which are assumed by the model in this Recommendation, for use in QoE/QoS planning. + +**Table 3 – Assumptions about monitor characteristics** + +| Monitor specifications | Value | +|--------------------------------------------------------------------------|---------------------------| +| Diagonal length (Note) | 2-10 inches | +| Dot pitch | <0.30 | +| Colour temperature | 6500 K | +| Bit depth | 8 bits/colour | +| Refresh rate | ≥60 Hz | +| Brightness | 100-300 cd/m 2 | +| NOTE – "Diagonal length" refers to the image size on the monitor screen. | | + +### 8.2.2 Environmental factors + +The nominal ambient illumination is taken to be 500 lux. The model assumes video content to be a so-called "bust shot" with a grey background; this does not however, take into consideration moving backgrounds in mobile applications, nor does it consider a camera shaking due to hand movement. + +## 8.3 Task-related assumptions + +Conversational tasks in subjective quality evaluation affect the resultant conversational quality. In particular, the effects of delay have great impact on the interactivity in a conversation. Therefore, it is desirable that the model takes into account the kind of task assumed in the service. However, the only task currently considered in the model is "free conversation". This means that the video image of a conversation partner is displayed on the screen. Modelling of conversational tasks other than free conversation is for further study. + +# 9 Model inputs + +This clause describes the input parameters used in the model. + +## 9.1 Speech quality parameters + +The parameters described in this clause are similar to those in [ITU-T G.107] and in [ITU-T G.107.1]. Speech quality parameters not listed in this clause are assumed to take their default values as defined in [ITU-T G.107] and [ITU-T G.107.1]. + +### 9.1.1 Speech delay ( $T_s$ [ms]) + +This refers to an end-to-end, one-way delay in speech. Considering the delay in terminals, such as the processing delay and jitter-buffer delay is extremely important. An input value of $T_s$ must be less than 1000 ms. + +### 9.1.2 Speech coding distortion (*Ies*, *Ies,WB*) + +Distortion due to speech coding needs to be quantified as $I_{es}$ and $I_{es,WB}$ . The $I_{es}$ and $I_{es,WB}$ values for ITU-T standard codecs are provided in Appendices I and IV of [ITU-T G.113], respectively. The $I_{es}$ and $I_{es,WB}$ values for other codecs should be derived by applying the methods defined in [ITU-T P.833] or [ITU-T P.834]. + +### 9.1.3 Speech packet-loss robustness (Bpls) + +Packet-loss robustness of a speech codec should be quantified as *Bpls*. The *Bpls* values for ITU-T standard codecs are provided in Appendices I and IV of [ITU-T G.113]. + +### 9.1.4 Speech packet-loss rate (Ppls [%]) + +This refers to the end-to-end IP packet-loss rate in speech. Considering the packet loss in a terminal-jitter buffer and the packet loss in networks is extremely important. The value should be less than 20 [%]. + +### 9.1.5 Talker echo loudness rating (*TELR*, *TELR*, *WB*) + +This is the sum of sending loudness rating (SLR), receiving loudness rating (RLR), and echo return loss (ERL) in the talker-echo path. SLR and RLR are defined in [ITU-T P.79], and ERL is defined in [ITU-T G.122]. + +## 9.2 Video quality parameters + +### 9.2.1 Video delay (*Tv* [ms]) + +This refers to an end-to-end one-way delay in video. Considering the delay in terminals, such as the processing delay and jitter-buffer delay is extremely important. An input value of *Tv* must be less than 1000 ms. + +### 9.2.2 Video codec specifications + +The model's coefficients (see Figure 2) for coding and packet-loss distortion are determined by looking up the coefficient database that is provided in Annex B. For conditions other than those in Annex B, one needs to derive coefficients by applying the method described in Annex A. + +#### 9.2.2.1 Codec type and implementation + +This information is used to identify the specific implementation of a video codec under evaluation so that the model utilizes the coefficients appropriate to that implementation. The method to derive coefficients is provided in Annex A. + +#### 9.2.2.2 Spatial resolution + +This parameter refers not to the actual/effective spatial resolution reflecting the performance of a camera and/or a display but to the theoretical spatial resolution employed in a codec. It is better to measure the effective spatial resolution, if possible, and reflect it in the quality estimation. [ITU-T P.800] provides a methodology for measuring the effective spatial resolution. However, how to reflect such results in the quality estimation model is still under study. + +The model handles video whose size is between quarter quarter VGA (QQVGA) and video graphics array (VGA). + +#### 9.2.2.3 Key frame interval + +This is the time interval in which video is coded solely from intra-frame information. This affects the effectiveness of video coding (i.e., quality versus video bit rate) and the robustness against packet-loss degradation. + +### 9.2.3 Video packet-loss rate (Pplv [%]) + +This refers to the end-to-end IP packet-loss rate in video. Considering the packet loss in a terminal-jitter buffer and the packet loss in networks is extremely important. The value should be less than 10 [%]. + +### 9.2.4 Video frame rate (Frv [fps]) + +This refers to the frame rate used in an encoder and does not reflect frame repetition used by a decoder, for example, in the case of packet loss. This Recommendation assumes that the range of the frame rate is from 1 to 30 fps. + +### 9.2.5 Video bit rate (Brv [kbit/s]) + +This refers to the video bit rate at an encoder. + +# 10 Model outputs + +The model outputs are multimedia quality ( $MM_q$ ), speech quality accounting for the influence of video quality ( $S_q(V_q)$ ), and video quality accounting for the influence of speech quality ( $V_q(S_q)$ ). + +NOTE – The determination of $V_q(S_q)$ and $S_q(V_q)$ is for further study. + +# 11 Model description + +## 11.1 Speech quality estimation function for narrowband speech + +First, the speech quality parameters defined in clause 9.1 are mapped to a quality index $Q$ as follows: + +$$Q = 93.193 - Idte - Ie-eff \quad (11-1)$$ + +NOTE 1 – The quality index $Q$ is equivalent to the transmission rating factor $R$ defined in [ITU-T G.107], but the definition in this Recommendation is simplified due to the smaller number of input parameters. + +NOTE 2 – Quality evaluation characteristics in multimedia applications might be different from those expected in telephony applications. Therefore, the model described in this clause is a provisional method. The applicability of [ITU-T G.107] in such applications is still under study. + +NOTE 3 – The delay quality is considered separately in the multimedia quality integration function (see Figure 1), so Equation 11-1 excludes $Idd$ , which represents the degradation caused by pure delay in [ITU-T G.107]. + +$Idte$ represents the degradation caused by talker echo and is defined as: + +$$Idte = \left[ \frac{94.769 - Re}{2} + \sqrt{\frac{(94.769 - Re)^2}{4} + 100} - 1 \right] (1 - e^{-T_s}) \quad (11-2)$$ + +where: + +$$Re = 80 + 2.5(TERV - 14) \quad (11-3)$$ + +and: + +$$TERV = TELR - 40 \log \frac{1 + \frac{T_s}{10}}{1 + \frac{T_s}{150}} + 6e^{-0.3T_s^2} \quad (11-4)$$ + +$Ie-eff$ represents the degradation caused by speech coding and packet loss and is defined as: + +$$Ie-eff = Ie_s + (95 - Ie_s) \cdot \frac{Ppl_s}{Ppl_s + Bpl_s} \quad (11-5)$$ + +Speech quality $S_q$ is defined as a function of the quality index $Q$ . + +For $Q < 0$ : + +$$S_q = 1$$ + +$$\text{For } 0 < Q < 100: \quad S_q = 1 + 0.035Q + Q(Q - 60)(100 - Q)7 \times 10^{-6} \quad (11-6)$$ + +$$\text{For } Q > 100: \quad S_q = 4.5$$ + +## 11.2 Speech quality estimation function for wideband speech + +The speech quality parameters defined in clause 9.1 are mapped to a quality index $Q$ as follows: + +$$Q = 129 - Idte, WB - Ie-eff, WB \quad (11-7)$$ + +NOTE 1 – The quality index $Q$ is equivalent to the transmission rating factor $R$ defined in [ITU-T G.107.1], but the definition in this Recommendation is simplified due to the smaller number of input parameters. + +NOTE 2 – Quality evaluation characteristics in multimedia applications might be different from those expected in telephony applications. Therefore, the model described in this clause is a provisional method. The applicability of [ITU-T G.107.1] in such applications is still under study. + +NOTE 3 – The delay quality is considered separately in the multimedia quality integration function (see Figure 1), so Equation 11-7 excludes $Idd, WB$ , which represents the degradation caused by pure delay in [ITU-T G.107.1]. + +$Idte, WB$ represents the degradation caused by talker echo and is defined as: + +$$Idte, WB = \left[ \frac{129 - Re, WB}{2} + \sqrt{\frac{(129 - Re, WB)^2}{4} + 100 - 1} \right] (1 - e^{-T_s}) \quad (11-8)$$ + +where: + +$$Re, WB = 80 + 3(TERV, WB - 14) \quad (11-9)$$ + +and: + +$$TERV, WB = TELR + K - 40 \log \frac{1 + \frac{T_s}{10}}{1 + \frac{T_s}{150}} + 6e^{-0.3T_s^2} \quad (11-10)$$ + +For $T_s < 100$ ms: + +$$K = 0.08 \cdot T_s + 10 \quad (11-11)$$ + +For $T_s \geq 100$ ms: + +$$K = 18 \quad (11-12)$$ + +$Ie-eff, WB$ represents the degradation caused by speech coding and packet loss and is defined as: + +$$Ie-eff, WB = Ie_s, WB + (95 - Ie_s, WB) \cdot \frac{Ppl_s}{Ppl_s + Bpl_s} \quad (11-13)$$ + +$$Qx = \frac{Q}{1.29} \quad (11-14)$$ + +Speech quality $S_q$ is defined as a function of the quality index $Qx$ . + +$$\text{For } Qx < 0: \quad S_q = 1 \quad (11-15)$$ + +$$\text{For } 0 < Qx < 100: \quad S_q = 1 + 0.035Qx + Qx(Qx - 60)(100 - Qx)7 \times 10^{-6}$$ + +$$\text{For } Qx > 100: \quad S_q = 4.5$$ + +## 11.3 Video quality estimation function + +### 11.3.1 Calculation of video quality, $V_q$ + +Video quality $V_q$ is calculated using the video quality parameters defined in clause 9.2. $V_q$ is expressed as: + +$$V_q = 1 + I_{coding} \exp\left(-\frac{PplV}{D_{PplV}}\right) \quad (11-16)$$ + +where $I_{coding}$ represents the basic video quality affected by the coding distortion under a combination of video bit rate ( $BrV$ [kbit/s]) and video frame rate ( $FrV$ [fps]), and the packet loss robustness factor $D_{PplV}$ expresses the degree of video quality robustness due to packet loss where $PplV$ [%] represents the packet-loss rate. + +### 11.3.2 Basic video quality affected by coding distortion, $I_{coding}$ + +The basic video quality affected by coding distortion $I_{coding}$ is expressed as: + +$$I_{coding} = I_{Ofir} \exp\left\{-\frac{(\ln(FrV) - \ln(O_{fir}))^2}{2D_{FrV}^2}\right\} \quad (11-17)$$ + +The $O_{fir}$ is an optimal frame rate that maximizes the video quality at each video bit rate ( $BrV$ ) and is expressed as: + +$$O_{fir} = v_1 + v_2 BrV, \quad 1 \leq O_{fir} \leq 30, \quad v_1 \text{ and } v_2: \text{const} \quad (11-18)$$ + +where $FrV = O_{fir}$ , $I_{coding} = I_{Ofir}$ , $I_{Ofir}$ represents the maximum video quality at each video bit rate ( $BrV$ ) and is expressed as: + +$$I_{Ofir} = v_3 - \frac{v_3}{1 + \left(\frac{BrV}{v_4}\right)^{v_5}}, \quad 0 \leq I_{Ofir} \leq 4, \quad v_3, v_4, \text{ and } v_5: \text{const} \quad (11-19)$$ + +$D_{FrV}$ represents the degree of video quality robustness due to frame rate ( $FrV$ ) and is expressed as: + +$$D_{FrV} = v_6 + v_7 BrV, \quad 0 < D_{FrV}, \quad v_6 \text{ and } v_7: \text{const} \quad (11-20)$$ + +Coefficients $v_1, v_2, \dots$ , and $v_7$ are dependent on the codec type (CT), video format (VF), key frame interval (KFI) and video display size (VDS); see Annex B. + +### 11.3.3 Packet loss robustness factor, $D_{PplV}$ + +The packet loss robustness factor $D_{PplV}$ represents the degree of video quality robustness against packet loss and is expressed as: + +$$D_{PplV} = v_{10} + v_{11} \exp\left(-\frac{FrV}{v_8}\right) + v_{12} \exp\left(-\frac{BrV}{v_9}\right), \quad 0 < D_{PplV} \quad (11-21)$$ + +where $PplV$ represents the packet-loss rate. + +Coefficients $v_8, v_9, \dots$ , and $v_{12}$ are dependent on the codec type, video format, key frame interval, and video display size (see Annex B). + +## 11.4 Multimedia quality integration function + +### 11.4.1 Calculation of the multimedia quality, $MM_q$ + +The multimedia quality $MM_q$ is calculated using speech quality $S_q$ , video quality $V_q$ , speech delay $T_S$ , and video delay $T_V$ . $MM_q$ is expressed as: + +$$MM_q = m_1 MM_{SV} + m_2 MM_T + m_3 MM_{SV} MM_T + m_4 \quad (11-22)$$ + +where $MM_{SV}$ represents audio-visual quality, $MM_T$ represents the audio-visual delay impairment factor, and coefficients $m_1, m_2, \dots$ , and $m_4$ are dependent on the video display size and conversational task. $MM_q$ is bounded between 1 and 5. + +### 11.4.2 Audio-visual quality, $MM_{SV}$ + +The audio-visual quality $MM_{SV}$ is expressed as: + +$$MM_{SV} = m_5 S_q + m_6 V_q + m_7 S_q V_q + m_8 \quad (11-23)$$ + +Coefficients $m_5, m_6, \dots$ , and $m_8$ are dependent on the video display size and conversational task. $MM_{SV}$ is bounded between 1 and 5. + +### 11.4.3 Audio-visual delay impairment factor, $MM_T$ + +The $MM_T$ represents the degree of the audio-visual quality degradation due to audio-visual delay and synchronization and is expressed as: + +$$MM_T = \max\{AD + MS, 1\} \quad (11-24)$$ + +$$AD = m_9 (T_S + T_V) + m_{10} \quad (11-25)$$ + +$$MS = \min\{m_{11} (T_S - T_V) + m_{12}, 0\} \quad \text{if } T_S \geq T_V \quad (11-26)$$ + +and: + +$$MS = \min\{m_{13} (T_V - T_S) + m_{14}, 0\} \quad \text{if } T_S < T_V \quad (11-27)$$ + +where $AD$ represents the absolute audio-visual delay and $MS$ represents the audio-visual media synchronization. + +Coefficients $m_9, m_{10}, \dots$ , and $m_{14}$ are dependent on the video display size and conversational task. + +NOTE 1 – Provisional values of $m_i$ were developed for two different video displays, namely a 4.2-inch video display size with a QVGA video format and a 2.1-inch video display with a QQVGA video format. The conversational task was free conversation. These values are provided in Annex C. + +NOTE 2 – Currently, the derivation of $V_q(S_q)$ and $S_q(V_q)$ , which are video quality affected by speech quality and vice versa, is under study. + +# 12 Accuracy of model + +The Pearson product-moment correlation between the empirical subjective quality and the quality estimate generated by the model was used for evaluating the accuracy of the speech quality estimation function, the video quality estimation function, and the multimedia quality integration function. The correlation $r$ should be calculated over all the test data sets as follows: + +$$r = \frac{\sum_{v=1}^V (y_v - \bar{y})(x_v - \bar{x})}{\sqrt{\sum_{v=1}^V (y_v - \bar{y})^2 \sum_{v=1}^V (x_v - \bar{x})^2}}$$ + +where $V$ is the number of test data sets, and the mean values of the data sets are calculated as follows: + +$$\bar{x} = \frac{1}{V} \sum_{v=1}^V x_v$$ + +and: + +$$\bar{y} = \frac{1}{V} \sum_{v=1}^V y_v$$ + +where: + +$x_v$ : represents the estimated quality of test data; and + +$y_v$ : represents the subjective quality of test data. + +The accuracy of the speech quality estimation function, which is presented in [ITU-T G.107], is described in [b-Möller]. + +The accuracy of the video quality estimation function was verified in the following manner: + +- 1) The validity of the forms (Equations 11-16 to 11-21) was verified by using the subjective quality database employing [ITU-T H.264] and MPEG-4 codecs (DB#1 to DB#4 in Table 4). Here, the coefficients $v_1, v_2, \dots$ , and $v_{12}$ were optimized for each database. The cross-correlation is about 0.975 on average [b-Yamagishi 1], [b-Yamagishi 2]. +- 2) The validity of the optimized coefficients $v_1, v_2, \dots$ , and $v_{12}$ was verified by applying them to unknown data. This was done by optimizing the coefficients by DB#5 and DB#7, and applying them to DB#6 and DB#8 (see Table 5). The cross-correlation is about 0.955 on average [b-Yamagishi 3]. + +**Table 4 – Verification of the form of video quality estimation function for various terminals** + +| | $r$ | CT | VF | KFI [s] | VDS [inches] | +|------|----------------------------------------|-------------|------|---------|--------------| +| DB#1 | 0.967 [b-Yamagishi 1] | ITU-T H.264 | QVGA | 1 | 4.2 | +| DB#2 | 0.987 [b-Yamagishi 1], [b-Yamagishi 2] | MPEG-4 | QVGA | 1 | 4.2 | +| DB#3 | 0.973 [b-Yamagishi 2] | MPEG-4 | QVGA | 1 | 8.5 | +| DB#4 | 0.972 [b-Yamagishi 2] | MPEG-4 | VGA | 1 | 8.5 | + +**Table 5 – Accuracy of the video quality estimation function** + +| | $r$ | CT | VF | KFI [s] | VDS [inches] | +|------|-----------------------|--------|-------|---------|--------------| +| DB#5 | 0.951 [b-Yamagishi 3] | MPEG-4 | QVGA | 1 | 4.2 | +| DB#6 | 0.961 [b-Yamagishi 3] | MPEG-4 | QVGA | 1 | 4.2 | +| DB#7 | 0.958 [b-Yamagishi 3] | MPEG-4 | QQVGA | 1 | 2.1 | +| DB#8 | 0.949 [b-Yamagishi 3] | MPEG-4 | QQVGA | 1 | 2.1 | + +The accuracy of the multimedia quality integration function was verified as follows. + +The speech and video quality ( $S_q$ and $V_q$ ) were estimated by the speech and video quality estimation functions described in clauses 11.1, 11.2 and 11.3, respectively. Next, these values and speech and video delay values ( $T_S$ and $T_V$ ) were fed into the multimedia quality integration function given in clause 11.4. By comparing the estimated multimedia quality with the multimedia quality obtained by a conversational subjective test, the validity of the multimedia quality integration function was evaluated. + +An [ITU-T G.711] codec without a packet-loss concealment algorithm was used as a speech codec. The speech packet-loss rate varied from 0 to 10%. No echo was introduced in the evaluation system. The video codec was MPEG-4, and the video bit rate was 2 Mbit/s and 1 Mbit/s for QVGA and QQVGA, respectively. The video packet-loss rate varied from 0 to 5%. The video frame rate was between 2 to 30 fps. One-way delay varied from 167 to 1000 ms and was controlled for speech and video separately to evaluate the effects of lip synchronization. The number of experimental conditions was 88. + +The subjective testing method was 5-grade conversational ACR defined in [ITU-T P.910]. There were 32 subjects. The viewing distances were 50 and 80 cm for QQVGA and QVGA, respectively. The number of judgments by each subject was 140. All the conditions (88) were assessed by each subject. Some were assessed twice or more. + +The estimation accuracy of the [ITU-T G.1070] model, including speech and video quality estimation functions, is demonstrated in Table 6. + +NOTE – These databases were used for optimizing the coefficients of the multimedia quality integration function under each VDS condition. The coefficients are provided in Annex C. + +**Table 6 – Accuracy of the multimedia communication quality assessment model** + +| | r | Speech codec | Video codec | VF | KFI [s] | VDS [inches] | +|-------|----------|---------------------|--------------------|-----------|----------------|---------------------| +| DB#9 | 0.83 | ITU-T G.711 | MPEG-4 at 2 Mbit/s | QVGA | 1 | 4.2 | +| DB#10 | 0.91 | ITU-T G.711 | MPEG-4 at 1 Mbit/s | QQVGA | 1 | 2.1 | + +# Annex A + +## Methodology for deriving the coefficients in the video quality estimation function with respect to coding and packet-loss degradation + +(This annex forms an integral part of this Recommendation.) + +### A.1 Methodology for deriving coefficients $v_1, v_2, \dots, \text{ and } v_7$ + +Using the subjective video quality MOS, which is called $V_{qs}$ hereafter, for various video bit rate ( $Br_V$ ) and video frame-rate ( $Fr_V$ ) conditions, coefficients $v_1, v_2, \dots, \text{ and } v_7$ are calculated in the following four steps. + +#### Step A.1.1: Calculation of values $I_{Of_V}, O_{Of_V}, \text{ and } D_{Of_V}$ + +- 1) By employing $M$ different frame rates for each video bit-rate condition $b_n$ , Table A.1 is obtained. + +**Table A.1 – Relationships among $Br_V, Fr_V, \text{ and } V_q$** + +| $Br_V$ | $Fr_V$ | $V_q$ | +|--------|--------|--------------------| +| $b_n$ | $f_1$ | $V_{qs}(b_n, f_1)$ | +| $b_n$ | $f_2$ | $V_{qs}(b_n, f_2)$ | +| ... | ... | ... | +| $b_n$ | $f_m$ | $V_{qs}(b_n, f_m)$ | +| ... | ... | ... | +| $b_n$ | $f_M$ | $V_{qs}(b_n, f_M)$ | + +NOTE 1 – $M$ represents the number of frame rate conditions. $f_1 > f_2 > \dots > f_M$ . + +NOTE 2 – $V_{qs}(b_n, f_m)$ represents the MOS under the condition with a video bit rate of $b_n$ and a frame rate of $f_m$ . + +- 2) By applying the data set in Table A.1 to Equation 11-16, $O_{Of_V}, I_{Of_V} \text{ and } D_{Of_V}$ are approximated for each video bit rate $b_n$ based on the least square approximation (LSA). The result is given in Table A.2. + +**Table A.2 – Relationship between $Br_V, I_{Of_V}, O_{Of_V}, \text{ and } D_{Of_V}$** + +| $Br_V$ | $O_{Of_V}$ | $I_{Of_V}$ | $D_{Of_V}$ | +|--------|------------|------------|------------| +| $b_1$ | $O_1$ | $I_1$ | $D_1$ | +| $b_2$ | $O_2$ | $I_2$ | $D_2$ | +| ... | ... | ... | ... | +| $b_n$ | $O_n$ | $I_n$ | $D_n$ | +| ... | ... | ... | ... | +| $b_N$ | $O_N$ | $I_N$ | $D_N$ | + +NOTE 3 – $N$ represents the number of video bit-rate conditions. $b_1 > b_2 > \dots > b_N$ . + +#### Step A.1.2: Calculation of coefficients $v_1 \text{ and } v_2$ + +By applying $b_n$ and $O_n$ for $n = 1, 2, \dots, N$ in Table A.2 to Equation 11-18, coefficients $v_1$ and $v_2$ are approximated based on the LSA. + +#### **Step A.1.3: Calculation of coefficients $v_3$ , $v_4$ , and $v_5$** + +By applying $b_n$ and $I_n$ for $n = 1, 2, \dots, N$ in Table A.2 to Equation 11-19, coefficients $v_3$ , $v_4$ and $v_5$ are approximated based on the LSA. + +#### **Step A.1.4: Calculation of coefficients $v_6$ and $v_7$** + +By applying $b_n$ and $D_n$ for $n = 1, 2, \dots, N$ to Equation 11-20, coefficients $v_6$ and $v_7$ are approximated based on the LSA. + +### **A.2 Methodology for deriving coefficients $v_8$ , $v_9$ , ..., and $v_{12}$** + +Using the subjective video quality ( $V_{qs}$ ) related to video bit rate ( $Br_V$ ), video frame rate ( $Fr_V$ ) and video packet-loss rate ( $P_{plV}$ ), coefficients $v_8$ , $v_9$ , ..., and $v_{12}$ are calculated in the following four steps. + +NOTE 1 – The subjective quality characteristics of packet-loss degradation often depend on the duration of video sequences used in a subjective test, so one should use video sequences that have a reasonable length (e.g., 1 min). + +#### **Step A.2.1: Calculation of values $D_{PplV}$** + +By applying $I_{coding}$ , which is calculated by using the coefficients derived in clause A.1, and subjective video quality ( $V_{qs}$ ) to Equation 11-16, the packet loss robustness factor $D_{PplV}$ is approximated based on the LSA for each combination of $Br_V$ and $Fr_V$ , as shown in Table A.3. + +**Table A.3 – Relationships among video bit rate, video frame rate, and $D_{PplV}$** + +| $D_{PplV}$ | | $Fr_V$ | | | | | | +|------------|-------|------------|------------|-----|------------|-----|------------| +| | | $f_1$ | $f_2$ | ... | $f_m$ | ... | $f_M$ | +| $Br_V$ | $b_1$ | $D_{b1f1}$ | $D_{b1f2}$ | ... | ... | ... | $D_{b1fM}$ | +| | $b_2$ | $D_{b2f1}$ | $D_{b2f2}$ | ... | ... | ... | $D_{b2fM}$ | +| | ... | ... | ... | ... | ... | ... | ... | +| | $b_n$ | $D_{bnf1}$ | $D_{bnf2}$ | ... | $D_{bnfm}$ | ... | $D_{bnfM}$ | +| | ... | ... | ... | ... | ... | ... | ... | +| | $b_N$ | $D_{bNf1}$ | $D_{bNf2}$ | ... | ... | ... | $D_{bNfM}$ | + +NOTE 1 – N represents the number of video bit-rate conditions. + +NOTE 2 – M represents the number of video frame-rate conditions. + +NOTE 3 – $D_{bnfm}$ indicates a temporary value of the packet-loss robustness factor $D_{PplV}$ for a video bit rate of $b_n$ and a frame rate of $f_m$ . + +#### **Step A.2.2: Calculation of coefficient $v_8$** + +By applying $f_m$ and $D_{PplV} = D_{b1fm}$ for $m = 1, 2, \dots, M$ to Equation A-1, coefficients $a$ , $b$ and $v_8$ are approximated based on the LSA. + +$$D_{PplV} = a + b \exp\left(-\frac{Fr_V}{v_8}\right) \tag{A-1}$$ + +#### **Step A.2.3: Calculation of coefficient $v_9$** + +By applying $b_n$ and $D_{PplV} = D_{bnf1}$ , for $n = 1, 2, \dots, N$ to Equation A-2, coefficients $c$ , $d$ and $v_9$ are approximated based on the LSA. + +$$D_{PplV} = c + d \exp\left(-\frac{Br_V}{v_9}\right) \tag{A-2}$$ + +NOTE 2 – Coefficients a, b, c and d are temporary and never used in the following calculation. + +#### **Step A.2.4: Calculation of coefficients $v_{10}$ , $v_{11}$ and $v_{12}$** + +By applying $v_8$ , $v_9$ , $D_{PpIV} = D_{bnfm}$ , $BrV = b_n$ , and $FrV = f_m$ for $n = 1, 2, \dots, N$ and $m = 1, 2, \dots, M$ to Equation 11-21, coefficients $v_{10}$ , $v_{11}$ and $v_{12}$ are approximated based on LSA. + +## Annex B + +## Coefficients in the video quality estimation function with respect to coding and packet-loss degradation + +(This annex forms an integral part of this Recommendation.) + +### B.1 Coefficients for small and medium screen + +This clause provides the coefficient tables to be used for video quality estimation. Table B.1 summarizes the conditions under which each coefficient table was constructed. + +NOTE 1 – The coefficient tables given in this annex cannot be applied to arbitrary MPEG-4 or MPEG-2 codecs. This is dependent on the implementation and setting of the codec, as noted in clause 7. Therefore, if one needs coefficient values for a codec which are not included in this table, the procedure described in Annex A should be used to create appropriate tables. + +**Table B.1 – Conditions for deriving coefficient tables** + +| Factors | # 1 | # 2 | # 3 | # 4 | # 5 | +|---------------------------|--------|--------|--------|--------|---------------| +| Codec type | MPEG-4 | MPEG-4 | MPEG-2 | MPEG-4 | [ITU-T H.264] | +| Video format | QVGA | QQVGA | VGA | VGA | VGA | +| Key frame interval (s) | 1 | 1 | 1 | 1 | 1 | +| Video display size (inch) | 4.2 | 2.1 | 9.2 | 9.2 | 9.2 | + +The resultant coefficient values are provided in Table B.2. + +NOTE 2 – These coefficient values were determined based on subjective tests with video sequences of 10 s. Therefore, the quality estimation based on these coefficients may result in an optimistic evaluation in comparison with that of the video quality of longer video sequences in evaluating the effects of packet loss. + +**Table B.2 – Coefficient table for the video quality estimation function** + +| Coefficients | # 1 | # 2 | # 3 | # 4 | # 5 | +|--------------|------------------------|------------------------|------------------------|------------------------|-----------------------| +| $v_1$ | 1.431 | 7.160 | 4.78 | 1.182 | 5.517 | +| $v_2$ | $2.228 \times 10^{-2}$ | $2.215 \times 10^{-2}$ | $1.22 \times 10^{-2}$ | $1.11 \times 10^{-2}$ | $1.29 \times 10^{-2}$ | +| $v_3$ | 3.759 | 3.461 | 2.614 | 4.286 | 3.459 | +| $v_4$ | 184.1 | 111.9 | 51.68 | 607.86 | 178.53 | +| $v_5$ | 1.161 | 2.091 | 1.063 | 1.184 | 1.02 | +| $v_6$ | 1.446 | 1.382 | 0.898 | 2.738 | 1.15 | +| $v_7$ | $3.881 \times 10^{-4}$ | $5.881 \times 10^{-4}$ | $6.923 \times 10^{-4}$ | $-9.98 \times 10^{-4}$ | $3.55 \times 10^{-4}$ | +| $v_8$ | 2.116 | 0.8401 | 0.7846 | 0.896 | 0.114 | +| $v_9$ | 467.4 | 113.9 | 85.15 | 187.24 | 513.77 | +| $v_{10}$ | 2.736 | 6.047 | 1.32 | 5.212 | 0.736 | +| $v_{11}$ | 15.28 | 46.87 | 539.48 | 254.11 | -6.451 | +| $v_{12}$ | 4.170 | 10.87 | 356.6 | 268.24 | 13.684 | + +NOTE 3 – The values for the condition number # 3 have been obtained for a packet loss rate smaller than or equal to 2% and for coding bit rates higher than 128 kbit/s. The coefficients of Table B.2 should be used only within the specified ranges. + +NOTE 4 – The values for the conditions numbered # 4 and # 5 have been obtained for bit rates higher than 300 and 400 kbit/s, respectively and below 1.5 and 2 Mbit/s, respectively. Packet loss rates were smaller than 5% and the frame rate was set between 5 and 25 fps. The coefficients of Table B.2 should be used within the specified ranges. + +### B.2 Coefficients for small screen (with screen size of 6 inches) + +Table B.3 summarizes the conditions under which each coefficient table was constructed. + +NOTE 5 – The coefficient tables given in this annex can be applied to the most popular ITU-T H.264 baseline profile (BP) and high profile (HP) settings, including format, bit rate, frame rate and packet loss rate. + +**Table B.3 – Conditions for deriving coefficient tables** + +| Factors | #1 | #2 | #3 | #4 | #5 | #6 | #7 | #8 | +|------------------|--------------------------|---------------------------|---------------------------|----------------------------|--------------------------|---------------------------|---------------------------|----------------------------| +| Codec | H.264 BP | H.264 BP | H.264 BP | H.264 BP | H.264 HP | H.264 HP | H.264 HP | H.264 HP | +| Format | VGA | 4CIF | 720p | 1080p | VGA | 4CIF | 720p | 1080p | +| Bit rate | 128, 192, 512, 768, 1024 | 128, 256, 512, 1024, 1280 | 256, 384, 512, 2048, 3200 | 512, 768, 1024, 4096, 6400 | 128, 192, 512, 768, 1024 | 128, 256, 512, 1024, 1280 | 256, 384, 512, 2048, 3200 | 512, 768, 1024, 4096, 6400 | +| Frame rate | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | +| Packet loss rate | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | + +The resultant coefficient values are provided in Table B.4. + +**Table B.4 – Coefficient table for the video quality estimation function** + +| Coefficients | #1 | #2 | #3 | #4 | #5 | #6 | #7 | #8 | +|--------------|-------------------------|-------------------------|-------------------------|-------------------------|-------------------------|-------------------------|-------------------------|-------------------------| +| $v_1$ | 6.743 | 3.854 | 2.040 | 1.711 | 5.610 | 6.964 | 6.311 | 2.773 | +| $v_2$ | $0.9998 \times 10^{-2}$ | $1.2010 \times 10^{-2}$ | $1.0991 \times 10^{-2}$ | $0.8978 \times 10^{-2}$ | $1.0113 \times 10^{-2}$ | $0.7019 \times 10^{-2}$ | $0.8123 \times 10^{-2}$ | $0.8987 \times 10^{-2}$ | +| $v_3$ | 3.051 | 3.240 | 3.593 | 4.283 | 3.379 | 3.582 | 3.681 | 3.952 | +| $v_4$ | 168.1 | 206.3 | 296.2 | 513.2 | 182.3 | 214.1 | 262.04 | 460.3 | +| $v_5$ | 1.766 | 1.681 | 1.322 | 0.850 | 1.310 | 1.200 | 1.280 | 1.281 | +| $v_6$ | 1.130 | 1.624 | 1.683 | 1.392 | 2.230 | 1.755 | 1.973 | 2.119 | +| $v_7$ | $18.340 \times 10^{-4}$ | $6.443 \times 10^{-4}$ | $4.297 \times 10^{-4}$ | $2.517 \times 10^{-4}$ | $7.512 \times 10^{-4}$ | $6.348 \times 10^{-4}$ | $3.332 \times 10^{-4}$ | $3.234 \times 10^{-4}$ | +| $v_8$ | 1.232 | 1.580 | 1.324 | 1.254 | 1.511 | 1.134 | 1.244 | 1.282 | +| $v_9$ | 53.25 | 208.34 | 102.00 | 307.35 | 136.21 | 170.99 | 343.33 | 262.44 | +| $v_{10}$ | 3.353 | 4.672 | 3.363 | 1.847 | 4.053 | 4.250 | 2.762 | 1.981 | +| $v_{11}$ | 6.025 | 7.874 | 18.534 | 17.460 | 20.162 | 7.982 | 6.251 | 22.839 | +| $v_{12}$ | 80.752 | 15.114 | 96.237 | 3.999 | 22.332 | 12.001 | 6.013 | 7.999 | + +### B.3 Coefficients for large screen (with screen size of 65 inches) + +Table B.5 summarizes the conditions under which each coefficient table was constructed. + +NOTE 6 – The coefficient tables given in this annex can be applied to most popular ITU-T H.264 BP and HP settings, including format, bit rate, frame rate and packet loss rate. + +**Table B.5 – Conditions for deriving coefficient tables** + +| Factors | #1 | #2 | #3 | #4 | #5 | #6 | #7 | #8 | +|------------------|--------------------------|---------------------------|---------------------------|----------------------------|--------------------------|---------------------------|---------------------------|----------------------------| +| Codec | H.264 BP | H.264 BP | H.264 BP | H.264 BP | H.264 HP | H.264 HP | H.264 HP | H.264 HP | +| Format | VGA | 4CIF | 720p | 1080p | VGA | 4CIF | 720p | 1080p | +| Bit rate | 128, 192, 512, 768, 1024 | 128, 256, 512, 1024, 1280 | 256, 384, 512, 2048, 3200 | 512, 768, 1024, 4096, 6400 | 128, 192, 512, 768, 1024 | 128, 256, 512, 1024, 1280 | 256, 384, 512, 2048, 3200 | 512, 768, 1024, 4096, 6400 | +| Frame rate | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | 8, 15, 30 | +| Packet loss rate | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | 0, 0.5, 1, 3 | + +The resultant coefficient values are provided in Table B.6. + +**Table B.6 – Coefficient table for the video quality estimation function** + +| Coefficients | #1 | #2 | #3 | #4 | #5 | #6 | #7 | #8 | +|--------------|-------------------------|------------------------|------------------------|------------------------|-------------------------|-------------------------|-------------------------|-------------------------| +| $v_1$ | 5.643 | 3.813 | 1.849 | 1.238 | 4.623 | 5.277 | 5.891 | 2.209 | +| $v_2$ | $1.042 \times 10^{-2}$ | $1.120 \times 10^{-2}$ | $1.060 \times 10^{-2}$ | $0.921 \times 10^{-2}$ | $0.7214 \times 10^{-2}$ | $0.8876 \times 10^{-2}$ | $0.9086 \times 10^{-2}$ | $0.6834 \times 10^{-2}$ | +| $v_3$ | 2.862 | 3.058 | 3.281 | 3.724 | 3.243 | 3.384 | 3.535 | 3.622 | +| $v_4$ | 178.2 | 250.2 | 306.4 | 364.2 | 193.5 | 238.2 | 222.8 | 312.1 | +| $v_5$ | 1.972 | 1.859 | 1.607 | 1.043 | 1.271 | 1.216 | 1.209 | 1.167 | +| $v_6$ | 1.263 | 1.369 | 1.858 | 1.378 | 1.977 | 1.686 | 1.875 | 1.577 | +| $v_7$ | $11.026 \times 10^{-4}$ | $9.324 \times 10^{-4}$ | $4.324 \times 10^{-4}$ | $3.461 \times 10^{-4}$ | $13.245 \times 10^{-4}$ | $9.122 \times 10^{-4}$ | $2.031 \times 10^{-4}$ | $3.786 \times 10^{-4}$ | +| $v_8$ | 1.125 | 1.368 | 1.121 | 1.344 | 1.477 | 1.221 | 1.409 | 1.322 | +| $v_9$ | 49.34 | 112.0 | 168.5 | 252.4 | 141.3 | 228.5 | 283.6 | 362.4 | +| $v_{10}$ | 3.047 | 3.564 | 2.449 | 1.365 | 3.464 | 4.434 | 2.764 | 1.486 | +| $v_{11}$ | 5.824 | 6.875 | 15.286 | 16.318 | 14.315 | 8.562 | 5.871 | 7.964 | +| $v_{12}$ | 92.465 | 25.977 | 9.888 | 2.015 | 18.225 | 9.998 | 6.110 | 2.122 | + +## Annex C + +## Coefficients in the multimedia quality integration function + +(This annex forms an integral part of this Recommendation.) + +This annex provides the coefficient values for the multimedia quality integration function. As stated in clause 11.3, the coefficients are dependent on the video display size and conversational task. The coefficient tables in this annex assume two different video display sizes, which are 4.2, and 2.1 [inch]. They were derived by using "free conversation" as a conversational task. + +**Table C.1 – Coefficients of the multimedia quality integration function** + +| Coefficients | 4.2 inch | 2.1 inch | +|--------------|-------------------------|-------------------------| +| $m_1$ | $-4.457 \times 10^{-1}$ | $-6.966 \times 10^{-1}$ | +| $m_2$ | $-6.638 \times 10^{-1}$ | $-8.127 \times 10^{-1}$ | +| $m_3$ | $4.042 \times 10^{-1}$ | $4.562 \times 10^{-1}$ | +| $m_4$ | 2.321 | 3.003 | +| $m_5$ | $-3.255 \times 10^{-1}$ | $-1.638 \times 10^{-1}$ | +| $m_6$ | $3.309 \times 10^{-1}$ | $3.626 \times 10^{-1}$ | +| $m_7$ | $1.494 \times 10^{-1}$ | $1.291 \times 10^{-1}$ | +| $m_8$ | $5.457 \times 10^{-1}$ | $5.456 \times 10^{-1}$ | +| $m_9$ | $-3.235 \times 10^{-4}$ | $-1.251 \times 10^{-4}$ | +| $m_{10}$ | 3.915 | 3.763 | +| $m_{11}$ | $-1.377 \times 10^{-3}$ | $-1.065 \times 10^{-3}$ | +| $m_{12}$ | 0.000 | $1.465 \times 10^{-2}$ | +| $m_{13}$ | $-1.095 \times 10^{-3}$ | $-1.002 \times 10^{-3}$ | +| $m_{14}$ | 0.000 | 0.000 | + +# Bibliography + +- [b-ITU-T G.1030] Recommendation ITU-T G.1030 (2005), *Estimating end-to-end performance in IP networks for data applications*. +- [b-Bijl] Bijl, P., and Valeten, J.M. (1999), *Guidelines for accurate TOD measurement, Proc. SPIE 3701, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing X*, 14. +- [b-Möller] Möller, S. (2000), *Assessment and Prediction of Speech Quality in Telecommunications*, Kluwer Academic Publishers. Boston, MA. +- [b-Yamagishi 1] Yamagishi, K., and Hayashi, T. (2006), *Verification of Video Quality Opinion Model for Videophone Services, 2nd ISCA/DEGA Tutorial and Research Workshop on Perceptual Quality of Systems*, pp.143-148. +- [b-Yamagishi 2] Yamagishi, K., and Hayashi, T. (2006), *QRP 08-1: Opinion Model for Estimating Video Quality of Videophone Services, GLOBECOM 2006, IEEE*. +- [b-Yamagishi 3] Yamagishi, K., and Hayashi, T. (2008), *Video-Quality Planning Model for Videophone Services, ITE, Vol. 62, No. 7*. + + + +# SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.111-199303-I_PDF-E/raw.md b/marked/G/T-REC-G.111-199303-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..b6b97c0667c8e11b4f7ed4bfaa127c6f97adeb4d --- /dev/null +++ b/marked/G/T-REC-G.111-199303-I_PDF-E/raw.md @@ -0,0 +1,678 @@ + + +![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +**G.111** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +(03/93) + +**TRANSMISSION SYSTEMS AND MEDIA** + +**GENERAL RECOMMENDATIONS ON THE +TRANSMISSION QUALITY FOR AN ENTIRE +INTERNATIONAL TELEPHONE CONNECTION** + +--- + +**LOUDNESS RATINGS (LRs) IN AN +INTERNATIONAL CONNECTION** + +**ITU-T Recommendation G.111** + +(Previously "CCITT Recommendation") + +--- + +# FOREWORD + +The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecommunication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +ITU-T Recommendation G.111 was revised by the ITU-T Study Group XII (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). + +--- + +# NOTES + +1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. + +In order not to delay publication of this Recommendation, no change has been made in the text to references containing the acronyms "CCITT, CCIR or IFRB" or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. + +2 In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +# CONTENTS + +| | | Page | +|------------|----------------------------------------------------------------------------------------------------------------------------|-------------| +| 1 | Nominal LRs of the national systems..... | 1 | +| 1.1 | Definition of nominal LRs of the national systems ..... | 1 | +| 1.2 | Recommended values ..... | 1 | +| 2 | Nominal overall loss of the international chain..... | 1 | +| 3 | LRs and directional effects in a complete connection..... | 2 | +| 3.1 | Nominal LRs for each transmission direction..... | 2 | +| 3.2 | Traffic-weighted mean values of OLRs..... | 2 | +| 3.3 | Difference in transmission loss between the two directions of transmission..... | 2 | +| 4 | Variation in time and effect of circuit noise..... | 3 | +| 4.1 | Variations in time..... | 3 | +| 4.2 | Effect of circuit noise..... | 3 | +| 5 | Practical limits of the OLR between two operators or one operator and one subscriber ..... | 3 | +| 6 | Incorporation of PCM digital processes in international connections..... | 4 | +| 6.1 | Connections with a digital 4-wire chain extending to the local exchanges ..... | 4 | +| 6.2 | Mixed analogue/digital connections ..... | 5 | +| Annex A | – Explanations related to Recommendations G.111, G.121, G.122, G.131, G.134: properties and uses of loudness ratings ..... | 5 | +| A.1 | General explanations of loudness rating terms as used in the G-Series Recommendations ..... | 5 | +| A.2 | Psycho-acoustic model for loudness ratings ..... | 6 | +| A.3 | Measurement of loudness ratings of telephone sets..... | 7 | +| A.4 | Application of loudness ratings in the Series-G Recommendations..... | 8 | +| Annex B | – Recommended values and limits of the loudness ratings for circuits in international connections ..... | 15 | +| Annex C | – Translation of LR values into CRE values ..... | 16 | +| References | ..... | 17 | + +# PREAMBLE + +Clauses 1 to 5 of this Recommendation apply in general to all-analogue, mixed analogue/digital and all-digital international telephone connections. However, where Recommendations are made on specific aspects in clause 6 for mixed analogue/digital or all-digital connections, clause 6 will govern. + +In the international transmission plan, the loudness rating (LR) between two subscribers is not strictly limited; its maximum value results from various Recommendations. + +The values given below, either in terms of LR should be used to verify that international telephone connections provide an adequate loudness of received speech. + +Administrations employing CREs should preferably translate the LRs of this Recommendation into their national CREs by the methods given in Annex C or, as a second choice, apply the values given in Volume III of the *Red Book* (ITU, Geneva, 1985). + +## NOTES + +- 1 The main terms used in this Recommendation are defined and/or explained in Annex A. +- 2 For many telephone sets using carbon microphones, the SLR and STMR values can only be determined with limited accuracy. + +# LOUDNESS RATINGS (LRs) IN AN INTERNATIONAL CONNECTION + +*(Geneva, 1964; amended at Mar del Plata, 1968; Geneva, 1972, 1976 and 1980; +Malaga-Torremolinos, 1984; Melbourne, 1988, and Helsinki, 1993)* + +## 1 Nominal LRs of the national systems + +### 1.1 Definition of nominal LRs of the national systems + +Send and receive loudness ratings, SLRs and RLRs respectively, may in principle be determined at any interface in the telephone network. In this Recommendation and in Recommendation G.121, the SLRs and RLRs of the national systems are referred to the Virtual International Connecting Points (VICPs) as defined in 2.12/G.101; see Figure 1. + +The **virtual international connecting point** is a point in the international circuit at the International Switching Centre (ISC). The relative levels at the VICP are: + +- Sending: 0 dBr; +- Receiving: 0 dBr for digital circuits; +–0.5 dBr for analogue or mixed analogue/digital circuits. + +The nominal circuit loss of international circuits at the reference frequency (1020 Hz) is therefore 0 dB for digital circuits and 0.5 dB for analogue and mixed analogue/digital circuits. + +###### NOTES + +1 In digital international circuits, the VICP will be at the digital bit stream. In analogue exchanges, the VICP often will be a hypothetical, not accessible point; see 2.12/G.101 and 2.13/G.101. + +2 Earlier, the Virtual Analogue Switching Points (VASPs) having the relative levels –3.5dBr and –4 dBr were used as the reference points. + +### 1.2 Recommended values + +Recommendation G.121 gives objectives for the nominal SLR and RLR of national systems. + +## 2 Nominal overall loss of the international chain + +Each international analogue and mixed analogue/digital circuit should in principle have a 0.5 dB loss at 1020 Hz. However, some circuits can be operated with higher losses (see 2.1/G.131) and certain analogue and mixed analogue/digital circuits may be operated at zero loss (see 4.2/G.101). Digital circuits have 0 dB transmission loss (see clause 6 below). + +As far as transmission is concerned, there is no strict limit on the number of international circuits which may be interconnected in tandem, provided each analogue and mixed analogue/digital circuit has 0.5 dB nominal loss, and provided there is a 4-wire interconnection. Naturally, the fewer the number of interconnected circuits the better the transmission performance is likely to be. + +NOTE – Information on the actual number of circuits which are found in international connections is given in 3/G.101. + +![Diagram (a) showing reference points for SLR and RLR in a digital international circuit. It depicts a 'National system' connected to an 'International circuit' via a VICP. The diagram shows two parallel paths, 'b' and 'a', with 'X' marks representing components. Reference points for SLR and RLR are indicated by double-headed arrows. On the international circuit side, '0 dBr' is marked at the top and bottom, and 'b', 'VICP', and 'a' are labeled.](547f726730e589392f239257a833ede3_img.jpg) + +Diagram (a) showing reference points for SLR and RLR in a digital international circuit. It depicts a 'National system' connected to an 'International circuit' via a VICP. The diagram shows two parallel paths, 'b' and 'a', with 'X' marks representing components. Reference points for SLR and RLR are indicated by double-headed arrows. On the international circuit side, '0 dBr' is marked at the top and bottom, and 'b', 'VICP', and 'a' are labeled. + +a) In the case of a digital international circuit + +![Diagram (b) showing reference points for SLR and RLR in an analogue or mixed analogue/digital circuit. It is similar to diagram (a) but with a different reference point on the international circuit side, marked as '-0.5 dBr'. The label 'T1204540-92/d01' is present at the bottom right.](a7d78d22e465dea388b31d0739f9d0cd_img.jpg) + +Diagram (b) showing reference points for SLR and RLR in an analogue or mixed analogue/digital circuit. It is similar to diagram (a) but with a different reference point on the international circuit side, marked as '-0.5 dBr'. The label 'T1204540-92/d01' is present at the bottom right. + +b) In the case of an analogue or mixed analogue/digital circuit + +FIGURE 1/G.111 + +Reference points for defining the SLR and RLR for a national system + +## 3 LRs and directional effects in a complete connection + +### 3.1 Nominal LRs for each transmission direction + +Subclauses A.3 and A.4 show how to calculate OLR, the overall loudness rating, of a complete connection. The nominal OLR of an international connection is the sum of + +- the nominal SLR, send loudness rating, of the national sending system (see 4/G.121 and Annex A); +- the nominal CLR, circuit loudness rating, of the international chain (see Annex A); +- the nominal RLR, receive loudness rating, of the national receiving system (see 4/G.121 and Annex A). + +### 3.2 Traffic-weighted mean values of OLRs + +For connections under practical conditions a suitable value of OLR seems to be 10 dB in most cases. + +The long-term objective for the traffic-weighted mean value should lie in the range of 8 to 12 dB. + +An objective for the mean value is necessary to ensure that satisfactory transmission is given to most subscribers. + +#### NOTES + +1 For connections totally free from echo and sidetone problems, investigations have shown the optimum OLR to be somewhat lower than 10 dB, about 5 dB, but the optimum is rather flat so that moderate deviations from the given value have little subjective effect. (However, the "preferred OLR" in a particular application will to some extent depend on what subscribers have become used to. Thus, in some analogue PBXs, internal calls have had a very low OLR. Replacing such a PBX by a digital PBX having a higher OLR might cause some subscriber comments on "low speech levels". Some Administrations have solved this problem by means of a manual volume control in the receive part of the telephone set, the total range of variation being in the order of 10 to 12 dB. Note that in mobile telephony a common practice is to include a volume control which affects both the receive and send sides but in opposite directions.) + +2 The long-term values cannot be attained at this time and an appropriate short-term objective for OLR is a range of 8 to 21 dB. + +3 The 0.5 dB transmission loss of each analogue and mixed analogue/digital circuit in the international chain (see clause 2 above) has been allowed for by noting that the average number of international circuits encountered in international connections is 1.1. (See 3/G.101.) + +As a result, the ranges mentioned above do not include allowances for connections between countries which + +- involve more than one 0.5 dB international circuit; +- involve a single international circuit which has a higher loss than 0.5 dB as permitted by 2.1/G.131. + +4 Clause 1/G.121 gives values for national systems based on the overall objectives of this Recommendation. + +5 The ranges stated for OLR are for planning and do not include measuring and manufacturing tolerances. + +6 Besides loudness, other important factors have to be considered in transmission planning. Sidetone, echo and stability problems may cause degradation of the overall speech quality in a connection. Thus, it is important to adopt an adequate impedance strategy in the national transmission plan to avoid harmful mismatches in the network; see Supplement No. 31/G.121. + +### 3.3 Difference in transmission loss between the two directions of transmission + +The difference in nominal loss between the two directions of transmission on an international connection should not exceed 8 dB, preferably not 6 dB. The asymmetry introduced by each of the two national systems is limited by the provisions of 2.2/G.121. The international circuits could, in practical circumstances outlined in the general remarks in 4/G.101, introduce additional asymmetry. This additional asymmetry will be acceptably small. + +## 4 Variation in time and effect of circuit noise + +### 4.1 Variations in time + +The LR values calculated for national systems (see 4/G.121) do not cover variations in time of the loss of various parts of the national system. Clause 3/G.151 gives the objectives recommended by the CCITT for transmission loss variations on international circuits and national extension circuits as compared with the nominal values. + +### 4.2 Effect of circuit noise + +See Recommendation G.113. + +## 5 Practical limits of the OLR between two operators or one operator and one subscriber + +The same loudness rating limits as between two subscribers should apply. + +## 6 Incorporation of PCM digital processes in international connections + +### 6.1 Connections with a digital 4-wire chain extending to the local exchanges + +As the national network develops, an international telephone connection might have the configuration indicated in Figure 2, in which the analogue/digital interface occurs at the local exchange. In such a connection, the nominal transmission loss introduced by the 4-wire chain of national and international digital circuits is 0 dB. Consequently, the 4-wire chain generally does not contribute to the control of stability and echo. However, part of the loss required to control stability and echo is at the local exchange, as indicated by the R and T pads, the remainder being provided by the balance return loss at the 2-wire/4-wire terminating unit (see also Recommendation G.122). + +![Diagram of an international connection configuration showing National, International, and National segments with various components like LE, DRS, and pads R and T. The diagram shows two local exchanges (LE) connected via a digital 4-wire chain. The chain consists of digital switching (DRS) and digital reference sequences (DRS). The international segment is labeled 'Type 1 circuit (s) 4/G.101'. The diagram includes various points labeled a1, a2, b1, b2, t1, t2, and 0 dBr. The legend indicates that solid lines represent analogue transmission and dashed lines represent digital transmission. Pads R and T are shown at the local exchange interfaces. The diagram is labeled T1204550-92/02.](d0abac95583b52a3b35f74a215567334_img.jpg) + +Diagram of an international connection configuration showing National, International, and National segments with various components like LE, DRS, and pads R and T. The diagram shows two local exchanges (LE) connected via a digital 4-wire chain. The chain consists of digital switching (DRS) and digital reference sequences (DRS). The international segment is labeled 'Type 1 circuit (s) 4/G.101'. The diagram includes various points labeled a1, a2, b1, b2, t1, t2, and 0 dBr. The legend indicates that solid lines represent analogue transmission and dashed lines represent digital transmission. Pads R and T are shown at the local exchange interfaces. The diagram is labeled T1204550-92/02. + +- Analogue transmission +- - - Digital transmission +- R T +| | +| | +Analogue pads (represent nominal loss between 4-wire and 2-wire point including loss of the 2-wire/4-wire terminating unit) +- - - X - - - Digital switching +- | - - - Analogue/digital or digital/analogue coder or decoder +- a, b Virtual international connecting points +- DRS Digital reference sequence +- LE Local exchange + +FIGURE 2/G.111 + +**Example of an international connection in which the digital 4-wire chain extends to a 4-wire local exchange with 2-wire analogue subscriber lines** + +Values of R and T are discussed in 6/G.121, where it is concluded that values can be chosen to cater for the national losses and levels, provided that the CCITT Recommendations for international connections are always met. For example, the sum of R and T will need to be at least so high that the requirements of Recommendation G.122 are met. This should be especially noted in cases when stability balance return losses approach 0 dB at the 2-wire/4-wire terminating unit. Examples of values for R and T that have been adopted by some Administrations are given in Annex C/G.121. + +Other transmission considerations to be taken into account in the planning of connections involving 4-wire local exchanges in a mixed analogue/digital network include system loading and crosstalk. + +Figure 2 also shows R and T as analogue pads. This need not always be the case since under some conditions it might be more practical or necessary to introduce the required loss by means of digital pads. However, if digital pads are used, their detrimental effect on digital data or other services requiring end-to-end bit integrity must be taken into account as indicated in 4.4/G.101 and 4/G.103. + +### 6.2 Mixed analogue/digital connections + +To provide satisfactory transmission on international connections in the mixed analogue/digital period, it is likely that existing national transmission plans will have to be amended or new ones developed to provide for appropriate national extensions. All the relevant CCITT Recommendations should be complied with. The Recommendations concerning national extensions with 4-wire chains extending to 4-wire local exchanges are given in 6/G.121. + +Thus, the transmission planning of transition phases should preferably not involve any degradation of the quality previously experienced. + +## Annex A + +## Explanations related to Recommendations G.111, G.121, G.122, G.131, G.134: properties and uses of loudness ratings + +(This annex forms an integral part of this Recommendation) + +### A.1 General explanations of loudness rating terms as used in the G-Series Recommendations + +#### A.1.1 Loudness rating (LR) + +As used in the G-Series Recommendations for planning; loudness rating is an objective measure of the loudness loss, i.e. a weighted, electro-acoustic loss between certain interfaces in the telephone network. (The nature of the weighting will be dealt with later.) If the circuit between the interfaces is subdivided into sections, the sum of the individual section LRs is equal to the total LR. + +How to determine and to apply LRs in the G-Series Recommendations is described in subclauses A.3 and A.4. The methods are sufficiently accurate for all practical purposes. (Fundamentally, loudness ratings are based on subjective methods as described in Recommendations P.76 and P.78. However, subjectively measured values, in general, vary too much with time and test teams to be really useful for transmission planning.) + +In loudness rating contexts, the subscribers are represented from a measuring point of view by an artificial mouth and an artificial ear respectively, both being accurately specified. + +**A.1.2 overall loudness rating (OLR):** The loudness loss between the speaking subscriber's mouth and the listening subscriber's ear via a connection. + +**A.1.3 send loudness rating (SLR):** The loudness loss between the speaking subscriber's mouth and an electric interface in the network. [The loudness loss is here defined as the weighted (dB) average of driving sound pressure to measured voltage.] + +**A.1.4 receive loudness rating (RLR):** The loudness loss between an electric interface in the network and the listening subscriber's ear. [The loudness loss is here defined as the weighted (dB) average of driving e.m.f. to measured sound pressure.] + +**A.1.5 circuit loudness rating (CLR):** The loudness loss between two electrical interfaces in a connection or circuit, each interface terminated by its nominal impedance which may be complex. [The loudness loss is here approximately equivalent to the weighted (dB) average of the composite electric loss.] + +NOTE – Junction loudness rating (JLR) is a special case of CLR, the terminations being 600 ohms resistive. + +#### **A.1.6 Sidetone loudness losses** + +**A.1.6.1 talker's sidetone, sidetone masking rating (STMR):** The loudness loss between a subscriber's mouth and his (earphone) ear via the electric sidetone path (see Recommendation P.10 for a full definition). + +**A.1.6.2 listener's sidetone rating (LSTR):** The loudness loss between a Hoth-type room noise source and the subscriber's (earphone) ear via the electric sidetone path (see Recommendation P.10 for a full definition). + +#### **A.1.7 Echo loudness losses** + +**A.1.7.1 talker echo loudness rating (TELR):** The loudness loss of the speaker's voice sound reaching his ear as a delayed echo. See 4.2/G.122 and Figure 2/G.131. + +**A.1.7.2 listener echo loudness rating (LELR):** The difference in loudness loss between the speaker's direct voice sound and its delayed echo reaching the listening subscriber's ear. + +**A.1.8 crosstalk receive loudness rating (XRLR):** The loudness loss from a disturbing electric interface to the disturbed subscriber's ear via the crosstalk path. + +### **A.2 Psycho-acoustic model for loudness ratings** + +By the fundamental definition of loudness ratings, a flat loss (i.e. a loss constant with frequency) introduced in a path increases the loudness rating by the same amount. When evaluating the influence of a frequency-dependent loss, however, one needs a psycho-acoustic model of how the brain interprets loudness impressions. Therefore, a short description will be given of a simple model found adequate for loudness rating planning considerations. (See Recommendation P.79 for more complete explanations.) + +The ear can be thought of as a bank of bandpass filters approximately equally spaced on a logarithmic frequency scale. If the sound signal in a certain band exceeds the threshold of hearing, the corresponding filter produces an output. All filter outputs are then added to create an impression of loudness, the rule of addition depending on the sound level. + +For very low sound levels (near the threshold of hearing) the filter outputs are added on a power basis. For normal speech sound levels, the loudness measure can be described as obtained neither as power nor voltage addition but rather as the sum of the logarithm of the filter outputs. The procedure can be described by equation (A.2-1) which covers sound levels from very low to normal. (This algorithm is in effect the same as the one given in Recommendation P.79, only written in a slightly different form.) + +$$LR = L_0 - \frac{10}{m} \log_{10} \left\{ \sum_{i=1}^N K_i \cdot 10^{-0.1mL_i} \right\} \quad (A.2-1)$$ + +where + +$L_0$ is a constant (for instance, $L_0$ is equal to 0 for CLR, LELR), depending on the particular LR in question. + +$N$ is the number of equivalent bandpass filters, the index $i$ refers to filter No. $i$ at frequency $f_i$ . (Usually, the "filters" are chosen with a 1/3-octave spacing in the frequency scale. The appropriate frequency range to consider will be discussed later.) + +$L_i$ is the loss at $f_i$ of the path under study. (Provided the sound level at that frequency is above the threshold of hearing.) + +$m$ (the “loudness growth factor”) is a constant depending on the sound level: + +$m = 0.2$ for normal speech levels; + +$m = 0.5$ for “lower” sound levels (corresponding to voltage addition); + +$m = 1$ for very low sound levels, near the threshold of hearing (corresponding to power addition). + +$m = 0.2$ is applicable for OLR, SLR, RLR, JLR, CLR and sidetone phenomena; while + +$m = 0.5$ and 1 are appropriate for echo and crosstalk. + +$K_i$ is the weighting coefficient at $f_i$ . The $K_i$ 's have the general property that their sum is equal to 1 in the frequency range considered: + +$$\sum_{i=1}^N K_i = 1 \quad (\text{A.2-2})$$ + +The $K_i$ 's are determined by the following factors: + +- voice spectrum of the “average” speaker; +- hearing acuity of the “average” listener; +- frequency response of the “nominal” path typical for the particular LR in question. + +The shape of the $K_i$ -weighting is not very critical. For transmission planning, most often a flat weighting will do. This topic is treated below in subclauses A.3 and A.4. (Note however, that for telephone sets the P.79 weighting is used for SLR, RLR, STMR and LSTR.) + +Equation (A.2-1) can be applied in various loudness-related rating calculations. Examples may be found in Supplement No. 19, Volume V of the *Blue Book*. + +What frequency range should be used in the computations? For LR planning purposes, only that frequency range should be considered in which the transmission is assured. In general, this means from 300 Hz to 3400 Hz for international calls. However, for very weak speech sounds, such as just discernable crosstalk, the proper band for computation is narrower, in the order of 500 Hz to 2000 Hz. This is because the human hearing acuity falls off at the band edges for low level sounds. + +NOTE – The $K_i$ 's are different for the 300-3400 Hz and the 500-2000 Hz bands. + +It is immediately apparent again from equations (A.2-1) and (A.2-2) that a flat loss of $L$ dB will increase the LR by the same amount. It also turns out that if the spread in the $L_i$ -values is moderate, equation (A.2-1) can be simplified to: + +$$\text{LR} = L_0 + \sum_{i=1}^N K_i \cdot L_i \quad (\text{A.2-3})$$ + +This linear approximation is the reason why the total loudness rating of a connection can be computed by simply adding the loudness ratings of its parts. The procedures to follow will be discussed in A.4. [A rule of thumb: if $m = 0.2$ and the spread in $L_i$ is less than 10-15 dB, equation (A.2-3) can be applied.] + +### A.3 Measurement of loudness ratings of telephone sets + +The loudness ratings of telephone sets are determined objectively by special measuring instruments conforming to Recommendations P.64, P.65 and P.79 with regard to the physical implementation and computational algorithm respectively. For analogue sets, the measurement set-up must provide a representative current feeding bridge and may or may not include different lengths of (artificial) unloaded subscriber lines. The parameters usually measured are SLR, RLR and STMR. + +Parameters of further interest to the planner are of course the telephone set input impedance $Z_c$ and/or its return loss against the nominal circuit impedance. + +Note that for STMR measurements the line terminating impedance must be so specified that it represents realistic network conditions, i.e. a termination not necessarily 600 ohms. + +In addition to straightforward STMR measurements, it is useful to determine the so-called “no sidetone line impedance” $Z_{s0}$ , or equivalent sidetone balance impedance. Knowing $Z_{s0}$ in addition to SLR and RLR, the transmission planner is able to estimate the sidetone performance better under the widely varying conditions which may occur in the network. See A.4.3 for further details. (Note that $Z_{s0}$ may vary with the line current.) + +Listener sidetone may cause some subscriber difficulties when modern, high-sensitivity sets having linear microphones are used in noisy environments. To get a quantitative understanding of the problem, the set sending sensitivity curves for both direct (speech) sound and diffuse (room noise) sound should be measured. (See the Handbook on Telephonometry and Recommendation P.64 for details.) The result is preferably presented as the difference: + +$$\text{DELSM} = S_s(\text{diffuse}) - S_s(\text{direct}) \quad (\text{A.3-2})$$ + +(See A.4.3.3.) + +###### NOTES + +1 DELSM is fairly constant with frequency. (The diffuse field sensitivity measurements should be made with an obstacle resembling the human head in front of the handset microphone. The present practice is to use the LR artificial mouth as such an obstacle. However, the detailed measurement procedure is under study.) + +2 The actual shape of the frequency-dependent $K_t$ -weighting in the P.79 algorithm as used for telephone set measurements is of no immediate concern to the transmission planner. However, the P.79 weighting seems not to represent “ordinary people’s” speech and hearing too well. Therefore, if one tries to analyse attenuation distortion and bandwidth limitation effects on loudness only, P.79 results must be interpreted with caution. + +3 Up to now, when making national transmission plans, most Administrations have used other forms of objective measuring instruments to characterize the telephone sets. Translating such a transmission plan into terms of loudness ratings means a corresponding conversion of the “old” telephone set data. This should be done by actually measuring the loudness ratings of typical examples of the sets in use. (There is too much uncertainty in general conversion formulas to obtain LRs from RE, CRE, OREM-B, IEEE-Objective LR, etc.) + +### A.4 Application of loudness ratings in the Series-G Recommendations + +#### A.4.1 General remarks + +Theoretically, one could determine the total attenuation/frequency response between the input and the output ports and compute the LR in question by an algorithm as given in A.2. However, for transmission planning it is far more convenient to evaluate the LR of the individual parts. This is especially true for the present situation with a proliferation of different types of telephone sets allowed in most Administrations’ networks. Therefore, in what follows the telephone set influence on loudness ratings will be characterized by its SLR and/or RLR value(s). + +Most important in transmission planning for loudness performance is to have consistent rules – even if they are simple. To strive for high precision in the computations is rather illusory. For example, the subscriber may control the subjective loudness quite substantially with his handset: voluntarily by pressing it more or less strongly to his ear (10 dB range?) and involuntarily by moving the microphone away from its optimum position. + +#### A.4.2 Normal speech transmission + +Figure A.1 depicts a speech connection between two subscribers, consisting of several cascaded parts. + +![Diagram of a normal speech connection showing loudness ratings (SLR, CLR, RLR) across a network of nodes (W, E) and interfaces (i=1 to N). The diagram illustrates the flow of signal from a 'Send' unit (W) to a 'Receive' unit (E) through a series of interfaces. The top line shows the signal path with nodes W and E, and interfaces labeled SLR(set), CLR1, CLRn, and RLR(set). Below this, three horizontal bars indicate the cumulative loudness ratings: SLR (from W to interface n), RLR (from interface n to E), and OLR (from W to E). The diagram is labeled T1205440-93/d03.](af7916c89a458fdab6c3f443217388ae_img.jpg) + +Diagram of a normal speech connection showing loudness ratings (SLR, CLR, RLR) across a network of nodes (W, E) and interfaces (i=1 to N). The diagram illustrates the flow of signal from a 'Send' unit (W) to a 'Receive' unit (E) through a series of interfaces. The top line shows the signal path with nodes W and E, and interfaces labeled SLR(set), CLR1, CLRn, and RLR(set). Below this, three horizontal bars indicate the cumulative loudness ratings: SLR (from W to interface n), RLR (from interface n to E), and OLR (from W to E). The diagram is labeled T1205440-93/d03. + +FIGURE A.1/G.111 +**LRs in a normal speech connection** + +The send and receive loudness ratings of the telephone sets themselves are designated as SLR(set) and RLR(set) respectively and the circuit loudness ratings as $CLR_n$ . (For explanations, see A.1.) Then, at interface $i = n$ in the direction from S to R we have: + +$$SLR = SLR(\text{poste}) + \sum_{i=1}^n CLR_i$$ + +$$RLR = RLR(\text{poste}) + \sum_{i=n+1}^N CLR_i \quad (\text{A.4-1})$$ + +$$OLR = SLR + RLR$$ + +SLR(set) and RLR(set) are determined (measured) according to the principles described in A.3. + +When the circuit loss is flat with frequency, the CLR is equal to the composite loss of the circuit at the reference frequency 1020 Hz, using the nominal impedances appropriate to the particular interfaces. (See A.1.5 above.) + +If the attenuation distortion is noticeable, the CLR is equal to the average loss over the frequency band 300 Hz to 3400 Hz on a logarithmic frequency scale, i.e. a flat $K_f$ -weighting in equation (A.2-3) and with the constant $L_0 = 0$ . [If the attenuation distortion is exceptionally high, equation (A.2-1) should be used with $m = 0.2$ .] The loss is to be measured or computed as a voltage loss, corrected by a frequency-independent term, i.e. the loss is equal to the sum of the composite loss at 1020 Hz and the voltage loss deviation from the value at 1020 Hz. (This practice is in accordance with 2.4/G.101.) + +NOTE 1 – Some Administrations may instead want to use the so-called composite loss distortion as a basis for computing the CLR of a circuit in their national transmission planning. Moreover, the various aspects of the complete user end-to-end loss distortion is being studied. + +When the loss is determined by measurement, it should be under nominally matched impedance conditions. In practice, this means either between two physical impedances as is the case for 600 ohms measurements or between a low-impedance generator and a high-impedance indicator. Either method can be used, depending on what is most practical. The measurement results do not differ very much. In the latter case, a 6 dB correction must of course be applied. + +It is interesting to note that, for unloaded subscriber cable sections, the CLRs are equal to the composite loss at the reference frequency 1020 Hz with sufficient accuracy for planning purposes, that is, they are equal to the difference in relative levels at the interfaces. (It turns out that, from a loudness point of view, the lower losses at frequencies below 1020 Hz compensate the higher losses at frequencies above 1020 Hz.) + +NOTE 2 – In the particular case of a subscriber cable, the telephone set and the exchange may have different nominal input impedances. Strictly speaking, one should then consider “insertion loss” rather than “composite loss” as the basis for CLR, as a zero length line should be associated with $CLR = 0$ . However, the impedance mismatch between set and exchange impedances usually does not result in a significant composite loss at 1020 Hz. Therefore, the designation “composite loss” may also be used in this case. + +The CLR per kilometer of an unloaded subscriber cable can also be estimated from the cable characteristics by the following expression: + +$$CLR = K\sqrt{R \cdot C} \quad (A.4-2)$$ + +where + +R is the cable resistance in ohms/km; + +C is the cable capacitance in nF/km; + +K is a constant, the value of which is dependent on the cable termination: + +$K = 0.014$ , if $Z_0 = 900$ ohms resistive; + +$K = 0.015$ , if $Z_0 = 600$ ohms resistive; + +$K = 0.016$ , if $Z_0$ is a complex impedance. + +NOTE 3 – “Complex impedance” means here such 3- or 2-element RC impedances as have been chosen by Administrations to resemble the image impedance of unloaded cables. + +NOTE 4 – Equation (A.4-2) gives the image attenuation at about 800 Hz for $K = 0.014$ , and at about 1020 Hz for $K = 0.016$ . Some Administrations have been using the cable image attenuation at a certain frequency (for instance 1600 Hz) as a measure of the permissible attenuation in the subscriber network. However, the same numerical value should not be used automatically as the permissible CLR when transforming the transmission plan into terms of loudness ratings. + +NOTE 5 – Most often the errors in CLR when using equation (A.4-2) are less than 0.4 dB. + +Most modern channel equipment, including digital exchanges, can be considered as having essentially flat attenuation/frequency characteristics when estimating CLRs. An example of a more pronounced channel attenuation distortion can be found in Recommendation G.132, dealing with attenuation/frequency distortion limits for twelve 4-wire circuits in tandem. Assuming a maximum attenuation variation curve just touching the upper corners in Figure 1/G.132, a calculation shows that the attenuation distortion contributes 2.4 dB to the CLR which is to be added to the loss value at 1020 Hz (i.e. about 0.2 dB per circuit). + +NOTE 6 – An OLR = 9 dB may be considered as being well within the optimum range for connection loudness. Interestingly, at that value, the average acoustic loss from the speaker’s mouth to the listener’s ear is about 0 dB, taken over a logarithmic frequency scale. + +#### A.4.3 Sidetone + +##### A.4.3.1 General remarks + +As mentioned above, the sidetone quantities STMR and LSTR refer specifically to the signals reaching the ear via the electric sidetone path. + +##### A.4.3.2 Talker’s sidetone STMR + +STMR can be measured as discussed in A.3, using the actual terminating impedances occurring in the network. + +In many circumstances it may be more convenient to compute STMR from telephone set data and network data. + +For transmission planning purposes, one can use the telephone set loudness ratings and the balance return loss between the line impedance and the sidetone balance impedance. In practice, the following algorithm is generally sufficiently accurate: + +$$\text{STMR} = \text{SLR}(\text{set}) + \text{RLR}(\text{set}) + A_m - 1 \quad (\text{A.4-3})$$ + +where + +SLR(set), RLR(set) refer to the telephone set as before. $A_m$ is a weighted mean of the sidetone balance return loss $A_{rst}$ : + +$$A_m = -\frac{10}{m} \log_{10} \left\{ \sum_{i=1}^N K_i \cdot 10^{-0.1mA_{rst}} \right\} \quad (\text{A.4-4})$$ + +where + +$m = 0.2$ ; the $K_i$ 's are found in Table A.1; and + +$$A_{rst} = 20 \log_{10} \left| \frac{Z_c + Z_{s0}}{2Z_c} \cdot \frac{Z + Z_c}{Z - Z_{s0}} \right| \quad (\text{A.4-5})$$ + +Here, + +$Z_c$ is the input impedance of the set; + +$Z_{s0}$ is the sidetone balance impedance of the set (equivalent); + +$Z$ is the impedance of the line, "seen" by the set when the connection is established. + +NOTE 1 – $A_{rst}$ is about equal to the return loss between $Z_{s0}$ and $Z$ . + +NOTE 2 – When the actual telephone set send and receive sensitivity curves as functions of frequency are known, it is possible to closely simulate STMR measurements by a more elaborate algorithm (see 8/P.79). + +As can be seen from Table A.1 and Figure A.2, there is very little emphasis on the lower frequencies in the STMR weighting. This is because the "human sidetone" path via head bone conduction dominates over the electric path in that frequency range. + +NOTE 3 – STMR = 7 or 8 dB is well within the preferred range of talker's sidetone. At that value, the average acoustic loss from the talker's mouth to his ear via the electric sidetone is typically about 0 dB (averaging done with the $K_i$ weighting given in Table A.1). + +##### A.4.3.3 Listener's sidetone rating (LSTR) + +High room noise at the listening subscriber's premises disturbs the received speech in several ways: + +- By noise picked up by the "free" ear. This disturbance can be disregarded here because the brain has a stereophonic analysis ability to "switch off" irrelevant signals coming from the wrong direction. +- By noise leaking past the ear at the handset ear. +- By noise picked up by the handset microphone and transmitted to the handset ear via the electric sidetone path. + +In practice, the phenomena under c) often are the most troublesome. (Of course, they are also the only ones within the control of the transmission planner.) + +TABLE A-1/G.111 + +##### **STMR weighting** + +| $i$ | $F_i$ (kHz) | $K_i$ | +|-----|-------------|-------| +| 1 | 0.2 | 0 | +| 2 | 0.25 | 0.01 | +| 3 | 0.315 | 0.02 | +| 4 | 0.4 | 0.03 | +| 5 | 0.5 | 0.04 | +| 6 | 0.63 | 0.05 | +| 7 | 0.8 | 0.08 | +| 8 | 1 | 0.12 | +| 9 | 1.25 | 0.12 | +| 10 | 1.6 | 0.12 | +| 11 | 2 | 0.12 | +| 12 | 2.5 | 0.12 | +| 13 | 3.15 | 0.12 | +| 14 | 4 | 0.05 | + +![Graph of STMR weighting Ki versus Frequency (kHz) on a log-log scale. The curve starts at (0.2, 0), rises to (1, 0.12), stays flat at 0.12 until approximately 2.5 kHz, and then drops to 0 at 4 kHz. The y-axis is labeled Ki and has a major tick at 0.5. The x-axis is labeled Frequency and has major ticks at 0.1, 0.2, 0.5, 1, 2, 3, 8, and 10 kHz. A small label T1205450-93/d04 is present at the bottom right of the graph area.](cbc4516eb885829fe8c9dabc0946dcbe_img.jpg) + +Graph of STMR weighting Ki versus Frequency (kHz) on a log-log scale. The curve starts at (0.2, 0), rises to (1, 0.12), stays flat at 0.12 until approximately 2.5 kHz, and then drops to 0 at 4 kHz. The y-axis is labeled Ki and has a major tick at 0.5. The x-axis is labeled Frequency and has major ticks at 0.1, 0.2, 0.5, 1, 2, 3, 8, and 10 kHz. A small label T1205450-93/d04 is present at the bottom right of the graph area. + +FIGURE A.2/G.111 +**Sidetone weighting $K_i$ as given in Table A.1** + +Investigations have shown that, at low frequencies, the earcap leakage dominates over the electric sidetone path in much the same way as bone conduction does for the talker's sidetone. Therefore, the same $K_i$ -weighting as for STMR can be applied. (At least if the earphone cap is not too awkwardly shaped.) Thus, the LSTR may be computed from STMR and the weighted mean of DELSM, the difference between diffuse and direct sound sensitivity curves of the set (see A.3): + +$$\text{LSTR} = \text{STMR} + D$$ + +$$D = - \sum_{i=1}^N K_i \cdot (\text{DELSM})_i \quad (\text{A.4-6})$$ + +###### NOTES + +1 For modern telephone sets with linear microphones, $D$ is in the order of 1.5 to 4 dB. The value of $D$ is, to some extent, dependent on the handset geometric shape but not on the room noise level. Sets with carbon microphones, however, typically have a sensitivity threshold, making them somewhat less susceptible to room noise. Their $D$ -value is in the order of 6 to 8 dB at 60 dBA room noise. However, some modern designs using linear microphones (notably headsets) also incorporate a sensitivity threshold making them less susceptible to room noise. + +2 Physically, above 800 to 1000 Hz, the earcap shields the listening ear from a direct pick-up of room noise but the electric path provides an indirect contribution. Under conditions of high room noise (60 dBA or higher) and high loss connections, the listener's sidetone rating should be greater than 13 dB. This corresponds approximately to the earcap having an equivalent room noise shielding effect of 5 to 6 dB at the higher frequencies. + +#### A.4.4 Echo and crosstalk + +##### A.4.4.1 General remarks + +Echo and crosstalk sounds are much less loud than normal speech. Therefore, the "loudness growth factor", $m$ in the evaluation algorithm [equation (A.2-1)] should be chosen higher than 0.2. Experience has shown the following procedure to be appropriate: + +The total loudness rating path under consideration is divided into parts, whose loudness ratings are added. The parts are: + +- 1) send and receive circuits of the telephone set(s); +- 2) the purely electric circuits. + +For the telephone set(s), the normal SLR and RLR values are used. For the electric circuits, the loudness loss is evaluated with $m = 0.5$ or 1, corresponding to voltage or power addition. (Which $m$ -value and which frequency range to use will be given below for each application.) + +The electric circuit loudness loss $LC$ is computed according to equation (A.2-1) with a flat weighting over the (logarithmic) frequency band 300 to 3400 Hz. The logarithmic band is divided into $(N-1)$ equal sections, i.e. by $N$ points. + +$$LC(m) = - \frac{10}{m} \log_{10} \sum_{i=1}^N K_i \cdot 10^{-0.1mL_i} \quad (\text{A.4-7})$$ + +where + +$$K_1 = K_N = \frac{1}{2(N-1)}$$ + +$$K_i = \frac{1}{N-1}; i = 2 \dots (N-1) \quad (\text{A.4-8})$$ + +If the summation (or integration) is done on a linear frequency scale, equation (A.4-7) transforms into + +$$LC(m) = \frac{1}{m} C - \frac{10}{m} \log_{10} \int_{300}^{3400} 10^{-0.1mL(f)} \frac{1}{f} df \quad (A.4-9)$$ + +where + +$$C = 10 \log_{10} \left\{ \ln \left( \frac{f_2}{f_1} \right) \right\} \quad (A.4-10)$$ + +Thus, if + +$$f_1 = 300 \text{ Hz}, f_2 = 3400 \text{ Hz}, \text{ then } C = 3.9 \text{ dB} \quad (A.4-11)$$ + +and if + +$$f_1 = 500 \text{ Hz}, f_2 = 2000 \text{ Hz}, \text{ then } C = 1.4 \text{ dB} \quad (A.4-12)$$ + +##### A.4.4.2 Talker echo loudness rating (TELR) + +Following the principles given in A.4.4.1, we have + +$$TELR = SLR(\text{set}) + RLR(\text{set}) + L_e \quad (A.4-13)$$ + +where SLR(set) and RLR(set) refer to the telephone set involved. + +The echo loss $L_e$ is computed according to equation (A.4-7) or (A.4-9) with $m = 1$ , $f_1 = 300 \text{ Hz}$ , $f_2 = 3400 \text{ Hz}$ . + +$$L_e = LC(m = 1) \quad (A.4-14)$$ + +###### NOTES + +1 For TELR = 9 dB, the echo of the speaker's voice would reach his ear with about 0 dB loss averaged over a logarithmic frequency scale. + +2 The value of $L_e$ computed by this method is identical to the value obtained using the method given in 4.2/G.122. + +3 The difference between talker's sidetone and talker echo is that the latter of course is associated with delay. Recent investigations indicate that, at about 2-4 ms delay, the effect of talker echo begins to be clearly distinguishable from even a strong talker's sidetone. To avoid subscriber annoyance from echo, the echo needs more suppression than sidetone signals, all the more so, the longer the delay is. The problem is under study. + +4 For circuits terminated by a digital 4-wire telephone set, an echo path is introduced by the acoustic path from earphone to microphone. In this case the echo path loss [ $L_i$ or $L(f)$ in equations (A.4-7) and (A.4-9) respectively] includes the acoustic path as well as the send and receive characteristics of the handset. It is practical to relate a weighted measure of the echo path loss to the 0 dBr 4-wire points, using equation (A.4-7) or (A.4-9) with $m = 1$ . This weighted measure is designated "terminal coupling loss" (TCL). + +##### A.4.4.3 Listener echo loudness rating (LELR) + +LELR is a weighted average of the listener echo LE over the frequency band 300 to 3400 Hz. The weighting should be done according to equations (A.4-6) or (A.4-8) with $m = 0.5$ . + +NOTE – In North American practice a term WEPL, "weighted echo path loss", is used. When one computes WEPL, the factor $m = 0.5$ but the weighting is flat over a linear frequency scale. In general, LELR and WEPL do not differ very much numerically. + +##### A.4.4.4 Crosstalk receive loudness rating (XRLR) + +The harmful effect of crosstalk is of course directly related to the actual speech level in the disturbing channel. Unfortunately, there is no firm relation between send loudness rating (SLR) and speech level in telephone networks, as investigations have shown. Therefore, it would be misleading to include SLR in a crosstalk loudness rating. Expected speech levels (mean and standard deviation) have to be estimated from other network data. The problem is dealt with in Recommendation P.16. + +Following the principles given in A.4.4.1, we have + +$$\text{XRLR} = \text{RLR}(\text{set}) + L_x \quad (\text{A.4-15})$$ + +where RLR(set) refers to the telephone set involved. + +The crosstalk $L_x$ is computed according to equation (A.4-9) or (A.4-8) with $m = 1$ , $f_1 = 500$ Hz, $f_2 = 2000$ Hz. + +$$L_x = \text{LC}(m = 1) \quad (\text{A.4-16})$$ + +NOTE – In practice, the crosstalk value at around 1020 Hz has been found to represent $L_x$ fairly well (see A.3.1/G.134). + +# Annex B + +## Recommended values and limits of the loudness ratings for circuits in international connections + +(This annex forms an integral part of this Recommendation) + +The connection configuration is shown in Figure B.1 and the LR values in Table B.1. + +The interfaces between the national and international part of the connection are at the Virtual International Connecting Points having the relative levels 0 dBr (sending) and 0 dBr or $-0.5$ dBr (receiving); see 1.1. + +NOTE – The long-term traffic weighted mean values of LRs should be the same for each main type of subscriber categories, such as urban, suburban and rural. Considering the mean value only for the whole country in the transmission plan might lead to a discrimination against some important customer groups. + +![Diagram of an international connection showing loudness rating designations.](f388cbdae6f0ef3aeb96fdf9984d1284_img.jpg) + +The diagram illustrates a transmission path for an international connection. It is divided into three main segments by vertical lines representing Virtual International Connecting Points (VICPs). On the left, a 'National system' contains a sending telephone set 'S'. The loudness rating from the telephone to the first VICP is labeled 'SLR'. The middle segment is the 'International system', with the loudness rating between the two VICPs labeled ' $\Sigma$ CLR'. On the right, another 'National system' contains a receiving telephone set 'R'. The loudness rating from the second VICP to the telephone is labeled 'RLR'. A bottom horizontal line with arrows at both ends spans the entire path from the telephone 'S' to the telephone 'R', labeled 'OLR'. The diagram also includes telephone handset icons at the far left and far right ends. A small code 'T1204560-92/d05' is located at the bottom right of the diagram. + +Diagram of an international connection showing loudness rating designations. + +FIGURE B.1/G.111 +Designation of LRs in an international connection + +TABLE B.1/G.111 + +### **LR values as cited in Recommendations G.111 and G.121** + +| | SLR | CLR
(per circuit) | RLR | OLR | +|--------------------------------------------------------------|-----------------------------------------|--------------------------------------------|------------------------------------------------|----------------------------------------------------------| +| Traffic-weighted mean values:

long term
short term | 7-9 b)
7-15 b) | 0-0.5 e)
0-0.5 e) | 1-3 b), f)
1-6 b), f) | 8-12 a), e), f)
8-21 a), c), f) | +| Maximum values for an
average-sized country | 16.5 c) | | 13 c) | | +| Minimum value | +2 d) | | | | + +a) See subclause 3.2. +b) See subclause 1/G.121. +c) See subclause 2.1/G.121. +d) See subclause 3/G.121. The value of +2 dB is for further study. +e) For a digital circuit CLR = 0 dB. For an analogue or mixed analogue/digital circuit CLR = 0.5 dB. (If the attenuation distortion with frequency is pronounced, the CLR may increase by 0.2 dB. See A.4.2.) +f) See also the remarks made in 3.2. + +# **Annex C** + +## **Translation of LR values into CRE values** + +(This annex forms an integral part of this Recommendation) + +A full discussion can be found in [1], on the general relations between reference equivalents (REs), corrected reference equivalents (CREs), and loudness ratings (LRs). Strictly speaking, one should make a distinction between: + +- CREs as derived by computation from subjective REs; +- R25 equivalents measured subjectively; +- Objective R25 equivalents (OR25Es) measured objectively. + +However, Administrations seem to use the term CRE for all three categories, and this practice has been adopted in this annex. + +The relation between CREs and LRs can be written as follows: + +$$\text{SCRE} = \text{SLR}_w + x$$ + +$$\text{RCRE} = \text{RLR}_w + y$$ + +(The index w here indicates a measurement according to Recommendation P.79, wideband, 0.2-4 kHz). + +In [2], we find + +$$x = 5; y = 5$$ + +However, these values are only general averages. Administrations should determine $x$ and $y$ by actual objective LR measurements on those typical sets which have been assigned CRE values in their national networks. Large variations may be found for specific sets, compared to the general averages. + +# References + +- [1] CCITT Recommendation *Loudness ratings (LRs) in an international connection*, Rec. G.111, Annex D, *Blue Book*, Geneva, 1989. +- [2] CCITT Recommendation *Corrected reference equivalents (CREs) and loudness ratings (LRs) in an international connection*, Rec. 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b/marked/G/T-REC-G.175-200005-I_PDF-E/raw.md @@ -0,0 +1,537 @@ + + +![ITU logo: A globe with the letters ITU and a lightning bolt.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with the letters ITU and a lightning bolt. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +**G.175** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +(05/2000) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +International telephone connections and circuits – +Transmission plan aspects of special circuits and +connections using the international telephone connection +network + +--- + +**Transmission planning for private/public +network interconnection of voice traffic** + +ITU-T Recommendation G.175 + +(Formerly CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS + +## TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| General definitions | G.100–G.109 | +| General Recommendations on the transmission quality for an entire international telephone connection | G.110–G.119 | +| General characteristics of national systems forming part of international connections | G.120–G.129 | +| General characteristics of the 4-wire chain formed by the international circuits and national extension circuits | G.130–G.139 | +| General characteristics of the 4-wire chain of international circuits; international transit | G.140–G.149 | +| General characteristics of international telephone circuits and national extension circuits | G.150–G.159 | +| Apparatus associated with long-distance telephone circuits | G.160–G.169 | +| Transmission plan aspects of special circuits and connections using the international telephone connection network | G.170–G.179 | +| Protection and restoration of transmission systems | G.180–G.189 | +| Software tools for transmission systems | G.190–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | G.500–G.599 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | + +For further details, please refer to the list of ITU-T Recommendations. + +# **Transmission planning for private/public network interconnection of voice traffic** + +## **Summary** + +This ITU-T Recommendation deals with the digital interconnection of public ISDN/PSTN and private networks. The primary application is to the overall quality of speech transmission for 3.1 kHz voiceband telephony using handsets, independent of all other types of services (e.g. facsimile and voiceband data) provided by those networks. The intention is to give guidance for transmission planning purposes, not only for a given network operator, but also for negotiations between the involved network operators. + +###### **Source** + +ITU-T Recommendation G.175 was revised by ITU-T Study Group 12 (1997-2000) and approved under the WTSC Resolution 1 procedure on 18 May 2000. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSC Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2001 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +## CONTENTS + +| | Page | +|-------------------------------------------------------------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 Normative references ..... | 1 | +| 3 Abbreviations..... | 2 | +| 4 Definitions ..... | 2 | +| 5 Reference configurations ..... | 4 | +| 6 Basic planning principle – the impairment factor method in conjunction with the E-Model ..... | 7 | +| 7 Planning method and limits ..... | 9 | +| 7.1 Planning method ..... | 9 | +| 7.2 Main parameters..... | 11 | +| 7.3 Quality expectation and absolute upper planning limits ..... | 12 | +| 7.4 Use of the E-Model..... | 12 | +| 7.4.1 Input parameters ..... | 13 | +| 7.4.2 Performing the calculation..... | 14 | +| 7.4.3 Default values ..... | 15 | +| 8 Implementation of echo cancellers ..... | 15 | + +# **Transmission planning for private/public network interconnection of voice traffic** + +# **1 Scope** + +Most of the ITU-T Recommendations in the G-series are presently based on configurations where the national part of an international connection is usually terminated by a single analogue telephone set or by a digital terminal. Consequently, these ITU-T Recommendations do not take into account PABXs (Private Automatic Branch Exchange) or private networks. However, modern private networks, mainly those of large size and/or using new technologies, will contribute in a specific, possibly significant amount to the overall transmission quality. + +This ITU-T Recommendation deals with the digital interconnection of public ISDN/PSTN and private networks. The primary application is to the overall quality of speech transmission for 3.1 kHz voiceband telephony using handsets, independent of all other types of services (e.g. facsimile and voiceband data) provided by those networks. The intention is to give guidance for transmission planning purposes, not only for a given network operator, but also for negotiations between the involved network operators. + +For the purpose of this ITU-T Recommendation, only call paths between the private network and other networks (private or public) including telephone sets or other speech terminals are considered. Consequently, the provision of through-connections between two interfaces to other networks, or a call path between two terminals inside the same network are not covered by this ITU-T Recommendation. + +NOTE – Although in principle the planning of internal- and through-connections of the Private Network is not covered here, the methods and rules described in this ITU-T Recommendation may be used for those applications as well. + +# **2 Normative references** + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- [1] ITU-T Recommendation G.100 (1993), *Definitions used in Recommendations on general characteristics of international telephone connections and circuits.* +- [2] ITU-T Recommendation G.101 (1996), *The transmission plan.* +- [3] ITU-T Recommendation G.107 (2000), *The E-Model, a computational model for use in transmission planning.* +- [4] ITU-T Recommendation G.108 (1999), *Application of the E-model: A planning guide.* +- [5] ITU-T Recommendation G.109 (1999), *Definition of categories of speech transmission quality.* +- [6] ITU-T Recommendation G.113 (1996), *Transmission impairments.* +- [7] ITU-T Recommendation G.122 (1993), *Influence of national systems on stability and talker echo in international connections.* + +- [8] ITU-T Recommendation G.165 (1993), *Echo cancellers*. +- [9] ITU-T Recommendation G.168 (2000), *Digital network echo cancellers*. +- [10] ITU-T Recommendation G.703 (1998), *Physical/electrical characteristics of hierarchical digital interfaces*. +- [11] CCITT Recommendation G.711 (1988), *Pulse code modulation (PCM) of voice frequencies*. + +# 3 Abbreviations + +This ITU-T Recommendation uses the following abbreviations: + +| | | +|------|------------------------------------------------| +| ATM | Asynchronous Transfer Mode | +| DCME | Digital Circuit Multiplication Equipment | +| ETSI | European Telecommunication Standards Institute | +| %GoB | Percentage Good or Better | +| ICP | International Connection Point | +| ISDN | Integrated Services Digital Network | +| LSTR | Listener SideTone Rating | +| MOS | Mean Opinion Score | +| OLR | Overall Loudness Rating | +| PABX | Private Automatic Branch eXchange | +| PCM | Pulse Code Modulation | +| %PoW | Percentage Poor or Worse | +| PSTN | Public Switched Telephone Network | +| qdu | Quantizing Distortion Unit | +| RLR | Receiving Loudness Rating | +| SLR | Sending Loudness Rating | +| STMR | SideTone Masking Rating | +| TELR | Talker Echo Loudness Rating | +| VPN | Virtual Private Network | +| WEPL | Weighted Echo Path Loss | + +# 4 Definitions + +This ITU-T Recommendation defines the following terms: + +**4.1 private network:** The term "private" is normally used in conjunction with several PABXs forming a network, mainly in an application for a restricted user group. In complement, the term "public" is usually used to describe main national or regional telecommunication networks providing services to general public. + +The following list, specifying in more detail the definition of a private network, is also based on the assumption that the call path within the private network is contributing a possibly significant amount of transmission impairments to the overall transmission quality, such as loss, transmission time, number of qdus, etc. + +The term "private network" is defined as follows: + +- 1) It consists normally of more than one switching equipment (PABX), connected via private or leased lines, forming a network, independent of its structure and hierarchy. Switching equipment and leased lines can be either digital or analogue. +- 2) It provides switching functions and all other features only to a single customer or a group of customers, but is not accessible to everyone. +- 3) There is no limitation by its geographical size, it is not restricted to the national area and it is not limited on the number of extensions and access points to other networks. + +A private network consists of private local exchanges providing interfaces for all types of terminal elements and for transmission elements to other private local or private transit exchanges and private transit exchanges with interfaces for transmission elements to other private transit or private local exchanges. + +**4.2 public network:** The term "public network" is used in this ITU-T Recommendation for all networks providing their switching functions and features not only to a specific user group, but also to the general public. The word "public" is not related to the legal status of the network operator. Public networks can be restricted to only a limited size of specific features and switching functions. + +Furthermore, public networks may provide access points only in a specific geographical area. From the point of view of a connection, public networks are mainly "transit networks". However, they may also be considered as a combination of "transit and terminating networks" in cases where the public network operator is also providing terminal equipment such as telephone sets, PABXs, or PABX-Features. + +**4.3 network elements:** All the components forming a connection can be divided into three main groups. The interconnection between private and public network is shown in the reference configurations of Figures 1 through 4. The private network is comprised of terminal elements, switching elements and transmission elements. + +**4.4 types of traffic:** In the case of some private networks, the "main types of traffic" via other networks (mainly public networks) may be taken into account for a possible higher amount of permitted impairments within the private network. The inclusion of the type of external traffic into planning enables the planner, wherever this is possible, to extend the limits for specific parameters (e.g. transmission time) within the private network, resulting in a more economical design of the network. + +As a basic distinction for the traffic via public networks, three different types can be identified for planning purposes and with respect to the amount of transmission impairments. Referred to the switching element (local exchange) of the public network providing the access to the private network, *Local Traffic* means all connections in the local public network or in a restricted geographical area of the public network. + +A second type of traffic is the *National Long Distance Call Traffic*, which designates all calls in the entire area of a country. Usually this area is identical to the area of coverage of the major public network(s) in this country. + +Finally, *International Calls* must be considered to contribute in most cases with a higher amount of transmission impairments than national calls. + +The distinction into these types of traffic may support negotiations between public and private network operators, not only for the partitioning of transmission impairments, but also in conjunction with other technical aspects, such as the correct insertion of echo cancellers, the use of ATM with nodes in different networks, etc. + +**4.5 access to the public network:** Among others, the type of access to a public network may also influence the transmission planning of the private network and may be helpful for negotiations between the network operators. "Access" in this context means not only the physical characteristics of the interfaces between public and private networks, but also the point of access with respect to the hierarchy of the public network and to additional features for private networks, provided by the public network. For large private networks, the point of access does not need to be identical to the access for single subscribers. According to the scope of this ITU-T Recommendation, only digital interfaces for the access to public networks are considered. + +**4.5.1 digital access at the local exchange:** In most cases the access to the public network will be provided by a local exchange, or by a comparable switching element in the same hierarchy of the public network, serving the area of the respective switching element within the private network. The physical characteristics of these digital interfaces will follow standardized and commonly used frame structures and bit rates, as described in ITU-T Recommendation G.703 [10]. + +**4.5.2 digital access at higher hierarchies (e.g. transit exchange):** For large and complex private networks with a high number of access channels to the public network, it could be advantageous for both public and private network operators to access the public network in a higher hierarchy (e.g. a transit exchange), bypassing the local exchange. This can be done either for the entirety of all access channels, or only for those channels carrying exclusively long distance or international traffic. In both applications, physical interfaces with higher bit rates and fibre optics as the transmission media may be used. + +**4.5.3 virtual private networks (VPN):** The meaning of the term Virtual Private Network (VPN) in this context is related to a feature where connections between two switching elements of the private network are established via switching and transmission elements of a public network on a "call-by-call" basis instead of a fixed leased line. For planning purposes, such a routing should be considered as part of the private network, taking into account that the impairments of a VPN may vary for every connection contrary to a fixed leased line. + +**4.6 access to other private networks:** Considering the access to another private network, it is necessary to clearly identify if there is in fact a distinction between these two networks with respect to the private network definition in 4.1, or if these two networks may be considered as one network for transmission planning. The planning guidelines in this ITU-T Recommendation may be also advantageous mainly in those cases, where the interconnection is only used for calls between these two networks without any routing via a public network. + +While standardized interfaces and access-points will be commonly used for the access to public networks, a wider variety of physical characteristics with respect to the used frame structures, bit rates and transmission media must be considered for the interconnection between different private networks. For transmission planning, it seems important to identify if the interconnection is performed directly, or via an additional transmission element (such as a leased line, radio, or satellite link etc.), which contributes with further impairments. + +# **5 Reference configurations** + +Due to the variety of hierarchies, structures, routing, and number and types of network elements in a private network, each connection investigated will result in a different reference configuration. Therefore, it is not possible to create only one basic figure for the whole task of private network planning. Figures 1 to 4 are to be considered only as examples, used mainly for definitions in this ITU-T Recommendation. + +The basic reference configuration for the interconnection between a public and a private network is shown in Figure 1. The private network contains transit and local exchanges with its terminals. The public network is only shown up to the international connection point of an international switching centre. + +![Diagram showing the basic reference configuration for the interconnection between private and public networks. The diagram is divided into 'Private network' (left) and 'Public network' (right) by a vertical dashed line. On the private network side, there are two sets of components: 'Private Local A' and 'Private Transit B' connected to 'Private Transit A'; and 'Private Local B' and 'Private Transit C' connected to a 'VPN' box. The 'VPN' box connects to the public network. The public network side includes 'Local exchange', 'Transit exchange', and 'International switching center'. Three access points are shown: T_I (Access point to international switching center), T_T (Access point to transit exchange), and T_L (Access point to local exchange). The ICP (International Connection Point) is located at the far right of the public network. A legend at the bottom left defines the acronyms: ICP, T_L, T_T, T_I, and VPN. A reference code 'T1208350-96' is in the bottom right.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg) + +ICP International Connection Point + $T_L$ Access point to local exchange of public network + $T_T$ Access point to transit exchange of public network + $T_I$ Access point to international switching center +VPN Virtual Private Network + +T1208350-96 + +Diagram showing the basic reference configuration for the interconnection between private and public networks. The diagram is divided into 'Private network' (left) and 'Public network' (right) by a vertical dashed line. On the private network side, there are two sets of components: 'Private Local A' and 'Private Transit B' connected to 'Private Transit A'; and 'Private Local B' and 'Private Transit C' connected to a 'VPN' box. The 'VPN' box connects to the public network. The public network side includes 'Local exchange', 'Transit exchange', and 'International switching center'. Three access points are shown: T\_I (Access point to international switching center), T\_T (Access point to transit exchange), and T\_L (Access point to local exchange). The ICP (International Connection Point) is located at the far right of the public network. A legend at the bottom left defines the acronyms: ICP, T\_L, T\_T, T\_I, and VPN. A reference code 'T1208350-96' is in the bottom right. + +**Figure 1/G.175 – Basic reference configuration for the interconnection +between private and public network** + +It is assumed that the permitted impairments between the access points for calls within the national network are partitioned symmetrically with reference to the International Connection Point (ICP), which will be considered as a virtual centre of the public network. Since calls can be terminated on both sides of private networks in the same configuration, it seems sufficient to draw Figure 1 in this simple way. From the planning point of view, the private network is also divided into local exchanges and into higher level transit exchanges, similar to the public network. The interconnection between the private and the public network is assumed in three different configurations. The access $T_L$ represents the standard interconnection to the local exchange of the public network. Further types of access called $T_T$ and $T_I$ are bypassing the local exchange and entering the public network in a higher hierarchy, either in a transit exchange or directly enter the international switching centre. + +Figures 2 through 4 present in more detail some examples of possible configurations within the private network, in conjunction with different types of access to the public network. + +![Diagram of a private network with fully digital routing. It shows a digital telephone set connected to a Private Local SE, which is connected via a TE to a Private Transit B SE, which is connected via a TE to a Private Transit A SE. The Private Transit A SE is connected to three digital access points: T_L (local exchange), T_T (transit exchange), and T_I (international switching center). An operator is shown connected to the Private Transit A SE. Reference T1208360-96 is present.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg) + +TL Digital access point to local exchange + TT Digital access point to transit exchange + TI Digital access point to international switching center + SE Switching Element + TE Transmission Element + +T1208360-96 + +Diagram of a private network with fully digital routing. It shows a digital telephone set connected to a Private Local SE, which is connected via a TE to a Private Transit B SE, which is connected via a TE to a Private Transit A SE. The Private Transit A SE is connected to three digital access points: T\_L (local exchange), T\_T (transit exchange), and T\_I (international switching center). An operator is shown connected to the Private Transit A SE. Reference T1208360-96 is present. + +**Figure 2/G.175 – Private network with fully digital routing** + +![Diagram of a private network with analogue/digital routing. It shows an analogue telephone set connected to a Private Local SE, which is connected via a TE to a Private Transit B SE (containing an analogue/digital converter), which is connected via a TE to a Private Transit A SE. The Private Transit A SE is connected to three digital access points: T_L (local exchange), T_T (transit exchange), and T_I (international switching center). Reference T1208370-96 is present.](e9314c83043183351ed74908e9bf2f90_img.jpg) + +TL Digital access point to local exchange + TT Digital access point to transit exchange + TI Digital access point to international switching center + SE Switching Element + TE Transmission Element + +T1208370-96 + +Diagram of a private network with analogue/digital routing. It shows an analogue telephone set connected to a Private Local SE, which is connected via a TE to a Private Transit B SE (containing an analogue/digital converter), which is connected via a TE to a Private Transit A SE. The Private Transit A SE is connected to three digital access points: T\_L (local exchange), T\_T (transit exchange), and T\_I (international switching center). Reference T1208370-96 is present. + +**Figure 3/G.175 – Private network with analogue/digital routing** + +![Diagram of a private network in conjunction with a digitally-connected wireless telephone. The diagram shows a 'Wireless telephone set' connected to a 'Base station' via a wireless link. The Base station is connected to a 'Private Local' switching element (SE). This SE is connected to a transmission element (TE), which is connected to another transmission element (TE), which is connected to a 'Private Transit' switching element (SE). On the right side of the Private Transit SE, three horizontal lines represent different network interfaces labeled T_L, T_T, and T_I from bottom to top. A reference code 'T1208380-96' is shown near the bottom right of the diagram.](d4af765160d04ecef538e5066006dc77_img.jpg) + +TL Digital access point to local exchange + TT Digital access point to transit exchange + TI Digital access point to international switching center + SE Switching Element + TE Transmission Element + +T1208380-96 + +Diagram of a private network in conjunction with a digitally-connected wireless telephone. The diagram shows a 'Wireless telephone set' connected to a 'Base station' via a wireless link. The Base station is connected to a 'Private Local' switching element (SE). This SE is connected to a transmission element (TE), which is connected to another transmission element (TE), which is connected to a 'Private Transit' switching element (SE). On the right side of the Private Transit SE, three horizontal lines represent different network interfaces labeled T\_L, T\_T, and T\_I from bottom to top. A reference code 'T1208380-96' is shown near the bottom right of the diagram. + +**Figure 4/G.175 – Private network in conjunction with a digitally-connected wireless telephone** + +# 6 Basic planning principle – the impairment factor method in conjunction with the E-Model + +In general, the quality of speech transmission via telephone channels is based on a subjective judgement by the users at both ends. Therefore, transmission planning as given in ITU-T Recommendation G.101 [2] is, in principle, derived from an end-to-end consideration in conjunction with a partitioning of all relevant parameters between different networks, or parts of a network, where applicable. For private networks, this method was in common use in the field of regulation for all calls via the public network, providing limits for the private network between the acoustical interface of the telephone set and an electrical interface to the public network. These limits were defined to guarantee a sufficient quality for all calls (national and international). + +In conjunction with increasing liberalization in many countries, the responsibility for a sufficient voice transmission quality is now shifted to the private network operator. However, planning of private networks with respect to voice transmission quality needs knowledge and experience in the field of transmission parameters and their influence to quality. Therefore, it seems necessary to provide a planning method, easy to handle and accompanied by tutorial information and planning tools. This is the main task of this ITU-T Recommendation. + +The basic planning principle as used in this ITU-T Recommendation deviates from previous planning methods for private/public network interconnection scenarios. These interconnection scenarios are not covered by other ITU-T Recommendations of the G.100-series, which still provide good guidance for end-to-end transmission planning. For all configurations subject to this ITU-T Recommendation, the planning of speech transmission quality should be based on an end-to-end consideration rather than on a specification of individual objective parameter limits. End-to-end speech transmission quality is expressed in terms of the E-Model Rating $R$ , as a result of calculations with the E-Model (described in ITU-T Recommendation G.107 [3]). The E-Model is a planning tool which is based on the equipment impairment factor method, as described in ITU-T Recommendation G.113 [6]. The E-Model Rating $R$ can be transformed into other quality measures, which have been + +used in transmission planning before, such as Mean Opinion Score (MOS), Percentage Good or Better (%GoB) or Percentage Poor or Worse (%PoW), according to Annex B/G.107. + +It should be noted that the preferable purpose of network planning is to control the summation of transmission impairments, caused by the different network elements in all possible configurations. It is not the task of network planning to limit the transmission impairment of a specific network element. Unless indicated otherwise, it is assumed that transmission, switching and terminal elements in general are designed to meet all relevant requirements as given in ITU-T Recommendations and in international or national standards applicable for this type of element. + +The introduction of a quality issue for planning purposes also enables the private network operator to make the design of the network on a cost versus quality relation, taking into account the specific requirements for the private network. + +Transmission planning based on the E-Model as recommended in this clause provides a prediction of the expected quality, as perceived by the user, for an investigated connection. Based on subjective testing users perception is expressed in terms of MOS, %GoB or %PoW. During transmission planning, however, it is not practical to perform subjective tests. Therefore, a method must be provided which enables the planner to combine by calculation all existing transmission impairments in the given connection to a total value of impairment. This calculation must be performed by using an algorithm based on subjective testing. In telephone connections consisting of a variety of network elements, different transmission parameters may also simultaneously contribute to the total impairment. Therefore, the planning method used must also incorporate combination effects. + +A planning method with the approach to meet the requirements given above is available with the impairment factor method [6] in conjunction with the E-Model [3]. + +Based on an end-to-end assessment for each transmission parameter (including the type and number of low bit-rate codecs) impairment values are derived. This method accounts for low bit-rate coding devices as well as for impairments introduced by standard PCM coders and for impairments not directly related to digital processing. + +The impairment factor method is based on the assumption that transmission impairments can be transformed into psychological factors and that these psychological factors are additive on the "Psychological Scale". An appropriate mathematical algorithm is provided by the E-Model, with which the different transmission parameters can be transformed into different "Impairment Factors". This method and the algorithm of the E-Model also include the combination effects of those impairments in the considered connection which occur simultaneously as well as some masking effects. With the E-Model, a very useful tool is available, which provides a simplified and easy-to-handle method for practical planning purposes. + +The final result of any calculation with the E-Model is the E-Model Rating $R$ . The relation between the different impairment values and $R$ is given by the equation: + +$$R = R_o - I_s - I_d - I_e + A \text{ (see Note)}$$ + +High values of the E-Model Rating $R$ in a range of $90 \leq R < 100$ should be interpreted as excellent quality, while a lower value of $R$ indicates a lower quality. + +NOTE – For the calculations shown in this ITU-T Recommendation the algorithm of the E-Model has been taken from G.107 at the time of publication. In case a later revision of G.107 does show a refined version of the algorithm, the value of $R = 94.1$ for all input values default may slightly change. Nevertheless, this ITU-T Recommendation will still provide valid guidance for tutorial purposes. For actual transmission planning tasks it should, in any case, be referred to the latest version of G.107. + +The term $R_o$ expresses the basic signal-to-noise ratio. + +The term $I_s$ represents all impairments which occur more or less simultaneously with the voice signal, such as: too loud speech level (non-optimum OLR), non-optimum sidetone (STMR), quantization noise (qdu), etc. + +The "delay impairment" factor $Id$ sums all impairments due to delay and echo effects, and the "equipment impairment factor", $Ie$ , represents impairments which are caused by low bit-rate codecs used in special equipment. + +The "Advantage Factor" $A$ represents an "Advantage of Access" which certain systems may provide in comparison to conventional systems. While all other impairment factors are subtracted from the basic signal-to-noise ratio $Ro$ , this value is added and thus compensates other impairments to a certain amount. It can be used to take into account the fact that the user will tolerate some decrease in transmission quality in exchange for the "Advantage of Access". Examples of such advantages are cordless and mobile systems or connections into hard-to-reach regions via multi satellite hops. The use and the amount of the Advantage Factor $A$ fall into the responsibility of the individual transmission planner and are for further study. + +It should be noted, that, in some cases, not only the final result for $R$ is of interest, but also the specific impairment values $Is$ , $Id$ and $Ie$ . Their individual contribution to the total value of impairments can be used for the determination of the major impairments in the given configuration and for possible solutions for the reduction of these impairments' severity: e.g. reducing $Id$ by the insertion of echo cancellers. + +A more detailed description of the different impairment factors can be found together with the algorithm of E-Model in ITU-T Recommendation G.107. + +# 7 Planning method and limits + +The introduction of the basic principles and of new planning methods were already shortly described in clause 6. Planning of private networks is performed in many cases by the operator of the private network, but it is in most applications strongly influenced by the transmission planning of the public network. Previous or still existing planning rules for interconnections with public ISDN/PSTN are applied only to the private network domain, i.e. between the acoustic interfaces and the interface to the public network. The planning values are based on a partitioning of permitted impairments, or on limits for each specific transmission parameter. + +Such a partitioning, usually not taking into account the specific size, structure and complexity of a private network, will result in a very rigid handling in conjunction with stringent limits for the different transmission parameters. To provide more flexibility in this field, the planning and design of private networks should therefore be based more on individual negotiations between public and private network operators than on partitioning. Although in most cases the borders between public and private networks can be clearly identified at specific interfaces, the priority of negotiations should be more in the determination of the actual impairments in the public and private network domain. This can be supported by considering the individual configurations and requirements of a private network, such as type and point of access to the public network and the majority of connection types (international, national long distance, or local calls). + +To meet these goals, a planning method is recommended and described as follows for the interconnection between public and private network. This method may also be generally applicable to multi-operator networks. + +## 7.1 Planning method + +The planning method for the interconnection of private networks and the public ISDN/PSTN can be considered as a sequence of steps. The following detailed description of these different steps may be used as a guidance. + +### – *Configuration and requirements of the individual private network* + +In a first step, the configuration of the private network, its features with all resulting possible routings, and the type and point of access to the public network, should be considered. + +Furthermore, the majority of traffic via public networks should be taken into account, whenever this seems applicable, and depending on the business affairs of the private network operator. + +### *Determination of reference configurations* + +As usual in network planning, it is advisable to develop a reference configuration mainly for the path within the private network. This makes it easier to clearly identify all network elements and their relevant transmission impairments. It is assumed that the most critical path with respect to transmission impairments is selected as the reference configuration. However, depending on the network operator's decision, some specific configurations or routings, achieved only in exceptional cases within the network, may be accepted with lower quality, but not taken as the reference configuration. + +### *Ascertainment of actual transmission impairments* + +For each of the network elements within the private network and for all main parameters, subject to planning as listed in 7.2, the actual values must be determined. It should be noticed that some elements may contribute with more than one parameter to the total impairment. For most of the main transmission parameters, the actual values of impairments for each element can be determined separately, followed by a simple addition of all element-related values. For some parameters such as echo and stability, however, the investigation must be performed for the relevant entire part of a connection. + +During this step it is also advisable to investigate some possible sources for further transmission impairments, such as impedance mismatching at analogue interfaces, relation between signal level and load capacity of codecs, and excessive room noise at specific locations. + +The determination of actual transmission impairments caused by public networks is subject to agreements between public and private network operators. Whenever possible, this ascertainment should include not only information about the contributing parameters and their actual values with respect to the different routing for local, national long distance and international calls, but also information about the use of echo cancellers and their performance. It must be taken into account that these values may vary in a wide range, only representing an estimate of the transmission performance of paths through the public network. Nevertheless, it is recommended that the preference should be more for a statistical than for a worst-case consideration. + +The same is valid for the opposite termination, which must be defined for the purpose of an end-to-end inspection. Most of the opposite terminations will be formed by a single analogue or digital telephone set, but PABXs or private networks must also be considered. The definition of these terminations and their transmission parameters, mainly SLR, RLR, distortions, delay and provided echo loss, should also be derived by a statistical consideration. If possible, the necessary information can be obtained from the public network operator with respect to the network configuration in the subscriber area. + +The actual values with respect to all relevant transmission parameters should also be determined for all types of digital or analogue leased lines. Although these leased lines will usually be provided by public network operators, they must be considered as part of the private network from the point of view of transmission planning. + +### *Planning calculation* + +All actual values of the main parameters from the different elements within the private network, the public network(s) and the opposite termination, are transformed to be used in the E-Model. A detailed description on the use of this model is given in 7.4. The results can be obtained as the E-Model Rating $R$ to be judged according to Table 1. More details about the planning calculations using the E-Model is given in 7.4.2. + +### – *Judgement of results* + +The results of planning investigation expressed in terms of E-Model Rating R should be judged according to the categories given in 7.3. It is worth noticing that this planning method may also be used to compare different technical solutions for a specific network element by means of their influence to the expected quality, e.g. influence of different codec algorithms, use of DCME in transmission elements, deployment of ATM, etc. For the benefit of an economical design for the private network, the final decision can be based on a ratio between costs and perceived quality. + +## 7.2 Main parameters + +Based on the assumption that in modern private networks the majority of exchanges and interconnecting (leased) lines uses digital technology and that interconnections to the public ISDN and to the PSTN are only digital, a rating of the different transmission parameters should be performed with respect to their influence on speech quality. In a digital environment, some parameters (e.g. frequency distortion, steady circuit noise, loss variation with time, etc.) have become less important. The following parameters are recommended to be included in the transmission planning. + +### – *Overall Loudness Rating (OLR)* + +In some configurations for private networks, mainly in the lower hierarchy, small PABXs connected via 2-wire analogue sections will be in use contributing with loss. Furthermore, analogue telephone sets designed in their SLR and RLR for previous fully-analogue connections may introduce impairments caused by a non-optimum overall loudness rating. + +### – *Absolute delay in echo-free connections* + +This parameter is mainly important in case of international calls. + +### – *Echo* + +The investigation of impairments due to echo effects tends to be one of the most important planning aspects in a digital environment. Two different parameters, the Talker Echo Loudness Rating (TELR) and the mean one-way-delay $T$ of the echo path must be considered. The investigation of echo should also include decisions about the use of echo cancellers. + +### – *Stability* + +According to the assumption that private networks are interconnected digitally with the public ISDN/PSTN, any 4-wire to 2-wire conversion within the private network may terminate the international chain, eventually affecting the stability. Calculations of the stability are not covered by the E-Model, although the provision of a sufficient stability loss is strongly recommended. Values and guidance can be found in ITU-T Recommendation G.122 [7]. + +### – *Quantization distortion* + +In modern private and public networks which are using more and more fully digital routing, the impairment due to quantization distortion expressed in a number of qdu is decreasing. The E-Model includes this parameter, however, it should only be used for a PCM coding process according to ITU-T Recommendation G.711 [11]. For all other coding algorithms, the equipment impairment factor $I_e$ , as shown in Appendix I/G.113 [6] should be used. + +### – *Equipment impairment factor $I_e$* + +The equipment impairment factor $I_e$ which expresses the impairments caused by low bit-rate coding algorithms and other processing devices is one of the most important impairments in modern networks. Available values to be used with the E-Model are given in Appendix I/G.113. + +## 7.3 Quality expectation and absolute upper planning limits + +As described in ITU-T Recommendation G.107 [3] and in 7.4, the results of planning calculations using the E-Model are primarily obtained in terms of an E-Model Rating $R$ for the considered configuration. The E-Model Rating $R$ can lie in the range from 0 to 100, where $R = 100$ is representing a very high transmission quality and $R = 0$ means extremely bad or unacceptable. The $R$ -value can be transformed into a number of different quality measures such as MOS, %GoB and %PoW using the Gaussian Error function as described in Annex B/G.107. + +Basically, the judgement of the resulting E-Model Rating $R$ is up to the planner's decision. However, it is strongly recommended to establish a specific limit which never should be exceeded, even in exceptional cases. + +In some cases, planners may not be familiar with the use of E-Model Rating $R$ as a result from planning calculations. Guidance in terms of a verbal description of the expected user satisfaction for the different $R$ -values is given in Table 1, taken from ITU-T Recommendation G.109 [5]. + +**Table 1/G.175 – Definition of categories of speech transmission quality** + +| R-value range | Speech transmission quality category | User satisfaction | +|-------------------------------------------------------------------|---------------------------------------------|-------------------------------| +| $90 \leq R < 100$ | Best | Very satisfied | +| $80 \leq R < 90$ | High | Satisfied | +| $70 \leq R < 80$ | Medium | Some users dissatisfied | +| $60 \leq R < 70$ | Low | Many users dissatisfied | +| $50 \leq R < 60$ | Poor | Nearly all users dissatisfied | +| NOTE – Connections with $R$ -values below 50 are not recommended. | | | + +## 7.4 Use of the E-Model + +The basic principles and the algorithm of the E-Model are contained in ITU-T Recommendation G.107 [3] including a reference configuration of the model. When using the E-Model for planning calculations, care should be taken for a correct input of all transmission parameters. The following list of all parameters will provide the necessary guidance, whereas in ITU-T Recommendation G.108 [4] tutorial information for different applications can be found. The model distinguishes between the send side and the receive side. Both sides and most of the parameters are referred to a virtual 0 dBr point. There are 18 input transmission parameters in total, but not all of them are varied for the purpose of transmission planning. It is important to note that the E-Model estimates the speech communication quality for both talking and listening as perceived by the user at the receive side. For transmission parameters not varied during planning calculations, default values should be set, as recommended in 7.4.3. + +### 7.4.1 Input parameters + +The following input parameters are used in the E-Model. + +#### – *Send Loudness Rating (SLR) and Receive Loudness Rating (RLR)* + +The values of SLR and RLR are not directly related to the values of the telephone sets which are used. SLR represents the loudness rating between the human mouth at the send side and the virtual 0 dBr point and RLR represents the loudness rating from the 0 dBr point to the human ear at the receive side. If network elements contributing with loss are inserted between the telephone set and the 0 dBr point and vice versa, the calculation of the total SLR and RLR must be performed separately, since the model does not allow for an input of Circuit Loudness Rating. The Overall Loudness Rating (OLR) is in any case the sum of SLR and RLR. Should a specific range of OLR be investigated, it is recommended to vary SLR and RLR simultaneously to avoid errors. If different values for SLR and RLR are existing for the telephone sets used on each end of the connection, the *R* values for both transmission directions must be calculated separately. In this application, only the SLR at the send side and the RLR at the receive side may be used as an input to the model. The remaining parameters (SLR at receive side and RLR at send side) are not used. Their influence to the speech transmission quality due to room noise and to talker echo is included via the parameters TELR, STMR and LSTR. + +#### – *Sidetone Masking Rating (STMR) and Listener Sidetone Rating (LSTR)* + +These parameters, which are directly related to the telephone sets used, are in most cases not subject to planning and should be set to the default values. They must only be taken into account if incorrect impedance matching of analogue telephone sets, or low values for STMR and LSTR should be expected. + +#### – *D-Factors (*Ds* and *Dr*)* + +The D-Factors *Ds* for the send side and *Dr* for the receive side are fixed values depending on the shape of the handsets of the telephone sets used. As a fixed value, they are usually not subject to planning. For the D-Factors and for the values for STMR and LSTR of a telephone set, a fixed relation is assumed: + +$$LSTR = STMR + D$$ + +#### – *Talker Echo Loudness Rating (TELR)* + +The TELR, expressing the loudness rating of the echo path, is defined as the sum of SLR and RLR of the talker's telephone and the echo loss of the echo path. This value has to be calculated separately using the SLR/RLR values at the receive side with respect to the E-Model. The echo path must be identified and calculated carefully within the reference configuration to avoid wrong inputs for the TELR. + +#### – *Weighted Echo Path Loss (WEPL)* + +In conjunction with the round-trip delay in a closed 4-wire loop, this parameter may cause impairments due to listener echo. Closed 4-wire loops may happen in a configuration if the connection includes 4-wire to 2-wire conversions. These conversions may be located in different networks and in different countries. The WEPL is defined as the sum of all losses and gains within the loop, also called the "Round-Trip Loss". In most cases, listener echo can be neglected, if sufficient echo control is provided in a telephone connection. + +#### – *Delay values (*T*, *Ta* and *Tr*)* + +The E-Model distinguishes three different values for delay, which must be determined and used separately in the model. The mean one-way delay time *T* in ms is used to calculate the impairments due to talker echo in conjunction with TELR. It should be noted that although this is an impairment to the talker, the estimate of the impairment is referred to the receive + +side of the model. The mean one-way delay $T$ has to be determined and calculated only for the sections in the reference configuration forming the echo path, i.e. from talker's telephone up to the identified point where signal reflections may occur, e.g. a 4-wire to 2-wire conversion. Complementarily, the absolute one-way delay $T_a$ in ms is in any case the total delay via the whole connection between the two subscribers. $T_a$ represents impairments due to too-long delay and must be included mainly in planning for international calls, even if perfect echo cancellation is provided. The round-trip delay $T_r$ in ms will cause listener echo in conjunction with WEPL. $T_r$ is defined as the total delay within the closed 4-wire loop. + +#### – *Equipment impairment factor ( $I_e$ )* + +The values for the equipment impairment factor $I_e$ as an input to the E-Model are representing impairments due to low bit-rate codecs in specific network elements. Values based on subjective tests are given in Appendix I/G.113. + +#### – *Advantage factor ( $A$ )* + +The algorithm of the E-Model also includes the Factor $A$ for the calculation of the E-Model Rating $R$ ; however, the inclusion and its value are subject to the planners' decision. For more information, see clause 6. + +#### – *Room Noise ( $P_s$ and $P_r$ )* + +Impairments perceived at the receive side may also be caused by the room noise at the send side and at the receive side, contributing to the basic signal-to-noise ratio. Values for the room noise $P_s$ in dB(A) at send side and $P_r$ in dB(A) at receive side are usually set to default values, but may be varied for planning purposes in case of excessive noise at a specific location. The algorithm in the E-Model transforms these values into an equivalent circuit noise referred to the 0 dBr point. + +#### – *Circuit Noise ( $N_c$ )* + +If necessary, the circuit noise $N_c$ in dBm0p can be obtained by a power addition of all electric noise sources in the connection, all referred to the 0 dBr point. In most cases, sources for steady noise in a digital environment may be neglected and the input parameter may be set to its default value. + +#### – *Noise Floor ( $N_{for}$ )* + +The input parameter noise floor in dBmp represents a basic noise in the equipment at the receive side. Its nominal value is set to –64 dBmp and should not be modified. + +#### – *Number of Quantizing Distortion Units ( $qdu_s$ )* + +Impairments due to quantization distortion are entered into the model as a number of qdu. It should be noted that qdu may only be used for a codec pair using PCM coding according to ITU-T Recommendation G.711 and for distortions arising from digital loss or gain pads (0.7 qdu). For all other coding algorithms, the relevant equipment impairment factors $I_e$ must be used. + +### 7.4.2 Performing the calculation + +If all input parameters are available, the calculation process can be described as follows: + +- a) Compute separately SLR and RLR and perform the calculation of the basic signal-to-noise ratio $R_o$ . +- b) Compute the simultaneous impairment factor $I_s$ . +- c) Calculate separately the mean one-way delay and TELR of the echo path, the absolute one-way delay $T_a$ and the round-trip delay $T_r$ , and compute the delayed impairment factor $I_d$ . + +- d) Add the equipment impairment factors $I_e$ for the different equipments. +- e) Compute the rating factor $R$ and add the $A$ factor if applicable. +- f) Check whether the recommended limit of $R = 50$ is violated. + +In practice, computer programs will be used for the calculations providing a total run via all steps a) through f). + +### 7.4.3 Default values + +For all input parameters used in the algorithm of the E-Model, the default values are listed in ITU-T Recommendation G.107. It is strongly recommended to use these default values for all parameters which are not varied during planning calculation. If all parameters are set to the default values, the calculation results in a very high quality with a rating factor of $R = 94.1$ (see Note in clause 6). + +# 8 Implementation of echo cancellers + +The increasing use of speech processing devices and digital radio sections also in modern private networks will increase the delay values within the private network by an amount, which requires the implementation of echo control devices not only for national long distance calls, but also for local or internal calls. Since less experience with the insertion of such devices in the private network domain can be expected, some guidance should be given to the planner. + +Primarily it is recommended to use echo cancellers, the use of echo suppressors (as per previous ITU-T Recommendation G.164) is no longer recommended. Echo cancellers should meet or exceed the requirements of ITU-T Recommendation G.168 [9], echo cancellers according to the older ITU-T Recommendation G.165 [8] may be used if no problems occur. Mainly in case of international calls, where echo cancellers are inserted by the public network operator, a tandeming of cancellers may occur. Practical experiences have shown that echo cancellers (recently designed according to ITU-T Recommendation G.165 [8]) will cause no major problems in a tandem configuration, but tandeming may impact the perceived speech quality in certain cases, such possible impact depends on various factors, which are not subject to transmission planning (e.g. double talk, highly interactive conversation, ECs from different manufacturers). It is advisable to inquire the application of cancellers and their performance of the public network operator. Depending on the permitted echo path delay of this equipment, on the point of access and on the routing within the public network, additional cancellers in the private network could possibly be avoided in some cases. + +The investigation and the final decision about the insertion of echo cancellers within the private network must not only cover the echo control for the talker in the private network but also for the talker at the opposite termination in case of local or national long-distance calls via the public network. + +Some terminal and transmission elements, such as cordless and mobile telephones, or speech companding devices, may provide integrated echo cancellers which must be taken into account. Those devices must be carefully investigated with respect to the relevant performance parameters, such as permitted echo path delay, residual echo loss, required echo path loss, etc. + +As a basic rule, echo cancellers should be located close to the echo source within the private network for the benefit of the opposite termination. For echo cancellers according to ITU-T Recommendation G.165 [8] a linear echo path with a minimum echo path loss of 6 dB must be provided. For the control of the talker echo experienced by the subscriber in the private network (echo path via the public network and the opposite termination), information about this echo path regarding delay, echo path loss and linearity should be obtained by negotiations between public and private network operator, to allow a careful selection of the necessary devices. In most cases, these echo cancellers will be located close to the interface to the public network. + +## **SERIES OF ITU-T RECOMMENDATIONS** + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure and Internet protocol aspects | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.421-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.421-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..64672153e39c851d9e16fdbc702e526c7ba7e8a7 --- /dev/null +++ b/marked/G/T-REC-G.421-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:454a9958ffe168868cb7d38a0eb24418dafe31a7a4245c992089b2316ac37d3e +size 7392 diff --git a/marked/G/T-REC-G.442-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.442-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..64672153e39c851d9e16fdbc702e526c7ba7e8a7 --- /dev/null +++ b/marked/G/T-REC-G.442-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:454a9958ffe168868cb7d38a0eb24418dafe31a7a4245c992089b2316ac37d3e +size 7392 diff --git a/marked/G/T-REC-G.442-198811-I_PDF-E/raw.md b/marked/G/T-REC-G.442-198811-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..657adf0fdf0dcb5560e0c3779e33ae6dc6c21ce2 --- /dev/null +++ b/marked/G/T-REC-G.442-198811-I_PDF-E/raw.md @@ -0,0 +1,60 @@ + + +![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +**G.442** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +# **INTERNATIONAL ANALOGUE CARRIER SYSTEMS GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO - RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINKS** --- + +## **RADIO - RELAY SYSTEM DESIGN OBJECTIVES FOR NOISE AT THE FAR END OF A HYPOTHETICAL REFERENCE CIRCUIT WITH REFERENCE TO TELEGRAPHY TRANSMISSION** + +**ITU-T Recommendation G.442** + +(Extract from the *Blue Book*) + +--- + +### NOTES + +- 1 ITU-T Recommendation G.442 was published in Fascicle III.2 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below). +- 2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +### **RADIO-RELAY SYSTEM DESIGN OBJECTIVES FOR NOISE AT THE FAR END OF A HYPOTHETICAL REFERENCE CIRCUIT WITH REFERENCE TO TELEGRAPHY TRANSMISSION** + +*(modified at Geneva, 1964)* + +As is shown in Recommendation G.222, if the intention is to use on radio links, amplitude-modulated voice-frequency telegraph equipment for 50 bauds conforming to Series R Recommendations, then in order to obtain telegraph connections with the quality indicated in Recommendation F.10 [1], the design of these radio links should include the objectives recommended for telephone transmission and signalling and, in addition, should include the objectives set out below: + +On any telephone channel constituted in accordance with the hypothetical reference circuit for the type of radio link considered, the unweighted noise power, measured or calculated with a time-constant (integrating time) of 5 ms and referred to a zero relative level point, should not exceed $10^6$ pW0 during more than $10^{-5}$ (i.e. 0.001%) of any month, nor more than 0.1% of any hour. + +Provided that short bursts of high-level noise due to causes other than propagation have been reduced to negligible proportions, and assuming that the fine structure of the noise is the same as white noise, it is assumed that, in designing line-of-sight radio links, the objective during any month is in practice equivalent to the following objective: + +The unweighted noise power on a telephone channel at a zero relative point, calculated from measurements made with an integrating time of 1 second, should not exceed $2 \times 10^5$ pW0 for more than $10^{-4}$ (i.e. for more than 0.01%) of any month. + +With regard to the objective to be met during any hour, it may happen that on certain radio links unforeseen exceptional propagation conditions may result in this objective not being met during certain most unfavourable hours. These hours, called "hours of interrupted telegraph traffic", will be those during which a noise level of $10^6$ pW0 is exceeded for more than 36 seconds. + +Every effort should be made to reduce the number of such hours to a very small fraction of the total time. Since it follows from the recommended objective for telephone signalling that the 5 ms unweighted noise power should not exceed $10^6$ pW0 during more than $10^{-4}$ (i.e. 0.01%) of any month, there should never be more than seven "hours of interrupted telegraph traffic" during a month. + +It may then be expected that the telegraph service will be satisfactory. Nevertheless, to achieve this object, it may be necessary in certain cases to select the channels allocated to amplitude-modulated voice-frequency telegraphy for 50 bauds from among those which are the least sensitive to propagation noise. + +*Note 1* - Use of a measuring instrument having a 5-ms time constant (integrating time) is recommended so as to detect, in particular, the presence of short high-level noise bursts, such as those caused by power supplies and by the equipment. Administrations should take all possible practical steps to eliminate such noise. + +It is expected that on the majority of line-of-sight radio links (if not on all) it will be possible to reduce short noise bursts to negligible proportions, and that for the majority of radio links, any remaining short high-level noise bursts will be due to propagation. Noise surges having a mean power in excess of about $10^5$ pW0 will then last from 1 to 10 seconds and will have an approximately constant level during this period. Under these conditions, for propagation measurements and preliminary design measurements for radio links, instruments having a time constant (integrating time) of 1 second could be used. + +*Note 2* - The fraction $10^{-5}$ of a month, for a 2500-km circuit, leads to impracticably small fractions of the time for shorter circuits (for example, $10^{-6}$ for a 250-km circuit). It is for this reason that the practical objective refers to a greater fraction of the time ( $10^{-4}$ for 2500 km), together with a reduced power ( $2 \times 10^5$ pW0), the latter measured with a time constant (integrating time) of 1 second. + +### **Reference** + +- [1] CCITT Recommendation *Character error rate objective for telegraph communication using 5-unit start-stop equipment*, Vol. II, Rec. 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It features a blue globe with white lines representing latitude and longitude, and the letters 'ITU' in a bold, blue, sans-serif font overlaid on the globe. + +ITU logo + +## ITU-T G-SERIES RECOMMENDATIONS + +## **Transmission systems and media, digital systems and networks** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100-G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200-G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300-G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400-G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450-G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600-G.699 | +| General | G.600-G.609 | +| Symmetric cable pairs | G.610-G.619 | +| Land coaxial cable pairs | G.620-G.629 | +| Submarine cables | G.630-G.639 | +| Free space optical systems | G.640-G.649 | +| Optical fibre cables | G.650-G.659 | +| Characteristics of optical components and subsystems | G.660-G.679 | +| Characteristics of optical systems | G.680-G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700-G.799 | +| DIGITAL NETWORKS | G.800-G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900-G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000-G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000-G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000-G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000-G.8999 | +| ACCESS NETWORKS | G.9000-G.9999 | + +For further details, please refer to the list of ITU-T Recommendations. + +# Recommendation ITU-T G.695 + +# Optical interfaces for coarse wavelength division multiplexing applications + +## Summary + +Recommendation ITU-T G.695 provides optical parameter values for physical layer interfaces of coarse wavelength division multiplexing (CWDM) applications with up to 16 channels and up to 100 Gbit/s. Applications are defined using two different methods, one using multichannel interface parameters and the other using single-channel interface parameters. Both unidirectional and bidirectional applications are specified. In this version of this Recommendation, an application code for 4-channel PAM4 100G black box applications has been added, which is suitable for carrying 4×FOIC1.1-RS and FOIC4.4-RS (400G striped across four physical lanes). + +## History\* + +| Edition | Recommendation | Approval | Study Group | Unique ID | +|---------|----------------|------------|-------------|--------------------| +| 1.0 | ITU-T G.695 | 2004-02-22 | 15 | 11.1002/1000/7058 | +| 2.0 | ITU-T G.695 | 2005-01-13 | 15 | 11.1002/1000/7474 | +| 3.0 | ITU-T G.695 | 2006-12-14 | 15 | 11.1002/1000/8979 | +| 4.0 | ITU-T G.695 | 2009-11-13 | 15 | 11.1002/1000/10393 | +| 5.0 | ITU-T G.695 | 2010-10-22 | 15 | 11.1002/1000/10872 | +| 6.0 | ITU-T G.695 | 2015-01-13 | 15 | 11.1002/1000/12362 | +| 7.0 | ITU-T G.695 | 2018-07-22 | 15 | 11.1002/1000/13517 | +| 8.0 | ITU-T G.695 | 2025-05-14 | 15 | 11.1002/1000/16333 | + +## Keywords + +Application codes, black box, black link, CWDM, multi-vendor, optical. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, and information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at . + +© ITU 2025 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +# Table of Contents + +| | | Page | +|-------|------------------------------------------------------------------------------------------------------------------------------------------|------| +| 1 | Scope..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions ..... | 2 | +| 3.1 | Terms defined elsewhere ..... | 2 | +| 3.2 | Terms defined in this Recommendation..... | 3 | +| 4 | Abbreviations and acronyms ..... | 3 | +| 5 | Conventions ..... | 4 | +| 6 | Classification of optical interfaces..... | 4 | +| 6.1 | Applications..... | 4 | +| 6.2 | Reference points ..... | 4 | +| 6.3 | Nomenclature ..... | 8 | +| 6.4 | Multichannel interfaces at the reference points MPI-S M and MPI-R M ..... | 9 | +| 6.5 | Single-channel interfaces at the reference points S S and RS..... | 12 | +| 7 | Transverse compatibility ..... | 13 | +| 8 | Parameter definitions ..... | 14 | +| 8.1 | General information..... | 16 | +| 8.2 | Interface at point MPI-S M or SS ..... | 17 | +| 8.3 | Common optical path parameters (single span) from point MPI-S M to
MPI-R M , or from S S to RS ..... | 20 | +| 8.4 | Interface at point MPI-R M or RS ..... | 23 | +| 8.5 | Additional parameters for the optical path from S S to RS..... | 25 | +| 9 | Parameter values ..... | 26 | +| 10 | Optical safety considerations..... | 55 | +| | Appendix I – Wavelength dependence of attenuation and chromatic dispersion ..... | 56 | +| I.1 | Attenuation ..... | 56 | +| I.2 | Chromatic dispersion..... | 57 | +| | Appendix II – Optical path from point RPs to RPR ..... | 59 | +| | Appendix III – Black links containing OADMs ..... | 61 | +| III.1 | Number of OADMs in a black link ..... | 61 | +| III.2 | Mixed application codes..... | 62 | +| III.3 | Protection..... | 63 | +| | Appendix IV Parameter values for 16-channel NRZ 2.5G applications..... | 64 | +| | Bibliography..... | 71 | + + + +# Recommendation ITU-T G.695 + +## Optical interfaces for coarse wavelength division multiplexing applications + +# 1 Scope + +This Recommendation applies to optical interfaces for coarse wavelength division multiplexing (CWDM) optical line systems for network applications using single-mode optical fibres. This Recommendation defines and provides values for optical interface parameters of physical point-to-point and ring CWDM system applications. Their principal purpose is to enable transversely (multi-vendor) compatible interfaces. + +Applications are defined using two different methods, one using multichannel interface parameters and the other using single-channel interface parameters. Both unidirectional and bidirectional applications are specified. + +This Recommendation describes optical line systems that include the following features: + +- Maximum number of channels: Up to 16; +- Bit rate of signal channel: Up to PAM4 100G. + +The CWDM wavelength grid is provided in [ITU-T G.694.2]. + +Specifications are organized according to application codes. + +In the future, applications enabling full transverse compatibility at both the multichannel and single-channel interface points may be included. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [[ITU-T G.652](#)] Recommendation ITU-T G.652 (2024), *Characteristics of a single-mode optical fibre and cable*. +- [[ITU-T G.653](#)] Recommendation ITU-T G.653 (2010), *Characteristics of a dispersion-shifted, single-mode optical fibre and cable*. +- [[ITU-T G.655](#)] Recommendation ITU-T G.655 (2009), *Characteristics of a non-zero dispersion-shifted single-mode optical fibre and cable*. +- [[ITU-T G.664](#)] Recommendation ITU-T G.664 (2012), *Optical safety procedures and requirements for optical transmission systems*. +- [[ITU-T G.671](#)] Recommendation ITU-T G.671 (2025), *Transmission characteristics of optical components and subsystems*. +- [[ITU-T G.691](#)] Recommendation ITU-T G.691 (2006), *Optical interfaces for single channel STM-64 and other SDH systems with optical amplifiers*. +- [[ITU-T G.694.2](#)] Recommendation ITU-T G.694.2 (2003), *Spectral grids for WDM applications: CWDM wavelength grid*. + +- [[ITU-T G.707](#)] Recommendation ITU-T G.707/Y.1322 (2007), *Network node interface for the synchronous digital hierarchy (SDH)*. +- [[ITU-T G.709](#)] Recommendation ITU-T G.709/Y.1331 (2020), *Interfaces for the optical transport network*. +- [[ITU-T G.709.5](#)] Recommendation ITU-T G.709.5 (2024), *Flexible OTN short-reach interfaces*. +- [[ITU-T G.872](#)] Recommendation ITU-T G.872 (2024), *Architecture of the optical transport network*. +- [[ITU-T G.957](#)] Recommendation ITU-T G.957 (2006), *Optical interfaces for equipments and systems relating to the synchronous digital hierarchy*. +- [[ITU-T G.959.1](#)] Recommendation ITU-T G.959.1 (2024), *Optical transport network physical layer interfaces*. +- [IEC 60825-1] IEC 60825-1 (2014), *Safety of laser products – Part 1: Equipment classification and requirements*. +- [IEC 60825-2] IEC 60825-2 (2021), *Safety of laser products – Part 2: Safety of optical fibre communication systems (OFCs)*. +- [IEEE 802.3] IEEE Std 802.3-2022, *IEEE Standard for Ethernet*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined in [[ITU-T G.671](#)]: + +- coarse wavelength division multiplexing (CWDM); +- optical wavelength multiplexer/demultiplexer; +- channel insertion loss; +- channel spacing; +- differential group delay; +- reflectance. + +This Recommendation uses the following term defined in [[ITU-T G.694.2](#)]: + +- wavelength grid. + +This Recommendation uses the following term defined in [[ITU-T G.709](#)]: + +- completely standardized OTUk (OTUk). + +This Recommendation uses the following terms defined in [[ITU-T G.957](#)]: + +- joint engineering; +- receiver sensitivity; +- transverse compatibility. + +This Recommendation uses the following terms defined in [[ITU-T G.959.1](#)]: + +- minimum equivalent sensitivity; +- optical tributary signal class NRZ 1.25G; +- optical tributary signal class NRZ 2.5G; +- optical tributary signal class NRZ 10G; +- optical tributary signal class NRZ 25G; + +- optical tributary signal class PAM4 50G; +- optical tributary signal class PAM4 100G. + +## 3.2 Terms defined in this Recommendation + +None. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|----------------------------|-----------------------------------------------------------------------------------------------| +| 3R | Reamplification, reshaping and retiming (regeneration) | +| ALS | Automatic Laser Shutdown | +| APR | Automatic Power Reduction | +| APSD | Automatic Power Shutdown | +| ASE | Amplified Spontaneous Emission | +| BER | Bit Error Ratio | +| DGD | Differential Group Delay | +| ER | Extinction Ratio | +| ffs | for further study | +| MPI | Main Path Interface | +| MPI-R M | Multichannel Main Path Interface reference point at the CWDM network element aggregate input | +| MPI-S M | Multichannel Main Path Interface reference point at the CWDM network element aggregate output | +| NA | Not Applicable | +| NE | Network Element | +| NRZ | Non-Return to Zero | +| OA | Optical Amplifier | +| OADM | Optical Add-Drop Multiplexer | +| OD | Optical Demultiplexer | +| OM | Optical Multiplexer | +| OMA outer | Optical Modulation Amplitude (between the outer levels for PAM4) | +| ONE | Optical Network Element | +| OTL | Optical channel Transport Lane | +| OTU k | completely standardized Optical channel Transport Unit – k | +| PAM4 | Pulse Amplitude Modulation with 4 levels | +| PMD | Polarization Mode Dispersion | +| R PR | Link reference point at the CWDM network element aggregate input | +| R PS | Link reference point at the CWDM network element aggregate output | +| R S | Single-channel reference point at the CWDM network element tributary output | + +| | | +|-------|----------------------------------------------------------------------------| +| SECQ | Stressed Eye Closure for PAM4 | +| Ss | Single-channel reference point at the CWDM network element tributary input | +| TDECQ | Transmitter and Dispersion Eye Closure for PAM4 | +| TECQ | Transmitter Eye Closure for PAM4 | +| UI | Unit Interval | +| WDM | Wavelength Division Multiplexing | + +# 5 Conventions + +None. + +# 6 Classification of optical interfaces + +## 6.1 Applications + +This Recommendation provides the physical layer parameters and values for CWDM multichannel and single-channel interfaces in physical point-to-point and ring applications. CWDM systems can realize cost-effective applications through a combination of uncooled single mode lasers, relaxed laser wavelength selection tolerances and wide passband filters. CWDM systems can be used in transport networks for a variety of clients, services and protocols. + +The specification method used in this Recommendation is categorized into two types. + +The first one is a "black box" approach, which means that it is not intended to restrict or specify the internal elements and/or the connections between the elements within the black box. There are, however, functional requirements for the black box, the most important being the inclusion of reamplification, reshaping and retiming (3R) regeneration. This approach enables transverse compatibility at the multichannel points. + +The second type is a "black link" approach which means that optical interface parameters for only (single-channel) optical tributary signals are specified. Additional informative descriptions are provided for the fibre link parameters of the multichannel section, such as maximum attenuation, chromatic dispersion and polarization mode dispersion. This approach enables transverse compatibility at the single-channel point using a direct wavelength-multiplexing configuration. However, it does not enable transverse compatibility at the multichannel points. In this approach, the optical multiplexer (OM) and optical demultiplexer (OD) are treated as a single set of optical devices and optical add-drop multiplexers (OADMs) can be included. + +This Recommendation considers non-amplified multichannel interfaces only; however, in the future, amplified interfaces may be considered. + +## 6.2 Reference points + +### 6.2.1 Unidirectional applications + +Figure 6-1 shows a set of reference points for multichannel connection (MPI-SM and MPI-RM) only, for the use of the "black box" approach. Here the CWDM network element includes an OM and transmitters, or an OD and receivers. + +![Diagram of the 'Black box' approach for CWDM network elements. On the left, a CWDM network element contains multiple transmitters (Tx λ1, Tx λ2, ..., Tx λN) connected to an Optical Multiplexer (OM). The output of the OM is labeled MPI-SM. On the right, another CWDM network element contains an Optical Demultiplexer (OD) connected to multiple receivers (Rx λ1, Rx λ2, ..., Rx λN). The input to the OD is labeled MPI-RM. A line connects the MPI-SM output to the MPI-RM input. The label G.695(25) is in the bottom right corner.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg) + +Diagram of the 'Black box' approach for CWDM network elements. On the left, a CWDM network element contains multiple transmitters (Tx λ1, Tx λ2, ..., Tx λN) connected to an Optical Multiplexer (OM). The output of the OM is labeled MPI-SM. On the right, another CWDM network element contains an Optical Demultiplexer (OD) connected to multiple receivers (Rx λ1, Rx λ2, ..., Rx λN). The input to the OD is labeled MPI-RM. A line connects the MPI-SM output to the MPI-RM input. The label G.695(25) is in the bottom right corner. + +**Figure 6-1 – "Black box" approach** + +Figure 6-2 shows a set of reference points for the linear "black link" approach, for single-channel connection (SS and RS) between transmitters (Tx) and receivers (Rx). Here the CWDM network elements include an OM and an OD, which are used as a pair with the opposing element and may also include one or more OADMs. + +![Diagram of the linear 'black link' approach. A large box labeled 'CWDM link' contains 'CWDM network elements'. Inside, transmitters (Tx λ1, Tx λ2, ..., Tx λN) are connected to an Optical Multiplexer (OM) via single-channel connection points labeled SS. The OM output is labeled RP_S. This is followed by an Optical Add-Drop Multiplexer (OADM) with two coupling points. The output of the OADM is labeled RP_R. This is followed by an Optical Demultiplexer (OD), which is connected to receivers (Rx λ1, Rx λ2, ..., Rx λN) via single-channel connection points labeled RS. Below the OADM, there are two dashed boxes: one labeled 'Rx λx' with an input labeled RS, and another labeled 'Tx λx' with an output labeled SS. The label G.695(25) is in the bottom right corner.](5a4e62bead259c258d069fd3663ea670_img.jpg) + +Diagram of the linear 'black link' approach. A large box labeled 'CWDM link' contains 'CWDM network elements'. Inside, transmitters (Tx λ1, Tx λ2, ..., Tx λN) are connected to an Optical Multiplexer (OM) via single-channel connection points labeled SS. The OM output is labeled RP\_S. This is followed by an Optical Add-Drop Multiplexer (OADM) with two coupling points. The output of the OADM is labeled RP\_R. This is followed by an Optical Demultiplexer (OD), which is connected to receivers (Rx λ1, Rx λ2, ..., Rx λN) via single-channel connection points labeled RS. Below the OADM, there are two dashed boxes: one labeled 'Rx λx' with an input labeled RS, and another labeled 'Tx λx' with an output labeled SS. The label G.695(25) is in the bottom right corner. + +**Figure 6-2 – Linear "black link" approach** + +Figure 6-3 shows a corresponding set of reference points for the ring "black link" approach, for single-channel connection (SS and RS) between transmitters (Tx) and receivers (Rx). Here the CWDM network elements include two or more OADMs connected in a ring. + +![Figure 6-3: Ring 'black link' approach diagram. The diagram shows a ring of four OADM (Optical Add-Drop Multiplexer) nodes connected by optical fibers. Each OADM node is connected to two external transceivers (Tx and Rx) via single-channel reference points Ss and Rs. The OADM nodes are labeled 'CWDM network elements' and the entire ring is labeled 'CWDM link'. The diagram is labeled G.695(25) in the bottom right corner.](d4af765160d04ecef538e5066006dc77_img.jpg) + +The diagram illustrates a ring network topology for the "black link" approach. It consists of four OADM (Optical Add-Drop Multiplexer) nodes connected in a closed loop. Each OADM node is connected to two external transceivers (Tx and Rx) via single-channel reference points Ss and Rs. The OADM nodes are labeled "CWDM network elements" and the entire ring is labeled "CWDM link". The diagram is labeled G.695(25) in the bottom right corner. + +Figure 6-3: Ring 'black link' approach diagram. The diagram shows a ring of four OADM (Optical Add-Drop Multiplexer) nodes connected by optical fibers. Each OADM node is connected to two external transceivers (Tx and Rx) via single-channel reference points Ss and Rs. The OADM nodes are labeled 'CWDM network elements' and the entire ring is labeled 'CWDM link'. The diagram is labeled G.695(25) in the bottom right corner. + +**Figure 6-3 – Ring "black link" approach** + +These reference models do not include any optical amplifiers in the CWDM system. However, in the future, applications including optical amplifiers may be introduced. + +The reference points in Figures 6-1, 6-2 and 6-3 are defined as follows: + +- Ss is a single-channel reference point at the CWDM network element tributary input; +- Rs is a single-channel reference point at the CWDM network element tributary output; +- MPI-SM is a multichannel reference point at the CWDM network element aggregate output; +- MPI-RM is a multichannel reference point at the CWDM network element aggregate input; +- RPs is a link reference point at the CWDM network element aggregate output; +- RPR is a link reference point at the CWDM network element aggregate input. + +Here, single-channel reference points Ss and Rs are applied to systems for the (linear or ring) "black link" approach where every path from Ss to its corresponding Rs must comply with the parameter values of the application codes in Tables 9-11 to 9-14 and Tables 9-17 to 9-22. Multichannel reference points MPI-SM and MPI-RM are applied to systems for the "black box" approach. Link reference points RPs and RPR are applied only to systems for the "black link" approach. + +Note that MPI-SM and MPI-RM are defined to provide normative specifications for optical interfaces. On the other hand, RPs and RPR are only defined to provide information for fibre links and not to provide signal characteristics at these points. + +### 6.2.2 Bidirectional applications + +Figure 6-4 shows a set of reference points for multichannel connection (MPI-SM and MPI-RM) only, for the use of the "black box" approach for single-fibre bidirectional applications. Here the CWDM network element includes an OM/OD, transmitters and receivers. + +![Diagram of the 'Black box' approach for bidirectional applications. Two CWDM network elements are connected by a single fiber. Each element contains multiple transmitters (Tx) and receivers (Rx) for different wavelengths (λ1, λ2, ..., λN-1, λN). The left element has Tx λ1, Tx λ2, ..., Rx λN-1, Rx λN connected to an OM/OD unit. The right element has Rx λ1, Rx λ2, ..., Tx λN-1, Tx λN connected to an OM/OD unit. The fiber between them carries MPI-SM signals (going right) and MPI-RM signals (going left).](af7916c89a458fdab6c3f443217388ae_img.jpg) + +G.695(25) + +Diagram of the 'Black box' approach for bidirectional applications. Two CWDM network elements are connected by a single fiber. Each element contains multiple transmitters (Tx) and receivers (Rx) for different wavelengths (λ1, λ2, ..., λN-1, λN). The left element has Tx λ1, Tx λ2, ..., Rx λN-1, Rx λN connected to an OM/OD unit. The right element has Rx λ1, Rx λ2, ..., Tx λN-1, Tx λN connected to an OM/OD unit. The fiber between them carries MPI-SM signals (going right) and MPI-RM signals (going left). + +**Figure 6-4 – "Black box" approach for bidirectional applications** + +Figure 6-5 shows a set of reference points for the single-fibre bidirectional linear "black link" approach, for single-channel connection (SS and RS) between transmitters (Tx) and receivers (Rx). Here the CWDM network elements include an OM/OD, which is used as a pair with the opposing element and may also include one or more OADMs. + +![Diagram of the linear 'black link' approach for bidirectional applications. A CWDM link is shown between two CWDM network elements. The left element contains Tx λ1, Tx λ2, ..., Rx λN-1, Rx λN connected to an OM/OD unit. The right element contains Rx λ1, Rx λ2, ..., Tx λN-1, Tx λN connected to an OM/OD unit. Between the OM/OD units is an OADM. Reference points (RP) are indicated for signals going right (RP_S) and signals going left (RP_R). The link is terminated at the ends with SS (Service Side) and RS (Request Side) interfaces. Below the link, a dashed box shows a single channel connection between a Rx λx and a Tx λx.](ff0952ef692c9d960ce5f6708bcc9711_img.jpg) + +G.695(25) + +Diagram of the linear 'black link' approach for bidirectional applications. A CWDM link is shown between two CWDM network elements. The left element contains Tx λ1, Tx λ2, ..., Rx λN-1, Rx λN connected to an OM/OD unit. The right element contains Rx λ1, Rx λ2, ..., Tx λN-1, Tx λN connected to an OM/OD unit. Between the OM/OD units is an OADM. Reference points (RP) are indicated for signals going right (RP\_S) and signals going left (RP\_R). The link is terminated at the ends with SS (Service Side) and RS (Request Side) interfaces. Below the link, a dashed box shows a single channel connection between a Rx λx and a Tx λx. + +**Figure 6-5 – Linear "black link" approach for bidirectional applications** + +Figure 6-6 shows a corresponding set of reference points for the single-fibre bidirectional ring "black link" approach, for single-channel connection (SS and RS) between transmitters (Tx) and receivers (Rx). Here the CWDM network elements include two or more OADMs connected in a ring. + +![Figure 6-6: Ring 'black link' approach for bidirectional applications. The diagram shows a CWDM link containing four CWDM network elements (OADM). Two OADM units are on the left and two on the right, connected by optical fibers forming a ring. Each OADM is connected to an external Tx/Rx pair. Reference points Ss and Rs are indicated at the interfaces between the external equipment and the CWDM link. The diagram is labeled G.695(25).](4801720824e4b5e2361a5564f91cfb70_img.jpg) + +Figure 6-6: Ring 'black link' approach for bidirectional applications. The diagram shows a CWDM link containing four CWDM network elements (OADM). Two OADM units are on the left and two on the right, connected by optical fibers forming a ring. Each OADM is connected to an external Tx/Rx pair. Reference points Ss and Rs are indicated at the interfaces between the external equipment and the CWDM link. The diagram is labeled G.695(25). + +**Figure 6-6 – Ring "black link" approach for bidirectional applications** + +The reference points in Figures 6-4, 6-5 and 6-6 are as defined in clause 6.2.1. + +## 6.3 Nomenclature + +The application code identifies the network, implementation and architectural characteristics of an application. + +The application code notation is constructed as follows: + +$$CnWx-ytz$$ + +where: + +- C** is the indicator of CWDM applications. +- n** is the maximum number of channels supported by the application code. +- W** is a letter indicating the span distance such as: + - **R** indicating very short reach (up to 4 dB span attenuation); + - **S** indicating short-haul; + - **L** indicating long-haul. +- x** is the maximum number of spans allowed within the application code. + +NOTE – In the current version of this Recommendation, $x = 1$ for all applications. + +- y** indicates the highest class of optical tributary signal supported: + - **0** indicating NRZ 1.25G; + - **1** indicating NRZ 2.5G; + - **2** indicating NRZ 10G; + - **4** indicating PAM4 50G; + - **9** indicating NRZ 25G; + - **5** indicating PAM4 100G. + +- t** is a placeholder letter indicating the configuration supported by the application code. In the current version of this Recommendation, the only value used is: +- **D** indicating that the application does not contain any optical amplifiers. +- z** indicates the fibre types, as follows: + - **1** indicating operation only in the 1310 nm region on [ITU-T G.652] fibre; + - **2** indicating operation on [ITU-T G.652] fibre; + - **3** indicating operation on [ITU-T G.653] fibre; + - **5** indicating operation on [ITU-T G.655] fibre. + +A bidirectional system is indicated by the addition of the letter **B** at the front of the application code. For CWDM application codes this will be: + +B-CnWx-ytz + +A system using the "black link" approach is indicated by the addition of the letter **S** at the front of the application code. For CWDM application codes this will be: + +S-CnWx-ytz + +For some application codes, a suffix is added to the end of the code defined as follows: + +- **F** to indicate that this application requires FEC bytes as specified in [ITU-T G.709] or [ITU-T G.709.5] as indicated for the application code to be transmitted. + +## 6.4 Multichannel interfaces at the reference points MPI-SM and MPI-RM + +The multichannel interfaces described in clauses 6.4.1 and 6.4.2 are intended to enable transverse compatibility. These interfaces may operate on [ITU-T G.652], [ITU-T G.653] or [ITU-T G.655] fibre, simultaneously transporting up to 16 channels, using either NRZ 1.25G, NRZ 2.5G, NRZ 10G, NRZ 25G, PAM4 50G or PAM4 100G optical tributary signals, depending on the particular application code. + +Further requirements related to transverse compatibility can be found in clause 7. + +Tables 6-1 to 6-5 summarize the multichannel application codes, which are structured according to the nomenclature in clause 6.3. + +**Table 6-1 – Classification of 4-channel unidirectional multichannel interfaces** + +| Application | Very short reach (R) | | | Short-haul (S) | | | Long-haul (L) | | | +|-------------------------------------------------|----------------------|---------------|---------------|----------------|---------------|---------------|---------------|---------------|---------------| +| | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Type of fibre | – | – | – | – | – | – | – | – | – | +| Optical tributary signal class NRZ 1.25G | – | – | – | – | – | – | – | – | – | +| Target distance for class NRZ 1.25G (km) (Note) | – | – | – | – | – | – | – | – | – | +| Optical tributary signal class NRZ 2.5G | – | – | – | C4S1-1D2 | C4S1-1D3 | C4S1-1D5 | C4L1-1D2 | C4L1-1D3 | C4L1-1D5 | + +**Table 6-1 – Classification of 4-channel unidirectional multichannel interfaces** + +| Application | Very short reach (R) | | | Short-haul (S) | | | Long-haul (L) | | | +|-------------------------------------------------|----------------------|---|---|----------------|----|----|---------------|----|----| +| | | | | | | | | | | +| Target distance for class NRZ 2.5G (km) (Note) | – | – | – | 37 | 37 | 37 | 69 | 72 | 72 | +| Optical tributary signal class NRZ 10G | – | – | – | C4S1-2D1 | – | – | C4L1-2D1 | – | – | +| Target distance for class NRZ 10G (km) (Note) | – | – | – | 10 | – | – | 40 | – | – | +| Optical tributary signal class NRZ 25G | – | – | – | C4S1-9D1F | – | – | – | – | – | +| Target distance for class NRZ 25G (km) (Note) | – | – | – | 2 | – | – | – | – | – | +| Optical tributary signal class PAM4 50G | – | – | – | C4S1-4D1F | – | – | – | – | – | +| Target distance for class PAM4 50G (km) (Note) | – | – | – | 2 | – | – | – | – | – | +| Optical tributary signal class PAM4 100G | C4R1-5D1F | – | – | C4S1-5D1F | – | – | – | – | – | +| Target distance for class PAM4 100G (km) (Note) | 2 | – | – | 6 | – | – | – | – | – | + +NOTE – These target distances are for classification and not for specification. + +**Table 6-2 – Classification of 4-channel bidirectional multichannel interfaces** + +| Application | Short-haul (S) | Long-haul (L) | | +|---------------------------------------------------------------------------------|----------------|---------------|---------------| +| Type of fibre | [ITU-T G.652] | [ITU-T G.652] | [ITU-T G.653] | +| Optical tributary signal class NRZ 1.25G | – | B-C4L1-0D2 | B-C4L1-0D3 | +| Target distance for class NRZ 1.25G (km) (Note) | – | 90 | 90 | +| Optical tributary signal class NRZ 2.5G | – | B-C4L1-1D2 | B-C4L1-1D3 | +| Target distance for class NRZ 2.5G (km) (Note) | – | 80 | 83 | +| NOTE – These target distances are for classification and not for specification. | | | | + +**Table 6-3 – Classification of 8-channel multichannel interfaces** + +| Application | Short-haul (S) | Long-haul (L) | | +|---------------------------------------------------------------------------------|------------------------|------------------------|---------------| +| Type of fibre | [ITU-T G.652] | [ITU-T G.652] | [ITU-T G.653] | +| Optical tributary signal class NRZ 1.25G | – | B-C8L1-0D2 | B-C8L1-0D3 | +| Target distance for class NRZ 1.25G (km) (Note) | – | 64 | 64 | +| Optical tributary signal class NRZ 2.5G | C8S1-1D2
B-C8S1-1D2 | C8L1-1D2
B-C8L1-1D2 | B-C8L1-1D3 | +| Target distance for class NRZ 2.5G (km) (Note) | 27 | 55 | 58 | +| Optical tributary signal class NRZ 10G | – | B-C8L1-2D2F | B-C8L1-2D3F | +| Target distance for class NRZ 10G (km) (Note) | – | 55 | 58 | +| NOTE – These target distances are for classification and not for specification. | | | | + +**Table 6-4 – Classification of 12-channel multichannel interfaces** + +| Application | Short-haul (S) | Long-haul (L) | | +|---------------------------------------------------------------------------------|----------------|---------------|---------------| +| Type of fibre | [ITU-T G.652] | [ITU-T G.652] | [ITU-T G.653] | +| Optical tributary signal class NRZ 1.25G | – | B-C12L1-0D2 | – | +| Target distance for class NRZ 1.25G (km) (Note) | – | 42 | – | +| Optical tributary signal class NRZ 2.5G | – | B-C12L1-1D2 | – | +| Target distance for class NRZ 2.5G (km) (Note) | – | 38 | – | +| NOTE – These target distances are for classification and not for specification. | | | | + +**Table 6-5 – Classification of 16-channel multichannel interfaces** + +| Application | Short-haul (S) | Long-haul (L) | | +|------------------------------------------|----------------|---------------|---------------| +| Type of fibre | [ITU-T G.652] | [ITU-T G.652] | [ITU-T G.653] | +| Optical tributary signal class NRZ 1.25G | – | – | – | + +**Table 6-5 – Classification of 16-channel multichannel interfaces** + +| Application | Short-haul (S) | Long-haul (L) | | +|---------------------------------------------------------------------------------|--------------------------|--------------------------|---| +| Target distance for class NRZ 1.25G (km) (Note) | – | – | – | +| Optical tributary signal class NRZ 2.5G | C16S1-1D2
B-C16S1-1D2 | C16L1-1D2
B-C16L1-1D2 | – | +| Target distance for class NRZ 2.5G (km) (Note) | 20 | 42 | – | +| NOTE – These target distances are for classification and not for specification. | | | | + +### 6.4.1 Non-amplified multichannel interfaces + +The non-amplified multichannel interfaces in this Recommendation are specified in Tables 9-1 to 9-10, 9-15 and 9-16. + +### 6.4.2 Amplified multichannel interfaces + +Amplified multichannel interfaces may be introduced into this Recommendation in the future. + +## 6.5 Single-channel interfaces at the reference points Ss and Rs + +The single-channel interfaces described in clause 6.5.1 are intended to enable transverse compatibility at the single-channel interfaces at either end of the CWDM link, as shown in Figures 6-2, 6-3, 6-5 and 6-6. + +Further requirements related to transverse compatibility can be found in clause 7. + +Tables 6-6 and 6-7 summarize the single-channel application codes, which are structured according to the nomenclature in clause 6.3. Expected distances for a variety of CWDM network element insertion loss values are provided in Appendix II, and information concerning black links containing OADMs is given in Appendix III. + +**Table 6-6 – Classification of 4-channel multichannel systems with single-channel interfaces** + +| Application | Short-haul (S) | Long-haul (L) | +|-----------------------------------------|---------------------------------------------------|-------------------------------------------------------------------------------| +| Type of fibre | [ITU-T G.652],
[ITU-T G.653],
[ITU-T G.655] | [ITU-T G.652],
[ITU-T G.653],
[ITU-T G.655] | +| Optical tributary signal class NRZ 2.5G | S-C4S1-1D2
S-C4S1-1D3
S-C4S1-1D5 | S-C4L1-1D2
S-C4L1-1D3
S-C4L1-1D5 | +| Optical tributary signal class NRZ 10G | S-C4S1-2D2F
S-C4S1-2D3F
S-C4S1-2D5F | S-C4L1-2D2, S-C4L1-2D2F
S-C4L1-2D3, S-C4L1-2D3F
S-C4L1-2D5, S-C4L1-2D5F | + +**Table 6-7 – Classification of 8-channel multichannel systems with single-channel interfaces** + +| Application | Short-haul (S) | Long-haul (L) | +|-----------------------------------------|---------------------------------------------------|-------------------------------------------------------------------------------| +| Type of fibre | [ITU-T G.652],
[ITU-T G.653],
[ITU-T G.655] | [ITU-T G.652],
[ITU-T G.653],
[ITU-T G.655] | +| Optical tributary signal class NRZ 2.5G | S-C8S1-1D2
S-C8S1-1D3
S-C8S1-1D5 | S-C8L1-1D2
S-C8L1-1D3
S-C8L1-1D5 | +| Optical tributary signal class NRZ 10G | S-C8S1-2D2F
S-C8S1-2D3F
S-C8S1-2D5F | S-C8L1-2D2, S-C8L1-2D2F
S-C8L1-2D3, S-C8L1-2D3F
S-C8L1-2D5, S-C8L1-2D5F | + +### **6.5.1 Non-amplified multichannel systems with single-channel interfaces** + +The non-amplified multichannel systems with single-channel interfaces in this Recommendation are specified in Tables 9-11 to 9-14 and Tables 9-17 to 9-22. + +### **6.5.2 Amplified multichannel systems with single-channel interfaces** + +Amplified multichannel systems with single-channel interfaces may be introduced into this Recommendation in the future. + +# **7 Transverse compatibility** + +This Recommendation specifies parameters in order to enable transverse (i.e., multivendor) compatibility at multichannel reference points MPI-SM and MPI-RM of the "black box" approach CWDM network elements (NEs), and at single-channel reference points SS and RS of the "black link" approach CWDM NEs. + +The multichannel reference points MPI-SM and MPI-RM are intended to interconnect two aggregate interfaces of CWDM NEs, which may be from two different vendors. + +The single-channel reference points SS and RS are intended to make multiple tributary interfaces of CWDM NEs transversely compatible. In this case, multiple tributary signal transmitters (Tx λi) and receivers (Rx λi) may be from many different vendors. Note that CWDM NEs (OM and OD) for the "black link" approach are from a single vendor, and considered as a single set of optical devices. + +Transverse (multivendor) compatibility is enabled for: + +- All multichannel reference points MPI-SM and MPI-RM of "black box" approach CWDM NEs having exactly the same application code. + +Interconnection of aggregate interfaces with different application codes is a matter of joint engineering. Care must be taken particularly with respect to critical parameters that must be matched, e.g., MPI-SM output power, MPI-RM input power. + +- All single-channel reference points SS and RS of "black link" approach CWDM NEs having exactly the same application code. + +Coexistence of tributary interfaces with different application codes is a matter of joint engineering. Care must be taken particularly with respect to critical parameters that must be consistent, e.g., SS output power and RS input power, SS bit rate/line coding and RS bit rate/line coding. + +# 8 Parameter definitions + +The parameters in Tables 8-1 and 8-2 are defined at the interface points, and the definitions are provided in the clauses below. + +**Table 8-1 – Physical layer parameters and values for CWDM applications using the "black box" approach** + +| Parameters | Units | For Tables 9-1 to 9-10, 9-15, 9-16 and 9-23 defined in | For Tables 9-24 and 9-25 defined in | +|--------------------------------------------------------------------------------|-------|--------------------------------------------------------|-------------------------------------| +| General information | | | | +| Maximum number of channels | – | 8.1.1 | 8.1.1 | +| Bit rate/line coding of optical tributary signals | – | 8.1.2 | 8.1.2 | +| Maximum bit error ratio | – | 8.1.3 | 8.1.3 | +| Fibre type | – | 8.1.4 | 8.1.4 | +| Interface at point MPI-SM | | | | +| Maximum mean channel output power | dBm | 8.2.1 | 8.2.1 | +| Minimum mean channel output power | dBm | 8.2.1 | 8.2.1 | +| Maximum mean total output power | dBm | 8.2.2 | 8.2.2 | +| Central wavelength | nm | 8.2.3 | 8.2.3 | +| Channel spacing | nm | 8.2.4 | 8.2.4 | +| Maximum central wavelength deviation | nm | 8.2.5 | 8.2.5 | +| Minimum channel extinction ratio (ER) | dB | 8.2.6 | 8.2.6 | +| Eye mask | – | 8.2.7 | NA | +| Maximum channel output OMA outer | dBm | NA | 8.2.8 | +| Minimum channel output OMA outer | dBm | NA | 8.2.8 | +| Maximum TDECQ | dB | NA | 8.2.9 | +| Minimum channel OMA outer minus TDECQ | dBm | NA | 8.2.10 | +| Maximum TECQ | dB | NA | 8.2.11 | +| Maximum TDECQ-TECQ | dB | NA | 8.2.12 | +| Optical path from point MPI-SM to MPI-RM | | | | +| Maximum attenuation | dB | 8.3.1 | 8.3.1 | +| Minimum attenuation | dB | 8.3.2 | 8.3.2 | +| Chromatic dispersion range | ps/nm | 8.3.3 | 8.3.3 | +| Minimum optical return loss at MPI-S M | dB | 8.3.4 | 8.3.4 | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | 8.3.5 | 8.3.5 | +| Maximum differential group delay | ps | 8.3.6 | 8.3.6 | + +**Table 8-1 – Physical layer parameters and values for CWDM applications using the "black box" approach** + +| Parameters | Units | For Tables 9-1 to 9-10, 9-15, 9-16 and 9-23 defined in | For Tables 9-24 and 9-25 defined in | +|------------------------------------------------------------------|-------|--------------------------------------------------------|-------------------------------------| +| Interface at point MPI-RM | | | | +| Maximum mean channel input power | dBm | 8.4.1 | 8.4.1 | +| Minimum mean channel input power | dBm | 8.4.2 | 8.4.2 | +| Maximum mean total input power | dBm | 8.4.3 | 8.4.3 | +| Maximum optical path penalty | dB | 8.4.4 | NA | +| Minimum equivalent sensitivity | dBm | 8.4.7 | NA | +| Maximum channel input OMA outer | dBm | NA | 8.4.8 | +| Minimum channel input OMA outer | dBm | NA | 8.4.8 | +| Maximum channel power difference | dB | NA | 8.4.9 | +| Maximum multi-path interference penalty allowance | dB | NA | 8.4.10 | +| Minimum equivalent sensitivity (OMA outer minus SECQ) | dBm | NA | 8.4.11 | +| Maximum reflectance of optical network element | dB | 8.4.5 | 8.4.5 | + +**Table 8-2 – Physical layer parameters and values for CWDM applications using the "black link" approach** + +| Parameter | Units | Defined in | +|---------------------------------------------------------------|-------|------------| +| General information | | | +| Maximum number of channels | – | 8.1.1 | +| Bit rate/line coding of optical tributary signals | – | 8.1.2 | +| Maximum bit error ratio | – | 8.1.3 | +| Fibre type | – | 8.1.4 | +| Interface at point Ss | | | +| Maximum mean channel output power | dBm | 8.2.1 | +| Minimum mean channel output power | dBm | 8.2.1 | +| Central wavelength | nm | 8.2.3 | +| Channel spacing | nm | 8.2.4 | +| Maximum central wavelength deviation | nm | 8.2.5 | +| Minimum channel extinction ratio | dB | 8.2.6 | +| Eye mask | – | 8.2.7 | +| Optical path from point Ss to Rs | | | +| Maximum channel insertion loss | dB | 8.5.1 | +| Minimum channel insertion loss | dB | 8.5.1 | + +**Table 8-2 – Physical layer parameters and values for CWDM applications using the "black link" approach** + +| Parameter | Units | Defined in | +|------------------------------------------------------|-------|------------| +| Chromatic dispersion range | ps/nm | 8.3.3 | +| Minimum optical return loss at $S_S$ | dB | 8.3.4 | +| Maximum discrete reflectance between $S_S$ and $R_S$ | dB | 8.3.5 | +| Maximum differential group delay | ps | 8.3.6 | +| Maximum inter-channel crosstalk at $R_S$ | dB | 8.5.2 | +| Maximum interferometric crosstalk at $R_S$ | dB | 8.5.3 | +| Interface at point R_S | | | +| Maximum mean channel input power | dBm | 8.4.1 | +| Receiver sensitivity | dBm | 8.4.6 | +| Maximum optical path penalty | dB | 8.4.4 | +| Maximum reflectance of receiver | dB | 8.4.5 | + +## 8.1 General information + +### 8.1.1 Maximum number of channels + +The maximum number of optical channels that may be simultaneously present at an interface. + +For bidirectional applications, the maximum number of channels is expressed in the form $n/2 + n/2$ where $n$ is the maximum number of channels supported by the application code, and $n/2$ is the number of channels in each direction. + +It should be noted that, if it is desired to be able to upgrade a link with a certain maximum channel count to a configuration with a higher maximum channel count, then the set of parameter values specified for the higher channel count application code should be met for the initial link. + +As an example, a system designed according to a 4-channel application code cannot be upgraded to an 8-channel system. Such an option should be implemented by under-equipping an 8-channel system and using the set of parameter values for an 8-channel application code. + +### 8.1.2 Bit rate/line coding of optical tributary signals + +Optical tributary signal class NRZ 1.25G applies to continuous digital signals with non-return to zero line coding, from nominally 622 Mbit/s to nominally 1.25 Gbit/s. Optical tributary signal class NRZ 2.5G applies to continuous digital signals with non-return to zero line coding, from nominally 622 Mbit/s to nominally 2.67 Gbit/s. Optical tributary signal class NRZ 10G applies to continuous digital signals with non-return to zero line coding, from nominally 2.4 Gbit/s to nominally 10.76 Gbit/s. Optical tributary signal class NRZ 10G includes a signal with STM-64 bit rate according to [ITU-T G.707], OTU2 bit rate according to [ITU-T G.709] and OTL3.4 bit rate (OTU3 striped across four physical lanes) according to [ITU-T G.709]. Optical tributary signal class NRZ 25G applies to continuous digital signals with NRZ line coding, from nominally 9.9 Gbit/s to nominally 28 Gbit/s. Optical tributary signal class PAM4 50G applies to continuous digital signals with PAM4 line coding, from nominally 53.1 Gbit/s to nominally 55.91 Gbit/s. The mapping from the input stream of bits to PAM4 optical symbols and back to the output stream of bits is performed according to 120.5.7, 122.5.2 and 122.5.3 of [IEEE 802.3]. Optical tributary signal class PAM4 100G applies to continuous digital signals with PAM4 line coding, from nominally 106.25 Gbit/s to nominally 111.8 Gbit/s. The mapping from the input stream of bits to PAM 4 100G optical symbols + +and back to the output stream of bits is performed according to sections 135.5.7, 140.5.2 and 140.5.3 of [IEEE 802.3]. + +### **8.1.3 Maximum bit error ratio** + +The parameters are specified relative to an optical section design objective of a bit error ratio (BER) not worse than the value specified by the application code. This value applies to each optical channel under the extreme case of optical path attenuation and dispersion conditions in each application. The possible effect on the definition of this parameter due to the presence of forward error correction (e.g., in an OTUk) has not been considered in the present version of this Recommendation. + +### **8.1.4 Fibre type** + +Single mode optical fibre types are chosen from those defined in [ITU-T G.652], [ITU-T G.653] and [ITU-T G.655]. + +## **8.2 Interface at point MPI-SM or Ss** + +### **8.2.1 Maximum and minimum mean channel output power** + +The mean launched power of each optical channel at reference point MPI-SM or Ss is the average power of a pseudo-random data sequence coupled into the fibre or the CWDM link. It is given as a range (maximum and minimum) to allow for some cost optimization and to cover allowances for operation under the standard operating conditions, connector degradations, measurement tolerances and aging effects. + +### **8.2.2 Maximum mean total output power** + +The maximum value of the mean launched optical power at point MPI-SM. + +NOTE – Optical safety aspects have been considered in determining the values given in this Recommendation, since it is desirable to avoid the need for automatic power reduction (APR), automatic power shutdown (APSD), or automatic laser shutdown (ALS) procedures, for cost reasons. + +### **8.2.3 Central wavelength** + +The nominal single-channel wavelengths on which the digital coded information of the particular optical channels are modulated by use of the NRZ line code (as defined in [ITU-T G.957] and [ITU-T G.691]) or PAM4 line code (as defined in clause 8.1.2). + +The central wavelengths are based on the wavelength grid given in [ITU-T G.694.2]. The allowed central wavelengths for the multichannel CWDM network element are specified in Tables 9-1 to 9-25. + +Note that the value of "c" (speed of light in a vacuum) that should be used for converting between frequency and wavelength is $2.99792458 \times 10^8$ m/s. + +### **8.2.4 Channel spacing** + +The nominal difference in wavelength between two adjacent channels. All possible tolerances of actual wavelengths are considered in clause 8.2.5. + +### **8.2.5 Maximum central wavelength deviation** + +The difference between the nominal central wavelength and the actual central wavelength. The central wavelength deviation is determined mainly by two factors. First, the laser manufacturer is allowed a wavelength variation around the nominal wavelength in order to achieve a higher yield and/or relax fabrication tolerances. Second, the use of uncooled lasers will cause the wavelength to change with temperature within the specified temperature range of the laser. + +Also included in the central wavelength deviation are all the processes that affect the instantaneous value of the source central wavelength over a measurement interval appropriate to the channel bit rate. + +These processes include source chirp, information bandwidth, broadening due to self-phase modulation, and effects due to aging. + +Maximum central wavelength deviation in CWDM point-to-point systems is provided in Tables 9-1 to 9-22. + +### 8.2.6 Minimum channel extinction ratio + +For NRZ optical transmit signals the extinction ratio (ER) is defined for a single-channel parameter, as: + +$$ER = 10 \log_{10} (A/B)$$ + +where: + +$A$ is the average optical power level at the centre of the logical "1"; and + +$B$ is the average optical power level at the centre of the logical "0". + +The convention adopted for optical logic levels is: + +- emission of light for a logical "1"; +- no emission for a logical "0". + +For PAM4 optical transmit signals the extinction ratio is defined as: + +$$ER = 10 \log_{10} (P_3/P_0)$$ + +where: + +$P_3$ is the average optical power over the central 2-unit interval (UI) of a run of 7 threes as illustrated in Figure 8-1; and + +$P_0$ is the average optical power over the central 2 UI of a run of 6 zeros as illustrated in Figure 8-1. + +![Figure 8-1 shows two waveforms illustrating power levels P0 and P3. The left waveform shows a run of 6 zeros, with a 2 UI interval marked and labeled P0. The right waveform shows a run of 7 threes, with a 2 UI interval marked and labeled P3. The text G.695(25) is visible in the bottom right corner of the right waveform.](f164f105be425961ae10cd65296ddceb_img.jpg) + +The figure consists of two side-by-side plots of optical power over time. The left plot shows a signal that is mostly low (logical '0') with some transitions. A horizontal bracket labeled '2 UI' is positioned over a low-power section, with the label 'P0' below it. The right plot shows a signal with more frequent transitions between high and low states. A horizontal bracket labeled '2 UI' is positioned over a high-power section, with the label 'P3' above it. In the bottom right corner of the right plot, the text 'G.695(25)' is visible. + +Figure 8-1 shows two waveforms illustrating power levels P0 and P3. The left waveform shows a run of 6 zeros, with a 2 UI interval marked and labeled P0. The right waveform shows a run of 7 threes, with a 2 UI interval marked and labeled P3. The text G.695(25) is visible in the bottom right corner of the right waveform. + +**Figure 8-1 – Example power levels $P_0$ and $P_3$** + +The minimum channel extinction ratio is not required to be met in the presence of a fourth-order Bessel-Thomson filter. + +For multichannel interfaces, two alternative methods can be used for the verification of this parameter as in [ITU-T G.959.1]: + +- Method A can be used when single-channel reference points are accessible at the transmit end of the link for verification. For this method, the procedures described in [ITU-T G.957] and [ITU-T G.691] are used. The configuration for this method is contained in Annex A of [ITU-T G.959.1]; + +- Method B employs a reference optical bandpass filter to isolate the individual transmitted signal. The characteristics of the reference optical bandpass filter are contained in Annex B of [ITU-T G.959.1]. + +### 8.2.7 Eye mask + +For NRZ optical transmit signals the definition and filter limits for this parameter are found in [ITU-T G.959.1]. This definition can be directly applied to single-channel interfaces of the "black link" approach. In the case of the multichannel interfaces of the "black box" approach, two alternative methods can be used as in [ITU-T G.959.1]: + +- Method A can be used when single-channel reference points are accessible at the transmit end of the link for verification. For this method, the procedures described in [ITU-T G.957] and [ITU-T G.691] are used. The configuration for this method is contained in Annex A of [ITU-T G.959.1]; +- Method B employs a reference optical bandpass filter to isolate the individual transmitted signals, followed by a reference receiver. The characteristics of the reference optical bandpass filter and the reference receiver are contained in Annex B of [ITU-T G.959.1]. + +### 8.2.8 Maximum and minimum channel output OMAouter + +For PAM4 optical signals the channel output OMAouter is defined as the difference between the average optical power $P_3$ , over the central 2 UI of a run of 7 threes, and the average optical power $P_0$ , over the central 2 UI of a run of 6 zeros, as illustrated in Figure 8-1. + +### 8.2.9 Maximum TDECQ + +For PAM4 50G optical signals, transmitter and dispersion eye closure for PAM4 (TDECQ) is defined as described in sections 121.8.5.1, 121.8.5.2 and 121.8.5.3 of [IEEE 802.3] with the following exceptions: + +- The signalling rate of the test pattern generator is the same as the application code signalling rate. For example, an application code with a bit rate/line coding of optical tributary signals of FOIC2.4 PAM4, has a bit rate of approximately 55.904737223 Gbit/s and an application code signalling rate of approximately 27.952368612 GBd. +- The combination of the O/E converter and the oscilloscope has a fourth-order Bessel-Thomson filter response with a bandwidth of approximately half of the application code signalling rate. +- The reference equalizer is a 5-tap, T-spaced, feed-forward equalizer (FFE), where T is the symbol period. The sum of the equalizer tap coefficients is equal to 1. + +NOTE 1 – This reference equalizer is part of the TDECQ test and does not imply any particular receiver equalizer implementation. + +- The normalized noise power density spectrum $N(f)$ is equivalent to white noise filtered by a fourth-order Bessel-Thomson response filter with a bandwidth of half of the application code signalling rate. + +For PAM4 100G optical signals transmitter and dispersion eye closure for PAM4 (TDECQ) is defined as described in section 140.7.5 of [IEEE 802.3] with the following exceptions: + +- The signalling rate of the test pattern generator is the same as the application code signalling rate. For example, an application code with a bit rate/line coding of optical tributary signals of FOIC1.1 PAM4, has a bit rate of approximately 111.809973 Gbit/s and an application code signalling rate of approximately 55.9049865 GBd. +- The combination of the O/E converter and the oscilloscope has a fourth-order Bessel-Thomson filter response with a bandwidth of approximately half of the application code signalling rate. + +- The reference equalizer is a 5 tap, T spaced, feed-forward equalizer (FFE), where T is the symbol period. The sum of the equalizer tap coefficients is equal to 1. +NOTE 2 – This reference equalizer is part of the TDECQ test and does not imply any particular receiver equalizer implementation. +- The normalized noise power density spectrum $N(f)$ is equivalent to white noise filtered by a fourth-order Bessel-Thomson response filter with a bandwidth of half of the application code signalling rate. + +### 8.2.10 Minimum channel OMAouter minus TDECQ + +For PAM4 optical signals, a transmitter with the maximum value of TDECQ is required to have a larger value of OMAouter than a transmitter with less than the maximum value of TDECQ. This is achieved by specifying a value for the OMAouter minus TDECQ. Note that even for transmitters with very low TDECQ, the minimum channel output OMAouter is required to be met. + +### 8.2.11 Maximum TECQ + +The transmitter eye closure for PAM4 (TECQ) is a measure of the optical transmitter's eye closure. TECQ is measured using the methods specified for TDECQ in clause 8.2.9, except that the test fibre is not used. + +### 8.2.12 Maximum |TDECQ-TECQ| + +This is the maximum value of the difference between TDECQ, as defined in clause 8.2.9, and TECQ, as defined in clause 8.2.11. + +## 8.3 Common optical path parameters (single span) from point MPI-SM to MPI-RM, or from Ss to Rs + +### 8.3.1 Maximum attenuation + +The maximum path attenuation, for all wavelengths used by the application, where the system in question operates under end-of-life conditions at a BER of $10^{-12}$ (or as given by the application code), under worst-case transmit-side signal and dispersion. The definition of effects included in the maximum attenuation is given in clause 6.3.1 of [ITU-T G.691]. + +The target distances for each application are based on the set of assumed maximum attenuation coefficients found in Appendix I. The values given represent installed fibre loss (including splices and cable margin). It should be noted that this method gives a theoretical value. Connector and splice losses as well as losses due to bending or optical monitoring, which can be present in practical implementations, may lead to other distances. + +### 8.3.2 Minimum attenuation + +The minimum path attenuation that allows the system in question, operating under worst-case transmit conditions to achieve a BER no worse than $10^{-12}$ (or as given by the application code). + +### 8.3.3 Chromatic dispersion range + +This parameter defines the range of values of the optical path chromatic dispersion that the system shall be able to tolerate. The limits are considered worst-case dispersion values. The worst-case approach on this parameter is intended to give some margins on a sensitive parameter, as well as making it possible to stretch the transmission distances for low-loss fibre plants. + +The process used to derive the limits of the chromatic dispersion range, contained in Tables 9-1 to 9-22 was: + +- Estimate the maximum link length supported by each application code from: + +- for black box applications, the maximum attenuation divided by the highest value of the minimum attenuation coefficient from Table I.1 across the range of wavelength channels specified for that application code; + - for black link applications, the maximum attenuation minus an allowance for the loss of an OM/OD pair, divided by the highest value of the minimum attenuation coefficient from Table I.1 across the range of wavelength channels specified for that application code. +- Estimate the maximum dispersion of this fibre length for the highest (absolute value) dispersion channel. + - Where the dispersion values obtained by this method were considered to be higher than is feasible for current cost-effective optical transmitters, the dispersion values were reduced in accordance with current technology capability (so these applications may be dispersion-limited, e.g., S-C4L1-1D2, whereas the others are loss-limited, e.g., C4S1-1D2). + +In this Recommendation, the per channel chromatic dispersion range is specified corresponding to a single maximum dispersion limited distance across the block of channels specified for each application code multiplied by the dispersion coefficient given in Table I.2. As a result of this approach, the dispersion limit at the channel with the highest dispersion coefficient is a rounded value, whereas the dispersion limit of the other channels is derived from this rounded value and the chromatic dispersion coefficients found in Table I.2. + +The allowed optical path penalty considers all deterministic effects due to chromatic dispersion as well as the penalty due to the maximum differential group delay. + +### 8.3.4 Minimum optical return loss at MPI-SM or SS + +Reflections are caused by refractive index discontinuities along the optical path. If not controlled, they can degrade system performance through their disturbing effect on the operation of the optical source, or through multiple reflections which lead to interferometric noise at the receiver. Reflections from the optical path are controlled by specifying the: + +- minimum optical return loss of the cable plant at the source reference point (i.e., MPI-SM, SS), including any connectors; and +- maximum discrete reflectance between source reference points (i.e., MPI-SM, SS) and receive reference points (i.e., MPI-RM, RS). + +Reflectance denotes the reflection from any single discrete reflection point, whereas the optical return loss is the ratio of the incident optical power to the total returned optical power from the entire fibre including both discrete reflections and distributed backscattering such as Rayleigh scattering. + +Measurement methods for reflections are described in Appendix I of [ITU-T G.957]. For the purpose of reflectance and return loss measurements, points SS and RS are assumed to coincide with the endface of each connector plug. It is recognized that this does not include the actual reflection performance of the respective connectors in the operational system. These reflections are assumed to have the nominal value of reflection for the specific type of connectors used. + +### 8.3.5 Maximum discrete reflectance between MPI-SM and MPI-RM or between SS and RS + +Optical reflectance is defined to be the ratio of the reflected optical power present at a point, to the optical power incident to that point. Control of reflections is discussed extensively in [ITU-T G.957]. The maximum number of connectors or other discrete reflection points which may be included in the optical path (e.g., for distribution frames, or WDM components) must be such as to allow the specified overall optical return loss to be achieved. If this cannot be done using connectors meeting the maximum discrete reflections cited in the tables of clause 9, then connectors having better reflection performance must be employed. Alternatively, the number of connectors must be reduced. It also may + +be necessary to limit the number of connectors or to use connectors having improved reflectance performance in order to avoid unacceptable impairments due to multiple reflections. + +In the tables of clause 9, the value of maximum discrete reflectance between source reference points and receive reference points is intended to minimize the effects of multiple reflections (e.g., interferometric noise). The value for maximum receiver reflectance is chosen to ensure acceptable penalties due to multiple reflections for all likely system configurations involving multiple connectors, etc. Systems employing fewer or higher performance connectors produce fewer multiple reflections and consequently are able to tolerate receivers exhibiting higher reflectance. + +For PAM4 application codes, the maximum value for each discrete reflectance is required to be less than or equal to the value shown in Table 8-3 corresponding to the number of discrete reflectances above $-55$ dB within the channel. For numbers of discrete reflectances in between two numbers shown in the table, the lower of the two corresponding maximum discrete reflectance values applies. + +**Table 8-3 – Maximum discrete reflectance for PAM4 application codes** + +| Number of discrete reflectances above $-55$ dB | Maximum value for each discrete reflectance | | | +|------------------------------------------------|---------------------------------------------|-----------|-----------| +| | C4S1-4D1F | C4R1-5D1F | C4S1-5D1F | +| 1 | $-25$ | $-25$ | $-22$ | +| 2 | $-31$ | $-31$ | $-29$ | +| 4 | $-35$ | $-35$ | $-33$ | +| 6 | $-38$ | $-38$ | $-35$ | +| 8 | $-40$ | $-40$ | $-37$ | +| 10 | $-41$ | $-41$ | $-39$ | + +### 8.3.6 Maximum differential group delay + +Differential group delay (DGD) is the time difference between the fractions of a pulse that are transmitted in the two principal states of polarization of an optical signal. For distances greater than several kilometres, and assuming random (strong) polarization mode coupling, DGD in a fibre can be statistically modelled as having a Maxwellian distribution. + +In this Recommendation, the maximum differential group delay is defined to be the value of DGD that the system must tolerate with a maximum sensitivity degradation of 1 dB. + +Due to the statistical nature of polarization mode dispersion (PMD), the relationship between maximum DGD and mean DGD can only be defined probabilistically. The probability of the instantaneous DGD exceeding any given value can be inferred from its Maxwellian statistics. Therefore, if we know the maximum DGD that the system can tolerate, we can derive the equivalent mean DGD by dividing by the ratio of maximum to mean that corresponds to an acceptable probability. Some example ratios are given below in Table 8-4. + +**Table 8-4 – DGD means and probabilities** + +| Ratio of maximum to mean | Probability of exceeding maximum | +|--------------------------|----------------------------------| +| 3.0 | $4.2 \times 10^{-5}$ | +| 3.5 | $7.7 \times 10^{-7}$ | +| 4.0 | $7.4 \times 10^{-9}$ | + +## 8.4 Interface at point MPI-RM or RS + +### 8.4.1 Maximum mean channel input power + +The maximum acceptable value of the average received channel power at point MPI-RM or RS to achieve the specified maximum BER of the application code. + +### 8.4.2 Minimum mean channel input power + +The minimum acceptable value of the average received channel power at point MPI-RM or RS. The minimum mean channel input power is the minimum mean channel output power minus the maximum attenuation of the application. + +NOTE – The minimum mean channel input power at MPI-RM must be higher than the minimum equivalent sensitivity by the value of the maximum optical path penalty. + +### 8.4.3 Maximum mean total input power + +The maximum acceptable total input power at point MPI-RM. + +### 8.4.4 Maximum optical path penalty + +The path penalty is the apparent reduction of receiver sensitivity (or equivalent sensitivity in the case of the "black box" approach) due to distortion of the signal waveform during its transmission over the path. It is manifested as a shift of the system's BER curves towards higher input power levels. This corresponds to a positive path penalty. Negative path penalties may exist under some circumstances, but should be small (a negative path penalty indicates that a less than perfect transmitter eye has been partially improved by the path dependent distortions). Ideally, the BER curves should be translated only, but shape variations are not uncommon, and may indicate the emergence of BER floors. Since the path penalty is a change in the receiver's sensitivity, it is measured at a BER level of $10^{-12}$ . + +In the "black box" approach (where minimum channel input power is specified), the maximum optical path penalty is equal to the difference between the minimum mean channel input power at MPI-RM and the minimum equivalent sensitivity. + +For the applications defined in this Recommendation, the path penalties are limited to a maximum of 1.5 dB for short-haul systems and 2.5 dB for long-haul systems. These limits are higher than in other Recommendations due to the additional penalty caused by optical crosstalk. + +In the future, systems employing dispersion accommodation techniques based on pre-distortion of the signal at the transmitter may be introduced. In this case, the path penalty in the above sense can only be defined between points with undistorted signals. These points, however, do not coincide with the main path interfaces, and may thus not even be accessible. The definition of path penalty for this case is for further study. + +The average value of the random dispersion penalties due to PMD is included in the allowed path penalty. In this respect, the transmitter/receiver combination is required to tolerate an actual DGD of 0.3-bit period with a maximum sensitivity degradation of 1 dB (with 50% of optical power in each principal state of polarization). For a well-designed receiver, this corresponds to a penalty of 0.1-0.2 dB for a DGD of 0.1-bit period. The actual DGD that may be encountered in operation is + +a randomly varying fibre/cable property, and cannot be specified in this Recommendation. This subject is further discussed in Appendix I of [ITU-T G.691]. + +Note that a signal-to-noise ratio reduction due to optical amplification is not considered a path penalty. + +For applications using the "black link" approach, path penalty includes crosstalk penalty. + +For multichannel interfaces, two alternative methods can be used for the verification of this parameter: + +- Method A can be used when single-channel reference points are accessible at the receive end of the link for verification. For this method, the procedures described in [ITU-T G.957] and [ITU-T G.691] are used. The configuration for this method is contained in Annex A of [ITU-T G.959.1]. +- Method B employs a reference optical bandpass filter to isolate the individual transmitted signals, followed by a reference receiver. The characteristics of the reference optical bandpass filter and the reference receiver are contained in Annex B of [ITU-T G.959.1]. + +NOTE – The optical path penalty observed in the reference receiver may not be exactly the same as actually experienced in the receiving equipment, depending on the design implementation. + +### **8.4.5 Maximum reflectance of CWDM network element or receiver** + +Reflections from the equipment back into the cable plant, or from the receiver back into the CWDM link, are specified by the maximum permissible reflectance of equipment or the receiver measured at reference point MPI-RM or at RS, respectively. Optical reflectance is defined in [ITU-T G.671]. + +### **8.4.6 Receiver sensitivity** + +Receiver sensitivity is defined as the minimum value of average received power at point RS to achieve a 10-12 BER. This must be met with a transmitter with worst-case values of transmitter eye mask, extinction ratio, optical return loss at point SS, receiver connector degradations and measurement tolerances. The receiver sensitivity does not have to be met in the presence of dispersion, reflections from the optical path or optical crosstalk; these effects are specified separately in the allocation of maximum optical path penalty. + +NOTE – The receiver sensitivity does not have to be met in the presence of transmitter jitter in excess of the appropriate jitter generation limit (e.g., [b-ITU-T G.8251] for OTN optical tributary signals). + +Aging effects are not specified separately since they are typically a matter between a network operator and an equipment manufacturer. + +### **8.4.7 Minimum equivalent sensitivity** + +This is the minimum sensitivity that would be required of a receiver placed at MPI-RM to achieve the specified maximum BER of the application code if all except one of the channels were to be removed (with an ideal lossless filter) at point MPI-RM. This would have to be met with a transmitter with worst-case values of transmitter eye mask, extinction ratio, optical return loss at point MPI-SM, connector degradations, transmit-side crosstalk, optical amplifier noise and measurement tolerances. This sensitivity would not have to be met in the presence of dispersion, non-linearity, reflections from the optical path or crosstalk; these effects are specified separately in the allocation of maximum optical path penalty. + +NOTE 1 – The minimum mean channel input power at MPI-RM must be higher than the minimum equivalent sensitivity by the value of the maximum optical path penalty. + +NOTE 2 – The receiver sensitivity does not have to be met in the presence of transmitter jitter in excess of the appropriate jitter generation limit (e.g., [b-ITU-T G.8251] for OTN optical tributary signals). + +Aging effects are not specified separately. Worst-case, end-of-life values are specified. + +### 8.4.8 Maximum and minimum channel input OMAouter + +The maximum acceptable value of the channel OMAouter (see clause 8.2.8 for the definition) at point MPI-RM or MPI-R to achieve the specified maximum BER of the application code. + +### 8.4.9 Maximum channel power difference + +The difference between the largest value of the mean channel input power and the smallest value of the mean channel input power present at the same time within a given optical resolution bandwidth, independent of the number of channels, within the application. + +### 8.4.10 Maximum multi-path interference penalty allowance + +For PAM4 application codes, the optical power budget includes an allowance for multi-path interference as a consequence of there being multiple discrete reflectances in the optical path between the transmitter and receiver (see clause 8.3.5). + +### 8.4.11 Minimum equivalent sensitivity (OMAouter minus SECQ) + +For PAM4 application codes, this is the minimum sensitivity that would be required of a receiver placed at MPI-RM in multichannel applications to achieve the specified maximum BER of the application code if all except one of the channels were to be removed (with an ideal lossless filter) at point MPI-RM. It is specified as the sensitivity the receiver would have if measured using a transmitter with a stressed eye closure for PAM4 (SECQ) of 0 dB, where SECQ is defined as for TDECQ in clause 8.2.9 with the exception that the test fibre is not used. The minimum equivalent sensitivity has to be met in the presence of the maximum differential group delay of the optical path. + +The receiver sensitivity should be measured using a test transmitter with as low a value of SECQ as is practical and then the equivalent sensitivity (OMAouter minus SECQ) value found from: + +$$\text{sensitivity} = \text{measured sensitivity OMA}_{\text{outer}} - \text{SECQ of the test transmitter}$$ + +## 8.5 Additional parameters for the optical path from Ss to Rs + +### 8.5.1 Minimum and maximum channel insertion loss + +Channel insertion loss is defined in [ITU-T G.671]. + +### 8.5.2 Maximum inter-channel crosstalk + +This parameter places a requirement on the isolation of a link conforming to the "black link" approach such that, under the worst-case operating conditions, the inter-channel crosstalk at any reference point RS is less than the maximum inter-channel crosstalk value. + +Inter-channel crosstalk is defined as the ratio of total power in all of the disturbing channels to that in the wanted channel, where the wanted and disturbing channels are at different wavelengths. + +Specifically, the isolation of the link shall be greater than the amount required to ensure that when any channel is operating at the minimum mean output power at point SS and all of the others are at the maximum mean output power, then the inter-channel crosstalk at the corresponding point RS is less than the maximum inter-channel crosstalk value. + +### 8.5.3 Maximum interferometric crosstalk + +This parameter places a requirement on the isolation of a link conforming to the "black link" approach such that, under the worst-case operating conditions, the interferometric crosstalk at any reference point RS is less than the maximum interferometric crosstalk value. + +Interferometric crosstalk is defined as the ratio of the disturbing power to the wanted power within a single-channel, where the disturbing power is the power (not including ASE) within the optical channel that would remain if the wanted signal were removed from the link while leaving all of the other link conditions the same. + +Specifically, the isolation of the link shall be greater than the amount required to ensure that when any channel is operating at the minimum mean output power at point Ss and all of the others are at the maximum mean output power, then the interferometric crosstalk at the corresponding point Rs is less than the maximum interferometric crosstalk value. + +# 9 Parameter values + +The physical layer parameters and values for multichannel interfaces, for "black box" systems, are given in Tables 9-3, 9-5 and 9-6 for NRZ 1.25G applications, in Tables 9-1 to 9-10 for NRZ 2.5G applications, in Tables 9-15 and 9-16 for NRZ 10G applications, in Table 9-23 for NRZ 25G applications, in Table 9-24 for PAM4 50G and very short reach PAM4 100G applications, and in Table 9-25 for short-haul PAM4 100G applications.. + +The physical layer parameters and values for single-channel interfaces, for "black link" systems, are given in Tables 9-11 to 9-14 for NRZ 2.5G applications and in Tables 9-17 to 9-22 for NRZ 10G applications. + +**Table 9-1 – Physical layer parameters and values for multichannel interfaces for 4-channel NRZ 2.5G short-haul black box applications** + +| Parameter | Units | C4S1-1D2 | C4S1-1D3 | C4S1-1D5 | +|-------------------------------------------------------------------------------------|-------|---------------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 4 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point MPI-SM | | | | | +| Maximum mean channel output power | dBm | +4.5 | | | +| Minimum mean channel output power | dBm | –3 | | | +| Maximum mean total output power | dBm | +10.5 | | | +| Central wavelength | nm | 1511 + 20 × m, m = 0 to 3 | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | ±6.5 | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | +| Maximum attenuation | dB | 10.5 | | | +| Minimum attenuation | dB | 4 | | | +| Chromatic dispersion range | | | | | +| – 1511 nm channel | ps/nm | 0 to +719 | –250 to +39 | 0 to +323 | +| – 1531 nm channel | ps/nm | 0 to +775 | –169 to +83 | 0 to +371 | +| – 1551 nm channel | ps/nm | 0 to +833 | –124 to +128 | 0 to +420 | + +**Table 9-1 – Physical layer parameters and values for multichannel interfaces for 4-channel NRZ 2.5G short-haul black box applications** + +| Parameter | Units | C4S1-1D2 | C4S1-1D3 | C4S1-1D5 | +|--------------------------------------------------------------------------------|-------|-----------|-------------|-----------| +| – 1571 nm channel | ps/nm | 0 to +890 | –79 to +177 | 0 to +470 | +| Minimum optical return loss at MPI-S M | dB | 24 | | | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –27 | | | +| Maximum differential group delay | ps | 120 | | | +| Interface at point MPI-RM | | | | | +| Maximum mean channel input power | dBm | +0.5 | | | +| Minimum mean channel input power | dBm | –13.5 | | | +| Maximum mean total input power | dBm | +6.5 | | | +| Maximum optical path penalty | dB | 1.5 | | | +| Minimum equivalent sensitivity | dBm | –15 | | | +| Maximum reflectance of optical network element | dB | –27 | | | + +**Table 9-2 – Physical layer parameters and values for multichannel interfaces for 4-channel NRZ 2.5G long-haul black box applications** + +| Parameter | Units | C4L1-1D2 | C4L1-1D3 | C4L1-1D5 | +|-------------------------------------------------------------------------------------|-------|---------------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 4 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point MPI-SM | | | | | +| Maximum mean channel output power | dBm | +4.5 | | | +| Minimum mean channel output power | dBm | –3 | | | +| Maximum mean total output power | dBm | +10.5 | | | +| Central wavelength | nm | 1511 + 20 × m, m = 0 to 3 | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | ±6.5 | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | +| Maximum attenuation | dB | 19.5 | 20.5 | 20 | +| Minimum attenuation | dB | | 13 | | + +**Table 9-2 – Physical layer parameters and values for multichannel interfaces for 4-channel NRZ 2.5G long-haul black box applications** + +| Parameter | Units | C4L1-1D2 | C4L1-1D3 | C4L1-1D5 | +|--------------------------------------------------------------------------------|-------|------------|--------------|-----------| +| Chromatic dispersion range | | | | | +| – 1511 nm channel | ps/nm | 0 to +1332 | –490 to +77 | 0 to +618 | +| – 1531 nm channel | ps/nm | 0 to +1437 | –331 to +164 | 0 to +711 | +| – 1551 nm channel | ps/nm | 0 to +1544 | –242 to +251 | 0 to +805 | +| – 1571 nm channel | ps/nm | 0 to +1650 | –155 to +347 | 0 to +900 | +| Minimum optical return loss at MPI-S M | dB | 24 | | | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –27 | | | +| Maximum differential group delay | ps | 120 | | | +| Interface at point MPI-RM | | | | | +| Maximum mean channel input power | dBm | | –8.5 | | +| Minimum mean channel input power | dBm | –22.5 | –23.5 | –23 | +| Maximum mean total input power | dBm | | –2.5 | | +| Maximum optical path penalty | dB | 2.5 | 1.5 | 2 | +| Minimum equivalent sensitivity | dBm | | –25 | | +| Maximum reflectance of optical network element | dB | | –27 | | + +**Table 9-3 – Physical layer parameters and values for multichannel interfaces for 4-channel NRZ 1.25G and NRZ 2.5G bidirectional long-haul black box applications** + +| Parameter | Units | B-C4L1-0D2 | B-C4L1-0D3 | B-C4L1-1D2 | B-C4L1-1D3 | +|---------------------------------------------------|-------|---------------------------------|---------------------------------|---------------------------------|---------------------------------| +| General information | | | | | | +| Maximum number of channels | – | 2 + 2 | 2 + 2 | 2 + 2 | 2 + 2 | +| Bit rate/line coding of optical tributary signals | – | NRZ 1.25G | NRZ 1.25G | NRZ 2.5G | NRZ 2.5G | +| Maximum bit error ratio | – | 10 –12 | 10 –12 | 10 –12 | 10 –12 | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.652] | [ITU-T G.653] | +| Interface at point MPI-SM | | | | | | +| Maximum mean channel output power | dBm | +5 (Note) | +5 (Note) | +5 (Note) | +5 (Note) | +| Minimum mean channel output power | dBm | 0 (Note) | 0 (Note) | 0 (Note) | +0 (Note) | +| Maximum mean total output power | dBm | +8 | +8 | +8 | +8 | +| Central wavelength | nm | 1511 +
20 × m, m = 0
to 3 | 1511 +
20 × m, m = 0
to 3 | 1511 +
20 × m, m = 0
to 3 | 1511 +
20 × m, m = 0
to 3 | + +**Table 9-3 – Physical layer parameters and values for multichannel interfaces for 4-channel NRZ 1.25G and NRZ 2.5G bidirectional long-haul black box applications** + +| Parameter | Units | B-C4L1-0D2 | B-C4L1-0D3 | B-C4L1-1D2 | B-C4L1-1D3 | +|-------------------------------------------------------------------------------------|-------|-------------------------|-------------------------|--------------------------|--------------------------| +| Channel spacing | nm | 20 | 20 | 20 | 20 | +| Maximum central wavelength deviation | nm | ±6.5 | ±6.5 | ±6.5 | ±6.5 | +| Minimum channel extinction ratio | dB | 8.2 | 8.2 | 8.2 | 8.2 | +| Eye mask | – | STM-4 per [ITU-T G.957] | STM-4 per [ITU-T G.957] | STM-16 per [ITU-T G.957] | STM-16 per [ITU-T G.957] | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | | +| Maximum attenuation | dB | 25.5 | 25.5 | 22.5 | 23.5 | +| Minimum attenuation | dB | 12 | 12 | 12 | 12 | +| Chromatic dispersion range | | | | | | +| – 1511 nm channel | ps/nm | 0 to +1735 | –610 to +95 | 0 to +1533 | –560 to +88 | +| – 1531 nm channel | ps/nm | 0 to +1872 | –412 to +204 | 0 to +1654 | –378 to +187 | +| – 1551 nm channel | ps/nm | 0 to +2012 | –302 to +312 | 0 to +1778 | –277 to +286 | +| – 1571 nm channel | ps/nm | 0 to +2150 | –193 to +432 | 0 to +1900 | –177 to +396 | +| Minimum optical return loss at MPI-S M | dB | 24 | 24 | 24 | 24 | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –27 | –27 | –27 | –27 | +| Maximum differential group delay | ps | 120 | 120 | 120 | 120 | +| Interface at point MPI-RM | | | | | | +| Maximum mean channel input power | dBm | –7 | –7 | –7 | –7 | +| Minimum mean channel input power | dBm | –25.5 | –25.5 | –22.5 | –23.5 | +| Maximum mean total input power | dBm | –4 | –4 | –4 | –4 | +| Maximum optical path penalty | dB | 1.5 | 1.5 | 2.5 | 1.5 | +| Minimum equivalent sensitivity | dBm | –27 | –27 | –25 | –25 | +| Maximum reflectance of optical network element | dB | –27 | –27 | –27 | –27 | + +**Table 9-3 – Physical layer parameters and values for multichannel interfaces for 4-channel NRZ 1.25G and NRZ 2.5G bidirectional long-haul black box applications** + +| Parameter | Units | B-C4L1-0D2 | B-C4L1-0D3 | B-C4L1-1D2 | B-C4L1-1D3 | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------|------------|------------|------------|------------| +| NOTE – The transmit power levels for these 2 + 2 channel bidirectional applications are higher than for other applications in this Recommendation, so that a target distance of 80 km is achievable for NRZ 2.5G. | | | | | | + +**Table 9-4 – Physical layer parameters and values for multichannel interfaces for 8-channel NRZ 2.5G black box applications** + +| Parameter | Units | C8S1-1D2 | B-C8S1-1D2 | C8L1-1D2 | +|-------------------------------------------------------------------------------------|-------|-------------------------------------------|-------------------------------------------|-------------------------------------------| +| General information | | | | | +| Maximum number of channels | – | 8 | 4 + 4 | 8 | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | NRZ 2.5G | NRZ 2.5G | +| Maximum bit error ratio | – | $10^{-12}$ | $10^{-12}$ | $10^{-12}$ | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.652] | [ITU-T G.652] | +| Interface at point MPI-SM | | | | | +| Maximum mean channel output power | dBm | +4 | +4 | +4 | +| Minimum mean channel output power | dBm | –3.5 | –3.5 | –3.5 | +| Maximum mean total output power | dBm | +13 | +10 | +13 | +| Central wavelength | nm | 1471 +
$20 \times m$ ,
$m = 0$ to 7 | 1471 +
$20 \times m$ ,
$m = 0$ to 7 | 1471 +
$20 \times m$ ,
$m = 0$ to 7 | +| Channel spacing | nm | 20 | 20 | 20 | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | $\pm 6.5$ | $\pm 6.5$ | +| Minimum channel extinction ratio | dB | 8.2 | 8.2 | 8.2 | +| Eye mask | – | STM-16 per [ITU-T G.957] | STM-16 per [ITU-T G.957] | STM-16 per [ITU-T G.957] | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | +| Maximum attenuation | dB | 9 | 9 | 18 | +| Minimum attenuation | dB | 3 | 3 | 12 | +| Chromatic dispersion range | | | | | +| – 1471 nm channel | ps/nm | 0 to +481 | 0 to +481 | 0 to +962 | +| – 1491 nm channel | ps/nm | 0 to +526 | 0 to +526 | 0 to +1051 | +| – 1511 nm channel | ps/nm | 0 to +571 | 0 to +571 | 0 to +1143 | +| – 1531 nm channel | ps/nm | 0 to +616 | 0 to +616 | 0 to +1233 | +| – 1551 nm channel | ps/nm | 0 to +662 | 0 to +662 | 0 to +1325 | +| – 1571 nm channel | ps/nm | 0 to +708 | 0 to +708 | 0 to +1416 | +| – 1591 nm channel | ps/nm | 0 to +754 | 0 to +754 | 0 to +1507 | +| – 1611 nm channel | ps/nm | 0 to +800 | 0 to +800 | 0 to +1600 | + +**Table 9-4 – Physical layer parameters and values for multichannel interfaces for 8-channel NRZ 2.5G black box applications** + +| Parameter | Units | C8S1-1D2 | B-C8S1-1D2 | C8L1-1D2 | +|--------------------------------------------------------------------------------|-------|----------|------------|----------| +| Minimum optical return loss at MPI-S M | dB | 24 | 24 | 24 | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | -27 | -27 | -27 | +| Maximum differential group delay | ps | 120 | 120 | 120 | +| Interface at point MPI-RM | | | | | +| Maximum mean channel input power | dBm | +1 | +1 | -8 | +| Minimum mean channel input power | dBm | -12.5 | -12.5 | -21.5 | +| Maximum mean total input power | dBm | +10 | +7 | +1 | +| Maximum optical path penalty | dB | 1.5 | 1.5 | 2.5 | +| Minimum equivalent sensitivity | dBm | -14 | -14 | -24 | +| Maximum reflectance of optical network element | dB | -27 | -27 | -27 | + +**Table 9-5 – Physical layer parameters and values for multichannel interfaces for 8-channel NRZ 1.25G and NRZ 2.5G bidirectional long-haul black box applications** + +| Parameter | Units | B-C8L1-0D2 | B-C8L1-0D3 | B-C8L1-1D2 | B-C8L1-1D3 | +|---------------------------------------------------|-------|---------------------------|---------------------------|---------------------------|---------------------------| +| General information | | | | | | +| Maximum number of channels | – | 4 + 4 | 4 + 4 | 4 + 4 | 4 + 4 | +| Bit rate/line coding of optical tributary signals | – | NRZ 1.25G | NRZ 1.25G | NRZ 2.5G | NRZ 2.5G | +| Maximum bit error ratio | – | 10 -12 | 10 -12 | 10 -12 | 10 -12 | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.652] | [ITU-T G.653] | +| Interface at point MPI-SM | | | | | | +| Maximum mean channel output power | dBm | +4 | +4 | +4 | +4 | +| Minimum mean channel output power | dBm | -3.5 | -3.5 | -3.5 | -3.5 | +| Maximum mean total output power | dBm | +10 | +10 | +10 | +10 | +| Central wavelength | nm | 1471 + 20 × m, m = 0 to 7 | 1471 + 20 × m, m = 0 to 7 | 1471 + 20 × m, m = 0 to 7 | 1471 + 20 × m, m = 0 to 7 | +| Channel spacing | nm | 20 | 20 | 20 | 20 | +| Maximum central wavelength deviation | nm | ±6.5 | ±6.5 | ±6.5 | ±6.5 | +| Minimum channel extinction ratio | dB | 8.2 | 8.2 | 8.2 | 8.2 | + +**Table 9-5 – Physical layer parameters and values for multichannel interfaces for 8-channel NRZ 1.25G and NRZ 2.5G bidirectional long-haul black box applications** + +| Parameter | Units | B-C8L1-0D2 | B-C8L1-0D3 | B-C8L1-1D2 | B-C8L1-1D3 | +|-------------------------------------------------------------------------------------|-------|-------------------------|-------------------------|--------------------------|--------------------------| +| Eye mask | – | STM-4 per [ITU-T G.957] | STM-4 per [ITU-T G.957] | STM-16 per [ITU-T G.957] | STM-16 per [ITU-T G.957] | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | | +| Maximum attenuation | dB | 21 | 21 | 18 | 19 | +| Minimum attenuation | dB | 12 | 12 | 12 | 12 | +| Chromatic dispersion range | | | | | | +| – 1471 nm channel | ps/nm | 0 to +1118 | –770 to 0 | 0 to +962 | –690 to 0 | +| – 1491 nm channel | ps/nm | 0 to +1222 | –618 to 0 | 0 to +1051 | –554 to 0 | +| – 1511 nm channel | ps/nm | 0 to +1328 | –467 to +73 | 0 to +1143 | –418 to +65 | +| – 1531 nm channel | ps/nm | 0 to +1433 | –315 to +156 | 0 to +1233 | –283 to +140 | +| – 1551 nm channel | ps/nm | 0 to +1540 | –231 to +239 | 0 to +1325 | –207 to +214 | +| – 1571 nm channel | ps/nm | 0 to +1646 | –148 to +331 | 0 to +1416 | –133 to +296 | +| – 1591 nm channel | ps/nm | 0 to +1752 | –64 to +482 | 0 to +1507 | –58 to +432 | +| – 1611 nm channel | ps/nm | 0 to +1860 | 0 to +634 | 0 to +1600 | 0 to +568 | +| Minimum optical return loss at MPI-S M | dB | 24 | 24 | 24 | 24 | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –27 | –27 | –27 | –27 | +| Maximum differential group delay | ps | 120 | 120 | 120 | 120 | +| Interface at point MPI-RM | | | | | | +| Maximum mean channel input power | dBm | –8 | –8 | –8 | –8 | +| Minimum mean channel input power | dBm | –24.5 | –24.5 | –21.5 | –22.5 | +| Maximum mean total input power | dBm | –2 | –2 | –2 | –2 | +| Maximum optical path penalty | dB | 1.5 | 1.5 | 2.5 | 1.5 | +| Minimum equivalent sensitivity | dBm | –26 | –26 | –24 | –24 | +| Maximum reflectance of optical network element | dB | –27 | –27 | –27 | –27 | + +**Table 9-6 – Physical layer parameters and values for multichannel interfaces for 12-channel NRZ 1.25G and NRZ 2.5G bidirectional long-haul black box applications** + +| Parameter | Units | B-C12L1-0D2 | | B-C12L1-1D2 | | +|-------------------------------------------------------------------------------------|-------|----------------------------------------|----------------------------------------|----------------------------------------|----------------------------------------| +| | | 1291-1351 | 1471-1611 | 1291-1351 | 1471-1611 | +| Wavelength block | nm | 1291-1351 | 1471-1611 | 1291-1351 | 1471-1611 | +| General information | | | | | | +| Maximum number of channels | – | 6 + 6 | | 6 + 6 | | +| Bit rate/line coding of optical tributary signals | – | NRZ 1.25G | | NRZ 2.5G | | +| Maximum bit error ratio | – | $10^{-12}$ | | $10^{-12}$ | | +| Fibre type | – | [ITU-T G.652] | | [ITU-T G.652] | | +| Interface at point MPI-SM | | | | | | +| Maximum mean channel output power | dBm | +3.5 | +1.5 | +3.5 | +1.5 | +| Minimum mean channel output power | dBm | –4 | –6 | –4 | –6 | +| Maximum mean total output power | dBm | +10.7 | | +10.7 | | +| Central wavelength | nm | 1291 + $20 \times m$ ,
$m = 0$ to 3 | 1471 + $20 \times m$ ,
$m = 0$ to 7 | 1291 + $20 \times m$ ,
$m = 0$ to 3 | 1471 + $20 \times m$ ,
$m = 0$ to 7 | +| Channel spacing | nm | 20 | | 20 | | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | $\pm 6.5$ | | +| Minimum channel extinction ratio | dB | 8.2 | | 8.2 | | +| Eye mask | – | STM-4 per [ITU-T G.957] | | STM-16 per [ITU-T G.957] | | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | | +| Maximum attenuation | dB | 20 | 14.7 | 18 | 12.8 | +| Minimum attenuation | dB | 11 | 7 | 11 | 7 | +| Chromatic dispersion range | | | | | | +| – 1291 nm channel | ps/nm | –208 to 0 | | –188 to 0 | | +| – 1311 nm channel | ps/nm | –100 to +86 | | –91 to +78 | | +| – 1331 nm channel | ps/nm | 0 to +181 | | 0 to +163 | | +| – 1351 nm channel | ps/nm | 0 to +271 | | 0 to +245 | | +| – 1471 nm channel | ps/nm | | 0 to +685 | | 0 to +619 | +| – 1491 nm channel | ps/nm | | 0 to +749 | | 0 to +677 | +| – 1511 nm channel | ps/nm | | 0 to +814 | | 0 to +736 | +| – 1531 nm channel | ps/nm | | 0 to +878 | | 0 to +794 | +| – 1551 nm channel | ps/nm | | 0 to +944 | | 0 to +853 | +| – 1571 nm channel | ps/nm | | 0 to +1009 | | 0 to +911 | + +**Table 9-6 – Physical layer parameters and values for multichannel interfaces for 12-channel NRZ 1.25G and NRZ 2.5G bidirectional long-haul black box applications** + +| Parameter | Units | B-C12L1-0D2 | | B-C12L1-1D2 | | +|--------------------------------------------------------------------------------|-------|-------------|------------|-------------|------------| +| – 1591 nm channel | ps/nm | | 0 to +1074 | | 0 to +970 | +| – 1611 nm channel | ps/nm | | 0 to +1140 | | 0 to +1030 | +| Minimum optical return loss at MPI-S M | dB | 24 | | 24 | | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –27 | | –27 | | +| Maximum differential group delay | ps | 120 | | 120 | | +| Interface at point MPI-RM | | | | | | +| Maximum mean channel input power | dBm | –7.5 | –5.5 | –7.5 | –5.5 | +| Minimum mean channel input power | dBm | –24 | –20.7 | –22 | –18.8 | +| Maximum mean total input power | dBm | +2.3 | | +2.3 | | +| Maximum optical path penalty | dB | 1 | 1 | 1 | 2 | +| Minimum equivalent sensitivity | dBm | –25 | –21.7 | –23 | –20.8 | +| Maximum reflectance of optical network element | dB | –27 | | –27 | | + +**Table 9-7 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application C16S1-1D2** + +| Parameter | Units | C16S1-1D2 | +|---------------------------------------------------|-------|--------------------------------| +| Wavelength block | nm | for further study (ffs) | +| General information | | | +| Maximum number of channels | – | 16 | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | +| Maximum bit error ratio | – | 10 –12 | +| Fibre type | – | ITU-T G.652.C or ITU-T G.652.D | +| Interface at point MPI-SM | | | +| Maximum mean channel output power | dBm | ffs | +| Minimum mean channel output power | dBm | ffs | +| Maximum mean total output power | dBm | ffs | +| Central wavelength | nm | ffs | +| Channel spacing | nm | 20 | +| Maximum central wavelength deviation | nm | ±6.5 | + +**Table 9-7 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application C16S1-1D2** + +| Parameter | Units | C16S1-1D2 | +|-------------------------------------------------------------------------------------|-------|--------------------------| +| Minimum channel extinction ratio | dB | 8.2 | +| Eye mask | – | STM-16 per [ITU-T G.957] | +| Optical path (single span) from point MPI-SM to MPI-RM | | | +| Maximum attenuation | dB | ffs | +| Minimum attenuation | dB | ffs | +| Chromatic dispersion range | ps/nm | ffs | +| Minimum optical return loss at MPI-S M | dB | ffs | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | ffs | +| Maximum differential group delay | ps | 120 | +| Interface at point MPI-RM | | | +| Maximum mean channel input power | dBm | ffs | +| Minimum mean channel input power | dBm | ffs | +| Maximum mean total input power | dBm | ffs | +| Maximum optical path penalty | dB | ffs | +| Minimum equivalent sensitivity | dBm | ffs | +| Maximum reflectance of optical network element | dB | ffs | + +**Table 9-8 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application C16L1-1D2** + +| Parameter | Units | C16L1-1D2 | +|---------------------------------------------------|-------|--------------------------------| +| Wavelength block | nm | ffs | +| General information | | | +| Maximum number of channels | – | 16 | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | +| Maximum bit error ratio | – | $10^{-12}$ | +| Fibre type | – | ITU-T G.652.C or ITU-T G.652.D | +| Interface at point MPI-SM | | | +| Maximum mean channel output power | dBm | ffs | +| Minimum mean channel output power | dBm | ffs | +| Maximum mean total output power | dBm | ffs | +| Central wavelength | nm | ffs | +| Channel spacing | nm | 20 | +| Maximum central wavelength deviation | nm | ±6.5 | + +**Table 9-8 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application C16L1-1D2** + +| Parameter | Units | C16L1-1D2 | +|-------------------------------------------------------------------------------------|-------|--------------------------| +| Minimum channel extinction ratio | dB | 8.2 | +| Eye mask | – | STM-16 per [ITU-T G.957] | +| Optical path (single span) from point MPI-SM to MPI-RM | | | +| Maximum attenuation | dB | ffs | +| Minimum attenuation | dB | ffs | +| Chromatic dispersion range | ps/nm | ffs | +| Minimum optical return loss at MPI-S M | dB | ffs | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | ffs | +| Maximum differential group delay | ps | 120 | +| Interface at point MPI-RM | | | +| Maximum mean channel input power | dBm | ffs | +| Minimum mean channel input power | dBm | ffs | +| Maximum mean total input power | dBm | ffs | +| Maximum optical path penalty | dB | ffs | +| Minimum equivalent sensitivity | dBm | ffs | +| Maximum reflectance of optical network element | dB | ffs | + +**Table 9-9 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application B-C16S1-1D2** + +| Parameter | Units | B-C16S1-1D2 | +|---------------------------------------------------|-------|--------------------------------| +| Wavelength block | nm | ffs | +| General information | | | +| Maximum number of channels | – | 8 + 8 | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | +| Maximum bit error ratio | – | 10 -12 | +| Fibre type | – | ITU-T G.652.C or ITU-T G.652.D | +| Interface at point MPI-SM | | | +| Maximum mean channel output power | dBm | ffs | +| Minimum mean channel output power | dBm | ffs | +| Maximum mean total output power | dBm | ffs | +| Central wavelength | nm | ffs | +| Channel spacing | nm | 20 | +| Maximum central wavelength deviation | nm | ±6.5 | + +**Table 9-9 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application B-C16S1-1D2** + +| Parameter | Units | B-C16S1-1D2 | +|-------------------------------------------------------------------------------------|-------|--------------------------| +| Minimum channel extinction ratio | dB | 8.2 | +| Eye mask | – | STM-16 per [ITU-T G.957] | +| Optical path (single span) from point MPI-SM to MPI-RM | | | +| Maximum attenuation | dB | ffs | +| Minimum attenuation | dB | ffs | +| Chromatic dispersion range | ps/nm | ffs | +| Minimum optical return loss at MPI-S M | dB | ffs | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | ffs | +| Maximum differential group delay | ps | 120 | +| Interface at point MPI-RM | | | +| Maximum mean channel input power | dBm | ffs | +| Minimum mean channel input power | dBm | ffs | +| Maximum mean total input power | dBm | ffs | +| Maximum optical path penalty | dB | ffs | +| Minimum equivalent sensitivity | dBm | ffs | +| Maximum reflectance of optical network element | dB | ffs | + +**Table 9-10 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application B-C16L1-1D2** + +| Parameter | Units | B-C16L1-1D2 | +|---------------------------------------------------|-------|--------------------------------| +| Wavelength block | nm | ffs | +| General information | | | +| Maximum number of channels | – | 8 + 8 | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | +| Maximum bit error ratio | – | 10 -12 | +| Fibre type | – | ITU-T G.652.C or ITU-T G.652.D | +| Interface at point MPI-SM | | | +| Maximum mean channel output power | dBm | ffs | +| Minimum mean channel output power | dBm | ffs | +| Maximum mean total output power | dBm | ffs | +| Central wavelength | nm | ffs | +| Channel spacing | nm | 20 | +| Maximum central wavelength deviation | nm | ±6.5 | + +**Table 9-10 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application B-C16L1-1D2** + +| Parameter | Units | B-C16L1-1D2 | +|-------------------------------------------------------------------------------------|-------|--------------------------| +| Minimum channel extinction ratio | dB | 8.2 | +| Eye mask | – | STM-16 per [ITU-T G.957] | +| Optical path (single span) from point MPI-SM to MPI-RM | | | +| Maximum attenuation | dB | ffs | +| Minimum attenuation | dB | ffs | +| Chromatic dispersion range | ps/nm | ffs | +| Minimum optical return loss at MPI-S M | dB | ffs | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | ffs | +| Maximum differential group delay | ps | 120 | +| Interface at point MPI-RM | | | +| Maximum mean channel input power | dBm | ffs | +| Minimum mean channel input power | dBm | ffs | +| Maximum mean total input power | dBm | ffs | +| Maximum optical path penalty | dB | ffs | +| Minimum equivalent sensitivity | dBm | ffs | +| Maximum reflectance of optical network element | dB | ffs | + +**Table 9-11 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ 2.5G short-haul black link applications** + +| Parameter | Units | S-C4S1-1D2 | S-C4S1-1D3 | S-C4S1-1D5 | +|---------------------------------------------------|-------|-------------------------------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 4 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point Ss | | | | | +| Maximum mean channel output power | dBm | +5 | | | +| Minimum mean channel output power | dBm | 0 | | | +| Central wavelength | nm | $1511 + 20 \times m, m = 0 \text{ to } 3$ | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | + +**Table 9-11 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ 2.5G short-haul black link applications** + +| Parameter | Units | S-C4S1-1D2 | S-C4S1-1D3 | S-C4S1-1D5 | +|------------------------------------------------------------------------|-------|------------|--------------|------------| +| Optical path from point Ss to Rs | | | | | +| Maximum channel insertion loss | dB | 16.5 | | | +| Minimum channel insertion loss | dB | 5 | | | +| Chromatic dispersion range | | | | | +| – 1511 nm channel | ps/nm | 0 to +807 | –350 to +55 | 0 to +446 | +| – 1531 nm channel | ps/nm | 0 to +872 | –236 to +117 | 0 to +513 | +| – 1551 nm channel | ps/nm | 0 to +936 | –173 to +179 | 0 to +581 | +| – 1571 nm channel | ps/nm | 0 to +1000 | –111 to +248 | 0 to +650 | +| Minimum optical return loss at S s | dB | 24 | | | +| Maximum discrete reflectance between S s and R s | dB | –27 | | | +| Maximum differential group delay | ps | 120 | | | +| Maximum inter-channel crosstalk | dB | –20 | | | +| Maximum interferometric crosstalk | dB | –45 | | | +| Interface at point Rs | | | | | +| Maximum mean channel input power | dBm | 0 | | | +| Minimum receiver sensitivity | dBm | –18 | | | +| Maximum optical path penalty | dB | 1.5 | | | +| Maximum reflectance of receiver | dB | –27 | | | + +**Table 9-12 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ 2.5G long-haul black link applications** + +| Parameter | Units | S-C4L1-1D2 | S-C4L1-1D3 | S-C4L1-1D5 | +|---------------------------------------------------------------|-------|-------------------------------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 4 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point Ss | | | | | +| Maximum mean channel output power | dBm | +5 | | | +| Minimum mean channel output power | dBm | 0 | | | +| Central wavelength | nm | $1511 + 20 \times m, m = 0 \text{ to } 3$ | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | +| Optical path from point Ss to Rs | | | | | + +**Table 9-12 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ 2.5G long-haul black link applications** + +| Parameter | Units | S-C4L1-1D2 | S-C4L1-1D3 | S-C4L1-1D5 | +|------------------------------------------------------------------------|-------|------------|--------------|------------| +| Maximum channel insertion loss | dB | 25.5 | 26.5 | 26 | +| Minimum channel insertion loss | dB | 14 | 14 | 14 | +| Chromatic dispersion range | | | | | +| – 1511 nm channel | ps/nm | 0 to +1332 | –600 to +94 | 0 to +756 | +| – 1531 nm channel | ps/nm | 0 to +1437 | –405 to +200 | 0 to +869 | +| – 1551 nm channel | ps/nm | 0 to +1544 | –297 to +307 | 0 to +983 | +| – 1571 nm channel | ps/nm | 0 to +1650 | –190 to +425 | 0 to +1100 | +| Minimum optical return loss at S S | dB | 24 | | | +| Maximum discrete reflectance between S S and R S | dB | –27 | | | +| Maximum differential group delay | ps | 120 | | | +| Maximum inter-channel crosstalk | dB | –20 | | | +| Maximum interferometric crosstalk | dB | –45 | | | +| Interface at point RS | | | | | +| Maximum mean channel input power | dBm | –9 | | | +| Minimum receiver sensitivity | dBm | –28 | | | +| Maximum optical path penalty | dB | 2.5 | 1.5 | 2 | +| Maximum reflectance of receiver | dB | –27 | | | + +**Table 9-13 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 8-channel NRZ 2.5G short-haul black link applications** + +| Parameter | Units | S-C8S1-1D2 | S-C8S1-1D3 | S-C8S1-1D5 | +|---------------------------------------------------|-------|---------------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 8 | 8 | 8 (Note) | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point SS | | | | | +| Maximum mean channel output power | dBm | +5 | | | +| Minimum mean channel output power | dBm | 0 | | | +| Central wavelength | nm | 1471 + 20 × m, m = 0 to 7 | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | ±6.5 | | | + +**Table 9-13 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 8-channel NRZ 2.5G short-haul black link applications** + +| Parameter | Units | S-C8S1-1D2 | S-C8S1-1D3 | S-C8S1-1D5 | +|------------------------------------------------------------------------|-------|--------------------------|--------------|--------------| +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | +| Optical path from point SS to RS | | | | | +| Maximum channel insertion loss | dB | 16.5 | | | +| Minimum channel insertion loss | dB | 5 | | | +| Chromatic dispersion range | | | | | +| – 1471 nm channel | ps/nm | 0 to +601 | –500 to 0 | –174 to +279 | +| – 1491 nm channel | ps/nm | 0 to +657 | –402 to 0 | –85 to +337 | +| – 1511 nm channel | ps/nm | 0 to +714 | –303 to +47 | 0 to +396 | +| – 1531 nm channel | ps/nm | 0 to +771 | –205 to +101 | 0 to +456 | +| – 1551 nm channel | ps/nm | 0 to +828 | –150 to +155 | 0 to +516 | +| – 1571 nm channel | ps/nm | 0 to +885 | –96 to +215 | 0 to +577 | +| – 1591 nm channel | ps/nm | 0 to +942 | –42 to +313 | 0 to +639 | +| – 1611 nm channel | ps/nm | 0 to +1000 | 0 to +411 | 0 to +700 | +| Minimum optical return loss at S S | dB | 24 | | | +| Maximum discrete reflectance between S S and R S | dB | –27 | | | +| Maximum differential group delay | ps | 120 | | | +| Maximum inter-channel crosstalk | dB | –20 | | | +| Maximum interferometric crosstalk | dB | –45 | | | +| Interface at point RS | | | | | +| Maximum mean channel input power | dBm | 0 | | | +| Minimum receiver sensitivity | dBm | –18 | | | +| Maximum optical path penalty | dB | 1.5 | | | +| Maximum reflectance of receiver | dB | –27 | | | + +NOTE – The 1471 nm channel may not be usable with older [ITU-T G.655] fibre that has a maximum cable cut-off wavelength specified as 1480 nm. + +**Table 9-14 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 8-channel NRZ 2.5G long-haul black link applications** + +| Parameter | Units | S-C8L1-1D2 | S-C8L1-1D3 | S-C8L1-1D5 | +|---------------------------------------------------|-------|-------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 8 | 8 | 8 (Note) | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | 10 –12 | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | + +**Table 9-14 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 8-channel NRZ 2.5G long-haul black link applications** + +| Parameter | Units | S-C8L1-1D2 | S-C8L1-1D3 | S-C8L1-1D5 | +|------------------------------------------------------------------------|-------|---------------------------|--------------|--------------| +| Interface at point Ss | | | | | +| Maximum mean channel output power | dBm | +5 | | | +| Minimum mean channel output power | dBm | 0 | | | +| Central wavelength | nm | 1471 + 20 × m, m = 0 to 7 | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | ±6.5 | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | +| Optical path from point Ss to Rs | | | | | +| Maximum channel insertion loss | dB | 25.5 | 26 | 26 | +| Minimum channel insertion loss | dB | 14 | | | +| Chromatic dispersion range | | | | | +| – 1471 nm channel | ps/nm | 0 to +1022 | –850 to 0 | –286 to +458 | +| – 1491 nm channel | ps/nm | 0 to +1118 | –683 to 0 | –139 to +554 | +| – 1511 nm channel | ps/nm | 0 to +1214 | –516 to +81 | 0 to +651 | +| – 1531 nm channel | ps/nm | 0 to +1310 | –348 to +172 | 0 to +749 | +| – 1551 nm channel | ps/nm | 0 to +1407 | –255 to +264 | 0 to +847 | +| – 1571 nm channel | ps/nm | 0 to +1504 | –163 to +365 | 0 to +948 | +| – 1591 nm channel | ps/nm | 0 to +1602 | –71 to +532 | 0 to +1049 | +| – 1611 nm channel | ps/nm | 0 to +1700 | 0 to +699 | 0 to +1150 | +| Minimum optical return loss at S s | dB | 24 | | | +| Maximum discrete reflectance between S s and R s | dB | –27 | | | +| Maximum differential group delay | ps | 120 | | | +| Maximum inter-channel crosstalk | dB | –20 | | | +| Maximum interferometric crosstalk | dB | –45 | | | +| Interface at point Rs | | | | | +| Maximum mean channel input power | dBm | –9 | | | +| Minimum receiver sensitivity | dBm | –28 | | | +| Maximum optical path penalty | dB | 2.5 | 2 | 2 | +| Maximum reflectance of receiver | dB | –27 | | | + +NOTE – The 1471 nm channel may not be usable with older [ITU-T G.655] fibre that has a maximum cable cut-off wavelength specified as 1480 nm. + +**Table 9-15 – Physical layer parameters and values for multichannel interfaces for optical tributary signal class NRZ 10G, 4-channel black box applications** + +| Parameter | Units | C4S1-2D1 | C4L1-2D1 | +|-------------------------------------------------------------------------------------|-------|-----------------------------------------|-----------------------------------------| +| General information | | | | +| Maximum number of channels | – | 4 | 4 | +| Bit rate/line coding of optical tributary signals | – | NRZ 10G | NRZ 10G | +| Maximum bit error ratio | – | $10^{-12}$ | $10^{-12}$ | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.652] | +| Interface at point MPI-SM | | | | +| Maximum mean channel output power | dBm | +2.3 | +4.5 | +| Minimum mean channel output power | dBm | –2.3 | +1.6 | +| Maximum mean total output power | dBm | +8.3 | +10.5 | +| Central wavelength | nm | $1271 + 20 \times m$ , $m = 0$ to $3$ | $1271 + 20 \times m$ , $m = 0$ to $3$ | +| Channel spacing | nm | 20 | 20 | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | $\pm 6.5$ | +| Minimum channel extinction ratio | dB | 4.5 | 5.5 | +| Eye mask | – | NRZ 10G Ratio small per [ITU-T G.959.1] | NRZ 10G Ratio small per [ITU-T G.959.1] | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | +| Maximum attenuation | dB | 6.7 | 18.5 | +| Minimum attenuation | dB | 0 | 9 | +| Chromatic dispersion range | | | | +| – 1271 nm channel | ps/nm | –59.5 to 0 | –238 to 0 | +| – 1291 nm channel | ps/nm | –39 to 0 | –156 to 0 | +| – 1311 nm channel | ps/nm | –19 to +16 | –76 to +64 | +| – 1331 nm channel | ps/nm | 0 to +33.5 | 0 to +134 | +| Minimum optical return loss at MPI-S M | dB | 20 | 20 | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –26 | –26 | +| Maximum differential group delay | ps | 10 | 12 | +| Interface at point MPI-RM | | | | +| Maximum mean channel input power | dBm | +2.3 | –4.5 | +| Minimum mean channel input power | dBm | –9 | –16.9 | +| Maximum mean total input power | dBm | +8.3 | +1.5 | +| Maximum optical path penalty | dB | 1.8 | 1.8 | +| Minimum equivalent sensitivity | dBm | –10.8 | –18.7 | + +**Table 9-15 – Physical layer parameters and values for multichannel interfaces for optical tributary signal class NRZ 10G, 4-channel black box applications** + +| Parameter | Units | C4S1-2D1 | C4L1-2D1 | +|------------------------------------------------|-------|----------|----------| +| Maximum reflectance of optical network element | dB | –26 | –26 | + +**Table 9-16 – Physical layer parameters and values for multichannel interfaces for 8-channel NRZ OTU2 bidirectional long-haul black box applications** + +| Parameter | Units | B-C8L1-2D2F | B-C8L1-2D3F | +|-------------------------------------------------------------------------------------|-------|-------------------------------------------|---------------| +| General information | | | | +| Maximum number of channels | – | 4 + 4 | | +| Bit rate/line coding of optical tributary signals | – | NRZ OTU2 FEC enabled | | +| Maximum bit error ratio | – | $10^{-12}$ | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | +| Interface at point MPI-SM | | | | +| Maximum mean channel output power | dBm | +5 | | +| Minimum mean channel output power | dBm | –2 | | +| Maximum mean total output power | dBm | +11 | | +| Central wavelength | nm | $1471 + 20 \times m, m = 0 \text{ to } 7$ | | +| Channel spacing | nm | 20 | | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | +| Minimum channel extinction ratio | dB | 8.2 | | +| Eye mask | – | NRZ 10G Ratio large per [ITU-T G.959.1] | | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | +| Maximum attenuation | dB | 18 | 19 | +| Minimum attenuation | dB | 12 | | +| Chromatic dispersion range | | | | +| – 1471 nm channel | ps/nm | 0 to +962 | –500 to 0 | +| – 1491 nm channel | ps/nm | 0 to +1051 | –402 to 0 | +| – 1511 nm channel | ps/nm | 0 to +1143 | –303 to +47 | +| – 1531 nm channel | ps/nm | 0 to +1233 | –205 to +101 | +| – 1551 nm channel | ps/nm | 0 to +1325 | –150 to +155 | +| – 1571 nm channel | ps/nm | 0 to +1416 | –96 to +215 | +| – 1591 nm channel | ps/nm | 0 to +1507 | –42 to +313 | +| – 1611 nm channel | ps/nm | 0 to +1600 | 0 to +411 | +| Minimum optical return loss at MPI-S M | dB | 24 | | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –27 | | +| Maximum differential group delay | ps | 30 | | + +**Table 9-16 – Physical layer parameters and values for multichannel interfaces for 8-channel NRZ OTU2 bidirectional long-haul black box applications** + +| Parameter | Units | B-C8L1-2D2F | B-C8L1-2D3F | +|------------------------------------------------|-------|-------------|-------------| +| Interface at point MPI-RM | | | | +| Maximum mean channel input power | dBm | -7 | | +| Minimum mean channel input power | dBm | -20 | -21 | +| Maximum mean total input power | dBm | -1 | | +| Maximum optical path penalty | dB | 2.5 | 1.5 | +| Minimum equivalent sensitivity | dBm | -22.5 | | +| Maximum reflectance of optical network element | dB | -27 | | + +NOTE – The BER for these application codes is required to be met only after the error correction (if used) has been applied. The BER at the input of the FEC decoder can, therefore, be significantly higher than $10^{-12}$ . + +**Table 9-17 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ OTU2 short-haul black link applications** + +| Parameter | Units | S-C4S1-2D2F | S-C4S1-2D3F | S-C4S1-2D5F | +|---------------------------------------------------------------|-------|-----------------------------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 4 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ OTU2 FEC enabled | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point Ss | | | | | +| Maximum mean channel output power | dBm | +4 | | | +| Minimum mean channel output power | dBm | 0 | | | +| Central wavelength | nm | 1511 + 20 × m, m = 0 to 3 | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | ±6.5 | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | NRZ 10G Ratio large per [ITU-T G.959.1] | | | +| Optical path from point Ss to Rs | | | | | +| Maximum channel insertion loss | dB | 14.5 | 15.5 | 15.0 | +| Minimum channel insertion loss | dB | 5 | | | +| Chromatic dispersion range | | | | | +| – 1511 nm channel | ps/nm | 0 to +807 | -350 to +55 | 0 to +413 | +| – 1531 nm channel | ps/nm | 0 to +872 | -236 to +117 | 0 to +474 | +| – 1551 nm channel | ps/nm | 0 to +936 | -173 to +179 | 0 to +537 | +| – 1571 nm channel | ps/nm | 0 to +1000 | -111 to +248 | 0 to +600 | + +**Table 9-17 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ OTU2 short-haul black link applications** + +| Parameter | Units | S-C4S1-2D2F | S-C4S1-2D3F | S-C4S1-2D5F | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------|-------------|-------------|-------------| +| Minimum optical return loss at S S | dB | 24 | | | +| Maximum discrete reflectance between S S and R S | dB | –27 | | | +| Maximum differential group delay | ps | 30 | | | +| Maximum inter-channel crosstalk | dB | –20 | | | +| Maximum interferometric crosstalk | dB | –45 | | | +| Interface at point RS | | | | | +| Maximum mean channel input power | dBm | –1 | | | +| Minimum receiver sensitivity | dBm | –17 | | | +| Maximum optical path penalty | dB | 2.5 | 1.5 | 2.0 | +| Maximum reflectance of receiver | dB | –27 | | | +|

NOTE – The BER for these application codes is required to be met only after the error correction (if used) has been applied. The BER at the input of the FEC decoder can, therefore, be significantly higher than 10^{-12}.

| | | | | + +**Table 9-18 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ 10G long-haul black link applications** + +| Parameter | Units | S-C4L1-2D2 | S-C4L1-2D3 | S-C4L1-2D5 | +|---------------------------------------------------|-------|-----------------------------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 4 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ 10G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point SS | | | | | +| Maximum mean channel output power | dBm | +5 | | | +| Minimum mean channel output power | dBm | +1 | | | +| Central wavelength | nm | 1511 + 20 × m, m = 0 to 3 | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | ±6.5 | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | NRZ 10G Ratio large per [ITU-T G.959.1] | | | + +**Table 9-18 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ 10G long-haul black link applications** + +| Parameter | Units | S-C4L1-2D2 | S-C4L1-2D3 | S-C4L1-2D5 | +|------------------------------------------------------------------------|-------|------------|--------------|------------| +| Optical path from point Ss to Rs | | | | | +| Maximum channel insertion loss | dB | 22.5 | 23.5 | 23 | +| Minimum channel insertion loss | dB | 12 | | | +| Chromatic dispersion range | | | | | +| – 1511 nm channel | ps/nm | 0 to +1130 | –550 to +86 | 0 to +653 | +| – 1531 nm channel | ps/nm | 0 to +1219 | –372 to +184 | 0 to +750 | +| – 1551 nm channel | ps/nm | 0 to +1310 | –272 to +281 | 0 to +849 | +| – 1571 nm channel | ps/nm | 0 to +1400 | –174 to +389 | 0 to +950 | +| Minimum optical return loss at S s | dB | 24 | | | +| Maximum discrete reflectance between S s and R s | dB | –27 | | | +| Maximum differential group delay | ps | 30 | | | +| Maximum inter-channel crosstalk | dB | –20 | | | +| Maximum interferometric crosstalk | dB | –45 | | | +| Interface at point Rs | | | | | +| Maximum mean channel input power | dBm | –7 | | | +| Minimum receiver sensitivity | dBm | –24 | | | +| Maximum optical path penalty | dB | 2.5 | 1.5 | 2 | +| Maximum reflectance of receiver | dB | –27 | | | + +**Table 9-19 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ OTU2 long-haul black link applications** + +| Parameter | Units | S-C4L1-2D2F | S-C4L1-2D3F | S-C4L1-2D5F | +|---------------------------------------------------|-------|-----------------------------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 4 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ OTU2 FEC enabled | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point Ss | | | | | +| Maximum mean channel output power | dBm | +5 | | | +| Minimum mean channel output power | dBm | +1 | | | +| Central wavelength | nm | $1511 + 20 \times m$ , $m = 0$ to $3$ | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | NRZ 10G Ratio large per [ITU-T G.959.1] | | | + +**Table 9-19 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 4-channel NRZ OTU2 long-haul black link applications** + +| Parameter | Units | S-C4L1-2D2F | S-C4L1-2D3F | S-C4L1-2D5F | +|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------|-------------|--------------|-------------| +| Optical path from point Ss to Rs | | | | | +| Maximum channel insertion loss | dB | 25.5 | 26.5 | 26 | +| Minimum channel insertion loss | dB | | 12 | | +| Chromatic dispersion range | | | | | +| – 1511 nm channel | ps/nm | 0 to +1332 | –600 to +94 | 0 to +756 | +| – 1531 nm channel | ps/nm | 0 to +1437 | –405 to +200 | 0 to +869 | +| – 1551 nm channel | ps/nm | 0 to +1544 | –297 to +307 | 0 to +983 | +| – 1571 nm channel | ps/nm | 0 to +1650 | –190 to +425 | 0 to +1100 | +| Minimum optical return loss at S s | dB | | 24 | | +| Maximum discrete reflectance between S s and R s | dB | | –27 | | +| Maximum differential group delay | ps | | 30 | | +| Maximum inter-channel crosstalk | dB | | –20 | | +| Maximum interferometric crosstalk | dB | | –45 | | +| Interface at point Rs | | | | | +| Maximum mean channel input power | dBm | | –7 | | +| Minimum receiver sensitivity | dBm | | –27 | | +| Maximum optical path penalty | dB | 2.5 | 1.5 | 2 | +| Maximum reflectance of receiver | dB | | –27 | | +| NOTE – The BER for these application codes is required to be met only after the error correction (if used) has been applied. The BER at the input of the FEC decoder can, therefore, be significantly higher than $10^{-12}$ . | | | | | + +**Table 9-20 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 8-channel NRZ OTU2 short-haul black link applications** + +| Parameter | Units | S-C8S1-2D2F | S-C8S1-2D3F | S-C8S1-2D5F | +|---------------------------------------------------|-------|-------------------------------------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 8 | 8 | 8 (Note 1) | +| Bit rate/line coding of optical tributary signals | – | NRZ OTU2 FEC enabled | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point Ss | | | | | +| Maximum mean channel output power | dBm | +4 | | | +| Minimum mean channel output power | dBm | 0 | | | +| Central wavelength | nm | $1471 + 20 \times m, m = 0 \text{ to } 7$ | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | NRZ 10G Ratio large per [ITU-T G.959.1] | | | + +**Table 9-20 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 8-channel NRZ OTU2 short-haul black link applications** + +| Parameter | Units | S-C8S1-2D2F | S-C8S1-2D3F | S-C8S1-2D5F | +|------------------------------------------------------------------------|-------|-------------|--------------|--------------| +| Optical path from point Ss to Rs | | | | | +| Maximum channel insertion loss | dB | 14.5 | 15.5 | 15.0 | +| Minimum channel insertion loss | dB | | 5 | | +| Chromatic dispersion range | | | | | +| – 1471 nm channel | ps/nm | 0 to +601 | –500 to 0 | –149 to +239 | +| – 1491 nm channel | ps/nm | 0 to +657 | –402 to 0 | –72 to +289 | +| – 1511 nm channel | ps/nm | 0 to +714 | –303 to +47 | 0 to +340 | +| – 1531 nm channel | ps/nm | 0 to +771 | –205 to +101 | 0 to +391 | +| – 1551 nm channel | ps/nm | 0 to +828 | –150 to +155 | 0 to +442 | +| – 1571 nm channel | ps/nm | 0 to +885 | –96 to +215 | 0 to +495 | +| – 1591 nm channel | ps/nm | 0 to +942 | –42 to +313 | 0 to +548 | +| – 1611 nm channel | ps/nm | 0 to +1000 | 0 to +411 | 0 to +600 | +| Minimum optical return loss at S s | dB | | 24 | | +| Maximum discrete reflectance between S s and R s | dB | | –27 | | +| Maximum differential group delay | ps | | 30 | | +| Maximum inter-channel crosstalk | dB | | –20 | | +| Maximum interferometric crosstalk | dB | | –45 | | +| Interface at point Rs | | | | | +| Maximum mean channel input power | dBm | | –1 | | +| Minimum receiver sensitivity | dBm | | –17 | | +| Maximum optical path penalty | dB | 2.5 | 1.5 | 2.0 | +| Maximum reflectance of receiver | dB | | –27 | | + +NOTE 1 – The 1471 nm channel may not be usable with older [ITU-T G.655] fibre that has a maximum cable cut-off wavelength specified as 1480 nm. + +NOTE 2 – The BER for these application codes is required to be met only after the error correction (if used) has been applied. The BER at the input of the FEC decoder can, therefore, be significantly higher than $10^{-12}$ . + +**Table 9-21 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 8-channel NRZ 10G long-haul black link applications** + +| Parameter | Units | S-C8L1-2D2 | S-C8L1-2D3 | S-C8L1-2D5 | +|---------------------------------------------------|-------|---------------|---------------|---------------| +| General information | | | | | +| Maximum number of channels | – | 8 | 8 | 8 (Note) | +| Bit rate/line coding of optical tributary signals | – | | NRZ 10G | | +| Maximum bit error ratio | – | | $10^{-12}$ | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point Ss | | | | | +| Maximum mean channel output power | dBm | | +5 | | +| Minimum mean channel output power | dBm | | +1 | | + +**Table 9-21 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 8-channel NRZ 10G long-haul black link applications** + +| Parameter | Units | S-C8L1-2D2 | S-C8L1-2D3 | S-C8L1-2D5 | +|------------------------------------------------------------------------|-------|-----------------------------------------|--------------|--------------| +| Central wavelength | nm | 1471 + 20 × m, m = 0 to 7 | | | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | ±6.5 | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | NRZ 10G Ratio large per [ITU-T G.959.1] | | | +| Optical path from point Ss to Rs | | | | | +| Maximum channel insertion loss | dB | 22.5 | 23 | 23 | +| Minimum channel insertion loss | dB | 12 | | | +| Chromatic dispersion range | | | | | +| – 1471 nm channel | ps/nm | 0 to +842 | –750 to 0 | –262 to +418 | +| – 1491 nm channel | ps/nm | 0 to +920 | –602 to 0 | –127 to +506 | +| – 1511 nm channel | ps/nm | 0 to +1000 | –455 to +71 | 0 to +595 | +| – 1531 nm channel | ps/nm | 0 to +1079 | –307 to +152 | 0 to +684 | +| – 1551 nm channel | ps/nm | 0 to +1159 | –225 to +233 | 0 to +774 | +| – 1571 nm channel | ps/nm | 0 to +1239 | –144 to +322 | 0 to +866 | +| – 1591 nm channel | ps/nm | 0 to +1319 | –63 to +470 | 0 to +958 | +| – 1611 nm channel | ps/nm | 0 to +1400 | 0 to +617 | 0 to +1050 | +| Minimum optical return loss at S s | dB | 24 | | | +| Maximum discrete reflectance between S s and R s | dB | –27 | | | +| Maximum differential group delay | ps | 30 | | | +| Maximum inter-channel crosstalk | dB | –20 | | | +| Maximum interferometric crosstalk | dB | –45 | | | +| Interface at point Rs | | | | | +| Maximum mean channel input power | dBm | –7 | | | +| Minimum receiver sensitivity | dBm | –24 | | | +| Maximum optical path penalty | dB | 2.5 | 2 | 2 | +| Maximum reflectance of receiver | dB | –27 | | | + +NOTE – The 1471 nm channel may not be usable with older [ITU-T G.655] fibre that has a maximum cable cut-off wavelength specified as 1480 nm. + +**Table 9-22 – Physical layer parameters and values for multichannel systems with single-channel interfaces for 8-channel NRZ OTU2 long-haul black link applications** + +| Parameter | Units | S-C8L1-2D2F | S-C8L1-2D3F | S-C8L1-2D5F | +|---------------------------------------------------|-------|----------------------|-------------|-------------| +| General information | | | | | +| Maximum number of channels | – | 8 | 8 | 8 (Note 1) | +| Bit rate/line coding of optical tributary signals | – | NRZ OTU2 FEC enabled | | | + +| | | | | | +|------------------------------------------------------------------------|-------|-----------------------------------------|---------------|---------------| +| Maximum bit error ratio | – | | $10^{-12}$ | | +| Fibre type | – | [ITU-T G.652] | [ITU-T G.653] | [ITU-T G.655] | +| Interface at point SS | | | | | +| Maximum mean channel output power | dBm | | +5 | | +| Minimum mean channel output power | dBm | | +1 | | +| Central wavelength | nm | 1471 + 20 × m, m = 0 to 7 | | | +| Channel spacing | nm | | 20 | | +| Maximum central wavelength deviation | nm | | ±6.5 | | +| Minimum channel extinction ratio | dB | | 8.2 | | +| Eye mask | – | NRZ 10G Ratio large per [ITU-T G.959.1] | | | +| Optical path from point SS to RS | | | | | +| Maximum channel insertion loss | dB | 25.5 | 26 | 26 | +| Minimum channel insertion loss | dB | | 12 | | +| Chromatic dispersion range | | | | | +| – 1471 nm channel | ps/nm | 0 to +1022 | –850 to 0 | –286 to +458 | +| – 1491 nm channel | ps/nm | 0 to +1118 | –683 to 0 | –139 to +554 | +| – 1511 nm channel | ps/nm | 0 to +1214 | –516 to +81 | 0 to +651 | +| – 1531 nm channel | ps/nm | 0 to +1310 | –348 to +172 | 0 to +749 | +| – 1551 nm channel | ps/nm | 0 to +1407 | –255 to +264 | 0 to +847 | +| – 1571 nm channel | ps/nm | 0 to +1504 | –163 to +365 | 0 to +948 | +| – 1591 nm channel | ps/nm | 0 to +1602 | –71 to +532 | 0 to +1049 | +| – 1611 nm channel | ps/nm | 0 to +1700 | 0 to +699 | 0 to +1150 | +| Minimum optical return loss at S S | dB | | 24 | | +| Maximum discrete reflectance between S S and R S | dB | | –27 | | +| Maximum differential group delay | ps | | 30 | | +| Maximum inter-channel crosstalk | dB | | –20 | | +| Maximum interferometric crosstalk | dB | | –45 | | +| Interface at point RS | | | | | +| Maximum mean channel input power | dBm | | –7 | | +| Minimum receiver sensitivity | dBm | | –27 | | +| Maximum optical path penalty | dB | 2.5 | 2 | 2 | +| Maximum reflectance of receiver | dB | | –27 | | + +NOTE 1 – The 1471 nm channel may not be usable with older [ITU-T G.655] fibre that has a maximum cable cut-off wavelength specified as 1480 nm. + +NOTE 2 – The BER for these application codes is required to be met only after the error correction (if used) has been applied. The BER at the input of the FEC decoder can, therefore, be significantly higher than $10^{-12}$ . + +**Table 9-23 – Physical layer parameters and values for multichannel interfaces for 4-channel NRZ OTL4.4 short-haul black box applications** + +| Parameter | Units | C4S1-9D1F | | +|-------------------------------------------------------------------------------------|-------|---------------------------------------|-----| +| General information | | | | +| Maximum number of channels | – | 4 | | +| Bit rate/line coding of optical tributary signals | – | OTL4.4 or FOIC1.4-RS | | +| Maximum bit error ratio | – | $10^{-12}$ | | +| Fibre type | – | [ITU-T G.652] | | +| Interface at point MPI-SM | | | | +| Maximum mean channel output power | dBm | +2.5 | | +| Minimum mean channel output power (Note 2) | dBm | –1 | –3 | +| Maximum mean total output power | dBm | +8.5 | | +| Central wavelength | nm | $1271 + 20 \times m$ , $m = 0$ to $3$ | | +| Channel spacing | nm | 20 | | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | +| Minimum channel extinction ratio (Note 2) | dB | 3.5 | 6.5 | +| Maximum channel extinction ratio (Note 2) | dB | 6.5 | – | +| Eye mask | – | NRZ 25G ratio per [ITU-T G.959.1] | | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | +| Maximum attenuation | dB | 4 | | +| Minimum attenuation | dB | 0 | | +| Chromatic dispersion range | | | | +| – 1271 nm channel | ps/nm | –12 to 0 | | +| – 1291 nm channel | ps/nm | –8 to 0 | | +| – 1311 nm channel | ps/nm | –4 to +3.5 | | +| – 1331 nm channel | ps/nm | 0 to +7 | | +| Minimum optical return loss at MPI-S M | dB | 20 | | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –26 | | +| Maximum differential group delay | ps | 3 | | +| Interface at point MPI-RM | | | | +| Maximum mean channel input power | dBm | +2.5 | | +| Minimum mean channel input power (Note 2) | dBm | –5 | –7 | +| Maximum mean total input power | dBm | +8.5 | | +| Maximum optical path penalty | dB | 3 (Note 3) | | +| Minimum equivalent sensitivity (Note 2) | dBm | –8 | –10 | +| Maximum reflectance of optical network element | dB | –26 | | + +NOTE 1 – The BER for these application codes is required to be met only after the error correction (if used) has been applied. The BER at the input of the FEC decoder can therefore be significantly higher than $10^{-12}$ . + +NOTE 2 – The parameters for C4S1 9D1F allow two options for the transmitter (shown via a split in the column) with different values for minimum mean channel output power, minimum and maximum channel extinction ratio. The two sets of transmitter parameter values provide different values for minimum mean channel input power and minimum equivalent sensitivity for the same physical receiver as indicated by the split values for these parameters. The transmitter must meet the specifications in one of the two columns and the receiver must meet the specifications in both columns. + +NOTE 3 – Within the maximum optical path penalty of 3 dB, the penalty due to chromatic dispersion must be less than 2 dB. + +**Table 9-24 – Physical layer parameters and values for multichannel interfaces for 4-channel PAM4 short-haul and very short reach black box applications** + +| Parameter | Units | C4S1-4D1F | | C4R1-5D1F | +|-------------------------------------------------------------------------------------|-------|------------------------------------------|------|------------------------------------------| +| General information | | | | | +| Maximum number of channels | – | 4 | | 4 | +| Bit rate/line coding of optical tributary signals | – | FOIC2.4 PAM4 | | FOIC4.4-RS PAM4/4×FOIC1.1-RS PAM4 | +| Maximum bit error ratio | – | $10^{-13}$ (Note 1) | | $10^{-13}$ (Note 1) | +| Fibre type | – | [ITU-T G.652] | | [ITU-T G.652] | +| Interface at point MPI-SM | | | | | +| Maximum mean channel output power | dBm | +4.7 | | +4.4 | +| Minimum mean channel output power | dBm | –4.2 | | –3.2 | +| Maximum mean total output power | dBm | +10.7 | | +10.4 | +| Central wavelength | nm | $1271 + 20 \times m$ ,
$m = 0$ to $3$ | | $1271 + 20 \times m$ ,
$m = 0$ to $3$ | +| Channel spacing | nm | 20 | | 20 | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | $\pm 6.5$ | +| Minimum channel extinction ratio (Note 2) | dB | 3.5 | 4.5 | 3.5 | +| Maximum channel extinction ratio (Note 2) | dB | 4.5 | – | – | +| Maximum channel output OMA outer | dBm | +4.5 | | +3.7 | +| Minimum channel output OMA outer | dBm | –1.2 | | –0.2 | +| Maximum channel power difference | dB | 4 | | 3.9 | +| Maximum TDECQ | dB | 3.3 | | 3.4 | +| Maximum TECQ | dB | | | 3.4 | +| Maximum TDECQ-TECQ | dB | | | 2.5 | +| Minimum channel OMA outer minus TDECQ (Note 2) | dBm | –2.5 | –2.6 | –1.6 | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | +| Maximum attenuation | dB | 4 | | 4 | +| Minimum attenuation | dB | 0 | | 0 | +| Chromatic dispersion range | | | | | +| – 1271 nm channel | ps/nm | –12 to 0 | | –12 to 0 | +| – 1291 nm channel | ps/nm | –8 to 0 | | –8 to 0 | +| – 1311 nm channel | ps/nm | –4 to +3.5 | | –4 to +3.5 | +| – 1331 nm channel | ps/nm | 0 to +7 | | 0 to +7 | +| Minimum optical return loss at MPI-S M | dB | 17.1 | | 17.1 | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | See clause 8.3.5 | | See clause 8.3.5 | +| Maximum differential group delay | ps | 3 | | 2.3 | +| Interface at point MPI-RM | | | | | +| Maximum mean channel input power | dBm | +4.7 | | +4.4 | +| Minimum mean channel input power (Note 2) | dBm | –8.2 | | –7.2 | +| Maximum mean total input power | dBm | +10.7 | | +10.4 | +| Maximum channel input OMA outer | dBm | +4.5 | | +3.7 | + +**Table 9-24 – Physical layer parameters and values for multichannel interfaces for 4-channel PAM4 short-haul and very short reach black box applications** + +| Parameter | Units | C4S1-4D1F | | C4R1-5D1F | +|------------------------------------------------------------------|-------|-----------|-----|-----------| +| Minimum channel input OMA outer | dBm | –5.2 | | –4.2 | +| Maximum channel power difference | dB | 4.1 | | 4.1 | +| Maximum multi-path interference penalty allowance (Note 2) | dB | 0.4 | 0.3 | 0.4 | +| Minimum equivalent sensitivity (OMA outer minus SECQ) | dBm | –6.9 | | –6.0 | +| Maximum reflectance of optical network element | dB | –26 | | –26 | + +NOTE 1 – The BER for these application codes is required to be met only after the error correction (if used) has been applied. The BER at the input of the FEC decoder can therefore be significantly higher than $10^{-13}$ . + +NOTE 2 – The parameters for C4S1-4D1F allow two options for the transmitter (shown via a split in the column) with different values for minimum and maximum channel extinction ratio and minimum channel OMAouter minus TDECQ. The two sets of transmitter parameter values provide different values for the maximum multi-path interference penalty allowance for the same physical receiver as indicated by the split values for this parameter. The transmitter must meet the specifications in one of the two columns and the receiver must meet the specifications in both columns. + +**Table 9-25 – Physical layer parameters and values for multichannel interfaces for 4-channel PAM4 short-haul black box applications** + +| Parameter | Units | C4S1-5D1F | +|---------------------------------------------------|-------|--------------------------------------| +| General information | | | +| Maximum number of channels | – | 4 | +| Bit rate/line coding of optical tributary signals | – | FOIC4.4-RS PAM4/4×FOIC1.1-RS PAM4 | +| Maximum bit error ratio | – | $10^{-13}$ (Note) | +| Fibre type | – | [ITU-T G.652] | +| Interface at point MPI-SM | | | +| Maximum mean channel output power | dBm | 5.1 | +| Minimum mean channel output power | dBm | –2.7 | +| Maximum mean total output power | dBm | +11.1 | +| Central wavelength | nm | $1271 + 20 \times m$ ,
m = 0 to 3 | +| Channel spacing | nm | 20 | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | +| Minimum channel extinction ratio | dB | 3.5 | +| Maximum channel extinction ratio | dB | – | +| Maximum channel output OMA outer | dBm | 4.4 | +| Minimum channel output OMA outer | dBm | 0.3 | +| Maximum channel power difference | dB | 4 | +| Maximum TDECQ | dB | 3.4 | +| Maximum TECQ | dB | 3.4 | +| Maximum TDECQ-TECQ | dB | 2.5 | + +**Table 9-25 – Physical layer parameters and values for multichannel interfaces for 4-channel PAM4 short-haul black box applications** + +| Parameter | Units | C4S1-5D1F | +|-------------------------------------------------------------------------------------|-------|------------------| +| Minimum channel OMA outer minus TDECQ | dBm | -1.1 | +| Optical path (single span) from point MPI-SM to MPI-RM | | | +| Maximum attenuation | dB | 6.3 | +| Minimum attenuation | dB | 0 | +| Chromatic dispersion range | | | +| – 1271 nm channel | ps/nm | -35 to 0 | +| – 1291 nm channel | ps/nm | -35 to 0 | +| – 1311 nm channel | ps/nm | -11 to +9.5 | +| – 1331 nm channel | ps/nm | +0.5 to +20 | +| Minimum optical return loss at MPI-S M | dB | 15.6 | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | See clause 8.3.5 | +| Maximum differential group delay | ps | 4 | +| Interface at point MPI-RM | | | +| Maximum mean channel input power | dBm | +5.1 | +| Minimum mean channel input power | dBm | -9 | +| Maximum mean total input power | dBm | +11.1 | +| Maximum channel input OMA outer | dBm | 4.4 | +| Minimum channel input OMA outer | dBm | -6.0 | +| Maximum channel power difference | dB | 4.3 | +| Maximum multi-path interference penalty allowance | dB | 0.6 | +| Minimum equivalent sensitivity (OMA outer minus SECQ) | dBm | -8.2 | +| Maximum reflectance of optical network element | dB | -26 | + +NOTE – The BER for these application codes is required to be met only after the error correction (if used) has been applied. The BER at the input of the FEC decoder can therefore be significantly higher than $10^{-13}$ . + +# 10 Optical safety considerations + +See [ITU-T G.664], [IEC 60825-1] and [IEC 60825-2] for optical safety considerations. + +NOTE – Accessible emission limits for wavelengths above and below 1400 nm differ. Therefore, appropriate consideration must be given to how wavelengths in each of these regions contribute to the hazard level classification for CWDM applications. + +# Appendix I + +## Wavelength dependence of attenuation and chromatic dispersion + +(This appendix does not form an integral part of this Recommendation.) + +## I.1 Attenuation + +The attenuation coefficient of an installed optical fibre cable is wavelength dependent, the value at a particular wavelength depending on the characteristics of the uncabled fibre together with additional losses caused by connectors, splicing and bending. + +Table I.1 contains the assumed minimum and maximum attenuation coefficient values for each CWDM wavelength. They are also depicted graphically in Figures I.1 and I.2. These values were obtained by combining measurements of the attenuation coefficient of underground and buried optical fibre cables at 1550 nm and 1625 nm with full spectrum measurements of uncabled fibres and with the limits specified in [ITU-T G.652]. + +**Table I.1 – Assumed attenuation coefficient values** + +| Nominal central wavelength (nm) | ITU-T G.652.A and ITU-T G.652.B cable | | ITU-T G.652.C and ITU-T G.652.D cable | | +|---------------------------------|-----------------------------------------|-----------------------------------------|-----------------------------------------|-----------------------------------------| +| | Minimum attenuation coefficient (dB/km) | Maximum attenuation coefficient (dB/km) | Minimum attenuation coefficient (dB/km) | Maximum attenuation coefficient (dB/km) | +| 1271 | 0.392 | 0.473 | 0.385 | 0.470 | +| 1291 | 0.370 | 0.447 | 0.365 | 0.441 | +| 1311 | 0.348 | 0.423 | 0.352 | 0.423 | +| 1331 | 0.331 | 0.425 | 0.340 | 0.411 | +| 1351 | 0.320 | 0.476 | 0.329 | 0.399 | +| 1371 | | | 0.316 | 0.386 | +| 1391 | | | 0.301 | 0.372 | +| 1411 | | | 0.285 | 0.357 | +| 1431 | 0.263 | 0.438 | 0.269 | 0.341 | +| 1451 | 0.250 | 0.368 | 0.254 | 0.326 | +| 1471 | 0.238 | 0.327 | 0.240 | 0.312 | +| 1491 | 0.229 | 0.303 | 0.229 | 0.300 | +| 1511 | 0.221 | 0.290 | 0.220 | 0.290 | +| 1531 | 0.215 | 0.283 | 0.213 | 0.283 | +| 1551 | 0.211 | 0.278 | 0.209 | 0.277 | +| 1571 | 0.208 | 0.276 | 0.208 | 0.273 | +| 1591 | 0.208 | 0.278 | 0.208 | 0.275 | +| 1611 | 0.208 | 0.289 | 0.212 | 0.283 | + +NOTE – These coefficient values include an allowance for maximum central wavelength deviation. + +![Figure I.1: Assumed attenuation coefficient values for ITU-T G.652.A and ITU-T G.652.B cable. The graph plots Attenuation coefficient (dB/km) on the y-axis (0.2 to 0.5) against Wavelength (nm) on the x-axis (1200 to 1700). Two curves are shown: 'Maximum' (triangles) and 'Minimum' (circles). The 'Maximum' curve starts at ~0.47 dB/km at 1275 nm, dips to ~0.42 dB/km at 1310 nm, rises to ~0.47 dB/km at 1350 nm, then drops sharply to ~0.29 dB/km at 1610 nm. The 'Minimum' curve starts at ~0.39 dB/km at 1275 nm and decreases steadily to ~0.21 dB/km at 1610 nm.](664c1180d8c525b316fb0985ec1c5337_img.jpg) + +Figure I.1: Assumed attenuation coefficient values for ITU-T G.652.A and ITU-T G.652.B cable. The graph plots Attenuation coefficient (dB/km) on the y-axis (0.2 to 0.5) against Wavelength (nm) on the x-axis (1200 to 1700). Two curves are shown: 'Maximum' (triangles) and 'Minimum' (circles). The 'Maximum' curve starts at ~0.47 dB/km at 1275 nm, dips to ~0.42 dB/km at 1310 nm, rises to ~0.47 dB/km at 1350 nm, then drops sharply to ~0.29 dB/km at 1610 nm. The 'Minimum' curve starts at ~0.39 dB/km at 1275 nm and decreases steadily to ~0.21 dB/km at 1610 nm. + +**Figure I.1 – Assumed attenuation coefficient values for ITU-T G.652.A and ITU-T G.652.B cable** + +![Figure I.2: Assumed attenuation coefficient values for ITU-T G.652.C and ITU-T G.652.D cable. The graph plots Attenuation coefficient (dB/km) on the y-axis (0.2 to 0.5) against Wavelength (nm) on the x-axis (1200 to 1700). Two curves are shown: 'Maximum' (triangles) and 'Minimum' (circles). The 'Maximum' curve starts at ~0.47 dB/km at 1275 nm and decreases steadily to ~0.28 dB/km at 1610 nm. The 'Minimum' curve starts at ~0.39 dB/km at 1275 nm and decreases steadily to ~0.21 dB/km at 1610 nm.](e91d950121dbb814d5c91603c7cd146e_img.jpg) + +Figure I.2: Assumed attenuation coefficient values for ITU-T G.652.C and ITU-T G.652.D cable. The graph plots Attenuation coefficient (dB/km) on the y-axis (0.2 to 0.5) against Wavelength (nm) on the x-axis (1200 to 1700). Two curves are shown: 'Maximum' (triangles) and 'Minimum' (circles). The 'Maximum' curve starts at ~0.47 dB/km at 1275 nm and decreases steadily to ~0.28 dB/km at 1610 nm. The 'Minimum' curve starts at ~0.39 dB/km at 1275 nm and decreases steadily to ~0.21 dB/km at 1610 nm. + +**Figure I.2 – Assumed attenuation coefficient values for ITU-T G.652.C and ITU-T G.652.D cable** + +These attenuation coefficient values are based on the spectral results of a limited number of fibres, together with an assumption of 0.275 dB/km at 1550 nm for the maximum attenuation coefficients and 0.210 dB/km at 1550 nm for the minimum attenuation coefficients. Actual installed cable attenuation is statistical in nature and these values should not be taken as specification limits on individual fibres, cable sections or splices. In actual installed optical fibre cables, the attenuation coefficient values will differ from those shown in Table I.1 and Figure I.1 depending on factors such as connector loss, splicing loss, bending loss or loss due to optical monitoring. + +## I.2 Chromatic dispersion + +As the chromatic dispersion coefficient is wavelength dependent, Table I.2 contains the assumed maximum chromatic dispersion coefficient values at the central wavelength (plus the maximum allowed central wavelength deviation) for each of the channels used in this Recommendation. The values of chromatic dispersion for [ITU-T G.652] fibres for the 1391 nm channel and above have been calculated using [b-ITU-T G-Sup.39] Equations 10-7a and 10-7b, with 1 sigma. For the 1371 nm channel and below, the dispersion values are derived from the equations found in [ITU-T G.652]. The + +values for [ITU-T G.655] fibres have been calculated using equations in Table I.5 of [ITU-T G.655] for the maximum dispersion coefficient with 1 sigma for ITU-T G.655.E fibre. The values for [ITU-T G.653] fibres have been calculated using the equations for the chromatic dispersion bounding curves provided in Table 2 of [ITU-T G.653] for ITU-T G.653.B attributes. + +**Table I.2 – Assumed chromatic dispersion coefficient values for [ITU-T G.652], [ITU-T G.653] and [ITU-T G.655] fibres** + +| Channel wavelength (nm) | Maximum dispersion coefficient (ps/nm/km) | | | | | | +|-------------------------|-------------------------------------------|----------|----------------------|----------|----------------------|----------| +| | [ITU-T G.652] fibres | | [ITU-T G.653] fibres | | [ITU-T G.655] fibres | | +| | Negative | Positive | Negative | Positive | Negative | Positive | +| 1291 | -3.85 | – | – | – | – | – | +| 1311 | -1.85 | 1.60 | – | – | – | – | +| 1331 | – | 3.34 | – | – | – | – | +| 1351 | – | 5.02 | – | – | – | – | +| 1371 | – | 6.62 | – | – | – | – | +| 1391 | – | 7.97 | – | – | – | – | +| 1411 | – | 9.14 | – | – | – | – | +| 1431 | – | 10.31 | – | – | – | – | +| 1451 | – | 11.49 | – | – | – | – | +| 1471 | – | 12.68 | -8.64 | – | -2.99 | 4.78 | +| 1491 | – | 13.86 | -6.94 | – | -1.45 | 5.79 | +| 1511 | – | 15.06 | -5.24 | 0.82 | – | 6.80 | +| 1531 | – | 16.25 | -3.54 | 1.75 | – | 7.82 | +| 1551 | – | 17.46 | -2.59 | 2.68 | – | 8.85 | +| 1571 | – | 18.66 | -1.66 | 3.71 | – | 9.90 | +| 1591 | – | 19.87 | -0.72 | 5.41 | – | 10.96 | +| 1611 | – | 21.09 | – | 7.11 | – | 12.01 | + +# Appendix II + +## Optical path from point RPS to RPR + +(This appendix does not form an integral part of this Recommendation.) + +Tables 9-11 to 9-14 and Tables 9-17 to 9-22 recommend physical layer parameter values for the optical path from point SS to point RS for black link applications. The optical path from point SS to RS includes the path from RPS to RPR and a number of other network elements (NEs). In the case of linear black link applications, the NEs include an OM, an OD and (optionally) one or more OADMs. For ring black link applications, the NEs include all of the OADMs that are traversed by the path from SS to RS being considered. The total insertion loss and the total chromatic dispersion of the CWDM NEs and the optical path from RPS to RPR must not exceed the values specified for the optical path from point SS to RS. + +Apportionment of (wavelength dependent) insertion loss to the CWDM NEs and to the optical path from RPS to RPR will depend on the characteristics of the NEs and the optical path from RPS to RPR. The assumed maximum attenuation coefficient values in Appendix I can be used to evaluate an assumed maximum channel insertion loss of each channel for the optical path from RPS to RPR and therefore expected distances for high loss fibre. Similarly, for low loss fibres, the minimum attenuation coefficient values in Appendix I can be used. In some cases, the expected distance will be dispersion limited. + +Tables II.1 and II.2 contain informative parameter values for the optical path from RPS to RPR for various CWDM NE insertion loss values. + +**Table II.1 – Parameters and values for optical path from RPS to RPR for application codes S-C8S1-1D2, -1D3 and -1D5** + +| Parameter | Units | Total CWDM network element insertion loss | | | | | +|-----------------------------------------------------------------|-------|-------------------------------------------|--------|--------|----------------|----------------| +| | | 7.5 dB | 6.5 dB | 5.5 dB | 4.5 dB | 3.5 dB | +| Optical path from point RPS to RPR | | | | | | | +| Maximum attenuation | dB | 9 | 10 | 11 | 12 | 13 | +| Minimum attenuation | dB | 0 | 0 | 0 | 0.5 | 1.5 | +| Maximum chromatic dispersion | ps/nm | 1000 | 1000 | 1000 | 1000 | 1000 | +| Maximum differential group delay | ps | 120 | 120 | 120 | 120 | 120 | +| Expected distance for high loss fibre | km | 27 | 30 | 33 | 36 | 39 | +| Expected distance for low loss fibre
(Note 1) | km | 38 | 42 | 46 | 50
(Note 2) | 55
(Note 2) | + +NOTE 1 – In actual installed optical fibre cables, the expected distance may differ from the values shown depending on variations in factors such as connector loss, splicing loss, bending loss. +NOTE 2 – For application code S-C8S1-1D2 which uses [ITU-T G.652] fibre, the expected distance is dispersion limited to approximately 47 km. + +**Table II.2 – Parameters and values for optical path from RPs to RPR for application codes S-C8L1-1D2, -1D3 and -1D5** + +| Parameter | Units | Total CWDM network element insertion loss | | | | | +|------------------------------------------------------|-------|-------------------------------------------|----------------|----------------|----------------|----------------| +| | | 7.5 dB | 6.5 dB | 5.5 dB | 4.5 dB | 3.5 dB | +| Optical path from point RPs to RPR | | | | | | | +| Maximum attenuation | dB | 18 | 19 | 20 | 21 | 22 | +| Minimum attenuation | dB | 6.5 | 7.5 | 8.5 | 9.5 | 10.5 | +| Maximum chromatic dispersion | ps/nm | 1600 | 1600 | 1600 | 1600 | 1600 | +| Maximum differential group delay | ps | 120 | 120 | 120 | 120 | 120 | +| Expected distance for high loss fibre (Note 1) | km | 55 | 58 | 61 | 64 | 67 | +| Expected distance for low loss fibre (Note 1) | km | 75 | 79
(Note 2) | 84
(Note 2) | 88
(Note 2) | 92
(Note 2) | + +NOTE 1– In actual installed optical fibre cables, the expected distance may differ from the values shown depending on variations in factors such as connector loss, splicing loss, bending loss. +NOTE 2– For application code S-C8L1-1D2 which uses [ITU-T G.652] fibre, the expected distance is dispersion limited to approximately 75 km. + +# Appendix III + +## Black links containing OADMs + +(This appendix does not form an integral part of this Recommendation.) + +## III.1 Number of OADMs in a black link + +The number of OADMs that can be used in a linear black link or on a black link ring depends on OM, OADM, OD, fibre and connector losses. The total loss from SS to RS must exceed the minimum channel insertion loss and must not exceed the maximum channel insertion loss for the application code being used for the path from SS to RS. Therefore we have: + +$$IL_{min} \leq IL_{total} \leq IL_{max}$$ + +where: + +$IL_{min}$ minimum channel insertion loss for the application code + +$IL_{max}$ maximum channel insertion loss for the application code + +and: + +$$IL_{total} = IL_{OM} + N_{OADM} IL_{OADM} + IL_{OD} + N_{con} IL_{con} + \alpha \cdot L$$ + +where: + +$IL_{OM}$ OM insertion loss or OADM add loss at point SS for the wavelength being used from SS to RS + +$N_{OADM}$ number of express OADMs + +$IL_{OADM}$ express OADM insertion loss for the wavelength being used from SS to RS + +$IL_{OD}$ OD insertion loss or OADM drop loss at point RS for the wavelength being used from SS to RS + +$N_{con}$ number of connectors between SS and RS + +$IL_{con}$ connector insertion loss + +$\alpha$ attenuation coefficient of the fibre, in dB/km, for the wavelength being used from SS to RS + +$L$ total length of fibre between SS and RS + +An express OADM is one through which the wavelength of interest passes without being added or dropped. The maximum number of express OADMs in a path between SS and RS is therefore given by: + +$$N_{OADM} = \left\lceil \frac{IL_{max} - IL_{OM} - IL_{OD} - N_{con} IL_{con} - \alpha \cdot L}{IL_{OADM}} \right\rceil$$ + +The evaluation of the maximum number of OADMs must be done for each SS to RS path in the network so that the maximum number of OADMs is not exceeded for any SS to RS path. This is quite simple for networks where all of the paths share a common hub (see Figure III.1), but becomes more complicated as the path topology becomes more complex (see Figure III.2). + +![Figure III.1: Simple example of linear black link topology. The diagram shows a linear sequence of four grey rectangular nodes connected by a single horizontal line. From left to right: the first node has three input arrows (blue, green, red) from the left; the second node has one output arrow (red) pointing downwards; the third node has one output arrow (green) pointing downwards; the fourth node has one output arrow (blue) pointing downwards. A label 'G.695(15)_FIII.1' is in the bottom right corner.](15de63f0b5df62e6ab9164f2a72e2e33_img.jpg) + +Figure III.1: Simple example of linear black link topology. The diagram shows a linear sequence of four grey rectangular nodes connected by a single horizontal line. From left to right: the first node has three input arrows (blue, green, red) from the left; the second node has one output arrow (red) pointing downwards; the third node has one output arrow (green) pointing downwards; the fourth node has one output arrow (blue) pointing downwards. A label 'G.695(15)\_FIII.1' is in the bottom right corner. + +**Figure III.1 – Simple example of linear black link topology** + +![Figure III.2: Complex example of ring black link topology. The diagram shows a square ring of four grey rectangular nodes. Each node is connected to two adjacent nodes, forming a closed loop. Multiple colored lines (red, orange, yellow, green, blue, purple) represent different paths that traverse the ring. External arrows of corresponding colors enter or exit the nodes: red, orange, and yellow on the left node; red, green, and blue on the top node; orange, green, and purple on the right node; and purple, blue, and yellow on the bottom node. A label 'G.695(15)_FIII.2' is in the bottom right corner.](27788c2a26d9641e68232a4eff1299b9_img.jpg) + +Figure III.2: Complex example of ring black link topology. The diagram shows a square ring of four grey rectangular nodes. Each node is connected to two adjacent nodes, forming a closed loop. Multiple colored lines (red, orange, yellow, green, blue, purple) represent different paths that traverse the ring. External arrows of corresponding colors enter or exit the nodes: red, orange, and yellow on the left node; red, green, and blue on the top node; orange, green, and purple on the right node; and purple, blue, and yellow on the bottom node. A label 'G.695(15)\_FIII.2' is in the bottom right corner. + +**Figure III.2 – Complex example of ring black link topology** + +For some paths, it may be necessary to add some optical attenuation on the black link side of the SS or RS interface so that the minimum channel insertion loss requirement of the black link between SS and RS is met, without affecting the loss for other paths. + +## **III.2 Mixed application codes** + +It is possible to use a mixture of different, but compatible, application codes on the same black link. For example, low loss paths may use S-C8S1-1D2 whilst high loss paths may use S-C8L1-1D2. + +## III.3 Protection + +CWDM black link rings offer the possibility of protected optical paths. Protection may be implemented by several means, including: + +- Client-level protection, with the CWDM black link ring providing two physically diverse optical paths between a pair of clients. These two optical paths may or may not use the same CWDM wavelength. +- Integrated protection, with the OADMs providing a single client interface and with protection switching within the OADM. + +The characteristics of systems that provide protection switching are outside the scope of this Recommendation; however, the application codes in this Recommendation can be used in these systems as long as the optical path between Ss and Rs always complies with the requirements of the relevant application code. + +# Appendix IV + +## Parameter values for 16-channel NRZ 2.5G applications + +(This appendix does not form an integral part of this Recommendation.) + +This appendix provides initial parameter values for 16-channel NRZ 2.5G applications. It is anticipated that, as the technology evolves, these values may need to be revised. See Tables IV.1 to IV.4 (also see Tables 9-7 to 9-10). + +**Table IV.1 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application C16S1-1D2** + +| Parameter | Units | C16S1-1D2 | | | +|-------------------------------------------------------------------------------------|-------|--------------------------------------|--------------------------------------|--------------------------------------| +| | | nm | 1311-1371 | 1391-1451 | +| General information | | | | | +| Maximum number of channels | – | 16 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | ITU-T G.652.C or ITU-T G.652.D | | | +| Interface at point MPI-SM | | | | | +| Maximum mean channel output power | dBm | +3.5 | +2.5 | +1.5 | +| Minimum mean channel output power | dBm | –4 | –5 | –6 | +| Maximum mean total output power | dBm | +14.2 | | | +| Central wavelength | nm | 1311 + $20 \times m$ ,
m = 0 to 3 | 1391 + $20 \times m$ ,
m = 0 to 3 | 1471 + $20 \times m$ ,
m = 0 to 7 | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | +| Maximum attenuation | dB | 8.5 | 7.5 | 6.5 | +| Minimum attenuation | dB | 3.5 | 2.5 | 1 | +| Chromatic dispersion range | | | | | +| – 1311 nm channel | ps/nm | –45 to +39 | | | +| – 1331 nm channel | ps/nm | 0 to +81 | | | +| – 1351 nm channel | ps/nm | 0 to +121 | | | +| – 1371 nm channel | ps/nm | 0 to +160 | | | +| – 1391 nm channel | ps/nm | | 0 to +193 | | +| – 1411 nm channel | ps/nm | | 0 to +221 | | +| – 1431 nm channel | ps/nm | | 0 to +249 | | + +**Table IV.1 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application C16S1-1D2** + +| Parameter | Units | C16S1-1D2 | | | +|--------------------------------------------------------------------------------|-------|-----------|-----------|-----------| +| – 1451 nm channel | ps/nm | | 0 to +278 | | +| – 1471 nm channel | ps/nm | | | 0 to +307 | +| – 1491 nm channel | ps/nm | | | 0 to +335 | +| – 1511 nm channel | ps/nm | | | 0 to +364 | +| – 1531 nm channel | ps/nm | | | 0 to +393 | +| – 1551 nm channel | ps/nm | | | 0 to +422 | +| – 1571 nm channel | ps/nm | | | 0 to +451 | +| – 1591 nm channel | ps/nm | | | 0 to +480 | +| – 1611 nm channel | ps/nm | | | 0 to +510 | +| Minimum optical return loss at MPI-S M | dB | 24 | | | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | -27 | | | +| Maximum differential group delay | ps | 120 | | | +| Interface at point MPI-RM | | | | | +| Maximum mean channel input power | dBm | 0 | 0 | +0.5 | +| Minimum mean channel input power | dBm | -12.5 | -12.5 | -13 | +| Maximum mean total input power | dBm | +12.3 | | | +| Maximum optical path penalty | dB | 1 | 1 | 1.5 | +| Minimum equivalent sensitivity | dBm | -13.5 | -13.5 | -14 | +| Maximum reflectance of optical network element | dB | -27 | | | + +**Table IV.2 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application C16L1-1D2** + +| Parameter | Units | C16L1-1D2 | | | +|---------------------------------------------------|-------|--------------------------------|-----------|-----------| +| Wavelength block | nm | 1311-1371 | 1391-1451 | 1471-1611 | +| General information | | | | | +| Maximum number of channels | – | 16 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | ITU-T G.652.C or ITU-T G.652.D | | | +| Interface at point MPI-SM | | | | | +| Maximum mean channel output power | dBm | +3.5 | +1.5 | -0.5 | +| Minimum mean channel output power | dBm | -4 | -6 | -8 | +| Maximum mean total output power | dBm | +13.4 | | | + +**Table IV.2 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application C16L1-1D2** + +| Parameter | Units | C16L1-1D2 | | | +|-------------------------------------------------------------------------------------|-------|---------------------------------|---------------------------------|---------------------------------| +| Central wavelength | nm | 1311 +
20 × m,
m = 0 to 3 | 1391 +
20 × m,
m = 0 to 3 | 1471 +
20 × m,
m = 0 to 7 | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | ±6.5 | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | +| Maximum attenuation | dB | 18 | 15.8 | 13.3 | +| Minimum attenuation | dB | 11 | 9 | 7 | +| Chromatic dispersion range | | | | | +| – 1311 nm channel | ps/nm | –95 to +82 | | | +| – 1331 nm channel | ps/nm | 0 to +171 | | | +| – 1351 nm channel | ps/nm | 0 to +257 | | | +| – 1371 nm channel | ps/nm | 0 to +339 | | | +| – 1391 nm channel | ps/nm | | 0 to +408 | | +| – 1411 nm channel | ps/nm | | 0 to +468 | | +| – 1431 nm channel | ps/nm | | 0 to +528 | | +| – 1451 nm channel | ps/nm | | 0 to +588 | | +| – 1471 nm channel | ps/nm | | | 0 to +649 | +| – 1491 nm channel | ps/nm | | | 0 to +710 | +| – 1511 nm channel | ps/nm | | | 0 to +771 | +| – 1531 nm channel | ps/nm | | | 0 to +832 | +| – 1551 nm channel | ps/nm | | | 0 to +894 | +| – 1571 nm channel | ps/nm | | | 0 to +956 | +| – 1591 nm channel | ps/nm | | | 0 to +1018 | +| – 1611 nm channel | ps/nm | | | 0 to +1080 | +| Minimum optical return loss at MPI-S M | dB | 24 | | | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –27 | | | +| Maximum differential group delay | ps | 120 | | | + +**Table IV.2 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application C16L1-1D2** + +| Parameter | Units | C16L1-1D2 | | | +|------------------------------------------------|-------|-----------|-------|-------| +| Interface at point MPI-RM | | | | | +| Maximum mean channel input power | dBm | −7.5 | | | +| Minimum mean channel input power | dBm | −22 | −21.8 | −21.3 | +| Maximum mean total input power | dBm | +4.5 | | | +| Maximum optical path penalty | dB | 1 | 1.5 | 2 | +| Minimum equivalent sensitivity | dBm | −23 | −23.3 | −23.3 | +| Maximum reflectance of optical network element | dB | −27 | | | + +**Table IV.3 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application B-C16S1-1D2** + +| Parameter | Units | B-C16S1-1D2 | | | +|---------------------------------------------------|-------|-------------------------------------------|-------------------------------------------|-------------------------------------------| +| Wavelength block | nm | 1311-1371 | 1391-1451 | 1471-1611 | +| General information | | | | | +| Maximum number of channels | – | 8 + 8 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | ITU-T G.652.C or ITU-T G.652.D | | | +| Interface at point MPI-SM | | | | | +| Maximum mean channel output power | dBm | +3.5 | +2 | +1.5 | +| Minimum mean channel output power | dBm | −4 | −5 | −6 | +| Maximum mean total output power | dBm | +11.8 | | | +| Central wavelength | nm | 1311 +
$20 \times m$ ,
$m = 0$ to 3 | 1391 +
$20 \times m$ ,
$m = 0$ to 3 | 1471 +
$20 \times m$ ,
$m = 0$ to 7 | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | $\pm 6.5$ | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | + +**Table IV.3 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application B-C16S1-1D2** + +| Parameter | Units | B-C16S1-1D2 | | | +|-------------------------------------------------------------------------------------|-------|-------------|-----------|-----------| +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | +| Maximum attenuation | dB | 8.5 | 7.5 | 6.3 | +| Minimum attenuation | dB | 3.5 | 2.5 | 1 | +| Chromatic dispersion range | | | | | +| – 1311 nm channel | ps/nm | –45 to +39 | | | +| – 1331 nm channel | ps/nm | 0 to +81 | | | +| – 1351 nm channel | ps/nm | 0 to +121 | | | +| – 1371 nm channel | ps/nm | 0 to +160 | | | +| – 1391 nm channel | ps/nm | | 0 to +193 | | +| – 1411 nm channel | ps/nm | | 0 to +221 | | +| – 1431 nm channel | ps/nm | | 0 to +249 | | +| – 1451 nm channel | ps/nm | | 0 to +278 | | +| – 1471 nm channel | ps/nm | | | 0 to +307 | +| – 1491 nm channel | ps/nm | | | 0 to +335 | +| – 1511 nm channel | ps/nm | | | 0 to +364 | +| – 1531 nm channel | ps/nm | | | 0 to +393 | +| – 1551 nm channel | ps/nm | | | 0 to +422 | +| – 1571 nm channel | ps/nm | | | 0 to +451 | +| – 1591 nm channel | ps/nm | | | 0 to +480 | +| – 1611 nm channel | ps/nm | | | 0 to +510 | +| Minimum optical return loss at MPI-S M | dB | 24 | | | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –27 | | | +| Maximum differential group delay | ps | 120 | | | +| Interface at point MPI-RM | | | | | +| Maximum mean channel input power | dBm | 0 | –0.5 | +0.5 | +| Minimum mean channel input power | dBm | –12.5 | –12.5 | –12.8 | +| Maximum mean total input power | dBm | +9.5 | | | +| Maximum optical path penalty | dB | 1 | 1 | 1.5 | +| Minimum equivalent sensitivity | dBm | –13.5 | –13.5 | –13.8 | +| Maximum reflectance of optical network element | dB | –27 | | | + +**Table IV.4 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application B-C16L1-1D2** + +| Parameter | Units | B-C16L1-1D2 | | | +|-------------------------------------------------------------------------------------|-------|---------------------------------|---------------------------------|---------------------------------| +| Wavelength block | nm | 1311-1371 | 1391-1451 | 1471-1611 | +| General information | | | | | +| Maximum number of channels | – | 8 + 8 | | | +| Bit rate/line coding of optical tributary signals | – | NRZ 2.5G | | | +| Maximum bit error ratio | – | $10^{-12}$ | | | +| Fibre type | – | ITU-T G.652.C or ITU-T G.652.D | | | +| Interface at point MPI-SM | | | | | +| Maximum mean channel output power | dBm | +3.5 | +1.5 | –0.5 | +| Minimum mean channel output power | dBm | –4 | –6 | –8 | +| Maximum mean total output power | dBm | +11.6 | | | +| Central wavelength | nm | 1311 +
20 × m,
m = 0 to 3 | 1391 +
20 × m,
m = 0 to 3 | 1471 +
20 × m,
m = 0 to 7 | +| Channel spacing | nm | 20 | | | +| Maximum central wavelength deviation | nm | ±6.5 | | | +| Minimum channel extinction ratio | dB | 8.2 | | | +| Eye mask | – | STM-16 per [ITU-T G.957] | | | +| Optical path (single span) from point MPI-SM to MPI-RM | | | | | +| Maximum attenuation | dB | 18 | 15.8 | 13.3 | +| Minimum attenuation | dB | 11 | 9 | 7 | +| Chromatic dispersion range | | | | | +| – 1311 nm channel | ps/nm | –95 to +82 | | | +| – 1331 nm channel | ps/nm | 0 to +171 | | | +| – 1351 nm channel | ps/nm | 0 to +257 | | | +| – 1371 nm channel | ps/nm | 0 to +339 | | | +| – 1391 nm channel | ps/nm | | 0 to +408 | | +| – 1411 nm channel | ps/nm | | 0 to +468 | | +| – 1431 nm channel | ps/nm | | 0 to +528 | | +| – 1451 nm channel | ps/nm | | 0 to +588 | | +| – 1471 nm channel | ps/nm | | | 0 to +649 | +| – 1491 nm channel | ps/nm | | | 0 to +710 | +| – 1511 nm channel | ps/nm | | | 0 to +771 | +| – 1531 nm channel | ps/nm | | | 0 to +832 | +| – 1551 nm channel | ps/nm | | | 0 to +894 | +| – 1571 nm channel | ps/nm | | | 0 to +956 | + +**Table IV.4 – Physical layer parameters and values for multichannel interfaces for 16-channel NRZ 2.5G black box application B-C16L1-1D2** + +| Parameter | Units | B-C16L1-1D2 | | | +|--------------------------------------------------------------------------------|--------------|--------------------|-------|------------| +| – 1591 nm channel | ps/nm | | | 0 to +1018 | +| – 1611 nm channel | ps/nm | | | 0 to +1080 | +| Minimum optical return loss at MPI-S M | dB | 24 | | | +| Maximum discrete reflectance between MPI-S M and MPI-R M | dB | –27 | | | +| Maximum differential group delay | ps | 120 | | | +| Interface at point MPI-RM | | | | | +| Maximum mean channel input power | dBm | –7.5 | | | +| Minimum mean channel input power | dBm | –22 | –21.8 | –21.3 | +| Maximum mean total input power | dBm | +1.5 | | | +| Maximum optical path penalty | dB | 1 | 1.5 | 2 | +| Minimum equivalent sensitivity | dBm | –23 | –23.3 | –23.3 | +| Maximum reflectance of optical network element | dB | –27 | | | + +# Bibliography + +- [b-ITU-T G.693] Recommendation ITU-T G.693 (2009), *Optical interfaces for intra-office systems.* +- [b-ITU-T G.8251] Recommendation ITU-T G.8251 (2022), *The control of jitter and wander within the optical transport network (OTN).* +- [b-ITU-T G-Sup.39] ITU-T G-series Recommendations – Supplement 39 (2025), *Optical system design and engineering considerations.* + + + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.696.1-201007-I_PDF-E/053f1077d592e6622cd21dc4bb4cb366_img.jpg b/marked/G/T-REC-G.696.1-201007-I_PDF-E/053f1077d592e6622cd21dc4bb4cb366_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..df50ab5a755c7294b5d51ec4b35bd34dfe439688 --- /dev/null +++ b/marked/G/T-REC-G.696.1-201007-I_PDF-E/053f1077d592e6622cd21dc4bb4cb366_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid 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0000000000000000000000000000000000000000..942333873b809baee276852a8624b1e1f3847fbf --- /dev/null +++ b/marked/G/T-REC-G.696.1-201007-I_PDF-E/raw.md @@ -0,0 +1,846 @@ + + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.696.1** + +(07/2010) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Transmission media and optical systems characteristics – +Characteristics of optical systems + +# --- **Longitudinally compatible intra-domain DWDM applications** + +Recommendation ITU-T G.696.1 + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| General | G.600–G.609 | +| Symmetric cable pairs | G.610–G.619 | +| Land coaxial cable pairs | G.620–G.629 | +| Submarine cables | G.630–G.639 | +| Free space optical systems | G.640–G.649 | +| Optical fibre cables | G.650–G.659 | +| Characteristics of optical components and subsystems | G.660–G.679 | +| Characteristics of optical systems | G.680–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## Recommendation ITU-T G.696.1 + +## Longitudinally compatible intra-domain DWDM applications + +# Summary + +Recommendation ITU-T G.696.1 provides physical layer specifications for intra-domain (IaD) DWDM optical networking applications. Longitudinally compatible applications inside a single administrative domain are described for point-to-point, multichannel line systems with or without line amplifiers. The application codes in this Recommendation provide a set of categories for DWDM transmission systems and fibre links. The primary purpose is to enable multiple vendors to design DWDM transmission equipment for fibre links that are compliant with this Recommendation. + +In this version of this Recommendation, the following topics have been added with respect to the version from 07/2005: + +- Client class 100G; +- Additional text for clause 8 "Optical safety considerations"; +- Comprehensive revision of Appendix I including new clauses I.2.6, I.3.6, I.3.7, I.4, I.5 and additional text for some clauses. + +# History + +| Edition | Recommendation | Approval | Study Group | +|---------|--------------------------------|------------|-------------| +| 1.0 | ITU-T G.696.1 | 2005-07-14 | 15 | +| 1.0 | ITU-T G.696.1 (2005) Erratum 1 | 2006-03-16 | 15 | +| 2.0 | ITU-T G.696.1 | 2010-07-29 | | + +# FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +# INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2011 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +# CONTENTS + +| | Page | +|----------------------------------------------------------------------------------------------|------| +| 1 Scope ..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 2 | +| 3.1 Terms defined elsewhere ..... | 2 | +| 3.2 Terms defined in this Recommendation..... | 2 | +| 4 Abbreviations and acronyms ..... | 3 | +| 5 Classification of optical interfaces..... | 4 | +| 5.1 Applications..... | 4 | +| 5.2 Reference configurations..... | 4 | +| 5.3 Nomenclature ..... | 5 | +| 6 Longitudinal compatibility ..... | 6 | +| 7 Parameters..... | 6 | +| 7.1 Maximum and minimum attenuation per span..... | 6 | +| 7.2 Fibre type..... | 7 | +| 7.3 Operating wavelength range..... | 7 | +| 7.4 Minimum and maximum chromatic dispersion per span ..... | 7 | +| 7.5 Minimum local chromatic dispersion coefficient..... | 8 | +| 7.6 Maximum chromatic dispersion deviation ..... | 8 | +| 7.7 Maximum differential group delay..... | 8 | +| 7.8 Minimum optical return loss at MPI-S M or S M ..... | 10 | +| 7.9 Maximum discrete reflectance between MPI-S M and MPI-R M ..... | 10 | +| 8 Optical safety considerations..... | 10 | +| Appendix I – Theoretical limits and design considerations for DWDM systems ..... | 11 | +| I.1 Enabling technologies and their limits ..... | 11 | +| I.2 Other effects which limit transmission distance..... | 14 | +| I.3 Techniques used to mitigate impairments ..... | 18 | +| I.4 Mixed transmission of 10 Gbit/s, 40 Gbit/s and 100 Gbit/s transmission wavelengths ..... | 19 | +| I.5 100G applications..... | 21 | +| Bibliography..... | 22 | + + + +## Recommendation ITU-T G.696.1 + +# Longitudinally compatible intra-domain DWDM applications + +# 1 Scope + +This Recommendation provides physical layer specifications for intra-domain (IaD) DWDM optical networking applications. These specifications are provided for point-to-point, multichannel line systems with or without line amplifiers. The goal is to enable longitudinally compatible applications inside an administrative domain. The primary purpose is to enable multiple vendors to provide transmission equipment for fibre links that are compliant with this Recommendation. + +In order to provide a framework for IaD application specifications, this Recommendation includes a generic reference model for the physical layer applications. The specifications are organized according to application codes, which take into account parameters such as operating wavelength ranges of the optical amplifiers, combinations of channel counts, client classes, span distances, fibre types and system configurations. + +This initial Recommendation focuses on IaD applications without intervening optical switching elements. It is expected that future versions and/or other new Recommendations may address more complex physical layer configurations and/or support a higher level of compatibility. For these applications, different parameters beyond those specified for a point-to-point configuration may be required. + +This Recommendation presumes that the optical tributary signals transported within optical channels are digital rather than analogue. Specifications for systems enabling transport of analogue optical tributary signals are for further study. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.650.2] Recommendation ITU-T G.650.2 (2007), *Definitions and test methods for statistical and non-linear related attributes of single-mode fibre and cable*. +- [ITU-T G.652] Recommendation ITU-T G.652 (2009), *Characteristics of a single-mode optical fibre and cable*. +- [ITU-T G.653] Recommendation ITU-T G.653 (2006), *Characteristics of a dispersion-shifted single-mode optical fibre and cable*. +- [ITU-T G.654] Recommendation ITU-T G.654 (2006), *Characteristics of a cut-off shifted single-mode optical fibre and cable*. +- [ITU-T G.655] Recommendation ITU-T G.655 (2009), *Characteristics of a non-zero dispersion-shifted single-mode optical fibre and cable*. +- [ITU-T G.663] Recommendation ITU-T G.663 (2000), *Application related aspects of optical amplifier devices and subsystems* plus Amendment 1 (2003), *Amendments to Appendix II*. + +- [ITU-T G.664] Recommendation ITU-T G.664 (2006), *Optical safety procedures and requirements for optical transport systems.* +- [ITU-T G.665] Recommendation ITU-T G.665 (2005), *Generic characteristics of Raman amplifiers and Raman amplified subsystems.* +- [ITU-T G.691] Recommendation ITU-T G.691 (2006), *Optical interfaces for single channel STM-64 and other SDH systems with optical amplifiers.* +- [ITU-T G.707] Recommendation ITU-T G.707/Y.1322 (2007), *Network node interface for the synchronous digital hierarchy (SDH).* +- [ITU-T G.709] Recommendation ITU-T G.709/Y.1331 (2009), *Interfaces for the Optical Transport Network (OTN).* +- [ITU-T G.870] Recommendation ITU-T G.870/Y.1352 (2010), *Terms and definitions for optical transport networks (OTN).* +- [ITU-T G.872] Recommendation ITU-T G.872 (2001), *Architecture of optical transport networks plus Amendment 1 (2003) and Corrigendum 1 (2005).* +- [ITU-T G.957] Recommendation ITU-T G.957 (2006), *Optical interfaces for equipments and systems relating to the synchronous digital hierarchy.* +- [ITU-T G.959.1] Recommendation ITU-T G.959.1 (2009), *Optical transport network physical layer interfaces.* +- [IEC 60825-1] IEC 60825-1 (2007), *Safety of laser products – Part 1: Equipment classification and requirements.* +- [IEC 60825-2] IEC 60825-2 (2007), *Safety of laser products – Part 2: Safety of optical fibre communication systems (OFCS).* + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined in [ITU-T G.872]: + +**3.1.1** intra-domain interface (IaDI); + +**3.1.2** 3R regeneration. + +This Recommendation uses the following term defined in [ITU-T G.870]: + +**3.1.3** optical channel data unit (ODUk). + +This Recommendation uses the following term defined in [ITU-T G.959.1]: + +**3.1.4** optical tributary signal. + +## 3.2 Terms defined in this Recommendation + +This Recommendation defines the following terms: + +**3.2.1 client class:** The client class refers to a class of bit rates of the client signal of a single optical tributary signal that is placed within an optical channel for transport across the optical network. In the context of this Recommendation, the client bit rate is the bit rate of a continuous digital signal before any additional FEC bytes have been added. In the case of a signal in accordance with [ITU-T G.707], this would be the rate of the ODUk. + +**3.2.2 client class 1.25G:** Applies to a continuous digital signal with a client bit rate from nominally 622 Mbit/s to nominally 1.25 Gbit/s. The client class 1.25G includes a signal with STM-4 bit rate according to [ITU-T G.707]. + +**3.2.3 client class 2.5G:** Applies to a continuous digital signal with a client bit rate from nominally 622 Mbit/s to nominally 2.5 Gbit/s. The client class 2.5G includes a signal with STM-16 bit rate according to [ITU-T G.707] and ODU1 bit rate according to [ITU-T G.709]. + +**3.2.4 client class 10G:** Applies to a continuous digital signal with a client bit rate from nominally 2.4 Gbit/s to nominally 10.5 Gbit/s. The client class 10G includes a signal with STM-64 bit rate according to [ITU-T G.707] and ODU2 bit rate according to [ITU-T G.709]. + +**3.2.5 client class 40G:** Applies to a continuous digital signal with a client bit rate from nominally 9.9 Gbit/s to nominally 42 Gbit/s. The client class 40G includes a signal with STM-256 bit rate according to [ITU-T G.707] and ODU3 bit rate according to [ITU-T G.709]. + +**3.2.6 client class 100G:** Applies to a continuous digital signal with a client bit rate from nominally 39 Gbit/s to nominally 105 Gbit/s. The client class 100G includes a signal with ODU4 bit rate according to [ITU-T G.709]. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations: + +| | | +|-------|---------------------------------------------------------| +| 3R | (Regeneration) Re-amplification, Reshaping and Retiming | +| APR | Automatic Power Reduction | +| ASE | Amplified Spontaneous Emission | +| ASK | Amplitude Shift Keying | +| BER | Bit Error Ratio | +| DCM | Dispersion Compensation Module | +| DEMUX | Demultiplexer | +| DGD | Differential Group Delay | +| DP | Dual Polarization | +| DPSK | Differential Phase Shift Keying | +| DQPSK | Differential Quadrature Phase Shift Keying | +| DRA | Distributed Raman Amplification | +| DWDM | Dense WDM | +| EDFA | Erbium Doped Fibre Amplifier | +| FEC | Forward Error Correction | +| FWM | Four-Wave Mixing | +| IaD | Intra-Domain | +| IaDI | Intra-Domain Interface | +| MPI | Main Path Interface | +| MUX | Multiplexer | +| NCG | Net Coding Gain | +| NRZ | Non-Return to Zero | +| OA | Optical Amplifier | +| ODB | Optical Duobinary | + +| | | +|------------------|---------------------------------------------| +| ODU k | Optical channel Data Unit k (k = 1, 2 or 3) | +| OPM | Optical Power Monitor | +| OSA | Optical Spectrum Analyser | +| OSNR | Optical Signal-to-Noise Ratio | +| PDG | Polarization-Dependent Gain | +| PDL | Polarization-Dependent Loss | +| PM | Polarization Multiplexing | +| PMD | Polarization Mode Dispersion | +| PMD Q | Statistical parameter for link PMD | +| PSK | Phase Shift Keying | +| QPSK | Quadrature Phase Shift Keying | +| RZ | Return to Zero | +| SOP | State of Polarization | +| SPM | Self-Phase Modulation | +| VOA | Variable Optical Attenuator | +| WDM | Wavelength Division Multiplexing | +| XPM | Cross-Phase Modulation | + +# 5 Classification of optical interfaces + +## 5.1 Applications + +This Recommendation addresses longitudinally compatible intra-domain DWDM applications with or without optical line amplifiers. Different line amplifier types may be used, in particular discrete line amplifiers as described in [ITU-T G.663], or Raman amplifiers according to [ITU-T G.665]. + +## 5.2 Reference configurations + +For the purpose of this Recommendation, the relevant reference points applicable to the intra-domain DWDM interface applications are shown in Figure 5-1. + +![Figure 5-1: Reference configuration for a multi-span DWDM system. The diagram shows two end systems connected by two intermediate optical amplifiers (OA). Each end system contains multiple 3R (Regenerator) units connected to a Multiplexer (MUX) or Demultiplexer (DEMUX), which is then connected to an Optical Amplifier (OA). The signal path is labeled with MPI-S_M, R_M, S_M, and MPI-R_M at various points along the chain. The diagram is labeled G.696.1_F5.1 at the bottom right.](053f1077d592e6622cd21dc4bb4cb366_img.jpg) + +Figure 5-1: Reference configuration for a multi-span DWDM system. The diagram shows two end systems connected by two intermediate optical amplifiers (OA). Each end system contains multiple 3R (Regenerator) units connected to a Multiplexer (MUX) or Demultiplexer (DEMUX), which is then connected to an Optical Amplifier (OA). The signal path is labeled with MPI-S\_M, R\_M, S\_M, and MPI-R\_M at various points along the chain. The diagram is labeled G.696.1\_F5.1 at the bottom right. + +Figure 5-1 – Reference configuration for a multi-span DWDM system + +The reference points in Figure 5-1 are defined as follows, using the same nomenclature as in [ITU-T G.959.1]: + +- MPI-SM is a (multichannel) reference point on the optical fibre just after the optical network element transport interface output optical connector; +- MPI-RM is a (multichannel) reference point on the optical fibre just before the optical network element transport interface input optical connector; +- SM is a reference point just after the line multichannel OA output optical connector; +- RM is a reference point on the optical fibre just before the line multichannel OA input optical connector. + +## 5.3 Nomenclature + +The application code notation is constructed as follows: + +**n.B-xWF(s)** + +where: + +- n** is the maximum number of channels supported by the application code, +- B** indicates the client class: + - 1.25G indicating a client bit rate in the range from 622 Mbit/s to 1.25 Gbit/s; + - 2.5G indicating a client bit rate in the range from 622 Mbit/s to 2.5 Gbit/s; + - 10G indicating a client bit rate in the range from 2.4 Gbit/s to 10.5 Gbit/s; + - 40G indicating a client bit rate in the range from 9.9 Gbit/s to 42 Gbit/s; + - 100G indicating a client bit rate in the range from 39 Gbit/s to 105 Gbit/s. +- x** is the number of spans within the application code, +- W** is a letter indicating the span attenuation, such as + - S indicating short-haul (up to 11 dB span attenuation), + - L indicating long-haul (up to 22 dB span attenuation), + - V indicating very long-haul (up to 33 dB span attenuation), +- F** is the (fully detailed) fibre type, such as G.652.A, ... G.652.D denoted by "652A" ... "652D" in the application code, respectively, +- s** indicates the operating wavelength range in terms of spectral bands (see [b-ITU-T G-Sup.39]): + +| s | Descriptor | Range (nm) | +|----------|-------------------|-------------------| +| O | Original | 1260 to 1360 | +| E | Extended | 1360 to 1460 | +| S | Short wavelength | 1460 to 1530 | +| C | Conventional | 1530 to 1565 | +| L | Long wavelength | 1565 to 1625 | + +If more than one spectral band is used, then **s** becomes the band letters separated by "+", e.g., for an application requiring the use of both of the C and L bands, **s** would be "C+L". In cases where more than one spectral band is used, the order of letters used is lower wavelengths to higher wavelengths. + +In case of a Raman amplified DWDM transmission system, a letter "R" shall be added at the end of the application code which is then written as: + +**n.B-xWF(s)R** + +An example of specific applications could look like this: + +**40.10G-20L652A(C)R** + +This application indicates a 40-channel system with signals of the 10G payload class, 20 long-haul spans of G.652A fibre which are suitable for use with Raman amplifiers. The C-band is used as the operating wavelength range. + +# 6 Longitudinal compatibility + +The applications covered by this Recommendation are longitudinally compatible according to the definition given in [b-ITU-T G-Sup.39]. + +# 7 Parameters + +The application codes used in this Recommendation (n.B-xWF(s)) consist of two separable sections. The first part "n.B" relates to the optical transmission system and the second part "xWF(s)" relates to the fibre infrastructure. + +Since this Recommendation covers longitudinally compatible systems, the parameters contained in Table 7-1 relate to the fibre infrastructure only, except where the system-related part of the application code affects the fibre requirements. + +**Table 7-1 – Fibre parameters for intra-domain DWDM applications** + +| Parameter | Clause | +|--------------------------------------------------------------------------------|--------| +| Maximum attenuation per span | 7.1 | +| Minimum attenuation per span | 7.1 | +| Fibre type | 7.2 | +| Operating wavelength range | 7.3 | +| Minimum chromatic dispersion per span | 7.4 | +| Maximum chromatic dispersion per span | 7.4 | +| Minimum local chromatic dispersion coefficient | 7.5 | +| Maximum chromatic dispersion deviation | 7.6 | +| Maximum differential group delay | 7.7 | +| Minimum optical return loss at MPI-S M or S M | 7.8 | +| Maximum discrete reflectance between MPI-S M and MPI-R M | 7.9 | + +## 7.1 Maximum and minimum attenuation per span + +The maximum and minimum span attenuations are given in Table 7-2. + +**Table 7-2 – Maximum and minimum span attenuations** + +| Parameter | Units | Value of "W" in application code | | | +|------------------------------|-------|----------------------------------|----|----| +| | | S | L | V | +| Maximum attenuation per span | dB | 11 | 22 | 33 | +| Minimum attenuation per span | dB | ffs | 11 | 22 | + +## 7.2 Fibre type + +This Recommendation covers all of the fibre types in the ITU-T G.65x series of Recommendations. This currently includes the types given in Table 7-3. + +**Table 7-3 – Fibre types** + +| | | | | | +|---------|---------|---------|---------|-------| +| G.652.A | G.653.A | G.654.A | G.655.A | G.656 | +| G.652.B | G.653.B | G.654.B | G.655.B | | +| G.652.C | | G.654.C | G.655.C | | +| G.652.D | | | | | + +## 7.3 Operating wavelength range + +The operating wavelength range consists of one or more of the wavelength bands as defined in [b-ITU-T G-Sup.39]. See Table 7-4. + +**Table 7-4 – Wavelength ranges** + +| s | Descriptor | Range (nm) | +|---|------------------|--------------| +| O | Original | 1260 to 1360 | +| E | Extended | 1360 to 1460 | +| S | Short wavelength | 1460 to 1530 | +| C | Conventional | 1530 to 1565 | +| L | Long wavelength | 1565 to 1625 | + +## 7.4 Minimum and maximum chromatic dispersion per span + +The minimum and maximum chromatic dispersion per span (excluding any dispersion compensation) can either be calculated by using standardized fibre parameters (from the ITU-T G.65x-series) or it can be measured. For 40G systems and for 10G systems with many spans, the measurement is often the more practical choice. + +A calculation of the minimum and maximum chromatic dispersion per span can be carried out by taking fibre parameters from Recommendations in the ITU-T G.65x series, plus additional parameters used in this Recommendation. In detail, the calculation is then done as follows: The maximum chromatic dispersion per span, $CD_{max}^{(span)}$ , is given by: + +$$CD_{max}^{(span)} = D_{max}(s) \cdot L_{max}^{(span)}$$ + +where: + +$$L_{max}^{(span)} = \frac{A_{max}(W)}{\alpha(s)}$$ + +is the maximum span length with the maximum span attenuation $A_{\max} (W)$ defined by the letter "W" (see Table 7-2), and the attenuation coefficient $\alpha(s)$ in the operating wavelength range "s" (see clause 5.3) where $\alpha(s)$ is the "typical link value" in the ITU-T G.65x series of Recommendations. The maximum chromatic dispersion coefficient in the operating wavelength range "s" is denoted as $D_{\max}(s)$ . + +Similarly, the minimum chromatic dispersion per span, $CD_{\min}^{(span)}$ , is given by: + +$$CD_{\min}^{(span)} = D_{\min}(s) \cdot L_{\min}^{(span)}$$ + +where: + +$$L_{\min}^{(span)} = \frac{A_{\min}(W)}{\alpha(s)}$$ + +is the minimum span length with the minimum span attenuation $A_{\min} (W)$ defined by the letter "W" (see Table 7-2), and the attenuation coefficient $\alpha(s)$ in the operating wavelength range "s" (see clause 5.3) where $\alpha(s)$ is the "typical link value" in the ITU-T G.65x series of Recommendations. The minimum chromatic dispersion coefficient in the operating wavelength range "s" is denoted as $D_{\min}(s)$ . + +Chromatic dispersion coefficients can be found for any fibre type in the ITU-T G.65x series of Recommendations using the "link attributes". Maximum and minimum span attenuations are defined in Table 7-2. + +## 7.5 Minimum local chromatic dispersion coefficient + +When considering the performance of individual channels in a multi-span transmission system, the end-to-end residual chromatic dispersion (including compensation) must be held within strict limits to allow acceptable system operation. + +For acceptable operation of DWDM transmission systems over long distances with small channel spacing (e.g., 100 GHz), however, there is also a requirement for the local dispersion coefficient of the transmission fibre to have a minimum value in order to avoid non-linear effects such as four wave-mixing (FWM) and cross-phase modulation (XPM). + +The value of local chromatic dispersion coefficient required to avoid significant penalties due to these effects depends on many factors of the transmission system design such as the channel spacing, power level, link length, etc., and is, therefore, outside the scope of this Recommendation. + +Further details of these non-linear effects are given in [ITU-T G.663] and in [b-ITU-T G-Sup.39], and some methods of mitigating them are discussed in clause I.3. + +## 7.6 Maximum chromatic dispersion deviation + +The requirements for maximum chromatic dispersion deviation are for further study. + +## 7.7 Maximum differential group delay + +The maximum differential group delay (DGD) applies to the whole link between a transmitter (shown as "3R" connected to a MUX in Figure 5-1) and the corresponding receiver ("3R" connected to the DEMUX in Figure 5-1). + +The equation below can be used to calculate the maximum DGD of a link (containing multiple components and fibre sections) with a defined probability of being exceeded. + +$$DGD_{\max|link} = \left[ DGD_{\max F}^2 + S^2 \sum_i PMD_{Ci}^2 \right]^{1/2}$$ + +where: + +$DGDmax_{link}$ is the maximum link DGD (ps) + +$DGDmax_F$ is the maximum concatenated optical fibre cable DGD (ps) + +$S$ is Maxwell adjustment factor (see Table 7-5) + +$PMD_{Ci}$ is PMD value of the $i$ th component (ps) + +This equation assumes that the statistics of the instantaneous DGD are approximated by a Maxwell distribution, with the probability of the instantaneous DGD exceeding $DGDmax_{link}$ being controlled by the value of the Maxwell adjustment factor taken from Table 7-5. + +**Table 7-5 – S values and probabilities** + +| Ratio of max. to mean (S) | Probability of exceeding max. | Ratio of max. to mean (S) | Probability of exceeding max. | +|---------------------------|-------------------------------|---------------------------|-------------------------------| +| 3 | $4.2 \times 10^{-5}$ | 4 | $7.4 \times 10^{-9}$ | +| 3.2 | $9.2 \times 10^{-6}$ | 4.2 | $9.6 \times 10^{-10}$ | +| 3.4 | $1.8 \times 10^{-6}$ | 4.4 | $1.1 \times 10^{-10}$ | +| 3.6 | $3.2 \times 10^{-7}$ | 4.6 | $1.2 \times 10^{-11}$ | +| 3.8 | $5.1 \times 10^{-8}$ | | | + +Further details can be found in [ITU-T G.650.2] and [ITU-T G.691]. The value of $DGDmax_F$ (the maximum DGD due to the fibre part) can either be measured or, alternatively, an upper limit can be calculated for a given fibre length using the $PMD_Q$ coefficient in the corresponding fibre Recommendation. + +The DGD limits for the entire link are given in Table 7-6 for NRZ systems and Table 7-7 for RZ. + +**Table 7-6 – Maximum link differential group delay for NRZ** + +| Client class | Units | Value | +|--------------|-------|-------| +| 1.25G | ps | 240 | +| 2.5G | ps | 120 | +| 10G | ps | 30 | +| 40G | ps | 7.5 | + +**Table 7-7 – Maximum link differential group delay for RZ** + +| Client class | Units | Value | +|--------------|-------|-------| +| 1.25G | ps | ffs | +| 2.5G | ps | ffs | +| 10G | ps | ffs | +| 40G | ps | ffs | + +## 7.8 Minimum optical return loss at MPI-SM or SM + +Reflections are caused by refractive index discontinuities along the optical path. If not controlled, they can degrade system performance through their disturbing effect on the operation of the optical source or amplifier, or through multiple reflections which lead to interferometric noise at the receiver. Reflections from the optical path are controlled by specifying: + +- the minimum optical return loss of the cable plant at the source reference point (e.g., MPI-SM, SM), including any connectors; and +- the maximum discrete reflectance between source reference points (e.g., MPI-SM, SM) and receive reference points (e.g., MPI-RM, RM). + +Reflectance denotes the reflection from any single discrete reflection point, whereas the optical return loss is the ratio of the incident optical power to the total returned optical power from the entire fibre, including both discrete reflections and distributed backscattering such as Rayleigh scattering. + +Measurement methods for reflections are described in Appendix I of [ITU-T G.957]. For the purpose of reflectance and return loss measurements, points MPI-S and MPI-R are assumed to coincide with the endface of each connector plug. It is recognized that this does not include the actual reflection performance of the respective connectors in the operational system. These reflections are assumed to have the nominal value of reflection for the specific type of connectors used. + +The minimum optical return loss of the cable plant at MPI-SM or SM is limited to $-24$ dB. + +## 7.9 Maximum discrete reflectance between MPI-SM and MPI-RM + +Optical reflectance is defined to be the ratio of the reflected optical power present at a point, to the optical power incident to that point. Control of reflections is discussed extensively in [ITU-T G.957]. The maximum number of connectors or other discrete reflection points which may be included in the optical path (e.g., for distribution frames, or WDM components), must be such as to allow the specified overall optical return loss to be achieved. If this cannot be done using connectors meeting the maximum discrete reflections cited here, then connectors having better reflection performance must be employed. Alternatively, the number of connectors must be reduced. It may also be necessary to limit the number of connectors or to use connectors having improved reflectance performance in order to avoid unacceptable impairments due to multiple reflections. + +The maximum discrete reflectance between MPI-SM and MPI-RM is limited to $-27$ dB. + +# 8 Optical safety considerations + +While this Recommendation relates to the fibre infrastructure and does not specify the characteristics of the optical transmission systems operating over it, such systems may well operate at relatively high optical power levels. Information on optical safety considerations can be found in [ITU-T G.664], [IEC 60825-1], [IEC 60825-2] and [b-IEC/TR 61292-4]. + +The hazard level, as defined in [IEC 60825-2], of transmission equipment according to this Recommendation should be limited to hazard level 1M (if necessary through the use of APR procedures) in order that it can be operated in restricted locations. + +# Appendix I + +## Theoretical limits and design considerations for DWDM systems + +(This appendix does not form an integral part of this Recommendation) + +This appendix presents some physical and technology limitations to the achievable link distances of intra-domain DWDM optical transmission systems. + +In clause I.1, the fundamental limits due to ASE noise and PMD are discussed. This is followed in clause I.2 with a discussion of other effects that limit the distances in practical systems, and in clause I.3, techniques to mitigate these effects are described. In clause I.4, mixed transmission of 10 Gbit/s, 40 Gbit/s and 100 Gbit/s transmission wavelengths is analysed, and in clause I.5, 100G applications are indicated. + +### I.1 Enabling technologies and their limits + +In this clause, some of the fundamental constraints for the technological feasibility of DWDM applications are indicated. + +It is assumed that the link optical attenuation is compensated for with optical amplifiers and the chromatic dispersion is compensated for with chromatic dispersion compensators. + +ASE noise and PMD are the most important impairments that limit the capacity and transmission distance of DWDM applications. + +The discussion in clause I.1 refers to NRZ line coding since this is commonly used in DWDM applications. Other line codings may give different results and might be more suitable in some cases (some alternatives to NRZ are discussed in clause I.3). + +#### I.1.1 ASE noise + +The influence of ASE noise is essentially characterized by OSNR. As shown in [b-ITU-T G-Sup.39], the OSNR of a multichannel $x$ span reference system with a booster amplifier, $x-1$ line amplifiers and a pre-amplifier is given by: + +$$OSNR = P_{out} - L - NF_{eff} - 10 \cdot \log \left( x + \frac{10^{\frac{G_{BA}}{10}}}{10^{\frac{L}{10}}} \right) - 10 \cdot \log[h \cdot \nu \cdot \nu_r] \quad (I-1)$$ + +$P_{out}$ is the output power (per channel) of the booster and line amplifiers in dBm, $L$ is the span loss in dB (which is assumed to be equal to the gain $G_{LA}$ of the line amplifiers), $G_{BA}$ is the gain of the optical booster amplifier in dB, $NF_{eff}$ is the noise figure of the optical amplifier in dB, $h$ is Planck's constant (in mJ\*s to be consistent with $P_{out}$ in dBm), $\nu$ is the optical frequency in Hz, $\nu_r$ is the reference bandwidth in Hz, $x-1$ is the total number of line amplifiers. + +Equation I-1 takes into account the shot noise and the signal-spontaneous beat noise as the most dominant noise contributions. Other noise contributions might be considered in some cases. + +This equation indicates that the ASE noise is accumulated from all $x + 1$ amplifiers. + +For this reference system, the following main assumptions are made: + +- All optical amplifiers in the chain including booster and pre-amplifier have the same noise figure. +- The losses (per channel) of all spans are equal. +- The output powers (per channel) of the booster and line amps are the same. + +For example, assuming the optical channel output power $P_{out} = 3$ dBm, the noise figure $NF_{eff} = 6.5$ dB, the reference bandwidth $v_r = 0.1$ nm and the span loss $L = 22$ dB we get the solid curve shown in Figure I.1. + +For a 10 Gbit/s data rate, and assuming an OSNR limitation of 25 dB for a BER of $10^{-12}$ without FEC, we get a theoretical limiting distance of 5 spans. + +If we assume the use of [ITU-T G.709] FEC with a net coding gain (NCG) of 5.6 dB, the limiting OSNR becomes 19.4 dB which is reached at 20 spans. + +Using stronger FEC, e.g., one of the schemes found in Appendix I of [b-ITU-T G.975.1], a net coding gain (NCG) of around 8 dB is feasible and the limiting OSNR becomes 17 dB which is reached at 35 spans. + +![Figure I.1: OSNR limits for a reference system, OSNR as a function of span number with and without Raman amplification. The graph plots OSNR (dB) on the y-axis (0 to 35) against the Number of spans on the x-axis (0 to 40). Two curves are shown: a dashed line for 'OSNR EDFA + Raman' and a solid line for 'OSNR EDFA only'. Three horizontal lines represent OSNR limits: 25 dB for 'OSNR-Limit without FEC', 19.4 dB for 'OSNR-Limit with G.709/Y.1331 FEC', and 17 dB for 'OSNR-Limit with super FEC'. The intersection points are marked with boxes: 5 spans for the 25 dB limit, 19 spans for the 19.4 dB limit, and 35 spans for the 17 dB limit.](ef25c3cf1fdb334fc8679e85ab5265ca_img.jpg) + +| OSNR Limit (dB) | Number of spans | System Type | +|-----------------|-----------------|--------------| +| 25 | 5 | EDFA only | +| 19.4 | 19 | EDFA + Raman | +| 17 | 35 | EDFA only | + +Figure I.1: OSNR limits for a reference system, OSNR as a function of span number with and without Raman amplification. The graph plots OSNR (dB) on the y-axis (0 to 35) against the Number of spans on the x-axis (0 to 40). Two curves are shown: a dashed line for 'OSNR EDFA + Raman' and a solid line for 'OSNR EDFA only'. Three horizontal lines represent OSNR limits: 25 dB for 'OSNR-Limit without FEC', 19.4 dB for 'OSNR-Limit with G.709/Y.1331 FEC', and 17 dB for 'OSNR-Limit with super FEC'. The intersection points are marked with boxes: 5 spans for the 25 dB limit, 19 spans for the 19.4 dB limit, and 35 spans for the 17 dB limit. + +G.696.1\_F1.1 + +**Figure I.1 – OSNR limits for a reference system, OSNR as a function of span number with and without Raman amplification** + +Distributed Raman amplification (DRA) is a further option to extend transmission distance. The OSNR improvement factor expected by DRA in backward pumping configuration can be calculated by the effective noise figure ( $NF_{eff}$ ) which can be expressed by Equation I-2 [b-Islam]. + +$$NF_{eff} = 10 \cdot \log \left( \left( NF'_{LA} + \frac{P_{ASE,Raman}}{h \cdot v \cdot v_r} \right) \cdot \frac{1}{G'_{Raman}} \right) \quad (I-2)$$ + +where $NF'_{LA}$ is the linear noise figure of the discrete line amplifier, $G'_{Raman}$ is the linear gain of DRA, $P_{ASE,Raman}$ is the ASE power resulting from DRA, $v_r$ is the reference bandwidth. The equation $NF_{LA} = 10 \cdot \log(NF'_{LA})$ holds where $NF_{LA}$ is the noise figure of the discrete line amplifier in dB. + +$P_{ASE,Raman}$ and $G_{Raman} = 10 \log(G'_{Raman})$ can be estimated analytically [b-Aoki]. + +![Figure I.2: A line graph showing the effective noise figure (NF_eff) in dB as a function of Raman gain in dB. The x-axis ranges from 0 to 12 dB, and the y-axis ranges from -1 to 7 dB. Three solid curves are shown for different EDFA noise figures (NF_LA): 6.5 dB (green), 4.5 dB (red), and 3 dB (blue). All curves show a linear decrease in NF_eff as Raman gain increases. A dashed blue line is also shown, representing the NF_eff for NF_LA = 6.5 dB at a Raman gain of approximately 9.3 dB, where NF_eff is 1 dB.](b2d16e07bfa79d67a8adabf7e26c7764_img.jpg) + +| Raman gain (dB) | NF eff (dB) for NF LA = 6.5 dB | NF eff (dB) for NF LA = 4.5 dB | NF eff (dB) for NF LA = 3 dB | +|-----------------|------------------------------------------------------|------------------------------------------------------|----------------------------------------------------| +| 0 | 6.5 | 4.5 | 3.0 | +| 2 | 5.5 | 3.5 | 2.0 | +| 4 | 4.5 | 2.5 | 1.0 | +| 6 | 3.5 | 1.5 | 0.0 | +| 8 | 2.5 | 0.5 | -1.0 | +| 10 | 1.5 | -0.5 | -2.0 | +| 12 | 0.5 | -1.5 | -3.0 | + +Figure I.2: A line graph showing the effective noise figure (NF\_eff) in dB as a function of Raman gain in dB. The x-axis ranges from 0 to 12 dB, and the y-axis ranges from -1 to 7 dB. Three solid curves are shown for different EDFA noise figures (NF\_LA): 6.5 dB (green), 4.5 dB (red), and 3 dB (blue). All curves show a linear decrease in NF\_eff as Raman gain increases. A dashed blue line is also shown, representing the NF\_eff for NF\_LA = 6.5 dB at a Raman gain of approximately 9.3 dB, where NF\_eff is 1 dB. + +**Figure I.2 – NFeff as a function of Raman gain** + +NFeff as a function of Raman gain $G_{\text{Raman}}$ is shown in Figure I.2. Here, the following parameters are assumed: Fibre length 80 km, attenuation coefficient 0.275 dB/km and 0.3 dB/km for signal and pump wavelength, respectively, effective area of fibre 80 $\mu\text{m}^2$ and Raman gain coefficient $3.1\text{E-}14$ . The noise figures of the EDFA are 3 dB, 4.5 dB and 6.5 dB, respectively. The maximum transmission distance with Raman – EDFA combined amplifiers can be estimated by inserting NFeff from Equation I-2 in the OSNR Equation I-1 and using $L = G_{\text{Raman}} + G_{\text{LA}}$ where again $G_{\text{LA}}$ is the gain of the line amplifier in dB. + +Assuming a Raman gain of approximately 9.3 dB and an EDFA noise figure of $\text{NF}_{\text{LA}} = 6.5$ dB, we get an effective noise figure of $\text{NF}_{\text{eff}} = 1$ dB which gives the dashed curve shown in Figure I.1. + +Now the theoretical limiting distance without FEC becomes 19 spans and the addition of [ITU-T G.709] FEC would allow a system with more than 40 spans. + +#### I.1.2 PMD + +The total PMD of a fibre link, with total length $L$ and a PMD coefficient for the individual cable sections $\text{PMD}_Q$ , is given by $\text{PMD} = \sqrt{L} \cdot \text{PMD}_Q$ . For a 10 Gbit/s NRZ interface, the total PMD should not exceed 10 ps (corresponding to an outage probability with "five nines" for a fibre induced maximum DGD = 30 ps). If the PMD coefficient $\text{PMD}_Q$ value is not greater than $0.5 \text{ ps/km}^{1/2}$ , this gives a total link length of 400 km; and with a maximum PMD coefficient $\text{PMD}_Q = 0.2 \text{ ps/km}^{1/2}$ , the total link length becomes 2500 km, see Figure I.3. + +![Figure I.3: PMD vs distance for different PMD coefficients and PMD limit for 10 Gbit/s NRZ systems with 99.999% availability. The graph plots PMD in ps (Y-axis, 0 to 30) against the number of spans of 80 km (X-axis, 0 to 40). Three curves are shown: a solid line for PMD for PMD_Q = 0.5 ps/sqrt(km), a dashed line for PMD for PMD_Q = 0.2 ps/sqrt(km), and a horizontal dotted line for PMD limit for Standard 10G NRZ.](3102c32204f998dba666e1e915d5babf_img.jpg) + +G.696.1\_F1.3 + +- PMD limit for Standard 10G NRZ +- PMD for $PMD_Q = 0.5 \text{ ps/\sqrt{km}}$ +- - - PMD for $PMD_Q = 0.2 \text{ ps/\sqrt{km}}$ + +Figure I.3: PMD vs distance for different PMD coefficients and PMD limit for 10 Gbit/s NRZ systems with 99.999% availability. The graph plots PMD in ps (Y-axis, 0 to 30) against the number of spans of 80 km (X-axis, 0 to 40). Three curves are shown: a solid line for PMD for PMD\_Q = 0.5 ps/sqrt(km), a dashed line for PMD for PMD\_Q = 0.2 ps/sqrt(km), and a horizontal dotted line for PMD limit for Standard 10G NRZ. + +**Figure I.3 – PMD vs distance for different PMD coefficients and PMD limit for 10 Gbit/s NRZ systems with 99.999% availability** + +Figure I.3 gives the guidance on maximum distance allowed according to fibre's maximum $PMD_Q$ for NRZ line coding based on its 1st-order DGD tolerance. The figure has not accounted for the PMD contribution from equipment. + +A real system on a real fibre link should consider the PMD limit from the combined contribution of both fibre link and equipment which comprises all the nodes in a link. + +In some circumstances, higher-order PMD should also be considered. + +### I.2 Other effects which limit transmission distance + +The limiting link distances calculated in the previous clauses are the distances that might be achieved in ideal circumstances. There are, however, several effects in practical systems that reduce the maximum link length. + +#### I.2.1 Accumulated gain ripples from EDFA cascading and tilt due to stimulated Raman effects + +A real system in a real link needs to consider power divergence among channels due to accumulated gain ripple and stimulated Raman effects. + +Technologies like gain flattening filters and dynamical gain/power equalization can be used to reduce the impact of such effects, but there will still be some impact, which will reduce the achievable distances to less than those shown in Figure I.1. + +#### I.2.2 Non-uniform span length + +The application codes in this Recommendation consider equal span lengths. For the discussion in this appendix, a constant attenuation of 22 dB per span has been used. In real systems, the span lengths are usually not equal, actually depending on the real network topology and topographical constraints. + +It is difficult to account for this "non-ideality" in a general manner, because, for the same system, longer spans mean an OSNR "debt" and shorter spans turn into an OSNR "credit". + +The OSNR "debt" due to longer spans can be partially or completely compensated by increasing the output power of the amplifier preceding the span itself, provided that the increased power does not cause non-linear effects that cannot be tolerated without extra penalty. + +Therefore, generally speaking, a link with longer spans may likely force the system to support a smaller number of spans, whereas a link with shorter spans may likely allow the system to support a larger number of spans. Given that this matter falls in the specific system design of the equipment vendor, it is simply mentioned here to give a more comprehensive view on these types of applications, without giving any details. + +#### 1.2.3 Optical non-linearity + +Non-linear effects like self-phase modulation (SPM) and/or cross-phase modulation (XPM) accumulate over spans and become significant as the number of spans becomes large. Thus, non-linear penalty may not be ignored in a real link. + +Higher channel power is good for OSNR, but is not necessarily good for BER. This is due to fibre non-linear effects. + +Considering NRZ with average channel power of 3 dBm on ITU-T G.652 fibre (the same power assumed in Figure I.1), accumulated non-linear (SPM) phase shift, $\Phi_{NL} = \gamma P_{ch} L_{eff} N_{span}$ after 10 spans is close to 1 radian and transmission is in a so-called "strong non-linear distortion" region where link distance may be non-linearity limited and accurate dispersion management becomes mandatory. In the case of keeping the launched power at +3 dBm irrespective of the total number of spans, the non-linear SPM phase shift is increasing far beyond 1 radian. Aiming to achieve a constant 1 radian value for the whole transmission link, whatever the total number of spans is, results in an adaptation of the launched power versus number of spans. + +Figure I.4 shows the comparison of the OSNR curve (EDFA only) from Figure I.1 (solid) applying constant fibre input power (P) value of 3 dBm together with the $\log(-N)$ adaptation (dotted) of fibre input power, where the non-linear SPM noise accumulation is a constant "integrated power product" (here 13 dBm) corresponding to a constant 1 radian of the non-linear phase shift. Thus, the two curves cross at 10 spans, showing a pessimistic and optimistic region of the solid curve compared to the dotted curve. + +![Figure I.4: OSNR versus Number of spans. The graph shows two curves: 'P varied (log(-N))' (dashed line) and 'P constant (3 dBm)' (solid line). The y-axis is OSNR (0.1 nm; dB) from 10 to 35. The x-axis is Number of spans from 0 to 30. The dashed line starts at approximately 35 dB at 2 spans and decreases to about 13 dB at 30 spans. The solid line starts at approximately 32 dB at 2 spans and decreases to about 18 dB at 30 spans. A small text 'G.696.1(10)_Fl.4' is located at the bottom right of the graph area.](60e9207be66a64332619bb4b667fe67b_img.jpg) + +Figure I.4: OSNR versus Number of spans. The graph shows two curves: 'P varied (log(-N))' (dashed line) and 'P constant (3 dBm)' (solid line). The y-axis is OSNR (0.1 nm; dB) from 10 to 35. The x-axis is Number of spans from 0 to 30. The dashed line starts at approximately 35 dB at 2 spans and decreases to about 13 dB at 30 spans. The solid line starts at approximately 32 dB at 2 spans and decreases to about 18 dB at 30 spans. A small text 'G.696.1(10)\_Fl.4' is located at the bottom right of the graph area. + +**Figure I.4 – OSNR versus No. of spans considering constant input power per span of 3 dBm and consideration of non-linear (SPM) phase accumulation according to variation of input power resulting in a reduction of input power per span according to $\log(-N)$** + +Further details of optical non-linearity are given in [ITU-T G.663] and in [b-ITU-T G-Sup.39] and some methods of mitigating these effects are discussed in clause I.3. + +#### I.2.4 Residual dispersion and dispersion tolerance + +The curves in Figure I.1 assume that each channel in the WDM system is perfectly dispersion compensated. While dispersion compensation modules (DCMs) with an exactly inverse dispersion vs wavelength slope to that of the fibre could be used, this is not usually the case and even then, higher order chromatic dispersion may need to be considered as the number of spans increases. + +In addition to the mismatched slopes causing residual dispersion for some of the WDM channels, non-linear distortion can, if not mitigated, broaden the spectrum and thus reduce the dispersion tolerance after fibre transmission. + +For example, for periodic dispersion compensated fibre link, non-linearity causes negative chirp which narrows dispersion compensation tolerance and moves the optimal dispersion compensation point to positive net dispersion. This effect is illustrated in Figure I.5. + +This example is based on simulation of an eight-channel DWDM system with NRZ 10G signals over $10 \times 80$ km of ITU-T G.652 fibre at an average output power of 3 dBm per channel. The simulation assumed that the chromatic dispersion of each 80 km section was exactly compensated at each line amplifier. + +![Figure I.5: A graph showing OSNR penalty (dB) versus Link residual dispersion (ps/nm). The x-axis ranges from -2000 to 2000 ps/nm, and the y-axis ranges from -1 to 5 dB. Two curves are plotted: a solid line with square markers representing 'Dispersion only, (no non-linear impairments)' and a dashed line with square markers representing 'After transmission non-linearity has shifted and narrowed the curve'. The solid curve is a wide U-shape with a minimum of 0 dB at 0 ps/nm. The dashed curve is a narrower U-shape, shifted to the right, with a minimum of approximately 0.2 dB at around 250 ps/nm.](0f79a59f3766fc341ff688a23692c1d9_img.jpg) + +Figure I.5: A graph showing OSNR penalty (dB) versus Link residual dispersion (ps/nm). The x-axis ranges from -2000 to 2000 ps/nm, and the y-axis ranges from -1 to 5 dB. Two curves are plotted: a solid line with square markers representing 'Dispersion only, (no non-linear impairments)' and a dashed line with square markers representing 'After transmission non-linearity has shifted and narrowed the curve'. The solid curve is a wide U-shape with a minimum of 0 dB at 0 ps/nm. The dashed curve is a narrower U-shape, shifted to the right, with a minimum of approximately 0.2 dB at around 250 ps/nm. + +G.696.1(10)\_FI.5 + +**Figure I.5 – Example of the effect of non-linearity on dispersion tolerance after transmission** + +#### I.2.5 Accumulated PDL effects + +Optical components such as WDM filters, VOAs or OAs exhibit finite polarization-dependent loss (PDL) that may range from 0.1 to 0.3 dB per device or even more. PDL exerts stochastic intensity modulation on optical signals due to variations in the signal polarization with time. The induced power fluctuations are transformed at OAs under the effects of polarization-dependent gain (PDG) into OSNR fluctuations. + +In an extended long-haul system where many optical network elements are concatenated, the accumulated PDL can cause significant power fluctuation, which could degrade system performance and stability. However, the correlation between power fluctuations and OSNR variations may not necessarily be one-to-one. The power fluctuations may be too fast to be fully compensated by means of dynamic gain equalization. + +In a WDM system utilizing polarization-multiplexed signals, PDL could change the state of polarization (SOP) and could degrade the degree of orthogonality in these signals, thereby degrading system performance. + +#### I.2.6 Filtering and crosstalk + +As the symbol rate of the transmission system increases, the width of the spectrum becomes broader and can approach the width of the optical multiplexer and/or demultiplexer. Also the signal of phase shift keying (PSK) modulation formats is more sensitive to the phase response of the optical filter. Consequently, the signal may suffer from filtering of optical multiplexer and/or demultiplexer, resulting in the reduction of transmission distance. + +Furthermore, the signal of broad spectrum bandwidth would also suffer from the finite isolation of optical multiplexer and/or demultiplexer, causing inter-channel crosstalk (refer to clause 9.6.2 in [b-ITU-T G-Sup.39]), which will consequently reduce the transmission distance. + +### **I.3 Techniques used to mitigate impairments** + +There are several practical techniques which may improve the performance of an IaDI link, such as by choosing: + +- i) dynamic gain equalization; +- ii) modulation format; +- iii) number of optical channels and their spacing; +- iv) fibre types; +- v) mixing different types of fibre within one span; +- vi) receiver (detection scheme); +- vii) digital equalization. + +#### **I.3.1 Dynamic gain equalization** + +In order to compensate for the gain tilt introduced by a long chain of amplifiers, the use of an integrated optical spectrum analyser (OSA) or optical power monitor (OPM) and adjustable gain flattening filters can be used to ensure good equalization across all the channels of the DWDM aggregate signal. + +#### **I.3.2 Modulation format** + +Modulation formats other than NRZ can provide some advantages under certain circumstances. + +As described in [b-ITU-T G-Sup.39], return to zero (RZ) line coded systems are significantly more tolerant to first-order PMD than NRZ systems. Also, modified RZ coding formats, such as phase-modulated RZ, can be additionally advantageous in terms of enhanced non-linear tolerance. These characteristics encourage the use of RZ line coding for very long link distances where PMD and non-linear effects are particularly significant. + +On the other hand, RZ coding has (due to the broader bandwidth to be used) a potential drawback of being less spectrally efficient compared to NRZ (see [b-ITU-T G-Sup.39]) and is usually more sensitive to residual chromatic dispersion than NRZ. For this reason, systems that adopt RZ modulation format require a more precise characterization and compensation of the dispersion associated with the link. + +Line codes other than NRZ and RZ can also be applied to DWDM systems, each of them having benefits and drawbacks. In particular, for very long link lengths and ultra-high capacity DWDM signals, the choice of a particular line code depends on the individual optimal system design. + +#### **I.3.3 Number of optical channels and their spacing** + +As a general trend, the maximum number of DWDM channels giving acceptable performance will tend to decrease with increasing link length and/or decreasing optical channel spacing, due to the increased impact of optical non-linearity. + +#### **I.3.4 Fibre types** + +One fibre type may have an advantage or disadvantage compared with another under certain conditions. In the C-band for example, ITU-T G.652 has larger chromatic dispersion than ITU-T G.655 or ITU-T G.653 fibre and, therefore, it may introduce less non-linear effects. However, Raman gain strongly depends on fibre type and ITU-T G.652 fibres, due to their large mode field diameters, show a smaller Raman gain for a given pump power than other fibres. + +#### **I.3.5 Mixing different types of fibre within one span** + +One technique that can be used to mitigate the effects of fibre non-linearity is to deliberately mix fibres with different characteristics within a single span. For example, a span containing alternating fibres with positive and negative dispersion results in a span with a high value of local dispersion (desirable to reduce the effects of XPM and four-wave mixing (FWM)) but a low net dispersion (which reduces the dispersion compensation requirements). + +In cases where a link has different fibre types in different spans, the launch power may have to be different in each span depending on the fibre types of the first 20 km of each span, in order to minimize the non-linear distortion. + +#### **I.3.6 Receiver (detection scheme)** + +In some higher speed transmission systems, other receivers can be used to enhance the performance of an IaDI link. + +Differential detection and coherent detection receivers are useful in that they provide superior receiver sensitivity or OSNR tolerance to a conventional direct detection receiver (NRZ receiver) using a single photodiode, and this can lead to the achievement of long distance transmission. + +In a differential detection receiver, the signal is mixed with a delayed signal (for example a 1-bit delayed signal) before the receiver. Differentially phase modulated optical signals are converted to amplitude modulated electrical signals using a delay optical interferometer and a balanced receiver. This differential detection provides approximately 3 dB higher sensitivity than direct detection because it can receive the signal with double the amplitude. + +In a coherent detection receiver, the signal light is mixed with a reference light called a local oscillator, which has a frequency close to that of the signal. The output signal with a difference frequency contains the phase information of the original signal. The modulated optical signal is converted to an electrical signal, for example, through an optical hybrid and a balanced receiver. Digital coherent detection, where an analog to digital converter and a digital signal processor are used to estimate the carrier phase in the receiver, is useful for reducing phase noise. This process is linear and it can also compensate for impairments such as chromatic dispersion and PMD. It provides a sensitivity more than 3 dB higher than that provided by a direct detection receiver. + +#### **I.3.7 Digital equalization** + +In some higher speed transmission systems, for the purpose of mitigating the effects of fibre non-linearity as much as possible, no inline chromatic dispersion compensation is adopted. Instead, the dispersion is compensated by digital equalization in conjunction with a coherent receiver, or alternatively, most compensation done by digital equalization in the receiver with a fraction of dispersion compensation done inline. Digital equalization is also able to compensate PMD. + +### **I.4 Mixed transmission of 10 Gbit/s, 40 Gbit/s and 100 Gbit/s transmission wavelengths** + +#### **I.4.1 Motivation for mixed 10G/40G/100G transmission** + +Transmission of 10G and 40G channels on the same fibre is of interest for operators for, at least, two reasons. Firstly, already installed networks designed for 10G transmission can be upgraded to 40G traffic. Secondly, networks designed for 40G traffic can be equipped with 10G wavelengths originating from low-traffic nodes. + +Benefits of mixed transmission include the possibility to optimize the usage of fibre capacity by means of spectrally efficient modulation formats and, at the same time, to use lower-cost interfaces where 10G capacity is enough. When operating an optical transport network, several factors, including the cost of optical equipment, the fibre ownership, the power consumption and the physical space needed for the equipment must be taken into account. Hence, mixed 10G/40G transmission can be an attractive solution for minimizing the total cost of operations. + +In current DWDM networks, most of the wavelengths are 10 Gbit/s and the modulation formats are purely amplitude shift keying (ASK) based on NRZ and RZ. However, in some applications including 40 Gbit/s, 100 Gbit/s and beyond, alternative modulation formats, including optical duobinary (ODB) or some form of phase shift keying (PSK) modulation format (see clause 7 of [b-ITU-T G-Sup.39]), can be used. + +#### **I.4.2 Issues and challenges of mixed ASK/PSK signal transmission** + +In the mixed ASK/PSK system, the amplitude variation of the ASK channels can induce significant XPM to the co-propagating PSK channels. In such a system, the PSK signal may be influenced by the adjacent ASK signals and its performance may be degraded. + +Interaction of ASK (NRZ and RZ) channels with PSK channels (such as DPSK, RZ-DQPSK, DP-QPSK and others) depends on several factors: + +- modulation formats; +- channel plan (i.e., frequency spacing and location of channels in different formats); +- fibre type (i.e., ITU-T G.652, ITU-T G.653, ITU-T G.654 or ITU-T G.655), or mixed; +- the dispersion map; +- channel power levels; +- filter rejection; +- the polarization relation between the channels; +- symbol rates. + +Regarding the symbol rate, higher symbol rate PSK signals often require more accurate dispersion management than 10 Gbit/s ASK signal alone in order to mitigate non-linearities and/or minimize dispersion penalty. An additional source of penalty from chromatic dispersion can be the coarse step of dispersion compensating modules used in the networks optimized for 10G ASK signals. Related issues are: + +- optimal choice of pre-compensation for mixed ASK/PSK signal transmission; +- rearrangement (if required) of dispersion compensating modules to allow or improve PSK transmission in a network optimized for 10G ASK transmission; +- optimal post-compensation. + +It is also known that the XPM impairment on PSK signals tends to be less when the symbol rate of the PSK channels is higher. References [b-Spinnler], [b-Griesser], [b-Vassilieva] contain further information. + +In general, XPM is stronger the closer the spacing between the wanted channel and the disturbing channel, the higher the power of the disturbing signal and when there is polarization alignment between the two signals. These are factors that can be exploited in mitigation of non-linear penalty in a mixed system. + +#### **I.4.3 Issues and challenges of mixed PSK/PSK signal transmission** + +If different channels employ phase shift keying (PSK), then additional challenges come into play. The large variety of possible modulation formats is indicated in clause 7 of [b-ITU-T G-Sup.39]. + +Although the modulation format is PSK, there may be some power fluctuation induced by filters, fibre dispersion, etc., during the transmission. These power fluctuations are similar to ASK signals, which can cause degradations on other PSK wavelengths via XPM. + +## I.5 100G applications + +There are certain points to be considered for 100 Gbit/s transmission. The OSNR limitation and the PMD limitation is crucial. In order to overcome the barriers, some advanced designs are necessary for 100 Gbit/s long distance (multi-span) transmission using amplifiers. + +For instance, the combination of a dual polarization or polarization multiplexed (DP or PM) quadrature phase shift keying (QPSK) format with a digital coherent receiver can improve OSNR tolerance and compensate for impairments caused by PMD and chromatic dispersion. + +An example of 112 Gbit/s DP-QPSK laboratory experimental result with a digital coherent receiver (with off-line processing) is shown in Figure I.6 which shows that the Q value vs OSNR and OSNR limitation (back-to-back) for $\text{BER} = 10^{-4}$ ( $Q=11.4$ ) is approximately 17 dB. The DGD tolerance for a 1 dB penalty is over 50 ps. + +![Figure I.6: A line graph showing the relationship between OSNR [dB] on the x-axis and Q value [dB] on the y-axis for a 112 Gbit/s DP-QPSK signal. The x-axis ranges from 12 to 22 dB with major ticks every 2 dB. The y-axis ranges from 8 to 15 dB with major ticks every 1 dB. A solid line with circular markers shows a linear increase in Q value with OSNR. The data points are approximately: (14, 9), (16, 10.5), (18, 12), (20, 13), and (22, 14). A horizontal dashed line is drawn at Q = 11.4 dB, intersecting the curve at an OSNR of approximately 17 dB.](939b79420df0cf962959ccef56f3371f_img.jpg) + +| OSNR [dB] | Q value [dB] | +|-----------|--------------| +| 14 | 9 | +| 16 | 10.5 | +| 18 | 12 | +| 20 | 13 | +| 22 | 14 | + +Figure I.6: A line graph showing the relationship between OSNR [dB] on the x-axis and Q value [dB] on the y-axis for a 112 Gbit/s DP-QPSK signal. The x-axis ranges from 12 to 22 dB with major ticks every 2 dB. The y-axis ranges from 8 to 15 dB with major ticks every 1 dB. A solid line with circular markers shows a linear increase in Q value with OSNR. The data points are approximately: (14, 9), (16, 10.5), (18, 12), (20, 13), and (22, 14). A horizontal dashed line is drawn at Q = 11.4 dB, intersecting the curve at an OSNR of approximately 17 dB. + +G.696.1(10)\_Fl.6 + +**Figure I.6 – Example of the Q value versus OSNR for 112 Gbit/s DP-QPSK signal** + +# Bibliography + +- [b-ITU-T G-Sup.39] ITU-T G-series Recommendations – Supplement 39 (2008), *Optical system design and engineering considerations*. +- [b-ITU-T G.975.1] Recommendation ITU-T G.975.1 (2004), *Forward error correction for high bit-rate DWDM submarine systems*. +- [b-IEC/TR 61292-4] IEC/TR 61292-4 (2010), *Optical amplifiers – Part 4: Maximum permissible optical power for the damage-free and safe use of optical amplifiers, including Raman amplifiers*. +- [b-Islam] Islam, M.N., (Ed.) (2004), *Raman Amplifiers for Telecommunications 2 Sub-Systems and Systems*, Springer Series in Optical Sciences, Vol. 90/2, pp. 432, (ISBN:0-387-40656-5). +- [b-Aoki] Aoki, Y. *et al.* (1988), *Properties of fibre Raman amplifiers and their applicability to digital optical communication systems*, IEEE J. Lightwave Technol., Vol. 6, pp. 1225-1239. +- [b-Spinnler] Spinnler B., *et al.* (March 2004), *Nonlinear tolerance of differential phase shift keying modulated signals reduced by XPM*, OFC2004, Paper TuF3. +- [b-Griesser] Griesser H., and Elbers J.-P. (Sept. 2005), *Influence of Cross-Phase Modulation Induced Nonlinear Phase Noise on DQPSK Signals from Neighbouring OOK Channels*, ECOC2005, Paper Tu1.2.2. +- [b-Vassilieva] Vassilieva O., *et al.* (Sept. 2008), *Symbol Rate Dependency of XPM-induced Phase Noise Penalty on QPSK-based Modulation Formats*, ECOC2008, Paper We.1.E.4. + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|---------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Terminals and subjective and objective assessment methods | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects and next-generation networks | +| Series Z | Languages and general 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Telecommunication Union (ITU) features a globe with a red lightning bolt striking it, symbolizing global connectivity and telecommunications. The letters "ITU" are prominently displayed in blue and red. + +ITU logo + +International +Telecommunication +Union + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| General | G.700–G.709 | +| Coding of voice and audio signals | G.710–G.729 | +| Principal characteristics of primary multiplex equipment | G.730–G.739 | +| Principal characteristics of second order multiplex equipment | G.740–G.749 | +| Principal characteristics of higher order multiplex equipment | G.750–G.759 | +| Principal characteristics of transcoder and digital multiplication equipment | G.760–G.769 | +| Operations, administration and maintenance features of transmission equipment | G.770–G.779 | +| Principal characteristics of multiplexing equipment for the synchronous digital hierarchy | G.780–G.789 | +| Other terminal equipment | G.790–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## Recommendation ITU-T G.703 + +# Physical/electrical characteristics of hierarchical digital interfaces + +## Summary + +Recommendation ITU-T G.703 specifies the recommended physical and electrical characteristics of the interfaces at hierarchical bit rates as described in Recommendations ITU-T G.702 (PDH) and ITU-T G.707 (SDH). The interfaces are defined in terms of general characteristics, specifications at the output ports and input ports and/or cross-connect points, earthing of outer conductor or screen and coding rules. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|---------------------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.703 | 1972-12-15 | | 11.1002/1000/11264 | +| 2.0 | ITU-T G.703 | 1976-10-08 | | 11.1002/1000/9993 | +| 3.0 | ITU-T G.703 | 1980-11-21 | | 11.1002/1000/7754 | +| 4.0 | ITU-T G.703 | 1984-10-19 | | 11.1002/1000/3630 | +| 5.0 | ITU-T G.703 | 1988-11-25 | | 11.1002/1000/894 | +| 6.0 | ITU-T G.703 | 1991-04-05 | XVIII | 11.1002/1000/895 | +| 7.0 | ITU-T G.703 | 1998-10-13 | 15 | 11.1002/1000/4514 | +| 8.0 | ITU-T G.703 | 2001-11-29 | 15 | 11.1002/1000/5602 | +| 8.1 | ITU-T G.703 (2001) Cor. 1 | 2008-03-29 | 15 | 11.1002/1000/9369 | +| 8.2 | ITU-T G.703 (2001) Amd. 1 | 2013-08-29 | 15 | 11.1002/1000/11989 | +| 9.0 | ITU-T G.703 | 2016-04-13 | 15 | 11.1002/1000/12788 | + +## Keywords + +Electrical interface, PDH, plesiochronous digital hierarchy, SDH, synchronous digital hierarchy, synchronization interface. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2016 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +###### Page + +| | | | +|------|---------------------------------------------|----| +| 1 | Scope..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions ..... | 3 | +| 3.1 | Terms defined elsewhere ..... | 3 | +| 3.2 | Terms defined in this Recommendation..... | 3 | +| 4 | Abbreviations and acronyms ..... | 3 | +| 5 | Conventions ..... | 4 | +| 6 | Interface at 64 kbit/s (E0) ..... | 4 | +| 6.1 | Functional requirements ..... | 4 | +| 6.2 | Electrical characteristics ..... | 6 | +| 7 | Interface at 1544 kbit/s (E11) ..... | 14 | +| 7.1 | General characteristics..... | 14 | +| 7.2 | Pulse specification ..... | 16 | +| 7.3 | Eye diagrams ..... | 16 | +| 8 | Interface at 6312 kbit/s (E21) ..... | 16 | +| 9 | Interface at 32 064 kbit/s ..... | 18 | +| 10 | Interface at 44 736 kbit/s (E32) ..... | 20 | +| 11 | Interface at 2048 kbit/s (E12) ..... | 22 | +| 11.1 | General characteristics..... | 22 | +| 11.2 | Specifications at the output ports ..... | 22 | +| 11.3 | Specifications at the input ports ..... | 23 | +| 11.4 | Grounding of outer conductor or screen..... | 24 | +| 12 | Interface at 8448 kbit/s (E22) ..... | 24 | +| 12.1 | General characteristics..... | 24 | +| 12.2 | Specification at the output ports ..... | 24 | +| 12.3 | Specifications at the input ports ..... | 26 | +| 12.4 | Grounding of outer conductor ..... | 26 | +| 13 | Interface at 34 368 kbit/s (E31) ..... | 26 | +| 13.1 | General characteristics..... | 26 | +| 13.2 | Specification at the output ports ..... | 27 | +| 13.3 | Specifications at the input ports ..... | 28 | +| 13.4 | Grounding of outer conductor ..... | 28 | +| 14 | Interface at 139 264 kbit/s (E4) ..... | 29 | +| 14.1 | General characteristics..... | 29 | +| 14.2 | Specifications at the output ports ..... | 29 | +| 14.3 | Specifications at the input ports ..... | 32 | +| 14.4 | Grounding of outer conductor ..... | 32 | + +| | Page | | +|--------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------|----| +| 15 | 2048 kHz synchronization interface (T12) ..... | 32 | +| 15.1 | General characteristics..... | 32 | +| 15.2 | Specifications at the output ports ..... | 32 | +| 15.3 | Specifications at the input ports ..... | 33 | +| 15.4 | Grounding of outer conductor or screen..... | 34 | +| 16 | Interface at 97 728 kbit/s ..... | 34 | +| 17 | Interface at 155 520 kbit/s – STM-1 interface (ES1) ..... | 35 | +| 17.1 | General characteristics..... | 35 | +| 17.2 | Specifications at the output ports ..... | 35 | +| 17.3 | Specifications at the input ports ..... | 36 | +| 17.4 | Specifications at the cross-connect points ..... | 36 | +| 17.5 | Grounding of outer conductor ..... | 39 | +| 18 | Interface at 51 840 kbit/s (STM-0 interface) ..... | 39 | +| 18.1 | General characteristics..... | 39 | +| 18.2 | Specifications at the output ports ..... | 40 | +| 18.3 | Specifications at the input ports ..... | 44 | +| 18.4 | Specifications at the cross-connect points ..... | 45 | +| 18.5 | Grounding of outer conductor ..... | 46 | +| 19 | Time synchronization interfaces defined in ITU-T G.8271/Y.1366 ..... | 46 | +| 19.1 | ITU-T V.11-based time/phase distribution interface..... | 46 | +| 19.2 | 1PPS 50 Ω phase-synchronization measurement interface ..... | 48 | +| 20 | 10 MHz synchronization interface..... | 49 | +| 20.1 | General characteristics..... | 49 | +| 20.2 | Specifications at the output ports ..... | 49 | +| 20.3 | Specifications at the input ports ..... | 50 | +| Annex A – Definition of codes ..... | | 51 | +| A.1 | Definition of B3ZS (also designated HDB2) and HDB3 ..... | 51 | +| A.2 | Definition of B6ZS and B8ZS ..... | 51 | +| A.3 | Definition of CMI..... | 51 | +| Appendix I – 1544 kbit/s specification in the 1991 version of this Recommendation ..... | | 52 | +| I.1 | General ..... | 52 | +| I.2 | Interface specification ..... | 52 | +| I.3 | Pulse mask..... | 52 | +| Appendix II – 64 and 6312 kHz synchronization interface specification for use in Japan..... | | 54 | +| II.1 | 64 kHz synchronization interface ..... | 54 | +| II.2 | 6312 kHz synchronization interface ..... | 55 | +| Appendix III – 3152 kbit/s interface specification for use in North America (From
Annex A – [ITU-T G.931])..... | | 56 | +| Bibliography..... | | 57 | + +## Recommendation ITU-T G.703 + +# Physical/electrical characteristics of hierarchical digital interfaces + +# 1 Scope + +This Recommendation provides the recommended physical and electrical characteristics of the interfaces at hierarchical bit rates as described in [ITU-T G.702] (PDH) and [ITU-T G.707] (SDH), to enable the interconnection of digital network components (digital sections, multiplex equipment, exchanges) to form an international digital link or connection. The characteristics given in this Recommendation should be applied to new equipment (component) designs. + +NOTE 1 – The characteristics of interfaces at non-hierarchical bit rates, except $n \times 64$ kbit/s interfaces conveyed by 1544 kbit/s or 2048 kbit/s interfaces and 3152 kbit/s interface in North American hierarchy, are specified in the respective equipment Recommendations. + +NOTE 2 – The jitter specifications contained in this Recommendation are intended to be imposed at international interconnection points. + +NOTE 3 – The interfaces described in clauses 5 to 12 correspond to the ports T (output port) and T' (input port) as recommended for interconnection in [b-ITU-R F.596-1] (Interconnection of digital radio-relay systems). + +NOTE 4 – For signals with bit rates of $n \times 64$ kbit/s ( $n = 2$ to 31) which are routed through multiplexing equipment specified for the 2048 kbit/s hierarchy, the interface shall have the same physical/electrical characteristics as those for the 2048 kbit/s interface specified in clause 9. For signals with bit rates of $n \times 64$ kbit/s ( $n = 2$ to 23) which are routed through multiplexing equipment specified for the 1544 kbit/s hierarchy, the interface shall have the same physical/electrical characteristics as those for the 1544 kbit/s interface specified in clause 5. + +NOTE 5 – The specifications contained in this Recommendation are related to the physical interface only (i.e., to characterize the line codes and input/output equipment interfaces); in particular, the required frequency tolerances do not imply overall equipment performances which may be driven by tighter requirements in Recommendations for specific network/equipment applications (e.g., [ITU-T G.813] and [b-ITU-T G.783]). + +NOTE 6 – When measuring the performance of the output port described in clauses 6.2.1.2, 11.2, 12.2, 13.2, 14.2, 15.2, 17.2, 18.2, and 20.2, the signal attenuation, signal distortion, and length of the cable should be as small as possible. The length of the cable used could be chosen to be less than three meters, for example. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.701] Recommendation ITU-T G.701 (1993), *Vocabulary of digital transmission and multiplexing, and pulse code modulation (PCM) terms.* +- [ITU-T G.702] Recommendation ITU-T G.702 (1988), *Digital hierarchy bit rates.* +- [ITU-T G.704] Recommendation ITU-T G.704 (1998), *Synchronous frame structures used at 1544, 6312, 2048, 8448 and 44 736 kbit/s hierarchical levels.* +- [ITU-T G.707] Recommendation ITU-T G.707/Y.1322 (2007), *Network node interface for the synchronous digital hierarchy (SDH).* +- [ITU-T G.742] Recommendation ITU-T G.742 (1988), *Second order digital multiplex equipment operating at 8448 kbit/s and using positive justification.* + +- [ITU-T G.747] Recommendation ITU-T G.747 (1988), *Second order digital multiplex equipment operating at 6312 kbit/s and multiplexing three tributaries at 2048 kbit/s.* +- [ITU-T G.751] Recommendation ITU-T G.751 (1988), *Digital multiplex equipments operating at the third order bit rate of 34 368 kbit/s and the fourth order bit rate of 139 264 kbit/s and using positive justification.* +- [ITU-T G.752] Recommendation ITU-T G.752 (1988), *Characteristics of digital multiplex equipments based on a second order bit rate of 6312 kbit/s and using positive justification.* +- [ITU-T G.753] Recommendation ITU-T G.753 (1988), *Third order digital multiplex equipment operating at 34 368 kbit/s and using positive/zero/ negative justification.* +- [ITU-T G.755] Recommendation ITU-T G.755 (1988), *Digital multiplex equipment operating at 139 264 kbit/s and multiplexing three tributaries at 44 736 kbit/s.* +- [ITU-T G.810] Recommendation ITU-T G.810 (1996), *Definitions and terminology for synchronization networks.* +- [ITU-T G.811] Recommendation ITU-T G.811 (1997), *Timing characteristics of primary reference clocks.* +- [ITU-T G.812] Recommendation ITU-T G.812 (2004), *Timing requirements of slave clocks suitable for use as node clocks in synchronization networks.* +- [ITU-T G.813] Recommendation ITU-T G.813 (2003), *Timing characteristics of SDH equipment slave clocks (SEC).* +- [ITU-T G.823] Recommendation ITU-T G.823 (2000), *The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy.* +- [ITU-T G.824] Recommendation ITU-T G.824 (2000), *The control of jitter and wander within digital networks which are based on the 1544 kbit/s hierarchy.* +- [ITU-T G.825] Recommendation ITU-T G.825 (2000), *The control of jitter and wander within digital networks which are based on the synchronous digital hierarchy (SDH).* +- [ITU-T G.8260] Recommendation ITU-T G.8260 (2015), *Definitions and terminology for synchronization in packet networks.* +- [ITU-T G.8271] Recommendation ITU-T ITU-T G.8271/Y.1366 (2012), *Time and phase synchronization aspects of packet networks.* +- [ITU-T G.8272] Recommendation ITU-T G.8272/Y.1367 (2015), *Timing characteristics of primary reference time clocks.* +- [ITU-T K.20] Recommendation ITU-T K.20 (2015), *Resistibility of telecommunication equipment installed in a telecommunication centre to overvoltages and overcurrents.* +- [ITU-T K.27] Recommendation ITU-T K.27 (2015), *Bonding configurations and earthing inside a telecommunication building.* +- [ITU-T O.151] Recommendation ITU-T O.151 (1992), *Error performance measuring equipment operating at the primary rate and above.* + +- [ITU-T O.172] Recommendation ITU-T O.172 (2005), *Jitter and wander measuring equipment for digital systems which are based on the synchronous digital hierarchy (SDH)*. +- [ITU-T V.11] Recommendation ITU-T ITU-T V.11 (1996), *Electrical characteristics for balanced double-current interchange circuits operating at data signalling rates up to 10 Mbit/s*. +- [ITU-R F.750-4] Recommendation ITU-R F.750-4 (2000), *Architectures and functional aspects of radio-relay systems for synchronous digital hierarchy (SDH)—based networks*. +- [IEC 60469] IEC 60469 (2013), *Transitions, pulses and related waveforms – Terms, definitions and algorithms*. +- [IEC 60469-2] IEC 60469-2 (1987), *Pulse techniques and apparatus – Part 2: Pulse measurement and analysis, general considerations*. +- [IEC 60603-7] IEC 60603-7 ed3.1 Consol. with am1 (2011), *Connectors for electronic equipment – Part 7: Detail specification for 8-way, unshielded, free and fixed connectors*. +- [ETSI ETS 300 166] ETSI ETS 300 166 (1993), *Transmission and Multiplexing (TM); Physical and electrical characteristics of hierarchical digital interfaces for equipment using the 2048 kbit/s-based plesiochronous or synchronous digital hierarchies*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined elsewhere: + +**3.1.1 (timing) jitter** [ITU-T G.810]. + +**3.1.2 time synchronization** [ITU-T G.8260]. + +## 3.2 Terms defined in this Recommendation + +None. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|-------|---------------------------------------| +| 1PPS | One Pulse Per Second | +| AIS | Alarm Indication Signal | +| AMI | Alternate Mark Inversion | +| B3ZS | Bipolar with three-Zero Substitution | +| B8ZS | Bipolar with eight-Zero Substitution | +| CMI | Coded Mark Inversion | +| DC | Direct Current | +| DSN | Digital Switching Network | +| EMC | Electromagnetic Compatibility | +| EPRTC | Enhanced Primary Reference Time Clock | + +| | | +|-------|--------------------------------------| +| GND | Ground | +| GNSS | Global Navigation Satellite System | +| HDB2 | High Density Bipolar of order 2 code | +| HDB3 | High Density Bipolar of order 3 code | +| PCM | Pulse Code Modulation | +| PRBS | Pseudo Random Bit Sequence | +| PRC | Primary Reference Clock | +| PRTC | Primary Reference Time Clock | +| PDH | Plesiochronous Digital Hierarchy | +| SDH | Synchronous Digital Hierarchy | +| SEC | SDH Equipment Clock | +| SSU | Synchronization Supply Unit | +| STM | Synchronous Transport Module | +| ZBTSI | Zero Byte Time Slot Interchange | + +# 5 Conventions + +None. + +# 6 Interface at 64 kbit/s (E0) + +## 6.1 Functional requirements + +The following basic requirements for the design of the interface are recommended. + +In both directions of transmission, three signals can be carried across the interface: + +- 64 kbit/s information signal; +- 64 kHz timing signal; +- 8 kHz timing signal. + +NOTE 1 – The 64 kbit/s information signal and the 64 kHz timing signal are mandatory. However, although an 8 kHz timing must be generated by the controlling equipment (e.g., PCM multiplex or time slot access equipment), it should not be mandatory for the subordinate equipment on the other side of the interface to either utilize the 8 kHz timing signal from the controlling equipment or to supply an 8 kHz timing signal. + +NOTE 2 – The detection of an upstream fault can be transmitted across the 64 kbit/s interface by transmitting an alarm indication signal (AIS) towards the subordinate equipment. + +The interface should be bit sequence independent at 64 kbit/s. + +NOTE 3 – An unrestricted 64 kbit/s signal can be transmitted across the interface. However, this does not imply that unrestricted 64 kbit/s paths are realizable on a global basis. This is because some Administrations presently have or are continuing to install extensive networks composed of digital line sections whose characteristics do not permit the transmission of long sequences of 0s. [b-ITU-T G.733] provides for PCM multiplexes with characteristics appropriate for such digital line sections.) Specifically, for octet-timed sources in 1544 kbit/s digital networks, it is required that at least one binary 1 should be contained in any octet of a 64 kbit/s digital signal. For a bit stream which is not octet-timed, no more than 7 consecutive 0s should appear in the 64 kbit/s signal. + +NOTE 4 – Although the interface is bit sequence independent, the use of the AIS (all 1s bit pattern) may result in some minor restrictions for the 64 kbit/s source. For example, an all 1s alignment signal could result in problems. + +#### 6.1.1 Three types of envisaged interfaces + +##### 6.1.1.1 Codirectional interface + +The term "codirectional" is used to describe an interface across which the information and its associated timing signal are transmitted in the same direction (see Figure 6-1). + +![Diagram of a codirectional interface between two pieces of equipment.](5a4e62bead259c258d069fd3663ea670_img.jpg) + +The diagram shows two rectangular blocks labeled "Equipment" connected by four horizontal lines. The top two lines are solid and point from the left equipment to the right equipment. The bottom two lines are dashed; the third line from the top points from right to left, and the fourth line points from left to right. A legend below the diagram shows a solid line labeled "Information signal" and a dashed line labeled "Timing signal". The text "G.703(16)\_F6-1" is in the bottom right corner. + +Diagram of a codirectional interface between two pieces of equipment. + +**Figure 6-1 – Codirectional interface** + +##### 6.1.1.2 Centralized clock interface + +The term "centralized clock" is used to describe an interface wherein for both directions of transmission of the information signal, the associated timing signals are supplied from a centralized clock, which may be derived for example from certain incoming line signals (see Figure 6-2). + +NOTE – The codirectional interface or centralized clock interface should be used for synchronized networks and for plesiochronous networks having clocks of the stability required (see [ITU-T G.811]) to ensure an adequate interval between the occurrence of slips. + +![Diagram of a centralized clock interface between two pieces of equipment.](c78c2eefd86269d1740ab85a916f24f2_img.jpg) + +The diagram shows two rectangular blocks labeled "Equipment" connected by four horizontal lines. A box labeled "Central clock" is positioned above the center of these lines, with dashed lines extending down to each of the four horizontal lines. The top two lines are solid and point from left to right. The third line from the top is dashed and points from right to left. The fourth line is solid and points from left to right. A legend below the diagram shows a solid line labeled "Information signal" and a dashed line labeled "Timing signal". The text "G.703(16)\_F6-2" is in the bottom right corner. + +Diagram of a centralized clock interface between two pieces of equipment. + +**Figure 6-2 – Centralized clock interface** + +##### 6.1.1.3 Contradirectional interface + +The term "contradirectional" is used to describe an interface across which the timing signals associated with both directions of transmission are directed towards the subordinate equipment (see Figure 6-3). + +![Diagram of a contradirectional interface between subordinate and controlling equipment.](ca7c7526ec57cd5a2f278c194c0a6a00_img.jpg) + +The diagram shows a rectangular block labeled "Subordinate equipment" on the left and a rectangular block labeled "Controlling equipment" on the right, connected by four horizontal lines. The top line is solid and points from left to right. The second line from the top is dashed and points from right to left. The third line from the top is dashed and points from right to left. The fourth line is solid and points from left to right. A legend below the diagram shows a solid line labeled "Information signal" and a dashed line labeled "Timing signal". The text "G.703(16)\_F6-3" is in the bottom right corner. + +Diagram of a contradirectional interface between subordinate and controlling equipment. + +**Figure 6-3 – Contradirectional interface** + +## 6.2 Electrical characteristics + +#### 6.2.1 Electrical characteristics of 64 kbit/s codirectional interface + +##### 6.2.1.1 General characteristics + +Nominal bit rate: 64 kbit/s. + +Bit rate accuracy: $\pm 100$ ppm ( $\pm 6.4$ bit/s) or better. + +64 kHz and 8 kHz timing signal to be transmitted in a codirectional way with the information signal. + +One balanced pair for each direction of transmission; the use of transformers is recommended. + +Code conversion rules: + +Step 1 – A 64 kbit/s bit period is divided into four unit intervals. + +Step 2 – A binary one is coded as a block of the following four bits: +1 1 0 0 + +Step 3 – A binary zero is coded as a block of the following four bits: +1 0 1 0 + +Step 4 – The binary signal is converted into a three-level signal by alternating the polarity of consecutive blocks. + +Step 5 – The alternation in polarity of the blocks is violated every 8th block. The violation block marks the last bit in an octet. + +These conversion rules are illustrated in Figure 6-4. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +![Figure 6-4: Illustration of the conversion rules. The figure shows a data table and four corresponding waveforms: Steps 1-3, Step 4, Step 5, and Octet timing.](9c2d934b3e757d887c4714eba96b6589_img.jpg) + +| | | | | | | | | | | | | +|----------------|---|---|---|---|---|---|---|---|---|---|---| +| Bit number | 7 | 8 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 1 | +| 64 kbit/s data | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | + +The figure contains four waveforms aligned with the data table above: + + +- Steps 1-3:** A binary waveform where '1' is represented by a '1100' pattern and '0' by a '1010' pattern. +- Step 4:** A three-level waveform where the polarity of each 4-bit block alternates (positive then negative). +- Step 5:** Similar to Step 4, but with 'Violations' indicated by arrows at the end of octets (every 8th block), where the polarity does not alternate as expected to mark the octet boundary. +- Octet timing:** A square wave that transitions at the end of an octet (after bit 8). + +Figure 6-4: Illustration of the conversion rules. The figure shows a data table and four corresponding waveforms: Steps 1-3, Step 4, Step 5, and Octet timing. + +**Figure 6-4 – Illustration of the conversion rules** + +##### 6.2.1.2 Specifications at the output ports + +See Table 6-1. See also Note 6 of clause 1. + +**Table 6-1 – Digital 64 kbit/s codirectional interface** + +| Symbol rate | 256 kBauds | +|------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------| +| Pulse shape (nominally rectangular) | All pulses of a valid signal must conform to the masks in Figure 6-5, irrespective of the polarity | +| Pair for each direction | One symmetric pair | +| Test load impedance | 120 ohms resistive | +| Nominal peak voltage of a "mark" (pulse) | 1.0 V | +| Peak voltage of a "space" (no pulse) | 0 V $\pm$ 0.10 V | +| Nominal pulse width | 3.9 $\mu$ s | +| Ratio of the amplitudes of positive and negative pulses at the centre of the pulses interval | 0.95 to 1.05 | +| Ratio of the widths of positive and negative pulses at the nominal half amplitude | 0.95 to 1.05 | +| Maximum peak-to-peak jitter at the output port (Note) | Refer to clause 5.1 of [ITU-T G.823] | +| NOTE – For the time being these values are valid only for equipment of the 2 Mbit/s hierarchy. | | + +![Diagram (a) showing the mask for a single pulse. The vertical axis represents voltage (V) with levels at 0, 0.5, and 1.0. The horizontal axis represents time in microseconds (μs). The pulse shape is a trapezoid with a flat top. Key time intervals are marked: 3.12 μs (3.9 - 0.78), 3.51 μs (3.9 - 0.39), 3.9 μs, 4.29 μs (3.9 + 0.39), 6.5 μs (3.9 + 2.6), and 7.8 μs (3.9 + 3.9). Voltage levels at the top are marked as 1.0 ± 0.1 and 0.2. The shaded area represents the allowed region for the pulse.](7c1f9e78e0f033d391b687f1652f6e47_img.jpg) + +Diagram (a) showing the mask for a single pulse. The vertical axis represents voltage (V) with levels at 0, 0.5, and 1.0. The horizontal axis represents time in microseconds (μs). The pulse shape is a trapezoid with a flat top. Key time intervals are marked: 3.12 μs (3.9 - 0.78), 3.51 μs (3.9 - 0.39), 3.9 μs, 4.29 μs (3.9 + 0.39), 6.5 μs (3.9 + 2.6), and 7.8 μs (3.9 + 3.9). Voltage levels at the top are marked as 1.0 ± 0.1 and 0.2. The shaded area represents the allowed region for the pulse. + +a) Mask for single pulse + +![Diagram (b) showing the mask for a double pulse. The vertical axis represents voltage (V) with levels at 0, 0.5, and 1.0. The horizontal axis represents time in microseconds (μs). The pulse shape is a trapezoid with a flat top. Key time intervals are marked: 7.02 μs (7.8 - 0.78), 7.42 μs (7.8 - 0.39), 7.8 μs, 8.19 μs (7.8 + 0.39), 10.4 μs (7.8 + 2.6), 11.7 μs (7.8 + 3.9). Voltage levels at the top are marked as 1.0 ± 0.1 and 0.2. The shaded area represents the allowed region for the pulse.](c2b98986bdf45e15707f6b2bd7ade2bd_img.jpg) + +Diagram (b) showing the mask for a double pulse. The vertical axis represents voltage (V) with levels at 0, 0.5, and 1.0. The horizontal axis represents time in microseconds (μs). The pulse shape is a trapezoid with a flat top. Key time intervals are marked: 7.02 μs (7.8 - 0.78), 7.42 μs (7.8 - 0.39), 7.8 μs, 8.19 μs (7.8 + 0.39), 10.4 μs (7.8 + 2.6), 11.7 μs (7.8 + 3.9). Voltage levels at the top are marked as 1.0 ± 0.1 and 0.2. The shaded area represents the allowed region for the pulse. + +b) Mask for double pulse + +G.703(16)\_F6-5 + +NOTE – The limits apply to pulses of either polarity. + +Figure 6-5 – Pulse masks of the 64 kbit/s codirectional interface + +The return loss at the output port should have the minimum values given in Table 6-2: + +**Table 6-2 – Digital 64 kbit/s codirectional interface output port minimum return loss** + +| Frequency range
(kHz) | Return loss
(dB) | +|--------------------------|---------------------| +| 6.4 to 13 | 6 | +| 13 to 384 | 8 | + +##### 6.2.1.3 Specifications at the input ports + +The digital signal presented at the input port shall be as defined above but modified by the characteristics of the interconnecting pairs. The attenuation of these pairs at a frequency of 128 kHz should be in the range 0 to 3 dB. This attenuation should take into account any losses incurred by the presence of a digital distribution frame between the equipment. + +For the jitter to be tolerated at the input port, refer to clause 7.1.1 of [ITU-T G.823]. + +The return loss at the input ports should have the minimum values given in Table 6-3: + +**Table 6-3 – Digital 64 kbit/s codirectional interface input port minimum return loss** + +| Frequency range
(kHz) | Return loss
(dB) | +|--------------------------|---------------------| +| 4 to 13 | 12 | +| 13 to 256 | 18 | +| 256 to 384 | 14 | + +To provide nominal immunity against interference, input ports are required to meet the following requirements: + +A nominal aggregate signal, encoded as a 64 kbit/s codirectional signal and having a pulse shape as defined in the pulse mask, shall have added to it an interfering signal with the same pulse shape as the wanted signal. The interfering signal should have a bit rate within the limits specified in this Recommendation, but should not be synchronous with the wanted signal. The interfering signal shall be combined with the wanted signal in a combining network, with an overall zero loss in the signal path and with the nominal impedance 120 ohms to give a signal-to-interference ratio of 20 dB. The binary content of the interfering signal should comply with [ITU-T O.152] ( $2^{11} - 1$ bit period). No errors shall result when the combined signal, attenuated by up to the maximum specified interconnecting cable loss, is applied to the input port. + +##### 6.2.1.4 Grounding of screen + +If the symmetrical pair is screened, the screen shall be connected to the bonding network both at the input port and output port. + +NOTE 1 – The cable routing is important if leaving the system block. Consult [ITU-T K.27] for guidance. + +NOTE 2 – The use of isolation to the bonding network is for further study. + +#### 6.2.2 Electrical characteristics of the 64 kbit/s centralized clock interface + +##### 6.2.2.1 General characteristics + +Nominal bit rate: 64 kbit/s. The tolerance is determined by the network clock stability (see [ITU-T G.811]). + +For each direction of transmission, there should be one symmetrical pair carrying the data signal. In addition, there should be symmetrical pairs carrying the composite timing signal (64 kHz and 8 kHz) from the central clock source to the office terminal equipment. The use of transformers is recommended. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +Code conversion rules: + +The data signals are coded in AMI code with a 100% duty ratio. The composite timing signals convey the 64 kHz bit-timing information using AMI code with a 50% to 70% duty ratio and the 8 kHz octet-phase information by introducing violations of the code rule. The structure of the signals and their nominal phase relationships are shown in Figure 6-6. + +![Figure 6-6: Signal structures of the 64-kbit/s central clock interface at office terminal output ports. The diagram shows two waveforms: 'Data' and 'Timing'. The 'Data' waveform is an AMI signal with bits 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2. The 'Timing' waveform is a composite signal with violations. Arrows indicate 'Violation' and 'Octet start' points. The diagram is labeled G.703(16)_F6-6.](e95f47f7a4c01c8889d6d46919b4c73d_img.jpg) + +Figure 6-6: Signal structures of the 64-kbit/s central clock interface at office terminal output ports. The diagram shows two waveforms: 'Data' and 'Timing'. The 'Data' waveform is an AMI signal with bits 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2. The 'Timing' waveform is a composite signal with violations. Arrows indicate 'Violation' and 'Octet start' points. The diagram is labeled G.703(16)\_F6-6. + +**Figure 6-6 – Signal structures of the 64-kbit/s central clock interface at office terminal output ports** + +The data stream at the output ports should be timed by the leading edge of the timing pulse and the detection instant at the input ports should be timed by the trailing edge of each timing pulse. + +##### 6.2.2.2 Characteristics at the output ports + +See Table 6-4. + +**Table 6-4 – Digital 64 kbit/s centralized clock interface** + +| Parameters | Data | Timing | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------|----------------------------------------------------------------| +| Pulse shape | Nominally rectangular, with rise and fall times less than 1 μs | Nominally rectangular, with rise and fall times less than 1 μs | +| Nominal test load impedance | 110 ohms resistive | 110 ohms resistive | +| Peak voltage of a "mark" (pulse) (Note 1) | a) $1.0 \pm 0.1$ V
b) $3.4 \pm 0.5$ V | a) $1.0 \pm 0.1$ V
b) $3.0 \pm 0.5$ V | +| Peak value of a "space" (no pulse) (Note 1) | a) $0 \pm 0.1$ V
b) $0 \pm 0.5$ V | a) $0 \pm 0.1$ V
b) $0 \pm 0.5$ V | +| Nominal pulse width (Note 1) | a) 15.6 μs
b) 15.6 μs | a) 7.8 μs
b) 9.8 to 10.9 μs | +| Maximum peak-to-peak jitter at the output port (Note 2) | Refer to clause 5.1 of [ITU-T G.823] | | +|

NOTE 1 – The choice between the set of parameters a) and b) allows for different office noise environments and different maximum cable lengths between the three involved office equipment.

NOTE 2 – For the time being, these values are valid only for equipment of the 2 Mbit/s hierarchy.

| | | + +##### 6.2.2.3 Characteristics at the input ports + +The digital signals presented at the input ports should be as defined above but modified by the characteristics of the interconnecting pairs. The varying parameters in Table 6-4 will allow typical maximum interconnecting distances of 350 to 450 m. + +##### 6.2.2.4 Cable characteristics + +The transmission characteristics of the cable to be used are subject to further study. + +#### 6.2.3 Electrical characteristics of 64 kbit/s contradirectional interface + +#### 6.2.3.1 General characteristics + +Nominal bit rate: 64 kbit/s. + +Bit rate accuracy: $\pm 100$ ppm ( $\pm 6.4$ bit/s) or better. + +For each direction of transmission there should be two symmetrical pairs of wires, one pair carrying the data signal and the other carrying a composite timing signal (64 kHz and 8 kHz). The use of transformers is recommended. + +NOTE – If there is a national requirement to provide a separate alarm signal across the interface, this can be done by cutting the 8 kHz timing signal for the transmission direction concerned, i.e., by inhibiting the code violations introduced in the corresponding composite timing signal (see below). + +Code conversion rules: + +The data signals are coded in AMI code with a 100% duty ratio. The composite timing signals convey the 64 kHz bit-timing information using AMI code with a 50% duty ratio and the 8 kHz octet-phase information by introducing violations of the code rule. The structures of the signals and their phase relationships at data output ports are shown in Figure 6-7. + +![Figure 6-7: Signal structures of the 64-kbit/s contradirectional interface at data output ports. The diagram shows two waveforms: Data and Timing. The Data waveform is an AMI signal with a 100% duty ratio. The Timing waveform is an AMI signal with a 50% duty ratio, with violations introduced to convey 8 kHz octet-phase information. The bit numbers 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2 are shown above the waveforms. The violations are marked as 'Violation' and the octet starts are marked as 'Octet start'.](95720c661c3650650edc281e74706340_img.jpg) + +The figure displays two digital signal waveforms over a sequence of 12 bits. The top waveform, labeled 'Data', is an AMI signal where a '1' is represented by a high-to-low transition and a '0' by a low-to-high transition. The bottom waveform, labeled 'Timing', is also an AMI signal but with a 50% duty ratio. It includes 'Violations' (transitions that do not follow the standard AMI rule) to indicate octet boundaries, marked as 'Octet start'. The bit sequence shown is 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2. The diagram is labeled G.703(16)\_F6-7. + +Figure 6-7: Signal structures of the 64-kbit/s contradirectional interface at data output ports. The diagram shows two waveforms: Data and Timing. The Data waveform is an AMI signal with a 100% duty ratio. The Timing waveform is an AMI signal with a 50% duty ratio, with violations introduced to convey 8 kHz octet-phase information. The bit numbers 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2 are shown above the waveforms. The violations are marked as 'Violation' and the octet starts are marked as 'Octet start'. + +**Figure 6-7 – Signal structures of the 64-kbit/s contradirectional interface at data output ports** + +The data pulses received from the service (e.g., data or signalling) side of the interface will be somewhat delayed in relation to the corresponding timing pulses. The detection instant for a received data pulse on the line side (e.g., PCM) of the interface should therefore be at the leading edge of the next timing pulse. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +**6.2.3.2 Specifications at the output ports** + +See Table 6-5. + +**Table 6-5 – Digital 64 kbit/s contradirectional interface** + +| Parameters | Data | Timing | +|------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------| +| Pulse shape (nominally rectangular) | All pulses of a valid signal must conform to the mask in Figure 6-8 irrespective of the polarity | All pulses of a valid signal must conform to the mask in Figure 6-9 irrespective of the polarity | +| Pairs in each direction of transmission | One symmetric pair | One symmetric pair | +| Test load impedance | 120 ohms resistive | 120 ohms resistive | +| Nominal peak voltage of a "mark" (pulse) | 1.0 V | 1.0 V | +| Peak voltage of a "space" (no pulse) | 0 V ± 0.1 V | 0 V ± 0.1 V | +| Nominal pulse width | 15.6 μs | 7.8 μs | +| Ratio of the amplitudes of positive and negative pulses at the centre of the pulse interval | 0.95 to 1.05 | 0.95 to 1.05 | +| Ratio of the widths of positive and negative pulses at the nominal half amplitude | 0.95 to 1.05 | 0.95 to 1.05 | +| Maximum peak-to-peak jitter at the output port (Note) | Refer to clause 5.1 of [ITU-T G.823] | | +| NOTE – For the time being these values are valid only for equipment of the 2 Mbit/s hierarchy. | | | + +**Figure 6-8 – Mask of the data pulse of the 64-kbit/s contradirectional interface** + +![Figure 6-8: Mask of the data pulse of the 64-kbit/s contradirectional interface. The diagram shows a pulse mask on a voltage (V) vs time axis. The nominal pulse height is 1.0V. The mask defines upper and lower boundaries for the pulse shape. Key timing measurements include a nominal pulse width of 15.6 μs, with inner mask widths of 12.4 μs (15.6 - 3.2) and 14.0 μs (15.6 - 1.6). Outer mask widths are 17.2 μs (15.6 + 1.6), 18.8 μs (15.6 + 3.2), and 31.2 μs (15.6 + 15.6). Voltage tolerances are shown as ±0.1V and ±0.2V at various points.](df7cb4ea9bd6c3f445f3e264773b125f_img.jpg) + +Figure 6-8: Mask of the data pulse of the 64-kbit/s contradirectional interface. The diagram shows a pulse mask on a voltage (V) vs time axis. The nominal pulse height is 1.0V. The mask defines upper and lower boundaries for the pulse shape. Key timing measurements include a nominal pulse width of 15.6 μs, with inner mask widths of 12.4 μs (15.6 - 3.2) and 14.0 μs (15.6 - 1.6). Outer mask widths are 17.2 μs (15.6 + 1.6), 18.8 μs (15.6 + 3.2), and 31.2 μs (15.6 + 15.6). Voltage tolerances are shown as ±0.1V and ±0.2V at various points. + +NOTE 1 – When one pulse is immediately followed by another pulse of the opposite polarity, the time limits at the zero-crossing between the pulses should be ±0.8 μs. + +NOTE 2 – The time instants at which a transition from one state to another in the data signal may occur are determined by the timing signal. On the service (e.g., data or signalling) side of the interface, it is essential that these transitions are not initiated in advance of the timing instants given by the received timing signal. + +12 Rec. ITU-T G.703 (04/2016) + +![Figure 6-9: Mask of the timing pulse of the 64-kbit/s contradirectional interface. The diagram shows a pulse shape with voltage (V) on the y-axis (0 to 1.0) and time on the x-axis. The nominal pulse is shown as a solid line, and the mask is indicated by hatched areas. Key timing parameters are: 6.2 μs (7.8 - 1.6), 7.0 μs (7.8 - 0.8), 7.8 μs, 8.6 μs (7.8 + 0.8), 9.4 μs (7.8 + 1.6), and 15.6 μs (7.8 + 7.8). Voltage levels are marked at 0.1, 0.2, 0.5, and 1.0 V.](b2d16e07bfa79d67a8adabf7e26c7764_img.jpg) + +Figure 6-9: Mask of the timing pulse of the 64-kbit/s contradirectional interface. The diagram shows a pulse shape with voltage (V) on the y-axis (0 to 1.0) and time on the x-axis. The nominal pulse is shown as a solid line, and the mask is indicated by hatched areas. Key timing parameters are: 6.2 μs (7.8 - 1.6), 7.0 μs (7.8 - 0.8), 7.8 μs, 8.6 μs (7.8 + 0.8), 9.4 μs (7.8 + 1.6), and 15.6 μs (7.8 + 7.8). Voltage levels are marked at 0.1, 0.2, 0.5, and 1.0 V. + +**Figure 6-9 – Mask of the timing pulse of the 64-kbit/s contradirectional interface** + +##### 6.2.3.3 Specifications at the input ports + +The digital signals presented at the input ports should be as defined above but modified by the characteristics of the interconnecting pairs. The attenuation of these pairs at a frequency of 32 kHz should be in the range 0 to 3 dB. This attenuation should take into account any losses incurred by the presence of a digital distribution frame between the equipment. + +The return loss at the input ports should have the minimum values given in Table 6-5: + +**Table 6-5 – Digital 64 kbit/s contradirectional interface input port minimum return loss** + +| Frequency range (kHz) | | Return loss (dB) | +|-----------------------|-------------------------|------------------| +| Data signal | Composite timing signal | | +| 1.6 to 3.2 | 3.2 to 6.4 | 12 | +| 3.2 to 64 | 6.4 to 128 | 18 | +| 64 to 96 | 128 to 192 | 14 | + +To provide nominal immunity against interference, input ports are required to meet the following requirement: + +A nominal aggregate signal, encoded as a 64 kbit/s contradirectional signal and having a pulse shape as defined in the pulse mask, shall have added to it an interfering signal with the same pulse shape as the wanted signal. The interfering signal should have a bit rate within the limits specified in this Recommendation, but should not be synchronous with the wanted signal. The interfering signal shall be combined with the wanted signal in a combining network, with an overall zero loss in the signal path and with the nominal impedance 120 ohms to give a signal-to-interference ratio of 20 dB. The binary content of the interfering signal should comply with [ITU-T O.152] ( $2^{11} - 1$ bit period). No errors shall result when the combined signal, attenuated by up to the maximum specified interconnecting cable loss, is applied to the input port. + +NOTE – The return loss specification applies for both the data signal and the composite timing signal input ports. + +##### 6.2.3.4 Grounding of screen + +If the symmetrical pairs are screened, the screens shall be connected to the bonding network both at the input port and the output port. + +NOTE 1 – The cable routing is important if leaving the system block. Consult [ITU-T K.27] for guidance. + +NOTE 2 – The use of isolation to the bonding network is for further study. + +# 7 Interface at 1544 kbit/s (E11) + +## 7.1 General characteristics + +The digital interface signal has a nominal bit rate of 1544 kbit/s. + +The 1544 kbit/s interface specification is defined in Table 7-1. All signals appearing at the 1544 kbit/s interface shall satisfy each requirement listed. + +**Table 7-1 –Digital interface at 1544 kbit/s** + +| Parameter | Specification | +|---------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Nominal bit rate | 1544 kbit/s | +| Line rate accuracy | In a self-timed, free running mode, the bit rate accuracy shall be $\pm 50$ bits/s ( $\pm 32$ ppm) or better. | +| Line code | Either 1) AMI with no more than 15 consecutive zeros, and at least N ones in each and every time window of $8(N + 1)$ digit time slots (where N can range from 1 to 23), or 2) B8ZS (Note 1). | +| Frame structure | No frame structure is required for 1544 kbit/s transmission or higher level multiplexing to higher level DSN signals. | +| Medium | One balanced twisted pair shall be used for each direction of transmission. | +| Test load impedance | A resistive test load of 100 ohms $\pm 5\%$ shall be used at the interface for the evaluation of pulse shape and the electrical parameters specified below. | +| Pulse amplitude | The amplitude (Note 2) of an isolated pulse shall be between 2.4 V and 3.6 V. | +| Pulse shape | The shape of every pulse that approximates an isolated pulse (is preceded by four zeros and followed by one or more zeros) shall conform to the mask in Figure 7-1. See clause 7.2 for allowable procedures to be followed in checking conformance. | +| Power level | For an all-one signal, the power in a $3\text{ kHz} \pm 1\text{ kHz}$ band centered at 772 kHz shall be between 12.6 dBm and 17.9 dBm. The power in a $3\text{ kHz} \pm 1\text{ kHz}$ band centered at 1544 kHz shall be at least 29 dB below that at 772 kHz. | +| Pulse imbalance | In any window of seventeen consecutive bits, the maximum variation in pulse amplitudes shall be less than 200 mV, and the maximum variation in pulse widths (half amplitude) shall be less than 20 ns. | +| DC power | There shall be no DC power applied at the interface. | +| Verification access | Access to the signal at the interface shall be provided for verification of these signal specifications. | + +NOTE 1 – B8ZS is one method of providing bit sequence independence. Bit sequence independence in turn allows unconstrained clear channel capability. Zero Byte Time Slot Interchange (ZBTSI) is another method of providing clear channel transmission. + +NOTE 2 – While both voltage and power requirements are given to assist in qualification of signals at the interface, the values are not equivalent. Voltage specifications are given for isolated pulses, while power levels are specified for all-ones signal. + +Jitter requirements: + +- for the maximum peak-to-peak jitter at the output port, refer to clause 5.1 of [ITU-T G.824]; +- for the jitter to be tolerated at the input port, refer to clause 7.2.1 of [ITU-T G.824]. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +An isolated pulse at the 1544 kbit/s interface shall fit within the mask shown in Figure 7-1. The corner points for this mask are shown below the figure. In this figure, the y axis shows normalized pulse amplitude. The x axis is time measured in unit intervals. For 1544 kbit/s, the unit interval is 648 ns. + +![Figure 7-1: 1544 kbit/s interface isolated pulse mask. The graph shows normalized amplitude (y-axis, -1.0 to 1.5) versus time in unit intervals (x-axis, -1.0 to 1.5). Two curves are plotted: a minimum curve and a maximum curve. The minimum curve starts at 0, drops to -0.45 at t=0.23, and returns to 0 at t=1.16. The maximum curve starts at 0, rises to 1.15 at t=-0.15, and returns to 0 at t=0.93.](79cb7fa0e9c78ec5cd0b0de977824f8d_img.jpg) + +Figure 7-1: 1544 kbit/s interface isolated pulse mask. The graph shows normalized amplitude (y-axis, -1.0 to 1.5) versus time in unit intervals (x-axis, -1.0 to 1.5). Two curves are plotted: a minimum curve and a maximum curve. The minimum curve starts at 0, drops to -0.45 at t=0.23, and returns to 0 at t=1.16. The maximum curve starts at 0, rises to 1.15 at t=-0.15, and returns to 0 at t=0.93. + +| Minimum curve | | Maximum curve | | +|---------------|----------------------|---------------|----------------------| +| Time | Normalized amplitude | Time | Normalized amplitude | +| -0.77 | -0.05 | -0.77 | 0.05 | +| -0.23 | -0.05 | -0.39 | 0.05 | +| -0.23 | 0.5 | -0.27 | 0.8 | +| -0.15 | 0.95 | -0.27 | 1.15 | +| 0.0 | 0.95 | -0.12 | 1.15 | +| 0.15 | 0.9 | 0.0 | 1.05 | +| 0.23 | 0.5 | 0.27 | 1.05 | +| 0.23 | -0.45 | 0.35 | -0.07 | +| 0.46 | -0.45 | 0.93 | 0.05 | +| 0.66 | -0.2 | 1.16 | 0.05 | +| 0.93 | -0.05 | | | +| 1.16 | -0.05 | | | + +G.703(16)\_F7-1 + +Figure 7-1 – 1544 kbit/s interface isolated pulse mask and corner points + +Some 1544 kbit/s interface equipment embedded in the network may have been designed using a different pulse mask than that in this Recommendation. Appendix I describes the earlier specification to provide information to designers of receiving equipment on the possible range of 1544 kbit/s signals in the network. + +To accommodate signals generated by equipment predating this Recommendation, the (1544 kbit/s) receivers should be capable of operation with a signal having a transmission rate of deviation of $\pm 200$ bit/s ( $\pm 130$ ppm) (see Appendix I for pulse characteristics of older equipment). + +## 7.2 Pulse specification + +For alternate mark inversion (AMI) coding, a pulse mask describing an isolated pulse appearing at the interface is used. In most cases, an ideal isolated pulse can only be approximated due to line coding constraints. + +Pulse masks are shown in normalized form, with the nominal pulse amplitude shown as 1.0. In judging conformance of an isolated pulse to the mask, it is only permissible to: + +- position the mask horizontally as needed to encompass the pulse; and +- uniformly scale the amplitude of the isolated pulse to fit the mask. + +The baseline of the signal shall coincide with the zero point of the baseline of the mask. (The determination of the signal baseline is described in [IEC 60469-2]). Judging the conformance of negative-going pulses shall be performed after determining the conformance of positive-going pulses in order to maintain the signal baseline reference. + +When viewing inverted negative-going pulses for 1544 kbit/s, only the horizontal positioning of the mask to encompass the pulse is permitted. Note that pulse streams with any significant DC component will not meet the requirements of this clause. + +## 7.3 Eye diagrams + +For signals not amenable to the use of pulse masks, another means of specifying the quality of pulses at the interface is an eye diagram, which is formed by superimposing the waveforms of all possible pulse sequences, including the effects of intersymbol interference. Eye diagrams are presented in normalized form with the peak pulse amplitudes normalized to 1.0 on the vertical scale and the time scale shown in terms of the unit interval. In judging the shape of an eye diagram, it is permissible to: + +- position the mask horizontally as needed to encompass the eye diagram; and +- uniformly scale the amplitude of the mask as needed to encompass the eye diagram. + +The baseline of the mask shall coincide with the signal baseline. The determination of signal baseline is described in [IEC 60469-2]. + +# 8 Interface at 6312 kbit/s (E21) + +Interconnection of 6312 kbit/s signals for transmission purposes is accomplished at a digital distribution frame. + +Nominal bit rate: 6312 kbit/s. + +Bit rate accuracy: $\pm 30$ ppm (189.4 bit/s) or better. + +A pseudo-ternary code shall be used as indicated in Table 8-1. + +The shape for an isolated pulse measured at the distribution frame shall fall within the mask either of Figure 8-1 or of Figure 8-2 and meet the other requirements of Table 8-1. + +**Table 8-1 – Digital interface at 6312 kbit/s (Note 1)** + +| Parameter | Specification | | +|-------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------|--------------------------------------------------------| +| Bit rate | 6312 kbit/s | | +| Pair(s) in each direction of transmission | One symmetric pair | One coaxial pair | +| Code | B6ZS (Note 2) | B8ZS (Note 2) | +| Test load impedance | 110 ohms $\pm$ 5% resistive | 75 ohms $\pm$ 5% resistive | +| Nominal pulse shape (Note 1) | Rectangular, shaped by cable loss (see Figure 11) | Rectangular (see Figure 12) | +| Signal level | For an all 1s pattern transmitted, the power measured in a 3 kHz bandwidth should be as follows: | | +| | 3156 kHz: 0.2 to 7.3 dBm
6312 kHz: -20 dBm or less | 3156 kHz: 6.2 to 13.3 dBm
6312 kHz: -14 dBm or less | +| NOTE 1 – The pulse mask for 2nd order digital interface is shown in Figures 8-1 and 8-2.
NOTE 2 – See Annex A. | | | + +The voltage within a time slot containing a zero (space) shall be no greater than either the value produced in that time slot by other pulses (marks) within the mask of Figure 11, or $\pm 0.1$ of the peak pulse (mark) amplitude, whichever is greater in magnitude. + +Jitter requirements: + +- For the maximum peak-to-peak jitter at the output port, refer to clause 5.1 of [ITU-T G.824]; +- For the jitter to be tolerated at the input port, refer to clause 7.2.2 of [ITU-T G.824]. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +| | T | Value of curve | +|-------------|--------------------------|--------------------------------------------------------------------------------| +| Lower curve | $T \leq 0.41$ | 0 | +| | $-0.41 \leq T \leq 0.24$ | $0.5 \left[ 1 + \sin \frac{\pi}{2} \left( 1 + \frac{T}{0.205} \right) \right]$ | +| | $0.24 \leq T$ | $0.331e^{-1.9(T-0.3)}$ | +| Upper curve | $T \leq 0.72$ | 0 | +| | $-0.72 \leq T \leq 0.2$ | $0.5 \left[ 1 + \sin \frac{\pi}{2} \left( 1 + \frac{T}{0.36} \right) \right]$ | +| | $0.2 \leq T$ | $0.1 + 0.721e^{-2.13(T-0.2)}$ | + +![Graph of Pulse amplitude vs Time slots relative to peak location (T) for the symmetric pair interface at 6312 kbit/s. The y-axis is labeled 'Pulse amplitude' and 'Peak pulse amplitude' with values from 0 to 1.0. The x-axis is labeled 'Time slots relative to peak location (T)' with values from -1.0 to 2.5. Two curves are shown: a lower curve and an upper curve, both peaking at 1.0 at T=0. The area between the curves is shaded. The text 'G.703(16)_F8-1' is in the bottom right corner.](df0685d2d1176d617ed1e642de4e5425_img.jpg) + +Graph of Pulse amplitude vs Time slots relative to peak location (T) for the symmetric pair interface at 6312 kbit/s. The y-axis is labeled 'Pulse amplitude' and 'Peak pulse amplitude' with values from 0 to 1.0. The x-axis is labeled 'Time slots relative to peak location (T)' with values from -1.0 to 2.5. Two curves are shown: a lower curve and an upper curve, both peaking at 1.0 at T=0. The area between the curves is shaded. The text 'G.703(16)\_F8-1' is in the bottom right corner. + +Figure 8-1 – Pulse mask for the symmetric pair interface at 6312 kbit/s + +![Graph of Pulse amplitude vs Time for the coaxial pair interface at 6312 kbit/s. The y-axis is labeled 'Pulse amplitude' with values V, V/2, and 0. The x-axis is labeled 'Time' with values -T/4, 0, T/4, T/2, and 3T. The graph shows a pulse shape with a rise time of T/8 and a decay time of T/6. Shaded regions indicate the pulse mask. The text 'T Time-slot width' and 'G.703(16)_F8-2' are present.](45329c7d9aa2bd1290af5b2027f08d7e_img.jpg) + +Graph of Pulse amplitude vs Time for the coaxial pair interface at 6312 kbit/s. The y-axis is labeled 'Pulse amplitude' with values V, V/2, and 0. The x-axis is labeled 'Time' with values -T/4, 0, T/4, T/2, and 3T. The graph shows a pulse shape with a rise time of T/8 and a decay time of T/6. Shaded regions indicate the pulse mask. The text 'T Time-slot width' and 'G.703(16)\_F8-2' are present. + +Figure 8-2 – Pulse mask for the coaxial pair interface at 6312 kbit/s + +# 9 Interface at 32 064 kbit/s + +Interconnection of 32 064 kbit/s signals for transmission purposes is accomplished at a digital distribution frame. + +Nominal bit rate: 32 064 kbit/s. + +Bit rate accuracy: $\pm 10$ ppm ( $\pm 320.6$ bit/s). + +One coaxial pair shall be used for each direction of transmission. + +The test load impedance shall be $75$ ohms $\pm 5\%$ resistive and the test method shall be direct. + +A scrambled AMI code shall be used. + +The shape for an isolated pulse measured at the point where the signal arrives at the distribution frame shall fall within the mask in Figure 9-1. + +![Figure 9-1: Pulse mask for the coaxial pair interface at 32 064 kbit/s. The graph shows Pulse amplitude (Peak pulse amplitude) on the y-axis (0 to 1.0) versus Time slots relative to peak location (T) on the x-axis (-1.0 to 2.0). The mask is defined by two curves: the Lower curve and the Upper curve. The Lower curve starts at T = -0.36, peaks at T = 0, and decays towards T = 2.0. The Upper curve starts at T = -0.65, peaks at T = 0, and decays towards T = 2.0. The area between the two curves is shaded, representing the allowed pulse shape region.](d8d893dd559845f86c5dd46147ef98b6_img.jpg) + +| | T | Value of curve | +|-------------|---------------------------|-------------------------------------------------------------------------------| +| Lower curve | $-0.36 \leq T \leq -0.30$ | $5.76T + 2.07$ | +| | $-0.30 \leq T < 0$ | $0.5 \left[ 1 + \sin \frac{\pi}{2} \left( 1 + \frac{T}{0.25} \right) \right]$ | +| | $0 \leq T < 0.22$ | $0.5 \left[ 1 + \sin \frac{\pi}{2} \left( 1 + \frac{T}{0.16} \right) \right]$ | +| | $0.22 \leq T$ | $0.11e^{-3.42(T-0.3)}$ | +| Upper curve | $-0.65 \leq T < 0$ | $1.05 \left[ 1 - e^{-4.6(T+0.65)} \right]$ | +| | $0 \leq T < 0.25$ | $0.5 \left[ 1 + \sin \frac{\pi}{2} \left( 1 + \frac{T}{0.28} \right) \right]$ | +| | $0.25 \leq T$ | $0.11 + 0.407e^{-2.1(T-0.29)}$ | + +Figure 9-1: Pulse mask for the coaxial pair interface at 32 064 kbit/s. The graph shows Pulse amplitude (Peak pulse amplitude) on the y-axis (0 to 1.0) versus Time slots relative to peak location (T) on the x-axis (-1.0 to 2.0). The mask is defined by two curves: the Lower curve and the Upper curve. The Lower curve starts at T = -0.36, peaks at T = 0, and decays towards T = 2.0. The Upper curve starts at T = -0.65, peaks at T = 0, and decays towards T = 2.0. The area between the two curves is shaded, representing the allowed pulse shape region. + +Figure 9-1 – Pulse mask for the coaxial pair interface at 32 064 kbit/s + +The voltage within a time slot containing a zero (space) shall be no greater than either the value produced in that time slot by other pulses (marks) within the mask of Figure 9-1 or $\pm 0.1$ of the peak pulse (mark) amplitude, whichever is greater in magnitude. + +For an all 1s pattern transmitted, the power measured in a 3 kHz bandwidth at the point where the signal arrives at the distribution frame shall be as follows: + +- 16 032 kHz: $+5$ dBm to $+12$ dBm; +- 32 064 kHz: at least $20$ dB below the power at 16 032 kHz. + +The connectors and coaxial cable pairs in the distribution frame shall be $75$ ohms $\pm 5\%$ . + +Jitter requirements: + +- For the maximum peak-to-peak jitter at the output port, refer to clause 5.1 of [ITU-T G.824]; +- For the jitter to be tolerated at the input port, refer to clause 7.2.3 of [ITU-T G.824]. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +# 10 Interface at 44 736 kbit/s (E32) + +44 736 kbit/s interface specification is defined in Table 10-1. + +**Table 10-1 – Digital interface at 44 736 kbit/s** + +| Parameter | Specification | +|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Nominal bit rate | 44 736 kbit/s | +| Bit rate accuracy | In a self-timed, free-running mode, the bit rate accuracy shall be $\pm 895$ bits/s ( $\pm 20$ ppm) or better. | +| Line code | B3ZS (bipolar with three-zero substitutions) | +| Frame structure | The signal shall have the frame structure defined in [ITU-T G.752] to ensure transmission through all types of 44 736 kbit/s transport equipment. The frame structure is not required for multiplexing to higher level DSN signals. | +| Medium | One unbalanced coaxial line shall be used for each direction of transmission. | +| Test load impedance | A resistive test load of 75 ohms $\pm 5\%$ shall be used at the interface for the evaluation of pulse shape and the electrical parameters specified below. | +| Pulse amplitude | The amplitude (Note 1) of an isolated pulse shall be between 0.36 V and 0.85 V peak. | +| Pulse shape | The shape of every pulse that approximates an isolated pulse (is preceded by two zeros and followed by one or more zeros) shall conform to the mask in Figure 10-1. See clause 7.2 for allowable procedures to be followed in checking conformance. This mask includes an allowance of $\pm 3\%$ of the peak pulse amplitude at any point on the mask relative to the pulse mask in the earlier version. Equations defining the various line segments making up the mask are listed below the figure. | +| Power level | A wideband power measurement of an AIS signal (as defined in [ITU-T G.704]) using a power level sensor with a working frequency range of 200 MHz shall be between $-4.7$ dBm and $+3.6$ dBm, including the effects of a range of connecting cable lengths between 68.6 meters (225 feet) and 137.2 meters (450 feet). A low-pass filter having a flat passband and cutoff frequency of 200 MHz shall be used. The rolloff characteristics of this filter are not important;
or
an alternate power level specification of the power of an all-ones signal (Note 2) is useful for some equipment qualifications. It requires that the power in a 3 kHz $\pm 1$ kHz band centered at 22 368 kHz be between $-1.8$ dBm and $+5.7$ dBm. It further requires that the power in a 3 kHz $\pm 1$ kHz band centered at 44 736 kHz be at least 20 dB below that at 22 368 kHz. | +| Pulse imbalance | 1) The ratio of amplitudes of positive and negative isolated pulses shall be between 0.90 and 1.10.
2) Positive and negative isolated pulses shall both conform to the mask of Figure 10-1. | +| DC power | There shall be no DC power applied at the interface. | +| Verification access | Access to the signal at the interface shall be provided for verification of these signal specifications. | +| NOTE 1 – While both voltage and power requirements are given to assist in qualification of signals at the interface, the values are not equivalent. Voltage specifications are given for isolated pulses, while power levels are specified for an AIS signal, or alternatively an all-ones signal.
NOTE 2 – The all-ones signal is not realizable within the frame structure specified in [ITU-T G.752], and is not encountered in North American telecommunication networks. | | + +All signals appearing at the 44 736 kbit/s interface shall satisfy each requirement listed. + +An isolated pulse (see pulse shape in Table 10-1) at the 44 736 kbit/s interface shall fit within the mask shown in Figure 14. Equations defining the various line segments making up the mask are listed below the figure. In this figure, the y axis shows normalized pulse amplitude. The x axis is time measured in unit intervals. For 44 736 kbit/s, the unit interval is 22.4 ns. + +To assure proper operation of transmission facilities and higher order multiplex equipment, all 44 736 kbit/s sources shall use the frame structured defined in [ITU-T G.752]. + +Jitter requirements: + +- for the maximum peak-to-peak jitter at the output port, refer to clause 5.1 of [ITU-T G.824]; +- for the jitter to be tolerated at the input port, refer to clause 7.2.4 of [ITU-T G.824]. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +![Figure 10-1: 44 736 kbit/s interface isolated pulse mask and equations. The graph shows normalized amplitude (y-axis, -1.0 to 1.5) versus time in unit intervals (x-axis, -1.0 to 1.5). Two curves are plotted: an upper curve and a lower curve. The upper curve starts at 0.03 for T < -0.85, rises to a peak of 1.0 at T = 0, and then decays towards 0.08 for T > 0.36. The lower curve starts at -0.03 for T < -0.85, drops to a minimum of -1.0 at T = 0, and then rises towards -0.03 for T > 0.36.](2bb33687a0af0373c35b56f023a2a1d4_img.jpg) + +Figure 10-1: 44 736 kbit/s interface isolated pulse mask and equations. The graph shows normalized amplitude (y-axis, -1.0 to 1.5) versus time in unit intervals (x-axis, -1.0 to 1.5). Two curves are plotted: an upper curve and a lower curve. The upper curve starts at 0.03 for T < -0.85, rises to a peak of 1.0 at T = 0, and then decays towards 0.08 for T > 0.36. The lower curve starts at -0.03 for T < -0.85, drops to a minimum of -1.0 at T = 0, and then rises towards -0.03 for T > 0.36. + +| Time axis range
(Unit Intervals) | Normalized amplitude equation | +|-------------------------------------|-------------------------------------------------------------------------------------------------------| +| Upper curve | | +| $-0.85 \leq T \leq -0.68$ | 0.03 | +| $-0.68 \leq T \leq 0.36$ | $0.5 \left\{ 1 + \sin \left[ \frac{\pi}{2} \left( 1 + \frac{T}{0.34} \right) \right] \right\} + 0.03$ | +| $0.36 \leq T \leq 1.4$ | $0.08 + 0.407 e^{-1.84(T-0.36)}$ | +| Lower curve | | +| $-0.85 \leq T \leq -0.36$ | -0.03 | +| $-0.36 \leq T \leq 0.36$ | $0.5 \left\{ 1 + \sin \left[ \frac{\pi}{2} \left( 1 + \frac{T}{0.18} \right) \right] \right\} - 0.03$ | +| $0.36 \leq T \leq 1.4$ | -0.03 | + +G.703(16)\_F + +Figure 10-1 – 44 736 kbit/s interface isolated pulse mask and equations + +# 11 Interface at 2048 kbit/s (E12) + +## 11.1 General characteristics + +Nominal bit rate: 2048 kbit/s. + +Bit rate accuracy: $\pm 50$ ppm ( $\pm 102.4$ bit/s). + +Code: High density bipolar of order 3 (HDB3) (a description of this code can be found in Annex A). + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +## 11.2 Specifications at the output ports + +See Table 11-1. See also Note 6 of clause 1. + +**Table 11-1 – Digital interface at 2048 kbit/s** + +| Parameter | Specification | | +|---------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------| +| Pulse shape (nominally rectangular) | All marks of a valid signal must conform with the mask (see Figure 11-1) irrespective of the sign. The value V corresponds to the nominal peak value. | | +| Pair(s) in each direction | One coaxial pair (see clause 11.4) | One symmetrical pair (see clause 11.4) | +| Test load impedance | 75 ohms resistive | 120 ohms resistive | +| Nominal peak voltage of a mark (pulse) | 2.37 V | 3 V | +| Peak voltage of a space (no pulse) | $0 \pm 0.237$ V | $0 \pm 0.3$ V | +| Nominal pulse width | 244 ns | | +| Ratio of the amplitudes of positive and negative pulses at the centre of the pulse interval | 0.95 to 1.05 | | +| Ratio of the widths of positive and negative pulses at the nominal half amplitude | 0.95 to 1.05 | | +| Maximum peak-to-peak jitter at an output port | Refer to clause 5.1 of [ITU-T G.823] | | + +The return loss at the output port should have the minimum values given in Table 11-2: + +**Table 11-2 – Digital interface at 2048 kbit/s output port minimum return loss** + +| Frequency range (kHz) | Return loss (dB) | +|-----------------------|------------------| +| 51 to 102 | 6 | +| 102 to 3072 | 8 | + +![Figure 11-1: Mask of the pulse at the 2048 kbit/s interface. The diagram shows a pulse waveform with various timing and voltage parameters. The vertical axis represents voltage (V) with markers at 0%, 50%, and 100% (V = 100%). The horizontal axis represents time in nanoseconds (ns). Key time intervals include: 269 ns (244 + 25) for the top pulse width, 194 ns (244 - 50) for the nominal pulse width, 244 ns for the main pulse width, 219 ns (244 - 25) for the bottom pulse width, and 488 ns (244 + 244) for the total period. Voltage levels are marked at 10% and 20% above and below the 50% level. A 'Nominal pulse' is indicated by a dotted rectangle.](4cec89a753c447a050c0171c274f2acb_img.jpg) + +Figure 11-1: Mask of the pulse at the 2048 kbit/s interface. The diagram shows a pulse waveform with various timing and voltage parameters. The vertical axis represents voltage (V) with markers at 0%, 50%, and 100% (V = 100%). The horizontal axis represents time in nanoseconds (ns). Key time intervals include: 269 ns (244 + 25) for the top pulse width, 194 ns (244 - 50) for the nominal pulse width, 244 ns for the main pulse width, 219 ns (244 - 25) for the bottom pulse width, and 488 ns (244 + 244) for the total period. Voltage levels are marked at 10% and 20% above and below the 50% level. A 'Nominal pulse' is indicated by a dotted rectangle. + +NOTE – V corresponds to the nominal peak value. + +G.703(16)\_F11-1 + +**Figure 11-1 – Mask of the pulse at the 2048 kbit/s interface** + +## 11.3 Specifications at the input ports + +The digital signal presented at the input port shall be as defined above but modified by the characteristic of the interconnecting pair. The attenuation of this pair shall be assumed to follow a $\sqrt{f}$ law and the loss at a frequency of 1024 kHz shall be in the range 0 to 6 dB. This attenuation should take into account any losses incurred by the presence of a digital distribution frame between the equipment. + +For the jitter to be tolerated at the input port, refer to clause 7.1.2 of [ITU-T G.823]. + +The return loss at the input port should have the provisional minimum values given in Table 11-3: + +**Table 11-3 – Digital interface at 2048 kbit/s input port minimum return loss** + +| Frequency range (kHz) | Return loss (dB) | +|-----------------------|------------------| +| 51 to 102 | 12 | +| 102 to 2048 | 18 | +| 2048 to 3072 | 14 | + +To ensure adequate immunity against signal reflections that can arise at the interface due to impedance irregularities at digital distribution frames and at digital output ports, input ports should meet the following requirement: + +A nominal aggregate signal, encoded into HDB3 and having a pulse shape as defined in the pulse mask, shall have added to it an interfering signal with the same pulse shape as the wanted signal. The interfering signal should have a bit rate within the limits specified in this Recommendation, but should not be synchronous with the wanted signal. The interfering signal shall be combined with the wanted signal in a combining network, with an overall zero loss in the signal path and with the nominal impedance 75 ohms (in the case of coaxial-pair interface) or 120 Ohms (in the case of symmetrical-pair interface), to give a signal-to-interference ratio of 18 dB. The binary content of the interfering signal should comply with [ITU-T O.151] ( $2^{15} - 1$ bit period). No errors shall result when the combined signal, attenuated by up to the maximum specified interconnecting cable loss, is applied to the input port. + +NOTE – A receiver implementation providing an adaptive rather than a fixed threshold is considered to be more robust against reflections and should therefore be preferred. + +## 11.4 Grounding of outer conductor or screen + +The outer conductor of the coaxial pair or the screen of the symmetrical pair shall be connected to the bonding network both at the input port and the output port. + +NOTE 1 – The cable routing is important if leaving the system block. Consult [ITU-T K.27] for guidance. + +NOTE 2 – The direct connection of the outer conductors of coaxial cables to the bonding network at the transmit and receive interfaces may, because of differences in earth potential at each end of the cable, result in unwanted current flowing in the outer conductor, through connectors and through the receiver input circuitry. This may result in errors or even permanent damage. To prevent this problem, DC isolation may be introduced between the outer conductor and bonding network at the receive interface. The method of DC isolation must not compromise the EMC compliance of the equipment and the overall installation. + +NOTE 3 – The use of isolation to the bonding network is for further study. + +# 12 Interface at 8448 kbit/s (E22) + +## 12.1 General characteristics + +Nominal bit rate: 8448 kbit/s. + +Bit rate accuracy: $\pm 30$ ppm ( $\pm 253.4$ bit/s). + +Code: High density bipolar of order 3 HDB3 (a description of this code can be found in Annex A). + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +## 12.2 Specification at the output ports + +See Table 12-1. See also Note 6 of clause 1. + +**Table 12-1 – Digital interface at 8448 kbit/s** + +| Parameter | Specification | +|----------------------------------------|------------------------------------------------------------------------------------------------| +| Pulse shape (nominally rectangular) | All marks of a valid signal must conform with the mask (Figure 12-1) irrespective of the sign. | +| Pair(s) in each direction | One coaxial pair (see clause 12.4) | +| Test load impedance | 75 ohms resistive | +| Nominal peak voltage of a mark (pulse) | 2.37 V | +| Peak voltage of a space (no pulse) | $0\text{ V} \pm 0.237\text{ V}$ | + +**Table 12-1 – Digital interface at 8448 kbit/s** + +| Parameter | Specification | +|---------------------------------------------------------------------------------------------|--------------------------------------| +| Nominal pulse width | 59 ns | +| Ratio of the amplitudes of positive and negative pulses at the centre of the pulse interval | 0.95 to 1.05 | +| Ratio of widths of positive and negative pulses at the nominal half amplitude | 0.95 to 1.05 | +| Maximum peak-to-peak jitter at an output port | Refer to clause 5.1 of [ITU-T G.823] | + +![Figure 12-1 – Pulse mask at the 8448 kbit/s interface. The diagram shows a pulse waveform with various timing and voltage parameters. The vertical axis represents voltage (V) with levels 0, 1.185, and 2.370. The horizontal axis represents time in nanoseconds (ns). Key timing parameters include: 69 ns (59 + 10) for the total pulse width at the top; 35 ns (59 - 24) for the width at the 0.474V level; 59 ns for the nominal pulse width; 49 ns (59 - 10) for the width at the 0.237V level; 100 ns (59 + 41) for the width at the 0V level; and 118 ns (59 + 59) for the total width at the bottom. Voltage levels 0.237V and 0.474V are indicated on both the rising and falling edges. The diagram is labeled G.703(16)_F12-1.](ec36a1ba48e13289c395fab4a7730bdb_img.jpg) + +Figure 12-1 – Pulse mask at the 8448 kbit/s interface. The diagram shows a pulse waveform with various timing and voltage parameters. The vertical axis represents voltage (V) with levels 0, 1.185, and 2.370. The horizontal axis represents time in nanoseconds (ns). Key timing parameters include: 69 ns (59 + 10) for the total pulse width at the top; 35 ns (59 - 24) for the width at the 0.474V level; 59 ns for the nominal pulse width; 49 ns (59 - 10) for the width at the 0.237V level; 100 ns (59 + 41) for the width at the 0V level; and 118 ns (59 + 59) for the total width at the bottom. Voltage levels 0.237V and 0.474V are indicated on both the rising and falling edges. The diagram is labeled G.703(16)\_F12-1. + +**Figure 12-1 – Pulse mask at the 8448 kbit/s interface** + +The return loss at the output port should have the minimum values given in Table 12-2: + +**Table 12-2 – Digital interface at 8448 kbit/s output port minimum return loss** + +| Frequency range (kHz) | Return loss (dB) | +|-----------------------|------------------| +| 211 to 422 | 6 | +| 422 to 12 672 | 8 | + +## 12.3 Specifications at the input ports + +The digital signal presented at the input port shall be as defined above but modified by the characteristics of the interconnecting pairs. The attenuation of this pair shall be assumed to follow a $\sqrt{f}$ law and the loss at a frequency of 4224 kHz shall be in the range 0 to 6 dB. This attenuation should take into account any losses incurred by the presence of a digital distribution frame between the equipment. + +For the jitter to be tolerated at the input port, refer to clause 7.1.3 of [ITU-T G.823]. + +The return loss at the input port should have the provisional minimum values given in Table 12-3: + +**Table 12-3 – Digital interface at 8448 kbit/s input port minimum return loss** + +| Frequency range
(kHz) | Return loss
(dB) | +|--------------------------|---------------------| +| 211 to 422 | 12 | +| 422 to 8448 | 18 | +| 8448 to 12 672 | 14 | + +To ensure adequate immunity against signal reflections that can arise at the interface due to impedance irregularities at digital distribution frames and at digital output ports, input ports should meet the following requirement: + +A nominal aggregate signal, encoded into HDB3 and having a pulse shape as defined in the pulse mask shall have added to it an interfering signal with the same pulse shape as the wanted signal. The interfering signal should have a bit rate within the limits specified in this Recommendation, but should not be synchronous with the wanted signal. The interfering signal shall be combined with the wanted signal in a combining network, with an overall zero loss in the signal path and with the nominal impedance 75 ohms to give a signal-to-interference ratio of 20 dB. The binary content of the interfering signal should comply with [ITU-T O.151] ( $2^{15} - 1$ bit period). No errors shall result when the combined signal, attenuated by up to the maximum specified interconnecting cable loss, is applied to the input port. + +## 12.4 Grounding of outer conductor + +The outer conductor of the coaxial pair shall be connected to the bonding network at the input port and the output port. + +NOTE 1 – The cable routing is important if leaving the system block. Consult [ITU-T K.27] for guidance. + +NOTE 2 – The use of isolation to the bonding network is for further study. + +# 13 Interface at 34 368 kbit/s (E31) + +## 13.1 General characteristics + +Nominal bit rate: 34 368 kbit/s. + +Bit rate accuracy: $\pm 20$ ppm ( $\pm 688$ bit/s). + +Code: HDB3 (a description of this code can be found in Annex A). + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +## 13.2 Specification at the output ports + +See Table 13-1. See also Note 6 of clause 1. + +**Table 13-1 – Digital interface at 34 368 kbit/s** + +| Parameter | Specification | +|-------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------| +| Pulse shape (nominally rectangular) | All marks of a valid signal must conform with the mask (see Figure 13-1), irrespective of the sign. | +| Pair(s) in each direction | One coaxial pair (see clause 13.4) | +| Test load impedance | 75 ohms resistive | +| Nominal peak voltage of a mark (pulse) | 1.0 V | +| Peak voltage of a space (no pulse) | 0 V $\pm$ 0.1 V | +| Nominal pulse width | 14.55 ns | +| Ratio of the amplitudes of positive and negative pulses at the center of a pulse interval | 0.95 to 1.05 | +| Ratio of the widths of positive and negative pulses at the nominal half amplitude | 0.95 to 1.05 | +| Maximum peak-to-peak jitter at an output port | Refer to clause 5.1 of [ITU-T G.823] | + +![Figure 13-1: Pulse mask at the 34 368 kbit/s interface. The diagram shows a voltage (V) vs. time plot with a nominal pulse width of 14.55 ns. The mask defines the allowed region for the signal. Key dimensions include: 17 ns (14.55 + 2.45) for the total pulse duration, 8.65 ns (14.55 - 5.90) for the top width, 12.1 ns (14.55 - 2.45) for the width at 0.5V, 24.5 ns (14.55 + 9.95) for the base width, and 29.1 ns (14.55 + 14.55) for the full base width. Voltage levels are marked at 0, 0.5, and 1.0 V, with tolerances of 0.1 V and 0.2 V indicated.](5dc5581cd2aad0e683c73b959f637b31_img.jpg) + +The figure illustrates the pulse mask for a digital signal at 34 368 kbit/s. The vertical axis represents voltage (V) with markers at 0, 0.5, and 1.0. The horizontal axis represents time. The nominal pulse width is 14.55 ns. The mask is defined by several time intervals and voltage levels: + +- 17 ns (14.55 + 2.45):** Total duration of the pulse at the 1.0 V level. +- 8.65 ns (14.55 - 5.90):** Width of the pulse at the 1.0 V level. +- 12.1 ns (14.55 - 2.45):** Width of the pulse at the 0.5 V level. +- 24.5 ns (14.55 + 9.95):** Width of the pulse at the 0 V level. +- 29.1 ns (14.55 + 14.55):** Full width of the pulse at the 0 V level. +- Nominal pulse:** The ideal rectangular pulse shape. +- Voltage tolerances:** 0.1 V and 0.2 V are indicated for the 1.0 V and 0 V levels. + +G.703(16)\_F13-1 + +Figure 13-1: Pulse mask at the 34 368 kbit/s interface. The diagram shows a voltage (V) vs. time plot with a nominal pulse width of 14.55 ns. The mask defines the allowed region for the signal. Key dimensions include: 17 ns (14.55 + 2.45) for the total pulse duration, 8.65 ns (14.55 - 5.90) for the top width, 12.1 ns (14.55 - 2.45) for the width at 0.5V, 24.5 ns (14.55 + 9.95) for the base width, and 29.1 ns (14.55 + 14.55) for the full base width. Voltage levels are marked at 0, 0.5, and 1.0 V, with tolerances of 0.1 V and 0.2 V indicated. + +**Figure 13-1 – Pulse mask at the 34 368 kbit/s interface** + +The return loss at the output port should have the minimum values shown in Table 13-2: + +**Table 13-2 – Digital interface at 34 368 kbit/s output port minimum return loss** + +| Frequency range
(kHz) | Return loss
(dB) | +|--------------------------|---------------------| +| 860 to 1720 | 6 | +| 1720 to 51 550 | 8 | + +## 13.3 Specifications at the input ports + +The digital signal presented at the input port shall be as defined above but modified by the characteristics of the interconnecting pair. The attenuation of this cable shall be assumed to follow approximately a $\sqrt{f}$ law (i.e., the attenuation increases as the square root of frequency; see [b-Bell Tx] and [b-Wiggington] for details) and the loss at a frequency of 17 184 kHz shall be in the range 0 to 12 dB. + +For the jitter to be tolerated at the input port, refer to clause 7.1.4 of [ITU-T G.823]. + +The return loss at the input port should have the provisional minimum values given in Table 13-3: + +**Table 13-3 – Digital interface at 34 368 kbit/s input port minimum return loss** + +| Frequency range
(kHz) | Return loss
(dB) | +|--------------------------|---------------------| +| 860 to 1720 | 12 | +| 1720 to 34 368 | 18 | +| 34 368 to 51 550 | 14 | + +To ensure adequate immunity against signal reflections that can arise at the interface due to impedance irregularities at digital distribution frames and at digital output ports, input ports are required to meet the following requirement: + +A nominal aggregate signal, encoded into HDB3 and having a pulse shape as defined in the pulse mask shall have added to it an interfering signal with the same pulse shape as the wanted signal. The interfering signal should have a bit rate within limits specified in this Recommendation, but should not be synchronous with the wanted signal. The interfering signal shall be combined with the wanted signal in a combining network, with an overall zero loss in the signal path and with the nominal impedance 75 ohms to give a signal-to-interference ratio of 20 dB. The binary content of the interfering signal should comply with [ITU-T O.151] ( $2^{23} - 1$ bit period). No errors shall result when the combined signal, attenuated by up to the maximum specified interconnecting cable loss, is applied to the input port. + +## 13.4 Grounding of outer conductor + +The outer conductor of the coaxial pair shall be connected to the bonding network both at the input port and the output port. + +NOTE 1 – The cable routing is important if leaving the system block. Consult [ITU-T K.27] for guidance. + +NOTE 2 – The use of isolation to the bonding network is for further study. + +# 14 Interface at 139 264 kbit/s (E4) + +## 14.1 General characteristics + +Nominal bit rate: 139 264 kbit/s. + +Bit rate accuracy: $\pm 15$ ppm ( $\pm 2089$ bit/s). + +Code: Coded mark inversion (CMI) (a description of this code can be found in Annex A). + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +## 14.2 Specifications at the output ports + +The specifications at the output ports are given in Table 14-1 and Figures 14-1 and 14-2. See also Note 6 of clause 1. + +NOTE – A method based on the measurement of the levels of the fundamental frequency component, the second (and possibly the third) harmonic of a signal corresponding to binary all 0s and binary all 1s, is considered to be a perfectly adequate method of checking that the requirements of Table 14-1 have been met. The relevant values of the harmonic components are under study. + +**Table 14-1 – Digital interface at 139 264 kbit/s** + +| Parameter | Specification | +|--------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Pulse shape | Nominally rectangular and conforming to the masks shown in Figures 14-1 and 14-2 | +| Pair(s) in each direction | One coaxial pair | +| Test load impedance | 75 ohms resistive | +| Peak-to-peak voltage | $1 \pm 0.1$ V | +| Rise time between 10% and 90% amplitudes of the measured steady state amplitude | $\leq 2$ ns | +| Transition timing tolerance (referred to the mean value of the 50% amplitude points of negative transitions) | Negative transitions: $\pm 0.1$ ns
Positive transitions at unit interval boundaries: $\pm 0.5$ ns
Positive transitions at mid-interval: $\pm 0.35$ ns | +| Return loss | $\geq 15$ dB over frequency range 7 MHz to 210 MHz | +| Maximum peak-to-peak jitter at an output port | Refer to clause 5.1 of [ITU-T G.823] | + +![Figure 14-1: Mask of a pulse corresponding to a binary 0 at the 139 264 kbit/s interface. The diagram shows a voltage (V) vs. time plot with a pulse shape. The vertical axis ranges from -0.60 V to 0.60 V. The horizontal axis shows a period T = 7.18 ns. The pulse has a nominal zero level (Note 2) at 0 V. The maximum steady-state amplitude is limited to 0.55 V (Note 1). The pulse shape includes negative transitions and a positive transition at the mid-unit interval. Timing parameters include 1 ns, 0.1 ns, 0.35 ns, and 1.795 ns. The diagram is labeled G.703(16)_F14-1.](152efae989544ee653283e8de26cc9b1_img.jpg) + +The figure illustrates a pulse mask for a binary 0 at the 139 264 kbit/s interface. The vertical axis represents voltage (V) from -0.60 to 0.60, with a nominal zero level (Note 2) at 0 V. The horizontal axis shows a period $T = 7.18$ ns. The pulse shape is defined by several timing and voltage constraints: + +- Timing:** The total period is $T = 7.18$ ns. The pulse width is 1.795 ns. The rise time and decay time are measured between -0.4 V and 0.4 V. The time from the start of the pulse to the start of the rise is 0.35 ns. The time from the start of the rise to the start of the pulse width is 1 ns. The time from the start of the pulse width to the start of the decay is 1 ns. The time from the start of the decay to the end of the pulse is 0.1 ns. The time from the end of the pulse to the start of the next pulse is 0.1 ns. +- Voltage:** The maximum steady-state amplitude is limited to 0.55 V (Note 1). The nominal zero level is 0 V (Note 2). The pulse shape includes negative transitions and a positive transition at the mid-unit interval. +- Notes:** + - Note 1: The maximum "steady state" amplitude should not exceed the 0.55 V limit. Overshoots and other transients are permitted to fall into the dotted area, bounded by the amplitude levels 0.55 V, provided that they do not exceed the steady state level by more than 0.05 V. The possibility of relaxing the amount by which the overshoot may exceed the steady state level is under study. + - Note 2: For all measurements using these masks, the signal should be AC coupled, using a capacitor of not less than 0.01 $\mu\text{F}$ , to the input of the oscilloscope used for measurements. + +Figure 14-1: Mask of a pulse corresponding to a binary 0 at the 139 264 kbit/s interface. The diagram shows a voltage (V) vs. time plot with a pulse shape. The vertical axis ranges from -0.60 V to 0.60 V. The horizontal axis shows a period T = 7.18 ns. The pulse has a nominal zero level (Note 2) at 0 V. The maximum steady-state amplitude is limited to 0.55 V (Note 1). The pulse shape includes negative transitions and a positive transition at the mid-unit interval. Timing parameters include 1 ns, 0.1 ns, 0.35 ns, and 1.795 ns. The diagram is labeled G.703(16)\_F14-1. + +**Figure 14-1 – Mask of a pulse corresponding to a binary 0 at the 139 264 kbit/s interface** + +NOTE 1 – The maximum "steady state" amplitude should not exceed the 0.55 V limit. Overshoots and other transients are permitted to fall into the dotted area, bounded by the amplitude levels 0.55 V, provided that they do not exceed the steady state level by more than 0.05 V. The possibility of relaxing the amount by which the overshoot may exceed the steady state level is under study. + +NOTE 2 – For all measurements using these masks, the signal should be AC coupled, using a capacitor of not less than 0.01 $\mu\text{F}$ , to the input of the oscilloscope used for measurements. + +The nominal zero level for both masks should be aligned with the oscilloscope trace with no input signal. With the signal then applied, the vertical position of the trace can be adjusted with the objective of meeting the limits of the masks. Any such adjustment should be the same for both masks and should not exceed $\pm 0.05$ V. This may be checked by removing the input signal again and verifying that the trace lies within $\pm 0.05$ V of the nominal zero level of the masks. + +NOTE 3 – Each pulse in a coded pulse sequence should meet the limits of the relevant mask, irrespective of the state of the preceding or succeeding pulses, with both pulse masks fixed in the same relation to a common timing reference, i.e., with their nominal start and finish edges coincident. + +The masks allow for HF jitter caused by intersymbol interference in the output stage, but not for jitter present in the timing signal associated with the source of the interface signal. + +When using an oscilloscope technique to determine pulse compliance with the mask, it is important that successive traces of the pulses overlay in order to suppress the effects of low frequency jitter. This can be accomplished by several techniques (e.g., a) triggering the oscilloscope on the measured waveform or b) providing both the oscilloscope and the pulse output circuits with the same clock signal). + +These techniques require further study. + +NOTE 4 – For the purpose of these masks, the rise time and decay time should be measured between -0.4 V and 0.4 V, and should not exceed 2 ns. + +![Figure 14-2: Mask of a pulse corresponding to a binary 1 at the 139 264 kbit/s interface. The diagram shows a voltage (V) vs. time plot with a pulse shape. The vertical axis ranges from -0.60 V to 0.60 V, with a nominal zero level at 0.05 V (Note 2). The pulse has a total duration T = 7.18 ns. The rise time is 1.795 ns, and the fall time is 1.795 ns. The pulse width is 3.59 ns. The pulse is labeled 'Nominal pulse'. The mask is defined by the shaded regions and the dotted lines. The mask limits are 0.55 V (Note 1) and -0.40 V (Note 1). The timing tolerance at the level of the negative and positive transitions are ±0.1 ns and ±0.5 ns respectively. The diagram also shows the 'Negative transition' and 'Positive transition' points.](f24d06b5e3b1d8ae12d4893e7619f6f5_img.jpg) + +The figure illustrates a pulse mask for a binary 1 at the 139 264 kbit/s interface. The vertical axis represents voltage (V) from -0.60 to 0.60, with a nominal zero level at 0.05 V (Note 2). The horizontal axis represents time, with a total pulse duration $T = 7.18$ ns. The pulse shape shows a rise time of 1.795 ns and a fall time of 1.795 ns. The pulse width is 3.59 ns. The mask is defined by shaded regions and dotted lines. The maximum "steady state" amplitude should not exceed 0.55 V (Note 1). The timing tolerance at the level of the negative and positive transitions are $\pm 0.1$ ns and $\pm 0.5$ ns respectively. The diagram also shows the "Negative transition" and "Positive transition" points. + +Figure 14-2: Mask of a pulse corresponding to a binary 1 at the 139 264 kbit/s interface. The diagram shows a voltage (V) vs. time plot with a pulse shape. The vertical axis ranges from -0.60 V to 0.60 V, with a nominal zero level at 0.05 V (Note 2). The pulse has a total duration T = 7.18 ns. The rise time is 1.795 ns, and the fall time is 1.795 ns. The pulse width is 3.59 ns. The pulse is labeled 'Nominal pulse'. The mask is defined by the shaded regions and the dotted lines. The mask limits are 0.55 V (Note 1) and -0.40 V (Note 1). The timing tolerance at the level of the negative and positive transitions are ±0.1 ns and ±0.5 ns respectively. The diagram also shows the 'Negative transition' and 'Positive transition' points. + +**Figure 14-2– Mask of a pulse corresponding to a binary 1 at the 139 264 kbit/s interface** + +NOTE 1 – The maximum "steady state" amplitude should not exceed the 0.55 V limit. Overshoots and other transients are permitted to fall into the dotted area, bounded by the amplitude levels 0.55 V, provided that they do not exceed the steady state level by more than 0.05 V. The possibility of relaxing the amount by which the overshoot may exceed the steady state level is under study. + +NOTE 2 – For all measurements using these masks, the signal should be AC coupled, using a capacitor of not less than 0.01 $\mu\text{F}$ , to the input of the oscilloscope used for measurements. + +The nominal zero level for both masks should be aligned with the oscilloscope trace with no input signal. With the signal then applied, the vertical position of the trace can be adjusted with the objective of meeting the limits of the masks. Any such adjustment should be the same for both masks and should not exceed $\pm 0.05$ V. This may be checked by removing the input signal again and verifying that the trace lies within $\pm 0.05$ V of the nominal zero level of the masks. + +NOTE 3 – Each pulse in a coded pulse sequence should meet the limits of the relevant mask, irrespective of the state of the preceding or succeeding pulses, with both pulse masks fixed in the same relation to a common timing reference, i.e., with their nominal start and finish edges coincident. + +The masks allow for HF jitter caused by intersymbol interference in the output stage, but not for jitter present in the timing signal associated with the source of the interface signal. + +When using an oscilloscope technique to determine pulse compliance with the mask, it is important that successive traces of the pulses overlay in order to suppress the effects of low frequency jitter. This can be accomplished by several techniques (e.g., a) triggering the oscilloscope on the measured waveform or b) providing both the oscilloscope and the pulse output circuits with the same clock signal). + +These techniques require further study. + +NOTE 4 – For the purpose of these masks, the rise time and decay time should be measured between $-0.4$ V and $0.4$ V, and should not exceed 2 ns. + +NOTE 5 – The inverse pulse will have the same characteristics, noting that the timing tolerance at the level of the negative and positive transitions are $\pm 0.1$ ns and $\pm 0.5$ ns respectively. + +## 14.3 Specifications at the input ports + +The digital signal presented at the input port should conform to Table 14-1 and Figures 14-1 and 14-2 modified by the characteristics of the interconnecting coaxial pair. + +The attenuation of the coaxial pair should be assumed to follow an approximate $\sqrt{f}$ law (i.e., the attenuation increases as the square root of frequency; see [b-Bell Tx] and [b-Wiggington] for details) and to have a maximum insertion loss of 12 dB at a frequency of 70 MHz. + +For the jitter to be tolerated at the input port, refer to clause 7.1.5 of [ITU-T G.823]. + +The return loss characteristics should be the same as that specified for the output port. + +## 14.4 Grounding of outer conductor + +The outer conductor of the coaxial pair shall be connected to the bonding network both at the input port and the output port. + +NOTE 1 – The cable routing is important if leaving the system block. Consult [ITU-T K.27] for guidance. + +NOTE 2 – The use of isolation to the bonding network is for further study. + +# 15 2048 kHz synchronization interface (T12) + +## 15.1 General characteristics + +The use of this interface is recommended for all applications where it is required to synchronize a digital equipment by an external 2048 kHz synchronization signal. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +## 15.2 Specifications at the output ports + +For general characteristics, see Table 15-1; for frequency accuracy requirements, see Table 15-2. See also Note 6 of clause 1. + +**Table 15-1 – Digital 2048 kHz clock interface** + +| Parameter | Specification | | +|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------| +| Pulse shape | The signal must conform with the mask (Figure 15-1).
The value $V$ corresponds to the maximum peak value.
The value $V_1$ corresponds to the minimum peak value. | | +| Type of pair | Coaxial pair
(see Note in clause 13.4) | Symmetrical pair
(see Note in clause 13.4) | +| Test load impedance | 75 ohms resistive | 120 ohms resistive | +| Maximum peak voltage ( $V$ ) | 1.5 V | 1.9 V | +| Minimum peak voltage ( $V_1$ ) | 0.75 V | 1.0 V | +| Maximum jitter at an output port | Refer to Table 5 in [ITU-T G.823] (Note) | | +| NOTE – This value is valid for network timing synchronization equipment. Other values may be specified for timing output ports of digital links carrying the network timing. | | | + +![Figure 15-1: Wave shape at an output port of the 2048 kHz synchronization interface. The diagram shows a periodic waveform with a period T. The waveform consists of a flat top section of duration T/30, a linear ramp down to a minimum of -V1, a flat bottom section of duration T/30, and a linear ramp up to a maximum of +V1. The total period T is divided into four segments of T/4. The voltage levels +V, +V1, 0, -V1, and -V are indicated on the right. Shaded areas indicate regions where the signal should be monotonic. The diagram is labeled G.703(16)_F15-1.](bd4a5cf22b8d8060c4bf3577beb30df8_img.jpg) + +$\frac{T}{30}$ $\frac{T}{30}$ $\frac{T}{30}$ $\frac{T}{30}$ $+V$ $+V_1$ $0$ $-V_1$ $-V$ $\frac{T}{4}$ $\frac{T}{4}$ $\frac{T}{4}$ $\frac{T}{4}$ $T$ $G.703(16)_F15-1$ + +Shaded area in which signal should be monotonic $T$ Average period of synchronizing signal + +Figure 15-1: Wave shape at an output port of the 2048 kHz synchronization interface. The diagram shows a periodic waveform with a period T. The waveform consists of a flat top section of duration T/30, a linear ramp down to a minimum of -V1, a flat bottom section of duration T/30, and a linear ramp up to a maximum of +V1. The total period T is divided into four segments of T/4. The voltage levels +V, +V1, 0, -V1, and -V are indicated on the right. Shaded areas indicate regions where the signal should be monotonic. The diagram is labeled G.703(16)\_F15-1. + +**Figure 15-1 – Wave shape at an output port of the 2048 kHz synchronization interface** + +**Table 15-2 – Digital 2048 kHz clock – Frequency accuracy at output ports** + +| Output interface | Required accuracy | +|--------------------------------------------------------------------|--------------------------------------| +| Primary reference clock – PRC | Refer to [ITU-T G.811] | +| Synchronization supply unit – SSU | Refer to [ITU-T G.812] | +| SDH equipment clock – SEC | 4.6 ppm; refer also to [ITU-T G.813] | +| Synchronization interfaces used in legacy applications (e.g., PDH) | $\pm 50$ ppm | + +## 15.3 Specifications at the input ports + +The signal presented at the input ports should be as defined above but modified by the characteristics of the interconnecting pair. + +The attenuation of this pair shall be assumed to follow a $\sqrt{f}$ law (i.e., the attenuation increases as the square root of frequency; see [b-Bell Tx] and [b-Wiggington] for details) and the loss at a frequency of 2048 kHz should be in the range 0 to 6 dB (minimum value). This attenuation should take into account any losses incurred by the presence of a digital distribution frame between the equipment. + +The input port shall be able to tolerate a digital signal with these electrical characteristics but modulated by jitter. See Table 15-3. + +The return loss at 2048 kHz should be $\geq 15$ dB. + +**Table 15-3 – Digital 2048 kHz clock – Noise tolerance at input ports** + +| Input interface | Jitter tolerance | +|--------------------------------------------------------------------|------------------------| +| Primary reference clock – PRC | Not applicable | +| Synchronization supply unit – SSU | Refer to [ITU-T G.812] | +| SDH equipment clock – SEC | Refer to [ITU-T G.813] | +| Synchronization interfaces used in legacy applications (e.g., PDH) | For further study | + +## 15.4 Grounding of outer conductor or screen + +The outer conductor of the coaxial pair or the screen of the symmetrical pair shall be connected to the bonding network both at the input port and the output port. + +NOTE 1 – The cable routing is important if leaving the system block. Consult [ITU-T K.27] for guidance. + +NOTE 2 – The use of isolation to the bonding network is for further study. + +# 16 Interface at 97 728 kbit/s + +Interconnection of 97 728 kbit/s signals for transmission purposes is accomplished at a digital distribution frame. + +Nominal bit rate: 97 728 kbit/s. + +Bit rate accuracy: $\pm 10$ ppm ( $\pm 978$ bit/s). + +One coaxial pair shall be used for each direction of transmission. + +The test load impedance shall be 75 ohms $\pm 5\%$ resistive. + +A scrambled AMI code1 shall be used. + +The shape for the 97 728 kbit/s output port shall fall within the mask in Figure 16-1. The shape at the point where the signal arrives at the distribution frame will be modified by the characteristics of the interconnecting cable. + +--- + +1 An AMI code is scrambled by a five-stage reset-type scrambler with the primitive polynomial of $x^5 + x^3 + 1$ . + +![Figure 16-1: Pulse mask at the 97 728 kbit/s output port. The diagram shows a pulse waveform with voltage levels on the y-axis (0, 0.9, 1.0, 1.7, 2.3 V) and time intervals on the x-axis. The nominal pulse is a solid line. The mask is defined by a dashed line. Time intervals are: 6.2 ns (top width), 10 ns (top width of mask), 5.12 ns (width at 1.7 V), 4.0 ns (width at 1.0 V), 9.0 ns (width at 0.9 V), and 10.0 ns (width at 0 V). The label 'Nominal pulse' points to the solid line. The code G.703(16)_F16-1 is at the bottom right.](32f80b2d70752613b6577797811f3a95_img.jpg) + +Figure 16-1: Pulse mask at the 97 728 kbit/s output port. The diagram shows a pulse waveform with voltage levels on the y-axis (0, 0.9, 1.0, 1.7, 2.3 V) and time intervals on the x-axis. The nominal pulse is a solid line. The mask is defined by a dashed line. Time intervals are: 6.2 ns (top width), 10 ns (top width of mask), 5.12 ns (width at 1.7 V), 4.0 ns (width at 1.0 V), 9.0 ns (width at 0.9 V), and 10.0 ns (width at 0 V). The label 'Nominal pulse' points to the solid line. The code G.703(16)\_F16-1 is at the bottom right. + +**Figure 16-1 – Pulse mask at the 97 728 kbit/s output port** + +The connectors and cable pairs in the distribution frame shall be 75 ohms $\pm 5\%$ . + +Jitter requirements: + +- For the maximum peak-to-peak jitter at the output port, refer to clause 5.1 of [ITU-T G.824]; +- For the jitter to be tolerated at the input port, refer to clause 7.2.5 of [ITU-T G.824]. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +# **17 Interface at 155 520 kbit/s – STM-1 interface (ES1)** + +## **17.1 General characteristics** + +Nominal bit rate: 155 520 kbit/s. + +Bit rate accuracy: $\pm 20$ ppm ( $\pm 3111$ bit/s). + +Code: Coded mark inversion (CMI) (a description of this code can be found in Annex A). + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +## **17.2 Specifications at the output ports** + +The specifications at the output ports are given in Table 17-1 and in Figures 17-1 and 17-2. See also Note 6 of clause 1. + +NOTE – A method based on the measurement of the levels of the fundamental frequency component, the second (and possibly the third) harmonic of a signal corresponding to the binary all 0s and binary all 1s, is considered to be a perfectly adequate method of checking that the requirements of Table 17-1 have been met. The relevant values of the harmonic components are under study. + +**Table 17-1 – Digital interface at 155 520 kbit/s** + +| Parameter | Specification | +|------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Pulse shape | Nominally rectangular and conforming to the masks shown in Figures 17-1 and 17-2 | +| Pair(s) in each direction | One coaxial pair | +| Test load impedance | 75 ohms resistive | +| Peak-to-peak voltage | $1 \pm 0.1$ V | +| Rise time between 10% and 90% amplitudes of the measured steady state amplitude | $\leq 2$ ns | +| Transition timing tolerance referred to the mean value of the 50% amplitude points of negative transitions | Negative transitions: $\pm 0.1$ ns
Positive transitions at unit interval boundaries: $\pm 0.5$ ns
Positive transitions at mid-unit intervals: $\pm 0.35$ ns | +| Return loss | $\geq 15$ dB over frequency range 8 MHz to 240 MHz | +| Maximum peak-to-peak jitter at an output port | Refer to clause 5.1 of [ITU-T G.825] | + +## 17.3 Specifications at the input ports + +The digital signal presented at the input port should conform to Table 17-1 and Figures 17-1 and 17-2 modified by the characteristics of the interconnecting coaxial pair. + +The attenuation of the coaxial pair should be assumed to follow an approximate $\sqrt{f}$ law (i.e., the attenuation increases as the square root of frequency; see [b-Bell Tx] and [b-Wigginton ] for details) and to have a maximum insertion loss of 12.7 dB at a frequency of 78 MHz. + +For the jitter to be tolerated at the input port, refer to clause 6.1.2.1 of [ITU-T G.825]. + +The return loss characteristics should be the same as that specified for the output port. + +## 17.4 Specifications at the cross-connect points + +- Signal power level: A wideband power measurement using a power level sensor with a working frequency range of at least 300 MHz shall be between $-2.5$ and $+4.3$ dBm. There shall be no DC power transmitted across the interface. +- Eye diagram: An eye diagram mask based on the maximum and minimum power levels given above is shown in Figure 17-3 where the voltage amplitude has been normalized to one, and the time scale is specified in terms of the pulse repetition period $T$ . The corner points of the eye diagram are shown in Figure 17-3. +- Termination: One coaxial cable shall be used for each direction of transmission. +- Impedance: A resistive test load of 75 ohms $\pm 5\%$ shall be used at the interface for the evaluation of the eye diagram and the electrical parameters of the signal. + +![Figure 17-1 – Mask of a pulse corresponding to a binary 0 (at the 155 520 kbit/s interface)](5fdd55201f3f090a54d10ffe9de2f068_img.jpg) + +The diagram shows a pulse mask with voltage on the vertical axis ranging from -0.60 V to 0.60 V. The horizontal axis represents time, with a total period T = 6.43 ns. The mask defines upper and lower limits for a pulse. Shaded regions at the top and bottom are marked '(Note 1)'. Specific time intervals are labeled: 1 ns, 0.1 ns, 0.35 ns, and 1.608 ns. The nominal zero level is at ±0.05 V. Transitions are labeled as 'Negative transitions' and 'Positive transition at mid-unit interval'. A 'Nominal pulse' is shown as a dashed line within the mask boundaries. + +Figure 17-1 – Mask of a pulse corresponding to a binary 0 (at the 155 520 kbit/s interface) + +**Figure 17-1 – Mask of a pulse corresponding to a binary 0 (at the 155 520 kbit/s interface)** + +NOTE 1 – The maximum "stead state" amplitude should not exceed the 0.55 V limit. Overshoots and other transients are permitted to fall into the dotted area, bounded by the amplitude levels 0.55 V, provided that they do not exceed the steady state level by more than 0.05 V. The possibility of relaxing the amount by which the overshoot may exceed the steady state level is under study. + +NOTE 2 – For all measurements using these masks, the signal should be AC coupled, using a capacitor of not less than 0.01 µF, to the input of the oscilloscope used for measurements. + +The nominal zero level for both masks should be aligned with the oscilloscope trace with no input signal. With the signal then applied, the vertical position of the trace can be adjusted with the objective of meeting the limits of the masks. Any such adjustment should be the same for both masks and should not exceed ±0.05 V. This may be checked by removing the input signal again and verifying that the trace lies within ±0.05 V of the nominal zero level of the masks. + +NOTE 3 – Each pulse in a coded pulse sequence should meet the limits of the relevant mask, irrespective of the state of the preceding or succeeding pulses, with both pulse masks fixed in the same relation to a common timing reference, i.e., with their nominal start and finish edges coincident. + +The masks allow for HF jitter caused by intersymbol interference in the output stage, but not for jitter present in the timing signal associated with the source of the interface signal. + +When using an oscilloscope technique to determine pulse compliance with the mask, it is important that successive traces of the pulses overlay in order to suppress the effects of low frequency jitter. This can be accomplished by several techniques (e.g., a) triggering the oscilloscope on the measured waveform or b) providing both the oscilloscope and the pulse output circuits with the same clock signal). + +These techniques require further study. + +NOTE 4 – For the purpose of these masks, the rise time and decay time should be measured between −0.4 V and 0.4 V, and should not exceed 2 ns. + +**Rec. ITU-T G.703 (04/2016)**      37 + +![Figure 17-2: Mask of a pulse corresponding to a binary 1 (at the 155 520 kbit/s interface). The diagram shows a pulse waveform with various timing and voltage parameters. The total period is T = 6.43 ns. The pulse is labeled 'Nominal pulse'. The voltage scale ranges from -0.60 V to 0.60 V. The nominal zero level is indicated at 0 V. The pulse has a negative transition and a positive transition. The rise time is 1 ns, and the decay time is 1 ns. The pulse width is 3.215 ns. The pulse is shown with a shaded area representing the mask. The mask is defined by the amplitude levels 0.55 V and -0.60 V. The timing parameters are: T = 6.43 ns, 1 ns, 0.1 ns, 0.1 ns, 3.215 ns, 1.2 ns, 1.2 ns, 1 ns, 1.608 ns, 1.608 ns, 0.5 ns, 0.5 ns, 1 ns. The diagram is labeled G.703(16)_F17-2.](fab98272229adb4efe6412d8e556fb67_img.jpg) + +Figure 17-2: Mask of a pulse corresponding to a binary 1 (at the 155 520 kbit/s interface). The diagram shows a pulse waveform with various timing and voltage parameters. The total period is T = 6.43 ns. The pulse is labeled 'Nominal pulse'. The voltage scale ranges from -0.60 V to 0.60 V. The nominal zero level is indicated at 0 V. The pulse has a negative transition and a positive transition. The rise time is 1 ns, and the decay time is 1 ns. The pulse width is 3.215 ns. The pulse is shown with a shaded area representing the mask. The mask is defined by the amplitude levels 0.55 V and -0.60 V. The timing parameters are: T = 6.43 ns, 1 ns, 0.1 ns, 0.1 ns, 3.215 ns, 1.2 ns, 1.2 ns, 1 ns, 1.608 ns, 1.608 ns, 0.5 ns, 0.5 ns, 1 ns. The diagram is labeled G.703(16)\_F17-2. + +**Figure 17-2 – Mask of a pulse corresponding to a binary 1 +(at the 155 520 kbit/s interface)** + +NOTE 1 – The maximum "steady state" amplitude should not exceed the 0.55 V limit. Overshoots and other transients are permitted to fall into the dotted area, bounded by the amplitude levels 0.55 V, provided that they do not exceed the steady state level by more than 0.05 V. The possibility of relaxing the amount by which the overshoot may exceed the steady state level is under study. + +NOTE 2 – For all measurements using these masks, the signal should be AC coupled, using a capacitor of not less than 0.01 $\mu\text{F}$ , to the input of the oscilloscope used for measurements. + +The nominal zero level for both masks should be aligned with the oscilloscope trace with no input signal. With the signal then applied, the vertical position of the trace can be adjusted with the objective of meeting the limits of the masks. Any such adjustment should be the same for both masks and should not exceed $\pm 0.05$ V. This may be checked by removing the input signal again and verifying that the trace lies within $\pm 0.05$ V of the nominal zero level of the masks. + +NOTE 3 – Each pulse in a coded pulse sequence should meet the limits of the relevant mask, irrespective of the state of the preceding or succeeding pulses, with both pulse masks fixed in the same relation to a common timing reference, i.e., with their nominal start and finish edges coincident. + +The masks allow for HF jitter caused by intersymbol interference in the output stage, but not for jitter present in the timing signal associated with the source of the interface signal. + +When using an oscilloscope technique to determine pulse compliance with the mask, it is important that successive traces of the pulses overlay in order to suppress the effects of low frequency jitter. This can be accomplished by several techniques (e.g., a) triggering the oscilloscope on the measured waveform or b) providing both the oscilloscope and the pulse output circuits with the same clock signal). + +These techniques require further study. + +NOTE 4 – For the purpose of these masks, the rise time and decay time should be measured between $-0.4$ V and $0.4$ V, and should not exceed 2 ns. + +NOTE 5 – The inverse pulse will have the same characteristics, noting that the timing tolerance at the level of the negative and positive transitions are $\pm 0.1$ ns and $\pm 0.5$ ns respectively. + +![Figure 17-3 – STM-1 interface eye diagram. The top part is a plot of amplitude versus normalized time. The y-axis ranges from -1 to +1, and the x-axis ranges from -0.5 to 0.5. The waveform starts at point 'a' (0.00 amplitude), rises to point 'b' (+0.25 amplitude), stays at +0.25 until point 'c', then falls to point 'd' (0.00 amplitude), falls further to point 'e' (-0.25 amplitude), stays at -0.25 until point 'f', and finally returns towards 0.00. The bottom part is a table with 3 columns: Point, Time, and Amplitude. The data is as follows: a: -0.25 T/2, 0.00; b: -0.05 T/2, +0.25; c: +0.05 T/2, +0.25; d: +0.20 T/2, 0.00; e: +0.05 T/2, -0.25; f: -0.05 T/2, -0.25. The figure is labeled G.703(16)_F17-3.](35135a8841884b7bb6fa58c3d9665c13_img.jpg) + +| Point | Time | Amplitude | +|-------|---------------------|-----------| +| a | $-0.25 \frac{T}{2}$ | 0.00 | +| b | $-0.05 \frac{T}{2}$ | +0.25 | +| c | $+0.05 \frac{T}{2}$ | +0.25 | +| d | $+0.20 \frac{T}{2}$ | 0.00 | +| e | $+0.05 \frac{T}{2}$ | -0.25 | +| f | $-0.05 \frac{T}{2}$ | -0.25 | + +G.703(16)\_F17-3 + +Figure 17-3 – STM-1 interface eye diagram. The top part is a plot of amplitude versus normalized time. The y-axis ranges from -1 to +1, and the x-axis ranges from -0.5 to 0.5. The waveform starts at point 'a' (0.00 amplitude), rises to point 'b' (+0.25 amplitude), stays at +0.25 until point 'c', then falls to point 'd' (0.00 amplitude), falls further to point 'e' (-0.25 amplitude), stays at -0.25 until point 'f', and finally returns towards 0.00. The bottom part is a table with 3 columns: Point, Time, and Amplitude. The data is as follows: a: -0.25 T/2, 0.00; b: -0.05 T/2, +0.25; c: +0.05 T/2, +0.25; d: +0.20 T/2, 0.00; e: +0.05 T/2, -0.25; f: -0.05 T/2, -0.25. The figure is labeled G.703(16)\_F17-3. + +**Figure 17-3 – STM-1 interface eye diagram** + +## 17.5 Grounding of outer conductor + +The outer conductor of the coaxial pair shall be connected to the bonding network both at the input port and the output port. + +NOTE 1 – The cable routing is important if leaving the system block. Consult [ITU-T K.27] for guidance. + +NOTE 2 – The use of isolation to the bonding network is for further study. + +# 18 Interface at 51 840 kbit/s (STM-0 interface) + +## 18.1 General characteristics + +Nominal bit rate: 51 840 kbit/s. + +Bit rate accuracy: $\pm 20$ ppm ( $\pm 1037$ bit/s). + +Code – Three line codes may be used: + +- Coded mark inversion (CMI); +- High density bipolar of order 2 (HDB2) code; +- High density bipolar of order 3 (HDB3) code. + +A description of these codes can be found in Annex A. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +## 18.2 Specifications at the output ports + +The specifications at the output ports are given in Table 18-1. See also Note 6 of clause 1. + +**Table 18-1 – Digital interface at 51 840 kbit/s** + +| Parameter | Specifications | +|------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Pair(s) in each direction | One coaxial pair | +| Test load impedance | 75 ohms resistive | +| Maximum peak-to-peak jitter at an output port | 1.5 UI pp in the bandwidth from 100 Hz to 400 kHz
0.15 UI pp in the bandwidth from 20 kHz to 400 kHz
NOTE 1 – The high-pass measurement filters have a first-order characteristic and a roll-off of –20 dB/decade. The low-pass measurement filters have a maximally flat, Butterworth characteristic and a roll-off of –60 dB/decade.
NOTE 2 –The values of jitter for CMI coded STM-0 signals are provisional and should be studied. | +| If HDB2 or HDB3 codes are used: | | +| Pulse shape | Nominally rectangular and conforming to the mask (Figure 18-1) irrespective of the sign. The value V corresponds to the nominal peak value. | +| Nominal peak voltage of a mark (pulse) | 1.0 V | +| Peak voltage of a space (no pulse) | 0 V $\pm$ 0.1 V | +| Nominal pulse width | 9.65 ns | +| Ratio of the amplitudes of positive and negative pulses at the center of a pulse interval | 0.95 to 1.05 | +| Ratio of the widths of positive and negative pulses at the nominal half amplitude | 0.95 to 1.05 | +| If CMI code is used: | | +| Pulse shape | Nominally rectangular and conforming to the masks shown in Figures 18-2 and 18-3 | +| Peak-to-peak voltage | 1 $\pm$ 0.1 V | +| Rise time between 10% and 90% amplitudes of the measured steady state amplitude | $\leq$ 6 ns | +| Transition timing tolerance referred to the mean value of the 50% amplitude points of negative transitions | Negative transitions: $\pm$ 0.3 ns
Positive transitions at unit interval boundaries: $\pm$ 1.5 ns
Positive transitions at mid-unit intervals: $\pm$ 1 ns | + +![Pulse mask diagram at the 51 840 kbit/s interface showing voltage (V) vs. time (ns) with various timing and voltage constraints.](25fab88fda841d5eec316c440656187e_img.jpg) + +The figure illustrates a pulse mask for the 51 840 kbit/s interface. The vertical axis represents voltage (V) with markers at 0, 0.5, and 1.0. The horizontal axis represents time in nanoseconds (ns). The mask defines the allowed region for the signal pulse, with a shaded area indicating the prohibited regions. + +Key timing parameters and calculations shown in the diagram: + +- Top width: 11.29 ns ( $9.65 + 1.64$ ) +- Upper plateau width: 5.69 ns ( $9.65 - 3.96$ ) +- Mid-width: 9.65 ns +- Lower plateau width: 8.01 ns ( $9.65 - 1.64$ ) +- Bottom width: 16.31 ns ( $9.65 + 6.66$ ) +- Total width: 19.3 ns ( $9.65 + 9.65$ ) + +Vertical dimensions and constraints: + +- Top voltage level: V +- Upper plateau voltage: 1.0 V +- Midline voltage: 0.5 V +- Bottom voltage level: 0 V +- Vertical offsets from 1.0 V: 0.1, 0.2 +- Vertical offsets from 0.5 V: 0.1, 0.2 +- Vertical offsets from 0 V: 0.1, 0.2 + +The diagram also includes a label "Nominal pulse" pointing to the central part of the mask and a reference code "G.703(16)\_F18-1" at the bottom right. + +Pulse mask diagram at the 51 840 kbit/s interface showing voltage (V) vs. time (ns) with various timing and voltage constraints. + +Figure 18-1 – Pulse mask at the 51 840 kbit/s interface (if HDB2 or HDB3 codes are used) + +![Figure 18-2: Mask of a pulse corresponding to a binary 0 (at the 51 840 kbit/s interface). The diagram shows a voltage (V) vs. time plot with a pulse shape. The vertical axis ranges from -0.60 V to 0.60 V, with a nominal zero level (Note 2) at 0 V. The horizontal axis shows time intervals. The pulse has a total duration T = 19.3 ns. The rise time and decay time are measured between -0.4 V and 0.4 V (Note 4). The maximum 'steady state' amplitude should not exceed 0.55 V (Note 1). The pulse is labeled 'Nominal pulse' and 'Positive transition at mid-unit interval'. The diagram also shows 'Negative transitions' and 'Positive transition at mid-unit interval'.](76959415a1298a6f58ea1fff16fb01b6_img.jpg) + +The figure illustrates a voltage waveform for a binary 0 pulse at a 51 840 kbit/s interface. The vertical axis represents voltage (V) from -0.60 to 0.60, with a nominal zero level at 0 V (Note 2). The horizontal axis represents time, with a total pulse duration T = 19.3 ns. The pulse shape shows a negative transition followed by a positive transition at the mid-unit interval. Key timing parameters include rise and decay times of 3 ns, and a 0.3 ns margin. The maximum steady-state amplitude is limited to 0.55 V (Note 1), with overshoots permitted in the dotted area up to 0.60 V. The nominal pulse width is 4.82 ns. The diagram also indicates 'Negative transitions' and 'Positive transition at mid-unit interval'. A reference code G.703(16)\_F18-2 is present in the bottom right. + +Figure 18-2: Mask of a pulse corresponding to a binary 0 (at the 51 840 kbit/s interface). The diagram shows a voltage (V) vs. time plot with a pulse shape. The vertical axis ranges from -0.60 V to 0.60 V, with a nominal zero level (Note 2) at 0 V. The horizontal axis shows time intervals. The pulse has a total duration T = 19.3 ns. The rise time and decay time are measured between -0.4 V and 0.4 V (Note 4). The maximum 'steady state' amplitude should not exceed 0.55 V (Note 1). The pulse is labeled 'Nominal pulse' and 'Positive transition at mid-unit interval'. The diagram also shows 'Negative transitions' and 'Positive transition at mid-unit interval'. + +**Figure 18-2 – Mask of a pulse corresponding to a binary 0 (at the 51 840 kbit/s interface)** + +NOTE 1 – The maximum "steady state" amplitude should not exceed the 0.55 V limit. Overshoots and other transients are permitted to fall into the dotted area, bounded by the amplitude levels 0.55 V, provided that they do not exceed the steady state level by more than 0.05 V. The possibility of relaxing the amount by which the overshoot may exceed the steady state level is under study. + +NOTE 2 – For all measurements using these masks, the signal should be AC coupled, using a capacitor of not less than 0.01 $\mu\text{F}$ , to the input of the oscilloscope used for measurements. + +The nominal zero level for both masks should be aligned with the oscilloscope trace with no input signal. With the signal then applied, the vertical position of the trace can be adjusted with the objective of meeting the limits of the masks. Any such adjustment should be the same for both masks and should not exceed $\pm 0.05$ V. This may be checked by removing the input signal again and verifying that the trace lies within $\pm 0.05$ V of the nominal zero level of the masks. + +NOTE 3 – Each pulse in a coded pulse sequence should meet the limits of the relevant mask, irrespective of the state of the preceding or succeeding pulses, with both pulse masks fixed in the same relation to a common timing reference, i.e., with their nominal start and finish edges coincident. + +The masks allow for HF jitter caused by intersymbol interference in the output stage, but not for jitter present in the timing signal associated with the source of the interface signal. + +When using an oscilloscope technique to determine pulse compliance with the mask, it is important that successive traces of the pulses overlay in order to suppress the effects of low frequency jitter. This can be accomplished by several techniques (e.g., a) triggering the oscilloscope on the measured waveform or b) providing both the oscilloscope and the pulse output circuits with the same clock signal). + +These techniques require further study. + +NOTE 4 – For the purpose of these masks, the rise time and decay time should be measured between $-0.4$ V and $0.4$ V, and should not exceed 6 ns. + +![Figure 18-3: Mask of a pulse corresponding to a binary 1 at the 51 840 kbit/s interface. The diagram shows a pulse waveform constrained within a shaded mask. Key parameters include: a total period T = 19.3 ns; nominal pulse width; rise and fall times measured between -0.4 V and 0.4 V (not exceeding 6 ns per Note 4); overshoot areas labeled 'Note 1'; nominal zero levels at ±0.05 V; and specific timing intervals such as 9.65 ns, 3.67 ns, 4.82 ns, and 3 ns at various voltage levels. The horizontal axis represents time and the vertical axis represents voltage in Volts (V).](657acccf744d33f1fc3a1652741a256e_img.jpg) + +**Figure 18-3 – Mask of a pulse corresponding to a binary 1 (at the 51 840 kbit/s interface)** + +Figure 18-3: Mask of a pulse corresponding to a binary 1 at the 51 840 kbit/s interface. The diagram shows a pulse waveform constrained within a shaded mask. Key parameters include: a total period T = 19.3 ns; nominal pulse width; rise and fall times measured between -0.4 V and 0.4 V (not exceeding 6 ns per Note 4); overshoot areas labeled 'Note 1'; nominal zero levels at ±0.05 V; and specific timing intervals such as 9.65 ns, 3.67 ns, 4.82 ns, and 3 ns at various voltage levels. The horizontal axis represents time and the vertical axis represents voltage in Volts (V). + +NOTE 1 – The maximum "stead state" amplitude should not exceed the 0.55 V limit. Overshoots and other transients are permitted to fall into the dotted area, bounded by the amplitude levels 0.55 V, provided that they do not exceed the steady state level by more than 0.05 V. The possibility of relaxing the amount by which the overshoot may exceed the steady state level is under study. + +NOTE 2 – For all measurements using these masks, the signal should be AC coupled, using a capacitor of not less than 0.01 μF, to the input of the oscilloscope used for measurements. + +The nominal zero level for both masks should be aligned with the oscilloscope trace with no input signal. With the signal then applied, the vertical position of the trace can be adjusted with the objective of meeting the limits of the masks. Any such adjustment should be the same for both masks and should not exceed ±0.05 V. This may be checked by removing the input signal again and verifying that the trace lies within ±0.05 V of the nominal zero level of the masks. + +NOTE 3 – Each pulse in a coded pulse sequence should meet the limits of the relevant mask, irrespective of the state of the preceding or succeeding pulses, with both pulse masks fixed in the same relation to a common timing reference, i.e., with their nominal start and finish edges coincident. + +The masks allow for HF jitter caused by intersymbol interference in the output stage, but not for jitter present in the timing signal associated with the source of the interface signal. + +When using an oscilloscope technique to determine pulse compliance with the mask, it is important that successive traces of the pulses overlay in order to suppress the effects of low frequency jitter. This can be accomplished by several techniques (e.g., a) triggering the oscilloscope on the measured waveform or b) providing both the oscilloscope and the pulse output circuits with the same clock signal). + +These techniques require further study. + +NOTE 4 – For the purpose of these masks, the rise time and decay time should be measured between –0.4 V and 0.4 V, and should not exceed 6 ns. + +NOTE 5 – The inverse pulse will have the same characteristics, noting that the timing tolerance at the level of the negative and positive transitions are ±0.3 ns and ±1.5 ns respectively. + +**Rec. ITU-T G.703 (04/2016)**     43 + +The return loss at the output port should have the minimum values given in Table 18-2: + +**Table 18-2 – Digital interface at 51 840 kbit/s output port minimum return loss** + +| Frequency range (kHz) | Return loss (dB) | +|-----------------------|------------------| +| 1296 to 2592 | 6 | +| 2592 to 77 760 | 8 | + +## 18.3 Specifications at the input ports + +The digital signal presented at the input port shall be as defined above but modified by the characteristics of the interconnecting pair. The attenuation of this cable shall be assumed to follow approximately a $\sqrt{f}$ law (i.e., the attenuation increases as the square root of frequency; see [b-Bell Tx] and [b-Wiggington] for details) and the loss at a frequency of 25 920 kHz shall be in the range from 0 to 12 dB. + +The return loss at the input port should have the provisional minimum values given in Table 18-3: + +**Table 18-3 – Digital interface at 51 840 kbit/s input port minimum return loss** + +| Frequency range (kHz) | Return loss (dB) | +|-----------------------|------------------| +| 1296 to 2592 | 12 | +| 2592 to 51 840 | 18 | +| 51 840 to 77 760 | 14 | + +The jitter to be tolerated at the input port expressed in peak-to-peak sinusoidal phase amplitude, shall exceed the values shown in Figure 18-4: + +![Figure 18-4: 51 840 kbit/s input jitter tolerance limit graph. The y-axis is 'Peak-to-peak jitter amplitude, UIpp' with values 0.15, 1.5, and 3.63. The x-axis is 'Jitter frequency, Hz' with values 10, 41.3, 100, 2k, 20k, and 400k. The graph shows a piecewise linear limit: 3.63 UIpp from 10 Hz to 41.3 Hz, a downward slope to 1.5 UIpp at 100 Hz, a horizontal line at 1.5 UIpp until 2k Hz, another downward slope to 0.15 UIpp at 20k Hz, and a horizontal line at 0.15 UIpp until 400k Hz.](d0e5691e25988dbacc6a4568af87574b_img.jpg) + +| Jitter frequency (Hz) | Peak-to-peak jitter amplitude, UIpp | +|-----------------------|-------------------------------------| +| 10 | 3.63 | +| 41.3 | 3.63 | +| 100 | 1.5 | +| 2k | 1.5 | +| 20k | 0.15 | +| 400k | 0.15 | + +G.703(16)\_F18-4 + +Figure 18-4: 51 840 kbit/s input jitter tolerance limit graph. The y-axis is 'Peak-to-peak jitter amplitude, UIpp' with values 0.15, 1.5, and 3.63. The x-axis is 'Jitter frequency, Hz' with values 10, 41.3, 100, 2k, 20k, and 400k. The graph shows a piecewise linear limit: 3.63 UIpp from 10 Hz to 41.3 Hz, a downward slope to 1.5 UIpp at 100 Hz, a horizontal line at 1.5 UIpp until 2k Hz, another downward slope to 0.15 UIpp at 20k Hz, and a horizontal line at 0.15 UIpp until 400k Hz. + +**Figure 18-4 – 51 840 kbit/s input jitter tolerance limit** + +NOTE – The values of jitter for CMI coded STM-0 signals are provisional and should be studied. + +## 18.4 Specifications at the cross-connect points + +### – Signal power level + +A wideband power measurement using a power level sensor with a working frequency range of at least four times the bit rate frequency shall be between $-2.7$ and $+4.7$ dBm, accounting for both transmitter variations and a range of connecting cable lengths between 68.6 m and 137 m. A filter with a characteristic equivalent to a Butterworth low pass filter with a cut-off frequency of 207.360 MHz shall be used. + +There shall be no DC power transmitted across the interface. + +#### – Eye diagram + +An eye diagram mask based on the maximum and minimum power levels and cable lengths given above is shown in Figure 18-5 where the voltage amplitude has been normalized to one, and the time scale is specified in terms of the unit interval T. Exclusionary regions are shown as shaded areas on the figure. The corner points of these regions are listed below the figure. + +![Figure 18-5 – STM-0 interface eye diagram. The plot shows normalized amplitude on the y-axis (from -1 to 1) versus time in unit intervals on the x-axis (from -0.50 to 0.50). The diagram features two shaded exclusionary regions: an outer region and an inner region. The outer region is bounded by points A, B, C, D, and E. The inner region is bounded by points F, G, H, I, J, and K. The eye opening is centered at (0, 0).](5314dd284c2a98c866862ee0f0fee301_img.jpg) + +Figure 18-5 – STM-0 interface eye diagram. The plot shows normalized amplitude on the y-axis (from -1 to 1) versus time in unit intervals on the x-axis (from -0.50 to 0.50). The diagram features two shaded exclusionary regions: an outer region and an inner region. The outer region is bounded by points A, B, C, D, and E. The inner region is bounded by points F, G, H, I, J, and K. The eye opening is centered at (0, 0). + +| Outer region corner points | | | Inner region corner points | | | +|----------------------------|-------|-----------|----------------------------|-------|-----------| +| Point | Time | Amplitude | Point | Time | Amplitude | +| A | -0.50 | 0.37 | F | 0.28 | 0.12 | +| B | -0.44 | 0.80 | G | 0.00 | 0.16 | +| C | -0.18 | 1.00 | H | -0.25 | 0.24 | +| D | 0.08 | 1.00 | I | -0.04 | 0.80 | +| E | 0.50 | 0.37 | J | 0.04 | 0.80 | +| | | | K | 0.11 | 0.22 | + +NOTE – Both inner and outer regions are symmetric about the zero amplitude axis. + +G.703(16)\_F18-5 + +Figure 18-5 – STM-0 interface eye diagram + +## 18.5 Grounding of outer conductor + +The outer conductor of the coaxial pair shall be connected to the bonding network both at the input port and the output port. + +NOTE 1 – The cable routing is important if leaving the system block. Consult [ITU-T K.27] for guidance. + +NOTE 2 – The use of isolation to the bonding network is for further study. + +# 19 Time synchronization interfaces defined in ITU-T G.8271/Y.1366 + +## 19.1 ITU-T V.11-based time/phase distribution interface + +The ITU-T V.11-based time/phase distribution interface provides an indication of the time of day and the one pulse per second (1PPS) signal as a phase indication. The expected physical connector is commonly referred to as the RJ-45 connector [IEC 60603-7]. + +The 1PPS time/phase interface uses a point-to-point [ITU-T V.11] interface as specified in [ITU-T V.11] with an additional requirement on the rise and fall times of the 1PPS signal. This is needed to provide the accuracy required for the 1PPS signal. + +This interface can be used for time synchronization distribution as well as for time measurement. + +The interface is a balanced interface that can tolerate significant common mode noise. + +The 1PPS interface consists of a balanced 100 ohm 1PPS differential signal that can be used to connect to another timing device or to measurement equipment. + +The following mapping of signals is defined for use with the RJ-45 connector: + +Two modes are supported: + +- 1) Time input mode (the unit receives a time synchronization signal from an external time sync master). +- 2) Time output mode (the unit outputs a time synchronization signal towards an interface). The receiver of this time sync signal would be a unit operating in time input mode. This could be either test equipment or a time slave clock. + +In the event that both time input and time output modes are required at the same time, two RJ-45 connectors are required. + +**Table 19-1 – RJ-45 connector operating in time input mode** + +| PIN | Signal name | Signal definition | +|-----|--------------|--------------------------------------| +| 1 | Reserved | For further study | +| 2 | Reserved | For further study | +| 3 | 1PPS_IN– | Rx 1PPS negative voltage | +| 4 | GND | [ITU-T V.11] signal ground | +| 5 | User defined | Note | +| 6 | 1PPS_IN+ | Rx 1PPS positive voltage | +| 7 | RX– | Rx TOD time message negative voltage | +| 8 | RX+ | Rx TOD time message positive voltage | + +NOTE – One possible use of Pin 5 may be ground (GND). An alternative use for this pin could be considered when connected to GNSS receivers. This is out of the scope of this Recommendation. If the signal is not used, it is recommended to pull it down with a resistor of 10 k $\Omega$ . + +**Table 19-2 – RJ-45 connector operating in time output mode** + +| PIN | Signal name | Signal definition | +|-----|-------------|--------------------------------------| +| 1 | Reserved | For further study | +| 2 | Reserved | For further study | +| 3 | 1PPS_OUT– | Tx 1PPS negative voltage | +| 4 | GND | ITU-T V.11 signal ground | +| 5 | GND (Note) | ITU-T V.11 signal ground | +| 6 | 1PPS_OUT+ | Tx 1PPS positive voltage | +| 7 | TX– | Tx TOD time message negative voltage | +| 8 | TX+ | Tx TOD time message positive voltage | + +NOTE – The time interface discussed in this Recommendation generally concerns transport equipment. For the time output mode interface of a GNSS receiver, similar considerations concerning Pin 5 to those made in the Note to Table 19-1 would be required. + +If only one mode is required, a single RJ-45 can be used and configured as time input or time output mode: + +**Table 19-3 – RJ-45 connector when only one mode is used** + +| PIN | Signal name –
Time input
configuration | Signal name –
Time output
configuration | Signal definition | +|-----|----------------------------------------------|-----------------------------------------------|--------------------------------------------| +| 1 | Reserved (Note 1) | Reserved | For further study | +| 2 | Reserved (Note 1) | Reserved | For further study | +| 3 | 1PPS_IN– | 1PPS_OUT– | Rx or Tx 1PPS negative voltage | +| 4 | GND | GND | ITU-T V.11 signal ground | +| 5 | User defined (Note 2) | GND | Note 2 | +| 6 | 1PPS_IN+ | 1PPS_OUT+ | Rx or Tx 1PPS positive voltage | +| 7 | RX– | TX– | Rx or Tx TOD time message negative voltage | +| 8 | RX+ | TX+ | Rx or Tx TOD time message positive voltage | + +NOTE 1 – The use of Pin 1 and Pin 2 is not yet defined. They may be used for the measurement of 1PPS signal delay or may be used for configuring a GNSS receiver unit. Pin 1 and Pin 2 may be differential signals. + +NOTE 2 – One possible use of Pin 5 in the input configuration may be GND. Alternative usage could be considered when connected to GPS receivers. This is out of the scope of this Recommendation. If the signal is not used, it is recommended to pull it down with a resistor of 10 k $\Omega$ . + +#### 19.1.1 1PPS rise and fall time specification + +The maximum rise and fall times of the 1PPS\_OUT signal pair at the output port are more stringent than those specified in clause 5.3 of [ITU-T V.11]. Values are for further study. The positive pulse width must be between 100 ns and 500 ms. + +#### 19.1.2 Signal timing + +The time master must generate a positive pulse on the 1PPS signal such that the midpoint of the leading edge of the differential [ITU-T V.11] signal at the edge of the chassis occurs at the change of the one-second time of the system. + +The cable delays of the 1PPS signal must be controlled and compensated if needed in the receiving side so as to meet the requirements stated in Table 19-4. This may be done either manually by the network operator or automatically by the equipment. + +**Table 19-4 – Timing budget for time distribution of the 1PPS interface** + +| Parameter | Tolerance | Reference point | +|------------------------------------------------------|-----------|--------------------------------------------------------| +| 1PPS signal generation accuracy of the timing master | ±10 ns | | +| Cable delay compensation accuracy (Note 1) | ±10 ns | From connector to connector with an [ITU-T V.11] pulse | +| 1PPS signal detection accuracy at the slave | Note 2 | | + +NOTE 1 – The applicable cable length is for further study (values between 3 m and 1 000 m have been proposed; contributions are invited). +NOTE 2 – A range between 10 and 30 ns has been mentioned, and 30 ns are agreed as worst case. +NOTE 3 – The specification of the rise and fall time is for further study. + +## 19.2 1PPS 50 Ω phase-synchronization measurement interface + +The 1PPS interface consists of an unbalanced 50 ohm 1PPS signal that can be used to connect to measurement equipment. + +NOTE – The unbalanced 50 ohm 1PPS measurement output may be used for phase distribution assuming that the distribution interface complies with the limits set in Table 19-4. If time distribution is required, an additional interface is required in order to transfer the corresponding time synchronization information. This additional interface is out of the scope of this Recommendation. + +As an example, a 1PPS interface consisting of an unbalanced 50 ohm signal has been used as the distribution interface in some legacy equipment that only required phase/frequency synchronization. + +#### 19.2.1 Performance specification + +This signal indicates the significant event occurring on the midpoint of the leading edge of the signal. + +The system must generate a positive pulse on the 1PPS signal such that the midpoint of the leading edge of the signal at the edge of the chassis occurs at the one second roll-over of the system. + +The timing specification for the 1PPS measurement interface is shown in Table 19.5. + +This interface is intended to be used with an impedance controlled 50 ohm cable with a maximum length of three metres to keep the influence of delay and rise time low. + +**Table 19-5 – Timing specification for the 1PPS measurement interface** + +| Parameter | Tolerance | Comment | +|-------------------------------------|------------------|----------------------------------------| +| 10-90% rise times of the 1PPS pulse | <5 ns | Measured at 1PPS interface | +| Pulse width | 100 ns to 500 ms | Measured at 1PPS interface | +| Maximum cable length | 3 m | Due to delay and rise time performance | + +NOTE – When the 1PPS output is configured with a simple 50/50 duty cycle, then some allowance to slightly exceed the 500 ms pulse width is permitted. The actual value for this allowance is for further study; a value of 100 ns has been proposed. (As an example, this allowance is to accommodate deviations from precisely 500 ms pulse width that may be due to rise/fall times of clock edges or a duty cycle error of the internal high speed clock that is divided down to create the 1PPS output). + +#### 19.2.2 Voltage levels + +Table 19-6 gives voltage levels for the interface for information. + +**Table 19-6 – Output voltage levels** + +| Interface | VOH (max) | VOH (min) | VOL (max) | VOL (min) | +|-----------------------------------------------|-----------|-----------|-----------|-----------| +| 1PPS (50 ohm single-ended) | 5.5 V | 1.2 V | 0.3 V | –0.3 V | +| NOTE – Measured with a 50 ohm load to ground. | | | | | + +# 20 10 MHz synchronization interface + +## 20.1 General characteristics + +The use of this interface is recommended for all applications where it is required to synchronize digital equipment by an external 10 MHz synchronization signal. + +## 20.2 Specifications at the output ports + +The 10 MHz interface consists of an unbalanced 50 ohm 10 MHz signal that can be used to connect to measurement equipment or other equipment using this synchronization signal. + +For general characteristics, see Table 20-1; for frequency accuracy requirements, see Table 20-2. See also Note 6 of clause 1. + +**Table 20-1 – 10 MHz synchronization interface** + +| | | +|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Pulse shape | The signal must conform to the mask (Figure 20-1).
The value $V$ corresponds to the maximum peak value relative to $M$ .
The value $V_1$ corresponds to the minimum peak value relative to $M$ . | +| Test load impedance | 50 ohms resistive | +| Maximum peak voltage ( $V$ ) | 2.5 V | +| Minimum peak voltage ( $V_1$ ) | 0.25 V (Note 4) | +| Offset voltage ( $M$ ) | 0 | +| Transition region factor ( $N$ ) | 30 | +| Maximum jitter at an output port | (Note 1) | +| NOTE 1 – For a primary reference 10 MHz output interface of the source clock of the synchronization network, refer to [ITU-T G.811] or [ITU-T G.8272]. Other cases are for further study.
NOTE 2 – $M$ is set to 0; non-zero values are for further study.
NOTE 3 – $N$ is set to accommodate both sinusoidal and square-wave signals. Equipment can generate any signal that fits within the mask.
NOTE 4 – For optimal signal characteristics to be delivered over a cable to the input port, a minimum peak voltage at the output port that is greater than or equal to 0.5 V is recommended. While some equipment designs can accommodate a smaller signal, a stronger signal assures a wide range of equipment, including legacy equipment, can be accommodated. | | + +**Table 20-2 – 10 MHz synchronization interface – Frequency accuracy at output ports** + +| Output interface | Required accuracy | +|-------------------------------------|-------------------------| +| Primary reference clock – PRC | Refer to [ITU-T G.811] | +| Primary reference time clock - PRTC | Refer to [ITU-T G.8272] | +| Others | For further study | + +![Figure 20-1: Wave shape at an output port of the 10 MHz synchronization interface. The diagram shows a periodic signal waveform with a period T. The waveform consists of a flat top and a linear ramp. The flat top duration is T/N. The ramp duration is T - T/N. The signal levels are labeled on the right: M+V for the top level, M+V1 for the start of the ramp, M for the midpoint, M-V1 for the end of the ramp, and M-V for the bottom level. The horizontal axis is divided into four segments of T/4. Shaded areas indicate regions where the signal should be monotonic. A legend at the bottom left shows a shaded box labeled 'Shaded area in which signal should be monotonic' and 'T Average period of synchronizing signal'. The diagram is labeled G.703(16)_F20-1.](119006c9a930f46881484f2229d3b927_img.jpg) + +Figure 20-1: Wave shape at an output port of the 10 MHz synchronization interface. The diagram shows a periodic signal waveform with a period T. The waveform consists of a flat top and a linear ramp. The flat top duration is T/N. The ramp duration is T - T/N. The signal levels are labeled on the right: M+V for the top level, M+V1 for the start of the ramp, M for the midpoint, M-V1 for the end of the ramp, and M-V for the bottom level. The horizontal axis is divided into four segments of T/4. Shaded areas indicate regions where the signal should be monotonic. A legend at the bottom left shows a shaded box labeled 'Shaded area in which signal should be monotonic' and 'T Average period of synchronizing signal'. The diagram is labeled G.703(16)\_F20-1. + +**Figure 20-1 – Wave shape at an output port of the 10 MHz synchronization interface** + +## 20.3 Specifications at the input ports + +The signal presented at the input ports should be as defined above but modified by the characteristics of the interconnecting cable. The attenuation of this cable shall be assumed to follow a $\sqrt{f}$ law (i.e., the attenuation increases as the square root of frequency; see [b-Bell Tx] and [b-Wiggington] for details); the loss at a frequency of 10 MHz should be minimized. The waveshape distortion caused by the cable should also be minimized. This can be achieved by the use of short cable runs, by the use of a low-loss, low-distortion cable, by the use of a strong signal at the originating output port, or by a combination of the above. The maximum allowed attenuation is for further study. + +The return loss at 10 MHz should be $\geq 15$ dB. + +The input port shall be able to tolerate a signal with these electrical characteristics but modulated by jitter. See Table 20-3. + +**Table 20-3 – 10 MHz synchronization interface – Noise tolerance at input ports** + +| Input interface | Jitter tolerance | +|-----------------------------------------------|-------------------| +| Enhanced primary reference time clock – ePRTC | For further study | +| Others | For further study | + +# Annex A + +## Definition of codes + +(This annex forms an integral part of this Recommendation.) + +This annex defines the modified alternate mark inversion codes (see [ITU-T G.701], item 9005) whose use is specified in this Recommendation. + +In these codes, binary 1 bits are generally represented by alternate positive and negative pulses, and binary 0 bits by spaces. Exceptions, as specified for the individual codes, are made when strings of successive 0 bits occur in the binary signal. + +In the definitions below, B represents an inserted pulse conforming to the AMI rule (ITU-T G.701, item 9004), and V represents an AMI violation (ITU-T G.701, item 9007). + +The encoding of binary signals in accordance with the rules given in this annex includes frame alignment bits, etc. + +## A.1 Definition of B3ZS (also designated HDB2) and HDB3 + +Each block of 3 (or 4) successive zeros is replaced by 00V (or 000V respectively) or B0V (B00V). The choice of 00V (000V) or B0V (B00V) is made so that the number of B pulses between consecutive V pulses is odd. In other words, successive V pulses are of alternate polarity so that no DC component is introduced. + +## A.2 Definition of B6ZS and B8ZS + +Each block of 6 (or 8) successive zeros is replaced by 0VB0VB (or 000VB0VB respectively). + +## A.3 Definition of CMI + +CMI is a 2-level non-return-to-zero code in which binary 0 is coded so that both amplitude levels, $A_1$ and $A_2$ , are attained consecutively, each for half a unit time interval ( $T/2$ ). + +Binary 1 is coded by either of the amplitude levels $A_1$ or $A_2$ , for one full unit time interval ( $T$ ), in such a way that the level alternates for successive binary 1s. + +An example is given in Figure A.1. + +NOTE 1 – For binary 0, there is always a positive transition at the midpoint of the binary unit time interval. + +NOTE 2 – For binary 1: + +- there is a positive transition at the start of the binary unit time interval if in the preceding time interval the level was $A_1$ ; +- there is a negative transition at the start of the binary unit time interval if the last binary 1 was encoded by level $A_2$ . + +![Figure A.1: Example of CMI coded binary signal. The diagram shows a waveform for the binary sequence 0, 0, 1, 0, 1, 1, 1. The first bit (0) is represented by a high-to-low transition at the start, staying high for T/2 and low for T/2. The second bit (0) is represented by a low-to-high transition at the start, staying low for T/2 and high for T/2. The third bit (1) is represented by a high level for the entire T interval. The fourth bit (0) is represented by a high-to-low transition at the start, staying high for T/2 and low for T/2. The fifth bit (1) is represented by a low level for the entire T interval. The sixth bit (1) is represented by a high level for the entire T interval. The seventh bit (1) is represented by a low level for the entire T interval. The diagram includes labels for 'Binary', 'Level A2', 'Level A1', and time intervals T/2 and T. The source code G.703(16)_FA.1 is shown in the bottom right corner.](5dce6af0634d63f5193f49c8795614da_img.jpg) + +Figure A.1: Example of CMI coded binary signal. The diagram shows a waveform for the binary sequence 0, 0, 1, 0, 1, 1, 1. The first bit (0) is represented by a high-to-low transition at the start, staying high for T/2 and low for T/2. The second bit (0) is represented by a low-to-high transition at the start, staying low for T/2 and high for T/2. The third bit (1) is represented by a high level for the entire T interval. The fourth bit (0) is represented by a high-to-low transition at the start, staying high for T/2 and low for T/2. The fifth bit (1) is represented by a low level for the entire T interval. The sixth bit (1) is represented by a high level for the entire T interval. The seventh bit (1) is represented by a low level for the entire T interval. The diagram includes labels for 'Binary', 'Level A2', 'Level A1', and time intervals T/2 and T. The source code G.703(16)\_FA.1 is shown in the bottom right corner. + +Figure A.1 – Example of CMI coded binary signal + +# Appendix I + +## 1544 kbit/s specification in the 1991 version of this Recommendation + +(This appendix does not form an integral part of this Recommendation.) + +## I.1 General + +This appendix describes an earlier 1544 kbit/s interface that included a pulse mask with substantially greater allowance for overshoot on the trailing edge of the pulse than the current Recommendation. While the current pulse mask has been socialized in a number of network compatibility publications since the late 1970s, equipment designed to the earlier specification may be widespread in the network. Hence, designers of equipment need to be aware of the nature of signals that may be delivered to that equipment. + +## I.2 Interface specification + +Most of the interface parameters in Table 7-1, including power levels and pulse amplitudes, apply to the older interface. One major difference is in the line rate tolerance. The older specification calls for a $\pm 130$ ppm tolerance, reflecting an earlier, now obsolete, technology for line driver circuitry. + +## I.3 Pulse mask + +Figure I.1 is the 1544 kbit/s pulse mask corresponding to the earlier interface specification. It is based on equipment generating pulses with considerably more overshoot on the trailing edge that is currently allowed in the Recommendation. + +![Graph of Normalized amplitude vs Time, in unit intervals. The graph shows two pulse shapes: a minimum curve (lower amplitude) and a maximum curve (higher amplitude). The minimum curve starts at 0, drops to -0.62 at t=0.23, and returns to 0 by t=1.16. The maximum curve starts at 0, rises to 1.22 at t=-0.12, and returns to 0 by t=1.16.](1dea2e515f706e8044ae79339efaa36c_img.jpg) + +Graph of Normalized amplitude vs Time, in unit intervals. The graph shows two pulse shapes: a minimum curve (lower amplitude) and a maximum curve (higher amplitude). The minimum curve starts at 0, drops to -0.62 at t=0.23, and returns to 0 by t=1.16. The maximum curve starts at 0, rises to 1.22 at t=-0.12, and returns to 0 by t=1.16. + +| Minimum curve | | Minimum curve | | +|---------------|----------------------|---------------|----------------------| +| Time | Normalized amplitude | Time | Normalized amplitude | +| -0.77 | -0.05 | -0.77 | 0.05 | +| -0.23 | -0.05 | -0.39 | 0.05 | +| -0.23 | 0.5 | -0.27 | 0.8 | +| -0.15 | 0.95 | -0.27 | 1.22 | +| -0.04 | 0.95 | -0.12 | 1.22 | +| 0.15 | 0.9 | 0.0 | 1.05 | +| 0.23 | 0.5 | 0.27 | 1.05 | +| 0.23 | -0.62 | 0.34 | 0.08 | +| 0.42 | -0.62 | 0.58 | 0.05 | +| 0.66 | -0.2 | 1.16 | 0.05 | +| 0.93 | -0.05 | | | +| 1.16 | -0.05 | | | + +G.703(16)\_FI.1 + +**Figure I.1 – Obsolete 1544 kbit/s interface isolated pulse mask and corner points** + +# Appendix II + +## 64 and 6312 kHz synchronization interface specification for use in Japan + +(This appendix does not form an integral part of this Recommendation.) + +## II.1 64 kHz synchronization interface + +The 64 kHz clock signals from the clock supply equipment have the frequencies of: + +- a) 64 kHz + 8 kHz or +- b) 64 kHz + 8 kHz + 400 Hz. + +Those signals consist of AMI code with: + +- a) an 8 kHz bipolar violation, or +- b) an 8 kHz bipolar violation removed at every 400 Hz. + +The signal structures of 64 kHz clock signals are illustrated in Figures II.1 and II.2. + +![Figure II.1: Signal structure of 64 kHz clock interface with a frequency of 64 kHz + 8 kHz. The diagram shows a series of square wave pulses. Below the pulses, there are three groups of numbers 1 through 8, each labeled '8 kHz (125 µs)'. Above the first and third groups, there are arrows pointing to specific pulse transitions labeled 'Violation'. The second group of numbers is partially obscured by a 'Violation' label. The diagram is labeled G.703(16)_FII.1 at the bottom right.](95520f6525ad4eba23a46d9cbb178902_img.jpg) + +Figure II.1: Signal structure of 64 kHz clock interface with a frequency of 64 kHz + 8 kHz. The diagram shows a series of square wave pulses. Below the pulses, there are three groups of numbers 1 through 8, each labeled '8 kHz (125 µs)'. Above the first and third groups, there are arrows pointing to specific pulse transitions labeled 'Violation'. The second group of numbers is partially obscured by a 'Violation' label. The diagram is labeled G.703(16)\_FII.1 at the bottom right. + +**Figure II.1 – Signal structure of 64 kHz clock interface with a frequency of 64 kHz + 8 kHz** + +![Figure II.2: Signal structure of 64 kHz clock interface with a frequency of 64 kHz + 8 kHz + 400 Hz. The diagram shows a series of square wave pulses. Below the pulses, there are four groups of numbers 1 through 8, each labeled '8 kHz (125 µs)'. Above the first, second, and fourth groups, there are arrows pointing to specific pulse transitions labeled 'Violation'. The third group of numbers is partially obscured by a 'Violation' label. Above the entire sequence of four groups, there is a long double-headed arrow labeled '0.4 kHz (2.5 ms)'. The diagram is labeled G.703(16)_FII.2 at the bottom right.](4ea91b26dd9e3d78632963246a40dec5_img.jpg) + +Figure II.2: Signal structure of 64 kHz clock interface with a frequency of 64 kHz + 8 kHz + 400 Hz. The diagram shows a series of square wave pulses. Below the pulses, there are four groups of numbers 1 through 8, each labeled '8 kHz (125 µs)'. Above the first, second, and fourth groups, there are arrows pointing to specific pulse transitions labeled 'Violation'. The third group of numbers is partially obscured by a 'Violation' label. Above the entire sequence of four groups, there is a long double-headed arrow labeled '0.4 kHz (2.5 ms)'. The diagram is labeled G.703(16)\_FII.2 at the bottom right. + +**Figure II.2 – Signal structure of 64 kHz clock interface with a frequency of 64 kHz + 8 kHz + 400 Hz** + +The specifications of 64 kHz clock signals at input port and output port are shown in Tables II.1 and II.2, respectively. + +**Table II.1 – Specification of 64 kHz clock signal at input port** + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------| +| Frequency | a) 64 kHz + 8 kHz or
b) 64 kHz + 8 kHz + 400 Hz | +| | a) AMI with 8 kHz bipolar violation;
b) AMI with 8 kHz bipolar violation removed at every 400 Hz | +| Alarm condition | Alarm should not be occurred against the amplitude ranged 0.63-1.1 V 0-P | + +**Table II.2 – Specification of 64 kHz clock signal at output port** + +| | | +|--------------------|----------------------------------------------------| +| Frequency | a) 64 kHz + 8 kHz or
b) 64 kHz + 8 kHz + 400 Hz | +| Load impedance | 110 ohms resistive | +| Transmission media | Symmetric pair cable | +| Pulse width (FWHM) | $\leq 7.8 \pm 0.78 \text{ } \mu\text{s}$ | +| Amplitude | $\leq 1 \text{ V}_{0\text{-P}} \pm 0.1 \text{ V}$ | + +## II.2 6312 kHz synchronization interface + +Figure II.3 shows the waveform of 6312 kHz clock signal. The specifications of 6312 kHz clock signals at input port and output port are shown in Tables II.3 and II.4, respectively. + +![Figure II.3 shows a sinusoidal waveform representing a 6312 kHz clock signal. The waveform is plotted against a horizontal axis. A horizontal double-headed arrow indicates the period between two consecutive peaks, labeled '6312 kHz'. The vertical axis has tick marks but no numerical values.](c9c3809709886a056c616a3aaece0c6d_img.jpg) + +Figure II.3 shows a sinusoidal waveform representing a 6312 kHz clock signal. The waveform is plotted against a horizontal axis. A horizontal double-headed arrow indicates the period between two consecutive peaks, labeled '6312 kHz'. The vertical axis has tick marks but no numerical values. + +G.703(16)\_FII.3 + +**Figure II.3 – Waveform of 6312 kHz clock signal** + +**Table II.3 – Specification of 6312 kHz clock signal at input port** + +| | | +|-----------------|-----------------------------------------------------------------------------| +| Frequency | 6312 kHz | +| Signal format | Sinusoidal wave | +| Alarm condition | Alarm should not be occurred against the amplitude ranged –16 dBm to +3 dBm | + +**Table II.4 – Specification of 6312 kHz clock signal at output port** + +| | | +|--------------------|--------------------| +| Frequency | 6312 kHz | +| Load impedance | 75 ohms resistive | +| Transmission media | Coaxial pair cable | +| Amplitude | 0 dBm $\pm$ 3 dB | + +# Appendix III + +## 3152 kbit/s interface specification for use in North America (From Annex A – [ITU-T G.931]) + +(This appendix does not form an integral part of this Recommendation.) + +Nominal bit rate: 3152 kbit/s. + +Bit rate accuracy: $\pm 30$ ppm ( $\pm 95$ bit/s). + +For specifications at the ports, see Table III.1. + +**Table III.1 – Digital interface at 3152 kbit/s** + +| Parameter | Specification | +|--------------------------------------------------------------|-------------------------------------------------------------------------------------------------| +| Nominal bit rate | 3152 kbit/s | +| Bit rate accuracy | $\pm 30$ ppm ( $\pm 95$ bit/s) | +| Test load impedance | 100 ohms $\pm 5\%$ resistive | +| Line code | AMI (Notes 1 and 2) | +| Pulse shape | Nominal rectangular | +| Pair(s) in each direction of transmission | One balanced twisted pair (Note 3) | +| Nominal amplitude | 3.0 V (Note 4) | +| Width (at 50% amplitude) | $159 \pm 30$ ns | +| Rise and fall times (20-80% of amplitude) | $\leq 50$ ns (difference between rise and fall times shall be $0 \pm 20$ ns) | +| Signal power (all is signal, measured over 10 MHz bandwidth) | $16.53 \pm 2$ dBm [ratio of (power in + pulses) to (power in – pulses) shall be $0 \pm 0.5$ dB] | + +NOTE 1 – An AMI code shall be used. For definitions of AMI code; see Annex A/[ITU-T G.703]. + +NOTE 2 – In order to guarantee adequate timing information, the minimum pulse density taken over any 130 consecutive time slots must be 1 in 8. The design intent is that the long-term pulse density be equal to 0.5. In order to provide adequate jitter performance for systems, timing extracting circuits should have a $Q$ of $1200 \pm 200$ that is representable by a single tuned network. + +NOTE 3 – One balanced twisted pair shall be used for each direction of transmission. The distribution frame jack connected to a pair bringing signals to the distribution frame is termed the in-jack. The distribution frame jack connected to a pair carrying signals away from the distribution frame is termed the out-jack. + +NOTE 4 – The peak-to-peak voltage within a time slot containing a zero (space) produced by other pulses meeting the specifications of Table III.1 should not exceed 0.1 of the peak pulse amplitude. + +Requirements for the maximum peak-to-peak jitter at the output port and the jitter to be tolerated at the input port are for further study. + +Overvoltage protection requirements: refer to [ITU-T K.20]. + +# Bibliography + +- [b-ITU-T G.733] Recommendation ITU-T G.733 (1988), *Characteristics of primary PCM multiplex equipment operating at 1544 kbit/s.* +- [b-ITU-T G.783] Recommendation ITU-T G.783 (2006), *Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks.* +- [b-ITU-R F.596-1] Recommendation ITU-R F.596-1 (1982-1994), *Interconnection of digital radio-relay systems.* +- [b-Bell Tx] *Transmission Systems for Communications*, Bell Telephone Laboratories, Fifth Edition, 1982, Chapter 5, Section 5.1, p.83. +- [b-Wigginton] R.L. Wigginton and N.S. Nahman (1957), *Transient Analysis of Coaxial Cable Considering Skin Effect*, Proceedings of the IRE, February, pp. 166-174, see Eq. (14). + + + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Terminals and subjective and objective assessment methods | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects and next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.709.20-202404-I_PDF-E/007b053fe94a8348f75128a584503fd0_img.jpg 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It features a blue circular emblem with a stylized globe and the letters 'ITU' in white. + +ITU logo + +## ITU-T G-SERIES RECOMMENDATIONS **Transmission systems and media, digital systems and networks** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100-G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200-G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300-G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400-G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450-G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600-G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700-G.799 | +| General | G.700-G.709 | +| Coding of voice and audio signals | G.710-G.729 | +| Principal characteristics of primary multiplex equipment | G.730-G.739 | +| Principal characteristics of second order multiplex equipment | G.740-G.749 | +| Principal characteristics of higher order multiplex equipment | G.750-G.759 | +| Principal characteristics of transcoder and digital multiplication equipment | G.760-G.769 | +| Operations, administration and maintenance features of transmission equipment | G.770-G.779 | +| Principal characteristics of multiplexing equipment for the synchronous digital hierarchy | G.780-G.789 | +| Other terminal equipment | G.790-G.799 | +| DIGITAL NETWORKS | G.800-G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900-G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000-G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000-G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000-G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000-G.8999 | +| ACCESS NETWORKS | G.9000-G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.709.20 + +## Overview of fine grain OTN + +## Summary + +Recommendation ITU-T G.709.20 provides an overview of functions provided by the fine grain OTN (fgOTN) layer network and identifies Recommendations where the functions are defined. + +## History \* + +| Edition | Recommendation | Approval | Study Group | Unique ID | +|---------|----------------|------------|-------------|--------------------| +| 1.0 | ITU-T G.709.20 | 2024-04-06 | 15 | 11.1002/1000/15796 | + +## Keywords + +Architecture, fgODUflex, fgOTN, functions, HRM, OTN, overview, requirements. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at . + +© ITU 2024 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|------------------------------------------------------------------------|------| +| 1 Scope ..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 1 | +| 3.1 Terms defined elsewhere ..... | 1 | +| 3.2 Terms defined in this Recommendation..... | 1 | +| 4 Abbreviations and acronyms ..... | 1 | +| 5 Conventions ..... | 2 | +| 6 Application scenario and hypothetical reference modes of fgOTN ..... | 2 | +| 6.1 Application scenario ..... | 2 | +| 6.2 Hypothetical reference model (HRM) of fgOTN ..... | 2 | +| 7 General functional requirements of fgOTN ..... | 5 | +| 8 Overview of fgOTN Recommendation series ..... | 5 | +| 8.1 fgOTN architecture..... | 5 | +| 8.2 fgOTN interface..... | 6 | +| 8.3 Hitless resizing ..... | 6 | +| Annex A – Reference network model example ..... | 7 | +| Annex B – Detailed functional requirements of fgOTN..... | 8 | +| B.1 fgOTN layer architecture..... | 8 | +| B.2 fgOTN frame format..... | 8 | +| B.3 fgOTN/client adaptation functions ..... | 8 | +| B.4 ODUk/fgOTN adaptation functions ..... | 9 | +| B.5 Protection..... | 9 | +| B.6 Equipment..... | 9 | +| B.7 Synchronization..... | 9 | +| B.8 Management ..... | 9 | +| B.9 Hitless resizing ..... | 10 | + + + +# Recommendation ITU-T G.709.20 + +## Overview of fine grain OTN + +# 1 Scope + +This Recommendation provides an overview of functions provided by the fine grain OTN (fgOTN) layer network and identifies Recommendations where the functions are defined. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.709] Recommendation ITU-T G.709/Y.1331 (2020), *Interfaces for the optical transport network*. +- [ITU-T G.823] Recommendation ITU-T G.823 (2000), *The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy*. +- [ITU-T G.825] Recommendation ITU-T G.825 (2000), *The control of jitter and wander within digital networks which are based on the synchronous digital hierarchy (SDH)*. +- [ITU-T G.872] Recommendation ITU-T G.872 (2024), *Architecture of the optical transport network*. +- [IEEE 802.3] IEEE 802.3-2018, *IEEE Standard for Ethernet*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined elsewhere: + +### 3.1.1 Terms defined in [ITU-T G.709] + +- optical transport network (OTN) +- optical data unit k (ODUk) + +## 3.2 Terms defined in this Recommendation + +None. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|-------|--------------------------------------| +| APS | Automatic Protection Switching | +| CBR | Constant Bit Rate | +| CPE | Customer Premises Equipment | +| fgGMP | Fine Grain Generic Mapping Procedure | + +| | | +|-----------|---------------------------------------| +| fgODUflex | Fine Grain Flexible Optical Data Unit | +| fgOPU | Fine Grain Optical Payload Unit | +| fgOTN | Fine Grain Optical Transport Network | +| fgTS | Fine Grain Tributary Slot | +| HRM | Hypothetical Reference Model | +| LPF | Low Pass Filtering | +| NE | Network Element | +| ODUflex | Flexible Optical Data Unit | +| ODUk | Optical Data Unit-k | +| OTN | Optical Transport Network | +| PM | Path Monitoring | +| SDH | Synchronous Digital Hierarchy | +| TCM | Tandem Connection Monitoring | +| TDM | Time Division Multiplexing | +| TS | Tributary Slot | +| VC | Virtual Container | + +# 5 Conventions + +This Recommendation uses the following conventions: + +None. + +# 6 Application scenario and hypothetical reference modes of fgOTN + +## 6.1 Application scenario + +As synchronous digital hierarchy (SDH) phases out in operators' networks, fine grain OTN (fgOTN) technology complementing the existing optical transport network (OTN) with an additional fgOTN path layer network is used as an alternative to carry private line services. Historically, SDH networks based on a time division multiplexing (TDM) mechanism are used to transport low-rate signals, while the minimal container of OTN defined in [ITU-T G.709] is ~1.25G which is inefficient to transport these low rate (e.g., sub1G) signals using existing methods. A new fine grain ODU layer network has been defined to carry these low rate signals across the OTN networks, to provide isolated, secure, reliable and TDM-based transport capabilities. + +## 6.2 Hypothetical reference model (HRM) of fgOTN + +A hypothetical reference network showing multiple sub1G clients using fgOTN connections is illustrated in Figure 6-1. The sub1G clients could be packet services or constant bit rate (CBR) services. + +![Figure 6-1: HRM for sub1G clients over fgOTN network. The diagram shows four 'Client remote site LAN' units on the left, each connected via an 'RP' (Reference point) to an 'fgOTN node'. These nodes are part of a central 'OTN network with fgOTN layer network with TDM-based sub1G granularity'. On the right, two 'fgOTN node' units are shown. The top node connects to 'Client A server' via an 'RP'. The bottom node connects to 'Client B server' and 'Client C server' via 'RP's. A 'Reference point (RP)' is indicated at the bottom center, pointing to the 'Client interface'.](ebff22fb5dd6f50a90e44dca0f82f285_img.jpg) + +Figure 6-1: HRM for sub1G clients over fgOTN network. The diagram shows four 'Client remote site LAN' units on the left, each connected via an 'RP' (Reference point) to an 'fgOTN node'. These nodes are part of a central 'OTN network with fgOTN layer network with TDM-based sub1G granularity'. On the right, two 'fgOTN node' units are shown. The top node connects to 'Client A server' via an 'RP'. The bottom node connects to 'Client B server' and 'Client C server' via 'RP's. A 'Reference point (RP)' is indicated at the bottom center, pointing to the 'Client interface'. + +**Figure 6-1 – HRM for sub1G clients over fgOTN network** + +![Figure 6-2: Example of packet clients over fgOTN connections. The diagram illustrates three 'Client remote site' boxes and one 'Client headquarters site' box. Each 'Client remote site' contains a 'Client remote site LAN' connected to an 'fgOTN CPE node' via 'Ethernet'. The 'Client headquarters site' contains a 'Client server' connected to an 'fgOTN CPE node' via 'Ethernet'. These CPE nodes connect to a central 'fgOTN network' cloud. The connections from the top-left and top-right CPE nodes are labeled 'OTUk'. The connections from the bottom-left CPE node and the headquarters CPE node are labeled 'Ethernet over fgODU'. The network cloud contains three 'fgOTN node' units.](562f471e8153729557e6a4ee6343c32c_img.jpg) + +Figure 6-2: Example of packet clients over fgOTN connections. The diagram illustrates three 'Client remote site' boxes and one 'Client headquarters site' box. Each 'Client remote site' contains a 'Client remote site LAN' connected to an 'fgOTN CPE node' via 'Ethernet'. The 'Client headquarters site' contains a 'Client server' connected to an 'fgOTN CPE node' via 'Ethernet'. These CPE nodes connect to a central 'fgOTN network' cloud. The connections from the top-left and top-right CPE nodes are labeled 'OTUk'. The connections from the bottom-left CPE node and the headquarters CPE node are labeled 'Ethernet over fgODU'. The network cloud contains three 'fgOTN node' units. + +**Figure 6-2 – Example of packet clients over fgOTN connections** + +Figure 6-2 shows an example of packet clients over fgOTN connections either between the remote sites and the headquarters or between the remote sites. The option of using customer premises equipment (CPE) to terminate the fgOTN connections is also illustrated. The packet client connections share the same type of interface at both the remote sites and at the headquarters site. Each Ethernet signal which contains the consolidated traffic of the remote site is encapsulated into a fgOTN container which is transported in the fgOTN networks. Ethernet signals could be connected to either fgOTN equipment which is within the operators' networks or fgOTN CPE equipment which is within the client remote sites. + +![Diagram illustrating CBR clients over fgOTN connections. A central fgOTN network cloud is connected to five fgOTN nodes. Two nodes connect to SDH sub-networks via STM-N and STM-1/STM-4 interfaces. Two nodes connect to client end nodes via E1 interfaces. One node connects to another fgOTN node via STM-1/4 over fgODU, which in turn connects to an SDH sub-network via STM-1/STM-4. Internal connections within the fgOTN network are shown as dashed lines representing STM-1/4 over fgODU, VC-n over fgODU, and E1 over VC over fgODU. The diagram is labeled G.709.20(24).](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg) + +Diagram illustrating CBR clients over fgOTN connections. A central fgOTN network cloud is connected to five fgOTN nodes. Two nodes connect to SDH sub-networks via STM-N and STM-1/STM-4 interfaces. Two nodes connect to client end nodes via E1 interfaces. One node connects to another fgOTN node via STM-1/4 over fgODU, which in turn connects to an SDH sub-network via STM-1/STM-4. Internal connections within the fgOTN network are shown as dashed lines representing STM-1/4 over fgODU, VC-n over fgODU, and E1 over VC over fgODU. The diagram is labeled G.709.20(24). + +**Figure 6-3 – Example of CBR clients over fgOTN connections** + +Figure 6-3 shows an example of CBR clients over fgOTN connections. fgOTN equipment could support STM-1, STM-4 and E1 interfaces, and fgOTN containers could carry CBR clients which include STM-1, STM-4, and VC-n/E1 (E1 signal from E1 interface is firstly mapped into VC-12 and subsequently mapped into a fgOTN container). Each CBR client is encapsulated into its own fgOTN container. CBR client signals could be connected to either fgOTN equipment which is within the operators' networks or fgOTN CPE equipment which is within the client remote sites. + +Table 6-1 gives the fgOTN network topology considerations. + +**Table 6-1 – fgOTN network topology** + +| | | | +|-----------------|-------------------------------------------------|-------------| +| Traffic pattern | Remote to headquarters | Y | +| | Between remote sites | Y | +| | Both | Y | +| Redundancy | Protection/restoration in transport network | Y | +| | Client interfaces | Y | +| | Physically diverse feeds to client locations | N | +| | Dual feed to redundant servers | Y | +| Network size | Number of fgOTN switching nodes | Max~20 | +| | TCM levels | 2 | +| | Number of remotes connected to the headquarters | 100 ~ 3,000 | +| | Max connection length | ~6,900 km | + +All connections provided by the fgOTN transport network are bidirectional point to point. + +Table 6-2 gives the fgOTN connection characteristics. + +**Table 6-2 – fgOTN connection characteristics** + +| | | | +|-------------------------------------------------------------------------------------------------------|----------------|----------------------------------------------------------------------------| +| Granularity of tributary slots | CBR service | $K \times 10$ Mbit/s | +| | Packet service | $N \times 10$ Mbit/s (Note) | +| Server capacity | | ODU0/1/2/flex(fgTS,n) (where $n = 3$ to $7$ ) | +| Maximum number of client connections | | ODU0 ~ 119
ODU1 ~ 238
ODU2 ~ 952
ODUflex(fgTS,n) ~ $n \times 119$ | +| Maximum client size | CBR service | STM-4 | +| | Packet service | ~1.19 Gbit/s | +| NOTE – A 10 Mbit/s tributary slot should support a full rate mapping of a 10 Mbit/s Ethernet service. | | | + +# 7 General functional requirements of fgOTN + +The general functional requirements of fgOTN are given as follows: + +- fgOTN should support TDM multiplexing. TDM multiplexing provides hard isolation for the client signals of fgOTN. fgOTN should support deterministic latency to guarantee the performance of OTN networks. +- fgOTN should support mapping services into a fine grain flexible optical data unit (fgODUflex) path layer, including Ethernet services such as $p \times 10\text{M}$ MAC data stream ( $p = 1$ to $119$ ), CBR services (STM-1/4, VC-n/E1) (E1 signal from E1 interface is encapsulated into VC-12 and subsequently encapsulated into the fgODUflex container). +- fgOTN should support multiplexing multiple fgODUflex signals into ODU0/1/2/flex(fgTS,n) (where $n = 3$ to $7$ ). +- fgOTN should support fgODUflex SNCP 1+1 protection (for 50M services and above the switching time should be within 50 ms, while for 10M~50M services the switching time within 50 ms is recommended). +- fgOTN should support the fgOTN equipment functions. +- fgOTN should support timing transparent transport for CBR services. For VC-n services, fgOTN should share a common synchronization source on both the source network element (NE) and the sink NE. +- fgOTN should support fgODUflex hitless bandwidth adjustment function for packet services. + +# 8 Overview of fgOTN Recommendation series + +This clause provides an overview of the fgOTN Recommendations where the functions are defined. + +## 8.1 fgOTN architecture + +The information structure for fgODUflex is represented by information containment relationships and flows. The principal information containment relationship is described in Figure 8-1. + +A client signal is mapped into the fgODUflex payload area and the generated justification control information is inserted into fgOPUflex overhead area. It generates the fgODUflex path connection monitoring information which is inserted into fgODUflex PM overhead. Furthermore, it generates the fgODUflex tandem connection monitoring information which is inserted into fgODUflex tandem connection monitoring (TCM) overhead. It supports two levels of fgODUflex tandem connection monitoring. The generated fgODUflex signal is mapped into one or multiple fine grain tributary slots of the server OPU. + +The fgOTN layer architecture is defined in Annex A of [ITU-T G.872]. + +![Diagram illustrating the fgODUflex principal information containment relationship. The diagram shows the hierarchy of data encapsulation: Client data is encapsulated into fgOPUflex (fgOPU flex OH + fgOPUflex payload). This is then encapsulated into an fgODUflex path (PM OH). The fgODUflex path is then encapsulated into an fgODUflex tandem connection (TCM OH). Finally, the fgODUflex tandem connection is encapsulated into one or more fgTSs of OPU. On the right side, the fgODUflex tandem connection is shown being split into two separate fgODUflex TC L1 and fgODUflex TC L2 paths, each with its own TCM OH.](007b053fe94a8348f75128a584503fd0_img.jpg) + +The diagram illustrates the principal information containment relationship for fgODUflex. At the top, a 'Client' block is shown. Below it, the 'fgOPUflex' layer is depicted, consisting of 'fgOPU flex OH' and 'fgOPUflex payload'. This is followed by the 'fgODUflex path' layer, which contains 'PM OH'. The next layer is the 'fgODUflex tandem connection', which contains 'TCM OH'. At the bottom, the 'One or more fgTSs of OPU' layer is shown. On the right side, the 'fgODUflex tandem connection' is shown branching into two separate paths: 'fgODUflex TC L1' and 'fgODUflex TC L2', each containing its own 'TCM OH'. + +G.709.20(24) + +Diagram illustrating the fgODUflex principal information containment relationship. The diagram shows the hierarchy of data encapsulation: Client data is encapsulated into fgOPUflex (fgOPU flex OH + fgOPUflex payload). This is then encapsulated into an fgODUflex path (PM OH). The fgODUflex path is then encapsulated into an fgODUflex tandem connection (TCM OH). Finally, the fgODUflex tandem connection is encapsulated into one or more fgTSs of OPU. On the right side, the fgODUflex tandem connection is shown being split into two separate fgODUflex TC L1 and fgODUflex TC L2 paths, each with its own TCM OH. + +**Figure 8-1 – fgODUflex principal information containment relationship** + +## 8.2 fgOTN interface + +The fgOTN interface is defined in Annex M of [ITU-T G.709]. + +OPU server/fgODUflex adaptation is defined in Annex N of [ITU-T G.709]. + +Hitless bandwidth adjustment of fgODUflex is defined in Annex O of [ITU-T G.709]. + +## 8.3 Hitless resizing + +The location of the hitless resizing specification(s) is given in Annex O of [ITU-T G.709]. + +## Annex A + +## Reference network model example + +(This annex forms an integral part of this Recommendation.) + +An example of a reference network model for a multi-domain fgOTN application is shown in Figure A.1. There is one backbone OTN network, two metro OTN networks and two fgOTN CPEs in this model. + +![Figure A.1: A reference network model for multi-domain fgOTN application. The diagram shows a sequence of nodes: fgOTN CPE, fgOTN access, fgOTN aggregation, fgOTN core, Backbone OTN (ODUk), fgOTN core, fgOTN aggregation, fgOTN access, and fgOTN CPE. The first four nodes are grouped as 'Metro OTN network A (fgOTN and ODUk)'. The last four nodes are grouped as 'Metro OTN network B (fgOTN and ODUk)'. The central 'Backbone OTN (ODUk)' connects the two metro networks. A reference number 'G.709.20(24)' is shown in the bottom right corner of the diagram area.](cab0834804fb031b43865554cc8d06ab_img.jpg) + +The diagram illustrates a multi-domain network architecture. On the far left and far right are 'fgOTN CPE' nodes. Each CPE is connected to an 'fgOTN access' node. Each 'fgOTN access' node is connected to an 'fgOTN aggregation' node, which in turn is connected to an 'fgOTN core' node. These four nodes (access, aggregation, core, and CPE) are grouped under the label 'Metro OTN network A (fgOTN and ODUk)' on the left and 'Metro OTN network B (fgOTN and ODUk)' on the right. The 'fgOTN core' node of Metro network A is connected to a central cloud labeled 'Backbone OTN (ODUk)'. The 'Backbone OTN (ODUk)' cloud is connected to the 'fgOTN core' node of Metro network B. A small label 'G.709.20(24)' is located in the bottom right corner of the diagram. + +Figure A.1: A reference network model for multi-domain fgOTN application. The diagram shows a sequence of nodes: fgOTN CPE, fgOTN access, fgOTN aggregation, fgOTN core, Backbone OTN (ODUk), fgOTN core, fgOTN aggregation, fgOTN access, and fgOTN CPE. The first four nodes are grouped as 'Metro OTN network A (fgOTN and ODUk)'. The last four nodes are grouped as 'Metro OTN network B (fgOTN and ODUk)'. The central 'Backbone OTN (ODUk)' connects the two metro networks. A reference number 'G.709.20(24)' is shown in the bottom right corner of the diagram area. + +**Figure A.1 – A reference network model for multi-domain fgOTN application** + +To support both fgOTN and optical data unit-k (ODUk) based services, metro OTN networks should support both fgODUflex and ODUk switching. At the boundary nodes (e.g., metro-core nodes) of the metro OTN networks, the fgODUflexes to other metro OTN networks are multiplexed into ODUk of backbone networks. Therefore, the backbone OTN network could only support ODUk switching. + +The metro OTNs consist of metro-core, metro-aggregation and metro-access nodes. For a fgOTN that spans across the backbone network, the maximum number of fgOTN cross-connect nodes is 20. + +# Annex B + +## Detailed functional requirements of fgOTN + +(This annex forms an integral part of this Recommendation.) + +The detailed functional requirements of fgOTN are given as follows: + +### B.1 fgOTN layer architecture + +The fgOTN complements the existing OTN with an additional fgOTN path layer network that provides bandwidth efficient TDM support for sub1G services. This fgOTN layer network is a service layer network of the OTN ODUk layer network. + +### B.2 fgOTN frame format + +The fgOTN frame format is a byte-oriented fgODUflex frame structure, enhanced to support the overhead performance requirements. The fgODUflex overheads include FAS/MFAS, PM (TTI, BIP-8, BEI, BDI, STAT, APS, and DM), 2 levels of TCM (TTI, BIP-8, BEI/BIAE, BDI, STAT, APS, and DM), PT, CSF, DAi, and overheads related to hitless bandwidth resizing. + +### B.3 fgOTN/client adaptation functions + +The requirements and functions defined for packet services and CBR services are given in clauses B.3.1 and B.3.2. + +#### B.3.1 Packet services + +The fgOTN should support packet services, and the packet services are assumed to be Ethernet. + +- 1) The support for the MEF 6.3 Ethernet services is required: + - Ethernet virtual private line (EVPL) service either between a pair of remote sites, or between a remote site and a headquarters site. + - Ethernet private line (EPL) service between a pair of remote sites. + +NOTE – The EPL service is only supported when the physical interfaces at both sites are dedicated to the remote-to-remote connection. + +- 2) Packet services that use a physical coding sublayer (PCS) codeword transparent mapping are not supported by fgOTN. +- 3) Packet services are mapped into the server layer which supports a granularity of ~10 Mbit/s. +- 4) Ethernet packet services will be encoded into 64B/66B blocks according to [IEEE 802.3] clause 82. Rate adaptation of encoded Ethernet packet stream into the fgOTN payload area is performed by IMP. Error marking is required for packet services. +- 5) Low pass filtering (LPF) function is not required at fgOTN intermediate switching nodes for fgODUflex carrying packet services. +- 6) Timing transparent transport is not required for packet services. +- 7) Hitless bandwidth adjustment should be supported for packet services. + +#### B.3.2 CBR services + +- 1) The main application for CBR services is to provide support for legacy SDH services after SDH equipment phases out. + +The following CBR services could be mapped into fgODUflex containers: + +- STM-1, STM-4, VC-n/E1. + +The following CBR interfaces could be provided by a fgOTN edge node: + +- STM-1, STM-4, E1. + +VC-n signals could be from STM-N (N=1,4,16, etc.) interfaces. + +E1 signal from E1 interfaces is encapsulated into VC-12 and subsequently encapsulated into fgODUflex containers. + +- 2) Functional requirements include timing transparency, DM and automatic protection switching (APS). +- 3) CBR services that could be mapped over the fgOTN path: STM-1/STM-4, $v_1*VC-12$ ( $v_1 = 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55$ and 60), $v_2*VC-3$ ( $v_2 = 1$ and 2), and VC-4. +- 4) Rate adaptation of CBR clients into the fgODUflex payload area is performed by generic mapping procedure (GMP). +- 5) Timing transparency, i.e., transfer of client timing information is required for CBR services. +- 6) For VC-n clients, the fgOTN should share a common synchronization source on both the source NE and the sink NE. The CnD is not required when mapping VC-n into fgODUflex via GMP, i.e., VC-n synchronization is performed with an additional synchronization network outside, without needing to transport timing synchronization. + +### **B.4 ODuk/fgOTN adaptation functions** + +FgGMP is used for adapting the fgODUflex path signal into the ODU server layer. The ODU server container is $\sim n*1.25$ Gbit/s ODUflex/ODUk, and the maximum rate of an ODU server for direct mapping of fgODUflex path signals is $\sim 10$ Gbit/s (ODU2). The interleaving granularity of tributary slots for mapping fgODUflex path signals into ODUflex/ODUk is 16-byte. The tributary slot (TS) bandwidth granularity is slightly above 10 Mbit/s. An ODU0 consists of 119 TSs. + +### **B.5 Protection** + +Unidirectional 1+1 protection and bidirectional 1+1 protection should be supported for fgOTN. For client rates which equal to or greater than 50 Mbit/s, 50 ms protection switch time is required. For client rate below 50 Mbit/s, protection switch time could be relaxed. The APS field encoding for bidirectional 1+1 protection could be different from the current ITU-T G.709 definition. One path monitoring (PM) level APS and two TCM level APS are needed. + +### **B.6 Equipment** + +The equipment aspects of fgODUflex trail termination functions, fgODUflex connection function, fgODUflex/client adaptation functions and ODUP/fgODUflex adaption function should be supported. + +FgOTN should support switching function based on fgODUflex. The PM/TCM monitoring of fgODUflex, PRBS testing and fgODUflex delay measurement are needed. + +### **B.7 Synchronization** + +When STM-1, STM-4 or VC/E1 is carried as a client of the fgOTN network, the jitter and wander should be as defined in [ITU-T G.823] and [ITU-T G.825]. These mappings should provide timing transparency but do not need to transfer SDH network synchronization information. An E1 carried by a VC-12 across the fgOTN network should meet the jitter and wander requirements as defined in [ITU-T G.823]. + +### **B.8 Management** + +Management requirements of fgOTN are to be determined. + +Protocol-neutral information model of fgOTN is to be determined. + +### **B.9 Hitless resizing** + +Hitless adjustment of fgODUflex should be supported to hitlessly increase or decrease the bandwidth of fgODUflex connections in OTN networks. Hitless resizing should be with a completion time in the order of seconds or less. The resizing uses a single-step mechanism rather than a ramp. The granularity of bandwidth adjustment is ~10 Mbit/s. The need for low-pass filtering at intermediate nodes should be avoided. + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.762-198811-I_PDF-E/2df09d249c38abee55dbf0526dd6da0a_img.jpg b/marked/G/T-REC-G.762-198811-I_PDF-E/2df09d249c38abee55dbf0526dd6da0a_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..e3a450ae4b1ea88b7997a25feb3b326edde61a4e --- /dev/null +++ b/marked/G/T-REC-G.762-198811-I_PDF-E/2df09d249c38abee55dbf0526dd6da0a_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:e93e9769e52b38c17b381337edb980b46fdf5044e67b42cd4ddc61ff88b36797 +size 28896 diff --git a/marked/G/T-REC-G.762-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.762-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..64672153e39c851d9e16fdbc702e526c7ba7e8a7 --- /dev/null +++ b/marked/G/T-REC-G.762-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:454a9958ffe168868cb7d38a0eb24418dafe31a7a4245c992089b2316ac37d3e +size 7392 diff --git a/marked/G/T-REC-G.764-199012-I_PDF-E/raw.md b/marked/G/T-REC-G.764-199012-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..aac99b6ab0d0961993f122f2f8dae0e938f675be --- /dev/null +++ b/marked/G/T-REC-G.764-199012-I_PDF-E/raw.md @@ -0,0 +1,890 @@ + + +![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**CCITT** + +**G.764** + +THE INTERNATIONAL +TELEGRAPH AND TELEPHONE +CONSULTATIVE COMMITTEE + +**GENERAL ASPECTS OF DIGITAL +TRANSMISSION SYSTEMS; +TERMINAL EQUIPMENTS** + +--- + +**VOICE PACKETIZATION – +PACKETIZED VOICE PROTOCOLS** + +**Recommendation G.764** + +--- + +![CCITT logo](6ed175c791b5e156d9c98a8dbcc3318c_img.jpg) + +The logo for the Consultative Committee on International Telegraphs and Telephones (CCITT) consists of the letters 'CCITT' in a bold, sans-serif font, enclosed within a circular border that has a globe-like pattern. + +CCITT logo + +Geneva, 1990 + +# FOREWORD + +The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCITT between Plenary Assemblies is covered by the procedure laid down in CCITT Resolution No. 2 (Melbourne, 1988). + +Recommendation G.764 was prepared by Study Group XV and was approved under the Resolution No. 2 procedure on the 14 of December 1990. + +## --- CCITT NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication Administration and a recognized private operating agency. + +# **VOICE PACKETIZATION — PACKETIZED VOICE PROTOCOLES** + +# **1 Introduction** + +This Recommendation defines a packet voice protocol for speech packetization in permanent virtual circuit applications. The principal application of the packetized voice protocol (PVP) is at the primary rate and in fractional primary rate applications. + +The protocol defines formats and procedures for the transport of voice information and channel associated signalling over a wideband packet network. + +The Recommendation accommodates additional future types including optional internetworking capabilities with the digital cellular radio networking applications currently under development. The extension of this Recommendation for baseband facsimile traffic is currently under study. + +This Recommendation does not address performance issues. + +This Recommendation does not address methods for coding speech samples, although particular recommended coding algorithms are specified in the protocol (e.g. the algorithms in Recommendation G.726). In particular, the Recommendation allows dynamic bandwidth allocation and graceful congestion control when the speech samples are coded with embedded algorithms such as those specified in Recommendation G.727. + +This Recommendation does not address the following issues: + +- 1) services based on the interface; +- 2) implementation techniques; +- 3) performance guidelines relative to the use of packetized speech; +- 4) equipment aspects; +- 5) trunk signalling, link establishment and call establishment procedures for switched virtual circuits; +- 6) data only issues, combined data/voice issues and frame relay issues; +- 7) speech packetization in Asynchronous Transfer Mode (ATM) (B-ISDN) systems. + +# **2 Overview** + +This Recommendation contains the specification of a protocol for packetized speech (PVP). PVP defines formats and procedures for the transport of voice information and channel associated signalling over a packet network. + +Before packetization, the input speech samples may be coded at the originating endpoint of the transmitting side by one of the coding methods indicated in this document. The stream of coded speech is transformed into packets with the format specified in this document. The samples are collected over a period of 16 ms and divided into blocks of 128 bits each. Silent intervals may be removed. The blocks are arranged to facilitate block dropping. + +Periods of activity and inactivity are respectively called “bursts” and “gaps”. It is not necessary to transmit packets during gaps. + +The terminating end at the receiving side reconstructs a continuous stream of speech from the incoming packets using the information in the packet header. The build-out delay procedure described in this document compensates for the variable delay that packets may experience within the network. Packets that arrive before their scheduled play-out time are placed in the proper sequence in a packet queue. Packets that arrive after their scheduled play-out time are discarded. The voice packet header contains information about the level of noise that was measured by the originating endpoint. The terminating endpoint uses this information to play out a matching noise level. + +An additional feature of PVP is the ability to drop blocks from a packet as a congestion control mechanism. The $n$ -th block consists of the $n$ -th bit from each sample collected during the sampling interval. The packet header indicates the number of droppable blocks contained in the packet. Congested nodes may use this information to drop the least significant block from packets to abate the congested state. + +The signalling associated with each voice connection shall be transported in signalling packets. Signalling packets shall be sent separately on a different logical channel. Transport of the signalling information requires a set of procedures, similar to those for voice transport, which are described in this document. + +*Note* — In a national network, the time stamp (TS) and the build-out procedures of §§ 5.1.1, 5.2 and 6.3 may be replaced by a fixed-delay for the first packet. At the originating end, the TS will be set to zero. In an intermediate node, the TS field will not be updated. However, the build-out procedure will be used always on network-network and user-network interfaces. + +# 3 Formats + +## 3.1 Physical layer + +For operations at 1536 kbit/s or 1920 kbit/s, the electrical characteristics and formats of the interface are those defined in Recommendations G.703, G.704 and I.431 for the primary rates of 1544 kbit/s and 2048 kbit/s, respectively. The packetized signal consists of one digital stream sent over conventional primary rate facilities. Hybrid situations containing one or more $N \times 64$ kbit/s packet streams and $M$ conventional 64 kbit/s channels are also considered. + +### 3.1.1 Bit inversion + +For primary rate applications that require code restrictions that maintain one's density, bit inversion is necessary so that the combined result of bit stuffing and bit inversion is to prevent the all 0 octet and to satisfy the one's density requirements of restricted DS 1 facilities. + +### 3.1.2 Order of transmission + +Bit 1 is the least significant bit (LSB) and is transmitted first. Bit 8 is the most significant bit (MSB) and is transmitted last. + +## 3.2 Link layer + +The link layer of PVP uses a similar approach to Recommendation Q.921/I.441 with the additions indicated in this Recommendation. Frames that transport voice and frames that transport channel associated signalling are assigned different layer 2 addresses, i.e. they are carried on two separate logical links. This, together with the use of a different unnumbered frame type for each type of traffic, provides an additional measure of security to protect from the misrouting of signalling information. + +### 3.2.1 Address field + +The address field is two octets in length with the first bit of each defined as an extension bit and bit 2 of octet 1 defined as the command/response (C/R) bit. The 13 bits that remain are concatenated to form a single data link connection identifier (DLCI). Address assignment starts with 128 and ends with 8063. Layer 2 addresses are already assigned and the implementation starts from the DLCI\_ASSIGNED state. + +### 3.2.2 Command/response bit + +The C/R bit (bit 2 of octet 1) is set to 0. + +### 3.2.3 Frame types + +The following two frame types are allowed in PVP. + +#### 3.2.3.1 Unnumbered information frames + +When a layer 3 or management entity requests unacknowledged information transfer, the unnumbered information (UI) command is used to send information to its peer without affecting data link layer variables. UI command frames do not carry a sequence number and therefore, the UI frame may be lost without notification. + +The control field for the UI command frame is a single octet in length. The format and encoding are the same as specified in Recommendation Q.921/I.441. The UI frame is used to transport channel associated signalling. + +#### 3.2.3.2 Unnumbered information with header check frame + +The unnumbered information with header check (UIH) frame has the same applications as the UI frame. The difference between the two is that the cyclic redundancy check (CRC) sequence is derived over the frame and packet headers (the first 8 octets excluding flags) rather than over the entire frame. The check sequence fills the last two octets of the UIH frame. + +The control field of the UIH is a single octet in length and is shown in Figure 1/G.764. + +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | Bit number | +|---|---|---|---|---|---|---|---|------------| +| 1 | 1 | 1 | P | 1 | 1 | 1 | 1 | | + +FIGURE 1/G.764 + +##### Control field of the UIH frame + +The UIH frame is used to transport voice (see Note). + +*Note* — The CRC check of the UIH protects 8 octets which contain the address field (to ensure correct delivery), the control field (to guarantee the validity of the frame type) and the layer 3 header. It does not protect the voice information because voice traffic is more sensitive to delay due to retransmission than to bit errors and because this allows reduction of the voice information by block dropping under congestion without recalculating the CRC check. As a consequence, the test for invalid frames in § 3.2.7 uses the minimum frame length of 10 octets. + +### 3.2.4 Poll bit + +The poll bit (P) is bit 5 of the UI/UIH frame control field. The P bit shall be set to 0. + +### 3.2.5 *Check sequence* + +The check sequence (CS) algorithm is the same as that described in ISO Recommendation ISO-3309. The CS field shall be a 16-bit sequence. It shall be the ones complement of the sum (modulo 2) of: + +- 1) The remainder of ( $x$ raised to $k$ power) ( $x^{15} + x^{14} + x^{13} + x^{12} + x^{11} + x^{10} + x^9 + x^8 + x^7 + x^6 + x^5 + x^4 + x^3 + x^2 + x^1 + 1$ ) divided (modulo 2) by the generator polynomial $x^{16} + x^{12} + x^5 + 1$ , where $k$ is the number of bits in the frame existing between, but not including, the final bit of the opening flag and the first bit of the first octet of the non-droppable octets for the header check sequence (HCS) or the first bit of the check sequence for the frame check sequence (FCS), excluding bits inserted for transparency, and +- 2) the remainder of the division (modulo 2) by the generator polynomial $x^{16} + x^{12} + x^5 + 1$ , of the product of $x^{16}$ by the content of the frame existing between, but not including, the final bit of the opening flag and the first bit of the first octet of the non-droppable octets for the HCS or the first bit of the CS for the FCS, excluding bits inserted for transparency. + +As a typical implementation at the transmitter, the initial content of the register of the device computing the remainder of the division is preset to all ones and is then modified by division by the generator polynomial (as described above) of the address, control and appropriate portion of the information fields; the ones complement of the resulting remainder is transmitted as the 16-bit CS. + +As a typical implementation at the receiver, the initial content of the register of the device computing the remainder is preset to all ones. The final remainder after multiplication by $x^{16}$ and then division (modulo 2) by the generator polynomial $x^{16} + x^{12} + x^5 + 1$ of the serial incoming protected bits and the CS, will be 0001110100001111 ( $x^{15}$ through $x^0$ , respectively) in the absence of transmission errors. + +### 3.2.6 *Frame abort* + +Receipt of seven or more contiguous 1 bits shall be interpreted as a frame abort, and the link layer entity shall ignore the frame currently being received. A frame following an abort must begin with an opening flag. + +### 3.2.7 *Invalid UI/UIH frames for PVP* + +For the purposes of PVP, an invalid UI/UIH frame is a frame which: + +- 1) is not properly bounded by two flags; or +- 2) has fewer than 10 octets between flags; or +- 3) has greater than 490 octets between flags; or +- 4) does not consist of an integral number of octets prior to zero bit insertion or following zero bit extractions; or +- 5) contains a FCS error. + +Invalid frames shall be discarded without notification to the sender. No action is taken as the result of that frame. + +## 3.3 *Packet layer* + +The packet layer procedures apply to the information transfer phase only. Call control procedures are outside the scope of this Recommendation. + +### 3.3.1 *Voice packet format* + +The format of voice packets is shown in Figure 2/G.764 within the UIH voice frame. + +*Note* — The reserved bits are set to 0 at the originating endpoint. They shall be ignored at the terminating endpoint. They shall not be used for testing or maintenance purposes in anticipation of possible future uses. + +![](fc46871d72c65d3381d9201646d23439_img.jpg) + +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | | +|-----------------------------|---|---|-------------|-------|---|---|---|---------|---------| +| Address (upper subfield) | | | | | | 0 | 0 | Octet 1 | | +| Address (lower subfield) | | | | | | | 1 | Octet 2 | | +| UIH control field | | | | | | | | | | +| 1 | 1 | 1 | P | 1 | 1 | 1 | 1 | Octet 3 | | +| Protocol discriminator | | | | | | | | | | +| 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | Octet 4 | | +| Block dropping indicator | | | | | | | | Octet 5 | | +| Time stamp | | | | | | | | Octet 6 | | +| M | R | R | Coding type | | | | | | Octet 7 | +| Sequence number | | | | Noise | | | | Octet 8 | | +| Non-droppable blocks | | | | | | | | | | +| Optionally droppable blocks | | | | | | | | | | +| Check sequence 2 octets | | | | | | | | | | + +M More bit + +P Poll bit = 0 (see § 3.2.4) + +R Reserved for future use + +FIGURE 2/G.764 + +##### **UIH voice frame format** + +#### 3.3.1.1 *Protocol discriminator* + +The protocol discriminator (PD) field is the first octet of the packet header (octet 4, the frame in Figure 2/G.764). Its value for the PVP is given in Figure 3/G.764. + +![](9791722d75115ddcc599b07d7bc35d73_img.jpg) + +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | Bit number | +|---|---|---|---|---|---|---|---|------------| +| 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | | + +FIGURE 3/G.764 + +##### **Protocol discriminator for the PVP** + +#### 3.3.1.2 Block dropping indicator + +The block dropping indicator (BDI) tracks the status of block dropping within the voice packet. A block consists of bits of the same significance collected from all speech samples that are packetized. The size of the block is 128 bits, which, for a sampling rate of 8 kHz, corresponds to a packetization interval of 16 ms. Blocks are arranged in decreasing order of significance. + +The format of the BDI is shown in Figure 4/G.764. + +| Bit number | | | | | | | | +|------------|---|----|----|---|---|----|----| +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| R | R | M2 | M1 | R | R | C2 | C1 | + +R Reserved for future use + +FIGURE 4/G.764 + +##### Block dropping indicator format + +The combination C1 and C2 form the C-subfield that indicates the number of blocks that are still droppable at any intermediate node in the network, as shown in Table 1/G.764: + +TABLE 1/G.764 + +##### C-subfield codings + +| C2 | C1 | No. of droppable blocks | +|----|----|-------------------------| +| 0 | 0 | 0 blocks | +| 0 | 1 | 1 block | +| 1 | 0 | 2 blocks | +| 1 | 1 | 3 blocks | + +As blocks are dropped from the packet, the value in the C-subfield is decremented to reflect the number of blocks still available for dropping. + +The combination M1 and M2 forms the M-subfield that indicates the total number of blocks that can be discarded from the packet as it traverses the network during periods of network congestion, as shown in Table 2/G.764. The value in the M-subfield is not changed from its initial value. + +TABLE 2/G.764 + +##### M-subfield codings + +| M2 | M1 | No. of droppable blocks | +|----|----|-------------------------| +| 0 | 0 | 0 blocks | +| 0 | 1 | 1 block | +| 1 | 0 | 2 blocks | +| 1 | 1 | 3 blocks | + +For fixed rate coding, both the M-subfield and the C-subfield are set to 0. + +#### 3.3.1.3 *Time stamp* + +The TS records the cumulative variable queueing delays experienced by a packet in traversing the network with a resolution of 1 ms. To prevent wrap-around, the maximum valid value in the TS field shall not exceed 200 ms. If, after update, the variable delay exceeds 20 ms, the value is set to 20 ms. + +#### 3.3.1.4 *Coding type* + +The coding type (CT) field indicates the method of coding the speech samples at the originating endpoint before packetization. Figure 5/G.764 shows the valid encodings for the field. + +When the coding type for voice-band signals is fixed or embedded adaptive differential pulse-code modulation (ADPCM), the polarity of ADPCM samples complies with Recommendations G.726/G.7271). When the coding type for voice-band signals is 8-bit pulse code modulation (PCM), the polarity of PCM samples complies with Recommendation G.711. + +#### 3.3.1.5 *M-bit* + +The M-bit is set to 1 for all packets except for the last packet of a burst where it is set to 0. The M-bit may be used by the terminating end point to recover from packet loss. + +#### 3.3.1.6 *Sequence number* + +The sequence number (SEQ) is used by endpoints in the build-out process to: + +- 1) determine the first packet of a burst; and +- 2) determine if a packet has been lost. + +The SEQ, in conjunction with the TS, allows the removal of variability in network delay. + +SEQ 0 is placed in the first packet of a voice burst. Subsequent packets in the same burst are given numbers 1 to 15, rolling back to 1. + +#### 3.3.1.7 *Noise field* + +The noise field indicates a background noise level as shown in Figure 6/G.764. The receiving end uses this field to determine the level of the background noise that may be played in the absence of packets. + +--- + +1) Recommendation G.726 completely replaces Recommendations G.721 and G.723 published in Volume III.4 of the Blue Book. It should be noted that systems designed in accordance with Recommendation G.726 will be compatible with systems designed in accordance with the Blue Book versions. + +| Bit number | | | | | Coding type a) | +|------------|---|-----|---|---|------------------------------------| +| 5 | 4 | 3 | 2 | 1 | | +| 0 | 0 | 0 | 0 | 0 | 8 bits/sample b) | +| 0 | 0 | 0 | 0 | 1 | 1 bit/sample b) | +| 0 | 0 | 0 | 1 | 0 | 2 bits/sample b) | +| 0 | 0 | 0 | 1 | 1 | 3 bits/sample b) | +| 0 | 0 | 1 | 0 | 0 | 4 bits/sample b) | +| 0 | 0 | 1 | 0 | 1 | 5 bits/sample b) | +| 0 | 0 | 1 | 1 | 0 | 6 bits/sample b) | +| 0 | 0 | 1 | 1 | 1 | 7 bits/sample b) | +| 0 | 1 | 0 | 0 | 0 | 8 bit A-law PCM c) | +| 0 | 1 | 0 | 0 | 1 | 8 bit $\mu$ -law PCM c) | +| 0 | 1 | 0 | 1 | 0 | 2 bits/sample ADPCM d) | +| 0 | 1 | 0 | 1 | 1 | 3 bits/sample ADPCM d) | +| 0 | 1 | 1 | 0 | 0 | 4 bits/sample ADPCM d) | +| 0 | 1 | 1 | 0 | 1 | 5 bits/sample ADPCM d) | +| 0 | 1 | 1 | 1 | 0 | Reserved for future use | +| 0 | 1 | 1 | 1 | 1 | Reserved for future use | +| 1 | 0 | 0 | 0 | 0 | Reserved for future use | +| 1 | 0 | 0 | 0 | 1 | Reserved for future use | +| 1 | 0 | 0 | 1 | 0 | Reserved for future use | +| 1 | 0 | 0 | 1 | 1 | Reserved for future use | +| 1 | 0 | 1 | 0 | 0 | (4,2) embedded ADPCM e) | +| 1 | 0 | 1 | 0 | 1 | (5,2) embedded ADPCM e) | +| 1 | 0 | 1 | 1 | 0 | Reserved for future use | +| 1 | 0 | 1 | 1 | 1 | Reserved for future use | +| 1 | 1 | 0 | 0 | 0 | (8,6) embedded ADPCM f) | +| 1 | 1 | 0 | 0 | 1 | Reserved for future use | +| | | ... | | | | +| | | ... | | | | +| 1 | 1 | 1 | 1 | 1 | Reserved for future use | + +- a) Reserved coding types will be assigned as other voice coding algorithms are standardized. In particular, coding types will be assigned for 8 kbit/s and 4 kbit/s coding algorithms intended for digital cellular radio applications. The specific voice packet information field format and length, and the voice transport procedures, will depend on the coding algorithm. In particular, these matters will depend on whether the coding algorithm has a natural block length, has variable rates, or has droppable bits. +- b) This is to carry $8 \times N$ kbit/s on transparent channels. +- c) Interoperability issues is an item for further study. +- d) Recommendation G.726. +- e) Applications of the (5,4), (5,3), (4,3), (3,3), and (3,2) ADPCM algorithms are left for study. +- f) Recommendation G.722. The procedure for going from an H.221 frame structure to Recommendation G.764 is an item for further study. + +FIGURE 5/G.764 + +##### Coding type (CT) format + +| Bit number | Noise leve | +|------------|------------| +| 4321 | (dBmc0) | +| 0000 | Idle Code | +| 0001 | 16.6 | +| 0010 | 19.7 | +| 0011 | 22.6 | +| 0100 | 24.9 | +| 0101 | 26.9 | +| 0110 | 29.0 | +| 0111 | 31.0 | +| 1000 | 32.8 | +| 1001 | 34.6 | +| 1010 | 36.2 | +| 1011 | 37.9 | +| 1100 | 39.7 | +| 1101 | 41.6 | +| 1110 | 43.8 | +| 1111 | 46.6 | + +FIGURE 6/G.764 + +###### **Noise field format** + +#### 3.3.1.8 *Voice information field* + +The voice information field contains blocks arranged according to the significance of the bits. The first block contains the MSBs of all samples, the second contains the second MSBs and so on. Within a block, bits are ordered according to their corresponding sample numbers. + +Figure 7/G.764 shows the bit nomenclature convention before packetization and the information field format after packetization. Figure 8/G.764 depicts the format of the entire voice packet where the voice is coded using an embedded (5,2) ADPCM algorithm. Here, up to 3 blocks can be dropped. Note the most significant bit for PCM is the sign bit. + +### 3.3.2 *Signalling packet format* + +The format of the channel associated signalling packets is shown in Figure 9/G.764 within a UI signalling frame format. See § 3.3.1 regarding the setting of the reserved bits. + +#### 3.3.2.1 *Protocol discriminator* + +The format and encoding of the PD field are the same as in the voice packet format (see § 3.3.1.1). + +#### 3.3.2.2 *Block dropping indicator* + +The format of the BDI field is the same as in the voice packet format (see § 3.3.1.2). Both the C-subfield and the M-subfield are set to 0. + +Sample number + +| | | | | | +|------|----------|--------------|-----|----------| +| S1 | MSB/S1 | (MSB-1)/S1 | ... | LSB/S1 | +| S2 | MSB/S2 | (MSB-1)/S2 | ... | LSB/S2 | +| . | | | | | +| . | | | | | +| . | | | | | +| S128 | MSB/S128 | (MSB-1)/S128 | ... | LSB/S128 | + +a) Pre-packetization bit format + +| Bit number | 8 | 7 | | 1 | +|-------------|--------------|--------------|-----|--------------| +| MSB block | MSB/S8 | MSB/S7 | ... | MSB/S1 | +| | . | | | | +| | MSB/S128 | MSB/S127 | ... | MSB/S121 | +| MSB-1 block | (MSB-1)/S8 | (MSB-1)/S7 | ... | (MSB-1)/S1 | +| | . | | | | +| | (MSB-1)/S128 | (MSB-1)/S127 | ... | (MSB-1)/S121 | +| . | . | | | | +| . | . | | | | +| . | . | | | | +| LSB block | LSB/S8 | LSB/S7 | ... | LSB/S1 | +| | . | | | | +| | LSB/S128 | LSB/S127 | ... | LSB/S121 | + +b) Voice packet information field + +FIGURE 7/G.764 + +##### **Bit-ordering within voice packet information fields** + +| | | | | | | | | +|--------------|----------------|-------------------------------------|-----------------------------------------|-------------------------|---------------------------|--------------------------|---------------| +| Frame header | Layer 3 header | Most significant non-droppable bits | 2nd Most significant non-droppable bits | Last-128-droppable bits | Second-128-droppable bits | First-128-droppable bits | Frame trailer | +|--------------|----------------|-------------------------------------|-----------------------------------------|-------------------------|---------------------------|--------------------------|---------------| + +FIGURE 8/G.764 + +##### **Block arrangement for (5,2) ADPCM coding** + +![](af7916c89a458fdab6c3f443217388ae_img.jpg) + +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | +|--------------------------|---|---|---|---|---|---|-----|---------| +| Address (upper subfield) | | | | | | 0 | 0 | Octet 1 | +| Address (lower subfield) | | | | | | | 1 | Octet 2 | +| UI control field | | | | | | | | | +| 0 | 0 | 0 | P | 0 | 0 | 1 | 1 | Octet 3 | +| Protocol discriminator | | | | | | | | | +| 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | Octet 4 | +| Block dropping indicator | | | | | | | | | +| R | R | 0 | 0 | R | R | 0 | 0 | Octet 5 | +| Time stamp | | | | | | | | Octet 6 | +| 0
M | R | R | R | R | R | R | N/A | Octet 7 | +| Sequence number | | | | A | B | C | D | Octet 8 | +| Check sequence 2 octets | | | | | | | | | + +M More bit + +P Poll bit = 0 (see § 3.2.4) + +R Reserved for future use + +FIGURE 9/G.764 + +##### **UIH signalling frame format** + +#### **3.3.2.3 Time stamp** + +The format of the TS field is the same as in the voice packet format (see § 3.3.1.3). + +#### **3.3.2.4 Normal/alarm state bit** + +The normal/alarm (N/A) bit is used to transfer information on alarm status across a virtual circuit in the direction of transmission from the full rate access side to the packet side. The N/A bit set to 0 indicates normal operation. The N/A bit set to 1 indicates the existence of an alarm on the full rate access facility or error condition on the virtual circuit. + +#### **3.3.2.5 M-bit** + +The M-bit shall be set to 0 in all signalling packets. + +#### **3.3.2.6 Sequence number** + +The SEQ for signalling packets is always set to 0. + +#### **3.3.2.7 ABCD signalling bits** + +The originating endpoint uses the ABCD signalling bits to indicate to the terminating endpoint on the far side the current signalling state of the full rate access channel in the direction of transmission. The value of the A bit alone is meaningful in two-state signalling systems. The value of the A and B bits alone are meaningful in four-state signalling + +systems. The values of all ABCD bits are meaningful in 16-state signalling systems. The values of the ABCD bits have no significance when there is no channel associated signalling. + +The number of signalling states must be the same for both the originating and terminating endpoints on a virtual circuit basis. The values coded in this field depend on the framing type and the number of signalling states. + +# 4 Link layer procedures + +## 4.1 Addressing + +Voice and signalling transport packets are transmitted on different layer 2 addresses. + +## 4.2 Endpoint procedures + +These procedures apply for UI and UIH frames. + +### 4.2.1 Transmitting UI frames + +Information received by the link layer entity from layer 3 by means of a DL-UNIT-DATA request shall be transmitted as unnumbered information with a FCS. The P bit shall be set to 0. The list of all primitives used in the procedures is given in § 9. + +### 4.2.2 Transmitting UIH frames + +Information received by the link layer entity from layer 3 by means of a DL-UNIT-H-DATA request shall be transmitted as unnumbered information with an HCS. The P bit shall be set to 0. + +### 4.2.3 Receiving UI frames + +When a link layer entity is not in a receiver busy condition and receives a valid UI frame, the link layer entity shall pass the information field of this frame to layer 3 using the primitive DL-UNIT-DATA indication. + +### 4.2.4 Receiving UIH frames + +When a link layer entity is not in a receiver busy condition and receives a valid UIH frame, the link layer entity shall pass the information field of this frame to layer 3 using the primitive DL-UNIT-H-DATA indication. + +## 4.3 Intermediate node procedures + +### 4.3.1 Transmitting a frame + +Whenever a frame is received from the link layer entity receive procedure, the frame shall be transmitted with the same frame type, including the P bit value, and the C/R bit value as in the received frame. + +### 4.3.2 Receiving a frame + +Detected invalid frames (e.g. failed FCS or HCS, unassigned DLCI) shall be discarded with no indication passed to layer 3. The control field of the frame shall be examined. Upon recognition of UI or UIH frame types, the frame is passed to layer 3 with the DL-PVP-DATA indication primitive for UI frames and DL-PVP-H-DATA indication primitive for UIH frames. + +The Address and CS are the only fields modified during the link layer procedure. + +# 5 Voice transport procedures + +Voice transport procedures are divided into originating, intermediate and terminating node (endpoint) procedures. Originating endpoints are nodes where user data are formulated into PVP packets for transport. Intermediate nodes are nodes that do not alter the packet format, but simply receive and transport PVP packets. Terminating endpoints are the destination nodes for PVP packets. It is assumed that the processing of primitives requires a fixed amount of time. Any time variance in the processing of primitives shall be accounted for in the value of the timer TVDELAY\_V. + +Figure 10/G.764 shows a functional viewpoint of an endpoint node, which shows that it consists of an originating endpoint and a terminating endpoint. + +![Diagram of an Endpoint node showing the flow between the Full rate side and the Packet side through Originating and Terminating end points.](33ed1f9b27c7c21c797aa928b0f06851_img.jpg) + +The diagram illustrates an 'Endpoint node' represented by a large circle. Inside the circle, there are two rectangular boxes: 'Originating end point' at the top and 'Terminating end point' at the bottom. On the left, two horizontal lines labeled 'Full rate side' enter the circle. The top line connects to the 'Originating end point', and the bottom line connects to the 'Terminating end point'. On the right, two horizontal lines labeled 'Packet side' exit the circle. The top line originates from the 'Originating end point', and the bottom line originates from the 'Terminating end point'. Arrows indicate the direction of data flow: from the 'Full rate side' into the 'Originating end point', from the 'Terminating end point' into the 'Packet side', and also from the 'Packet side' into the 'Terminating end point'. + +Diagram of an Endpoint node showing the flow between the Full rate side and the Packet side through Originating and Terminating end points. + +T1506570-90 + +FIGURE 10/G.764 +**Endpoint node** + +## 5.1 *Originating endpoint procedures* + +The originating endpoint receives segmented data from a higher layer entity via the primitives PL-START request(CODE, NOISE), PL-DATA request(CODE, NOISE) and PL-STOP request(CODE, NOISE). These primitives include information on the type of encoding and noise level associated with the packet. + +### 5.1.1 *Receipt of PL-START request primitive* + +The higher level entity will send to the layer 3 entity, the PL-START request(CODE, NOISE) primitive after it has collected all the samples of the first packet. When the originating endpoint receives the PL-START request(CODE, NOISE) primitive, the layer 3 entity shall start the timer TVDELAY\_V associated with the first packet and shall form a voice packet with M-bit set to 1 and SEQ set to 0. The BDI, CT and Noise fields are encoded based on the coding type and noise level indicated in the primitive PL-START request(CODE, NOISE). + +The layer 3 entity sets the send sequence state variable (SSEQ) to 1 and checks its own congestion level indicator (CLI) to determine whether blocks should be dropped from the packet and the number of blocks to be dropped. If the CLI is greater than 0, then the block dropping procedures of § 5.4 shall be followed. If the CLI is 0, then the block dropping procedures are omitted. The CLI is a local parameter of the node. + +The layer 3 entity shall buffer the packet until notified by the layer 2 entity that layer 1 is ready to transport data. In the absence of facility alarms, this notification shall be conveyed by the primitive DL-L1-READY indication. Upon receipt of the primitive, the timer TVDELAY\_V is stopped and its value shall be copied to the TS field. The value of the TS field shall not exceed 200. + +The packet is then delivered to the layer 2 entity with the primitive DL-UNIT-H-DATA request. + +### 5.1.2 *Receipt of the PL-DATA request primitive* + +After receiving the PL-DATA request(CODE, NOISE) primitive from a higher layer entity, the PVP layer 3 entity shall start the timer TVDELAY\_V and form a voice packet with the M-bit set to 1 and the SEQ set to the value of the SSEQ. The BDI, CT and noise fields are encoded on the basis of the corresponding information in the PL-DATA request primitive. The layer 3 entity increments the SSEQ (value from 1 to 15 with a roll over to 1). It shall check the CLI to determine the need for block dropping. If the CLI is greater than 0, then the block dropping procedure of 5.4 shall be followed. If the CLI is 0, then the block dropping procedure shall be omitted. + +The layer 3 entity shall await the arrival of the DL-L1-READY indication primitive from layer 2. Upon receipt of the primitive, the timer TVDELAY\_V is stopped and its value shall be copied to the TS field. The layer 3 entity shall pass the voice packet to the layer 2 entity for transport using the DL-UNIT-H-DATA request primitive. + +### 5.1.3 Receipt of the PL-STOP request primitive + +When a higher layer entity detects a gap in the speech, it will continue the packetization until all 128 samples have been packetized. It will then send the PL-STOP request primitive to the layer 3 entity. The layer 3 entity shall follow the procedures outlined above following receipt of the PL-DATA request except that it shall set the M-bit to 0. + +### 5.1.4 Number of blocks and packetization interval + +The packetization interval is 16 ms. The number of blocks of 128 bits collected during this interval depends on the coding type, as shown in Table 3/G.764. + +TABLE 3/G.764 + +#### **Blocks collected during the packetization interval for various coding types** + +| Coding type | Number of blocks | +|---------------------------------|------------------| +| 8 bits/sample | 8 | +| 1 bit/sample | 1 | +| 2 bits/sample | 2 | +| 3 bits/sample | 3 | +| 4 bits/sample | 4 | +| 5 bits/sample | 5 | +| 6 bits/sample | 6 | +| 7 bits/sample | 7 | +| 8 bit PCM (A-law or $\mu$ -law) | 8 | +| 2 bits/sample ADPCM | 2 | +| 3 bits/sample ADPCM | 3 | +| 4 bits/sample ADPCM | 4 | +| 5 bits/sample ADPCM | 5 | +| (4,2) embedded ADPCM | 4 | +| (5,2) embedded ADPCM | 5 | +| (8,6) embedded ADPCM | 8 | + +### 5.1.5 Coder reset + +When the coding type represents that of Recommendations G.722, G.726 or G.727, a voice packet at the beginning of a speech burst (*i.e.* with SEQ = 0) must start with a reset coder. + +Interoperability issues with PCM coding is an issue for further study. + +## 5.2 Intermediate node procedures + +Upon receipt of the DL-PVP-H-DATA indication primitive, the layer 3 entity will start timer TVDELAY\_V associated with that packet. The layer 3 entity shall examine the value encoded in the PD field. If this value matches that for PVP, the layer 3 entity shall examine the CLI which is a system variable. The CLI shall be set by the management entity to indicate the number of blocks to be dropped from packets containing droppable blocks (0, 1, 2 or 3 blocks may be specified). + +If the CLI is greater than 0, then blocks may be dropped from the packet according to the block dropping procedures described below. If the CLI is 0, then no block dropping shall occur. + +The packet shall then be buffered until the layer 3 entity receives the primitive DL-L1-READY indication from layer 2. Upon receipt of this primitive, the variable delay timer TVDELAY\_V shall be stopped and its value shall be used to update the packet's time stamp. The resolution of TVDELAY\_V is 1 ms. The value of the TS field shall not exceed 200 ms. + +The layer 3 entity shall then pass the information to the layer 2 entity via the DL-PVP-H-DATA request primitive. + +## 5.3 Terminating endpoint procedures + +Upon receipt of the DL-UNIT-H-DATA indication primitive, the layer 3 entity shall examine the value encoded in the PD field. If this value matches that for PVP, the layer 3 entity will proceed as below. + +### 5.3.1 Illegal BDI/coding type combinations + +The packet is dropped if the combination of the CT field and the BDI is illegal. The state variable RSEQ is not updated. + +Illegal combinations are those where the C-subfield value and/or the M-subfield value of the BDI field exceed the number of droppable bits specified by the coding type. Valid combinations are defined in Table 4/G.764. + +TABLE 4/G.764 + +**Valid BDI/CT combinations** + +| Coding type | M-subfield value | C-subfield value | +|----------------------|------------------|------------------| +| PCM | 0 | 0 | +| Fixed ADPCM | 0 | 0 | +| (m,n) embedded ADPCM | $(m-n)$ | $\leq (m-n)$ | + +### 5.3.2 *Wrong packet length* + +A voice packet shall be dropped if its length is not consistent with the BDI and CT fields. The state variable RSEQ shall not be updated. The following equation gives the valid packet length based on the BDI subfield values and the CT: + +$$l = \frac{[S - (M - C)] \times R \times T}{8} + 5$$ + +where + +*l* is the packet length in octets + +*S* is the number of bits per sample (from coding type) + +*M* is the value of M-subfield (from BDI) + +*C* is the value of C-subfield (from BDI) + +*R* is the sampling rate (8000 samples/sec) + +*T* is the sampling period (16 ms) + +### 5.3.3 *Play-out procedures* + +#### 5.3.3.1 *Decoder reset* + +When the coding type represents that of G.722, G.726 or G.727, a voice packet at the beginning of a speech burst (i.e. with SEQ = 0) must cause the decoder to reset. This is done by sending to the management entity the primitive MPL-DECODER-RESET request. + +Interoperability issues with PCM coding is an issue for further study. + +#### 5.3.3.2 *Build-out delay procedures* + +The build-out delay is a system variable that defines at each end the maximum allowable variable delay in the transmission path. The purpose is to mask the variability in the delay that each packet may experience so that all packets are played at regular intervals thereby achieving packet voice synchronization. This value shall be always $\leq 199$ ms. Packets that experience delays beyond the build-out value are discarded. The policy of packet replacement is left for further study. + +Packets that are played out based on the TS value are: + +- 1) packets with SEQ = 0, i.e. the first packet in a voice burst and all signalling packets; +- 2) the voice packet that follows a missing packet, i.e. SEQ in the received packet is different from receive sequence state variable (RSEQ). + +When the time for playing out a packet is based on the TS, the duration it is held before play-out is given by: + +$$(\text{Build-out delay}) - (\text{TS value}) = (\text{ms to hold packet before play-out}).$$ + +The packet shall be played out at the end of this period. + +Packets with non-zero sequence numbers that are received in sequence are played out without a gap after the preceding packet. + +The state variable RSEQ is updated after a voice packet has been scheduled for play-out. + +#### 5.3.3.3 *Embedded ADPCM* + +For embedded ADPCM, the receiving end determines the algorithm to use for decoding the speech through the BDI and CT fields. + +#### 5.3.3.4 *Absence of packets* + +In the absence of packets to be played, the M-bit of the previous packet can be used to determine whether an interpolation procedure is necessary. + +The M\_LAST system variable stores the value of the M-bit in the last packet. + +If M\_LAST = 0, the gap is legitimate and the terminating endpoint shall play out the background noise level that corresponds to the value encoded in the noise field of the last received voice packet, as given in the table of Figure 6/G.764. If M\_LAST = 1, then a packet was lost. Recommended interpolation procedures, e.g. noise fill or last packet replay, are left for further study. + +## 5.4 *Block dropping procedures* + +Embedded coding algorithms allow for droppable and non-droppable bits within the packet. Dropping the first droppable bit of each sample corresponds to dropping the last block in the packet. + +When the CLI specifies the dropping of 1 or more blocks, the layer 3 entity shall determine from the C-subfield (in the BDI field) of a packet the number of droppable blocks available for dropping. The number of blocks that can be still dropped is given by: + +$$\min(\text{value in C-subfield}, \text{value in CLI})$$ + +The C-subfield of the BDI shall be updated to indicate the number of blocks that can be dropped at the following nodes. This number can be set to 0 if no blocks can be dropped at the following nodes. + +# 6 **Signalling transport procedures** + +## 6.1 *General principles* + +Channel associated signalling is transported across the packet network using signalling packets. To minimize the incorrect delivery of signalling information, channel associated signalling is transported in a UI frame with a different logical address than that of the corresponding UIH frame that transports the voice information. + +There are two types of signalling packets: signalling transition packets and refresh packets. Both have the same structure shown in Figure 9/G.764 and are enclosed in UI frames. The originating end sends a signalling transition packet whenever the signalling state changes. It sends refresh packets on a periodic basis to indicate that the link is still active. + +The endpoints will generate and receive signalling packets for each virtual circuit provisioned for channel associated signalling. To account for a variety of signalling schemes, the endpoints shall provide for the following variations: + +- 1) No signalling packets. +- 2) Signalling refresh packets only. +- 3) Signalling refresh packets and signalling transition packets for 2-state signalling using the A bit. Changes in the A bit result in transition packets while other bits are ignored. +- 4) Four-state signalling using the A and B bits so that signalling refresh packets and signalling transition packets for changes in the A and B bits result in transition packets while other bits are ignored. +- 5) Signalling refresh packets and signalling transition packets for 16-state signalling using the A, B, C, and D bits so that transitions in any of the four signalling bits trigger transition packets. + +The number of signalling states must be the same for both the originating and terminating endpoints on a virtual circuit basis. The values coded in this field depend on the framing type and the number of signalling states. + +It is assumed that the processing of primitives requires a fixed amount of time. Any time variance in the processing of primitives shall be accounted for in the value of the timer TVDELAY\_SIG. + +## 6.2 *Originating endpoint procedures* + +The management entity of the originating endpoint shall perform the following procedures for each virtual circuit provisioned to support channel associated signalling: + +- 1) Determine, once per extended superframe, the current state of the ABCD bits and determine whether a transition has occurred in accordance with the number of signalling states supported. +- 2) When a transition occurs, the management entity shall send MPL-SIG-PKT request (A,B,C,D,N/A) primitive to the originating end of the PVP entity. This originating endpoint must then transmit a transition signalling packet containing the current signalling and alarm states. + +The originating endpoint starts in the NORM state. In this state, signalling packets (refresh packets) with the current signalling and alarm states as indicated by the N/A bit must be sent at least every TSIG\_REF s. The default value for the refresh timer, TSIG\_REF, is 10 seconds. + +The N/A bit is set to 0 as long as there are no facility alarms (out-of-frame, red or yellow alarms) and that TSIG\_KA timer has not expired. The N/A bit shall be set to 1 if there is a facility alarm or if the TSIG\_KA timer of the associated terminating end has expired (i.e. the terminating end is in state L\_ALARM). Upon the occurrence of a facility alarm, the originating end of the PVP entity shall move from the NORM state to the ALARM state and shall stop transmitting transition packets. It shall continue to send refresh packets every TSIG\_REF seconds with the N/A bit set to 1. + +The signalling state is frozen until the alarm condition is terminated and the originating endpoint moves back to the NORM state. In the NORM state, the originating endpoint sends packets with the N/A bit set to 0 after the associated terminating endpoint has received a signalling packet. + +## 6.3 *Intermediate node signalling procedures* + +Upon receipt of the DL-PVP-DATA indication primitive, the layer 3 entity will start timer TVDELAY\_SIG associated with that packet. The layer 3 entity shall examine the value encoded in the PD field. If this value matches that for PVP, the layer 3 entity shall buffer the packet until it receives the primitive DL-L1-READY indication from layer 2. Upon receipt of this primitive, the variable delay timer TVDELAY\_SIG shall be stopped and its value shall be used to update the packet's time stamp. The resolution of TVDELAY\_SIG is 1 ms. The value of the TS field shall not exceed 200 ms. + +The layer 3 entity shall then pass the signalling information to the layer 2 entity via the DL-PVP-DATA request primitive. + +## 6.4 *Terminating endpoint procedures* + +The terminating endpoint shall perform the following procedures for each 64 kbit/s stream provisioned for channel associated signalling: + +- 1) In the NORM state: Upon receipt of a signalling packet, the terminating endpoint shall build out the packet according to the time stamp and reinsert the A B C D bits into the PCM bit stream. The build-out procedure is the same as for voice packets (see § 6.3.3.2) except that at play-out time, the layer 3 entity informs the Management Entity of the signalling packet with the primitive MPL-SIG-PKT indication (A,B,C,D,N/A). The terminating endpoint shall continue to use the most recent signalling bits until another signalling packet is received. +- 2) If no signalling packet is received for a time TSIG\_KA (i.e. TSIG\_KA has expired), the terminating endpoint shall move to the L\_ALARM state and shall initiate trunk conditioning towards the full rate access side. The default value for TSIG\_KA is 25 seconds. Upon receipt of a signalling packet with the N/A bit set to 0, the terminating end of the PVP entity shall move to the NORM state and shall terminate the trunk conditioning. + +- 3) In the NORM state: Upon receipt of a signalling packet with the N/A bit set to 1, the terminating end of the PVP entity shall move to the R\_ALARM state and shall initiate trunk conditioning towards the full rate access side. It shall return to the NORM state and terminate the trunk conditioning when it receives a signalling packet with the N/A bit set to 0. +- 4) If the TSIG\_KA expires in the R\_ALARM state, the terminating end shall move to the L\_ALARM state. +- 5) If a signalling packet arrives with N/A = 1 in the L\_ALARM state, the terminating end shall move to the R\_ALARM state. + +## 6.5 *Signalling states* + +### 6.5.1 *Originating end signalling states* + +The originating end has two signalling states, as follows: + +#### 6.5.1.1 *Normal state* + +In this state there are no access facility alarms on the full rate access side. + +#### 6.5.1.2 *Alarm state* + +This is the state when there is a facility alarm on the full rate access side. + +### 6.5.2 *Terminating end signalling states* + +The terminating endpoint has three signalling states: + +#### 6.5.2.1 *Normal state (NORM)* + +The terminating endpoint remains in this state as long as signalling packets arrive with N/A bit set to 0 and TSIG\_KA has not expired. + +#### 6.5.2.2 *Loss of keep alive alarm (L\_ALARM)* + +The timer TSIG\_KA has expired without the reception of a signalling packet. This indicates that a failure has occurred with the packet portion of the connection and normal signalling packet transport has been interrupted. + +#### 6.5.2.3 *Remote alarm (R\_ALARM)* + +Receipt of signalling packet with N/A bit set to 1 indicates that the far end is experiencing an alarm condition. + +# 7 **System variables** + +## 7.1 *Send sequence state variable* + +Each transmitting endpoint shall have an associated SSEQ that stores the value of the SEQ of the next packet to be transmitted. SSEQ can take on the value of 0 through 15 and is incremented by 1 after each successful packet transmission. When SSEQ has the value 15 and another packet of the same voice burst is transmitted, the value of SSEQ is updated to 1. + +## 7.2 *Receive sequence state variable* + +Each terminating endpoint shall have an associated RSEQ that stores the sequence number of the next in-sequence voice packet expected to arrive. RSEQ can take on the value of 0 through 15 and is incremented by 1 (with roll-over to 0) after the voice packet is scheduled for play-out. RSEQ takes on the value 0 only when the last packet of a voice burst has been scheduled for play-out. + +## 7.3 *M\_LAST variable* + +*M\_LAST* stores the value of the M-bit in the last packet. + +## 7.4 *Congestion level indicator (CLI) variable* + +The CLI is set by the management entity to indicate the number of blocks to be dropped from packets containing droppable blocks (0, 1, 2, or 3 blocks may be specified). + +# 8 **Protocol parameters** + +## 8.1 *Build-out delay* + +The value of the build-out delay shall be equal to the maximum allowable variable delay in the transmission path of voice-band traffic. This value shall be $\leq 199$ ms. The resolution of the build-out delay is 1 ms. + +## 8.2 *TSIG\_REF* + +The interval between successive transmissions of refresh signalling packets from the originating end point of the node containing the PVP entity. It may take the values of 1, 5, 10 or 20 s. The default value is 10 s. + +## 8.3 *TSIG\_KA* + +This is the maximum time allowed without receiving a signalling packet at the terminating end of a node containing the PVP entity before it must take recovery actions. *TSIG\_KA* is a multiple of *TSIG\_REF*. The multiplier may be set to 1.5, 2.5, 3.5 or 4.5. The default value of the multiplier is 2.5. + +## 8.4 *TVDELAY\_V* + +This timer is used to measure the variable queueing delay in a node that a voiceband packet encounters. It is used to update the TS field of a voice-band packet. + +## 8.5 *TVDELAY\_SIG* + +This timer is used to measure the variable queueing delay in a node that a signalling packet encounters. + +It is used to update the TS field of a signalling packet. + +# 9 **Summary of primitives** + +## 9.1 *Primitives for the interface with layer 2* + +The layer 2 primitives used for PVP are described below: + +### 9.1.1 *DL-LI-READY indication* + +This primitive is used to indicate to layer 3 that layer 1 is ready for transmission. + +### 9.1.2 *DL-UNIT-DATA request* + +The DL-UNIT-DATA request primitive is used by the layer 3 entity to request the transmission of layer 3 messages which are to be transmitted by the data link layer in UI frames using the unacknowledged information transfer service. + +### 9.1.3 *DL-UNIT-DATA indication* + +The DL-UNIT-DATA indication primitive is used to indicate receipt by the data link layer of PVP at the terminating endpoint of layer 3 messages that are enclosed UI frames. + +### 9.1.4 *DL-UNIT-H\_DATA request* + +The DL-UNIT-H\_DATA request primitive is used by the layer 3 entity to request the transmission of layer 3 messages which are to be transmitted by the data link layer in UIH frames using the unacknowledged information transfer service. + +### 9.1.5 *DL-UNIT-H-DATA indication* + +The DL-UNIT-H-DATA indication primitive is used to indicate receipt by the data link layer of PVP at the terminating endpoint of layer 3 messages that are enclosed in UIH frames. + +### 9.1.6 *DL-PVP-H-DATA indication* + +The DL-PVP-H-DATA indication primitive is used to indicate receipt by the data link layer of PVP at intermediate nodes of layer 3 messages in UIH frames. + +### 9.1.7 *DL-PVP-DATA indication* + +The DL-PVP-DATA indication primitive is used by the data link layer of PVP intermediate nodes to indicate receipt of layer 3 messages in UI frames. + +### 9.1.8 *DL-PVP-H-DATA request* + +The DL-PVP-H-DATA request primitive is used by the layer 3 entity of an intermediate node to indicate to the data link layer a layer 3 message to be transported in a UIH frame. + +### 9.1.9 *DL-PVP-DATA request* + +The DL-PVP-DATA request primitive is used by the layer 3 entity of an intermediate node to indicate to the data link layer a layer 3 message to be transported in a UI frame. + +## 9.2 *Primitives for the interface with upper layers* + +### 9.2.1 *PL-START request(CODE, NOISE)* + +The PL-START request(CODE, NOISE) primitive is used by the higher layer of the originating endpoint to request that the layer 3 entity begin formatting voice packets with the CT = CODE and the Noise = NOISE. + +### 9.2.2 *PL-DATA request(CODE, NOISE)* + +The PL-DATA request(CODE, NOISE) primitive is used by the higher layer of the originating endpoint to continue the formatting voice packets with the CT = CODE and the Noise = NOISE. + +### 9.2.3 *PL-STOP request* + +The PL-STOP request primitive is used by upper layers to indicate the end of a speech burst. + +## 9.3 *Primitives for the interface with the management entity* + +### 9.3.1 *MPL-DECODER-RESET request* + +The MPL-DECODER-RESET request primitive is used by layer 3 of the PVP originating endpoint to request resetting of the decoder by the management entity. + +### 9.3.2 *MPL-SIG-PKT request(A,B,C,D,N/A)* + +This primitive is used by the management entity to request transmission of a transition signalling packet by the PVP layer 3. + +### 9.3.3 *MPL-SIG-PKT indication(A,B,C,D,N/A)* + +This primitive is used by the layer 3 entity to inform the management entity of the play-out of a signalling packet by the PVP layer 3. \ No newline at end of file diff --git a/marked/G/T-REC-G.766-199611-I_PDF-E/01d733d2c659cc6ddafbe79ae770c01f_img.jpg b/marked/G/T-REC-G.766-199611-I_PDF-E/01d733d2c659cc6ddafbe79ae770c01f_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..1c1f74e5c1444de1c988e616c8be26b8cce91da3 --- /dev/null +++ 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ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with a lightning bolt and the letters ITU. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.766** + +(11/96) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA + +Digital transmission systems – Terminal equipments – +Principal characteristics of transcoder and digital +multiplication equipment + +--- + +**Facsimile demodulation/remodulation for +digital circuit multiplication equipment** + +ITU-T Recommendation G.766 + +(Previously CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| INTERNATIONAL ANALOGUE CARRIER SYSTEM | | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA CHARACTERISTICS | | +| DIGITAL TRANSMISSION SYSTEMS | | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| General | G.700–G.709 | +| Coding of analogue signals by pulse code modulation | G.710–G.719 | +| Coding of analogue signals by methods other than PCM | G.720–G.729 | +| Principal characteristics of primary multiplex equipment | G.730–G.739 | +| Principal characteristics of second order multiplex equipment | G.740–G.749 | +| Principal characteristics of higher order multiplex equipment | G.750–G.759 | +| Principal characteristics of transcoder and digital multiplication equipment | G.760–G.769 | +| Operations, administration and maintenance features of transmission equipment | G.770–G.779 | +| Principal characteristics of multiplexing equipment for the synchronous digital hierarchy | G.780–G.789 | +| Other terminal equipment | G.790–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| General | G.900–G.909 | +| Parameters for optical fibre cable systems | G.910–G.919 | +| Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s | G.920–G.929 | +| Digital line transmission systems on cable at non-hierarchical bit rates | G.930–G.939 | +| Digital line systems provided by FDM transmission bearers | G.940–G.949 | +| Digital line systems | G.950–G.959 | +| Digital section and digital transmission systems for customer access to ISDN | G.960–G.969 | +| Optical fibre submarine cable systems | G.970–G.979 | +| Optical line systems for local and access networks | G.980–G.999 | + +For further details, please refer to ITU-T List of Recommendations. + +# **ITU-T RECOMMENDATION G.766** + +# **FACSIMILE DEMODULATION/REMODULATION FOR DIGITAL CIRCUIT MULTIPLICATION EQUIPMENT** + +###### **Source** + +ITU-T Recommendation G.766 was revised by ITU-T Study Group 15 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 8th of November 1996. + +## FOREWORD + +ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, the ITU had/had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 1997 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +## CONTENTS + +###### Page + +| | | | +|-------|------------------------------------------------------------------|----| +| 1 | General..... | 1 | +| 1.1 | Abbreviations..... | 1 | +| 2 | Definitions of facsimile demodulation/remodulation in DCME ..... | 3 | +| 3 | Functions of the facsimile module..... | 3 | +| 4 | Facsimile module structure..... | 5 | +| 5 | Facsimile frame assembler/disassembler blocks ..... | 7 | +| 5.1 | Facsimile data channel..... | 7 | +| 5.2 | Facsimile module frame..... | 9 | +| 5.2.1 | Facsimile control channel..... | 10 | +| 5.3 | Facsimile blocks ..... | 11 | +| 5.3.1 | FEC encoding ..... | 11 | +| 5.4 | Facsimile transport channels..... | 11 | +| 6 | Facsimile module controller ..... | 13 | +| 6.1 | Common control function..... | 13 | +| 6.1.1 | Communication with the ADF ..... | 14 | +| 6.1.2 | Other communication functions ..... | 14 | +| 6.1.3 | Capacity management..... | 14 | +| 6.1.4 | FCH management..... | 15 | +| 6.1.5 | Demodulator/remodulator pool management..... | 15 | +| 6.2 | Facsimile Channel Handler (FCH) ..... | 15 | +| 6.2.1 | FCH requirements..... | 17 | +| 6.2.2 | FCH protocol ..... | 17 | +| 7 | Use of the facsimile control channel..... | 24 | +| 7.1 | Message field structure ..... | 24 | +| 7.2 | Message transmission procedure ..... | 29 | +| 7.3 | Service channel ..... | 30 | +| 8 | Timing and delay requirements..... | 30 | +| 8.1 | Clock difference compensation..... | 30 | +| 8.1.1 | Demodulator side..... | 30 | +| 8.1.2 | Remodulator side..... | 31 | +| 8.2 | Critical time gaps of the T.30 signals ..... | 31 | +| 8.2.1 | Demodulator side requirements..... | 31 | +| 8.2.2 | Remodulator side requirements..... | 31 | + +| | Page | | +|------------------------------------------------------------------------|-------------------------------------------------------------|-----| +| 8.3 | Front-End Delay (FED) buffer..... | 32 | +| 9 | Multi-clique and multi-destination operation ..... | 32 | +| 10 | Facsimile module operation and maintenance..... | 32 | +| 10.1 | Facsimile module statistics ..... | 32 | +| 10.2 | Facsimile module configuration data..... | 34 | +| 10.3 | Error count ..... | 34 | +| 10.4 | FEC activation ..... | 34 | +| 11 | Required DCME modifications ..... | 35 | +| 11.1 | Facsimile data handling ..... | 35 | +| 11.2 | Changes in the DCME processes..... | 35 | +| Annex A – Examples of FCH protocol exchanges ..... | | 36 | +| A.1 | SF-T.30 cases with matched capabilities..... | 36 | +| A.2 | NSF-T.30 proprietary cases with matched capabilities..... | 55 | +| A.3 | SF-T.30 cases with unmatched capabilities..... | 58 | +| A.4 | NSF-T.30 proprietary cases with unmatched capabilities..... | 62 | +| Annex B – Formal description of the facsimile module controller..... | | 64 | +| B.1 | Introduction..... | 64 | +| B.2 | FMC interfaces..... | 64 | +| B.3 | Internal structure of the FMC..... | 70 | +| B.4 | Common control function (CCF)..... | 72 | +| B.5 | FCH..... | 73 | +| Supplement No. 1 – Dimensioning example for facsimile compression..... | | 100 | +| S.1 | Introduction..... | 100 | +| S.2 | Assumptions..... | 100 | +| S.3 | Method ..... | 100 | + +# **FACSIMILE DEMODULATION/REMODULATION FOR DIGITAL CIRCUIT MULTIPLICATION EQUIPMENT** + +*(revised in 1996)* + +# **1 General** + +This Recommendation for a Digital Circuit Multiplication Equipment (DCME) facsimile module is intended to be as flexible as possible in an open-network environment, while providing manufacturers of equipment the license to invent, whilst maintaining equipment interoperability. Use of the facsimile module provides a solution to the DCME traffic loading problem created by the rapid growth of facsimile traffic, which is transmitted via DCME using 40 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) encoding, that rapidly depletes DCME bearer capacity resulting in reduced speech quality. + +The facsimile module (see Figure 1) is a functional unit which permits adding the facsimile compression feature to the DCME. The basic function of the facsimile module is to detect facsimile calls, demodulate the facsimile signals and transmit the demodulated data to the remote facsimile module via the DCME. At the remote facsimile module, the voiceband signal is reconstructed to its original format for transmission to the local terminal equipment. Calls which cannot be demodulated are routed through the G.726 40 kbit/s ADPCM channels of the DCME. + +It is recognized that Group 3 facsimile demodulation/remodulation is only the first feature of a series of voiceband data demodulation/remodulation capabilities which will in all likelihood be extended to the next generation of voiceband data modems operating at bit rates greater than 9600 bit/s. It is anticipated that the modulation schemes for high speed modems will also be incorporated into facsimile machines and such traffic, when presented to DCMEs, must be accommodated. The design of the DCME facsimile module has been structured to carry demodulated data at bit rates up to 24 kbit/s to permit future flexibility. The DCME facsimile module is fully compatible with all of the operating modes of Recommendation G.763 which includes, point-to-point, multi-clique and multi-destination operating modes. + +Careful consideration has been given to error protection. The Forward Error Correction (FEC) provided in the DCME facsimile module is robust against randomly distributed single bit errors. It also fully protects against errors as long as the error event is less than one frame of the primary multiplex multiframe or provided that only one error burst event occurs within a single DCME frame (2 ms). + +There have been two approaches integrated into the DCME facsimile module, a Protocol Analysis (PA) approach and a Waveform Analysis (WA) approach. In order to retain the interoperability objective, compromises were introduced which slightly increased the equipment complexity. If one were to consider only a PA approach or only a WA approach, some simplification would be possible. However, such simplification is not recommended as the open-network interoperability would then be lost. + +## **1.1 Abbreviations** + +This Recommendation uses the following abbreviations: + +ADF ADPCM/DSI Function + +ADPCM Adaptive Differential Pulse Code Modulation + +| | | +|----------|-------------------------------------------------------------| +| BC | Bearer Channel | +| CCF | Common Control Function | +| CRC | Cyclic Redundancy Check | +| DCME | Digital Circuit Multiplication Equipment | +| DCN | Disconnect | +| DCOA | Digital Channel Occupancy Analyser | +| DCS | Digital Command Signal | +| DIS | Digital Identification Signal | +| DSI | Digital Speech Interpolation | +| DTC | Digital Transmit Command | +| EOM | End of Message | +| EOP | End of Procedure | +| EPT | Echo Protection Tone | +| FA | Frame Assembler | +| FCC | Facsimile Control Channel | +| FCH | Facsimile Channel Handler | +| FCM | Facsimile Compression Module | +| FD | Frame Disassembler | +| FDC | Facsimile Data Channel | +| FEC | Forward Error Correction | +| FED | Front-End Delay | +| FMC | Facsimile Module Controller | +| FSTI | Facsimile Statistical Time Interval | +| FTC | Facsimile Transport Channel | +| HDLC | High level Data Link Control | +| HSC | Hangover control and Signal Classification | +| IT | Intermediate Trunk | +| LRE | Low Rate Encoding | +| NSF-T.30 | Non-Standard Facility-T.30 | +| NSS | Non-Standard Set-up | +| O&M | Operation and Maintenance | +| PA | Protocol Analysis | +| RAG | Resource management and Assignment Generation | +| Rx | Receive | +| RUD | Receive channel status Update and overload channel Decoding | +| SDL | Specification and Description Language | +| SF-T.30 | Standard Facility-T.30 | +| Tx | Transmit | +| WA | Waveform Analysis | + +# 2 Definitions of facsimile demodulation/remodulation in DCME + +This Recommendation defines the following terms: + +**2.1 facsimile module:** A functional unit performing the demodulation/remodulation of the facsimile signal and transmission/reception of control codes and demodulated image information via the associated ADPCM/DSI function of the DCME. + +**2.2 ADPCM/DSI function (ADF):** The ADPCM/DSI Function (ADF) of the DCME encompasses all the traffic handling functions specified in Recommendation G.763. + +**2.3 facsimile control channel (FCC):** An unidirectional 32-bit channel (21 information bits, 10 parity bits and 1 dummy bit) used between the transmit unit of one facsimile module to the receive unit of one or more associated facsimile modules which is dedicated primarily to carrying channel assignment messages and control messages. + +**2.4 facsimile data channel (FDC):** A variable length data block containing bits of the demodulated image information or procedural signals, accumulated over a period of 2 ms from one intermediate trunk (IT) (see 2.10/G.763), and clock alignment overhead bits. + +**2.5 facsimile module frame:** A bit sequence consisting of the FDCs ordered by ascending IT number. The sequence starts with the facsimile control channel. + +**2.6 facsimile block:** This is a 32-bit block consisting of either 32 contiguous bits of the facsimile module frame or 21 contiguous bits of the frame FEC encoded with the addition of 10 parity bits and 1 dummy bit. + +**2.7 facsimile transport channel (FTC):** A 32-kbit/s channel that carries a facsimile block from/to the facsimile module to/from the ADF where the facsimile block is placed into/removed (from) a 32-kbit/s bearer channel (see 2.8/G.763). + +**2.8 facsimile compression:** The real time process of demodulating the facsimile signal to its basic digital rate for transparent transmission and subsequent remodulation at the remote end of the DCME link. + +**2.9 facsimile data interface:** The functional interface which permits the transfer of FTC information between the facsimile module and the ADF. + +# 3 Functions of the facsimile module + +The facsimile module (see Figure 1) is a functional unit which permits adding the facsimile compression feature to the DCME. The basic function of the facsimile module is to detect facsimile calls, demodulate the facsimile signals and transmit demodulated data to the remote facsimile module via the DCME bearer. At the remote facsimile module, the voiceband signal is reconstructed to its original format for transmission to the local terminal equipment. Calls which cannot be demodulated are routed through the G.726 40 kbit/s ADPCM channels of the ADF specified in Recommendation G.763. + +The requirements for the facsimile compression function are listed in Table 1. + +![System concept diagram of a Facsimile module connected to Trunks and an ADF. The diagram shows a central 'Facsimile module' box. On the left, a bundle of lines labeled 'Trunks' enters the module. On the right, four numbered interfaces connect the module to a large grey box labeled 'ADF': (1) Transmit fax data interface (outward arrow), (2) Receive fax data interface (inward arrow), (3) Fax control interface (outward arrow), and (4) Fax O&M interface (inward arrow). Above the module, another bundle of lines labeled 'Trunks' exits. A dotted line encloses the module and its associated trunk connections, separating them from the ADF.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg) + +System concept diagram of a Facsimile module connected to Trunks and an ADF. The diagram shows a central 'Facsimile module' box. On the left, a bundle of lines labeled 'Trunks' enters the module. On the right, four numbered interfaces connect the module to a large grey box labeled 'ADF': (1) Transmit fax data interface (outward arrow), (2) Receive fax data interface (inward arrow), (3) Fax control interface (outward arrow), and (4) Fax O&M interface (inward arrow). Above the module, another bundle of lines labeled 'Trunks' exits. A dotted line encloses the module and its associated trunk connections, separating them from the ADF. + +T1522170-96 + +ADF ADPCM/DSI Function + +- ① Transmit fax data interface +- ② Receive fax data interface +- ③ Fax control interface +- ④ Fax O&M interface + +**Figure 1/G.766 – Facsimile module – System concept** + +**Table 1/G.766 – Facsimile compression requirements** + +| | | +|----------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------| +| Facsimile calls compressed | CCITT G3 fax as per T.30 and T.4 standard facilities; optionally, T.30 non-standard facilities | +| Facsimile calls non-compressed (handled by 40 kbit/s ADPCM) | CCITT G1 and G2, some or all non-standard facilities T.30 schemes | +| Image data rate modulation schemes and rates (Note 1) | V.33 (14 400, 12 000, 9600, 7200 bit/s);
V.17 (14 400, 12 000, 9600, 7200 bit/s);
V.29 (9600, 7200 bit/s);
V.27 ter (4800, 2400 bit/s) | +| Control signals demodulated (Note 1) | V.21 (300 bit/s) | +| Remodulated signal level (Note 2) | Demodulator input level processed via 16-level quantizer | +| Facsimile terminal type | Automatic and manual | +| Compression deactivation | Possible on selected circuits | +| DCME operation supported | Single destination, multi-clique and multi-destination operation | +| NOTE 1 – The support of other modulation schemes is for further study.
NOTE 2 – See 7.1 for the quantizer levels. | | + +# 4 Facsimile module structure + +The facsimile module may be external or internal to the DCME depending on the implementation. For purposes of illustration the functional representation of the system concept assumes the facsimile module is external to the DCME. However, an equivalent architecture can be based on an implementation with the facsimile module internal to the DCME. The facsimile module system concept is illustrated in Figure 1. The figure shows functional interfaces between the facsimile module and the ADF, namely the facsimile data interface, the facsimile control interface, and the facsimile Operation and Maintenance (O&M) interface. + +The facsimile data interface is a communication channel which permits the transfer of facsimile image data and auxiliary information between the facsimile module and the DCME. There is one transmit and one receive data interface in single destination operation, two transmit and two receive interfaces in multi-clique operation and one transmit and up to four receive interfaces in multi-destination operation. + +The facsimile control interface carries status and control data for the module interaction with the DCME. The O&M interface is used for the exchange of O&M data with the operation and maintenance subsystem of the DCME or DCME cluster. + +Figure 2 shows the internal structure of the facsimile module. The representation in Figure 2 is only functional and could be replaced by equivalent architectures. The structure in Figure 2 is compatible with two different design approaches for the facsimile compression feature. The first approach, called the Protocol Analysis (PA) approach, is based on decoding and interpreting the procedural signals exchanged between the facsimile terminals. A minimum amount of signal analysis, such as activity detection and low/high speed discrimination, is also performed in this approach. The second approach, called the Waveform Analysis (WA) approach, is based on analysis and classification of + +the modulated waveforms transmitted by the facsimile terminals. This subject is addressed in more detail in 6.2. + +The structure in Figure 2 contains the following blocks: + +- a) demodulator/analysis block; +- b) front-end delay buffer; +- c) facsimile frame assembler and disassembler blocks; +- d) remodulator block; +- e) facsimile module controller. + +The demodulator/analysis block performs signal analysis (WA approach) and demodulates the image data and the low speed procedural signals of the facsimile call. The front-end delay buffer is used to provide sufficient time for signal validation (PA) or analysis (WA). In the PA approach, the contents of the procedural messages are provided to the facsimile module controller. Both the high speed and low speed demodulated data are provided to the facsimile Frame Assembler (FA) for transmission over the facsimile data interface to the ADF. The facsimile Frame Disassembler (FD) extracts the demodulated data from the facsimile frame received from the DCME and passes it to the remodulator block for transmission to the facsimile terminal. + +The Facsimile Module Controller (FMC) is the process that oversees the operation of the entire facsimile module and its interaction with the DCME and the corresponding facsimile module(s). + +The functions of the various blocks are specified in the following clauses. + +![Figure 2/G.766 – Facsimile module structure. A block diagram showing the internal components of a facsimile module. The module is enclosed in a dashed box labeled 'Facsimile module'. Inside, there are several blocks: 'FED buffer', 'Demodulator/analysis block', 'Fax Module Controller (FMC)', 'Fax Frame Assembler (FA)', 'Fax Frame Disassembler (FD)', and 'Remodulator block'. The 'FED buffer' is connected to an input switch (S) and its output is connected to the 'Demodulator/analysis block'. The 'Demodulator/analysis block' is connected to the 'FMC' and the 'FA'. The 'FMC' is connected to the 'FA', 'FD', and 'Remodulator block'. The 'FA' is connected to the 'ADF' (ADPCM/DSI Function) and the 'FD'. The 'FD' is connected to the 'Remodulator block' and the 'ADF'. The 'Remodulator block' is connected to an output switch (S). Control signals from the 'FMC' are sent to the 'FA', 'FD', and switches. A circled '1' is shown on the line between the 'FMC' and the 'FA'. A circled 'S' is shown on the line between the 'FMC' and the 'Remodulator block'. A circled 'C' is shown on the input line. The 'ADF' is shown as a large grey block on the right. A legend at the bottom left defines the symbols: ADF ADPCM/DSI Function, FED Front-end delay, S Switch. A reference code T1522180-96 is at the bottom right.](08441fa90c5fd11994626f662ac13f19_img.jpg) + +ADF ADPCM/DSI Function +FED Front-end delay +S Switch + +T1522180-96 + +Figure 2/G.766 – Facsimile module structure. A block diagram showing the internal components of a facsimile module. The module is enclosed in a dashed box labeled 'Facsimile module'. Inside, there are several blocks: 'FED buffer', 'Demodulator/analysis block', 'Fax Module Controller (FMC)', 'Fax Frame Assembler (FA)', 'Fax Frame Disassembler (FD)', and 'Remodulator block'. The 'FED buffer' is connected to an input switch (S) and its output is connected to the 'Demodulator/analysis block'. The 'Demodulator/analysis block' is connected to the 'FMC' and the 'FA'. The 'FMC' is connected to the 'FA', 'FD', and 'Remodulator block'. The 'FA' is connected to the 'ADF' (ADPCM/DSI Function) and the 'FD'. The 'FD' is connected to the 'Remodulator block' and the 'ADF'. The 'Remodulator block' is connected to an output switch (S). Control signals from the 'FMC' are sent to the 'FA', 'FD', and switches. A circled '1' is shown on the line between the 'FMC' and the 'FA'. A circled 'S' is shown on the line between the 'FMC' and the 'Remodulator block'. A circled 'C' is shown on the input line. The 'ADF' is shown as a large grey block on the right. A legend at the bottom left defines the symbols: ADF ADPCM/DSI Function, FED Front-end delay, S Switch. A reference code T1522180-96 is at the bottom right. + +**Figure 2/G.766 – Facsimile module structure** + +# 5 Facsimile frame assembler/disassembler blocks + +The data formatted by the FA for transmission over the facsimile data interface can be represented as multiple 32-kbit/s channels. However, a number of building blocks must be defined. These are the Facsimile Data Channel (FDC), carrying the demodulated facsimile data of one intermediate trunk (IT) (see 2.10/G.763), the facsimile module frame, where the FDCs are grouped in ascending IT order, the facsimile block, consisting of a block of 32 contiguous bits of the facsimile module frame, and the Facsimile Transport Channel (FTC), a 32-kbit/s channel that provides the facsimile block information, suitably mapped, to the ADF for insertion into the DCME bearer frame. + +An example is provided below in order to illustrate how the demodulated facsimile data is structured for transmission over the DCME bearer. Assume the case where two facsimile calls, both originating at the near end of the DCME link, are being handled by the facsimile module. For both calls, image data is being transmitted at 9.6 kbit/s. + +The demodulated image data of each facsimile call is accumulated for 2 ms before transmission. This corresponds to 21 bits (see 5.1). If the FEC option is used, 10 parity bits and 1 dummy bit are added to the data bits, for a total of 32 bits. This is a facsimile block. At the end of a 2-ms period there will be two facsimile blocks plus one additional 32-bit block, used for control. The three blocks are arranged in an ordered structure (facsimile frame), where the control block is first, and the two image data blocks follow, ordered by ascending trunk number. A total of 96 bits need to be transmitted over the next 2-ms time interval. This is achieved by allocating two 4-bit slots (fax banks) in the 2048 kbit/s DCME bearer. Each 4-bit channel has a capacity of 32 kbit/s; therefore, 128 bits can be transported over a 2-ms period. Two bits of a fax bank are mapped to two bits of one block and the other two bits are mapped to 2 bits of the next block in the frame (see Figure 7). Dummy bits are inserted when there are no more facsimile frame bits to be transported. In this example, fax bank No. 1 will transport facsimile block No. 1 (the control block) and facsimile block No. 2. Fax bank No. 2 will transport facsimile block No. 3 and 32 dummy bits. + +## 5.1 Facsimile data channel + +The demodulated data obtained from each trunk carrying a facsimile call is accumulated for a period of 2 ms (coincident with the DCME frame). Depending on the data rate, the number of bits in 2 ms may be a non-integer number. In order to compensate for this and also for timing differences between the facsimile signal clock and the facsimile frame clock (slaved to the DCME clock), one or two stuffing bits and a control bit are used. Two stuffing bits are used, instead of one, for those rates where the nominal number of data bits accumulated in 2 ms would be an integer number. The stuffing bit(s) may or may not be used in any given frame. If used, the control bit is set to 1. If not used, the control bit is set to 0. When the stuffing bits are not used, their positions are occupied by data bits. Error protection is added to the V.21 (300 baud) demodulated bits by repeating the FDC bits (1 control bit and 1 data/stuffing bit) three times. Majority logic decision is used for decoding. If it is required to transmit stuffing bits after the last V.21 signal bit in the FDC, the maximum allowed number of stuffing bits to be sent shall be 30. The resulting bit structures referred to as a Facsimile Data Channel (FDC) for the three cases above are shown in Figure 3. + +As an example, the case of the 9.6 kbit/s data rate is discussed. In this case, the number of bits accumulated in a 2-ms interval is slightly in excess of 19, so that sometimes 19 and sometimes 20 data bits will be transmitted. The 20th bit of the FDC will therefore be either a dummy bit or a data bit. The 21st bit of the FDC, the control bit, will indicate which of the two cases applies. + +As an additional example, the case of the 12 kbit/s data rate is discussed. In this case, the number of bits accumulated in a 2-ms interval would be theoretically 24, but, in practice, it will be somewhat more or less. Sometimes 23 bits and sometimes 25 bits will be transmitted and, therefore, the 24th bit + +and the 25th bit of the FDC will be either dummy bits or data bits, as indicated by the control bit (the 26th bit of the FDC). + +The number of bits in the FDC depends on the transmission rate of the facsimile signal. Table 2 provides the total number of bits of an FDC, for the different bit rates listed in Table 1 and considering the error protection scheme for V.21 signals (300 bit/s). + +**Table 2/G.766 – Facsimile data channel length** + +| Facsimile transmission rate (kbit/s) | Nominal number of bits in DCME frame | FDC length (bits) | +|--------------------------------------|--------------------------------------|---------------------| +| R | $I(2 \times R)$ | $I(2 \times R) + 2$ | +| 14.4 | 28 | 30 | +| 12.0 | 24 | 26 | +| 9.6 | 19 | 21 | +| 7.2 | 14 | 16 | +| 4.8 | 9 | 11 | +| 2.4 | 4 | 6 | +| 0.3 (Note) | 1 | 6 | + +R Rate in kbit/s (new modems) where the maximum limit is anticipated to be in the range of 24 kbit/s. + +$I()$ Integer part of a number. + +NOTE – Facsimile transmission rate of 0.3 kbit/s is a special case for which the formula does not apply. + +### *FDC with 1 bit stuffing* + +1 bit is either data or a dummy bit as indicated by the control bit value + +![Diagram of FDC with 1 bit stuffing showing a 1-bit data bit, an n-bit data block, a control bit, and data stuffing.](724c7777b608e53be38b12b6fb3c43bc_img.jpg) + +This diagram illustrates the structure of an FDC with 1-bit stuffing. It consists of four vertical segments: a single '1' bit labeled 'Data bits', a block of 'n' bits, a shaded 'Control bit' section, and a hatched 'Data stuffing' section. Arrows point from the labels to their respective sections. + +Diagram of FDC with 1 bit stuffing showing a 1-bit data bit, an n-bit data block, a control bit, and data stuffing. + +### *FDC with 2-bit stuffing* + +A pair of bits are either data or dummy bits as per the control bit value + +![Diagram of FDC with 2-bit stuffing showing a 1-bit data bit, an n-bit data block, a control bit, and data stuffing.](9b6b5924b48bf2fd5f347f88f06f45b3_img.jpg) + +This diagram illustrates the structure of an FDC with 2-bit stuffing. It consists of four vertical segments: a single '1' bit labeled 'Data bits', a block of 'n' bits, a shaded 'Control bit' section, and a hatched 'Data stuffing' section. Arrows point from the labels to their respective sections. + +Diagram of FDC with 2-bit stuffing showing a 1-bit data bit, an n-bit data block, a control bit, and data stuffing. + +### *FDC for V.21 signals* + +1 data/dummy bit and 1 control bit are repeated 3 times for redundancy. Interleaving is provided at transmission (see 5.4). + +![Diagram of FDC for V.21 signals showing three repeats of data and control bits, followed by data stuffing.](c67d21fb3d9042e88cdc669f071b4e7c_img.jpg) + +This diagram illustrates the structure of an FDC for V.21 signals. It consists of three repeating pairs of segments labeled '1st repeat', '2nd repeat', and '3rd repeat'. Each pair contains a shaded 'Data bits' section and a hatched 'Control bit' section. This is followed by a hatched 'Data stuffing' section. Arrows point from the labels to their respective sections. + +Diagram of FDC for V.21 signals showing three repeats of data and control bits, followed by data stuffing. + +T1507170-92 + +**Figure 3/G.766 – Facsimile data channel** + +## **5.2 Facsimile module frame** + +The FDCs of the various trunks are arranged in a contiguous sequence. Such a sequence, preceded by the Facsimile Control Channel (FCC), constitutes the facsimile module frame (see Figure 4). The FCC is a 21-bit block which, among other functions, describes the frame structure. The facsimile module frame is assembled every 2 ms, and its content may change from one 2-ms period to the next. The facsimile data associated with a specific IT can only be located in the frame by decoding the contents of the FCC. + +FEC is always applied to the FCC. FEC may be optionally applied to the entire facsimile module frame in blocks of 21 consecutive bits. The application of FEC adds 11 additional bits to 21 data bits, changing a 21-bit block into a 32-bit block (see 5.1). The length of the facsimile module frame should be such that after the application of FEC (to the FCC only or to the entire frame depending on the option selected), an even integer number of 32 blocks is obtained. This may require that dummy bits be appended to the end of the frame, as shown in Figure 4. At most, 63 (31 + 32) dummy bits would be required to meet the above requirement. However, additional blocks of 32 dummy bits may be added to accommodate, without delay, a possible sudden traffic increase. The total number, $m$ , of 32-bit blocks, determines the transmission capacity requirement (see 6.1.3). + +![Figure 4/G.766 – Facsimile module frame diagram. The diagram shows a horizontal bar representing the frame structure. At the top, a double-headed arrow labeled 'Frame length (p-bits)' spans the entire width. Below this, another double-headed arrow labeled 'Facsimile data channels Used for demodulated bits' spans from the start of the data channels to the start of the frame filling. To the left of the data channels, a section labeled '21 bits' contains the 'Fax control channel'. The data channels are represented by several vertical segments labeled ITh, ITi, ITj, and ITq. To the right of ITq is a shaded area labeled 'Frame filling'. Below the segments, the text 'IT No. → ITh ITi ITj ITq' and 'ITh < ITi < ITj ... ITq' is shown. The code 'T1522190-96' is in the bottom right corner.](5cab96b2d23174c25919840ecd50aa48_img.jpg) + +Figure 4/G.766 – Facsimile module frame diagram. The diagram shows a horizontal bar representing the frame structure. At the top, a double-headed arrow labeled 'Frame length (p-bits)' spans the entire width. Below this, another double-headed arrow labeled 'Facsimile data channels Used for demodulated bits' spans from the start of the data channels to the start of the frame filling. To the left of the data channels, a section labeled '21 bits' contains the 'Fax control channel'. The data channels are represented by several vertical segments labeled ITh, ITi, ITj, and ITq. To the right of ITq is a shaded area labeled 'Frame filling'. Below the segments, the text 'IT No. → ITh ITi ITj ITq' and 'ITh < ITi < ITj ... ITq' is shown. The code 'T1522190-96' is in the bottom right corner. + +**Figure 4/G.766 – Facsimile module frame** + +### 5.2.1 Facsimile control channel + +The Facsimile Control Channel (FCC) is provided for the transmission of frame description messages, facsimile call control codes and auxiliary information. The structure of the FCC is shown in Figure 5. This 21-bit block is divided into two parts, namely the IT field (9 bits) and the message field (12 bits). The use of the FCC is addressed in clause 7. + +![Figure 5/G.766 – Facsimile control channel diagram. The diagram shows a rectangular box divided into two parts. The left part is labeled 'IT field (9 bits)' and the right part is labeled 'Message fielda) (12 bits)'. The code 'T1507190-92' is in the bottom right corner.](a83ba9e3e2c1e21dd69953a7b09e45b4_img.jpg) + +Figure 5/G.766 – Facsimile control channel diagram. The diagram shows a rectangular box divided into two parts. The left part is labeled 'IT field (9 bits)' and the right part is labeled 'Message fielda) (12 bits)'. The code 'T1507190-92' is in the bottom right corner. + +a) Message field structure specified in clause 7. + +**Figure 5/G.766 – Facsimile control channel** + +## 5.3 Facsimile blocks + +A facsimile block is a 32-bit block, consisting of either: + +- a) 21 contiguous bits of the facsimile module frame, with the addition of 10 FEC check bits and 1 dummy bit; or +- b) 32 contiguous bits of the facsimile module frame. + +Cases a) or b), respectively apply when FEC is either used or not used. The first 21 bits of the facsimile module frame (i.e. the FCC) are always FEC encoded. The remaining part of the frame (i.e. the facsimile data) may be FEC encoded depending on the operator selection. + +Regrouping the bits of the facsimile module frame in accordance with the definition of facsimile blocks, given above, results in the facsimile block structure illustrated in Figure 6. Note that, because of the considerations discussed in the previous clause, the number of facsimile blocks is $m$ . The facsimile blocks are numbered, from 1 to $m$ , with lower numbered blocks containing the facsimile data associated with the lower number ITs. The FCC is entirely contained in facsimile block 1. + +![Diagram of facsimile blocks showing the structure of Block 1, Block 2, Block 3, and Block m. Block 1 is divided into Info bits (21 bits) and Check bits (10 bits). A dummy bit is shown between Block 1 and Block 2. The total length of each block is 32 bits. The diagram is labeled T1507200-92 and m even.](33a8f3f01dfa8bce75d23017855a13c5_img.jpg) + +The diagram illustrates the structure of facsimile blocks. At the top, a horizontal line is divided into two segments: 'FCC' on the left and 'Data' on the right. Below this, the blocks are shown as a series of rectangles. Block 1 is the first rectangle, containing 'Info bits' (21 bits) and 'Check bits' (10 bits). A vertical dashed line separates the info bits from the check bits. Block 2 is the second rectangle, starting with a 'Dummy bit' (indicated by a shaded vertical bar) followed by '32 bits' of data. Block 3 is the third rectangle, also containing 32 bits of data. An ellipsis (...) indicates that there are more blocks. Block $m$ is the last rectangle, also containing 32 bits of data. Below the blocks, the text 'T1507200-92' and 'm even' are present. + +Diagram of facsimile blocks showing the structure of Block 1, Block 2, Block 3, and Block m. Block 1 is divided into Info bits (21 bits) and Check bits (10 bits). A dummy bit is shown between Block 1 and Block 2. The total length of each block is 32 bits. The diagram is labeled T1507200-92 and m even. + +Figure 6/G.766 – Facsimile blocks + +### 5.3.1 FEC encoding + +The FEC encoding scheme uses a double error correcting BCH (Bose, Chaudhuri and Hocquengham) code of length 31, of minimum distance 5. The code is applicable to blocks of 21 information bits. The generator polynomial for this code is: + +$$G(x) = 1 + x + x^2 + x^4 + x^5 + x^7 + x^{10}$$ + +## 5.4 Facsimile transport channels + +To every DCME frame, the facsimile data interface delivers $m$ facsimile blocks to the DCME. The facsimile blocks are transported by special 32-kbit/s channels defined as Facsimile Transport Channels (FTC). The procedure for mapping the facsimile blocks onto the FTCs is shown in Figure 7. The figure shows that the bits of a block are inserted in an FTC at the rate of 2 bits per PCM frame, so that, in 16 PCM frames (2 ms) all the bits of the block are transmitted. This interleaving of the two blocks on one FTC provides protection against burst error events which could affect all 4 bits of the FTC but only 2 bits in any one facsimile block. + +![Diagram of Facsimile transport channels showing blocks and their mapping to FTCs and PCM frames.](76b0cd79baaedd942af4dc42f2e764b8_img.jpg) + +The diagram illustrates the mapping of facsimile blocks to transport channels (FTCs) and PCM frames. At the top, a sequence of blocks is shown: Block 1 (containing bits 1, 2, ..., 32), Block 2 (containing bits 1, 2, ..., 32), an ellipsis, and Block $m$ (containing bits 1, 2, ..., 32). Below this, a dashed line indicates a specific bit $j(n)$ from block $n$ . The bottom section shows the mapping to FTCs and PCM frames. For PCM frame No. 1, FTC 1 carries bits 1(1), 2(1), 1(2), and 2(2); FTC 2 carries bits 1(3), 2(3), 1(4), and 2(4). For PCM frame No. 2, FTC 1 carries bits 3(1), 4(1), 3(2), and 4(2); FTC 2 carries bits 3(3), 4(3), 3(4), and 4(4). An ellipsis indicates intermediate frames. For the final PCM frame No. 16, FTC 1 carries bits 31(1), 32(1), 31(2), and 32(2); FTC 2 carries bits 31(3), 32(3), 31(4), and 32(4). The text "TI507210-92" is located in the bottom right corner. + +Diagram of Facsimile transport channels showing blocks and their mapping to FTCs and PCM frames. + +**Figure 7/G.766 – Facsimile transport channels** + +The FTC are numbered, FTC 1 transporting blocks 1 and 2, FTC 2 transporting block 3 and 4, etc. The number of FTCs required to transmit the $m$ facsimile blocks is $m/2$ , since each FTC can transport two blocks. Note that FTC 1 always carries the FCC. Note also that the FTCs are transported in the DCME bearer frame, by "fax banks" (see clause 11). FTC 1 is mapped to the first leftmost fax bank in the DCME bearer. FTC 2 is mapped to the second leftmost fax bank, etc. The last FTC is mapped to the rightmost fax bank (see Figure 8). + +![Figure 8/G.766 – Mapping of FTCs to fax banks. The diagram shows two examples of mapping. On the left, 'PCM frame No. 1' contains 'Block 1' with sub-blocks 1(1), 2(1), 1(2), 2(2) and 'Block 2' with sub-blocks 1(3), 2(3), 1(4), 2(4). These are mapped via FTC 1, FTC 2, and FTC k to a row of 'k fax banks', specifically to the 2nd, 4th, and 8th banks (labeled BC 1 to BC 61). A 'CC' (Common Control) block is shown in the 1st bank. On the right, 'PCM frame No. 16' contains 'Block 31' with sub-blocks 31(1), 32(1), 31(2), 32(2) and 'Block 32' with sub-blocks 31(3), 32(3), 31(4), 32(4). These are mapped via FTC 1, FTC 2, and FTC k to the same 'k fax banks', specifically to the 2nd, 4th, and 8th banks. A 'CC' block is shown in the 1st bank. A legend at the top indicates 'j(n) = bit j of block n'. A reference code 'TI1507220-92' is at the bottom right.](9c6461e1e94afae4dec455e69a2ce152_img.jpg) + +Figure 8/G.766 – Mapping of FTCs to fax banks. The diagram shows two examples of mapping. On the left, 'PCM frame No. 1' contains 'Block 1' with sub-blocks 1(1), 2(1), 1(2), 2(2) and 'Block 2' with sub-blocks 1(3), 2(3), 1(4), 2(4). These are mapped via FTC 1, FTC 2, and FTC k to a row of 'k fax banks', specifically to the 2nd, 4th, and 8th banks (labeled BC 1 to BC 61). A 'CC' (Common Control) block is shown in the 1st bank. On the right, 'PCM frame No. 16' contains 'Block 31' with sub-blocks 31(1), 32(1), 31(2), 32(2) and 'Block 32' with sub-blocks 31(3), 32(3), 31(4), 32(4). These are mapped via FTC 1, FTC 2, and FTC k to the same 'k fax banks', specifically to the 2nd, 4th, and 8th banks. A 'CC' block is shown in the 1st bank. A legend at the top indicates 'j(n) = bit j of block n'. A reference code 'TI1507220-92' is at the bottom right. + +**Figure 8/G.766 – Mapping of FTCs to fax banks** + +# 6 Facsimile module controller + +The Facsimile Module Controller (FMC) performs a supervisory and control function for the entire module and acts as a gateway for all communication with the external environment. The FMC can be conceptually represented (see Figure 9), as the combination of a common outer process, called the Common Control Function (CCF), and an inner process, called the Facsimile Channel Handler (FCH). There are as many FCH processes as there are facsimile calls. A formal description of the FMC is provided in Annex B. There are as many CCF processes as there are cliques (see 2.27/G.763) handled by the DCME, i.e. one in single destination mode and two in multi-clique mode. + +## 6.1 Common control function + +The Common Control Function (CCF) performs a communication function and a resource management function. External communication is with the DCME, other facsimile module blocks, and with the remote facsimile module(s). The resources managed are module processes/hardware and capacity. A schematic representation of the CCF and the blocks it interacts with is shown in Figure 9. A complete definition of the signals exchanged among the blocks and the environment is provided in Annex B. + +![Figure 9/G.766 – FMC structure and interfaces. The diagram shows a central 'CCF' block containing a stack of 'FCH' blocks. To the left is an 'ADF' block, to the right is a 'Fax assembler/disassembler' block, and at the bottom is a 'Remodulation' block. Above the CCF is an 'Analysis/Demodulation' block. Arrows indicate bidirectional communication between the CCF and the ADF, the Fax assembler/disassembler, and the Analysis/Demodulation block. A single arrow points from the CCF to the Remodulation block, labeled 'FMC'. A small label 'T1507230-92' is in the bottom right corner.](b6671cfafda3820aafe9a24fa7a4d8c7_img.jpg) + +Figure 9/G.766 – FMC structure and interfaces. The diagram shows a central 'CCF' block containing a stack of 'FCH' blocks. To the left is an 'ADF' block, to the right is a 'Fax assembler/disassembler' block, and at the bottom is a 'Remodulation' block. Above the CCF is an 'Analysis/Demodulation' block. Arrows indicate bidirectional communication between the CCF and the ADF, the Fax assembler/disassembler, and the Analysis/Demodulation block. A single arrow points from the CCF to the Remodulation block, labeled 'FMC'. A small label 'T1507230-92' is in the bottom right corner. + +**Figure 9/G.766 – FMC structure and interfaces** + +### 6.1.1 Communication with the ADF + +The CCF exchanges information with the Hangover control and Signal Classification (HSC) and the Resource management and Assignment Generation (RAG) processes of the DCME via the facsimile control interface. The HSC messages processed by the CCF are Data(IT), for the classification of the call as a potential facsimile call, and DataInact(IT), Voice(IT), Rx\_data(IT) or Transp(IT) for the detection of termination of the facsimile call. The CCF provides two messages to the HSC. The first message forces an "inactive" declaration for the IT (this disables DSI/ADPCM processing of the IT). The second message removes this condition. + +The messages provided to the RAG place requests for the creation/deletion of a fax bank in the DCME bearer. + +The CCF also communicates with the O&M system. + +### 6.1.2 Other communication functions + +The CCF relays messages between the FCH and the signal analyser (WA approach), the modulators, demodulators and the associated switches (see Figure 11). The CCF also relays messages between an FCH and its peer process in the remote facsimile module. The CCF provides HSC messages to the FCH indicating the termination of the facsimile call. + +### 6.1.3 Capacity management + +The task of requesting and releasing facsimile banks resides with the CCF. The number, $n$ , of facsimile banks needed depends on the number $m$ (see 5.2) of facsimile blocks in the facsimile frame, i.e. from the selected frame length. The relationship between $n$ and $m$ is the following: + +$$n = m / 2$$ + +At the beginning of operation, $m$ shall be set to 2, i.e. one facsimile bank shall be requested. This facsimile bank will carry the facsimile control channel and one additional facsimile block. More facsimile banks shall then be requested, one at a time, in order to accommodate the selected facsimile frame length. + +The traffic content of the frame varies dynamically because the number of calls in progress changes and because each call transitions independently through different stages of the call procedure, often with different amounts of transmitted data. It is desirable that these short-term variations do not cause frequent requests for assignment and deletion of the facsimile banks. The margin built into the frame length should be large enough to accommodate without delay a sudden traffic increase and yet not cause an excessive reduction of the frame efficiency1. + +Reduction in the facsimile traffic will cause $m$ to be reduced from its current value to a lower value, with the consequent release of facsimile banks (one at a time). + +### 6.1.4 FCH management + +Upon reception of a Data(IT) or a Rx\_data(IT) message from the ADF, the CCF shall create an FCH for that IT and the IT shall be entered in the list of facsimile ITs. Upon reception of a CONNECT(IT) message from the corresponding FCH and the IT is not in the list of facsimile ITs, the CCF shall create an FCH for that IT and pass the CONNECT(IT) message to the FCH. The IT shall be entered in the list of facsimile ITs. If remodulator/demodulator resources are not available, the FCH shall not be created. + +When the Terminate(IT) message is generated by an FCH, its associated IT shall be deleted from the list of facsimile ITs. + +### 6.1.5 Demodulator/remodulator pool management + +If a shared pool approach is implemented, the CCF will be responsible for the assignment of the demodulator/remodulator to each FCH, as needed. At creation of the FCH a "complete" set of demodulators/remodulators should be allocated to the FCH. When the FCH terminates, the associated demodulator/remodulator resources are released to the pool. + +## 6.2 Facsimile Channel Handler (FCH) + +The FCH is a process that monitors the facsimile call, determines the call parameters, and generates control information for demodulators, remodulators and associated devices. There is interactive communication between the two FCH processes handling the call at the two ends of the link. All FCH communications are via the CCF. + +The FCH process for an IT is created by the CCF when the Data(IT) message or the Rx\_data(IT) message is received from the HSC process. The FCH associated with either the called end or the calling end may be required to operate in a transmit (Tx) or receive (Rcv) mode (direction of page transmission or reception), depending on whether polling is used. + +The Tx FCH must decide whether demodulation of the facsimile call can take place. The criterion for the decision is whether the Tx FCH has the capability and the resources (demodulators) to handle the call and whether the remote facsimile module has available the corresponding remodulators (this information is provided to the Tx FCH). If the facsimile call cannot be demodulated it will be routed via the 40 kbit/s ADPCM channel (the call continues to be monitored by the FCH until completion). + +In clause 4, two different facsimile compression approaches were introduced, the Protocol Analysis (PA) approach and the Waveform Analysis (WA) approach. Correspondingly, there are two types of FCH, the PA FCH and the WA FCH. Both can be in either Tx or Rcv modes. The Tx and Rcv FCH can, in turn, be in either a normal mode (demodulation and remodulation is used) or in the ADPCM mode. + +--- + +1 An optimized procedure for the selection of the facsimile frame length and the request/release of the facsimile bank should be employed. + +In a PA FCH, operating in the normal mode, there is the possibility for the FCH of being either in standard facilities T.30 mode (SF-T.30) or in a non-standard facilities T.30 mode (NSF-T.30). + +Figure 10 shows the possible progression paths for the PA and WA FCH processes. To permit interworking, compatibility must be ensured for all paths. There are 14 basic interworking configurations, as shown in Table 3. + +![Figure 10/G.766 – Progression paths for the PA FCH and the WA FCH protocols. The diagram is split into two parts by a vertical dashed line. The left part, labeled 'PA FCH', shows a 'Pre-fax' node connected to a 'Calling' node, which is connected to a 'Tx' node. The 'Tx' node is connected to three nodes: 'ADPCM', 'SF-T.30', and 'NSF-T.30'. A dashed line labeled 'Polling' connects the 'Calling' node to a 'Called' node. The 'Called' node is connected to a 'Rcv' node, which is connected to three nodes: 'ADPCM', 'NSF-T.30', and 'SF-T.30'. The right part, labeled 'WA FCH', shows a 'Pre-fax' node connected to a central node. This central node is connected to three nodes: 'Tx fax demodulation', 'ADPCM', and 'Rcv fax demodulation'. A label 'Fax demodulation SF-T.30 and NSF-T.30 (Tx/Rcv)' is placed near the central node. A small code 'T1507240-92' is at the bottom right.](d53cd0fd1cf896a9353fd63de1505ba2_img.jpg) + +Figure 10/G.766 – Progression paths for the PA FCH and the WA FCH protocols. The diagram is split into two parts by a vertical dashed line. The left part, labeled 'PA FCH', shows a 'Pre-fax' node connected to a 'Calling' node, which is connected to a 'Tx' node. The 'Tx' node is connected to three nodes: 'ADPCM', 'SF-T.30', and 'NSF-T.30'. A dashed line labeled 'Polling' connects the 'Calling' node to a 'Called' node. The 'Called' node is connected to a 'Rcv' node, which is connected to three nodes: 'ADPCM', 'NSF-T.30', and 'SF-T.30'. The right part, labeled 'WA FCH', shows a 'Pre-fax' node connected to a central node. This central node is connected to three nodes: 'Tx fax demodulation', 'ADPCM', and 'Rcv fax demodulation'. A label 'Fax demodulation SF-T.30 and NSF-T.30 (Tx/Rcv)' is placed near the central node. A small code 'T1507240-92' is at the bottom right. + +SF-T.30 Standard facilities T.30 protocol + NSF-T.30 Non-standard facilities T.30 protocol + +**Figure 10/G.766 – Progression paths for the PA FCH and the WA FCH protocols** + +The general FCH protocol requirements are addressed below. The application of the protocol to a comprehensive set of interworking cases is analysed in Annex A. + +**Table 3/G.766 – Interworking FCH configurations** + +| Call type | Calling → called FCH | | | | +|--------------------------------------------|----------------------|---------|---------|---------| +| | PA → PA | PA → WA | WA → PA | WA → WA | +| SF-T.30
matched resources | 1 | 2 | 3 | | +| NSF-T.30
matched resources | 5 | 6 | 7 | 4 | +| SF-T.30
unmatched resources
(ADPCM) | 8 | 9 | 10 | | +| NSF-T.30
unmatched resources
(ADPCM) | 12 | 13 | 14 | 11 | + +### 6.2.1 FCH requirements + +In both the PA and the WA approaches, control codes are sent to and received from the corresponding FCH to exchange information necessary for the demodulation/remodulation process. The information provided by the control codes is the following: + +- 1) activation of the demodulated path; +- 2) allocated remodulator resources; +- 3) contents of the facsimile frame; +- 4) start/end and frequency of echo protection tones; +- 5) start of training sequence, type, modulation type and bit rate; +- 6) call transfer to the ADPCM channel; +- 7) acknowledgement of certain messages; +- 8) refreshment of previous messages; +- 9) termination of the call. + +In addition to decoding the control codes, the PA FCH, when handling a T.30 call, reads and interprets the procedural messages exchanged between the communicating facsimile terminals. The messages transmitted by the local facsimile terminal are obtained by demodulating the low-speed voiceband signal. Those originated by the distant terminal are received in digital form in the facsimile frame. + +Using the message information, the PA FCH keeps track of the state of the SF-T.30 call and obtains the necessary information to control the demodulators, remodulators and associated devices. + +The FCH of the WA type does not read the procedural signals of the facsimile calls and, therefore, does not keep track of the progress of the call through its different states. On the transmit side, the method relies entirely on local signal analysis. The Rcv mode WA FCH, unlike the PA FCH, obtains information on the modulation type and rate from a control code [see 6.2.1, item 5) above]. In the WA approach there is no difference between an SF-T.30 and a NSF-T.30 call. + +The NSF-T.30 mode of operation of the PA FCH is not specified. Its principle of operation is based on recognizing the NSF-T.30 protocol identification code, interpreting the information exchanged between the facsimile terminals and demodulating/remodulating the facsimile signals accordingly. + +### 6.2.2 FCH protocol + +The specification for the FCH protocol is provided below as a list of procedural steps. A notation placed next to each step number indicates a significant event which may occur in that step. The requirements associated with each step are provided separately for the two sides of the link. The requirements listed apply to both the PA and WA FCH, except where noted. The symbols {PA} and {WA}, at the beginning of a paragraph, indicate that the requirement applies only to the PA FCH or to the WA FCH, respectively. Message field structure and variables are defined in clause 7. + +#### *Step 1 (Initial state) – Called side* + +The called side FCH for an IT is started at the reception of the Data(IT) message from the HSC process or the RxData(IT) message from the Receive channel status Update and overload channel Decoding (RUD) process. The initial state, entered by the FCH at creation, is referred to as the pre-fax state. If the FCH remains in the pre-fax state for more than 15 seconds, the terminate(IT) message shall be sent to the CCF and the FCH shall terminate. + +#### *Step 1 (Initial state) – Calling side* + +The calling side FCH for an IT is started, in the pre-fax state, at the reception of the Data(IT) or RxData(IT) messages. If the FCH remains in the pre-fax state for more than 15 seconds, the terminate(IT) code shall be generated and the FCH shall terminate. + +#### *Step 2 (DIS) – Called side* + +The called side FCH monitors the IT in order to detect the High level Data Link Control (HDLC) flags of the V.21 signal (DIS) received from the local called side facsimile terminal (the transmission of the signal through the DCME is via the ADPCM path). Upon detection of eight flags, the called side FCH shall enter the called state and the CONNECT code shall be sent to the remote calling FCH process. Together with the CONNECT code, the "resource list" (allocated remodulators) shall be sent to the remote calling FCH. The response to the CONNECT code is the RESOURCE code (see step 2, calling side). Failure to receive this code within three seconds shall result in generation of the DISCONNECT code and termination of the FCH process. + +{WA} The called side FCH shall assign a waveform analysis unit to the IT in order to detect and classify the facsimile signals (the unit could be time-shared among different ITs on an as needed basis). + +Upon termination of the V.21 signal (DIS), a SWITCH\_TO\_DEMOD code shall be sent to the remote calling FCH. The FED buffer (see Figure 2) shall be inserted in front of the demodulated path and the IT shall be switched to the digital path (the demodulator/remodulator path). + +#### *Step 2 (DIS) – Calling side* + +Upon reception of the CONNECT code, the calling side FCH shall enter the calling state and shall transmit the RESOURCE code (containing the resource list). Upon reception of the SWITCH\_TO\_DEMOD code, the FED buffer shall be inserted in front of the demodulated path and the IT shall be switched to the digital path. + +{WA} The calling side FCH shall assign a waveform analysis unit to the IT in order to detect and classify the facsimile signals (the unit could be time shared among different ITs on an as needed basis). + +#### *Step 3 (DCS) – Calling side* + +Upon reception of a V.21 signal from the local calling side facsimile terminal, the calling side FCH shall assign a V.21 demodulator to the IT, send the SIGNALLING code (indicating the presence of the new facsimile data channel in the facsimile frame), and insert the demodulated bits into the allocated data channel. This action will continue until termination of the V.21 signal, at which time the IDLE code shall be transmitted to indicate the removal of the facsimile data channel from the facsimile frame. (The function of the IDLE code may be combined with the path switching function and performed by the SWITCH\_TO\_ADPCM code. See below.) + +V.21 signals are passed transparently even when errors are detected [e.g. cyclic redundancy check (CRC) failure]. HDLC zero stuffing is also passed transparently. + +{PA} Upon termination of the V.21 signal, the calling side FCH shall decode the received V.21 message and take consequent action. Three possible cases, corresponding to the messages DTC, DCS and NSS, are addressed separately below. + +DTC – This is the polling message, meaning that the called side will be the transmit side. In this case, the calling side FCH shall enter the Recv mode and remove the FED buffer from the demodulated path. + +- DCS – In this case, the calling side FCH shall enter the Tx mode (the FED buffer shall be kept). The calling side FCH shall decode the modulation and rate of the call from the DCS message and determine whether demodulation/remodulation is possible from knowledge of the available local demodulators, and remote remodulators exchanged in step 2. If demodulation/remodulation is not possible, the SWITCH\_TO\_ADPCM code shall replace the IDLE code at the termination of the demodulated DCS signal. The IT path, with the FED buffer inserted, shall be switched to ADPCM, and the calling side FCH will enter the ADPCM mode. +- NSS – This code indicates a non-standard protocol. If the calling side FCH recognizes the non-standard protocol as one it can handle, and if appropriate demodulator and remodulator resources are available, the calling side FCH shall enter the appropriate Tx NSF-T.30 mode. If any of the above conditions are not satisfied, the SWITCH\_TO\_ADPCM code shall replace the IDLE code at the termination of the demodulated NSS signal. The IT path, with the FED buffer inserted, shall be switched to ADPCM, and the calling side FCH will enter the ADPCM mode. + +#### *Step 3 (DCS) – Called side* + +The called side FCH shall select a V.21 remodulator and the V.21 data extracted from the facsimile data channel shall be transmitted to the local facsimile terminal. If the code received at termination of the V.21 data is SWITCH\_TO\_ADPCM, the IT path shall be switched back to ADPCM and the calling side FCH will enter the ADPCM mode. + +V.21 signals are passed transparently even when errors are detected (e.g. CRC failure). HDLC zero stuffing is also passed transparently. + +When the V.21 data is not received for three seconds, the called side FCH may transmit a flag sequence to the local facsimile terminal to prevent expiration of the link timer. This option may be used throughout the FCH procedure. + +{PA} If the SWITCH\_TO\_ADPCM code is not received, the called side FCH shall decode the demodulated V.21 message (zero stuffing is removed) and take consequent action. Three possible cases, corresponding to the DTC, DCS and NSS messages are addressed separately below. + +- DTC – This is the polling message, meaning that the called side will be the transmit side. In this case, the FCH shall enter the Tx mode and the FED buffer shall be inserted in front of the demodulated path. +- DCS – In this case, the called side FCH shall enter the Rcv mode. The FCH shall read the modulation and rate of the call from the DCS message for later use. +- NSS – When the called side FCH recognizes the NSS code, the call side FCH shall enter the Rcv NSF-T.30 mode. + +#### *Step 4 (EPT) – Transmit side* + +Upon detection of an Echo Protection Tone (EPT) and its frequency (f), the transmit side FCH shall generate the EPT(f) code for the remote receive side FCH. The tone frequency, f, and level shall be provided with the code as defined in Table 7. Upon termination of the tone, the transmit side FCH shall generate the EPT\_END code. + +#### *Step 4 (EPT) – Receive side* + +Upon reception of the EPT(f) code from the remote transmit side FCH, the receive side FCH shall generate the echo protection tone of frequency f and level in accordance with Table 7. Upon reception of the EPT\_END code, the receive side FCH shall cease transmission of the tone. + +#### *Step 5 (Training sequence) – Transmit side* + +Upon detection of a high speed signal, if no echo protection tone was received as part of this burst then the code LEVEL shall be transmitted prior to the code TRAINING. + +{PA} Upon detection of a high speed signal (i.e. other than V.21). The transmit side FCH shall generate the code TRAINING (mode, rate, long). The parameters mode, rate and the Boolean variable "long" indicate the modulation type, the modulation rate, and whether the training sequence is long or short (note that for V.17 modulation, the training sequence is long before the training check and short before page data). The values of the parameters included in the TRAINING code are obtained from the DCS message (or from codes in the NSF-T.30 protocol). + +{WA} Upon detection of a high speed signal, the FCH shall enter the transmit mode and the FED buffer shall be kept. Upon detection and classification of the training signal, the transmit side FCH shall generate the code TRAINING (mode, rate, long). The parameters mode and rate are determined by signal analysis. In some cases (long training sequence), rate information will not be available and, therefore, it will be set to "unavailable" in the message. The variable "long" shall always be set to FALSE. If the signal analysis later determines that a long training sequence is being received, the code LONG\_TRAINING (rate), with appended rate information, shall be generated by the transmit side FCH. + +The delayed version of the training sequence (delayed by the FED buffer) shall be used to train the selected high speed demodulator. + +#### *Step 5 (Training sequence) – Receive side* + +Upon reception of the code TRAINING (mode, rate, long), generation of a training sequence of the required modulation type, modulation rate, and length shall be started by the receive side FCH at a level consistent with Table 7 based on the level field of the EPT or LEVEL codes. + +{PA} The parameters of the training sequence are obtained from the DCS code or from codes in the NSF-T.30 mode. If the code LONG TRAINING is received, it shall be ignored. + +{WA} Upon reception of the code TRAINING, the FCH shall enter the receive mode. The FED buffer shall be removed from the demodulation path. The parameters (mode, rate, long) of the training sequence are obtained from the received TRAINING code. If the code LONG\_TRAINING is received from the remote transmit side FCH while the training sequence (short) is being generated, the sequence shall be extended (i.e. changed to a long sequence) by the receive side FCH, using the rate indicated in the LONG\_TRAINING (rate) code. + +#### *Step 6 (Training check/page data) – Transmit side* + +When data bits are output by the selected high speed demodulator, the FAX\_DATA code shall be generated by the transmit side FCH to indicate the presence of the new facsimile data channel in the facsimile frame, and the data bits shall be inserted in the data channel. This will continue until termination of the data, at which time the IDLE code shall be transmitted to signal the removal of the facsimile data channel from the facsimile frame. + +Page data shall be transmitted unscrambled. The fill bits for incomplete or empty facsimile channels shall be "1". + +#### *Step 6 (Training check/page data) – Receive side* + +When data bits for an IT are received in the facsimile frame, as signalled by the FAX\_DATA code, the data extracted from the allocated facsimile data channel shall be provided to the selected high speed remodulator for transmission to the local receive facsimile terminal. The modulated data shall follow the regenerated training sequence without any gap. Transmission of the data will continue until reception of the IDLE code for the IT. + +#### *Step n (Disconnection) – Originating side2* + +When the signal Voice(IT) or Transp(IT) is received from the HSC process of the DCME, the disconnection process shall be started. When the signal DataInact(IT) is received in the transmit mode, the disconnection process shall also be started. + +{PA} When the DISCONNECT (DCN) message generated either by the local or remote facsimile terminal, is detected, the disconnection process shall be started. + +The disconnection process requires transmission of the DISCONNECT code to the remote FCH, switching of the IT path to ADPCM and termination of the FCH. + +#### *Step n (Disconnection) – Notified side2* + +When the DISCONNECT code is received, the IT path shall be switched to ADPCM and the FCH process shall terminate. + +#### **6.2.2.1 Examples of the FCH protocol** + +Figure 11 provides an example of an FCH functional decomposition. Table 4 is an example of FCH interworking using the functional decomposition of Figure 11 for the WA-PA configuration where PA is the calling side. The EPT and the high speed data transmission phases are not included in Table 4. + +--- + +2 The disconnection process may originate from either side of the connection. + +![Functional decomposition diagram of FCH showing Called side (WA) and Calling side (PA) with various functional blocks like DCME control, ADPCM, Signal analysis and demodulation, FMC, Remodulation, and Demodulation and decode. It includes switches s1-s4 and connection points A, B.](8c348bf9c2c81b018017ae1d19506a9a_img.jpg) + +The diagram illustrates the functional decomposition of an FCH interworking example. It is divided into two main sides: the Called side (WA) and the Calling side (PA), connected by eight numbered paths. On the WA side, the signal flow starts from Path 8, goes through switch s4, then through ADPCM and DCME control blocks. It then passes through a Remodulation block, an FMC block, and a Signal analysis and demodulation block. Switches s1, s2, and s3 are used to route signals between these blocks and through a Delay block. Connection point A is shown at two locations. On the PA side, the signal flow starts from Path 7, goes through switch s4, then through ADPCM and DCME control blocks. It passes through a Demodulation and decode block, an FMC block, and a Remodulation block. Switches s1, s2, and s3 are used to route signals between these blocks and through a Delay block. Connection point B is shown at two locations. Vertical dashed lines labeled FA (Fax frame assembler) and FD (Fax frame disassembler) indicate the boundaries for the fax data paths between the WA and PA sides. + +Functional decomposition diagram of FCH showing Called side (WA) and Calling side (PA) with various functional blocks like DCME control, ADPCM, Signal analysis and demodulation, FMC, Remodulation, and Demodulation and decode. It includes switches s1-s4 and connection points A, B. + +T1522210-96 + +- FA Fax frame assembler +- FD Fax frame disassembler (+V.21 decode in PA) +- s1, s2, s3, s4 Switches +- a, b, c Switch positions +- A, B Connection points + +Figure 11/G.766 – An example of FCH functional decomposition + +Table 4/G.766 – An FCH interworking example using the FCH functional decomposition of Figure 11 + +| | (Called) WA | | | | | (Calling) PA | | | | | Path | | | | | | | | +|---------------------------------|-------------|-----|-----|-----|-------------|--------------|-----|-----|-----|-------------|------------------|------------------|---|-------------|---|---|------------------|---| +| | s 1 | s 2 | s 3 | s 4 | S T | s 1 | s 2 | s 3 | s 4 | S T | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | +| 2100 Hz tone (WA action) | a | b | a | a | P
F
X | a | a | a | a | | d
a
t
a | t
o
n
e | | | | | t
o
n
e | | +| Start of DIS (WA action) | a | b | a | b | C
L
D | a | b | a | a | P
F
X | d
a
t
a | D
I
S | | C
N
C | | | D
I
S | | + +**Table 4/G.766 – An FCH interworking example +using the FCH functional decomposition of Figure 11 (concluded)** + +| | (Called) WA | | | | | (Calling) PA | | | | | Path | | | | | | | | +|------------------------------------------|-------------|----|----|----|-------------|--------------|----|----|----|-------------|------------------|-------------|---|-------------|-------------|-------------|-------------|-------------| +| | s1 | s2 | s3 | s4 | S T | s1 | s2 | s3 | s4 | S T | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | +| Start of DIS
(PA action) | a | b | a | b | C
L
D | a | b | a | a | C
L
G | d
a
t
a | D
I
S | | | R
S
C | | D
I
S | | +| End of DIS
(WA action) | b | b | b | b | C
L
D | a | b | a | a | C
L
G | d
a
t
a | D
I
S | | S
W
D | | | D
I
S | | +| End of DIS
(PA action) | b | b | b | b | C
L
D | b | b | b | b | C
L
G | d
a
t
a | D
I
S | | | | | D
I
S | | +| DCS
(PA action) | b | b | b | b | C
L
D | b | b | b | b | C
L
G | | | | | S
I
G | D
C
S | | D
C
S | +| DCS
(WA action) | b | b | b | b | C
L
D | b | b | b | b | T
X | | | | | I
D
L | | | D
C
S | +| Training
(PA action) | b | b | b | b | C
L
D | b | b | b | b | T
X | | | | | T
R
N | | | | +| Training
(WA action) | a | a | a | b | R
C
V | b | b | b | b | T
X | | | | | | | | T
R
N | +| Disconnect
(PA action) | a | a | a | b | R
C
V | a | a | a | a | T
X | | | | | D
S
C | | | | +| Disconnect
(WA action) | a | a | a | a | R
C
V | a | a | a | a | T
X | | | | D
S
C | | | | | +| Disconnect
(WA and PA action) | a | a | a | a | | a | a | a | a | | | | | | | | | | + +ST, PFX, CLD, CLG, TX, RCV      State, Pre-Fax, Called, Calling, Transmit, Receive +CNC, RSC, SIG, IDL                  CONNECT, RESOURCE, SIGNALLING, IDLE +TRN, DSC, SWD                    TRAINING, DISCONNECT, SWITCH\_TO\_DEMOD +s1, s2, s3, s4, a, b                  See Figure 11. + +#### 6.2.2.2 SDL representation of the FCH protocol + +The FCH protocol for the PA case can be modelled as a state machine and represented by means of Specification and Description Language (SDL) diagrams. The SDL representation of the PA standard facility T.30 protocol is given in Annex B and provides a more detailed description. The + +SDL representation of WA FCH is not provided since this protocol is adequately described in a text only form. + +# **7 Use of the facsimile control channel** + +The facsimile control channel (see 5.2.1) consists of a 9-bit IT field and a 12-bit message field. The 21-bit FCC is transmitted once per DCME frame (2 ms). The value of the IT field defines ITs numbered from 1 to 511. The numbering range from 1 to 216, the "normal" range, is used to designate traffic trunks. The "special range", from 500 to 511, is reserved for inter-module functions. + +The value 0 in the IT field applies collectively to all facsimile ITs and it is used, together with its associated message field, to indicate whether the facsimile frame is FEC encoded. + +## **7.1 Message field structure** + +When the IT is in the normal range, the 12-bit message field (see Figure 5) is structured into a 4-bit "message ID" part and an 8-bit "message content" part. The message ID defines either a single control code with appended parameters, such as TRAINING (long, mode, rate), or a group of codes without appended parameters. + +The structure of the message content part depends on the message ID. The different structures are shown in Figures 12 and 13. Note the 4-bit signal level field, used to transmit the input signal level encoded through a 16-level quantizer (requirement in Table 1). + +The specific bit patterns assigned to the various codes of the message content part of the FCC are provided in Tables 5 through 8. + +When the IT number is 0, the message field consists of either 12 binary "1"s or 12 binary "0"s. The all "1"s message indicates that FEC is applied to the facsimile frame. The all "0" message indicates that the FEC is not used. + +![](c494cd874a082a97b50b3c4d3938f467_img.jpg) + +Code                      Message ID                      Message contents + +TRAINING + +| | | | | | | | | | | | | | | | | +|---|---|---|---|------|---|---|---|------------|---|---|---|------|--|--|--| +| | | | | Long | | | | Modulation | | | | Rate | | | | +| 0 | 0 | 0 | 0 | a | a | b | c | a | b | c | d | | | | | + +LONG\_TRAINING + +| | | | | | | | | | | | | | | | | +|---|---|---|---|----------|---|---|---|------|---|---|---|--|--|--|--| +| | | | | Reserved | | | | Rate | | | | | | | | +| 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | a | b | c | d | | | | | + +V\_FAST + +| | | | | | | | | | | | | | | | | +|---|---|---|---|---------------------|---|---|---|---|---|---|---|--|--|--|--| +| | | | | (For further study) | | | | | | | | | | | | +| 0 | 0 | 1 | 0 | a | b | c | d | e | f | g | h | | | | | + +CONNECT + +| | | | | | | | | | | | | | | | | +|---|---|---|---|-----------------|---|---|---|-----------------|---|---|---|--|--|--|--| +| | | | | 1 : 2 : 3 : 4 : | | | | 5 : 6 : 7 : 8 : | | | | | | | | +| | | | | Modulators | | | | | | | | | | | | +| 0 | 0 | 1 | 1 | a | a | a | a | a | a | a | a | | | | | + + + +| | | | | | | | | | | | | | | +|--------|--------|--------|---|---|---|---|---|---|---|---|---|---|---| +| FEC ON | IT = 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | +| | FEC OF | IT = 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | + +NOTE – The bit designations a, b, ... are defined for each field of the FCC message independently. + +T1522220-96 + +**Figure 12/G.766 – Structure of FCC messages – Part 1** +(See Tables 5 to 8) + +![](692541e65db4dc852988ce77ebb60ce5_img.jpg) + +Code                      Message ID                      Message contents + +RESOURCE + +| | | | | | | | | | | | | +|----------------|---|---|---|-------|-------|-------|------------|-------|-------|-------|-------| +| ← Message ID → | | | | : 1 : | : 2 : | : 3 : | : 4 : | : 5 : | : 6 : | : 7 : | : 8 : | +| 0 | 1 | 0 | 0 | | | | Modulators | | | | | +| | | | | a | a | a | a | a | a | a | a | + +EPT + +| | | | | | | | | | | | | +|----------------|---|---|---|-------|---|----------|---|-----------|---|---|---| +| ← Message ID → | | | | ← f → | | Reserved | | ← Level → | | | | +| 0 | 1 | 0 | 1 | a | b | 0 | 0 | a | b | c | d | + +MISC\_CODES\_1 + +| | | | | | | | | | | | | +|----------------|---|---|---|----------------|---|---|---|-----------|---|---|---| +| ← Message ID → | | | | ← Code field → | | | | ← Level → | | | | +| 0 | 1 | 1 | 0 | a | b | c | d | a | b | c | d | + +MISC\_CODES\_2 + +| | | | | | | | | | | | | +|----------------|---|---|---|----------------|---|---|---|-----------|---|---|---| +| ← Message ID → | | | | ← Code field → | | | | ← Level → | | | | +| 0 | 1 | 1 | 1 | a | b | c | d | a | b | c | d | + +T1522230-96 + +NOTE – The bit designations a, b, ... are defined for each field of the FCC message independently. + +**Figure 13/G.766 – Structure of FCC messages – Part 2** +(See Tables 5 to 8) + +**Table 5/G.766 – Training message: Code list** +(See Figure 12) + +| "Long" field | | | | | +|--------------------|-------|-------|-------|-----------------| +| Bit a | | | | Meaning | +| 0 | | | | False | +| 1 | | | | True | +| "Modulation" field | | | | | +| Bit a | Bit b | Bit c | | Meaning | +| 0 | 0 | 0 | | V.17 | +| 0 | 0 | 1 | | V.21 | +| 0 | 1 | 0 | | V.27 ter | +| 0 | 1 | 1 | | V.29 | +| 1 | 0 | 0 | | V.33 | +| "Rate" field | | | | | +| Bit a | Bit b | Bit c | Bit d | Meaning | +| 0 | 0 | 0 | 0 | "Unavailable" | +| 0 | 0 | 0 | 1 | 300 bit/s | +| 0 | 0 | 1 | 0 | 2 400 bit/s | +| 0 | 0 | 1 | 1 | 4 800 bit/s | +| 0 | 1 | 0 | 0 | 7 200 bit/s | +| 0 | 1 | 0 | 1 | 9 600 bit/s | +| 0 | 1 | 1 | 0 | 12 000 bit/s | +| 0 | 1 | 1 | 1 | 14 400 bit/s | + +**Table 6/G.766 – Connect/resource message: Code list** +(See Figures 12 and 13) + +| "Modulator" field | | | | | | | | | +|-------------------|--------|--------|--------|--------|--------|----------|--------|---------------| +| Mod. 1 | Mod. 2 | Mod. 3 | Mod. 4 | Mod. 5 | Mod. 6 | Mod. 7 | Mod. 8 | | +| V.21 | V.27 | V.29 | V.17 | V.33 | < | Reserved | > | | +| Bit a | Bit a | Bit a | Bit a | Bit a | Bit a | Bit a | Bit a | Meaning | +| 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | Available | +| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | Not available | + +**Table 7/G.766 – EPT message: Code list** +(See Figure 13) + +| "Frequency" field | | | | | | +|-------------------------------|-------|-------|----------|-------|------------------------------------------------| +| | Bit a | Bit b | Meaning | | | +| | 0 | 0 | 1 700 Hz | | | +| | 0 | 1 | 1 800 Hz | | | +| "Level" field | | | | | | +| Demodulator input
p (dBm0) | Bit a | Bit b | Bit c | Bit d | Remodulator output
p (dBm0) | +| $-13 \leq p$ | 0 | 0 | 0 | 0 | | +| $-15 \leq p < -13$ | 0 | 0 | 0 | 1 | | +| $-17 \leq p < -15$ | 0 | 0 | 1 | 0 | | +| $-19 \leq p < -17$ | 0 | 0 | 1 | 1 | | +| $-21 \leq p < -19$ | 0 | 1 | 0 | 0 | To be determined by the operator | +| $-23 \leq p < -21$ | 0 | 1 | 0 | 1 | | +| $-25 \leq p < -23$ | 0 | 1 | 1 | 0 | | +| $-27 \leq p < -25$ | 0 | 1 | 1 | 1 | Default level of $-17$ dBm0 suggested (Note 1) | +| $-29 \leq p < -27$ | 1 | 0 | 0 | 0 | | +| $-31 \leq p < -29$ | 1 | 0 | 0 | 1 | | +| $-33 \leq p < -31$ | 1 | 0 | 1 | 0 | | +| $-35 \leq p < -33$ | 1 | 0 | 1 | 1 | | +| $-37 \leq p < -35$ | 1 | 1 | 0 | 0 | | +| $-39 \leq p < -37$ | 1 | 1 | 0 | 1 | | +| $p < -39$ | 1 | 1 | 1 | 0 | | +| Level not measured | 1 | 1 | 1 | 1 | | + +NOTE 1 – The receive demodulator input level may not be constant throughout the call; however, the selected level for the remodulated echo protection tone, training and data signals shall be equal and remain the same throughout the call. + +NOTE 2 – Precautions shall be taken to ensure that the demodulator input is not sensitive to the echo received from its local end hybrid. + +**Table 8/G.766 – Miscellaneous codes message: Code list** +(See Figure 13) + +| a) Miscellaneous Codes No. 1 | | | | | +|----------------------------------|-------|-------|-------|-----------------| +| "Code" field | | | | Code | +| Bit a | Bit b | Bit c | Bit d | | +| 0 | 0 | 0 | 0 | SWITCH_TO_ADPCM | +| 0 | 0 | 0 | 1 | END_EPT | +| 0 | 0 | 1 | 0 | SIGNALLING | +| 0 | 0 | 1 | 1 | IDLE | +| 0 | 1 | 0 | 0 | FAX_DATA | +| 0 | 1 | 0 | 1 | LEVEL | +| 0 | 1 | 1 | 0 | SWITCH_TO_DEMOD | +| "Level" field | | | | | +| As for EPT message (see Table 7) | | | | | +| b) Miscellaneous Codes No. 2 | | | | | +| "Code" field | | | | Code | +| Bit a | Bit b | Bit c | Bit d | | +| 0 | 1 | 0 | 1 | DISCONNECT | + +## 7.2 Message transmission procedure + +Since independently originated messages may compete for transmission over the FCC, queuing is necessary. A priority system shall be used, giving the highest priority to messages that affect the critical time gaps of the facsimile call (see 8.2). The priority list for the FCC codes is provided in Table 9. + +**Table 9/G.766 – Priority list for FCC codes** + +| Priority 1 | Priority 2 | Priority 3 | +|---------------|-------------------------|------------| +| MISC_CODES_1 | MISC_CODES_2 | FEC_ON | +| TRAINING | Service channel message | FEC_OFF | +| V_FAST | | | +| LONG_TRAINING | | | +| CONNECT | | | +| RESOURCE | | | +| EPT | | | +| LEVEL | | | + +Transmitted messages shall be "refreshed" (e.g. repeated). The ITs logged in the list of "facsimile ITs" shall be refreshed, when permitted by the queuing system, from the low to the high numbers, in a cyclical fashion. The IT number 0 is always included in the facsimile list. + +If a message indicates a change in the facsimile frame (i.e. the appearance or disappearance of a facsimile data channel), the change shall be implemented three frames after the frame in which the relevant control code is transmitted as shown in Figure 14. + +![Timing diagram showing four frames: Frame n, Frame n+1, Frame n+2, and Frame n+3. A double-headed arrow labeled 'FCC message' spans the duration of Frame n. An upward arrow labeled 'Implementation' points to the boundary between Frame n+2 and Frame n+3. The text 'T1507280-92' is in the bottom right corner.](e451401f8fa77b466f401d5fce15b26c_img.jpg) + +Timing diagram showing four frames: Frame n, Frame n+1, Frame n+2, and Frame n+3. A double-headed arrow labeled 'FCC message' spans the duration of Frame n. An upward arrow labeled 'Implementation' points to the boundary between Frame n+2 and Frame n+3. The text 'T1507280-92' is in the bottom right corner. + +**Figure 14/G.766 – FCC codes implementation timing** + +## 7.3 Service channel + +The service channel is a channel established, on an as needed basis, for communication among the corresponding modules of a DCME link. The "special range" IT numbers (see clause 7) are used for this function. + +When communication is needed, the message with the appropriate IT number, will be inserted in the queue for the FCC and transmitted as permitted by the status of the queue and the priority selected. + +The service channel ITs shall not be refreshed. + +The message field associated with a service channel IT is structured in a 4-bit message ID part and an 8-bit message content part. The information exchanged via the service channel is defined in Table 10. + +**Table 10/G.766 – Service channel messages** + +| Message | IT No./ID | Message content | +|----------------------------------------------------------------|----------------------------------------------|------------------------------------------------------------------------------------------------------------------| +| Error count | 500/0000
500/0001
500/0002
500/0003 | Destination A error count
Destination B error count
Destination C error count
Destination D error count | +| NOTE 1 – Other service channel messages are for further study. | | | +| NOTE 2 – See 10.3 for the error count definition. | | | + +# 8 Timing and delay requirements + +## 8.1 Clock difference compensation + +### 8.1.1 Demodulator side + +The timing of the incoming facsimile data is controlled by the transmitting facsimile terminal clock, which has an accuracy requirement of $1 \times 10^{-4}$ . The timing of the demodulated data transmitted in the facsimile frame is controlled by the DCME clock (see 13.1.1/G.763). The mechanism for compensating the clock rate differences is the use of stuffing bits in the facsimile data channels (see 5.1). + +### 8.1.2 Remodulator side + +The timing of the facsimile data extracted from the facsimile frame, after bit destuffing, is controlled by the transmitting facsimile terminal clock. The timing of the remodulated data transmitted to the local facsimile terminal is controlled by the modulator clock. The modulator clock is either the DCME clock or a variable clock. + +If the DCME clock is used, a slip buffer of at least 200 ms is required to absorb the cumulative effects of the clock differences over the time of a page transmission (for an assumed high density, normal length page, transmitted at 9.6 kbit/s with a $1 \times 10^{-4}$ clock accuracy). The buffer will be started at its central point at the start of each transmission block. + +If the variable modulator clock approach is selected, the clock rate shall be adjusted to keep the accumulated excess bits (or shortage of bits) within narrow limits at all times. This will permit the use of a small buffer and accommodate pages of any length. + +## 8.2 Critical time gaps of the T.30 signals + +In the T.30 protocol, there are time gaps between certain consecutive signals that are required to be kept within a specified tolerance. Specifically, there is a requirement of a gap of 75 ms $\pm 20$ ms between the end of certain low speed signals (e.g. DCS) and the start of the following high speed signal (EPT or training). There is the same requirement between the end of certain high speed signals (e.g. page data) and the start of the following low speed signal [e.g. End-of-Procedure (EOP)]. + +The constraint placed on the facsimile compression function is that the combined action of the demodulator side module and the modulator side module should not shorten the critical gaps but could extend them by additional interval of up to 40 ms. + +Another requirement of the facsimile transmission protocol is that there should be no gap between the end of the training sequence and the beginning of the data. The gap between the EPT and the training sequence is 20 to 25 ms. The task of ensuring that these requirements are met is assigned to the remodulator side module. + +### 8.2.1 Demodulator side requirements + +For the demodulator side module, the following requirements apply: + +- 1) The gap between DCS and EPT/training shall not be shortened and, if extended, it shall not be increased by more than 20 ms. This requirement applies whether path switching to ADPCM occurs or does not occur during the time gap. +- 2) The gap between image data and EOP shall not be shortened and, if extended, it shall not be increased by more than 20 ms. +- 3) The delay in the demodulator shall not exceed 220 ms. + +### 8.2.2 Remodulator side requirements + +- 1) The gap between DCS and EPT/training shall not be shortened and, if extended, it shall not be increased by more than 20 ms. This requirement applies whether path switching to ADPCM occurs or does not occur during the time gap. +- 2) The gap between image data and EOP shall not be shortened and, if extended, it shall not be increased by more than 20 ms. For the remodulator side module, the following requirements apply: + +Note that, to meet the gap requirement between the data signal and EOP, if a slip delay buffer is used (see 8.1.2), a delay buffer must also be used in the EOP path. This buffer must be set to a delay value equal to the delay the slip buffer introduced in the high speed path at termination of the image signal. + +The nominal delay on the remodulator side shall not exceed 120 ms. If a slip buffer is used, the average delay value must be assumed in the determination of the nominal delay. + +The remodulator side module shall introduce no gap between the end of the training sequence and the beginning of the data. The gap between the EPT and the training sequence shall be 20 to 25 ms. + +## **8.3 Front-End Delay (FED) buffer** + +The FED buffer is a PCM delay buffer inserted, when needed, in front of the demodulator, to provide sufficient time for signal validation (PA) or signal analysis (WA). + +In the PA method, although the type of input signal expected can be predicted from the status of the protocol, there are fault conditions that could cause the local facsimile terminal to transmit a low speed signal instead of a high speed signal. The FED buffer provides sufficient time to detect the presence of the low speed signal. + +In the WA approach, a signal analysis unit is applied to the input signal for signal classification, while the delayed version of the input is propagating through the delay buffer. + +The delay value of the FED buffer may be different for the two approaches. This value is not explicitly specified; however, the total delay for the facsimile module is specified. + +# **9 Multi-clique and multi-destination operation** + +The facsimile module shall permit multi-clique and multi-destination operation of the DCME. In multi-clique operation, the facsimile module shall process up to four received facsimile frames. The ITs directed to the module shall be sorted out by processing the FCCs of the received frames and by means of the IT allocation map (IT allocation to DCME links), down-loaded at configuration set-up. + +In multi-destination mode, if one or more corresponding DCMEs are not equipped with a facsimile module, an operational problem will occur unless the unit without the facsimile module is specially modified to recognize fax banks to permit their exclusion from voice-list, so that overload channels are properly recovered. + +# **10 Facsimile module operation and maintenance** + +The O&M and configuration data should be transported over the O&M interface with the DCME. The data should be accessed by means of the same operator facility (e.g. PC/workstation) used for the DCME. + +## **10.1 Facsimile module statistics** + +Relevant parameters of the facsimile module operations shall be monitored and displayed. Parameters shall be measured over a predetermined time period called the Facsimile Statistical Time Interval (FSTI). The FSTI shall be selectable in the range from 10 minutes to 60 minutes (in 10-minute steps). The summary statistics calculated at the end of the FSTI shall be kept in a statistic data file on a secured storage medium (e.g. non-volatile RAM, hard disk, etc.) (see Note 1). The parameters to be monitored include: + +### a) *Number of facsimile calls* (required) + +Defined as the number of calls (see Note 3) classified as facsimile calls during the FSTI period. + +- b) *Percent of time FEC activated* (required) + +Defined as the ratio of FEC ON time over FSTI. This statistic shall be calculated once every 1-minute interval with the accumulated data from every sampled DCME frame (each 100th frame). + +The percentage should be calculated to one decimal place. + +$$\frac{\text{Sum of FEC active time}}{\text{FSTI}} \times 100$$ + +- c) *Peak number of facsimile banks allocated* (required) + +Defined as the highest number of allocated facsimile banks during FSTI. Intermediate statistic shall be calculated once every 1-minute interval with the accumulated data from every sampled DCME frame (each 100th frame). At the end of FSTI, the biggest number among intermediate statistic is picked as the peak number of facsimile banks. + +- d) *Mean number of facsimile banks allocated* (required) + +Every 100 DCME frames, the number of allocated facsimile bank is recorded. Every minute, the average number of allocated facsimile banks is calculated using the recorded data for that minute. These one-minute average values are again averaged over FSTI. The number should be calculated to one decimal point. + +- e) *Facsimile bank shortage due to bearer congestion* (required) + +Defined as the ratio of DCME frames in which the information contents of the facsimile frame can not be entirely accommodated by the capacity provided by the facsimile banks. The ratio should be expressed as a percentage. + +$$\frac{\text{No. of DCME frames with faxbank shortage}}{\text{No. of DCME frames in FSTI}} \times 100$$ + +- f) *Local and remote error count* (as defined in 10.3) (required) + +*Local error count* + +Defined as the average number of error count (see 10.3) over a FSTI period. The number shall be calculated to two decimal points. Any non-zero error count value shall be stored with a time-stamp in a non-volatile storage medium. + +$$\frac{\text{Sum of error block count in a FSTI period}}{\text{Number of measurement intervals in a FSTI period}}$$ + +*Remote error count* + +Defined as the average number of received error count from a destination over a FSTI period. The number shall be calculated to two decimal points. Any non-zero error count value shall be stored with a time-stamp in a non-volatile storage medium. + +$$\frac{\text{Sum of received error count in the local FSTI period}}{\text{Number of error count reception in the local FSTI period}}$$ + +- g) *Number of calls set up using standard facilities* (optional) (see Note 2) + +Defined as an accumulated number of facsimile calls (see Note 3) which are classified as standard T.30 calls during the FSTI period. + +- h) *numbers of calls set up using non-standard facilities* (optional) + +Defined as an accumulated number of facsimile calls (see Note 3) which are classified as non-standard T.30 calls during the FSTI period. + +- i) *Number of image blocks sent through the facsimile module at each bit rate* (optional) + +Defined as the accumulated count of image blocks (pages, excluding TCF) belonging to the demodulated facsimile calls during the FSTI period. The count of image blocks shall be performed for each bit rate. + +### j) *Number of fallbacks to ADPCM (optional)* + +Defined as an accumulated number of facsimile calls which are switched to ADPCM path during the FSTI period (i.e. "SWITCH\_TO\_ADPCM" code is generated). + +### k) *Number of fallbacks to ADPCM due to failure or inability to handle a call involving NSF (optional)* + +Defined as an accumulated count of facsimile calls which are switched to ADPCM path due to non-standard T.30 facility during the FSTI period. This is a subset of the calls counted in item j). + +### l) *Average number of image blocks per demodulated call (optional)* + +Defined as the ratio of accumulated count of image blocks (pages, excluding TCF) to the number of demodulated and completed facsimile calls during the FSTI period. The number shall be calculated to the first decimal point. + +$$\frac{\text{Accumulated number of image blocks for demodulated signal}}{\text{Number of calls as per item a) – number of calls as per item j)}}$$ + +NOTE 1 – Facsimile module statistics listed as items a) and f) through l) should be provided on a per destination basis. Items b) through e) should be provided on a per pool basis. + +NOTE 2 – If the optional parameters are implemented, they should be done as specified. + +NOTE 3 – The number of calls can be counted either by call start or by call termination at the manufacturer's option. The manufacturer may also divide the calls into transmit calls and receive calls. + +## 10.2 Facsimile module configuration data + +An example of a facsimile module configuration is provided below: + +- 1) FEC activation used or not; +- 2) maximum number of facsimile demodulation/remodulation units; +- 3) option of remodulation output level setting through OMC; +- 4) level of remodulation output. If level option is not selected, the remodulation output level for high and low speed signals shall be set as the first received high and low speed signal levels from the corresponding DCME, respectively. + +## 10.3 Error count + +The facsimile module error monitor shall accumulate, over a 30-second interval, the count of the number of facsimile control channel blocks (32 bits per block) in which the syndrome of the FEC code indicates that bits within the block required correction. If 255 or more of such blocks are accumulated, the count indication will remain at 255 until reset for the next measurement interval. The error count shall be transmitted over the service channel (see 7.3) after every measurement interval. + +## 10.4 FEC activation + +FEC activation shall be under operator control. The optional feature of automatic FEC activation based on remote error measurements and local load conditions is for further study. + +# 11 Required DCME modifications + +The major impact of integrating the facsimile module described in this Recommendation with equipment conforming to Recommendation G.763 is summarized below. + +## 11.1 Facsimile data handling + +The facsimile data provided to the DCME via the facsimile data interface is inserted by the DCME into its bearer frame. The FTCs are transmitted by means of special 4-bit channels (32 kbit/s) called "fax banks". Fax banks are created and deleted in response to requests from the facsimile module, so that there are always as many fax banks in the bearer frame as there are FTCs in the facsimile data interface. + +Assignment messages are generated by the DCME for the creation of the fax banks. These can symbolically be represented as follows: + +**(BC, 251)** + +where BC is the BC number (normal range) to which the fax bank is assigned, and 251 is the IT number used to identify the BC number as a fax bank. The synchronous data word will contain ineffective message code "0000". + +The deletion of a fax bank is associated with the generation of an explicit disconnection message of the type: + +**(BC, 0)** + +where BC is the number to be disconnected and the synchronous data word will contain the ineffective message code "0000". + +In order to handle assignments of 64 kbit/s unrestricted calls, reassignment of a fax bank may be required. The reassignment shall be made in two steps. First, a new fax bank is assigned to the bearer channel number to which the old fax bank will be reassigned. Second, the old fax bank shall be disconnected through an explicit disconnection message. + +## 11.2 Changes in the DCME processes + +The HSC process of the DCME must provide five messages to the CCF, Data(IT), Data Inact(IT), Voice(IT), Transp(IT) and RxData(IT). + +The CCF provides two messages to the HSC. The first message forces an "inactive" declaration for the IT. The second message removes this condition. + +The CCF sends messages to the RAG process for the creation and release of fax banks. Two new queues need to be added to the input pre-processing task. One queue is for the creation of a fax bank. The priority should be immediately below the current priority 3 (64 kbit/s unrestricted request as per A.1.1.2.1.1/G.763). The second queue is for the release of a fax bank. Its priority should be immediately below the current priority 1 (unrestricted 64 kbit/s release). + +ANNEX A + +**Examples of FCH protocol exchanges** + +Example cases of possible protocol exchanges were analysed and are described in this annex. The polling of 18 cases were analysed (from 0 to 4 cases per configuration). Table A.1 shows which configurations were addressed by the different example cases. In cases 1 to 18, the SDL states for the PA approach are included within parentheses. Corresponding states for the WA approach are omitted because the SDL for WA is not provided. + +**Table A.1/G.766 – Cases analysed in Annex A** + +| | Calling FCH → Called FCH | | | | +|------------------------------------------------------------------------------|--------------------------|---------|------------|---------| +| | PA → PA | PA → PA | WA → PA | WA → WA | +| Call type | PA → PA | PA → PA | WA → PA | WA → WA | +| SF-T.30
Matched resources | 1, 2 | 3, 4 | 5, 6, 7, 8 | 9, 10 | +| NSF-T.30
Matched resources | 11 | 12 | 13 | | +| SF-T.30
Unmatched resources
(ADPCM) | 14 | 15 | 16 | 18 | +| NSF-T.30
Unmatched resources
(ADPCM) | 17 | | | | +| NOTE – Case numbers applicable to each configuration are shown in the table. | | | | | + +**A.1 SF-T.30 cases with matched capabilities** + +**Case 1: Protocol analysis (PA)-PA, no polling** + +PA (Receive, Called) PA (Transmit, Calling) + +--- + +1. Call start + +← + +--- + +(Pre\_FAX) (Pre\_FAX) +Start DIS timer Start DIS timer + +2. BEGINNING OF DIS (ADPCM) + +→ + +--- + +3. + +CONNECT (list) → + +--- + +Start resource timer +Allocate resource +(Called\_FAX) + +4. + +← RESOURCE (list) + +--- + +Allocate resource + (Calling\_FAX) + +36 **Recommendation G.766 (11/96)** + +5. END OF DIS (ADPCM) + +—————→ + +6. + +—————SWITCH\_TO\_DEMOD—————→ + +Start DCS timer +Start demodulation path + +Start DCS timer +Start demodulation path +Insert fixed delay + +7. + +←————— SIGNALLING —————→ +Demodulated DCS + +8. + +←————— IDLE —————→ + +Compatibility is verified for both +DCMEs with received DCS + +(Receive\_Fax) + +(Transmit\_FAX) + +9. + +←————— EPT(f) —————→ +Code only + +(Remote\_EPT) + +(Local\_EPT) + +10. + +←————— END\_EPT —————→ + +(Remote\_Training) + +(Local\_Training) + +11. + +←————— TRAINING (mode, rate, long) —————→ +Code only + +12. + +←————— FAX\_DATA —————→ +Demodulated TCF + +(Remodulate\_Data) + +(Demodulate\_Data) + +13. + +←————— IDLE —————→ + +The differentiation between data and +TCF is handled by receive side of +PA\_FCH + +(Rx\_Local\_Signal) + +(Tx\_Remote\_Signal) + +14. + +————— SIGNALLING —————→ +Demodulated CFR + +15. + +————— IDLE —————→ + +(Receive\_FAX) + +(Transmit\_FAX) + +16. + +← TRAINING (mode, rate, long) → + +Code only + +(Remote\_Training) (Local\_Training) + +17. + +← FAX DATA → + +Demodulated data + +(Remodulate\_Data) (Demodulate\_Data) + +18. + +← IDLE → + +(Rx\_Remote\_Signal) (Tx\_Local\_Signal) + +19. + +← SIGNALLING → + +Demodulated EOP + +20. + +← IDLE → + +(Rx\_Local\_Signal) (Tx\_Remote\_Signal) + +21. + +SIGNALLING → + +Demodulated MCF + +22. + +IDLE → + +(Rx\_Remote\_Signal) (Tx\_Local\_Signal) + +23. + +← SIGNALLING + +Demodulated DCN + +24. + +← DISCONNECT + +Close demodulation path Close demodulation path +Fixed delay is removed +Termination of FCH process + +25. + +DISCONNECT → + +Termination of FCH process + +**Case 2: PA-PA, polling** + +PA (Receive, Calling) PA (Transmit, Called) + +1. Call start + +→ + +(Pre\_FAX) (Pre\_FAX) +Start DIS timer Start DIS timer + +38 **Recommendation G.766 (11/96)** + +### 2. BEGINNING OF DIS (ADPCM) + +< + +| | | | +|-------------------|--------------------|----------------------| +| 3. | < CONNECT (list) > | | +| | | Start RESOURCE timer | +| Allocate resource | | | +| | | (Called_FAX) | + +| | | | +|----|-------------------|-------------------| +| 4. | RESOURCE (list) > | | +| | | Allocate resource | +| | | (Calling_FAX) | + +### 5. END OF DIS (ADPCM) + +< + +| | | | +|------------------------------------------------------------------|---------------------|--------------------------------------------| +| 6. | < SWITCH_TO_DEMOD > | | +| Start DCS timer
Start demodulation path
Insert fixed delay | | Start demodulation path
Start DCS timer | + +| | | | +|----|-----------------|--| +| 7. | SIGNALLING > | | +| | Demodulated DTC | | + +| | | | +|--------------------|--------|--------------------| +| 8. | IDLE > | | +| Delete fixed delay | | Insert fixed delay | + +| | | | +|----|-----------------|--| +| 9. | < SIGNALLING > | | +| | Demodulated DCS | | + +| | | | +|---------------|----------|------------------------------------------------------------| +| 10. | < IDLE > | | +| | | Compatibility is verified for both DCMEs with received DCS | +| (Receive_FAX) | | (Transmit_FAX) | + +NOTE – From now on, procedure is same as case 1, line 9. + +#### **Case 3: PA calling – WA called, no polling** + +| | | +|----------------------|------------------------| +| WA (Receive, Called) | PA (Transmit, Calling) | +|----------------------|------------------------| + +| | | | +|-----------------|---|-----------------| +| 1. Call start | | | +| | < | | +| | | (Pre_FAX) | +| Start DIS timer | | Start DIS timer | + +#### 2. BEGINNING OF DIS (ADPCM) + +> + +3. + +\_\_\_\_\_ CONNECT (list) \_\_\_\_\_> +Start RESOURCE timer +Allocate resource + +4. + +<\_\_\_\_\_ RESOURCE (list) \_\_\_\_\_ +Allocate resource +(Calling\_FAX) + +5. END OF DIS (ADPCM) + +\_\_\_\_\_> + +6. + +\_\_\_\_\_SWITCH\_TO\_DEMOD\_\_\_\_\_> +Insert fixed delay +Start demodulation path +Start DCS timer +Start DCS timer +Start demodulation path +Insert fixed delay + +7. + +<\_\_\_\_\_ SIGNALLING \_\_\_\_\_ +Demodulated DCS + +8. + +<\_\_\_\_\_ IDLE \_\_\_\_\_ +Compatibility is verified for both +DCMEs with received DCS +(Transmit\_FAX) + +9. + +<\_\_\_\_\_ EPT(f) \_\_\_\_\_ +Code only +(Local\_EPT) + +10. + +<\_\_\_\_\_ END\_EPT \_\_\_\_\_ +Local\_Training + +11. + +<\_\_\_\_\_ TRAINING (mode, rate, long) \_\_\_\_\_ +Code only +Delete fixed delay + +12. + +<\_\_\_\_\_ FAX\_DATA \_\_\_\_\_ +Demodulated TCF +(Demodulate\_Data) + +13. + +<\_\_\_\_\_ IDLE \_\_\_\_\_ +No differentiation between data and +TCF signals + +14. + +————— SIGNALLING —————> +Demodulated CFR + +15. + +————— IDLE —————> +(Transmit\_FAX) + +16. + +<————— EPT(f) ————— + +17. + +<————— END\_EPT ————— + +18. + +<————— TRAINING (mode, rate, long) ————— +Code only +(Local\_Training) + +19. + +<————— FAX DATA ————— +Demodulated data +(Demodulated\_Data) + +20. + +<————— IDLE ————— +(Tx\_Local\_Signal) + +21. + +<————— SIGNALLING ————— +Demodulated EOP + +22. + +<————— IDLE ————— +(Tx\_Remote\_Signal) + +23. + +————— SIGNALLING —————> +Demodulated MCF + +24. + +————— IDLE —————> +(Tx\_Local\_Signal) + +25. + +<————— SIGNALLING ————— +Demodulated DCN + +26. + +<————— DISCONNECT ————— + +Close demodulation path + +Close demodulation path +Fixed delay is removed +Termination of FCH process + +27. + +\_\_\_\_\_ DISCONNECT \_\_\_\_\_> +Termination of FCH process + +#### **Case 4: PA calling – WA called, polling** + +Waveform analysis DCME communicates with protocol analysis DCME. Protocol analysis DCME initiates a call, but receives facsimile pages. + +![](7fe5741e83bc9702d1b1d7585ddf66bd_img.jpg) + +| WA (Transmit, Called) | PA (Receive, Calling) | +|-------------------------------|-------------------------| +| 1. Call start | | +| ← _____ | | +| | (Pre_FAX) | +| Start DIS timer | Start DIS timer | +| 2. BEGINNING OF DIS (ADPCM) | | +| _____> | | +| 3. | | +| _____ CONNECT (list) _____> | | +| Start RESOURCE timer | | +| Allocate resource | | +| 4. | | +| ← _____ RESOURCE (list) _____ | | +| | Allocate resource | +| | (Calling_FAX) | +| 5. END OF DIS (ADPCM) | | +| _____> | | +| 6. | | +| _____ SWITCH_TO_DEMOD _____> | | +| Insert fixed delay | Start DCS timer | +| Start demodulation path | Insert fixed delay | +| | Start demodulation path | +| 7. | | +| ← _____ SIGNALLING _____ | | +| | Demodulated DTC | +| 8. | | +| ← _____ IDLE _____ | | +| | Delete fixed delay | +| 9. | | +| ← _____ SIGNALLING _____ | | +| | Demodulated DCS | +| 10. | | +| ← _____ IDLE _____ | | +| | (Receive_FAX) | + +11. + +![Sequence diagram for step 11: A left-pointing arrow labeled EPT(f) with 'Code only' below it. To the right of the arrow is '(Remote_EPT)'.](ae0a735d106290c594b0bafb1f5e72e7_img.jpg) + +← EPT(f) +Code only +(Remote\_EPT) + +Sequence diagram for step 11: A left-pointing arrow labeled EPT(f) with 'Code only' below it. To the right of the arrow is '(Remote\_EPT)'. + +12. + +![Sequence diagram for step 12: A left-pointing arrow labeled END_EPT.](8d66c9c295023a1380f9986d3663bb1e_img.jpg) + +← END\_EPT + +Sequence diagram for step 12: A left-pointing arrow labeled END\_EPT. + +13. + +![Sequence diagram for step 13: A left-pointing arrow labeled TRAINING (mode, rate, long) with 'Code only' below it.](1ce027dfd26183da52137cf990213724_img.jpg) + +← TRAINING (mode, rate, long) +Code only + +Sequence diagram for step 13: A left-pointing arrow labeled TRAINING (mode, rate, long) with 'Code only' below it. + +Compatibility is verified for both DCMEs + +The PA\_FCH determines the training sequence parameters from independent protocol analysis. The training code is only used to start a training sequence. + +14. + +![Sequence diagram for step 14: A right-pointing arrow labeled LONG_TRAINING (rate).](b4f6d3668f7e851eaff07ccf26001623_img.jpg) + +→ LONG\_TRAINING (rate) + +Sequence diagram for step 14: A right-pointing arrow labeled LONG\_TRAINING (rate). + +The rate information comes later because WA\_FCH does not know it beforehand. + +15. + +![Sequence diagram for step 15: A right-pointing arrow labeled FAX_DATA with 'Demodulated data' below it. To the right of the arrow is '(Remodulate_Data)'.](da434ee158d8bd56122f990b91dc17ba_img.jpg) + +→ FAX\_DATA +Demodulated data +(Remodulate\_Data) + +Sequence diagram for step 15: A right-pointing arrow labeled FAX\_DATA with 'Demodulated data' below it. To the right of the arrow is '(Remodulate\_Data)'. + +16. + +![Sequence diagram for step 16: A right-pointing arrow labeled IDLE. To the right of the arrow are 'No differentiation between data and TCF signals' and '(Rx_Local_Signal)'.](901800172164e0494762ffa57a09993f_img.jpg) + +→ IDLE +No differentiation between data and TCF signals +(Rx\_Local\_Signal) + +Sequence diagram for step 16: A right-pointing arrow labeled IDLE. To the right of the arrow are 'No differentiation between data and TCF signals' and '(Rx\_Local\_Signal)'. + +17. + +![Sequence diagram for step 17: A left-pointing arrow labeled SIGNALLING with 'Demodulated CFR' below it.](ca322f838ed1785bc0de168636f7b426_img.jpg) + +← SIGNALLING +Demodulated CFR + +Sequence diagram for step 17: A left-pointing arrow labeled SIGNALLING with 'Demodulated CFR' below it. + +18. + +![Sequence diagram for step 18: A right-pointing arrow labeled IDLE. To the right of the arrow is '(Receive_FAX)'.](35656f382b89337af282106bd74b4f50_img.jpg) + +→ IDLE +(Receive\_FAX) + +Sequence diagram for step 18: A right-pointing arrow labeled IDLE. To the right of the arrow is '(Receive\_FAX)'. + +19. + +![Sequence diagram for step 19: A right-pointing arrow labeled EPT(f) with 'Code only' below it. To the right of the arrow is '(Remote_EPT)'.](e1a3f5045f139b39707b3ebb76ad254c_img.jpg) + +→ EPT(f) +Code only +(Remote\_EPT) + +Sequence diagram for step 19: A right-pointing arrow labeled EPT(f) with 'Code only' below it. To the right of the arrow is '(Remote\_EPT)'. + +20. + +![Sequence diagram for step 20: A right-pointing arrow labeled END_EPT. To the right of the arrow is '(Remote_Training)'.](a1d890ccd945825108be7514701d9e0d_img.jpg) + +→ END\_EPT +(Remote\_Training) + +Sequence diagram for step 20: A right-pointing arrow labeled END\_EPT. To the right of the arrow is '(Remote\_Training)'. + +21. + +![Sequence diagram for step 21: A right-pointing arrow labeled TRAINING (mode, rate, long).](a8a53b4bdc49bf9d622633e0764fe151_img.jpg) + +→ TRAINING (mode, rate, long) + +Sequence diagram for step 21: A right-pointing arrow labeled TRAINING (mode, rate, long). + + + +3. + +![Sequence diagram step 3: CONNECT (list) message from right to left. On the right side, actions include: Start RESOURCE timer, Allocate resource, and (Called_FAX).](3d6f5edac3d5e7113d960c2202f1b0fa_img.jpg) + +← CONNECT (list) → +Start RESOURCE timer +Allocate resource +(Called\_FAX) + +Sequence diagram step 3: CONNECT (list) message from right to left. On the right side, actions include: Start RESOURCE timer, Allocate resource, and (Called\_FAX). + +4. + +![Sequence diagram step 4: RESOURCE (list) message from left to right. On the left side, action: Allocate resource.](187d05bf7ead21e1394b61320d8b3632_img.jpg) + +→ RESOURCE (list) → +Allocate resource + +Sequence diagram step 4: RESOURCE (list) message from left to right. On the left side, action: Allocate resource. + +5. END OF DIS (ADPCM) + +![Sequence diagram step 5: END OF DIS (ADPCM) message from right to left.](036c200da9b64c3eb5aae2d67bb53e1f_img.jpg) + +← + +Sequence diagram step 5: END OF DIS (ADPCM) message from right to left. + +6. + +![Sequence diagram step 6: SWITCH_TO_DEMOD message from left to right. On the left side, actions: Insert fixed delay, Start demodulation path. On the right side, actions: Start DCS timer, Start demodulation path.](396197257cf9437b526bb6585b6a9c8a_img.jpg) + +← SWITCH\_TO\_DEMOD → +Insert fixed delay +Start demodulation path +Start DCS timer +Start demodulation path + +Sequence diagram step 6: SWITCH\_TO\_DEMOD message from left to right. On the left side, actions: Insert fixed delay, Start demodulation path. On the right side, actions: Start DCS timer, Start demodulation path. + +7. + +![Sequence diagram step 7: SIGNALLING message from left to right. Below the message line, text: Demodulated DCS.](2aa94b70ba3fadcba8420d9e3128253a_img.jpg) + +→ SIGNALLING → +Demodulated DCS + +Sequence diagram step 7: SIGNALLING message from left to right. Below the message line, text: Demodulated DCS. + +8. + +![Sequence diagram step 8: IDLE message from left to right. On the right side, action: (Receive_FAX).](5c65cabec7c5062117fb0d578916cf8b_img.jpg) + +→ IDLE → +(Receive\_FAX) + +Sequence diagram step 8: IDLE message from left to right. On the right side, action: (Receive\_FAX). + +9. + +![Sequence diagram step 9: EPT message from left to right. Below the message line, text: Code only. On the right side, action: (Remote_EPT).](fdc47b9a20953c3611add6122f6831bf_img.jpg) + +→ EPT → +Code only +(Remote\_EPT) + +Sequence diagram step 9: EPT message from left to right. Below the message line, text: Code only. On the right side, action: (Remote\_EPT). + +10. + +![Sequence diagram step 10: END_EPT message from left to right.](85c4282df510941b5d97b3cf36b11e2a_img.jpg) + +→ END\_EPT → + +Sequence diagram step 10: END\_EPT message from left to right. + +11. + +![Sequence diagram step 11: TRAINING (mode, rate, long) message from left to right. On the left side, text: Code only, Compatibility is verified for both DCMEs. On the right side, text: The PA_FCH determines the training sequence parameters from independent protocol analysis. The training code is only used to start a training sequence.](1a74cf06fd2a1f8dcf7932224b617c57_img.jpg) + +→ TRAINING (mode, rate, long) → +Code only +Compatibility is verified for both DCMEs +The PA\_FCH determines the training sequence parameters from independent protocol analysis. The training code is only used to start a training sequence. + +Sequence diagram step 11: TRAINING (mode, rate, long) message from left to right. On the left side, text: Code only, Compatibility is verified for both DCMEs. On the right side, text: The PA\_FCH determines the training sequence parameters from independent protocol analysis. The training code is only used to start a training sequence. + +12. + +![Sequence diagram step 12: LONG_TRAINING (rate) message from left to right. Below the message line, text: The rate information comes later because WA_FCH does not know it beforehand.](64292f0aa64a9b2e9b1c9516700433a4_img.jpg) + +→ LONG\_TRAINING (rate) → +The rate information comes later because WA\_FCH does not know it beforehand + +Sequence diagram step 12: LONG\_TRAINING (rate) message from left to right. Below the message line, text: The rate information comes later because WA\_FCH does not know it beforehand. + +13. + +![Sequence diagram step 13: FAX_DATA message from left to right. Below the message line, text: Demodulated Data. On the right side, action: (Remodulate_Data).](3ca3a374ff4460d3b2bf220ebb287fa9_img.jpg) + +→ FAX\_DATA → +Demodulated Data +(Remodulate\_Data) + +Sequence diagram step 13: FAX\_DATA message from left to right. Below the message line, text: Demodulated Data. On the right side, action: (Remodulate\_Data). + +![](2580688a4de0a29692805cc6ba4822d7_img.jpg) + +14. \_\_\_\_\_ IDLE \_\_\_\_\_> + No differentiation between data and TCF signals + (Rx\_Local\_Signal) + +15. <\_\_\_\_\_SIGNALLING\_\_\_\_\_> + Demodulated CFR + +16. <\_\_\_\_\_ IDLE \_\_\_\_\_> + (Receive\_FAX) + +17. \_\_\_\_\_ EPT(f) \_\_\_\_\_> + Code only + (Remote\_EPT) + +18. \_\_\_\_\_ END\_EPT \_\_\_\_\_> + (Remote\_Training) + +19. \_\_\_\_\_ TRAINING (mode, rate, long) \_\_\_\_\_> + +20. \_\_\_\_\_ FAX DATA \_\_\_\_\_> + Demodulated data + (Remodulate\_Data) + +21. \_\_\_\_\_ IDLE \_\_\_\_\_> + (Rx\_Remote\_Signal) + +22. \_\_\_\_\_ SIGNALLING \_\_\_\_\_> + Demodulated EOP + +23. \_\_\_\_\_ IDLE \_\_\_\_\_> + (Rx\_Local\_Signal) + +24. <\_\_\_\_\_ SIGNALLING \_\_\_\_\_> + Demodulated MCF + +25. <\_\_\_\_\_ IDLE \_\_\_\_\_> + (Rx\_Remote\_Signal) + +26. \_\_\_\_\_ SIGNALLING \_\_\_\_\_> + Demodulated DCN + +27. + +\_\_\_\_\_ IDLE \_\_\_\_\_> + +Since DCN signal is not decoded, the +end of call is known when: + +- 1) data hangover timer +(G.763) expires; or +- 2) voice is detected. + +DCN is detected + +28. + +<\_\_\_\_\_ DISCONNECT \_\_\_\_\_ + +Delete fixed delay +Close demonstration path + +Close demodulation path +Termination of FCH process + +29. + +<\_\_\_\_\_ DISCONNECT \_\_\_\_\_ + +Termination of FCH process + +#### Case 6: WA calling – PA called, polling + +WA (Receive, Calling) + +PA (Transmit, Called) + +1. Call start + +\_\_\_\_\_> + +(Pre\_FAX) + +Start DIS timer + +Start DIS timer + +2. BEGINNING OF DIS (ADPCM) + +<\_\_\_\_\_ + +3. + +<\_\_\_\_\_ CONNECT (list) \_\_\_\_\_ + +Start RESOURCE timer +Allocate resource + +(Called\_FAX) + +4. + +\_\_\_\_\_ RESOURCE (list) \_\_\_\_\_> + +Allocate resource + +5. END OF DIS (ADPCM) + +<\_\_\_\_\_ + +6. + +<\_\_\_\_\_ SWITCH\_TO\_DEMOD \_\_\_\_\_ + +Start demodulation path +Insert fixed delay + +Start DCS timer +Start demodulation path + +7. + +\_\_\_\_\_ SIGNALLING \_\_\_\_\_> + +Demodulated DTC + +8. + +\_\_\_\_\_ IDLE \_\_\_\_\_> + +Insert fixed delay + +9. + +← ————— SIGNALLING ————— +Demodulated DCS + +10. + +← ————— IDLE ————— + +Compatibility is verified for both +DCMEs with received DCS + +11. + +(Transmit\_FAX) + +← ————— EPT(f) ————— +Code only + +(Local\_EPT) + +12. + +← ————— END\_EPT ————— + +(Local\_Training) + +13. + +← ————— TRAINING (mode, rate, long) ————— +Code only + +Delete fixed delay + +14. + +← ————— FAX\_DATA ————— +Demodulated TCF + +(Demodulate\_Data) + +15. + +← ————— IDLE ————— + +No differentiation between data and +TCF signals + +16. + +————— SIGNALLING —————→ +Demodulated CFR + +17. + +————— IDLE —————→ + +(Transmit\_FAX) + +18. + +← ————— EPT(f) ————— +Code only + +(Local\_EPT) + +19. + +← ————— END\_EPT ————— + +(Local\_Training) + +20. + +← ————— TRAINING (mode, rate, long) ————— + +21. + +![Sequence diagram for step 21: WA sends FAX DATA to PA. PA receives Demodulated data and sends (Demodulate_Data) back to WA.](284768c5ee1a05aa1b9ce396f606a040_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 21. + WA->>PA: FAX DATA + Note right of PA: Demodulated data + PA-->>WA: (Demodulate_Data) + +``` + +Sequence diagram for step 21: WA sends FAX DATA to PA. PA receives Demodulated data and sends (Demodulate\_Data) back to WA. + +22. + +![Sequence diagram for step 22: PA sends IDLE signal back to WA. WA receives (Tx_Local_Signal).](9e8ebf03cae78f4f81b697548c2d7250_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 22. + PA-->>WA: IDLE + Note right of WA: (Tx_Local_Signal) + +``` + +Sequence diagram for step 22: PA sends IDLE signal back to WA. WA receives (Tx\_Local\_Signal). + +23. + +![Sequence diagram for step 23: WA sends SIGNALLING to PA. PA receives Demodulated EOP.](18e519d1f91133e080347562f681dfb5_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 23. + WA->>PA: SIGNALLING + Note right of PA: Demodulated EOP + +``` + +Sequence diagram for step 23: WA sends SIGNALLING to PA. PA receives Demodulated EOP. + +24. + +![Sequence diagram for step 24: PA sends IDLE signal back to WA. WA receives (Tx_Remote_Signal).](3e2dcee303cecdd31b7f9ec0d8942fed_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 24. + PA-->>WA: IDLE + Note right of WA: (Tx_Remote_Signal) + +``` + +Sequence diagram for step 24: PA sends IDLE signal back to WA. WA receives (Tx\_Remote\_Signal). + +25. + +![Sequence diagram for step 25: WA sends SIGNALLING to PA. PA receives Demodulated MCF.](b06a4c871dfd0ce034cf801519d0039a_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 25. + WA->>PA: SIGNALLING + Note right of PA: Demodulated MCF + +``` + +Sequence diagram for step 25: WA sends SIGNALLING to PA. PA receives Demodulated MCF. + +26. + +![Sequence diagram for step 26: PA sends IDLE signal back to WA. WA receives (Tx_Local_Signal).](daf05db9f13b34fb12da52f007bbfe5b_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 26. + PA-->>WA: IDLE + Note right of WA: (Tx_Local_Signal) + +``` + +Sequence diagram for step 26: PA sends IDLE signal back to WA. WA receives (Tx\_Local\_Signal). + +27. + +![Sequence diagram for step 27: WA sends SIGNALLING to PA. PA receives Demodulated DCN.](1a1484a99fee36bd3ca4e40fe1538bf8_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 27. + WA->>PA: SIGNALLING + Note right of PA: Demodulated DCN + +``` + +Sequence diagram for step 27: WA sends SIGNALLING to PA. PA receives Demodulated DCN. + +28. + +![Sequence diagram for step 28: WA sends DISCONNECT to PA. PA receives Close demodulation path, Fixed delay is removed, and Termination of FCH process.](0ed8d001e745e9b2bb07fc63eb8525d5_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 28. + WA->>PA: DISCONNECT + Note left of WA: Close demodulation path + Note right of PA: Close demodulation path +Fixed delay is removed +Termination of FCH process + +``` + +Sequence diagram for step 28: WA sends DISCONNECT to PA. PA receives Close demodulation path, Fixed delay is removed, and Termination of FCH process. + +29. + +![Sequence diagram for step 29: PA sends DISCONNECT back to WA. WA receives Termination of FCH process.](f98674fcf898dbd5225f8f732a393e1c_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 29. + PA-->>WA: DISCONNECT + Note left of WA: Termination of FCH process + +``` + +Sequence diagram for step 29: PA sends DISCONNECT back to WA. WA receives Termination of FCH process. + +#### **Case 7: WA calling – PA called, no polling, error (voice detection)** + +WA (Transmit, Calling) + +PA (Receive, Called) + +1. Call start + +![Sequence diagram for step 1: WA sends signal to PA. PA receives (Pre_FAX) and starts DIS timer. WA also starts DIS timer.](6d4bd1fba2f3fb769b206d775f6e25cd_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 1. Call start + WA->>PA: + Note right of PA: (Pre_FAX) +Start DIS timer + Note left of WA: Start DIS timer + +``` + +Sequence diagram for step 1: WA sends signal to PA. PA receives (Pre\_FAX) and starts DIS timer. WA also starts DIS timer. + +2. BEGINNING OF DIS (ADPCM) + +![Sequence diagram for step 2: PA sends signal to WA.](de49f6a0c38160bb2518f02810660388_img.jpg) + +``` + +sequenceDiagram + participant WA + participant PA + Note left of WA: 2. BEGINNING OF DIS (ADPCM) + PA-->>WA: + +``` + +Sequence diagram for step 2: PA sends signal to WA. + +3. + +← ————— CONNECT (list) —————> +Start RESOURCE timer +Allocate resource +(Called\_FAX) + +4. + +————— RESOURCE (list) —————> +Allocate resource + +5. END OF DIS (ADPCM) + +← ————— + +6. + +← ————— SWITCH\_TO\_DEMOD —————> +Insert fixed delay +Start demodulation path +Start DCS timer +Start demodulation path + +7. + +————— SIGNALLING —————> +Demodulated DCS + +8. + +————— IDLE —————> +(Receive\_FAX) + +9. + +————— EPT(f) —————> +Code only + +10. + +————— END\_EPT —————> +(Remote\_EPT) + +11. + +————— TRAINING (mode, rate, long) —————> +Code only + +Compatibility is verified for both +DCMEs + +The PA\_FCH determines the training +sequence parameters from independent +protocol analysis. The training code is +only used to start a training sequence. + +12. + +————— LONG\_TRAINING (rate) —————> + +The rate information comes later +because WA\_FCH does not know it +beforehand + +13. + +————— FAX\_DATA —————> +Demodulated data +(Remodulate\_Data) + + + +9. + +![Sequence diagram step 9: An arrow points from left to right. Above the arrow is 'EPT(f)'. Below the arrow on the left is 'Code only'. Below the arrow on the right is '(Remote_EPT)'.](7d929ba1b7d09ea8e00b9e7abbbe50c9_img.jpg) + +EPT(f) → +Code only +(Remote\_EPT) + +Sequence diagram step 9: An arrow points from left to right. Above the arrow is 'EPT(f)'. Below the arrow on the left is 'Code only'. Below the arrow on the right is '(Remote\_EPT)'. + +10. + +![Sequence diagram step 10: An arrow points from left to right. Above the arrow is 'END_EPT'. Below the arrow on the right is '(Remote_Training)'.](3337af75dfee8af7687b4f49914d6c93_img.jpg) + +END\_EPT → +(Remote\_Training) + +Sequence diagram step 10: An arrow points from left to right. Above the arrow is 'END\_EPT'. Below the arrow on the right is '(Remote\_Training)'. + +11. + +![Sequence diagram step 11: An arrow points from left to right. Above the arrow is 'TRAINING (mode, rate, long)'. Below the arrow on the left is 'Code only'.](1033dc9fde75540d224c907681b1b7aa_img.jpg) + +TRAINING (mode, rate, long) → +Code only + +Sequence diagram step 11: An arrow points from left to right. Above the arrow is 'TRAINING (mode, rate, long)'. Below the arrow on the left is 'Code only'. + +Compatibility is verified for both DCMEs + +The PA\_FCH determines the training sequence parameters from independent protocol analysis. The training code is only used to start a training sequence. + +12. + +![Sequence diagram step 12: An arrow points from left to right. Above the arrow is 'LONG_TRAINING (rate)'.](85b53faf49a839f512153285c78fbbdb_img.jpg) + +LONG\_TRAINING (rate) → + +Sequence diagram step 12: An arrow points from left to right. Above the arrow is 'LONG\_TRAINING (rate)'. + +Rate information is misclassified and modem will not lock + +13. + +![Sequence diagram step 13: An arrow points from right to left. Above the arrow is 'DISCONNECT'.](3bd9d303382ff0566369ed81a9226ade_img.jpg) + +← DISCONNECT + +Sequence diagram step 13: An arrow points from right to left. Above the arrow is 'DISCONNECT'. + +Delete fixed delay +Close demodulation path +Termination of FCH process + +Close demodulation path + +14. + +![Sequence diagram step 14: An arrow points from left to right. Above the arrow is 'DISCONNECT'. Below the arrow on the right is 'Termination of FCH process'.](5593facb376cb360bd4b0960b2911b3e_img.jpg) + +DISCONNECT → +Termination of FCH process + +Sequence diagram step 14: An arrow points from left to right. Above the arrow is 'DISCONNECT'. Below the arrow on the right is 'Termination of FCH process'. + +#### Case 9: WA-WA, no polling + +WA (Transmit, Calling) + +WA (Receive, Called) + +1. Call start + +![Sequence diagram step 1: A plain arrow points from left to right.](d12f6e3a624c7ad7d0ec11ff32f93c7e_img.jpg) + +→ + +Sequence diagram step 1: A plain arrow points from left to right. + +Start DIS timer + +Start DIS timer + +2. BEGINNING OF DIS (ADPCM) + +![Sequence diagram step 2: A plain arrow points from right to left.](d3aca6b44569b30f904a41c162ee4574_img.jpg) + +← + +Sequence diagram step 2: A plain arrow points from right to left. + +3. + +![Sequence diagram step 3: An arrow points from right to left. Above the arrow is 'CONNECT (list)'.](db3992e73a52d7fc21170e88fbf5c9a4_img.jpg) + +← CONNECT (list) + +Sequence diagram step 3: An arrow points from right to left. Above the arrow is 'CONNECT (list)'. + +Start RESOURCE timer +Allocate resource + +4. + +![Sequence diagram step 4: An arrow points from left to right. Above the arrow is 'RESOURCE (list)'.](3df2b955344187203a2110b5884d3a25_img.jpg) + +RESOURCE (list) → + +Sequence diagram step 4: An arrow points from left to right. Above the arrow is 'RESOURCE (list)'. + +Allocate resource + +5. END OF DIS (ADPCM) + +![Sequence diagram step 5: A plain arrow points from right to left.](e9d3c71f5a5965571c277554a7e33ea9_img.jpg) + +← + +Sequence diagram step 5: A plain arrow points from right to left. + +6. + +<----- SWITCH\_TO\_DEMOD -----> + +Insert fixed delay +Start demodulation path + +Start demodulation path +Insert fixed delay + +7. + +-----> SIGNALLING -----> + +Demodulated DCS + +8. + +----- IDLE -----> + +9. + +----- EPT(f) -----> + +Code only + +10. + +----- END\_EPT -----> + +11. + +----- TRAINING (mode, rate, long) -----> + +Code only + +Compatibility is verified for both +DCMEs + +Delete fixed delay + +12. + +----- LONG\_TRAINING (rate) -----> + +The rate information comes later + +13. + +----- FAX\_DATA -----> + +Demodulated data + +14. + +----- IDLE -----> + +No differentiation between data and +TCF signals + +15. + +<----- SIGNALLING -----> + +Demodulated CFR + +16. + +<----- IDLE -----> + +17. + +----- EPT(f) -----> + +Code only + +18. + +----- END\_EPT -----> + +19. + +----- TRAINING (mode, rate, long) -----> + +20. + +![Sequence diagram for step 20: A horizontal line with an arrow pointing right, labeled 'FAX_DATA' above and 'Demodulated data' below.](0ccaa59b5bc46884777e728ee3dadaa7_img.jpg) + +FAX\_DATA +Demodulated data + +Sequence diagram for step 20: A horizontal line with an arrow pointing right, labeled 'FAX\_DATA' above and 'Demodulated data' below. + +21. + +![Sequence diagram for step 21: A horizontal line with an arrow pointing right, labeled 'IDLE' above.](b34c69e1ec326b01c3a485b27b1df5f6_img.jpg) + +IDLE + +Sequence diagram for step 21: A horizontal line with an arrow pointing right, labeled 'IDLE' above. + +22. + +![Sequence diagram for step 22: A horizontal line with an arrow pointing right, labeled 'SIGNALLING' above and 'Demodulated EOP' below.](848073118eebfdbfdb9a60e3923fe0b3_img.jpg) + +SIGNALLING +Demodulated EOP + +Sequence diagram for step 22: A horizontal line with an arrow pointing right, labeled 'SIGNALLING' above and 'Demodulated EOP' below. + +23. + +![Sequence diagram for step 23: A horizontal line with an arrow pointing right, labeled 'IDLE' above.](802707b774f2d2973b49cea2020e8453_img.jpg) + +IDLE + +Sequence diagram for step 23: A horizontal line with an arrow pointing right, labeled 'IDLE' above. + +24. + +![Sequence diagram for step 24: A horizontal line with an arrow pointing left, labeled 'SIGNALLING' above and 'Demodulated MCF' below.](b5987d63203a5fa601921039922ac520_img.jpg) + +SIGNALLING +Demodulated MCF + +Sequence diagram for step 24: A horizontal line with an arrow pointing left, labeled 'SIGNALLING' above and 'Demodulated MCF' below. + +25. + +![Sequence diagram for step 25: A horizontal line with an arrow pointing left, labeled 'IDLE' above.](ec035e97a11ce40541dec6d88d54c7cb_img.jpg) + +IDLE + +Sequence diagram for step 25: A horizontal line with an arrow pointing left, labeled 'IDLE' above. + +26. + +![Sequence diagram for step 26: A horizontal line with an arrow pointing right, labeled 'SIGNALLING' above and 'Demodulated DCN' below.](9dd03da031e134bfc9ecc730dd5f6583_img.jpg) + +SIGNALLING +Demodulated DCN + +Sequence diagram for step 26: A horizontal line with an arrow pointing right, labeled 'SIGNALLING' above and 'Demodulated DCN' below. + +27. + +![Sequence diagram for step 27: A horizontal line with an arrow pointing right, labeled 'IDLE' above.](aff7d03f930d62115362cc026be487ed_img.jpg) + +IDLE + +Sequence diagram for step 27: A horizontal line with an arrow pointing right, labeled 'IDLE' above. + +Since DCN signal is not decoded, the end of a call is known when: + +- 1) data hangover timer (G.763) is expired; or +- 2) voice is detected. + +The end of a call is known when: + +- 1) data hangover timer (G.763) is expired; or +- 2) voice is detected; or +- 3) transparent request is received. + +28. + +![Sequence diagram for step 28: A horizontal line with an arrow pointing right, labeled 'DISCONNECT' above.](e64b41a22015ac3a9c17115aabd51e53_img.jpg) + +DISCONNECT + +Sequence diagram for step 28: A horizontal line with an arrow pointing right, labeled 'DISCONNECT' above. + +Delete fixed delay +Close demodulation path +Termination of FCH process + +Close demodulation path + +29. + +![Sequence diagram for step 29: A horizontal line with an arrow pointing left, labeled 'DISCONNECT' above.](01d733d2c659cc6ddafbe79ae770c01f_img.jpg) + +DISCONNECT + +Sequence diagram for step 29: A horizontal line with an arrow pointing left, labeled 'DISCONNECT' above. + +Termination of FCH process + +#### Case 10: WA-WA, polling + +WA (Transmit, Called) + +WA (Receive, Calling) + +1. Call start + +![Sequence diagram for step 1: A horizontal line with an arrow pointing left.](d26948e4a1aaabe873bcc9c1ad19c6b1_img.jpg) + +Sequence diagram for step 1: A horizontal line with an arrow pointing left. + +Start DIS timer + +Start DIS timer + +#### 2. BEGINNING OF DIS (ADPCM) + +![](3766b291e69420b0437ae278b057b5ee_img.jpg) + +``` + +sequenceDiagram + Note over PA_Called, PA_Calling: 2. BEGINNING OF DIS (ADPCM) + PA_Called->>PA_Calling: + Note over PA_Called: 3. + PA_Called->>PA_Calling: CONNECT (list) + Note left of PA_Called: Start RESOURCE timer +Allocate resource + Note over PA_Called: 4. + PA_Calling->>PA_Called: RESOURCE (list) + Note right of PA_Calling: Allocate resource + Note over PA_Called, PA_Calling: 5. END OF DIS (ADPCM) + PA_Called->>PA_Calling: + Note over PA_Called: 6. + PA_Called->>PA_Calling: SWITCH_TO_DEMOD + Note left of PA_Called: Start demodulation path +Insert fixed delay + Note right of PA_Calling: Start demodulation path +Insert fixed delay + Note over PA_Called: 7. + PA_Calling->>PA_Called: SIGNALLING + Note over PA_Called, PA_Calling: Demodulated DTC + Note over PA_Called: 8. + PA_Calling->>PA_Called: IDLE + Note over PA_Called: 9. + PA_Called->>PA_Calling: SIGNALLING + Note over PA_Called, PA_Calling: Demodulated DCS + Note over PA_Called: 10. + PA_Called->>PA_Calling: IDLE + +``` + +NOTE – From now on, procedure is same as case 9, line 9. + +### **A.2 NSF-T.30 proprietary cases with matched capabilities** + +#### **Case 11: PA Calling – PA Called, no polling** + +![](68a5a1a1a761c652b4b4c56da7cf9914_img.jpg) + +``` + +sequenceDiagram + participant PA_Called as PA (Receive, Called) + participant PA_Calling as PA (Transmit, Calling) + Note over PA_Called: 1. Call start + PA_Calling->>PA_Called: + Note left of PA_Called: (Pre_FAX) +Start DIS timer + Note right of PA_Calling: (Pre_FAX) +Start DIS timer + Note over PA_Called, PA_Calling: 2. BEGINNING OF DIS (ADPCM) + PA_Called->>PA_Calling: + Note over PA_Called: 3. + PA_Called->>PA_Calling: CONNECT (list) + Note left of PA_Called: Start resource timer +Allocate resource +(Called_FAX) + Note right of PA_Calling: (Calling_FAX) + +``` + +![](7e14467740b2570a44379b347a697921_img.jpg) + +4. + +← RESOURCE (list) → + +Allocate resource + +5. END OF DIS (ADPCM) + +→ + +6. + +← SWITCH\_TO\_DEMOD → + +Start DCS timer +Start demodulation path +Start DCS timer +Start demodulation path +Insert fixed delay + +7. + +← SIGNALLING → + +Demodulated NSS +Compatibility is verified for both +DCMEs with received NSS + +8. + +← IDLE → + +Compatibility is verified for both +DCMEs (Rx\_NSF\_T30) +(Tx\_NSF\_T30) + +\*\*\* Many interactions (non-standard image transmission) \*\*\* + +1) Data hangover timer (G.763) is expired; or +2) voice is detected in the channel; or +3) transparent request is received. + +9. + +← DISCONNECT → + +Demodulation path is closed +Demodulation path is closed +Fixed delay is deleted +Termination of FCH process + +10. + +DISCONNECT → + +Termination of FCH process + +#### **Case 12: PA Calling – WA Called, no polling** + +![](fed4a04822c24fb22cca3a14f4ddae83_img.jpg) + +| | | +|----------------------|------------------------| +| WA (Receive, Called) | PA (Transmit, Calling) | +|----------------------|------------------------| + +1. Call start + +← + +Start DIS timer +(Pre\_FAX) +Start DIS timer + +2. BEGINNING OF DIS (ADPCM) + +→ + +![](5a9cdc1fed33ae8fb871a8cd4d591729_img.jpg) + +3. CONNECT (list) > + +(Calling\_FAX) + +Allocate resource + +4. < RESOURCE (list) + +Allocate resource + +5. END OF DIS (ADPCM) > + +--- + +6. SWITCH\_TO\_DEMOD > + +Start demodulation path Start demodulation path +Insert fixed delay +Start DCS timer + +--- + +7. < SIGNALLING + +Demodulated NSS + +Compatibility is not verified for both +DCMEs with received NSS + +--- + +8. < IDLE + +(Tx\_NSF\_T30) + +\*\*\* Many interactions (non-standard image transmission)\*\*\* + +1) Data hangover timer (G.763) is +expired; or +2) voice is detected in the channel; or +3) transparent request is received. + +--- + +9. < DISCONNECT + +Demodulation path is closed Demodulation path is closed +Fixed delay is deleted +Termination of FCH process + +--- + +10. DISCONNECT > + +Termination of FCH process + +#### **Case 13: WA Calling – PA Called, no polling** + +![](107c8e1abcb7033ad244e30e7a910045_img.jpg) + +| | | +|----------------------|------------------------| +| PA (Receive, Called) | WA (Transmit, Calling) | +|----------------------|------------------------| + +1. Call start + +< + +(Pre\_FAX) + +Start DIS timer Start DIS timer + +2. BEGINNING OF DIS (ADPCM) > + +--- + +3. + +\_\_\_\_\_ CONNECT (list) \_\_\_\_\_> + +Start RESOURCE timer +Allocate resource + +(Called\_FAX) + +4. + +<\_\_\_\_\_ RESOURCE (list) \_\_\_\_\_ + +Allocate resource + +5. END OF DIS (ADPCM) + +\_\_\_\_\_> + +6. + +\_\_\_\_\_SWITCH\_TO\_DEMOD\_\_\_\_\_> + +Start DCS timer +Start demodulation path + +Start demodulation path +Insert fixed delay + +7. + +<\_\_\_\_\_ SIGNALLING \_\_\_\_\_ + +Demodulated NSS + +8. + +<\_\_\_\_\_ IDLE \_\_\_\_\_ + +Compatibility is verified for both DCMEs with received NSS + +(Rx\_NSF\_T30) + +\*\*\* Many interactions (non-standard image transmission)\*\*\* + +- 1) Data hangover timer (G.763) is expired; or +- 2) voice is detected in the channel; or +- 3) transparent request is received. + +9. + +<\_\_\_\_\_ DISCONNECT \_\_\_\_\_ + +Demodulation path is closed + +Demodulation path is closed +Fixed delay is deleted +Termination of FCH process + +10. + +\_\_\_\_\_ DISCONNECT \_\_\_\_\_> + +Termination of FCH process + +### A.3 SF-T.30 cases with unmatched capabilities + +#### Case 14: PA Calling – PA Called, no polling + +PA (Receive, Called) + +PA (Transmit, Calling) + +1. Call start + +<\_\_\_\_\_> + +(Pre\_FAX) + +(Pre\_FAX) + +Start DIS timer + +Start DIS timer + +#### 2. BEGINNING OF DIS (ADPCM) + +![Timeline arrow pointing right](2cc973099f02f2cc67558feea3b18cde_img.jpg) + +Timeline arrow pointing right + +3. + +![Timeline arrow pointing right with CONNECT (list) message](61a7f401eb46fe99a71f27bc37493f04_img.jpg) + +Timeline arrow pointing right with CONNECT (list) message + +Start RESOURCE timer +Allocate resource + +(Called\_FAX) + +4. + +![Timeline arrow pointing left with RESOURCE (list) message](dd6c544ab685b25dd17f59456efcfbfc_img.jpg) + +Timeline arrow pointing left with RESOURCE (list) message + +Allocate resource +(Calling\_FAX) + +#### 5. END OF DIS (ADPCM) + +![Timeline arrow pointing right](bdd96f20e71f079cad85240efb3d3f24_img.jpg) + +Timeline arrow pointing right + +6. + +![Timeline arrow pointing right with SWITCH_TO_DEMOD message](a82bc78bff7fbefef1c0fb744365f957_img.jpg) + +Timeline arrow pointing right with SWITCH\_TO\_DEMOD message + +Start DCS timer +Start demodulation path + +Start DCS timer +Start demodulation path +Insert fixed delay + +7. + +![Timeline arrow pointing left with SIGNALLING message](d5d5c87be8e612be9d06d406bc894fd5_img.jpg) + +Timeline arrow pointing left with SIGNALLING message + +Demodulated DCS + +Compatibility is not verified for both +DCMEs with received DCS + +8. + +![Timeline arrow pointing left with SWITCH_TO_ADPCM message](a915fe7ec1bccc475614b7075a618c90_img.jpg) + +Timeline arrow pointing left with SWITCH\_TO\_ADPCM message + +Switch to 40 kbit/s channel +Release resource + +Switch to 40 kbit/s channel with fixed +delay +Release resource +(Tx\_ADPCM\_FAX) + +(Rx\_ADPCM\_FAX) + +\*\*\* Many interactions (call continues via ADPCM) \*\*\* + +- 1) Data hangover timer (G.763) is expired; or +- 2) voice is detected in the channel; or +- 3) transparent request is received. + +9. + +![Timeline arrow pointing left with DISCONNECT message](9996a266e30235be0b94cf77b9bc35d5_img.jpg) + +Timeline arrow pointing left with DISCONNECT message + +The fixed delay is deleted +Termination of FCH process + +10. + +![Timeline arrow pointing right with DISCONNECT message](8fc8a38540d89d143284a858bfae5ea9_img.jpg) + +Timeline arrow pointing right with DISCONNECT message + +Termination of FCH process + +#### **Case 15: PA Calling – WA Called, no polling** + +![](e0627c8e3dfda5da1ee8d5a90c9f7489_img.jpg) + +| WA (Receive, Called) | PA (Transmit, Calling) | +|--------------------------------------------------------|----------------------------------------------------------------| +|
| | +| 1. Call start | | +|
| | +| | (Pre_FAX) | +| Start DIS timer | Start DIS timer | +| 2. BEGINNING OF DIS (ADPCM) | | +|
| | +| 3. | | +| | CONNECT (list) | +|
| | +| Start RESOURCE timer | | +| Allocate resource | | +| 4. | | +| | RESOURCE (list) | +|
| | +| | Allocate resource | +| | (Calling_FAX) | +| 5. END OF DIS (ADPCM) | | +|
| | +| 6. | | +| | SWITCH_TO_DEMOD | +|
| | +| Insert fixed delay | Start DCS timer | +| Start demodulation path | Start demodulation path | +| | Insert fixed delay | +| 7. | | +| | SIGNALLING | +|
| | +| | Demodulated DCS | +| | Compatibility is not verified for both DCMEs with received DCS | +| 8. | | +| | SWITCH_TO_ADPCM | +|
| | +| Switch to 40 kbit/s channel | Switch to 40 kbit/s channel with fixed delay | +| Release resource | Release resource | +| Delete delay | (Tx_ADPCM_FAX) | +| *** Many interactions (call continues using ADPCM) *** | | +| | 1) Data hangover timer (G.763) is expired; or | +| | 2) voice is detected in the channel; or | +| | 3) transparent request is received. | +| 9. | | +| | DISCONNECT | +|
| | +| | The fixed delay is deleted | +| | Termination of FCH process | + +10. + +![](649d03e4c5c42598e91826f372146f65_img.jpg) + +\_\_\_\_\_ DISCONNECT \_\_\_\_\_> + +Termination of FCH process + +#### **Case 16: WA Calling – PA Called, no polling** + +![](5801c19431e76330430e92a598cc7a16_img.jpg) + +| PA (Receive, Called) | WA (Transmit, Calling) | +|-------------------------------|-----------------------------------------------| +| 1. Call start | | +| ← _____ | | +| (Pre_FAX) | | +| Start DIS timer | Start DIS timer | +| 2. BEGINNING OF DIS (ADPCM) | | +| _____> | | +| 3. | | +| _____ CONNECT (list) _____> | | +| Start RESOURCE timer | | +| Allocate resource | | +| (Called_FAX) | | +| 4. | | +| ← _____ RESOURCE (list) _____ | | +| | Allocate resource | +| 5. END OF DIS (ADPCM) | | +| _____> | | +| 6. | | +| _____SWITCH_TO_DEMOD_____> | | +| Start DCS timer | Start demodulation path | +| Start demodulation path | Insert fixed delay | +| 7. | | +| ← _____ SIGNALLING _____ | | +| | Demodulated DCS | +| 8. | | +| ← _____ IDLE _____ | | +| (Receive_FAX) | | +| 9. | | +| ← _____ SWITCH_TO_ADPCM _____ | | +| | Received training sequence can not be handled | +| Switch to 40 kbit/s channel | Switch to 40 kbit/s channel with fixed delay | +| Release resource | Release resource | +| (Rx_ADPCM_FAX) | | + +\*\*\* Many interactions (call continues via ADPCM) \*\*\* + +- 1) Data hangover timer (G.763) is expired; or +- 2) voice is detected in the channel; or +- 3) transparent request is received. + +10. + +← DISCONNECT + +The fixed delay is deleted +Termination of FCH process + +11. + +DISCONNECT → + +Termination of FCH process + +### A.4 NSF-T.30 proprietary cases with unmatched capabilities + +#### Case 17: PA Calling – PA Called, no polling + +![](343e05a9fd8a8c8743428fa4ae6e2736_img.jpg) + +PA (Receive, Called) PA (Transmit, Calling) + +--- + +1. Call start + +← + +(Pre\_FAX) (Pre\_FAX) +Start DIS timer Start DIS timer + +2. BEGINNING OF DIS (ADPCM) + +→ + +3. + +CONNECT (list) → + +Start RESOURCE timer +Allocate resource +(Called\_FAX) + +4. + +← RESOURCE (list) + +Allocate resource +(Calling\_FAX) + +5. END OF DIS (ADPCM) + +→ + +6. + +SWITCH\_TO\_DEMOD → + +Start DCS timer Start DCS timer +Start demodulation path Start demodulation path +Insert fixed delay + +7. + +← SIGNALLING + +Demodulated NSS + +Compatibility is not verified for both +DCMEs with received NSS + +``` + + sequenceDiagram + participant Called as PA (Receive, Called) + participant Calling as PA (Transmit, Calling) + Note over Called, Calling: 1. Call start + Calling->>Called: + Note left of Called: (Pre_FAX) +Start DIS timer + Note right of Calling: (Pre_FAX) +Start DIS timer + Note over Called, Calling: 2. BEGINNING OF DIS (ADPCM) + Called->>Calling: + Note over Called, Calling: 3. + Called->>Calling: CONNECT (list) + Note left of Called: Start RESOURCE timer +Allocate resource +(Called_FAX) + Note over Called, Calling: 4. + Calling->>Called: RESOURCE (list) + Note right of Calling: Allocate resource +(Calling_FAX) + Note over Called, Calling: 5. END OF DIS (ADPCM) + Called->>Calling: + Note over Called, Calling: 6. + Called->>Calling: SWITCH_TO_DEMOD + Note left of Called: Start DCS timer +Start demodulation path + Note right of Calling: Start DCS timer +Start demodulation path +Insert fixed delay + Note over Called, Calling: 7. + Calling->>Called: SIGNALLING + Note over Called, Calling: Demodulated NSS + Note right of Calling: Compatibility is not verified for both +DCMEs with received NSS + +``` + +62 **Recommendation G.766 (11/96)** + + + +8. + +![Sequence diagram for step 8: IDLE message from right to left. The right side has the text 'Received training sequence cannot be handled'.](0af1ba85ab6e4e50befbef3d63e017dc_img.jpg) + +← IDLE → +Received training sequence cannot be handled + +Sequence diagram for step 8: IDLE message from right to left. The right side has the text 'Received training sequence cannot be handled'. + +9. + +![Sequence diagram for step 9: SWITCH_TO_ADPCM message from right to left. The left side has 'Switch to 40 kbit/s channel' and 'Release resource'. The right side has 'Switch to 40 kbit/s channel with fixed delay' and 'Release resource'.](0f6e3cdce0f01d6ccceabcced508bb5b_img.jpg) + +← SWITCH\_TO\_ADPCM → +Switch to 40 kbit/s channel +Release resource +Switch to 40 kbit/s channel with fixed delay +Release resource + +Sequence diagram for step 9: SWITCH\_TO\_ADPCM message from right to left. The left side has 'Switch to 40 kbit/s channel' and 'Release resource'. The right side has 'Switch to 40 kbit/s channel with fixed delay' and 'Release resource'. + +\*\*\* Many interactions (call continues via ADPCM) \*\*\* + +- 1) Data hangover timer (G.763) is expired; or +- 2) voice is detected in the channel; or +- 3) transparent request is received. + +10. + +![Sequence diagram for step 10: DISCONNECT message from right to left. The right side has 'Fixed delay is deleted' and 'Termination of FCH process'.](0c88b98a59dd5d549fed7b13c0ca6536_img.jpg) + +← DISCONNECT → +Fixed delay is deleted +Termination of FCH process + +Sequence diagram for step 10: DISCONNECT message from right to left. The right side has 'Fixed delay is deleted' and 'Termination of FCH process'. + +11. + +![Sequence diagram for step 11: DISCONNECT message from left to right. The left side has 'Termination of FCH process'.](8d1bb05debbaef0f72751449b2b55172_img.jpg) + +→ DISCONNECT → +Termination of FCH process + +Sequence diagram for step 11: DISCONNECT message from left to right. The left side has 'Termination of FCH process'. + +# ANNEX B + +## Formal description of the facsimile module controller + +### B.1 Introduction + +This annex provides a formal description, based on the use of the SDL language, of the interfaces and certain functions of the facsimile module controller FMC. + +## B.2 FMC interfaces + +Figure B.1 shows the FMC and its interfaces with other DCME functions (ADF) and other facsimile module blocks. Signal lists L1 through L7 are defined, with the following origins/destinations (see Figure 9): + +- L1: from ADF; +- L2: to ADF; +- L3: to analysis/demodulation block; +- L4: from analysis/demodulation block; +- L5: to fax assembler/disassembler; +- L6: from fax assembler/disassembler; +- L7: to remodulation block. + +The message carried by the different signals are listed in Tables B.1 through B.11. + +![FMC system diagram showing a central FMC block connected to seven interfaces labeled C1 through C7, each with associated layer identifiers like [(L1)] or [(L3)].](99698c448635861b7dc8d352f87a1b2b_img.jpg) + +The diagram illustrates the FMC (Flexible Message Controller) system architecture. At the center is a large rectangular block labeled "FMC". Seven communication interfaces are shown, each represented by a line with an arrow pointing towards the FMC block: + +- C1** (top left): An arrow pointing right into the FMC block, with the label **[(L1)]** below it. +- C2** (bottom left): An arrow pointing right into the FMC block, with the label **[(L2)]** below it. +- C3** (top center): An arrow pointing down into the FMC block, with the label **[(L3)]** below it. +- C4** (top center): An arrow pointing down into the FMC block, with the label **[(L4)]** below it. +- C5** (top right): An arrow pointing left into the FMC block, with the label **[(L5)]** below it. +- C6** (bottom right): An arrow pointing left into the FMC block, with the label **[(L6)]** below it. +- C7** (bottom center): An arrow pointing down into the FMC block, with the label **[(L7)]** below it. + +The entire diagram is enclosed in a large rectangular frame. In the bottom right corner of the frame, the text "T1507290-92" is present. + +FMC system diagram showing a central FMC block connected to seven interfaces labeled C1 through C7, each with associated layer identifiers like [(L1)] or [(L3)]. + +T1507290-92 + +**Figure B.1/G.766 – FMC system diagram** + +**Table B.1/G.766 – Signals received from the HSC process (L1)** + +| Signals | Description | +|----------------|-------------------------------------------------------------------------------------| +| Data (ch) | Data call is detected in IT numbered as "ch". | +| DataInact (ch) | Data hangover timer is expired in IT numbered as "ch". | +| Voice (ch) | Voice call is detected in IT numbered as "ch". | +| Transp (ch) | Transparent call request is detected in IT numbered as "ch". | +| Rx_data (ch) | Data call is detected at receive side channel corresponding to IT numbered as "ch". | + +**Table B.2/G.766 – Signals sent to the RAG process (L2)** + +| Signals | Description | +|----------------|-----------------------------------------------| +| Faxbank_req | Request an additional fax bank to be created. | +| Faxbank_rel | Request to delete a fax bank. | + +**Table B.3/G.766 – Signals sent to the HSC process (L2)** + +| Signals | Description | +|----------------------|-----------------------------------------------------------------------------------------------------------------------------------| +| Fax (ch) | Inform the HSC that the IT numbered as "ch" is now handled by the fax module (DSI processing is not needed). | +| Non_fax (ch) | Inform the HSC that the IT numbered as "ch" is now out of the fax module control (DSI processing is needed). | +| Switch_to_ADPCM (ch) | Inform the HSC that the IT numbered as "ch" could not be handled by the facsimile module and a 40 kbit/s ADPCM channel is needed. | + +**Table B.4/G.766 – Signals sent to the O&M facility (L2)** + +| Signal | Description | +|---------------|---------------------------------------------------------------------------| +| Alarm (ch) | Response from corresponding FCH did not arrive within the specified time. | + +**Table B.5/G.766 – Signals sent to the demodulator switches (L3)** +**(Switch positions a, b, c as per Figure 11)** + +| Signals | Switch number | | | Description | +|-----------------|---------------|----------|----------------|------------------------------------------------------------------------------------------------------------------------| +| | 1 | 2 | 3 | | +| Demod_SW_1 (ch) | OFF
a | OFF
a | OFF (N/A)
b | The signal goes through ADPCM path and no signal is diverted to demodulator. | +| Demod_SW_2 (ch) | OFF
a | ON
b | OFF (N/A)
b | The signal still goes through ADPCM path but the same signal is also sent to demodulator to detect V.21 flag sequence. | +| Demod_SW_3 (ch) | ON
b | ON
b | OPEN
a | The signal only goes through demodulator without the fixed delay. | +| Demod_SW_4 (ch) | ON
b | ON
b | OFF
b | The signal only goes through demodulator with the fixed delay. | +| Demod_SW_5 (ch) | ON
b | OFF
a | ON
c | The signal only goes through ADPCM path with the fixed delay. | + +**Table B.6/G.766 – Signals sent to the remodulator switch (L3)** +**(Switch positions a, b as per Figure 11)** + +| Signals | Switch number | Description | +|-----------------|---------------|-------------------------------------| +| | 4 | | +| Remod_SW_1 (ch) | OFF
a | The signal goes through ADPCM path. | +| Remod_SW_2 (ch) | b
b | Flag_detect
CONNECT | + +**Table B.7/G.766 – Signals sent to the demodulator/decoder (L3)** + +| Signals | Description | +|-------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Start_demod (ch, demod, mode, rate) | Start sending the output of the demodulator number "demod" connected to IT number "ch" and modulation scheme of "mode" and speed of "rate" to frame assembler. | +| Stop_demod (ch, demod, mode, rate) | Stop sending the output of demodulator number "demod" to frame assembler. | + +**Table B.8/G.766 – Signals received from demodulator/decoder (L4)** + +| Signals | Description | +|------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Inact (ch, code, mode, rate) | When the end of signalling data is detected at the demodulator for an IT, demodulator decodes the signal and inserts IT number in "ch" name of code in "code", modulation scheme in "mode" and bit rate in "rate" variables of Inact signal. If only code is given, mode and rate variables contain "BLANK". | +| Low_speed (ch) | When low speed data is detected, demodulator generates this signal. | +| Fax_ept (ch, f) | When echo protection tone is detected, this signal is generated. | +| End_of_ept (ch) | When the end of echo protection tone is detected, this signal is generated. | +| Fax_Training (ch) | When training code is detected, this signal is generated. | +| End_of_Training (ch) | When the end of training is detected, this signal is generated. | +| Inact_Data (ch) | When the end of facsimile page data is detected, this signal is generated. | +| Flag_detect (ch) | When V.21 flag sequence is detected, this signal is generated. | +| End_of_DIS (ch) | When the end of DIS signal is detected, this signal is generated. | + +**Table B.9/G.766 – Signals received from the FCH and relayed to the remote FCH (L5)** + +| Signals | Description | +|---------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| CONNECT (ch, list) | When FCH detects DIS signal in the incoming signal from IT number "ch", this code is generated. It informs the corresponding FCH that a facsimile call is detected. The variable "list" contains the list of allocated remodulator set. | +| RESOURCE (ch, list) | This code is generated by FCH in response to CONNECT code. The list of allocated remodulator set is given in the "list" variable. | +| DISCONNECT (ch) | This code is generated when FCH detects the end of facsimile call. | +| SWITCH_TO_ADPCM (ch) | When FCH determines that a call can not be handled by itself, this code is generated. The signal path is changed from demodulation path to ADPCM path. | +| EPT (ch, f) | This signal requests the corresponding FCH to generate EPT tone with "f" frequency. | +| END_EPT (ch) | This signal indicates the end of EPT tone. | +| SIGNALLING (ch) | This signal indicates that demodulated supervisory data is started in fax data channel for IT number "ch". | +| IDLE (ch) | This signal indicates that demodulated page or supervisory data is ended in fax data channel for IT number "ch". | +| TRAINING (ch, mode, rate, long) | This signal requests the corresponding FCH to generate training sequence for IT number "ch" with modulation scheme of "mode" and speed of "rate". If logical variable "long" is "true", long training sequence shall be generated, otherwise short training sequence shall be generated. Receiving WA_FCH uses this information. The receiving PA_FCH does not use this information for the T.30 protocol. If long training sequence is given, "rate" variable is not available from WA_FCH. | + +**Table B.9/G.766 – Signals received from the FCH and relayed to the remote FCH (L5) (concluded)** + +| Signals | Description | +|---------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| FAX_DATA (ch) | When the end of training is detected, this code is generated. This code also indicates that the demodulated data is in fax data channel. The number of bits for this call is known by the corresponding FCH. | +| LONG_TRAINING (ch, rate) | This code contains rate information for the training sequence and is generated only by WA_FCH. The receiving PA_FCH ignores this code. | +| V_FAST (to be determined) | To be determined. | +| SWITCH_TO_DEMOD (ch) | This signal is generated at the end of non-demodulated DIS signal and indicates that a path change from ADPCM to Facsimile demod/remod shall occur for IT number "ch". | + +**Table B.10/G.766 – Signals received from the fax frame disassembler (L6)** + +The list is the same as the codes exchanged between corresponding FCHs via their CCFs. In addition, when the reception of a supervisory message is completed, as signalled by the IDLE code, the frame disassembler decodes its content and passes it to the CCF. + +| Signal | Description | +|---------------------------------|-----------------------------------------------------------------------------------------| +| Fax_Idle (ch, code, mode, rate) | Variables "code", "mode" and "rate" are given by the decoder in the frame disassembler. | + +**Table B.11/G.766 – Signals sent to the remodulator (L7)** + +| Signals | Description | +|------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Start_remod (ch, remod, mode, rate) | When CCF receives Start_remod signal from FCH, CCF passes the signal to remodulator. The remodulator number is not specified in the FCH signal but it is given in CCF signal. This signal initiates remodulation of data sent from Frame reassembler to the remodulator "remod". | +| Stop_remod (ch, remod, mode, rate) | When CCF receives Stop_remod signal from FCH, CCF passes the signal to Remodulator. This signal stops remodulation of data at the remodulator "remod". | +| Start_EPT (ch, f) | This signal initiates the generation of EPT signal with frequency "f" for the IT number "ch". | +| Stop_EPT (ch) | This signal stops the generation of EPT signal for the IT number "ch". | +| Generate_Short_Training (ch, mode, rate) | This signal initiates the generation of short training sequence for IT number "ch" with modulation scheme of "mode" and speed of "rate". | +| Generate_Long_Training (ch, mode, rate) | This signal initiates the generation of long training sequence for IT number "ch" with modulation scheme of "mode" and speed of "rate". | + +## B.3 Internal structure of the FMC + +The FMC consists of the CCF and the FCH processes, as shown in Figure B.2. Signals L8 and L9 define the interfaces between these two processes. The messages carried by the two signals are listed in Tables B.12 through B.14. + +![FMC block diagram showing CCF and PA_FCH processes and their interfaces.](8ab30dbff406204a68c59ae7c1b77413_img.jpg) + +The diagram illustrates the internal structure of the FMC, enclosed in a large rectangular frame. It contains two main process blocks: CCF (top) and PA\_FCH (bottom). The CCF block is labeled with (0, 2) in its top right corner. The PA\_FCH block is labeled with (0,) in its top right corner. External signals are shown as follows: [(L3)] entering from the top, [(L4)] exiting to the top, and [(L7)] entering from the top. On the left, [(L1)] enters and [(L2)] exits. On the right, [(L5)] exits and [(L6)] enters. Between the CCF and PA\_FCH blocks, [(L8)] exits from CCF to PA\_FCH, [(L9)] enters from PA\_FCH to CCF, and a dashed line indicates a third interface. A small text 'T1507300-92' is located at the bottom right of the frame. + +FMC block diagram showing CCF and PA\_FCH processes and their interfaces. + +Figure B.2/G.766 – FMC block diagram + +**Table B.12/G.766 – Signals provided to the FCH (L8)** + +| Signals | Table | +|----------------------------------|--------------| +| (Signals are previously defined) | | +| DataInact (ch) | B.1 | +| Voice (ch) | B.1 | +| Transp (ch) | B.1 | +| Inact (ch, code, mode, rate) | B.8 | +| Low_speed (ch) | B.8 | +| Fax_ept (ch, f) | B.8 | +| End_of_Training (ch) | B.8 | +| Inact_Data (ch) | B.8 | +| Flag_detect (ch) | B.8 | +| End_of_DIS (ch) | B.8 | +| Fax_Idle (ch, code, mode, rate) | B.10 | +| CONNECT (ch, list) | B.9 | +| RESOURCE (ch, list) | B.9 | +| DISCONNECT (ch) | B.9 | +| SWITCH_TO_ADPCM (ch) | B.9 | +| EPT (ch, f) | B.9 | +| End_EPT (ch) | B.9 | +| SIGNALLING (ch) | B.9 | +| IDLE (ch) | B.9 | +| TRAINING (ch, mode, rate, long) | B.9 | +| FAX_DATA (ch) | B.9 | +| LONG_TRAINING (ch, rate) | B.9 | +| V_FAST | B.9 | +| SWITCH_TO_DEMOD (ch) | B.9 | + +**Table B.13/G.766 – PA FCH control signals (L9)** + +| Signals | Table | +|----------------------------------|--------------| +| (Signals are previously defined) | | +| Fax (ch) | B.3 | +| Non_fax (ch) | B.3 | +| Switch_to_ADPCM (ch) | B.3 | +| Demod_SW_1 (ch) | B.5 | +| Demod_SW_2 (ch) | B.5 | +| Demod_SW_3 (ch) | B.5 | +| Demod_SW_4 (ch) | B.5 | + +**Table B.13/G.766 – PA FCH control signals (L9)** +*(concluded)* + +| Signals | Table | +|------------------------------------------|-------| +| Demod_SW_5 (ch) | B.5 | +| Remod_SW_1 (ch) | B.6 | +| Remod_SW_2 (ch) | B.6 | +| Start_demod (ch, mode, rate) | B.7 | +| Stop_demod (ch, mode, rate) | B.7 | +| Start_remod (ch, mode, rate) | B.11 | +| Stop_remod (ch, mode, rate) | B.11 | +| Start_EPT (ch, f) | B.11 | +| Stop_EPT (ch) | B.11 | +| Generate_Short_Training (ch, mode, rate) | B.11 | +| Generate_Long_Training (ch, mode, rate) | B.11 | +| CONNECT (ch, list) | B.9 | +| RESOURCE (ch, list) | B.9 | +| DISCONNECT (ch) | B.9 | +| SWITCH_TO_ADPCM (ch) | B.9 | +| EPT (ch, f) | B.9 | +| End_EPT (ch) | B.9 | +| SIGNALLING (ch) | B.9 | +| IDLE (ch) | B.9 | +| TRAINING (ch, mode, rate, long) | B.9 | +| FAX_DATA (ch) | B.9 | +| LONG_TRAINING (ch, rate) | B.9 | +| V_FAST | B.9 | +| Alarm (ch) | B.4 | +| SWITCH_TO_DEMOD (ch) | B.9 | + +**Table B.14/G.766 – Status signals received from FCH (L9)** + +| Signals | Description | +|----------------|-----------------------------------------------------------------| +| Calling (ch) | FCH informs CCF that it is a calling party. | +| Called (ch) | FCH informs CCF that it is a called party. | +| Transmit (ch) | FCH informs CCF that it is a facsimile page transmitting party. | +| Receive (ch) | FCH informs CCF that it is a facsimile page receiving party. | +| Terminate (ch) | FCH informs CCF that the process is terminating. | + +## **B.4 Common control function (CCF)** + +The functions of the CCF are defined in 6.1. + +## **B.5 FCH** + +The FCH requirements are specified in 6.2. The SDL representation of the PA FCH is provided here. Figure B.3 shows an overall state transition diagram for the PA FCH. Tables B.15 and B.16 define + +the protocol variables and the procedures, respectively. The SDL connector is given in Table B.17. + The SDL representation of the PA FCH is provided by 25 SDL diagrams. + +![Figure B.3/G.766 – FCH for the PA approach](2281492deb1b39494451c7c123dc449c_img.jpg) + +``` + + graph TD + Transmit_FAX((Transmit_FAX)) -- "Training" --> Local_EPT((Local_EPT)) + Local_EPT -- "EPT (f)" --> Transmit_FAX + Local_EPT -- "Inact (EPT)" --> Local_Training((Local_Training)) + Local_Training -- "End_of_Training" --> Demodulate_DATA((Demodulate_DATA)) + Demodulate_DATA -- "Inact_Data" --> Tx_Local_Signal((Tx_Local_Signal)) + Demodulate_DATA -- "Inact_Data" --> Tx_Remote_Signal((Tx_Remote_Signal)) + Tx_Local_Signal -- "Inact (code)" --> Tx_Remote_Signal + Tx_Remote_Signal -- "IDLE (PRI)" --> DISC((DISC)) + Tx_Remote_Signal -- "Training" --> Rx_Local_Signal((Rx_Local_Signal)) + + Calling_FAX((Calling_FAX)) -- "Inact (DCS)" --> Transmit_FAX + Calling_FAX -- "Inact (NSS)" --> Tx_NSF_T30((Tx_NSF-T.30)) + Calling_FAX -- "SWITCH-TO-ADPCM" --> Tx_ADPCM_FAX((Tx_ADPCM_FAX)) + + Pre_FAX((Pre_FAX)) -- "CONNECT /*new call*/" --> Calling_FAX + Pre_FAX -- "ti" --> DISC + Pre_FAX -- "CONNECT(Tx)" --> Called_FAX((Called_FAX)) + + Tx_NSF_T30 -- "Voice DataInact" --> DISC + Tx_ADPCM_FAX -- "Low_Speed" --> DISC + + Called_FAX -- "IDLE (NSS)" --> Rx_NSF_T30((Rx_NSF-T.30)) + Called_FAX -- "SWITCH-TO-ADPCM" --> Rx_ADPCM_FAX((Rx_ADPCM_FAX)) + Called_FAX -- "IDLE (DCS)" --> Receive_FAX((Receive_FAX)) + + Rx_NSF_T30 -- "ts" --> DISC + Rx_ADPCM_FAX -- "Training" --> DISC + + Receive_FAX -- "EPT (f)" --> Remote_EPT((Remote_EPT)) + Receive_FAX -- "TRAINING" --> Remote_Training((Remote_Training)) + Remote_EPT -- "END_EPT" --> Remote_Training + Remote_Training -- "DATA" --> Remodulate_DATA((Remodulate_DATA)) + Remodulate_DATA -- "IDLE" --> Rx_Local_Signal + Remodulate_DATA -- "IDLE" --> Rx_Remote_Signal((Rx_Remote_Signal)) + + Rx_Local_Signal -- "IDLE (code)" --> Rx_Remote_Signal + Rx_Local_Signal -- "IDLE (DCN)" --> DISC + + Transmit_FAX -- "Inact (DCS) /*polling*/" --> Receive_FAX + Receive_FAX -- "IDLE (DCS) /*polling*/" --> Transmit_FAX + + Local_Training -- "IDLE (CFR, MCF)" --> Transmit_FAX + Rx_Local_Signal -- "Inact (CFR, MCF)" --> Receive_FAX + +``` + +Figure B.3/G.766 – FCH for the PA approach + +**Figure B.3/G.766 – FCH for the PA approach** + +**Recommendation G.766 (11/96)**      73 + +**Table B.15/G.766 – Definition of the PA FCH variables and timers** + +| Variables and timers | Definitions | +|-----------------------------|-----------------------------------------------------------------------------------------------------------------------------| +| t_DIS | DIS timer value (15 s). | +| ti | DIS timer variable. | +| t_DCS | DCS timer value (15 s). | +| td | DCS timer variable. | +| t_RES | RESOURCE code reception timer value (3 s). | +| ts | RESOURCE code reception timer variable. | +| t_EPT | EPT length value (1 s). | +| te | EPT timer variable. | +| code | A variable to hold current supervisory code. | +| sig_mode | Supervisory signal modulation scheme. | +| sig_rate | Supervisory signal rate. | +| prev | The variable holding previous signalling code. | +| PPR_count | PPR command counter. | +| long | The logical variable for training. It is "true" for the long training sequence and "false" for the short training sequence. | +| data_training | A logical variable. If "true" the expected signal is a facsimile page data, else TCF sequence is expected. | + +**Table B.16/G.766 – Definition of the PA FCH procedures** + +| Procedures | Definitions | +|----------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Allocate_Resource (list) | This procedure allocates remodulators and puts the names of remodulators in the "list". | +| Release_Resource (list) | This procedure releases all allocated remodulators and demodulators. The names of remodulators are given in the "list". | +| Save_List (list) | This procedure stores the received remodulator list from remote PA_FCH process. | +| Capability_Check (Proceed) | When NSF-T.30 protocol is detected, PA_FCH process checks its capability. if this call can be handled, the variable "proceed" is set to "true", else "false". | +| Check_Resource (Proceed) | When DCS is detected, it examines its demodulation and remodulation capability with the remote remodulator list and determines if a facsimile call can be handled or not. If PA_FCH can handle a call, the variable "Proceed" is set "true", else "false". If the DCS includes 2400 bit/s handshaking, a variable "proceed" shall be set to "false". | +| Tx_NSF_T30_Handling | When NSF-T.30 protocol is accepted, this procedure handles the protocol. There is no restriction how to handle the call as long as the output signals are restricted to the defined codes as specified in Table B.10. | +| Rx_NSF_T30_Handling | When NSF-T.30 protocol is accepted, this procedure handles the protocol. It accepts all signals and acts upon without decoding the code. When TRAINING code is received, "long" variable is taken as is. | +| Store (list) | When RESOURCE code is received, the list of remote remodulator is stored by this procedure. | + +**Table B.17/G.766 – SDL connector** + +| rdx | From SDL-(n) | To SDL-(n) | +|------------|---------------------|-------------------| +| 1 | 14, 22 | 3 | +| 2 | 4, 23 | 13 | +| 3 | 16, 18, 20 | 23 | +| 4 | 18, 23 | 20 | +| 5 | 12 | 10 | +| 6 | 6, 10 | 12 | +| 7 | 10 | 11 | +| 8 | 20 | 21 | +| 9 | 6 | 8 | +| 10 | 16 | 18 | +| 11 | 21 | 22 | + +![Flowchart for Process PA_FCH](364054adcd1b427fa259450e006c6b38_img.jpg) + +``` +graph TD; + Start([ ]) --> Set1[Set NOW+t_dis, ti]; + Set1 --> Set2["sig_mode:='V21', +sig_rate:=300"]; + Set2 --> Set3["Prev:=NULL, +PPR_count:=0, +long:=true"]; + Set3 --> Set4[send_DISC:=true]; + Set4 --> Set5[Data_training:=false]; + Set5 --> Demod{{Demod_SW_2(ch) +TO CCFPID}}; + Demod --> Remod{{Remod_SW_1(ch) +TO CCFPID}}; + Remod --> End([Pre +FAX]); +``` + +DCL +send\_DISC boolean, +Data\_training boolean, +long boolean, +ch, list integer, +pre, level boolean, +code, preceed boolean; + +Flowchart for Process PA\_FCH + +T1522250-96 + +![State transition diagram for Process PA_FCH. It shows transitions between states Voice(ch), ti, Transp(ch), Pre_FAX, Flag_detect(ch), and CONNECT(ch,list). Transitions include actions like Terminate(ch TO CCFPID), Reset(ti), Allocate_Resource(list), CONNECT(ch,list TO CCFPID), Fax(ch TO CCFPID), Called(ch TO CCFPID), Set(NOW+t_RES ts), Calling(ch TO CCFPID), Save_List(list), and RESOURCE(ch,list TO CCFPID). Final states are Called_FAX and Calling_FAX. A note indicates a DIS timer expiration transition from ti to Voice(ch).](b1784a5cbeeb3d9fb9e60b333019c721_img.jpg) + +``` + +stateDiagram-v2 + [*] --> Voice(ch) + Voice(ch) --> ti + ti --> Transp(ch) + Transp(ch) --> Voice(ch) + ti --> Pre_FAX : /* DIS timer expiration */ + Pre_FAX --> Flag_detect(ch) + Flag_detect(ch) --> CONNECT(ch,list) + Flag_detect(ch) --> Reset(ti) + CONNECT(ch,list) --> Reset(ti) + Reset(ti) --> Allocate_Resource(list) + Allocate_Resource(list) --> CONNECT(ch,list TO CCFPID) + CONNECT(ch,list TO CCFPID) --> Fax(ch TO CCFPID) + Fax(ch TO CCFPID) --> Called(ch TO CCFPID) + Called(ch TO CCFPID) --> Set(NOW+t_RES ts) + Set(NOW+t_RES ts) --> Called_FAX + Reset(ti) --> Calling(ch TO CCFPID) + Calling(ch TO CCFPID) --> Fax(ch TO CCFPID) + Fax(ch TO CCFPID) --> Save_List(list) + Save_List(list) --> Allocate_Resource(list) + Allocate_Resource(list) --> RESOURCE(ch,list TO CCFPID) + RESOURCE(ch,list TO CCFPID) --> Calling_FAX + Voice(ch) --> Terminate(ch TO CCFPID) + Terminate(ch TO CCFPID) --> [*] + +``` + +State transition diagram for Process PA\_FCH. It shows transitions between states Voice(ch), ti, Transp(ch), Pre\_FAX, Flag\_detect(ch), and CONNECT(ch,list). Transitions include actions like Terminate(ch TO CCFPID), Reset(ti), Allocate\_Resource(list), CONNECT(ch,list TO CCFPID), Fax(ch TO CCFPID), Called(ch TO CCFPID), Set(NOW+t\_RES ts), Calling(ch TO CCFPID), Save\_List(list), and RESOURCE(ch,list TO CCFPID). Final states are Called\_FAX and Calling\_FAX. A note indicates a DIS timer expiration transition from ti to Voice(ch). + +T1522260-96 + +Process PA\_FCH + +3(24) + +![Flowchart for Process PA_FCH showing various states and transitions for a fax process. It starts with Calling_FAX and Inact(ch,code, mode,rate), leading to Stop_demod and decision diamonds for (code), (NSS), and (DTC).](d510bddda14c44163bbeee33b491a105_img.jpg) + +``` + +graph TD + Calling_FAX1([Calling_FAX]) --> Inact[Inact(ch,code, mode,rate)] + Inact --> Stop_demod[Stop_demod(ch, sig_mode,sig_rate) TO CCFPID] + Stop_demod --> code1{(code)} + code1 -- (DCS) --> 1((1)) + code1 -- else --> code2{(code)} + code2 -- (NSS) --> Capability_Check[Capability_Check (proceed)] + code2 -- else --> code3{(code)} + Capability_Check --> Reset1[Reset(td)] + Reset1 --> proceed1{(proceed)} + proceed1 -- (true) --> IDLE1[IDLE(ch) TO CCFPID] + proceed1 -- (false) --> SWITCH_TO[SWITCH_TO ADPCM(ch) TO CCFPID] + SWITCH_TO --> Release[Release Resource(list)] + Release --> Demod_SW_5[Demod_SW_5(ch) TO CCFPID] + Demod_SW_5 --> Remod_SW_1[Remod_SW_1(ch) TO CCFPID] + Remod_SW_1 --> Switch_to[Switch_to ADPCM(ch) TO CCFPID] + Switch_to --> Tx_ADPCM_FAX([Tx_ADPCM_FAX]) + IDLE1 --> prev[prev:=DCS'] + prev --> Data_training[Data_training:= FALSE] + Data_training --> Transmit_FAX([Transmit_FAX]) + code3 -- (DTC) --> Reset2[Reset(td)] + Reset2 --> IDLE2[IDLE(ch) TO CCFPID] + IDLE2 --> Demod_SW_3[Demod_SW_3(ch) TO CCFPID] + Demod_SW_3 --> Calling_FAX2([Calling_FAX]) + code3 -- else --> IDLE3[IDLE(ch) TO CCFPID] + IDLE3 --> Calling_FAX3([Calling_FAX]) + +``` + +Flowchart for Process PA\_FCH showing various states and transitions for a fax process. It starts with Calling\_FAX and Inact(ch,code, mode,rate), leading to Stop\_demod and decision diamonds for (code), (NSS), and (DTC). + +T1522270-96 + +![Flowchart for Process PA_FCH showing various states and transitions for a fax call.](37806e0fc150d857046ebc7e47893d7a_img.jpg) + +``` + +graph TD + subgraph PA_FCH [Process PA_FCH] + direction TB + C1([Calling_FAX]) --> L1[Low_speed(ch)] + C1 --> S1[SIGNALLING(ch)] + C1 --> F1[Fax_Idle(ch, code, mode, rate)] + C1 --> W1[SWITCH TO ADPCM(ch)] + C1 --> T1[td] + L1 --> SD1[Start_demod(ch, sig_mode, sig_rate) TO CCFPID] + SD1 --> SIG1[SIGNALLING(ch) TO CCFPID] + SIG1 --> C2([Calling_FAX]) + C2 --> SW1[SWITCH_TO DEMOD(ch)] + SW1 --> SET1[Set(NOW+t_DCS, td)] + SET1 --> DS1[Demod_SW_4(ch) TO CCFPID] + DS1 --> RS1[Remod_SW_2(ch) TO CCFPID] + RS1 --> C3([Calling_FAX]) + S1 --> SR1[Start_remod(ch, sig_mode, sig_rate) TO CCFPID] + SR1 --> C4([Calling_FAX]) + F1 --> ST1[Stop_remod(ch, sig_mode, sig_rate) TO CCFPID] + ST1 --> CODE{(code)} + CODE --> DCS[DCS] + CODE --> ELSE[else] + DCS --> DS2[Demod_SW_3(ch) TO CCFPID] + DS2 --> RES1[Reset(td)] + RES1 --> J2((2)) + ELSE --> C5([Calling_FAX]) + W1 --> SD2[Stop_demod(ch, sig_mode, sig_rate) TO CCFPID] + SD2 --> RES2[Reset(td); Reset(ts)] + RES2 --> CODE + T1 --> SW2[SWITCH_TO ADPCM(ch) TO CCFPID] + SW2 --> RES3[Release_Resource(list)] + RES3 --> DS3[Demod_SW_5(ch) TO CCFPID] + DS3 --> RS2[Remod_SW_1(ch) TO CCFPID] + RS2 --> SW3[Switch_to ADPCM(ch) TO CCFPID] + SW3 --> TX([Tx_ADPCM_FAX]) + end + T1 -.-> T1_note[/* DCS timer expiration */] + +``` + +The flowchart illustrates the state transitions for Process PA\_FCH. It begins with the **Calling\_FAX** state, which branches into five initial actions: **Low\_speed(ch)**, **SIGNALLING(ch)**, **Fax\_Idle(ch, code, mode, rate)**, **SWITCH TO ADPCM(ch)**, and **td**. The **Low\_speed(ch)** path leads to **Start\_demod(ch, sig\_mode, sig\_rate) TO CCFPID**, then **SIGNALLING(ch) TO CCFPID**, and back to **Calling\_FAX**. From there, it proceeds through **SWITCH\_TO DEMOD(ch)**, **Set(NOW+t\_DCS, td)**, **Demod\_SW\_4(ch) TO CCFPID**, and **Remod\_SW\_2(ch) TO CCFPID** to return to **Calling\_FAX**. The **SIGNALLING(ch)** path leads to **Start\_remod(ch, sig\_mode, sig\_rate) TO CCFPID** and back to **Calling\_FAX**. The **Fax\_Idle(ch, code, mode, rate)** path leads to **Stop\_remod(ch, sig\_mode, sig\_rate) TO CCFPID**, which then leads to a decision diamond **(code)**. If the condition **(DCS)** is met, it proceeds to **Demod\_SW\_3(ch) TO CCFPID**, **Reset(td)**, and then to connector **2**. If the condition is **else**, it returns to **Calling\_FAX**. The **SWITCH TO ADPCM(ch)** path leads to **Stop\_demod(ch, sig\_mode, sig\_rate) TO CCFPID**, then **Reset(td); Reset(ts)**, which loops back to the **(code)** decision. The **td** path leads to **SWITCH\_TO ADPCM(ch) TO CCFPID**, **Release\_Resource(list)**, **Demod\_SW\_5(ch) TO CCFPID**, **Remod\_SW\_1(ch) TO CCFPID**, **Switch\_to ADPCM(ch) TO CCFPID**, and finally to **Tx\_ADPCM\_FAX**. A note indicates that **td** is the **DCS timer expiration**. + +Flowchart for Process PA\_FCH showing various states and transitions for a fax call. + +T1522490-96 + +![Flowchart showing two parallel process flows for PA_FCH. The left flow starts with Tx_NSF_T30, branches into Voice(ch) and DataInact(ch) leading to a series of TO CCFPID commands (Demod_SW_1, Remod_SW_1, Non_Fax, DISCONNECT, Release_Resource, Terminate), and a * branch leading to Tx_NSF_T30_Handling which loops back to Tx_NSF_T30. The right flow starts with Tx_ADPCM_FAX, branches into Voice(ch) and DataInact(ch) leading to a series of TO CCFPID commands (Demod_SW_1, Remod_SW_1, Non_Fax, DISCONNECT, Terminate), and ends with an X mark. Both flows end with an X mark.](2b60ebe01f77d22e53da1fbe73083b01_img.jpg) + +``` +graph TD; subgraph LeftFlow [ ]; Tx_NSF_T30_1([Tx_NSF_T30]); Voice_L[Voice(ch)]; DataInact_L[DataInact(ch)]; Star_L[*]; Demod_SW_1_L[Demod_SW_1(ch) TO CCFPID]; Remod_SW_1_L[Remod_SW_1(ch) TO CCFPID]; Non_Fax_L[Non_Fax(ch) TO CCFPID]; DISCONNECT_L[DISCONNECT(ch) TO CCFPID]; Release_Resource[Release_Resource(list)]; Terminate_L[Terminate(ch) TO CCFPID]; End_L[X]; Tx_NSF_T30_1 --> Voice_L; Tx_NSF_T30_1 --> DataInact_L; Voice_L --> Demod_SW_1_L; DataInact_L --> Demod_SW_1_L; Demod_SW_1_L --> Remod_SW_1_L; Remod_SW_1_L --> Non_Fax_L; Non_Fax_L --> DISCONNECT_L; DISCONNECT_L --> Release_Resource; Release_Resource --> Terminate_L; Terminate_L --> End_L; Star_L --> Tx_NSF_T30_Handling[Tx_NSF_T30_Handling]; Tx_NSF_T30_Handling --> Tx_NSF_T30_2([Tx_NSF_T30]); end; subgraph RightFlow [ ]; Tx_ADPCM_FAX([Tx_ADPCM_FAX]); Voice_R[Voice(ch)]; DataInact_R[DataInact(ch)]; Demod_SW_1_R[Demod_SW_1(ch) TO CCFPID]; Remod_SW_1_R[Remod_SW_1(ch) TO CCFPID]; Non_Fax_R[Non_Fax(ch) TO CCFPID]; DISCONNECT_R[DISCONNECT(ch) TO CCFPID]; Terminate_R[Terminate(ch) TO CCFPID]; End_R[X]; Tx_ADPCM_FAX --> Voice_R; Tx_ADPCM_FAX --> DataInact_R; Voice_R --> Demod_SW_1_R; DataInact_R --> Demod_SW_1_R; Demod_SW_1_R --> Remod_SW_1_R; Remod_SW_1_R --> Non_Fax_R; Non_Fax_R --> DISCONNECT_R; DISCONNECT_R --> Terminate_R; Terminate_R --> End_R; end; +``` + +Flowchart showing two parallel process flows for PA\_FCH. The left flow starts with Tx\_NSF\_T30, branches into Voice(ch) and DataInact(ch) leading to a series of TO CCFPID commands (Demod\_SW\_1, Remod\_SW\_1, Non\_Fax, DISCONNECT, Release\_Resource, Terminate), and a \* branch leading to Tx\_NSF\_T30\_Handling which loops back to Tx\_NSF\_T30. The right flow starts with Tx\_ADPCM\_FAX, branches into Voice(ch) and DataInact(ch) leading to a series of TO CCFPID commands (Demod\_SW\_1, Remod\_SW\_1, Non\_Fax, DISCONNECT, Terminate), and ends with an X mark. Both flows end with an X mark. + +T1522290-96 + +Process PA\_FCH + +6(24) + +![Flowchart for Process PA_FCH starting with Transmit_FAX. It branches into four paths: Low_speed(ch) leading to connector 6; Fax_ept(ch) leading to EPT(ch) TO CCFPID, Set(NOW+t_ept,te), and Local_EPT; Fax_Training(ch) leading to LEVEL(ch,level) and connector 9; and DataInact(ch) leading to DISCONNECT(ch) TO CCFPID, Release_Resource(list), Demod_SW_1(ch) TO CCFPID, Remod_SW_1(ch) TO CCFPID, Non_Fax(ch) TO CCFPID, Terminate(ch) TO CCFPID, and finally an exit point labeled T1522500-96.](4a2b39fa33747a6553031cfe1e0947fa_img.jpg) + +``` +graph TD; Start([Transmit_FAX]) --> Branch(( )); Branch --> Low_speed{Low_speed(ch)}; Branch --> Fax_ept{Fax_ept(ch)}; Branch --> Fax_Training{Fax_Training(ch)}; Branch --> DataInact{DataInact(ch)}; Low_speed --> C6((6)); Fax_ept --> EPT[EPT(ch) TO CCFPID]; EPT --> Set[Set(NOW+t_ept,te)]; Set --> Local_EPT([Local_EPT]); Fax_Training --> LEVEL[LEVEL(ch,level)]; LEVEL --> C9((9)); DataInact --> DISCONNECT[DISCONNECT(ch) TO CCFPID]; DISCONNECT --> Release[Release_Resource(list)]; Release --> Demod[Demod_SW_1(ch) TO CCFPID]; Demod --> Remod[Remod_SW_1(ch) TO CCFPID]; Remod --> Non_Fax[Non_Fax(ch) TO CCFPID]; Non_Fax --> Terminate[Terminate(ch) TO CCFPID]; Terminate --> Exit[⊗ T1522500-96]; +``` + +Flowchart for Process PA\_FCH starting with Transmit\_FAX. It branches into four paths: Low\_speed(ch) leading to connector 6; Fax\_ept(ch) leading to EPT(ch) TO CCFPID, Set(NOW+t\_ept,te), and Local\_EPT; Fax\_Training(ch) leading to LEVEL(ch,level) and connector 9; and DataInact(ch) leading to DISCONNECT(ch) TO CCFPID, Release\_Resource(list), Demod\_SW\_1(ch) TO CCFPID, Remod\_SW\_1(ch) TO CCFPID, Non\_Fax(ch) TO CCFPID, Terminate(ch) TO CCFPID, and finally an exit point labeled T1522500-96. + +![Dashed rectangular box with a folded top-right corner, likely a placeholder or a specific graphical element.](0726a38dffe30284a71229ae0bcf1f45_img.jpg) + +Dashed rectangular box with a folded top-right corner, likely a placeholder or a specific graphical element. + +/\* EPT timer expiration \*/ + +![Flowchart showing the process flow: Local_EPT -> End_of_ept(ch) / te -> Reset(te) -> END_EPT(ch) TO CCFPID -> Local_Training.](8f8caebe58364416a2eda21039d8c7bf_img.jpg) + +``` +graph TD + Local_EPT([Local_EPT]) + Local_EPT --- split(( )) + split --- End_of_ept_ch[/End_of_ept(ch)/] + split --- te[/te/] + End_of_ept_ch --> Reset_te[Reset(te)] + Reset_te --- join(( )) + te --- join + join --> END_EPT_ch_TO_CCFPID{{END_EPT(ch) +TO CCFPID}} + END_EPT_ch_TO_CCFPID --> Local_Training([Local_Training]) +``` + +Flowchart showing the process flow: Local\_EPT -> End\_of\_ept(ch) / te -> Reset(te) -> END\_EPT(ch) TO CCFPID -> Local\_Training. + +T1522310-96 + +![Flowchart for Process PA_FCH. It starts with Local_Training, branches into Fax_Training, End_of_Training, Low_speed, and DataInact. Fax_Training leads to a (Data_training) decision. If true, it goes to long:=true and then to a (mode) decision. If false, it goes to FAX_DATA. End_of_Training leads to FAX_DATA. Low_speed leads to DISCONNECT. DataInact leads to DISCONNECT. The (mode) decision leads to long:=true or long:=false, both leading to TRAINING. TRAINING leads to Local_Training. FAX_DATA leads to Start_demod. Start_demod leads to Demodulate_Data. DISCONNECT leads to Release_Resource. Release_Resource leads to Demod_SW_1, Remod_SW_1, Non_Fax, and Terminate. Terminate leads to an exit symbol with T1522510-96.](778a90bfa183fbf83bfe2bf1ed8fa827_img.jpg) + +``` + +graph TD + subgraph Process_PA_FCH [Process PA_FCH] + LT1([Local_Training]) --> FT{Fax_Training(ch)} + LT1 --> ET{End_of_Training(ch)} + LT1 --> LS{Low_speed(ch)} + LT1 --> DI{DataInact(ch)} + + FT --> DT{(Data_training)} + DT -- true --> L1[long:=true] + DT -- false --> FD{FAX_DATA(ch) TO CCFPID} + + ET --> FD + + LS --> DISC{DISCONNECT(ch) TO CCFPID} + DI --> DISC + + DISC --> RR[Release_Resource(list)] + RR --> DS1{Demod_SW_1(ch) TO CCFPID} + DS1 --> RS1{Remod_SW_1(ch) TO CCFPID} + RS1 --> NF{Non_Fax(ch) TO CCFPID} + NF --> T{Terminate(ch) TO CCFPID} + T --> Exit((X T1522510-96)) + + FD --> SD{Start_demod(ch, sig_mode, sig_rate) TO CCFPID} + SD --> DD([Demodulate_Data]) + + L1 --> M{(mode) (V.17)} + M -- true --> L2[long:=true] + M -- false --> L3[long:=false] + L2 --> TR{TRAINING(ch, mode, rate, long) TO CCFPID} + L3 --> TR + TR --> LT2([Local_Training]) + + 9((9)) --> FT + end + +``` + +Flowchart for Process PA\_FCH. It starts with Local\_Training, branches into Fax\_Training, End\_of\_Training, Low\_speed, and DataInact. Fax\_Training leads to a (Data\_training) decision. If true, it goes to long:=true and then to a (mode) decision. If false, it goes to FAX\_DATA. End\_of\_Training leads to FAX\_DATA. Low\_speed leads to DISCONNECT. DataInact leads to DISCONNECT. The (mode) decision leads to long:=true or long:=false, both leading to TRAINING. TRAINING leads to Local\_Training. FAX\_DATA leads to Start\_demod. Start\_demod leads to Demodulate\_Data. DISCONNECT leads to Release\_Resource. Release\_Resource leads to Demod\_SW\_1, Remod\_SW\_1, Non\_Fax, and Terminate. Terminate leads to an exit symbol with T1522510-96. + +![Flowchart for Process PA_FCH](bd0283b61b6a59829e9370b29076c79a_img.jpg) + +``` + +graph TD + Start([Demodulate_ +Data]) --> Inact_Data_In[/Inact_Data(ch)/] + Start --> DataInact_In[/DataInact(ch)/] + + Inact_Data_In --> Stop_demod[/Stop_demod(ch, +sig_mode,sig_rate) +TO CCFPID/] + Stop_demod --> Data_training{Data_training} + + Data_training -- false --> Data_training_assign[Data_training:= +true] + Data_training_assign --> IDLE_remote[/IDLE(ch) +TO CCFPID/] + IDLE_remote --> Tx_Remote([Tx_Remote_ +Signal]) + + Data_training -- true --> IDLE_local[/IDLE(ch) +TO CCFPID/] + IDLE_local --> Tx_Local([Tx_Local_ +Signal]) + + DataInact_In --> DISCONNECT[/DISCONNECT(ch) +TO CCFPID/] + DISCONNECT --> Release_Resource[[Release_ +Resource(list)]] + Release_Resource --> Demod_SW_1[/Demod_SW_1(ch) +TO CCFPID/] + Demod_SW_1 --> Remod_SW_1[/Remod_SW_1(ch) +TO CCFPID/] + Remod_SW_1 --> Non_Fax[/Non_Fax(ch) +TO CCFPID/] + Non_Fax --> Terminate[/Terminate(ch) +TO CCFPID/] + Terminate --> End((X)) + +``` + +The flowchart illustrates the 'Process PA\_FCH'. It begins with the state 'Demodulate\_Data'. From there, two input signals are possible: 'Inact\_Data(ch)' and 'DataInact(ch)'. + +If 'Inact\_Data(ch)' is received, the process sends 'Stop\_demod(ch, sig\_mode, sig\_rate) TO CCFPID'. It then checks the condition 'Data\_training'. If false, it sets 'Data\_training := true', sends 'IDLE(ch) TO CCFPID', and transitions to the 'Tx\_Remote\_Signal' state. If 'Data\_training' is true, it sends 'IDLE(ch) TO CCFPID' and transitions to the 'Tx\_Local\_Signal' state. + +If 'DataInact(ch)' is received, the process sends 'DISCONNECT(ch) TO CCFPID', calls the procedure 'Release\_Resource(list)', and then sends a sequence of signals to CCFPID: 'Demod\_SW\_1(ch)', 'Remod\_SW\_1(ch)', 'Non\_Fax(ch)', and 'Terminate(ch)'. The process then terminates (indicated by the X symbol). + +Flowchart for Process PA\_FCH + +T1522330-96 + +![Flowchart for Process PA_FCH showing signal processing paths for signalling, data inactivity, fax idle, and low speed channels.](90183a52275501da5a0fd5c63d837009_img.jpg) + +The flowchart illustrates the processing logic for Process PA\_FCH. It begins with a 'Tx\_Remote\_Signal' input that branches into four channel types: **SIGNALLING(ch)**, **DataInact(ch)**, **Fax\_Idle(ch, code, mode, rate)**, and **Low\_speed(ch)**. + +- SIGNALLING(ch)** path: Leads to connector **5**, then to **Start\_remod(ch, sig\_mode, sig\_rate) TO CCFPID**, then to another **Tx\_Remote\_Signal** output. +- DataInact(ch)** path: Leads to **DISCONNECT(ch) TO CCFPID**, then to **Release\_Resource(list)**, then to **Demod\_SW\_1(ch) TO CCFPID**. A label **('PRI', 'PIN', 'PIP')** is associated with this transition. This is followed by **Remod\_SW\_1(ch) TO CCFPID**, **Non\_Fax(ch) TO CCFPID**, and **Terminate(ch) TO CCFPID**, which ends in a termination symbol (X). +- Fax\_Idle(ch, code, mode, rate)** path: Leads to **Stop\_remod(ch, sig\_mode, sig\_rate) TO CCFPID**, then to a decision diamond **(code)**. + - If the **(code)** decision leads to **DISCONNECT(ch) TO CCFPID**, the path continues through **Release\_Resource(list)**, **Demod\_SW\_1(ch) TO CCFPID**, **Remod\_SW\_1(ch) TO CCFPID**, **Non\_Fax(ch) TO CCFPID**, and **Terminate(ch) TO CCFPID**, ending in a termination symbol (X). + - If the **(code)** decision leads to an **else** path, it goes to another decision diamond **(code)**. + - This second **(code)** decision has an **else** path leading to connector **7**. + - It also has a **'(DCS)'** path leading to connector **2**. +- Low\_speed(ch)** path: Leads directly to connector **6**. + +Flowchart for Process PA\_FCH showing signal processing paths for signalling, data inactivity, fax idle, and low speed channels. + +T1522340-96 + +![Flowchart for Process PA_FCH. It starts with a connector '7' leading to a decision diamond '(code)'. The flow branches based on '(CFR', 'CTR')', '(PPR')', '(ERR', 'MCF')', '(code=DCN')', '(PPR_count=4)', '(prev=EOP')', and '(prev)'. It includes process blocks like 'PPR_count:= PPR_count+1', 'PPR_count:=0', 'DISCONNECT(ch) TO CCFPID', 'Release Resource(list)', 'Demod SW_1(ch) TO CCFPID', 'Remod SW_1(ch) TO CCFPID', 'Non_Fax(ch) TO CCFPID', and 'Terminate(ch) TO CCFPID'. It ends with output blocks 'Transmit_FAX', 'Tx local_Signal', 'Tx Remote_Signal', and 'Tx_Local_Signal', and a note '/* Remote is WA */'.](8a781a0a8c956859f63a1ca7f2bb1644_img.jpg) + +``` +graph TD + Start((7)) --> Code1{ (code) } + Code1 -- "('CFR','CTR')" --> TransmitFax1([Transmit_ FAX _]) + Code1 -- else --> Code2{ (code) } + Code2 -- "('PPR')" --> PPRInc[PPR_count:= PPR_count+1] + PPRInc --> PPR4{ (PPR_count=4) } + PPR4 -- (false) --> Code1 + PPR4 -- (true) --> PPR0_1[PPR_count:=0] + PPR0_1 --> TxLocal1([Tx_local_ Signal _]) + Code2 -- else --> Code3{ (code) } + Code3 -- "('ERR','MCF')" --> PPR0_2[PPR_count:=0] + PPR0_2 --> PrevEOP{ (prev='EOP') } + PrevEOP -- (true) --> TxLocal2([Tx_Local_ Signal]) + TxLocal2 --> Code1 + PrevEOP -- (false) --> Prev{ (prev) } + Prev -- "('EOM')" --> TxRemote([Tx_Remote_ Signal _]) + Prev -- else --> TransmitFax2([Transmit_ FAX _]) + Code3 -- else --> CodeDCN{ (code='DCN') } + CodeDCN -- (false) --> Code1 + CodeDCN -- (true) --> Disconnect[DISCONNECT(ch) TO CCFPID] + Disconnect --> Release[Release Resource(list)] + Release --> Demod[Demod_SW_1(ch) TO CCFPID] + Demod --> Remod[Remod_SW_1(ch) TO CCFPID] + Remod --> NonFax[Non_Fax(ch) TO CCFPID] + NonFax --> Terminate[Terminate(ch) TO CCFPID] + Terminate --> End((X)) + Disconnect -.-> Note[/* Remote is WA */] +``` + +Flowchart for Process PA\_FCH. It starts with a connector '7' leading to a decision diamond '(code)'. The flow branches based on '(CFR', 'CTR')', '(PPR')', '(ERR', 'MCF')', '(code=DCN')', '(PPR\_count=4)', '(prev=EOP')', and '(prev)'. It includes process blocks like 'PPR\_count:= PPR\_count+1', 'PPR\_count:=0', 'DISCONNECT(ch) TO CCFPID', 'Release Resource(list)', 'Demod SW\_1(ch) TO CCFPID', 'Remod SW\_1(ch) TO CCFPID', 'Non\_Fax(ch) TO CCFPID', and 'Terminate(ch) TO CCFPID'. It ends with output blocks 'Transmit\_FAX', 'Tx local\_Signal', 'Tx Remote\_Signal', and 'Tx\_Local\_Signal', and a note '/\* Remote is WA \*/'. + +T1522350-96 + +![SDL flowchart for Process PA_FCH showing signal processing paths for Low_speed, Inact, SIGNALLING, DataInact, and Fax_Training.](8ba270d9a35a905e16a9b78e6b3ad2b8_img.jpg) + +``` + +graph TD + State1([Tx_Local_Signal]) --> In1{{Low_speed(ch)}} + State1 --> In2{{Inact(ch,code,mode,rate)}} + State1 --> In3{{SIGNALLING(ch)}} + State1 --> In4{{DataInact(ch)}} + State1 --> In5{{Fax_Training(ch)}} + + In1 --> Conn6((6)) + Conn6 --> Out1>Start_demod(ch, sig_mode, sig_rate) TO CCFPID] + Out1 --> Out2>SIGNALLING(ch, sig_mode, sig_rate) TO CCFPID] + Out2 --> State2([Tx_Local_Signal]) + + In2 --> Out3>Stop_demod(ch, sig_mode, sig_rate) TO CCFPID] + Out3 --> Task1[prev:=code] + Task1 --> Dec1{code} + Dec1 --> |'DCS'| Out4>IDLE(ch) TO CCFPID] + Out4 --> Task2[Data_Training :=false] + Task2 --> State3([Transmit FAX]) + + In3 --> Conn5((5)) + Conn5 --> Dec2{code} + Dec2 --> |'DCN'| Out5>DISCONNECT(ch) TO CCFPID] + Out5 --> Proc1[[Release Resource(list)]] + Proc1 --> Out6>Demod_SW_1(ch) TO CCFPID] + Out6 --> Out7>Remod_SW_1(ch) TO CCFPID] + Out7 --> Out8>Non_Fax(ch) TO CCFPID] + Out8 --> Out9>Terminate(ch) TO CCFPID] + Out9 --> Term1((X)) + + Dec2 --> |else| Out10>IDLE(ch) TO CCFPID] + Out10 --> State4([Tx_Remote_Signal]) + + In4 --> Out11>DISCONNECT(ch) TO CCFPID] + Out11 --> Proc2[[Release Resource(list)]] + Proc2 --> Out12>Demod_SW_1(ch) TO CCFPID] + Out12 --> Out13>Remod_SW_1(ch) TO CCFPID] + Out13 --> Out14>Non_Fax(ch) TO CCFPID] + Out14 --> Out15>Terminate(ch) TO CCFPID] + Out15 --> Term2((X)) + + In5 --> Out11 + Dec1 --> |else| Dec2 + +``` + +SDL flowchart for Process PA\_FCH showing signal processing paths for Low\_speed, Inact, SIGNALLING, DataInact, and Fax\_Training. + +T1522360-96 + +![Flowchart for Process PA_FCH showing various states and transitions for FAX communication. It includes decision diamonds for (code), (DCS'), (DTC'), (NSS'), and (proceed), and process blocks like Stop_remod, Reset, Check_Resource, and various TO CCFPID messages.](abeba89144744fac6a1571aa9f94889e_img.jpg) + +``` + +graph TD + State_Called_FAX([Called_FAX]) --> Input_Group{ } + + Input_Group --> Fax_Idle[Fax_Idle(ch, code, mode, rate)] + Input_Group --> SIGNALLING[SIGNALLING(ch)] + Input_Group --> RESOURCE[RESOURCE(ch, list)] + Input_Group --> SWITCH_TO_ADPCM[SWITCH_TO_ADPCM(ch)] + + %% Path from Fax_Idle + Fax_Idle --> Stop_remod_1[Stop_remod(ch, sig_mode, sig_rate) TO CCFPID] + Stop_remod_1 --> Dec_code_1{"(code)"} + + Dec_code_1 -- "(DCS')" --> Reset_1[Reset(td) +Reset(ts)] + Reset_1 --> Conn_2((2)) + Conn_2 --> Check_Res[[Check_Resource(proceed)]] + Check_Res --> Dec_proceed_1{"(proceed)"} + Dec_proceed_1 -- "(proceed)" --> Receive_1[Receive(ch) TO CCFPID] + Receive_1 --> Data_train[Data_training := FALSE] + Data_train --> Prev_DCS[prev:='DCS'] + Prev_DCS --> State_Receive_FAX([Receive_FAX]) + + Dec_code_1 -- "else" --> Dec_code_2{"(code)"} + Dec_code_2 -- "(DTC')" --> Reset_2[Reset(td); +Reset(ts)] + Reset_2 --> Demod_SW_4[Demod_SW_4(ch) TO CCFPID] + Demod_SW_4 --> State_Called_FAX_2([Called_FAX]) + + %% Path from SIGNALLING + SIGNALLING --> Start_remod[Start_remod(ch, sig_mode, sig_rate) TO CCFPID] + Start_remod --> State_Called_FAX_3([Called_FAX]) + + %% Path from RESOURCE + RESOURCE --> Reset_ts[Reset(ts)] + Reset_ts --> Store_list[Store(list)] + Store_list --> State_Called_FAX_4([Called_FAX]) + + %% Path from SWITCH_TO_ADPCM + SWITCH_TO_ADPCM --> Stop_remod_2[Stop_remod(ch, sig_mode, sig_rate) TO CCFPID] + Stop_remod_2 --> Release_Res_1[[Release_Resource(list)]] + Release_Res_1 --> Demod_SW_1_1[Demod_SW_1(ch) TO CCFPID] + Demod_SW_1_1 --> Remod_SW_1_1[Remod_SW_1(ch) TO CCFPID] + Remod_SW_1_1 --> Switch_to_ADPCM_1[Switch_to_ADPCM(ch) TO CCFPID] + Switch_to_ADPCM_1 --> Reset_3[Reset(td) +Reset(ts)] + Reset_3 --> State_Rx_ADPCM_FAX_1([Rx_ADPCM_FAX]) + + %% Sub-logic for (code) else path + Dec_code_2 -- "else" --> Dec_code_3{"(code)"} + Dec_code_3 -- "(NSS')" --> Cap_Check[[Capability_Check(proceed)]] + Cap_Check --> Reset_4[Reset(td) +Reset(ts)] + Reset_4 --> Dec_proceed_2{"(proceed)"} + Dec_proceed_2 -- "(true)" --> State_Rx_NSF_T30([Rx_NSF_T30]) + Dec_proceed_2 -- "(false)" --> Switch_CCFPID[SWITCH(ch) TO CCFPID] + + Dec_proceed_1 -- "(false)" --> Switch_CCFPID + Switch_CCFPID --> Release_Res_2[[Release_Resource(list)]] + Release_Res_2 --> Demod_SW_1_2[Demod_SW_1(ch) TO CCFPID] + Demod_SW_1_2 --> Remod_SW_1_2[Remod_SW_1(ch) TO CCFPID] + Remod_SW_1_2 --> Switch_to_ADPCM_2[Switch_to_ADPCM(ch) TO CCFPID] + Switch_to_ADPCM_2 --> State_Rx_ADPCM_FAX_2([Rx_ADPCM_FAX]) + + Dec_code_3 -- "else" --> State_Called_FAX_5([Called_FAX]) + +``` + +Flowchart for Process PA\_FCH showing various states and transitions for FAX communication. It includes decision diamonds for (code), (DCS'), (DTC'), (NSS'), and (proceed), and process blocks like Stop\_remod, Reset, Check\_Resource, and various TO CCFPID messages. + +T1522370-96 + +![Flowchart for Process PA_FCH showing state transitions for Called_FAX, Low_speed(ch), Inact(ch, code, mode, rate), td, and ts. It includes actions like Start_demod, Stop_demod, SIGNALLING, IDLE, Reset, SWITCH_TO, Demod_SW_1, Remod_SW_1, Switch_to, Rx_ADPCM_FAX, Non_Fax, and Terminate. Includes notes for DCS and RESOURCE timer expirations.](b3d488012fdceacab867cf24c5efef05_img.jpg) + +``` + +stateDiagram-v2 + state "Called_FAX" as Called_FAX + state "Low_speed(ch)" as Low_speed_ch + state "Inact(ch, code, mode, rate)" as Inact + state "td" as td + state "ts" as ts + state "Start_demod(ch, sig_mode, sig_rate)" as Start_demod + state "Stop_demod(ch, sig_mode, sig_rate)" as Stop_demod + state "SIGNALLING(ch) TO CCFPID" as SIGNALLING + state "IDLE(ch) TO CCFPID" as IDLE + state "End_of_DIS(ch)" as End_of_DIS + state "Set(NOW+t_DCS, td)" as Set_td + state "SWITCH_TO_DEMOD(ch) TO CCFPID" as SWITCH_TO_DEMOD + state "Remod_SW_3(ch) TO CCFPID" as Remod_SW_3 + state "Reset(ts)" as Reset_ts + state "Reset(td)" as Reset_td + state "SWITCH_TO_ADPCM(ch) TO CCFPID" as SWITCH_TO_ADPCM + state "Alarm(ch) TO CCFPID" as Alarm + state "Release_Resource(list)" as Release_Resource + state "DISCONNECT(ch) TO CCFPID" as DISCONNECT + state "Demod_SW_1(ch) TO CCFPID" as Demod_SW_1 + state "Remod_SW_1(ch) TO CCFPID" as Remod_SW_1 + state "Switch_to ADPCM(ch) TO CCFPID" as Switch_to_ADPCM_2 + state "Rx_ADPCM_FAX" as Rx_ADPCM_FAX + state "Non_Fax(ch) TO CCFPID" as Non_Fax + state "Terminate(ch) TO CCFPID" as Terminate + + [*] --> Called_FAX + Called_FAX --> Low_speed_ch + Called_FAX --> Inact + Called_FAX --> td + Called_FAX --> ts + + Low_speed_ch --> Start_demod + Start_demod --> SIGNALLING + SIGNALLING --> End_of_DIS + End_of_DIS --> Set_td + Set_td --> SWITCH_TO_DEMOD + SWITCH_TO_DEMOD --> Remod_SW_3 + Remod_SW_3 --> Called_FAX + + Inact --> Stop_demod + Stop_demod --> code_decision + state code_decision <> + code_decision --> IDLE: else + code_decision --> Reset_td_ts: ('DCS') + IDLE --> Called_FAX + Reset_td_ts --> 1 + + td --> Reset_ts + Reset_ts --> SWITCH_TO_ADPCM + SWITCH_TO_ADPCM --> Release_Resource + Release_Resource --> Demod_SW_1 + Demod_SW_1 --> Remod_SW_1 + Remod_SW_1 --> Switch_to_ADPCM_2 + Switch_to_ADPCM_2 --> Rx_ADPCM_FAX + + ts --> Reset_td + Reset_td --> Alarm + Alarm --> DISCONNECT + DISCONNECT --> Release_Resource_2 + state "Release_Resource(list)" as Release_Resource_2 + Release_Resource_2 --> Demod_SW_1_2 + state "Demod_SW_1(ch) TO CCFPID" as Demod_SW_1_2 + Demod_SW_1_2 --> Remod_SW_1_2 + state "Remod_SW_1(ch) TO CCFPID" as Remod_SW_1_2 + Remod_SW_1_2 --> Non_Fax + Non_Fax --> Terminate + Terminate --> [*] + + note right of td: /* DCS timer expiration */ + note right of ts: /* RESOURCE timer expiration */ + +``` + +Flowchart for Process PA\_FCH showing state transitions for Called\_FAX, Low\_speed(ch), Inact(ch, code, mode, rate), td, and ts. It includes actions like Start\_demod, Stop\_demod, SIGNALLING, IDLE, Reset, SWITCH\_TO, Demod\_SW\_1, Remod\_SW\_1, Switch\_to, Rx\_ADPCM\_FAX, Non\_Fax, and Terminate. Includes notes for DCS and RESOURCE timer expirations. + +T1522520-96 + +![Flowchart for Process PA_FCH showing two main paths: Rx_NSF_T30 and Rx_ADPCM_FAX. The Rx_NSF_T30 path includes steps for Voice(ch), DataInact(ch), DISCONNECT(ch) TO CCFPID, Release_Resource(list), Demod_SW_1(ch) TO CCFPID, Remod_SW_1(ch) TO CCFPID, Non_Fax(ch) TO CCFPID, and TERMINATE(ch) TO CCFPID. The Rx_ADPCM_FAX path includes steps for Voice(ch), DISCONNECT(ch) TO CCFPID, Demod_SW_1(ch) TO CCFPID, Remod_SW_1(ch) TO CCFPID, Non_Fax(ch) TO CCFPID, and Terminate(ch) TO CCFPID.](487c58c79e44e6cf98b6368b6667b9c6_img.jpg) + +``` +graph TD; subgraph PA_FCH [Process PA_FCH]; direction TB; Rx_NSF_T30_1([Rx_NSF_T30]) --> V1[Voice(ch)]; Rx_NSF_T30_1 --> D1[DataInact(ch)]; Rx_NSF_T30_1 --> S1[*]; V1 --> DISCONNECT1[DISCONNECT(ch) TO CCFPID]; DISCONNECT1 --> RELEASE[Release_Resource(list)]; RELEASE --> DEMOD1[Demod_SW_1(ch) TO CCFPID]; DEMOD1 --> REMOD1[Remod_SW_1(ch) TO CCFPID]; REMOD1 --> NONFAX1[Non_Fax(ch) TO CCFPID]; NONFAX1 --> TERMINATE1[TERMINATE(ch) TO CCFPID]; TERMINATE1 --> X1((X)); S1 --> HANDLING[Rx_NSF_T30_Handling]; HANDLING --> Rx_NSF_T30_2([Rx_NSF_T30]); Rx_ADPCM_FAX_1([Rx_ADPCM_FAX]) --> V2[Voice(ch)]; V2 --> DISCONNECT2[DISCONNECT(ch) TO CCFPID]; DISCONNECT2 --> DEMOD2[Demod_SW_1(ch) TO CCFPID]; DEMOD2 --> REMOD2[Remod_SW_1(ch) TO CCFPID]; REMOD2 --> NONFAX2[Non_Fax(ch) TO CCFPID]; NONFAX2 --> TERMINATE2[Terminate(ch) TO CCFPID]; TERMINATE2 --> X2((X)); end +``` + +Flowchart for Process PA\_FCH showing two main paths: Rx\_NSF\_T30 and Rx\_ADPCM\_FAX. The Rx\_NSF\_T30 path includes steps for Voice(ch), DataInact(ch), DISCONNECT(ch) TO CCFPID, Release\_Resource(list), Demod\_SW\_1(ch) TO CCFPID, Remod\_SW\_1(ch) TO CCFPID, Non\_Fax(ch) TO CCFPID, and TERMINATE(ch) TO CCFPID. The Rx\_ADPCM\_FAX path includes steps for Voice(ch), DISCONNECT(ch) TO CCFPID, Demod\_SW\_1(ch) TO CCFPID, Remod\_SW\_1(ch) TO CCFPID, Non\_Fax(ch) TO CCFPID, and Terminate(ch) TO CCFPID. + +T1522530-96 + +![Placeholder box with dashed border and a small L-shaped corner marker.](153cae80a07f05406529e6c3344bc896_img.jpg) + +Placeholder box with dashed border and a small L-shaped corner marker. + +![Flowchart for Process PA_FCH. It starts with 'Receive_FAX' (oval), which branches into four chevron-shaped decision blocks: 'EPT(ch,f)', 'SIGNALLING(ch)', 'LEVEL(ch, level)', and 'TRAINING(ch, mode, rate, long)'. 'EPT(ch,f)' leads to 'Start_EPT(ch,f) TO CCFPID' (parallelogram), then 'Set(NOW+t_ept,te)' (rectangle), and finally 'Remote_EPT' (oval). 'SIGNALLING(ch)' leads to a circle with '3'. 'LEVEL(ch, level)' leads to 'Receive_FAX' (oval). 'TRAINING(ch, mode, rate, long)' leads to a circle with '10'.](0dfdff10c725fe9c332b07ade9d23a5e_img.jpg) + +``` +graph TD; A([Receive_FAX]) --> B{EPT(ch,f)}; A --> C{SIGNALLING(ch)}; A --> D{LEVEL(ch, level)}; A --> E{TRAINING(ch, mode, rate, long)}; B --> F[/Start_EPT(ch,f) TO CCFPID/]; F --> G[Set(NOW+t_ept,te)]; G --> H([Remote_EPT]); C --> I((3)); D --> J([Receive_FAX]); E --> K((10)); +``` + +Flowchart for Process PA\_FCH. It starts with 'Receive\_FAX' (oval), which branches into four chevron-shaped decision blocks: 'EPT(ch,f)', 'SIGNALLING(ch)', 'LEVEL(ch, level)', and 'TRAINING(ch, mode, rate, long)'. 'EPT(ch,f)' leads to 'Start\_EPT(ch,f) TO CCFPID' (parallelogram), then 'Set(NOW+t\_ept,te)' (rectangle), and finally 'Remote\_EPT' (oval). 'SIGNALLING(ch)' leads to a circle with '3'. 'LEVEL(ch, level)' leads to 'Receive\_FAX' (oval). 'TRAINING(ch, mode, rate, long)' leads to a circle with '10'. + +T1522400-96 + +![Dashed rectangular box with a folded top-right corner, a standard SDL process reference symbol.](ec01eef8e1a76c2b3661db5292900140_img.jpg) + +Dashed rectangular box with a folded top-right corner, a standard SDL process reference symbol. + +![SDL process diagram for PA_FCH showing state transitions from Remote_EPT to Remote_Training based on inputs END_EPT(ch) or te.](ffe0fef452a0ae9a20253c319c54e13c_img.jpg) + +``` + +graph TD + State1([Remote_EPT]) + State1 --- Split(( )) + Split --- Input1[/END_EPT ch/] + Split --- Input2[/te/] + Input1 --> Task1[Reset te] + Task1 --- Merge(( )) + Input2 --- Merge + Merge --> Output1[/Stop_EPT ch,f
TO CCFPID/] + Output1 --> State2([Remote_Training]) + + Note[/* EPT timer expiration */] + Note -.- Input2 + +``` + +SDL process diagram for PA\_FCH showing state transitions from Remote\_EPT to Remote\_Training based on inputs END\_EPT(ch) or te. + +T1522410-96 + +![Flowchart for Process PA_FCH showing various training and data processing steps. It starts with Remote Training, branches into TRAINING, FAX_DATA, SIGNALLING, Low_speed, and LONG_TRAINING. TRAINING leads to connector 10 and Start_remod. FAX_DATA leads to Start_remod and Remodulate_Data. SIGNALLING leads to connector 3. Low_speed leads to connector 4. LONG_TRAINING leads to Remote Training. From Remodulate_Data, it goes to Data_training decision. If true, it goes to mode decision. If mode is (V.17), it generates Short Training and sets long=false. If mode is not (V.17) or Data_training is false, it generates Long Training and sets Data_training=true, long=true. Both paths lead to Remote Training.](592f13acca3e6d5152dd4489f030d004_img.jpg) + +``` + +graph TD + RT1([Remote Training]) --> TRAINING[TRAINING(ch, mode, rate, long)] + RT1 --> FAX_DATA[FAX_DATA(ch)] + RT1 --> SIGNALLING[SIGNALLING(ch)] + RT1 --> Low_speed[Low_speed(ch)] + RT1 --> LONG_TRAINING[LONG_TRAINING(ch, rate)] + TRAINING --> C10((10)) + C10 --> SR1[Start_remod(ch, mode, rate) TO CCFPID] + FAX_DATA --> SR2[Start_remod(ch, mode, rate) TO CCFPID] + SR2 --> RD([Remodulate Data]) + SIGNALLING --> C3((3)) + Low_speed --> C4((4)) + LONG_TRAINING --> RT2([Remote Training]) + RD --> DT{(Data_training)} + DT -- true --> M{(mode)} + DT -- false --> GLT[Generate Long Training(ch, mode, rate) TO CCFPID] + M -- "(V.17)" --> GST[Generate Short Training(ch, mode, rate) TO CCFPID] + GST --> LF[long:=false] + LF --> RT3([Remote Training]) + GLT --> DT2[Data_training := true, long:=true] + DT2 --> RT4([Remote Training]) + +``` + +Flowchart for Process PA\_FCH showing various training and data processing steps. It starts with Remote Training, branches into TRAINING, FAX\_DATA, SIGNALLING, Low\_speed, and LONG\_TRAINING. TRAINING leads to connector 10 and Start\_remod. FAX\_DATA leads to Start\_remod and Remodulate\_Data. SIGNALLING leads to connector 3. Low\_speed leads to connector 4. LONG\_TRAINING leads to Remote Training. From Remodulate\_Data, it goes to Data\_training decision. If true, it goes to mode decision. If mode is (V.17), it generates Short Training and sets long=false. If mode is not (V.17) or Data\_training is false, it generates Long Training and sets Data\_training=true, long=true. Both paths lead to Remote Training. + +T1522420-96 + +![A dashed rectangular box with a folded top-right corner, likely a placeholder or a specific graphical element.](d0fb35ebe641d0754d6776b064de4d74_img.jpg) + +A dashed rectangular box with a folded top-right corner, likely a placeholder or a specific graphical element. + +![Flowchart showing signal processing steps: Remodulate_Data, IDLE(ch), Stop_remod(ch, sig_mode, sig_rate) TO CCFPID, a decision diamond (prev='DCS'), and two output signals: Rx_Remote_Signal and Rx_Local_Signal.](de63e4b6d8b0aa76b85e1fe3236eac27_img.jpg) + +``` +graph TD; A([Remodulate_Data]) --> B[/IDLE(ch)/]; B --> C[/Stop_remod(ch, sig_mode, sig_rate) TO CCFPID/]; C --> D{prev='DCS'}; D -- (false) --> E([Rx_Remote_Signal]); D -- (true) --> F([Rx_Local_Signal]); +``` + +Flowchart showing signal processing steps: Remodulate\_Data, IDLE(ch), Stop\_remod(ch, sig\_mode, sig\_rate) TO CCFPID, a decision diamond (prev='DCS'), and two output signals: Rx\_Remote\_Signal and Rx\_Local\_Signal. + +T1522430-96 + +![SDL flowchart for Process PA_FCH starting from state Rx_Local_Signal. It branches into four input signals: Low_speed(ch), Inact(ch, code, mode, rate), SIGNALLING(ch), and Fax_Training(ch). The Low_speed branch goes through connector 4 to Start_demod and SIGNALLING outputs, returning to Rx_Local_Signal. The Inact branch goes to Stop_demod, then a decision on 'code'. If 'DCN', it proceeds through DISCONNECT, Release_Resource, Demod_SW_1, Remod_SW_1, Non_Fax, and Terminate outputs to a process end. If 'else', it goes to IDLE output and connector 8. The SIGNALLING branch goes to connector 3. The Fax_Training branch goes through DISCONNECT, Release_Resource, Demod_SW_1, Remod_SW_1, Non_Fax, and Terminate outputs to a process end.](140bd031d724324269168296afd1e04d_img.jpg) + +``` +graph TD + Start([Rx_Local_Signal]) + Start --> LowSpeed[/Low_speed(ch)/] + Start --> Inact[/Inact(ch, code, mode, rate)/] + Start --> Signalling[/SIGNALLING(ch)/] + Start --> FaxTraining[/Fax_Training(ch)/] + + LowSpeed --> Conn4((4)) + Conn4 --> StartDemod{{Start_demod(ch, +sig_mode,sig_rate) +TO CCFPID}} + StartDemod --> SignallingOut{{SIGNALLING(ch) +TO CCFPID}} + SignallingOut --> EndState([Rx_Local_Signal]) + + Inact --> StopDemod{{Stop_demod(ch, +sig_mode,sig_rate) +TO CCFPID}} + StopDemod --> CodeDecision{ (code) } + CodeDecision -- DCN --> Disconnect1{{DISCONNECT(ch) +TO CCFPID}} + Disconnect1 --> Release1[[Release_ +Resource(list)]] + Release1 --> DemodSW1{{Demod_SW_1(ch) +TO CCFPID}} + DemodSW1 --> RemodSW1{{Remod_SW_1(ch) +TO CCFPID}} + RemodSW1 --> NonFax1{{Non_Fax(ch) +TO CCFPID}} + NonFax1 --> Terminate1{{Terminate(ch) +TO CCFPID}} + Terminate1 --> Stop1[X] + + CodeDecision -- else --> Idle{{IDLE(ch) +TO CCFPID}} + Idle --> Conn8((8)) + + Signalling --> Conn3((3)) + + FaxTraining --> Disconnect2{{DISCONNECT(ch) +TO CCFPID}} + Disconnect2 --> Release2[[Release_ +Resource(list)]] + Release2 --> DemodSW2{{Demod_SW_1(ch) +TO CCFPID}} + DemodSW2 --> RemodSW2{{Remod_SW_1(ch) +TO CCFPID}} + RemodSW2 --> NonFax2{{Non_Fax(ch) +TO CCFPID}} + NonFax2 --> Terminate2{{Terminate(ch) +TO CCFPID}} + Terminate2 --> Stop2[X] +``` + +SDL flowchart for Process PA\_FCH starting from state Rx\_Local\_Signal. It branches into four input signals: Low\_speed(ch), Inact(ch, code, mode, rate), SIGNALLING(ch), and Fax\_Training(ch). The Low\_speed branch goes through connector 4 to Start\_demod and SIGNALLING outputs, returning to Rx\_Local\_Signal. The Inact branch goes to Stop\_demod, then a decision on 'code'. If 'DCN', it proceeds through DISCONNECT, Release\_Resource, Demod\_SW\_1, Remod\_SW\_1, Non\_Fax, and Terminate outputs to a process end. If 'else', it goes to IDLE output and connector 8. The SIGNALLING branch goes to connector 3. The Fax\_Training branch goes through DISCONNECT, Release\_Resource, Demod\_SW\_1, Remod\_SW\_1, Non\_Fax, and Terminate outputs to a process end. + +T1522440-96 + +![Placeholder box for Process PA_FCH](12b4eb155a09c29b8e15b9d23930cefb_img.jpg) + +Placeholder box for Process PA\_FCH + +![Flowchart for Process PA_FCH starting at node 8, with decision diamonds for (code), (code='PPR?'), and (PPR_count=4), and process blocks like DISCONNECT, Release_Resource, Demod_SW_1, Remod_SW_1, Non_Fax, Terminate, PPR_count:=PPR_count+1, and PPR_count:=0. It ends at nodes 11, Receive_FAX, and Rx_Remote_Signal.](c0ca823603794512478906b302176bca_img.jpg) + +``` +graph TD; 8((8)) --> code1{code}; code1 -- "(PIP', PIN')" --> DISCONNECT[DISCONNECT(ch) TO CCFPID]; DISCONNECT --> Release_Resource[Release_Resource(list)]; Release_Resource --> Demod_SW_1[Demod_SW_1(ch) TO CCFPID]; Demod_SW_1 --> Remod_SW_1[Remod_SW_1(ch) TO CCFPID]; Remod_SW_1 --> Non_Fax[Non_Fax(ch) TO CCFPID]; Non_Fax --> Terminate[Terminate(ch) TO CCFPID]; Terminate --> X[ ]; code1 -- else --> code2{code}; code2 -- "(CFR', CTR', ERR')" --> Receive_FAX[Receive_FAX]; code2 -- else --> code3{code='PPR?'}; code3 -- (true) --> PPR_count_plus[PPR_count:=PPR_count+1]; code3 -- (false) --> 11((11)); PPR_count_plus --> PPR_count_eq4{PPR_count=4}; PPR_count_eq4 -- (false) --> code2; PPR_count_eq4 -- (true) --> PPR_count_zero[PPR_count:=0]; PPR_count_zero --> Rx_Remote_Signal[Rx_Remote_Signal]; +``` + +Flowchart for Process PA\_FCH starting at node 8, with decision diamonds for (code), (code='PPR?'), and (PPR\_count=4), and process blocks like DISCONNECT, Release\_Resource, Demod\_SW\_1, Remod\_SW\_1, Non\_Fax, Terminate, PPR\_count:=PPR\_count+1, and PPR\_count:=0. It ends at nodes 11, Receive\_FAX, and Rx\_Remote\_Signal. + +T1522450-96 + +![Flowchart for Process PA_FCH starting at node 11, with decision diamonds for (code), (prev=EOP), and (prev=EOM), and processes like PPR_count:=0, Transmit(ch) TO CCFPID, Rx_Local_Signal, and Receive_FAX.](cf36ccd7ff79531e18e5b0ab1f0c46d4_img.jpg) + +``` +graph TD; 11((11)) --> code{code}; code -- "(MCF)" --> PPR[PPR_count:=0]; code -- else --> DCS{code='DCS'}; PPR --> EOP{prev='EOP'}; EOP -- (true) --> DCS; EOP -- (false) --> EOM{prev='EOM'}; EOM -- (true) --> RxLocal((Rx_Local_Signal)); EOM -- (false) --> ReceiveFAX((Receive_FAX)); DCS -- (true) --> Transmit{{Transmit(ch) TO CCFPID}}; DCS -- (false) --> RxRemote((Rx_Remote_Signal)); Transmit --> 1((1)); +``` + +The flowchart illustrates the logic for Process PA\_FCH. It begins at connector node 11, leading to a decision diamond labeled (code). If the condition '(MCF)' is met, the process moves to a rectangular block 'PPR\_count:=0', which then leads to a decision diamond '(prev=EOP)'. If '(prev=EOP)' is true, it leads to decision diamond '(code=DCS)'. If '(prev=EOP)' is false, it leads to decision diamond '(prev=EOM)'. If '(prev=EOM)' is true, it leads to an oval terminal 'Rx\_Local\_Signal'. If '(prev=EOM)' is false, it leads to an oval terminal 'Receive\_FAX'. If the initial '(code)' decision is 'else', it leads to decision diamond '(code=DCS)'. If '(code=DCS)' is true, it leads to a pentagonal process block 'Transmit(ch) TO CCFPID', which then leads to connector node 1. If '(code=DCS)' is false, it leads to an oval terminal 'Rx\_Remote\_Signal'. + +Flowchart for Process PA\_FCH starting at node 11, with decision diamonds for (code), (prev=EOP), and (prev=EOM), and processes like PPR\_count:=0, Transmit(ch) TO CCFPID, Rx\_Local\_Signal, and Receive\_FAX. + +T1522540-96 + +![Flowchart for Process PA_FCH. It starts with an entry point 'Rx_Remote_Signal' leading to three parallel paths: 'SIGNALLING(ch)' leading to connector '3', 'Fax_Idle(ch, code, mode, rate)' leading to 'Stop_remod(ch, sig_mode, sig_rate) TO CCFPID', and 'Low_speed(ch)' leading to connector '4'. All three paths converge to 'prev:=code'. A decision diamond '(code=CTC)' follows. The '(false)' path leads to another decision '(code)'. If '(DCS)' is true, it goes to 'Capability_Check(proceed)' then 'Reset(td)'. If '(DCS)' is false, it goes to 'DISCONNECT(ch) TO CCFPID'. From 'Reset(td)', a decision '(proceed)' follows. The '(true)' path leads to 'Data_Training:=false' then connector '2'. The '(false)' path leads to 'SWITCH_TO_ADPCM(ch) TO CCFPID'. Both paths lead to 'Release_Resource(list)'. From 'Release_Resource(list)', the flow goes to 'Demod_SW_1(ch) TO CCFPID', then 'Remod_SW_1(ch) TO CCFPID', then 'Switch_to_ADPCM(ch) TO CCFPID', and finally 'Terminate(ch) TO CCFPID' which ends. The '(code)' decision after '(code=CTC)' has a '(DCN)' path leading to 'DISCONNECT(ch) TO CCFPID' and an 'else' path leading to 'Rx_Local_Signal'. The '(DCN)' path leads to 'Release_Resource(list)' then 'Demod_SW_1(ch) TO CCFPID', 'Remod_SW_1(ch) TO CCFPID', 'Non_Fax(ch) TO CCFPID', and 'Terminate(ch) TO CCFPID' which ends. A note 'T1522470-96' is present near the bottom right.](df803281854ce2cbde7019b5aeefd8cd_img.jpg) + +Process PA\_FCH 23(24) + +``` + +graph TD + Entry([Rx_Remote_Signal]) --> SIG[SIGNALLING(ch)] + Entry --> FAX[Fax_Idle(ch, code, mode, rate)] + Entry --> LOW[Low_speed(ch)] + SIG --> C3((3)) + FAX --> STOP[Stop_remod(ch, sig_mode, sig_rate) TO CCFPID] + LOW --> C4((4)) + C3 --> START[Start_remod(ch, sig_mode, sig_rate) TO CCFPID] + START --> Entry + STOP --> PREV[prev:=code] + LOW --> PREV + PREV --> CTC{code=CTC} + CTC -- (false) --> CODE{code} + CTC -- (true) --> LOCAL([Rx_Local_Signal]) + CODE -- (DCS) --> CHECK[Capability_Check(proceed)] + CODE -- else --> DISCONN[DISCONNECT(ch) TO CCFPID] + CHECK --> RESET[Reset(td)] + RESET --> PROCEED{proceed} + PROCEED -- (true) --> TRAIN[Data_Training:=false] + TRAIN --> C2((2)) + PROCEED -- (false) --> SWITCH[SWITCH_TO_ADPCM(ch) TO CCFPID] + SWITCH --> RES1[Release_Resource(list)] + RES1 --> DEMOD1[Demod_SW_1(ch) TO CCFPID] + DEMOD1 --> REMOD1[Remod_SW_1(ch) TO CCFPID] + REMOD1 --> SWITCH2[Switch_to_ADPCM(ch) TO CCFPID] + SWITCH2 --> TERM1[Terminate(ch) TO CCFPID] + TERM1 --> X1((X)) + DISCONN --> RES2[Release_Resource(list)] + RES2 --> DEMOD2[Demod_SW_1(ch) TO CCFPID] + DEMOD2 --> REMOD2[Remod_SW_1(ch) TO CCFPID] + REMOD2 --> NONFAX[Non_Fax(ch) TO CCFPID] + NONFAX --> TERM2[Terminate(ch) TO CCFPID] + TERM2 --> X2((X)) + LOCAL --> X3((X)) + +``` + +T1522470-96 + +Flowchart for Process PA\_FCH. It starts with an entry point 'Rx\_Remote\_Signal' leading to three parallel paths: 'SIGNALLING(ch)' leading to connector '3', 'Fax\_Idle(ch, code, mode, rate)' leading to 'Stop\_remod(ch, sig\_mode, sig\_rate) TO CCFPID', and 'Low\_speed(ch)' leading to connector '4'. All three paths converge to 'prev:=code'. A decision diamond '(code=CTC)' follows. The '(false)' path leads to another decision '(code)'. If '(DCS)' is true, it goes to 'Capability\_Check(proceed)' then 'Reset(td)'. If '(DCS)' is false, it goes to 'DISCONNECT(ch) TO CCFPID'. From 'Reset(td)', a decision '(proceed)' follows. The '(true)' path leads to 'Data\_Training:=false' then connector '2'. The '(false)' path leads to 'SWITCH\_TO\_ADPCM(ch) TO CCFPID'. Both paths lead to 'Release\_Resource(list)'. From 'Release\_Resource(list)', the flow goes to 'Demod\_SW\_1(ch) TO CCFPID', then 'Remod\_SW\_1(ch) TO CCFPID', then 'Switch\_to\_ADPCM(ch) TO CCFPID', and finally 'Terminate(ch) TO CCFPID' which ends. The '(code)' decision after '(code=CTC)' has a '(DCN)' path leading to 'DISCONNECT(ch) TO CCFPID' and an 'else' path leading to 'Rx\_Local\_Signal'. The '(DCN)' path leads to 'Release\_Resource(list)' then 'Demod\_SW\_1(ch) TO CCFPID', 'Remod\_SW\_1(ch) TO CCFPID', 'Non\_Fax(ch) TO CCFPID', and 'Terminate(ch) TO CCFPID' which ends. A note 'T1522470-96' is present near the bottom right. + +![Dashed box icon with a folded corner, likely a placeholder or a specific symbol.](0a30df67544ebe636d1086ae0ce2e09d_img.jpg) + +Dashed box icon with a folded corner, likely a placeholder or a specific symbol. + +![Flowchart showing three parallel process paths for PA_FCH. Path 1: *(Pre_FAX) -> Voice(ch) -> DISCONNECT(ch) TO CCFPID -> Demod_SW_1(ch) TO CCFPID -> Remod_SW_1(ch) TO CCFPID -> Non_Fax(ch) TO CCFPID -> SWITCH_to_ADPCM(ch) TO CCFPID -> Terminate(ch) TO CCFPID -> X. Path 2: *(Pre_FAX) -> DISCONNECT(ch) -> Demod_SW_1(ch) TO CCFPID -> Remod_SW_1(ch) TO CCFPID -> Non_Fax(ch) TO CCFPID -> Terminate(ch) TO CCFPID -> X. Path 3: *(Pre_FAX) -> Transp(ch) -> DISCONNECT(ch) TO CCFPID -> Demod_SW_1(ch) TO CCFPID -> Remod_SW_1(ch) TO CCFPID -> Terminate(ch) TO CCFPID -> X.](d04c50badc78d5ba47bf4e352af4a754_img.jpg) + +``` +graph TD; subgraph Path1; P1_1([*(Pre_FAX)]) --> P1_2(Voice(ch)); P1_2 --> P1_3[DISCONNECT(ch) TO CCFPID]; P1_3 --> P1_4[Demod_SW_1(ch) TO CCFPID]; P1_4 --> P1_5[Remod_SW_1(ch) TO CCFPID]; P1_5 --> P1_6[Non_Fax(ch) TO CCFPID]; P1_6 --> P1_7[SWITCH_to_ADPCM(ch) TO CCFPID]; P1_7 --> P1_8[Terminate(ch) TO CCFPID]; P1_8 --> P1_9((X)); subgraph Path2; P2_1([*(Pre_FAX)]) --> P2_2[DISCONNECT(ch)]; P2_2 --> P2_3[Demod_SW_1(ch) TO CCFPID]; P2_3 --> P2_4[Remod_SW_1(ch) TO CCFPID]; P2_4 --> P2_5[Non_Fax(ch) TO CCFPID]; P2_5 --> P2_6[Terminate(ch) TO CCFPID]; P2_6 --> P2_7((X)); subgraph Path3; P3_1([*(Pre_FAX)]) --> P3_2(Transp(ch)); P3_2 --> P3_3[DISCONNECT(ch) TO CCFPID]; P3_3 --> P3_4[Demod_SW_1(ch) TO CCFPID]; P3_4 --> P3_5[Remod_SW_1(ch) TO CCFPID]; P3_5 --> P3_6[Terminate(ch) TO CCFPID]; P3_6 --> P3_7((X)); end +``` + +Flowchart showing three parallel process paths for PA\_FCH. Path 1: \*(Pre\_FAX) -> Voice(ch) -> DISCONNECT(ch) TO CCFPID -> Demod\_SW\_1(ch) TO CCFPID -> Remod\_SW\_1(ch) TO CCFPID -> Non\_Fax(ch) TO CCFPID -> SWITCH\_to\_ADPCM(ch) TO CCFPID -> Terminate(ch) TO CCFPID -> X. Path 2: \*(Pre\_FAX) -> DISCONNECT(ch) -> Demod\_SW\_1(ch) TO CCFPID -> Remod\_SW\_1(ch) TO CCFPID -> Non\_Fax(ch) TO CCFPID -> Terminate(ch) TO CCFPID -> X. Path 3: \*(Pre\_FAX) -> Transp(ch) -> DISCONNECT(ch) TO CCFPID -> Demod\_SW\_1(ch) TO CCFPID -> Remod\_SW\_1(ch) TO CCFPID -> Terminate(ch) TO CCFPID -> X. + +T1522550-96 + +## Dimensioning example for facsimile compression + +### S.1 Introduction + +This example is intended to be used in conjunction with the DCME dimensioning method outlined in Supplement No. 2 to Recommendation G.763, "DCME dimensioning for different route characteristics". + +### S.2 Assumptions + +It is assumed that: + +- most facsimile calls are carried out at 9.6 kbit/s; +- approximately 20% of facsimile calls are between machines which have a compatible set of non-standard facilities, which they therefore use, and which cannot be compressed; +- non-facsimile voiceband data is approximately 10% of the total; +- forward error correction is switched on, on the FCMs; +- most facsimile calls are of two pages in length; +- typical page transmission time is 30 s. + +### S.3 Method + +Determination of the peak data loading period must follow the procedure of Supplement No. 2 to Recommendation G.763, taking due cognizance of the caveats of 4.3/G.763, "Two pitfalls for the unwary". That done, taking the example given in 4.2.1 of Supplement No. 2 to Recommendation G.763, "DCME dimensioning using the profile of a route without silence elimination", the example may be reworked as follows to include facsimile compression: + +Assumption: + +Number of trunk channels at service date = 240 + +NOTE – For facsimile compression, the gain for the voiceband data element of the Digital Channel Occupancy Analyser (DCOA) profile is increased. Therefore, for moderate voiceband data percentages and rates of 14.4 kbit/s and below, the channel occupancy profile of the bearer is quite similar to that of the trunk side. Furthermore, actual values of gain on facsimile traffic are likely to be numerically similar to the gain for voice traffic. These facts suggest that with facsimile compression, two DCMEs may be sufficient to carry the traffic. + +From Figure 6 of Supplement No. 2 to Recommendation G.763 there are two peaks to be considered: one is dominated by the amount of data (data peak) and the other is dominated by the amount of voice (voice peak). + +Data Peak: + +59% of data: + +$$\text{Number of fax trunks} = 240 \times 0.59 \times 0.9$$ + +$$= 128$$ + +$$\text{of which} \quad 128 \times 0.8$$ + +$$= 102 \text{ have standard facilities}$$ + +$$128 \times 0.2$$ + +$$= 26 \text{ have non-standard facilities}$$ + +$$\text{Number of non-fax data trunks} = 240 \times 0.59 \times 0.1$$ + +$$= 14$$ + +Therefore, number of data trunks which must be carried through ADPCM + +$$= 14 + 26$$ + +$$= 40$$ + +Number of ADPCM data trunks per DCME + +$$= \frac{40}{2}$$ + +$$\text{DSI gain} = 1 \quad (\text{Silence elimination advantage cannot generally be assumed for non-facsimile and non-standard facilities facsimile data})$$ + +$$\text{LRE gain} = \frac{8}{5}$$ + +On a single channel, the low-speed signals which are carried through for compression are: + +DCS (1.46 s) + +CFR (1.36 s) + +MPS (1.36 s) + +MCF (1.36 s) + +EOP (1.36 s) + +MCF (1.36 s) + +DCN (1.36 s) + +Total time duration of low-speed signals = 9.62 s (worst case) both directions included. + +Since fax is half-duplex, in each direction the average duration (worst case) is: + +$$\frac{9.62}{2} = 4.81 \text{ s}$$ + +These are 300 bit/s signals with 100% stuffing control overhead, 60% FDC fill, and triple redundancy. Therefore, the bearer channel rate is: + +$$6 \text{ bits}/2 \text{ ms} = 3 \text{ kbit/s}$$ + +Image data is sent at 9.6 kbit/s using a 21-bit FDC, which therefore gives a bearer channel rate of: + +$$21 \text{ bits}/2 \text{ ms} = 10.5 \text{ kbit/s}$$ + +The mean bit rate for single call is therefore: + +$$\frac{3 \times 4.81 + 10.5 \times 30}{34.81} = 9.46 \text{ kbit/s}$$ + +and fax compression gain is $\frac{64}{9.46} = 6.77$ + +However, since we have assumed that FEC is ON in each terminal, the actual bearer channel rate will be: + +$$\frac{9.46 \times 32}{21} = 14.42 \text{ kbit/s}$$ + +and the fax compression gain is $64/14.42 = 4.44$ + +Since 102 trunk channels are compressible, the bearer capacity allocated to the facsimile compression is: + +$$\frac{102}{4.44} = 23 \text{ (fax bearer 64 kbit/s channels)}$$ + +For 17% voice: + +$$\begin{aligned} \text{number of voice trunks} &= 240 \times 0.17 \\ &= 41 \text{ trunks totals} \end{aligned}$$ + +$$\begin{aligned} \text{number of voice trunks} \\ \text{per DCME} &= 20 \end{aligned}$$ + +$$\text{DSI gain (for 20 trunks)} = 1.43 \text{ (from tables)}$$ + +$$\text{LRE gain} = \frac{8}{3.6}$$ + +Hence, the 64 kbit/s bearer channel requirement is: + +$$\begin{aligned} &\frac{20 \times 5}{8} + \frac{20 \times 3.6}{1.43 \times 8} + \frac{23}{2} \\ &= 12.5 \text{ (data)} + 6.29 \text{ (voice)} + 11.5 \text{ (fax)} \\ &= 30.29 \text{ bearer channels per DCME} \end{aligned}$$ + +NOTE – This is marginal, in view of the fact that a half-bearer channel must be allocated for the control channel, and a quarter-bearer channel for the FCC (when present). Nevertheless, the calculation illustrates the method which may be used in dimensioning DCMEs with a facsimile compression facility. The same method may be applied to the remainder of the example calculations in Supplement No. 2 to Recommendation G.763. + +# ITU-T RECOMMENDATIONS SERIES + +| | | +|-----------------|----------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of the ITU-T | +| Series B | Means of expression | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Telephone network and ISDN | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media | +| Series H | Transmission of non-telephone signals | +| Series I | Integrated services digital network | +| Series J | Transmission of sound-programme and television signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | Maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound-programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminal equipments and protocols for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communication | +| Series Z | Programming languages | \ No newline at end of file diff --git a/marked/G/T-REC-G.7713.1-200303-I_PDF-E/raw.md b/marked/G/T-REC-G.7713.1-200303-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..e49fadd48bbfb4a50f88de81cfd5d5ede1521d72 --- /dev/null +++ b/marked/G/T-REC-G.7713.1-200303-I_PDF-E/raw.md @@ -0,0 +1,1927 @@ + + +![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with a lightning bolt and the letters ITU. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +**G.7713.1/Y.1704.1** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +(03/2003) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital terminal equipments – Operations, administration +and maintenance features of transmission equipment + +SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE +AND INTERNET PROTOCOL ASPECTS + +Internet protocol aspects – Operation, administration and +maintenance + +--- + +**Distributed call and connection management +(DCM) based on PNNI** + +ITU-T Recommendation G.7713.1/Y.1704.1 + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | G.500–G.599 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| QUALITY OF SERVICE AND PERFORMANCE | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DIGITAL TERMINAL EQUIPMENTS | G.7000–G.7999 | +| General | G.7000–G.7099 | +| Coding of analogue signals by pulse code modulation | G.7100–G.7199 | +| Coding of analogue signals by methods other than PCM | G.7200–G.7299 | +| Principal characteristics of primary multiplex equipment | G.7300–G.7399 | +| Principal characteristics of second order multiplex equipment | G.7400–G.7499 | +| Principal characteristics of higher order multiplex equipment | G.7500–G.7599 | +| Principal characteristics of transcoder and digital multiplication equipment | G.7600–G.7699 | +| Operations, administration and maintenance features of transmission equipment | G.7700–G.7799 | +| Principal characteristics of multiplexing equipment for the synchronous digital hierarchy | G.7800–G.7899 | +| Other terminal equipment | G.7900–G.7999 | +| DIGITAL NETWORKS | G.8000–G.8999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## ITU-T Recommendation G.7713.1/Y.1704.1 + +# Distributed call and connection management (DCM) based on PNNI + +## Summary + +This Recommendation provides the protocol specifications for distributed call and connection management based on PNNI/Q.2931. This Recommendation meets the requirements of ITU-T Rec. G.7713/Y.1704 and is functionally similar to other ITU-T Recommendations in the G.7713 series. The protocol specification in this Recommendation specifies the communications across interfaces to effect automated call operations and connection operations. This version of the Recommendation is concerned with the specification for soft permanent connections. Items covered in this Recommendation include: + +- message functional definition and content; +- general message format and information element coding; +- call/connection control procedures. + +This Recommendation does not cover any aspects related to routing, or automatic discovery. + +## Source + +ITU-T Recommendation G.7713.1/Y.1704.1 was prepared by ITU-T Study Group 15 (2001-2004) and approved under the WTSA Resolution 1 procedure on 16 March 2003. + +## History + +This Recommendation forms part of a suite of Recommendations covering the full functionality of the automatic switched transport network (ASTN). + +| Document History | | | +|------------------|-------------------|------------| +| Version | | Approval | +| 0.1 | G.7713.1/Y.1704.1 | 2003-03-16 | + +## Keywords + +Automatic switched optical network, Automatic switched transport network, Distributed call and Connection management, Exterior network-node interface, PNNI, Q.2931, User network interface. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2003 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## CONTENTS + +| | | Page | +|---------|------------------------------------------------------------------------|------| +| 1 | Scope ..... | 1 | +| 2 | References..... | 1 | +| 3 | Terms and Definitions ..... | 2 | +| 4 | Abbreviations and acronyms ..... | 2 | +| 5 | Conventions ..... | 3 | +| 6 | Assumptions ..... | 3 | +| 7 | Applications..... | 3 | +| 7.1 | Overview of PNNI..... | 4 | +| 7.2 | Defect handling ..... | 4 | +| 7.3 | Example signalling flows ..... | 5 | +| 8 | Message functional definition and content..... | 6 | +| 8.1 | Messages for distributed connection management..... | 6 | +| 8.2 | Messages used with the global call reference..... | 12 | +| 9 | General message format and Information Element coding ..... | 13 | +| 9.1 | Overview ..... | 13 | +| 9.2 | Protocol discriminator ..... | 14 | +| 9.3 | Call Reference ..... | 14 | +| 9.4 | Message type and length ..... | 14 | +| 9.5 | Variable length Information Elements ..... | 15 | +| 10 | Updated procedures ..... | 26 | +| 10.1 | Link Connection Identifier allocation/selection ..... | 27 | +| 10.2 | Connection clearing for non-persistent connections ..... | 30 | +| 10.3 | Procedures for connections persistent across signalling failures ..... | 30 | +| 10.4 | Bearer Plane failures..... | 31 | +| 10.5 | Receipt of NOTIFY messages..... | 32 | +| Annex A | – Transport of G.7713.1/Y.1704.1 messages over DCN network..... | 32 | +| A.1 | Introduction ..... | 32 | +| A.2 | Differences in boundary interfaces..... | 32 | +| A.3 | Overview of SSCOPMCE link management process ..... | 33 | +| A.4 | Changes required to ITU-T Rec. Q.2931 ..... | 35 | +| A.5 | Changes required to the SSCF (ITU-T Rec. Q.2130) ..... | 35 | +| A.6 | Applicability of SSCOPMCE specific parameters and timers..... | 35 | +| A.7 | Layer management boundary ..... | 35 | +| A.8 | Link types ..... | 36 | +| Annex B | – Graceful deletion ..... | 37 | +| B.1 | Introduction ..... | 37 | +| B.2 | Sending deletion notification..... | 37 | + +| | Page | +|------------------------------------------------------------------------------|------| +| B.3 Receiving deletion notification..... | 37 | +| B.4 Receiving ready for deletion ..... | 37 | +| Annex C – DTL processing in the absence of routing protocols ..... | 38 | +| Annex D – ASON call identifier ..... | 38 | +| Appendix I – Mapping of G.7713/Y.1704 UNI attributes to Q.2931/PNNI ..... | 40 | +| Appendix II – Mapping of G.7713/Y.1704 E-NNI Attributes to Q.2931/PNNI ..... | 40 | +| Appendix III – Link connection scope..... | 41 | +| III.1 Scope of the link connection identifier..... | 41 | +| III.2 A link connection identifier association function..... | 42 | + +# **Distributed call and connection management (DCM) based on PNNI** + +# **1 Scope** + +This Recommendation provides the protocol specifications for distributed call and connection management based on PNNI/Q.2931, developed within the context of G.7713/Y.1704 DCM requirements. The protocol specifications in this Recommendation specify the communications across interfaces to effect automated call operations and connection operations. This version of the Recommendation is concerned with the specification for soft permanent connections. As such the call model is based on the concept of a null call as described in ITU-T Rec. G.8080/Y.1304. By providing a call identifier in the soft permanent connection model, the specification can be extended in later versions to include switched connections. As such, name translation/directory services and call capability sets are not included. Items covered in this Recommendation include: + +- message functional definition and content; +- general message format and information element coding; +- call/connection control procedures. + +This Recommendation does not cover any aspects related to routing, or automatic discovery. + +This Recommendation does not specify the use of the PNNI routing algorithm, nor does it restrict the use of PNNI to an ATM transport implementation, indeed PNNI can be transported using protocols other than ATM, e.g., Internet Protocol. + +# **2 References** + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [1] ITU-T Recommendation Q.931 (1998), *ISDN user-network interface layer 3 specification for call control*. +- [2] ATM Forum af-cs-0125.000 (1999), *ATM Inter-Network (ANNI) Specification*. +- [3] ATM Forum af-pnni-0055.002 (2002), *Private Network-Network Interface Specification v.1.1*. +- [4] ITU-T Recommendation Q.2111 (1999), *B-ISDN ATM adaptation layer – Service specific connection oriented protocol in a multi-link and connectionless environment (SSCOPMCE)*. +- [5] ITU-T Recommendation Q.2931 (1995), *Digital Subscriber Signalling System No. 2 (DSS2) – User-Network Interface (UNI) layer 3 specification for basic call/connection*. +- [6] ATM Forum af-cs-0127.000 (1999), *PNNI SPVC Addendum Version 1.0*. +- [7] ITU-T Recommendation Q.2610 (1999), *Usage of cause and location in B-ISDN user part and DSS2*. +- [8] ATM Forum af-sig-0140.000 (2000), *Network Call Correlation Identifier v.1.0*. +- [9] ATM Forum af-sig-0061.000 (1996), *UNI Signalling v.4.0*. + +- [10] ATM Forum af-cs-0141.000 (2000), *PNNI Addendum for Path and Connection Trace, Version 1.0.* +- [11] ATM Forum af-cs-0148.000 (2000), *Modification of Traffic Descriptor for an Active Connection, Addendum to UNI 4.0/PNNI 1.0/AINI.* +- [12] ATM Forum af-cs-0173.000 (2001), *Domain-based rerouting for active point-to-point calls, Version 1.0.* +- [13] ITU-T Recommendation G.807/Y.1302 (2001), *Requirements for automatic switched transport networks (ASTN).* +- [14] ITU-T Recommendation G.7712/Y.1703 (2003), *Architecture and specification of data communication network.* +- [15] ITU-T Recommendation G.7713/Y.1704 (2001), *Distributed call and connection management (DCM).* +- [16] ITU-T Recommendation G.7714/Y.1705, (2001), *Generalized automatic discovery techniques.* +- [17] ITU-T Recommendation G.8080/Y.1304 (2001), *Architecture for the automatically switched optical networks (ASON).* +- [18] ITU-T Recommendation E.360.1 (2002), *Framework for QoS routing and related traffic engineering methods for IP-, ATM-, and TDM-based multiservice networks.* +- [19] ITU-T Recommendation G.707/Y.1322 (2000), *Network node interface for the synchronous digital hierarchy (SDH).* +- [20] ITU-T Recommendation G.709/Y.1331 (2003), *Interfaces for the Optical Transport Network (OTN).* + +# 3 Terms and Definitions + +The following terms are defined in ITU-T Rec. G.8080/Y.1304: + +- connection controller; +- link resource manager; +- subnetwork point; +- subnetwork point pool. + +The following term is defined in ITU-T Rec. G.807/Y.1302: + +- soft permanent connection. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations: + +| | | +|------|--------------------------------------| +| AESA | ATM End System Address | +| ASON | Automatic Switched Optical Network | +| ASTN | Automatic Switched Transport Network | +| CC | Connection Controller | +| DTL | Designated Transit List | +| IE | Information Element | + +| | | +|------|-------------------------------------| +| LCI | Link Connection Identifier | +| LRM | Link Resource Manager | +| M | Mandatory | +| NCCI | Network Call Correlation Identifier | +| O | Optional | +| PNNI | Private Network-Network Interface | +| SNP | Subnetwork Point | +| SNPP | Subnetwork Point Pool | +| SPC | Soft Permanent Connection | +| TLV | Type, Length, Value | + +# 5 Conventions + +In this Recommendation, the acronym PNNI is used to refer to the signalling protocol portion of PNNI [5], together with a number of extension specifications. + +# 6 Assumptions + +This Recommendation assumes a subset of the messages and information elements defined by the PNNI [5] as the basis for the protocol specification for the Automatic Switched Transport Network (ASTN). Signalling procedures defined by the PNNI are assumed to apply except for the modifications identified in clause 10. + +This Recommendation supports the NSAP address format for addressing information. Other address formats such as IP version 4 and IP version 6 can be supported through conversion to NSAP format. Addressing of transport resources in the protocol is done via Subnetwork Point Pool (SNPP) identifiers. A pair of these SNPP identifiers identify an SNPP link. SNPP names are defined from transport name spaces (see clause 10/G.8080/Y.1304) and it is important to note that control plane names/addresses are not used for these. For example, neither routing controller nor connection manager identifiers are used for bearer link names. + +The terms Quality of Service (QoS), Class of Service (CoS), and Grade of Service (GoS) with respect to the transport plane are used in this Recommendation in the sense of ITU-T Rec. E.360.1. It is expected that ASON specific characteristics and parameters will be associated with these terms in later versions of this Recommendation. + +# 7 Applications + +Figure 7-1 provides an overall view of control plane partitioning and the main interfaces of the control plane that pertain to signalling. + +![Diagram illustrating the overall view of control plane partition. It shows three user administration domains connected to three provider administration domains (A, B, and C). Provider A is further divided into two sub-domains, A1 and A2. Interfaces are labeled UNI, E-NNI, and I-NNI. Callouts explain that Provider A's network is divided into multiple control domains (e.g., vendor, geographic, technology, political, etc.), while Provider B's network is a single control domain.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg) + +The diagram illustrates the overall view of control plane partition in a network. At the top, two 'User admin. domain' clouds are shown, each containing several nodes. These are connected via UNI (User Network Interface) to 'Provider A admin. domain' and 'Provider C admin. domain' respectively. 'Provider A admin. domain' is connected to 'Provider B admin. domain' via an E-NNI (Edge Network-to-Network Interface). 'Provider B admin. domain' is connected to 'Provider C admin. domain' via an E-NNI. Below 'Provider A admin. domain', a callout box states: 'Provider A has divided their network into multiple control domains (e.g., vendor, geographic, technology, political, etc.)'. This is visually represented by two green clouds labeled 'Domain A1 I-NNI' and 'Domain A2 I-NNI' connected by an E-NNI. A second callout box next to 'Provider B admin. domain' states: 'Provider B's network is a single control domain'. The diagram is labeled G.7713.1\_F7-1 in the bottom right corner. + +Diagram illustrating the overall view of control plane partition. It shows three user administration domains connected to three provider administration domains (A, B, and C). Provider A is further divided into two sub-domains, A1 and A2. Interfaces are labeled UNI, E-NNI, and I-NNI. Callouts explain that Provider A's network is divided into multiple control domains (e.g., vendor, geographic, technology, political, etc.), while Provider B's network is a single control domain. + +**Figure 7-1/G.7713.1/Y.1704.1 – Overall view of control plane partition** + +## 7.1 Overview of PNNI + +The ATM Forum's PNNI [3] signalling specifications provide a scalable network-network interface. It is based on ATM Forums UNI specification [9] and on ITU-T Rec. Q.2931 signalling protocol specification [5] and related extension documents. Minor modifications are defined in this specification to allow the signalling protocol to be applied to the distributed call and connection management of an Automatic Switched Optical Network (ASON) transport networks. + +### 7.1.1 New formats for transport networks + +A new Connection Identifier Information Element (IE) format is defined for use with transport networks allowing the specification of new connection types, and to include the concepts of Subnetwork Point (SNP) and Subnetwork Point Pool (SNPP). A new Traffic Descriptors IE format is defined for use with transport networks allowing the specification of traffic descriptor attributes suitable for transport networks. + +## 7.2 Defect handling + +There are different types of defects that may affect the control plane. These defects may range from a simple signalling channel failure to multiple control plane node failures. The control plane needs to support appropriate behaviours to recover from these defects, initially attempting to recover from failures based on local control plane mechanisms, local interaction with the transport plane, and subsequently attempting to recover based on control plane interactions with external components. General guidelines for defect handling include: + +- Control plane failures are notified to the management plane. The management plane may direct the control plane to take certain actions due to the failure. These actions may include + +cleaning up of partial connections, release of certain connections, or other protocol-specific actions for state maintenance and recovery. + +- A control plane node may provide a persistent storage of relevant information, such as call and connection state information, configuration information, and control plane neighbour information. +- After repair if connection/call states cannot be recovered, the control plane node may communicate with an external component to attempt state information recovery. External components may include neighbour control plane nodes or a persistent storage provided by a centralised (e.g., management plane) component. +- A control plane node notifies the management plane of the inability to recover (subset of) relevant information (e.g., inability to synchronize state of connections). The management plane may respond with the following actions (the default control plane action should be to retain the connections): + - release the impacted connections; + - retain the impacted connections. In this case, a connection may remain non-synchronized from the control plane perspective; however, the connection may remain valid. +- A control plane node (after recovering from node failure) may not be able to recover neighbour connection state from its local persistent storage and thus may lose information on connections. In this case the control plane node should request an external controller (e.g., the management system) for information to recover the connections. Similarly call state may be unrecovered and require management intervention to resolve. Specifics of the interactions between the control plane and management plane are beyond the scope of this Recommendation. + +Thus, as a general rule: + +- A control plane failure must not result in the release of established connections. Setup requests in the process of been completed may be removed (either during the failure or after recovery from failure). Established connections associated with a pending release request must be released (either during the failure or after recovery from failure). +- Additional actions by the control plane may be dependent on provisioned default behaviour for a particular type of connection. + +However, a transport plane node failure may result in the release of established connections. This depends on the type of connection and the service level associated with each connection. For example, a "best-effort unprotected" connection may be released during a transport plane node failure while a "protected" connection must be restored (or maintained) based on the service level specification associated with that connection. Note that even in the case of a protected connection, the original connection may be released while a new connection is set up (this also depends on the type of protection used for the particular connection). + +## 7.3 Example signalling flows + +The following example signalling flows illustrate the basic operation of the signalling protocol for simple setup and release scenarios. + +### 7.3.1 Setup with no monitoring + +Figure 7-2 illustrates call setup with no monitoring. T303 and T310 are timers as described in ITU-T Rec. Q.2931. + +![Sequence diagram for call setup scenario with no monitoring. It shows three nodes: End system, Switch, and Switch. The sequence of messages is: Call setup (End system to Switch), Call proceeding (Switch to End system), Call setup (Switch to Switch), Call proceeding (Switch to Switch), Connect (Switch to End system), and Connect (Switch to Switch). Timers T303 and T310 are shown on the first Switch.](d4af765160d04ecef538e5066006dc77_img.jpg) + +The diagram illustrates a call setup scenario with no monitoring. It features three nodes: an End system, a Switch, and another Switch. The sequence of messages is as follows: + + +- The End system sends a 'Call setup' message to the first Switch. +- The first Switch responds with a 'Call proceeding' message to the End system. +- The first Switch then sends a 'Call setup' message to the second Switch. +- The second Switch responds with a 'Call proceeding' message to the first Switch. +- Finally, the second Switch sends a 'Connect' message to the End system, and the first Switch also sends a 'Connect' message to the End system. + + Timers T303 and T310 are indicated on the first Switch. The diagram is labeled G.7713.1\_F7-2. + +Sequence diagram for call setup scenario with no monitoring. It shows three nodes: End system, Switch, and Switch. The sequence of messages is: Call setup (End system to Switch), Call proceeding (Switch to End system), Call setup (Switch to Switch), Call proceeding (Switch to Switch), Connect (Switch to End system), and Connect (Switch to Switch). Timers T303 and T310 are shown on the first Switch. + +Figure 7-2/G.7713.1/Y.1704.1 – Call setup scenario with no monitoring + +### 7.3.2 Call Release with no monitoring + +Figure 7-3 illustrates call release with no monitoring. T308 is a timer as defined in ITU-T Rec. Q.2931. + +![Sequence diagram for call release scenario with no monitoring. It shows three nodes: End system, Switch, and Switch. The sequence of messages is: Release (End system to Switch), Release (Switch to Switch), Release complete (Switch to End system), and Release complete (Switch to Switch). Timer T308 is shown on the first Switch.](1439cb942d9e363bbb3161b5540dd8c6_img.jpg) + +The diagram illustrates a call release scenario with no monitoring. It features three nodes: an End system, a Switch, and another Switch. The sequence of messages is as follows: + + +- The End system sends a 'Release' message to the first Switch. +- The first Switch then sends a 'Release' message to the second Switch. +- The second Switch responds with a 'Release complete' message to the first Switch. +- Finally, the first Switch sends a 'Release complete' message to the End system. + + A timer T308 is indicated on the first Switch. The diagram is labeled G.7713.1\_F7-3. + +Sequence diagram for call release scenario with no monitoring. It shows three nodes: End system, Switch, and Switch. The sequence of messages is: Release (End system to Switch), Release (Switch to Switch), Release complete (Switch to End system), and Release complete (Switch to Switch). Timer T308 is shown on the first Switch. + +Figure 7-3/G.7713.1/Y.1704.1 – Call release scenario with no monitoring + +# 8 Message functional definition and content + +## 8.1 Messages for distributed connection management + +Table 8-1 summarizes the messages for point-to-point call and connection control. + +Table 8-1/G.7713.1/Y.1704.1 – Messages for distributed connection management + +| Message | Reference af-pnni-0055.002
(unless otherwise indicated) | +|------------------------------|------------------------------------------------------------| +| Call establishment messages: | | +| CALL PROCEEDING | 6.3.1.2 | +| CONNECT | 6.3.1.3 | +| SETUP | 6.3.1.6 | +| Call clearing messages: | | +| RELEASE | 6.3.1.4 | +| RELEASE COMPLETE | 6.3.1.5 | + +**Table 8-1/G.7713.1/Y.1704.1 – Messages for distributed connection management** + +| Message | Reference af-pnni-0055.002
(unless otherwise indicated) | +|----------------------------------------------------------|------------------------------------------------------------| +| Miscellaneous messages: | | +| CONNECTION AVAILABLE | 6.3.1.10 | +| MODIFY ACKNOWLEDGE (Note) | 2.1.2.2 of [11] | +| MODIFY REJECT (Note) | 2.1.2.3 of [11] | +| MODIFY REQUEST (Note) | 2.1.2.1 of [11] | +| NOTIFY | 6.3.1.9 | +| STATUS | 6.3.1.7 | +| STATUS ENQUIRY | 6.3.1.8 | +| TRACE CONNECTION | 5.2 of [10] | +| TRACE CONNECTION ACKNOWLEDGE | 5.2 of [10] | +| NOTE – Detailed format and procedures for further study. | | + +### **8.1.1 Call proceeding message** + +This message is sent by the Succeeding side to indicate that call establishment has been initiated and no more call establishment information will be accepted. Table 8-2 describes the CALL PROCEEDING message content. + +Message type: CALL PROCEEDING + +Direction: Succeeding to Preceding + +Significance: Local + +**Table 8-2/G.7713.1/Y.1704.1 – CALL PROCEEDING message content** + +| Information Element | Type | Length | +|------------------------|------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Connection identifier | M | 5-* | + +### **8.1.2 Connect message** + +This message is sent by the Succeeding and delivered to the Preceding side to indicate call/connection acceptance by the called user. Table 8-3 describes the CONNECT message content. + +Message type: CONNECT + Direction: Succeeding to Preceding + Significance: Global + +**Table 8-3/G.7713.1/Y.1704.1 – CONNECT message content** + +| Information Element | Type | Length | +|---------------------------------------------------------------------------------|-------------------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Broadband low layer information | O (Note 1) | 5-20 | +| Called party SPC | O (Note 2) | 8-* | +| Notification indicator | O (Notes 1 and 3) | 5-* | +| Rerouting | O (Note 1) | 11-80 | +| Rerouting Services | O | 8 | +| NOTE 1 – Included if the received connect indication contains this information. | | | +| NOTE 2 – Included in case of soft permanent connection setup. | | | +| NOTE 3 – May be present up to three times. | | | + +### 8.1.3 Release message + +This message is sent by a network node to an adjacent network node to indicate that it has cleared the connection (if any) and is waiting to release the call reference. Table 8-4 describes the RELEASE message content. + +Message type: RELEASE + Direction: Both + Significance: Global + +**Table 8-4/G.7713.1/Y.1704.1 – RELEASE message content** + +| Information Element | Type | Length | +|--------------------------------------------------------------------|------------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Cause | M (Note 1) | 6-34 | +| Crankback | O (Note 2) | 7-72 | +| Notification indicator | O | 5-* | +| Rerouting cause | O | 5 | +| NOTE 1 – This information element may appear twice in the message. | | | +| NOTE 2 – Included to indicate crankback. | | | + +### 8.1.4 Release complete message + +This message is sent by a network node to an adjacent network node to indicate that it has cleared internally the connection (if any) and released the call reference. Table 8-5 describes the RELEASE COMPLETE message content. + +Message type: RELEASE COMPLETE + +Direction: Both + +Significance: Local (Note 1) + +**Table 8-5/G.7713.1/Y.1704.1 – RELEASE COMPLETE message content** + +| Information Element | Type | Length | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Cause | O (Note 2) | 6-34 | +| Crankback | O (Note 3) | 7-72 | +| Rerouting cause | O | 5 | +| NOTE 1 – This message has local significance; however, it may carry information of global significance when used as the first call-clearing message.
NOTE 2 – Mandatory in the first call-clearing message; including when the RELEASE COMPLETE message is sent as a result of an error condition. This information element may appear twice in the message.
NOTE 3 – Included to indicate crankback. | | | + +### 8.1.5 Setup message + +This message is sent by the Preceding side to the Succeeding side to initiate call/connection establishment. Table 8-6 describes the SETUP message content. + +Message type: SETUP + +Direction: Preceding to Succeeding + +Significance: Global + +**Table 8-6/G.7713.1/Y.1704.1 – SETUP message content** + +| Information Element | Type | Length | +|----------------------------------|-------------------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Traffic descriptor | M | 13-19 | +| Broadband bearer capability | M | 6-7 | +| Broadband high layer information | O (Note 1) | 5-13 | +| Broadband low layer information | O (Note 1) | 5-20 | +| Broadband repeat indicator | O (Note 3) | 5 | +| Broadband report type | O (Notes 1 and 6) | 5 | + +**Table 8-6/G.7713.1/Y.1704.1 – SETUP message content** + +| Information Element | Type | Length | +|--------------------------------------------|------------|---------| +| Called party number | M | (2) | +| Called party soft permanent connection | O | 5-30 | +| Calling party number | O (Note 1) | 6-26 | +| Calling party soft permanent connection | O (Note 2) | 6-29 | +| Connection Identifier | O | 5-* | +| Designated transit list | M (Note 4) | 33-546 | +| Network call correlation identifier (NCCI) | O (Note 5) | 33-73 | +| Notification indicator | O (Note 1) | 5-* | +| Extended QoS parameter | O | 6 | +| Rerouting services | O | 8 | +| Rerouting | O | 11-80 | +| Trace transit list | O (Note 1) | 38-1466 | + +NOTE 1 – Included if the received setup indication contains this information. +NOTE 2 – May be included in case of soft permanent connection setup, when the calling endpoint wants to inform the destination network interface of the values used for the soft permanent segment at the calling end. +NOTE 3 – When the Broadband Repeat Indicator Information Element immediately precedes the Designated Transit List (DTL) information element, it indicates the order of Designated Transit List information elements in the DTL stack. This information element is mandatory, even when there is only one Designated Transit List Information Element. When the Broadband Repeat Indicator Information Element immediately precedes any other information element, it is included if the received setup indication contains this information. +NOTE 4 – Included by the source node to indicate the hierarchical source route for the call. Included by the node at the entry to a hierarchical level to indicate the path through that hierarchical level. This information element may be repeated up to 10 times (so a connection can traverse 10 logical groups). +NOTE 5 – Included by the source node, to uniquely identify a call across various hops in the network. It is also needed to correlate various connections that correspond to the same call, at various nodes in the network. +NOTE 6 – May be present twice. + +### 8.1.6 Status message + +This message is sent by either side in response to a STATUS ENQUIRY message or at any time to report certain error conditions. Table 8-7 describes the STATUS message content. + +Message type: STATUS + +Direction: Both + +Significance: Local + +**Table 8-7/G.7713.1/Y.1704.1 – STATUS message content** + +| Information Element | Type | Length | +|------------------------|------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Call state | M | 5 | +| Cause | M | 6-34 | +| Connection identifier | O | 5-* | + +### **8.1.7 Status enquiry** + +The STATUS ENQUIRY message may be sent by either side at any time to solicit a STATUS message from the peer entity. Sending a STATUS message in response to a STATUS ENQUIRY message is mandatory. Table 8-8 describes the STATUS ENQUIRY message content. + +Message type: STATUS ENQUIRY + +Direction: Both + +Significance: Local + +**Table 8-8/G.7713.1/Y.1704.1 – STATUS ENQUIRY message content** + +| Information Element | Type | Length | +|------------------------|------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Connection identifier | O | 5-* | + +#### **8.1.8 Notify message** + +This message is sent to indicate information pertaining to a call/connection. Table 8-9 describes the NOTIFY message content. + +Message type: NOTIFY + +Direction: Both + +Significance: Access + +**Table 8-9/G.7713.1/Y.1704.1 – NOTIFY message content** + +| Information Element | Type | Length | +|------------------------|------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Notification indicator | M | 5-* | + +#### 8.1.9 Connection Available message + +This message is passed without change by PNNI to confirm the availability of a connection from the calling user to the called user. Table 8-10 describes the CONNECTION AVAILABLE message content. + +Message type: CONNECTION AVAILABLE + +Direction: Preceding to Succeeding + +Significance: Global + +**Table 8-10/G.7713.1/Y.1704.1 – CONNECTION AVAILABLE message content** + +| Information Element | Type | Length | +|------------------------------|----------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Notification indicator | M | 5-* | +| Broadband report type | O (Note) | 5 | +| NOTE – May be present twice. | | | + +## 8.2 Messages used with the global call reference + +Table 8-11 summarizes the messages for point-to-point call and connection control. + +**Table 8-11/G.7713.1/Y.1704.1 – Messages Used with the Global Call Reference** + +| Message | Reference af-pnni-0055.002 | +|---------------------|----------------------------| +| RESTART | 6.3.3.1 | +| RESTART ACKNOWLEDGE | 6.3.3.2 | +| STATUS | 6.3.1.7 | +| STATUS ENQUIRY | 18.3.1.2 | + +### 8.2.1 Restart message + +This message is sent by either side to request the recipient to restart (i.e., release all resources associated with) the indicated connection controlled by the signalling channel. Table 8-12 describes the RESTART message content. + +Message type: RESTART + +Direction: Both + +Significance: Local + +**Table 8-12/G.7713.1/Y.1704.1 – RESTART message content** + +| Information Element | Type | Length | +|------------------------|------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Connection identifier | M | 5-* | +| Restart indicator | M | 5 | + +### 8.2.2 Restart Acknowledge message + +This message is sent to acknowledge the receipt of a RESTART message and to indicate that the requested restart is complete. Table 8-13 describes the RESTART ACKNOWLEDGE message content. + +Message type: RESTART ACKNOWLEDGE + +Direction: Both + +Significance: Local + +**Table 8-13/G.7713.1/Y.1704.1 – RESTART ACKNOWLEDGE message content** + +| Information Element | Type | Length | +|------------------------|------|--------| +| Protocol discriminator | M | 1 | +| Call reference | M | 4 | +| Message type | M | 2 | +| Message length | M | 2 | +| Connection identifier | M | 5-* | +| Restart indicator | M | 5 | + +# 9 General message format and Information Element coding + +The figures and text in this clause describe message contents. + +## 9.1 Overview + +Within the signalling protocol, every message shall consist of the following: + +- protocol discriminator; +- call reference; +- message type; +- variable length information elements as required. + +The format of 4-1/Q.2931 applies with the following change: + +The last sentence of the paragraph immediately below Figure 4-1/Q.2931 does not apply. + +## 9.2 Protocol discriminator + +This (one octet) IE is used to distinguish messages of different ATM Forum and ITU-T Recommendations and other standards. The format shall be as in 4.2/Q.2931. The value assigned for this Recommendation is 0000 1011. + +## 9.3 Call Reference + +The Call Reference is used to identify the call/connection at the local interface to which the particular message applies. The format shall be as in 4.3/Q.2931. + +## 9.4 Message type and length + +The format for message type and message length shall be as in 4.4/Q.2931. + +The following message types are used for G.7713.1/Y.1704.1 Distributed Connection Management. See Table 9-1. + +**Table 9-1/G.7713.1/Y.1704.1 – Message type (Octet 1)** + +| Bits | | +|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------| +| 8 7 6 5 4 3 2 1 | | +| 0 0 0 0 0 0 0 0 | Escape to nationally specific message type (Note) | +| 0 0 0 - - - - - | CALL ESTABLISHMENT MESSAGES: | +| 0 0 0 1 0 | Call Proceeding | +| 0 0 1 1 1 | Connect | +| 0 0 1 0 1 | Setup | +| 0 1 0 - - - - - | CALL CLEARING MESSAGES: | +| 0 1 1 0 1 | Release | +| 1 1 0 1 0 | Release Complete | +| 0 0 1 1 0 | Restart | +| 0 1 1 1 0 | Restart Acknowledge | +| 0 1 1 - - - - - | MISCELLANEOUS MESSAGES: | +| 0 1 1 1 0 | Notify | +| 1 1 1 0 1 | Status | +| 1 0 1 0 1 | Status Enquiry | +| 1 0 0 0 1 0 1 1 | Connection Available | +| 1 0 0 0 1 0 0 1 | Modify Acknowledge | +| 1 0 0 0 1 0 1 0 | Modify Reject | +| 1 0 0 0 1 0 0 0 | Modify Request | +| 1 0 0 0 1 1 0 0 | Trace Connection | +| 1 0 0 0 1 1 0 1 | Trace Connection Acknowledge | +| NOTE – When used, the message type (excluding the message compatibility instruction indicator) is defined in Octet 10 of the message, and the contents follow in the subsequent octets, both according to the national specification. | | + +## 9.5 Variable length Information Elements + +The coding rules for Information Elements shall be as in 4.5/Q.2931. See Tables 9-2 and 9-3. + +**Table 9-2/G.7713.1/Y.1704.1 – Information element identifiers adopted from ITU-T Rec. Q.2931** + +| Bits | | +|------------------------|------------------------------------------| +| 8 7 6 5 4 3 2 1 | | +| 0 1 1 1 0 0 0 0 | Called party number | +| 0 1 1 0 0 0 1 1 | Broadband repeat indicator | +| 0 1 1 0 1 1 0 0 | Calling party number | +| 0 1 0 1 1 0 0 1 | Traffic descriptor | +| 0 1 0 1 1 0 1 0 | Connection identifier | +| 0 1 0 1 1 1 1 0 | Broadband bearer capability | +| 0 1 0 1 1 1 1 1 | Broadband Low Layer Information (B-LLI) | +| 0 1 0 1 1 1 0 1 | Broadband High Layer Information (B-HLI) | +| 0 0 1 0 0 1 1 1 | Notification indicator | +| 0 0 0 1 0 1 0 0 | Call state | +| 0 0 0 0 1 0 0 0 | Cause | +| 1 1 1 0 1 1 0 0 | Extended Quality of Service parameter | +| 0 1 1 0 0 0 0 0 | Broadband locking shift | +| 0 1 1 0 0 0 0 1 | Broadband non-locking shift | +| 0 1 1 0 0 0 1 1 | Broadband repeat indicator | +| 0 1 1 1 1 0 0 0 | Transit network selection | +| 0 1 1 1 1 0 0 1 | Restart indicator | + +**Table 9-3/G.7713.1/Y.1704.1 – Information element identifiers adopted from PNNI or other documents** + +| Bits | | +|------------------------|-----------------------------------------| +| 8 7 6 5 4 3 2 1 | | +| 1 1 1 0 0 0 0 0 | Called party soft permanent connection | +| 1 1 1 1 0 0 1 1 | Calling party soft permanent connection | +| 1 1 1 0 0 0 0 1 | Crankback | +| 1 1 1 0 1 1 1 1 | Network Call Correlation Identifier | +| 1 0 0 0 1 0 0 1 | Broadband report type | +| 1 1 1 0 0 0 1 0 | Designated Transit List (DTL) | +| 1 1 1 0 0 1 1 0 | Transported address | +| 1 1 1 0 1 1 1 0 | Trace transit list | +| 1 1 1 1 0 0 1 0 | Rerouting services | +| 1 1 1 1 0 0 1 0 | Rerouting | +| 1 1 1 1 0 1 0 0 | Rerouting cause | +| 1 1 1 1 0 1 0 1 | Reference list | + +### 9.5.1 Broadband Bearer Capability Information Element + +This Information Element is used to indicate what kind of network connection is required. The format is as specified in 4.5.7/Q.2931 with the following indications: + +- bearer class: unspecified (00000); +- susceptibility to clipping: not susceptible (00); +- user-plane connection configuration: point-to-point or point-to-multipoint as required. + +### 9.5.2 Broadband High Layer Information (B-HLI) Information Element + +This Information Element is used to indicate the protocol type carried in the connection. The format shall be based on 4.5.8/Q.2931. The definition of new protocol types is for further study. + +### 9.5.3 Broadband Low Layer Information (B-LLI) Information Element + +This Information Element is used to indicate the protocol type carried in the connection. The format shall be based on 4.5.9/Q.2931. + +| Broadband low layer information | | | | | | | | | | | | | | | | +|---------------------------------|--------------------|---|---------------------------------|---|---|---|---|-----------|--|--|--|--|--|--|--| +| 0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | | | | | | | | +| ext.
1 | Coding
standard | | IE instruction field | | | | | 2 | | | | | | | | +| IE length | | | | | | | | 3 | | | | | | | | +| IE length (continued) | | | | | | | | 4 | | | | | | | | +| ext.
1 | Layer id.
0 0 | | User information layer protocol | | | | | 5* | | | | | | | | +| Generalized Protocol ID | | | | | | | | 5a* | | | | | | | | +| Layer 1 id | | | | | | | | 6* (Note) | | | | | | | | +| Layer 2 id | | | | | | | | 7* (Note) | | | | | | | | +| Layer 3 id | | | | | | | | 8* (Note) | | | | | | | | + +NOTE – Octet groups 6, 7 and 8 correspond to octet groups 5, 6 and 7, respectively, in 4.5.9/Q.2931. + +**Figure 9-1/G.7713.1/Y.1704.1 – B-LLI Information element** + +The format of the User Information Layer Protocol field (contained in Octet 5) is shown in Figure 9-2. + +| | | +|-----------|-------------------------| +| Bits | | +| 5 4 3 2 1 | | +| 1 1 1 1 1 | Generalized Protocol ID | + +Other values are reserved. + +**Figure 9-2/G.7713.1/Y.1704.1 – Format of User Information Layer Protocol** + +The values and types of the Generalised Protocol ID in octet 5a are as follows: + +| Value | Type | +|-------|----------| +| 0 | Unknown | +| 1 | Reserved | +| 2 | Reserved | + +| Value | Type | +|-------|---------------------------------------------------------------| +| 3 | Reserved | +| 4 | Reserved | +| 5 | Asynchronous mapping of 139 264 kbit/s (P4x) into VC-4 | +| 6 | Asynchronous mapping of 44 736 kbit/s (P32x) into VC-3 | +| 7 | Asynchronous mapping of 34 368 kbit/s (P31x) into VC-3 | +| 10 | Asynchronous mapping of 6 312 kbit/s (P21x) into VC-2 | +| 11 | Bit synchronous mapping of 6 312 kbit/s (P21x) into VC-2 | +| 13 | Asynchronous mapping of 2 048 kbit/s (P12x) into VC-12 | +| 14 | Byte synchronous mapping of 2 048 kbit/s (P12s) into VC-12 | +| 15 | Byte synchronous mapping of 31 * 64 kbit/s (P0) into VC-12 | +| 16 | Asynchronous mapping of 1 544 kbit/s (P11x) into VC-11 | +| 17 | Bit synchronous mapping of 1 544 kbit/s (P11x-bit) into VC-11 | +| 18 | Byte synchronous mapping of 1 544 kbit/s (P11s) into VC-11 | +| 25 | Multiplexing of SDH LOVC via TUG-2 into a VC-3 | +| 26 | Multiplexing of SDH LOVC via TUG-3s into a VC-4 | +| 27 | Multiplexing of SDH HOVC into STM-N | +| 28 | POS – No Scrambling, 16-bit CRC | +| 29 | POS – No Scrambling, 32-bit CRC | +| 30 | POS – Scrambling, 16-bit CRC | +| 31 | POS – Scrambling, 32-bit CRC | +| 41 | FDDI mapping into VC-4 | +| 42 | DQDB mapping into VC-4 | + +NOTE – The reference to the particular mapping schemes may be found in ITU-T Rec. G.707/Y.1322. + +Other values are reserved. + +### 9.5.4 Broadband Repeat Indicator Information Element + +The purpose of this Information Element is to indicate how repeated information elements shall be interpreted, when included in a message. The Broadband repeat indicator information element is included before the first occurrence of the information element which will be repeated in a message. The format of the Broadband Repeat Indicator Information Element IE shall be as in 4.5.19/Q.2931. + +### 9.5.5 Call State Information Element + +The purpose of the Call State Information Element is to describe the current status of a call at the PNNI or a global interface. + +The format of the Call State Information Element shall be as in 4.5.10/Q.2931. + + + +#### 9.5.10 Cause Information Element + +The Cause Information Element describes the reason for generating certain messages, providing diagnostic information in the event of procedural errors, and indicates the location of the cause originator. The Cause Information Element and diagnostic may be repeated in a message. + +The format of the Cause Information Element shall be as in ITU-T Rec. Q.2610. + +The following values in Table 9-4 apply in this Recommendation. + +**Table 9-4/G.7713.1/Y.1704.1 – Cause Information values** + +| Number | Meaning | +|--------|----------------------------------------------------------------| +| 1 | Unallocated (unassigned number) | +| 3 | No route to destination | +| 16 | Normal call clearing | +| 18 | No user responding | +| 21 | Call rejected | +| 22 | Number changed | +| 27 | Destination out of order | +| 28 | Invalid number format (address incomplete) | +| 30 | Response to STATUS ENQUIRY | +| 31 | Normal, unspecified | +| 34 | Requested called party soft permanent connection not available | +| 37 | Requested bandwidth unavailable | +| 38 | Network out of order | +| 41 | Temporary failure | +| 43 | Access information discarded | +| 47 | Resource unavailable, unspecified | +| 81 | Invalid call reference value | +| 82 | Identified channel does not exist | +| 88 | Incompatible destination | +| 89 | Invalid endpoint reference | +| 96 | Mandatory IE is missing | +| 97 | Message type non-existent or not implemented | +| 99 | Information element/parameter non-existent or not implemented | +| 101 | Message not compatible with call state | +| 102 | Recovery on timer expiry | +| 111 | Protocol error, unspecified | + +The originator of the release message in non-crankback situations will include a 2-octet blocked transit pointer in the first diagnostic. This information can be used by the originator if it attempts to reroute the call right away. + +#### 9.5.11 Connection Identifier Information Element + +The Connection Identifier identifies the local connection resources on an interface. This information element is optionally present (mandatory for some technologies) in the SETUP message, and mandatory in the first response to the SETUP message. + +The Connection Identifier information element is coded as shown in Figure 9-6 and Tables 9-5 to 9-7. + +| Bits | | | | | | | | Octets | +|------------------------------------------------------|--------------------|---|--------------------------------------|------|------------------------------------|---|---|--------------------------| +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | +| Connection identifier information element identifier | | | | | | | | | +| 0 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | +| ext.
1 | Coding
standard | | IE instruction field | | | | | | +| | | | Flag | Res. | IE action Ind. | | | | +| Length of connection identifier contents | | | | | | | | 3
4 | +| ext.
0 | Spare | | Link assoc.
signalling | | Preferred/
exclusive | | | 5 | +| ext.
1 | Symmetry | | Asymmetric link
assoc. signalling | | Asymmetric preferred/
exclusive | | | 5a | +| Link ID tag | | | | | | | | | +| 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 6 | +| Length of link ID | | | | | | | | 6.1 | +| Link ID value | | | | | | | | 6.2
6.3
6.4
6.5 | +| Link connection identifier tag | | | | | | | | | +| x | x | x | x | x | x | x | x | 7 | +| Length of link connection identifier | | | | | | | | 7.1 | +| Link connection identifier (forward) value | | | | | | | | 7.2
7.3
7.4
7.5 | +| Link connection identifier tag | | | | | | | | | +| x | x | x | x | x | x | x | x | 8 | +| Length of link connection identifier | | | | | | | | 8.1 | +| Link connection identifier (backward) value | | | | | | | | 8.2
8.3
8.4
8.5 | + +Figure 9-6/G.7713.1/Y.1704.1 – Connection identifier information element + +The link associated signalling field format (bits 5 and 6 of octet 5) has the following values: + +Table 9-5/G.7713.1/Y.1704.1 – Asymmetric link associated signalling field format + +| | | +|------------|--------------------------------| +| Bits | | +| 5 4 | | +| 0 0 | Link-associated signalling | +| 0 1 | Explicit Indication of link ID | + +The Pre/Ex (preferred/exclusive) field format (bits 1, 2 and 3 of octet 5) has the following values: + +**Table 9-6/G.7713.1/Y.1704.1 – Pre/Ex field format** + +| | | +|--------------|---------------------------------------------------------------------------| +| Bits | | +| 3 2 1 | | +| 0 0 0 | Exclusive Link ID; Exclusive LCI | +| 0 0 1 | Exclusive Link ID; Any LCI | +| 0 1 0 | Any Link ID, Exclusive LCI (note this is not used in this Recommendation) | +| 0 1 1 | Any Link ID; any LCI | + +The Symmetry field format (bits 6 and 7 of octet 5a) has the following values: + +**Table 9-7/G.7713.1/Y.1704.1 – Symmetry field format** + +| | | +|------------|-----------------------------| +| Bits | | +| 5 4 | | +| 0 0 | Bidirectional, symmetrical | +| 0 1 | Bidirectional, asymmetrical | +| 1 0 | Unidirectional, downstream | +| 1 1 | Unidirectional, upstream | + +The Asymmetric Link Associated signalling field format (bits 5 and 4 of octet 5a) is not used. It is reserved for technologies that require asymmetric assignment of identifiers (e.g., preceding assigns the backward direction and succeeding assigns the forward direction). + +The Asymmetric Preferred/Exclusive field format (bits 1, 2 and 3 of octet 5a) is not used. It is reserved for technologies that require asymmetric assignment of identifiers (e.g., preceding assigns the backward direction and succeeding assigns the forward direction). + +The Link ID Tag (octet 6) identifies the Link ID TLV. + +The Length of Link ID field (octet 6.1) indicates the length of the Identifier Group, including the Identifier Tag and Identifier length octets. + +The Link ID value (octets 6.2 to 6.n) identifies the link. + +The Identifier octet group may be repeated. The number of times this appears is to be defined on a per connection technology basis. + +For use of the Link ID see 10.1.3. The range of Link ID values will be determined at subscription time. + +The value of the LCI field is technology dependent. See below for defined codings. + +Some values of the LCI may not be available for user-plane connections. + +The SDH Link Connection Identifier TLV has the format shown in Figure 9-7 + +| | | | | | | | | | +|------------------------------------|---|---|---|---|---|---|---|------------| +| SDH link connection identifier tag | | | | | | | | | +| 0 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 7 | +| SDH identifier length | | | | | | | | 7.1 | +| S | | | | | | | | 7.2
7.3 | +| U | | | | K | | | | 7.4 | +| L | | | | M | | | | 7.5 | + +**Figure 9-7/G.7713.1/Y.1704.1 – SDH link connection identifier format (1)** + +The values (S, U, K, L, M) are set from the (E, D, C, B, A) (K, L, M) numbering scheme. + +S indicates the first column in which the AU-4 or AU-4-Xc signal can be found. It is calculated as follows: + +$$S = 64(E - 1) + 16(D - 1) + 4(C - 1) + B$$ + +If E, D, C or B is not used then that term is 0 + +If VC-4-Xc then $S = S + 1$ + +U = A +K = K +L = L +M = M + 2 (VC12) +M = M + 5 (VC11) + +To calculate (E,D,C,B) from S: + +$$S = S - 1$$ + +$$E = (S \bmod 64) + 1$$ + +$$D = (R \bmod 16) + 1$$ + +$$C = (R \bmod 4) + 1$$ + +$$B = R$$ + +If VC-4 then $B = B + 1$ + +If VC-4-4c then $C = C + 1$ + +If VC-4-16c then $D = D + 1$ + +If VC-4-64c then $E = E + 1$ + +$$R = S - 64(E - 1)$$ + +$$R = R - 16(D - 1)$$ + +$$R = R - 4(C - 1)$$ + +Examples for S using (E, D, C, B, A) where A = 0 for VC-4: + +| Type | Link | G.707/Y.1322 number | S | +|----------|---------|---------------------|-----| +| VC-4 | STM-256 | (1,1,1,1,0) | 1 | +| VC-4 | STM-256 | (1,1,3,1,0) | 9 | +| VC-4 | STM-256 | (3,4,4,4,0) | 192 | +| VC-4 | STM-256 | (4,1,1,1,0) | 193 | +| VC-4 | STM-256 | (4,4,4,4,0) | 256 | +| VC-4-4c | STM-256 | (1,1,1,0,0) | 1 | +| VC-4-4c | STM-64 | (1,3,0,0) | 9 | +| VC-4-4c | STM-256 | (1,1,3,0,0) | 9 | +| VC-4-64c | STM-256 | (4,0,0,0,0) | 193 | + +The Link Connection Pool Identifier format is shown in Figure 9-8. It is proposed to allow SNP Pool identification through the inclusion of a Link Connection Pool Identifier TLV as a sub-element of the Connection Identifier Information Element when it is intended to specify a set or range of allowed or excluded values. + +| | | | | | | | | | +|-------------------------------------|---|---|---|---|---|-----|-----|-----| +| Link connection pool identifier tag | | | | | | | | | +| 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 7 | +| Element length | | | | | | | | 7.1 | +| 0 | 0 | 0 | 0 | 0 | 0 | A/E | R/S | 7.2 | +| Link connection identifier TLVs | | | | | | | | 7.3 | +| | | | | | | | | 7.n | + +Figure 9-8/G.7713.1/Y.1704.1 – Link connection pool identifier format + +The Allowed/Excluded (A/E) field values are: + +- 0      Allowed Values +- 1      Excluded Values + +The Range/Set (R/S) field values are: + +- 0      Range (only 2 LCI TLVs are allowed) +- 1      Set + +#### **9.5.12 Crankback Information Element** + +The purpose of the Crankback Information Element is to indicate that crankback procedures have been initiated. It also indicates the node or link where the call/connection or party cannot be accepted, and the level of hierarchy at which hierarchy is being carried out. The format of the IE shall be as in 6.4.6.3 of [3] with the following exceptions: + +- The need to introduce an ITU rather than an ATM Forum coding standard is for further study. +- Crankback cause 37 "User cell rate not available" to be replaced with "Requested bandwidth not available". +- The need or modification of crankback causes 2, 35, 45, 49, 57, 58, 65, 73 is for further study. + +#### **9.5.13 DTL Information Element** + +A sequence of nodes and links that specifies the chosen end-to-end path is placed in this IE. It is used in SETUP messages. The format of the DTL IE shall be as in 6.4.6.4 of [3]. It is assumed that the path is determined using configuration, management system input or a routing protocol. + +#### **9.5.14 Notification Indicator Information Element** + +The format of the Notification Indicator IE shall be as in 4.5.23/Q.2931. The following value is used to indicate graceful release in progress: + +Notification description 1010001 = deletion in progress. + +Notification description 1010010 = ready for deletion. + +#### **9.5.15 Network Call Correlation Identifier (NCCI) Information Element** + +This IE is included by the source node, to uniquely identify a call across various hops in the network. It is also needed to correlate various connections that correspond to the same call, at various nodes in the network. It contains an additional identifier, which is used by the management system to transport a user specified name (string) for each connection. This id is optional and is of variable length. The format is adopted from [8]. + +The following Identifier types are defined: + +- Identifier type = 0000 0001 – AESA-based NCCI. +- Identifier type = 1000 0001 – Operator-specific ASON call identifier. +- Identifier type = 1000 0010 – Globally unique ASON call identifier. +- Other values are reserved. + +The AESA-based NCCI format is defined in [8]. + +The Operator-specific ASON identifier format and Globally unique ASON identifier format are defined in Annex D. + +#### 9.5.16 Extended Quality of Service (Service Level) + +The Extended Quality of Service parameter information element is coded as shown in Figure 9-9. The length of this information element is 6 octets + +![](fa01531ea2c45beeb4036005da3037a4_img.jpg) + +| | | | | | | | | | +|------------------------------------|--------------------|---|----------------------|---|---|---|---|------------| +| Extended QoS parameter | | | | | | | | | +| 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | +| ext.
1 | Coding
standard | | IE instruction field | | | | | 2 | +| IE length | | | | | | | | 3 | +| IE length (continued) | | | | | | | | 4 | +| Origin | | | | | | | | 5 | +| Transport service level identifier | | | | | | | | | +| 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 6 | +| Element length | | | | | | | | 6.1 | +| Transport service level | | | | | | | | 6.2
6.3 | + +**Figure 9-9/G.7713.1/Y.1704.1 – Extended QoS parameter Information Element** + +The Origin field (octet 5) indicates the origin of this information element. If the origin is the calling party, then the called party can assume that the received cumulative values are end-to-end values. Otherwise, the received cumulative values do not represent end-to-end values. The bit assignment and meaning is as shown in Figure 9-10. + +![](7d2d1d3870cd224c4430d19334557716_img.jpg) + +| | | +|------------------------|----------------------| +| Bits | | +| 8 7 6 5 4 3 2 1 | | +| 0 0 0 0 0 0 0 0 | Originating user | +| 0 0 0 0 0 0 0 1 | Intermediate network | + +**Figure 9-10/G.7713.1/Y.1704.1 – Bit assignment and meaning of Origin field** + +The use of the Transport Service Level value is defined by the individual network operator. The operator may specify a range of different classes of service with predefined characteristics, corresponding to different types of network restoration, setup and hold priority, reversion strategies, persistence, etc. The Transport Service Level is then used to request a particular class of service for a connection entering that operator's network, e.g., through a UNI or E-NNI interface. + +### 9.5.17 Rerouting information element + +The Rerouting information element contains information exchanged between the source and destination nodes to initialize the rerouting mechanism. It is also used between the rerouting node and the rendezvous node to control a rerouting operation. The Rerouting information element is present in both the SETUP and the CONNECT messages during the initial connection establishment and in the SETUP message during the rerouting connection establishment. The content of the Rerouting information element depends on the context in which it is used. The context (signalling message, rerouting state) in which a Rerouting information element is used determines which octet groups are included and their significance. Format modifications for ASTN are for further study. + +### 9.5.18 Rerouting services information element + +The Rerouting services information element is used to negotiate the set of rerouting services requested/activated for the call and to exchange the availability of rerouting services between the + +source node and the destination node of a rerouting domain. The Rerouting services information element is present in both the SETUP and the CONNECT messages during the initial call establishment. Format modifications for ASTN are for further study. + +### 9.5.19 Rerouting cause information element + +The Rerouting cause information element is used to convey the cause of the RELEASE message that is specifically related to a rerouting operation. + +### 9.5.20 Traffic descriptor + +The purpose of the Traffic Descriptor Information Element is to specify the set of traffic parameters, which, together, specify a traffic control capability. (The original ATM traffic descriptor described forward and backward cell rates for an ATM connection.) + +A new format for Traffic Descriptor is defined to carry parameters applying to distributed connection management of connection types covered by this Recommendation. + +| Traffic descriptors | | | | | | | | | | | | | | | | +|------------------------------------------------|----------------------|---|----------------------|---|---|---|---|------|--|--|--|--|--|--|--| +| 0 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | | | | | | | | +| ext.
1 | Coding
standard | | IE instruction field | | | | | 2 | | | | | | | | +| IE length | | | | | | | | 3 | | | | | | | | +| IE length (continued) | | | | | | | | 4 | | | | | | | | +| Recovery/protection tag | | | | | | | | | | | | | | | | +| 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 5 | | | | | | | | +| Element length | | | | | | | | 5.1 | | | | | | | | +| P/S | Link protection type | | | | | | | 5.2 | | | | | | | | +| Forward SDH descriptor tag | | | | | | | | | | | | | | | | +| 0 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 6 | | | | | | | | +| Element length | | | | | | | | 6.1 | | | | | | | | +| Elementary signal type | | | | | | | | 6.2 | | | | | | | | +| Number of contiguously concatenated components | | | | | | | | 6.3 | | | | | | | | +| | | | | | | | | 6.4 | | | | | | | | +| Transparency | | | | | | | | 6.5 | | | | | | | | +| Backward SDH descriptor tag (Note) | | | | | | | | | | | | | | | | +| 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 7 | | | | | | | | +| Element length | | | | | | | | 7.1* | | | | | | | | +| Elementary signal type | | | | | | | | 7.2* | | | | | | | | +| Number of contiguously concatenated components | | | | | | | | 7.3* | | | | | | | | +| | | | | | | | | 7.4* | | | | | | | | +| Transparency | | | | | | | | 7.5* | | | | | | | | + +NOTE – Omitted if bidirectional symmetric connection. + +**Figure 9-11/G.7713.1/Y.1704.1 – Traffic Descriptors Information Element** + +The Recovery/Protection TLV identifies the link protection attributes that are required from the local transport link supporting the connection, and whether the connection will be used as a primary or secondary connection. If secondary is indicated, then the connection is being used as backup for a separate primary connection, and its allocated resources will not be used until the related primary connection fails. + +The Primary/Secondary – (P/S) field values and types are: + +0 – Primary connection. + +1 – Secondary connection. + +The Link Protection Type field values and types are: + +| Value | Indication | +|--------------|-------------------| +|--------------|-------------------| + +| | | +|----|-----------------------------------------------------------------------------------------------------------------------------------| +| 0 | No indication. | +| 1 | Extra traffic – link is used for protection of primary links and its use may be preempted in case of failure of the primary link. | +| 2 | Unprotected – link has no protection. | +| 4 | Shared – link uses a shared (e.g., 1:N) protection scheme. | +| 8 | Dedicated 1:1 – link uses a dedicated 1:1 protection scheme. | +| 16 | Dedicated 1+1 – link uses a dedicated 1+1 protection scheme. | +| 32 | Enhanced – link uses a more redundant scheme than 1+1, e.g., 4-Fiber MS-SPRing. | + +Other values are reserved + +The Forward and Backward SDH Descriptor TLVs identify SDH traffic descriptor information for the forward and backward directions, respectively. + +The Elementary Signal Type field values and types are: + +| Value | Type | +|--------------|-------------| +| 1 | VC-11 | +| 2 | VC-12 | +| 3 | Reserved | +| 4 | VC-2 | +| 5 | VC-3 | +| 6 | VC-4 | +| 7 | STM-0 | +| 8 | STM-1 | +| 9 | STM-4 | +| 10 | STM-16 | +| 11 | STM-64 | +| 12 | STM-256 | + +The Number of Contiguously Concatenated Components field specifies the number of elementary signals to be contiguously concatenated. + +The use of the Transparency field is for further study. Values defined are as follows: + +Bit 1: 0 – no indication; 1 – Regenerator Section layer. + +Bit 2: 0 – no indication; 1 – Multiplex Section layer. + +Other bits are reserved. + +# **10 Updated procedures** + +## **NNI signalling procedures** + +The procedures in [3] apply with the changes specified in this clause. + +## 10.1 Link Connection Identifier allocation/selection + +Two cases exist: + +- i) Link associated signalling: The layer 3 signalling entity exclusively controls the channels in the Link which carries its signalling channel. +- ii) Non-Link associated signalling: The layer 3 signalling entity controls channels which may or may not be in the Link which carries the signalling channel. + +When a network node receives a Connection Identifier information element with the Link associated signalling field coded with a value not supported by this network node, the call shall be rejected with cause No. 29 "Link rejected". + +The following identifiers must be present in the specified order for the indicated symmetries: + +- Bidirectional, symmetric – Link ID, LCI +- Bidirectional, asymmetric – Link ID, LCI (forward), LCI (backward) +- Unidirectional, downstream – Link ID, LCI (forward) +- Unidirectional, upstream – Link ID, LCI (backward) + +### 10.1.1 Link associated signalling + +For Link associated signalling, a connection is requested in the Link carrying the signalling connection. The Link carrying the signalling connection is implicitly indicated. + +In the Connection Identifier information element, the Link-associated signalling field is coded as "Link associated signalling", and one of the following values is indicated in the preferred/exclusive field based on the symmetry: + +- a) Exclusive Link ID; any LCI; or +- b) Exclusive Link ID; exclusive LCI. + +In case a) the succeeding side selects any available LCI within the Link carrying the signalling channel. + +In case b), if the indicated LCI within the Link carrying the signalling channel is available, the succeeding side selects it for the call. + +The selected LCI value is indicated in the Connection Identifier information element in the first message returned in response to the SETUP message (e.g., CALL PROCEEDING message). The Link associated signalling field is coded as "Link-associated signalling". The preferred/exclusive field is coded as "exclusive Link ID; exclusive LCI". + +In case a), if no LCI is available, a RELEASE COMPLETE message with cause No. 34 "No circuit/channel available" is sent by the network. If Crankback is supported on the signalling channel, a Crankback information element is included with crankback cause No. 34. + +In case b), if the indicated LCI is not available, a RELEASE COMPLETE message with cause No. 44 "Requested circuit/channel not available" is sent by the network. If Crankback is supported on the signalling channel, a Crankback information element is included with crankback cause No. 44. + +Call collision can occur when both sides of an interface simultaneously transfer SETUP messages indicating the same exclusive Link ID and LCI. For PNNI interfaces, in order to avoid call collision, the side which has the higher node identifier shall allocate the Link Connection Identifier value. The node identifiers used for this comparison shall be the lowest-level node identifiers used on each side of the interface. These node identifiers are the ones indicated in the Node ID field (octets 11 to 32) in PNNI Hellos transmitted and received over the same interface. A preceding side which has a higher node identifier shall include a Connection Identifier information element in the + +SETUP message with option (b) (exclusive Link ID and exclusive LCI). A SETUP message from a preceding side which has a lower node identifier shall use option (a). + +### **10.1.2 Non-Link Associated signalling** + +In the request for a connection in the SETUP message, the preceding side shall indicate one of the following: + +- a) Exclusive Link ID; any LCI; +- b) Exclusive Link ID; exclusive LCI; or +- c) Any Link ID; any LCI + +In cases a), and b) the Link associated signalling field is coded as either "explicit indication of Link ID". + +In cases a) and b), if the indicated Link ID is available, the succeeding side selects it for the call. In case a), the succeeding side selects any available LCI in the Link. In case b), if the indicated LCI is available within the Link, the succeeding side selects it for the call. + +In cases c) the succeeding side selects any available Link ID and LCI. + +The selected Link ID and LCI values are indicated in the Connection Identifier information element in the first message returned by the succeeding side in response to the SETUP message (i.e., CALL PROCEEDING message). The Link associated signalling field is coded as "explicit indication of Facility". The Preferred/exclusive field is coded as "exclusive Link ID; exclusive LCI". + +In cases a) and b), if the specified Link ID is not available, a RELEASE COMPLETE message with cause No. 29, "Link ID rejected", is sent by the succeeding side. If Crankback is supported on the signalling channel, a Crankback information element is included with crankback cause No. 29. + +In case a), if no LCI is available, a RELEASE COMPLETE message with cause No. 34, "No circuit/channel available", is sent by the succeeding side. If Crankback is supported on the signalling channel, a Crankback information element is included with crankback cause No. 34. + +In case b), if the LCI in the indicated Link is not available, a RELEASE COMPLETE message with cause No. 34, "No circuit/channel available", is sent by the succeeding side. If Crankback is supported on the signalling channel, a Crankback information element is included with crankback cause No. 34. + +In case c), if the succeeding side is not able to allocate a LCI any Link, a RELEASE COMPLETE message with cause No. 44, "Requested circuit/channel not available", is sent by the succeeding side. If Crankback is supported on the signalling channel, a Crankback information element is included with crankback cause No. 44. + +Call collision can occur when both sides of an interface simultaneously transfer SETUP messages indicating the same exclusive Link ID and LCI. For PNNI interfaces, in order to avoid call collision, the side which has the higher node identifier shall allocate the Link Connection Identifier (Link ID, LCI) values. A preceding side which has a higher node identifier shall include a Connection Identifier information element in the SETUP message with option (b) (exclusive Link ID and exclusive LCI). A SETUP message from a preceding side which has a lower node identifier shall use options (a) or (c). + +### **10.1.3 Use of the Link ID** + +The LinkID provides the capability for a signalling channel to control connections over multiple links. Two possible configurations exist: + +- 1) Link associated signalling: The layer 3 signalling entity exclusively controls the channels in the Link which carries its signalling channel. + +- 2) Non-Link associated signalling: The layer 3 signalling entity controls channels which may or may not be in the Link which carries the signalling channel. + +The LinkID is an opaque value with no pre-defined format. It is a logical pointer to the link over which the connection is to be established. + +In case (1) above, the LinkID has no significance and is coded as zero. + +In case (2) above, the LinkID contains a reference to the link over which the connection is to be established. + +The case where the control plane element is physically separate from the transport node is equivalent to case (2). In this case the LinkID contains a reference to the node/link over which the connection is to be established. + +The default value for the LinkID in case (2) is the concatenation of the two node IDs, lower value first, and the SNP identifier. + +### **10.1.4 Link ID Ranges** + +The default length of the Link ID is four (4) octets and shall be supported. Other lengths may optionally be supported. If the succeeding side receives a Connection Identifier Information Element with an unsupported Link ID length, it shall treat the specified Link ID as unavailable. + +There are no reserved values for the Link ID. + +### **10.1.5 LCI ranges and values** + +#### **10.1.5.1 SDH specific values** + +The identifier contents use the numbering plan specified in clause 7/G.707/Y.1322. The high order payload columns are addressed using S. The location of the column is indicated using values starting at 1. A value of zero indicates the number is not used. + +### **10.1.6 Service category, traffic parameter and QoS selection procedures** + +The QoS shall be indicated in the Extended QoS information element. + +If the network is able to provide the requested QoS class, the network shall progress the call to the called user. If the network is not able to provide the requested QoS class, the network shall reject the call, returning a RELEASE COMPLETE message with cause No. 49, "Quality of Service not available". + +The connection type shall be indicated in the Traffic Descriptor information element. + +If the network is able to provide the requested connection, the network shall progress the call to the called user. If the network is not able to provide the requested connection, the network shall reject the call, returning a RELEASE COMPLETE message with one of the following cause codes: + +- No. 57 "bearer capability not authorized"; +- No. 58 "bearer capability not presently available"; +- No. 65 "bearer capability not implemented". + +If the Recovery/Protection information element is included, if the network is able to provide the requested service, the network shall progress the call to the called user. If the network is not able to provide the requested service, the network shall reject the call, returning a RELEASE COMPLETE message with cause No. 63, "Service or option not available, unspecified". + +## **10.2 Connection clearing for non-persistent connections** + +These procedures only apply to connections that have not indicated any type of connection persistence. + +The procedures of PNNI 1.1 in 6.5.3 are used. + +## **10.3 Procedures for connections persistent across signalling failures** + +These procedures only apply to connections that have indicated persistence across control plane failures either implicitly through the service class or through configuration. + +### **10.3.1 Connection clearing for persistent connections** + +The procedures in 10.2 are used with the following modifications. + +Delete the sentences: + +"If no RELEASE COMPLETE message is received from the succeeding side before timer T308 expires a second time, the preceding side shall; release the call reference; and return to the Null state. Additional recovery procedures, such as initiating restart, are implementation dependent" + +And replace them with: + +"If no RELEASE COMPLETE message is received from the succeeding side before timer T308 expires a second time, the preceding side shall remain in the Release Request (NN11) state. The preceding side shall periodically re-attempt the connection clearing procedures. The frequency of these attempts are implementation dependent." + +### **10.3.2 Signalling AAL connection reset for persistent connections** + +Whenever a Q.2931 entity is informed of a spontaneous Signalling AAL reset by means of the AAL-ESTABLISH-indication primitive, the following procedures apply: + +- a) for calls in the clearing phase (states N11, N12), no action shall be taken; +- b) calls in the establishment phase (states N1, N3, N4, N6, N7, N8, N9) shall be maintained. Optionally, the status enquiry procedure in 10.3.4 may be invoked; +- c) calls in the Active state shall be maintained, and the entity shall invoke the status enquiry procedures described in 10.3.4. + +### **10.3.3 Signalling AAL connection release for persistent connections** + +When a Q.2931 entity is notified by its Signalling AAL connection release by means of the AAL-RELEASE-indication primitive, the following procedures shall apply: + +- a) any calls not in the Active state shall be cleared locally; +- b) for calls in the Active state, no action shall be taken. + +The Q.2931 entity shall request Signalling AAL re-establishment by sending an AAL-ESTABLISH-request primitive. + +When informed of Signalling AAL re-establishment by means of the AAL-ESTABLISH-confirm primitive, the following procedure shall apply: + +- perform the status enquiry procedure according to 10.3.4. + +### **10.3.4 Status Enquiry Procedures** + +The procedures in 6.5.6.11 of PNNI 1.1 shall apply with the following addition: + +Additional procedures for Signalling state recovery: + +Connections that require restoration of connection state shall include the Connection Identifier Information Element in the STATUS ENQUIRY message. The Link ID and LCI shall be set to the + +values associated with the indicated Call Reference. The Link-associated signalling field shall indicate "explicit in indication of Link ID". The preferred/exclusive field shall indicate "exclusive link ID; exclusive LCI". A node that has lost state information, but verifies the existence of the indicated connection identifier shall respond with a STATUS message with the state indicated as Null with cause No.30, "Response to STATUS ENQUIRY". + +A node that has lost state information and cannot verify the existence of the indicated connection identifier shall respond with a STATUS message with the state indicated as Null with cause No. 101, "Message not compatible with call state". + +A node that has lost state information, but is capable of performing local state recovery, shall respond with a STATUS message with the state indicated as Active with cause No. 30, "Response to STATUS ENQUIRY". + +### **10.3.5 Receiving a STATUS message** + +The procedures in 6.5.6.12 of PNNI 1.1 shall apply with the following additions. + +For connections in the Active state requiring Persistence Across Control Channel Failures: + +- 1) If the received state is Release Request, no action shall be taken. + +For connections requiring recovery of state information, the received STATUS message shall include a Connection Identifier information element and the following procedures shall apply: + +- 1) If the received state is Null with cause No. 30, "Response to STATUS ENQUIRY", the state recovery procedures in 10.3.6 shall be invoked. +- 2) If the received state is Null with cause No. 101, "Message not compatible with call state", connection clearing procedures shall be initiated. + +### **10.3.6 Enhanced Status Enquiry** + +The procedures in Annex R of PNNI 1.1 shall apply with the following exceptions: + +Procedures for point-to-multipoint connections are not supported. + +### **10.3.7 Recovery of signalling state for persistent connections** + +The procedures for recovering the state of a connection, including the use of the Connection Identifier in STATUS and STATUS ENQUIRY messages, are for further study. + +### **10.3.8 Processing of messages during failure of the control channel** + +These procedures apply to connections that remain persistent across signalling channel failures when the control channel has notified Q.2931 of a failure by means of the AAL-RELEASE-indication primitive. + +These procedures apply to messages which should be progressed across the failed control channel. + +Messages other than RELEASE and RELEASE COMPLETE messages shall be rejected back towards the source with cause No. 101, "Message not compatible with call state". + +RELEASE and RELEASE COMPLETE messages should be retained until recovery of the control channel. Upon recovery of the control channel, normal processing for these messages apply. + +## **10.4 Bearer Plane failures** + +When a notification is received indicating the failure of the bearer transport link ID containing the bearer channel, the following actions shall be taken: + +If the connection supports Persistence Across Bearer Plane failures, no action shall be taken. + +Otherwise, normal connection clearing procedures shall be followed. + +## 10.5 Receipt of NOTIFY messages + +NOTIFY messages provide information about a connection and do not affect the state of the connection. A node receiving a NOTIFY message shall take the following actions: + +- If the node is an endpoint for the connection, it shall issue a notify indication primitive and take no further action. +- If the node is an intermediate node for the connection, it shall issue a notify indication primitive and continue to progress the NOTIFY message in the direction of transmission. No other action shall be taken. + +# Annex A + +## Transport of G.7713.1/Y.1704.1 messages over DCN network + +## A.1 Introduction + +The signalling protocol defined in this Recommendation must be capable of operating over any of the Data Communications Network (DCN) technologies defined by ITU-T Rec. G.7712/Y.1703. The DCN provides network elements a general communication capability for transporting application messages. Examples of applications include management, signalling and software downloads. + +The DCN is defined using Layer 3 connectionless protocols (i.e., OSI/CLNP and IP) for the transport of all messages. The choice of Layer 3 protocol, and the underlying Layer 2 protocol is made on a per-interface basis. A network element may be required to support both OSI/CLNP and IP simultaneously. + +The SSCOP protocol currently used by Q.2931 assumes that the data link is a single point-to-point connection providing in-sequence delivery. The DCN uses connectionless protocols, which do not guarantee in-sequence delivery. The DCN may also use multiple links for added reliability. + +ITU-T Rec. Q.2111 (SSCOPMCE), as updated by Amendment 1, extends the original capabilities of SSCOP to include support for connectionless networks and multiple links for each signalling channel. + +The major differences between SSCOP and SSCOPMCE are: + +- 1) independent of underlying transport (e.g., ATM, IP, OSI/CLNP, Ethernet, HDLC); +- 2) connectionless transport of signalling connections; +- 3) multi-link transport of signalling connections; +- 4) re-sequencing of arriving packets to ensure in-sequence delivery to upper layers; +- 5) active monitoring of all configured links; +- 6) addition/removal of links during active operation; +- 7) compatibility mode with SSCOP. + +## A.2 Differences in boundary interfaces + +The SSCOPMCE protocol provides almost identical boundary interfaces to the SSCF and to Layer management when compared to what is provided by the SSCOP protocol. This allows SSCOPMCE to be substituted for SSCOP without changing the SSCF or Q.2931 protocols or implementation. + +The differences in the boundary interfaces are: + +- 1) *Boundary to SSCF* + - a) Addition of the Out-of-Sequence delivery (OoS) parameter to AA-DATA primitive. For the Request signal, this parameter indicates if out-of-sequence delivery of the message unit is permitted. For the Indication Signal, this parameter indicates the message unit may be out-of-sequence. + - b) Absence of the OoS parameter indicates in-sequence delivery is required. This allows complete compatibility with the existing SSCOP/SSCF boundary interface. +- 2) *Boundary to Layer Management* + - a) Addition of the MAA-SET-TIMER primitive. This primitive supports only the Request signalling. It allows layer management to change the value of Timer\_RESEQ during operation. This timer determines how long SSCOPMCE will wait for the arrival of out-of-sequence messages before requesting a retransmission. + - b) Addition of the MAA-ADD-LINK primitive. This primitive supports only the Request signal. It is used to add a new link to the link set for a SSCOPMCE connection. A link may be added anytime after SSCOPMCE first initializes. + - c) Addition of the MAA-REMOVE-LINK primitive. This primitive supports the Request and Indication signals. The Request signal is used to remove an active link from the current link set. A link may be removed at any time. The Indication signal is used to notify layer management of a successful remove operation, or in response to an add request to indicate the requested link was not added. + +## **A.3 Overview of SSCOPMCE link management process** + +#### **A.3.1 SSCOPMCE initialization** + +SSCOPMCE differs from SSCOP during initialization by adding State 0 (Guard). Timer\_GUARD is started as the first step in the initialization process. The Guard state waits for this timer to expire prior to continuing with the initialization. The purpose of the Guard state is to provide sufficient time for any outstanding messages from a previous instance of SSCOPMCE to be cleared from the transport network. + +After Timer\_GUARD expires, the initialization process is completed and SSCOPMCE goes into the Idle state. All states, except for the Guard state, are identical to SSCOPMCE. + +#### **A.3.2 Link activation** + +SSCOPMCE maintains an array of active links, referred to as a LinkSet. It also maintains a counter of the number of active links. Layer Management may request to add a link anytime after entering the Guard state using the MAA-ADD-LINK.Request signal. The SSCOPMCE process adds the link to the LinkSet and increments the number of active links. + +The request to add a link may fail either because the maximum number of links supported by an implementation has been exceeded. It may also fail because the operating mode is SSCOP compatibility mode, which allows only one active link. A failure will be reported using the MAA-REMOVE-LINK.Indication signal + +After successfully adding the new link to the LinkSet, Timer\_NO-RESPONSE is set for the link. This timer is used to detect a failure of the link. + +A new link is immediately available for use after being added to the LinkSet. + +NOTE – If the new link is not configured at the remote end, this will be detected as a link failure and reported using MAA-REMOVE-LINK.Indication. The link will be removed from the LinkSet. It is the responsibility of Layer Management to attempt to retry the link by issuing another add request. + +#### A.3.3 Link removal + +Layer Management may request the removal of a link at anytime during operation using the MAA-REMOVE-LINK.Request signal. The SSCOPMCE process removes the link from the LinkSet and decrements the number of active links. Layer Management is notified the process is complete by using the MAA-REMOVE-LINK.Indication signal. + +The remote end will detect the removal of the link as a link failure, and will remove the link from its LinkSet. It will also notify its Layer Management using the MAA-REMOVE-LINK.Indication signal. + +If the removal of the link causes the number of active links to become zero, the SSCOPMCE process will release the SSCOPMCE connection and send an AA-RELEASE.Indication signal to the SSCF. + +#### A.3.4 Link keep alive + +SSCOPMCE uses the same basic procedures used by SSCOP to detect a link failure. POLL and STAT messages are sent on each individual link. The frequency at which POLL and STAT messages are sent follow the same procedures used by SSCOP and depends on whether it is in the *active, transient, idle or connection control* phase. + +#### A.3.5 Link failure + +Timer-NO-RESPONSE is used to detect the failure of a link. The procedures are similar to SSCOP, except that detection is performed separately for each link. When the SSCOPMCE process determines that a link has failed, it will remove the link from the LinkSet and decrement the number of active links. It will then send a MAA-REMOVE-LINK.Indication signal to Layer Management. + +SSCOPMCE does not try to recover failed links. It is up to Layer Management to decide if it should attempt to add the failed link back into the LinkSet. + +If the removal of the link causes the number of active links to become zero, the SSCOPMCE process will release the SSCOPMCE connection and send an AA-RELEASE.Indication signal to the SSCF. + +#### A.3.6 Link connectivity verification + +SSCOPMCE does not perform link connectivity verification. This is the responsibility of the underlying transport layer. + +NOTE – In a Connectionless environment, a successful exchange of POLL and STAT messages on the link implies proper link connectivity. A connectionless link is defined as a source/destination address pair. The source and destination addresses also identify the network element. Arriving messages that do not match a configured source/destination address pair will be discarded. A successful POLL and STAT exchange can only occur if both sides are properly configured. + +#### A.3.7 SSCOPMCE connection establishment + +The establishment of the SSCOPMCE connection follows the same procedures used for SSCOP. The SSCF sends an AA-ESTABLISH.Request signal to SSCOPMCE. The SSCOPMCE process follows the same procedures used by SSCOP to establish the connection. + +The exception to this process is that if the number of active links is zero, SSCOPMCE will immediately indicate a failure by sending a AA-RELEASE.Indication signal to the SSCF. + +#### A.3.8 SSCOPMCE connection release + +Releasing a SSCOPMCE connection may be requested by the SSCF following the same procedures used for SSCOP. When the connection is successfully released, SSCOPMCE will notify the SSCF using the AA-RELEASE.Indication signal. The SSCOPMCE process will not make any changes to the LinkSet or number of active links. + +The failure of a link when there were more than two active links is not reported to the SSCF. The SSCOPMCE connection remains established and message processing continues normally. + +The failure of a link when there was only one active link remaining causes the number of active links to go to zero. The SSCOPMCE process will notify the SSCF of a SSCOPMCE connection failure using the AA-RELEASE.Indication signal. + +#### A.3.9 Message transmission + +Message Units are passed from the SSCF to SSCOPMCE following the same procedures found in SSCOP. The SSCOPMCE process may transmit the message over any active link. The procedure for choosing the link is an implementation issue. + +## A.4 Changes required to ITU-T Rec. Q.2931 + +The use of ITU-T Rec. Q.2111 does not require changes to ITU-T Rec. Q.2931. The interface to the SSCF (ITU-T Rec. Q.2130) remains unchanged. + +### A.5 Changes required to the SSCF (ITU-T Rec. Q.2130) + +The use of SSCOPMCE in place of SSCOP is almost completely transparent. The only difference is the inclusion of an Out-of-Sequence delivery (OoS) parameter in the AA-DATA.Request and AA-DATA. Indication signals at the boundary between SSCF and SSCOPMCE. + +The OoS parameter is used to indicate for each message unit (MU) whether out-of-sequence delivery is permitted. The value of zero, or the absence of parameter, indicates in-sequence delivery of the MU is required. The value of one indicates that out-of-sequence delivery of the MU is allowed. + +Implementations may continue to use the same boundary interface to the SSCF defined by SSCOP. If an implementation updates the boundary interface to the SSCF to include the OoS parameter, the value of this parameter must be zero. + +Use of out-of-sequence delivery is not supported. + +### A.6 Applicability of SSCOPMCE specific parameters and timers + +The following additional parameters and timers, and their default values, are defined as shown in Table A.1. + +**Table A.1/G.7713.1/Y.1704.1 – SSCOPMCE parameters and timers** + +| SSCOPMCE parameter | Default value | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------| +| Timer_GUARD | 22 seconds (Note 3) | +| Timer_RESEQ | 250 ms (Note 4) | +| Mode | "B" | +| NOTE 3 – The value for Timer_GUARD is based on the formula in 8.6/Q.2111.
NOTE 4 – The value for Timer_RESEQ is based on the guidelines in 8.6/Q.2111 using the value of k (Maximum SSCOP SDU size) and a transmission rate of 128 kbits/s. | | + +## A.7 Layer management boundary + +#### A.7.1 Link activation at SSCOPMCE initialization + +SSCOPMCE requires that at least one link has been added prior to the SSCF issuing an AA-ESTABLISH.Request signal. If the number of active links is zero, SSCOPMCE will return the AA-RELEASE.Indication signalling indicating an error. + +The SSCOPMCE process will queue any signals issued during the guard time when in the Guard state. These signals will be processed immediately after SSCOPMCE goes into the Idle state. + +Layer Management should request the addition of at least one link during the guard time. It may request the addition of multiple links, if the implementation supports queuing multiple signals. If only one link is requested, Layer Management on both network elements attempting to establish a link must request the same link. + +#### **A.7.2 Retries after link failure** + +Layer Management is responsible for deciding when to attempt to establish a failed link. A retry is attempted by requesting to add the link to the LinkSet. To prevent excessive overhead when trying to retry a failed link, Layer Management should wait for at least 15 seconds after a failure indication before attempt to retry the link. Note that SSCOPMCE will attempt to verify the link using POLL and STAT messages prior to indicating a failure. + +For persistent failures lasting more than 5 minutes, Layer Management should change the retry delay to 5 minutes. Layer management may also stop retrying, awaiting administrative action. + +#### **A.7.3 Value of LinkID** + +The value and format of the parameter LinkID used in the MAA-ADD-LINK and MAA-REMOVE-LINK primitives is implementation dependent. Possible values are the concatenated source/destination address for the link, or an index into a table. + +#### **A.7.4 Value of Tval** + +The value and format of the parameter Tval used in the MAA-SET-TIMER primitive is implementation dependent. + +## **A.8 Link types** + +#### **A.8.1 IP based DCN links** + +The encapsulation for IP-based networks is defined in ITU-T Rec. Q.2111, Amendment 1. + +The default encapsulation shall be the IP interface as defined in D.3.1/Q.2111 Amendment 1. A link is defined as an IPv4 source/destination address pair using protocol ID "128". + +Implementations may also support the UDP interface as defined in D.3.2/Q.2111 Amendment 1. A link is defined as the source/src\_port/destination/dst\_port tuple. The value of the src\_port and dst\_port must be administratively agreed. + +Procedures for the auto discovery of neighbouring network elements are for further study. + +Encapsulations using IPv6 are for further study. + +#### **A.8.2 OSI/CLNP based DCN links** + +ITU-T Rec. Q.2111 and ITU-T Rec. Q.2111, Amendment 1, do not define the encapsulation for OSI/CLNP networks. It is defined here to provide support for all interface types defined in ITU-T Rec. G.7712/Y.1703. Future amendments to ITU-T Rec. Q.2111 that include the definition of OSI/CLNP encapsulations will supersede the encapsulation defined in this Recommendation. + +An OSI/CLNP link is defined as an NSAP source/destination address pair. + +NOTE – Encapsulation for OSI/CLNP is for further study. + +#### **A.8.3 Ethernet based DCN links** + +The encapsulation for Ethernet networks is defined Annex E/Q.2111 Amendment 1. Support for the Ethernet interface is for further study. + +# Annex B + +## Graceful deletion + +## B.1 Introduction + +Graceful deletion provides a warning that a connection is about to be cleared. This allows affected nodes to take appropriate actions, such as the suppression of alarm indications. + +To ensure all nodes have received the warning, two types of notifications are used: "deletion in progress" and "ready for deletion". + +The procedures defined in this annex occur outside of the connection control function. NOTIFY messages are sent and received using the notify request and notify indication primitives, respectively. + +The transmission and receipt of NOTIFY messages do not affect the state of the call. + +## B.2 Sending deletion notification + +A node that desires to use graceful deletion shall send a notify request with "deletion in progress". No other action shall be taken. + +If the node performing the graceful deletion is not one of the endpoints for the connection, it shall send a notify request in both the preceding and succeeding directions. + +The node should then wait for a notify indication with "ready for deletion" before requesting the initiation of connection clearing procedures. The amount of time to wait is outside the scope of this Recommendation. + +If a notify indication with "ready for deletion" is not received within the determined amount of time, the node may re-issue the notify indication. If no response is received to the second attempt, the node shall proceed with requesting the initiation of connection clearing procedures. + +## B.3 Receiving deletion notification + +Upon the receipt of a notify indication with "deletion in progress", the following actions shall be taken: + +- The node should perform any actions necessary to prepare for the eventual deletion of the connection (i.e., alarm suppression). +- If the node is an endpoint for the connection, it shall send a notify request with "ready for deletion". +- If the node is not an endpoint for a connection, but progressing the notify request is not possible due to a signalling channel failure, the node may send a notify request "ready for deletion" in the direction from which the message was received. +- Otherwise, no action is taken. + +## B.4 Receiving ready for deletion + +Upon the receipt of a notify indication with "ready for deletion", the following actions shall be taken: + +- If the node sent a notify request with "deletion in progress", it shall proceed by sending a release request primitive to connection control. +- If the node did not send a notify request with "deletion in progress", it should take any actions necessary (e.g., suppression of alarms) needed to prepare for the eventual deletion of the connection. + +# Annex C + +## DTL processing in the absence of routing protocols + +The PNNI signalling specification assumes the presence of the PNNI routing protocol when processing the Designated Transit List (DTL) in signalling messages. The DTL contains the PNNI Node Identifier for the next hop. + +A normal PNNI node learns the identity and location of neighbouring PNNI nodes through PNNI Hello messages. + +A node not running PNNI routing must use some other mechanism for determining the identity and location of neighbouring nodes. This may be through manual configuration or via G.7714/Y.1705 based discovery procedures. If G.7714/Y.1705 procedures are used, it will be necessary for the node to map this to a PNNI Node ID suitable for use in a DTL. + +The actual procedures for determining the PNNI Node ID for neighbouring nodes are outside the scope of this Recommendation. + +If the DTL used by the network always includes the logical port identifier, neighbour discovery procedures are not required. The SETUP message is forwarded on the signalling control channel responsible for the indicated logical port identifier. + +When receiving a SETUP messages, the node shall always validate the current PNNI Node ID indicated by the DTL is this node as required by normal DTL processing procedures. + +# Annex D + +## ASON call identifier + +The ASON call identifier is a generic identifier with length being a multiple of 32 bits, and a minimum length of 32 bits. + +The format of the Operator Specific ASON Call identifier is shown below: + +| | | +|------------------------------------------|--------| +| Type | 1 | +| reserved | 2 | +| reserved | 3 | +| reserved | 4 | +| Source transport network element address | 5 etc. | +| Local identifier | 6 etc. | + +The format of the Globally Unique ASON Call Identifier is shown below: + +| | | +|------------------------------------------|--------| +| Type | 1 | +| IS | 2 etc. | +| ... | | +| NS | 3 etc. | +| ... | | +| Source transport network element address | 4 etc. | +| Local identifier | 5 etc. | + +In both cases, a "Type" field is defined to indicate the type of format used for the source transport network element address. + +The Type field has the following meaning: + +For Type = 1, the source transport network element address is 4 bytes. + +For Type = 2, the source transport network element address is 16 bytes. + +For Type = 3, the source transport network element address is 20 bytes. + +For Type = 4, the source transport network element address is 6 bytes. + +For Type = 127, the source transport network element address has the length defined by the vendor. + +Other values are reserved. + +Source transport network element address: + +An address of the transport network element (SSN) controlled by the source network. + +Local identifier: + +A 64-bit identifier that remains constant over the life of the call. + +The structure for the globally unique call identifier (to guarantee global uniqueness) is to concatenate a globally unique fixed ID (composed of country code, carrier code, unique access point code) with an operator specific ID (where the operator specific ID is composed of a source transport network element address – and a local identifier). + +Therefore, a generic CALL\_ID with global uniqueness includes (composed of plus plus ) and (composed of plus ). For a CALL\_ID that only requires operator specific uniqueness only the is needed, while for a CALL\_ID that requires to be globally unique both and are needed. + +The shall consist of a three-character International Segment (the ) and a twelve-character National Segment (the plus ). These characters shall be coded according to ITU-T Rec. T.50. The International Segment (IS) field provides a 3-character ISO 3166 Geographic/Political Country Code. The country code shall be based on the three-character uppercase alphabetic ISO 3166 Country Code (e.g., USA, FRA). + +The National Segment (NS) field consists of two sub-fields: the ITU Carrier Code followed by a Unique Access Point Code. The ITU Carrier Code is a code assigned to a network operator/service provider, maintained by the ITU-T Telecommunication Standardization Bureau in association with ITU-T Rec. M.1400. This code shall consist of 1-6 left-justified characters, alphabetic, or leading alphabetic with trailing numeric. The unique access point code shall be a matter for the organization to which the country code and ITU carrier code have been assigned, provided that uniqueness is guaranteed. This code shall consist of 6-11 characters, with trailing NULL, completing the 12-character National Segment. + +Note that if the source transport network element address is assigned from an address space that is globally unique, then the operator-specific CALL\_ID may also be used to represent a globally unique CALL\_ID. However, this is not guaranteed since this address may be assigned from an operator-specific address space. + +# Appendix I + +## Mapping of G.7713/Y.1704 UNI attributes to Q.2931/PNNI + +Table I.1 describes the mapping of G.7713/Y.1704 UNI attributes to Q.2931/PNNI. + +NOTE – Q.2931 [4] and ATM UNI [8] already define a UNI form of the protocol. + +**Table I.1/G.7713.1/Y.1704.1 – Mapping of G.7713/Y.1704 UNI attributes to Q.2931/PNNI** + +| | Attributes | Format | Scope | Q.2931/PNNI | +|---------------------|---------------------------|--------|------------|-------------------------------------------------| +| Identity Attributes | A-end user name | String | End-to-end | Calling Party Number | +| | Z-end user name | String | End-to-end | Called Party Number | +| | Initiating CC/CallC name | | | Implicit | +| | Terminating CC/CallC name | | | Implicit | +| | Connection name | | Local | Connection ID | +| | Call name | | | Network Call Correlation ID | +| Service | SNP ID | | | Connection ID | +| | SNPP ID | | | Connection ID + Link Connection Pool | +| | Directionality | | | Connection ID | +| Policy Attributes | CoS | | | Extended QoS parameters | +| | GoS | | | Traffic Descriptors and Extended QoS parameters | +| | Security | | | Security Services | + +## Appendix II + +## Mapping of G.7713/Y.1704 E-NNI Attributes to Q.2931/PNNI + +Table II.1 describes the mapping of G.7713/Y.1704 E-NNI attributes to Q.2931/PNNI. + +**Table II.1/G.7713.1/Y.1704.1 – Mapping of G.7713/Y.1704 UNI attributes to Q.2931/PNNI** + +| | Attributes | Format | Scope | Q.2931/PNNI | +|---------------------|---------------------------|--------|------------|-------------| +| Identity Attributes | A-end user name | String | End-to-end | As in UNI | +| | Z-end user name | String | End-to-end | As in UNI | +| | Initiating CC/CallC name | | | As in UNI | +| | Terminating CC/CallC name | | | As in UNI | +| | Connection name | | Local | As in UNI | +| | Call name | | | As in UNI | + +**Table II.1/G.7713.1/Y.1704.1 – Mapping of G.7713/Y.1704 UNI attributes to Q.2931/PNNI** + +| | Attributes | Format | Scope | Q.2931/PNNI | +|-------------------|------------------------|--------|-------|-------------------------| +| Service | SNP ID | | | As in UNI | +| | SNPP ID | | | As in UNI | +| | Directionality | | | As in UNI | +| Policy Attributes | CoS | | | As in UNI | +| | GoS | | | As in UNI | +| | Explicit resource list | | | Designated Transit List | +| | Recovery | | | Traffic Descriptors | + +# Appendix III + +## Link connection scope + +## III.1 Scope of the link connection identifier + +Link connection identifiers provide information that is useful only to the CC/LRM using them. Link connection identifiers may have an associated structure imposed on them for local use. Once the link connection identifiers are transmitted to another CC or LRM, the structure of a link connection identifier should no longer be important. This issue does not present a problem in a simple point-to-point connection between two control plane-enabled nodes. However, once a subnetwork is introduced between these nodes (where the subnetwork provides rearrangement capability for the signals) link connection identifier scoping becomes an issue. Figure III.1 illustrates the case of a connection traversing a non-control-plane rearrangeable subnetwork (e.g., link connection identifier rearrangement may be performed via a management system). There is an implicit assumption that the non-control-plane connection already exists prior to any connection request. + +![Diagram illustrating a link connection traversing a non-control plane network. Node A and Node B are connected via a non-control plane network cloud. The link is shown as a dashed line passing through two intermediate nodes (represented by squares with an 'X') within the cloud. The link connection identifier is shown as a dashed line passing through the intermediate nodes, indicating that the identifier is rearranged within the non-control plane network.](683f755e8456c884716de4fce48c7e63_img.jpg) + +The diagram shows Node A on the left and Node B on the right, both represented by grey cubes with an 'X' inside. A cloud labeled 'Non-control plane network' contains two intermediate nodes, also represented by grey cubes with an 'X'. A dashed line representing the link connection identifier starts at Node A, passes through the first intermediate node, then the second, and finally reaches Node B. The link itself is shown as a solid line passing through the same nodes. The text 'G.7713.1\_FIII.1' is in the bottom right corner. + +Diagram illustrating a link connection traversing a non-control plane network. Node A and Node B are connected via a non-control plane network cloud. The link is shown as a dashed line passing through two intermediate nodes (represented by squares with an 'X') within the cloud. The link connection identifier is shown as a dashed line passing through the intermediate nodes, indicating that the identifier is rearranged within the non-control plane network. + +**Figure III.1/G.7713.1/Y.1704.1 – Example link where link connection identifiers are rearranged via non-control plane network** + +The only characteristic of a link connection identifier that is important once it is transmitted is the format of the link connection identifier and the uniqueness of the link connection identifier values. Characteristics such as the structure of the link connection identifier are no longer important or + +useful. In fact, imposing structure of a link connection identifier outside of the local space may result in restrictions to the architecture of a network. + +## **III.2 A link connection identifier association function** + +In order to support the capability to map a received link connection identifier value to a locally significant link connection identifier value, an additional function is needed as part of the local process: that of link connection identifier association. This function takes as input a received link connection identifier value and provides as output a locally significant link connection identifier value. As such, this function may be considered generally to provide a table look-up function. + +The information necessary to allow mapping from received link connection identifier value to a locally significant link connection identifier value may be derived in several ways: + +- via manual provisioning of the association; +- via automatic discovery of the association. + +Either method may be used. In the case of automatic discovery of the association, this implies that the discovery mechanism operates at the SNP level, as per ITU-T Rec. G.7714/Y.1705. Note that in the simple case where two NEs may be directly connected, no association may be necessary. In such instances, the link connection identifier association function provides a one-to-one mapping of the input-to-output link connection identifier values. + +# ITU-T Y-SERIES RECOMMENDATIONS **GLOBAL INFORMATION INFRASTRUCTURE AND INTERNET PROTOCOL ASPECTS** + +## **GLOBAL INFORMATION INFRASTRUCTURE** + +| | | +|-------------------------------------------|-------------| +| General | Y.100–Y.199 | +| Services, applications and middleware | Y.200–Y.299 | +| Network aspects | Y.300–Y.399 | +| Interfaces and protocols | Y.400–Y.499 | +| Numbering, addressing and naming | Y.500–Y.599 | +| Operation, administration and maintenance | Y.600–Y.699 | +| Security | Y.700–Y.799 | +| Performances | Y.800–Y.899 | + +## **INTERNET PROTOCOL ASPECTS** + +| | | +|--------------------------------------------------------------------|----------------------| +| General | Y.1000–Y.1099 | +| Services and applications | Y.1100–Y.1199 | +| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 | +| Transport | Y.1300–Y.1399 | +| Interworking | Y.1400–Y.1499 | +| Quality of service and network performance | Y.1500–Y.1599 | +| Signalling | Y.1600–Y.1699 | +| Operation, administration and maintenance | Y.1700–Y.1799 | +| Charging | Y.1800–Y.1899 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication 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A lightning bolt symbol is positioned to the right of the globe. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +**G.792** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**GENERAL ASPECTS OF DIGITAL TRANSMISSION +SYSTEMS** + +**TERMINAL EQUIPMENTS** + +--- + +**CHARACTERISTICS COMMON TO ALL +TRANSMULTIPLEXING EQUIPMENTS** + +**ITU-T Recommendation G.792** + +(Extract from the *Blue Book*) + +--- + +# NOTES + +1 ITU-T Recommendation G.792 was published in Fascicle III.4 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below). + +2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +# **CHARACTERISTICS COMMON TO ALL TRANSMULTIPLEXING EQUIPMENTS** + +*(Geneva, 1980; further amended)* + +The CCITT, + +*recommends* + +that the characteristics below be respected by all the transmultiplexing equipments defined in Recommendation G.791. + +Recommendation O.133 contains information about test equipment. Account should be taken of the measurement accuracy provided by test equipment designed in accordance with that Recommendation. + +The following specifications are based on ideal measuring equipment. Therefore, they do not include any margin for measurement errors. + +To avoid level errors produced as a result of the use of test frequencies which are sub-multiples of the PCM sampling rate, the use of integer sub-multiples of 8 kHz should be avoided. + +Where a nominal reference frequency of 1020 Hz is indicated (measurement of attenuation/frequency distortion and adjustment of relative levels), the actual frequency should be 1020, +2 to -7 Hz in accordance with Recommendation O.6 [18]. + +## **1 Coding law** + +Transmultiplexers should satisfy Recommendation G.711, § 3. + +## **2 Sampling rate of PCM channels** + +The nominal sampling rate of PCM channels is $8000 \text{ Hz} \pm 50 \cdot 10^{-6}$ according to Recommendation G.711, § 2. + +## **3 Amplitude limitation of PCM channels** + +In accordance with Recommendation G.711, § 4, the theoretical load capacity of PCM channel is + 3.14 dBm0 for the A-law and + 3.17 dBm0 for the $\mu$ -law. + +## **4 Accuracy of the analogue virtual carriers** + +The analogue virtual carriers should satisfy the Recommendation cited in [1]. + +## **5 Saturation level at the input of the analogue group** + +The transmultiplexers should be able to accept at their analogue inputs, levels corresponding to the equivalent peak powers defined in Table 3/G.223 [5] (for example, + 19 dBm0 for a group and + 20.8 dBm0 for a supergroup). + +*Note* - Attention is drawn to the possibility of using a transmultiplexer on the interpolated side of a digital speech interpolation (DSI) device. Given an interpolation rate of 2, this would lead to equivalent peak powers of 19.5 dBm0 for TMUX-P and 21.2 dBm0 for TMUX-S (see Table 3/G.223 [5]). + +## 6 Methods of measuring quality in the audio band + +The various possible methods of measuring quality characteristics in the audio band are indicated in Figure 1/G.792. + +| Category | Measuring method | Remarks | +|----------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------| +| A |

Image: Block diagram for method A: A TMUX block containing F/T and T/F conversion stages. An arrow labeled 'Analogue carrier frequency' points into the F/T stage from the right.

| Measurement in analogue carrier frequency | +| B |

Image: Block diagram for method B: A TMUX block containing T/F and F/T conversion stages. An arrow labeled 'PCM multiplexed signal' points into the T/F stage from the left.

| Measurement in PCM multiplexed level | +| C |

Image: Block diagram for method C: A TMUX block (F/T, T/F) connected to a 'Group modulator*' (S, R) and then to a 'Channel modulator' (S, R). An arrow labeled 'Audio frequency' points into the final R stage from the right.

* Group modulator is not required for the TMUX-P

| Measurement in audio frequency | +| D |

Image: Block diagram for method D: A TMUX block containing T/F and F/T conversion stages. An arrow labeled 'PCM multiplexed signal' points into the T/F stage from the left, and an arrow labeled 'Analogue carrier frequency' points into the F/T stage from the right.

| Measurement for one direction in PCM multiplexed level and analogue carrier frequency | +| E |

Image: Block diagram for method E: An 'Analogue carrier frequency' input goes into an F/T stage, producing a 'PCM multiplex signal'. This signal goes into a T/F stage, which outputs an 'Analogue carrier frequency'.

| Measurement in analogue carrier frequency | +| F |

Image: Block diagram for method F: A 'PCM multiplexed signal' input goes into a T/F stage, producing an 'Analogue carrier frequency'. This signal goes into an F/T stage, which outputs a 'PCM multiplexed signal'.

| Measurement in PCM multiplexed level | + +T/F TDM-to-FDM conversion +F/T FDM-to-TDM conversion + +S Sender +R Receiver + +CCITT-27811 + +FIGURE 1/G.792 + +Block diagrams of measuring methods for transmultiplexers + +When method B cannot be used because it requires digital signal generators and analyzers, which certain Administrations do not yet possess, method C can be used provisionally [looping of the digital ports, use of the terminals of auxiliary analogue channels (and possibly group modulators), assumption of the additivity of impairments and deduction of the impairments at the terminals of the channels (and possibly modulators) previously measured]. + +Method D corresponds in fact to four possible methods, depending on whether the emission of the test signal and its detection takes place on the analogue side or the digital side. + +Methods E and F are used for crosstalk measurements. + +For the sake of the convenience and precision of the measurements, it is desirable that the regulation, when included in the transmultiplexer, can be blocked with a gain equal to unity. The specifications in §§ 7 to 23 assume such blocking. + +## 7 Attenuation distortion in the voice-frequency band as a function of frequency + +The measuring method is method A. + +The variation of the attenuation of each channel of a transmultiplexer as a function of frequency must remain within the limits of the mask in Figure 2/G.792. The level of emission is -10 dBm0; the reference frequency is 1020 Hz. + +## 8 Group delay + +### 8.1 Absolute value of the group delay + +The measuring method is method A. + +The absolute value of group delay defined as the minimum value of group delay in the speech band 300-3400 Hz should remain less than 3 ms for all the channels of a transmultiplexer. + +*Note* - When the transmultiplexer is used for satellite digital communication at the earth station the minimum value of the group propagation time in the audiofrequency band may be increased from 3 ms to 6.5 ms. In all other cases, the value of 3 ms should be complied with. + +![Figure 2/G.792: Attenuation distortion mask as a function of the frequency to be observed for all channels of a transmultiplexer. The graph shows attenuation in dB on the y-axis (from -0.6 to 2.4) against frequency in Hz on the x-axis (from 200 to 4000). A shaded region represents the allowed attenuation range. The mask is defined by several horizontal and vertical lines, with diagonal hatching at the corners. A reference point is marked with a circle and cross at 1020 Hz and 0 dB.](867fce43c58fda6178b06e454b4ed73a_img.jpg) + +| Frequency (Hz) | Attenuation (dB) | +|----------------|------------------| +| 200 | -0.6 | +| 300 | 1.7 | +| 400 | 2.4 | +| 600 | 1.0 | +| 1020 | 0.0 | +| 2400 | 1.0 | +| 3000 | 2.4 | +| 3400 | 2.4 | +| 3600 | -0.6 | +| 4000 | -0.6 | + +Figure 2/G.792: Attenuation distortion mask as a function of the frequency to be observed for all channels of a transmultiplexer. The graph shows attenuation in dB on the y-axis (from -0.6 to 2.4) against frequency in Hz on the x-axis (from 200 to 4000). A shaded region represents the allowed attenuation range. The mask is defined by several horizontal and vertical lines, with diagonal hatching at the corners. A reference point is marked with a circle and cross at 1020 Hz and 0 dB. + +FIGURE 2/G.792 + +**Attenuation distortion mask as a function of the frequency to be observed for all channels of a transmultiplexer** + +### 8.2 Group-delay distortion + +The measuring method is method A. + +The group-delay distortion should not exceed the limits of the mask in Figure 3/G.792. + +The minimum group delay is taken as a reference; the power level at the input is 0 dBm0. + +![Figure 3/G.792: Mask of group-delay distortion as a function of frequency. The graph shows group-delay distortion in ms on the y-axis (0 to 2.0) against frequency (f) in Hz on the x-axis (0 to 2800). The mask is defined by several shaded regions: 1) Above 2.0 ms for f < 600 Hz. 2) Between 1.5 ms and 2.0 ms for 600 Hz < f < 1000 Hz. 3) Between 0.5 ms and 1.5 ms for f > 1000 Hz up to 2600 Hz. 4) Above 2.0 ms for f > 2600 Hz up to 2800 Hz.](ac99eff233b8fe51d30f499e7413c345_img.jpg) + +Figure 3/G.792: Mask of group-delay distortion as a function of frequency. The graph shows group-delay distortion in ms on the y-axis (0 to 2.0) against frequency (f) in Hz on the x-axis (0 to 2800). The mask is defined by several shaded regions: 1) Above 2.0 ms for f < 600 Hz. 2) Between 1.5 ms and 2.0 ms for 600 Hz < f < 1000 Hz. 3) Between 0.5 ms and 1.5 ms for f > 1000 Hz up to 2600 Hz. 4) Above 2.0 ms for f > 2600 Hz up to 2800 Hz. + +FIGURE 3/G.792 +Mask of group-delay distortion as a function of frequency + +## 9 Noise + +### 9.1 Idle channel noise, with all channels idle + +The measuring method is method B. + +When a PCM signal corresponding to amplitude 0 for the $\mu$ -law and the number 1 for the A-law in all channels of the transmultiplexer is applied to the digital input of the transmultiplexer, the psophometric noise measured over any channel at the digital output should not exceed -65 dBm0p. The measurement is conducted in the presence of pilots. + +### 9.2 Channel noise, with all channels loaded except the one measured + +The measuring method is method A. In this case an intermodulation measuring set-up using the white noise method is employed, as described in the Recommendation cited in [6]. + +The level of emission of the noise signal being equal to the conventional load of the FDM signal considered (the Recommendation cited in [7]: 3.3 dBm0 for the group, 6.1 dBm0 for the supergroup), the noise measured in any given measuring slot should not exceed -62.5 dBm0p (i.e., -60 dBm0 in a 3100 Hz band). + +The centre frequencies of the specified measuring slots (CCITT Recommendation G.230 [8] and CCIR Recommendation 482 [9]) applicable to the transmultiplexers are: + +- for the base group: 70 and 98 kHz +- for the base supergroup: 394 and 534 kHz. + +This measurement is carried out without emitting pilots or out-of-band signalling. + +*Note* - Attention is drawn to the possibility of using a transmultiplexer on the interpolated side of a digital speech interpolation (DSI) device. Given an interpolation rate of 2, this would lead to conventional loads of 4.5 dBm0 for TMUX-P and 7.3 dBm0 for TMUX-S (see Table 2/G.223, [7]). + +### 9.3 *Single frequency noise outside the band 300-3400 Hz* + +The measuring method is B. + +When a PCM signal corresponding to amplitude 0 for the $\mu$ -law and amplitude 1 for the A-law in all channels is applied to the digital input of the transmultiplexer, the noise over any frequency should not exceed -50 dBm0 with the exception of the frequency of 80 Hz where it should not exceed -40 dBm0. + +### 9.4 *Idle noise in the PCM - FDM direction all channels idle* + +The measuring method is method D. A PCM signal, amplitude 0 for the $\mu$ -law and 1 for the A-law is applied at the digital input of the transmultiplexer in all channels. The power of the noise measured at the analogue output in any channel must be less than -70 dBm0p. + +*Note* - White noise is assumed, and to take account of the psophometric weighting, the measurement can be made in a band of 1740 Hz, centred on the odd multiples of 2 kHz. The measurement may be difficult in certain channels due to the presence of pilots. + +## 10 **Intermodulation** + +The measuring method is method A. + +If two sine-wave signals of different frequencies $f_1$ and $f_2$ belonging to the band 300-3400 Hz of the channel considered, having no harmonic relation and of equivalent levels in the -4 to -21 dBm0 range, are applied simultaneously to the analogue ports of the transmultiplexer, there should be no intermodulation product of the type $2f_1 - f_2$ of a level higher than -35 dB with respect to the level of one of the two input signals. + +## 11 **Total distortion including quantizing distortion** + +The measuring method is method B (or provisionally method C). + +If method B is used, the test signal is generated digitally and is therefore affected by theoretical quantizing distortion. + +A choice between the two following methods is recommended: + +### *Method 1* + +The signal-to-total distortion ratio measured according to method 1 described in § 8 of Recommendation G.712 should respect the mask of Figure 4/G.792. The mask is to be complied with by all channels of the transmultiplexer. + +### *Method 2* + +With a sine-wave signal at a frequency between 700 and 1100 Hz or 350 and 550 Hz (e.g. $420 \pm 20$ Hz) (except for submultiples of 8 kHz) being applied in the channel concerned at the digital input of the transmultiplexer, the ratio of signal-to-total distortion power, measured with appropriate noise weighting (see the Recommendation cited in [10]), should be below the limits of the mask represented in Figure 5/G.792. The mask is to be complied with by all the channels of the transmultiplexer. + +## 12 **In-band spurious signals** + +The measuring method is method A. + +The transmultiplexers must meet the provisions of Recommendation G.712, § 9. + +## 13 Variation of gain with the input level + +The measuring method is method A, the pilots being present at the analogue input. + +With a sine-wave signal at a frequency between 700 and 1100 Hz (except for submultiples of 8 kHz) and a level between -55 and +3 dBm0 being applied in the channel concerned at the analogue input of the transmultiplexer, the variation of gain with respect to its value for an input level of -10 dBm0 should remain between the limits of the mask shown in Figure 6/G.792. The mask is to be complied with by all channels of a transmultiplexer. + +![Two graphs showing the signal-to-total distortion ratio as a function of input level for Method C and Method B.](ecb25d766719ce041cf4cc390791a098_img.jpg) + +The figure consists of two vertically stacked graphs, (a) and (b), showing the signal-to-total distortion ratio in dB as a function of input level in dBm0. Both graphs have a shaded region representing the allowed mask. + +**a) Method C** + +| Input level (dBm0) | Lower limit of mask (dB) | Upper limit of mask (dB) | +|--------------------|--------------------------|--------------------------| +| -55 | 10.0 | 33.9 | +| -40 | 25.0 | 33.2 | +| -34 | 26.3 | 30.2 | +| -27 | 30.2 | 30.2 | +| -6 | 30.2 | 30.2 | +| -3 | 25.0 | 25.0 | +| 0 | 0 | 0 | + +**b) Method B** + +| Input level (dBm0) | Lower limit of mask (dB) | Upper limit of mask (dB) | +|--------------------|--------------------------|--------------------------| +| -55 | 9.2 | 32.5 | +| -40 | 24.2 | 31.8 | +| -34 | 24.9 | 29.1 | +| -27 | 29.1 | 29.1 | +| -6 | 29.1 | 29.1 | +| -3 | 24.2 | 24.2 | +| 0 | 0 | 0 | + +CCITT-27031 + +Two graphs showing the signal-to-total distortion ratio as a function of input level for Method C and Method B. + +FIGURE 4/G.792 + +Signal-to-total distortion ratio as a function of the input level +according to method 1 (Recommendation G.712, § 8) + +![Graph (a) Method C showing Signal-to-total distortion ratio (dB) vs Input level (dBm0). The y-axis ranges from 0 to 33.0 dB with marked values at 0, 20.5, 25.5, 32.3, and 33.0. The x-axis ranges from -45 to 0 dBm0 with marked values at -45, -40, -30, and 0. The graph shows a piecewise linear increase in the distortion ratio, with shaded regions indicating specific operating areas.](352c5fab6f936356e9570761a02ab71e_img.jpg) + +Graph (a) Method C: Signal-to-total distortion ratio (dB) vs Input level (dBm0). The y-axis has values 0, 20.5, 25.5, 32.3, and 33.0. The x-axis has values -45, -40, -30, and 0 dBm0. The curve starts at 20.5 dB at -45 dBm0, rises to 25.5 dB at -40 dBm0, and reaches 32.3 dB at -30 dBm0, remaining constant at 32.3 dB up to 0 dBm0. Shaded regions are shown between the curve and the horizontal lines at 20.5 dB, 25.5 dB, and 32.3 dB. + +Graph (a) Method C showing Signal-to-total distortion ratio (dB) vs Input level (dBm0). The y-axis ranges from 0 to 33.0 dB with marked values at 0, 20.5, 25.5, 32.3, and 33.0. The x-axis ranges from -45 to 0 dBm0 with marked values at -45, -40, -30, and 0. The graph shows a piecewise linear increase in the distortion ratio, with shaded regions indicating specific operating areas. + +a) Method C + +![Graph (b) Method B showing Signal-to-total distortion ratio (dB) vs Input level (dBm0). The y-axis ranges from 0 to 32.0 dB with marked values at 0, 19.9, 24.9, 31.3, and 32.0. The x-axis ranges from -45 to 0 dBm0 with marked values at -45, -40, -30, and 0 dBm0. The graph shows a piecewise linear increase in the distortion ratio, with shaded regions indicating specific operating areas. CCITT-27841 is noted at the bottom right.](91be14371a97fb5ce9eeb29ae18d07c3_img.jpg) + +Graph (b) Method B: Signal-to-total distortion ratio (dB) vs Input level (dBm0). The y-axis has values 0, 19.9, 24.9, 31.3, and 32.0. The x-axis has values -45, -40, -30, and 0 dBm0. The curve starts at 19.9 dB at -45 dBm0, rises to 24.9 dB at -40 dBm0, and reaches 31.3 dB at -30 dBm0, remaining constant at 31.3 dB up to 0 dBm0. Shaded regions are shown between the curve and the horizontal lines at 19.9 dB, 24.9 dB, and 31.3 dB. The text 'CCITT-27841' is present at the bottom right of the graph. + +Graph (b) Method B showing Signal-to-total distortion ratio (dB) vs Input level (dBm0). The y-axis ranges from 0 to 32.0 dB with marked values at 0, 19.9, 24.9, 31.3, and 32.0. The x-axis ranges from -45 to 0 dBm0 with marked values at -45, -40, -30, and 0 dBm0. The graph shows a piecewise linear increase in the distortion ratio, with shaded regions indicating specific operating areas. CCITT-27841 is noted at the bottom right. + +b) Method B + +FIGURE 5/G.792 + +Signal-to-total distortion ratio as a function of the input level according to method 2 (Recommendation G.712, § 8) + +![Figure 6/G.792: Gain variation as a function of input level S. The graph shows gain variation (ΔG) in dB on the y-axis (from -3 to +3) against input level (S) in dBm0 on the x-axis (from -55 to +3). The gain variation is constant at -3 dB for input levels from -55 to -50 dBm0, then steps up to -1 dB for -50 to -40 dBm0, 0 dB for -40 to -10 dBm0, +0.5 dB for -10 to 0 dBm0, and +1 dB for 0 to +3 dBm0. Shaded regions indicate the tolerance limits for each gain step.](adb1f42239329fa8283d1a40005f989f_img.jpg) + +Figure 6/G.792: Gain variation as a function of input level S. The graph shows gain variation (ΔG) in dB on the y-axis (from -3 to +3) against input level (S) in dBm0 on the x-axis (from -55 to +3). The gain variation is constant at -3 dB for input levels from -55 to -50 dBm0, then steps up to -1 dB for -50 to -40 dBm0, 0 dB for -40 to -10 dBm0, +0.5 dB for -10 to 0 dBm0, and +1 dB for 0 to +3 dBm0. Shaded regions indicate the tolerance limits for each gain step. + +CCITT - 27850 + +FIGURE 6/G.792 + +**Gain variation as a function of input level S, +Method 2 in Recommendation G.712, § 10 (sinusoidal test signal)** + +## 14 Crosstalk + +For measuring crosstalk, two transmultiplexers must be connected back-to-back (methods E and F). There are two possible configurations and four possible measurements (see Figure 7/G.792): + +- far-end crosstalk digital to digital (see Note 1) +- near-end crosstalk digital to digital (see Note 1) +- far-end crosstalk analogue to analogue +- near-end crosstalk analogue to analogue + +### 14.1 *Intelligible crosstalk* + +When a sine-wave signal between 700 and 1100 Hz and with a level of 0 dBm0 is injected in any channel on the digital or analogue side of the transmultiplexer, the crosstalk ratio between the signal channel and any other channel must be greater than 65 dB for any of the four crosstalk contributions identified above (see Note 2). + +### 14.2 *Unintelligible crosstalk* + +When a conventional telephone signal according to Recommendation G.227 [11] is injected in any channel on the digital or analogue side of the transmultiplexer, at a level of 0 dBm0, the level of crosstalk measured in any other channel for any of the four crosstalk contributions identified above must be below -60 dBm0p (see Note 3). + +*Note 1* - In this configuration, the two transmultiplexers are connected at the level of the analogue FDM signal and there will generally be a problem of level adaptation between the send and the receive sides. This can be solved with the use of attenuators or amplifiers of appropriate gain. Attention must be given on the risk of introduction of additional crosstalk in these complementary devices. It should be desirable to include the level adaptation facilities in the transmultiplexer itself. + +*Note 2* - In order to overcome fundamental gain enhancement effects associated with PCM encoders, which can mask the true crosstalk, measuring methods using activating signals based on those defined in Recommendation G.712 can be used. + +*Note 3* - Recognizing the difficulty of generating conventional telephone signals according to Recommendation G.227 in a suitable format for insertion into either the analogue or digital input to the transmultiplexer, it shall be adequate to demonstrate, via suitable single frequency crosstalk tests, that the intent of the above specification is met, without actually using a conventional telephone signal. + +![Figure 7/G.792: Measurements of crosstalk with methods E and F. Diagram (a) shows Far-end crosstalk measurement where a Perturbing signal and Activating signal are input to TMUX 1, and the output is connected to TMUX 2, where the measurement is taken. Diagram (b) shows Near-end crosstalk measurement where a Perturbing signal is input to TMUX 1 and measured at the same side, while an Activating signal is input to TMUX 2.](5a4e62bead259c258d069fd3663ea670_img.jpg) + +``` + +graph LR + subgraph a [a Far-end crosstalk measurement] + PS1[Perturbing signal] --> TMUX1_a[TMUX 1] + AS1[Activating signal] --> TMUX1_a + TMUX1_a --> TMUX2_a[TMUX 2] + TMUX2_a --> M1[Measure] + end + + subgraph b [b Near-end crosstalk measurement] + PS2[Perturbing signal] --> TMUX1_b[TMUX 1] + TMUX1_b <--> M2[Measure] + TMUX1_b <--> TMUX2_b[TMUX 2] + AS2[Activating signal] --> TMUX2_b + end + +``` + +The diagram consists of two parts, (a) and (b), illustrating crosstalk measurement setups using two transmultiplexers, TMUX 1 and TMUX 2. + +**a) Far-end crosstalk measurement**: A 'Perturbing signal' and an 'Activating signal' are input into the left side of TMUX 1. The output of TMUX 1 is connected to the input of TMUX 2. The output of TMUX 2 is labeled 'Measure'. + +**b) Near-end crosstalk measurement**: A 'Perturbing signal' is input into the left side of TMUX 1. The output of TMUX 1 is labeled 'Measure' (with a bidirectional arrow). The output of TMUX 1 is also connected to the input of TMUX 2 (bidirectional). An 'Activating signal' is input into the right side of TMUX 2. The text 'CCITT-69640' is written below TMUX 2. + +Figure 7/G.792: Measurements of crosstalk with methods E and F. Diagram (a) shows Far-end crosstalk measurement where a Perturbing signal and Activating signal are input to TMUX 1, and the output is connected to TMUX 2, where the measurement is taken. Diagram (b) shows Near-end crosstalk measurement where a Perturbing signal is input to TMUX 1 and measured at the same side, while an Activating signal is input to TMUX 2. + +FIGURE 7/G.792 +**Measurements of crosstalk with methods E and F** + +## 15 Go-to-return crosstalk + +For measuring go-to-return crosstalk, two transmultiplexers must be connected back-to-back (methods E and F). There are two possible configurations and two possible measurements (see Figure 7b/G.792): + +- near-end crosstalk digital to digital (see Note 1 of § 14); +- near-end crosstalk analogue to analogue. + +When a sine-wave signal between 300 and 3400 Hz and with a level of 0 dBm0 is injected in any channel on the digital or analogue side of the transmultiplexer, the crosstalk ratio between the signal channel and the associated return channel must be greater than 58 dB for each contribution identified above. + +When using method F, a PCM signal corresponding to amplitude 0 for the $\mu$ -law and amplitude 1 for the A-law, should be inserted into the digital input of all return channels. + +*Note* - Concerning the activating signal for method F, see Recommendation G.712, § 10. + +## 16 Variation of the equivalent of the channels within the FDM assembly + +Measuring method A. + +When a test tone at the equivalent of 1020 Hz in any channel, and with a level of -10 dBm0 is applied to the analogue input of the transmultiplexer, the level measured at the analogue output of the transmultiplexer shall be within a tolerance of $\pm 1$ dB of the level measured when that test tone is applied at the equivalent of 1020 Hz in the channel containing the reference pilot of the FDM assembly considered. + +## 17 Adjustment of the relation between the coding law and the analogue level + +Measuring method D. + +To measure the correspondence between the coding laws and the analogue levels, the sequence of character signals from Table 5/G.711 for the A-law and from Table 6/G.711 for the $\mu$ -law may be applied periodically at the digital input of the transmultiplexer: the signal at the analogue output of the transmultiplexer should correspond to a sine-wave signal of frequency 1 kHz in the corresponding channel at a level between -0.5 and +0.5 dBm0. + +*Note* - The use of another digital periodic sequence representing a nominal reference frequency of 1020 Hz at a nominal level of 0 dBm0 is acceptable, provided that the theoretical level accuracy is better than $\pm 0.03$ dB. + +To check the load capacity of the PCM coder contained in the transmultiplexer, a sine-wave signal at a nominal frequency of 1020 Hz can be applied for any channel at the analogue input of the transmultiplexer. Initially the level of this signal is considerably below the load capacity, then it is raised gradually. Note is taken of the input level at which the character signal corresponding to the extreme quantization interval for positive and negative amplitudes first appears at the digital output in the channel considered. The load capacity is then taken to be equal to this input level, increased by 0.3 dB. The values obtained for the various channels should be between 2.64 and 3.64 dBm0 for the A-law and between 2.67 and 3.67 dBm0 for the $\mu$ -law. + +## 18 Carrier leak at the analogue ports + +Measuring method A, the analogue input of the transmultiplexer being looped to its nominal impedance. + +The transmultiplexers should meet the provisions of the Recommendation cited in [12]. + +## 19 Protection against out-of-band signals at the analogue ports + +### 19.1 Out-of-band spurious signals at the analogue output + +The measuring method is C for the TMUX-P, range a) (see below), otherwise A. The test signal has a level of 0 dBm0. For the TMUX-P, range a), a signal according to Recommendation G.227 is used, otherwise a sine-wave signal (300 to 3400 Hz). The level of spurious signals outside the group or supergroup band ( $f_1$ to $f_2$ ) at the analogue output should not exceed the following limits: + +| | | | | +|-----------|---------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------|--------------------------------------| +| TMUX-P a) | $f_1 > f_x > (f_1 - 4 \text{ kHz})$
and
$f_2 < f_x < (f_2 + 4 \text{ kHz})$ | $\left. \begin{matrix} ] \\ \} \\ ] \end{matrix} \right\}$ | $\leq -60 \text{ dBm0p}$
(Note 1) | +| b) | $(f_1 - 4 \text{ kHz}) > f_x > (f_1 - 12 \text{ kHz})$ }
and
$(f_2 + 4 \text{ kHz}) < f_x < (f_2 + 12 \text{ kHz})$ | $\left. \begin{matrix} ] \\ \} \\ ] \end{matrix} \right\}$ | $\leq -70 \text{ dBm0}$
(Note 2) | +| c) | $f_x \leq (f_1 - 12 \text{ kHz})$
and
$f_x \geq (f_2 + 12 \text{ kHz})$ | $\left. \begin{matrix} ] \\ \} \\ ] \end{matrix} \right\}$ | $\leq -80 \text{ dBm0}$ | + +| | | | | +|-----------|-------------------------------------------------------------------------------------------------------------------------|--------|-------------------------------------| +| TMUX-S a) | $f_x = f_1 - 4 \text{ kHz}$
and
$f_x = f_2 + 4 \text{ kHz}$ | }
} | $\leq -60 \text{ dBm0}$
(Note 3) | +| b) | $(f_1 - 8 \text{ kHz}) > f_x > (f_1 - 20 \text{ kHz})$
and
$(f_2 + 8 \text{ kHz}) < f_x < (f_2 + 20 \text{ kHz})$ | }
} | $\leq -70 \text{ dBm0}$
(Note 2) | +| c) | $f_x \leq (f_1 - 20 \text{ kHz})$
and
$f_x \geq (f_2 + 20 \text{ kHz})$ | }
} | $\leq -80 \text{ dBm0}$ | + +Note 1 - Telephony channels, pilots or additional test frequencies are possible in this frequency range. + +Note 2 - Adjacent carrier-frequency sound-programme channels may begin in this range (with reduced requirements). + +Note 3 - This range may contain pilots or additional measuring frequencies. + +### 19.2 Crosstalk due to out-of-band signals at the analogue input + +Measuring methods C and A, respectively (see § 19.1). With test signals as in § 19.1 in a channel of an adjacent FDM assembly, the level at the transmultiplexer output should not exceed the following limits: + +| | | | | +|-----------|-----------------------------------------------------------------------------------|--------|------------------------------------| +| TMUX-P a) | $f_1 > f_x > (f_1 - 4 \text{ kHz})$
and
$f_2 < f_x < (f_2 + 4 \text{ kHz})$ | }
} | $\leq -60 \text{ dBm0p}$
(Note) | +| b) | $f_x < (f_1 - 4 \text{ kHz})$
and
$f_x > (f_2 + 4 \text{ kHz})$ | }
} | $\leq -70 \text{ dBm0}$
(Note) | +| TMUX-S a) | $f_x = f_1 - 4 \text{ kHz}$
and
$f_x = f_2 + 4 \text{ kHz}$ | }
} | $\leq -50 \text{ dBm0}$
(Note) | +| b) | $f_x < (f_1 - 8 \text{ kHz})$
and
$f_x > (f_2 + 8 \text{ kHz})$ | }
} | $\leq -70 \text{ dBm0}$
(Note) | + +*Note* - For this measurement, a low-level auxiliary signal is injected into the disturbed channel. The appropriate auxiliary signal is a sine-wave signal between -33 and -40 dBm0. The frequency and characteristics of the filter in the measuring equipment must be carefully selected to ensure that the auxiliary signal does not appreciably reduce the accuracy of the crosstalk measurement. + +## 20 Protection and suppression of pilots + +Measuring method D. + +The transmultiplexers should meet the provisions of the Recommendation cited in [14]. + +## 21 Protection and suppression of out-of-band signalling + +### 21.1 *Protection of the out-of-band signalling channel for transmultiplexers using signalling system R2* + +Measuring method D. + +When a transmultiplexer is capable of emitting out-of-band signalling waves at frequency 3825 Hz, it should meet the provisions of Recommendation Q.414 [15], Figure 6/Q.414 being replaced by Figure 7/G.792. The measuring method associated with the latter figure is recalled in Note 1. + +*Note 1* - The signalling channel must be protected at the sending end against disturbance from the associated and the adjacent channel. + +When a sine-wave at 0 dBm0 level is applied to the digital input of the associated channel, the level measured at the analogue output of the transmultiplexer must not exceed the levels shown in Figure 8/G.792. + +When a sine-wave of frequency $f$ is applied to the digital input of the adjacent channel, it produces two signals that appear on the frequency scale of Figure 8/G.792 as having the frequencies $(4000 + f)$ and $(4000 - f)$ . The level of the $(4000 + f)$ signal measured at the analogue output of the transmultiplexer shall not be higher than -33 dBm0, when the sine-wave with frequency $f$ is applied to the digital input of the adjacent channel at a level shown in Figure 8/G.792 for the frequency of $(4000 + f)$ . The level of the $(4000 - f)$ signal, measured at the analogue output of the transmultiplexer, shall not be higher than -33 dBm0, when the sine-wave with frequency $f$ is applied to the digital input of the adjacent channel at any level below the value shown in Figure 8/G.792 for the frequency $(4000 - f)$ . + +### 21.2 *Disturbance of telephone channels by out-of-band signalling frequency for transmultiplexers using signalling system R2* + +The measuring method is method B or D. + +Interference at 175 Hz and 3825 Hz should not exceed -53 dBm0 respectively -63 dBm0 when a continuous tone of 3825 Hz with a nominal level of -20 dBm0 is applied to all channels. These values correspond to a contribution to the channel noise in the order of -73 dBm0p (design objective). + +![Figure 8/G.792: Protection of the signalling channel at the sending end. A graph showing power levels in dBm0 versus frequency in Hz. The y-axis ranges from -50 to +3 dBm0. The x-axis ranges from 3550 to 4250 Hz. Two curves are shown: a solid line for the 'Associated channel' and a dashed line for the 'Adjacent channel'. The associated channel is flat at 0 dBm0 until 3550 Hz, then drops to -33 dBm0 at 3750 Hz, and remains flat. The adjacent channel is flat at +3 dBm0 until 3900 Hz, then drops to -33 dBm0 at 4250 Hz, and remains flat.](71ab4df17511d75261da8d462d643b1a_img.jpg) + +| Frequency (Hz) | Associated channel (dBm0) | Adjacent channel (dBm0) | +|----------------|---------------------------|-------------------------| +| 3550 | 0 | 0 | +| 3750 | -33 | -33 | +| 3900 | -33 | +3 | +| 4100 | -33 | -23 | +| 4250 | -33 | -33 | + +Figure 8/G.792: Protection of the signalling channel at the sending end. A graph showing power levels in dBm0 versus frequency in Hz. The y-axis ranges from -50 to +3 dBm0. The x-axis ranges from 3550 to 4250 Hz. Two curves are shown: a solid line for the 'Associated channel' and a dashed line for the 'Adjacent channel'. The associated channel is flat at 0 dBm0 until 3550 Hz, then drops to -33 dBm0 at 3750 Hz, and remains flat. The adjacent channel is flat at +3 dBm0 until 3900 Hz, then drops to -33 dBm0 at 4250 Hz, and remains flat. + +*Note* - The frequency of the virtual carrier of the associated speech channel is the origin of the frequency scale (zero frequency) + +FIGURE 8/G.792 +**Protection of the signalling channel at the sending end** + +### 21.3 Other out-of-band signalling systems + +See Annex A. + +## 22 Mutual interference between pilots and out-of-band signalling + +The transmultiplexers capable of emitting and receiving out-of-band signalling should meet the provisions of the Recommendation cited in [17]. + +## 23 Short- and long-term variation of loss with time + +The measuring method is A. When a sine-wave signal at level -10 dBm0 and at a nominal frequency of 1020 Hz is applied at the analogue input of the transmultiplexer, the level measured at the analogue output should not vary by more than $\pm 0.2$ dB during 10 consecutive minutes of normal operation, more than $\pm 0.5$ dB during 3 consecutive days nor by more than $\pm 1$ dB for one year, allowing for the authorized variations of power supply, voltages and temperature. + +# ANNEX A + +(to Recommendation G.792) + +## Out-of-band signalling systems using a burst-mode method + +The possibility of such systems is mentioned in Annex A to Recommendation Q.21 and Annex B to Recommendation G.232. These annexes should be taken into consideration. When a transmultiplexer is capable of converting such systems, the following applies: + +- Signalling frequency at the sending point: $3825 \text{ Hz} \pm 4 \text{ Hz}$ . +- Send level of the signalling frequency: $-5 \text{ dBm0} \pm 1 \text{ dB}$ . +- Protection of the out-of-band signalling channel: see Figure 8/G.792. + +- Disturbance of telephone channels by the out-of-band signalling frequency: the measuring method is method B. +- Channel noise should not exceed -63 dBm0p in the call channel (continuous tone). +- In the adjacent channel (the closest to the signalling frequency) likewise -63 dBm0p burst or continuous tone. +- In every other channel -76 dBm0p burst or continuous tone. + +*Note 1* - Burst tones do not occur in the call channel after call set-up has taken place. + +*Note 2* - Burst rates are in the order of 10 to 25 Hz. + +*Note 3* - Charge metering pulses are of long duration, e.g. 150/450 ms and are evaluated as a continuous tone. + +# References + +- [1] CCITT Recommendation *Recommendations relating to the accuracy of carrier frequencies*, Vol. III, Rec. G.225, § 1. +- [2] CCITT Recommendation *Pilots on groups, supergroups, etc.*, Vol. III, Rec. G.241, § 1. +- [3] *Ibid.*, § 2. +- [4] *Ibid.*, § 3. +- [5] CCITT Recommendation *Assumptions for the calculation of noise on hypothetical reference circuits for telephony*, Vol. III, Rec. G.223, Table 3/G.223, § 6. +- [6] CCITT Recommendation *Measurement of circuit noise in cable systems using a uniform-spectrum random noise loading*, Vol. III, Rec. G.228, §§ A.1, A.2.2. +- [7] CCITT Recommendation *Assumptions for the calculation of noise on hypothetical reference circuits for telephony*, Vol. III, Rec. G.223, § 2.1. +- [8] CCITT Recommendation *Measuring method and through-connection filters for noise produced by modulating equipment*, Vol. III, Rec. G.230. +- [9] CCIR Recommendation *Measurement of performance by means of a signal of a uniform spectrum for systems using frequency-division multiplex telephony in the fixed satellite service*, Vol. IV, Rec. 482, ITU, Geneva, 1978. +- [10] CCITT Recommendation *Assumptions for the calculation of noise on hypothetical reference circuits for telephony*, Vol. III, Rec. G.223, § 7. +- [11] CCITT Recommendation *Conventional telephone signal*, Vol. III, Rec. G.227. +- [12] CCITT Recommendation *12-channel terminal equipments*, Vol. III, Rec. G.232, §§ 5.1, 5.2. +- [13] CCITT Recommendation *Through-connection of groups, supergroups, etc.*, Vol. III, Rec. G.242, § 1. +- [14] CCITT Recommendation *12-channel terminal equipments*, Vol. III, Rec. G.232, §§ 12.1, 12.2 and Annex A. +- [15] CCITT Recommendation *Signal sender*, Vol. VI, Rec. Q.414, Figure 6/Q.414. +- [16] CCITT Recommendation *12-channel terminal equipments*, Vol. III, Rec. G.232. +- [17] *Ibid.*, § 12.3 and Annex B. +- [18] CCITT Recommendation *1020 Hz reference test frequency*, Vol. IV, Rec. O.6. \ No newline at end of file diff --git a/marked/G/T-REC-G.793-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.793-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..81e3e7d616c91b604004f1504405e37afb17b333 --- /dev/null +++ b/marked/G/T-REC-G.793-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:0e63988e160a5a663f5a0496675594529a7c13c153518b0cee3b6016e695b52c +size 7455 diff --git a/marked/G/T-REC-G.793-198811-I_PDF-E/raw.md b/marked/G/T-REC-G.793-198811-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..d2387be25b870eae7e46764a103c7c8ff7d6e917 --- /dev/null +++ b/marked/G/T-REC-G.793-198811-I_PDF-E/raw.md @@ -0,0 +1,288 @@ + + +![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.793** + +**GENERAL ASPECTS OF DIGITAL +TRANSMISSION SYSTEMS +TERMINAL EQUIPMENTS** + +--- + +**CHARACTERISTICS OF 60-CHANNEL +TRANSMULTIPLEXING EQUIPMENTS** + +**ITU-T Recommendation G.793** + +(Extract from the *Blue Book*) + +--- + +# NOTES + +1 ITU-T Recommendation G.793 was published in Fascicle III.4 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below). + +2 In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +# **CHARACTERISTICS OF 60-CHANNEL TRANSMULTIPLEXING EQUIPMENTS** + +*(Geneva, 1980; further amended)* + +## **1 Introduction** + +The 60-channel transmultiplexer is a transmultiplexing equipment which satisfies Recommendations G.791 and G.792 and provides interconnection between two digital signals at 2048 kbit/s and an analogue supergroup (60-channel TMUX-S). + +## **2 Digital interfaces** + +### **2.1 *Coding law*** + +The coding law used is A-law specified in Recommendation G.711. + +### **2.2 *Interfaces*** + +The 2048-kbit/s interfaces satisfy Recommendation G.703, § 6. + +### **2.3 *Frame structure*** + +The structure is specified in Recommendation G.704, § 3.3.1. + +The strategy and the criteria for loss and recovery of frame alignment satisfy Recommendation G.706, § 4.1. + +### **2.4 *Multiframe structure*** + +The multiframe structure of time slot 16 satisfies Recommendation G.704, § 3.3.3. + +The strategy and the criteria for loss and recovery of multiframe alignment satisfy Recommendation G.732, § 5.2. + +## **3 Analogue interfaces** + +### **3.1 *Ports*** + +The analogue interface consists of a 60-channel supergroup (band 312-552 kHz) which satisfies Recommendation G.233 [1]. + +The preferred signal levels at the supergroup distribution frame should be: + +- for sending -36 dBr +- for receiving -30 dBr + +The impedances are: 75 ohms (unbalanced). + +### **3.2 *Pilots*** + +The 60-channel transmultiplexer should transmit the following pilots: + +TMUX-S: A supergroup pilot with a frequency 411 920 Hz and a level of -20 dBm0, +one pilot per group with a level of -20 dBm0 and frequencies of: + +- Group 1: 335 920 Hz +- Group 2: 383 920 Hz +- Group 3: 431 920 Hz +- Group 4: 479 920 Hz +- Group 5: 527 920 Hz + +The transfer of pilot alarms individually for each group in a supergroup and the consequence for the split channels of group 3 can be seen in Figure 1 of Supplement No. 32. + +Other sets of pilots as recommended in Recommendation G.241 can be used. Special attention should be given to the compatibility of the set of pilots adopted with the out-of-band signalling system using a frequency at 3825 Hz. + +The characteristics relating to the generation and transmission of these pilots are given in Recommendation G.241 [2]. + +### 3.3 Pilot detection and regulation + +The transmultiplexer may or may not regulate levels on the basis of the levels of the group and supergroup pilots. If so, the transmultiplexer must meet the conditions of the Recommendation cited in [2]. Detection of the levels of the group pilots and or supergroup mentioned in § 3.2 should, however, be effected to ensure operation of the interruption control system (Recommendation Q.416 [3]), when R2 signalling is used. + +## 4 Correspondence between analogue and digital channels + +A fixed correspondence is established between the analogue and digital channels. The correspondence shown in Table 1/G.793 (which facilitates the transfer of alarms and results in a natural order of the channels on the analogue side) is recommended. + +TABLE 1/G.793 + +| | | +|----------------------------|------------------------| +| PCM 1
channels 1 to 12 | Group 1
312-360 kHz | +| PCM 1
channels 13 to 24 | Group 2
360-408 kHz | +| PCM 1
channels 25 to 30 | Group 3
408-432 kHz | +| PCM 2
channels 1 to 6 | Group 3
432-456 kHz | +| PCM 2
channels 7 to 18 | Group 4
456-504 kHz | +| PCM 2
channels 19 to 30 | Group 5
504-552 kHz | + +*Note* - In national networks or by agreement between Administrations, other schemes of correspondence between analogue and digital channels may be used. + +## 5 Plesiochronous operation of incoming PCM streams + +Sixty-channel transmultiplexers should be able to accept two mutually plesiochronous incoming PCM streams within the limits laid down in Recommendation G.703 (bit rate 2048 kbit/s, $\pm 50 \cdot 10^{-6}$ ). + +In the case of transmultiplexers with digital filtering, this means that the two input ports at 2048 kbit/s are fitted with frame aligners (jump or repetition of samples) and multiframe aligners for synchronizing the incoming PCM streams with the transmultiplexer clock. In order to avoid a major slip frequency, the two incoming PCM streams should be either synchronous with the transmultiplexer or plesiochronous with each other and with the transmultiplexer clock, so that Recommendation G.811 on the plesiochronous network is satisfied. + +## 6 Synchronization of transmultiplexer + +The transmultiplexer must produce virtual analogue carrier frequencies with the accuracy specified in Recommendation G.225 [4] ( $\pm 10^{-7}$ ). + +For this purpose, it is recommended: + +- a) either that the transmultiplexer should have an internal clock of sufficient accuracy; +- b) or that the transmultiplexer should be synchronizable with an external signal which may be: + - 1) a frequency (see Note 3) produced by a central FDM generator: 4, 12 or 124 kHz; + - 2) or one of the incoming PCM streams which has sufficient accuracy (this may be the case, for example, when this PCM stream at 2048 kbit/s is produced by a TDM switching equipment). If both 2048-kbit/s streams are of sufficient accuracy, the use of PCM stream No. 1 is preferred. In most cases this avoids, at the digital filtering transmultiplexer input, the slipping phenomena which, when too frequent, cause high error rates on in-band data signals. + +*Note 1* - In the case of a digital filtering transmultiplexer, when synchronization on one of the incoming PCM streams is not possible, the remote digital terminal should have the sending side synchronized with the receiving side so as to avoid slipping at the transmultiplexer input. + +*Note 2* - In the case of external synchronization, transmultiplexers often have an internal oscillator locked to the external signal. If, upon loss of the external sync signal, this internal oscillator is allowed to continue to supply the clock for the outgoing digital signal (now in the free-running mode), then this oscillator should have a minimum free-running accuracy of $50 \times 10^{-6}$ . This is intended to allow the distant end digital terminal to receive an adequate frequency for alarm purposes only, so as not to confuse maintenance and trouble-shooting activities. Also, a local alarm should be given in the event of a fault in the synchronization system or in the absence of the external synchronization signal (Tables 2/G.793, 3/G.793 and 2 of Supplement No. 32). + +*Note 3* - In the case where the transmultiplexer is to be used in a TDMA satellite application, the effect of the satellite Doppler frequency variation must be taken into account. This can be done in two ways: + +- either, the TDMA terminal incorporates the Doppler buffer memories of appropriate capacity in the earth station to satellite direction. In this case, the two directions of the TMUX must be synchronized from one of the two 2048 kbit/s PCM streams transmitted by the TDMA receive terminal; +- or, the TDMA terminal does not incorporate Doppler buffers. In this case, the PCM to FDM direction of the TMUX may be synchronized from one of the two 2048 kbit/s streams transmitted by the TDMA receive terminal. In the FDM to PCM direction, the 2048 kbit/s streams transmitted by the TMUX must be made synchronous with the TDMA system transmit clock: this supposes that a synchronization signal (contradirectional with the data) is provided by the TDMA transmit terminal to the TMUX. In the case where the processing in a digital filtering transmultiplexer is made synchronously for the two directions, Doppler buffer memories of appropriate capacity must be incorporated in the PCM interfaces. + +## 7 Signalling + +Different kinds of signalling systems can be envisaged. + +### 7.1 *In-band signalling* + +The 60-channel transmultiplexer is transparent for channel-associated in-band signalling. + +### 7.2 *Common channel signalling* + +In the case when common channel signalling must be routed through the transmultiplexer, attention is drawn to the fact that the transmission capabilities of a channel in the transmultiplexer is limited to the band 300-3400 Hz (i.e. data rates corresponding to this frequency band). Information on signalling bit rates is given in § 2 of Recommendation Q.702. + +In the opposite case, when common channel signalling is not routed through the TMUX, no special problems are recognized. + +### 7.3 *Out-of-band signalling* + +As regards Signalling System R2, signalling conversion between the analogue and digital versions of line signalling as recommended in Recommendation Q.430 is to be used in the case of international interconnection and should conform to the following specifications. + +The transmultiplexer, or an additional equipment associated with it, converts the analogue version to the 2-bit digital version of the R2 line Signalling System, and vice versa. In all cases, the transmultiplexer should provide the following facilities for signalling: + +#### a) *Analogue side* + +- 1) recognition of the signalling frequency at 3825 Hz in accordance with Recommendation Q.415 [5]; +- 2) transmission of the signalling frequency at 3825 Hz in accordance with Recommendation Q.414 [6]; +- 3) supervision of group pilots (and supergroup pilots if necessary) in accordance with Recommendation Q.416 [3]. + +#### b) *Digital side* + +- 1) extraction of signalling bits *a* and *b* of time slots 16 received in accordance with the Recommendation cited in [7]; +- 2) insertion of appropriate signalling data in bits *a* and *b* of time slots 16 transmitted in accordance with the Recommendation cited in [7]; +- 3) detection of PCM system faults. + +The conversion between the analogue and digital versions of the R2 line Signalling System should be made in accordance with [8]. When the conversion is made in an external equipment, the transmultiplexer should supply the necessary ports. + +For national networks, a method of using the analogue line signalling version on both analogue and digital transmission systems is described in Supplement No. 32. + +## 8 Fault conditions and consequent action + +### 8.1 *Principles of the action to be taken* + +The principles governing the handling of alarms is as follows: The behaviour of a transmultiplexer vis-à-vis a 30-channel PCM multiplex should be the same as that of another 30-channel PCM multiplex. However, the transmultiplexer performs certain functions peculiar to digital multiplexing equipments such as the transmission of the Alarm Indication Signal (AIS). Vis-à-vis a group modulator, it should behave like another group modulator. + +The principles of alarm transfer are described in Supplement No. 32 which also contains particular solution used in national networks. + +### 8.2 *Digital version of R2 signalling system* + +Table 2/G.793 summarizes the fault conditions and the consequent actions. + +### 8.3 *In-band signalling and common channel signalling* + +Table 3/G.793 summarizes the fault conditions and the consequent actions (see Note). + +*Note* - The problem of per channel alarm transfer needs further study. For applications where the TMUX is used in TDMA configuration, Recommendation Q.33 should be considered [11]. + +**TABLE 2/G.793** +**Fault conditions and consequent actions, applicable if Signalling System R2 is used (see Note 1)** + +| Fault conditions | | Prompt maintenance alarm indication generated | Alarm indication transmitted to the remote end | | Consequent actions | | | | +|----------------------|-----------------------------------------------------------------------------------|-----------------------------------------------|------------------------------------------------|--------------------------------------------------|------------------------------------|----------------------------------------------------|------------------------|-----------------------| +| | | | Bit 3
0 to 1 (see Note 2) | Bit 6 time slot 16,
frame 0 to 1 (see Note 2) | Blocking of faulty speech channels | Information to be taken into account in conversion | Transmission of alarms | | +| | | | | | | | Pilot cut-out | AIS sent (see Note 2) | +| PCM alarms | Loss of signal
Error ratio $> 10^{-3}$
Loss of frame alignment (see Note 2) | Yes (see Note 3) | Yes | | Yes
PCM → FDM | $a = b = 1$ | (see Note 4) | | +| | Loss of multiframe alignment (see Note 2) | Yes (see Note 3) | | Yes | | $a = b = 1$ | (see Note 4) | | +| | Reception of bit 3, time slot 0 or bit 6, time slot 16, frame 0 (see Note 2) | | | | | $a = b = 1$ | | | +| FDM alarms | Absence of the received group pilot (see Note 5) | Yes | | | Yes
FDM → PCM | Absence of pilot | | Yes (see Note 6) | +| | Absence of the received supergroup pilot (see Note 7) | Yes | | | | Absence of pilot | | | +| | Pilot level deviation alarm (Note 8) | Yes | | | | | | | +| System alarms | Failure of power supply | Yes | | | | | Yes, if possible | Yes, if possible | +| | System failure (see Note 9) | Yes | | | | | Yes | Yes (see Note 6) | +| | Synchronization failure (see Note 10) | Yes | | | | | | | + +*Note 1* - A *Yes* in the table signifies that an action should be taken as a consequence of the relevant fault conditions. An open space in the table signifies that the relevant action should *not* be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present, the relevant action should be taken if, for at least one of the conditions, a *Yes* is defined in relation to this action. + +*Note 2* - The fault conditions "Loss of signal at 2 Mbit/s", "Error ratio $> 10^{-3}$ ", "Loss of frame alignment", "Loss of multiframe alignment", "Reception of bit 3, time slot 0", "Reception of bit 6, time slot 16, frame 0" and the consequent action "Bit 3, time slot 0 to 1", "Bit 6, time slot 16, frame 0 to 1", "Bit 6, time slot 16, frame 0 to 1" and "AIS sent" are defined in Recommendation G.732. + +*Note 3* - The 60-channel transmultiplexer should be able to detect the alarm indication signal (AIS) on incoming streams at 2048 kbit/s. When AIS is detected, the prompt maintenance indication associated with the loss of frame alignment, with an excessive error rate or with the loss of multiframe alignment should be blocked. + +*Note 4* - This action is not necessary when the digital version of Signalling System R2 is used, but may be useful with other applications. + +*Note 5* - The definition of absence of group pilot used for the operation of the interruption control system is given in the Recommendation cited in [9]. The supergroup pilot can also be used. + +*Note 6* - The AIS is sent only if the 30 channels of a single PCM stream are in the alarm condition. + +*Note 7* - Detection of "absence of supergroup pilot" is not obligatory. If the supergroup pilot is not sent, this alarm function can be performed by supervision of the 5 group pilots. + +*Note 8* - The concept of pilot level deviation alarm corresponds to a variation on the level of the pilot from its nominal value by more than $\pm 4$ dB, as stated in [10]. This applies only to transmultiplexers with automatic internal level regulation. + +*Note 9* - The "system" fault condition corresponds to a fault on the transmultiplexer detected by the transmultiplexers supervision system, when it has one. + +*Note 10* - The "synchronization" fault is that mentioned in § 6 of Recommendation G.793. When the transmultiplexer is synchronized with an external signal or with one of two incoming PCM streams at 2048 kbit/s, the transmultiplexer should transmit an alarm signal in the event of synchronization loss. + +TABLE 3/G.793 + +#### **Fault conditions and consequent actions, applicable for in-band signalling and common channel signalling (Note 1)** + +| Fault conditions | | Consequent actions | | | | | +|----------------------|-----------------------------------------------------------------------------------|-----------------------------------------------|------------------------------------------------|------------------------------------|------------------------|-----------------------| +| | | Prompt maintenance alarm indication generated | Alarm indication transmitted to the remote end | Blocking of faulty speech channels | Transmission of alarms | | +| | | | Bit 3, time slot 0 to 1 (see Note 2) | | Pilot cut-out | AIS sent (see Note 2) | +| PCM alarms | Loss of signal
Error ratio $> 10^{-3}$
Loss of frame alignment (see Note 2) | Yes (see Note 3) | Yes | Yes
PCM $\rightarrow$ FDM | Yes (see Note 4) | | +| IDM alarms | Absence of the received supergroup pilot (see Note 5) | Yes | | Yes
FDM $\rightarrow$ PCM | | Yes (see Note 6) | +| | Absence of the received group pilot (see Note 7) | Yes | | | | | +| | Pilot level deviation alarm (see Note 8) | Yes | | | | | +| System alarms | Failure of power supply | Yes | | | Yes, if possible | Yes, if possible | +| | System failure (see Note 9) | Yes | | | Yes, 5 groups | Yes (see Note 7) | +| | Synchronization failure (see Note 10) | Yes | | | | | + +*Note 1* - A *Yes* in the table signifies that an action should be taken as a consequence of the relevant fault conditions. An open space in the table signifies that the relevant action should *not* be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present, the relevant action should be taken if, for at least one of the conditions, a *Yes* is defined in relation to this action. + +*Note 2* - The fault conditions "Loss of signal at 2 Mbit/s", "Error ratio $> 10^{-3}$ ", "Loss of frame alignment", and the consequent action "Bit 3, time slot 0 to 1", and "AIS sent" are defined in Recommendation G.732. + +*Note 3* - The 60-channel transmultiplexer should be able to detect the alarm indication signal (AIS) on incoming streams at 2048 kbit/s. When AIS is detected, the prompt maintenance indication associated with the loss of frame alignment, with an excessive error rate should be blocked. + +*Note 4* - In the PCM $\rightarrow$ FDM direction, the pilots must be cut for the 3 groups associated with a PCM multiplex signal in the event of the detection of a fault on the PCM multiplex signal stream. When a single PCM multiplex signal is faulty, this involves the blocking of 6 channels which are not faulty. + +*Note 5* - The definition of absence of group pilot used for the operation of the interruption control system is given in the Recommendation cited in [9]. The supergroup pilot can also be used. + +*Note 6* - The AIS is sent only if the 30 channels of a single PCM stream are in the alarm condition. + +*Note 7* - Detection of "absence of supergroup pilot" is not obligatory. If the supergroup pilot is not sent, this alarm function can be performed by supervision of the 5 group pilots. + +*Note 8* - The concept of pilot level deviation alarm corresponds to a variation on the level of the pilot from its nominal value by more than $\pm 4$ dB as stated in the Recommendation cited in [10]. This applies only to transmultiplexers with automatic internal level regulation. + +*Note 9* - The "system" fault condition corresponds to a fault on the transmultiplexer detected by the transmultiplexer's supervision system, when it has one. + +*Note 10* - The "synchronization" fault is that mentioned in § 6 of the Recommendation G.793. When the transmultiplexer is synchronized with an external signal or with one of the two incoming PCM streams at 2048 kbit/s, the transmultiplexer should transmit an alarm signal in the event of synchronization loss. + +## References + +- [1] CCITT Recommendation *Recommendations concerning translating equipments*, Vol. III, Rec. G.233. +- [2] CCITT Recommendation *Pilots on groups, supergroups, etc.*, Vol. III, Rec. G.241. +- [3] CCITT Recommendation *Interruption control*, Vol. VI, Rec. Q.416. +- [4] CCITT Recommendation *Recommendations relating to the accuracy of carrier frequencies*, Vol. III, Rec. G.225. +- [5] CCITT Recommendation *Signal receiver*, Vol. VI, Rec. Q.415. +- [6] CCITT Recommendation *Signal sender*, Vol. VI, Rec. Q.414. +- [7] CCITT Recommendation *Digital line signalling code*, Vol. VI, Rec. Q.421, § 3.1.2. +- [8] CCITT Recommendation *Conversion between analogue and digital versions of system R2 line signalling*, Vol. VI, Rec. Q.430. +- [9] CCITT Recommendation *Interruption control*, Vol. VI, Rec. Q.416, §§ 2.4.3.2 and 2.4.3.3. +- [10] CCITT Recommendation *Pilots on groups, supergroups, etc.*, Vol. III, Rec. G.241, § 1. +- [11] CCITT Recommendation *Protection against the effect of faulty transmission on groups of circuits*, Vol. VI, Rec. Q.33. \ No newline at end of file diff --git a/marked/G/T-REC-G.795-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.795-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..64672153e39c851d9e16fdbc702e526c7ba7e8a7 --- /dev/null +++ b/marked/G/T-REC-G.795-198811-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:454a9958ffe168868cb7d38a0eb24418dafe31a7a4245c992089b2316ac37d3e +size 7392 diff --git a/marked/G/T-REC-G.8013-202306-I_PDF-E/raw.md b/marked/G/T-REC-G.8013-202306-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..62cce7d4f55cda9f9e44dc64253c429aa707de13 --- /dev/null +++ b/marked/G/T-REC-G.8013-202306-I_PDF-E/raw.md @@ -0,0 +1,3795 @@ + + +# Recommendation **ITU-T G.8013/Y.1731 (06/2023)** + +SERIES G: Transmission systems and media, digital systems and networks + +Packet over Transport aspects – Ethernet over Transport aspects + +SERIES Y: Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities + +Internet protocol aspects – Operation, administration and maintenance + +--- + +## **Operation, administration and maintenance (OAM) functions and mechanisms for Ethernet-based networks** + +![ITU logo](6ed175c791b5e156d9c98a8dbcc3318c_img.jpg) + +The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with white lines representing latitude and longitude, and the letters 'ITU' in a bold, blue, sans-serif font superimposed on the globe. + +ITU logo + +## ITU-T G-SERIES RECOMMENDATIONS **Transmission systems and media, digital systems and networks** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100-G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200-G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300-G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400-G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450-G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600-G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700-G.799 | +| DIGITAL NETWORKS | G.800-G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900-G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000-G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000-G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000-G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000-G.8999 | +| Ethernet over Transport aspects | G.8000-G.8099 | +| MPLS over Transport aspects | G.8100-G.8199 | +| Synchronization, quality and availability targets | G.8200-G.8299 | +| Mobile network transport aspects | G.8300-G.8399 | +| Service Management | G.8600-G.8699 | +| ACCESS NETWORKS | G.9000-G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.8013/Y.1731 + +# Operation, administration and maintenance (OAM) functions and mechanisms for Ethernet-based networks + +## Summary + +Recommendation ITU-T G.8013/Y.1731 provides mechanisms for user-plane OAM functionality in Ethernet networks according to the requirements and principles given in Recommendation ITU-T Y.1730. This Recommendation is designed specifically to support point-to-point connections and multipoint connectivity in the ETH layer as identified in Recommendation ITU-T G.8010/Y.1306. + +The OAM mechanisms defined in this Recommendation offer capabilities to operate and maintain network and service aspects of the ETH layer. + +## History \* + +| Edition | Recommendation | Approval | Study Group | Unique ID | +|---------|-----------------------------------|------------|-------------|--------------------| +| 1.0 | ITU-T Y.1731 | 2006-05-22 | 13 | 11.1002/1000/7192 | +| 2.0 | ITU-T Y.1731 | 2008-02-29 | 13 | 11.1002/1000/9347 | +| 2.1 | ITU-T Y.1731 (2008) Amd. 1 | 2010-07-29 | 15 | 11.1002/1000/10925 | +| 3.0 | ITU-T G.8013/Y.1731 | 2011-07-22 | 15 | 11.1002/1000/11136 | +| 3.1 | ITU-T G.8013/Y.1731 (2011) Cor. 1 | 2011-10-29 | 15 | 11.1002/1000/11418 | +| 3.2 | ITU-T G.8013/Y.1731 (2011) Amd. 1 | 2012-05-07 | 15 | 11.1002/1000/11511 | +| 4.0 | ITU-T G.8013/Y.1731 | 2013-11-06 | 15 | 11.1002/1000/12029 | +| 4.1 | ITU-T G.8013/Y.1731 (2013) Amd. 1 | 2015-02-22 | 15 | 11.1002/1000/12381 | +| 5.0 | ITU-T G.8013/Y.1731 | 2015-08-13 | 15 | 11.1002/1000/12552 | +| 5.1 | ITU-T G.8013/Y.1731 (2015) Cor. 1 | 2018-03-16 | 15 | 11.1002/1000/13542 | +| 5.2 | ITU-T G.8013/Y.1731 (2015) Amd. 1 | 2018-11-29 | 15 | 11.1002/1000/13757 | +| 5.3 | ITU-T G.8013/Y.1731 (2015) Cor. 2 | 2019-08-29 | 15 | 11.1002/1000/14007 | +| 6.0 | ITU-T G.8013/Y.1731 | 2023-06-13 | 15 | 11.1002/1000/15553 | + +## Keywords + +Ethernet OAM, fault management, IEEE 802.1Q, OAM frame format, OAM mechanism, performance monitoring. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at . + +© ITU 2023 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +###### Page + +| | | | +|------|-----------------------------------------------------------|----| +| 1 | Scope..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions ..... | 2 | +| 3.1 | Terms defined elsewhere ..... | 2 | +| 3.2 | Terms defined in this Recommendation..... | 3 | +| 4 | Abbreviations and acronyms ..... | 4 | +| 5 | Conventions ..... | 7 | +| 5.1 | ME group (MEG) ..... | 7 | +| 5.2 | Traffic conditioning point (TrCP) ..... | 7 | +| 5.3 | MEG level ..... | 7 | +| 5.4 | OAM transparency ..... | 8 | +| 5.5 | Representation of octets ..... | 8 | +| 6 | OAM relationships..... | 8 | +| 6.1 | MEs, MEPs, MIPs and TrCPs relationship ..... | 8 | +| 6.2 | MEs, MEGs and MEG level relationship..... | 9 | +| 6.3 | MEPs and MIPs configuration ..... | 10 | +| 7 | OAM functions for fault management..... | 10 | +| 7.1 | Ethernet continuity check (ETH-CC)..... | 10 | +| 7.2 | Ethernet loopback (ETH-LB)..... | 12 | +| 7.3 | Ethernet link trace (ETH-LT)..... | 15 | +| 7.4 | Ethernet alarm indication signal (ETH-AIS)..... | 18 | +| 7.5 | Ethernet remote defect indication (ETH-RDI)..... | 19 | +| 7.6 | Ethernet locked signal (ETH-LCK)..... | 20 | +| 7.7 | Ethernet test signal (ETH-Test)..... | 21 | +| 7.8 | Ethernet automatic protection switching (ETH-APS)..... | 23 | +| 7.9 | Ethernet management communication channel (ETH-MCC) ..... | 23 | +| 7.10 | Ethernet experimental OAM (ETH-EXP) ..... | 23 | +| 7.11 | Ethernet vendor-specific OAM (ETH-VSP) ..... | 24 | +| 7.12 | Ethernet client signal fail (ETH-CSF)..... | 24 | +| 7.13 | Ethernet bandwidth notification (ETH-BN)..... | 25 | +| 7.14 | Ethernet expected defect (ETH-ED) ..... | 27 | +| 8 | OAM functions for performance monitoring ..... | 28 | +| 8.1 | Ethernet frame loss measurement (ETH-LM)..... | 29 | +| 8.2 | Ethernet frame delay measurement (ETH-DM)..... | 32 | +| 8.3 | Throughput measurement..... | 35 | +| 8.4 | Ethernet synthetic loss measurement (ETH-SLM)..... | 35 | +| 9 | OAM PDU types..... | 39 | +| 9.1 | Common OAM information elements..... | 39 | + +| | | Page | +|-------|---------------------------------------|------| +| 9.2 | CCM PDU ..... | 41 | +| 9.3 | LBM PDU ..... | 43 | +| 9.4 | LBR PDU ..... | 45 | +| 9.5 | LTM PDU ..... | 46 | +| 9.6 | LTR PDU ..... | 48 | +| 9.7 | AIS PDU ..... | 50 | +| 9.8 | LCK PDU ..... | 51 | +| 9.9 | TST PDU ..... | 52 | +| 9.10 | APS PDU ..... | 52 | +| 9.11 | MCC PDU ..... | 53 | +| 9.12 | LMM PDU ..... | 54 | +| 9.13 | LMR PDU ..... | 55 | +| 9.14 | IDM PDU ..... | 56 | +| 9.15 | DMM PDU ..... | 57 | +| 9.16 | DMR PDU ..... | 58 | +| 9.17 | EXM PDU ..... | 59 | +| 9.18 | EXR PDU ..... | 60 | +| 9.19 | VSM PDU ..... | 61 | +| 9.20 | VSR PDU ..... | 62 | +| 9.21 | CSF PDU ..... | 63 | +| 9.22 | SLM PDU ..... | 64 | +| 9.23 | SLR PDU ..... | 65 | +| 9.24 | 1SL PDU ..... | 66 | +| 9.25 | BNM PDU ..... | 67 | +| 9.26 | EDM PDU ..... | 69 | +| 10 | OAM frame addresses ..... | 69 | +| 10.1 | Multicast destination addresses ..... | 70 | +| 10.2 | CCM ..... | 71 | +| 10.3 | LBM ..... | 71 | +| 10.4 | LBR ..... | 71 | +| 10.5 | LTM ..... | 71 | +| 10.6 | LTR ..... | 71 | +| 10.7 | AIS ..... | 71 | +| 10.8 | LCK ..... | 71 | +| 10.9 | TST ..... | 71 | +| 10.10 | APS ..... | 72 | +| 10.11 | MCC ..... | 72 | +| 10.12 | LMM ..... | 72 | +| 10.13 | LMR ..... | 72 | +| 10.14 | IDM ..... | 72 | + +| | Page | +|-------------------------------------------------------------------------------------------|------| +| 10.15 DMM ..... | 72 | +| 10.16 DMR ..... | 72 | +| 10.17 EXM ..... | 72 | +| 10.18 EXR ..... | 72 | +| 10.19 VSM ..... | 72 | +| 10.20 VSR ..... | 72 | +| 10.21 CSF ..... | 72 | +| 10.22 SLM ..... | 72 | +| 10.23 SLR ..... | 73 | +| 10.24 1SL ..... | 73 | +| 10.25 BNM ..... | 73 | +| 10.26 EDM ..... | 73 | +| 11 OAM PDU validation and versioning ..... | 73 | +| 11.1 OAM PDU transmission ..... | 73 | +| 11.2 OAM PDU validation in reception ..... | 74 | +| 11.3 OAM PDU reception after validation ..... | 75 | +| Annex A – MEG ID format ..... | 76 | +| A.1 ICC-based MEG_ID format ..... | 76 | +| A.2 Global MEG ID format based on CC and ICC ..... | 77 | +| Annex B – Ethernet link trace (ETH-LT) of ITU-T Y.1731 interoperability considerations .. | 79 | +| B.1 Ethernet link trace (ETH-LT) as specified in ITU-T Y.1731 ..... | 79 | +| B.2 Interworking with ITU-T Y.1731 ..... | 79 | +| Appendix I – Ethernet network scenarios ..... | 81 | +| I.1 Shared MEG levels example ..... | 81 | +| I.2 Independent MEG levels example ..... | 82 | +| Appendix II – Frame loss measurement ..... | 83 | +| II.1 Simplified calculation for frame loss ..... | 84 | +| II.2 Frame counter wrapping periodicity ..... | 85 | +| Appendix III – Network OAM interworking ..... | 86 | +| Appendix IV – Mismerge detection limitation ..... | 87 | +| Appendix V – Terminology alignment with IEEE 802.1Q ..... | 88 | +| Appendix VI – Examples showing accuracy for ETH-SLM measurement ..... | 89 | +| Appendix VII – ETH-LM and link aggregation ..... | 90 | +| Bibliography ..... | 92 | + +# **Introduction** + +Recommendation ITU-T G.8013/Y.1731 was prepared in cooperation with the now completed IEEE 802.1ag Connectivity Fault Management project. This Recommendation includes material in full alignment with the published IEEE standard and includes appropriate normative references to this and other IEEE standards. Moreover, ITU-T has undertaken further detailed work on the implementation details (i.e., the specification of the equipment functions). + +# Recommendation ITU-T G.8013/Y.1731 + +# Operation, administration and maintenance (OAM) functions and mechanisms for Ethernet-based networks + +# 1 Scope + +This Recommendation specifies mechanisms required to operate and maintain the network and service aspects of the ETH layer. It also specifies the Ethernet OAM frame formats and syntax and semantics of OAM frame fields. The OAM mechanisms as described in this Recommendation apply to both point-to-point ETH connections and multipoint ETH connectivity including both multipoint-to-multipoint and rooted-multipoint connections. The OAM mechanisms described in this Recommendation are applicable to any environment independently of how the ETH layer is managed (e.g., using network management systems or operational support systems). + +The architectural basis for this Recommendation is the Ethernet specification [ITU-T G.8010] which also accounts for [IEEE 802.1Q] and [IEEE 802.3]. The OAM functions of the server layer networks used by the Ethernet network are not within the scope of this Recommendation. The OAM functions of the layers above the ETH layer are not within the scope of this Recommendation either. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.805] Recommendation ITU-T G.805 (2000), *Generic functional architecture of transport networks*. +- [ITU-T G.806] Recommendation ITU-T G.806 (2012), *Characteristics of transport equipment – Description methodology and generic functionality*. +- [ITU-T G.809] Recommendation ITU-T G.809 (2003), *Functional architecture of connectionless layer networks*. +- [ITU-T G.826] Recommendation ITU-T G.826 (2002), *End-to-end error performance parameters and objectives for international, constant bit-rate digital paths and connections*. +- [ITU-T G.7710] Recommendation ITU-T G.7710/Y.1701 (2020), *Common equipment management function requirements*. +- [ITU-T G.8010] Recommendation ITU-T G.8010/Y.1306 (2004), *Architecture of Ethernet layer networks*. +- [ITU-T G.8021] Recommendation ITU-T G.8021/Y.1341 (2022), *Characteristics of Ethernet transport network equipment functional blocks*. +- [ITU-T G.8031] Recommendation ITU-T G.8031/Y.1342 (2015), *Ethernet linear protection switching*. +- [ITU-T G.8032] Recommendation ITU-T G.8032/Y.1344 (2020), *Ethernet ring protection switching*. + +- [ITU-T G.8113.1] Recommendation ITU-T G.8113.1/Y.1372.1 (2016), *Operations, administration and maintenance mechanism for MPLS-TP in packet transport networks*. +- [ITU-T M.1400] Recommendation ITU-T M.1400 (2015), *Designations for interconnections among operators' networks*. +- [ITU-T O.150] Recommendation ITU-T O.150 (1996), *General requirements for instrumentation for performance measurements on digital transmission equipment*. +- [ITU-T T.50] Recommendation ITU-T T.50 (1992), *International Reference Alphabet (IRA) (Formerly International Alphabet No. 5 or IA5) – Information technology – 7-bit coded character set for information interchange*. +- [ITU-T Y.1563] Recommendation ITU-T Y.1563 (2009), *Ethernet frame transfer and availability performance*. +- [ITU-T Y.1564] Recommendation ITU-T Y.1564 (2011), *Ethernet service activation test methodology*. +- [ITU-T Y.1730] Recommendation ITU-T Y.1730 (2004), *Requirements for OAM functions in Ethernet-based networks and Ethernet services*. +- [ITU-T Y.1731] Recommendation ITU-T Y.1731 (2006), *OAM functions and mechanisms for Ethernet based networks*. +- [IEEE 802] IEEE 802-2014, *IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture*. +- [IEEE 802.1Q] IEEE 802.1Q-2022, *IEEE Standard for Local and metropolitan area networks – Bridges and Bridged Networks*. +- [IEEE 802.3] IEEE 802.3-2022, *IEEE Standard for Ethernet*. +- [IEEE 1588] IEEE 1588-2002, *IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems*. +- [ISO 3166-1] ISO 3166-1 (2013), *Codes for the representation of names of countries and their subdivisions – Part 1: Country codes*. +- [MEF 10.4] MEF 10.4 (2018), *Subscriber Ethernet Service Attributes*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined elsewhere: + +- 3.1.1 adaptation:** [ITU-T G.809]. +- 3.1.2 connection point:** [ITU-T G.805]. +- 3.1.3 defect:** [ITU-T G.806]. +- 3.1.4 failure:** [ITU-T G.806]. +- 3.1.5 flow:** [ITU-T G.809]. +- 3.1.6 flow domain:** [ITU-T G.809]. +- 3.1.7 flow point:** [ITU-T G.809]. +- 3.1.8 flow point pool:** [ITU-T G.809]. + +- 3.1.9 **layer network:** [ITU-T G.809]. +- 3.1.10 **link:** [ITU-T G.805]. +- 3.1.11 **link connection:** [ITU-T G.805]. +- 3.1.12 **network:** [ITU-T G.809]. +- 3.1.13 **organizationally unique identifier:** [IEEE 802]. +- 3.1.14 **port:** [ITU-T G.809]. +- 3.1.15 **reference point:** [ITU-T G.809]. +- 3.1.16 **termination flow point:** [ITU-T G.809]. +- 3.1.17 **transport:** [ITU-T G.809]. +- 3.1.18 **transport entity:** [ITU-T G.809]. + +## 3.2 Terms defined in this Recommendation + +This Recommendation defines the following terms: + +- 3.2.1 **dual-ended:** A type of protocol messaging whereby an initiating MEP sends a request PDU to a receiving peer MEP, which does not send any response. In performance monitoring, the receiving MEP performs measurement calculations. +- 3.2.2 **far-end:** In single-ended or dual-ended messaging, the direction and information relating to a one-way measurement from an initiating MEP to a receiving or responding peer MEP. +- 3.2.3 **initiating MEP:** A MEP initiating measurements by sending request PDUs, and in the case of single-ended messaging, receiving response PDUs. +- 3.2.4 **in-profile:** For frames that belong to the same instance of an Ethernet service and priority, the frames for which priority corresponds to a common value and the network has determined that drop eligibility corresponds to . Procedures to determine drop eligibility for a frame and procedures to convey priority and drop-eligibility on a frame are network and service specific. +- 3.2.5 **in-service:** OAM actions that are carried out while the data traffic is not interrupted, with an expectation that data traffic remains transparent to OAM actions. +- 3.2.6 **maintenance entity (ME):** The entity between two of the flow/connection points in a maintenance entity group. +- 3.2.7 **maintenance entity group (MEG):** A group defined, for the purpose of fragment or connection monitoring, between a set of flow or connection points within a fragment/connection. This set of flow or connection points may be located at the boundary of one administrative domain or a protection domain, or at the boundaries of two adjacent administrative domains. The maintenance entity group consists of one or more maintenance entities. +- 3.2.8 **MEG end point (MEP):** A point marking the end of an ETH MEG that is capable of initiating and terminating OAM frames for fault management and performance monitoring. A MEP does not add a new forwarding identifier to the transit ETH flows. A MEP does not terminate the transit ETH flows, though it can observe these flows (e.g., count frames). +- 3.2.9 **MEG intermediate point (MIP):** An intermediate point in a MEG that is capable of reacting to some OAM frames. A MIP does not initiate OAM frames. A MIP takes no action on the transit ETH flows. +- 3.2.10 **near-end:** In single-ended messaging, the direction and information relating to a one-way measurement from a responding peer MEP to an initiating MEP. + +- 3.2.11 on-demand:** OAM actions that are initiated via manual intervention for a limited time to carry out diagnostics, and can result in singular or periodic OAM actions during the diagnostics time interval. +- 3.2.12 one-way:** A measurement of the performance of frames that is achieved in one direction from an initiating MEP to a peer MEP, or vice versa; i.e., a unidirectional measurement. +- 3.2.13 out-of-service:** OAM actions that are carried out while the data traffic is interrupted. +- 3.2.14 peer MEP:** For a given MEP, all of the other MEPs in the same MEG. +- 3.2.15 proactive:** OAM actions that are carried out continuously to permit proactive reporting of fault or performance results. +- 3.2.16 responding MEP:** In single-ended messaging, a MEP that receives request PDUs from an initiating MEP and transmits corresponding response PDUs. +- 3.2.17 receiving MEP:** In dual-ended messaging, a MEP that receives request PDUs from an initiating MEP, and does not respond to them. +- 3.2.18 server MEP:** A server MEP represents the compound function of the server layer termination function and server/ETH adaptation function, which is used to notify the ETH layer MEPs of conditions of the server layer that may be relevant to these ETH MEPs (e.g., failure or degradation detection by the server layer termination function or server/ETH adaptation function), where the server layer termination function is expected to run OAM mechanisms specific to that server layer. +- 3.2.19 single-ended:** A type of protocol messaging whereby an initiating MEP sends a request PDU to a responding peer MEP, and the peer MEP responds by sending a response PDU that contains the original request data plus any additional data added by the responder. In performance monitoring, the initiating MEP performs measurement calculations. +- 3.2.20 two-way:** A measurement of the performance of frames that is achieved from an initiating MEP to a responding peer MEP, and back to the initiating MEP, i.e., a bidirectional or round-trip measurement. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|-------|------------------------------------| +| IDM | One-way Delay Measurement | +| 1SL | One-way Synthetic Loss measurement | +| AIS | Alarm Indication Signal | +| APS | Automatic Protection Switching | +| BNM | Bandwidth Notification Message | +| C-DCI | Client Defect Clear Indication | +| C-FDI | Client Forward Defect Indication | +| C-LOS | Client Loss Of Signal | +| C-RDI | Client Reverse Defect Indication | +| CCM | Continuity Check Message | +| CoS | Class of Service | +| CSF | Client Signal Fail | +| DA | Destination MAC Address | +| DEI | Drop Eligible Indicator | + +| | | +|----------|-------------------------------------------| +| DMM | Delay Measurement Message | +| DMR | Delay Measurement Reply | +| EDM | Expected Defect Message | +| ETH | Ethernet MAC layer network | +| ETH-AIS | Ethernet Alarm Indication Signal | +| ETH-APS | Ethernet Automatic Protection Switching | +| ETH-BN | Ethernet Bandwidth Notification | +| ETH-CC | Ethernet Continuity Check | +| ETH-CSF | Ethernet Client Signal Fail | +| ETH-DM | Ethernet Delay Measurement | +| ETH-ED | Ethernet Expected Defect | +| ETH-EXP | Ethernet Experimental OAM | +| ETH-LB | Ethernet Loopback | +| ETH-LCK | Ethernet Lock signal | +| ETH-LM | Ethernet Loss Measurement | +| ETH-LT | Ethernet Link Trace | +| ETH-MCC | Ethernet Management Communication Channel | +| ETH-RDI | Ethernet Remote Defect Indication | +| ETH-SLM | Ethernet Synthetic Loss Measurement | +| ETH-Test | Ethernet Test | +| ETH-TFP | Ethernet Termination Flow Point | +| ETH-VSP | Ethernet Vendor-Specific OAM | +| ETY | Ethernet PHY layer network | +| EXM | Experimental OAM Message | +| EXR | Experimental OAM Reply | +| FLR | Frame Loss Ratio | +| FP | Flow Point | +| FPP | Flow Point Pool | +| GNM | Generic Notification Message | +| ICC | ITU Carrier Code | +| LBM | Loopback Message | +| LBR | Loopback Reply | +| LCK | Locked | +| LMM | Loss Measurement Message | +| LMR | Loss Measurement Reply | +| LOC | Loss Of Continuity | +| LSB | Least Significant Bit | + +| | | +|-------|-------------------------------------------| +| LTM | Link Trace Message | +| LTR | Link Trace Reply | +| MAC | Media Access Control | +| MCC | Management Communication Channel | +| ME | Maintenance Entity | +| MEG | ME Group | +| MEL | MEG Level | +| MEP | MEG End Point | +| MIP | MEG Intermediate Point | +| MSB | Most Significant Bit | +| NMS | Network Management System | +| NNI | Network Node Interface | +| OAM | Operation, Administration and Maintenance | +| OUI | Organizationally Unique Identifier | +| PCP | Priority Code Point | +| PDU | Protocol Data Unit | +| PE | Provider Edge | +| PHY | Ethernet Physical layer | +| PRBS | Pseudo-Random Bit Sequence | +| RDI | Remote Defect Indication | +| SA | Source MAC Address | +| SES | Severely Errored Seconds | +| SLM | Synthetic Loss Message | +| SLR | Synthetic Loss Reply | +| TCI | Tag Control Information | +| TFP | Termination Flow Point | +| TLV | Type, Length and Value | +| TrCP | Traffic Conditioning Point | +| TST | Test PDU | +| TTL | Time To Live | +| UMC | Unique MEG ID Code | +| UNI | User-to-Network Interface | +| UNI-C | Customer side of UNI | +| UNI-N | Network side of UNI | +| VLAN | Virtual LAN | +| VSM | Vendor-Specific OAM Message | +| VSR | Vendor-Specific OAM Reply | + +# 5 Conventions + +The diagrammatic conventions for connection-oriented and connectionless layer networks described in this Recommendation are those of [ITU-T G.805], [ITU-T G.809] and [ITU-T G.8010]. + +For the purposes of this Recommendation, the following OAM terms and diagrammatic conventions are also defined. + +## 5.1 ME group (MEG) + +An ME group (MEG) includes different MEs that satisfy the following conditions: + +- All MEs in a MEG exist in one same administrative boundary. +- All MEs in a MEG have the same MEG level (see clause 5.3). +- All MEs in a MEG belong to the same point-to-point ETH connection or multipoint ETH connection. + +For a point-to-point ETH connection, a MEG contains a single ME. + +For a multipoint ETH connection containing $n$ end points, a MEG contains $n \times (n - 1) / 2$ MEs. + +For a rooted-multipoint ETH connection containing $k$ root and $m$ leaf end points, it is possible, but not required, for a MEG to contain MEs between leaf end points; if it does not, the MEG contains $k \times (k - 1) / 2 + k \times m$ MEs. + +## 5.2 Traffic conditioning point (TrCP) + +A traffic conditioning point (TrCP) is an ETH flow point which is capable of an ETH traffic conditioning function, as specified in [ITU-T G.8010]. + +## 5.3 MEG level + +In the case where MEGs are nested, the OAM flow of each MEG has to be clearly identifiable and separable from the OAM flows of the other MEGs. In cases where the OAM flows are not distinguishable by the ETH layer encapsulation itself, the MEG level in the OAM frame distinguishes between the OAM flows of nested MEGs. + +Eight MEG levels are available to accommodate different network deployment scenarios. + +When customer, provider and operator data path flows are not distinguishable based on the means of the ETH layer encapsulations, the eight MEG levels can be shared amongst them to distinguish between OAM frames belonging to nested MEGs of customers, providers and operators. The default MEG level assignment amongst customer, provider and operator roles is: + +- The customer role is assigned three MEG levels: 7, 6 and 5. +- The provider role is assigned two MEG levels: 4 and 3. +- The operator role is assigned three MEG levels: 2, 1 and 0. + +The default MEG level assignment can be changed via a mutual agreement among customer, provider and/or operator roles. + +Though eight MEG levels are available, not all MEG levels may be used. When not all eight MEG levels are used, there is no constraint on the continuity of MEG levels (e.g., MEG levels 7, 5, 2 and 0 may be used). The number of MEG levels used depends on the number of nested MEs for which the OAM flows are not distinguishable based on the means of the ETH layer encapsulation. + +The specific assignment of MEG levels across different roles in specific deployments is outside of the scope of this Recommendation. Refer to [ITU-T G.8010] for some examples. + +## 5.4 OAM transparency + +OAM transparency refers to the ability to allow the transparent carrying of OAM frames belonging to higher-level MEGs across other lower-level MEGs when the MEGs are nested. + +OAM frames belonging to an administrative domain originate and terminate in MEPs present at the boundary of that administrative domain. A MEP prevents OAM frames corresponding to a MEG in the administrative domain, from leaking outside that administrative domain. However, when a MEP is not present or is faulty, the associated OAM frames could leave the administrative domain. + +Similarly, a MEP present at the boundary of an administrative domain protects the administrative domain from OAM frames belonging to other administrative domains. The MEP allows OAM frames from outside administrative domains belonging to higher-level MEs to pass transparently, while it blocks OAM frames from outside administrative domains belonging to same or lower-level MEs. + +The customer role can use any of the eight MEG levels when the MEG levels are not shared with provider and operator roles, as mentioned in clause 5.3. However, if MEG levels are shared with provider and operator roles, the transparency of customer's OAM frames across provider's and/or operator's administrative domains is guaranteed for mutually agreed MEG levels, e.g., default MEG levels 7, 6 and 5. Similarly, the transparency of a provider's OAM frames across an operator's administrative domain when MEG levels are shared is guaranteed for mutually agreed MEG levels, e.g., default MEG levels 4 and 3, while the operator role can use default MEG levels 2, 1, and 0. + +OAM frames can be prevented from leaking by implementing an OAM filtering process in the MEP atomic functions. + +## 5.5 Representation of octets + +In this Recommendation, octets are represented as specified in [IEEE 802.1Q]. + +When consecutive octets are used to represent a binary number, the lower octet number has the most significant value. As an example, if Octet1 and Octet2 in Figure 5.5-1 represent a binary number, Octet1 has the most significant value. + +The bits in an octet are numbered from 1 to 8, where bit 1 is the least significant bit (LSB) and bit 8 is the most significant bit (MSB). + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|---|--------|---|---|---|---|---|---|---|---------|---|---|---|---|---|---|---|---------|---|---|---|---|---|---|---|---------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | Octet1 | | | | | | | | Octet2 | | | | | | | | Octet3 | | | | | | | | Octet4 | | | | | | | | +| 5 | Octet5 | | | | | | | | Octet6 | | | | | | | | Octet7 | | | | | | | | Octet8 | | | | | | | | +| 9 | Octet9 | | | | | | | | Octet10 | | | | | | | | Octet11 | | | | | | | | Octet12 | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +Figure 5.5-1 – Example PDU format + +# 6 OAM relationships + +## 6.1 MEs, MEPs, MIPs and TrCPs relationship + +Appendix I provides different network scenarios to show how MEGs, MEPs and MIPs at different MEG levels can be deployed, and where TrCPs are likely to be placed. + +NOTE – Not all MEGs and corresponding MEPs and MIPs may be used or provided in the example network scenarios in Appendix I. For example, providers may not provide customer MIPs. + +## 6.2 MEs, MEGs and MEG level relationship + +The MEPs associated with an administrative domain operate at an assigned MEG level. Inter-domain MEPs, associated with MEGs between two administrative domains, can operate at a MEG level agreeable between the two administrative domains, so that associated inter-domain OAM flows are prevented from leaking into either administrative domain. The default MEG level for inter-domain OAM flows is 0. + +MEs in Ethernet networks are indicated in Figures 7-1 and 7-2 of [ITU-T G.8010] and Ethernet MEs are defined in clause 9 of [ITU-T Y.1730]. MEs can nest but not overlap. Figure 6.2-1 illustrates an example of MEs associated with a point-to-point connection administrative domain. + +![Diagram illustrating the relationship between MEs and MEGs in a point-to-point connection administrative domain. The diagram shows a 'Service provider Y' (blue box) containing 'Network operator A' and 'Network operator B'. On the left, 'User X' (green box) connects via an 'ETH_TFP' and 'ETH_FP' to an 'ETH_FPP link' at a 'UNI'. This link connects to 'Network operator A' via an 'ETH_FP'. Inside 'Network operator A', there is an 'ETH_FPP link' at an 'NNI'. This link connects to 'Network operator B' via an 'ETH_FP'. Inside 'Network operator B', there is another 'ETH_FPP link' at an 'NNI'. This link connects to 'User X' (green box) via an 'ETH_TFP' and 'ETH_FP' at a 'UNI'. Below the diagram, horizontal double-headed arrows indicate various maintenance entities: 'UNI_C to UNI_C maintenance entity' (spanning the entire path), 'UNI_N to UNI_N maintenance entity' (spanning the path between the two NNIs), 'Intra domain ME' (spanning the path within each network operator), and 'Access link ME' (spanning the path between each User X and the corresponding UNI). The text 'G.8013-Y.1731(15)-Amd.1(18)_F6.2-1' is visible in the bottom right corner.](8307f6b04df072c9332f9987e034272c_img.jpg) + +Diagram illustrating the relationship between MEs and MEGs in a point-to-point connection administrative domain. The diagram shows a 'Service provider Y' (blue box) containing 'Network operator A' and 'Network operator B'. On the left, 'User X' (green box) connects via an 'ETH\_TFP' and 'ETH\_FP' to an 'ETH\_FPP link' at a 'UNI'. This link connects to 'Network operator A' via an 'ETH\_FP'. Inside 'Network operator A', there is an 'ETH\_FPP link' at an 'NNI'. This link connects to 'Network operator B' via an 'ETH\_FP'. Inside 'Network operator B', there is another 'ETH\_FPP link' at an 'NNI'. This link connects to 'User X' (green box) via an 'ETH\_TFP' and 'ETH\_FP' at a 'UNI'. Below the diagram, horizontal double-headed arrows indicate various maintenance entities: 'UNI\_C to UNI\_C maintenance entity' (spanning the entire path), 'UNI\_N to UNI\_N maintenance entity' (spanning the path between the two NNIs), 'Intra domain ME' (spanning the path within each network operator), and 'Access link ME' (spanning the path between each User X and the corresponding UNI). The text 'G.8013-Y.1731(15)-Amd.1(18)\_F6.2-1' is visible in the bottom right corner. + +**Figure 6.2-1 – Example of MEs associated with a point-to-point connection administrative domain shown in Figure 7-1 of [ITU-T G.8010]** + +Table 6-1 highlights possible MEG level assignments for MEGs within the context of customer, provider and operator administrative domains that share the MEG levels, as mapped to [ITU-T G.8010] and [ITU-T Y.1730]. + +**Table 6-1 – Example MEG level assignments for shared MEG levels** + +| ITU-T G.8010 MEG | ITU-T Y.1730 ME | MEG level(s) | +|-------------------|------------------------------------------------------|--------------| +| UNI-C to UNI-C ME | UNI-UNI (Customer) | 7, 6, or 5 | +| UNI-N to UNI-N ME | UNI-UNI (Provider) | 4, or 3 | +| Intra-domain ME | Segment (PE-PE) intra-provider | 4, or 3 | +| Inter-domain ME | Segment (PE-PE) inter-provider (Provider – Provider) | 0 (default) | +| Access link ME | ETY link OAM – UNI (Customer – Provider) | 0 (default) | +| Inter-domain ME | ETY link OAM – NNI (Operator – Operator) | 0 (default) | + +As mentioned in clause 5.3, MEG levels are shared when the OAM flows of nested MEGs of customer, provider and operator cannot be distinguished based on ETH layer encapsulation. However, when OAM flows of nested MEGs of customer, provider and operator can be distinguished based on ETH layer encapsulation, MEG levels are not shared except for inter-domain MEGs (e.g., MEGs between customer and provider, MEGs between provider and operator, MEGs between operators, MEs between providers, etc.). + +Table 6-2 highlights possible MEG level assignments for MEs within the context of customer, provider and operator administrative domains that do not share the MEG levels but require inter-domain MEs. + +**Table 6-2 – Example MEG level assignments for independent MEG levels** + +| ITU-T G.8010 MEG | ITU-T Y.1730 ME | MEG level(s) | +|-------------------|------------------------------------------------------|--------------| +| UNI-C to UNI-C ME | UNI-UNI (Customer) | 7to1 | +| UNI-N to UNI-N ME | UNI-UNI (Provider) | 7to1 | +| Intra-domain ME | Segment (PE-PE) intra-provider | 7to1 | +| Inter-domain ME | Segment (PE-PE) inter-provider (Provider – Provider) | 0 (default) | +| Access link ME | ETY link OAM – UNI (Customer – Provider) | 0 (default) | +| Inter-domain ME | ETY link OAM – NNI (Operator – Operator) | 0 (default) | + +Furthermore, if inter-domain MEs are not required, each customer, provider and operator can use any of the eight MEG levels. However, as already stated in clause 5.3, not all MEG levels may be used. + +## 6.3 MEPs and MIPs configuration + +MEG end points (MEPs) and MEG intermediate points (MIPs) are configured via the management plane and/or control plane. The management plane configurations may be carried out through manual local administration of each device or via network management systems (NMS). + +This configuration is outside the scope of this Recommendation. + +# 7 OAM functions for fault management + +OAM functions for fault management allow detection, verification, localization and notification of different defect conditions. + +## 7.1 Ethernet continuity check (ETH-CC) + +The Ethernet continuity check (ETH-CC) function is used for proactive OAM. It is used to detect loss of continuity (LOC) between any pair of MEPs in a MEG. The ETH-CC function also allows detection of unintended connectivity between two MEGs (mismatch), unintended connectivity within the MEG with an unexpected MEP (unexpected MEP) and other defect conditions (e.g., unexpected MEG level, unexpected period, etc.). The ETH-CC function is applicable for fault management, performance monitoring, or protection switching applications. + +A MEP must always report reception of a frame with unexpected ETH-CC information. ETH-CC transmission (i.e., the transmission of frames with ETH-CC information) may be enabled or disabled in a MEG. When ETH-CC transmission is enabled in a MEG, all MEPs are enabled to periodically transmit frames with ETH-CC information to their peer MEPs in the MEG. The ETH-CC transmission period is the same for all MEPs in the MEG. When a MEP is enabled to generate frames with ETH-CC information, it also expects to receive frames with ETH-CC information from its peer MEPs in the MEG. + +When ETH-CC transmission is disabled in a MEG, all MEPs are disabled from transmitting frames with ETH-CC information. + +The specific configuration information required by each MEP to support the ETH-CC function is as follows: + +- MEG ID – Identifies the MEG to which the MEP belongs. +- MEP ID – MEP's own identity in the MEG. + +- List of peer MEP IDs – List of peer MEPs in the MEG. For a point-to-point MEG with a single ME, the list would consist of a single MEP ID for the peer. +- MEG level – MEG level at which the MEP exists. +- ETH-CC transmission period – This is application dependent. The ETH-CC function has three different applications (for each application, a default transmission period is specified): + - Fault management: default transmission period is 1 s (i.e., transmission rate of 1 frame/second); + - Performance monitoring: default transmission period is 100 ms (i.e., transmission rate of 10 frames/second); + - Protection switching: default transmission period is 3.33 ms (i.e., transmission rate of 300 frames/second). +- Priority – The priority of frames with ETH-CC information. By default, the frame with ETH-CC information is transmitted with the highest priority available to the data traffic. This information is configurable per operation. +- Drop eligibility – Frames with ETH-CC information are always marked as drop ineligible. This information is not necessarily configured. + +A MIP is transparent to the ETH-CC information and therefore does not require any configuration information to support the ETH-CC function. + +When a MEP does not receive ETH-CC information from a peer MEP, in the list of peer MEPs, within an interval of 3.5 times the ETH-CC transmission period, it detects loss of continuity to that peer MEP. The interval corresponds to a loss of three consecutive frames carrying ETH-CC information from the peer MEP. The ETH-CC function also allows detection of other defect conditions as described in clause 7.1.2. + +The OAM PDU used for ETH-CC information is CCM, as described in clause 9.2. Frames which carry the CCM PDU are called CCM frames. + +### 7.1.1 CCM (with ETH-CC information) transmission + +When the ETH-CC function is enabled, a MEP periodically transmits CCM frames as often as the configured transmission period. The transmission period can be one of the following seven values: + +- 3.33 ms: default transmission period for protection switching application (transmission rate of 300 frames/second); +- 10 ms: (transmission rate of 100 frames/second); +- 100 ms: default transmission period for performance monitoring application (transmission rate of 10 frames/second); +- 1 s: default transmission period for fault management application (transmission rate of 1 frame/second); +- 10 s: (transmission rate of 6 frames/minute); +- 1 min: (transmission rate of 1 frame/minute); +- 10 min: (transmission rate of 6 frames/hour); + +NOTE – Even though seven different values are specified for the transmission period, the default values are recommended based on the application area for which the ETH-CC function is being used. When a transmission period other than the default value for an application area is used, the behaviour of the intended application is not guaranteed. + +The Period field in a CCM PDU is transmitted with a value for the transmission period configured at the transmitting MEP, so that a receiving MEP can detect an unexpected period, if the transmission period is not the same across the transmitting and receiving MEPs. + +### 7.1.2 CCM (with ETH-CC information) reception + +When a MEP receives a CCM frame, it examines it to ensure that its MEG ID matches the configured MEG ID in the receiving MEP, and that the MEP ID in the CCM frame is one from the configured list of peer MEP IDs. The information in the CCM frame is catalogued in the receiving MEP. + +CCM frames allow the detection of different defect conditions, which include: + +- If no CCM frames from a peer MEP are received within the interval equal to 3.5 times, the receiving MEP's CCM transmission period, loss of continuity with peer MEP is detected. +- If a CCM frame with a MEG level lower than the receiving MEP's MEG level is received, unexpected MEG level is detected. +- If a CCM frame with the same MEG level but a MEG ID different than the receiving MEP's own MEG ID is received, mismerge is detected. +- If a CCM frame with the same MEG level and a correct MEG ID but with an incorrect MEP ID, including the receiving MEP's own MEP ID, is received, unexpected MEP is detected. +- If a CCM frame is received with a correct MEG level, a correct MEG ID, a correct MEP ID, but with a Period field value different from the receiving MEP's own CCM transmission period, unexpected period is detected. + +A receiving MEP must notify the equipment fault management process when it detects the above defect conditions. + +## 7.2 Ethernet loopback (ETH-LB) + +The Ethernet loopback (ETH-LB) function is used to verify the connectivity of a MEP with a MIP or peer MEP(s). There are two ETH-LB types: + +- Unicast ETH-LB. +- Multicast ETH-LB. + +### 7.2.1 Unicast ETH-LB + +Unicast ETH-LB is an on-demand OAM function that can be used for the following applications: + +- To verify bidirectional connectivity of a MEP with a MIP or a peer MEP; +- To perform a bidirectional in-service or out-of-service diagnostics test between a pair of peer MEPs. This includes verifying bandwidth throughput, detecting bit errors, etc. + +Frames with unicast ETH-LB information can be transmitted in several ways for different on-demand command types, e.g., single transmission, repetitive transmission, etc. The specific on-demand command types are outside the scope of this Recommendation. + +When used to verify bidirectional connectivity, a MEP sends a unicast frame with ETH-LB request information and expects to receive a unicast frame with ETH-LB reply information from a MIP or peer MEP within a specified period of time. The MIP or peer MEP is identified by its MAC address. This MAC address is encoded in the DA of the unicast request frame. If the MEP does not receive the unicast frame with ETH-LB reply information within the specified period of time, loss of connectivity with the MIP or peer MEP can be inferred. Unicast ETH-LB can also be used to test the bidirectional connectivity with different frame sizes between a MEP and a MIP or peer MEP. + +When used for performing bidirectional diagnostics tests, a MEP sends unicast frames with ETH-LB request information to a peer MEP. This ETH-LB request information includes test patterns. When out-of-service diagnostic tests are performed, data traffic is not delivered on either side of the diagnosed ME. Instead, the MEPs are configured to send frames with ETH-LCK information, as described in clause 7.6, for the immediate client MEG level on either side of the ME. + +NOTE 1 – Unicast ETH-LB can be used to perform only one of the two applications at any time. It must finish the pending on-demand command related to one application (either connectivity verification or diagnostic test) before it can act on a new on-demand command for the other application. + +NOTE 2 – The maximum rate at which frames with unicast ETH-LB information can be sent without adversely impacting the data traffic for in-service bidirectional connectivity verification or in-service bidirectional diagnostic tests is outside the scope of this Recommendation. It may be mutually agreed between the user of unicast ETH-LB and the user of the service. + +Specific configuration information required by a MEP to support unicast ETH-LB is as follows: + +- MEG level – MEG level at which the MEP exists. +- Unicast MAC address of remote MIP or MEP to which ETH-LB is intended. This information is configurable per operation. +- Data – Optional element whose length and contents are configurable at the MEP. The contents can be a test pattern and an optional checksum. Examples of test patterns include pseudo-random bit sequence (PRBS) ( $2^{31}-1$ ) as specified in clause 5.8 of [ITU-T O.150], all '0' pattern, etc. For bidirectional diagnostic test applications, configuration is required for a test signal generator and a test signal detector associated with the MEP. +- Priority – The priority of frames with unicast ETH-LB information. +- Drop eligibility – The eligibility of frames with unicast ETH-LB information to be discarded when congestion conditions are encountered. + +NOTE 3 – Additional configuration information elements may be needed for repetitive transmission, e.g., repetition rate, total interval of repetition, etc. These additional configuration information elements are outside the scope of this Recommendation. + +A remote MIP or MEP, upon receiving the unicast frame with ETH-LB request information which is addressed to the MIP or MEP, responds with a unicast frame with ETH-LB reply information. + +Specific configuration information required by a MIP to support unicast ETH-LB is as follows: + +- MEG level – MEG level at which the MIP exists. + +The OAM PDU used for unicast ETH-LB request information is LBM, as described in clause 9.3. The OAM PDU used for unicast ETH-LB reply information is LBR, as described in clause 9.4. Unicast frames carrying the LBM PDU are called unicast LBM frames. Unicast frames carrying the LBR PDU are called unicast LBR frames. + +#### 7.2.1.1 Unicast LBM transmission + +Unicast LBM frames are transmitted by a MEP on an on-demand basis. + +When used for bidirectional connectivity verification, a MEP transmits a unicast LBM frame addressed to a MIP or peer MEP with a specific transaction ID inserted in the Transaction ID/Sequence Number field. After unicast LBM frame transmission, a MEP expects to receive a unicast LBR frame within 5 seconds. The transmitted transaction ID is therefore retained by the MEP for at least 5 seconds after the unicast LBM frame is transmitted. A different transaction ID must be used for every unicast LBM frame and no transaction ID from the same MEP may be repeated within one minute. + +A MEP can optionally use a Data TLV or Test TLV. When configured for checking the successful transmission of different frame sizes, the MEP uses a Data TLV. However, when used for diagnostic tests, a MEP transmits a unicast LBM frame addressed to the peer MEP with a test TLV. The test TLV is used to carry the test pattern generated by a test signal generator associated with the MEP. When the MEP is configured for an out-of-service diagnostic test, the MEP also generates LCK frames, as described in clause 7.6, at the client MEG level. + +#### 7.2.1.2 Unicast LBM reception and LBR transmission + +Whenever a valid unicast LBM frame is received by a MIP or MEP, an LBR frame is generated and transmitted to the initiating MEP. A unicast LBM frame with a valid MEG level and a destination MAC address equal to the MAC address of the responding MIP or MEP is considered to be a valid unicast LBM frame. Every field in the unicast LBM frame is copied to the LBR frame with the following exceptions: + +- The source and destination MAC addresses are swapped. +- The OpCode field is changed from LBM to LBR. + +Furthermore, when a responding MEP is configured for an out-of-service diagnostic test, it also generates LCK frames, as described in clause 7.6, at the client MEG level. + +#### 7.2.1.3 LBR reception + +When a MEP configured for connectivity verification receives an LBR frame addressed to it with the same MEG level as its own MEG level, with an expected transaction ID, and within 5 seconds after transmitting the unicast LBM frame, the LBR frame is valid. Otherwise, the LBR frame addressed to it is invalid and is discarded. + +When a MEP configured for a diagnostics test receives an LBR frame addressed to it with the same MEG level as its own MEG level, the LBR frame is valid. The test signal receiver associated with the MEP may also validate the received sequence number against expected sequence numbers. + +If a MIP receives an LBR frame addressed to it, such an LBR frame is invalid and the MIP should discard it. + +### 7.2.2 Multicast ETH-LB + +The multicast ETH-LB function is used to verify bidirectional connectivity of a MEP with its peer MEPs. Multicast ETH-LB is an on-demand OAM function. When a multicast ETH-LB function is invoked on a MEP, the MEP returns to the initiator of multicast ETH-LB a list of its peer MEPs with which the bidirectional connectivity is detected. + +When multicast ETH-LB is invoked on a MEP, a multicast frame with ETH-LB request information is sent from a MEP to its peer MEPs. The MEP expects to receive a unicast frame with ETH-LB reply information from its peer MEPs within a specified period of time. Upon reception of a multicast frame with ETH-LB request information, the receiving MEPs validate the multicast frame with ETH-LB request information and transmit a unicast frame with ETH-LB reply information after a randomized delay in the range of 0 to 1 second. + +Specific configuration information required by each MEP to support multicast ETH-LB is as follows: + +- MEG level – MEG level at which the MEP exists. +- Priority – The priority of multicast frames with ETH-LB request information. This information is configurable per operation. +- Drop eligibility – Multicast frames with ETH-LB request information are always marked as drop ineligible. This information is not necessarily configured. + +A MIP is transparent to the multicast frames with ETH-LB request information and therefore does not require any information to support multicast ETH-LB. + +The OAM PDU used for multicast ETH-LB request information is LBM, as described in clause 9.3. The OAM PDU used for ETH-LB reply is LBR, as described in clause 9.4. Multicast frames carrying the LBM PDU are called multicast LBM frames. + +#### 7.2.2.1 Multicast LBM transmission + +Multicast LBM frames are transmitted by a MEP on an on-demand basis. After transmitting the multicast LBM frame with a specific transaction ID, the MEP expects to receive LBR frames within 5 seconds. The transmitted transaction ID is therefore retained for at least 5 seconds after the multicast LBM frame has been transmitted. A different transaction ID must be used for every multicast LBM frame, and no transaction ID from the same MEP may be repeated within one minute. + +#### 7.2.2.2 Multicast LBM reception and LBR transmission + +Whenever a valid multicast LBM frame is received by a MEP, an LBR frame is generated and transmitted to the initiating MEP after a randomized delay in the range of 0 to 1 second. The validity of the multicast LBM frame is determined based on the correct MEG level. + +Every field in the multicast LBM frame is copied to the LBR frame with the following exceptions: + +- The source MAC address in the LBR frame is the unicast MAC address of the responding MEP. The destination MAC address in the LBR frame is copied from the source MAC address of the multicast LBM frame which should be a unicast address. +- The OpCode field is changed from LBM to LBR. + +#### 7.2.2.3 LBR reception + +When an LBR frame is received by a MEP with an expected transaction ID and within 5 seconds of transmitting the multicast LBM frame, the LBR frame is valid. If a MEP receives an LBR frame with a transaction ID that is not in the list of transmitted transaction IDs maintained by the MEP, the LBR frame is invalid and is discarded. + +If a MIP receives an LBR frame addressed to it, such an LBR frame is invalid and the MIP should discard it. + +## 7.3 Ethernet link trace (ETH-LT) + +The Ethernet link trace (ETH-LT) function is an on-demand OAM function that can be used for the following two purposes: + +- Adjacent relation retrieval – The ETH-LT function can be used to retrieve an adjacency relationship between a MEP and a peer MEP or MIP. The result of running ETH-LT function is a sequence of MIPs from the initiating MEP until the target MIP or MEP. Each MIP and/or MEP is identified by its MAC address. +- Fault localization – The ETH-LT function can be used for fault localization. When a fault (e.g., a link and/or a device failure) or a forwarding plane loop occurs, the sequence of MIPs and/or MEP is likely to be different from the expected one. Difference in the sequences provides information about the fault location. + +ETH-LT request information is initiated in a MEP on an on-demand basis. After transmitting a frame with ETH-LT request information, the MEP expects to receive frames with ETH-LT reply information within a specified period of time. Network elements containing MIPs or MEPs and receiving the frame with ETH-LT request information respond selectively with frames containing ETH-LT reply information. + +A network element containing MIP or MEP responds with a frame with ETH-LT reply information upon receiving a valid frame with ETH-LT request information only if: + +- The network element where the MIP or MEP resides is aware of the TargetMAC address in the ETH-LT request information and associates it to a single egress port, where the egress port is not the same as the port on which the frame with ETH-LT request information was received; or +- The TargetMAC address is the same as the MIP's or MEP's own MAC address. + +A network element containing MIPs may also relay the frame with ETH-LT request information, as described in clause 7.3.2. + +The specific configuration information required by a MEP to support the ETH-LT function is as follows: + +- MEG level – MEG level at which the MEP exists. +- Priority – The priority of the frames with ETH-LT request information. This information is configurable per operation. +- Drop eligibility – Frames with ETH-LT information are always marked as drop ineligible. This information is not necessarily configured. +- Target MAC address (usually of MIPs or MEPs of the MEG, but not limited to that) for which ETH-LT is intended. This information is configurable per operation. +- TTL – Allows the receiver to determine if frames with ETH-LT request information can be terminated. TTL is decremented every time frames with ETH-LT request information are relayed. Frames with ETH-LT request information with TTL $\leq 1$ are not relayed. + +The specific configuration information required by a MIP to support the ETH-LT function is as follows: + +- MEG level – MEG level at which the MIP exists. + +The PDU used for ETH-LT request information is LTM, as described in clause 9.5. The PDU used for ETH-LT reply information is LTR, as described in clause 9.6. Frames carrying the LTM PDU are called LTM frames. Frames carrying the LTR PDU are called LTR frames. + +NOTE 1 – As each network element, containing the MIPs or MEP, needs to be aware of the TargetMAC address in the received LTM frame and associates it to a single egress port, a unicast ETH-LB to the TargetMAC address could be performed by a MEP before transmitting the LTM frame so that the MIP or MEP can process the received LTM frames. This would ensure that the network elements along the path to the TargetMAC address would have information about the route to the TargetMAC address if the TargetMAC address is reachable in the same MEG. + +NOTE 2 – During a failure condition the information about the route to the TargetMAC address may age out after a certain time. The ETH-LT function has to be performed before the age out occurs in order to provide information about the route. + +### 7.3.1 LTM transmission + +An LTM frame is transmitted by a MEP on an on-demand basis. If the MEP resides at an ingress port, the LTM frame is forwarded towards the network element's own ETH-LT responder. However, if the MEP resides on an egress port, the LTM frame is transmitted out of that egress port. The LTM frame contains an LTM Egress Identifier TLV which identifies the network element initiating the LTM frame. + +NOTE – In [ITU-T Y.1731], no ETH-LT responder is specified, only MEP and MIP located at ingress and egress ports are specified, and the LTM Egress Identifier TLV is regarded as optional. + +After transmitting the LTM frame with a specific transaction number, the MEP expects to receive LTR frames within 5 seconds. The transaction number of each LTM frame transmitted is therefore retained for at least 5 seconds after the LTM frame is transmitted. A different transaction number must be used for every LTM frame, and no transaction number from the same MEP may be repeated within one minute. + +### 7.3.2 LTM reception and forwarding, and LTR transmission + +If an LTM frame is received by a MEP or MIP, it forwards the LTM frame to the network element's ETH-LT responder, which performs the following validation: + +- Only LTM frames with the same MEG level as the receiving MEP's or MIP's own MEG level are validated. + +- Thereafter, the TTL field value of the LTM frame is checked. If the TTL field value is 0, the LTM frame is discarded (a TTL field value of 0 is an invalid value). +- Thereafter, the LTM frame is checked to see if the LTM Egress Identifier TLV is present. The LTM frame is discarded if it does not contain the LTM Egress Identifier TLV. It is noted that an LTM frame generated by [ITU-T Y.1731] may not contain the LTM Egress Identifier TLV: see Annex B for keeping the compatibility with equipment where the LTM frame TLV may be processed at the MIP or MEP even if the LTM Egress Identifier TLV is absent. + +If the LTM frame is valid, the ETH-LT responder does the following: + +- It determines the destination address for the LTR frame from the OriginMAC address in the received LTM frame. +- If the network element is aware of the TargetMAC address in the LTM frame and associates it with a single egress port, where the egress port is not the same as the ingress port, or the LTM frame terminates at the MIP or MEP (when the TargetMAC address is the MIP's or MEP's own MAC address), an LTR frame is sent backwards to the initiating MEP after a random time interval in the range of 0 to 1 second. +- Furthermore, if the above condition applies and the LTM frame does not terminate at the MIP (when the TargetMAC address is not the same as the MIP's own address, if received by a MIP) and the TTL field in the LTM frame is greater than 1, the LTM frame is forwarded towards the single egress port. All the fields of the relayed LTM frame are the same as the original LTM frame except for TTL which is decremented by 1, the source address which becomes the MIP's own MAC address, and LTM Egress Identifier TLV which identifies the network element relaying the modified LTM frame. It is noted that MIPs supporting [ITU-T Y.1731] may forward the LTM Egress Identifier TLV as it is: see Annex B for keeping the compatibility. +- Furthermore, when the TargetMAC address is not the same as the MEP's own address, if received by a MEP, the LTM frames are always terminated at the MEP and the MEP does not send back the LTR frames. + +The LTR frame contains an LTR Egress Identifier TLV which identifies the source and destination of the LTM that triggered the transmission of this LTR. The LTR Egress Identifier TLV contains the Last Egress Identifier field which identifies the network element that originated or forwarded the LTM frame for which this LTR frame is the response. This field takes the same value as the LTM Egress Identifier TLV of that LTM frame. The LTR Egress Identifier TLV also contains the Next Egress Identifier field which identifies the network element that transmitted this LTR frame, and can relay a modified LTM frame to the next hop. This field takes the same value as the LTM Egress Identifier TLV of the relayed modified LTM frame, if any. If no modified LTM frame is relayed, the FwdYes bit of the Flags field in the LTM frame is clear and the contents of Next Egress Identifier are undefined, and must be ignored by the LTR frame receiver. + +Additionally, if the LTM frame was received by a MIP or MEP at an ingress port, the LTR frame includes a Reply Ingress TLV which describes the MIP or MEP at the ingress port. + +Similarly, if the LTM frame was not received by a MEP at the ingress port, and if the egress port has a MIP or MEP, the LTR frame includes a Reply Egress TLV which describes the MIP or MEP at the egress port. + +It is noted that both included Reply Ingress TLV and Reply Egress TLV are documented as optional in [ITU-T Y.1731] so that they may not be included in the LTR frame of that version: see Annex B for keeping the compatibility. + +### 7.3.3 LTR reception + +When an LTR frame is received by a MEP with an expected transaction number and within 5 seconds of transmitting the LTM frame, the LTR frame is valid. If a MEP receives an LTR frame with a transaction number that is not in the list of transmitted transaction numbers maintained by the MEP, the LTR frame is invalid. + +If a MIP receives an LTR frame addressed to it, such an LTR frame is invalid and the MIP should discard it. + +## 7.4 Ethernet alarm indication signal (ETH-AIS) + +The Ethernet alarm indication signal (ETH-AIS) function is used to suppress alarms following detection of defect conditions at the server (sub) layer. Due to independent restoration capabilities provided within some environments like those based on the spanning tree algorithm, the ETH-AIS function is not expected to be applied in such environments. + +Transmission of frames with ETH-AIS information can be enabled or disabled on a MEP (or on a server MEP). + +Frames with ETH-AIS information can be issued at the client MEG level by a MEP, including a server MEP, upon detecting defect conditions. For example, the defect conditions may include: + +- Signal fail conditions in the case that the ETH-CC function is enabled; +- AIS condition or LCK condition in the case that the ETH-CC function is disabled. + +NOTE – Since a server MEP does not run the ETH-CC function, a server MEP can transmit frames with ETH-AIS information upon detection of any signal fail condition. + +For multipoint ETH connectivity, a MEP cannot determine the specific server (sub) layer entity that has encountered defect conditions upon receiving a frame with ETH-AIS information. More importantly, it cannot determine the associated subset of its peer MEPs for which it should suppress alarms since the received ETH-AIS information does not contain that information. Therefore, upon reception of a frame with ETH-AIS information, the MEP suppresses alarms for all peer MEPs whether there is still connectivity or not. + +However, for a point-to-point ETH connection, a MEP has only a single peer MEP. Therefore, there is no ambiguity regarding the peer MEP for which it should suppress alarms when it receives the ETH-AIS information. + +Only a MEP, including a server MEP, is configured to issue frames with ETH-AIS information. Upon detecting a defect condition the MEP can immediately start transmitting periodic frames with ETH-AIS information at a configured client MEG level. A MEP continues to transmit periodic frames with ETH-AIS information until the defect condition is removed. Upon receiving a frame with ETH-AIS information a MEP detects the AIS condition and suppresses loss of continuity alarms associated with all its peer MEPs. A MEP resumes loss of continuity alarm generation upon detecting loss of continuity defect conditions in the absence of an AIS condition. + +The specific configuration information required by a MEP to support ETH-AIS transmission is as follows: + +- Client MEG level – MEG level at which the most immediate client layer MIPs and MEPs exist. +- ETH-AIS transmission period – The transmission periodicity of frames with ETH-AIS information. +- Priority – The priority of frames with ETH-AIS information. +- Drop eligibility – Frames with ETH-AIS information are always marked as drop ineligible. This information is not necessarily configured. + +Specific configuration information required by a MEP to support ETH-AIS reception is as follows: + +- Local MEG level – MEG level at which the MEP operates. + +A MIP is transparent to frames with ETH-AIS information and therefore does not require any information to support ETH-AIS functionality. + +The PDU used for ETH-AIS information is AIS, as described in clause 9.7. Frames carrying the AIS PDU are called AIS frames. + +### 7.4.1 AIS transmission + +A MEP, upon detecting a defect condition, can transmit AIS frames in a direction opposite to its peer MEP(s). The periodicity of AIS frames transmission is based on the AIS transmission period. An AIS transmission period of 1 second is recommended. The first AIS frame must always be transmitted immediately following the detection of a defect condition. + +The client (sub) layer may consist of multiple MEGs that should be notified to suppress alarms resulting from defect conditions detected by the server (sub) layer MEP. The server (sub) layer MEP, upon detecting the signal fail condition, needs to send AIS frames to each of these client (sub) layer MEGs. In such cases, the first AIS frame for all client (sub) layer MEGs must be transmitted within 1 second of defect condition. + +NOTE – To support the ETH-AIS function across equipment which may be stressed when issuing AIS frames every 1 second potentially across all 4094 VLANs, another AIS transmission period of 1 minute is also supported. An AIS frame communicates the used AIS transmission period via the Period field. + +### 7.4.2 AIS reception + +Upon receiving an AIS frame, a MEP examines it to ensure that its MEG level corresponds to its own MEG level. The Period field indicates the period at which the AIS frames can be expected. Upon receiving an AIS frame, the MEP detects the AIS defect condition. Following the detection of the AIS defect condition, if no AIS frames are received within an interval of 3.5 times the AIS transmission period indicated in the AIS frames received before, the MEP clears the AIS defect condition. + +## 7.5 Ethernet remote defect indication (ETH-RDI) + +The Ethernet remote defect indication (ETH-RDI) function can be used by a MEP to communicate to its peer MEPs that a defect condition has been encountered. The ETH-RDI function is used only when ETH-CC transmission is enabled. + +The ETH-RDI function has the following two applications: + +- Single-ended fault management: The receiving MEP detects an RDI defect condition, which gets correlated with other defect conditions in this MEP and may become a fault cause. The absence of received ETH-RDI information in a single MEP indicates the absence of defects in the entire MEG. +- Contribution to far-end performance monitoring: It reflects that there was a defect condition in the far-end which is used as an input to the performance monitoring process. + +A MEP that is in a defect condition transmits frames with ETH-RDI information. A MEP, upon receiving frames with ETH-RDI information, determines that its peer MEP has encountered a defect condition. However, for multipoint ETH connectivity, a MEP, upon receiving frames with ETH-RDI information, cannot determine the associated subset of its peer MEPs with which the MEP transmitting RDI information encounters defect conditions, as the transmitting MEP itself does not always have that information. + +The specific configuration information required by a MEP to support the ETH-RDI function is as follows: + +- MEG level – MEG level at which the MEP exists. +- ETH-RDI transmission period – Application dependent and configured to be the same as ETH-CC transmission period. +- Priority – The priority of frames with ETH-RDI information. The priority is the same as ETH-CC priority. +- Drop eligibility – Frames with ETH-RDI information are always marked as drop ineligible. This information is not necessarily configured. + +A MIP is transparent to frames with ETH-RDI information and therefore does not require any configuration information to support the ETH-RDI function. + +The PDU used to carry ETH-RDI information is CCM, as described in clause 9.2. + +### 7.5.1 CCM with ETH-RDI transmission + +A MEP, upon detecting a defect condition with its peer MEP, sets the RDI field in the CCM frames for the duration of the defect condition. CCM frames, as described in clause 7.1.1, are transmitted periodically based on the CCM transmission period, when the MEP is enabled for CCM frames transmission. When the defect condition clears, the MEP clears the RDI field in the CCM frames in subsequent transmissions. + +### 7.5.2 CCM with ETH-RDI reception + +Upon receiving a CCM frame, a MEP examines it to ensure that its MEG level corresponds to its configured MEG level and detects RDI condition if the RDI field is set. For a point-to-point ETH connection, a MEP can clear the RDI condition when it receives the first CCM frame from its peer MEP with the RDI field cleared. For multipoint ETH connectivity, a MEP can clear the RDI condition when it receives the CCM frames from its entire list of peer MEP with the RDI field cleared. + +## 7.6 Ethernet locked signal (ETH-LCK) + +The Ethernet locked signal (ETH-LCK) function is used to communicate the administrative locking of a server (sub) layer MEP and consequential interruption of data traffic forwarding towards the MEP expecting this traffic. It allows a MEP receiving frames with ETH-LCK information to differentiate between a defect condition and an administrative locking action at the server (sub) layer MEP. An example of an application that would require administrative locking of a MEP is the out-of-service ETH-Test, as described in clause 7.7. + +A MEP continues to transmit periodic frames with ETH-LCK information at the configured client MEG level until the administrative/diagnostic condition is removed. + +A MEP extracts frames with ETH-LCK information at its own MEG level and detects a LCK condition, which contributes to the signal fail condition of the MEP. The signal fail condition may result in the transmission of AIS frames to its client MEPs. + +Specific configuration information required by a MEP to support the transmission of frames with ETH-LCK information is as follows: + +- Client MEG level – MEG level at which the most immediate client layer MIPs and MEPs exist. +- ETH-LCK transmission period – The transmission periodicity of frames with ETH-LCK information. +- Priority – The priority of frames with ETH-LCK information. +- Drop eligibility – Frames with ETH-LCK information are always marked as drop ineligible. This information is not necessarily configured. + +The specific configuration information required by a MEP to support the reception of frames with ETH-LCK information is as follows: + +- Local MEG level – MEG level at which the MEP operates. + +A MIP is transparent to the frames with ETH-LCK information and therefore does not require any information to support the ETH-LCK function. + +The PDU used for ETH-LCK information is LCK, as described in clause 9.8. Frames carrying the LCK PDU are called LCK frames. + +### 7.6.1 LCK transmission + +A (server) MEP, when administratively locked, transmits LCK frames to each of its client (sub-) layer MEGs as shown in Figure 7.6-1. + +![Diagram illustrating LCK transmission from a server layer MEP to client layer MEGs.](f0a97d0d3818a253c1d2a009966081b1_img.jpg) + +The diagram shows two layers separated by a dashed horizontal line. The top layer is labeled 'Client layer MEG' and contains two boxes labeled 'MEP'. A solid double-headed arrow connects these two MEPs. The bottom layer is labeled 'Server layer MEG' and contains two boxes labeled '(server) MEP'. A solid double-headed arrow connects these two (server) MEPs. From the left (server) MEP, a red dashed line labeled 'LCK' extends upwards into the client layer and branches out to both client layer MEPs. A small text label 'G.8013-Y.1731(11)\_F7.6-1' is located in the bottom right corner of the diagram area. + +Diagram illustrating LCK transmission from a server layer MEP to client layer MEGs. + +**Figure 7.6-1 – Example of LCK transmission** + +The periodicity of LCK frames transmission is based on the LCK transmission period. The LCK transmission period is the same as the AIS transmission period. The first LCK frame must always be transmitted immediately following the administrative/diagnostic action. + +The client (sub) layer may consist of multiple MEGs that should be notified to suppress alarms resulting from intentional maintenance/diagnostic related configuration at the server (sub) layer MEP. The server (sub) layer MEP, upon being administratively locked, needs to send LCK frames to each of its client (sub) layer MEGs. In such cases, the first LCK frame for all client (sub) layer MEGs must be transmitted within 1 second of defect condition. + +### 7.6.2 LCK reception + +Upon receiving an LCK frame, a MEP examines it to ensure that its MEG level corresponds to its configured MEG level. The Period field indicates the periodicity at which the LCK frames can be expected. Upon receiving an LCK frame, the MEP detects an LCK condition. Following detection of an LCK condition, if no LCK frames are received within an interval of 3.5 times the LCK transmission period indicated in the LCK frames received before, the MEP clears the LCK condition. + +## 7.7 Ethernet test signal (ETH-Test) + +The Ethernet test signal (ETH-Test) function is used to perform one-way on-demand in-service or out-of-service diagnostics tests. This includes verifying bandwidth throughput, frame loss, bit errors, etc. + +When configured to perform such tests, a MEP inserts frames with ETH-Test information with specified throughput, frame size and transmission patterns. + +When the out-of-service ETH-Test function is performed, client data traffic is disrupted in the diagnosed entity. The MEP configured for the out-of-service test transmits LCK frames, as described in clause 7.6, for the immediate client ETH (sub) layer. + +When an in-service ETH-Test function is performed, data traffic is not disrupted and the frames with ETH-Test information are transmitted in such a manner that a limited part of the service bandwidth + +is utilized. This rate of transmission for frames with ETH-Test information is pre-determined for in-service ETH-Test function. + +NOTE 1 – The maximum rate at which frames with ETH-Test information can be sent without adversely impacting the data traffic for an in-service ETH-Test-based diagnostics test is outside the scope of this Recommendation. It may be mutually agreed between the user of the ETH-Test function and the user of the service. + +The specific configuration information required by a MEP to support the ETH-Test function is as follows: + +- MEG level – MEG level at which the MEP exists. +- Unicast MAC address of the peer MEP for which the ETH-Test function is intended; this information is configurable per operation. +- Data – Optional element whose length and contents are configurable at the MEP. The contents can be a test pattern and an optional checksum. Examples of test patterns include pseudo-random bit sequence (PRBS) ( $2^{31}-1$ ) as specified in clause 5.8 of [ITU-T O.150], all '0' pattern, etc. At the initiating MEP, configuration is required for a test signal generator which is associated with the MEP. At a receiving MEP, configuration is required for a test signal detector which is associated with the MEP. +- Priority – The priority of frames with ETH-Test information. This information is configurable per operation. +- Drop eligibility – The eligibility of frames with ETH-Test information to be dropped when congestion conditions are encountered. + +NOTE 2 – Additional configuration information elements may be needed, such as the transmission rate of frames with ETH-Test information, the total interval of the ETH-Test-based test, etc. These additional configuration information elements are outside the scope of this Recommendation. + +A MIP is transparent to the frames with ETH-Test information and therefore does not require any configuration information to support the ETH-Test function. + +A MEP inserts frames with ETH-Test information towards a targeted peer MEP. The receiving MEP detects these frames with ETH-Test information and makes the intended measurements. + +The PDU used for ETH-Test information is TST, as described in clause 9.9. Frames carrying the TST PDU are called TST frames. + +### 7.7.1 TST transmission + +A test signal generator associated with a MEP can transmit TST frames as often as the test signal generator configuration. Each TST frame is transmitted with a specific sequence number. A different sequence number must be used for every TST frame, and no sequence number from the same MEP may be repeated within one minute. + +When a MEP is configured for an out-of-service test, the MEP also generates LCK frames for the immediate client MEG level. + +### 7.7.2 TST reception + +When a MEP receives TST frames, it examines them to ensure that the MEG level corresponds to its own configured MEG level. If the receiving MEP is configured for ETH-Test function, the test signal detector associated with the MEP detects bit errors from the pseudo-random bit sequence of the received TST frames and reports such errors. Furthermore, when the receiving MEP is configured for an out-of-service test, it also generates LCK frames for the client MEG level. + +## 7.8 Ethernet automatic protection switching (ETH-APS) + +The Ethernet automatic protection switching (ETH-APS) function is used to control protection switching operations to enhance reliability. The specific details of protection switching operations are outside the scope of this Recommendation. + +The OAM frame type used for ETH-APS is APS frame, as described in clause 9.10. + +Applications of ETH-APS mechanisms are defined in [ITU-T G.8031] and [ITU-T G.8032]. + +## 7.9 Ethernet management communication channel (ETH-MCC) + +The Ethernet management communication channel (ETH-MCC) function provides a management communication channel between a pair of MEPs. The ETH-MCC function can be used to perform remote management. The specific use of the ETH-MCC function with an OUI other than the ITU-T OUI (00-19-A7) is outside the scope of this Recommendation. + +A MEP can send a frame with ETH-MCC information to its peer MEP with remote maintenance request, remote maintenance reply, notification, etc. + +Specific configuration information required by a MEP to support the ETH-MCC function is as follows: + +- MEG level – MEG level at which the MEP exists. +- Unicast MAC address of the remote MEP for which ETH-MCC is intended. +- OUI – Organizationally unique identifier (OUI) used to identify the organization defining a specific format and meaning for the ETH-MCC function. +- Data – Additional information that may be needed and is dependent on the specific application of ETH-MCC. Application specific information is outside the scope of this Recommendation. +- Priority – The priority of frames with ETH-MCC information. This information is configurable per operation. +- Drop eligibility – Frames with ETH-MCC information are always marked as drop ineligible. This information is not necessarily configured. + +A peer MEP, upon receiving a frame with ETH-MCC information and with a correct MEG level, passes the ETH-MCC information to the management agent which may additionally respond. + +A MIP is transparent to the frames with ETH-MCC information and therefore does not require any configuration information to support the ETH-MCC function. + +The PDU used for ETH-MCC information is MCC, as described in clause 9.11. Frames carrying the MCC PDU are called MCC frames. + +## 7.10 Ethernet experimental OAM (ETH-EXP) + +Ethernet experimental OAM (ETH-EXP) is used for the experimental OAM functionality that can be provided within an administrative domain on a temporary basis. Interoperability of the experimental OAM functionality and hence use of ETH-EXP containing a given OUI, is not expected across different administrative domains. + +NOTE – Use for other different purposes, requiring for example processing of an embedded SDO-specific OUI, is undesirable and not recommended. + +The specific application of ETH-EXP is outside the scope of this Recommendation. + +EXM PDU, as described in clause 9.17, and EXR PDU, as described in clause 9.18, can be used for experimental OAM. Details of experimental OAM mechanisms are outside the scope of this Recommendation. + +## 7.11 Ethernet vendor-specific OAM (ETH-VSP) + +Ethernet vendor-specific OAM (ETH-VSP) is used for vendor-specific OAM functionality that may be provided by a vendor across its own equipment. Interoperability of vendor-specific OAM functionality and hence use of ETH-VSP containing a given OUI, is not expected across different vendors' equipment. + +NOTE – Use for other different purposes, requiring for example processing of an embedded SDO-specific OUI, is undesirable and not recommended. + +The specific application of ETH-VSP is outside the scope of this Recommendation. + +VSM PDU, as described in clause 9.19, and VSR PDU, as described in clause 9.20, can be used for vendor-specific OAM. Details of vendor-specific OAM mechanisms are outside the scope of this Recommendation. + +## 7.12 Ethernet client signal fail (ETH-CSF) + +The Ethernet client signal fail (ETH-CSF) function is used by a MEP to propagate to a peer MEP the detection of a failure or defect event in an Ethernet client signal when the client itself does not support appropriate fault or defect detection or propagation mechanisms such as ETH-CC or ETH-AIS. The ETH-CSF messages propagate in the direction from the Ethernet MEP, associated with the ingress client port detecting the failure or defect event, to the Ethernet peer MEP. + +The ETH-CSF function is only applicable to point-to-point Ethernet transport applications. In particular, the use of the ETH-CSF function with [IEEE 802.1Q] or other Ethernet-based networking environments is strictly restricted to point-to-point segments of the Ethernet flow. The use of client signal fail indications to support client failure applications is described in Appendix VIII of [ITU-T G.806]. + +Specific configuration information required by a MEP to support the transmission of frames with ETH-CSF information is: + +- Local MEG level – MEG level at which the initiating MEP operates. +- ETH-CSF transmission period – The transmission periodicity of frames with ETH-CSF information. +- Priority – The priority of frames with ETH-CSF information. +- Drop eligibility – Frames with ETH-CSF information are always marked as drop ineligible. + +Specific configuration information required by a MEP to support the reception of frames with ETH-CSF information is: + +- Local MEG level – MEG level at which the receiving MEP operates. + +A MIP is transparent to frames with ETH-CSF information and therefore does not require any information to support the ETH-CSF function. + +The ETH-CSF message indicates also the type of defect. Three CSF defect types are specified: + +- Client loss of signal (C-LOS); +- Client forward defect indication (C-FDI); +- Client reverse defect indication (C-RDI). + +The PDU used to convey ETH-CSF information is referred to as CSF PDU, as described in clause 9.21. Frames carrying the ETH-CSF indications are also referred to as CSF frames. + +### 7.12.1 CSF transmission + +Frames with ETH-CSF information can be issued by a MEP, upon notification of an Ethernet CSF event from the corresponding ingress client port. Detection rules for Ethernet CSF events are Ethernet client and application specific. + +Transmission of frames with ETH-CSF information can be enabled or disabled on a MEP. + +Upon receiving notification of an Ethernet CSF event from the ingress client port, the associated MEP can immediately start periodic transmission of frames with ETH-CSF information. A MEP continues periodic transmission of frames with ETH-CSF information until the Ethernet CSF indication is removed by the source adaptation function. + +Clearing an Ethernet CSF condition is Ethernet client and application specific. The clearance of the Ethernet CSF condition by the source adaptation function is communicated to the peer MEP via: + +- Not transmitting frames with ETH-CSF information, or +- The forwarding of a CSF PDU with client defect clear indication (C-DCI) information. + +### 7.12.2 CSF reception + +Upon receiving a CSF frame with ETH-CSF information a MEP declares the beginning or end of an Ethernet remote CSF condition, depending on the received ETH-CSF information as described in [ITU-T G.8021] and propagates this Ethernet client defect condition towards the corresponding egress client port. An Ethernet MEP detects an Ethernet remote CSF condition when a CSF PDU with no C-DCI information is received. + +The clearance of the Ethernet remote CSF condition by the Ethernet client is detected when: + +- No CSF frame is received within an interval of N times the CSF transmission period in ms (suggested value of N is 3.5), or +- A CSF PDU with C-DCI information is received. + +Note that consequent actions by the sink adaptation function associated with the MEP to propagate the received ETH-CSF information to the Ethernet client are by definition Ethernet client and application specific. + +## 7.13 Ethernet bandwidth notification (ETH-BN) + +The Ethernet Bandwidth Notification (ETH-BN) function is used by a server MEP to signal the server layer link bandwidth in the transmit direction to a MEP at the client layer, for example when the server layer runs over a microwave link which has the capability to adapt its bandwidth according to the prevailing atmospheric conditions. Frames with ETH-BN information carry the current and nominal bandwidth of the server layer link. On receiving frames with ETH-BN information, the client layer MEP can use bandwidth information to adjust service policies, e.g., to reduce the rate of traffic being directed towards the degraded link. + +Transmission of frames with ETH-BN information can be enabled or disabled on a server MEP. Only a server MEP can transmit frames with ETH-BN information. + +When enabled, frames with ETH-BN information are transmitted at the client MEG level by a server MEP, upon detecting bandwidth degradation conditions. A server MEP continues to transmit periodic frames with ETH-BN information until the full bandwidth is restored. In addition, periodic frames with ETH-BN information may optionally be sent when there is no degradation or when the bandwidth degrades to 0. + +In a multipoint client MEG, frames with ETH-BN information may need to include a Port Identification (Port ID), to identify which port is associated with the ETH-BN information. This is required if server MEPs for different links transmit frames using the same source MAC address. + +Upon receiving a frame with ETH-BN information, a MEP passes the received information to the management system. The management system may take further action to reduce the rate of traffic being directed towards the degraded link or otherwise adjust the service policy for the link. + +The specific configuration information required by a server MEP to support the transmission of frames with ETH-BN information is as follows: + +- Client MEG level – MEG level at which the most immediate client layer MIPs and MEPs exist. +- ETH-BN transmission period – The transmission periodicity of frames with ETH-BN information. +- Hold time – The time between detecting degradation, and transmission of the first frame with BNM information that indicates degradation (up to 10 s). +- Priority – The priority of frames with ETH-BN information. +- Drop eligibility – Frames with ETH-BN information are always marked as drop ineligible. This information is not necessarily configured. +- Port ID – A 32-bit unique identifier for the port; this is needed in multipoint MEGs if frames with ETH-BN information about different ports would otherwise be identical. It is optional otherwise. The value must be unique over all server links within the client MEG. + +Specific configuration information required by a MEP to support the reception of frames with ETH-BN information is as follows: + +- Local MEG level – MEG level at which the MEP operates. + +A MIP is transparent to frames with ETH-BN information and therefore does not require any information to support the ETH-BN function. + +The PDU used for ETH-BN information is BNM, as described in clause 9.25. Frames carrying the BNM PDU are called BNM frames. + +**7.13.1 BNM transmission** + +A server MEP, upon detecting a transmission bandwidth degrade condition, can transmit periodic BNM frames in a direction opposite to its peer server MEP, indicating that the current bandwidth is less than the nominal bandwidth. Transmission of BNM frames is shown in Figure 7.13-1. + +![Figure 7.13-1 – Example of BNM transmission](54b5c00e104d6abae06037df2ce1f075_img.jpg) + +The diagram illustrates two layers: Client layer MEG (top) and Server layer MEG (bottom), separated by a dashed horizontal line. + In the Client layer MEG, there are two MEP boxes connected by a horizontal line with arrows. + In the Server layer MEG, there are two Server MEP boxes. + Red dashed arrows indicate BNM message flows: + - From the left Server MEP up to the Client layer and then right towards the right Client MEP, labeled 'BNM (B1)'. + - From the right Server MEP up to the Client layer and then left towards the left Client MEP, labeled 'BNM (B2)'. + Between the Server MEPs, there are two horizontal arrows labeled 'Bandwidth = B1' (pointing right) and 'Bandwidth = B2' (pointing left). + A note below the diagram states: 'NOTE – B1 and B2 can be the same or different values'. + Reference code: G.8013-Y.1731(1 5)\_F7.13-1 + +Figure 7.13-1 – Example of BNM transmission + +**Figure 7.13-1 – Example of BNM transmission** + +A server MEP may also transmit periodic BNM frames when there is no degradation, indicating that the current and nominal bandwidth are the same, or when the port detects failure, to indicate that the current bandwidth is 0. + +NOTE 1 – When the port detects failure, AIS frames are also transmitted by the peer server MEP. + +Upon detecting a change in the transmission bandwidth, the first BNM frame that indicates the new transmission bandwidth must be transmitted after the hold time (up to 10s) after detection of the transmission bandwidth change provided the condition has persisted for that time. If the change lasts for less than the hold time, no BNM frame indicating the change of transmission bandwidth is transmitted. + +NOTE 2 – BNM notifications are expected to be used where the server layer is a microwave link that uses adaptive bandwidth modulation. A hold time is used to prevent notifications if the degradation is very short, such as might be cause by an object passing through the line of sight of the microwave. + +26 Rec. ITU-T G.8013/Y.1731 (06/2023) + +The first BNM frames, indicating the change of transmission bandwidth, are transmitted in quick succession so that reliable and fast actions at the receiver MEP are possible even if some BNM frames are lost or corrupted. The interval and the number of the first BNM frames are implementation specific. + +When detecting transmission bandwidth degrade, after the transmission of the first BNM frames, the server MEP starts transmission of periodic BNM frames; otherwise, when detecting the full bandwidth recovery or a link failure, after the transmission of first BNM frames, the server MEP may cease transmission of BNM frames. Alternatively, the periodic BNM frames may be transmitted by configuration even when there is no degradation. The interval of periodic BNM frame transmission is based on the configured value, and this is also communicated via the Period field in all the BNM frames. + +### 7.13.2 BNM reception + +Upon receiving a BNM frame, a MEP examines it to ensure that its MEG level corresponds to its own MEG level. The Period field indicates the period at which the BNM frames can be expected. The source MAC, Port ID and bandwidth information are extracted and passed to the management system. Subsequently, if no BNM frames are received within an interval of 3.5 times the BNM transmission period indicated in the last BNM frame received, the MEP signals to the management system that it no longer has any bandwidth information (e.g., because the full bandwidth has been restored). + +As described in clause 7.13.1, the first BNM frames are transmitted in quick succession upon detecting a change in the transmission bandwidth. In this case, BNM frames are also received in quick succession to detect the change of bandwidth. + +## 7.14 Ethernet expected defect (ETH-ED) + +The Ethernet expected defect (ETH-ED) function is used by a MEP to signal to its peer MEPs that transmission of CCM frames is expected to be interrupted, without any interruption to data frames, and that the consequent loss of continuity defects at the peer MEPs should therefore be suppressed. Frames with ETH-ED information carry the MEP ID of the MEP and the expected duration of the interruption. + +Frames with ETH-ED information are transmitted by a MEP shortly in advance of an expected interruption of CCM frame transmission, if no interruption is expected in the forwarding of data frames. Examples of this are when an in-service software or firmware upgrade is performed, or when a new MEP is added to an existing MEG. + +Upon receiving a frame with ETH-ED information, a MEP passes the received information to the element management function (EMF). If enabled by the management system, the EMF can take action to disable the reception of CCMs, and hence avoid any loss of continuity defects that would otherwise be triggered. + +NOTE – Further details on how expected defect notifications can be used, and considerations on handling received notifications in the EMF at the peer MEP can be found in Appendix IX of [ITU-T G.8021]. + +The specific configuration information required by a MEP to support the transmission of frames with ETH-ED information is as follows: + +- MEG level – MEG level at which the MEP exists. +- MEP ID – The MEP's identity within the MEG. +- Expected defect duration – Duration for which the peer MEPs are requested to suppress loss of continuity alarms. +- ETH-ED transmission period – The transmission periodicity of frames with ETH-ED information. +- Priority – The priority of frames with ETH-ED information. + +- Drop eligibility – Frames with ETH-ED information are always marked as drop ineligible. This information is not necessarily configured. + +Specific configuration information required by a MEP to support the reception of frames with ETH-ED information is as follows: + +- Local MEG level – MEG level at which the MEP operates. + +A MIP is transparent to frames with ETH-ED information and therefore does not require any information to support the ETH-ED function. + +The PDU used for ETH-ED information is EDM, as described in clause 9.26. Frames carrying the EDM PDU are called EDM frames. + +### 7.14.1 EDM transmission + +A MEP can transmit one or more periodic EDM frames shortly in advance of an expected interruption of CCM frame transmission, or when CCM frame transmission has not yet commenced. Transmission of EDM frames ceases once the interruption occurs or when normal CCM transmission is (re)started. + +### 7.14.2 EDM reception + +Upon receiving an EDM frame, a MEP examines it to ensure that its MEG level corresponds to its own MEG level. The source MEP ID and the expected duration are extracted and passed to the management system. + +# 8 OAM functions for performance monitoring + +OAM functions for performance monitoring allow measurement of different performance parameters. The functions and measurement methods for point-to-point ETH connections and multipoint ETH connectivity are specified. + +This Recommendation covers the following performance parameters which are based on [MEF 10.4]. + +- **Frame loss ratio** + +Frame loss ratio is defined as a ratio, expressed as a percentage, of the number of frames not delivered divided by the total number of frames during time interval T, where the number of frames not delivered is the difference between the number of frames arriving at the ingress ETH flow point to be delivered to the egress ETH flow point and the number of frames delivered at the egress ETH flow point in a point-to-point ETH connection or multipoint ETH connectivity. The frame loss ratio may be measured using either service frames or synthetic frames, belonging to single CoS. The use of synthetic frames can also be applicable for multipoint ETH connectivity. The use of service frames is applicable only to point-to-point ETH connection where all the frames arriving at the ingress ETH flow point are to be delivered to the egress ETH flow point. + +- **Frame delay** + +Frame delay can be expressed as a one-way delay for a frame, where one-way frame delay is defined as the time elapsed from the start of transmission of the first bit of the frame at a source reference point until the reception of the last bit of the same frame at the destination reference point. When a two-way delay is measured, a loopback is performed at the frame's destination reference point and the frame is received at the original source reference point. In the round-trip case, there are four timestamps available which enable both one-way and two-way delay calculations. Ideally, the mean one-way frame delay should be accessible for a set of frames. Mean one-way frame delay is defined in [ITU-T Y.1563]. The service frames belong to the same CoS instance on a point-to-point ETH connection or multipoint ETH connectivity. + +## – **Frame delay variation** + +Frame delay variation is a measure of the variations in the frame delay between a pair of service frames. The service frames belong to the same CoS instance on a point-to-point ETH connection or multipoint ETH connectivity. + +## – **Availability** + +The Ethernet service definition is defined in [ITU-T Y.1563]. Although the mechanisms defined in this Recommendation can contribute to availability-related measurements, this Recommendation does not specify the details of suitable measurement methods. + +Frame performance parameters are applicable to frames that conform to an agreed-upon priority level X and that are deemed by the network as not drop-eligible (i.e., so called "green" frames) of bandwidth profile conformance. Such "green" frames are also called in-profile (see [ITU-T G.8021]). Service frames are admitted at the ingress ETH flow point of a point-to-point ETH network, tandem or link connection and should be delivered to the egress ETH flow point. + +In addition, another performance parameter is identified as per [b-IETF RFC 2544]: + +## – **Throughput** + +Throughput is the average rate of successful traffic delivery over a communication channel. This is typically measured under test conditions, i.e., an out-of-service test, where there is no service traffic for the Ethernet service under test. [ITU-T Y.1564] defines a methodology to test Ethernet-based services at the service activation stage, using an out-of-service test. The Recommendation describes service configuration tests to verify bandwidth profiles and other Ethernet service attributes. Procedures used for out-of-service testing other than for Ethernet service activation can also be found in [b-IETF RFC 2544]. + +## 8.1 Ethernet frame loss measurement (ETH-LM) + +The Ethernet frame loss measurement (ETH-LM) function is used to collect counter values applicable for ingress and egress service frames where the counters maintain a count of transmitted and received data frames between a pair of MEPs. + +The ETH-LM function is performed by sending frames with ETH-LM information to a peer MEP and similarly receiving frames with ETH-LM information from the peer MEP. Each MEP performs frame loss measurements which contribute to unavailable time. Since a bidirectional service is defined as unavailable if either of the two directions is declared unavailable, the ETH-LM function must facilitate each MEP to perform near-end and far-end frame loss measurements. + +For a MEP, near-end frame loss refers to frame loss associated with ingress data frames while far-end frame loss refers to frame loss associated with egress data frames. Both near-end and far-end frame loss measurements contribute to near-end severely errored seconds (near-end SES) and far-end severely errored seconds (far-end SES), respectively, which together contribute to unavailable time, in a manner similar to [ITU-T G.826] and [ITU-T G.7710]. + +A MEP maintains the following two local counters for each peer MEP and for each priority class being monitored in a point-to-point ME for which loss measurements are to be performed: + +- TxFCI: Counter for in-profile data frames transmitted towards the peer MEP. +- RxFCI: Counter for in-profile data frames received from the peer MEP. + +TxFCI and RxFCI counters do not count the OAM frames transmitted or received by the MEP at the MEP's MEG level in some conditions (see Notes). However, the counters do count OAM frames from the higher MEG levels that pass through the MEPs in a manner similar to the data frames. + +NOTE 1 – Both proactive and on-demand ETH-LM functions count OAM frames as follows: + +- For single-ended ETH-LM, OAM frames that are only used for proactive functions used by termination functions (e.g., those for ETH-CC) are counted. + +- For dual-ended ETH-LM, OAM frames for proactive functions used by termination functions are NOT counted. + +In both cases: + +- Proactive OAM frames used by adaptation functions (e.g., those for ETH-APS and ETH-CSF) are counted. +- OAM frames that can be used for on-demand functions (e.g., those for ETH-LB, ETH-LT and on-demand ETH-LM, ETH-DM and ETH-SLM) are NOT counted. + +NOTE 2 – As OAM frames for ETH-AIS and ETH-LCK are only sent in the defect conditions where the result of loss measurements is invalid, it is unnecessary to count these frames. + +The method of loss measurement involving pairs of consecutive frames with ETH-LM information, as shown in clauses 8.1.1.2 and 8.1.2.3, alleviates lack of synchronization across the initial counter values at the initiating and receiving MEPs. Furthermore, when a MEP detects a loss-of-continuity defect condition, it ignores loss measurements during the defect condition and assumes 100% losses. + +NOTE 3 – The level of accuracy in the loss measurements is dependent on how frames with ETH-LM information are added to the data stream after the counter values are copied in the ETH-LM information. For example, if additional data frames get transmitted and/or received between the time of reading the counter values and adding the frame with ETH-LM information to the data stream, the counter values copied in ETH-LM information become inaccurate. However, a hardware-based implementation which is able to add frames with ETH-LM information to the data stream immediately after reading the counter values, provides enhanced accuracy. + +NOTE 4 – Details on the processing of counters used for the transmitted and received data frames are described in [ITU-T G.8021]. + +NOTE 5 – In profile frames are so called 'green' frames where drop-eligibility is 'false'. Network operators or administrators can configure the encoding method to identify green frames. For example, green frames are those where DEI field is 'false', and yellow frames are those where such field is 'true'. PCP or PCP/DEI can be used for this identification. + +Specific configuration information required by a MEP to support the ETH-LM function is as follows: + +- MEG level – MEG level at which the MEP exists. +- Unicast MAC address of a peer MEP to which ETH-LM is intended. Multicast Class 1 MAC address is also allowed. +- ETH-LM transmission period – The default transmission period is 100 ms (i.e., a transmission rate of 10 frames/second). The ETH-LM transmission period should be such that the frame and/or octet counters whose values are carried in ETH-LM information should not wrap around to the same value even if one or more ETH-LM frames are lost. This is primarily a concern for frame loss measurements at lower priority levels. Refer to clause II.2 for examples of frame counter wrapping periods. +- Priority – The priority of the frames with ETH-LM information. This information is configurable per operation. +- Drop eligibility – Frames with ETH-LM information are always marked as drop ineligible. This information is not necessarily configured. + +A MIP is transparent to frames with ETH-LM information and therefore does not require any information to support the ETH-LM function. + +ETH-LM can be performed in two ways: + +- Dual-ended ETH-LM (see clause 8.1.1); +- Single-ended ETH-LM (see clause 8.1.2). + +### 8.1.1 Dual-ended ETH-LM + +Dual-ended ETH-LM is used as proactive OAM for performance monitoring and is applicable to fault management. In this case, each MEP sends periodic dual-ended frames with ETH-LM information to its peer MEP in a point-to-point ME to facilitate frame loss measurements at the peer MEP. Each MEP terminates the dual-ended frames with ETH-LM information and makes the near-end and far-end loss measurements. This function is used for performance monitoring at the same priority level as used for ETH-CC. + +The PDU used for dual-ended ETH-LM information is CCM, as described in clause 9.2. + +#### 8.1.1.1 CCM with dual-ended ETH-LM transmission + +When configured for proactive loss measurement, a MEP periodically transmits CCM frames with the following information elements: + +- TxFCf: The value of the local counter TxFCf at the time of transmission of the CCM frame. +- RxFCb: The value of the local counter RxFCb at the time of reception of the last CCM frame from the peer MEP. +- TxFCb: The value of TxFCf in the last received CCM frame from the peer MEP. + +The CCM PDU is transmitted with a period value equal to the CCM transmission period configured for performance monitoring application at the transmitting MEP. The receiving MEP detects an unexpected period defect condition if the CCM transmission period is not the same as the configured value. + +#### 8.1.1.2 CCM with dual-ended ETH-LM frame reception + +When configured for proactive loss measurement, a MEP, upon receiving a CCM frame, uses the following values to make near-end and far-end loss measurements: + +- Received CCM frame's TxFCf, RxFCb, and TxFCb values and local counter RxFCf value at time this CCM frame was received. These values are represented as TxFCf[ $t_c$ ], RxFCb[ $t_c$ ], TxFCb[ $t_c$ ], and RxFCf[ $t_c$ ], where $t_c$ is the reception time of the current frame. +- Previous CCM frame's TxFCf, RxFCb, and TxFCb values and local counter RxFCf value at time the previous CCM frame was received. These values are represented as TxFCf[ $t_p$ ], RxFCb[ $t_p$ ], TxFCb[ $t_p$ ], and RxFCf[ $t_p$ ], where $t_p$ is the reception time of the previous frame. + +$$\text{Frame Loss}_{\text{far-end}} = |\text{TxFCb}[t_c] - \text{TxFCb}[t_p]| - |\text{RxFCb}[t_c] - \text{RxFCb}[t_p]|$$ + +$$\text{Frame Loss}_{\text{near-end}} = |\text{TxFCf}[t_c] - \text{TxFCf}[t_p]| - |\text{RxFCf}[t_c] - \text{RxFCf}[t_p]|$$ + +If the Period field value in the received CCM frame is different than the MEP's own configured CCM transmission period, the MEP detects an unexpected period defect condition. + +### 8.1.2 Single-ended ETH-LM + +Single-ended ETH-LM is used for on-demand and proactive OAM. In this case, a MEP sends frames with ETH-LM request information to its peer MEP and receives frames with ETH-LM reply information from its peer MEP to carry out loss measurements. + +The PDU used for single-ended ETH-LM request is LMM, as described in clause 9.12. The PDU used for single-ended ETH-LM reply is LMR, as described in clause 9.13. Frames which carry the LMM PDU are called LMM frames. Frames which carry the LMR PDU are called LMR frames. The same LMM and LMR frame formats can be used for proactive and on-demand single-ended ETH-LM. The distinction of proactive LMM/LMR frames from on-demand LMM/LMR frames is by the value of a flag field in the LMM/LMR frames. + +#### 8.1.2.1 LMM transmission + +When configured for single-ended loss measurement, a MEP periodically transmits LMM frames with the following information element: + +- TxFCf: Value of the local counter TxFCI at the time of LMM frame transmission. + +#### 8.1.2.2 LMM reception and LMR transmission + +Whenever a valid LMM frame is received by a MEP, an LMR frame is generated and transmitted to the initiating MEP. An LMM frame with a valid MEG level and a destination MAC address equal to the receiving MEP's MAC address is considered to be a valid LMM frame. An LMR frame contains the following values: + +- TxFCf: Value of TxFCf copied from the LMM frame. +- RxFCf: Value of local counter RxFCI at the time of LMM frame reception. +- TxFCb: Value of local counter TxFCI at the time of LMR frame transmission. + +#### 8.1.2.3 LMR reception + +Upon receiving an LMR frame, a MEP uses the following values to make near-end and far-end loss measurements: + +- Received LMR frame's TxFCf, RxFCf, and TxFCb values and local counter RxFCI value at the time this LMR frame was received. These values are represented as $\text{TxFCf}[t_c]$ , $\text{RxFCf}[t_c]$ , $\text{TxFCb}[t_c]$ , and $\text{RxFCI}[t_c]$ , where $t_c$ is the reception time of the current reply frame. +- Previous LMR frame's TxFCf, RxFCf, and TxFCb values and local counter RxFCI value at the time the previous LMR frame was received. These values are represented as $\text{TxFCf}[t_p]$ , $\text{RxFCf}[t_p]$ , $\text{TxFCb}[t_p]$ , and $\text{RxFCI}[t_p]$ , where $t_p$ is the reception time of the previous reply frame. + +$$\text{Frame Loss}_{\text{far-end}} = |\text{TxFCf}[t_c] - \text{TxFCf}[t_p]| - |\text{RxFCf}[t_c] - \text{RxFCf}[t_p]|$$ + +$$\text{Frame Loss}_{\text{near-end}} = |\text{TxFCb}[t_c] - \text{TxFCb}[t_p]| - |\text{RxFCI}[t_c] - \text{RxFCI}[t_p]|$$ + +## 8.2 Ethernet frame delay measurement (ETH-DM) + +The Ethernet frame delay measurement (ETH-DM) function can be used for on-demand or proactive OAM to measure frame delay and frame delay variation. Frame delay and frame delay variation measurements are performed by sending periodic frames with ETH-DM information to the peer MEP and receiving frames with ETH-DM information from the peer MEP during a proactive measurement session and/or diagnostic interval. Each MEP may perform frame delay and frame delay variation measurement. + +When a MEP is enabled to generate frames with ETH-DM information, it periodically sends frames with ETH-DM information to its peer MEP in the same ME. When a MEP is enabled to generate frames with ETH-DM information, it also expects to receive frames with ETH-DM information from its peer MEP in the same ME. + +Specific configuration information required by a MEP to support the ETH-DM function is as follows: + +- MEG level – MEG level at which the MEP exists. +- Unicast MAC address of a peer MEP to which ETH-DM is intended. Multicast MAC address is also allowed for multipoint ETH connectivity. In case of a multipoint ETH connectivity, a MEP may activate multiple monitoring towards different peer MEPs simultaneously. In this case, each MEP needs to manage the result of monitoring on a per peer-MEP basis. +- DM application – Identifies the application, i.e., proactive versus on-demand delay measurement. This information is configurable per operation. A MEP may activate proactive and on-demand monitoring simultaneously on the same CoS level and towards the same peer + +MEP. In this case, each MEP needs to manage the result of monitoring on a per peer-MEP basis. + +- Data – Optional data element whose length is configurable at the MEP. The inclusion of the optional data element in the DM frame is to support configurable DM frame size. +- Priority – The priority of the frames with ETH-DM information. This information is configurable per operation. A MEP may activate the multiple monitoring on different CoS levels simultaneously. In this case, each MEP needs to manage the result of monitoring per CoS level. +- Drop eligibility – Frames with ETH-DM information are always marked as drop ineligible. This information is not necessarily configured. +- Test ID – Optionally used to distinguish each DM measurement if multiple measurements are simultaneously activated. It must be unique at least within the context of any DM measurement type (single-ended/dual-ended and on-demand/proactive) for the MEG and initiating MEP. + +NOTE 1 – Additional configuration information elements may be needed, such as the transmission rate of frames with ETH-DM information, the total interval of the ETH-DM, etc. These additional configuration information elements are outside the scope of this Recommendation. + +A MIP is transparent to the frames with ETH-DM information and therefore does not require any information to support the ETH-DM function. + +A MEP transmits frames with ETH-DM information with the following information element: + +- TxTimeStampf: Timestamp at the transmission time of ETH-DM frame + +The receiving MEP can compare this value with the RxTimef, the time at the reception of a frame with ETH-DM information and calculate the one-way frame delay as: + +$$\text{Frame Delay} = \text{RxTimef} - \text{TxTimeStampf}$$ + +However, one-way frame delay measurement requires that the time and phase at the initiating MEP and the receiving MEPs are synchronized. For the purposes of frame delay variation measurement, which is based on the difference between subsequent frame delay measurements, the requirement for the time and phase synchronizations can be relaxed since the out-of-phase period can be eliminated in the difference of subsequent frame delay measurements. + +If it is not practical for the clocks to be synchronized, which is expected to be the most common scenario, the frame delay measurement can be made only for two-way measurements, where the MEP transmits a frame with ETH-DM request information with the TxTimeStampf, and the receiving MEP responds with a frame with ETH-DM reply information with TxTimeStampf copied from the ETH-DM request information. The MEP receiving the frame with ETH-DM reply information compares the TxTimeStampf with the RxTimeb, which is the time at the reception of frame with ETH-DM reply information and calculates the two-way frame delay as: + +$$\text{Frame Delay} = \text{RxTimeb} - \text{TxTimeStampf}$$ + +The MEP can also make two-way frame delay variation measurements based on its ability to calculate the difference between two subsequent two-way frame delay measurements. + +NOTE 2 – To allow a more precise two-way frame delay measurement, the MEP replying to frame with ETH-DM request information can also include two additional timestamps in the ETH-DM reply information: RxTimeStampf (Timestamp at the time of receiving frame with ETH-DM request information), and TxTimeStampb (Timestamp at the time of transmitting frame with ETH-DM reply information). + +ETH-DM can be performed in two ways: + +- Dual-ended ETH-DM (see clause 8.2.1). +- Single-ended ETH-DM (see clause 8.2.2). + +NOTE 3 – In previous revisions of this recommendation, dual-ended ETH-DM and single-ended ETH-DM were known as one-way ETH-DM and two-way ETH-DM respectively. + +### 8.2.1 Dual-ended ETH-DM + +In this case, each MEP sends frames with dual-ended ETH-DM information to its peer MEP to facilitate one-way frame delay and/or one-way frame delay variation measurements at the peer MEP. + +NOTE 1– If the clocks between the two MEPs are synchronized, one-way frame delay measurement can be carried out; otherwise, only one-way frame delay variation measurement can be performed. + +The PDU used for dual-ended ETH-DM is 1DM, as described in clause 9.14. Frames which carry the 1DM PDU are called as 1DM frames. The same 1DM frame format can be used for proactive and on-demand dual-ended ETH-DM. The distinction of a proactive 1DM frame from an on-demand 1DM frame is by the value of a flag field in the 1DM frame. + +NOTE 2– In previous revisions of this recommendation, dual-ended ETH-DM was known as one-way ETH-DM. + +#### 8.2.1.1 1DM transmission + +When configured for dual-ended ETH-DM, a MEP periodically transmits 1DM frames with the TxTimeStampf value. A MEP can optionally use a Test ID TLV and/or a Data TLV. The MEP uses a Test ID TLV, containing a Test ID that is used to run multiple tests simultaneously, when configured. The MEP uses a Data TLV when configured for measuring delay and delay variation for different frame sizes. + +#### 8.2.1.2 1DM reception + +When configured for dual-ended ETH-DM, a MEP, upon receiving a valid 1DM frame, uses the following values to make one-way frame delay measurement. A 1DM frame with a valid MEG level and a destination MAC address equal to the receiving MEP's MAC address or multicast Class 1 MAC Address is considered to be a valid 1DM frame. These values serve as input to the one-way frame delay variation measurement: + +- 1DM frame's TxTimeStampf value +- RxTimef, which is the time at reception of the 1DM frame + +$$\text{Frame Delay}_{\text{one-way}} = \text{RxTimef} - \text{TxTimeStampf}$$ + +### 8.2.2 Single-ended ETH-DM + +A MEP sends frames with ETH-DM request information to its peer MEP and receives frames with ETH-DM reply information from its peer MEP to carry out two-way frame delay and two-way frame delay variation measurements. If two optional timestamps of RxTimeStampf and TxTimeStampb are supported on its peer MEP, the results of one-way frame delay and one-way frame delay variation measurements can be also calculated by the same ETH-DM request/reply information. + +NOTE 1 – Regarding the one-way measurements, if the clocks between the two MEPs are synchronized, one-way frame delay measurement can be carried out. Otherwise, only one-way frame delay variation measurement can be performed. + +The PDU used for ETH-DM request is DMM, as described in clause 9.15. The PDU used for ETH-DM reply is DMR, as described in clause 9.16. Frames which carry the DMM PDU are called DMM frames. Frames which carry the DMR PDU are called DMR frames. The same DMM and DMR frame formats can be used for proactive and on-demand single-ended ETH-DM. The distinction between proactive DMM/DMR frames and on-demand DMM/DMR frames is by the value of a flag field in the DMM/DMR frames. + +NOTE 2 – In previous revisions of this recommendation, single-ended ETH-DM was known as two-way ETH-DM. + +#### 8.2.2.1 DMM transmission + +When configured for single-ended ETH-DM, a MEP periodically transmits DMM frames with the TxTimeStampf value. A MEP can optionally use a Test ID TLV and/or a Data TLV. The MEP uses a Test ID TLV, containing a Test ID that is used to run multiple tests simultaneously, when configured. The MEP uses a Data TLV when configured for measuring delay and delay variation for different frame sizes. + +#### 8.2.2.2 DMM reception and DMR transmission + +Whenever a valid DMM frame is received by a MEP, a DMR frame is generated and transmitted to the initiating MEP. A DMM frame with a valid MEG level and a destination MAC address equal to the responding MEP's MAC or multicast Class 1 MAC Address is considered to be a valid DMM frame. Every field in the DMM frame is copied to the DMR frame with the following exceptions: + +- The source MAC address is copied to the destination MAC address and the source MAC address is filled with the MEP MAC address. +- The OpCode field is changed from DMM to DMR. + +NOTE – As an option, two additional timestamps may be used in the DMR frame to take into account the processing time at the responding MEP: RxTimeStampf (timestamp at the time of receiving the DMM frame) and TxTimeStampb (timestamp at the time of transmitting the DMR frame). + +#### 8.2.2.3 DMR reception + +Upon receiving a DMR frame, a MEP uses the following values to calculate two-way frame delay. This value serves as input for two-way frame delay variation measurement: + +- DMR frame's TxTimeStampf value + - RxTimeb – reception time of the DMR frame +- $$\text{Frame Delay}_{\text{two-way}} = \text{RxTimeb} - \text{TxTimeStampf}$$ + +If the additional timestamps are carried in the DMR frame, which is determined by non-zero values of the RxTimeStampf and TxTimeStampb fields, the frame delay for one-way and two-way can be calculated to be: + +$$\text{Frame Delay}_{\text{two-way}} = (\text{RxTimeb} - \text{TxTimeStampf}) - (\text{TxTimeStampb} - \text{RxTimeStampf})$$ + +$$\text{Frame Delay}_{\text{one-way\_far}} = \text{RxTimeStampf} - \text{TxTimeStampf}$$ + +$$\text{Frame Delay}_{\text{one-way\_near}} = \text{RxTimeb} - \text{TxTimeStampb}$$ + +## 8.3 Throughput measurement + +[b-IETF RFC 2544] specifies measuring the throughput by sending frames at an increasing rate (up to the theoretical maximum), graphing the percentage of frames received and reporting the rate at which frames start being dropped. In general, this rate is dependent on the frame size. + +The mechanisms specified in this Recommendation, e.g., unicast ETH-LB (e.g., LBM and LBR frames with the data field) and ETH-Test (e.g., TST frames with the data field) can be used for performing the throughput measurements. A MEP can insert TST frames or LBM frames with configured size, pattern, etc., at a rate to exercise the throughput and make one-way or two-way measurements. + +## 8.4 Ethernet synthetic loss measurement (ETH-SLM) + +Ethernet synthetic loss measurement (ETH-SLM) is a mechanism to measure frame loss using synthetic frames, rather than data traffic. A number of synthetic frames are sent and received, and the number of those that are lost is hence calculated. This can be treated as a statistical sample, and used to approximate the frame loss ratio of data traffic. + +The ETH-SLM function collects counters so as to maintain a count of transmitted and received synthetic frames between a set of MEPs. + +ETH-SLM is used to perform on-demand or proactive tests by sending a finite number of frames with ETH-SLM information to one or multiple peer MEPs and similarly receiving frames with ETH-SLM information from the peer MEPs. Each MEP then performs frame loss measurements which contribute to unavailable time. Since a bidirectional service is defined as unavailable if either of the two directions is declared unavailable, the ETH-SLM function must facilitate each MEP to perform near-end and far-end synthetic frame loss measurements. + +A MEP maintains the following local counters for each Test ID and for each peer MEP being monitored in a ME for which synthetic frame loss measurements are to be performed: + +- TxFCI: Number of synthetic frames transmitted towards the peer MEP, part of a given Test ID. An initiating MEP increments this number for successive transmission of synthetic frames with ETH-SLM request information while a responding MEP increments it for successive transmission of synthetic frames with ETH-SLM reply information. +- RxFCI: Number of synthetic frames received from the peer MEP and part of a given Test ID. An initiating MEP increments this number for successive reception of synthetic frames with ETH-SLM reply information while a responding MEP increments it for successive reception of synthetic frames with ETH-SLM request information. + +The method of loss measurement involves series of frames with increasing values of TxFCI with ETH-SLM information, as shown in clauses 8.4.1 and 8.4.2. + +NOTE 1 – No synchronization is required of the Test ID value between initiating and responding MEPs, as the Test ID is configured at the initiating MEP, and the responding MEP uses the Test ID it receives from the initiating MEP. The allocation and release of local counter resources for each Test ID at the responding MEP is outside the scope of this Recommendation. + +The specific configuration information required by a MEP to support the ETH-SLM function is as follows: + +- MEG level – MEG level at which the MEP exists. +- Data – Optional data element whose length is configurable at the MEP. The inclusion of the optional data element in the SLM frame is to support configurable SLM frame size. +- Destination MAC address – Identifies the target peer MEP. +- Test ID – Used to distinguish each SL measurement because multiple measurements can be simultaneously activated also on a given CoS and MEP pair. It must be unique at least within the context of any SL measurement for the MEG and initiating MEP. +- Priority – The priority of the frames with ETH-SLM information. This information is configurable per operation. +- Drop eligibility – Frames with ETH-SLM information are always marked as drop ineligible. This information is not necessarily configured. + +A MIP is transparent to frames with ETH-SLM information and therefore does not require any information to support the ETH-SLM function. + +NOTE 2 – As ETH-SLM is a sampling technique, it is inevitably less accurate than counting the service frames. Furthermore, the accuracy depends on the number of SLM frames used or the period for transmitting SLM frames. The number of SLM frames or the period for SLM frames is outside the scope of this Recommendation, but some examples of accuracy are included for information in Appendix VI. + +### 8.4.1 Single-ended ETH-SLM + +Single-ended ETH-SLM is used for proactive or on-demand OAM. It carries out synthetic loss measurements applicable to both point-to-point ETH connection and multipoint ETH connectivity. It allows a MEP to initiate and report far-end and near-end loss measurements associated with one or a set of peer MEPs part of the same MEG. + +The selection of on-demand or proactive is performed by the management function that initiates the test, however this is local information and does not need to be conveyed in the PDU. + +For single-ended operation, a MEP sends frames with ETH-SLM request information to its peer MEP(s) and receives frames with ETH-SLM reply information from its peer MEP(s) to carry out synthetic loss measurements. + +The PDU used for single-ended ETH-SLM request is SLM, as described in clause 9.22. The PDU used for single-ended ETH-SLM reply is SLR, as described in clause 9.23. Frames which carry the SLM PDU are called SLM frames. Frames which carry the SLR PDU are called SLR frames. + +#### 8.4.1.1 SLM transmission + +A MEP periodically transmits SLM frames with the following information elements included: + +- Test ID: Test ID is a value containing a number configured by the MEP and then used to run multiple tests simultaneously. +- Source MEP ID: The MEP's own identity in the MEG. +- TxFCf: The value of the local counter TxFCI at the time of SLM frame transmission. +- TxFCb: Set always to zero. Reserved for SLR transmission. + +#### 8.4.1.2 SLM reception and SLR transmission + +Whenever a valid SLM frame is received by a MEP, an SLR frame is generated and transmitted to the initiating MEP. An SLM frame with a valid MEG level and a destination MAC address equal to the responding MEP's MAC address or a multicast Class 1 MAC address is considered to be a valid SLM frame. Every field in the SLM frame is copied to the SLR frame with the following exceptions: + +- The source MAC address is copied to the destination MAC address and the source MAC address is filled with the MEP MAC address. +- The OpCode is changed from SLM to SLR. +- Responder MEP ID: MEP's own identity in the MEG. +- TxFCb: Value of the local counter RxFCI at the time of SLR frame transmission. + +Note that as an SLR frame is generated every time an SLM frame is received, RxFCI in the responder is equal to the number of SLM frames received and also equal to the number of SLR frames sent. In other words, in the responder, $RxFCI = TxFCI$ . + +#### 8.4.1.3 SLR reception + +After transmission of a SLM frame (with a given TxFCf value), a MEP expects to receive a corresponding SLR frame (carrying same TxFCf value) from its peer MEP(s). In on-demand mode, SLR frames received more than 5 s after the command that terminates SL measurement must be discarded, as specified in [ITU-T G.8021]. + +With the information contained in SLR frames, a MEP determines frame loss for given measurement periods. The measurement period is a time interval during which the number of SLM frames transmitted is statistically adequate to make a measurement at a given accuracy. (See Appendix VI.) A MEP uses the following values to determine near-end and far-end frame loss in the measurement period: + +- Last received SLR frame's TxFCf and TxFCb values and local counter RxFCI at the end of the measurement period. These values are represented as TxFCf[tc], TxFCb[tc] and RxFCI[tc], where tc is the end time of the measurement period. +- SLR frame's TxFCf and TxFCb values of the first received SLR frame after the test starts and local counter RxFCI at the beginning of the measurement period. These values are represented as TxFCf[tp], TxFCb[tp] and RxFCI[tp], where tp is the start time of the measurement period. + +$$\text{Frame loss}_{\text{far-end}} = | \text{TxFCf}[t_c] - \text{TxFCf}[t_p] | - | \text{TxFCb}[t_c] - \text{TxFCb}[t_p] |$$ + +$$\text{Frame loss}_{\text{near-end}} = | \text{TxFCb}[t_c] - \text{TxFCb}[t_p] | - | \text{RxFCI}[t_c] - \text{RxFCI}[t_p] |$$ + +NOTE – If there are SLMs at the end of the measurement period for which no corresponding SLRs have been received within the timeout period (i.e., SLMs with sequence numbers after the sequence number of the last SLR received), it is not possible to determine whether they were lost in the near-end or far-end direction. + +### 8.4.2 Dual-ended ETH-SLM + +Dual-ended ETH-SLM can be used for on-demand and proactive OAM. It carries out loss measurements applicable to both point-to-point ETH connection or multipoint ETH connectivity. It allows a MEP in a MEG to send periodic dual-ended frames with ETH-SLM information to its peer MEP(s) to facilitate frame loss measurement at the peer MEP. The receiving MEP terminates the dual-ended frames and makes the near-end loss measurements. + +The selection of on-demand or proactive is performed by the management function that initiates the test; however, this is local information and does not need to be conveyed in the PDU. + +Dual-ended ETH-SLM is suitable where it is required and practical to measure unidirectional FLR from every MEP to all its peer MEPs (e.g., any-to-any measurements). + +The PDU used for dual-ended ETH-SLM information is 1SL, as described in clause 9.24. Frames which carry the 1SL PDU are called 1SL frames. + +#### 8.4.2.1 1SL transmission + +When configured for dual-ended operation, a MEP periodically transmits 1SL frames with the following information elements: + +- Test ID: The value containing a number configured by the MEP and then used to run multiple tests simultaneously. +- Source MEP ID: Source MEP ID is the MEP's own identity in the MEG. +- TxFCf: Value of the local counter TxFCI at the time of 1SL frame transmission. + +The 1SL PDU is transmitted with a period value equal to the 1SL transmission period configured for performance monitoring application at the transmitting MEP. + +#### 8.4.2.2 1SL reception + +When configured for one-way synthetic loss measurements, a MEP, upon receiving a valid 1SL frame, uses the following values to make one-way frame loss measurement. A 1SL frame with a valid MEG level and a destination MAC address equal to the receiving MEP's MAC address or multicast Class 1 MAC address is considered to be a valid 1SL frame. + +Whenever a valid 1SL frame is received by a MEP with a given **TxFCf** value, the MEP expects to receive a subsequent 1SL frame (**TxFCf** value incremented by one). + +For a given measurement period, a MEP uses the following values to determine near-end frame loss in the period: + +- Last received 1SL frame's **TxFCf** value and local counter **RxFCI** at the end of the measurement period. These values are represented as **TxFCf**[tc] and **RxFCI**[tc], where tc is the end time of the measurement period. + +- 1SL frame's **TxFCf** value of the first received 1SL after the test starts and local counter **RxFCl** at the beginning of the measurement period. These values are represented as **TxFCl[tp]** and **RxFCl[tp]**, where tp is the start time of the measurement period. + +$$\text{Frame loss}_{\text{near-end}} = | \text{TxFCl}[t_c] - \text{TxFCl}[t_p] | - | \text{RxFCl}[t_c] - \text{RxFCl}[t_p] |$$ + +# 9 OAM PDU types + +This clause describes the information elements and formats for different OAM PDU types used to meet the requirements of OAM functions described in clauses 7 and 8. + +NOTE – When the values of OAM PDU fields are fixed, they are shown in parentheses in the OAM PDU formats in the following clauses. + +## 9.1 Common OAM information elements + +Some information elements are common across the OAM PDUs that are identified in this Recommendation. These information elements are: + +- MEG level: A 3-bit field. It contains an integer value that identifies the MEG level of OAM PDU. Value ranges from 0 to 7. +- Version: A 5-bit field. It contains an integer value that identifies the OAM protocol version. Clause 11 discusses the specifics of OAM PDU validation and versioning with respect to this field. +- OpCode: A 1-octet field. It contains an OpCode that identifies an OAM PDU type. OpCode is used to identify the remaining content of an OAM PDU. The values of this information field are shown in Table 9-1. +- Flags: An 8-bit field. Use of the bits in this field is dependent on the OAM PDU type. +- TLV Offset: A 1-octet field. It contains the offset to the first TLV in an OAM PDU relative to the TLV Offset field. The value of this field is associated with an OAM PDU type. When the TLV Offset is 0, it points to the first octet following the TLV Offset field. + +Other information elements which are not present in OAM PDUs but are conveyed in frames carrying OAM PDUs include: + +- Priority: The priority of a specific OAM frame. +- Drop eligibility: The drop eligibility of a specific OAM frame. + +**Table 9-1 – OpCode values** + +| OpCode value | OAM PDU type | OpCode relevance for MEPs/MIPs | +|-----------------------------------------|-------------------|-------------------------------------------| +| OpCodes common with IEEE 802.1 | | | +| 1 | CCM | MEPs | +| 3 | LBM | MEPs and MIPs (connectivity verification) | +| 2 | LBR | MEPs and MIPs (connectivity verification) | +| 5 | LTM | MEPs and MIPs | +| 4 | LTR | MEPs and MIPs | +| 0, 6-31, 64-255 | Reserved (Note 1) | | +| OpCodes specific to this Recommendation | | | +| 32 | GNM (Note 4) | MEPs | +| 33 | AIS | MEPs | +| 35 | LCK | MEPs | + +**Table 9-1 – OpCode values** + +| OpCode value | OAM PDU type | OpCode relevance for MEPs/MIPs | +|-----------------------|-------------------|------------------------------------------| +| 37 | TST | MEPs | +| 39 | Linear APS | Refer to [ITU-T G.8031] | +| 40 | Ring APS | Refer to [ITU-T G.8032] | +| 41 | MCC | MEPs | +| 43 | LMM | MEPs | +| 42 | LMR | MEPs | +| 45 | 1DM | MEPs | +| 47 | DMM | MEPs | +| 46 | DMR | MEPs | +| 49 | EXM | Outside the scope of this Recommendation | +| 48 | EXR | Outside the scope of this Recommendation | +| 51 | VSM | Outside the scope of this Recommendation | +| 50 | VSR | Outside the scope of this Recommendation | +| 52 | CSF | MEPs | +| 53 | 1SL | MEPs | +| 55 | SLM | MEPs | +| 54 | SLR | MEPs | +| 34, 36, 38, 44, 60-63 | Reserved (Note 2) | | +| 56-59 | Reserved (Note 3) | | + +NOTE 1 – Reserved for definition by IEEE 802.1. +NOTE 2 – Reserved for future standardization by ITU-T. +NOTE 3 – Reserved for definition by MEF. The definition is outside the scope of this Recommendation. +NOTE 4 – The Generic Notification Message (GNM) PDU type is used to carry other OAM PDUs using the Sub-OpCodes in Table 9-1a + +### 9.1.1 Common OAM PDU format + +The common format used in all OAM PDUs is shown in Figure 9.1-1. + +![](7fe5741e83bc9702d1b1d7585ddf66bd_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|-------------|---|---|---------|---|---|---|---|--------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | | Version | | | | | OpCode | | | | | | | | Flags | | | | | | | | TLV Offset | | | | | | | | +| 5 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.1-1 – Common OAM PDU format** + +When OpCode 32 (GNM) is used, there is an additional one-octet Sub-OpCode field following the TLV Offset field. Sub-OpCode values are shown in Table 9-1a. + +**Table 9-1a – Sub-OpCode values** + +| Sub-OpCode value | OAM PDU type | +|------------------------------------------------------|-----------------| +| 1 | BNM | +| 0, 2-255 | Reserved (Note) | +| NOTE – Reserved for future standardization by ITU-T. | | + +The general format of TLVs is shown in Figure 9.1-2. Type values are specified in Table 9-2. + +![Figure 9.1-2 – Generic TLV format diagram showing four fields: 1. Type (8 bits), 2. Length (16 bits), 3. Value [optional] (variable length), and 4. End TLV (Type=0).](8d66c9c295023a1380f9986d3663bb1e_img.jpg) + +The diagram illustrates the generic TLV format with four numbered fields: + +- Field 1 (Type):** 8 bits (bits 8 to 1). +- Field 2 (Length):** 16 bits (bits 8 to 1 of the second octet, and bits 8 to 1 of the third octet). +- Field 3 (Value [optional]):** Variable length, starting from bit 8 of the third octet. +- Field 4:** Indicated by a '0' in the Type field (bits 8 to 1 of the final octet). + +Figure 9.1-2 – Generic TLV format diagram showing four fields: 1. Type (8 bits), 2. Length (16 bits), 3. Value [optional] (variable length), and 4. End TLV (Type=0). + +**Figure 9.1-2 – Generic TLV format** + +NOTE – In an End TLV, Type = 0, and both Length and Value fields are not used. + +**Table 9-2 – Type values** + +| Type value | TLV name | +|------------------------------------------------------------------------------------------------------|---------------------------| +| Types common with IEEE 802.1 | | +| 0 | End TLV | +| 3 | Data TLV | +| 5 | Reply Ingress TLV | +| 6 | Reply Egress TLV | +| 7 | LTM Egress Identifier TLV | +| 8 | LTR Egress Identifier TLV | +| 2, 4, 9-31, 64-255 | Reserved (Note 1) | +| Types specific to this Recommendation | | +| 32 | Test TLV | +| 33-35 | Reserved (Note 2) | +| 36 | Test ID TLV | +| 37, 38 | Reserved (Note 3) | +| 39-63 | Reserved (Note 4) | +| NOTE 1 – Reserved for definition by IEEE 802.1. | | +| NOTE 2 – Reserved for definition by [ITU-T G.8113.1]. | | +| NOTE 3 – Reserved for definition by MEF. The definition is outside the scope of this Recommendation. | | +| NOTE 4 – Reserved for future standardization by ITU-T. | | + +## 9.2 CCM PDU + +The CCM PDU is used to support the ETH-CC function, as described in clause 7.1, ETH-RDI function, as described in clause 7.5, and dual-ended ETH-LM function, as described in clause 8.1.1. + +### 9.2.1 CCM information elements + +Information elements carried in a CCM PDU to support the ETH-CC function are: + +- Period: A 3-bit information element carried in the three least significant bits of the Flags field. Period contains the value of the CCM transmission period configured at the CCM source. CCM Period values are specified in Table 9-3. + +- MEG ID: A 48-octet field which contains the MEG ID of the MEG to which the MEP transmitting the CCM frame belongs. See Annex A. +- MEP ID: A 2-octet field where the 13 least significant bits are used to identify the MEP transmitting the CCM frame. MEP ID is unique within the MEG. + +Information element carried in a CCM PDU to support the ETH-RDI function is: + +- RDI: A 1-bit information element carried in most significant bit of Flags field. When the RDI bit is 1, detection of a defect is indicated by the transmitting MEP. When the RDI bit is 0, no defect indication is communicated by the transmitting MEP. + +The information elements carried in a CCM PDU to support the dual-ended ETH-LM function are: + +- TxFCf: A 4-octet field which carries the value of the counter of in-profile data frames transmitted by the MEP towards its peer MEP, at the time of CCM frame transmission. +- RxFCb: A 4-octet field which carries the value of the counter of in-profile data frames received by the MEP from its peer MEP, at the time of receiving the last CCM frame from that peer MEP. +- TxFCb: A 4-octet field which carries the value of the TxFCf field in the last CCM frame received by the MEP from its peer MEP. + +### 9.2.2 CCM PDU format + +The CCM PDU format used by a MEP to transmit CCM information is shown in Figure 9.2-1. + +![](fd76efce549d3713543bb5ed9b023c2e_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|----|---------------------|---|---|-------------|---|---|---|---|----------------|---|---|---|---|---|---|---|--------------------|---|---|---|---|---|---|---|-----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | | Version (0) | | | | | OpCode (CCM=1) | | | | | | | | Flags | | | | | | | | TLV Offset (70) | | | | | | | | +| 5 | Sequence Number (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | MEP ID | | | | | | | | | | | | | | | | MEG ID (48 octets) | | | | | | | | | | | | | | | | +| 13 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 21 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 25 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 29 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 33 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 37 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 41 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 45 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 49 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 53 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 57 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 57 | | | | | | | | | | | | | | | | | TxFCf | | | | | | | | | | | | | | | | +| 61 | TxFCf | | | | | | | | | | | | | | | | RxFCb | | | | | | | | | | | | | | | | +| 65 | RxFCb | | | | | | | | | | | | | | | | TxFCb | | | | | | | | | | | | | | | | +| 69 | TxFCb | | | | | | | | | | | | | | | | Reserved (0) | | | | | | | | | | | | | | | | +| 73 | Reserved (0) | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | | | | | | | | | + +Figure 9.2-1 – CCM PDU format + +The fields of the CCM PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is CCM (1). + +- Flags: Two information elements in the Flags field for CCM PDU: RDI, and Period as follows: + +| MSB | | LSB | | | | | | +|-----|--------------|-----|---|---|--------|---|---| +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| RDI | Reserved (0) | | | | Period | | | + +**Figure 9.2-2 – Flags format in CCM PDU** + +- RDI: Bit 8 is set to 1 to indicate RDI, otherwise it is set to 0. +- Period: Bits 3 to 1 indicate the transmission period with the encoding shown in Table 9-3. + +**Table 9-3 – CCM period values** + +| Flags[3:1] | Period value | Comments | +|------------|---------------|----------------------------| +| 000 | Invalid value | Invalid value for CCM PDUs | +| 001 | 3.33 ms | 300 frames per second | +| 010 | 10 ms | 100 frames per second | +| 011 | 100 ms | 10 frames per second | +| 100 | 1 s | 1 frame per second | +| 101 | 10 s | 6 frames per minute | +| 110 | 1 min | 1 frame per minute | +| 111 | 10 min | 6 frame per hour | + +- TLV Offset: Set to 70. +- Sequence Number: Set to all-ZEROes for this Recommendation. +- MEP ID: A 13-bit integer value identifying the transmitting MEP within the MEG. The three MSBs of the first octet are not used and set to ZERO: + +| MSB | | | LSB | | | | | | | | | | | | | +|---------|---|---|--------|---|---|---|---|----------|---|---|---|---|---|---|---| +| octet 9 | | | | | | | | octet 10 | | | | | | | | +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 0 | 0 | 0 | MEP ID | | | | | | | | | | | | | + +**Figure 9.2-3 – MEP ID format in CCM PDU** + +- MEG ID: 48-octet field. Refer to Annex A for the format used for the MEG ID field. +- TxFCf, TxFCb, RxFCb: 4-octet integer values with samples of the wrap-around frame counters, as specified in clause 9.2.1. These fields are set to all-ZEROes when not used. +- Reserved: Reserved fields are set to all ZEROes. +- End TLV: An all-ZEROes octet value. + +## 9.3 LBM PDU + +The LBM PDU is used to support ETH-LB request, as described in clause 7.2. + +### 9.3.1 LBM information elements + +Information elements carried in an LBM PDU are: + +- Transaction ID/Sequence Number: A 4-octet field that contains the transaction ID/sequence number for the LBM. The receiver is expected to copy the Transaction ID /Sequence Number in the LBR PDU, as described in clause 9.4. + +- Data/Test Pattern: Data is an optional field whose length and contents are determined at the transmitting MEP. The contents of the Data field can be a test pattern with an additional, optional checksum. The test pattern can be a pseudo-random bit sequence (PRBS) $(2^{31} - 1)$ as specified in clause 5.8 of [ITU-T O.150], an all '0' pattern, etc. + +### 9.3.2 LBM PDU format + +The LBM PDU format used by a MEP to transmit LBM information is shown in Figure 9.3-1. + +![](40a8c30f7ea5ecea4912e040c97c5b9c_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|------|------------------------------------------------------|---|-------------|---|---|---|---|---|----------------|---|---|---|---|---|---|---|-----------|---|---|---|---|---|---|---|----------------|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (LBM=3) | | | | | | | | Flags (0) | | | | | | | | TLV Offset (4) | | | | | | | | +| 5 | Transaction ID/Sequence Number | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | [Optional TLV starts here; otherwise End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | | | | | | | | | | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | + +Figure 9.3-1 – LBM PDU format + +The fields of the LBM PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is LBM (3). +- Flags: Set to all-ZEROes. + +![](adc59ed6840bcb2d392ea323abfccedc_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|--|--------------|---|---|---|---|---|---|---|--|--|--|--|--|--|--|--|-----|--|--|--|--|--|--|--|--|--|--|--|--|--|--|--| +| | MSB | | | | | | | | | | | | | | | | LSB | | | | | | | | | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | | | | | | | | | | | | | | | | | | | | | | | | +| | Reserved (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +Figure 9.3-2 – Flags format in LBM PDU + +- TLV Offset: Set to 4. +- Transaction ID/Sequence Number: A 4-octet value containing either the transaction number for the LBM PDU without test pattern or a Sequence number incremented for successive LBM PDUs with a test pattern. +- Optional TLV: A Data TLV or Test TLV as specified in Figure 9.3-3 or Figure 9.3-4 respectively may be included in any LBM transmitted. +- End TLV: All-ZEROes octet value. + +![](ddfa5b18550d1a022a941e3c31843814_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|---|--------------|---|---|---|---|---|---|---|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | Type (3) | | | | | | | | Length | | | | | | | | | | | | | | | | | | | | | | | | +| : | Data Pattern | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +Figure 9.3-3 – Data TLV format + +The fields of the Data TLV format are as follows: + +- Type: The TLV type; value for this TLV type is Data (3). + +- Length: The size, in octets, of the Value field containing the Data Pattern. In a frame where the PDU is limited to 1492 octets, the maximum length value is 1480 (since 12 octets are required for 8 octets of LBM PDU overhead, 3 octets of Data TLV overhead, and 1 octet of End TLV). Any other TLVs, if present in LBM, furthermore detract from the maximum length value of 1480. +- Data Pattern: An n-octet ( $n = \text{Length}$ ) arbitrary bit pattern. The receiver should ignore it. + +![](fc02903382cebe6fc11e4c0d74b5313f_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|---|---------------------------|---|---|---|---|---|---|---|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|--------------|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | Type (32) | | | | | | | | Length | | | | | | | | | | | | | | | | Pattern Type | | | | | | | | +| : | Test Pattern (NULL, PRBS) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | CRC-32 (optional) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.3-4 – Test TLV format** + +The fields of the Test TLV format are as follows: + +- Type: The TLV type; value for this TLV type is Test (32). +- Length: The size, in octets, of the Value field containing the pattern type, test pattern and CRC-32. In a frame where the PDU is limited to 1492 octets, the maximum length value is 1480 octets (since 12 octets are required for 8 octets of LBM PDU overhead, 3 octets of Test TLV overhead, and 1 octet of End TLV). Any other TLVs, if present in LBM, furthermore detract from the maximum length value of 1480. (As one octet is used for pattern type, 1479 octets are available for the test pattern.) +- Pattern Type: The test pattern type; values are: + - 0 'Null signal without CRC-32' + - 1 'Null signal with CRC-32' + - 2 'PRBS $2^{-31} - 1$ without CRC-32' + - 3 'PRBS $2^{-31} - 1$ with CRC-32' + - 4-255 Reserved for future standardization +- Test Pattern: An n-octet ( $n \leq \text{Length}$ ) test pattern: PRBS $2^{-31} - 1$ or Null (all-zeroes) pattern. +- CRC-32: Covers all fields (from Type to last octet before CRC-32). + +## 9.4 LBR PDU + +The LBR PDU is used to support ETH-LB reply, as described in clause 7.2. + +### 9.4.1 LBR information elements + +The information elements carried in an LBR PDU include: + +- Transaction ID/Sequence Number: A 4-octet field that is copied from the Transaction ID/Sequence Number field in LBM. +- Data: A field that is copied from the Data field in LBM. + +### 9.4.2 LBR PDU format + +The LBR PDU format used by a MEP or MIP to transmit LBR information is shown in Figure 9.4-1. + +![](640d28a694bbdbaf9b11a3bfdcc800fc_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|-----------------------------------------------------------|---|---------|---|---|---|---|---|----------------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version | | | | | | OpCode (LBR=2) | | | | | | | | Flags | | | | | | | | TLV Offset | | | | | | | | +| 5 | Transaction ID/Sequence Number | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | [Optional TLV(s) start(s) here, otherwise End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.4-1 – LBR PDU format** + +The fields for the LBR PDU format are as follows: + +- MEG level: A 3-bit field the value of which is copied from the received LBM PDU. +- Version: A 5-bit field the value of which is copied from the LBM PDU. +- OpCode: Value for this PDU type is LBR (2). +- Flags: A 1-octet field the value of which is copied from the LBM PDU. +- TLV Offset: A 1-octet field the value of which is copied from the LBM PDU. +- Transaction ID/Sequence Number: A 4-octet field the value of which is copied from the LBM PDU. +- Optional TLV(s): If present in LBM PDU, (is)are copied from the LBM PDU. +NOTE – Per [IEEE 802.1Q], Data TLV or Test TLV are not the only type of TLVs that could be present in an LBM PDU, hence an LBR PDU could include additional TLVs. +- End TLV: A 1-octet field the value of which is copied from the LBM PDU. + +## 9.5 LTM PDU + +The LTM PDU is used to support ETH-LT request, as described in clause 7.3. + +### 9.5.1 LTM information elements + +The information elements carried in an LTM PDU include: + +- Transaction ID: A 4-octet field that contains the transaction number for the LTM. The receiver is expected to copy Transaction ID in the LTR PDU, as described in clause 9.6. +- TTL: A 1-octet field used to indicate whether an LTM should be terminated or not by the receiver. When a MIP receives LTM with TTL=1, the LTM is not relayed. A network element receiving LTM decrements the received TTL value by one and copies it into the TTL field of LTR PDU, as described in clause 9.6, as well as into the LTM that it forwards towards the next hop. +- TargetMAC Address: A 6-octet field used to carry MAC address of the targeted end-point. An intermediate MIP copies this field into the LTM that it forwards towards the next hop. +- OriginMAC Address: A 6-octet field used to carry the MAC address of the originating MEP. An intermediate MIP copies this field into the LTM that it forwards towards the next hop. + +### 9.5.2 LTM PDU format + +The LTM PDU format used by a MEP or MIP to transmit LTM information is shown in Figure 9.5-1. +NOTE – MIPs only transmit LTM information in response to received LTM information. + +![](89f8aefc01866631793087542316cef2_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|------|-------------------------------------|---|-------------|---|---|---|-------------------|---|----------------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|-----------------|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (LTM=5) | | | | | | | | Flags | | | | | | | | TLV Offset (17) | | | | | | | | +| 5 | Transaction ID | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | TTL | | | | | | OriginMAC Address | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | | | | | | | TargetMAC Address | | | | | | | | | | | | | | | | | | | | | | | | | | +| 21 | [Additional TLV starts here] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 25 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 29 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.5-1 – LTM PDU format** + +The fields of the LTM PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is LTM (5). +- Flags: The format is as shown in Figure 9.5-2. + +![](fe7304192caf64cda93b580c5e7e5c06_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | +|--|--------|---|--------------|---|---|---|---|---|--|--|--|--|--|--|--|--|-----|--|--|--|--|--|--|--|--| +| | MSB | | | | | | | | | | | | | | | | LSB | | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | | | | | | | | | | | | | | | | | +| | HWonly | | Reserved (0) | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.5-2 – Flags format in LTM PDU** + +- HWonly: Bit 8 set to 1. Value 1 indicates that only MAC addresses learned in a bridge's active data forwarding tables are to be used to forward the LTM to the next hop. When forwarding a received LTM, HWonly is copied from the incoming LTM value. +- TLV Offset: Set to 17. +- Transaction ID: A 4-octet value containing the transaction ID for the LTM PDU. +- TTL: 1-octet field used to carry a TTL value as specified in clause 9.5.1. +- OriginMAC Address: A 6-octet OriginMAC as specified in clause 9.5.1. +- TargetMAC Address: A 6-octet TargetMAC as specified in clause 9.5.1. +- Additional TLV: LTM Egress Identifier TLV as specified in Figure 9.5-3. +- End TLV: All-ZEROes octet value. + +![](3e2dcee303cecdd31b7f9ec0d8942fed_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|---|-------------------|---|---|---|---|---|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | Type (7) | | | | | | Length | | | | | | | | | | | | | | | | | | | | | | | | | | +| 2 | Egress Identifier | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 3 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.5-3 – LTM Egress Identifier TLV format** + +The fields of the LTM Egress Identifier TLV format are as follows: + +- Type: The TLV type; value for this TLV type is LTM Egress Identifier (7). +- Length: The size, in octets, of the Value field containing the egress identifier. This is set to 8. + +- Egress Identifier: Identifies the MEP initiating the LTM frame or ETH-LT responder relaying the modified LTM frame. Octets 4 and 5 are ZEROes while the remaining six octets 6-11 contain a 48-bit IEEE MAC address unique to the network element where the MEP or ETH-LT responder resides. + +## 9.6 LTR PDU + +The LTR PDU is used to support ETH-LT reply, as described in clause 7.3. + +### 9.6.1 LTR information elements + +The information elements carried in an LTR PDU include: + +- Transaction ID: A 4-octet field that is copied from the Transaction ID field in LTM. +- TTL: A 1-octet field that contains the TTL field value decremented by 1 from the LTM for which the LTR is being sent. + +### 9.6.2 LTR PDU format + +The LTR PDU format used by a MEP or MIP to transmit LTR information is shown in Figure 9.6-1. + +![](65d47e1d0e5982c00e9bd116b89e2b6a_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|----------------|---|-------------|---|---|---|---|---|----------------|---|---|---|---|---|---|---|-------------------------------------|---|---|---|---|---|---|---|----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (LTR=4) | | | | | | | | Flags | | | | | | | | TLV Offset (6) | | | | | | | | +| 5 | Transaction ID | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | TTL | | | | | | | | Relay Action | | | | | | | | [Additional TLVs start here] | | | | | | | | | | | | | | | | +| 17 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 21 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +Figure 9.6-1 – LTR PDU format + +The fields of the LTR PDU format are as follows: + +- MEG level: A 3-bit field the value of which is copied from the received LTM PDU. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is LTR (4). +- Flags: The format is as shown in Figure 9.6-2. + +![](3252037b597c9317aced0feed4cb5af0_img.jpg) + +| MSB | | | LSB | | | | | +|--------|--------|-------------|--------------|---|---|---|---| +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| HWOnly | FwdYes | TerminalMEP | Reserved (0) | | | | | + +Figure 9.6-2 – Flags format in LTR PDU + +- HWOnly: Bit 8 (HWOnly) is copied from the incoming LTM value. +- FwdYes: Bit 7 is set to 1 if modified LTM frame was relayed, or set to 0 if no LTM frame was relayed. +- TerminalMEP: Bit 6 is set to 1 if Reply Egress TLV (or Reply Ingress TLV, if the Reply Egress TLV is not present) is a MEP, or set to 0 otherwise. +- TLV Offset: Set to 6. +- Transaction ID: A 4-octet field, the value of which is copied from the LTM PDU. +- TTL: A 1-octet field, the value of which is copied from the LTM PDU after decrementing it by one. + +- Relay Action: A 1-octet field that reports how the data frame targeted by the LTM would be passed through the MAC relay entity to the egress bridge port as described in clause 21.9.5 of [IEEE 802.1Q]. The value is defined in Table 21-27 of [IEEE 802.1Q]. + - Additional TLVs: LTR Egress Identifier TLV, Reply Ingress TLV and/or Reply Egress TLV as specified in Figures 9.6-3, 9.6-4 and 9.6-5 respectively. +- NOTE – Per [IEEE 802.1Q], LTR Egress Identifier TLV, Reply Ingress TLV or Reply Egress TLV are not the only types of TLVs that could be present in an LTM PDU, hence an LTR PDU could include additional TLVs. +- End TLV: All-ZEROes octet value. + +![](8a9f4764511ce90622893ec65c065eeb_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|---|------------------------|---|---|---|---|---|---|---|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | Type (8) | | | | | | | | Length | | | | | | | | | | | | | | | | | | | | | | | | +| 2 | Last Egress Identifier | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 3 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 4 | Next Egress Identifier | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.6-3 – LTR Egress Identifier TLV format** + +The fields of the LTR Egress Identifier TLV format are as follows: + +- Type: The TLV type; value for this TLV type is LTR Egress Identifier (8). +- Length: The size, in octets, of the Value field containing the last egress identifier and next egress identifier. This is set to 16. +- Last Egress Identifier: Identifies the MEP that initiated, or ETH-LT responder that relayed the LTM frame to which this LTR frame is the response. This field is the same as the egress identifier in the LTM Egress Identifier TLV of the incoming LTM frame. +- Next Egress Identifier: Identifies the ETH-LT responder that transmitted this LTR frame, and that can relay a modified LTM frame to the next hop. If the FwdYes bit of the Flags field is 0, the contents of this field are undefined, and ignored by the LTR frame receiver. When not undefined, octets 12 and 13 are ZEROes while the remaining six octets 14-19 contain a 48-bit IEEE MAC address unique to the network element where the ETH-LT responder resides. + +![](c419b566d720267c499087add1506018_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|---|---------------------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | Type (5) | | | | | | | | Length (7) | | | | | | | | | | | | | | | | Ingress Action | | | | | | | | +| : | Ingress MAC Address | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.6-4 – Reply ingress TLV format** + +The fields of the Reply Ingress TLV format are as follows: + +- Type: The TLV type; value for this TLV type is ingress reply (5). +- Length: The size, in octets, of the Value field. This is set to 7. +- Ingress Action: A 1-octet field which is reserved for definition by [IEEE 802.1]. +- Ingress MAC Address: A 6-octet field which is reserved for definition by [IEEE 802.1]. + +![](c0b9e5fc63e19306394e0d4249da62cd_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|---|--------------------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---|---------------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | Type (6) | | | | | | | | Length (7) | | | | | | | | Egress Action | | | | | | | | | | | | | | | | +| : | Egress MAC Address | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.6-5 – Reply Egress TLV format** + +The fields of the Reply Egress TLV format are as follows: + +- Type: The TLV type; value for this TLV type is egress reply (6). +- Length: The size, in octets, of the Value field. This is set to 7. +- Egress Action: A 1-octet field which is reserved for definition by [IEEE 802.1]. +- Egress MAC Address: A 6-octet field which is reserved for definition by [IEEE 802.1]. + +## **9.7 AIS PDU** + +The AIS PDU is used to support the ETH-AIS function, as described in clause 7.4. + +### **9.7.1 AIS information element** + +The information element carried in AIS is: + +- Period: A 3-bit information element carried in the three least significant bits of the Flags field. Period contains the value of AIS transmission periodicity. AIS period values are specified in Table 9-4. + +### **9.7.2 AIS PDU format** + +The AIS PDU format used by a MEP to transmit AIS information is shown in Figure 9.7-1. + +![](3263a25e110201638bda790456af2909_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|---|-------------|---|---|---|-------------|---|---|---|-----------------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|----------------|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | | | Version (0) | | | | OpCode (AIS=33) | | | | | | | | Flags | | | | | | | | TLV Offset (0) | | | | | | | | +| 5 | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.7-1 – AIS PDU format** + +The fields of the AIS PDU format are as follows: + +- MEG level: A 3-bit field that is used to carry the MEG level of the client MEG. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is AIS (33). +- Flags: One information element in the Flags field for the AIS PDU, Period, as follows: + +![](c0f4777175572d5c52cae16fdddd70be_img.jpg) + +| | | | | | | | | | | | | | +|--|--------------|---|---|---|--------|---|---|---|-----|--|--|--| +| | MSB | | | | | | | | LSB | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | | | | +| | Reserved (0) | | | | Period | | | | | | | | + +**Figure 9.7-2 – Flags format in AIS PDU** + +- Period: Bits 3 to 1 indicate transmission period with the encoding in Table 9-4. + +**Table 9-4 – AIS/LCK period values** + +| Flags[3:1] | Period value | Comments | +|------------|---------------|--------------------------------| +| 000-011 | Invalid value | Invalid value for AIS/LCK PDUs | +| 100 | 1s | 1 frame per second | +| 101 | Invalid value | Invalid value for AIS/LCK PDUs | +| 110 | 1 min | 1 frame per minute | +| 111 | Invalid value | Invalid value for AIS/LCK PDUs | + +- TLV Offset: Set to 0. +- End TLV: All-ZEROes octet value. + +## 9.8 LCK PDU + +The LCK PDU is used to support the ETH-LCK function, as described in clause 7.6. + +### 9.8.1 LCK information elements + +The information element carried in an LCK PDU is: + +- Period: A 3-bit information element carried in the three least significant bits of the Flags field. Period contains the value of LCK transmission periodicity. LCK period values are specified in Table 9-4. + +### 9.8.2 LCK PDU format + +The LCK PDU format used by a MEP to transmit LCK information is shown in Figure 9.8-1. + +![](7dfd8dd318dcfc36eaf4c967ddfb94c1_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|---|-------------|---|-------------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|----------------|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (LCK=35) | | | | | | | | Flags | | | | | | | | TLV Offset (0) | | | | | | | | +| 5 | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.8-1 – LCK PDU format** + +The fields of the LCK PDU format are as follows: + +- MEG level: A 3-bit field that is used to carry the MEG level of the client MEG. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is LCK (35). +- Flags: One information element in the Flags field for the LCK PDU, Period, as follows: + +![](167a6aea873669eb91492f33d35d16de_img.jpg) + +| | | | | | | | | | | +|--|--------------|---|---|---|---|--------|---|---|--| +| | MSB | | | | | LSB | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | +| | Reserved (0) | | | | | Period | | | | + +**Figure 9.8-2 – Flags format in LCK PDU** + +- Period: Bits 3 to 1 indicate transmission period with the encoding in Table 9-4. +- TLV Offset: Set to 0. +- End TLV: All-ZEROes octet value. + +## 9.9 TST PDU + +The TST PDU is used to support the unidirectional ETH-Test function, as described in clause 7.7. + +### 9.9.1 TST information elements + +The information elements carried in a TST PDU are: + +- Sequence Number: A 4-octet field that contains the sequence number for the TST frames. +- Test: An optional field whose length and contents are determined at the transmitting MEP. The contents of the Test field indicate a test pattern and also carry an optional checksum. The test pattern can be a pseudo-random bit sequence (PRBS) $(2^{31} - 1)$ as specified in clause 5.8 of [ITU-T O.150], an all '0' pattern, etc. + +### 9.9.2 TST PDU format + +The TST PDU format used by a MEP to transmit TST information is shown in Figure 9.9-1. + +![](802707b774f2d2973b49cea2020e8453_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|-----------------|---|-------------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-----------|---|---|---|---|---|---|---|----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (TST=37) | | | | | | | | Flags (0) | | | | | | | | TLV Offset (4) | | | | | | | | +| 5 | Sequence Number | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | [Test TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | | | | | | | | | | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | + +Figure 9.9-1 – TST PDU format + +The fields of the TST PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is TST (37). +- Flags: Set to all-ZEROes. + +![](ec035e97a11ce40541dec6d88d54c7cb_img.jpg) + +| MSB | | | | | | | | LSB | | | | | | | | +|--------------|---|---|---|---|---|---|---|-----|--|--|--|--|--|--|--| +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | | | | | | | | +| Reserved (0) | | | | | | | | | | | | | | | | + +Figure 9.9-2 – Flags format in TST PDU + +- TLV Offset: Set to 4. +- Sequence Number: A 4-octet value containing the sequence number incremented for successive TST PDUs. +- Test TLV: Test TLV as specified in Figure 9.3-4. +- End TLV: All-ZEROes octet value. + +## 9.10 APS PDU + +The APS PDU is used to support the ETH-APS function, as described in clause 7.8. + +### 9.10.1 APS information elements + +Information elements carried in an APS PDU are outside the scope of this Recommendation. + +### 9.10.2 APS PDU format + +The APS PDU format used by the entities specified in [ITU-T G.8031] and [ITU-T G.8032] to transmit APS information is shown in Figure 9.10-1. + +![](b4b91e1f5ced9a2bc4a7f3b038cf3fb6_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|---|-------------|---|-------------|---|---|---|---|---|--------------|---|---|---|---|---|---|---|-----------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (APS) | | | | | | | | Flags (0) | | | | | | | | TLV Offset | | | | | | | | +| 5 | [APS Data] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +Figure 9.10-1 – APS PDU format + +The fields of the APS PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value is outside the scope of this Recommendation and defined in [ITU-T G.8031] for linear APS and in [ITU-T G.8032] for ring APS. +- OpCode: Value for this PDU type is (39) for linear APS and (40) for ring APS. +- Flags: Its specific value for APS is outside the scope of this Recommendation. +- TLV Offset: 1-octet field. Its specific value for APS is outside the scope of this Recommendation. +- APS Data: The format and length of this field are outside the scope of this Recommendation. +- End TLV: All-ZEROes octet value. + +## 9.11 MCC PDU + +The MCC PDU is used to support the ETH-MCC function, as described in clause 7.9. + +### 9.11.1 MCC information elements + +Information elements carried in an MCC PDU are: + +- OUI: A 3-octet field that contains the organizationally unique identifier of the organization defining the format of MCC Data and values SubOpCode. +- SubOpCode: A 1-octet field that is used to interpret the remaining fields in the MCC PDU. +- MCC Data: Depending on the functionality indicated by the OUI and organizationally specific SubOpCode, MCC Data may carry one or more TLVs. MCC Data is outside the scope of this Recommendation. + +### 9.11.2 MCC PDU format + +The MCC PDU format used by a MEP to transmit MCC information is shown in Figure 9.11-1. + +![](3d5f590e40a34de3e874fd845a4efd53_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|------|-----------------------------------|---|-------------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-----------|---|---|---|---|---|---|---|-------------|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (MCC=41) | | | | | | | | Flags (0) | | | | | | | | TLV Offset | | | | | | | | +| 5 | OUI | | | | | | | | | | | | | | | | SubOpCode | | | | | | | | | | | | | | | | +| 9 | [Optional MCC Data; else End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| Last | | | | | | | | | | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | + +Figure 9.11-1 – MCC PDU format + +The fields of the MCC PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: ETH-ED uses this field as described in clause 9.26. Other uses of this field are outside the scope of this Recommendation, but they must conform to clause 9.1. +- OpCode: Value for this PDU type is MCC (41). +- Flags: ETH-ED uses this field as described in clause 9.26. Other uses of this field are outside the scope of this Recommendation; however, if not otherwise specified, it shall be set to all-ZEROes. + +![](fed4a04822c24fb22cca3a14f4ddae83_img.jpg) + +| | | | | | | | | | | | | | | | | +|--------------|---|---|---|---|---|---|---|-----|--|--|--|--|--|--|--| +| MSB | | | | | | | | LSB | | | | | | | | +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | | | | | | | | +| Reserved (0) | | | | | | | | | | | | | | | | + +**Figure 9.11-2 – Flags format in MCC PDU** + +- TLV Offset: 1-octet field. ETH-ED uses this field as described in clause 9.26. Other uses of this field are outside the scope of this Recommendation but they must conform to clause 9.1. +- OUI: 3-octet field that contains the organizationally unique identifier of the organization defining the format of MCC Data and values SubOpCode. +- SubOpCode: 1-octet field. When the OUI field contains the ITU-T OUI (00-19-A7), ETH-ED uses SubOpCode (1) as described in clause 9.26 and other values are reserved. When a different OUI is used, the values of the SubOpCode are outside the scope of this Recommendation. +- MCC Data: ETH-ED uses this field as described in clause 9.26. Other uses of this field are outside the scope of this Recommendation. +- End TLV: All-ZEROes octet value. + +## 9.12 LMM PDU + +The LMM PDU is used to support a single-ended proactive or on-demand ETH-LM request, as described in clause 8.1.2. + +### 9.12.1 LMM information element + +The information element carried in an LMM PDU include: + +- TxFCf: A 4-octet field which carries the value of counter responsible for counting in-profile data frames transmitted by the MEP towards its peer MEP, at the time of LMM frame transmission. + +### 9.12.2 LMM PDU format + +The LMM PDU format used by a MEP to transmit LMM information is shown in Figure 9.12-1. + +![](9cd7ec4a653f07d02def283cb6f2309e_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|----|---------------------------|---|-------------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|-----------------|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (1) | | | | | | OpCode (LMM=43) | | | | | | | | Flags | | | | | | | | TLV Offset (12) | | | | | | | | +| 5 | TxFCf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | Reserved for RxFCf in LMR | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | Reserved for TxFCb in LMR | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.12-1 – LMM PDU format** + +The fields of the LMM PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value for the LMM PDU on this version is set to 1. +- OpCode: Value for this PDU type is LMM (43). +- Flags: One information elements in the Flags field, the LSB bit (Type), is used to indicate the type of the LMM operation as follows: + +![](107c8e1abcb7033ad244e30e7a910045_img.jpg) + +| | | | | | | | | | | | | | | | | +|--------------|---|---|---|---|---|---|---|-----|---|---|---|---|---|---|------| +| MSB | | | | | | | | LSB | | | | | | | | +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| Reserved (0) | | | | | | | | | | | | | | | Type | + +**Figure 9.12-2 – Flags format in LMM PDU** + +- Type: Bit 1 is set to 1 if it is the proactive operation, or set to 0 if it is the on-demand operation. +- TLV Offset: Set to 12. +- TxFCf: 4-octet integer values with samples of the frame counters, as specified in clause 9.12.1. +- Reserved: Reserved fields are set to all ZEROes. +- End TLV: An all-ZEROes octet value. + +## 9.13 LMR PDU + +The LMR PDU is used to support a single-ended proactive and on-demand ETH-LM reply, as described in clause 8.1.2. + +### 9.13.1 LMR information elements + +Information elements carried in an LMR PDU are: + +- TxFCf: A 4-octet field which carries the value of the TxFCf field in the last LMM PDU received by the MEP from its peer MEP. +- TxFCb: A 4-octet field which carries the value of the counter of in-profile data frames transmitted by the MEP towards its peer MEP at the time of LMR frame transmission. +- RxFCf: A 4-octet field which carries the value of the counter of in-profile data frames received by the MEP from its peer MEP, at the time of receiving last LMM frame from that peer MEP. + +### 9.13.2 LMR PDU format + +The LMR PDU format used by a MEP to transmit LMR information is shown in Figure 9.13-1. + +![](a1dc2b799cd6ca93414adab971763c3e_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|----|-------------|---|---------|---|---|-----------------|---|---|-------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version | | | OpCode (LMR=42) | | | Flags | | | | | | | | TLV Offset | | | | | | | | | | | | | | | | +| 5 | TxFCf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | RxFCf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | TxFCb | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.13-1 – LMR PDU format** + +The fields of the LMR PDU format are as follows: + +- MEG level: A 3-bit field the value of which is copied from the last received LMM PDU. + +- Version: A 5-bit field the value of which is copied from the last received LMM PDU. +- OpCode: Value for this PDU type is LMR (42). +- Flags: A 1-octet field the value of which is copied from the last received LMM PDU. +- TLV Offset: A 1-octet field the value of which is copied from the last received LMM PDU. +- TxFCf: 4-octet field the value of which is copied from the last received LMM PDU. +- RxFCf: 4-octet integer values with samples of the frame counters, as specified in clause 9.13.1. +- TxFCb: 4-octet integer values with samples of the frame counters, as specified in clause 9.13.1. +- End TLV: A 1-octet field the value of which is copied from the LMM PDU. + +## 9.14 1DM PDU + +The 1DM PDU is used to support the proactive and on-demand dual-ended ETH-DM function, as described in clause 8.2.1. + +### 9.14.1 1DM information element + +The information element carried in a 1DM PDU includes: + +- TxTimeStampf: An 8-octet field that contains the timestamp of 1DM transmission. The format of TxTimeStampf is equal to the TimeRepresentation format in [IEEE 1588]. + +### 9.14.2 1DM PDU format + +The 1DM PDU format used by a MEP to transmit 1DM information is shown in Figure 9.14-1. + +![](a057800564be3506d2d87b6a4daee25b_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|-----------------------------------------------------------------------|---|-------------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|-----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (1) | | | | | | OpCode (1DM=45) | | | | | | | | Flags | | | | | | | | TLV Offset (16) | | | | | | | | +| 5 | TxTimeStampf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | Reserved for 1DM receiving equipment (0)
(for RxTimeStampf) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 21 | [Optional TLVs start here; otherwise End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 25 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 29 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +Figure 9.14-1 – 1DM PDU format + +The fields of the 1DM PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value for the 1DM PDU on this version is set to 1. +- OpCode: Value for this PDU type is 1DM (45). +- Flags: One information element in the Flags field, the LSB bit (Type), is used to indicate the type of the 1DM operation as follows: + +![](8b9e9fdabfd2a37e4475d78f8fdcf15c_img.jpg) + +| MSB | | | | | | | LSB | +|--------------|---|---|---|---|---|---|------| +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| Reserved (0) | | | | | | | Type | + +Figure 9.14-2 – Flags format in 1DM PDU + +- Type: Bit 1 is set to 1 if it is the proactive operation, or set to 0 if it is the on-demand operation. +- TLV Offset: Set to 16. +- TxTimeStampf: An 8-octet transmit time stamp field as described in clause 9.14.1. +- Reserved: An 8-octet reserved field set to all-ZEROes. +- Optional TLV(s): A Test ID TLV as specified in Figure 9.14-3 and/or a Data TLV as specified in Figure 9.3-3, with configurable size, in octets may be included in any 1DM transmitted. When a Test ID TLV is included in this field, it is recommended to put Test ID TLV first (prior to Data TLV). For the purpose of ETH-DM, the value part of Data TLV is unspecified. +- End TLV: All-ZEROes octet value. + +![](2cc973099f02f2cc67558feea3b18cde_img.jpg) + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|---|-----------|---|---|---|---|---|---|---|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---------|---|---|---|---|---|---|---| +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | Type (36) | | | | | | | | Length | | | | | | | | | | | | | | | | Test ID | | | | | | | | +| 5 | Test ID | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.14-3 – Test ID TLV format** + +The fields of the Test ID TLV format are as follows: + +- Type: The TLV type; value for this TLV type is Test ID (36). +- Length: The size, in octets, of the Value field. Must be 32. +- Test ID: A 4-octet field set by the transmitting MEP when used to run multiple tests simultaneously between MEPs. + +## 9.15 DMM PDU + +The DMM PDU is used to support proactive or on-demand Single-Ended ETH-DM request, as described in clause 8.2.2. + +### 9.15.1 DMM information element + +The information element carried in a DMM PDU includes: + +- TxTimeStampf: An 8-octet field that contains the timestamp of DMM transmission. The format of TxTimeStampf is equal to the TimeRepresentation format in [IEEE 1588]. + +### 9.15.2 DMM PDU format + +The DMM PDU format used by a MEP to transmit DMM information is shown in Figure 9.15-1. + +![](fd8f5da2b60cdca94896f3cde8ee81f0_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|-----------------------------------------------------------|---|-------------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|-----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (1) | | | | | | OpCode (DMM=47) | | | | | | | | Flags | | | | | | | | TLV Offset (32) | | | | | | | | +| 5 | TxTimeStampf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | Reserved for DMM receiving equipment (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | (for RxTimeStampf) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 21 | Reserved for DMR (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 25 | (for TxStampb) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 29 | Reserved for DMR receiving equipment (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 33 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 37 | [Optional TLV(s) start(s) here; otherwise End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 41 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 45 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.15-1 – DMM PDU format** + +The fields of the DMM PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value for the DMM PDU is set to 1. +- OpCode: Value for this PDU type is DMM (47). +- Flags: Set to all-ZEROes. One information elements in the Flags field, the LSB bit (Type), is used to indicate the type of the DMM operation as follows: + +![](74b540f71bcf10a8a66b2f01ea8c08ec_img.jpg) + +| MSB | | | | | | | LSB | +|--------------|---|---|---|---|---|---|------| +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| Reserved (0) | | | | | | | Type | + +**Figure 9.15-2 – Flags format in DMM PDU** + +- Type: Bit 1 is set to 1 if it is the proactive operation, or set to 0 if it is the on-demand operation. +- TLV Offset: Set to 32. +- TxTimeStampf: An 8-octet transmit time stamp field as described in clause 9.15.1. +- Reserved: The 24-octet of reserved fields are set to all-ZEROes. +- Optional TLV: A Test ID TLV as specified in Figure 9.14-3 and/or a Data TLV as specified in Figure 9.3-3, with configurable size, in octets may be included in any DMM transmitted. When a Test ID TLV is included in this field, it is recommended to put Test ID TLV first (prior to Data TLV). For the purpose of ETH-DM, the value part of Data TLV is unspecified. +- End TLV: An all-ZEROes octet value. + +## 9.16 DMR PDU + +The DMR PDU is used to support a single-ended ETH-DM reply, as described in clause 8.2.2. + +### 9.16.1 DMR information elements + +The information elements carried in a DMR PDU are: + +- TxTimeStampf: An 8-octet field that contains the copy of TxTimeStampf field in received DMM. + +- RxTimeStampf: An optional 8-octet field that contains the timestamp of DMM reception. The format of RxTimeStampf is equal to the TimeRepresentation format in [IEEE 1588]. When not used, a value of all 0 is used. +- TxTimeStampb: An optional 8-octet field that contains the timestamp of DMR transmission. The format of TxTimeStampb is equal to the TimeRepresentation format in [IEEE 1588]. When not used, a value of all 0 is used. + +### 9.16.2 DMR PDU format + +The DMR PDU format used by a MEP to transmit DMR information is shown in Figure 9.16-1. + +![](5801c19431e76330430e92a598cc7a16_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|-----------------------------------------------------------|---|---------|---|---|-----------------|---|---|-------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version | | | OpCode (DMR=46) | | | Flags | | | | | | | | TLV Offset | | | | | | | | | | | | | | | | +| 5 | TxTimeStampf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | RxTimeStampf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 21 | TxTimeStampb | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 25 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 29 | Reserved for DMR receiving equipment (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 33 | (for RxTimeStampb) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 37 | [Optional TLV(s) start(s) here; otherwise End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 41 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 45 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| t | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +Figure 9.16-1 – DMR PDU format + +The fields of the DMR PDU format are as follows: + +- MEG level: A 3-bit field the value of which is copied from the last received DMM PDU. +- Version: A 5-bit field the value of which is copied from the last received DMM PDU. +- OpCode: Value for this PDU type is DMR (46). +- Flags: A 1-octet field the value of which is copied from the last received DMM PDU. +- TLV Offset: A 1-octet field the value of which is copied from the last received DMM PDU. +- TxTimeStampf: An 8-octet field the value of which is copied from last received DMM PDU. +- RxTimeStampf: An 8-octet transmit time stamp field as described in clause 9.16.1. +- TxTimeStampb: An 8-octet transmit time stamp field as described in clause 9.16.1. +- Reserved: Reserved fields are set to all ZEROes. +- Optional TLV(s): If present in DMM PDU, is (are) copied from the DMM PDU. The order of the Optional TLVs is preserved. +- End TLV: A 1-octet field the value of which is copied from the DMM PDU. + +## 9.17 EXM PDU + +The EXM PDU is used as an experimental OAM request PDU. + +### 9.17.1 EXM information elements + +The information elements carried in an EXM PDU include: + +- OUI: A 3-octet field that contains the organizationally unique identifier of the organization using the EXM. +- SubOpCode: A 1-octet field that is used to interpret the remaining fields in the EXM frame. +- EXM Data: Depending on the functionality indicated by the OUI and organizationally specific SubOpCode, EXM Data may carry one or more TLVs. EXM Data is outside the scope of this Recommendation. + +### 9.17.2 EXM PDU format + +The EXM PDU format used by a MEP to transmit EXM information is shown in Figure 9.17-1. + +![](bfca6639dd4b8480f2d96d2b61c806d9_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|---|------------------------------------------|---|-------------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-------------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (EXM=49) | | | | | | | | Flags | | | | | | | | TLV Offset | | | | | | | | +| 5 | OUI | | | | | | | | | | | | | | | | SubOpCode | | | | | | | | | | | | | | | | +| 9 | [optional EXM Data; else End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| ⋮ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| ⋮ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| ⋮ | | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | | | | | | | | | + +Figure 9.17-1 – EXM PDU format + +The fields of the EXM PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Its specific value for EXM is outside the scope of this Recommendation but it must conform to clause 9.1. +- OpCode: Value for this PDU type is EXM (49). +- Flags: Outside the scope of this Recommendation. +- TLV Offset: 1-octet field. Its specific value for EXM is outside the scope of this Recommendation but it must conform to clause 9.1. +- OUI: 3-octet field the values of which are outside the scope of this Recommendation. +- SubOpCode: 1-octet field the values of which are outside the scope of this Recommendation. +- EXM Data: Format and length of this field are outside the scope of this Recommendation. +- End TLV: All-ZEROes octet value. + +## 9.18 EXR PDU + +The EXR PDU is used as an experimental OAM reply PDU. + +### 9.18.1 EXR information elements + +The information elements carried in an EXR PDU include: + +- OUI: A 3-octet field that contains the organizationally unique identifier of the organization using the EXR. +- SubOpCode: A 1-octet field that is used to interpret the remaining fields in the EXR frame. +- EXR Data: Depending on the functionality indicated by the OUI and organizationally specific SubOpCode, EXR Data may carry one or more TLVs. EXR Data is outside the scope of this Recommendation. + +### 9.18.2 EXR PDU format + +The EXR PDU format used to transmit EXR information is shown in Figure 9.18-1. + +![](e2b7490a3455c66c85db12872c78fcc3_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|---|------------------------------------------|---|---------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-------------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version | | | | | | OpCode (EXR=48) | | | | | | | | Flags | | | | | | | | TLV Offset | | | | | | | | +| 5 | OUI | | | | | | | | | | | | | | | | SubOpCode | | | | | | | | | | | | | | | | +| 9 | [Optional EXR Data; else End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | | | | | | | | | + +**Figure 9.18-1 – EXR PDU format** + +The fields of the EXR PDU format are as follows: + +- MEG level: A 3-bit field the value of which is copied from the last received EXM PDU. +- Version: A 5-bit field the value of which is copied from the last received EXM PDU. +- OpCode: Value for this PDU type is EXR (48). +- Flags: Outside the scope of this Recommendation. +- TLV Offset: 1-octet field. Its specific value for EXR is outside the scope of this Recommendation but it must conform to clause 9.1. +- OUI: 3-octet field the value of which is copied from the last received EXM PDU. +- SubOpCode: 1-octet field the values of which are outside the scope of this Recommendation. +- EXR Data: Format and length of this field are outside the scope of this Recommendation. +- End TLV: All-ZEROes octet value. + +## 9.19 VSM PDU + +The VSM PDU is used as a vendor-specific OAM request PDU. + +### 9.19.1 VSM information elements + +The information elements carried in VSM include: + +- OUI: A 3-octet field that contains the organizationally unique identifier of the organization using the VSM. +- SubOpCode: A 1-octet field that is used to interpret the remaining fields in the VSM frame. +- VSM Data: Depending on the functionality indicated by the OUI and organizationally specific SubOpCode, VSM Data may carry one or more TLVs. VSM Data is outside the scope of this Recommendation. + +### 9.19.2 VSM PDU format + +The VSM PDU format used by a MEP to transmit VSM information is shown in Figure 9.19-1. + +![](b35ea3e304aad7d350a9902270413930_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|---|------------------------------------------|---|-------------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-------------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (VSM=51) | | | | | | | | Flags | | | | | | | | TLV Offset | | | | | | | | +| 5 | OUI | | | | | | | | | | | | | | | | SubOpCode | | | | | | | | | | | | | | | | +| 9 | [Optional VSM Data; else End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | | | | | | | | | + +**Figure 9.19-1 – VSM PDU format** + +The fields of the VSM PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Its specific value for VSM is outside the scope of this Recommendation but it must conform to clause 9.1. +- OpCode: Value for this PDU type is VSM (51). +- Flags: Outside the scope of this Recommendation. +- TLV Offset: 1-octet field. Its specific value for VSM is outside the scope of this Recommendation but it must conform to clause 9.1. +- OUI: 3-octet field the values of which are outside the scope of this Recommendation. +- SubOpCode: 1-octet field the values of which are outside the scope of this Recommendation. +- VSM Data: Format and length of this field are outside the scope of this Recommendation. +- End TLV: All-ZEROes octet value. + +## 9.20 VSR PDU + +The VSR PDU is used as a vendor-specific OAM reply PDU. + +### 9.20.1 VSR information elements + +The information elements carried in a VSR PDU include: + +- OUI: A 3-octet field that contains the organizationally unique identifier of the organization using the VSR. +- SubOpCode: A 1-octet field that is used to interpret the remaining fields in the VSR frame. +- VSR Data: Depending on the functionality indicated by the OUI and organizationally specific SubOpCode, VSR Data may carry one or more TLVs. VSR Data is outside the scope of this Recommendation. + +### 9.20.2 VSR PDU format + +The VSR PDU format used to transmit VSR information is shown in Figure 9.20-1. + +![](99698c448635861b7dc8d352f87a1b2b_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|---|-----------------------------------|---|---------|---|---|---|---|---|-----------------|---|---|---|---|---|---|---|-------------|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version | | | | | | OpCode (VSR=50) | | | | | | | | Flags | | | | | | | | TLV Offset | | | | | | | | +| 5 | OUI | | | | | | | | | | | | | | | | SubOpCode | | | | | | | | | | | | | | | | +| 9 | [Optional VSR Data; else End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| ⋮ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| ⋮ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| ⋮ | | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | | | | | | | | | + +**Figure 9.20-1 – VSR PDU format** + +The fields of the VSR PDU format are as follows: + +- MEG level: A 3-bit field the value of which is copied from the last received VSM PDU. +- Version: A 5-bit field the value of which is copied from the last received VSM PDU. +- OpCode: Value for this PDU type is VSR (50). +- Flags: Outside the scope of this Recommendation. +- TLV Offset: 1-octet field. Its specific value for EXR is outside the scope of this Recommendation but it must conform to clause 9.1. +- OUI: 3-octet field the value of which is copied from the last received VSM PDU. +- SubOpCode: 1-octet field the values of which are outside the scope of this Recommendation. +- VSR Data: The format and length of this field are outside the scope of this Recommendation. +- End TLV: All-ZEROes octet value. + +## **9.21 CSF PDU** + +The CSF PDU is used to support the ETH-CSF function, as described in clause 7.12. + +### **9.21.1 CSF information elements** + +The information elements carried in a CSF PDU are: + +- Period: A 3-bit information element carried in the three least significant bits of the Flags field. Period contains the value of CSF transmission periodicity. CSF period values are specified in Table 9-6. +- Type: A 3-bit information element carried in the three bits next to the three least significant bits of the Flags field. Type contains the value of the CSF type. CSF type values are specified in Table 9-5. + +### **9.21.2 CSF PDU format** + +The CSF PDU format is shown in Figure 9.21-1. + +![](7136ef99edf9289cc069898bd584d3aa_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|---|-------------|---|-------------|---|---|---|---|---|------------------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (CSF= 52) | | | | | | | | Flags | | | | | | | | TLV Offset (0) | | | | | | | | +| 5 | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.21-1 – CSF PDU format** + +The fields of the CSF PDU format are as follows: + +- MEG level: A 3-bit field that is used to carry the local MEG level. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is CSF (52). + + + +### 9.22.2 SLM PDU format + +The SLM PDU format used by a MEP to transmit SLM information is shown in Figure 9.22-1. + +![](7f7211748473542096717109ebe5a9d6_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|------------------------------------------------------|---|-------------|---|---|---|---|---|-------------------|---|---|---|---|---|---|---|-----------------------------------|---|---|---|---|---|---|---|-------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (SLM = 55) | | | | | | | | Flags (0) | | | | | | | | TLV Offset | | | | | | | | +| 5 | Source MEP ID | | | | | | | | | | | | | | | | Reserved for Responder MEP ID (0) | | | | | | | | | | | | | | | | +| 9 | Test ID | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | TxFCf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | Reserved for SLR: TxFCb (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 21 | [Optional TLV starts here, otherwise End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 25 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | | | | | | | | | | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | + +Figure 9.22-1 – SLM PDU format + +The fields of the SLM PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is SLM (55). +- Flags: Set to all-ZEROes. +- TLV Offset: Set to 16. +- Reserved: Reserved fields are set to all ZEROes. +- Source MEP ID: A 2-octet field used to identify the MEP transmitting the SLM frame, as specified in clause 9.22.1. +- Test ID: A 4-octet field used to identify a unique test among MEPs, as specified in clause 9.22.1. +- TxFCf: A 4-octet integer value representing the number of SLM frames transmitted, as specified in clause 9.22.1. +- Optional TLV: A Data TLV as specified in Figure 9.3-3 may be included in any SLM transmitted. For the purpose of ETH-SLM, the value part of Data TLV is unspecified. +- End TLV: An all-ZEROes octet value. + +## 9.23 SLR PDU + +The SLR PDU is used to support a single-ended ETH-SLM reply, as described in clause 8.4.1. + +### 9.23.1 SLR information elements + +The information elements carried in SLR include: + +- Source MEP ID: A 2-octet field that contains the copy of the Source MEP ID field in the received SLM. +- Responder MEP ID: A 2-octet field where the last 13 least significant bits are used to identify the MEP transmitting the SLR frame. MEP ID is unique within the MEG. +- Test ID: A 4-octet field that contains the copy of the Test ID field in the received SLM. +- TxFCf: A 4-octet field that contains the copy of the TxFCf field in the received SLM. +- TxFCb: A 4-octet field that carries the number of SLR frames transmitted by the MEP towards its peer MEP. + +### 9.23.2 SLR PDU format + +The SLR PDU format used by a MEP to transmit SLR information is shown in Figure 9.23-1. + +![](c06fd7dbef68a8b788158f2081d9d734_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|------------------------------------------------------|---|---------|---|---|-------------------|---|---|------------------|---|---|---|----------------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version | | | OpCode (SLR = 54) | | | Flags | | | | TLV Offset(16) | | | | | | | | | | | | | | | | | | | | +| 5 | Source MEP ID | | | | | | | | Responder MEP ID | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | Test ID | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | TxFCf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | TxFCb | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 21 | [Optional TLV starts here, otherwise End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | + +Figure 9.23-1 – SLR PDU format + +The fields of the SLR PDU format are as follows: + +- MEG level: A 3-bit field the value of which is copied from the last received SLM PDU. +- Version: A 5-bit field the value of which is copied from the last received SLM PDU. +- OpCode: Value for this PDU type is SLR (54). +- Flags: A 1-octet field the value of which is copied from the SLM PDU. +- TLV Offset: A 1-octet field the value of which is copied from the SLM PDU. +- Reserved: Reserved fields are set to all ZEROes. +- Source MEP ID: A 2-octet field the value of which is copied from the SLM PDU. +- Responder MEP ID: A 2-octet field used to identify the MEP transmitting the SLR frame, as specified in clause 9.22.1. +- Test ID: A 4-octet field the value of which is copied from the SLM PDU. +- TxFCf: A 4-octet field the value of which is copied from the SLM PDU. +- TxFCb: A 4-octet integer value representing the number of SLR frames transmitted, as specified in clause 9.22.1. +- Optional TLV: If present in SLM PDU, is copied from the SLM PDU. +- End TLV: A 1-octet field the value of which is copied from the SLM PDU. + +## 9.24 1SL PDU + +The 1SL PDU is used to support proactive and on-demand dual-ended ETH-SLM, as described in clause 8.4.2. + +### 9.24.1 1SL information elements + +Information elements carried in a 1SL PDU include: + +- Source MEP ID: A 2-octet field where the last 13 least significant bits are used to identify the MEP transmitting the 1SL frame. MEP ID is unique within the MEG. +- Test ID: A 4-octet field set by the transmitting MEP and used to identify when multiple tests run simultaneously towards different MEPs including concurrent on-demand and proactive tests. +- TxTCf: A 4-octet field that carries the number of 1SL frame transmitted by the MEP towards its peer MEPs. + +### 9.24.2 1SL PDU format + +The 1SL PDU format used by a MEP to transmit 1SL information is shown in Figure 9.24-1. + +![](d512ce4e3ac0de6c26d0e74a85ef2cbd_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|------|------------------------------------------------------|---|-------------|---|---|---|---|---|-------------------|---|---|---|----------|---|---|---|-----------|---|---|---|-------------|---|---|---|-----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (1SL = 53) | | | | | | | | Flags (0) | | | | | | | | TLV Offset (16) | | | | | | | | +| 5 | Source MEP ID | | | | | | | | | | | | Reserved | | | | | | | | | | | | | | | | | | | | +| 9 | Test ID | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | TxFCf | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | Reserved | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 21 | [Optional TLV starts here, otherwise End TLV] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| 25 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| : | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +| last | | | | | | | | | | | | | | | | | | | | | End TLV (0) | | | | | | | | | | | | + +Figure 9.24-1 – 1SL PDU format + +The fields of the 1SL PDU format are as follows: + +- MEG level: Refer to clause 9.1. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is 1SL (53). +- Flags: Set to all-ZEROes. +- TLV Offset: Set to 16. +- Reserved: Reserved fields are set to all ZEROes. +- Source MEP ID: A 2-octet field used to identify the MEP transmitting the 1SL frame, as specified in clause 9.24.1. +- Test ID: A 4-octet field used to identify a unique test among MEPs, as specified in clause 9.24.1. +- TxFCf: A 4-octet integer value representing the number of 1SL frames transmitted, as specified in clause 9.24.1. +- Optional TLV: A Data TLV as specified in Figure 9.3-3 may be included in any 1SL transmitted. For the purpose of ETH-SLM, the value part of Data TLV is unspecified. +- End TLV: An all-ZEROes octet value. + +## 9.25 BNM PDU + +The BNM PDU is used to support the ETH-BNM function, as described in clause 7.13. + +### 9.25.1 BNM information elements + +The information elements carried in a BNM PDU are: + +- Period: A 3-bit information element carried in the three least significant bits of the Flags field. Period contains the value of BNM transmission periodicity. BNM period values are specified in Table 9-7. +- Nominal Bandwidth: The nominal full bandwidth of the link, expressed in integer Mb/s. +- Current Bandwidth: The current bandwidth of the link, expressed in integer Mb/s. +- Port ID: Either a non-zero unique identifier for the port or zero if this identifier is not used. + +The nominal full bandwidth and the current bandwidth values represent the available bandwidth of the server layer. + +### 9.25.2 BNM PDU format + +The BNM PDU format used by a server MEP to transmit BNM information is shown in Figure 9.25-1. + +![](8ab30dbff406204a68c59ae7c1b77413_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|----|--------------------------|---|-------------|---|---|---|---|---|-------------------|---|---|---|---|---|---|---|-------|---|---|---|---|---|---|---|-----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (GNM=32) | | | | | | | | Flags | | | | | | | | TLV Offset (13) | | | | | | | | +| 5 | Sub-OpCode (BNM=1) | | | | | | | | Nominal Bandwidth | | | | | | | | | | | | | | | | | | | | | | | | +| 9 | Nominal Bandwidth (cont) | | | | | | | | Current Bandwidth | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | Current Bandwidth (Cont) | | | | | | | | Port ID | | | | | | | | | | | | | | | | | | | | | | | | +| 17 | Port ID (Cont) | | | | | | | | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.25-1 – BNM PDU format** + +The fields of the BNM PDU format are as follows: + +- MEG level: A 3-bit field that is used to carry the MEG level of the client MEG. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is GNM (32). +- Flags: One information element in the Flags field for the BNM PDU, Period, as follows: + +![](350dece6293a0ac3d4c9e4bf41eefa5d_img.jpg) + +| MSB | | | | LSB | | | | +|--------------|---|---|---|--------|---|---|---| +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| Reserved (0) | | | | Period | | | | + +**Figure 9.25-2 – Flags format in BNM PDU** + +- Period: Bits 3 to 1 indicate a transmission period with the encoding in Table 9-7. + +**Table 9-7 – BNM period values** + +| Flags[3:1] | Period value | Comments | +|------------------------------------------------------|-----------------|----------------------------| +| 000 | Invalid value | Invalid value for BNM PDUs | +| 001 | Reserved (Note) | | +| 010 | Reserved (Note) | | +| 011 | Reserved (Note) | | +| 100 | 1s | 1 frame per second | +| 101 | 10s | 1 frame per 10 seconds | +| 110 | 1 min | 1 frame per minute | +| 111 | Invalid value | Invalid value for BNM PDUs | +| NOTE – Reserved for future standardization by ITU-T. | | | + +- TLV Offset: Set to 13. +- Sub-OpCode: Value for this PDU type is BNM (1). +- Nominal bandwidth: The nominal full bandwidth of the link, expressed as integer Mb/s. +- Current bandwidth: The current bandwidth of the link, expressed as integer Mb/s. +- Port ID: An optionally used non-zero 32-bit identifier for the port to which the bandwidth information pertains. The value must be unique over all server links within the client MEG. If this identifier is not used, the value should be zero. +- End TLV: All-ZEROes octet value. + +## 9.26 EDM PDU + +The EDM PDU is used to support the ETH-ED function, as described in clause 7.14. + +### 9.26.1 EDM information elements + +The information elements carried in EDM are: + +- MEP ID: A 2-octet field where the 13 least significant bits are used to identify the MEP transmitting the EDM frame. MEP ID is unique within the MEG. +- Expected Duration: Expected duration for which the peer MEP is requested to suppress Loss of Continuity defects. + +### 9.26.2 EDM PDU format + +The EDM PDU format used by a MEP to transmit EDM information is shown in Figure 9.26-1. + +![](91c33f8e1713989e8192322ec2d1212b_img.jpg) + +| | 1 | | | | | | | | 2 | | | | | | | | 3 | | | | | | | | 4 | | | | | | | | +|----|--------------------------|---|-------------|---|---|---|---|---|-------------------|---|---|---|---|---|---|---|------------------|---|---|---|---|---|---|---|-----------------|---|---|---|---|---|---|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| 1 | MEL | | Version (0) | | | | | | OpCode (MCC=41) | | | | | | | | Flags (0) | | | | | | | | TLV Offset (10) | | | | | | | | +| 5 | OUI | | | | | | | | | | | | | | | | SubOpCode(EDM=1) | | | | | | | | | | | | | | | | +| 9 | MEP ID | | | | | | | | Expected Duration | | | | | | | | | | | | | | | | | | | | | | | | +| 13 | Expected Duration (cont) | | | | | | | | End TLV (0) | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9.26 – EDM PDU format** + +The fields of the EDM PDU format are as follows: + +- MEG level: A 3-bit field that is used to carry the MEG level of the client MEG. +- Version: Refer to clause 9.1; value is 0 in the current version of this Recommendation. +- OpCode: Value for this PDU type is MCC (41). +- Flags: Set to all ZEROes. +- TLV Offset: Set to 10. +- OUI: Set to the ITU-T OUI, 00-19-A7. +- Sub-OpCode: Value for this PDU type is EDM (1). +- MEP ID: A 13-bit integer value identifying the transmitting MEP within the MEG. The three MSBs of the first octet are not used and set to ZERO. +- Expected Duration: The duration, in seconds, for which the loss of continuity is expected to last (starting from when the first EDM is transmitted). +- End TLV: all-ZEROes octet value. + +# 10 OAM frame addresses + +OAM frames are identified by a unique EtherType the value of which is 0x8902. OAM frames processing and filtering at a MEP is based on the OAM EtherType and MEG level fields for both unicast and multicast DA. + +As indicated in clauses 7 and 8, the DA in an OAM frame could be multicast or unicast depending on the specific OAM functionality. The SA in an OAM frame is always unicast. + +This clause provides further discussion on the choice of DA in specific OAM functions. Table 10-1 provides a summary of the DAs that are applicable for different OAM types. + +NOTE – The choice of MAC DA for Ethernet OAM frames is application-specific. Implementations are not required to support all of the addresses specified in this Recommendation; however, support for those addresses specified in [ITU-T G.8021] is required. + +**Table 10-1 – OAM frame DA** + +| OAM type | DAs for frames with OAM PDU | +|--------------------|------------------------------------------| +| CCM | Multicast Class 1 DA or unicast DA | +| LBM | Unicast DA or multicast Class 1 DA | +| LBR | Unicast DA | +| LTM | Multicast Class 2 DA | +| LTR | Unicast DA | +| AIS | Multicast Class 1 DA or unicast DA | +| LCK | Multicast Class 1 DA or unicast DA | +| TST | Unicast DA or multicast Class 1 DA | +| Linear APS | Refer to [ITU-T G.8031] | +| Ring APS | Refer to [ITU-T G.8032] | +| MCC | Unicast DA or multicast Class 1 DA | +| LMM | Unicast DA or multicast Class 1 DA | +| LMR | Unicast DA | +| 1DM | Unicast DA or multicast Class 1 DA | +| DMM | Unicast DA or multicast Class 1 DA | +| DMR | Unicast DA | +| EXM, EXR, VSM, VSR | Outside the scope of this Recommendation | +| CSF | Multicast Class 1 DA or unicast DA | +| SLM | Unicast DA or multicast Class 1 DA | +| SLR | Unicast DA | +| 1SL | Unicast DA or Multicast Class 1 DA | +| BNM | Multicast Class 1 DA or unicast DA | +| EDM | Multicast Class 1 DA or unicast DA | + +## 10.1 Multicast destination addresses + +The following types of multicast addresses are required depending on the type of OAM function: + +- Multicast DA Class 1: OAM frames that are addressed to all peer MEPs in a MEG (e.g., CCM, Multicast LBM, AIS, etc.). +- Multicast DA Class 2: OAM frames that are addressed to all MIPs and peer MEPs in a MEG (e.g., LTM). +- Multicast DA for Ring APS: OAM frames used for Ethernet ring protection. + +Normally, a single multicast DA Class 1 address and a single multicast DA Class 2 address would be sufficient. However, for a short-term deployment of Ethernet OAM across the current Ethernet equipment, a multicast DA could also implicitly carry the MEG level. This would require 8 distinct addresses for each of the multicast DA Classes 1 and 2 for the 8 different MEG levels. + +Specific values for 8 multicast addresses for Class 1 and 8 Multicast addresses for Class 2 are 01-80-C2-00-00-3x and 01-80-C2-00-00-3y respectively; x represents the MEG level, with x being a value in the range 0-7, and y represents the MEG level, with y being a value in the range 8-F. + +In addition, a specific range of multicast DA with ITU OUI (01-19-A7) is used for Ring APS frames. See more details in [ITU-T G.8032]. + +## 10.2 CCM + +CCM frames are generated with multicast Class 1 DA in a multipoint MEG, and are typically generated with a multicast DA in a point-to-point MEG except as described below. + +Using a multicast DA, CCM frames allow discovery of MAC addresses associated with peer MEPs of the receiving MEP. The use of a multicast DA also allows for the detection of misconnections among flow domain fragments. Detection of misconnections is described in clause 7.1. + +When detection of the above conditions is important, a multicast DA must be used for CCM frames. When the above conditions are not expected or are not required to be detected and the data frames in different services instances are distinguished using unicast DAs (as in provisioned environments for point-to-point connections), CCM frames are generated with the unicast DA of the peer MEP. + +## 10.3 LBM + +LBM frames can be generated with unicast or multicast Class 1 DAs, as per the unicast ETH-LB or multicast ETH-LB functions respectively. + +## 10.4 LBR + +LBR frames are always generated with unicast DAs. + +## 10.5 LTM + +LTM frames are generated with a multicast Class 2 DA. + +A multicast DA is used instead of a unicast DA for LTM frames since in current bridges, the MIPs would not be able to intercept a frame with a unicast DA which was not their own address. Therefore, the MIPs would not be able to reply and would simply forward the LTM frame with the unicast DA. The limitation is that current ports do not look at the EtherType before looking at the DA. + +## 10.6 LTR + +LTR frames are always generated with unicast DAs. + +## 10.7 AIS + +AIS frames are generated with a multicast Class 1 DA in a multipoint MEG, and are typically generated with a multicast Class 1 DA in a point-to-point MEG except as described below. + +In provisioned environments for point-to-point connections where the data frames in different services instances are distinguished using unicast DAs, AIS frames are generated with the unicast DA of the downstream MEP. + +## 10.8 LCK + +LCK frames are generated with multicast Class 1 DA in a multipoint MEG, and are typically generated with a multicast Class 1 DA in a point-to-point MEG except as described below. + +In provisioned environments for point-to-point connections where the data frames in different services instances are distinguished using unicast DAs, AIS frames are generated with the unicast DA of the downstream MEP. + +## 10.9 TST + +TST frames are generated with unicast DAs. TST frames may be generated with a multicast Class 1 DA if multipoint diagnostics are desired. + +## **10.10 APS** + +For linear APS, refer to [ITU-T G.8031]. For ring APS, refer to [ITU-T G.8032]. + +## **10.11 MCC** + +MCC frames are generated with unicast DAs. For the case when a point-to-point VLAN is being used, a multicast Class 1 DA may be used. + +## **10.12 LMM** + +LMM frames are generated with unicast DAs. LMM frames may be generated with a multicast Class 1 DA if multipoint measurements are desired. + +## **10.13 LMR** + +LMR frames are always generated with unicast DAs. + +## **10.14 IDM** + +IDM frames are generated with unicast DAs. IDM frames may be generated with a multicast Class 1 DA if multipoint measurements are desired. + +## **10.15 DMM** + +DMM frames are generated with unicast DAs. DMM frames may be generated with a multicast Class 1 DA if multipoint measurements are desired. + +## **10.16 DMR** + +DMR frames are always generated with unicast DAs. + +## **10.17 EXM** + +EXM frames DA is outside the scope of this Recommendation. + +## **10.18 EXR** + +EXR frames DA is outside the scope of this Recommendation. + +## **10.19 VSM** + +VSM frames DA is outside the scope of this Recommendation. + +## **10.20 VSR** + +VSR frames DA is outside the scope of this Recommendation. + +## **10.21 CSF** + +CSF frames are generated with a multicast Class 1 DA in a multipoint MEG, and are typically generated with a multicast class 1 DA in a point-to-point MEG except as described below. + +In provisioned environments for point-to-point connections where the data frames in different services instances are distinguished using unicast DA, CSF frames are generated with the unicast DA of the downstream MEP. + +## **10.22 SLM** + +SLM frames are generated with unicast DAs. SLM frames may be generated with a multicast Class 1 DA if multipoint measurements are desired. + +## 10.23 SLR + +SLR frames are always generated with unicast DAs. + +## 10.24 1SL + +1SL frames are generated with unicast DAs. 1SL frames may be generated with a multicast Class 1 DA if multipoint measurements are desired. + +## 10.25 BNM + +BNM frames are generated with a multicast Class 1 DA in a multipoint MEG, and are typically generated with a multicast class 1 DA in a point-to-point MEG except as described below. + +In provisioned environments for point-to-point connections where the data frames in different services instances are distinguished using unicast DAs, BNM frames are generated with the unicast DA of the downstream MEP. + +## 10.26 EDM + +EDM frames are generated with a multicast Class 1 DA in a multipoint MEG, and are typically generated with a multicast class 1 DA in a point-to-point MEG except as described below. + +In provisioned environments for point-to-point connections where the data frames in different services instances are distinguished using unicast DAs, EDM frames are generated with the unicast DA of the downstream MEP. + +# 11 OAM PDU validation and versioning + +This clause describes rules for validation and versioning of OAM PDUs that are designed to ensure that implementations of this Recommendation will interoperate with implementations of future versions of this Recommendation. In addition, these rules allow implementations to provide proprietary, non-standard extensions to the protocol in a way that does not jeopardize interoperability with future versions of this Recommendation or restrict the ability of future versions of this Recommendation to extend the Recommendation functionality. + +NOTE 1 – The change to the LTM format between the 2006 and 2008 versions of this Recommendation did not change the version number; however, future revisions to this Recommendation must align with these rules. + +NOTE 2 – The rules described here only apply to how PDUs with different versions are interpreted. Further details regarding how PDUs are subsequently processed, where applicable, may be found in the atomic function definitions in [ITU-T G.8021] and [ITU-T G.8032]. + +NOTE 3 – These rules do not apply to parts of PDUs that are not specified in ITU-T Recommendations, for example, the data fields of VSM, VSR, EXM and EXR PDUs. + +## 11.1 OAM PDU transmission + +OAM PDU transmission is required to meet the following requirements: + +- The fixed header fields shall be transmitted exactly as specified in this Recommendation. +- All bits defined as "reserved" in this Recommendation shall be transmitted as 0. +- Additional fields shall not be added to the fixed header specified in this Recommendation. +- Code points reserved in this Recommendation or [IEEE 802.1Q] shall not be transmitted in any OAM PDU; for example, reserved values of the OpCode field (Table 9-1), the TLV Type field (Table 9-2), or the MEG ID format field (Table A.1). +- Additional fields shall not be added to any TLV specified in this Recommendation. + +## 11.2 OAM PDU validation in reception + +Received OAM PDUs are subject to a number of validation tests and are discarded without further processing if they fail these tests. This clause does not provide an exhaustive list of such tests, it covers only those aspects that are most important for future compatibility. In addition to the tests specified here, it may be assumed that if an OAM PDU with a particular OpCode does not conform to the corresponding description in clause 9, it fails the tests. The initial validation test is to ensure that the OAM PDU is sufficiently long to contain the MEG level and version fields. OAM PDUs that fail this test are discarded. + +The OAM PDU is subsequently processed in accordance with whichever is numerically the lower of 1) the Version field in the OAM PDU and 2) the highest version number known to the receiving implementation. That is, a version 1 implementation receiving a version 0 OAM PDU processes it according to version 0, and it processes a version 1 OAM PDU according to version 1. The imposition is on future versions of this Recommendation that all earlier version implementations can process received OAM PDUs correctly, that is, OAM PDUs specified by later versions of this Recommendation must remain valid when processed according to version 0. + +The following validation tests are used, according to the version selected as described above: + +- The fixed header length, as determined by the TLV Offset field, is not shorter than the length specified by the selected version. +- The OAM PDU is sufficiently long to contain a fixed header of the length specified by the selected version. + +If the OAM PDU contains a TLV that needs to be processed, the following validation tests are used, according to the version selected as described above: + +- The OAM PDU is sufficiently long to contain a TLV Value field whose length is specified by the TLV Length field. +- A TLV Length field does not indicate a length that is shorter than the minimum length for that TLV as specified by the selected version. + +The following criteria shall not be used to validate a received OAM PDU: + +- The fixed header can be longer than the length specified by the selected version. +- Bits can be set in the reserved bits of the Flags field. +- A TLV can have a Type field not specified by the selected version of the standard. +- A TLV's Length field can be larger than the value (if any) specified in the selected version of the standard. +- Either the TLV Offset field, or the Length field of the last TLV in the OAM PDU, can indicate a position for the first (next) TLV that coincides with the end of the OAM PDU. That is, the end TLV can be missing from the OAM PDU. +- TLVs may occur in any order in the OAM PDU, unless the descriptions in clause 9 specify otherwise. + +NOTE – The selection of the version to be used for processing a received OAM PDU does not impact the version copying requirement if an OAM PDU reply needs to be generated. This means that a version 0 implementation receiving a version 1 OAM PDU request interprets it according to version 0, but replies depending on the replying rule, unless this rule has version dependency. In this case, the reception of a version 1 OAM PDU reply cannot be used as an indication that the OAM PDU request has been processed according to version 1. + +## 11.3 OAM PDU reception after validation + +Received OAM PDUs that pass the validation tests described above must be processed in accordance with the following rules, and in accordance with the same version selected for the validation tests (that is, the numerically lower one of the Version field in the OAM PDU and the highest version number known to the receiving implementation). + +- Only those fields in the fixed header portion of the OAM PDU that are defined in the selected version are processed; any extra octets in the fixed header, if it is longer than the length specified by the selected version, are ignored. +- Any TLV with a Type field not specified by the selected version is ignored, except if the OAM PDU is forwarded or retransmitted (with or without modification), or if a new OAM PDU is sent in response to the received OAM PDU, the TLV is copied without modification into the forwarded or retransmitted PDU or into the response PDU. +- Any part of the OAM PDU following the end TLV is ignored (the lack of an end TLV is not an error). +- If any TLV's Length field is larger than the value (if any) specified by the selected version, then any octets following those specified by the selected version are ignored. +- All bits undefined in this Recommendation, e.g., reserved bits in the Flags field, are ignored. + +# Annex A + +## MEG ID format + +(This annex forms an integral part of this Recommendation.) + +The features of maintenance entity group identifiers (MEG IDs) are: + +- Each MEG ID must be globally unique. +- Where it may be expected that the MEG may be required for path set-up across an inter-operator boundary, the MEG ID must be available to other network operators. +- The MEG ID should not change while the MEG remains in existence. +- The MEG ID should be able to identify the network operator which is responsible for the MEG. +- The generic format of MEG IDs specific to this Recommendation is shown in Figure A.1. + +![](4a390493f601ce1ac6b9201db4e28b5a_img.jpg) + +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +|----|---------------|---|---|---|---|---|---|---| +| 1 | Reserved (01) | | | | | | | | +| 2 | MEG ID Format | | | | | | | | +| 3 | MEG ID Length | | | | | | | | +| 4 | MEG ID Value | | | | | | | | +| 5 | | | | | | | | | +| : | | | | | | | | | +| : | | | | | | | | | +| : | | | | | | | | | +| 48 | | | | | | | | | + +Figure A.1 – Generic MEG ID format + +The MEG ID format type is identified by the MEG ID Format field. Specific values of MEG ID format type are defined in Table A.1 and described in clauses A.1 and A.2 below. + +Table A.1 – MEG ID format type + +| MEG ID format type value | TLV name | +|-----------------------------------------------------------------|-------------------------| +| 00, 5-31, 64-255 | Reserved (Note 1) | +| 1-4 | See below (Note 2) | +| Types specific to this Recommendation | | +| 32 | ICC-based format | +| 33 | ICC and CC based Format | +| 34-63 | Reserved (Note 3) | +| NOTE 1 – Reserved for definition by [IEEE 802.1]. | | +| NOTE 2 – Use values as defined in Table 21-20 of [IEEE 802.1Q]. | | +| NOTE 3 – Reserved for future standardization by ITU-T. | | + +## A.1 ICC-based MEG\_ID format + +Figure A.2 shows the format that uses the ITU carrier code (ICC). ICC is a code assigned to a network operator/service provider, maintained by the ITU Telecommunication Standardization Bureau (TSB) as per [ITU-T M.1400]. + +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | | | | | | | +|----|-----------------------|------------------|---|---|---|---|---|---|--|--|--|--|--|--|--| +| 1 | Reserved (01) | | | | | | | | | | | | | | | +| 2 | MEG ID Format (32) | | | | | | | | | | | | | | | +| 3 | MEG ID Length (13) | | | | | | | | | | | | | | | +| 4 | 0 | MEG ID Value[1] | | | | | | | | | | | | | | +| 5 | 0 | MEG ID Value[2] | | | | | | | | | | | | | | +| 15 | 0 | MEG ID Value[12] | | | | | | | | | | | | | | +| 16 | 0 | MEG ID Value[13] | | | | | | | | | | | | | | +| 19 | Unused (= all-ZEROes) | | | | | | | | | | | | | | | +| 20 | | | | | | | | | | | | | | | | +| 47 | | | | | | | | | | | | | | | | +| 48 | | | | | | | | | | | | | | | | + +**Figure A.2 – ICC-based MEG ID format** + +The MEG ID value identified by Type 32 consists of 13 characters coded according to [ITU-T T.50] (International Reference Alphabet – 7-bit coded character set for information exchange). + +Note that the MEG\_ID Type 32 may not be globally unique because, as described in [ITU-T M.1400], the same ICC can exist in different countries. Therefore, the MEG ID Type 32 provides uniqueness only within a country. + +Figure A.3 shows the structure of an ICC-based MEG ID Value. + +| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | +|-----|-----|-----|-----|-----|-----|---|---|---|----|----|----|----| +| ICC | UMC | | | | | | | | | | | | +| ICC | UMC | | | | | | | | | | | | +| ICC | | UMC | | | | | | | | | | | +| ICC | | | UMC | | | | | | | | | | +| ICC | | | | UMC | | | | | | | | | +| ICC | | | | | UMC | | | | | | | | + +**Figure A.3 – Structure of ICC- based MEG ID Value** + +It consists of two subfields: the ITU carrier code (ICC) followed by a unique MEG ID code (UMC). + +The ITU carrier code consists of 1-6 alphabetic (i.e., A-Z) and or numeric (i.e., 0-9), left-justified characters. The UMC code immediately follows the ICC and shall consist of 7-12 characters, with trailing NULLs, completing the 13-character MEG ID value. The UMC shall be a matter for the organization to which the ICC has been assigned, provided that uniqueness is guaranteed within a country. + +## A.2 Global MEG ID format based on CC and ICC + +Figure A.4 shows the format that uses the ITU carrier code (ICC) with country code (CC). The MEG ID Value is identified by Type 33 and consists of 15 characters coded according to [ITU-T T.50]. + +Figure A.5 shows the MEG ID Value structure identified by CC and ICC. It consists of three subfields: the Country Code (CC), the ITU carrier code (ICC), followed by a unique MEG ID code (UMC). The country code (alpha-2) is a string of 2 alphabetic characters represented by upper case letters (i.e., A-Z). The country code format is defined in [ISO 3166-1]. The ITU carrier code consists of 1-6 alphabetic, (i.e., A-Z) and or numeric (i.e., 0-9), left-justified characters. + +The UMC code immediately follows the ICC and shall consist of 7-12 characters, with trailing NULLs, completing the 15-character MEG ID Value. The UMC shall start with the character "/" if the ICC is less than 6 characters (as illustrated in Figure A.5) and be unique within the context of the organization to which the ITU carrier codes have been assigned. + +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | | | | | | | +|----|-----------------------|------------------|---|---|---|---|---|---|--|--|--|--|--|--|--| +| 1 | Reserved (01) | | | | | | | | | | | | | | | +| 2 | MEG ID Format (33) | | | | | | | | | | | | | | | +| 3 | MEG ID Length (15) | | | | | | | | | | | | | | | +| 4 | 0 | MEG ID Value[1] | | | | | | | | | | | | | | +| 5 | 0 | MEG ID Value[2] | | | | | | | | | | | | | | +| 17 | 0 | MEG ID Value[14] | | | | | | | | | | | | | | +| 18 | 0 | MEG ID Value[15] | | | | | | | | | | | | | | +| 19 | Unused (= all-ZEROes) | | | | | | | | | | | | | | | +| 20 | | | | | | | | | | | | | | | | +| 47 | | | | | | | | | | | | | | | | +| 48 | | | | | | | | | | | | | | | | + +**Figure A.4 – CC and ICC based global MEG ID format** + +| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | | | +|----|-----|---|-----|-----|---|-----|-----|---|----|----|----|----|----|----|--|--| +| CC | ICC | / | UMC | | | | | | | | | | | | | | +| CC | ICC | / | UMC | | | | | | | | | | | | | | +| CC | ICC | / | | UMC | | | | | | | | | | | | | +| CC | ICC | | | / | | UMC | | | | | | | | | | | +| CC | ICC | | | | / | | UMC | | | | | | | | | | +| CC | ICC | | | | | | UMC | | | | | | | | | | + +**Figure A.5 – Structure of CC and ICC based global MEG ID Value** + +# Annex B + +## Ethernet link trace (ETH-LT) of ITU-T Y.1731 interoperability considerations + +(This annex forms an integral part of this Recommendation.) + +This annex describes the interworking of Ethernet MEPs and MIPs, supporting different types of Ethernet link trace (ETH-LT) (i.e., ETH-LT as specified in [ITU-T Y.1731] and in this Recommendation) and identifies the basic requirements to support interworking under the ME where two types of MEPs or MIPs exist. + +## B.1 Ethernet link trace (ETH-LT) as specified in ITU-T Y.1731 + +The ETH-LT function specified in [ITU-T Y.1731] differs from that specified in this Recommendation as follows: + +- The LTM Egress Identifier TLV and its format are not specified as part of the specification of the LTM transmission and its PDU in clauses 7.3.1 and 9.5 of [ITU-T Y.1731] whereas they are specified as mandatory in this Recommendation. +- The LTR Egress Identifier TLV and its format are not specified as part of the specification of the LTR transmission and its PDU in clauses 7.3.2 and 9.6 of [ITU-T Y.1731] but are specified as mandatory in this Recommendation. Also, Reply Ingress TLV and Reply Egress TLV are optional in [ITU-T Y.1731], whereas they are specified as mandatory in this Recommendation. +- FwdYes and TerminalMEP are specified in bit 7 and bit 6, respectively, of the Flags field of the LTR PDU format in clause 9.6.2 of this Recommendation, whereas they are not specified in [ITU-T Y.1731]. +- [ITU-T Y.1731] does not specify the ETH-LT responder at a MIP, and a MIP could reside at both ingress and egress ports in equipment compliant with [ITU-T Y.1731] (hereafter referred to as 'v2006', which preceded version 2007 or 'v2008' of this Recommendation), whereas in this Recommendation the ETH-LT responder is specified so that equipment compliant with this Recommendation can only host one MIP. + +## B.2 Interworking with ITU-T Y.1731 + +In the case of an ME consisting of a v2006 MEP that transmits an LTM frame and some v2008 MIPs, or the case of an ME consisting of a v2006 MEP that transmits an LTM frame and a v2008 MEP that receives the LTM frame and transmits an LTR frame, the v2008 MIP or v2008 MEP may discard the LTM frame from the v2006 MEP due to the absence of the LTM Egress Identifier TLV. In this case, to maintain interoperability, the v2008 MIP may forward the LTM frame and transmit the LTR frame by recognizing that the LTM frame does not have the TLV and by behaving as a v2006 MIP. Similarly, the v2008 MEP may transmit the LTR frame by recognizing that the LTM frame does not have the TLV and by behaving as a v2006 MEP. See Figure B.1. + +![Figure B.1 – Interoperability case 1. The diagram shows two network configurations. The top configuration features a v2006 MEP (yellow triangle) sending an LTM frame to a v2008 MIP (blue circle). The v2008 MIP has a self-loop for LTM and LTR frames. The bottom configuration shows a v2006 MEP (yellow triangle) sending an LTM frame to a v2008 MEP (blue triangle), which then responds with an LTR frame. The text 'G.8013-Y.1731(11)_FB-1' is at the bottom right.](e8f5117fb031f413a836525061addd61_img.jpg) + +Figure B.1 – Interoperability case 1. The diagram shows two network configurations. The top configuration features a v2006 MEP (yellow triangle) sending an LTM frame to a v2008 MIP (blue circle). The v2008 MIP has a self-loop for LTM and LTR frames. The bottom configuration shows a v2006 MEP (yellow triangle) sending an LTM frame to a v2008 MEP (blue triangle), which then responds with an LTR frame. The text 'G.8013-Y.1731(11)\_FB-1' is at the bottom right. + +**Figure B.1 – Interoperability case 1** + +In the case of an ME consisting of a v2008 MEP that transmits an LTM frame and some v2006 MIPs and/or the case of a v2008 MEP that receives an LTM frame and transmits an LTR frame, the v2008 MEP receives the LTR frame without the LTR Egress Identifier TLV and without the Reply Ingress TLV or Reply Egress TLV generated by v2006 MIPs and/or MEP. The absence of these TLVs in the LTR frame is considered invalid in the v2008 version. In order to maintain interoperability, equipment compliant with the v2008 version may be configured to identify this LTR frame as valid. See Figure B.2. + +![Figure B.2 – Interoperability case 2. The diagram shows a v2008 MEP (blue triangle) sending an LTM frame to a v2006 MIP (yellow circle), which in turn sends an LTM frame to a v2006 MEP (yellow triangle). The v2006 MEP sends an LTR frame back to the v2006 MIP, which then forwards it to the v2008 MEP. The text 'G.8013-Y.1731(11)_FB-2' is at the bottom right.](5cf80bac69830ea773ac17c87e0ae24d_img.jpg) + +Figure B.2 – Interoperability case 2. The diagram shows a v2008 MEP (blue triangle) sending an LTM frame to a v2006 MIP (yellow circle), which in turn sends an LTM frame to a v2006 MEP (yellow triangle). The v2006 MEP sends an LTR frame back to the v2006 MIP, which then forwards it to the v2008 MEP. The text 'G.8013-Y.1731(11)\_FB-2' is at the bottom right. + +**Figure B.2 – Interoperability case 2** + +In the case of an ME consisting of a v2008 MEP that transmits an LTM frame and some v2006 MIPs located in both the ingress and egress ports of a piece of equipment, the piece of equipment may transmit two LTR frames to the v2008 MEP. In receiving the LTR frames at the v2008 MEP, the behaviour is the same as in the case mentioned above (see Figure B.3). It is noted that this behaviour is compatible with the LTR analysis according to Annex J.5 of [IEEE 802.1Q], as long as each of the MPs that decrement the LTM's TTL field also return an LTR. + +![Figure B.3 – Interoperability case 3. The diagram shows a v2008 MEP (blue triangle) sending an LTM frame to a v2006 MIP (Ingress) (yellow circle). The Ingress MIP sends an LTM frame to another v2006 MIP (Egress) (yellow circle), which then sends an LTR frame back to the Ingress MIP, which finally forwards it to the v2008 MEP. The text 'G.8013-Y.1731(11)_FB-3' is at the bottom right.](b3cd59f24a21fab4cd8ac6fe743ab3a9_img.jpg) + +Figure B.3 – Interoperability case 3. The diagram shows a v2008 MEP (blue triangle) sending an LTM frame to a v2006 MIP (Ingress) (yellow circle). The Ingress MIP sends an LTM frame to another v2006 MIP (Egress) (yellow circle), which then sends an LTR frame back to the Ingress MIP, which finally forwards it to the v2008 MEP. The text 'G.8013-Y.1731(11)\_FB-3' is at the bottom right. + +**Figure B.3 – Interoperability case 3** + +# Appendix I + +## Ethernet network scenarios + +(This appendix does not form an integral part of this Recommendation.) + +## I.1 Shared MEG levels example + +Figure I.1 provides an example scenario with the default assignment of MEG levels, where the customer, provider and operator roles share the MEG levels. In the figure, triangles represent MEPs, circles represent MIPs, and diamonds represent TrCPs. + +![Diagram of Ethernet network scenarios showing shared MEG levels. The diagram illustrates a network path from Customer equipment (1) to Operator A bridges (2, 3, 4) to Operator B bridges (5, 6, 7) to Customer equipment (9). Various MEG levels are assigned to different types of network elements: Ca1a (green line), IPa (blue line), IPb (blue line), Oa1a (orange line), IOa (pink line), Ob1a (pink line), Ob2a (blue line), and Ob2b (blue line). The diagram also shows the relationship between ETH and ETHor SRV layers.](dcf83796ccf494110638fbd4677b931d_img.jpg) + +The diagram illustrates a network path from Customer equipment (1) to Operator A bridges (2, 3, 4) to Operator B bridges (5, 6, 7) to Customer equipment (9). Various MEG levels are assigned to different types of network elements: Ca1a (green line), IPa (blue line), IPb (blue line), Oa1a (orange line), IOa (pink line), Ob1a (pink line), Ob2a (blue line), and Ob2b (blue line). The diagram also shows the relationship between ETH and ETHor SRV layers. + +Diagram of Ethernet network scenarios showing shared MEG levels. The diagram illustrates a network path from Customer equipment (1) to Operator A bridges (2, 3, 4) to Operator B bridges (5, 6, 7) to Customer equipment (9). Various MEG levels are assigned to different types of network elements: Ca1a (green line), IPa (blue line), IPb (blue line), Oa1a (orange line), IOa (pink line), Ob1a (pink line), Ob2a (blue line), and Ob2b (blue line). The diagram also shows the relationship between ETH and ETHor SRV layers. + +**Figure I.1 – Example MEG level assignment for shared MEG levels** + +- Customer ME (Ca1a) can be assigned a customer MEG level 5. This allows for more customer MEs to be created at higher MEG levels, i.e., 6 and 7, if these customer MEs at additional customer MEG levels are needed. +- Provider ME (Pa1a) can be assigned a provider MEG level 4. This allows for more provider MEs to be created at a lower MEG level, i.e., 3, if additional MEs at a lower provider MEG level are needed. +- End-to-end operator MEs (Oa1a and Ob1a) can be assigned an operator MEG level 2. This allows for more operator MEs to be created at lower MEG levels, i.e., 1 and 0, if these operator MEs at additional operator MEG levels are needed in each operator network. +- Segment operator MEs in Operator B's network (Ob2a and Ob2b) can be now assigned a lower MEG level, for example 1, if Operator B needs such MEs. +- MEs between the customer and provider (IPa and IPb) can be assigned a MEG level 0. This allows providers to filter such OAM frames at UNI\_N since the provider is required to provide transparency only to customer MEG levels 7, 6, and 5. +- Inter-operator ME (IOa) can be assigned a MEG level 0. This allows the operator to filter such OAM frames since the operator is required to provide transparency only to customer and provider MEG levels. + +## I.2 Independent MEG levels example + +Figure I.2 provides an example scenario where the customer and service provider do not share the MEG levels. However, the service provider and operator share the MEG levels. In the figure, triangles represent MEPs, circles represent MIPs, and diamonds represent TrCPs. + +![Diagram illustrating independent MEG level assignment. The top part shows a network path: Customer equipment (1) - Operator A bridges (2a, 2b) - Bridge (3) - Bridge (4) - Bridge (5) - Operator B bridges (6b, 6a) - Customer equipment (7). Below this, the C-TAG (Customer VLANs 11, 12, 21, 22) is shown as a green line with green triangles (MEPs) at the customer equipment and green circles (MIPs) at the bridges. The S-TAG (Service VLANs 10, 20) is shown as a blue line with blue triangles (MEPs) at the bridges and blue circles (MIPs) at the bridges. Below the S-TAG, an orange line with orange triangles (MEPs) and circles (MIPs) represents another service VLAN, and a pink line with pink triangles (MEPs) and circles (MIPs) represents a third service VLAN. The diagram is labeled G.8013-Y.1731(15)-Amd.1(18)_FI.2.](bd0283b61b6a59829e9370b29076c79a_img.jpg) + +Diagram illustrating independent MEG level assignment. The top part shows a network path: Customer equipment (1) - Operator A bridges (2a, 2b) - Bridge (3) - Bridge (4) - Bridge (5) - Operator B bridges (6b, 6a) - Customer equipment (7). Below this, the C-TAG (Customer VLANs 11, 12, 21, 22) is shown as a green line with green triangles (MEPs) at the customer equipment and green circles (MIPs) at the bridges. The S-TAG (Service VLANs 10, 20) is shown as a blue line with blue triangles (MEPs) at the bridges and blue circles (MIPs) at the bridges. Below the S-TAG, an orange line with orange triangles (MEPs) and circles (MIPs) represents another service VLAN, and a pink line with pink triangles (MEPs) and circles (MIPs) represents a third service VLAN. The diagram is labeled G.8013-Y.1731(15)-Amd.1(18)\_FI.2. + +**Figure I.2 – Example MEG level assignment for independent MEG levels** + +- In the above example, four customer VLANs (11, 12, 21 and 22) and the corresponding customer MEGs (C-TAG, in the figure) are completely independent of the two service provider VLANs (20 and 10) and corresponding service provider MEGs (S-TAG in the Figure). +- As a consequence, the customer and service provider can independently use all eight MEG levels. +- The service provider and operator however share the MEG level space, in a manner similar to the one of Figure I.1. In this case, the eight MEG levels can be agreed mutually between the service provider and the operator. +- In the above example, the customer must send OAM frames as VLAN-tagged or priority-tagged frames to utilize all eight MEG levels independently. However, if the customer uses untagged OAM frames, the MEG levels may not be independent anymore and the customer and provider MEG levels need to be mutually agreed between the customer and the service provider. + +# Appendix II + +## Frame loss measurement + +(This appendix does not form an integral part of this Recommendation.) + +The four cases below should be taken into account for frame loss calculation. + +- a) No wraparound for either the transmit or the receive counter. +- b) Only the transmit counter wraps around. +- c) Only the receive counter wraps around. +- d) Both transmit and receive counters wrap around. + +For each case, the frame loss can be calculated as follows: + +- a) No wrapping around for both transmit and receive counters. + +![Figure II.1: No wraparound. Diagram showing transmit and receive counters with no wraparound. The transmit counter (CT1 to CT2) and receive counter (CR1 to CR2) both increase linearly. Frames are shown at time T and T+t. The frame loss is indicated by a red bar at the bottom right.](b1e7bb95fa1587d870de03df02477df4_img.jpg) + +The diagram illustrates the 'No wraparound' case. On the left, the 'Transmit counter' shows a linear increase from CT1 to CT2. Two frames are shown: one at time T (blue hatched) and one at time T+t (blue hatched). The frame at T+t is partially lost. On the right, the 'Receive counter' shows a linear increase from CR1 to CR2. Two frames are shown: one at time T (yellow hatched) and one at time T+t (yellow hatched). The frame at T+t is partially lost. Below the counters, a red bar labeled 'Frame loss' indicates the lost portion of the frame at T+t. The text 'G.8013-Y.1731(15)\_FII.1' is visible in the bottom right. + +Figure II.1: No wraparound. Diagram showing transmit and receive counters with no wraparound. The transmit counter (CT1 to CT2) and receive counter (CR1 to CR2) both increase linearly. Frames are shown at time T and T+t. The frame loss is indicated by a red bar at the bottom right. + +Figure II.1 – No wraparound + +For this case, the frame loss can be calculated by the simple calculation: + +$$\text{Frame loss} = (CT2 - CT1) - (CR2 - CR1)$$ + +- b) Only transmit counter wraps around. + +![Figure II.2: Transmit counter wraps around. Diagram showing the transmit counter wrapping around from CTMAX to CT2. The receive counter (CR1 to CR2) increases linearly. Frames are shown at time T and T+t. The frame loss is indicated by a red bar at the bottom right.](cc3d87694102054bcd694ae696bc41fa_img.jpg) + +The diagram illustrates the case where 'Only transmit counter wraps around'. On the left, the 'Transmit counter' shows a wraparound from CTMAX to CT2. Two frames are shown: one at time T (blue hatched) and one at time T+t (blue hatched). The frame at T+t is partially lost. On the right, the 'Receive counter' shows a linear increase from CR1 to CR2. Two frames are shown: one at time T (yellow hatched) and one at time T+t (yellow hatched). The frame at T+t is partially lost. Below the counters, a red bar labeled 'Frame loss' indicates the lost portion of the frame at T+t. The text 'G.8013-Y.1731(15)\_FII.2' is visible in the bottom right. + +Figure II.2: Transmit counter wraps around. Diagram showing the transmit counter wrapping around from CTMAX to CT2. The receive counter (CR1 to CR2) increases linearly. Frames are shown at time T and T+t. The frame loss is indicated by a red bar at the bottom right. + +Figure II.2 – Transmit counter wraps around + +In this case, frame loss can be calculated by the following equation, as described in the previous clause + +$$\begin{aligned} \text{Frame loss} &= ((CTMAX - CT1) + CT2 + 1) - (CR2 - CR1) \\ &= (CT2 - CT1) - (CR2 - CR1) + (CTMAX + 1) \end{aligned}$$ + +- c) Only the receive counter wraps around. + +![Figure II.3: Diagram showing only the receive counter wrapping around. The transmit counter (CT) increases from CT1 to CT2. The receive counter (CR) wraps around from CRMAX to CR1. A frame is lost between CT1 and CT2, and between CR2 and CR1. The diagram includes a 'Frame loss' label and the reference G.8013-Y.1731(15)_FII.3.](66bf96eec8f739d5e7c9957a178e34e2_img.jpg) + +The diagram illustrates a scenario where only the receive counter wraps around. The transmit counter (CT) starts at CT1 and increases to CT2. The receive counter (CR) starts at CR2, wraps around from CRMAX to CR1, and then increases to CR2. A frame is lost between CT1 and CT2, and between CR2 and CR1. The diagram includes a 'Frame loss' label and the reference G.8013-Y.1731(15)\_FII.3. + +Figure II.3: Diagram showing only the receive counter wrapping around. The transmit counter (CT) increases from CT1 to CT2. The receive counter (CR) wraps around from CRMAX to CR1. A frame is lost between CT1 and CT2, and between CR2 and CR1. The diagram includes a 'Frame loss' label and the reference G.8013-Y.1731(15)\_FII.3. + +**Figure II.3 – Receive counter wraps around** + +$$\begin{aligned} \text{Frame loss} &= (CT2 - CT1) - ((CRMAX - CR1) + CR2 + 1) \\ &= (CT2 - CT1) - (CR2 - CR1) - (CRMAX + 1) \end{aligned}$$ + +- d) Both transmit and receive counters wrap around. + +![Figure II.4: Diagram showing both transmit and receive counters wrapping around. The transmit counter (CT) wraps around from CTMAX to CT1. The receive counter (CR) wraps around from CRMAX to CR1. A frame is lost between CT1 and CT2, and between CR2 and CR1. The diagram includes a 'Frame loss' label and the reference G.8013-Y.1731(15)_FII.4.](333992a0b3b7a9d826f72f7bf199221b_img.jpg) + +The diagram illustrates a scenario where both the transmit and receive counters wrap around. The transmit counter (CT) starts at CT1, wraps around from CTMAX to CT2, and then increases to CT1. The receive counter (CR) starts at CR2, wraps around from CRMAX to CR1, and then increases to CR2. A frame is lost between CT1 and CT2, and between CR2 and CR1. The diagram includes a 'Frame loss' label and the reference G.8013-Y.1731(15)\_FII.4. + +Figure II.4: Diagram showing both transmit and receive counters wrapping around. The transmit counter (CT) wraps around from CTMAX to CT1. The receive counter (CR) wraps around from CRMAX to CR1. A frame is lost between CT1 and CT2, and between CR2 and CR1. The diagram includes a 'Frame loss' label and the reference G.8013-Y.1731(15)\_FII.4. + +**Figure II.4 – Both counters wrap around** + +$$\begin{aligned} \text{Frame loss} &= ((CTMAX - CT1) + CT2 + 1) - ((CRMAX - CR1) + CR2 + 1) \\ &= (CT2 - CT1) - (CR2 - CR1) + (CTMAX + 1) - (CRMAX + 1) \end{aligned}$$ + +## II.1 Simplified calculation for frame loss + +If the calculation is processed in an unsigned value schema, the calculation formula for the frame loss can be greatly simplified by the following characteristics: + +$$N + (MAX + 1) \equiv N \bmod (MAX + 1)$$ + +$$N - (MAX + 1) \equiv N \bmod (MAX + 1)$$ + +Therefore, the formulas for frame loss (described in clauses 8.1.1 and 8.1.2) can be transformed as follows. + +- a) Frame loss = (CT2 - CT1) - (CR2 - CR1) +- b) Frame loss = (CT2 - CT1) - (CR2 - CR1) + CTMAX + 1 += ((CT2 + (CTMAX + 1)) - CT1) - (CR2 - CR1) += (CT2 - CT1) - (CR2 - CR1) +- c) Frame loss = (CT2 - CT1) - (CR2 - CR1) - (CRMAX + 1) += (CT2 - CT1) - ((CR2 + CRMAX + 1) - CR1) += (CT2 - CT1) - (CR2 - CR1) +- d) Frame loss = (CT2 - CT1) - (CR2 - CR1) + (CTMAX + 1) - (CRMAX + 1) += ((CT2 + (CTMAX + 1)) - CT1) - ((CR2 + (CRMAX + 1)) - CR1) += (CT2 - CT1) - (CR2 - CR1) + +As described above, frame loss can be calculated by the single calculation formula for any case if it is calculated in unsigned value schema. + +## II.2 Frame counter wrapping periodicity + +This clause provides a view of wrapping periodicity of 4-octet frame counters for different interface rates and different frame sizes. The interface rates considered are 1 Gbit/s, 10 Gbit/s, and 100 Gbit/s. The frame sizes considered are 64 octets (minimum Ethernet frame size) and 1522 octets (maximum Ethernet frame size). + +**Table II.1 – Frame counter wrapping period** + +| Interface rate | Frame size | 4-octet frame counter wrapping period | +|----------------|--------------|-------------------------------------------------------------------------------| +| 1 Gbit/s | 64 octets | $(2^{32}) / ((10^9) / ((64 + 12) \times 8)) = 2\ 611$ seconds | +| 1 Gbit/s | 1 522 octets | $(2^{32}) / ((10^9) / ((1\ 522 + 12) \times 8)) = 52\ 707$ seconds | +| 10 Gbit/s | 64 octets | $(2^{32}) / ((10 \times (10^9)) / ((64 + 12) \times 8)) = 261$ seconds | +| 10 Gbit/s | 1 522 octets | $(2^{32}) / ((10 \times (10^9)) / ((1\ 522 + 12) \times 8)) = 5\ 270$ seconds | +| 100 Gbit/s | 64 octets | $(2^{32}) / ((100 \times (10^9)) / ((64 + 12) \times 8)) = 26$ seconds | +| 100 Gbit/s | 1 522 octets | $(2^{32}) / ((100 \times (10^9)) / ((1\ 522 + 12) \times 8)) = 527$ seconds | + +# Appendix III + +## Network OAM interworking + +(This appendix does not form an integral part of this Recommendation.) + +The requirements for interworking between layered networks are the following: + +- Upon detection of a defect condition in the server layer, the adaptation function between the server and client layer should be able to insert AIS in the client layer. +- The format of AIS inserted is specific to the client layer. + +As an example, when the client layer is Ethernet, a server MEP is used. + +# Appendix IV + +## Mismerge detection limitation + +(This appendix does not form an integral part of this Recommendation.) + +MEPs consider only CCM frames with their own or lower MEG level for defect detection. CCM frames with higher MEG levels are passed through in order to provide OAM transparency as defined in clause 5.4. This behaviour leads to a limitation in the Mismerge detection as shown in Figure IV.1 below. + +In case of a mismerge between MEGs with different MEG levels, the MEPs of the MEG with the lower MEG level do not detect any defect as the CCM frames coming from the MEG with the higher MEG level are passed through transparently by the MEPs. The MEPs of the MEG with the higher MEG level do detect Unexpected MEG level. + +In case of a unidirectional mismerge from the MEG with the higher MEG level to the MEG with the lower MEG level, no defect is detected. + +**No defects detected by MEPs of MEG A as only MEG levels 3 and lower are considered!** + +![Diagram of bidirectional mismerge detection limitation](a63c7eab8da2ec07cbb94399fd60fc62_img.jpg) + +The diagram illustrates a bidirectional mismerge between two MEGs. MEG A (top) is represented by a green oval with endpoints A1 and A2, labeled 'MEG A' and 'MEG level = 3'. MEG B (bottom) is represented by a red oval with endpoints B1 and B2, labeled 'MEG B' and 'MEG level = 4'. Both MEGs have 'MEP' labels at their endpoints. A red double-headed arrow labeled 'Mismerge' connects the two MEGs. The text 'No defects detected by MEPs of MEG A as only MEG levels 3 and lower are considered!' is at the top, and 'Unexpected MEG level detected by MEPs of MEG B' is at the bottom. + +Diagram of bidirectional mismerge detection limitation + +**a) Bidirectional mismerge** + +**No defects detected by MEPs of MEG A , as only MEG levels 3 and lower are considered!** + +![Diagram of unidirectional mismerge detection limitation](2e8dcf3d807269a64340a9c292ea7f5d_img.jpg) + +The diagram illustrates a unidirectional mismerge from MEG B to MEG A. MEG A (top) is a green oval with endpoints A1 and A2, labeled 'MEG A' and 'MEG level = 3'. MEG B (bottom) is a red oval with endpoints B1 and B2, labeled 'MEG B' and 'MEG level = 4'. Both MEGs have 'MEP' labels at their endpoints. A red single-headed arrow labeled 'Mismerge' points from MEG B to MEG A. The text 'No defects detected by MEPs of MEG A , as only MEG levels 3 and lower are considered!' is at the top, and 'No defects as no mismerge exists to MEG B' is at the bottom. + +Diagram of unidirectional mismerge detection limitation + +**No defects as no mismerge exists to MEG B** + +**b) Unidirectional mismerge** + +G.8013-Y.1731(15)\_FM-1 + +**Figure IV.1 – Mismerge detection limitation** + +# Appendix V + +## Terminology alignment with IEEE 802.1Q + +(This appendix does not form an integral part of this Recommendation.) + +The relationship of the terminology used in this Recommendation and [IEEE 802.1Q] is captured below. + +**Table V.1 – Terminology mapping** + +| ITU-T G.8013/Y.1731 term | IEEE 802.1Q term | Comments | +|--------------------------|------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------| +| MEG | MA | | +| MEG ID | MAID
(Domain Name +
Short MA Name) | Unlike in [IEEE 802.1Q], the MEG ID does not imply a split between domain name and a short MEG name in this Recommendation. | +| MEG level | MD Level | | + +# Appendix VI + +## Examples showing accuracy for ETH-SLM measurement + +(This appendix does not form an integral part of this Recommendation.) + +Synthetic loss measurement is a sampling technique for measuring frame loss; therefore, the measured FLR is distributed around the actual loss value according to a binomial distribution. The mean measured FLR is always equal to the actual FLR, while the standard deviation depends on the number of samples. The standard deviation can therefore be used to illustrate the accuracy of the measured FLR result. Table VI.1 shows the standard deviation for various real loss values and numbers of samples (i.e., number of SLM frames sent). When ETH-SLM is used, the number of samples should be chosen so that the standard deviation is low, when compared to any FLR threshold that is being used to trigger an action. This ensures the chance of false positives is low. + +**Table VI.1 – Standard deviation for various real loss values and number of samples** + +| Actual FLR | Number of samples | Transmission interval | Std. Dev. (FLR % points) | +|------------|-------------------|-----------------------|--------------------------| +| 50% | 10 | 100 ms | 15.81% | +| 50% | 100 | 10 ms | 5.00% | +| 50% | 1 000 | 1 ms | 1.58% | +| 10% | 10 | 100 ms | 9.49% | +| 10% | 100 | 10 ms | 3.00% | +| 10% | 1 000 | 1 ms | 0.95% | +| 1% | 10 | 100 ms | 3.15% | +| 1% | 100 | 10 ms | 0.99% | +| 1% | 1 000 | 1 ms | 0.31% | +| 0.1% | 10 | 100 ms | 1.00% | +| 0.1% | 100 | 10 ms | 0.31% | +| 0.1% | 1 000 | 1 ms | 0.1% | + +Note that if the number of samples is increased by a factor of $n$ , the standard deviation is reduced by a factor of $\sqrt{n}$ . + +# Appendix VII + +## ETH-LM and link aggregation + +(This appendix does not form an integral part of this Recommendation.) + +Link aggregation (LAG), as specified in [b-IEEE 802.1AX], may impact the effectiveness of OAM mechanisms specified in this Recommendation and in [ITU-T G.8021] and [IEEE 802.1Q]. These OAM mechanisms based on service frames such as ETH-LM require frame ordering preservation while those based on synthetic frames such as ETH-DM and ETH-SLM (and ETH-CC) presume suitable sampling of all feasible transmission links/paths. Though this appendix focuses on ETH-LM, other OAM mechanisms may encounter similar issues when they monitor a fraction of the intended flow. These issues can be avoided for example if LAG is used for protection switching (i.e., a LAG with two aggregated links in which all traffic is forwarded onto the active transport entity) or if LAG is used with flow-aware hashing (i.e., all traffic in a given flow is placed on the same aggregated link). + +Specifically considering Ethernet frame loss measurement, the ETH-LM mechanism is in principle capable of accurately detecting single frame loss events on a point-to-point ETH connection between two terminating MEPs (e.g., MEPs A and Z in Figure VII.1 illustrating the scenario discussed hereafter). However, this accuracy may be affected by frame reordering on the ETH connection. The ordering of ETH-LM PDUs relative to the frames that are counted is important. + +![Diagram illustrating the path monitored for frame loss between two terminating MEPs (A and Z) through a LAG distributor and collector.](e60c2d24a97a2855d98671d27ea43d0f_img.jpg) + +The diagram shows a network path for frame loss measurement. On the left, a box labeled 'Data frames' points to a grey rectangle representing 'MEP A'. Inside this rectangle is a yellow triangle labeled 'A'. Below the rectangle is the text 'MEP A starts monitored path'. An arrow points from the triangle to a grey rectangle labeled 'LAG distributor'. Above this rectangle, a box labeled 'Data frames + LMM PDUs' points to it. From the 'LAG distributor', two parallel horizontal lines lead to another grey rectangle labeled 'LAG collector'. From the 'LAG collector', an arrow points to a grey rectangle representing 'MEP Z'. Inside this rectangle is a green triangle labeled 'Z'. Below the rectangle is the text 'MEP Z ends monitored path'. In the bottom right corner of the diagram area, the text 'G.8013-Y.1731(13)\_FVII.1' is present. + +Diagram illustrating the path monitored for frame loss between two terminating MEPs (A and Z) through a LAG distributor and collector. + +**Figure VII.1 – Path monitored for frame loss between two terminating MEPs** + +The ETH-LM measurement method is based on the assumption that the position of ETH-LM PDUs in the flow of counted frames stays the same between source and sink MEPs. This provides the required synchronization between the counters at both ends of the link. It is a characteristic property of the forwarding in Ethernet bridges to preserve the frame ordering of the MAC service. Some implementations of LAG however may not guarantee frame ordering preservation over the full aggregated bandwidth. LAG avoids frame reordering by assigning all frames in a given "conversation" to a single aggregated link. This ensures that frame ordering is maintained within each "conversation", but not necessarily between "conversations". + +Common implementations of the LAG frame distributor function (the "Distributor") operate largely autonomously and detect "conversations" by hashing not necessarily only on the VLAN identifier (VID) and priority of the exchanged ETH-LM PDUs and counted frames, but rather for example on source and destination MAC and/or IP addresses. The set of ETH-LM PDUs and the frames they are supposed to count will generally contain a variety of values in the fields on which the Distributor bases the assigned hash-value and hence the aggregated link assignment. + +Assuming a LAG section/aggregation is to be traversed somewhere along the path between the two terminating MEPs, ETH-LM PDUs and counted frames may be forwarded onto different aggregated links. This takes place even if they are all transmitted in the same VID and at the same priority because the Distributor may consider more frame fields to decide aggregated link assignment. The counted frames themselves may be spread over different aggregated links if they belong to different "conversations". Reordering may also depend on other factors such as the amount of traffic on the LAG section, the variety of frame lengths, or the number of "conversations" that the Distributor can detect. + +The LAG frame collector function (the "Collector") is relatively simple compared to the Distributor as it relies on the latter for frame ordering (within "conversations"). As such, it simply passes frames received from aggregated links in the order that it receives them. Because of this, frames with the same VID and at the same priority that were forwarded onto different aggregated links by the Distributor are not reordered by the Collector and are likely to be in a different order before and after traversing the LAG section. + +The sink MEP reads its local counter exactly when an LMM PDU is received and compares this reading with the counter in the LMM PDU itself, providing the equivalent count from the source MEP. As illustrated in Figure VII.2, if the LMM PDU shifts position relative to the frames that surround it, i.e., the ones subject to counting, such a comparison will indicate artificial frame loss (or gain), even if there is no actual frame loss (or gain) in reality. This puts a limit on the accuracy that can be achieved with this method of measuring frame loss. + +![Diagram illustrating LMM PDU overtaking a data frame, causing artificial frame loss or gain.](a963ca41bde1669b18a4b783616f228b_img.jpg) + +The diagram shows two horizontal timelines representing network streams. The top timeline, labeled "Stream transmitted by A to Z", shows a sequence of frames: a grey frame, a green LMM PDU, three grey frames, a red data frame, another green LMM PDU, and a final grey frame. A green callout box above the second LMM PDU states "5 frames transmitted since previous LMM PDU". An arrow points from the red data frame to the bottom timeline. The bottom timeline, labeled "Stream received by Z from A", shows the frames after they have been processed. The sequence is: a grey frame, a yellow LMM PDU, three grey frames, a yellow LMM PDU, a red data frame, and a grey frame. A yellow callout box below the second yellow LMM PDU states "4 frames received since previous LMM PDU". A red callout box with an arrow pointing to the red data frame (which is now after the second yellow LMM PDU) states "LMM PDU overtakes data frame". The diagram illustrates that because the LMM PDU overtook the data frame during transmission, the receiver counted one fewer frame (4 instead of 5) between the two LMM PDUs, leading to an artificial frame loss. + +Diagram illustrating LMM PDU overtaking a data frame, causing artificial frame loss or gain. + +**Figure VII.2 – LMM PDU overtakes data frame causing artificial frame loss (or gain)** + +Due to the many factors affecting ordering on a LAG section, it is difficult to predict how often such errors occur. The error is likely to be plus or minus a few frames. Since ETH-LM PDUs are short they tend to overtake longer frames on a LAG section. Hence an artificial frame loss may be measured before the compensating artificial frame gain is measured. Also, there may be measurement intervals in which there is very little end-user traffic (e.g., on standby connections). In such intervals the (relative) error in the reported frame loss rate caused by reordering can increase significantly. Note that a LAG section typically handles a lot more traffic than just the flow measured by ETH-LM, so the probability of reordering may not depend much on the amount of traffic in the ETH-LM monitored flow itself. + +In practice, because the service-frame counters are continuously running, the artificial frame loss or gain cancels out at the next LMR but may be replaced by a new error if misordering continues. If the last LMM and LMR PDUs that are used in a given measurement interval (typically 15-minute or 24-hour long) are both not subject to reordering, any errors made up to that point are compensated. When the measurement interval is long, the errors may be small compared to the number of service frames. However, there may only be a few service frames in the small time intervals used to assess availability, so that the reordering error may be sufficient to cause false or missed unavailability FLR threshold crossings, leading to incorrect unavailability time. + +# Bibliography + +- [b-IEEE 802.1AX] IEEE 802.1AX (2020), *IEEE Standard for Local and metropolitan area networks: Link Aggregation.* +- [b-IETF RFC 2544] IETF RFC 2544 (1999), *Benchmarking Methodology for Network Interconnect Devices.* + +# ITU-T Y-SERIES RECOMMENDATIONS + +## **Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities** + +| | | +|--------------------------------------------------------------------|----------------------| +| GLOBAL INFORMATION INFRASTRUCTURE | Y.100-Y.999 | +| INTERNET PROTOCOL ASPECTS | Y.1000-Y.1999 | +| General | Y.1000-Y.1099 | +| Services and applications | Y.1100-Y.1199 | +| Architecture, access, network capabilities and resource management | Y.1200-Y.1299 | +| Transport | Y.1300-Y.1399 | +| Interworking | Y.1400-Y.1499 | +| Quality of service and network performance | Y.1500-Y.1599 | +| Signalling | Y.1600-Y.1699 | +| Operation, administration and maintenance | Y.1700-Y.1799 | +| Charging | Y.1800-Y.1899 | +| IPTV over NGN | Y.1900-Y.1999 | +| NEXT GENERATION NETWORKS | Y.2000-Y.2999 | +| FUTURE NETWORKS | Y.3000-Y.3499 | +| CLOUD COMPUTING | Y.3500-Y.3599 | +| BIG DATA | Y.3600-Y.3799 | +| QUANTUM KEY DISTRIBUTION NETWORKS | Y.3800-Y.3999 | +| INTERNET OF THINGS AND SMART CITIES AND COMMUNITIES | Y.4000-Y.4999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.8020.3-202511-I_PDF-E/0538daaa5583c23e17db3a12f2281a55_img.jpg b/marked/G/T-REC-G.8020.3-202511-I_PDF-E/0538daaa5583c23e17db3a12f2281a55_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..25f8fbfaef317942ed3102c74b40a7d42f80608b --- /dev/null +++ b/marked/G/T-REC-G.8020.3-202511-I_PDF-E/0538daaa5583c23e17db3a12f2281a55_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:83cab7dcabfe939b223d97242d8523e461968d21f7c5432693c30a64f2d95521 +size 7050 diff --git a/marked/G/T-REC-G.8020.3-202511-I_PDF-E/raw.md b/marked/G/T-REC-G.8020.3-202511-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..e39d061e8e91530fb70265ab1061c43d6c3d5bef --- /dev/null +++ b/marked/G/T-REC-G.8020.3-202511-I_PDF-E/raw.md @@ -0,0 +1,304 @@ + + +# Recommendation**ITU-T G.802.3 (11/2025)** + +SERIES G: Transmission systems and media, digital systems and networks + +Packet over Transport aspects – Ethernet over Transport aspects + +--- + +## **Ethernet** + +![ITU logo](0538daaa5583c23e17db3a12f2281a55_img.jpg) + +The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with white lines representing latitude and longitude, and the letters "ITU" in a bold, blue, sans-serif font superimposed on the globe. + +ITU logo + +## ITU-T G-SERIES RECOMMENDATIONS **Transmission systems and media, digital systems and networks** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100-G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200-G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300-G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400-G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450-G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600-G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700-G.799 | +| DIGITAL NETWORKS | G.800-G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900-G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000-G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000-G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000-G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000-G.8999 | +| Ethernet over Transport aspects | G.8000-G.8099 | +| MPLS over Transport aspects | G.8100-G.8199 | +| Synchronization, quality and availability targets | G.8200-G.8299 | +| Mobile network transport aspects | G.8300-G.8399 | +| Service Management | G.8600-G.8699 | +| ACCESS NETWORKS | G.9000-G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.8020.3 + +## Ethernet + +## Summary + +Recommendation ITU-T G.8020.3 incorporates by reference the definition of Ethernet local area, access and metropolitan area networks as specified in IEEE Std 802.3-2022 "IEEE Standard for Ethernet" and its approved amendments, corrigenda and errata. + +## History \* + +| Edition | Recommendation | Approval | Study Group | Unique ID | +|---------|----------------|------------|-------------|--------------------| +| 1.0 | ITU-T G.8020.3 | 2025-05-14 | 15 | 11.1002/1000/16351 | +| 2.0 | ITU-T G.8020.3 | 2025-11-29 | 15 | 11.1002/1000/16541 | + +## Keywords + +Ethernet. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, and information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at . + +© ITU 2026 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|-------------------------------------------------------------------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 2 | +| 3.1 Terms defined elsewhere ..... | 2 | +| 3.2 Terms defined in this Recommendation..... | 2 | +| 4 Abbreviations and acronyms ..... | 2 | +| 5 Conventions ..... | 2 | +| 6 Ethernet..... | 3 | +| Appendix I – Obtaining the full text of [IEEE 802.3] and its amendments, corrigenda, and errata ..... | 4 | +| Appendix II – Summary of [IEEE 802.3] and its amendments ..... | 5 | +| II.1 Introduction ..... | 5 | + + + +# Recommendation ITU-T G.8020.3 + +## Ethernet + +# 1 Scope + +This Recommendation incorporates by reference the definition of Ethernet local area, access and metropolitan area networks. Ethernet is specified at selected speeds of operation; and uses a common media access control (MAC) specification and management information base (MIB). The carrier sense multiple access with collision detection (CSMA/CD) MAC protocol specifies shared medium (half duplex) operation, as well as full duplex operation. Speed specific media independent interfaces (MIIs) provide an architectural and optional implementation interface to selected physical layer devices (PHYs). The physical layer encodes frames for transmission and decodes received frames with the modulation specified for the speed of operation, transmission medium and supported link length. Other specified capabilities include control and management protocols, and the provision of power over selected twisted pair PHY types. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [IEEE 802.3] IEEE Std 802.3-2022, *IEEE Standard for Ethernet*. +- [IEEE 802.3ck] IEEE Std 802.3ck™-2022, *IEEE Standard for Ethernet Amendment 4: Physical Layer Specifications and Management Parameters for 100 Gb/s, 200 Gb/s, and 400 Gb/s Electrical Interfaces Based on 100 Gb/s Signaling*. +- [IEEE 802.3cs] IEEE Std 802.3cs™-2022, *IEEE Standard for Ethernet Amendment 2: Physical Layers and Management Parameters for Increased-Reach Point-to-Multipoint Ethernet Optical Subscriber Access (Super-PON)*. +- [IEEE 802.3cx] IEEE Std 802.3cx™-2023, *IEEE Standard for Ethernet Amendment 6: Media Access Control (MAC) Service Interface and Management Parameters to Support Improved Precision Time Protocol (PTP) Timestamping Accuracy*. +- [IEEE 802.3cy] IEEE Std 802.3cy™-2023, *IEEE Standard for Ethernet Amendment 8: Physical Layer Specifications and Management Parameters for 25 Gb/s - Electrical Automotive Ethernet*. +- [IEEE 802.3cz] IEEE Std 802.3cz™-2023, *IEEE Standard for Ethernet Amendment 7: Physical Layer Specifications and Management Parameters for Multi-Gigabit Glass Optical Fiber Automotive Ethernet*. +- [IEEE 802.3db] IEEE Std 802.3db™-2022, *IEEE Standard for Ethernet - Amendment 3: Physical Layer Specifications and Management Parameters for 100 Gb/s, 200 Gb/s, and 400 Gb/s Operation over Optical Fiber using 100 Gb/s Signaling*. +- [IEEE 802.3dd] IEEE Std 802.3dd™-2022, *IEEE Standard for Ethernet Amendment 1: Power over Data Lines of Single Pair Ethernet*. + +- [IEEE 802.3de] IEEE Std 802.3de™-2022, *IEEE Standard for Ethernet - Amendment 5: Enhancements to the MAC Merge and Time Synchronization Service Interface for Point-to-Point 10 Mb/s Single Pair Ethernet.* +- [IEEE 802.3df] IEEE Std 802.3df™-2024, *IEEE Standard for Ethernet Amendment 9: Media Access Control Parameters for 800 Gb/s and Physical Layers and Management Parameters for 400 Gb/s and 800 Gb/s Operation.* +- [IEEE 802.3 Cor 1] IEEE Std 802.3-2022/Cor 1-2024, *IEEE Standard for Ethernet Corrigendum 1: multi-Gigabit Automotive Medium Dependent Interface (MDI) Return Loss.* + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +None. + +## 3.2 Terms defined in this Recommendation + +None. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|---------|--------------------------------------------------------| +| CSMA/CD | Carrier Sense Multiple Access with Collision Detection | +| EPON | Ethernet Passive Optical Network | +| LAN | Local Area Network | +| LLDP | Link Layer Discovery Protocol | +| MAC | Media Access Control | +| MDI | Medium-Dependent Interface | +| MIB | Management Information Base | +| MII | Media Independent Interface | +| ODN | Optical Distribution Network | +| ONU | Optical Network Unit | +| PCS | Physical Coding Sublayer | +| PHY | Physical Layer device | +| PMA | Physical Medium Attachment | +| PMD | Physical Medium Dependent | +| PON | Passive Optical Network | +| RS | Reconciliation Sublayer | +| TLV | Type, Length, and Value | + +# 5 Conventions + +ITU-T documents that need to reference a clause, annex, figure or table of any of the IEEE 802.3 documents that are normatively referenced in this Recommendation use the following text: + +{clause | annex | figure | table} x as incorporated by reference in [ITU-T G.8020.3] + +where {clause | annex | figure | table} is indicating a choice of one of those words and x is the appropriate designation from the normatively referenced document. + +As an example, a reference to clause 119.2 of [IEEE 802.3] would be written as "clause 119.2 as incorporated by reference in [ITU-T G.8020.3]". + +# **6 Ethernet** + +This Recommendation incorporates by reference the contents of [IEEE 802.3], as amended by [IEEE 802.3dd], [IEEE 802.3cs], [IEEE 802.3db], [IEEE 802.3ck], [IEEE 802.3de], [IEEE 802.3cx], [IEEE 802.3cz], [IEEE 802.3cy], [IEEE 802.3df] and [IEEE 802.3 Cor 1]. + +# Appendix I + +## Obtaining the full text of [IEEE 802.3] and its amendments, corrigenda, and errata + +(This appendix does not form an integral part of this Recommendation.) + +The full text of [IEEE 802.3] and its amendments, corrigenda, and errata is available as follows: + +- Published IEEE 802 standards are available on IEEE Xplore for those with subscriptions, and for sale individually from the following website: . +- Published IEEE 802 standards are also available at no cost six months after publication from IEEE Xplore: . + +# Appendix II + +## Summary of [IEEE 802.3] and its amendments + +(This appendix does not form an integral part of this Recommendation.) + +### II.1 Introduction + +IEEE Std 802.3TM was first published in 1985. Since the initial publication, many projects have added functionality or provided maintenance updates to the specifications and text included in the standard. Each IEEE 802.3 project/amendment is identified with a suffix (e.g., IEEE Std 802.3baTM-2010). + +The half duplex Media Access Control (MAC) protocol specified in IEEE Std 802.3-1985 is Carrier Sense Multiple Access with Collision Detection (CSMA/CD). This MAC protocol was key to the experimental Ethernet developed at Xerox Palo Alto Research Center, which had a 2.94 Mb/s data rate. Ethernet at 10 Mb/s was jointly released as a public specification by Digital Equipment Corporation (DEC), Intel and Xerox in 1980. "Local Area Networks: Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specifications" was approved as an IEEE standard by the IEEE Standards Board in 1983 and subsequently published in 1985 as IEEE Std 802.3-1985. Since 1985, new media options, new speeds of operation, and new capabilities have been added to [IEEE 802.3]. A full duplex MAC protocol and the ability to use an EtherType to specify the MAC client protocol were added in 1997. The title was changed to Standard for Ethernet with the 2012 Revision. + +Some of the major additions to [IEEE 802.3] are identified in the marketplace with their project number. This is most common for projects adding higher speeds of operation or new protocols. For example, IEEE Std 802.3uTM added 100 Mb/s operation (also called Fast Ethernet), IEEE Std 802.3zTM added 1000 Mb/s operation (also called Gigabit Ethernet), IEEE Std 802.3aeTM added 10 Gb/s operation (also called 10 Gigabit Ethernet), IEEE Std 802.3ahTM specified access network Ethernet (also called Ethernet in the First Mile) and IEEE Std 802.3ba added 40 Gb/s operation (also called 40 Gigabit Ethernet) and 100 Gb/s operation (also called 100 Gigabit Ethernet). These major additions are all now included in and are superseded by IEEE Std 802.3-2022 and are not maintained as separate documents. + +At the date of Recommendation ITU-T G.8020.3 publication, [IEEE 802.3] was composed of the following documents. + +#### II.1.1 IEEE Std 802.3TM-2022 + +Section One – Includes clause 1 through clause 20 and Annex A through Annex K and Annex 4A. Section One includes the specifications for 10 Mb/s operation and the MAC, frame formats and service interfaces used for all speeds of operation. + +Section Two – Includes clause 21 through clause 33 and Annex 22A through Annex 33A. Section Two includes management attributes for multiple protocols and speed of operation as well as specifications for providing power over twisted pair cabling for multiple operational speeds. It also includes general information on 100 Mb/s operation as well as most of the 100 Mb/s Physical Layer specifications. + +Section Three – Includes clause 34 through clause 43 and Annex 36A through Annex 43C. Section Three includes general information on 1000 Mb/s operation as well as most of the 1000 Mb/s Physical Layer specifications. + +Section Four – Includes clause 44 through clause 55 and Annex 44A through Annex 55B. Section Four includes general information on 10 Gb/s operation as well as most of the 10 Gb/s Physical Layer specifications. + +Section Five – Includes clause 56 through clause 77 and Annex 57A through Annex 76A. Clause 56 through clause 67 and clause 75 through clause 77, as well as associated annexes, specify subscriber access and other Physical Layers and sublayers for operation from 512 kb/s to 10 Gb/s, and defines services and protocol elements that enable the exchange of IEEE Std 802.3 format frames between stations in a subscriber access network. Clause 68 specifies a 10 Gb/s Physical Layer specification. Clause 69 through clause 74 and associated annexes specify Ethernet operation over electrical backplanes at speeds of 1000 Mb/s and 10 Gb/s. + +Section Six – Includes clause 78 through clause 95 and Annex 83A through Annex 93C. Clause 78 specifies Energy-Efficient Ethernet. Clause 79 specifies IEEE 802.3 Organizational Specific Link Layer Discovery Protocol (LLDP) type, length, and value (TLV) information elements. Clause 80 through clause 95 and associated annexes include general information on 40 Gb/s and 100 Gb/s operation as well as 40 Gb/s and 100 Gb/s Physical Layer specifications. Clause 90 specifies Ethernet support for time synchronization protocols. + +Section Seven – Includes clause 96 through clause 115 and Annex 97A through Annex 115A. Clause 96 through clause 98, clause 104, and associated annexes, specify Physical Layers and optional features for 100 Mb/s and 1000 Mb/s operation over a single twisted pair. Clause 100 through clause 103, as well as associated annexes, specify Physical Layers for the operation of the EPON protocol over coaxial distribution networks. Clause 105 through clause 114 and associated annexes include general information on 25 Gb/s operation as well as 25 Gb/s Physical Layer specifications. Clause 99 specifies a MAC merge sublayer for the interspersing of express traffic. Clause 115 and its associated annex specify a Physical Layer for 1000 Mb/s operation over plastic optical fiber. + +Section Eight – Includes clause 116 through clause 140 and Annex 119A through Annex 136D. Clause 116 through clause 124 and associated annexes include general information on 200 Gb/s and 400 Gb/s operation as well as 200 Gb/s and 400 Gb/s Physical Layer specifications. Clause 125 includes general information on 2.5 Gb/s and 5 Gb/s operation. Clause 126 through clause 130 and associated annexes include 2.5 Gb/s and 5 Gb/s Physical Layer specifications. Clause 131 provides general information on 50 Gb/s operation. Clause 132 through clause 140 and associated annexes include 50 Gb/s Physical Layer specifications and additional 100 Gb/s, 200 Gb/s, and 400 Gb/s Physical Layer specifications. + +Section Nine – Includes clause 141 through clause 160 and Annex 142A through Annex 154A. Clause 141 through clause 144 and associated annexes specify symmetric and asymmetric operation of Ethernet passive optical networks over multiple 25 Gb/s channels. Clause 145 and associated annexes specify increased power delivery using all four pairs in the structured wiring plant. Clause 146 through clause 149 and associated annexes specify Physical Layers for 10 Mb/s, 2.5 Gb/s, 5 Gb/s, and 10 Gb/s operation over a single balanced pair of conductors. Clause 150 and clause 151 include additional 400 Gb/s Physical Layer specifications. Clause 153 and clause 154 specify 100 Gb/s operation over DWDM channels. Clause 157 through clause 160 include 10 Gb/s, 25 Gb/s, and 50 Gb/s bidirectional Physical Layer specifications. + +#### **II.1.2 IEEE Std 802.3dd™-2022 [IEEE 802.3dd]** + +Amendment 1 – This amendment includes editorial and technical corrections, refinements, and clarifications to clause 104, Power over Data Lines of Single Pair Ethernet, and related portions of the standard. + +#### **II.1.3 IEEE Std 802.3cs™-2022 [IEEE 802.3cs]** + +Amendment 2 – This amendment to IEEE Std 802.3-2022 defines Super-PON optical subscriber access networks, in the family of Ethernet passive optical networks (EPONs). Super-PON has a reach of up to 50 km and up to 1024 ONUs over a point-to-multipoint passive optical distribution network wavelength router that determines the channels used by the ODN. This standard specifies the Super-PON Reconciliation Sublayer (RS), Physical Coding Sublayer (PCS), Physical Medium Attachment + +(PMA) sublayer, and Physical Medium Dependent (PMD) sublayer at a MAC data rate of 10 Gb/s in the downstream direction and of 10 Gb/s or 2.5 Gb/s in the upstream direction. + +#### **II.1.4 IEEE Std 802.3db™-2022 [IEEE 802.3db]** + +Amendment 3 – This amendment includes changes to IEEE Std 802.3-2022 and adds clause 167. This amendment adds Physical Layer specifications and management parameters for 100 Gb/s, 200 Gb/s, and 400 Gb/s over one, two, and four pairs of multimode fiber based on 100 Gb/s optical signaling. + +#### **II.1.5 IEEE Std 802.3ck™-2022 [IEEE 802.3ck]** + +Amendment 4 – This amendment includes changes to IEEE Std 802.3-2022 and adds clause 161 through clause 163, Annex 120F, Annex 120G, Annex 162A through Annex 162D, Annex 163A, and Annex 163B. This amendment includes Physical Layer specifications and management parameters for 100 Gb/s, 200 Gb/s, and 400 Gb/s electrical interfaces based on 100 Gb/s signaling. + +#### **II.1.6 IEEE Std 802.3de™-2022 [IEEE 802.3de]** + +Amendment 5 – This amendment includes changes to IEEE Std 802.3-2022 to add 10 Mb/s Single-Pair Ethernet point-to-point PHYs to the PHYs supporting the MAC Merge function and the Time Synchronization Service Interface (TSSI). + +#### **II.1.7 IEEE Std 802.3cx™-2023 [IEEE 802.3cx]** + +Amendment 6 – This amendment to IEEE Std 802.3-2022 modifies clause 30, clause 45, and clause 90, and adds Annex 90A to enhance support for time synchronization protocols by providing options for sub-nanosecond reporting of the transmit and receive path data delays, selection of the data delay measurement point, and dynamic reporting of path data delay variation. + +#### **II.1.8 IEEE Std 802.3cz™-2023 [IEEE 802.3cz]** + +Amendment 7 – This amendment includes changes to IEEE Std 802.3-2022 and adds clause 166. This amendment adds 2.5 Gb/s, 5 Gb/s, 10 Gb/s, 25 Gb/s, and 50 Gb/s Physical Layer specifications and management parameters for optical automotive Ethernet using graded-index glass optical fiber. + +#### **II.1.9 IEEE Std 802.3cy™-2023 [IEEE 802.3cy]** + +Amendment 8 – This amendment includes changes to IEEE Std 802.3-2022 and adds clause 165 and Annex 165A. This amendment adds Physical Layer specifications and management parameters for operation at 25 Gb/s over a single balanced pair of conductors. + +#### **II.1.10 IEEE Std 802.3df™-2024 [IEEE 802.3df]** + +Amendment 9 – This amendment includes changes to IEEE Std 802.3-2022 and adds clause 169 through clause 173, Annex 172A, and Annex 173A. This amendment includes Physical Layer specifications and management parameters for 400 Gb/s and 800 Gb/s operation. + +#### **II.1.11 IEEE Std 802.3™-2022 Cor 1-2024 [IEEE 802.3 Cor 1]** + +Corrigendum 1 – This corrigendum includes changes to IEEE Std 802.3-2022 to correct the MDI return loss specifications in clause 149 and clause 165. + + + + + +# SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.803-200003-I_PDF-E/76b0cd79baaedd942af4dc42f2e764b8_img.jpg b/marked/G/T-REC-G.803-200003-I_PDF-E/76b0cd79baaedd942af4dc42f2e764b8_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..b4c65471f2d5c4705ddb6fcda4ff5f192cc8868b --- /dev/null +++ b/marked/G/T-REC-G.803-200003-I_PDF-E/76b0cd79baaedd942af4dc42f2e764b8_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:3fa2f2618381c98a43a0045f8f71f64a1ab42ef1eb6f5bb04cfdf6eb2c68ca28 +size 55509 diff --git a/marked/G/T-REC-G.803-200003-I_PDF-E/cbab05075b3d7dc0d27c4cbb0c914a94_img.jpg b/marked/G/T-REC-G.803-200003-I_PDF-E/cbab05075b3d7dc0d27c4cbb0c914a94_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..2ac6b63921e45a571167ef47cb5014069bf96838 --- /dev/null +++ b/marked/G/T-REC-G.803-200003-I_PDF-E/cbab05075b3d7dc0d27c4cbb0c914a94_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:05feb611ff77f79db994fe3d59db3af444f7e1ba6172ee13073d66fe54000b30 +size 96933 diff --git a/marked/G/T-REC-G.803-200003-I_PDF-E/raw.md b/marked/G/T-REC-G.803-200003-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..6bdb164932ec471be6a95e7c771711bb4514fe3c --- /dev/null +++ b/marked/G/T-REC-G.803-200003-I_PDF-E/raw.md @@ -0,0 +1,1594 @@ + + +![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with a lightning bolt and the letters ITU. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.803** + +(03/2000) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital transmission systems – Digital networks – General +aspects + +--- + +**Architecture of transport networks based on the +synchronous digital hierarchy (SDH)** + +ITU-T Recommendation G.803 + +(Formerly CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# **Architecture of transport networks based on the synchronous digital hierarchy (SDH)** + +## **Summary** + +This ITU-T Recommendation describes the functional architecture of transport networks including network synchronization principles for networks that are based on the SDH. This ITU-T Recommendation uses the architectural description defined in ITU-T Recommendation G.805, the generic functional architecture of transport networks. The application of various mappings is also included. + +## **Source** + +ITU-T Recommendation G.803 was revised by ITU-T Study Group 13 (1997-2000) and approved under the WTSC Resolution 1 procedure on 10 March 2000. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2001 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +# CONTENTS + +###### Page + +| | | | +|-------|-----------------------------------------------------------------|----| +| 1 | Scope..... | 1 | +| 2 | References..... | 1 | +| 3 | Terms and definitions ..... | 2 | +| 4 | Abbreviations..... | 3 | +| 5 | Application of the G.805 layering concept ..... | 3 | +| 5.1 | Multiplexing of multiple clients ..... | 5 | +| 5.2 | Support of ATM over SDH ..... | 6 | +| 5.3 | Concatenation ..... | 7 | +| 5.3.1 | Contiguous concatenation..... | 7 | +| 5.3.2 | Virtual concatenation..... | 7 | +| 5.3.3 | Interworking between contiguous and virtual concatenation ..... | 10 | +| 6 | Connection supervision..... | 11 | +| 6.1 | Inherent monitoring ..... | 11 | +| 6.2 | Non-intrusive monitoring ..... | 11 | +| 6.3 | Sublayer monitoring..... | 11 | +| 7 | SDH transport network availability enhancement techniques ..... | 16 | +| 7.1 | SDH multiplex section protection..... | 16 | +| 7.1.1 | SDH multiplex section 1+1 protection ..... | 16 | +| 7.1.2 | SDH multiplex section 1:N protection ..... | 16 | +| 7.1.3 | SDH multiplex section shared protection rings ..... | 16 | +| 7.1.4 | SDH multiplex section dedicated rings ..... | 16 | +| 7.2 | SDH subnetwork connection protection examples..... | 17 | +| 8 | Architecture of synchronization networks ..... | 17 | +| 8.1 | Introduction..... | 17 | +| 8.2 | Synchronization network aspects..... | 17 | +| 8.2.1 | Synchronization methods..... | 17 | +| 8.2.2 | Synchronization network architecture ..... | 18 | +| 8.2.3 | Synchronization modes..... | 22 | +| 8.2.4 | Synchronization network reference chain..... | 23 | +| 8.2.5 | Synchronization strategy..... | 25 | +| 8.2.6 | Synchronization network evolution..... | 25 | +| 8.2.7 | Synchronization network robustness ..... | 25 | +| 8.3 | Payload jitter and wander..... | 26 | +| 8.3.1 | SDH network model for pointer activity simulation ..... | 27 | +| 8.3.2 | Jitter at a SDH/PDH boundary ..... | 27 | + +| | Page | +|------------------------------------------------------------------------------|-------------| +| 8.4 PDH/SDH interworking implications ..... | 28 | +| 9 Selection of a primary rate mapping ..... | 29 | +| Appendix I – Client server associations of SDH layer networks ..... | 29 | +| Appendix II – Introduction of SDH-based transport networks ..... | 31 | +| II.1 General ..... | 31 | +| II.2 Types of client layer signals ..... | 32 | +| II.2.1 SDH case ..... | 32 | +| II.2.2 PDH case ..... | 32 | +| II.3 Initial introduction of SDH-based equipment ..... | 33 | +| II.4 Interworking between PDH- and SDH-based transport networks ..... | 33 | +| II.4.1 Interworking levels ..... | 33 | +| II.4.2 SDH overlay ..... | 34 | +| II.4.3 SDH DXC/ADM ..... | 34 | +| II.4.4 SDH line systems ..... | 34 | +| II.5 Introduction of STM-N interfaces on 64 kbit/s switches (and DXCs) ..... | 35 | +| Appendix III – Guidelines for synchronization network engineering ..... | 37 | +| III.1 Introduction ..... | 37 | +| III.2 Purpose of the synchronization network ..... | 37 | +| III.3 Requirements for synchronization networks ..... | 38 | +| III.4 Analysis of synchronization networks ..... | 39 | +| III.5 PRC-Level options ..... | 41 | +| III.6 SSU-Level solutions ..... | 42 | +| III.6.1 Checking reference provisionings at the SSU-Level ..... | 43 | +| III.6.2 Absolute frequency offset guarding ..... | 45 | +| III.7 SEC-Level solutions ..... | 46 | +| III.7.1 Application of the SSM protocol in the SSU-Level ..... | 47 | +| III.7.2 Examples of SEC subnetworks with SSM parameters ..... | 47 | +| III.8 Synthesis of the synchronization network ..... | 51 | +| III.9 Definitions used in Appendix III ..... | 52 | + +# **Architecture of transport networks based on the synchronous digital hierarchy (SDH)** + +# **1 Scope** + +This ITU-T Recommendation describes the functional architecture of transport networks including network synchronization principles for networks that are based on the SDH. This ITU-T Recommendation uses the architectural description defined in ITU-T Recommendation G.805, the generic functional architecture of transport networks. The application of various mappings is also included. + +# **2 References** + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- CCITT Recommendation G.702 (1988), *Digital hierarchy bit rates*. +- CCITT Recommendation G.703 (1991), *Physical/electrical characteristics of hierarchical digital interfaces*. +- ITU-T Recommendation G.704 (1995), *Synchronous frame structures used at 1544, 6312, 2048, 8488 and 44 736 kbit/s hierarchical levels*. +- ITU-T Recommendation G.707 (1996), *Network node interface for the Synchronous Digital Hierarchy (SDH)*. +- CCITT Recommendation G.774 (1992), *Synchronous Digital Hierarchy (SDH) management information model for the network element view*. +- ITU-T Recommendation G.783 (1997), *Characteristics of Synchronous Digital Hierarchy (SDH) equipment functional blocks*. +- ITU-T Recommendation G.805 (1995), *Generic functional architecture of transport networks*. +- ITU-T Recommendation G.810 (1996), *Definitions and terminology for synchronization networks*. +- CCITT Recommendation G.811 (1988), *Timing requirements at the outputs of primary reference clocks suitable for plesiochronous operation of international digital links*. +- CCITT Recommendation G.812 (1988), *Timing requirements at the outputs of slave clocks suitable for plesiochronous operation of international digital links*. +- ITU-T Recommendation G.813 (1996), *Timing characteristics of SDH equipment slave clocks (SEC)*. +- CCITT Recommendation G.822 (1988), *Controlled slip rate objectives on an international digital connection*. +- ITU-T Recommendation G.823 (1993), *The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy*. + +- ITU-T Recommendation G.824 (1993), *The control of jitter and wander within digital networks which are based on the 1544 kbit/s hierarchy.* +- ITU-T Recommendation G.832 (1995), *Transport of SDH elements on PDH networks – Frame and multiplexing structures.* +- ITU-T Recommendation G.841 (1995), *Types and characteristics of SDH network protection architectures.* +- ITU-T Recommendation G.964 (1994), *V-Interfaces at the digital Local Exchange (LE) – V5.1 Interface (based on 2048 kbit/s) for the support of Access Network (AN).* +- ITU-T Recommendation G.965 (1995), *V-Interfaces at the digital Local Exchange (LE) – V5.2 Interface (based on 2048 kbit/s) for the support of Access Network (AN).* +- ITU-T Recommendation I.326 (1995), *Functional architecture of transport networks based on ATM.* + +# 3 Terms and definitions + +This ITU-T Recommendation uses the terminology defined in ITU-T Recommendations G.783, G.805 and G.841; the following terms are specific to this ITU-T Recommendation. The layer networks defined below terminate and generate the overheads defined in ITU-T Recommendation G.707. + +**3.1 SDH higher-order path layer networks:** Those layer networks with characteristic information of VC-31, VC-3-Xv ( $X = 2 \dots 48$ )2, VC-4, VC-4-Xc ( $X = 4, 16$ )3 or VC-4-Xv ( $X = 2 \dots 16$ )3. + +**3.2 SDH lower-order path layer networks:** Those layer networks with characteristic information of VC-11, VC-11-Xv ( $X = 2 \dots 84$ ), VC-12, VC-12-Xv ( $X = 2 \dots 63$ ), VC-2, VC-2-Xc ( $X = 2 \dots 7$ )4, VC-2-Xv ( $X = 2 \dots 21$ )5 or VC-31 or VC-3-Xv ( $X = 2 \dots 3$ )5. + +**3.3 SDH path layer:** A transport assembly composed of the SDH higher-order path layer network and lower-order path layer network together with the associated adaptation functions. + +**3.4 SDH section layer:** A transport assembly composed of the SDH multiplex section layer network and regenerator section layer network together with the associated adaptation functions. + +**3.5 SDH multiplex section layer:** A layer network with characteristic information of STM-N, i.e. with a bit rate of STM-N and the multiplex section overhead as defined in ITU-T Recommendation G.707. + +**3.6 SDH regenerator section layer:** A layer network with characteristic information of STM-N, i.e. with a bit rate of STM-N and the regenerator section overhead as defined in ITU-T Recommendation G.707. + +--- + +1 The VC-3 is considered to be a higher-order path if it is supported directly by an AU-3 in a multiplex section layer network; it is considered a lower-order path if it is supported by a TU-3 in a VC-4 layer network. + +2 Values of X larger than 48 may be required. + +3 Values of X larger than 16 may be required. + +4 Transported in one higher order VC-3. + +5 Transported in one higher order VC-4. + +# 4 Abbreviations + +This ITU-T Recommendation uses the following abbreviations: + +| | | +|---------|---------------------------------------------------------------| +| ADM | Add/Drop Multiplex | +| AIS | Alarm Indication Signal | +| APS | Automatic Protection Switching | +| ATM | Asynchronous Transfer Mode | +| AUG | Administrative Unit Group | +| AU-n | Administrative Unit (level) n | +| DXC | Digital Cross-Connect | +| HOP | Higher-Order Path | +| HOPT | Higher-Order Path Termination | +| HOTCA | Higher-Order Tandem Connection Adaptation | +| HOTCT | Higher-Order Tandem Connection Termination | +| HOPM | Higher-Order Path Matrix | +| LOP | Lower-Order Path | +| MS | Multiplex Section | +| PDH | Plesiochronous Digital Hierarchy | +| PRC | Primary Reference Clock | +| PSTN | Public Switched Telephone Network | +| RS | Regenerator Section | +| SDH | Synchronous Digital Hierarchy | +| STM-N | Synchronous Transport Module (level) N | +| TU-n | Tributary Unit (level) n | +| TUG-n | Tributary Unit Group (level) n | +| VC-n | Virtual Container (level) n | +| VC-n-X | Concatenation of X virtual containers (of level n) | +| VC-n-Xc | Contiguous concatenation of X virtual containers (of level n) | +| VC-n-Xv | Virtual concatenation of X virtual containers (of level n) | +| VP | ATM virtual path | + +# 5 Application of the G.805 layering concept + +The functional architecture of SDH transport networks is described using the generic rules defined in ITU-T Recommendation G.805. The specific aspects regarding the characteristic information, client/server associations, the topology, the connection supervision and protection switching of SDH transport networks are provided in this ITU-T Recommendation. This ITU-T Recommendation uses the terminology and functional architecture and diagrammatic conventions defined in ITU-T Recommendation G.805. + +A transport network based on the SDH can be decomposed into a number of independent transport layer networks with a client/server association between adjacent layer networks. Each layer network can be separately partitioned in a way which reflects the internal structure of that layer network or the way that it will be managed. The structure of the SDH layer networks and the adaptation functions is shown in Figure 5-1. + +![Diagram of SDH layer networks and adaptation functions showing five layers: LOP, LOPT, HOP, MS, and RS. Each layer has source and sink components connected by trails and network connections (NC).](f4fdd410cdb84df81274da55721e56fb_img.jpg) + +The diagram illustrates the hierarchical structure of SDH layer networks and adaptation functions. It consists of five layers, each with a source and a sink component connected by a trail and a network connection (NC). The layers are stacked vertically, with the LOP layer at the top and the RS layer at the bottom. + +- LOP Layer:** LOPA source and LOPA sink are connected by a dashed line labeled "LOP trail". Below each LOPA component is a circle labeled "LOP AP". +- LOPT Layer:** LOPT source and LOPT sink are connected by a dashed line labeled "LOP NC". Below each LOPT component is a circle labeled "LOP TCP". +- HOP Layer:** HOPA source and HOPA sink are connected by a dashed line labeled "HOP trail". Below each HOPA component is a circle labeled "HOP AP". +- MS Layer:** MST source and MST sink are connected by a dashed line labeled "MS NC". Below each MST component is a circle labeled "MS TCP". +- RS Layer:** RSA source and RSA sink are connected by a dashed line labeled "RS trail". Below each RSA component is a circle labeled "RS AP". +- Bottom Layer:** RST source and RST sink are connected by a dashed line labeled "RS NC". Below each RST component is a circle labeled "RS TCP". + +The diagram shows the flow of data through these layers, with adaptation functions (LOPA, LOPT, HOPA, HOP, MST, RSA, RST) and termination/connection points (AP, TCP) at the interfaces between layers. The source and sink components are represented by trapezoidal shapes, and the adaptation functions are represented by circles. + +T1308670-96 + +Diagram of SDH layer networks and adaptation functions showing five layers: LOP, LOPT, HOP, MS, and RS. Each layer has source and sink components connected by trails and network connections (NC). + +| | | +|------|---------------------------------| +| AP | Access Point | +| HOPA | Higher-Order Path Adaptation | +| HOPT | Higher-Order Path Termination | +| LOPA | Lower-Order Path Adaptation | +| LOPT | Lower-Order Path Termination | +| MSA | Multiplex Section Adaptation | +| MST | Multiplex Section Termination | +| NC | Network Connection | +| RSA | Regenerator Section Adaptation | +| RST | Regenerator Section Termination | +| TCP | Termination Connection Point | + +Figure 5-1/G.803 – SDH layer networks and adaptation functions + +For the purposes of description of the SDH, the interlayer adaptation function is named in relation to the server layer network. In this ITU-T Recommendation, the G.805 transport assembly is called a "layer" to maintain continuity of the terminology used in the 1992 version of ITU-T Recommendation G.803. The current set of client server associations is listed in Appendix I together with the Figure I.1 that identifies the corresponding SDH layers (or transport assemblies). + +A detailed description of each of these functions is provided in ITU-T Recommendation G.783. + +## 5.1 Multiplexing of multiple clients + +When supporting multiple clients, the adaptation function is grouped with the server layer network. Figure 5-2 illustrates the case of a VC-4 Higher-Order Path (HOP) server layer supporting VC-12, VC-2 and VC-3 Lower-Order Path (LOP) client layer networks. Figure 5-2 provides further details of the internal structure of the HOP interlayer adaptation function to show the grouping of three TU-12s into a TUG-2 and seven TUG-2s into a TUG-3 to reflect the SDH multiplex structure defined in ITU-T Recommendation G.707. Note that the TUG only describes grouping and does not change the format of the signal. + +![Diagram illustrating the multiplexing of multiple client layer networks (VC-12, VC-2, VC-3) into a VC-4 Higher-Order Path (HOP) server layer. The diagram shows the hierarchy from client APs down to the HOP layer and back up to the VC-4 TCP.](d26959f4514c26ca19c3d6f00da85956_img.jpg) + +The diagram illustrates the multiplexing of multiple client layer networks into a VC-4 Higher-Order Path (HOP) server layer. The hierarchy is as follows: + +- Client Layer Networks (Top):** + - VC-12 AP (Transport Assembly) + - VC-12 (Lower-Order Path) + - VC-12 TCP (Transport Container) +- Multiplexing Stage (Middle):** + - The VC-12 TCP is mapped into a TU-12 (Transport Unit). + - Three TU-12s are grouped into a TUG-2 (Transport Unit Group). + - The VC-2 AP, VC-2, and VC-2 TCP are mapped into a TU-2. + - The VC-3 AP, VC-3, and VC-3 TCP are mapped into a TU-3. + - Seven TUG-2s and one TU-3 are grouped into a TUG-3. + - The TUG-3 is mapped into the HOPA (Higher-Order Path Assembly). +- HOP Layer (Bottom):** + - The HOPA is mapped into a VC-4 AP. + - The VC-4 (Higher-Order Path) + - The VC-4 TCP + +A vertical double-headed arrow on the right side of the diagram is labeled "HOP layera)", indicating the scope of the Higher-Order Path layer. + +a) G.805 Transport Assembly. + +T1308680-96 + +Diagram illustrating the multiplexing of multiple client layer networks (VC-12, VC-2, VC-3) into a VC-4 Higher-Order Path (HOP) server layer. The diagram shows the hierarchy from client APs down to the HOP layer and back up to the VC-4 TCP. + +Figure 5-2/G.803 – VC-4 supporting multiple client layer networks + +The case of a STM-4 supporting VC-3 and VC-4 clients is illustrated in Figure 5-3; again, the figure provides more details of the internal structure of the Multiplex Section (MS) interlayer adaptation function to show the grouping of 3 AU-3s into an AUG to reflect the G.707 multiplex structure. This grouping within the multiplex structure is reflected in ITU-T Recommendation G.774 using the indirect adaptor object class. + +![Diagram of Multiplex Section (MS) supporting VC-3 and VC-4 clients. The diagram shows two client paths (VC-3 and VC-4) entering a large shaded area labeled 'Multiplex section layer a)'. Inside, VC-3 clients are mapped to AU-3s, which are then grouped into an AUG. VC-4 clients are mapped to AU-4s. Both AUG and AU-4 are then multiplexed into a single stream. Below the shaded area, the stream passes through a series of Multiplex Section (MS) layers: MS AP, MS, and MS TCP. A vertical double-headed arrow on the right indicates the 'Multiplex section layer a)'.](007b053fe94a8348f75128a584503fd0_img.jpg) + +The diagram illustrates the internal structure of the Multiplex Section (MS) interlayer adaptation function for a STM-4 supporting VC-3 and VC-4 clients. On the left, three VC-3 clients (AP, VC-3, TCP) are shown. On the right, three VC-4 clients (AP, VC-4, TCP) are shown. Both sets of clients are mapped into AU-3 and AU-4 containers respectively. These containers are then grouped into an AUG (for AU-3s) and directly into the MS (for AU-4s). The MS is shown as a large shaded area. Below the MS, the stream passes through a series of MS layers: MS AP, MS, and MS TCP. A vertical double-headed arrow on the right indicates the 'Multiplex section layer a)'. A small note at the bottom left indicates 'a) G.805 Transport Assembly.' and a code 'T1308690-96' is at the bottom right. + +Diagram of Multiplex Section (MS) supporting VC-3 and VC-4 clients. The diagram shows two client paths (VC-3 and VC-4) entering a large shaded area labeled 'Multiplex section layer a)'. Inside, VC-3 clients are mapped to AU-3s, which are then grouped into an AUG. VC-4 clients are mapped to AU-4s. Both AUG and AU-4 are then multiplexed into a single stream. Below the shaded area, the stream passes through a series of Multiplex Section (MS) layers: MS AP, MS, and MS TCP. A vertical double-headed arrow on the right indicates the 'Multiplex section layer a)'. + +**Figure 5-3/G.803 – Multiplex Section (MS) supporting VC-3 and VC-4** + +## 5.2 Support of ATM over SDH + +For the purpose of describing transport networks based on ATM, ITU-T Recommendation I.326 shows the ATM transport assembly that groups the VP to VC-n, VC-n-Xv and VC-n-Xc adaptation functions with the client layer network. This difference in grouping of the adaptation function for the description of ATM and SDH-based transport networks has no impact on the actual functions performed by these networks. The interface between the ATM transport assembly and one of these VC-n, VC-n-Xv and VC-n-Xc layer networks is the access point. + +Note that when the client is an ATM VP layer network, the VC-n, VC-n-Xv and VC-n-Xc server layer networks can only support a single client layer network. + +## 5.3 Concatenation + +For the transport of client layer signals with transmission rates above or between the transmission rate of any single SDH VC the payload capacity of individual VCs can be combined by means of concatenation. + +Two types of concatenation are defined in ITU-T Recommendation G.707: contiguous (VC-n-Xc) and virtual concatenation (VC-n-Xv). ITU-T Recommendation G.707 defines contiguous and virtual concatenation in such a way that the payload capacities of a VC-n-Xc and a VC-n-Xv are identical. By implication the adaptation functions for a particular client layer network to either a VC-n-Xc or a VC-n-Xv for the same index X are also the same. The current set of client server associations for concatenated layer networks is listed in Appendix I and depicted in Figure I.1. + +### 5.3.1 Contiguous concatenation + +The characteristic information of a contiguous concatenated VC-n-Xc layer network is transported via a VC-n-Xc network connection. + +Figure 5-4 shows the functional architecture for contiguous concatenation. + +![Functional architecture for contiguous concatenation diagram](3ad00ce93ad9dea9ee0f47535e5355e6_img.jpg) + +The diagram illustrates the functional architecture for contiguous concatenation. It shows two client systems at the top, each consisting of a 'VC-n-X/Client' connected to a 'VC-n-X AP'. A dashed line labeled 'VC-n-X Trail' connects these two APs. Below each 'VC-n-X AP' is a 'VC-n-Xc' layer (represented by a triangle). Below each 'VC-n-Xc' layer is a 'VC-n-Xc TCP'. A dashed line labeled 'VC-n-Xc NC' connects the two 'VC-n-Xc TCP's. In the center, between the two 'VC-n-Xc TCP's, is a 'VC-n-Xc SNC' (represented by an oval) connected to two 'VC-n-Xc CP' nodes. Below each 'VC-n-Xc TCP' is a 'Server/VC-n-Xc' layer (represented by a trapezoid). At the bottom, a dashed line connects the two 'Server/VC-n-Xc' layers. Small circles with dots are shown at various interfaces throughout the diagram. The text 'T1316310-99' is in the bottom right corner. + +Functional architecture for contiguous concatenation diagram + +Figure 5-4/G.803 – Functional architecture for contiguous concatenation + +### 5.3.2 Virtual concatenation + +Virtual concatenation is the SDH implementation of inverse multiplexing as described in ITU-T Recommendation G.805. The characteristic information of a virtual concatenated VC-n-Xv layer network is transported via a bundle of X VC-n network connections. The VC-n-Xv trail termination sink function has to compensate this differential delay in order to provide a contiguous payload at its output. + +The differential delay that has to be compensated for, for virtual concatenated VC-n, is at least 125 $\mu$ sec. + +The connection monitoring techniques defined in clause 7 are applied per data stream on the VC-n characteristic information. + +Figure 5-5a shows the functional architecture for a VC-n-Xv. + +![Functional architecture for virtual concatenation diagram showing VC-n-X Trail, VC-n-Xv, VC-n NC, VC-n SNC, and various client/server components.](4ee27dbf5ef12e7b58b0ef0937bc5a5e_img.jpg) + +The diagram illustrates the functional architecture for virtual concatenation (VC-n-Xv). At the top, two 'VC-n-X/Client' units are connected to 'VC-n-X AP' units. These are linked by a 'VC-n-X Trail'. Below each 'VC-n-X AP' is a 'VC-n-Xv' block, which contains 'VC-n TCP' components. Each 'VC-n-Xv' block is connected to a 'Server/VC-n' unit. The central part of the diagram shows a 'VC-n NC' (Network Concatenation) block containing a 'VC-n SNC' (Sub-Network Concatenation) block. This central structure is flanked by 'VC-n CP' (Concatenation Point) units. Below the central 'VC-n SNC' block, there is a formula: $VC-n-Xv\ SNC = X * VC-n\ SNC$ . At the bottom, four 'Server/VC-n' units are shown, connected to 'VC-n TCP' units, which are in turn connected to the central 'VC-n NC' block. The entire architecture is supported by a series of small circles representing interfaces or nodes. + +Functional architecture for virtual concatenation diagram showing VC-n-X Trail, VC-n-Xv, VC-n NC, VC-n SNC, and various client/server components. + +T1316320-99 + +Figure 5-5a/G.803 – Functional architecture for virtual concatenation + +The compound function VC-n-Xv indicated in Figure 5-5a is further composed to basic atomic functions as shown in Figure 5-5b. + +![Diagram of the Inverse Multiplexing/Virtual Concatenation Model (ITU-T G.803).](33ed1f9b27c7c21c797aa928b0f06851_img.jpg) + +The diagram illustrates the Inverse Multiplexing/Virtual Concatenation (I-MUX/VC-n) model. On the left, a vertical double-headed arrow is labeled "VC-n Inverse Multiplexing Sublayer". At the top, a circle labeled "Client\_CP" connects to a trapezoidal block labeled "VC-n-X/Client". Below this block is a square labeled "VC-n-X\_AP", which connects to a trapezoidal block labeled "VC-n-X". Below that is a circle labeled "VC-n-X\_TCP", which connects to a wide trapezoidal block labeled "VC-n/VC-n-X". This block has four output lines labeled "1", "2", "Y", and "X". Lines "1", "2", and "Y" each pass through a square labeled "VC-n\_AP" and then a trapezoidal block labeled "VC-n", ending at a circle. Line "X" passes through a square labeled "VC-n\_AP", then a trapezoidal block labeled "VC-n", and ends at a circle labeled "VC-n\_TCP". On the right, a circle connects to a trapezoidal block labeled "VC-n-X/Client", which connects to a large trapezoidal block labeled "VC-n-Xv". At the bottom right of the diagram is the text "T1316330-99". + +Diagram of the Inverse Multiplexing/Virtual Concatenation Model (ITU-T G.803). + +**Figure 5-5b/G.803 – Inverse multiplexing/virtual concatenation model** + +The VC-n/VC-n-Xv\_A\_So function performs the following processing between its input and output: + +- determine if variable group size can be handled by client signal; +- determine maximum size of the group (X); +- determine actual size of the group (Y); +- determine temporarily failed signals in actual group; +- support temporarily group size reduction, and support hitless addition of a previously failed signal coordinated with remote end; +- support hitless increase and decrease of the actual group Y, coordinated with the remote end; +- perform 8-bits or byte disinterleave operation of incoming signal; map 8-bits/byte into payload of signal $T_i$ , the next 8-bits/byte into signal $T_{i+1}$ , etc. that belong to the actual group and are not temporarily removed; +- insert differential delay detecting multiframe indicator in each of the signals; +- insert sequence number (need is to be confirmed in SDH) in each of the signals; +- insert payload type identification into the signal label of each of the signals. + +The VC-n/VC-n-X\_A\_Sk function performs the following processing between its input and output: + +- compare payload type identification within the signal label of each of the signals with the expect value, detect defect payload mismatch, report the received values; +- determine if variable group size can be handled by client signal; +- determine maximum size of the group (X); +- determine actual size of the group (Y); + +- determine temporarily failed signals in actual group; +- support temporarily group size reduction, and support hitless addition of a previously failed signal coordinated with remote end; +- support hitless increase and decrease of the actual group Y, coordinated with the remote end; +- recover multiframe start phase of each of the individual signals; +- compare sequence number (need is to be confirmed in SDH) in each of the signals with expected one, detect defect and report received values; +- realign all individual signals that belong to the actual group and are not temporarily removed by means of compensation of the differential delay; +- perform interleave operation of incoming signals that belong to the actual group and are not temporarily removed; +- determine signal fail status and if failed insert AIS. + +The VC-n-X\_TT\_So function performs the following processing between its input and output: + +- report signal fail status; +- for case of interworking with contiguous concatenated remote endpoint, report approximated composite status and performance. + +The VC-n-X\_TT\_So function performs the following processing between its input and output: + +- no specific processing is foreseen for the moment. + +### **5.3.3 Interworking between contiguous and virtual concatenation** + +Contiguous and virtual concatenation for the same index X transport the same adapted information and have similar characteristic information. This enables the possibility for layer network interworking as defined in ITU-T Recommendation G.805 between a VC-n-Xc and a VC-n-Xv layer network with the same index. Figure 5-6 shows the functional architecture. The interworking processing function performs the semantically "transparent" conversion of the virtual concatenation trail overhead to contiguous concatenation trail overhead and vice versa. A VC-n-X trail may contain one or more interworking processing functions. + + + +![Diagram of tandem connection monitoring by means of a sublayer trail. It shows a 'Trail' (top dashed line), a 'Sublayer trail' (middle dashed line), and a 'Tandem connection' (solid line) between two network elements. Various nodes are represented by circles and triangles, with some connected by solid lines and others by dashed lines. A label 'T1308700-96' is in the bottom right corner.](76b0cd79baaedd942af4dc42f2e764b8_img.jpg) + +Diagram of tandem connection monitoring by means of a sublayer trail. It shows a 'Trail' (top dashed line), a 'Sublayer trail' (middle dashed line), and a 'Tandem connection' (solid line) between two network elements. Various nodes are represented by circles and triangles, with some connected by solid lines and others by dashed lines. A label 'T1308700-96' is in the bottom right corner. + +**Figure 6-1/G.803 – Tandem connection monitoring by means of a sublayer trail** + +Figure 6-2 illustrates a SDH network application of tandem connection monitoring within the administrative domain of a network operator. A tandem connection may however also extend across multiple administrative domains with the cooperation of the operators involved. Also in the latter case there is in general no need to support consecutive tandem connections within a single network element. + +![Diagram of a multi-operator domain VC-n trail monitored via tandem connections. It shows three domains: Domain A, Domain B, and Domain C, each containing Network Elements (NE). A 'VC-4 trail (VC-12 trail)' spans across all three domains. Below this, a sequence of components is shown: 'VC-4 TC (VC-12 TC)', 'MS trail (VC-4 trail)', 'VC-4 TC (VC-12 TC)', 'MS trail (VC-4 trail)', 'VC-4 TC (VC-12 TC)', and 'MS trail (VC-4 trail)'. A legend at the bottom left defines 'TC' as 'Tandem Connection'. A label 'T1308710-96' is in the bottom right corner.](4356776ca004ecba5d599667a155d7d4_img.jpg) + +Diagram of a multi-operator domain VC-n trail monitored via tandem connections. It shows three domains: Domain A, Domain B, and Domain C, each containing Network Elements (NE). A 'VC-4 trail (VC-12 trail)' spans across all three domains. Below this, a sequence of components is shown: 'VC-4 TC (VC-12 TC)', 'MS trail (VC-4 trail)', 'VC-4 TC (VC-12 TC)', 'MS trail (VC-4 trail)', 'VC-4 TC (VC-12 TC)', and 'MS trail (VC-4 trail)'. A legend at the bottom left defines 'TC' as 'Tandem Connection'. A label 'T1308710-96' is in the bottom right corner. + +**Figure 6-2/G.803 – Multi-operator domain VC-n trail, monitored via tandem connections** + +Figures 6-3 and 6-4 are examples of tandem connection arrangements, based on a VC-4 trail. The VC-4 trail consists of the two VC-4 trail terminations (HOPT), and the VC-4 network connection. + +The Tandem Connection (TC) may include or exclude the matrix (connection function) within an equipment. Where practicable it is preferred to include the connection functions at the ingress and egress equipment within a tandem connection, which is why this possibility is shown in both examples. + +In Figure 6-3, the VC-4 network connection is partitioned into two subnetwork connections, one in Telecom Operator (TO) domain A and the other in TO domain B. Both subnetworks are interconnected by a link connection supported by a multiplex section. + +The two TO subnetworks are implemented as TC sublayers (monitored subnetworks). This adds the VC-4 TC Adaptation (HOTCA) and Trail Termination (HOTCT) functions to the TO subnetworks. + +The TO subnetworks are further partitioned into a series of subnetworks, represented by the VC-4 Matrices (HOPM), and intermediate link connections. + +In Figure 6-4, the VC-4 network connection is partitioned into three subnetwork connections, interconnected by link connections supported by multiplex sections. + +One of the three subnetworks is implemented as a TC sublayer (monitored subnetworks). This adds the VC-4 TC Adaptation (HOTCA) and Trail Termination (HOTCT) functions to the TO subnetwork. + +The TO subnetwork is further partitioned into a series of subnetworks, represented by the VC-4 matrices (HOPM), and intermediate link connections. + +In the network element in which the tandem connection starts, the tandem connection overhead is inserted in the signal before the signal is applied at the layer's connection function (if present). Similarly, the tandem connection overhead is removed from the signal after it is passed through the layer's connection function (if present) within the network element in which the tandem connection ends. + +![A hierarchical diagram of a VC-4 trail passing through two operator domains, Network A and Network B. The trail starts at a HOPT, passes through HOTCA and HOTCT components, and traverses multiple link connections with HOPM and MSA/MST units. It then switches to Network B, repeating the sequence of components before ending at another HOPT.](5445597cceefaca1ac89e710fe339325_img.jpg) + +The diagram illustrates a VC-4 trail passing through two operator domains, Network A and Network B. The trail is shown as a dashed line at the top, labeled 'VC-4 trail'. It connects to a 'VC-4 network connection' which is further divided into '(Network A) Tandem connection' and '(Network B) Tandem connection'. Each tandem connection contains a '(TC A) Trail' or '(TC B) Trail' which passes through HOTCA (Higher-Order Tandem Connection Adaptation) and HOTCT (Higher-Order Tandem Connection Termination) components. These trails then connect to '(TC A) Network connection' or '(TC B) Network connection', which in turn connect to a series of 'Link connection' segments. Each link connection contains a HOPM (Higher-Order Path Matrix) and an MSA/MST (Multiplex Section Adaptation/Multiplex Section Termination) unit. The trail ends at another HOPT (Higher-Order Path Termination) at the far right. + +A hierarchical diagram of a VC-4 trail passing through two operator domains, Network A and Network B. The trail starts at a HOPT, passes through HOTCA and HOTCT components, and traverses multiple link connections with HOPM and MSA/MST units. It then switches to Network B, repeating the sequence of components before ending at another HOPT. + +T1308720-96 + +- | | | | | +|-------|--------------------------------------------|-----|-------------------------------| +| HOPM | Higher-Order Path Matrix | MSA | Multiplex Section Adaptation | +| HOPT | Higher-Order Path Termination | MST | Multiplex Section Termination | +| HOTCA | Higher-Order Tandem Connection Adaptation | | | +| HOTCT | Higher-Order Tandem Connection Termination | | | + +Figure 6-3/G.803 – Example of a VC-4 trail passing two operator domains + +![Diagram of a VC-4 trail with a tandem connection in an intermediate operator domain. The diagram shows a path from a source HOPT through a series of HOPM, MSA/MST, HOTCT, and HOTCA components, including link connections and a (TC) Trail, to a destination HOPT. The path is labeled with VC-4 trail, VC-4 network connection, VC-4 tandem connection, and (TC) Trail.](5b8a756d9a71c35f17db8bcb90b438a3_img.jpg) + +The diagram illustrates a VC-4 trail path. At the top, a dashed line represents the 'VC-4 trail' between two 'HOPT' (Higher-Order Path Termination) units. Below this, a dashed line represents the 'VC-4 network connection'. The path then enters an intermediate operator domain via a 'VC-4 tandem connection'. This connection consists of a 'HOTCA' (Higher-Order Tandem Connection Adaptation) unit, a '(TC) Trail', and another 'HOTCA' unit. Below the HOTCA units are 'HOTCT' (Higher-Order Tandem Connection Termination) units. The path continues through a series of 'Link connection' units, each containing a 'HOPM' (Higher-Order Path Matrix) unit and an 'MSA/MST' (Multiplex Section Adaptation/Multiplex Section Termination) unit. The path ends at the destination 'HOPT' unit. + +Diagram of a VC-4 trail with a tandem connection in an intermediate operator domain. The diagram shows a path from a source HOPT through a series of HOPM, MSA/MST, HOTCT, and HOTCA components, including link connections and a (TC) Trail, to a destination HOPT. The path is labeled with VC-4 trail, VC-4 network connection, VC-4 tandem connection, and (TC) Trail. + +T1308730-96 + +HOPM Higher-Order Path Matrix + HOPT Higher-Order Path Termination + HOTCA Higher-Order Tandem Connection Adaptation + HOTCT Higher-Order Tandem Connection Termination + MSA Multiplex Section Adaptation + MST Multiplex Section Termination + +**Figure 6-4/G.803 – Example of a VC-trail with a tandem connection in an intermediate operator domain** + +# **7 SDH transport network availability enhancement techniques** + +A description of the generic protection types is provided in ITU-T Recommendation G.805. This ITU-T Recommendation indicates how these generic types are applied in the case of the SDH. A detailed description of the implementation of some of these schemes is provided in ITU-T Recommendations G.783 and G.841. + +## **7.1 SDH multiplex section protection** + +SDH multiplex section protection is a type of trail protection as described in ITU-T Recommendation G.805. Failure events are detected by the Multiplex Section Termination (MST) function and the reconfiguration uses the protection switching functions that are in the multiplex section protection sublayer. The resultant reconfiguration may involve protection switching in multiple SDH network elements. The coordination of such switching in multiple SDH network elements is by means of an Automatic Protection Switching (APS) protocol. + +### **7.1.1 SDH multiplex section 1+1 protection** + +In a 1+1 SDH multiplex section protection system, two multiplex sections are provided; one carries the traffic, the other acts as a standby. A description of multiplex section 1+1 protection is given in ITU-T Recommendation G.783. + +### **7.1.2 SDH multiplex section 1:N protection** + +A 1:N SDH multiplex section protection system consists of N traffic carrying multiplex sections that are to be protected, together with an additional multiplex section to provide protection. When not required for protection, this additional multiplex section capacity can be used to support lower priority "extra traffic". This extra traffic is not itself protected. A description of multiplex section 1:N protection together with the APS protocol is given in ITU-T Recommendation G.783. + +### **7.1.3 SDH multiplex section shared protection rings** + +Multiplex section shared protection rings are characterized by dividing the total payload per multiplex section equally into working and protection capacity, e.g. for a two-fibre STM-N ring, there are N/2 administrative unit groups (AUGs) available for working and N/2 AUGs for protection whilst in a four-fibre STM-N ring, there are N AUGs available for working and N AUGs available for protection. The ring protection capacity can be accessed by any multiplex section of a multinode ring under a section or node failure condition. Thus, the protection capacity is shared between multiple multiplex sections. This sharing of protection capacity may allow a multiplex section shared protection ring to carry more traffic under normal conditions than other ring types. Under non-failure conditions, the protection capacity can be used to support lower priority "extra traffic". This extra traffic is not itself protected. A description of multiplex section shared protection rings including the definition of the APS protocol is provided in ITU-T Recommendation G.841. + +### **7.1.4 SDH multiplex section dedicated rings** + +A multiplex section dedicated protection ring is a 1:N protection scheme where $N = 1$ . A system consists of two counter rotating rings (each transmitting in opposite directions relative to each other). Under failure conditions, the entire working channel is looped to the protection channel. The APS protocol required for this scheme is not provided in ITU-T Recommendation G.841, since the maximum capacity of this type of ring is the sum of the capacity on each span and therefore, the applications for this type of protection scheme are limited. + +## 7.2 SDH subnetwork connection protection examples + +Subnetwork connection protection is described in ITU-T Recommendation G.805. It may be applied to either a SDH higher-order path or lower-order path. To support subnetwork protection, two dedicated subnetwork connections are provided; one carries the traffic, the other acts as a standby. This protection mechanism can be used on any physical transport structure (e.g. meshed, rings or mixed). It can be used to protect a complete end-to-end network connection or a portion of a network connection. Further details of the application of this scheme in the SDH are provided in ITU-T Recommendation G.841. + +# 8 Architecture of synchronization networks + +## 8.1 Introduction + +This clause describes architectural aspects of the distribution of timing information within a SDH network. It focuses on the need for SDH clocks to be traceable to a Primary Reference Clock (PRC) and have good short-term stability performance in order to comply with the generic slip rate objectives in ITU-T Recommendation G.822. + +It is further explained that, provided the SDH clock meets the short-term stability mask, there are no practical limitations to the number of pointer processing elements that can be cascaded in a SDH network to comply with the payload output jitter requirements at a SDH/PDH boundary. + +Evolutionary scenarios are presented to identify how SDH network synchronization can be integrated with the existing synchronization network. + +Appendix III provides additional guidance on the subject of network synchronization with the focus on the practical engineering aspects. + +## 8.2 Synchronization network aspects + +### 8.2.1 Synchronization methods + +There are two fundamental methods of synchronizing nodal clocks. These are identified in ITU-T Recommendation G.810: + +- master-slave synchronization; +- mutual synchronization. + +Master-slave synchronization is appropriate for synchronizing SDH networks and the following material offers guidance on using this method. The feasibility of employing mutual synchronization is left for further study. + +Master-slave synchronization uses a hierarchy of clocks in which each level of the hierarchy is synchronized with reference to a higher level, the highest level being the PRC. Clock reference signals are distributed between levels of the hierarchy via a distribution network which may use the facilities of the transport network. The hierarchical levels are shown below: + +- PRC G.811. +- Slave clock (transit node) G.812. +- Slave clock (local node) G.812. +- SDH network element clock G.813. + +The distribution of timing between hierarchical node clocks must be done by a method which avoids intermediate pointer processing. Two possible methods are as follows: + +- 1) Recover timing from a received STM-N signal. This avoids the unpredictable effect of a pointer adjustment on the downstream slave clock. The exact technique to adopt is for further study. +- 2) Derive timing from a synchronization trail that is not supported by a SDH network. + +The master-slave method uses a single-ended synchronization technique with the slave clock determining the synchronization trail to be used as its reference and changing to an alternative if the original trail fails. This is a unilateral control scheme. + +### **8.2.2 Synchronization network architecture** + +The architecture employed in SDH requires the timing of all network element clocks to be traceable to a PRC which is compliant with ITU-T Recommendation G.811. The discussion below details the target architecture for SDH network synchronization. Evolutionary aspects are discussed in 8.2.6. + +The distribution of synchronization can be categorized into intra-station within stations containing a G.812 level clock and inter-station as follows: + +- a) Intra-station distribution within stations containing a G.812 level clock conforms to a logical star topology. All lower level network element clocks within a station boundary derive timing from the highest hierarchical level in the station. Only the clock of the highest hierarchical level in the station will recover timing from synchronization links from other stations. Timing is distributed from network elements within the boundary to network elements beyond the boundary via the SDH transmission medium. The relationship between clocks within a station is shown in Figure 8-1. +- b) Inter-station distribution conforms to a tree-like topology and enables all the stations in the SDH network to be synchronized. The hierarchical relationship between clocks is shown in Figure 8-2. With this architecture, it is important for the correct operation of the synchronization network that clocks of lower hierarchical level only accept timing from clocks of the same or higher hierarchical level and that timing loops are avoided. To ensure that this relationship is preserved, the distribution network must be designed so that, even under fault conditions, only valid higher level references are presented to hierarchical clocks. + +Clocks of a lower hierarchical level must have a capture range sufficiently wide to ensure they can automatically acquire and lock to the timing signal generated by the same or higher level clock that they are using as a reference. + +![Diagram of synchronization network architecture intra-node distribution. A central 'Node clock' is connected to four 'SDH network element clock' units. An external 'Synchronization link(s)' enters from the left. A dashed circle labeled 'Node boundary' encloses the central node clock and the four SDH network element clocks. Arrows labeled 'a)' point from the SDH network element clocks to the Node clock. Arrows point from the SDH network element clocks outwards, with one labeled 'Distribution to other G.813 clocks outside the node'.](7133ccf78043568ca62ecbcd43628a4a_img.jpg) + +Diagram of synchronization network architecture intra-node distribution. A central 'Node clock' is connected to four 'SDH network element clock' units. An external 'Synchronization link(s)' enters from the left. A dashed circle labeled 'Node boundary' encloses the central node clock and the four SDH network element clocks. Arrows labeled 'a)' point from the SDH network element clocks to the Node clock. Arrows point from the SDH network element clocks outwards, with one labeled 'Distribution to other G.813 clocks outside the node'. + +a) Timing only. + +T1816890-92 + +**Figure 8-1/G.803 – Synchronization network architecture intra-node distribution** + +![Diagram of synchronization network architecture inter-node distribution. A top-level 'G.811 PRC' (Primary reference clock) is connected to two 'G.812 node clock' units. Each of these 'G.812 node clock' units is further connected to two more 'G.812 node clock' units, for a total of four at the bottom level. Arrows indicate the flow of synchronization from the PRC down to the node clocks.](e354b57563dae469c00b412b2abdf765_img.jpg) + +Diagram of synchronization network architecture inter-node distribution. A top-level 'G.811 PRC' (Primary reference clock) is connected to two 'G.812 node clock' units. Each of these 'G.812 node clock' units is further connected to two more 'G.812 node clock' units, for a total of four at the bottom level. Arrows indicate the flow of synchronization from the PRC down to the node clocks. + +PRC Primary reference clock + +T1816900-92 + +**Figure 8-2/G.803 – Synchronization network architecture inter-node distribution** + +The functional architecture of synchronization networks deals with the modelling of the transfer of timing information between hierarchical synchronization clocks. An example is provided in Figure 8-3. The three clocks defined in ITU-T Recommendations G.811, G.812 and G.813 are represented as adaptation functions which modify the quality of the timing information according to their quality level. + +All synchronization clocks are located in a single layer: the Synchronization Distribution (SD) layer. The SD layer network provides the trails for the transfer of timing information from one clock to another. The SD layer network is concerned with unidirectional transfer of information; therefore, all access points of the SD layer network are unidirectional. + +The SD layer may be supported by any multiplex section or path layer provided that these server layers are transparent for timing information. SDH VC-*n* layers and PDH path layers that are supported by SDH path layers do not qualify as such, because pointer processing impacts the timing information. + +Figure 8-3 also shows the client of the SD layer as the Network Synchronization (NS) layer. The NS layer is solely responsible for providing the point-to-multipoint through connections from the PRC to all other clocks in the network. At every connection point in the NS layer there is an estimate of Universal Time Coordinated (UTC) available. The quality of the estimate of UTC depends on the configuration of the NS layer network and the timing quality of the SD trails provided by the SD layer network. + +Note that line system regenerator clocks are not shown in the SD layer. They are contained in the section layer that supports the SD layer. The difference between these regenerator clocks and the clocks in the SD layer is that the former are "transparent". The regenerator clocks transfer timing or squelch the timing information. Conversely, the SD clocks provide timing even in case of a failure of the SD trail that transfers the timing from the previous clock in the NS connection. + +The connection matrices shown in the NS layer provide for the configuration of the synchronization network. The link connections between the matrices are supported by trails in the SD layer. Autonomous reconfiguration of the synchronization network, including protection switching, is also performed via these matrices. + +The connection matrices in the SD layer are for the provisioning of the SD trails. They are used to select the multiplex sections or paths that support the SD trails. + +Synchronization status messaging may be used to convey timing quality information (see 8.2.7). This information is inserted at the SD trail termination source and extracted at the SD trail termination sink. Furthermore, it is the SD trail termination that reports the failure of an SD trail. + +Figure 8-4 shows a specific example of synchronization distribution from the public network across a PDH primary rate user network interface to a G.812 clock in a private network. In this example the primary rate signal is retimed from the SDH network element clock. + +Alternative methods of passing synchronization across the user network interface are for further study. + +![Diagram of synchronization distribution layers showing Network synchronization, Synchronization distribution, and Multiplex section layers across multiple paths (G.811, G.813, G.812).](aaf3e6e44cdeabd6d1df869c5f392ea1_img.jpg) + +The diagram illustrates the synchronization distribution layers across three parallel paths. At the top, a dashed line represents the UTC reference. The first path (left) consists of an NS link connection to a G.811 node, followed by an SD trail to an SD node, then an MS trail to an MS/SD node, and finally an MS node. The second path (middle) consists of an NS link connection to an SD/NS node, followed by an SD trail to an SD node, then an MS trail to an MS/SD node, and finally an MS node. The third path (right) consists of an NS link connection to a G.813 node, followed by an SD trail to an SD node, then an MS trail to an MS/SD node, and finally an MS node. The fourth path (far right) consists of an NS link connection to an SD/NS node, followed by an SD trail to an SD node, then an MS trail to an MS/SD node, and finally an MS node. The layers are labeled on the right: Network synchronization layer (top), Synchronization distribution layer (middle), and Multiplex section layer (bottom). A legend at the bottom defines the abbreviations: MS/SD (MS to SD adaptation), MST (Multiplex Section Termination), NS (Network Synchronization), SD (Synchronization Distribution), SD/NS (SD to NS adaptation), and UTC (Universal Time Coordinated). The diagram is labeled T1308740-96. + +UTC + +NS link connection + +G.811 + +SD trail + +SD + +MS trail + +MS/SD + +MS + +SD/NS + +G.813 + +SD + +MS/SD + +MS + +SD/NS + +G.812 + +SD + +MS/SD + +MS + +Network synchronization layer + +Synchronization distribution layer + +Multiplex section layer + +T1308740-96 + +MS/SD MS to SD adaptation +MST Multiplex Section Termination +NS Network Synchronization +SD Synchronization Distribution +SD/NS SD to NS adaptation +UTC Universal Time Coordinated + +Diagram of synchronization distribution layers showing Network synchronization, Synchronization distribution, and Multiplex section layers across multiple paths (G.811, G.813, G.812). + +**Figure 8-3/G.803 – Example of synchronization distribution showing the synchronization layers** + +![Diagram illustrating synchronization distribution across a PDH UNI. The diagram shows four vertical paths of synchronization distribution. At the top, a dashed line labeled 'UTC' spans all paths. Below it, four ovals labeled 'NS link connection' are shown. The first path (leftmost) goes from an NS link connection down through a G.811 box, an SD trail, an SD box, and an unlabeled oval to a PDH primary rate section box. The second path goes from an NS link connection down through an SD/NS box, an SD trail, an SD box, and an MS/SD box to an MS box. The third path goes from an NS link connection down through a G.813 box, an SD trail, an SD box, and an MS/SD box to an MS box. The fourth path (rightmost) goes from an NS link connection down through an SD/NS box, an SD trail, an SD box, and a PDH primary rate section box. Horizontal dashed lines connect the SD/NS and SD/NS boxes, and the MS/SD and MS/SD boxes, labeled 'SD trail' and 'SDH MS trail' respectively. A vertical dashed line labeled 'UNI' separates the rightmost path from the others. At the bottom right, the text 'T1308750-96' is present.](8c348bf9c2c81b018017ae1d19506a9a_img.jpg) + +Diagram illustrating synchronization distribution across a PDH UNI. The diagram shows four vertical paths of synchronization distribution. At the top, a dashed line labeled 'UTC' spans all paths. Below it, four ovals labeled 'NS link connection' are shown. The first path (leftmost) goes from an NS link connection down through a G.811 box, an SD trail, an SD box, and an unlabeled oval to a PDH primary rate section box. The second path goes from an NS link connection down through an SD/NS box, an SD trail, an SD box, and an MS/SD box to an MS box. The third path goes from an NS link connection down through a G.813 box, an SD trail, an SD box, and an MS/SD box to an MS box. The fourth path (rightmost) goes from an NS link connection down through an SD/NS box, an SD trail, an SD box, and a PDH primary rate section box. Horizontal dashed lines connect the SD/NS and SD/NS boxes, and the MS/SD and MS/SD boxes, labeled 'SD trail' and 'SDH MS trail' respectively. A vertical dashed line labeled 'UNI' separates the rightmost path from the others. At the bottom right, the text 'T1308750-96' is present. + +| | | | | +|-------|-------------------------------|-------|------------------------------| +| MS/SD | MS to SD adaptation | SD | Synchronization Distribution | +| MST | Multiplex Section Termination | SD/NS | SD to NS adaptation | +| NS | Network Synchronization | UTC | Universal Time Coordinated | + +**Figure 8-4/G.803 – Example of synchronization distribution across a PDH UNI** + +### 8.2.3 Synchronization modes + +Four synchronization modes can be identified. These are: + +- synchronous; +- pseudo-synchronous; +- plesiochronous; +- asynchronous. + +In synchronous mode, all clocks in the network will be traceable to the network PRC. Pointer adjustments will only occur randomly. This is the normal mode of operation within a single operator's domain. + +In pseudo-synchronous mode, not all clocks in the network will be traceable to the same PRC. However, each PRC will comply with ITU-T Recommendation G.811 and therefore pointer adjustments will occur at the synchronization boundary network element. This is the normal mode of operation for the international and inter-operator network. + +In plesiochronous mode, the synchronization trail and the fallback alternatives to one or more clocks in the network will have been disabled. The clock will enter holdover or free-run mode. If synchronization is lost to a SDH network element performing asynchronous mapping, the frequency offset and drift of the clock will cause pointer adjustments persisting through the whole SDH network connection. If synchronization is lost to the last network element in the SDH network connection (or the penultimate network element in the case where the last one is slaved, e.g. consists of a loop-timed multiplexer), there will also be pointer adjustments to cater for at the SDH network output. However, if the synchronization failure occurs at an intermediate network element, this will not result in a net pointer adjustment at the final output network element provided the input network element remains synchronized with the PRC. Pointer movement at the intermediate network element will be corrected by the next network element in the connection which is still synchronized. + +Asynchronous mode corresponds to the situation where large frequency offsets occur. The SDH network is not required to maintain traffic with a clock accuracy less than that specified in Recommendation G.813. A clock accuracy of $\pm 20$ ppm is required to send AIS (applicable for regenerators and any other SDH equipment where loss of all synchronization inputs implies loss of all traffic). + +### **8.2.4 Synchronization network reference chain** + +The synchronization network reference chain is shown in Figure 8-5. The node clocks are interconnected via $N$ network elements each having clocks compliant with ITU-T Recommendation G.813. + +The longest chain should not exceed $K$ slave clocks compliant with ITU-T Recommendation G.812. Only one type of G.812 slave clock is shown because the difference in holdover performance of the transit and local clock is not relevant for SDH network synchronization. This contrasts with the situation in the PSTN environment which is sensitive to long-term instability. + +The quality of timing will deteriorate as the number of synchronization links increases. + +The value of $N$ will be limited by the quality of timing required by the last network element in the chain. This ensures the short-term stability requirements, defined in Appendix I/G.813, will be met. + +To determine synchronization clock specifications, the values for the worst-case synchronization reference chain are: $K = 10$ , $N = 20$ with the total number of SDH network element clocks limited to 60. These values are only applicable to "option 1" clocks as defined in ITU-T Recommendation G.813; the values for "option 2" clocks are for further study. The "option 1" values have been derived from theoretical calculations; practical measurements are required for their verification. It should be noted, however, that in practical synchronization network design, the number of network elements in tandem should be minimized for reliability reasons. + +![Diagram of a synchronization network reference chain. It shows a vertical sequence of nodes: PRC G.811 at the top, followed by '1st Slave G.812 transit', 'K-1th Slave G.812 transit', and 'Kth Slave G.812 transit or local' at the bottom. Between each pair of main nodes are three small circles representing SDH network element clocks, grouped by a bracket and labeled 'N G.813 SDH network element clocks'. The label 'T1816920-92' is at the bottom.](11edb7fcedf09ac6a817f8d7b8c61eec_img.jpg) + +PRC G.811 + +1st Slave G.812 transit + +$K-1\text{th}$ Slave G.812 transit + +$K\text{th}$ Slave G.812 transit or local + +$N$ G.813 SDH network element clocks + +$N$ G.813 SDH network element clocks + +$N$ G.813 SDH network element clocks + +$N$ G.813 SDH network element clocks + +T1816920-92 + +Diagram of a synchronization network reference chain. It shows a vertical sequence of nodes: PRC G.811 at the top, followed by '1st Slave G.812 transit', 'K-1th Slave G.812 transit', and 'Kth Slave G.812 transit or local' at the bottom. Between each pair of main nodes are three small circles representing SDH network element clocks, grouped by a bracket and labeled 'N G.813 SDH network element clocks'. The label 'T1816920-92' is at the bottom. + +For worst-case scenario calculation purposes: + +$$K = 10$$ + +$N = 20$ with restriction that total number of SDH network element clocks is limited to 60 + +**Figure 8-5/G.803 – Synchronization network reference chain** + +### **8.2.5 Synchronization strategy** + +The synchronization strategy is to integrate SDH network synchronization with the existing PSTN network synchronization architecture with the minimum of disruption and reconfiguration. Present node clocks are either separate units or integrated in the exchanges. With the introduction of SDH there is also the possibility to integrate the node clock in certain types of SDH equipment, typically in large SDH cross-connects. In that case, the G.813 network element clock is replaced by a G.811 or G.812 quality clock. + +### **8.2.6 Synchronization network evolution** + +The SDH is designed to operate in pseudo-synchronous mode. The network elements can be integrated into existing synchronization hierarchies. + +When SDH equipment is initially introduced, the network element must be timed from either the PRC or one of the slave clocks. Timing is distributed throughout the SDH network using the master-slave approach. This may require a new interface on the slave clock to time the SDH network element. + +If the SDH network introduction results in PDH islands, steps must be taken so that synchronization links supported by primary rate PDH trails do not transit the SDH network. This requires a reconfiguration of the synchronization architecture since all synchronization links transiting the SDH network must be supported on SDH multiplex section trails. This may require new interfaces on the slave clocks and on the PRC. + +Where a network is fully SDH-based, then the synchronization distribution will be determined solely by the synchronization network reference chain. + +During the evolution of the network to SDH, the network synchronization plan will have to be altered to accommodate the SDH network elements. This requires careful planning to ensure that network synchronization is not jeopardized. + +Evolutionary scenarios with multiple SDH islands supporting the transport of a PDH payload need further study. + +### **8.2.7 Synchronization network robustness** + +It is preferable if all node clocks and network element clocks are able to recover timing from at least two synchronization distribution trails. The slave clock must reconfigure to recover timing from an alternative trail if the original trail fails. Where possible, synchronization trails should be provided over diversely routed paths. + +In the event of a failure of synchronization distribution, all network elements will seek to recover timing from the highest hierarchical level clock source available. To effect this, both G.812 and G.813 clocks may have to reconfigure and recover timing from one of their alternate synchronization distribution trails. This will ensure that a SDH network element clock-timed network element rarely enters holdover or free-run mode. However, it may have to recover timing from a G.812 clock which is itself in holdover if this is the highest hierarchical level source available to it. + +Within SDH subnetworks, timing is distributed between network nodes via a number of network elements with clocks of lower hierarchical level. A timing marking scheme is provided to allow selection and confirmation of the synchronization trail, where a choice is available, with the highest hierarchical clock source quality level (including under synchronization failure conditions). + +The quality marking scheme provides an indication of the clock source quality level of the timing using a status messaging approach. The status message is conveyed in the multiplex section overhead as described in ITU-T Recommendation G.707. When an output is used to support a synchronization trail with synchronization status messaging, then the synchronization status message shall indicate the clock source quality level of the clock that originally generated the synchronization + +signal. Note that it does not reflect any degradation caused by the accumulation of jitter or wander as a result of transmission through a transport network. + +Within SDH subnetworks, the status message is conveyed in the multiplex section overhead as described in ITU-T Recommendation G.707. In PDH distribution trails, it is possible to convey the status message as described in ITU-T Recommendation G.704. For PDH distribution trails carrying ATM, the status message is described in ITU-T Recommendation G.832. + +Synchronization status messages contain clock source quality level information that may assist clocks to select the most suitable synchronization reference from the set of available references. The purpose of these messages is to allow clocks to reconfigure their synchronization references autonomously while avoiding the creation of timing loops. The use of synchronization status messages can minimize the length of time a clock is in holdover. However, it is critical to realize that the use of synchronization status messages alone will not avoid the creation of timing loops. Synchronization planning and engineering is still required. + +To provide an example of a reconfiguration, if the first network element from the PRC loses its synchronization trail from the PRC, it must reconfigure and accept timing from the G.812 slave clock. This is shown in Figure 8-6. + +![Diagram illustrating a reconfiguration example in a synchronization network. The diagram is split into two parts: 'Before recovery' and 'After reconfiguration'.](9f9386d5b3d6cbeb1ed104a799320ebf_img.jpg) + +The diagram shows two states of a synchronization network chain. On the left, labeled "Before recovery", timing flows downwards from a Primary Reference Clock (PRC) through a series of Network Elements (1st NE, 2nd NE, ..., Nth NE) to a G.812 clock. Solid arrows indicate the flow of timing recovery downwards. On the right, labeled "After reconfiguration", a fault (marked with an 'X') has occurred between the PRC and the 1st NE. The timing flow has reversed; the G.812 clock now provides the timing reference, which flows upwards through the chain (Nth NE, 2nd NE, 1st NE) as indicated by upward-pointing solid arrows. A dashed line between the 2nd NE and Nth NE indicates intermediate elements. The technical reference T1816930-92 is noted at the bottom right. + +Diagram illustrating a reconfiguration example in a synchronization network. The diagram is split into two parts: 'Before recovery' and 'After reconfiguration'. + +**Figure 8-6/G.803 – Reconfiguration example** + +## 8.3 Payload jitter and wander + +In SDH, the quality of the timing information of a payload signal is influenced by several sources: + +- the synchronization network; +- the pointer processing mechanism; +- the payload mapping mechanisms. + +Subclause 8.2 defines a synchronization reference chain which is used to calculate the accumulation of jitter and wander in the synchronization network. The resulting short-term stability requirements, which are specified in Appendix I/G.813, represent a network limit for the clock stability of the timing source internal to a network element. This clock stability determines the statistics of the pointer adjustments resulting from the pointer processing mechanism. + +The purpose of this subclause is to define the network topologies that have to be supported by a SDH network taking into account the network limits for payload jitter and wander given in ITU-T Recommendations G.823 and G.824. In addition, reference configurations are specified that may occur when SDH is introduced in the existing PDH environment. + +### **8.3.1 SDH network model for pointer activity simulation** + +For the transport of PDH signals through a SDH network, the model shown in Figure 8-7 is used to simulate the accumulation of jitter and wander through a reference connection due to pointer activity. The clock acting upon each pointer processing node is assumed to have the stability specified in ITU-T Recommendation G.813. Since this specification reflects the network limit, this represents a worst-case scenario. + +Simulations have shown that the pointer statistics are bounded when the number of processing nodes increases. With the pointer processor buffer threshold spacings specified in ITU-T Recommendation G.783, pointer adjustments at the TU-1 level are an extremely rare event, even when intermediate pointer processing at the administrative unit level is taken into account. This means that the pointer mechanism does not impose a practical upper bound on the number of tributary unit processing nodes that can be put in tandem. At the administrative unit level, pointer adjustments, including some double pointer adjustments, do occur with statistical saturation starting to show at about 10 nodes. This implies that there is also no practical constraint on the number of administrative unit pointer processing nodes that can be cascaded, provided the short-term stability mask is met at each node clock. + +### **8.3.2 Jitter at a SDH/PDH boundary** + +Jitter appearing at a SDH/PDH boundary consists of pointer adjustment jitter and payload mapping jitter. Since pointer adjustments occur in 8 unit interval steps (24 unit intervals at the AU-4 level), stringent requirements are placed on the desynchronizer at the SDH/PDH boundary. This also applies at the TU-1 level since, although pointer adjustment events are unlikely under normal operational conditions (i.e. all nodes synchronized), they will occur under degraded conditions (i.e. pseudo-synchronous or plesiochronous modes) when the originating or terminating node looses synchronization. This requires desynchronizers with relatively narrow equivalent bandwidth. It should be noted that, even with narrow-band desynchronizers, the effect of pointer justifications on signals that are used to convey third party timing may be larger than assumed in the design of customer premises equipment synchronization utilities. Therefore, they may not be able to adequately track the phase variations. The desynchronizer will also filter the line jitter that may accumulate along a chain of regenerators if not already filtered by the characteristics of the SDH network element clock equipment clock. Mapping jitter is generated at the originating node at the SDH/PDH boundary but does not accumulate across a SDH network. Its relative contribution to the output jitter at a SDH/PDH boundary will depend upon desynchronizer design. Its maximum value is specified in ITU-T Recommendation G.783. + +As a result, the output jitter limit at a SDH/PDH boundary is dominated by pointer adjustment jitter which in turn is governed by the short-term stability of the clocks at each node. + +![Figure 8-7/G.803 – SDH network model for pointer activity simulation. The diagram shows a sequence of five SDH processing blocks: SDH multiplex and pointer processing terminal, Pointer processing terminal, Pointer processing terminal, Pointer processing terminal, and SDH demultiplex and pointer processing terminal. A plesiochronous payload input enters the first block, and a plesiochronous payload output exits the last block. A timing reference block with a clock symbol provides a common timing signal to all five blocks via a dashed line. Each block contains a small circle with a sine wave symbol. The diagram is labeled T1816940-92.](7ae836e598020d937ed1478c2ef13025_img.jpg) + +Figure 8-7/G.803 – SDH network model for pointer activity simulation. The diagram shows a sequence of five SDH processing blocks: SDH multiplex and pointer processing terminal, Pointer processing terminal, Pointer processing terminal, Pointer processing terminal, and SDH demultiplex and pointer processing terminal. A plesiochronous payload input enters the first block, and a plesiochronous payload output exits the last block. A timing reference block with a clock symbol provides a common timing signal to all five blocks via a dashed line. Each block contains a small circle with a sine wave symbol. The diagram is labeled T1816940-92. + +**Figure 8-7/G.803 – SDH network model for pointer activity simulation** + +## 8.4 PDH/SDH interworking implications + +In many evolutionary scenarios, there is a need to carry a PDH payload across multiple SDH islands. This is shown in Figure 8-8. Although the payload jitter and wander specification in ITU-T Recommendation G.783 have been determined with this application in mind, there is no absolute guarantee that every PDH multiplex chain will accept the output jitter appearing at the SDH/PDH boundary. This is because there is no specified lower limit to the corner frequency of the PDH demultiplex transfer characteristic. + +If synchronous islands are put in tandem, a certain accumulation of the phase transients caused by more or less simultaneous pointer adjustments in multiple islands will occur. The nature of the pointer statistics is such that this will limit the maximum number of cascaded islands for the transport of 34 368, 44 736 and 139 264 kbit/s signals, unless the desynchronizer specification is enhanced to provide adequate attenuation of jitter and wander appearing at the input of the SDH island. The trade-off between the maximum number of islands, short-term clock stability and desynchronizer specification is for further study. + +![Figure 8-8/G.803 – PDH/SDH interworking. The diagram shows a sequence of five alternating SDH and PDH blocks: SDH, PDH, SDH, PDH, and SDH. Each block is connected to the next by a vertical line labeled G.703. The entire sequence is flanked by vertical lines labeled G.703 at both ends. The diagram is labeled T1816950-92.](a4b963a07cc368283154762c4b156fe7_img.jpg) + +Figure 8-8/G.803 – PDH/SDH interworking. The diagram shows a sequence of five alternating SDH and PDH blocks: SDH, PDH, SDH, PDH, and SDH. Each block is connected to the next by a vertical line labeled G.703. The entire sequence is flanked by vertical lines labeled G.703 at both ends. The diagram is labeled T1816950-92. + +**Figure 8-8/G.803 – PDH/SDH interworking** + +# 9 Selection of a primary rate mapping + +There are three ways of mapping 1544 and 2048 kbit/s primary rate signals into the VC-11 and VC-12, respectively, as defined in ITU-T Recommendation G.707: asynchronous, bit synchronous and byte synchronous. These mappings have different features and networking considerations. The choice of mapping is application-dependent. + +Given the features of the mappings the following is recommended for SDH networking: + +- a) asynchronous mapping should be used only for asynchronous/plesiochronous type signals. This includes PDH path mappings into SDH paths (i.e. 64 kbit/s signals in PDH format may be carried via the asynchronous mapping); +- b) bit synchronous mapping should not be used in international interconnection; +- c) byte synchronous floating mode mapping should be used for primary rate signals as defined in ITU-T Recommendation G.704, provided that the bit rate of the signal can, under normal operating conditions, be traced to a Primary Reference Clock. This applies, for example, to the use of a V5.1 or V5.2 interface as defined in ITU-T Recommendations G.964 and G.965 respectively. In the case where a network operator chooses to use the asynchronous mapping for such a synchronous signal that is intended to be interconnected via a SDH LOP to another network operator that uses the recommended byte synchronous mapping, then responsibility for providing the interworking functionality rests with the operator that used the asynchronous mapping unless otherwise agreed bilaterally. + +Appendix II provides more information on interworking of 64 and $N \times 64$ kbit/s signals between PDH-based transport networks and SDH-based transport networks. + +# APPENDIX I + +## Client server associations of SDH layer networks + +| Client layer | Server layer | Client characteristic information | +|------------------------|--------------------------------------------------------------------------------------------|-----------------------------------------------| +| 1544 kbit/s asynch | VC-11 LOP | 1544 kbit/s $\pm 50$ ppm | +| 1544 kbit/s byte synch | VC-11 LOP | 1544 kbit/s nominal
G.704 octet structured | +| 2048 kbit/s asynch | VC-12 LOP | 2048 kbit/s $\pm 50$ ppm | +| 2048 kbit/s byte synch | VC-12 LOP | 2048 kbit/s nominal
G.704 octet structured | +| 6312 kbit/s asynch | VC-2 LOP | 6312 kbit/s $\pm 30$ ppm | +| 34 368 kbit/s asynch | VC-3 LOP or HOP | 34 368 kbit/s $\pm 20$ ppm | +| 44 736 kbit/s asynch | VC-3 LOP or HOP | 44 736 kbit/s $\pm 20$ ppm | +| 139 264 kbit/s asynch | VC-4 HOP | 139 264 kbit/s $\pm 15$ ppm | +| ATM virtual path | VC-11, VC-12, VC-2, VC-2-Xc, VC-2-Xv or VC-3 LOP or:
VC-3, VC-4, VC-4-Xc or VC-4-Xv HOP | 53-octet cells | +| HDLC framed signals | VC-11, VC-12, VC-2, VC-2-Xc, VC-2-Xv or VC-3 LOP or:
VC-3, VC-4, VC-4-Xc or VC-4-Xv HOP | variable length frames | +| VC-11 LOP | VC-3 or VC-4 HOP or
sSTM 2n Multiplex section (TUG-2 based) | VC-11 + frame offset | + +| Client layer | Server layer | Client characteristic information | +|-----------------------------------------|--------------------------------------------------------------------------------------------------------------|-------------------------------------------------| +| VC-12 LOP | VC-3 or VC-4 HOP or
sSTM-1k Multiplex section (TU-12 based)
or sSTM-2n Multiplex section (TUG-2 based) | VC-12 + frame offset | +| VC-2 LOP | VC-3 or VC-4 HOP or
sSTM-2n Multiplex section (TUG-2 based) | VC-2 + frame offset | +| VC-2-Xc LOP | VC-3 HOP | VC-2-Xc + frame offset,
X = 2 ... 7 | +| VC-2-Xv LOP | VC-4 HOP | VC-2-Xv + frame offset,
X = 2 ... 21 | +| VC-3 LOP | VC-4 HOP | VC-3 + frame offset | +| VC-3 HOP | STM-0 or STM-N Multiplex section | VC-3 + frame offset | +| VC-4 HOP | STM-N Multiplex section | VC-4 + frame offset | +| VC-4-Xc HOP | STM-N Multiplex section | VC-4-Xc + frame offset,
X = 4, 16 (>16 tbd) | +| VC-4-Xv HOP | STM-N Multiplex section | VC-4-Xv + frame offset,
X = 2...16 (>16 tbd) | +| sSTM-1k Multiplex section (TU-12 based) | sSTM-1k Regenerator section (TU-12 based) | sSTM-1k rate, k = 1, 2, 8 or 16 TU-12s | +| sSTM-2n Multiplex section (TUG-2 based) | sSTM-2n Regenerator section (TUG-2 based) | sSTM-2n rate, n = 1, 2 or 4 TUG-2s | +| STM-0 Multiplex section | STM-0 Regenerator section | STM-0 rate | +| STM-N Multiplex section | STM-N Regenerator section | STM-N rate, N = 1, 4, 16, 64 | + +![Diagram showing client server associations and corresponding SDH Layer networks. The diagram is organized into four horizontal layers. The top layer, 'PDH, ATM VP or other packet-based layer networks', connects to the second layer, 'Lower-order path layer networks', which contains VC-11, VC-12, VC-2, VC-2-Xc, VC-2-Xv, and VC-3. The third layer, 'Higher-order path layer networks', contains VC-3, VC-4, VC-4-Xc, and VC-4-Xv. The fourth layer, 'Multiplex section layer networks', contains sSTM-1k (TU-12 based), sSTM-2n (TUG-2 based), STM-0, and STM-N. The bottom layer, 'Regenerator section layer networks', contains sSTM-1k (TU-12 based), sSTM-2n (TUG-2 based), STM-0, and STM-N. Lines show various associations between elements in adjacent layers. A label 'T1316350-99' is in the bottom right.](f57c7b37d7a05a99618104f390089f03_img.jpg) + +Diagram showing client server associations and corresponding SDH Layer networks. The diagram is organized into four horizontal layers. The top layer, 'PDH, ATM VP or other packet-based layer networks', connects to the second layer, 'Lower-order path layer networks', which contains VC-11, VC-12, VC-2, VC-2-Xc, VC-2-Xv, and VC-3. The third layer, 'Higher-order path layer networks', contains VC-3, VC-4, VC-4-Xc, and VC-4-Xv. The fourth layer, 'Multiplex section layer networks', contains sSTM-1k (TU-12 based), sSTM-2n (TUG-2 based), STM-0, and STM-N. The bottom layer, 'Regenerator section layer networks', contains sSTM-1k (TU-12 based), sSTM-2n (TUG-2 based), STM-0, and STM-N. Lines show various associations between elements in adjacent layers. A label 'T1316350-99' is in the bottom right. + +NOTE – Collectively referred to as sub-STM-0 layer networks. + +**Figure I.1/G.803 – Client server associations and corresponding SDH Layer networks** + +# APPENDIX II + +## Introduction of SDH-based transport networks + +## II.1 General + +This appendix provides information on how a transport network could evolve to one based on SDH. There are many choices which must be made when introducing SDH-based transport networks. These choices, such as the time order in which different types of SDH-based equipment are introduced and the types of mapping used, will affect subsequent stages of evolution to SDH-based transport networks and may pose networking or PDH/SDH interworking constraints. These choices and the level of deployment of SDH-based transport networks compared with PDH or other transport networks are a matter for the network operator concerned. Although this appendix illustrates the issues by discussing the steps required to migrate to fully SDH-based transport networks, fully SDH-based transport networks are not necessarily the goal. + +This appendix firstly identifies the types of client layer signals which can be supported on SDH paths and the types of client layer signals which can be supported on PDH paths. It then describes the three basic introductory scenarios for SDH-based equipment. For each type of SDH client layer signal and introductory scenario, this appendix describes the consequences on networking, PDH/SDH interworking and subsequent transport network evolution. + +Figure II.1 shows the introductory paths that are available and illustrates the basic choices and provides a reference during the following discussion. + +## II.2 Types of client layer signals + +### II.2.1 SDH case + +SDH path layers support the following client layer signals in accordance with the mappings defined in ITU-T Recommendation G.707. For the purpose of interworking two cases must be considered: + +- a) client layer signals such as: + - i) 64 kbit/s-based signals (adapted into the SDH path layers using byte synchronous mappings); + - ii) leased line signals at G.702 bit rates at or above the primary rate; + - iii) other signals (e.g. ATM VP cells), the bit rate of which might be optimized to the payload of the SDH path layers; +- b) PDH path layer signals (at G.702 bit rates at or above the primary rate) which, in turn, support either: + - i) client layer signals as in II.2.1 a); + - ii) lower-order PDH path layer signals. + +SDH-based transport network equipment is concerned with control of connectivity of SDH paths and not with control of connectivity of the client layer. Therefore, in case b) above, the SDH-based equipment cannot be used to individually network the signals identified in b) i) and ii); primary rate and/or higher-order PDH multiplexing functionality is required to facilitate this connectivity. This constraint could be significant in cases where SDH-based transport networks become widespread. Where this is likely to be the case, it is recommended that the support of such signal is minimized from the outset or, that during subsequent stages of transport network evolution, steps are taken to minimize the redundant PDH path layer signals. + +### II.2.2 PDH case + +In the case of PDH, path layer signals support the following two types of client layer signals which must be considered for interworking: + +- a) client layer signals such as: + - i) 64 kbit/s-based signals (adapted into the PDH path layers in accordance with ITU-T Recommendation G.704); + - ii) leased line signals at G.702 bit rates at or above the primary rate; + - iii) other signals (e.g. ATM VP cells), the bit rate of which might be optimized to the payload of the PDH layers; +- b) SDH path layer signals which, in turn, support the client layer signals identified in II.2.1 (see Note below). + +NOTE – Mappings of SDH path layer signals into PDH path layer signals are defined in ITU-T Recommendation G.832. The possibility is mentioned in this appendix in order to outline a possible transitional stage of transport network evolution. The functionality required to provide these mappings is referred to below as "modem" functionality (since it is analogous to the transition from the "old" analogue network to the "new" digital network where modems allowed signals from the "new" network to be supported over the "old" network). In cases where the modem functionality provides multiplexing of several SDH path layer signals into the PDH path layer, control of the connectivity of the individual SDH path layer signals is not possible in the PDH path layer network. + +## II.3 Initial introduction of SDH-based equipment + +There are three basic ways of initially introducing SDH-based equipment: + +- a) Deployment of an overlay network comprising the simultaneous deployment of SDH line systems and VC-*n* cross-connect functionality to provide widespread path layer connectivity (see Note below). In addition, to increase geographical coverage in such overlay network, the link connections in the SDH path layer could be adapted into PDH paths using the modem functionality as mentioned in II.2.2 b). Initially, this overlay network is likely to be "thin" and might be targeted at supporting particular client layer types (e.g. a leased line service) but later "thickened" to include other services. + +NOTE – VC-*n* cross-connect functionality is realized in SDH digital cross-connect equipment (DXC) and/or add/drop multiplex equipment (ADM). Such functionality is referred to below as DXC/ADM. + +- b) Deployment of SDH DXC/ADMs only with interfaces at G.702 bit rates. This is likely to take the form of DXCs in central locations where control of the connectivity of PDH paths at the site is the desired initial benefit. In terms of the functional network architecture, VC-*n* paths in the DXC/ADMs provide subnetwork connections in the PDH path layer. SDH line systems could be deployed at a later stage to provide more widespread VC connectivity. Similarly, PDH paths with the modem functionality could be used as mentioned in a) above to provide more widespread VC-*n* connectivity. +- c) Deployment of SDH line systems only with intra-office interfaces at G.702 bit rates. Such systems are functionally similar to PDH line systems in that they support link connections in the PDH path layer. In terms of the functional network architecture, VC-*n* paths in the SDH line systems provide link connections in the PDH path layer. SDH DXC/ADMs could be deployed at a later date to provide more widespread VC-*n* connectivity. + +Each option is valid and the choice of one or more options is determined by the initial requirements of the network operator. The choice of one option by one network operator need not affect the choice of another network operator. The three options can coexist. + +## II.4 Interworking between PDH- and SDH-based transport networks + +### II.4.1 Interworking levels + +Interworking between PDH-based transport networks and SDH-based transport networks can occur at one of the following three levels: + +- a) at the client layer for signals identified in II.2.1 a) and II.2.2 a): Such interworking generally requires the termination of the respective PDH and SDH paths and the adaptation functions between the respective path layers and the client layer. This combination of functions is referred to below as transmultiplexing (TMUX). This approach does not necessarily imply additional physical interfaces. In the particular case of 64 kbit/s client layer signals, the byte synchronous mappings given in ITU-T Recommendation G.707 allow client layer interworking without necessarily terminating the PDH path. In the particular case of leased line signals at G.702 bit rates at or above the primary rate, the asynchronous mappings given in ITU-T Recommendation G.707 allow client layer interworking. In cases where the PDH and SDH client layer signals have the same bit rate, interworking at the client level does not necessarily require processing of the client layer signal; +- b) at the PDH path level for signals identified in II.2.1 b): Such interworking requires the adaptation of the PDH path layer signals into appropriate SDH path layers using the asynchronous mappings described in ITU-T Recommendation G.707 for G.702 bit rates; + +- c) at the SDH path level where the SDH path layer signals, described in II.2.2 b), are adapted into PDH paths using the modem functionality: This case is described in ITU-T Recommendation G.832. + +The choice of interworking level and SDH equipment introduction scenario will have an impact on subsequent transport network evolution stages as discussed below. + +### II.4.2 SDH overlay + +The two interworking levels are considered as follows: + +- a) The requirements for interworking at the client level are given in II.4.1 a). + +In cases where PDH paths are used to provide VC-*n* connectivity, "modem" functionality will be required for adaptation to the PDH path layer. + +In cases where subsequently STM-N interfaces are provided on network elements which process the client layer signals identified in II.2.1 a) (e.g. a 64 kbit/s switch), there are no interworking requirements between such network elements and the SDH transport network. + +- b) The requirements for interworking at the PDH path level are given in II.4.1 b). Primary rate and/or higher-order PDH multiplexing functionality will continue to be required in the PDH-based transport network. + +In cases where PDH paths are used to provide VC-*n* connectivity, "modem" functionality will be required for adaptation to the PDH path layer. + +In cases where subsequently STM-N interfaces are provided on network elements which process the client layer signals identified in II.2.1 a), primary rate and/or higher-order PDH multiplexing functionality and G.707 asynchronous mappings of G.702 bit rates will continue to be required to provide interworking functionality between such network elements and the SDH transport network. + +In cases where it is subsequently desired to interwork at the client level, it will be necessary to cease the SDH paths supporting PDH path layers and provide new SDH paths which directly support the client layer. Primary rate and/or higher-order PDH multiplexing functionality will not be required. + +### II.4.3 SDH DXC/ADMs + +The two interworking levels are considered as follows: + +- a) The requirements for interworking at the client level are given in II.4.1 a). + +In cases where subsequently more widespread SDH path layer networking is required, SDH line systems could be deployed; interworking functionality is not required between DXC/ADM and the SDH line systems. The considerations in II.4.2 a) also apply. + +- b) The requirements for interworking at the PDH path level are given in II.4.1 b). + +In cases where subsequently more widespread SDH path layer networking is required, SDH line systems could be deployed; interworking functionality is not required between the DXC/ADM and the SDH line systems. The considerations in II.4.2 b) also apply. + +### II.4.4 SDH line systems + +The two interworking levels are considered as follows: + +- a) The requirements for interworking at the client level are given in II.4.1 a). + +In cases where subsequently more widespread SDH path layer networking is required, SDH DXC/ADMs could be deployed; interworking functionality is not required between DXC/ADM and the SDH line systems. The considerations in II.4.2 a) also apply. + +- b) The requirements for interworking at the PDH path level are given in II.4.1 b). +In cases where subsequently more widespread SDH path layer networking is required, SDH DXC/ADM could be deployed; interworking functionality is not required between the DXC/ADM and the SDH line systems. The considerations in II.4.2 b) also apply. + +## **II.5 Introduction of STM-N interfaces on 64 kbit/s switches (and DXCs)** + +In the case of PDH-based transport networks, 64 kbit/s switches are interconnected by G.704 structured primary or secondary rate synchronous paths. In terms of the functional architecture, the link connections between subnetworks in the 64 kbit/s layer network are supported by paths in the PDH path layer network. The introduction of STM-N interfaces on one of two interconnected 64 kbit/s switches requires PDH/SDH interworking. + +Interworking can take place at either the 64 kbit/s level or the PDH path level. Considering these two cases: + +- a) interworking at the 64 kbit/s level requires the use of byte synchronous mappings to adapt the 64 kbit/s layer signals into the SDH path layer (see Note below); + +NOTE – ITU-T Recommendation G.707 defines byte synchronous mappings into VC-11 and VC-12 only. Current ITU-T Recommendations do not define byte synchronous mappings into higher bit rate VC-*n*s. + +- b) interworking at the PDH path level requires the use of asynchronous mappings to adapt the PDH paths into the SDH path layer. + +In the case where subsequently STM-N interfaces are introduced on the other 64 kbit/s switch and there is the potential for SDH path layer connectivity between the two switches, interworking functionality will be required if one switch uses byte synchronous mapping and the other switch uses asynchronous mapping. In cases where the two switches are in different operators' networks, responsibility for providing the interworking functionality (if required) rests with the operator of the switch which uses asynchronous mapping unless otherwise agreed bilaterally. + +![Flowchart titled 'Introductory paths for SDH transport networks' showing decision paths for Client layer and PDH path layer inputs.](1ab49904e6a60be337d5b75cb7cc8ab7_img.jpg) + +``` + +graph TD + Start((Decide +interworking +level)) --> CL[Client +layer] + Start --> PDHL[PDH +path +layer] + + subgraph Client_Path [Client Layer Path] + CL --> DIS1((Decide +introduction +scenario)) + DIS1 --> O1[Overlay] + DIS1 --> DA1[DXC & ADM +first] + DIS1 --> SL1[STM-N line +system first] + + O1 --> TM1[TMUX and/or +byte synch +mapping] + DA1 --> TM2[TMUX and/or +byte synch +mapping] + SL1 --> TM3[TMUX and/or +byte synch +mapping] + + TM1 --> IF1{{Interworking +function +required}} + TM2 --> SD1{{Subsequent +deployment of +widespread +VC-n +connectivity}} + TM3 --> IF2{{Interworking +function required +as STM-N +interfaces on +64 kbit/s switches +are deployed}} + + TM1 --> DSN1[Deploy +STM-N line +systems] + TM2 --> DSN2[Deploy +STM-N line +systems] + TM3 --> DDA1[Deploy +DXC & ADM] + + DSN1 --> NIW[No +interworking +function +required] + DSN2 --> NIW + DDA1 --> NIW + end + + subgraph PDH_Path [PDH Path Layer Path] + PDHL --> DIS2((Decide +introduction +scenario)) + DIS2 --> O2[Overlay] + DIS2 --> DA2[DXC & ADM +first] + DIS2 --> SL2[STM-N line +system first] + + O2 --> G1[G.707 +asynch +mappings] + DA2 --> G2[G.707 +asynch +mappings] + SL2 --> G3[G.707 +asynch +mappings] + + G1 --> DFIL((Decide +future +interworking +level)) + G2 --> DSN3[Deploy +STM-N line +systems] + G3 --> DDA2[Deploy +DXC & ADM] + + DSN3 --> DFIL + DDA2 --> DFIL + + DFIL --> CL2[Client layer] + DFIL --> PDHL2[PDH +path layer] + + CL2 --> CP[Cease PDH +paths provide +SDH path and +TMUX and/or +byte synch +mappings] + PDHL2 --> RPR[Retain +PDH +rates] + + CP --> NIW + RPR --> G4[G.707 +asynch +mappings +required] + end + +``` + +The flowchart illustrates the introductory paths for SDH transport networks, starting from a central decision node 'Decide interworking level'. This leads to two main branches: 'Client layer' and 'PDH path layer'. Both branches lead to a 'Decide introduction scenario' node, which offers three options: 'Overlay', 'DXC & ADM first', and 'STM-N line system first'. In the Client layer branch, these options lead through 'TMUX and/or byte synch mapping' to various deployment steps ('Deploy STM-N line systems' or 'Deploy DXC & ADM') and eventually to 'No interworking function required'. There are also specific requirements noted in pentagonal boxes: 'Interworking function required', 'Subsequent deployment of widespread VC-n connectivity', and 'Interworking function required as STM-N interfaces on 64 kbit/s switches are deployed'. In the PDH path layer branch, the options lead through 'G.707 asynch mappings' to deployment steps and then to a 'Decide future interworking level' node. This decision leads either back to the 'Client layer' (resulting in 'Cease PDH paths...' and then 'No interworking function required') or to the 'PDH path layer' (resulting in 'Retain PDH rates' and 'G.707 asynch mappings required'). + +Flowchart titled 'Introductory paths for SDH transport networks' showing decision paths for Client layer and PDH path layer inputs. + +**Figure II.1/G.803 – Introductory paths for SDH transport networks** + +T1308770-96 + +# APPENDIX III + +## Guidelines for synchronization network engineering + +### III.1 Introduction + +This appendix presents additional guidance on the subject of network synchronization as it is provided in this ITU-T Recommendation, clause 8, with a focus on the practical engineering aspects. It builds on the principles described in the main body of this ITU-T Recommendation. In particular, the following principles: + +- the use of master-slave synchronization; +- the synchronization reference chain; +- the use of STM-N for timing transport in SDH networks; and +- the rules for intra-node synchronization engineering, + +are, for the purpose of this appendix, taken as a given starting point and are not further discussed. + +The guidelines outlined in this appendix are applicable to both Option I and Option II networks. However, the examples given in this appendix are only drawn from Option I type networks. To apply them to Option II networks, the 2048 kbit/s and 2048 kHz timing links between SSUs and SECs have to be substituted by 1544 kbit/s "derived DS1" links. + +## III.2 Purpose of the synchronization network + +The synchronization network is the network that is responsible for distributing synchronization information to network elements that need to operate synchronously in order to meet ITU-T Recommendation G.822 octet slip performance requirements. These network elements are in principle all types of network elements that perform routing or multiplexing functionality on the 64 kbit/s or 2048 kbit/s signals, like switches, primary multiplexers, ISDN equipment, PBXs, PDH DXCs, etc. + +The "physical layer" for transportation of synchronization information is formed by 2048 kbit/s signals over PDH transport networks and STM-N signals over SDH transport networks and, in addition, some dedicated 2048 kHz or 2048 kbit/s links for intra-office synchronization transport. Finally, clock equipment, stand-alone or built-in, in network elements, are part of the synchronization network. Added to this can be a management system that is used specifically for synchronization purposes or is integrated in a general network management system. + +Synchronous operation of the above-mentioned network element types is usually arranged over a certain geographic area, in which all such network elements are synchronized to a "master-clock". Such an area in which all relevant network elements are (in normal operation) synchronized to a master-clock is called a "synchronization area". + +The master-clock of a synchronization area should meet the requirements described in ITU-T Recommendation G.811. An end-to-end traffic connection may cross several synchronization areas. The nominal controlled octet slip-rate between adjacent synchronization areas is 1 slip per 70 days or better. ITU-T Recommendation G.822 presents a model and performance objectives involving traffic crossing multiple synchronization areas. + +## III.3 Requirements for synchronization networks + +Impairments in the synchronization network may force clocks to operate (temporarily) without reference. This leads in general to increased octet-slip rates, which degrades the performance of the end-to-end service. Three methods exist to counter these problems: + +- using clocks with very good hold-over performance, which allows operation without reference during the repair period of the reference link; +- duplication (or triplication, etc.) of the clock reference inputs, preferably over geographically separated links from independent sources, in order to minimize the probability of losing all references; or +- a combination of the two methods mentioned above. + +All three methods are used in the designs of clocks and synchronization networks. In the upper parts of the synchronization network hierarchy the first approach tends to be favoured, while in the lower parts of the synchronization network hierarchy it is the second approach that is prevalent. In general a balance must be struck between initial investment, "cost of ownership" and reliability. + +As soon as multiple references are offered to a clock, there needs to be a reference selection mechanism in the clock. Several reference selection mechanisms are possible: + +- manually controlled restoration from a central management system; +- automatic restoration from a central management system; +- automatic restoration based on local decisions of the clock equipment using pre-programmed reference priorities; or +- automatic restoration based on local decisions of the clock equipment using the SSM protocol. + +Using a combination of clock types and restoration mechanisms, it is the objective of the synchronization network engineer to construct a synchronization network that reliably distributes synchronization using the following principles: + +- 1) The synchronization network in each synchronization area forms a tree shaped topology with the master-clock in the top of the tree. No parts of the synchronization network operate isolated from the master-clock and no internal loops are present. +- 2) The lengths of the branches of the synchronization tree are kept as short as possible. The longer a certain synchronization trail becomes, the more susceptible it will be to impairments and wander accumulation. The synchronization reference chain presented in clause 8 is a model for a "reasonable worst case" synchronization link. +- 3) A clock should never lock to a reference which is traceable, at that time, to a clock of lower quality. In such a case this clock should revert to hold-over operation. + +In general, it is not possible to fulfil the above objectives under all (combinations of) failure conditions. The following guidelines can be applied: + +- during all single failures, all clocks in the synchronization area should remain synchronized to the master-clock; +- in most cases of double failures, most clocks should remain synchronized to the master clock; and +- no combination of two simultaneous failures should lead to the formation of timing loops, or the slaving of a clock to a clock of worse traceability, or an oscillating or unstable behaviour of reference selectors. + +## III.4 Analysis of synchronization networks + +To simplify the process of engineering the synchronization network in a certain synchronization area, it is suggested to define several stages, which can be handled in order, one at a time: + +- 1) Engineer the synchronization network considering only PRCs and SSUs (the "SSU-Level") in a synchronization area. +- 2) Engineer the synchronization network considering only SECs (the "SEC-Level") in a synchronization area. +- 3) Engineer the intra-office synchronization of each office. This stage is not further discussed in this appendix. See clause 8 for more information. + +In the first stage the "SSU-Level" is considered. The SSU-Level of the synchronization network consists of the PRCs and SSUs in a synchronization area plus all transport facilities that are active or stand-by carriers for synchronization information between these clocks. The transport facilities between the PRCs and SSUs are considered transparent for the timing information in the SSU-Level view. The resulting network contains only the SSUs and PRCs of the synchronization area. Figures III.1a and III.1b present an example where the SSU-Level is constructed from the complete synchronization network. + +![Synchronization network map showing PRCs, SSUs, and SECs connected by sync carrying facilities.](f142b022cfc716cd967297f027efe647_img.jpg) + +The diagram illustrates a synchronization network map. It features various nodes: PRCs (Primary Reference Clocks) represented by a circle with a central dot, SSU-A (Synchronization Switching Unit type A) represented by a dark grey circle, SSU-B (Synchronization Switching Unit type B) represented by a light grey circle, and SECs (Slave Equipment) represented by small black dots. These nodes are interconnected by lines representing 'Sync carrying facility (PDH or STM-N)'. Arrows on these lines indicate the 'Flow of synchronization information', generally pointing from PRCs and SSU-A nodes towards SSU-B and SEC nodes. The network has a mesh-like structure with multiple paths for synchronization information. A small text label 'T1316360-99' is located in the bottom right corner of the diagram area. + +Legend: + +- PRC +- SSU-A +- SSU-B +- SEC +- Sync carrying facility (PDH or STM-N) +- Flow of synchronization information + +Synchronization network map showing PRCs, SSUs, and SECs connected by sync carrying facilities. + +Figure III.1a/G.803 – Synchronization network map in a synchronization area (example) + +![Diagram of an SSU-Level synchronization network. It shows a mesh of nodes: PRC (black circle with white center), SSU-A (dark grey circle), and SSU-B (light grey circle). Thick lines represent 'Sync carrying facility (PDH or STM-N)' and thin lines with arrows represent 'Flow of synchronization information'. The flow originates from the PRC and spreads through the network of SSUs. A reference code 'T1316370-99' is in the top right.](0a42e05c07941450f34e4f7117725834_img.jpg) + +T1316370-99 + +● PRC                      ● SSU-B + ● SSU-A + — Sync carrying facility (PDH or STM-N) + → Flow of synchronization information + +Diagram of an SSU-Level synchronization network. It shows a mesh of nodes: PRC (black circle with white center), SSU-A (dark grey circle), and SSU-B (light grey circle). Thick lines represent 'Sync carrying facility (PDH or STM-N)' and thin lines with arrows represent 'Flow of synchronization information'. The flow originates from the PRC and spreads through the network of SSUs. A reference code 'T1316370-99' is in the top right. + +**Figure III.1b/G.803 – SSU-Level constructed from Figure III.1a/G.803** + +In the second stage the "SEC-Level" is considered. The SEC-Level part of the synchronization network can be constructed by considering all SSUs (and PRCs) as "no-pass" filters, i.e. barriers for synchronization information. The result is that the SEC-Level consists of a number of unconnected "SEC subnetworks", each consisting of SECs connected by STM-N connections. These SEC subnetworks can be engineered separately. See Figure III.1c for an example. + +![Diagram of SEC-Level synchronization network showing SEC sub-networks, sync carrying facilities, and flow of synchronization information.](c1df61cc3717e878a48e530218403403_img.jpg) + +The diagram illustrates a synchronization network at the SEC level. It features several nodes represented by black dots, labeled as 'SEC' in the legend. These nodes are interconnected by solid lines representing 'Sync carrying facility (PDH or STM-N)'. Arrows indicate the 'Flow of synchronization information'. Two specific groups of nodes and their connections are circled and labeled as 'SEC Sub-networks' via a callout box. The overall network shows a hierarchical structure of synchronization flows. + +● SEC + +—— Sync carrying facility (PDH or STM-N) + +→ Flow of synchronization information + +T1316380-99 + +Diagram of SEC-Level synchronization network showing SEC sub-networks, sync carrying facilities, and flow of synchronization information. + +**Figure III.1c/G.803 – SEC-Level with SEC subnetworks constructed from Figure III.1a/G.803** + +## III.5 PRC-Level options + +Before embarking on the first stage of the synchronization network engineering, the synchronization islands have to be known. This defines the PRC-Level. + +The PRC-Level determines the way in which a certain operator domain is divided in synchronization areas. In each synchronization area at most one PRC is active at any moment (but additional stand-by PRCs can be part of a synchronization area). Two strategies can be followed to determine the size of each synchronization area. Strategy I is to make one big synchronization area and strategy II is to make each office a separate synchronization area. In fact, these two strategies can be considered as "extremes" on a continuous scale. Actual sizes of synchronization areas can be anywhere in between these "extreme" positions. + +Strategy I (one big synchronization area covering the whole operator domain) has the advantage that the number of synchronization areas that an end-to-end traffic connection has to cross is minimized and hence the impact on controlled octet slip-rate performance (as defined in ITU-T Recommendation G.822) under normal conditions is minimized. However, the synchronization network is more complex, so harder to engineer, and the synchronization trails become longer, hence more susceptible to impairments and wander accumulation (which may eventually have a negative effect on the octet-slip rate). + +Strategy II (each telecommunication office forms a synchronization area) makes the engineering of each synchronization area almost trivial. The synchronization network will be very reliable, since the length of the synchronization trail is reduced to some (dedicated) intra-office cabling. + +Generally, for an actual synchronization network a strategy somewhere between I and II is selected, i.e. some (major) nodes have a PRC supplying the synchronization for a certain sub-domain of the total operator domain. Networks closer to a strategy II implementation have shorter, thus more reliable, synchronization trails and also have smaller, hence easier to engineer, synchronization areas. Networks closer to a strategy I implementation have fewer synchronization areas, hence fewer plesiochronous area boundary crossings in end-to-end connections and fewer installed PRC clocks. + +## III.6 SSU-Level solutions + +The synchronization network that is obtained by considering all SSUs, PRCs and all potential synchronization transport facilities (viewed as transparent connections) is called the SSU-Level. The SSU clocks in this network can be classified according to their ability to maintain their output phase/frequency, in case all input references are disqualified, within the network limits that can be derived from ITU-T Recommendation G.825 for STM-N synchronization connections6. The time period over which these limits can be maintained is called the "PRC Autonomy Period" of a clock. In general, the higher the stability of the internal oscillators, the longer the PRC Autonomy Period. See Figure III.2. + +![Figure III.2/G.803 – Determining the PRC Autonomy Period of an SSU. The graph plots Phase Deviation (μs) on the y-axis against Time (s) on the x-axis. It shows two curves representing the hold-over stability of different quality SSUs: a dashed line for 'lower quality SSU' and a solid line for 'higher quality SSU'. Both curves start at a constant phase deviation and then curve upwards. A horizontal line represents the 'SSU Synchronization Network Limit'. The 'PRC Autonomy Period' is indicated by a horizontal double-headed arrow from the start until the lower quality SSU curve reaches the network limit. The higher quality SSU curve reaches the network limit at a later time, indicating a longer autonomy period. The label 'T1316390-99' is in the bottom right corner.](9857175bc98d86591d24a161fe615f12_img.jpg) + +Figure III.2/G.803 – Determining the PRC Autonomy Period of an SSU. The graph plots Phase Deviation (μs) on the y-axis against Time (s) on the x-axis. It shows two curves representing the hold-over stability of different quality SSUs: a dashed line for 'lower quality SSU' and a solid line for 'higher quality SSU'. Both curves start at a constant phase deviation and then curve upwards. A horizontal line represents the 'SSU Synchronization Network Limit'. The 'PRC Autonomy Period' is indicated by a horizontal double-headed arrow from the start until the lower quality SSU curve reaches the network limit. The higher quality SSU curve reaches the network limit at a later time, indicating a longer autonomy period. The label 'T1316390-99' is in the bottom right corner. + +**Figure III.2/G.803 – Determining the PRC Autonomy Period of an SSU** + +The notion of "PRC Autonomy Period" sets a quality parameter for a clock. Knowing the PRC Autonomy Period of a clock, one can determine the following: + +- Are multiple references necessary? If the PRC Autonomy Period is longer than the time it takes to repair a failure in the only reference, operation with a single reference is sufficient. +- How much time is available for a reference switch? If the PRC Autonomy Period is very long, one can make reference switches manually after judging the impairments and consequences. On the other hand shorter PRC Autonomy Periods require some kind of automatic reference switch process, which can be from a central manager (generally a slower process) or made locally by the clock itself (generally a faster process). +- What staffing levels are required to maintain the synchronization network? Do they need to be, for example, on a 24-hour/7-day week stand-by or is an 8-hour/5-day week sufficient? + +The PRC Autonomy Period can be used to classify all SSUs in a synchronization area. The purpose of such a classification is to be able to provide a hierarchy, based on the above defined "PRC Autonomy Period", among the SSUs in the synchronization network. A division of SSUs according + +6 Strictly speaking, ITU-T Recommendation G.825 only specifies the Jitter and Wander Network Limits for SDH networks. In practice, these same limits are often applied for other transport networks like GSM, ATM, etc. as currently no alternative ITU-T Recommendations exist for such networks. + +to their PRC Autonomy Period, the number of Classes and their boundaries, will in general turn out to be different for different operators, depending on the size of the synchronization areas, the number of SSUs per area and their quality. In most cases two Classes will suffice, but more (or fewer) Classes are possible. + +In general one should avoid an SSU of a "lower Class of PRC Autonomy" providing the active reference for an SSU of a "higher Class of PRC Autonomy". This means that in the tree diagram of the SSU network, the PRCs are at the top and that in a downward direction the SSUs are ordered according to their PRC Autonomy classification; the best ones close to the top, the lowest at the bottom of the tree. + +The restoration mechanism for most SSUs will in general be automatic, based on local decisions by the SSUs themselves. All SSUs support a reference selection mechanism locally controlled by pre-programmed priorities (in addition they may also support other selection mechanisms). The method outlined here to design the SSU-Level synchronization network is based on the presence of this selection mechanism in all SSUs. Other methods, e.g. based on centralized management can also be applied, but are not considered here. + +### III.6.1 Checking reference provisioningings at the SSU-Level + +SSUs below a certain PRC Autonomy Class need to have at least two independent references. It is important to verify that no timing loops are formed or can be formed, especially during or after reference rearrangements in the SSU-Level. A labelling scheme can be applied in the engineering stage as a simple tool to check whether a proposed scheme of service and stand-by reference provisioningings (i.e. 1st, 2nd, etc. reference priorities) for the SSU-Level is consistent in this respect. This labelling scheme is described below. Several alternative methods exist to perform this type of checking. + +The idea is to assign to each SSU a label of the format $N(m)$ , where the $N$ represents the PRC Autonomy Class to which the SSU belongs and $m$ is a sub-number within that Class. A *lower* value of $N$ or $m$ represents an SSU that is *higher* in the hierarchy. The PRC gets the value $N = 1$ assigned. The SSUs are labelled according to the following rules: + +- Rule A: Any SSU that belongs to Class $N$ and which gets all its references (i.e. including the stand-by references) from clocks of Class $N-1$ or better, gets the label $N(1)$ assigned. +- Rule B: If an SSU of Class $N$ gets some reference(s) from other clocks of the same Class $N$ that have labels $N(k1)$ , $N(k2)$ , etc., then it gets the label $N(m)$ assigned, where $m = 1 + \text{MAX}\{k1, k2, \dots\}$ . +- Rule C: An SSU of Class $N$ should never be allowed to use a reference of an SSU of Class $N + 1$ or worse. + +If it is possible to label all SSUs in a certain synchronization area according to the above rules, no timing loops can be formed in the SSU-Level during, or after, synchronization reference switching with the proposed scheme of service and stand-by reference assignments. In order to apply $N(m)$ labelling successfully and to provide each SSU with at least two independent references, a sufficient number of interconnections between the SSUs in the SSU-Level needs to be present (in other words the SSU-Level network needs to be sufficiently meshed). + +Each time new SSUs are added to the SSU-Level or new interconnections are assigned to act as reference (service or stand-by), the complete SSU-Level has to be checked again for potential timing loops. + +Figures III.3a and III.3b give examples of a network where $N(m)$ labelling can be applied successfully and one where it is not possible. + +![A network synchronization diagram showing nodes labeled with N(m) values. It includes a PRC, higher quality SSUs (dark grey), and lower quality SSUs (light grey). Solid arrows denote primary references, and dashed arrows denote secondary references. A GPS source feeds into node 4. The diagram demonstrates a loop-free labeling scheme.](5ee1bbbf85b473f78af9ec8368a4159a_img.jpg) + +``` + +graph TD + PRC((PRC)) -- Primary --> N2((2)) + PRC -- Primary --> N4((4)) + GPS[GPS] -. Secondary .-> N4 + N2 -- Primary --> N3((3)) + N2 -- Primary --> N8((8)) + N3 -- Primary --> N5((5)) + N3 -. Secondary .-> N6((6)) + N4 -- Primary --> N6 + N6 -. Secondary .-> N5 + N6 -. Secondary .-> N7((7)) + N5 -. Secondary .-> N8 + N8 -- Primary --> N7 + N7 -. Secondary .-> N8 + + subgraph Labels + N2_L[2\(1\)] --- N2 + N3_L[2\(2\)] --- N3 + N4_L[2\(1\)] --- N4 + N5_L[3\(2\)] --- N5 + N6_L[3\(1\)] --- N6 + N8_L[3\(3\)] --- N8 + N7_L[3\(4\)] --- N7 + end + +``` + +The diagram illustrates a synchronization network. A Primary Reference Clock (PRC) provides timing to node 2 (labeled 2(1), higher quality SSU) and node 4 (labeled 2(1), lower quality SSU) via primary reference links (solid arrows). Node 4 also receives a secondary reference (dashed arrow) from GPS. Node 2 provides a primary reference to node 3 (labeled 2(2), higher quality SSU) and node 8 (labeled 3(3), lower quality SSU). Node 3 provides a primary reference to node 5 (labeled 3(2)) and a secondary reference to node 6 (labeled 3(1)). Node 4 provides a primary reference to node 6. Node 6 provides secondary references to node 5 and node 7 (labeled 3(4)). Node 5 provides a secondary reference to node 8. Node 8 provides a primary reference to node 7, while node 7 provides a secondary reference back to node 8. The legend indicates that solid arrows are primary references, dashed arrows are secondary references, dark grey circles are higher quality SSUs, and light grey circles are lower quality SSUs. Technical reference: T1316400-99. + +A network synchronization diagram showing nodes labeled with N(m) values. It includes a PRC, higher quality SSUs (dark grey), and lower quality SSUs (light grey). Solid arrows denote primary references, and dashed arrows denote secondary references. A GPS source feeds into node 4. The diagram demonstrates a loop-free labeling scheme. + +**Figure III.3a/G.803 – Successful N(m) labelling of SSUs: No potential timing loops** + +![Diagram of a synchronization network showing nodes 2 through 10. Node 2 is a PRC. Nodes 3, 4, and 6 are Higher quality SSUs. Nodes 5, 7, 8, 9, and 10 are Lower quality SSUs. Solid arrows represent primary references, dashed arrows represent secondary references. A starburst around node 5 indicates a violation of the N(m) numbering rule because it receives a reference from node 6, which has a higher N(m) value in its label 3(6) compared to node 5's 3(2). Solid arrow Dashed arrow Black circle Dark grey circle Light grey circle](dbd074feb5cce1300f42f91da8f673d1_img.jpg) + +``` + +graph TD + PRC(( )) -- Primary --> 2(2\(1\)) + PRC -- Primary --> 4(2\(1\)) + GPS -.-> 4 + 2 -- Primary --> 3(2\(2\)) + 2 -- Primary --> 8(3\(3\)) + 3 -.-> 5(3\(2\)) + 3 -.-> 6(3\(1\)) + 4 -- Primary --> 6 + 6 -- Primary --> 5 + 6 -- Primary --> 10(3\(6\)) + 10 -.-> 5 + 10 -- Primary --> 7(3\(5\)) + 7 -- Primary --> 9(3\(4\)) + 9 -.-> 5 + 8 -- Primary --> 9 + 5 -.-> 8 + +``` + +Violation of N(m) +numbering rule: 3(2) +receives a reference from 3(6). + +Primary reference + +Secondary reference + +PRC + +Higher quality SSU + +Lower quality SSU + +T1316410-99 + +Diagram of a synchronization network showing nodes 2 through 10. Node 2 is a PRC. Nodes 3, 4, and 6 are Higher quality SSUs. Nodes 5, 7, 8, 9, and 10 are Lower quality SSUs. Solid arrows represent primary references, dashed arrows represent secondary references. A starburst around node 5 indicates a violation of the N(m) numbering rule because it receives a reference from node 6, which has a higher N(m) value in its label 3(6) compared to node 5's 3(2). Solid arrow Dashed arrow Black circle Dark grey circle Light grey circle + +**Figure III.3b/G.803 – N(m) labelling is not possible: Potential timing loop(s)** + +The scheme described above assumes that reference assignments and priorities are static. If the information regarding all active and stand-by synchronization trails and their status is known at some central location, priorities and assignments can in principle be dynamically re-provisioned, to counter failure situations. Each re-provisioning should be checked for potential timing loops. This whole process could be performed manually or automatically. + +### III.6.2 Absolute frequency offset guarding + +Although timing loops should always be avoided by applying sound engineering of the synchronization network, the insertion of SSUs with an absolute frequency offset detection at strategic places in the network can provide an additional safeguard. Whenever a timing loop is formed, the clocks in the loop, as a group, will start drifting in frequency in an uncontrolled manner. This may increase the slip-rate on traffic between equipment timed by clocks in the loop and equipment outside the loop to unacceptable levels. Eventually, large frequency deviations may cause the network to stop processing traffic altogether. + +However, if one of the clocks in the loop is capable of detecting absolute frequency deviations (sustained over some period of time) at an early stage, it can disqualify its current reference and thereby break the loop. The better this frequency offset detection is, the lower the maximum slip-rate will be that can affect traffic from/to/via equipment in the loop. For example, an absolute frequency guard at $1 \times 10^{-8}$ will limit the slip rate to 6.9 slips/day, i.e. almost within the limits for acceptable performance (5 slips/day) according to ITU-T Recommendation G.822. + +The more clocks in the network that support this frequency guarding, the higher the probability that one of those clocks is actually part of a timing loop if it is accidentally created. Moreover, the size of the affected area will generally be smaller in cases where timing loops are formed without a clock with frequency guarding being part of it. + +The frequency guard method is not able to anticipate generation of timing loops but is only able to measure their effects when they already may have a significant effect on the network performance. + +Note that the presence of absolute frequency offset guard functionality is not specified in ITU-T Recommendation G.812. + +## III.7 SEC-Level solutions + +The SEC-Level consists of many separated islands of SDH equipment with SEC clocks built in (see Figure III.1c). Each island is called an "SEC subnetwork". Within the SEC subnetwork automatic restoration is mandatory because the PRC Autonomy Period of an SEC is typically well below 1 minute. Restoration based on local SEC decisions is the fastest method. It is in most cases not practical to apply the N(m) numbering scheme of the SSU-Level also in the SEC-Level. The number of available independent references is usually not large enough to apply N(m) numbering successfully (i.e. the SEC network is in general not sufficiently "meshed"). For example in linear or ring-type networks reference can only be from both neighbours, but only the upstream one can have a "lower" N(m) number and so be a suitable reference. A back-up reference is then not available. + +By enhancing the priority selection with traceability information this problem can be overcome. This mechanism is described in the Synchronization Status Message (SSM) protocol, specified in ITU-T Recommendation G.781. This protocol is proposed to be used as reference restoration control mechanism at the SEC-Level. + +When the synchronization network for an SEC subnetwork is engineered, the SSUs that directly interface with this subnetwork have to be considered as well. Such an SSU is either: + +- 1) providing synchronization reference signals to the SEC subnetwork; or +- 2) is taking a reference from the subnetwork; or +- 3) is filtering a synchronization signal by taking reference from an SDH network element and feeding the filtered signal back to its SEC. SSUs in this role require special attention. + +The task of the synchronization engineer is to determine the provisionable parameters of the SSM algorithm in each SEC subnetwork, such that under normal conditions the flow of the timing information between the SSUs is according to the plan engineered for the SSU-Level and that in failure situations the synchronization restores as well as possible without creating timing loops, hierarchy violations (i.e. references with insufficient traceability becoming active), or instabilities. The variables at his disposal are the selection of possible references (assignments/un-assignments), the setting of priorities for the assigned references, using fixed SSM assignments to certain reference inputs and setting the squelch thresholds for synchronization outputs. Assignment and priority setting have in general to be provisioned both for the internal oscillator (denoted as "T0" in ITU-T Recommendation G.783) and for the external clock output (denoted as "T4" in ITU-T Recommendation G.783) of an SDH network element. The interface between stand-alone SSUs and SECs is assumed to be a 2048 kHz interface according to clause 13/G.703 or a non-SSM carrying dedicated 2048 kbit/s link according to clause 9/G.703. + +The number of possible different SEC subnetwork topologies is very big, but the size of the SEC subnetworks will be restricted, since in most cases the recommendation to limit the number of SECs between SSUs that are adjacent in the SSU-Level, to at most 20 clocks, will be honoured. Although the number of possible SEC subnetworks is very big, they mostly do not differ much in principle, hence it is possible to come up with a limited number of example SEC subnetworks, work out the SSM parameters for those, and adapt those examples for application to real SEC subnetworks. + +### III.7.1 Application of the SSM protocol in the SSU-Level + +ITU-T Recommendation G.704 defines the message set and transmission format for the transport of Synchronization Status Messages over the 2048 kbit/s interface between a Network Element (with an SEC) and an SSU. + +Such an interface makes it in principle possible to include the SSU-Level in the application of the SSM algorithm. However, this issue is for further study. In today's installed base the interface between the SSU and SDH NE in general does not support the transport of SSMs. Moreover, additional study is required to investigate the engineering and the stability of the SSM algorithm when it encompasses both SECs and SSUs. A result of further study could be that the SSM protocol needs to be amended when it is applied on the SSU-Level as well. + +One property of SSM controlled synchronization restoration is that, once the protocol is set up, it runs autonomously. The operator has no direct control. This fact makes it highly desirable that rigorous simulation is performed before an SSM scheme is deployed. The more complex the network, the more important this will be. Obviously, the inclusion of SSUs in synchronization restoration schemes controlled by SSMs may complicate the synchronization network enormously, since in that case it could cover the whole synchronization area, instead of just one SEC subnetwork. + +For these reasons, the assumption made in this appendix is that the SSM protocol is only supported on the SEC-Level and that the interface between the SSU and the SEC does not support transmission of SSMs. + +### III.7.2 Examples of SEC subnetworks with SSM parameters + +This subclause gives a number of principally different SEC subnetworks and their SSM parameters. The parameters of other SEC subnetworks can be worked out by adapting the principal schemes presented here. The number of principal schemes may grow over time. + +In Figures III.5 through III.9 a certain notation is used to indicate how the parameters of the SSM protocol are provisioned and what the resulting traceability messages are on the outgoing STM-N signals under normal conditions (no failures). The notational conventions are shown in Figure III.4. The network element (grey box) has two parts separated by a dotted line to depict the independent selection processes for the internal SEC (T0) and the external synchronization output (T4). If T4 is slaved to T0 this is indicated by a direct arrow between the two parts (not shown in Figure III.4). The arrows arriving at and leaving from the network element denote the synchronization carrying in- and outputs (either STM-N, 2048 kHz or non-SSM-carrying 2048 kbit/s). The solid arrows denote the active carrier under normal conditions, while stand-by reference inputs are represented by dashed arrows. Unassigned references are shown by dotted arrows. Note that the fact whether a reference is currently active, stand-by or unassigned is determined by the receiving equipment. Some arrows are split to show that they serve as an input to both the T0 reference selection process and the T4 reference selection process. If such a split input fails, it fails for both inputs simultaneously. + +The numbers in white circles denote the assigned priorities (no number means that a reference is not assigned to participate in the reference selection process). The labels in the ellipses denote the computed outgoing synchronization status messages (which will be the received message by the downstream network element). The "≥ SSM" in the external synchronization output box indicates the squelch level (all signals with traceability "SSM" or better are passed through). Finally, the "= SSM" in a grey box denotes that the fixed value "SSM" assigned to a reference input. In these cases "SSM" can be "PRC", "SSU-A", "SSU-B" or "SEC". + +![Diagram of an SDH Network Element (SEC) showing synchronization inputs and outputs. The SEC has three input ports: 1 (top), 2 (middle), and 3 (bottom). Port 1 receives an assigned reference (active) from a DNU and an assigned reference (stand-by) from a PRC. Port 2 receives an assigned reference (active) from a PRC and an assigned reference (stand-by) from a PRC. Port 3 receives an assigned (fixed) SSM value from an SSU-A and an assigned squelch threshold for synchronization output (≥ PRC). The SEC produces a synchronization output (T4) and a computed output message (PRC).](701bc79e78b382bcfd3ba85597dbb9c3_img.jpg) + +SDH Network Element + +DNU PRC + +SEC + +① ② ③ + +② ① + +③ ≥ PRC + += SSU-A + +Synchronization Output (T4) + +T1316420-99 + +≥ PRC Assigned squelch threshold for synchronization output + → Assigned reference (active) + - - - Assigned reference (stand-by) + - - - Unassigned reference + ② Assigned priority + = SSU-A Assigned (fixed) SSM value to input + PRC Computed output message + +Diagram of an SDH Network Element (SEC) showing synchronization inputs and outputs. The SEC has three input ports: 1 (top), 2 (middle), and 3 (bottom). Port 1 receives an assigned reference (active) from a DNU and an assigned reference (stand-by) from a PRC. Port 2 receives an assigned reference (active) from a PRC and an assigned reference (stand-by) from a PRC. Port 3 receives an assigned (fixed) SSM value from an SSU-A and an assigned squelch threshold for synchronization output (≥ PRC). The SEC produces a synchronization output (T4) and a computed output message (PRC). + +Figure III.4/G.803 – Conventions used in SEC subnetwork drawings + +![Diagram of an SDH ring network with one source SSU source and one sink SSU. The network consists of six SEC nodes (A, B, C, D, E, F) and two SSU nodes (1 and 2). SSU 1 is the source, and SSU 2 is the sink. The SEC nodes are interconnected in a ring. SEC F is connected to SSU 1. SEC C is connected to SSU 2. The diagram shows various synchronization paths and references (PRC, DNU, ≥ PRC) between the nodes. An inset labeled 'SSU layer view' shows a simplified view of the SSU nodes and their connections.](640d28a694bbdbaf9b11a3bfdcc800fc_img.jpg) + +PRC DNU + +SEC A SEC B + +① ② ① ② + +PRC DNU + +SEC F SEC E + +① ② ③ ① ② + +PRC DNU + +SEC D SEC C + +① ② ① ② + +≥ PRC + +SSU 1 SSU 2 + +① ② ① ② + +SSU layer view + +T1316430-99 + +Diagram of an SDH ring network with one source SSU source and one sink SSU. The network consists of six SEC nodes (A, B, C, D, E, F) and two SSU nodes (1 and 2). SSU 1 is the source, and SSU 2 is the sink. The SEC nodes are interconnected in a ring. SEC F is connected to SSU 1. SEC C is connected to SSU 2. The diagram shows various synchronization paths and references (PRC, DNU, ≥ PRC) between the nodes. An inset labeled 'SSU layer view' shows a simplified view of the SSU nodes and their connections. + +Figure III.5/G.803 – SDH ring network with one source SSU source and one sink SSU + +In the SSU-Level the synchronization flow is from SSU-1 to SSU-2. SSU-2 needs another reference from another source, this is outside the scope of this SEC subnetwork, as well as the references of SSU-1. + +![Diagram of an SDH ring network with two source SSUs and one sink SSU. The diagram shows various components including SSU 1, SSU 2, SSU 3, SEC A, SEC B, SEC C, SEC D, SEC E, SEC F, and an SSU layer view. Arrows indicate synchronization paths, with labels like PRC, DNU, and SSU-B.](89f8aefc01866631793087542316cef2_img.jpg) + +The diagram illustrates an SDH ring network configuration. At the top, two source SSUs, SSU 1 and SSU 2, are shown. SSU 1 is connected to SEC F, which is part of a ring containing SEC A, SEC B, SEC C, SEC D, and SEC E. SEC A and SEC B are connected via DNU (Data Network Unit) and PRC (Path Resynchronization) labels. SEC C is connected to SSU 2 via SSU-B interfaces. SEC D is connected to a box labeled ≥ SSU-A, which in turn connects to SSU 3. SEC E and SEC F are also connected to the ring. The SSU layer view at the bottom right shows SSU 1, SSU 2, and SSU 3 connected in a mesh-like fashion, with SSU 1 and SSU 3 being the primary synchronization path, and SSU 2 and SSU 3 being a backup path. The diagram is labeled T1316440-99. + +Diagram of an SDH ring network with two source SSUs and one sink SSU. The diagram shows various components including SSU 1, SSU 2, SSU 3, SEC A, SEC B, SEC C, SEC D, SEC E, SEC F, and an SSU layer view. Arrows indicate synchronization paths, with labels like PRC, DNU, and SSU-B. + +**Figure III.6/G.803 – SDH ring network with two source SSUs and one sink SSU** + +Normally the synchronization flow in the SSU-Level is between SSU-1 and SSU-3, the path between SSU-2 and SSU-3 is a back-up. + +![Diagram of an SDH Y-network with two source SSUs (SSU 1 and SSU 2) and one sink SSU (SSU 3). The network consists of several SEC (Synchronization Equipment) units labeled A, B, C, D, E, and F. SSU 1 and SSU 2 are connected to SEC A and SEC C respectively. SEC A is connected to SEC B, which is connected to SEC E. SEC C is connected to SEC D, which is also connected to SEC E. SEC E is connected to SEC F, which is connected to SSU 3. Various synchronization signals are indicated by labels like PRC (Primary Reference Clock), DNU (Data Network Unit), and SSU-B. A 'SSU layer view' inset shows the logical connections between SSU 1, SSU 2, and SSU 3.](a2251e3bbfcd726b68cc50b091e53b02_img.jpg) + +Diagram of an SDH Y-network with two source SSUs (SSU 1 and SSU 2) and one sink SSU (SSU 3). The network consists of several SEC (Synchronization Equipment) units labeled A, B, C, D, E, and F. SSU 1 and SSU 2 are connected to SEC A and SEC C respectively. SEC A is connected to SEC B, which is connected to SEC E. SEC C is connected to SEC D, which is also connected to SEC E. SEC E is connected to SEC F, which is connected to SSU 3. Various synchronization signals are indicated by labels like PRC (Primary Reference Clock), DNU (Data Network Unit), and SSU-B. A 'SSU layer view' inset shows the logical connections between SSU 1, SSU 2, and SSU 3. + +Figure III.7/G.803 – SDH Y-network with two source SSUs and one sink SSU + +Normally the synchronization flow in the SSU-Level is between SSU-1 and SSU-3, the path between SSU-2 and SSU-3 is a back-up. + +![Diagram of an SDH linear network with filtering SSUs. The network is a linear sequence of SEC units: SEC A, SEC B, SEC C, SEC D, and SEC E. SSU 1 is connected to SEC A. SEC A is connected to SEC B, which is connected to SEC C. SEC C is connected to SEC D, which is connected to SEC E. SEC E is connected to SSU 3. SSU 2 is connected to SEC C. Various synchronization signals are indicated by labels like PRC (Primary Reference Clock), DNU (Data Network Unit), and SSU-B. A 'SSU layer view' inset shows the logical connections between SSU 1, SSU 2, and SSU 3.](2cf3896394a2342a2b46c504ab9a8830_img.jpg) + +Diagram of an SDH linear network with filtering SSUs. The network is a linear sequence of SEC units: SEC A, SEC B, SEC C, SEC D, and SEC E. SSU 1 is connected to SEC A. SEC A is connected to SEC B, which is connected to SEC C. SEC C is connected to SEC D, which is connected to SEC E. SEC E is connected to SSU 3. SSU 2 is connected to SEC C. Various synchronization signals are indicated by labels like PRC (Primary Reference Clock), DNU (Data Network Unit), and SSU-B. A 'SSU layer view' inset shows the logical connections between SSU 1, SSU 2, and SSU 3. + +Figure III.8/G.803 – SDH linear network with filtering SSUs + +![Figure III.9/G.803 – SDH ring network with filtering SSU. The diagram illustrates a complex SDH ring network architecture. At the top, two SEC (Synchronization Equipment) units, labeled SEC A and SEC B, are connected in a ring. SEC A has two ports: port 1 is connected to a PRC (Primary Reference Clock) and port 2 is connected to SEC B. SEC B has port 1 connected to SEC A and port 2 connected to another PRC. Below this top ring, there are two more SEC units, SEC E and SEC D, also connected in a ring. SEC E port 2 is connected to SEC D port 1, and SEC D port 2 is connected back to SEC E port 1. SEC E port 1 is connected to a PRC, and SEC D port 1 is connected to a DNU (Data Network Unit). On the left, an SSU 1 (Synchronization Switching Unit) is shown. It has port 1 connected to a PRC and port 2 connected to SEC F. SEC F is a large unit containing a PRC and a DNU. SEC F port 1 is connected to SEC A port 2, and SEC F port 2 is connected to SEC E port 2. On the right, SEC C is shown. It has port 1 connected to SEC B port 2, port 2 connected to SEC D port 2, and port 3 connected to a PRC. SEC C also has a label '≥ PRC'. Below SEC C, there is an SSU 2. Port 1 of SSU 2 is connected to SEC C port 1, and port 2 is connected to SEC D port 1. At the bottom right, a separate box labeled 'SSU layer view' shows SSU 1 and SSU 2 connected by a zigzag line. Various other labels like '= PRC' and 'DNU' are present throughout the diagram. The text 'T1316470-99' is in the bottom right corner.](cbab05075b3d7dc0d27c4cbb0c914a94_img.jpg) + +Figure III.9/G.803 – SDH ring network with filtering SSU. The diagram illustrates a complex SDH ring network architecture. At the top, two SEC (Synchronization Equipment) units, labeled SEC A and SEC B, are connected in a ring. SEC A has two ports: port 1 is connected to a PRC (Primary Reference Clock) and port 2 is connected to SEC B. SEC B has port 1 connected to SEC A and port 2 connected to another PRC. Below this top ring, there are two more SEC units, SEC E and SEC D, also connected in a ring. SEC E port 2 is connected to SEC D port 1, and SEC D port 2 is connected back to SEC E port 1. SEC E port 1 is connected to a PRC, and SEC D port 1 is connected to a DNU (Data Network Unit). On the left, an SSU 1 (Synchronization Switching Unit) is shown. It has port 1 connected to a PRC and port 2 connected to SEC F. SEC F is a large unit containing a PRC and a DNU. SEC F port 1 is connected to SEC A port 2, and SEC F port 2 is connected to SEC E port 2. On the right, SEC C is shown. It has port 1 connected to SEC B port 2, port 2 connected to SEC D port 2, and port 3 connected to a PRC. SEC C also has a label '≥ PRC'. Below SEC C, there is an SSU 2. Port 1 of SSU 2 is connected to SEC C port 1, and port 2 is connected to SEC D port 1. At the bottom right, a separate box labeled 'SSU layer view' shows SSU 1 and SSU 2 connected by a zigzag line. Various other labels like '= PRC' and 'DNU' are present throughout the diagram. The text 'T1316470-99' is in the bottom right corner. + +**Figure III.9/G.803 – SDH ring network with filtering SSU** + +## III.8 Synthesis of the synchronization network + +The methodology of engineering a synchronization network, as outlined in this appendix, consists of several steps: + +- a) Divide a synchronization area into an SSU-Level and SEC subnetworks. +- b) Group the SSUs according to their quality, defined as PRC Autonomy Period, in a number of Classes. +- c) Assign primary and secondary, etc. references to each SSU in a manner compliant with the N(m) labelling scheme (or an equivalent alternative). +- d) Define the SSM protocol parameters for each SEC subnetwork using the body of example networks, taking the directly interconnected SSUs into account. +- e) Design the intra-office synchronization for each office. This last stage is not further discussed in this appendix. + +The engineering of the synchronization area should be carried out before the equipment is commissioned. The results of the network synchronization engineering process are often described in a synchronization plan. This plan may contain maps of the area and all offices with the normal and fall-back references indicated, the values of all provisioned parameters that affect the synchronization in the area and a log of all synchronization related maintenance activities. The plan may also contain results of measurements and evaluations on the synchronization network. The synchronization plan should be revised each time new equipment is installed in a synchronization area. A synchronization coordinator is usually nominated to maintain the synchronization plan and to coordinate the synchronization related activities in the synchronization areas. + +## III.9 Definitions used in Appendix III + +| | | +|-----------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| PRC Autonomy (Period) | The period of time over which a clock, after it disqualified all its reference inputs, can restrict its phase drift within the bounds given by the network limits for synchronization signals. | +| PRC-Level | The collection of G.811 compliant clocks in an operator domain that are the master-clocks for the different synchronization areas when the synchronization network does not experience failures. | +| SEC-Level |

The collection of G.813 compliant clocks in a synchronization area and their interconnections. SSUs are not part of the SEC-Level.

Note that some networks may have SDH Network Elements containing clocks other than G.813 clocks. Provided that the quality level of these clocks is of lower quality than the SSUs deployed in the network, for the purposes of this appendix they can be considered as SEC clocks.

| +| SEC subnetwork | A collection of SEC clocks in SDH network elements interconnected by STM-N reference carriers. When engineering the synchronization in an SEC subnetwork, the directly connected SSUs need also to be considered. | +| SSU-Level | The collection of G.812 compliant clocks in a synchronization area and their interconnections. SECs are not part of the SSU-Level, but are considered to be transparent on connections between SSUs. Under failure-free conditions, there is only one interconnected SSU-Level in a synchronization area. | +| Synchronization area | Geographic area in which all equipment which needs to operate synchronously is synchronized to the one master-clock in that area. | + +# **SERIES OF ITU-T RECOMMENDATIONS** + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | 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It features a blue circular emblem with a stylized globe and the letters 'ITU' in white. + +ITU logo + +## ITU-T G-SERIES RECOMMENDATIONS **Transmission systems and media, digital systems and networks** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100-G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200-G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300-G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400-G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450-G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600-G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700-G.799 | +| DIGITAL NETWORKS | G.800-G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900-G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000-G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000-G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000-G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000-G.8999 | +| Ethernet over Transport aspects | G.8000-G.8099 | +| MPLS over Transport aspects | G.8100-G.8199 | +| Synchronization, quality and availability targets | G.8200-G.8299 | +| Mobile network transport aspects | G.8300-G.8399 | +| Service Management | G.8600-G.8699 | +| ACCESS NETWORKS | G.9000-G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# **Recommendation ITU-T G.8051** + +## **Management aspects of the Ethernet transport (ET) capable network element** + +## **Summary** + +Recommendation ITU-T G.8051 addresses management aspects of the Ethernet transport (ET) capable network element containing transport functions of one or more of the layer networks of the Ethernet transport network. The management of the Ethernet layer networks is separable from that of its client layer networks so that the same means of management can be used regardless of the client. The management functions for fault management, configuration management, performance monitoring and security management are specified. + +The 2009 revision of this Recommendation added the management of additional transport functions that were introduced in the 2009 revision of Recommendation ITU-T G.8021/Y.1341. + +The 2013 revision of this Recommendation added the management of additional functions, including: client signal fail (CSF); proactive loss measurement using loss measurement message (LMM)/loss measurement reply (LMR); proactive delay measurement using delay measurement message (DMM)/delay measurement reply (DMR) and one-way delay measurement (IDM); synthetic loss measurement using synthetic loss message (SLM)/synthetic loss reply (SLR) and one-way synthetic loss measurement (ISL) (proactive and on-demand); performance management (PM) requirements on protocol data unit (PDU) generation type, message period, measurement interval, repetition period, start time, stop time and session duration; and PM data collection requirements. + +The 2015 revision of this Recommendation updated the management information (MI) signals for the ETHx\_FT function in clause 8.5, the MI signals for the ETHx/MCC function in clause 8.6, the one-way synthetic loss measurement (ISL) management information (MI) signal for the ETHDe\_FT\_Sk function in clause 8.8 and the on-demand and proactive loss measurement requirements in clause 10.2. + +The 2018 revision of this Recommendation updated the fault cause persistency function at the ETH connection (ETH-C) function for ring protection, the configuration management for protection switching and connection functions. Finally, in alignment with Recommendation ITU-T G.8021/Y.1341, this revision removed both fault management functions and the management information (MI) signals that are related to ETYn\_TT, ODUkP-X-L/MT\_A and ETYn/ETH\_A. This revision also removed the MI signals to activate processes in adaptation functions (i.e., MI\_Active). + +The 2020 revision of this Recommendation has updated clause 6 to clause 8 by referring to Recommendation ITU-T G.7710/Y.1701; the fault cause persistency function, and the provisioning and reporting for adaptation functions for FlexE related functions as defined in Recommendation ITU-T G.8023; and transferring ODU related adaptation functions in some tables to Recommendation ITU-T G.874. + +ITU-T G.8051/Y.1345 (2020) Amendment 1 (2023) updated the fault cause persistency function; alarm reporting control function; operational state function in clause 7; the provisioning and reporting for flow termination and adaptation functions in clause 8 in alignment with ITU-T G.8021 and ITU-T G.8023. Also, this Amendment created clause 8.14 "Administrative state" in alignment with ITU-T G.7710. + +ITU-T G.8051/Y.1345 (2020) Corrigendum 1 (2024) removed 4 MIs of ETHx-Np/ETH-LAG-Na\_A\_Sk in Table 8-3 because they should not be in this table as they are already in Table 10-1. + +The 2024 revision of this Recommendation has updated LM related MIs in Table 8-1, some default values in CSF related MIs in Table 8-3, and OAM-related Priority MIs in Table 8-1, Table 8-2 and Table 8-3.2. + +## History \* + +| Edition | Recommendation | Approval | Study Group | Unique ID | +|---------|-----------------------------------|------------|-------------|--------------------| +| 1.0 | ITU-T G.8051/Y.1345 | 2007-10-22 | 15 | 11.1002/1000/9186 | +| 2.0 | ITU-T G.8051/Y.1345 | 2009-11-13 | 15 | 11.1002/1000/10430 | +| 2.1 | ITU-T G.8051/Y.1345 (2009) Amd. 1 | 2011-06-06 | 15 | 11.1002/1000/11139 | +| 3.0 | ITU-T G.8051/Y.1345 | 2013-08-29 | 15 | 11.1002/1000/12024 | +| 3.1 | ITU-T G.8051/Y.1345 (2013) Amd. 1 | 2014-05-14 | 15 | 11.1002/1000/12186 | +| 4.0 | ITU-T G.8051/Y.1345 | 2015-08-13 | 15 | 11.1002/1000/12549 | +| 4.1 | ITU-T G.8051/Y.1345 (2015) Amd. 1 | 2017-08-13 | 15 | 11.1002/1000/13314 | +| 5.0 | ITU-T G.8051/Y.1345 | 2018-03-16 | 15 | 11.1002/1000/13546 | +| 6.0 | ITU-T G.8051/Y.1345 | 2020-12-07 | 15 | 11.1002/1000/14505 | +| 6.1 | ITU-T G.8051/Y.1345 (2020) Amd. 1 | 2023-06-13 | 15 | 11.1002/1000/15564 | +| 6.2 | ITU-T G.8051/Y.1345 (2020) Cor. 1 | 2024-01-13 | 15 | 11.1002/1000/15833 | +| 7.0 | ITU-T G.8051 | 2024-08-29 | 15 | 11.1002/1000/16091 | + +## Keywords + +Carrier Ethernet, network management, transport resource. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, and information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at . + +© ITU 2025 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|-----------------------------------------------------------------------|------| +| 1 Scope ..... | 1 | +| 2 References ..... | 1 | +| 3 Definitions ..... | 2 | +| 3.1 Terms defined elsewhere ..... | 2 | +| 3.2 Terms defined in this Recommendation ..... | 3 | +| 4 Abbreviations and acronyms ..... | 4 | +| 5 Conventions ..... | 7 | +| 6 ET management architecture ..... | 7 | +| 6.1 ET management network architecture ..... | 7 | +| 6.2 ET equipment management function architecture ..... | 10 | +| 6.3 Information flows over management points ..... | 11 | +| 7 Fault (maintenance) management ..... | 11 | +| 7.1 Fault management applications ..... | 11 | +| 7.2 Fault management functions ..... | 13 | +| 8 Configuration management ..... | 18 | +| 8.1 Hardware ..... | 18 | +| 8.2 Software ..... | 18 | +| 8.3 Protection switching ..... | 18 | +| 8.4 Trail termination ..... | 18 | +| 8.5 Flow termination ..... | 18 | +| 8.6 Adaptation ..... | 23 | +| 8.7 Connection ..... | 30 | +| 8.8 Diagnostic ..... | 32 | +| 8.9 Traffic conditioning and shaping ..... | 34 | +| 8.10 ZZZ_Reported ..... | 35 | +| 8.11 Alarm severity ..... | 35 | +| 8.12 Alarm reporting control (ARC) ..... | 35 | +| 8.13 Date and time ..... | 35 | +| 8.14 Administrative state ..... | 36 | +| 9 Accounting management ..... | 36 | +| 10 Performance management ..... | 36 | +| 10.1 Performance management applications ..... | 36 | +| 10.2 Performance monitoring functions ..... | 36 | +| 11 Security management ..... | 47 | +| Appendix I – MI signals/parameters for PM tools in ITU-T G.8021 ..... | 48 | +| Bibliography ..... | 50 | + +# Recommendation ITU-T G.8051 + +## Management aspects of the Ethernet transport (ET) capable network element + +# 1 Scope + +This Recommendation addresses management aspects of the Ethernet transport (ET) capable network element containing transport functions of one or more of the layer networks of the Ethernet transport network. The management of the Ethernet layer networks is separable from that of its client layer networks so that the same means of management can be used regardless of the client. In this version of this Recommendation, fault management, configuration management, performance management (PM) and security management are specified. Furthermore, only the management information (MI) of the following ET equipment functions is addressed: + +- Ethernet MAC layer (ETH) flow forwarding, flow termination, connection, diagnostic and traffic conditioning/shaping functions; +- ETH server to ETH client adaptation functions (including ETH/ETH-m, ETHG/ETH, FlexEC/ETH); +- ETH link aggregation functions; +- Flex Ethernet (FlexE) trail termination functions; and +- FlexE to FlexE client adaptation functions. + +This Recommendation also describes the management network organizational model for communication between an element management layer (EML) operations system and the ET equipment management function (EMF) within an ET network element. + +The architecture described in this Recommendation for the management of Ethernet transport networks is based upon the following considerations: + +- the management view of network element functional elements should be uniform whether those elements form part of an inter-domain interface or part of an intra-domain interface. Those properties necessary to form such a uniform management view are to be included in this Recommendation; +- Ethernet layer network entities (ELNEs) refer to trail termination, adaptation and connection functions as described in [ITU-T G.8010]; +- a network element may only contain Ethernet layer network entities (ELNEs); +- a network element may contain both Ethernet layer network entities (ELNEs) and client layer network entities (CLNEs); +- client layer entities are managed as part of their own logical domain; +- CLNEs and ELNEs may or may not share a common message communication function (MCF) and management application function (MAF) depending on application; and +- CLNEs and ELNEs may or may not share the same agent, +- server layer network entities (SLNEs) and ELNEs may or may not share the same agent. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently + +valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.806] Recommendation ITU-T G.806 (2012), *Characteristics of transport equipment – Description methodology and generic functionality*. +- [ITU-T G.7710] Recommendation ITU-T G.7710/Y.1701 (2020), *Common equipment management function requirements*. +- [ITU-T G.7712] Recommendation ITU-T G.7712/Y.1703 (2019), *Architecture and specification of data communication network*. +- [ITU-T G.8010] Recommendation ITU-T G.8010/Y.1306 (2004), *Architecture of Ethernet layer networks*. +- [ITU-T G.8012] Recommendation ITU-T G.8012/Y.1308 (2022), *Ethernet UNI and Ethernet NNI*. +- [ITU-T G.8013] Recommendation ITU-T G.8013/Y.1731 (2023), *Operations, administration and maintenance (OAM) functions and mechanisms for Ethernet-based networks*. +- [ITU-T G.8021] Recommendation ITU-T G.8021/Y.1341 (2022), *Characteristics of Ethernet transport network equipment functional blocks*. +- [ITU-T G.8023] Recommendation ITU-T G.8023 (2018), *Characteristics of equipment functional blocks supporting Ethernet physical layer and Flex Ethernet interfaces*. +- [ITU-T M.3010] Recommendation ITU-T M.3010 (2000), *Principles for a telecommunications management network*. +- [ITU-T M.3013] Recommendation ITU-T M.3013 (2000), *Considerations for a telecommunications management network*. +- [ITU-T M.3100] Recommendation ITU-T M.3100 (2005), *Generic network information model*. +- [ITU-T X.700] Recommendation ITU-T X.700 (1992), *Management framework for Open Systems Interconnection (OSI) for CCITT applications*. +- [ITU-T X.701] Recommendation ITU-T X.701 (1997) | ISO/IEC 10040:1998, *Information technology – Open Systems Interconnection – Systems management overview*. +- [ITU-T Y.1563] Recommendation ITU-T Y.1563 (2009), *Ethernet frame transfer and availability performance*. +- [IEEE 802.1AX] IEEE 802.1AX-2020, *IEEE Standard for Local and Metropolitan Area Networks – Link Aggregation*. +- [IEEE 802.3] IEEE 802.3-2022, *IEEE Standard for Ethernet*. +- [OIF FLEXE IA] OIF IA OIF-FLEXE 2.2 (2019), *Flex Ethernet Implementation Agreement 2.2*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined elsewhere: + +### 3.1.1 Terms defined in [ITU-T G.806]: + +- Atomic function (AF); +- Management point (MP). + +- 3.1.2 Terms defined in [ITU-T G.7710]: + - Local craft terminal; + - Management application function (MAF). +- 3.1.3 Term defined in [ITU-T G.7712]: + - Data communication network (DCN). +- 3.1.4 Terms defined in [ITU-T G.8021]: + - Traffic shaping function +- 3.1.5 Terms defined in [ITU-T M.3010]: + - Network element (NE); + - Network element function (NEF); + - Operations system (OS); + - Q-interface; + - Workstation function (WF). +- 3.1.6 Term defined in [ITU-T M.3013]: + - Message communication function (MCF). +- 3.1.7 Terms defined in [ITU-T M.3100]: + - Alarm reporting; + - Alarm reporting control (ARC); + - Managed entity; + - Management interface; + - Persistence interval; + - Operations system (OS); + - Operations system function (OSF); + - Qualified problem; + - Reset threshold report; + - Threshold report; + - Timed interval. +- 3.1.8 Term defined in [ITU-T X.700]: + - Managed object (MO). +- 3.1.9 Terms defined in [ITU-T X.701]: + - Agent; + - Manager; + - Managed object class (MOC). + +## 3.2 Terms defined in this Recommendation + +This Recommendation defines the following terms: + +- 3.2.1 **ET management network (ET.MN)**: A subset of a telecommunication management network (TMN) that is responsible for managing those parts of a network element that contain Ethernet transport (ET) layer network entities. + +NOTE – An ET.MN may be subdivided into a set of ET management subnetworks. + +**3.2.2 ET management subnetwork (ET.MSN):** Subnetwork consisting of a set of separate embedded communication channels (ECCs) and associated intra-site data communication links that are interconnected to form a data communication network (DCN) within any given Ethernet transport (ET) topology. + +NOTE – For ET, the physical channel supporting the ECC is the Ethernet management communication channel (MCC) as defined in clause 6.1.4.2. An ET.MSN represents an ET specific local communication network (LCN) portion of a network operator's overall data communication network or TMN. + +**3.2.3 ET network element (ET.NE):** Element containing entities from one or more ET layer networks. + +NOTE – An ET.NE may be a stand-alone physical entity or a subset of a network element. It supports at least network element functions (NEFs) and may also support an operations system function (OSF). It contains managed objects (MOs), a message communication function (MCF) and a management application function (MAF). The functions of an ET.NE may be contained within an NE that also supports other layer networks. These layer network entities are considered to be managed separately from ET entities. As such, they are not part of the ET.MN or ET.MSN. + +**3.2.4 Ethernet management communication channel (ET.MCC):** A function providing a management communication channel between Ethernet transport (ET) network elements (NEs). + +NOTE – The management communication channel (MCC) can be used to perform remote management. The specific use of MCC is outside the scope of this Recommendation. + +**3.2.5 traffic-conditioning function:** A transport processing function that accepts the characteristic information of the layer network at its input, classifies the traffic units according to configured rules, meters each traffic unit within its class to determine its eligibility, polices non-conformant traffic units and presents the remaining traffic units at its output as characteristic information of the layer network. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|-------|------------------------------------| +| IDM | One-way Delay Measurement | +| ISL | One-way Synthetic Loss measurement | +| AcSL | Accepted Signal Label | +| AF | Atomic Function | +| AIS | Alarm Indication Signal | +| ALM | Alarm reporting | +| APP | Access Point Pool | +| ARC | Alarm Reporting Control | +| CC | Continuity Check | +| CCM | Continuity Check Message | +| CLNE | Client Layer Network Entity | +| COMMS | Communication channel | +| CSF | Client Signal Fail | +| CTP | Connection Termination Point | +| CtrlP | Control Plane | + +| | | +|----------|----------------------------------------------------------------------------------------------------------------| +| DA | Destination Address | +| DCN | Data Communication Network | +| DE | Drop Eligibility | +| DEG | Degraded | +| DEGM | Degraded M | +| DEGTHR | Degraded Threshold | +| DMM | Delay Measurement Message | +| DMR | Delay Measurement Reply | +| ECC | Embedded Communication Channel | +| ELNE | Ethernet Layer Network Entity | +| EMF | Equipment Management Function | +| EMS | Element Management System | +| ET | Ethernet Transport | +| ET.C | ET Channel layer | +| ET.MN | ET MN | +| ET.MSN | ET MSN | +| ET.NE | ET NE | +| ET.P | ET Path layer | +| ET.S | ET Section layer | +| ETC | Ethernet Coding | +| ETCy | Ethernet Coding sublayer for PHY y | +| ETH | Ethernet MAC layer | +| ETH-C | ETH Connection | +| ETHx | Ethernet MAC layer network – x, x=s for section, x=p for path, x=t for TCM | +| FCAPS | Fault management, Configuration management, Account management, Performance management and Security management | +| FlexE | Flex-Ethernet | +| FlexEC | Flex-Ethernet Client | +| FlexESGM | Flex Ethernet subgroup member | +| FLR | Frame Loss Ratio | +| FM | Fault Management | +| FTS | Forced Transmitter Shutdown | +| GNE | Gateway Network Element | +| IP | Interworking Protocol | +| IS | Intermediate System | +| LAN | Local Area Network | +| LCK | Locked defect | + +| | | +|---------|----------------------------------------------------------| +| LCN | Local Communication Network | +| LMM | Loss Measurement Message | +| LMR | Loss Measurement Reply | +| MAF | Management Application Function | +| M-AI | Media layer Adapted Information | +| MCC | Management Communication Channel | +| MCF | Message Communication Function | +| MD | Mediation Device | +| ME | Maintenance Entity | +| MEG | ME Group | +| MEL | MEG Level | +| MEP | MEG End Point | +| MF | Mediation Function | +| MgmtP | Management Plane | +| MI | Management Information | +| MIB | Management Information Base | +| MIP | MEG Intermediate Point | +| MN | Management Network | +| MO | Managed Object | +| MOC | Managed Object Class | +| MP | Management Point | +| MSN | Management SubNetwork | +| NALM | No ALaRm reporting | +| NALM-CD | No ALaRm reporting, CountDown | +| NALM-NR | No ALaRm reporting, NotReady | +| NALM-QI | No ALaRm reporting, Qualified Inhibit | +| NALM-TI | No ALaRm reporting, Timed Inhibit | +| NE | Network Element | +| NEF | Network Element Function | +| NEL | Network Element Layer | +| OAM | Operations, Administration, Maintenance | +| OAM&P | Operations, Administration, Maintenance and Provisioning | +| OS | Operations System | +| OSF | Operations System Function | +| OSI | Open Systems Interconnection | +| P | Priority | +| PDU | Protocol Data Unit | + +| | | +|------|---------------------------------------| +| PM | Performance Management | +| PMC | Performance Monitoring Clock | +| PS | Protection Switching | +| QoS | Quality of Service | +| RDI | Remote Defect Indication | +| RTC | Real-Time Clock | +| SA | Source Address | +| SES | Severely Errored Seconds | +| SL | Synthetic Loss | +| SLM | Synthetic Loss Message | +| SLNE | Server Layer Network Entity | +| SLR | Synthetic Loss Reply | +| TCM | Tandem Connection Monitoring | +| TF | Transmitted Frames | +| TMN | Telecommunications Management Network | +| TTP | Trail Termination Point | +| WTR | Wait To Restore | + +# 5 Conventions + +In this Recommendation, ET.MN stands for ET management network, ET.MSN for ET management subnetwork, ET.NE for ET NE, ET.C for ET channel layer, ET.P for ET path layer and ET.S for ET section layer. + +# 6 ET management architecture + +See clause 6 of [ITU-T G.7710] for the generic architecture for managing transport equipment. + +The transport layer networks of Ethernet over Transport (ET) are described in [ITU-T G.8010], [ITU-T G.8012], [ITU-T G.8021], and [ITU-T G.8023]. The management of the ET layer networks is separable from that of its client layer networks so that the same means of management can be used regardless of the client. + +## 6.1 ET management network architecture + +### 6.1.1 Relationship between TMN, ET.MN and ET.MSN + +The inter-relationship between a management network, its subnetworks and a telecommunications management network (TMN), as generically described in clause 6.1.1 of [ITU-T G.7710], is applicable to ET. + +This Recommendation defines the ET management network (ET.MN) and subnetworks (ET.MSNs). + +### 6.1.2 Access to the ET.MSN + +See clause 6.1.2 of [ITU-T G.7710] for the generic requirements. + +### 6.1.3 ET.MSN requirements + +See clause 6.1.3 of [ITU-T G.7710] for the generic requirements. + +Furthermore, all ET network elements (ET.NEs) must support management communication functions. The message communication function (MCF) of an ET.NE initiates/terminates (in the sense of the lower protocol layers), forwards, or otherwise processes management messages over management communication channels (MCCs), or over other data communication network (DCN) interfaces. In addition: + +- All ET.NEs are required to terminate the ET.S-MCCs, see clause 6.1.4. In OSI terms, this means that each network element (NE) must be able to perform the functions of an end system. +- ET.NEs may also be required to forward management messages between ports according to routing control information held in the ET.NE. In open systems interconnection (OSI) terms, this means that some ET.NEs may be required to perform the functions of an intermediate system. +- In addition to supporting interfaces for the ET.S-MCC, an ET.NE may also be required to support other DCN interfaces, which may include ET.P-MCCs or ET.C-MCCs or an Ethernet DCN interface. + +The use of the ET.P-MCCs and ET.C-MCCs for management communications is within the scope of this Recommendation, see clause 6.1.7. + +### 6.1.4 ET.MSN data communication network + +Refer to clause 6.1.4 of [ITU-T G.7710] for the generic requirements. + +#### 6.1.4.1 Management communication channel + +The ET.MN supports three management communication channels (MCCs): + +- 1) ET.S-MCC (MCCS) +- 2) ET.P-MCC (MCCP) +- 3) ET.C-MCC (MCCC) + +Figure 6-1 illustrates a network scenario consisting of two operators. Operator B provides an ET path layer service to operator A (i.e., Operator B transports the ET Path layer signal that begins and ends Operator A's domain). + +![Diagram illustrating MCC scenarios across three operator domains: Operator A, Operator B, and Operator A. The diagram shows two horizontal lines representing management communication channels. The top line is segmented into five parts, each labeled 'MCC_S', with double-headed arrows indicating bidirectional communication within each segment. The bottom line is a single continuous segment labeled 'MCC_P or MCC_C', also with double-headed arrows at both ends, spanning across all three operator domains.](c036e2540a94b31357ceb0002f0cacab_img.jpg) + +The diagram shows three ovals labeled 'Operator A', 'Operator B', and 'Operator A' from left to right. Below these ovals, two horizontal lines represent management communication channels. The top line is divided into five segments by vertical tick marks, each labeled 'MCCS'. Each segment has a double-headed arrow, indicating communication within that segment. The bottom line is a single continuous line labeled 'MCCP or MCCC', with double-headed arrows at both the left and right ends, spanning across all three operator domains. + +Diagram illustrating MCC scenarios across three operator domains: Operator A, Operator B, and Operator A. The diagram shows two horizontal lines representing management communication channels. The top line is segmented into five parts, each labeled 'MCC\_S', with double-headed arrows indicating bidirectional communication within each segment. The bottom line is a single continuous segment labeled 'MCC\_P or MCC\_C', also with double-headed arrows at both ends, spanning across all three operator domains. + +G.8051-Y.1345(07)\_F6-1 + +**Figure 6-1 – MCC scenarios** + +The physical layer is terminated in every network element and its related adaptation function provides the ET section layer signals as well as the MCCS. Hence, the MCCS cannot cross administrative domains. Figures 6-1, 6-2 and 6-3 illustrate scenarios where the MCCP is transported transparently through Operator B's domain (the Operator B network elements are not shown in Figures 6-2 + +and 6-3). In these scenarios, it is possible that Operator B may use the MCCs within its own domain for the management of its domain. + +![Figure 6-2: MCCp scenario example. This diagram shows two network elements, NE A1 and NE A2, connected via a DCN (Data Communication Network). NE A1 contains an ET CTP (yellow box) and an EMF (purple box) connected to DCN forwarding and routing processes. These processes are connected to two IP nodes (red and blue circles). Below the IP nodes are CCCp (red text) and MCCp (black text) labels. The stack below includes ET channel, ET path, ET section, and Physical layer layers, each with a corresponding symbol. NE A2 has a similar structure but the EMF and ET CP (yellow box) are swapped in position. A central vertical bar labeled 'EoT data plane' is shown between the two elements. The reference G.8051-Y.1345(20)-Amd.1(23)_F6-2 is at the bottom right.](bd0b93e7a46ede276d0a3b79ac487bd9_img.jpg) + +Figure 6-2: MCCp scenario example. This diagram shows two network elements, NE A1 and NE A2, connected via a DCN (Data Communication Network). NE A1 contains an ET CTP (yellow box) and an EMF (purple box) connected to DCN forwarding and routing processes. These processes are connected to two IP nodes (red and blue circles). Below the IP nodes are CCCp (red text) and MCCp (black text) labels. The stack below includes ET channel, ET path, ET section, and Physical layer layers, each with a corresponding symbol. NE A2 has a similar structure but the EMF and ET CP (yellow box) are swapped in position. A central vertical bar labeled 'EoT data plane' is shown between the two elements. The reference G.8051-Y.1345(20)-Amd.1(23)\_F6-2 is at the bottom right. + +Figure 6-2 – MCCp scenario example + +![Figure 6-3: MCCp scenario example. This diagram is similar to Figure 6-2 but shows a different configuration. In NE A1, the ET CP (yellow box) and EMF (purple box) are present, but only one IP node (red circle) is shown, connected to both. The label below the IP node is MCCp+CCCp (red text). NE A2 has a similar single IP node configuration. The stack of ET channel, ET path, ET section, and Physical layer layers is also present. The reference G.8051-Y.1345(20)-Amd.1(23)_F6-3 is at the bottom right.](7efae06af3af43ffe5d4b956a679cf54_img.jpg) + +Figure 6-3: MCCp scenario example. This diagram is similar to Figure 6-2 but shows a different configuration. In NE A1, the ET CP (yellow box) and EMF (purple box) are present, but only one IP node (red circle) is shown, connected to both. The label below the IP node is MCCp+CCCp (red text). NE A2 has a similar single IP node configuration. The stack of ET channel, ET path, ET section, and Physical layer layers is also present. The reference G.8051-Y.1345(20)-Amd.1(23)\_F6-3 is at the bottom right. + +Figure 6-3 – MCCp scenario example + +#### 6.1.4.2 MCC physical characteristics + +The ET.S-, ET.C- and ET.P-MCCs are logical elements within the ET transport module (ETM-n). The MCC provides general management communications between two ET network elements with access to the ET.S, ET.P and ET.C characteristic information respectively. The ET.S-, ET.P-, or ET.C-MCC is provided by the ET OAM function at section, path, or channel layer as defined in [ITU-T G.8013] or by any other ECC of the ET transport network. + +The ET.S management communication channel (MCCS) shall operate as a single message channel between ET.S termination points. The bit rate of the MCCS shall be configurable. + +The ET.P management communication channel (MCCP) shall operate as a single message channel between any network elements that terminate the ET.P layer. The MCCP is transported transparently through ET.NEs that only terminate the ET.S layer and forward the ET.P signal. The bit rate of the MCCP shall be configurable. + +The ET.C management communication channel (MCCC) shall operate as a single message channel between any network elements that terminate the ET.C layer. The MCCC is transported transparently through ET.NEs that only terminate the ET.S layer or the ET.S and ET.P layers and forward the ET.C signal. The bit rate of the MCCC shall be configurable. + +#### **6.1.4.3 MCC data link layer protocol** + +The MCC data link protocols for management applications are under study for [ITU-T G.7712]. + +### **6.1.5 Management of DCN** + +See clause 6.1.5 of [ITU-T G.7710] for the generic requirements. + +### **6.1.6 Remote log-in** + +See clause 6.1.6 of [ITU-T G.7710] for the generic requirements. + +### **6.1.7 Relationship between technology domains** + +See clause 6.1.7 of [ITU-T G.7710] for the generic requirements. + +## **6.2 ET equipment management function architecture** + +See clause 6.2 of [ITU-T G.7710] for a generic description of the equipment management architecture. + +Figure 6-4 below, taken from Figure 5 of [ITU-T G.7710], shows the functions inside the ET NE. + +![Diagram of ET equipment management function (EMF) showing internal components and external interfaces.](8fbdfc3d17fb1dae7b2d8f5a287fa9fc_img.jpg) + +The diagram illustrates the internal structure and external interfaces of the Equipment Management Function (EMF) within a Network Element Function (NEF). On the left, 'Transport plane atomic functions' are shown as a vertical stack of pink triangles. An arrow labeled 'Management information' points from this stack to an 'MP reference point' (a black dot). From the MP reference point, the information flows into the EMF. The EMF is divided into two main vertical sections. The left section contains a list of management functions: 'Date and time functions', 'Fault management', 'Configuration management', 'Account management', 'Performance management', 'Security management', and 'Control plane function'. Below these is an 'Agent' box with three green square icons. The right section of the EMF contains corresponding interfaces: 'Date and time interface', 'Management plane interface', 'Control plane interface', and 'Local alarm interface'. At the bottom of the EMF is a 'MIB' (Management Information Base) represented by a blue cylinder containing six 'MO' (Managed object) icons. To the right of the EMF, within the NEF, are communication functions: 'Message communication function (MCF)', 'Date and time communication', 'Management plane communication', 'Control plane communication', and 'Local alarm communication'. Arrows show information flows between the EMF interfaces and these communication functions: 'Date and time information', 'Management plane information', 'Control plane information', and 'Local alarm information'. External arrows on the far right show connections for 'Date and time communication' (from external time source), 'Management plane communication' (to/from management plane e.g., EMS, peer NE), 'Control plane communication' (to/from control plane e.g., EMS, peer NE), and 'Local alarm communication' (to local craft terminal and to local alarms). A legend at the bottom identifies the blue cylinder as the 'Management information base' and the circle with 'MO' as a 'Managed object'. The code 'G.8051-Y.1345(18)\_F6-4' is in the bottom right corner. + +Diagram of ET equipment management function (EMF) showing internal components and external interfaces. + +Figure 6-4 – ET equipment management function (from Figure 5 of [ITU-T G.7710]) + +## 6.3 Information flows over management points + +See clause 6.3 of [ITU-T G.7710] for the generic description of the information flows over management points (MPs). + +The information flow over the MP reference points is described in specific detail for each atomic function in [ITU-T G.8021]. Note that these information flows and associated functions apply equally to both the client and supervisory channel due to the independent nature of these signals. This implies neither that the supervisory channel shall provide all the functions described, nor that [ITU-T G.8021] will provide the details of which functions are available. + +# 7 Fault (maintenance) management + +See clause 7 of [ITU-T G.7710] for the generic requirements for fault management. ET-specific specifications, if needed, are explicitly described. + +## 7.1 Fault management applications + +See clause 7.1 of [ITU-T G.7710] for a description of the basic fault management applications. + +### 7.1.1 Supervision + +The supervision philosophy is based on the concepts underlying the functional model ET of [ITU-T G.8010]. + +The five basic supervision categories are related to transmission, quality of service, processing, equipment and environment. These supervision processes can declare fault causes, which need further validation before the appropriate alarm is reported. See [ITU-T G.7710] for additional discussion of these categories. + +The ET NE shall indicate to the OS when a termination point is no longer able to supervise the signal (e.g., implementing equipment has a fault or loss of power). + +#### **7.1.1.1 Transmission supervision** + +See clause 7.1.1.1 of [ITU-T G.7710] for a general description of transmission supervision. + +For ET NE, the following defects are monitored for the purpose of transmission supervision: + +- Continuity supervision: Loss of continuity defect (dLOC[i]) +Ethernet continuity check (CC) management jobs, using ITU-T G.8013/Y.1731 continuity check message (CCM), can be separately established (within a MEP) for fault management, performance management and protection switching. +As a default, one MEG end point (MEP) (with MEL = 7, OAM message period = 1 second and priority = 7) has to be instantiated per trail termination point (TTP) for fault management (i.e., RDI) +- Connectivity supervision: Unexpected MEL defect (dUNL), MisMerge defect (dMMG) and Unexpected MEP defect (dUNM) +- Signal quality supervision: Degraded Signal defect (dDEG) +- Configuration supervision: Unexpected periodicity defect (dUNP) and Unexpected priority defect (dUNPr) +- Maintenance signal supervision: Remote defect indicator defect (dRDI[]), alarm indication signal defect (dAIS) and locked defect (dLCK) + +The atomic function associated failure conditions are listed in clause 7.2.1. + +#### **7.1.1.2 Quality of service supervision** + +See clause 7.1.1.2 of [ITU-T G.7710] for a description of quality of service supervision. + +#### **7.1.1.3 Processing supervision** + +See clause 7.1.1.3 of [ITU-T G.7710] for a description of processing supervision. + +#### **7.1.1.4 Hardware supervision** + +See clause 7.1.1.4 of [ITU-T G.7710] for a description of equipment supervision. + +#### **7.1.1.5 Environment supervision** + +See clause 7.1.1.5 of [ITU-T G.7710] for a description of environment supervision. + +### **7.1.2 Validation** + +See clause 7.1.2 of [ITU-T G.7710] for a description of fault cause validation. + +### **7.1.3 Alarm handling** + +#### **7.1.3.1 Severity assignment** + +See clause 7.1.3.1 of [ITU-T G.7710] for a description of severity categories. + +#### **7.1.3.2 Alarm reporting control** + +See clause 7.1.3.2 of [ITU-T G.7710] for a description of alarm reporting control (ARC). + +Alarm reporting control (ARC) provides an automatic in-service provisioning capability. + +#### 7.1.3.3 Reportable failures + +See clause 7.1.3.3 of [ITU-T G.7710] for a description of reportable failures. + +#### 7.1.3.4 Alarm reporting + +See clause 7.1.3.4 of [ITU-T G.7710] for a description of alarm surveillance. + +##### 7.1.3.4.1 Local reporting + +See clause 7.1.3.4.1 of [ITU-T G.7710] for a description of local reporting. + +##### 7.1.3.4.2 TMN reporting + +See clause 7.1.3.4.2 of [ITU-T G.7710] for a description of TMN reporting. + +## 7.2 Fault management functions + +See clause 7.2 of [ITU-T G.7710] for a description of fault management inside the EMF. + +Figure 7-1 below is from Figure 7-1 of [ITU-T G.7710] that shows the functional model of fault management inside the ET EMF. + +![Functional model of fault management within the ET EMF diagram](f388cbdae6f0ef3aeb96fdf9984d1284_img.jpg) + +The diagram illustrates the functional model of fault management within the ET EMF. It is structured as follows: + +- Central Area:** A large green box labeled "Fault management". + - Inputs:** "Fault cause" (MI\_cZZZ) and "Failure" (fZZZ-value) enter from the left. + - Flow:** "Failure" (fZZZ-value) goes to "PRS" (MI\_cZZZ), which then goes to "SEV" (fZZZ-value, fZZZ-severity). "SEV" goes to "ARC" (fZZZ-value, fZZZ-severity). "ARC" goes to "REP" (rZZZ-value, rZZZ-severity). "REP" goes to "TEP" (rZZZ-value, rZZZ-severity). "TEP" branches to "ASY" (Alarm synchronization), "LOG" (Query, Report TMN alarm event notifications), and "TAN" (Alarm synchronization). + - Outputs to Management applications function:** "UNA" (Unit alarms), "NEA" (Network element alarms), "STA" (Station alarms), "ASY" (Alarm synchronization), "LOG" (Query, Report TMN alarm event notifications), "TAN" (Alarm synchronization), "CPL" (Current problem list), "AST" (Alarm status), and "OPS" (Operational state). + - External References:** "Alarm severity assignment profile" and "ARC information" are shown as external inputs to the "Fault management" box. +- Side Labels:** + - Left: "Atomic functions" (vertical label). + - Right: "Management applications function" (vertical label). +- Bottom Section:** + - A box labeled "NE-RTC" is at the bottom left. + - A box labeled "Date and time functions" is at the bottom center. + +Functional model of fault management within the ET EMF diagram + +G.8051-Y.1345(20)\_F7-1 + +Figure 7-1 – Fault management within the ET EMF (from Figure 7-1 of [ITU-T G.7710]) + +### 7.2.1 Fault cause persistency function – PRS + +See clause 7.2.1 of [ITU-T G.7710] for a description of PRS. + +For an ET.NE that supports the atomic functions listed in Table 7-1, the EMF PRS process shall support the persistency check for the associated fault causes. + +**Table 7-1 – Inputs/outputs for the fault cause persistency function** + +| Atomic function | Input | Output | +|------------------------------------|----------------------------------------------------------------------------------|----------------------------------------------------------------------------------| +| ETH_C per SNC/S protection process | cFOP-PM
cFOP-CM
cFOP-NR
cFOP-TO | fFOP-PM
fFOP-CM
fFOP-NR
fFOP-TO | +| ETH_C per Ring protection process | cFOP-PM
cFOP-TO[0..1] | fFOP-PM
fFOP-TO[0..1] | +| ETHx_FT_Sk | cSSF
cLCK
cLOC[i]
cMMG
cUNM
cUNP
cUNPr
cUNL
cDEG
cRDI | fSSF
fLCK
fLOC[i]
fMMG
fUNM
fUNP
fUNPr
fUNL
fDEG
fRDI | +| ETHG_FT_Sk | cLOC[i]
cUNL
cMMG
cUNM
cDEG
cUNP
cUNPr
cRDI
cSSF
cLCK | fLOC[i]
fUNL
fMMG
fUNM
fDEG
fUNP
fUNPr
fRDI
fSSF
fLCK | +| FlexE_TT_Sk | cRPF
cSSF | fRPF
fSSF | +| ETHx/ETH_A_Sk | cCSF | fCSF | +| ETHx/ETH-m_A_Sk | cCSF | fCSF | +| ETHG/ETH_A_Sk | cCSF | fCSF | +| ETHx-Np/ETH-LAG-Na_A_Sk | cPLL[1..Na]
cTLL[1..Na] | fPLL[1..Na]
fTLL[1..Na] | +| ETH-LAG_FT_Sk | cSSF | fSSF | +| M-AI/FlexE_A_Sk | cLOF
cLOM | fLOF
fLOM | +| FlexE-n/FlexEC_A_Sk | cCCM[1..r]
cLOL
cFMM
cGIDM | fCCM[1..r]
fLOL
fFMM
fGIDM | +| M-AI/FlexESGM_A_Sk | cLOF
cLOM | fLOF
fLOM | + +### 7.2.2 Severity assignment function – SEV + +See [ITU-T G.7710] for a description of the severity assignment function. + +### 7.2.3 Alarm reporting control function – ARC + +See clause 7.2.3 of [ITU-T G.7710] for a description of the severity reporting control function (ARC). + +The alarms that can be controlled with this function are defined for each AF in [ITU-T G.8021]. + +In Table 7-2 below, for each managed entity a subset of the plausible failures (defined in Table 7-1) are selected as qualified problems. These qualified problems are recommended as they are deemed essential to the operability of the subject managed entity. Note that for each managed entity, one or more of the qualified problems could then be further selected by the management system to be included in the ARC list for controlling the reporting of alarm for the entity. + +Default ARC state is also specified for each managed entity. If the ARC function is supported by the ET.NE and an ARC state is not explicitly provisioned from the management system for the managed entity, then the default ARC specified in Table 7-2 should be in effect. + +For an ET.NE that supports the AFs listed in Table 7-2, the EMF ARC process shall support alarm reporting control for the associated fault causes. + +**Table 7-2 – ARC specifications for ET** + +| Atomic function | Qualified problems | Default state value | +|------------------------------------|----------------------------------------------------------------------------------|---------------------| +| ETH_C per SNC/S protection process | fFOP-PM
fFOP-CM
fFOP-NR
fFOP-TO | ALM | +| ETH_C per Ring protection process | fFOP-PM
fFOP-TO[0..1] | ALM | +| ETHx_FT_Sk | fSSF
fLCK
fLOC[i]
fMMG
fUNM
fUNP
fUNPr
fUNL
fDEG
fRDI | ALM | +| ETHG_FT_Sk | fLOC[i]
fUNL
fMMG
fUNM
fDEG
fUNP
fUNPr
fRDI
fSSF
fLCK | ALM | +| ETHx/ETH_A_Sk | fCSF | ALM | +| ETHx/ETH-m_A_Sk | fCSF | ALM | +| ETHG/ETH_A_Sk | fCSF | ALM | + +**Table 7-2 – ARC specifications for ET** + +| Atomic function | Qualified problems | Default state value | +|-------------------------|-------------------------------------|----------------------------| +| ETHx-Np/ETH-LAG-Na_A_Sk | fPLL[1..Na]
fTLL[1..Na] | ALM | +| ETH-LAG_FT_Sk | fSSF | ALM | +| FlexE_TT_Sk | fRPF
fSSF | ALM | +| M-AI/FlexE_A_Sk | fLOF
fLOM | ALM | +| FlexE-n/FlexEC_A_Sk | fCCM[1..r]
fLOL
fFMM
fGIDM | ALM | +| M-AI/FlexESGM_A_Sk | fLOF
fLOM | ALM | + +### **7.2.4 Reportable failure function – REP** + +See clause 7.2.4 of [ITU-T G.7710] for a description of the reportable failure function. + +### **7.2.5 Unit alarms function – UNA** + +See clause 7.2.5 of [ITU-T G.7710] for a description of the unit alarms function. + +### **7.2.6 Network element alarms function – NEA** + +See clause 7.2.6 of [ITU-T G.7710] for a description of the network element alarms function. + +### **7.2.7 Station alarms function – STA** + +See clause 7.2.7 of [ITU-T G.7710] for a description of the station alarms function. + +### **7.2.8 TMN event pre-processing function – TEP** + +See clause 7.2.8 of [ITU-T G.7710] for a description of the TMN event pre-processing alarm function. + +### **7.2.9 Alarm synchronization function – ASY** + +See clause 7.2.9 of [ITU-T G.7710] for a description of the alarm synchronization function. + +### **7.2.10 Logging function – LOG** + +See clause 7.2.4 of [ITU-T G.7710] for a description of the logging function. + +### **7.2.11 TMN alarm event notifications function – TAN** + +See clause 7.2.4 of [ITU-T G.7710] for a description of the TMN alarm event notifications function. + +### **7.2.12 Current problem list function – CPL** + +See clause 7.2.4 of [ITU-T G.7710] for a description of the current problem list function. + +### **7.2.13 Alarm status function – AST** + +See clause 7.2.4 of [ITU-T G.7710] for a description of the alarm status function. + +### **7.2.14 Operational state function – OPS** + +See clause 7.2.4 of [ITU-T G.7710] for a description of the operational state function. + +Table 7-3 lists the failures that could influence the operational state of the related objects. + +For an ET.NE that supports the AFs listed in Table 7-3, the EMF OPS process shall support operational state for the associated fault causes. + +**Table 7-3 – Operational state function input and output signals for Ethernet** + +| Atomic function | Failure input
(fZZZ value) | Operational state output
(Enabled/Disabled)
of the trail object | +|------------------------------------|----------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------| +| ETH_C per SNC/S protection process | fFOP-PM
fFOP-CM
fFOP-NR
fFOP-TO | Enabled
Enabled
Enabled
Enabled | +| ETH_C per Ring protection process | fFOP-PM
fFOP-TO[0..1] | Enabled
Enabled | +| ETHx_FT_Sk | fSSF
fLCK
fLOC[i]
fMMG
fUNM
fUNP
fUNPr
fUNL
fDEG
fRDI | Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled | +| ETHG_FT_Sk | fLOC[i]
fUNL
fMMG
fUNM
fDEG
fUNP
fUNPr
fRDI
fSSF
fLCK | Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled | +| ETHx/ETH_A_Sk | fCSF | Enabled | +| ETHx/ETH-m_A_Sk | fCSF | Enabled | +| ETHG/ETH_A_Sk | fCSF | Enabled | +| ETHx-Np/ETH-LAG-Na_A_Sk | fPLL[1..Na]
fTLL[1..Na] | Enabled
Enabled | +| ETH-LAG_FT_Sk | fSSF | Enabled | +| FlexE_TT_Sk | fRPF
fSSF | Enabled
Enabled | +| M-AI/FlexE_A_Sk | fLOF
fLOM | Enabled
Enabled | +| FlexE-n/FlexEC_A_Sk | fCCM[1..r]
fLOL
fFMM
fGIDM | Enabled
Enabled
Enabled
Enabled | +| M-AI/FlexESGM_A_Sk | fLOF
fLOM | Enabled
Enabled | + +# **8 Configuration management** + +See clause 8 of [ITU-T G.7710] for the generic requirements for configuration management. ET specific specifications, if needed, are explicitly described. + +## **8.1 Hardware** + +See clause 8.1 of [ITU-T G.7710] for a description of hardware management. + +## **8.2 Software** + +See clause 8.2 of [ITU-T G.7710] for a description of software management. + +## **8.3 Protection switching** + +See clause 8.3 of [ITU-T G.7710] for a description of protection switching. + +This function allows a user to provision and monitor the operation of protection processes deployed in an ETH connection (ETH-C) process. + +MI signals concerning the protection processes are listed in Table 8-4 and communicated between the EMF and the protection process through the management point. According to these MI signals, the EMF generates a corresponding event notification and state report signals to the MAF. + +For the protection processes supported by an ET.NE, the ET.NE EMF shall support the following management functions: + +- Provisioning the protection switching management information +- Retrieving the protection switching management information +- Notifying the changes of the protection switching management information +- Receiving the monitored protection switching management information + +## **8.4 Trail termination** + +See clause 8.4 of [ITU-T G.7710] for a description of trail termination management. + +## **8.5 Flow termination** + +This function allows a user to provision and monitor the operation of the ETHx and ETH-LAG flow termination processes. + +The MI signals listed in Table 8-2 are communicated between the EMF and the flow termination processes across the management point within the ET NE. + +For the flow termination functions supported by an ET.NE, the ET.NE EMF shall support the following management functions: + +- Provisioning the trail termination management information +- Retrieving the trail termination management information +- Notifying the changes of the trail termination management information +- Receiving the monitored trail termination management information + +**Table 8-2 – Provisioning and reporting for flow termination functions** + +| MI signal | Value range | Default value | +|--------------------------------------------------|-----------------------------------------------------------------------------------|---------------| +| Provisioning | | | +| ETHx_FT_So_MI_MEL | 0, 1, 2, 3, 4, 5, 6, 7 | By agreement | +| ETHx_FT_So_MI_MEP_MAC | Per [ITU-T G.8021] | – | +| ETHx_FT_So_MI_CC_Enable | True, false | False | +| ETHx_FT_So_MI_LMC_Enable | True, false | True | +| ETHx_FT_So_MI_MEG_ID | See Annex A of [ITU-T G.8013] | – | +| ETHx_FT_So_MI_MEP_ID | 0..8191; see Figure 9.2-3 of [ITU-T G.8013] | – | +| ETHx_FT_So_MI_CC_Period | 3.33 ms, 10 ms, 100 ms, 1 s, 10 s, 1 min, 10 min | 1 s | +| ETHx_FT_So_MI_CC_Pri | 0, 1, 2, 3, 4, 5, 6, 7 | 7 | +| ETHx_FT_So_MI_LML_Enable[1...M LM ] | True, false | True | +| ETHx_FT_So_MI_LM_MAC_DA[1...M LM ] | Per [ITU-T G.8021] | – | +| ETHx_FT_So_MI_LM_Period[1...M LM ] | 100 ms, 1 s, 10 s | 100 ms | +| ETHx_FT_So_MI_LM_Pri[1...M LM ] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | +| ETHx_FT_So_MI_DM_Enable[1...M DM ] | True, false | False | +| ETHx_FT_So_MI_DM_MAC_DA[1...M DM ] | Per [ITU-T G.8021] | – | +| ETHx_FT_So_MI_DM_Test_ID[1...M DM ] | Non-negative integer (optional) | – | +| ETHx_FT_So_MI_DM_Length[1...M DM ] | Non-negative integer representing number of bytes for the length of the Data TLV. | 0 | +| ETHx_FT_So_MI_DM_Period[1...M DM ] | 100 ms, 1 s, 10 s | 100 ms | +| ETHx_FT_So_MI_DM_Pri[1...M DM ] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | +| ETHx_FT_So_MI_1DM_Enable[1...M 1DM ] | True, false | False | +| ETHx_FT_So_MI_1DM_MAC_DA[1...M 1DM ] | Per [ITU-T G.8021] | – | +| ETHx_FT_So_MI_1DM_Test_ID[1...M 1DM ] | Non-negative integer (optional) | – | +| ETHx_FT_So_MI_1DM_Length[1...M 1DM ] | Non-negative integer representing number of bytes for the length of the Data TLV. | 0 | +| ETHx_FT_So_MI_1DM_Period[1...M 1DM ] | 100 ms, 1 s, 10 s | 100 ms | +| ETHx_FT_So_MI_1DM_Pri[1...M 1DM ] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | +| ETHx_FT_So_MI_SL_Enable[1...M SL ] | True, false | False | +| ETHx_FT_So_MI_SL_MAC_DA[1...M SL ] | Per [ITU-T G.8021] | – | +| ETHx_FT_So_MI_SL_Test_ID[1...M SL ] | Non-negative integer | – | +| ETHx_FT_So_MI_SL_Length[1...M SL ] | Non-negative integer representing number of bytes for the length of the Data TLV. | 0 | +| ETHx_FT_So_MI_SL_Period[1...M SL ] | 10 ms, 100 ms, 1 s, 10 s | 100 ms | +| ETHx_FT_So_MI_SL_Pri[1...M SL ] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | +| ETHx_FT_So_MI_1SL_Enable[1...M 1SL ] | True, false | False | + +**Table 8-2 – Provisioning and reporting for flow termination functions** + +| MI signal | Value range | Default value | +|-----------------------------------------------------------|---------------------------------------------------------------------------------------|---------------------------------| +| ETHx_FT_So_MI_1SL_MAC_DA[1...M 1SL ] | Per [ITU-T G.8021] | – | +| ETHx_FT_So_MI_1SL_Test_ID[1...M 1SL ] | Non-negative integer | – | +| ETHx_FT_So_MI_1SL_Length[1...M 1SL ] | Non-negative integer representing number of bytes for the length of the Data TLV. | 0 | +| ETHx_FT_So_MI_1SL_Period[1...M 1SL ] | 10 ms, 100 ms, 1 s, 10 s | 100 ms | +| ETHx_FT_So_MI_1SL_Pri[1...M 1SL ] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | +| ETHx_FT_Sk_MI_CC_Enable | True, false | False | +| ETHx_FT_Sk_MI_LMC_Enable | True, false | True | +| ETHx_FT_Sk_MI_1second | – | – | +| ETHx_FT_Sk_MI_LM_DEGM | 2-10; see Table 7-1 of [ITU-T G.806] | 7 (Note 1) | +| ETHx_FT_Sk_MI_LM_M | 2-10 | 7 (Note 1) | +| ETHx_FT_Sk_MI_LM_DEGTHR | 0% .. 100%; see Table 7-1 of [ITU-T G.806] | Near-end SES threshold (Note 1) | +| ETHx_FT_Sk_MI_LM_TFMIN | 0..(2 32 -1) | – | +| ETHx_FT_Sk_MI_MEL | 0, 1, 2, 3, 4, 5, 6, 7 | By agreement | +| ETHx_FT_Sk_MI_MEG_ID | See Annex A of [ITU-T G.8013] | – | +| ETHx_FT_Sk_MI_PeerMEP_ID[i] | List of peer MEP IDs; 0..8191 for each ID; see Figure 9.2-3 of [ITU-T G.8013] | – | +| ETHx_FT_Sk_MI_CC_Period | 3.33 ms, 10 ms, 100 ms, 1 s, 10 s, 1 min, 10 min | 1 s | +| ETHx_FT_Sk_MI_CC_Pri | 0..7 | 7 | +| ETHx_FT_Sk_MI_GetSvdCCM | (NOTE – Use to request the saved latest CCM frame that caused a defect to be raised.) | – | +| ETHx_FT_Sk_MI_1DM_Enable[1...M 1DM ] | True, false | False | +| ETHx_FT_Sk_MI_1DM_MAC_SA[1...M 1DM ] | Per [ITU-T G.8021] | – | +| ETHx_FT_Sk_MI_1DM_Pri[1...M 1DM ] | 0..7 | (Note 2) | +| ETHx_FT_Sk_MI_1DM_Test_ID[1...M 1DM ] | Non-negative integer (optional) | – | +| ETHx_FT_Sk_MI_1SL_Enable[1...M 1SL ] | True, false | False | +| ETHx_FT_Sk_MI_1SL_MAC_SA[1...M 1SL ] | Per [ITU-T G.8021] | – | +| ETHx_FT_Sk_MI_1SL_Test_ID[1...M 1SL ] | Non-negative integer (optional) | – | +| ETHx_FT_Sk_MI_MEP_MAC | Per [ITU-T G.8021] | – | +| Reporting | | | +| ETHx_FT_Sk_MI_SvdCCM | Last received CCM frame that caused defect | – | +| ETHx_FT_Sk_MI_BW_Report(SA, PortID, NominalBW, CurrentBW) | Per configured at peer source | – | + +**Table 8-2 – Provisioning and reporting for flow termination functions** + +| MI signal | Value range | Default value | +|-------------------------------------|-----------------------------------------------------------------------------------|---------------| +| Provisioning | | | +| ETHG_FT_So_MI_MEL | 0, 1, 2, 3, 4, 5, 6, 7 | By agreement | +| ETHG_FT_So_MI_MEP_MAC | Per [ITU-T G.8021] | – | +| ETHG_FT_So_MI_CC_Enable | True, false | False | +| ETHG_FT_So_MI_LMC_Enable | True, false | True | +| ETHG_FT_So_MI_MEG_ID | See Annex A of [ITU-TG.8013] | – | +| ETHG_FT_So_MI_MEP_ID | 0..8191; see Figure 9.2-3 of [ITU-T G.8013] | – | +| ETHG_FT_So_MI_CC_Period | 3.33 ms, 10 ms, 100 ms, 1 s, 10 s, 1 min, 10 min | 1 s | +| ETHG_FT_So_MI_CC_Pri | 0, 1, 2, 3, 4, 5, 6, 7 | 7 | +| ETHG_FT_So_MI_LML_Enable[1...MLM] | True, false | True | +| ETHG_FT_So_MI_LM_MAC_DA[1...MLM] | Per [ITU-T G.8021] | – | +| ETHG_FT_So_MI_LM_Period[1...MLM] | 100 ms, 1 s, 10 s | 100 ms | +| ETHG_FT_So_MI_LM_Pri[1...MLM] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | +| ETHG_FT_So_MI_DM_Enable[1...MDM] | True, false | False | +| ETHG_FT_So_MI_DM_MAC_DA[1...MDM] | Per [ITU-T G.8021] | – | +| ETHG_FT_So_MI_DM_Test_ID[1...MDM] | Non-negative integer (optional) | – | +| ETHG_FT_So_MI_DM_Length[1...MDM] | Non-negative integer representing number of bytes for the length of the Data TLV. | 0 | +| ETHG_FT_So_MI_DM_Period[1...MDM] | 100 ms, 1 s, 10 s | 100 ms | +| ETHG_FT_So_MI_DM_Pri[1...MDM] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | +| ETHG_FT_So_MI_IDM_Enable[1...M1DM] | True, false | False | +| ETHG_FT_So_MI_IDM_MAC_DA[1...M1DM] | Per [ITU-T G.8021] | – | +| ETHG_FT_So_MI_IDM_Test_ID[1...M1DM] | Non-negative integer (optional) | – | +| ETHG_FT_So_MI_IDM_Length[1...M1DM] | Non-negative integer representing number of bytes for the length of the Data TLV. | 0 | +| ETHG_FT_So_MI_IDM_Period[1...M1DM] | 100 ms, 1 s, 10 s | 100 ms | +| ETHG_FT_So_MI_IDM_Pri[1...M1DM] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | +| ETHG_FT_So_MI_SL_Enable[1...MSL] | True, false | False | +| Provisioning | | | +| ETHG_FT_So_MI_SL_MAC_DA[1...MSL] | Per [ITU-T G.8021] | – | +| ETHG_FT_So_MI_SL_Test_ID[1...MSL] | Non-negative integer | – | +| ETHG_FT_So_MI_SL_Length[1...MSL] | Non-negative integer representing number of bytes for the length of the Data TLV. | 0 | +| ETHG_FT_So_MI_SL_Period[1...MSL] | 10 ms, 100 ms, 1 s, 10 s | 100 ms | +| ETHG_FT_So_MI_SL_Pri[1...MSL] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | + +**Table 8-2 – Provisioning and reporting for flow termination functions** + +| MI signal | Value range | Default value | +|-------------------------------------|---------------------------------------------------------------------------------------|---------------------------------| +| ETHG_FT_So_MI_1SL_Enable[1...M1SL] | True, false | False | +| ETHG_FT_So_MI_1SL_MAC_DA[1...M1SL] | Per [ITU-T G.8021] | – | +| ETHG_FT_So_MI_1SL_Test_ID[1...M1SL] | Non-negative integer | – | +| ETHG_FT_So_MI_1SL_Length[1...M1SL] | Non-negative integer representing number of bytes for the length of the Data TLV. | 0 | +| ETHG_FT_So_MI_1SL_Period[1...M1SL] | 10 ms, 100 ms, 1 s, 10 s | 100 ms | +| ETHG_FT_So_MI_1SL_Pri[1...M1SL] | 0, 1, 2, 3, 4, 5, 6, 7 | (Note 2) | +| ETHG_FT_Sk_MI_CC_Enable | True, false | False | +| ETHG_FT_Sk_MI_LMC_Enable | True, false | True | +| ETHG_FT_Sk_MI_1Second | – | – | +| ETHG_FT_Sk_MI_LM_DEGM | 2-10; see Table 7-1 of [ITU-T G.806] | 7 (Note 1) | +| ETHG_FT_Sk_MI_LM_M | 2-10 | 7 (Note 1) | +| ETHG_FT_Sk_MI_LM_DEGTHR | 0% .. 100%; see Table 7-1 of [ITU-T G.806] | Near-end SES threshold (Note 1) | +| ETHG_FT_Sk_MI_LM_TFMIN | 0..(232-1) | N/A | +| ETHG_FT_Sk_MI_MEL | 0, 1, 2, 3, 4, 5, 6, 7 | By agreement | +| ETHG_FT_Sk_MI_MEG_ID | See Annex A of [ITU-T G.8013] | – | +| ETHG_FT_Sk_MI_PeerMEP_ID[i] | List of peer MEP IDs; 0..8191 for each ID; see Figure 9.2-3 of [ITU-T G.8013] | – | +| ETHG_FT_Sk_MI_CC_Period | 3.33 ms, 10 ms, 100 ms, 1 s, 10 s, 1 min, 10 min | 1 s | +| ETHG_FT_Sk_MI_CC_Pri | 0..7 | 7 | +| ETHG_FT_Sk_MI_GetSvdCCM | (NOTE – Use to request the saved latest CCM frame that caused a defect to be raised.) | – | +| Provisioning | | | +| ETHG_FT_Sk_MI_1DM_Enable[1...M1DM] | True, false | False | +| ETHG_FT_Sk_MI_1DM_MAC_SA[1...M1DM] | Per [ITU-T G.8021] | – | +| ETHG_FT_Sk_MI_1DM_Pri [1...M1DM] | 0..7 | (Note 2) | +| ETHG_FT_Sk_MI_1DM_Test_ID[1...M1DM] | Non-negative integer (optional) | – | +| ETHG_FT_Sk_MI_1SL_Enable[1...M1SL] | True, false | False | +| ETHG_FT_Sk_MI_1SL_MAC_SA[1...M1SL] | Per [ITU-T G.8021] | – | +| ETHG_FT_Sk_MI_1SL_Test_ID[1...M1SL] | Non-negative integer | – | +| ETHG_FT_Sk_MI_MEP_MAC | Per [ITU-T G.8021] | – | +| Reporting | | | +| ETHG_FT_Sk_MI_SvdCCM | Last received CCM frame that caused defect | – | + +**Table 8-2 – Provisioning and reporting for flow termination functions** + +| MI signal | Value range | Default value | +|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------|---------------| +| ETHG_FT_Sk_MI_BW_Report(SA, PortID, NominalBW, CurrentBW) | Per configured at peer source | – | +| Provisioning | | | +| ETH-LAG_FT_Sk_MI_SSF_Reported | True, false | True | +| NOTE 1 – Equipment designed prior to the 2024 version of ITU-T G.8051 may use a default value 30% for MI_LM_DEGTHR, 10% for MI_LM_DEGM, and 10% for MI_LM_M.
NOTE 2 – The default value is the MI_CC_Pri in the same atomic function. | | | + +## 8.6 Adaptation + +See clause 8.5 of [ITU-T G.7710] for a description of adaptation management. + +An access point that has multiple adaptation functions connected to it, thereby allowing different clients to be transported via the server signal, requires a mechanism for the selection of the active client. + +This function allows a user to provision and monitor the operation of the ET adaptation processes. + +The MI signals listed in Table 8-3 are communicated between the EMF and the adaptation processes across the management point within the ET NE. + +For the adaptation functions supported by an ET.NE, the ET.NE EMF shall support the following management functions: + +- Provisioning the adaptation management information. +- Retrieving the adaptation management information. +- Notifying the changes of the adaptation management information. + +**Table 8-3 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|---------------------------------------|----------------------------|---------------| +| ETHx/ETH_A_So Provisioning | | | +| ETHx/ETH_A_So_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHx/ETH_A_So_MI_Client_MEL | 0..7 | – | +| ETHx/ETH_A_So_MI_LCK_Period | 1 s, 1 min | 1 s | +| ETHx/ETH_A_So_MI_LCK_Pri | 0..7 | (Note 7) | +| ETHx/ETH_A_So_MI_Admin_State (Note 6) | LCK, Normal | Normal | +| ETHx/ETH_A_So_MI_MEL | 0..7 | – | +| ETHx/ETH_A_So_MI_APS_Pri | 0..7 | (Note 7) | +| ETHx/ETH_A_So_MI_CSF_Period | 1 s, 1 min | 1 s | +| ETHx/ETH_A_So_MI_CSF_Pri | 0..7 | (Note 7) | +| ETHx/ETH_A_So_MI_CSF_Enable | True, false | False | +| ETHx/ETH_A_So_MI_CSFrdifdiEnable | True, false | False | +| ETHx/ETH_A_So_MI_CSFdciEnable | True, false | False | + +**Table 8-3 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|-------------------------------------------------------------------------|-----------------------------------|--------------------------------------| +| ETHx/ETH_A_Sk Provisioning | | | +| ETHx/ETH_A_Sk_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHx/ETH_A_Sk_MI_Client_MEL | 0..7 | – | +| ETHx/ETH_A_Sk_MI_LCK_Period | 1 s, 1 min | 1 s | +| ETHx/ETH_A_Sk_MI_LCK_Pri | 0..7 | (Note 7) | +| ETHx/ETH_A_Sk_MI_Admin_State (Note 6) | LCK, Normal | Normal | +| ETHx/ETH_A_Sk_MI_AIS_Period | 1 s, 1 min | 1 s | +| ETHx/ETH_A_Sk_MI_AIS_Pri | 0..7 | (Note 7) | +| ETHx/ETH_A_Sk_MI_MEL | 0..7 | 7 | +| ETHx/ETH_A_Sk_MI_CSF_Reported | True, false | True | +| ETHx/ETH_A_Sk_MI_CSFrdifdiEnable | True, false | False | +| ETHx/ETH-m_A_So Provisioning | | | +| ETHx/ETH-m_A_So_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHx/ETH-m_A_So_MI_Client_MEL[1..M] | 0..7 | – | +| ETHx/ETH-m_A_So_MI_LCK_Period[1..M] (for each of the 1 through M VLANs) | 1 s, 1 min | 1 s | +| ETHx/ETH-m_A_So_MI_LCK_Pri[1..M] | 0..7 | (Note 7) | +| ETHx/ETH-m_A_So_MI_Admin_State (Note 6) | LCK, Normal | Normal | +| ETHx/ETH-m_A_So_MI_VLAN_Config[1..M] | (Note 1) | (Note 1) | +| ETHx/ETH-m_A_So_MI_Etype | 2-byte integer $\geq$ 0x0600 | S-Tag:
0x88a8
C-Tag:
0x8100 | +| ETHx/ETH-m_A_So_PCP_Config | 8P0D, 7P1D, 6P2D, 5P3D, 4P4D, DEI | 8P0D | +| ETHx/ETH-m_A_So_MI_MEL | 0..7 | 7 | +| ETHx/ETH-m_A_So Provisioning | | | +| ETHx/ETH-m_A_So_MI_CSF_Period | 1 s, 1 min | 1 s | +| ETHx/ETH-m_A_So_MI_CSF_Pri | 0..7 | (Note 7) | +| ETHx/ETH-m_A_So_MI_CSF_Enable | True, false | False | +| ETHx/ETH-m_A_So_MI_CSFrdifdiEnable | True, false | False | +| ETHx/ETH-m_A_So_MI_CSFdciEnable | True, false | False | +| ETHx/ETH-m_A_Sk Provisioning | | | +| ETHx/ETH-m_A_Sk_MI_Admin_State (Note 6) | LCK, Normal | Normal | +| ETHx/ETH-m_A_Sk_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHx/ETH-m_A_Sk_MI_Client_MEL[1..M] | 0..7 | – | +| ETHx/ETH-m_A_Sk_MI_LCK_Period[1..M] | 1 s, 1 min | 1 s | + +**Table 8-3 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|---------------------------------------|----------------------------------------------------|--------------------------------------| +| ETHx/ETH-m_A_Sk_MI_LCK_Pri[1...M] | 0..7 | (Note 7) | +| ETHx/ETH-m_A_Sk_MI_AIS_Period[1...M] | 1 s, 1 min | 1 s | +| ETHx/ETH-m_A_Sk_MI_AIS_Pri[1...M] | 0..7 | (Note 7) | +| ETHx/ETH-m_A_Sk_MI_VLAN_Config[1...M] | (Note 1) | (Note 1) | +| ETHx/ETH-m_A_Sk_MI_P_Regenerate | (Note 1) | (Note 1) | +| ETHx/ETH-m_A_Sk_MI_PVID | (Note 1) | (Note 1) | +| ETHx/ETH-m_A_Sk_MI_PCP_Config | 8P0D, 7P1D, 6P2D, 5P3D, 4P4D, DEI | 8P0D | +| ETHx/ETH-m_A_Sk_MI_Etype | 2-byte integer $\geq$ 0x0600 | S-Tag:
0x88a8
C-Tag:
0x8100 | +| ETHx/ETH-m_A_Sk_MI_MEL | 0..7 | – | +| ETHx/ETH-m_A_Sk_MI_CSF_Reported | True, false | True | +| ETHx/ETH-m_A_Sk_MI_CSFrdifdiEnable | True, false | False | +| ETHx/ETH-m_A_Sk_MI_Frametype_Config | AllowTaggedOnly;
AllowUntaggedOnly;
AllowAll | AllowUntaggedOnly | +| ETHx/ETH-m_A_Sk_MI_FilterConfig | (Note 2) | (Note 2) | +| ETHG/ETH_A_So Provisioning | | | +| ETHG/ETH_A_So_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHG/ETH_A_So_MI_Client_MEL[1...M] | 0..7 | – | +| ETHG/ETH_A_So_MI_LCK_Period[1...M] | 1 s, 1 min | 1 s | +| ETHG/ETH_A_So_MI_LCK_Pri[1...M] | 0..7 | (Note 7) | +| ETHG/ETH_A_So_MI_Admin_State (Note 6) | LCK, Normal | Normal | +| ETHG/ETH_A_So_MI_MEL | 0..7 | – | +| ETHG/ETH_A_So_MI_APS_Pri | 0..7 | (Note 7) | +| ETHG/ETH_A_So_MI_CSF_Period | 1 s, 1 min | 1 s | +| ETHG/ETH_A_So Provisioning | | | +| ETHG/ETH_A_So_MI_CSF_Pri | 0..7 | (Note 7) | +| ETHG/ETH_A_So_MI_CSF_Enable | True, false | False | +| ETHG/ETH_A_So_MI_CSFrdifdiEnable | True, false | False | +| ETHG/ETH_A_So_MI_CSFdciEnable | True, false | False | +| ETHG/ETH_A_Sk Provisioning | | | +| ETHG/ETH_A_Sk_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHG/ETH_A_Sk_MI_Client_MEL[1...M] | 0..7 | – | +| ETHG/ETH_A_Sk_MI_LCK_Period[1...M] | 1 s, 1 min | 1 s | +| ETHG/ETH_A_Sk_MI_LCK_Pri[1...M] | 0..7 | (Note 7) | + +**Table 8-3 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|------------------------------------------------------------------------|-----------------------------------|--------------------------------------| +| ETHG/ETH_A_Sk_MI_Admin_State (Note 6) | LCK, Normal | Normal | +| ETHG/ETH_A_Sk_MI_AIS_Period[1..M] | 1 s, 1min | 1 s | +| ETHG/ETH_A_Sk_MI_AIS_Pri[1..M] | 0..7 | (Note 7) | +| ETHG/ETH_A_Sk_MI_MEL | 0..7 | – | +| ETHG/ETH_A_Sk_MI_CSF_Reported | True, false | True | +| ETHG/ETH_A_Sk_MI_CSFrdifdiEnable | True, false | False | +| ETHx/ETHG_A_So Provisioning | | | +| ETHx/ETHG_A_So_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHx/ETHG_A_So_MI_Client_MEL[1..M] | 0..7 | – | +| ETHx/ETHG_A_So_MI_LCK_Period[1..M] (for each of the 1 through M VLANs) | 1 s, 1 min | 1 s | +| ETHx/ETHG_A_So_MI_LCK_Pri[1..M] | 0..7 | (Note 7) | +| ETHx/ETHG_A_So_MI_Admin_State (Note 6) | LCK, Normal | Normal | +| ETHx/ETHG_A_So_MI_VLAN_Config[1..M] | (Note 1) | (Note 1) | +| ETHx/ETHG_A_So_MI_Etype | 2-byte integer $\geq$ 0x0600 | S-Tag:
0x88a8
C-Tag:
0x8100 | +| ETHx/ETHG_A_So_PCP_Config | 8P0D, 7P1D, 6P2D, 5P3D, 4P4D, DEI | 8P0D | +| ETHx/ETHG_A_So_MI_MEL | 0..7 | 7 | +| ETHx/ETHG_A_Sk Provisioning | | | +| ETHx/ETHG_A_Sk_MI_Admin_State (Note 6) | LCK, Normal | Normal | +| ETHx/ETHG_A_Sk_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHx/ETHG_A_Sk_MI_Client_MEL[1..M] | 0..7 | – | +| ETHx/ETHG_A_Sk_MI_LCK_Period[1..M] | 1 s, 1 min | 1 s | +| ETHx/ETHG_A_Sk_MI_LCK_Pri[1..M] | 0..7 | (Note 7) | +| ETHx/ETHG_A_Sk_MI_AIS_Period[1..M] | 1 s, 1 min | 1 s | +| ETHx/ETHG_A_Sk_MI_AIS_Pri[1..M] | 0..7 | (Note 7) | +| ETHx/ETHG_A_Sk Provisioning | | | +| ETHx/ETHG_A_Sk_MI_VLAN_Config[1..M] | (Note 1) | (Note 1) | +| ETHx/ETHG_A_Sk_MI_P_Regenerate | (Note 1) | (Note 1) | +| ETHx/ETHG_A_Sk_MI_PVID | (Note 1) | (Note 1) | +| ETHx/ETHG_A_Sk_MI_PCP_Config | 8P0D, 7P1D, 6P2D, 5P3D, 4P4D, DEI | 8P0D | +| ETHx/ETHG_A_Sk_MI_Etype | 2-byte integer $\geq$ 0x0600 | S-Tag:
0x88a8
C-Tag:
0x8100 | + +**Table 8-3 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|------------------------------------------------------------------------------------|----------------------------------------------------|-------------------| +| ETHx/ETHG_A_Sk_MI_MEL | 0..7 | – | +| ETHx/ETHG_A_Sk_MI_Frametype_Config | AllowTaggedOnly;
AllowUntaggedOnly;
AllowAll | AllowUntaggedOnly | +| ETHx/ETHG_A_Sk_MI_FilterConfig | (Note 2) | (Note 2) | +| ETHx/MCC_A_So Provisioning | | | +| ETHx/MCC_A_So_MI_MEL | 0..7 | – | +| ETHx/MCC_A_So_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHx/MCC_A_So_MI_MCC_Pri | 0..7 | (Note 7) | +| ETHx/MCC_A_So_MI_MEP_ID | 0..8191; see Figure 9.2-3 of [ITU-T G.8013] | – | +| ETHx/MCC_A_So_MI_EDM_Enable | True, false | False | +| ETHx/MCC_A_So_MI_EDM_Period | (Note 8) | (Note 8) | +| ETHx/MCC_A_So_MI_EDM_Duration | Integer represents number of seconds | = | +| ETHx/MCC_A_Sk Provisioning | | | +| ETHx/MCC_A_Sk_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHx/MCC_A_Sk_MI_MEL | 0..7 | – | +| ETHx/MCC_A_Sk Reporting | | | +| ETHx/MCC_A_Sk_MI_EDM_received (MEP_ID, Duration) | Per provisioning at ETHx/MCC_A_So | – | +| ETHDi/ETH_A_So Provisioning | | | +| ETHDi/ETH_A_So_MI_MEL | 0..7 | – | +| ETHDi/ETH_A_So_MI_RAPS_Pri | 0..7 | (Note 7) | +| ETHDi/ETH_A_So_MI_MIP_MAC | 6-byte MAC unicast address | – | +| ETHDi/ETH_A_Sk Provisioning | | | +| ETHDi/ETH_A_Sk_MI_MEL | 0..7 | – | +| ETHx-Np/ETH-LAG-Na_A_So Provisioning | | | +| ETHx-Np/ETH-LAG-Na_A_So_MI_Agg[1..Na]_AP_List | (Note 1) | (Note 1) | +| ETHx-Np/ETH-LAG-Na_A_So_MI_AggPort[1..Np]_ActorAdmin_State | See clause 7.3 of [IEEE 802.1AX] | – | +| ETHx-Np/ETH-LAG-Na_A_Sk Provisioning | | | +| ETHx-Np/ETH-LAG-Na_A_Sk_MI_PLLThr[1..Na] | (Note 1) | (Note 1) | +| ETHx-Np/ETH-LAG-Na_A_So Reporting | | | +| ETHx-Np/ETH-LAG-Na_A_So_MI_Agg[1..Na] [IEEE 802.1AX oAggregator mandatory objects] | See clause 7.3 of [IEEE 802.1AX] | – | + +**Table 8-3 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|-----------------------------------------------------------------------------------------|----------------------------------|---------------| +| ETHx-Np/ETH-LAG-Na_A_So_MI_Agg[1..Na] [IEEE 802.1AX oAggregationPort mandatory objects] | See clause 7.3 of [IEEE 802.1AX] | – | +| ETHx-Np/ETH-LAG-Na_A_Sk_MI_PLLThr[1..Na] | (Note 1) | (Note 1) | +| ETHx-Np/ETH-LAG-Na_A_Sk Reporting | | | +| ETH-LAG/ETH_A_So Provisioning | | | +| ETH-LAG/ETH_A_Sk Provisioning | | | +| ETH-LAG/ETH_A_Sk_MI_FilterConfig | (Note 2) | (Note 2) | +| M-AI/ETH_A_So Provisioning | | | +| M-AI/ETH_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ETH_A_So_MI_FTSEnable | True, false | False | +| M-AI/ETH_A_So_MI_ESMC_Enable | True, false | False | +| M-AI/ETH_A_Sk Provisioning | | | +| M-AI/ETH_A_Sk_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ETH_A_So_MI_ESMC_Enable | True, false | False | +| M-AI/ETH_A_So Reporting | | | +| M-AI/ETH_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ETH_A_Sk Reporting | | | +| M-AI/ETH_A_Sk_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ERS10G_A_So Provisioning | | | +| M-AI/ERS10G_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ERS10G_A_Sk Provisioning | | | +| M-AI/ERS10G_A_Sk_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ERS10G_A_So Reporting | | | +| M-AI/ERS10G_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ERS10_A_Sk Reporting | | | +| M-AI/ERS10G_A_Sk_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ETCy_A_So Provisioning | | | +| M-AI/ETCy_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ETCy_A_Sk Provisioning | | | +| M-AI/ETCy_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ETCy_A_So Reporting | | | +| M-AI/ETCy_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/ETCy_A_Sk Reporting | | | +| M-AI/ETCy_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/CBR10G3_A_So Provisioning | | | +| M-AI/CBR10G3_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/CBR10G3_A_Sk Provisioning | | | +| M-AI/CBR10G3_A_Sk_MI [IEEE 802.3] | See [IEEE 802.3] | – | + +**Table 8-3 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|---------------------------------------------------|------------------------------------|---------------| +| M-AI/CBR10G3_A_So Reporting | | | +| M-AI/CBR10G3_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/CBR10G3_A_Sk Reporting | | | +| M-AI/CBR10G3_A_Sk_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/FlexE_A_So Provisioning | | | +| M-AI/FlexE_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/FlexE_A_Sk Provisioning | | | +| M-AI/FlexE_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/FlexE_A_So Reporting | | | +| M-AI/FlexE_A_So_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/FlexE_A_Sk Reporting | | | +| M-AI/FlexE_A_Sk_MI [IEEE 802.3] | See [IEEE 802.3] | – | +| FlexE-n/FlexEC_A_So Provisioning | | | +| FlexE-n/FlexEC_A_So_MI_TxCC (Note 4) | 0, 1 | By agreement | +| FlexE-n/FlexEC_A_So_MI_TxCCA (Notes 4 and 5) | See clause 7.3.4 of [OIF FlexE IA] | – | +| FlexE-n/FlexEC_A_So_MI_TxCCB (Notes 4 and 5) | See clause 7.3.4 of [OIF FlexE IA] | – | +| FlexE-n/FlexEC_A_So_MI_TxCR (Note 4) | 0, 1 | – | +| FlexE-n/FlexEC_A_So_MI_TxCA (Note 4) | 0, 1 | – | +| FlexE-n/FlexEC_A_So_MI_TxGID (Notes 4 and 5) | 1..1048575 | – | +| FlexE-n/FlexEC_A_So_MI_TxFlexEMAP (Notes 4 and 5) | String, length 256 | – | +| FlexE-n/FlexE_A_Sk Provisioning | | | +| FlexE-n/FlexEC_A_Sk_MI_ExCC (Note 4) | (Note 3) | – | +| FlexE-n/FlexEC_A_Sk_MI_ExCCA (Note 5) | (Note 3) | – | +| FlexE-n/FlexEC_A_Sk_MI_ExCCB (Note 5) | (Note 3) | – | +| FlexE-n/FlexEC_A_Sk_MI_ExGID (Note 5) | (Note 3) | – | +| FlexE-n/FlexEC_A_Sk_MI_ExFlexEMAP (Note 5) | (Note 3) | – | +| FlexE-n/FlexEC_A_So Reporting | | | +| – | | – | +| FlexE-n/FlexEC_A_Sk Reporting | | | +| FlexE-n/FlexEC_A_Sk_MI_AcCC | (Note 3) | – | +| FlexE-n/FlexEC_A_Sk_MI_AcCR | (Note 3) | – | +| FlexE-n/FlexEC_A_Sk_MI_AcCA | (Note 3) | – | +| FlexE-n/FlexEC_A_Sk_MI_AcCCA | | | +| FlexE-n/FlexEC_A_Sk_MI_AcCCB | | | +| FlexE-n/FlexEC_A_Sk_MI_AcFlexEMAP[1..n] | | | + +**Table 8-3 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------|---------------| +| FlexE-n/FlexEC_A_Sk_MI_AcGID[1..n] | | | +| FlexE-n/FlexEC_A_Sk_MI_AcIID[1..n] | | | +| FlexEC/ETH_A_So Provisioning | | | +| FlexEC/ETH_A_So_MI_[IEEE 802.3] | See [IEEE 802.3] | – | +| FlexEC/ETH_A_Sk Provisioning | | | +| FlexEC/ETH_A_Sk_MI_[IEEE 802.3] | See [IEEE 802.3] | – | +| FlexEC/ETH_A_So Reporting | | | +| FlexEC/ETH_A_So_MI_[IEEE 802.3] | See [IEEE 802.3] | – | +| FlexEC/ETH_A_Sk Reporting | | | +| FlexEC/ETH_A_Sk_MI_[IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/FlexESGM_A_So Provisioning | | | +| M-AI/FlexESGM_A_So_MI_[IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/FlexESGM_A_Sk Provisioning | | | +| M-AI/FlexESGM_A_Sk_MI_[IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/FlexESGM_A_So Reporting | | | +| M-AI/FlexESGM_A_So_MI_[IEEE 802.3] | See [IEEE 802.3] | – | +| M-AI/FlexESGM_A_Sk Reporting | | | +| M-AI/FlexESGM_A_Sk_MI_[IEEE 802.3] | See [IEEE 802.3] | – | +| NOTE 1 – According to [ITU-T G.8021].
NOTE 2 – According to clause 8.3 of [ITU-T G.8021]. It is not exposed to the operator as a configuration parameter of the equipment management interface.
NOTE 3 – According to [ITU-T G.8023].
NOTE 4 – The EMF configures this value according to clause 7.3.2 and 7.3.4 of [OIF Flex IA].
NOTE 5 – The EMF shall configure the same value for the MI_Tx** and MI_Ex** signals of the paired FlexE-n/FlexEC_A_So and FlexE-n/FlexEC_A_Sk functions.
NOTE 6 – See clause 8.14 for Administrative state management.
NOTE 7 – The default value is the MI_CC_Pri of the sever ETHx_FT or ETHG_FT.
NOTE 8 – The value range is implementation specific in ms between 1 and (2 16 -1). The default value is implementation specific. | | | + +## 8.7 Connection + +See clause 8.6 of [ITU-T G.7710] for a description of connection management. + +This function allows a user to provision the operation of an ETH connection function. + +The MI signals listed in Table 8-4 are communicated from the EMF to the connection function through the management point. + +For the connection functions supported by an ET.NE, the ET.NE EMF shall support the following management functions: + +- Provisioning the connection management information +- Retrieving the connection management information +- Notifying the changes of the connection management information + +**Table 8-4 – Provisioning and reporting for connection functions** + +| MI signal | Value range | Default value | +|--------------------------------------------------------|---------------------------------------------------------------------------------|---------------| +| ETH_C Provisioning per flow forwarding process | | | +| ETH_C_MI_FF_[IEEE 802.1Q] | (Note) | (Note) | +| ETH_C Provisioning per SNC/S protection process | | | +| ETH_C_MI_PS_WorkingPortId | (Note) | (Note) | +| ETH_C_MI_PS_ProtectionPortId | (Note) | (Note) | +| ETH_C_MI_PS_ProtType | (Note) | (Note) | +| ETH_C_MI_PS_OperType | (Note) | (Note) | +| ETH_C_MI_PS_HoTime | 0 and 10 s in steps of 100 ms (Note) | 0 ms | +| ETH_C_MI_PS_WTR | 1-minute steps between 5 and 12 minutes (Note) | 5 minutes | +| ETH_C_MI_PS_ExtCMD | (Note) | (Note) | +| ETH_C_MI_PS_BridgeType | 0 (Selector bridge),
1 (Broadcast bridge) | 0 | +| ETH_C_MI_PS_SD_Protection | disabled, enabled | disabled | +| ETH_C Reporting per SNC/S protection process | | | +| ETH_C_MI_PS_RequestState | "LO", "SF-P", "FS",
"SF", "SD", "MS",
"WTR", "EXER", "RR",
"DNR", "NR" | – | +| ETH_C_MI_PS_RequestedSignal | "Null", "Normal" | – | +| ETH_C_MI_PS_BridgedSignal | "Null", "Normal" | – | +| ETH_C Provisioning per ring protection process | | | +| ETH_C_MI_RAPS_PortIds[0...1] | (Note) | (Note) | +| ETH_C_MI_RAPS_RPL_Owner_Node | (Note) | (Note) | +| ETH_C_MI_RAPS_RPL_Neighbour_Node | (Note) | (Note) | +| ETH_C_MI_RAPS_Propagate_TC[1..M] | (Note) | (Note) | +| ETH_C_MI_RAPS_Compatible_Version | (Note) | (Note) | +| ETH_C_MI_RAPS_Revertive | (Note) | (Note) | +| ETH_C_MI_RAPS_Sub_Ring_Without_Virtual_Channel | (Note) | (Note) | +| ETH_C_MI_RAPS_HoTime | (Note) | (Note) | +| ETH_C_MI_RAPS_WTR | (Note) | (Note) | +| ETH_C_MI_RAPS_GuardTime | (Note) | (Note) | +| ETH_C_MI_RAPS_ExtCMD | (Note) | (Note) | +| ETH_C_MI_RAPS_RingID | 1to239 (0x01toEF) | 1 | +| ETH_C Reporting per ring protection process | | | +| ETH_C_MI_RAPS_NodeState | "-", "Idle", "Protection",
"Manual switch",
"Forced switch",
"Pending" | – | + +**Table 8-4 – Provisioning and reporting for connection functions** + +| MI signal | Value range | Default value | +|-------------------------------------|------------------------|---------------| +| ETH_C_MI_RAPS_PortState[0...1] | "Blocked", "Unblocked" | – | +| NOTE – According to [ITU-T G.8021]. | | | + +## 8.8 Diagnostic + +This function allows a user to provision the operation of an ETH diagnostic process. + +The MI signals listed in Table 8-5 are communicated from the EMF to the diagnostic process across the management point within the ET NE. + +For the diagnostic functions supported by an ET.NE, the ET.NE EMF shall support the following management functions: + +- Provisioning the trail termination management information +- Retrieving the trail termination management information +- Notifying the changes of the trail termination management information +- Receiving the monitored trail termination management information + +**Table 8-5 – Provisioning and reporting for diagnostic functions** + +| MI signal | Value range | Default value | +|-------------------------------------------------------------------|------------------------------------------------------------------------------------|-----------------------| +| Provisioning of diagnostic flow termination source for MEP | | | +| ETHDe_FT_So_MI_LM_Start(DA,P,Period) | For period:
100 ms, 1 s,
10 s
(Also see
Notes 1 and 2
for DA and P) | For period:
100 ms | +| ETHDe_FT_So_MI_LM_Intermediate_Request | – | – | +| ETHDe_FT_So_MI_LM_Terminate | – | – | +| ETHDe_FT_So_MI_LB_Discover(P) | (Note 2) | – | +| ETHDe_FT_So_MI_LB_Series(DA,DE,P,N,Length,Period) | (Notes 1 and 2) | – | +| ETHDe_FT_So_MI_LB_Test(DA,DE,P,Pattern, Length, Period) | (Notes 1 and 2) | – | +| ETHDe_FT_So_MI_LB_Test_Terminate | – | – | +| ETHDe_FT_So_MI_DM_Start(DA,P, Test_ID,Length,Period) | For period:
100 ms, 1 s,
10 s
(Also see
Notes 1 and 2
for DA and P) | For period:
100 ms | +| ETHDe_FT_So_MI_DM_Intermediate_Request | – | – | +| ETHDe_FT_So_MI_DM_Terminate | – | – | + +**Table 8-5 – Provisioning and reporting for diagnostic functions** + +| MI signal | Value range | Default value | +|-------------------------------------------------------------------|-------------------------------------------------------------------------------------------|-----------------------| +| ETHDe_FT_So_MI_1DM_Start(DA,P, Test_ID,Length,Period) | For period:
100 ms, 1 s,
10 s
(Also see
Notes 1 and 2
for DA and P) | For period:
100 ms | +| ETHDe_FT_So_MI_1DM_Terminate | – | – | +| ETHDe_FT_So_MI_TST(DA,DE,P,Pattern, Length, Period) | (Notes 1 and 2) | – | +| ETHDe_FT_So_MI_TST_Terminate | – | – | +| ETHDe_FT_So_MI_LT(TA,TTL,P) | (Note 1) | – | +| ETHDe_FT_So_MI_MEP_MAC | 6-byte MAC
unicast address | – | +| ETHDe_FT_So_MI_MEL | 0..7 | – | +| ETHDe_FT_So_MI_MEP_ID | 0..8191; see
Figure 9.2-3 of
[ITU-T G.8013] | – | +| ETHDe_FT_So_MI_SL_Start(DA,P, Test_ID,Length,Period) | For period:
10 ms, 100 ms,
1 s, 10 s
(Also see
Notes 1 and 2
for DA and P) | For period:
100 ms | +| ETHDe_FT_So_MI_SL_Intermediate_Request | – | – | +| ETHDe_FT_So_MI_SL_Terminate | – | – | +| Provisioning of diagnostic flow termination source for MEP | | | +| ETHDe_FT_So_MI_1SL_Start(DA,P,Test_ID,Length,Period) | For period:
10 ms, 100 ms,
1 s, 10 s
(Also see
Notes 1 and 2
for DA and P) | For period:
100 ms | +| ETHDe_FT_So_MI_1SL_Terminate | – | – | +| Reporting of diagnostic flow termination source for MEP | | | +| ETHDe_FT_So_MI_LM_Result(N_TF, N_LF, F_TF, F_LF) | (Note 1) | – | +| ETHDe_FT_So_MI_LB_Discover_Result(MACs) | 6-byte MAC
unicast address | – | +| ETHDe_FT_So_MI_DM_Result(count,B_FD[],F_FD[],N_FD[]) | | | +| ETHDe_FT_So_MI_LB_Series_Result(REC,ERR,OO) | (Note 1) | – | +| ETHDe_FT_So_MI_LB_Test_Result(Sent, REC, CRC, BER, OO) | (Note 1) | – | +| ETHDe_FT_So_MI_TST_Result(Sent) | (Note 1) | – | +| ETHDe_FT_So_MI_LT_Results(Results) | (Note 1) | – | +| ETHDe_FT_So_MI_SL_Result(N_TF,N_LF,F_TF,F_LF) | (Note 1) | – | + +**Table 8-5 – Provisioning and reporting for diagnostic functions** + +| MI signal | Value range | Default value | +|----------------------------------------------------------------------------------------------------|--------------------------------------------------|---------------| +| Provisioning of diagnostic flow termination sink for MEP | | | +| ETHDe_FT_Sk_MI_MEL | 0..7 | – | +| ETHDe_FT_Sk_MI_MEP_MAC | 6-byte Unicast MAC address | – | +| ETHDe_FT_Sk_MI_1DM_Start(SA, P, Test_ID) | 6-byte Unicast MAC address, Non-negative integer | – | +| ETHDe_FT_Sk_MI_1DM_Intermediate_Request | – | – | +| ETHDe_FT_Sk_MI_1DM_Terminate | – | – | +| ETHDe_FT_Sk_MI_TST_Start(SA, pattern) | (Note 1) | – | +| ETHDe_FT_Sk_MI_TST_Terminate | – | – | +| ETHDe_FT_Sk_MI_1SL_Start(SA, MEP ID, Test ID) | (Notes 1 and 2) | – | +| ETHDe_FT_Sk_MI_1SL_Intermediate_Request | – | – | +| ETHDe_FT_Sk_MI_1SL_Terminate | – | – | +| Reporting of diagnostic flow termination sink for MEP | | | +| ETHDe_FT_Sk_MI_1DM_Result(count, N_FD[]) | (Note 1) | – | +| ETHDe_FT_Sk_MI_1SL_Result(N_TF, N_LF) | (Note 1) | – | +| ETHDe_FT_Sk_MI_TST_Result(REC, CRC, BER, OO) | (Note 1) | – | +| Provisioning of diagnostic flow termination source for MIP | | | +| ETHDi_FT_So_MI_MEL | 0..7 | – | +| ETHDi_FT_So_MI_MIP_MAC | 6-byte MAC unicast address | – | +| Provisioning of diagnostic flow termination sink for MIP | | | +| ETHDi_FT_Sk_MI_MEL | 0..7 | – | +| ETHDi_FT_Sk_MI_MIP_MAC | 6-byte MAC unicast address | – | +| NOTE 1 – According to [ITU-T G.8021].
NOTE 2 – DA is 6-byte MAC address, P is 0..7, DE is 0..1. | | | + +## 8.9 Traffic conditioning and shaping + +This function allows a user to provision the operation of an ETH traffic conditioning and shaping process. + +The MI signals listed in Table 8-6 are communicated between the EMF and the traffic conditioning and shaping process across the management point within the ET NE. + +For the traffic conditioning and shaping functions supported by an ET.NE, the ET.NE EMF shall support the following management functions: + +- Provisioning the trail termination management information +- Retrieving the trail termination management information +- Notifying the changes of the trail termination management information +- Receiving the monitored trail termination management information + +**Table 8-6 – Provisioning for traffic conditioning and shaping functions** + +| MI signal | Value range | Default value | +|-------------------------------------|-------------|---------------| +| ETH_TCS_So Provisioning | | | +| ETH_TCS_So_MI_[IEEE 802.1Q] | (Note) | (Note) | +| ETH_TCS_Sk Provisioning | | | +| ETH_TCS_Sk_MI_[IEEE 802.1Q] | (Note) | (Note) | +| NOTE – According to [ITU-T G.8021]. | | | + +## **8.10 ZZZ\_ Reported** + +See clause 8.8 of [ITU-T G.7710] for a description of ZZZ\_ Reported management. + +Table 8-7 provides the MI signals that need to be provisioned for consequential defect/failure. + +For the XXX\_ Reported functions supported by an ET.NE, the ET.NE EMF shall support the following management functions: + +- Provisioning the trail termination management information +- Retrieving the trail termination management information + +**Table 8-7 – Notifying the changes of the trail termination management information – Consequential defect/failure related provisioning** + +| MI signal | Value range | Default value | +|------------------|-------------|---------------| +| MI_CSF_ Reported | True, false | False | + +## **8.11 Alarm severity** + +See clause 8.9 of [ITU-T G.7710] for a description of alarm severity. + +## **8.12 Alarm reporting control (ARC)** + +See clause 8.10 of [ITU-T G.7710] for a description of alarm reporting control. + +## **8.13 Date and time** + +The date and time functions within the ET EMF comprise the local real-time clock (RTC) function and the performance monitoring clock (PMC) function. The message communication function within the ET NEF shall be capable of setting the local real-time clock function. + +The date and time values are incremented by a free running local clock, or by an external timing source. The fault, configuration, account, performance and security management (FCAPS) functions that need date and time information, e.g., to time stamp event reports, obtain this information from the date and time function. + +### **8.13.1 Date and time application** + +Clause 8.13.1 of [ITU-T G.7710] identifies three date and time applications. These are: + +- time-stamping; +- performance monitoring clock signals; +- activity scheduling. + +The ET NEF functional requirements for these applications are specified in the following clauses. + +#### **8.13.1.1 Time-stamping** + +See clause 8.13.1.1 of [ITU-T G.7710] for a description of the time-stamping application. + +#### **8.13.1.2 Performance monitoring clock signals** + +See clause 8.13.1.2 of [ITU-T G.7710] for a description of the PMC signals. + +#### **8.13.1.3 Activity scheduling** + +See clause 8.13.1.3 of [ITU-T G.7710] for a description of the activity scheduling application. + +### **8.13.2 Date and time functions** + +See clause 8.13.2 of [ITU-T G.7710] for a description of the date and time application. + +#### **8.13.2.1 Local real-time clock function** + +The local real-time clock (RTC) function is specified in clause 8.13.2.1 of [ITU-T G.7710]. + +#### **8.13.2.2 Local real-time clock alignment function with external time reference** + +The local real-time clock alignment function with external time reference is specified in clause 8.13.2.2 of [ITU-T G.7710]. + +#### **8.13.2.3 Performance monitoring clock function** + +The performance monitoring clock (PMC) function is specified in clause 8.13.2.3 of [ITU-T G.7710]. + +## **8.14 Administrative state** + +See clause 8.15 of [ITU-T G.7710] for a description of Administrative state configuration functions. + +The ETH atomic functions supporting the Administrative state are listed within Table 8-3, i.e., those adaptation functions that are appended with MI\_Admin\_State. + +NOTE – In this Recommendation the state values LCK and Normal are used in place of LOCKED and UNLOCKED respectively. + +# **9 Accounting management** + +Accounting management is not defined in this version of the Recommendation. + +# **10 Performance management** + +See clause 10 of [ITU-T G.7710] for the generic requirements for performance management. ET specific management requirements are described below. + +## **10.1 Performance management applications** + +See clause 10.1 of [ITU-T G.7710] for the generic description for performance management applications. + +## **10.2 Performance monitoring functions** + +See clause 10.2 of [ITU-T G.7710] for the generic requirements of performance monitoring functions. + +The following are ET specific performance management requirements: + +- 1) PM measurements are managed at TTPs and CTPs (i.e., MEPs/MIPs are created and deleted) +- 2) One MEP has to be created per MEL if that has to be supervised +- 3) Two kinds of measurement jobs have to be supported (ProActive, OnDemand) +- 4) ProActive measurement jobs are managed at MEPs (establish, disable, enable, terminate) + +- 5) OnDemand measurement jobs are managed at MEPs (establish, modify, abort) +- 6) On-Demand measurements can be done using 4 different OAM PDU generation mechanisms: single instance, repetitive instance, single series and repetitive series. To describe these mechanisms, the following terms are used: + - OAM PDU generation type: +Generation pattern of the on-demand OAM message +Valid types are: single instance, repetitive instance, single series and repetitive series. + - Message period (*x*) +Frequency of the OAM message generation within a series. +Note that a value of zero (i.e., $x = 0$ ) means that only one OAM message per measurement interval is generated. + - Measurement interval (*y*) +Defines discrete non overlapping periods of time during which measurements are performed (i.e., OAM messages are generated) and reports are gathered at the end of the measurement intervals. +Note that a value of zero means a degenerated measurement interval with a single OAM message and the report is sent as immediately as possible. + - Repetition period (*z*) +Defines the time between the start of two measurement intervals. This IS applicable for the repetitive instance type and MAY be applicable for the repetitive series type. +Note that a value of zero means not applicable (NA), which is for the cases of single instance, single series, or repetitive series without extra gap in between the measurement intervals (i.e., also as known as continuous series). + - Start time +Defines the start of the on-demand session + - Stop time +Defines the stop of the on-demand session + - Session Duration +Stop time – Start time. + +Note that session duration is not a configuration parameter. That is, it is not needed in the configuration. + +The four on-demand measurements are illustrated in Figure 10-1. In each mechanism, the mandatory parameters (i.e., the required minimum set of parameters) are in red font. The optional parameters are in black font. Optional parameters are not needed but may be used for validation purposes. + +![Diagram of Single instance OAM PDU generation mechanism. A horizontal timeline labeled 'Time' shows a green upward arrow for 'Start time' and a red upward arrow for 'Stop time'. A blue arrow labeled 'Report' points upwards from the timeline at the start time. The text 'Single instance' is above the timeline.](fab98272229adb4efe6412d8e556fb67_img.jpg) + +Diagram of Single instance OAM PDU generation mechanism. A horizontal timeline labeled 'Time' shows a green upward arrow for 'Start time' and a red upward arrow for 'Stop time'. A blue arrow labeled 'Report' points upwards from the timeline at the start time. The text 'Single instance' is above the timeline. + +Configuration parameters for this example: + - OAM PDU generation type = single instance + - Start time = any time + - Stop time = same as Start time + - Message period = 0 + - Repetition period = 0 (i.e., NA) + - Measurement interval = 0 + - Session duration = 0 + +![Diagram of Repetitive instance OAM PDU generation mechanism. A horizontal timeline labeled 'Time' shows a green upward arrow for 'Start time' and a red upward arrow for 'Stop time'. Four blue arrows labeled 'Report' point upwards from the timeline at regular intervals. The first interval is labeled 'z' with a double-headed arrow. The text 'Repetitive instance' and 'Repetition period' are to the left of the timeline.](94796d524bd7e0f31f89a379bae95996_img.jpg) + +Diagram of Repetitive instance OAM PDU generation mechanism. A horizontal timeline labeled 'Time' shows a green upward arrow for 'Start time' and a red upward arrow for 'Stop time'. Four blue arrows labeled 'Report' point upwards from the timeline at regular intervals. The first interval is labeled 'z' with a double-headed arrow. The text 'Repetitive instance' and 'Repetition period' are to the left of the timeline. + +Configuration parameters for this example: + - OAM PDU generation type = Repetitive instance + - Start time = any time + - Stop time > Start time + - Message period = 0 + - Measurement interval = 0 + - Repetition period = z + - Session duration > 0 and $\geq$ Repetition period + +![Diagram of Single series OAM PDU generation mechanism. A horizontal timeline labeled 'Time' shows a green upward arrow for 'Start time' and a red upward arrow for 'Stop time'. Blue arrows labeled 'Report' point upwards from the timeline. The first is 'Intermediate report on request' at start time. Subsequent reports are at intervals of 'x' (Message period). A red double-headed arrow labeled 'y' (Measurement interval) spans from start time to the third report. The text 'Single series', 'Message period', and 'Measurement interval' are to the left of the timeline.](ebd9fdefdb8b316d7bc166aa3ed924a3_img.jpg) + +Diagram of Single series OAM PDU generation mechanism. A horizontal timeline labeled 'Time' shows a green upward arrow for 'Start time' and a red upward arrow for 'Stop time'. Blue arrows labeled 'Report' point upwards from the timeline. The first is 'Intermediate report on request' at start time. Subsequent reports are at intervals of 'x' (Message period). A red double-headed arrow labeled 'y' (Measurement interval) spans from start time to the third report. The text 'Single series', 'Message period', and 'Measurement interval' are to the left of the timeline. + +Configuration parameters for this example: + - OAM PDU generation type = single series + - Start time = any time + - Stop time $\Rightarrow$ Start time (= start + y) + - Message period = x + - Measurement interval = y (>x) + - Repetition period = 0 (i.e., NA) + - Session duration > 0 + +![Diagram of Repetitive series OAM PDU generation mechanism. A horizontal timeline labeled 'Time' shows a green upward arrow for 'Start time' and a red upward arrow for 'Stop time'. Blue arrows labeled 'Report' point upwards from the timeline. The first is 'Intermediate report on request' at start time. Subsequent reports are at intervals of 'x' (Message period). A red double-headed arrow labeled 'y' (Measurement interval) spans from start time to the third report. A blue double-headed arrow labeled 'z' (Repetition period) spans from start time to the start of the second measurement interval (the fourth report). The text 'Repetitive series', 'Message period', 'Measurement interval', and 'Repetition period' are to the left of the timeline. A note 'Start of second measurement interval' points to the fourth report.](8f7b458d3cc18ca96924473839d68ae6_img.jpg) + +Diagram of Repetitive series OAM PDU generation mechanism. A horizontal timeline labeled 'Time' shows a green upward arrow for 'Start time' and a red upward arrow for 'Stop time'. Blue arrows labeled 'Report' point upwards from the timeline. The first is 'Intermediate report on request' at start time. Subsequent reports are at intervals of 'x' (Message period). A red double-headed arrow labeled 'y' (Measurement interval) spans from start time to the third report. A blue double-headed arrow labeled 'z' (Repetition period) spans from start time to the start of the second measurement interval (the fourth report). The text 'Repetitive series', 'Message period', 'Measurement interval', and 'Repetition period' are to the left of the timeline. A note 'Start of second measurement interval' points to the fourth report. + +Configuration parameters for this example: + - OAM PDU generation type = repetitive series + - Start time = any time + - Stop time $\Rightarrow$ Start time + - Message period = x + - Measurement interval = y (>x, and $\leq$ stop time) + - Repetition period = z (>y), optional but needed when there is extra gap between the measurement intervals. + +Note – If repetition period $z = y + x$ , or it is not provisioned, then there is no extra gap between the end of the measurement interval and the start of the new measurement interval. + +G.8051-Y.1345(18)\_F10-1 + +**Figure 10-1 – On-demand OAM PDU generation mechanisms** + +Note that in the repetitive series case, if the repetition period $z = y + x$ , or the value is not provisioned, then there is no extra gap between the end of the measurement interval and the start of the new measurement interval. This pattern is also known as the continuous series cases. The repetition period ( $z$ ) is needed if there is extra gap between the measurement intervals. + +- 7) It shall be possible to configure the following on-demand measurement parameters (including the default values) + - a) OAM PDU generation type; default = repetitive instance + - b) Start time; default = current time + - c) Stop time; default = never stop + +- d) OAM message period; default = 0 + - e) Measurement interval; default = 0 + - e) Repetition period; default = 0 +- 8) Parallel measurement jobs, one per priority, can be established +- 9) Performance data is stored in registers associated to the measurement job +- 10) Behaviour of on-demand OAM process with respect to the creation/deletion should follow Start time and Stop time on on-demand measurement job +- a) The behaviour of on-demand OAM process, resources, message and PM data with respect to the status of the current time is summarized in Table 10-0A. + +**Table 10-0A – Behaviour of on-demand OAM process, resources, message and PM data** + +| Status of currentTime | | Dual-ended measurement job | | Single-ended measurement job | +|-------------------------------------------------------------------------|---------------------------|------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| | | The initiator controller | The target controller | | +| The start time is not reached yet. | | The OAM PM process is not running;
The OAM PM resources are allocated but the OAM messages are not generated. | The OAM PM process is not running;
The OAM PM resources are allocated but any received OAM message is ignored and no PM data is reported. | The OAM PM process is not running;
The OAM PM resources are allocated;
The OAM messages are not generated and any received OAM message is ignored;
No PM data is reported. | +| The start time is reached and;

The stop time is not reached yet. | | The OAM PM process may be running or not running, based on the behaviour of the configured OAM PDU generation type. | The OAM PM process may be running or not running and some PM data may be reported. | The OAM PM process may be running or not running;
Some PM data may be reported, based on the behaviour of the configured OAM PDU generation type. | +| | The stop time is reached. | The OAM PM process is stopped;
The OAM PM process resources are still allocated but OAM messages are not generated. | The OAM PM process is stopped;
The OAM PM process resources are still allocated but any received OAM message is ignored;
The PM data collected at the time the measurement job has been stopped are still reported. | The OAM PM process is stopped;
The OAM PM process resources are still allocated but OAM messages are not generated;
Any received OAM message is ignored;
The PM data collected at the time the measurement job has been stopped are still reported. | + +- b) For the request of the deletion of measurement job instance, the behaviour with respect to the status of the current time is summarized in Table 10-0B. + +**Table 10-0B – Behaviour of the measurement job instance for deletion** + +| Status of currentTime | Dual-ended measurement job | | Single-ended measurement job | +|----------------------------------|-------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| | The initiator controller | The target controller | | +| Before the stop time is reached. | The ongoing OAM PM process is stopped; the OAM PM process resources are released, and then the measurement job instance is deleted. | The ongoing OAM PM process is stopped, the OAM PM process resources are released, and then the measurement job instance is deleted, including all of its reports. | The ongoing OAM PM process is stopped, the OAM PM process resources are released, and then the measurement job instance is deleted, including all of its reports. | +| After the stop time is reached. | The OAM PM process resources are released and then the measurement job instance is deleted. | The OAM PM process resources are released, and then the measurement job instance is deleted, including all of its reports. | The OAM PM process resources are released, and then the measurement job instance is deleted, including all of its reports. | + +- c) Allowed re-configuration of the start time and/or stop time +- i) If the current time is less than (i.e., before) the configured start time +The following reconfiguration are allowed: + - $currentTime < new\_startTime < stopTime$ + - $currentTime < startTime < new\_stopTime$ + - $currentTime < new\_startTime < new\_stopTime$ + - ii) If the current time is between the configured start time and configured stop time +The following reconfiguration is allowed: + - $currentTime < new\_stopTime$ + - iii) If the current time is greater than (i.e., already passed) the configured stop time +The following reconfiguration is allowed: + - $currentTime < new\_StartTime < new\_stopTime$ + +Figure 10-1a illustrates the allowed reconfiguration of the start time and/or stop time. + +![Figure 10-1a: Allowed reconfiguration to startTime and/or stopTime. The diagram shows four horizontal timelines representing 'time'. The first timeline has 'startTime' (green arrow) and 'stopTime' (red arrow). The second timeline shows 'currentTime' (blue arrow) before 'startTime', with conditions: currentTime < new_startTime < stopTime, currentTime < startTime < new_stopTime, and currentTime < new_startTime < new_stopTime. The third timeline shows 'currentTime' between 'startTime' and 'stopTime', with condition: currentTime < new_stopTime. The fourth timeline shows 'currentTime' after 'stopTime', with condition: currentTime < new_startTime < new_stopTime. A reference code G.8051-Y.1345(20)-Amd.1(23)_F10-1a is at the bottom right.](c1df61cc3717e878a48e530218403403_img.jpg) + +*Allowed reconfiguration to startTime and/or stopTime* + +``` + +graph LR + subgraph Timeline1 + T1[ ] --- ST1((startTime)) --- ET1((stopTime)) --- Time1((time)) + end + subgraph Timeline2 + CT2((currentTime)) --- T2[ ] --- Time2((time)) + end + subgraph Timeline3 + T3[ ] --- CT3((currentTime)) --- Time3((time)) + end + subgraph Timeline4 + T4[ ] --- CT4((currentTime)) --- Time4((time)) + end + +``` + +G.8051-Y.1345(20)-Amd.1(23)\_F10-1a + +Figure 10-1a: Allowed reconfiguration to startTime and/or stopTime. The diagram shows four horizontal timelines representing 'time'. The first timeline has 'startTime' (green arrow) and 'stopTime' (red arrow). The second timeline shows 'currentTime' (blue arrow) before 'startTime', with conditions: currentTime < new\_startTime < stopTime, currentTime < startTime < new\_stopTime, and currentTime < new\_startTime < new\_stopTime. The third timeline shows 'currentTime' between 'startTime' and 'stopTime', with condition: currentTime < new\_stopTime. The fourth timeline shows 'currentTime' after 'stopTime', with condition: currentTime < new\_startTime < new\_stopTime. A reference code G.8051-Y.1345(20)-Amd.1(23)\_F10-1a is at the bottom right. + +**Figure 10-1a – Allowed reconfiguration to startTime and/or stopTime** + +- d) When the start time is reached, the list of the existing reports, if any, is emptied out +- 11) Threshold profiles are managed at the managed element (create, modify, delete) +- 12) It shall be possible to retrieve the following configuration information: +- a) all existing MEPs/MIPs within a TP (TTP or CTP) + - b) all existing measurement jobs within a MEP + - c) all existing threshold profiles within a network element + - d) all threshold settings within a ProActive PM measurement job +- 13) It shall be possible to retrieve all ProActive PM measurement current and history performance data within a MEP +- 14) It shall be possible to request intermediate reports on an on-demand PM measurement job of "single series" and "repetitive series" types +- 15) It shall be possible to request an autonomous continuous reporting of performance data from all proactive PM measurement jobs within a MEP (i.e., automatic "push" of the measured PM data) +- 16) On-demand loss measurement can be measured by directly counting the data traffic (e.g., using the [ITU-T G.8013] defined loss measurement message (LMM)/loss measurement reply (LMR)) or can be inferred by counting the synthetic traffic (e.g., using the [ITU-T G.8013] defined SLM/SLR or 1SL). If on-demand loss measurement is supported, for each measurement interval, the Ethernet NE should: +- Receive from the transport plane the measurements (i.e., N\_TF, N\_LF, F\_TF, F\_LF) at the end of each measurement interval. +- Note that according to the definition of near-end and far-end frame loss in clause 8.1 of [ITU-T G.8013], for a MEP, N\_TF and N\_LF refer to the transmitted and lost ingress frames while F\_TF and F\_LF refer to the transmitted and lost egress frames. +- Note that 1SL can provide only near-end measurement (i.e., N\_TF, N\_LF). +- Store the measurements (TN\_TF, TN\_LF, TF\_TF, TF\_LF) and calculate the frame loss ratios (FLRs) ( $TN\_FLR = TN\_LF / TN\_TF$ , $TF\_FLR = TF\_LF / TF\_TF$ ). The measurements and FLRs shall be reported to the management system. + +- At the instruction of the management system, the NE shall be able to request from the transport plane the intermediate (i.e., before the end of the measurement interval) measurements, calculate the intermediate FLRs and report the intermediate results (TN\_TF, TN\_LF, TN\_FLR, TF\_TF, TF\_LF, TF\_FLR) to the management system. + +NOTE – An on-demand LM or DM session could be a single series of OAM messages or a single instance of OAM message. A single instance OAM could be considered as a special case of a single series OAM. + +- 17) Proactive loss measurement can be measured by directly counting the data traffic (e.g., using the [ITU-T G.8013] defined CCM or LMM/LMR) or can be inferred by counting the synthetic traffic (e.g., using the [ITU-T G.8013] defined SLM/SLR or 1SL). If proactive loss measurement is supported, for each loss measurement session the Ethernet NE should: + +- Receive from the transport plane the measurements (i.e., pN\_TF, pN\_LF, pF\_TF, pF\_LF) for each OAM period. + +Note that 1SL can support only near-end measurement (i.e., N\_TF, N\_LF). + +- Calculate the FLRs ( $N\_FLR = pN\_LF / pN\_TF$ , $F\_FLR = pF\_LF / pF\_TF$ ) for each OAM period; store the temporal minimum, average and maximum statistics (mN\_FLR, aN\_FLR, xN\_FLR, mF\_FLR, aF\_FLR, xF\_FLR) in the current 15-minute and 24-hour registers. The stored statistics shall be available for retrieval by the management system. +- The FLR measurements of a monitored entity measured during an SES shall be included in the computation of its FLR statistics, unless the SES is part of the unavailable time period. + +NOTE – This is in line with the definition made in Note 1 of clause 1 in [ITU-T Y.1563]. + +- At the maturity of the current 15-minute and 24-hour periods, the statistics in the current registers shall move to the history registers and then reset the current registers to zeros. See detailed requirements in [ITU-T G.7710]. + +- 18) If on-demand 1-way DM (i.e., 1DM) is supported, for each on-demand 1-way DM measurement interval, the Ethernet NE should: + +- Receive from the transport plane the array of near-end measurements (count, N\_FD[]) at the end of each measurement interval. +- Store the measurements, compute the corresponding array of N\_FDV[] and report the near-end measurements (count, N\_FD[], N\_FDV[]) to the management system. +- At the instruction of the management system, the NE shall be able to request from the transport plane the intermediate measurements, calculate the intermediate N\_FDV[] and report the intermediate results (count, N\_FD[], N\_FDV[]) to the management system. + +- 19) If proactive 1-way DM (i.e., 1DM) is supported, for each proactive 1-way DM session the Ethernet NE should: + +- Receive from the transport plane the near-end measurements (pN\_FD, pN\_FDV) for each OAM period. +- Store the temporal minimum, average and maximum (N\_FD, N\_FDV) in the current 15-minute and 24-hour registers. The stored statistics shall be available for retrieval by the management system. +- At the maturity of the current 15-minute and 24-hour periods, the statistics in the current registers shall move to the history registers and then reset the current registers to zeros. See detailed requirements in [ITU-T G.7710]. + +NOTE – Version 1 of the 1DM PDU format has been defined in the 2011 revision of [ITU-T G.8013] to support both proactive and on-demand 1-way DM applications, in which proactive and on-demand 1DM applications are distinguished by using the Type bit of the Flags field of the 1DM PDU. Proactive 1DM application is configured at the ETHx Flow Termination + +functions (ETHx\_FT) with the Type bit is set to 1, while the on-demand 1DM application is configured at the ETH Diagnostic Flow Termination Function (ETHDe\_FT) with the Type bit being set to 0. See clause 8.1.11 of [ITU-T G.8021] for details. + +- 20) If on-demand 2-way DM (i.e., delay measurement message (DMM)/delay measurement reply (DMR)) is supported, for each on-demand 2-way DM measurement interval, the Ethernet NE should: +- Receive from the transport plane the array of near-end, far-end and bidirectional measurements (count, N\_FD[], F\_FD[], B\_FD[]) at the end of each measurement interval. + - Store the measurements, compute the corresponding array of FDV[] and report the near-end, far-end and bidirectional (2-way) measurements (count, N\_FD[], F\_FD[], B\_FD[]; N\_FDV[], F\_FDV[], B\_FDV[]) to the management system. + - At the instruction of the management system, the NE shall be able to request from the transport plane the intermediate measurements, calculate the intermediate FDV[] and report the intermediate results (count, N\_FD[], F\_FD[], B\_FD[]; N\_FDV[], F\_FDV[], B\_FDV[]) to the management system. +- 21) If proactive 2-way DM (i.e., DMM/DMR) is supported, for each proactive 2-way DM session the Ethernet NE should: +- Receive from the transport plane the near-end, far-end and bidirectional measurements (N\_FD, F\_FD, B\_FD; N\_FDV, F\_FDV, B\_FDV) for each OAM period. + - Store the temporal minimum, average and maximum for each type of the measurements (N\_FD, F\_FD, B\_FD; N\_FDV, F\_FDV, B\_FDV) for the current 15-minute and 24-hour registers. The stored statistics shall be available for retrieval by the management system. + - At the maturity of the current 15-minute and 24-hour periods, the statistics in the current registers shall move to the history registers and then reset current registers to zeros. See detailed requirements in [ITU-T G.7710]. +- NOTE – Version 1 of the 1DM PDU format has been defined in the 2011 revision of [ITU-T G.8013] to support both proactive and on-demand 1-way DM applications, in which proactive and on-demand 1DM applications are distinguished by using the Type bit of the Flags field of the 1DM PDU. Proactive 1DM application is configured at the ETHx Flow Termination functions (ETHx\_FT) with the Type bit is set to 1, while the on-demand 1DM application is configured at the ETH Diagnostic Flow Termination Function (ETHDe\_FT) with the Type bit being set to 0. See clause 8.1.11 of [ITU-T G.8021] for details. +- 22) The Ethernet NE should support the ability to configure for the start and stop at the respondent-end MEP of a single-ended measurement session (such as LMM/LMR and DMM/DMR). + +For illustrative purposes, Figure 10-2 through Figure 10-5 below illustrate the derivation of the loss measurement from the counter values provided by the single-ended and dual-ended mechanisms. + +![Diagram showing single-ended loss measurement using LMM/LMR between nodes A and Z. Node A has Local TxFC, Local RxFC, and a box with RxFCI, TxFCb, TxFCf, RxFCf. Node Z has Local RxFC, Local TxFC, and a box with TxFCb, TxFCf, RxFCf. Arrows show LMM PDU from A to Z and LMR PDU from Z to A.](5ee1bbbf85b473f78af9ec8368a4159a_img.jpg) + +Diagram showing single-ended loss measurement using LMM/LMR between nodes A and Z. Node A has Local TxFC, Local RxFC, and a box with RxFCI, TxFCb, TxFCf, RxFCf. Node Z has Local RxFC, Local TxFC, and a box with TxFCb, TxFCf, RxFCf. Arrows show LMM PDU from A to Z and LMR PDU from Z to A. + +**ITU-T G.8013** + +$\text{Frame loss}_{\text{far-end}} = \Delta \text{TxFCf} - \Delta \text{RxFCf}$ + $\text{Frame loss}_{\text{near-end}} = \Delta \text{TxFCb} - \Delta \text{RxFCI}$ + +$\text{Frame loss}_{\text{far-end}} = |\text{TxFCf}[t_c] - \text{TxFCf}[t_p]| - |\text{RxFCf}[t_c] - \text{RxFCf}[t_p]|$ + $\text{Frame loss}_{\text{near-end}} = |\text{TxFCb}[t_c] - \text{TxFCb}[t_p]| - |\text{RxFCI}[t_c] - \text{RxFCI}[t_p]|$ + +From clause 8.1.2.3 "LMR reception" of [ITU-T G.8013] + +**ITU-T G.8021** + +$\text{N\_TF} = \Delta \text{TxFCb}$ + $\text{N\_LF} = \Delta \text{TxFCb} - \Delta \text{RxFCI}$ + +$\text{F\_TF} = \Delta \text{TxFCf}$ + $\text{F\_LF} = \Delta \text{TxFCf} - \Delta \text{RxFCf}$ + +IF saved THEN + { + $\text{N\_TF} += |\text{TxFCb} - \text{TxFCb\_svd}|$ + $\text{N\_LF} += |\text{TxFCb} - \text{TxFCb\_svd}| - |\text{RxFCI} - \text{RxFCI\_svd}|$ + $\text{F\_TF} += |\text{TxFCf} - \text{TxFCf\_svd}|$ + $\text{F\_LF} += |\text{TxFCf} - \text{TxFCf\_svd}| - |\text{RxFCf} - \text{RxFCf\_svd}|$ + } + +From Figure 8-37 of [ITU-T G.8021] + +G.8051-Y.1345(18)\_F10-2 + +**Figure 10-2 – Single-ended loss measurement using LMM/LMR** + +![Diagram showing dual-ended loss measurement using CCM PDUs between nodes A and Z. Node A has Local TxFC and Local RxFC components. Node Z also has Local TxFC and Local RxFC components. CCM PDUs are exchanged between them. Arrows indicate frame flow and measurement points (TxFCf, RxFCf, TxFCb, RxFCb).](dbd074feb5cce1300f42f91da8f673d1_img.jpg) + +Diagram showing dual-ended loss measurement using CCM PDUs between nodes A and Z. Node A has Local TxFC and Local RxFC components. Node Z also has Local TxFC and Local RxFC components. CCM PDUs are exchanged between them. Arrows indicate frame flow and measurement points (TxFCf, RxFCf, TxFCb, RxFCb). + +| | | | | +|---------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------| +| ITU-T G.8013 | $\text{Frame loss}_{\text{far-end}} = \Delta \text{TxFCb} - \Delta \text{RxFCb}$ $\text{Frame loss}_{\text{near-end}} = \Delta \text{TxFCf} - \Delta \text{RxFCf}$ | $\text{Frame loss}_{\text{far-end}} = \text{TxFCb}[t_c] - \text{TxFCb}[t_p] - \text{RxFCb}[t_c] - \text{RxFCb}[t_p] $ $\text{Frame loss}_{\text{near-end}} = \text{TxFCf}[t_c] - \text{TxFCf}[t_p] - \text{RxFCf}[t_c] - \text{RxFCf}[t_p] $ | From clause 8.1.1.2 "CCM with dual-ended ETH-LM frame reception" of [ITU-T G.8013] | +| | | | | + +| | | | | +|---------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------| +| ITU-T G.8021 | $\text{N\_TF} = \Delta \text{TxFCf}$ $\text{N\_LF} = \Delta \text{TxFCf} - \Delta \text{RxFCf}$
$\text{F\_TF} = \Delta \text{TxFCb}$ $\text{F\_LF} = \Delta \text{TxFCb} - \Delta \text{RxFCb}$ | 
 IF saved THEN { N_TF +=   TxFCf - TxFCf_svd   N_LF +=   TxFCf - TxFCf_svd   -   RxFCf - RxFCf_svd    F_TF +=   TxFCb - TxFCb_svd   F_LF +=   TxFCb - TxFCb_svd   -   RxFCb - RxFCb_svd   }
| From Figure 8-22 of [ITU-T G.8021] | +| | | | | + +G.8051-Y.1345(18)\_F10-3 + +**Figure 10-3 – Dual-ended loss measurement using CCM** +(Note that for loss measurement, CCM is proactive only.) + +![Diagram of single-ended loss measurement using SLM/SLR. It shows two nodes, A and Z, connected by SLM PDU and SLR PDU. Node A has Local TxFC and Local RxFC. Node Z has Local RxFC and Local TxFC. Below the diagram are two tables showing ITU-T G.8013 and ITU-T G.8021 formulas for frame loss measurement.](2580688a4de0a29692805cc6ba4822d7_img.jpg) + +**ITU-T G.8013** + +$\text{Frame loss}_{\text{far-end}} = \Delta \text{TxFCf} - \Delta \text{TxFCb}$ + $\text{Frame loss}_{\text{near-end}} = \Delta \text{TxFCb} - \Delta \text{RxFCf}$ + +$\text{Frame loss}_{\text{far-end}} = |\text{TxFCf}[t_c] - \text{TxFCf}[t_p]| - |\text{RxFCb}[t_c] - \text{RxFCb}[t_p]|$ + $\text{Frame loss}_{\text{near-end}} = |\text{TxFCb}[t_c] - \text{TxFCb}[t_p]| - |\text{RxFCf}[t_c] - \text{RxFCf}[t_p]|$ + +From clause 8.4.1.3 "SLR reception" of [ITU-T G.8013] + +**ITU-T G.8021** + +$\text{N\_TF} = \Delta \text{TxFCb}$ + $\text{N\_LF} = \Delta \text{TxFCb} - \Delta \text{RxFCf}$ + $\text{F\_TF} = \Delta \text{TxFCf}$ + $\text{F\_LF} = \Delta \text{TxFCf} - \Delta \text{TxFCb}$ + +IF saved THEN + { + $\text{N\_TF} += |\text{TxFCb} - \text{TxFCb\_svd}|$ + $\text{N\_LF} += |\text{TxFCb} - \text{TxFCb\_svd}| - |\text{RxFCf} - \text{RxFCf\_svd}|$ + $\text{F\_TF} += |\text{TxFCf} - \text{TxFCf\_svd}|$ + $\text{F\_LF} += |\text{TxFCf} - \text{TxFCf\_svd}| - |\text{RxFCb} - \text{RxFCb\_svd}|$ + } + +From Figure 8-83 of [ITU-T G.8021] + +G.8051-Y.1345(18)\_F10-4 + +Diagram of single-ended loss measurement using SLM/SLR. It shows two nodes, A and Z, connected by SLM PDU and SLR PDU. Node A has Local TxFC and Local RxFC. Node Z has Local RxFC and Local TxFC. Below the diagram are two tables showing ITU-T G.8013 and ITU-T G.8021 formulas for frame loss measurement. + +Figure 10-4 – Single-ended loss measurement using SLM/SLR + +![Diagram of dual-ended loss measurement using 1SL. It shows two nodes, A and Z, connected by 1SL PDU. Node A has Local TxFC. Node Z has Local RxFC and Local TxFC. Below the diagram are two tables showing ITU-T G.8013 and ITU-T G.8021 formulas for frame loss measurement.](40ebe9179df298f1b6d76822f28d90aa_img.jpg) + +**ITU-T G.8013** + +$\text{Frame loss}_{\text{near-end}} = \Delta \text{TxFCf} - \Delta \text{RxFCf}$ + +$\text{Frame loss}_{\text{near-end}} = |\text{TxFCf}[t_c] - \text{TxFCf}[t_p]| - |\text{RxFCf}[t_c] - \text{RxFCf}[t_p]|$ + +From clause 8.4.2.2 "1SL reception" of [ITU-T G.8013] + +**ITU-T G.8021** + +$\text{N\_TF} = \Delta \text{TxFCf}$ + $\text{N\_LF} = \Delta \text{TxFCf} - \Delta \text{RxFCf}$ + +IF saved THEN + { + $\text{N\_TF} += |\text{TxFCf} - \text{TxFCf\_svd}|$ + $\text{N\_LF} += |\text{TxFCf} - \text{TxFCf\_svd}| - |\text{RxFCf} - \text{RxFCf\_svd}|$ + } + +From Figure 8-98 of [ITU-T G.8021] + +G.8051-Y.1345(18)\_F10-5 + +Diagram of dual-ended loss measurement using 1SL. It shows two nodes, A and Z, connected by 1SL PDU. Node A has Local TxFC. Node Z has Local RxFC and Local TxFC. Below the diagram are two tables showing ITU-T G.8013 and ITU-T G.8021 formulas for frame loss measurement. + +Figure 10-5 – Dual-ended loss measurement using 1SL + +ET NE provides the following PM management information (see Table 10-1). + +**Table 10-1 – PM management information** + +| PM management information | ITU-T G.8021 function | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------| +| ETHx_FT_Sk_MI_pN_LF
ETHx_FT_Sk_MI_pN_TF
ETHx_FT_Sk_MI_pF_LF
ETHx_FT_Sk_MI_pF_TF
ETHx_FT_Sk_MI_pF_DS
ETHx_FT_Sk_MI_pN_DS
ETHx_FT_Sk_MI_pB_FD
ETHx_FT_Sk_MI_pB_FDV
ETHx_FT_Sk_MI_pF_FD
ETHx_FT_Sk_MI_pF_FDV
ETHx_FT_Sk_MI_pN_FD
ETHx_FT_Sk_MI_pN_FDV | ETHx_FT_Sk | +| ETHG_FT_Sk_MI_pN_TF
ETHG_FT_Sk_MI_pN_LF
ETHG_FT_Sk_MI_pF_TF
ETHG_FT_Sk_MI_pF_LF
ETHG_FT_Sk_MI_pF_DS
ETHG_FT_Sk_MI_pN_DS
ETHG_FT_Sk_MI_pB_FD
ETHG_FT_Sk_MI_pB_FDV
ETHG_FT_Sk_MI_pF_FD
ETHG_FT_Sk_MI_pF_FDV
ETHG_FT_Sk_MI_pN_FD
ETHG_FT_Sk_MI_pN_FDV | ETHG_FT_Sk | +| ETHx-Np/ETH-LAG-Na_A_So_MI_pAggOctetsTxOK[1..Na]
ETHx-Np/ETH-LAG-Na_A_So_MI_pAggFramesTxOK[1..Na] | ETHx-Np/ETH-LAG-Na_A_So | +| ETHx-Np/ETH-LAG-Na_A_Sk_MI_pAggOctetsRxOK[1..Na]
ETHx-Np/ETH-LAG-Na_A_Sk_MI_pAggFramesRxOK[1..Na] | ETHx-Np/ETH-LAG-Na_A_Sk | + +The EMF shall support the following functions: + +- Notifying of the PM management information. + +# 11 Security management + +See [ITU-T G.7710] for a description of security management. + +# Appendix I + +## MI signals/parameters for PM tools in ITU-T G.8021 + +(This appendix does not form an integral part of this Recommendation.) + +Tables I.1 and I.2 summarize the MI signals defined in [ITU-T G.8021] for the proactive and on-demand performance monitoring tools. + +**Table I.1 – MI signals for proactive PM (ETHx\_FT)** + +| OAM Type | dir | MI signals | | | | | | | | | +|----------|-----|------------|------|--------|------|------|--------|--------|--------|------------------------| +| | | Enable | MAC | | ID | | Length | Period | Pri | Others | +| | | | DA | SA | Test | MEP | | | | | +| CC | So | ✓LMC (*1) | (*6) | | | | (*5) | ✓ | ✓ | | +| | Sk | ✓LMC (*1) | | | | | | ✓ (*7) | ✓ (*7) | GetSvdCCM, SvtCCM | +| LM | So | ✓LML (*1) | ✓ | | (*3) | | (*5) | ✓ | ✓ | | +| | Sk | | | | | | | | | DEGM, M, DEGTHR, TFMIN | +| 1SL | So | ✓ | ✓ | | ✓ | | ✓ | ✓ | ✓ | | +| | Sk | ✓ | | ✓ (*2) | ✓ | (*4) | | | | | +| SL | So | ✓ | ✓ | | ✓ | | ✓ | ✓ | ✓ | | +| | Sk | | | | | | | | | | +| 1DM | So | ✓ | ✓ | | ✓ | | ✓ | ✓ | ✓ | | +| | Sk | ✓ | | ✓ (*2) | ✓ | | | | | | +| DM | So | ✓ | ✓ | | ✓ | | ✓ | ✓ | ✓ | | +| | Sk | | | | | | | | | | + +### **NOTES:** + +- \*1 MI\_{LMC,LML}\_Enable are used to activate the loss measurement process by proactive CCM/ LMx, respectively. Since the calculation of CCM is performed at sink side, the MI\_LMC\_Enable signal is required at sink side (as well as source side, where other protocols have). Note that the latest [ITU-T G.8021] has removed the functionality of MI signals for the allocation of the local counter resources. +- \*2 MI\_MAC\_SA for 1SL/1DM is used to verify that the received PDU is properly sent from the expected peer node. +- \*3 MI\_Test\_ID is not specified in LM until now. +- \*4 MI\_MEP\_ID was removed during [ITU-T G.8021] v4 AAP because MEP\_ID carried in PDU is not evaluated at sink side +- \*5 MI\_Length is not applicable for CC/LM because the length of both PDUs is always fixed. +- \*6 MI\_MAC\_DA is not explicitly specified for CCM protocol because it uses the multicast class 1 address as the default MAC DA. +- \*7 MI\_Period/Priority are configured for sink side of CCM process (as well as the source side) to detect the mismatch defects (dUNP and dUNPr). Note that other protocols do not need to specify neither of MI signals at sink side. + +**Table I.2 – MI signals/parameters for on-demand PM (ETHDe\_FT)** + +| OAM Type | dir | MI_Enable | MI_Start () | | | | | | | MIs for retrieval | | | +|----------|-----|-----------|-------------|------|------|------|--------|--------|-----|-------------------|-------------------------|--------------------------------------------| +| | | | MAC | | ID | | Length | Period | Pri | MI_Terminate | MI_Intermediate_Request | MI_Result() | +| | | | DA | SA | Test | MEP | | | | | | | +| LM | So | (*1) | ✓ | | (*3) | | (*5) | ✓ | ✓ | ✓ | ✓ | ✓
(N_TF,
N_LF,
F_TF,
F_LF) | +| | Sk | (*1) | | | | | | | | | | | +| 1SL | So | | ✓ | | ✓ | | ✓ | ✓ | ✓ | ✓ | | | +| | Sk | | | (*2) | ✓ | (*4) | | | | ✓ | ✓ | ✓
(N_TF,
N_LF) | +| SL | So | | ✓ | | ✓ | | ✓ | ✓ | ✓ | ✓ | ✓ | ✓
(N_TF,
N_LF,
F_TF,
F_LF) | +| | Sk | | | | | | | | | | | | +| 1DM | So | | ✓ | | ✓ | | ✓ | ✓ | ✓ | ✓ | | | +| | Sk | | | (*2) | ✓ | | | | | ✓ | ✓ | ✓ (count,
N_FD[]) | +| DM | So | | ✓ | | ✓ | | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ (count,
B_FD[],
F_FD[],
N_FD[]) | +| | Sk | | | | | | | | | | | | + +### NOTES: + +\*1 MI\_Enable is no longer used to allocate the counter resources for loss measurement. Note that the latest [ITU-T G.8021] has removed MI signals for the allocation of the local counter resources. + +\*2 The parameter 'SA' for MI\_{1SL,1DM}\_Start() is used to verify that the received PDU is properly sent from the expected peer node. + +\*3 The parameter 'Test\_ID' for MI\_LM\_Start() is not specified in LM until now. + +\*4 The parameter 'MEP\_ID' for MI\_1SL\_Start() was removed during [ITU-T G.8021] v4 AAP because MEP\_ID carried in PDU is not evaluated at sink side. + +\*5 The parameter 'Length' is not applicable for CC/LM because the length of both PDUs is always fixed. + +# Bibliography + +- [b-ITU-T G.874] Recommendation ITU-T G.874 (2020), *Management aspects of optical transport network elements*. + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.808.4-202408-I_PDF-E/0538daaa5583c23e17db3a12f2281a55_img.jpg b/marked/G/T-REC-G.808.4-202408-I_PDF-E/0538daaa5583c23e17db3a12f2281a55_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..c1629394c02f697f60ae954ad36bf274fa8082cb --- /dev/null +++ b/marked/G/T-REC-G.808.4-202408-I_PDF-E/0538daaa5583c23e17db3a12f2281a55_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:3763acd7a0ed56aa30f3f90468c1fb0cb54573eb9045bca3eddf8976b4f0f41d +size 7219 diff --git a/marked/G/T-REC-G.808.4-202408-I_PDF-E/1eadbbe42cfcac5c0023577110aec5e3_img.jpg b/marked/G/T-REC-G.808.4-202408-I_PDF-E/1eadbbe42cfcac5c0023577110aec5e3_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..9660e0ac902f495506fb2577e4a3d4415e0ca58c --- /dev/null +++ b/marked/G/T-REC-G.808.4-202408-I_PDF-E/1eadbbe42cfcac5c0023577110aec5e3_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:73fc26773955e0d7c6cc01fd850941c4f89afc5a775e01129502a741836a7644 +size 25438 diff --git a/marked/G/T-REC-G.808.4-202408-I_PDF-E/2cde062fd82833415971a8bd1a2cafab_img.jpg b/marked/G/T-REC-G.808.4-202408-I_PDF-E/2cde062fd82833415971a8bd1a2cafab_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..91721182053c6e0e8942b55a6af4575ea20e48d8 --- /dev/null +++ b/marked/G/T-REC-G.808.4-202408-I_PDF-E/2cde062fd82833415971a8bd1a2cafab_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:54a071e17d2fd74c6c8f2d55189049bd256f985b8cd14e37a48442a7ce663cf7 +size 54349 diff --git a/marked/G/T-REC-G.808.4-202408-I_PDF-E/cb4cfa42ce34febde7bdb882f3fc3094_img.jpg b/marked/G/T-REC-G.808.4-202408-I_PDF-E/cb4cfa42ce34febde7bdb882f3fc3094_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..e1cc6abf3487fd966de45f33436d76188a9e111a --- /dev/null +++ b/marked/G/T-REC-G.808.4-202408-I_PDF-E/cb4cfa42ce34febde7bdb882f3fc3094_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:00a898da5572e4360aefe9bfadfb03930aa1b7d6ce9e41d75e69ff805a866a8e +size 74170 diff --git a/marked/G/T-REC-G.808.4-202408-I_PDF-E/raw.md b/marked/G/T-REC-G.808.4-202408-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..1585293f32a4ad8c53cafe5e8e2f8576a4a7d84f --- /dev/null +++ b/marked/G/T-REC-G.808.4-202408-I_PDF-E/raw.md @@ -0,0 +1,549 @@ + + +# Recommendation**ITU-T G.808.4 (08/2024)** + +SERIES G: Transmission systems and media, digital systems and networks + +Digital networks – General aspects + +--- + +### **Linear protection for fine grain metro transport network (fgMTN) and fine grain optical transport network (fgOTN)** + +![ITU logo](0538daaa5583c23e17db3a12f2281a55_img.jpg) + +The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with white lines representing latitude and longitude, and the letters 'ITU' in a bold, blue, sans-serif font superimposed on the globe. + +ITU logo + +## ITU-T G-SERIES RECOMMENDATIONS + +## Transmission systems and media, digital systems and networks + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100-G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200-G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300-G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400-G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450-G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600-G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700-G.799 | +| DIGITAL NETWORKS | G.800-G.899 | +| General aspects | G.800-G.809 | +| Design objectives for digital networks | G.810-G.819 | +| Synchronization, quality and availability targets | G.820-G.829 | +| Network capabilities and functions | G.830-G.839 | +| SDH network characteristics | G.840-G.849 | +| Management of transport network | G.850-G.859 | +| SDH radio and satellite systems integration | G.860-G.869 | +| Optical transport networks | G.870-G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900-G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000-G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000-G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000-G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000-G.8999 | +| ACCESS NETWORKS | G.9000-G.9999 | + +For further details, please refer to the list of ITU-T Recommendations. + +# Recommendation ITU-T G.808.4 + +# Linear protection for fine grain metro transport network (fgMTN) and fine grain optical transport network (fgOTN) + +## Summary + +Recommendation ITU-T G.808.4 defines the operation of linear protection switching schemes for both fine grain metro transport network (fgMTN) layer network and fine grain optical transport network (fgOTN) layer network, including the automatic protection switching (APS) protocol. + +## History\* + +| Edition | Recommendation | Approval | Study Group | Unique ID | +|---------|----------------|------------|-------------|--------------------| +| 1.0 | ITU-T G.808.4 | 2024-08-29 | 15 | 11.1002/1000/16049 | + +## Keywords + +APS, fgMTN, fgOTN, linear protection. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, and information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at . + +© ITU 2025 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +###### Page + +| | | | +|------------|------------------------------------------------------------------------------|----| +| 1 | Scope ..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions ..... | 1 | +| 3.1 | Terms defined elsewhere ..... | 1 | +| 3.2 | Terms defined in this Recommendation..... | 2 | +| 4 | Abbreviations and acronyms ..... | 2 | +| 5 | Conventions ..... | 3 | +| 6 | Protection architecture and characteristics ..... | 3 | +| 6.1 | Architecture class ..... | 3 | +| 6.2 | Architecture types..... | 3 | +| 6.3 | Switching types ..... | 3 | +| 6.4 | Operation types..... | 3 | +| 6.5 | Protection switching trigger ..... | 3 | +| 6.6 | Protection switching performance..... | 4 | +| 7 | Protection group commands ..... | 4 | +| 8 | Automatic protection switching protocol ..... | 4 | +| 8.1 | Automatic protection switching – specific information format ..... | 4 | +| 8.2 | Principle of 1-phase APS operation ..... | 5 | +| 8.3 | Revertive mode..... | 5 | +| 8.4 | Non-revertive mode..... | 6 | +| 8.5 | Transmission and acceptance of APS protocol ..... | 6 | +| 8.6 | Request type ..... | 6 | +| 8.7 | Protection types ..... | 7 | +| 8.8 | Requested signal ..... | 7 | +| 8.9 | Bridged signal..... | 7 | +| 8.10 | Control of bridge ..... | 7 | +| 8.11 | Control of selector ..... | 7 | +| 8.12 | Signal Fail of the protection transport entity ..... | 7 | +| 8.13 | Equal priority requests..... | 7 | +| 8.14 | Command acceptance and retention..... | 8 | +| 8.15 | Hold-off timer..... | 8 | +| 8.16 | Wait-to-restore timer ..... | 8 | +| 8.17 | Exercise operation ..... | 8 | +| 8.18 | Failure of protocol defects..... | 8 | +| Appendix I | – Operation examples of linear protection protocol for fgMTN and fgOTN ..... | 10 | +| I.1 | 1+1 unidirectional switching ..... | 10 | +| I.2 | 1+1 bidirectional switching ..... | 11 | + + + +# Recommendation ITU-T G.808.4 + +# Linear protection for fine grain metro transport network (fgMTN) and fine grain optical transport network (fgOTN) + +# 1 Scope + +This Recommendation defines the operation of a 1+1 linear protection switching scheme for both fine grain metro transport network (fgMTN) layer network and fine grain optical transport network (fgOTN) layer network, including the automatic protection switching (APS) protocol. The mechanism is based on the generic linear protection specifications in [ITU-T G.808.1]. + +This document describes the common characteristics applicable to both fgMTN and fgOTN. If different characteristics or behaviours between fgMTN and fgOTN exist, they are clearly described in separate subclauses or paragraphs in this recommendation. The APS protocol defined in this Recommendation is identical to that described in [ITU-T G.8331]. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.709] Recommendation ITU-T G.709/Y.1331 (2020), *Interfaces for the optical transport network*. +- [ITU-T G.798] Recommendation ITU-T G.798 (2023) *Characteristics of optical transport network hierarchy equipment functional blocks*. +- [ITU-T G.808] Recommendation ITU-T G.808 (2016), *Terms and definitions for network protection and restoration*. +- [ITU-T G.808.1] Recommendation ITU-T G.808.1 (2014), *Generic protection switching – Linear trail and subnetwork protection*. +- [ITU-T G.8312] Recommendation ITU-T G.8312 (2020), *Interfaces for metro transport networks*. +- [ITU-T G.8321] Recommendation ITU-T G.8321 (2022), *Characteristics of metro transport network equipment functional blocks*. +- [ITU-T G.8331] Recommendation ITU-T G.8331 (2022), *Metro transport network linear protection*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined elsewhere: + +- 3.1.1 **1+1 (protection) architecture** [ITU-T G.808] +- 3.1.2 **active transport entity** [ITU-T G.808] +- 3.1.3 **APS channel** [ITU-T G.808] + +- 3.1.4 **APS protocol: 1-phase** [ITU-T G.808] +- 3.1.5 **bridge** [ITU-T G.808] +- 3.1.6 **head-end** [ITU-T G.808] +- 3.1.7 **non-revertive (protection) operation** [ITU-T G.808] +- 3.1.8 **normal traffic signal** [ITU-T G.808] +- 3.1.9 **null signal** [ITU-T G.808] +- 3.1.10 **permanent bridge** [ITU-T G.808] +- 3.1.11 **protected domain** [ITU-T G.808] +- 3.1.12 **protection class: individual** [ITU-T G.808] +- 3.1.13 **protection class: trail-protection** [ITU-T G.808] +- 3.1.14 **protection group** [ITU-T G.808] +- 3.1.15 **protection transport entity** [ITU-T G.808] +- 3.1.16 **revertive (protection) operation** [ITU-T G.808] +- 3.1.17 **subnetwork connection protection** [ITU-T G.808] +- 3.1.18 **selector** [ITU-T G.808] +- 3.1.19 **tail-end** [ITU-T G.808] +- 3.1.20 **working transport entity** [ITU-T G.808] + +## 3.2 Terms defined in this Recommendation + +None. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|-----------|-----------------------------------------| +| APS | Automatic Protection Switching | +| CRC | Cyclic Redundancy Check | +| DNR | Do Not Revert | +| EXER | Exercise | +| fgMTN | fine grain Metro Transport Network | +| fgMTNP | fine grain Metro Transport Network Path | +| fgODUflex | fine grain Flexible Optical Data Unit | +| fgOTN | fine grain Optical Transport Network | +| FS | Forced Switch | +| LO | Lockout of protection | +| MS | Manual Switch | +| NR | No Request | +| OH | Overhead | +| RR | Reverse Request | +| SD | Signal Degrade | + +| | | +|-------|----------------------------------| +| SF | Signal Fail | +| SNC/S | SNCP with Sublayer monitoring | +| SNCP | Subnetwork Connection Protection | +| TCM | Tandem Connection Monitoring | +| WTR | Wait-To-Restore | + +# 5 Conventions + +None. + +# 6 Protection architecture and characteristics + +## 6.1 Architecture class + +In the fine grain metro transport network (fgMTN), individual trail protection is supported. For a description of individual trail protection, refer to clause 11.1.1 of [ITU-T G.808.1]. + +In the fine grain optical transport network (fgOTN), individual subnetwork connection protection (SNCP) with sublayer monitoring (SNC/S) is supported. For a description of individual SNC/S protection, refer to clause 11.2.1.1 of [ITU-T G.808.1]. + +## 6.2 Architecture types + +Both fgMTN and fgOTN provide 1+1 protection architecture as described in clause 7.1 of [ITU-T G.808.1]. + +## 6.3 Switching types + +Both fgMTN and fgOTN provide unidirectional and bidirectional switching as described in clause 8 of [ITU-T G.808.1]. + +## 6.4 Operation types + +Both fgMTN and fgOTN linear protection support non-revertive and revertive operation types. For the descriptions of non-revertive and revertive operation types, refer to clause 9 of [ITU-T G.808.1]. + +## 6.5 Protection switching trigger + +Protection switching shall be activated when: + +- Initiated by operator control (e.g., manual switch (MS), forced switch (FS) and lockout of protection (LO)), provided no higher priority switch request is in effect; +- Signal fail (SF) or signal degrade (SD) is declared on the active transport entity and the hold-off timer has expired, and no higher priority switch request is in effect; +- The wait-to-restore (WTR) timer expires (in revertive operation) without a higher priority switch request being in effect; or +- The received automatic protection switching (APS) signal requests to switch and has a higher priority than any other local request. + +### 6.5.1 Signal fail declaration conditions + +For SF declaration conditions refer to [ITU-T G.8321] and [ITU-T G.798] as appropriate. + +### 6.5.2 Signal degrade declaration conditions + +For SD declaration conditions refer to [ITU-T G.8321] and [ITU-T G.798] as appropriate. + +## 6.6 Protection switching performance + +For both fgOTN and fgMTN, the transfer time $T_t$ , as defined in [ITU-T G.808], shall not exceed 50 ms for a protection span length that does not exceed 1,200 km. + +# 7 Protection group commands + +Protection group commands, such as Lockout of protection (LO), forced switch (FS), manual switch (MS), exercise, clear, freeze, and clear freeze, are provided as described in clause 19 of [ITU-T G.808.1]. + +# 8 Automatic protection switching protocol + +## 8.1 Automatic protection switching – specific information format + +In the fgMTN, the APS-specific information is carried over two APS bytes in an APS message. The format of the APS message is defined in [ITU-T G.8312]. + +In the fgOTN, three independent APS channels are available to support protection; one at the fine grain flexible optical data unit (fgODUflex) path and two at the fgODUflex tandem connection monitoring (TCM) levels as defined in Annex M.2.2.7 of [ITU-T G.709]. Each APS channel is used to carry two bytes of APS-specific information. + +The formats of the APS-specific information for both fgMTN and fgOTN are identical, as defined in Figure 8-1. + +![](1eadbbe42cfcac5c0023577110aec5e3_img.jpg) + +| APS1 | | | | | | | | APS2 | | | | | | | | +|-------------------|---|---|---|------------|---|---|---|---------------------|---|---|---|-------------------|---|---|---| +| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | +| Request/
State | | | | Prot. Type | | | | Requested
Signal | | | | Bridged
Signal | | | | +| | | | | A | B | D | R | | | | | | | | | + +**Figure 8-1 – Format of APS-specific information** + +Table 8-1 describes code points and values for the APS-specific information. + +**Table 8-1 – Code points and field values** + +| | | | | +|---------------|--------|-----------------------------------|------------------| +| Request/State | 1111 | Lockout of protection (LO) | Highest priority | +| | 1110 | Signal fail on Pprotection (SF-P) | | +| | 1101 | Forced switch (FS) | | +| | 1011 | Signal fail on working (SF-W) | | +| | 1001 | Signal degrade (SD) | | +| | 0111 | Manual switch (MS) | | +| | 0101 | Wait-to-restore (WTR) | | +| | 0100 | Exercise (EXER) | | +| | 0010 | Reverse request (RR) | | +| | 0001 | Do not revert (DNR) | | +| | 0000 | No request (NR) | Lowest priority | +| | Others | Reserved | | +| | | | | + +**Table 8-1 – Code points and field values** + +| | | | | +|-----------------|------------------|------|--------------------------| +| Protection type | A | 0 | No APS channel | +| | | 1 | APS channel | +| | B | 0 | 1+1 (permanent bridge) | +| | | 1 | Reserved | +| | D | 0 | Unidirectional switching | +| | | 1 | Bidirectional switching | +| | R | 0 | Non-revertive operation | +| | | 1 | Revertive operation | +| | Requested signal | 0 | Null signal | +| | | 1 | Normal traffic signal | +| | | 2-15 | Reserved | +| Bridged signal | | 0 | Reserved | +| | | 1 | Normal traffic signal | +| | | 2-15 | Reserved | + +For the protection architectures defined in this Recommendation, a 1-phase APS is used. + +## 8.2 Principle of 1-phase APS operation + +1-phase APS Protocol is defined in [ITU-T G.808]. The 1+1 linear protection switching algorithm is performed in network elements at both ends of a protected domain. Bidirectional switching is achieved by transmitting local switching requests to the far end via the "Request/State" in the first octet (APS1) of the APS-specific information (see Figure 8-1). The transmitted "Requested Signal" and "Bridged Signal" in the second octet (APS2) of the APS-specific information contain the local bridge/selector status information. A persistent mismatch between both ends may thus be detected and leads to an alarm. + +## 8.3 Revertive mode + +In the revertive mode of unidirectional protection switching operation, when a normal traffic signal is being received via the protection transport entity, and if local protection switching requests that were previously active become inactive, a local WTR state is entered. Since this state now represents the highest priority local request, it is indicated in the transmitted "Request/State" information, maintaining the switch. + +In the case of bidirectional protection switching, a local WTR state is entered only when there is no higher-priority of request received from the far end than that the WTR state. + +This state normally times out and becomes a No Request (NR) state after the WTR timer has expired. The WTR timer is deactivated earlier if any local request of higher priority pre-empts this state. + +A switch to the protection transport entity may be maintained by a local WTR state or by a remote request (WTR or other) received via the "Request/State" information. Therefore, in the case of a bidirectional failure of the working transport entity and a subsequent repair, the bidirectional reversion back to the working transport entity will not take place until WTR timers at both ends have expired. + +## 8.4 Non-revertive mode + +In non-revertive mode of unidirectional protection switching operation, when a normal traffic signal is being transmitted via the protection transport entity, and if local protection switching requests that were previously active become inactive, a local do not revert (DNR) state is entered. This state is indicated in the transmitted "Request/State" information, maintaining the switch, and thus preventing reversion back to the released selector position in non-revertive mode under NR conditions. + +In the case of bidirectional protection switching operation, a local DNR state is entered when there is no higher priority of request received from the far end than that the DNR state, or when both the local state and far-end state are NR with the requested signal number 1. + +## 8.5 Transmission and acceptance of APS protocol + +The APS protocol is transported via the protection transport entity only, being inserted by the head-end of the protected domain and extracted by the tail-end of the protected domain. Although it may also be transmitted identically on the working transport entity, receivers should not assume this and should have the capability to ignore this information on the working transport entity. + +In the fgMTN, the APS messages are transmitted in every "A" opportunity within the BABL block insertion pattern defined in [ITU-T G.8312]. Note that the APS message consists of two 66B blocks, and complete messages are always transmitted; if the APS status changes during the transmission of a message, the status is updated in the next message. The APS-specific information received from the far end is accepted only when the received APS message contains a correct cyclic redundancy check (CRC). The integrity of APS-specific information is protected by the CRC described in clause 9.3.3.1.1 of [ITU-T G.8312]. New APS-specific information shall be accepted when the first APS-specific information with a different value from the previous one is received. + +In the fgOTN, each of three independent APS channels is carried via two bytes in the fgODUflex overhead (OH) defined in Annex M of [ITU-T G.709]. For each of the three channels, an independent acceptance process shall be performed. A new APS-specific information value shall be accepted if an identical value is received in the two bytes of a given channel three times consecutively. + +If no valid APS-specific information is received, the last received valid information remains applicable except in case of SF condition on the protection transport entity. + +NOTE 1 – (fgOTN) – If no errors occur, acceptance is reached after 35.268/p ms for fgODUflex(p), where p=1, ..., 119. + +NOTE 2 – (fgMTN) – If no errors occur, acceptance is reached after 26 ms for fine grain metro transport network path (fgMTNP). + +## 8.6 Request type + +The request types reflect the highest priority condition, command or state. In the case of unidirectional switching, this is the highest priority value determined from the near end only. In bidirectional switching, the sent "Request/State" shall indicate: + +- a) A reverse request (RR) if one of the following applies: + - I. the remote request is of higher priority; + - II. the requests are of the same level (and are higher priority than a NR/DNR) and the sent "Request/State" already indicates RR; + - III. the requests are of the same level (and are higher priority than a NR/DNR) and the sent "Request/State" does not indicate RR and the remote request indicates a lower requested signal number. +- b) The local request in all other cases. + +## 8.7 Protection types + +The valid configurations of the protection type are as specified below: + +000x: 1+1 unidirectional, no APS + +100x: 1+1 unidirectional w/APS + +101x: 1+1 bidirectional w/APS + +The default value for the protection type is all zeros, i.e., ABDR = 0b0000. Note that when the protection type has the default value, no APS messages are sent. + +If the "B" bit mismatches, the selector is released. This will result in a defect. + +Provided the "B" bit matches: + +- a) If the "A" bit mismatches, the side expecting APS will fall back to 1+1 unidirectional switching without APS communication; +- b) If the "D" bit mismatches, the bidirectional side will fall back to unidirectional switching; +- c) If the "R" bit mismatches, one side will clear switches to "WTR" and the other will clear to "DNR". The two sides will interwork and the traffic is protected; + +## 8.8 Requested signal + +This indicates the signal that the near-end requests to be carried over the protection transport entity. + +For NR and LO, this can only be the null signal (0). For exercise, this can be the null signal (0) when exercise replaces NR, or the normal traffic signal (1) when Exercise replaces DNR. For SF or SD, this will be the normal traffic signal, or the null signal to indicate that protection is failed or degraded. For all other requests, this will be the normal traffic signal requested to be carried over the protection transport entity. + +## 8.9 Bridged signal + +This indicates the signal that is bridged onto the protection transport entity. For 1+1 protection, the value of this field is always "1" to indicate the normal traffic signal. + +### 8.10 Control of bridge + +In 1+1 architectures, the normal traffic signal is permanently bridged to the protection transport entity. + +## 8.11 Control of selector + +In 1+1 unidirectional architectures (with or without APS communication), the selector is set entirely according to the highest priority local request. + +In 1+1 bidirectional architectures, the normal traffic signal will be selected from the protection transport entity when the outgoing "requested signal" indicates the normal traffic signal. + +## 8.12 Signal Fail of the protection transport entity + +Signal fail on the protection transport entity (SF-P) is of higher priority than any defect that would cause the normal traffic signal to be selected from the protection transport entity. When an APS signal is in use, a SF on the protection transport entity (over which the APS signal is routed) has priority over the FS. LO command has higher priority than SF-P; during failure conditions, lockout status is kept active. + +## 8.13 Equal priority requests + +In general, once a switch has been completed due to a request, it will not be overridden by another request of the same priority (first come, first served behaviour). When equal priority requests occur + +simultaneously, the conflict is resolved in favour of the request with the lower requested signal number. For a 1+1 protection architecture, this is relevant only when APS signal is enabled and for bidirectional switching. For example, SD for the null signal is considered to have higher priority than SD for the normal traffic signal, resulting in both tail-ends selecting the working transport entity. Equal priority requests for the same requested signal number from both sides of a bidirectional protection group are both considered valid, and equivalent to a received "RR" from a near-end processing standpoint. + +## **8.14 Command acceptance and retention** + +The commands clear, LO, FS, MS and EXER are accepted or rejected in the context of previous commands, the condition of the working and protection transport entities in a protection group, and (in bidirectional switching only) the received APS information. + +The clear command is only valid if a near-end LO, FS, MS, or EXER command is in effect, or if a WTR state is present at the near end; otherwise, it is rejected. This command will remove the near-end command or WTR state, allowing the next lower priority condition or (in bidirectional switching) APS request to be asserted. + +Other commands are rejected unless they have a higher priority than the previously existing command, condition or (in bidirectional switching) APS request. If a new command is accepted, any previous, lower priority command that is overridden is forgotten. If a higher priority command overrides a lower priority condition or (in bidirectional switching) APS request, that other request will be reasserted if it still exists at the time the command is cleared. + +If a command is overridden by a condition or (in bidirectional switching) APS request, that command is forgotten. + +### **8.15 Hold-off timer** + +A hold-off timer as defined in [ITU-T G.808.1] is supported. The value is configurable with a suggested range of 0 to 10 seconds in steps of 100 ms (accuracy of $\pm 5$ ms). + +## **8.16 Wait-to-restore timer** + +A WTR timer as defined in [ITU-T G.808.1] is supported. The value is configurable with a suggested range of 5 to 12 minutes in steps of 1 minute. The default is 5 minutes. + +## **8.17 Exercise operation** + +An exercise command as defined in [ITU-T G.808.1] is supported. In 1-phase APS protocol, the valid response will be an RR with the corresponding requested and bridged signal numbers. When exercise commands are input at both ends, an EXER, instead of RR, is transmitted from both ends. The standard response to DNR should be DNR rather than NR. When the exercise command is cleared, it will be replaced with NR or RR if the requested signal number is 0, and DNR or RR if the requested signal number is 1. + +## **8.18 Failure of protocol defects** + +"Failure of protocol" situations for protection types requiring APS are as follows: + +- a) Fully incompatible provisioning (the "B" bit mismatch, described in clause 8.7); +- b) No match in sent "Requested Signal" and received "Requested Signal" in case of bidirectional switching for $> 50$ ms; +- c) In case of fgMTN, three consecutive APS messages are not received when there are no defects on the protection transport entity. + +Fully incompatible provisioning is detected according to the APS-specific information acceptance criteria described in clause 8.5. + +If an unknown request or a request for an invalid signal number is received, it will be ignored. + +# Appendix I + +## Operation examples of linear protection protocol for fgMTN and fgOTN + +(This appendix does not form an integral part of this Recommendation.) + +The sequence diagrams shown in this appendix are only a few examples of linear protection protocol operation for fgMTN and fgOTN. The first protocol message that differs from the previous message is shown. The operation of the hold-off timer is omitted. An APS message is expressed as, for example, $NR(r = 0, b = 1)$ , which contains the following field values: Request/State = NR, requested signal ( $r = 0$ ), and bridged signal ( $b = 1$ ). The values of the other fields remain unchanged from the initial configuration. $W(A \rightarrow Z)$ indicates the working transport entity in the direction of A to Z. + +### I.1 1+1 unidirectional switching + +1+1 unidirectional switching can be performed with or without APS communication. In case the APS is used, the APS-specific information is informational only and do not control the operation of the protection group. Switches are performed according to the local request only. + +Figure I.1 illustrates an example of 1+1 unidirectional switching operation. This example describes overlapping SF and SD requests from opposite sides. For illustration, the example in Figure I.1 shows mismatched provisioning with side A being non-revertive and side Z being revertive. + +![Sequence diagram illustrating 1+1 unidirectional switching operation between nodes A and Z.](cb4cfa42ce34febde7bdb882f3fc3094_img.jpg) + +The diagram illustrates the sequence of events for 1+1 unidirectional switching between nodes A and Z. The timeline starts with both nodes sending $NR(r = 0, b = 1)$ messages. Node A then detects a failure in the working transport entity $W(A \leftarrow Z)$ and sends an $SF(r = 1, b = 1)$ message. Node Z detects a degrade condition in the working transport entity $W(A \rightarrow Z)$ and sends an $SD(r = 1, b = 1)$ message. Node A receives the $SD$ message and enters a recovery state for $W(A \leftarrow Z)$ , sending a $DNR(r = 1, b = 1)$ message. Node Z receives the $DNR$ message and enters a recovery state for $W(A \rightarrow Z)$ , sending a $WTR(r = 1, b = 1)$ message. Node Z then starts a WTR timer. After the timer expires, Node Z sends an $NR(r = 0, b = 1)$ message, and Node A receives it, completing the switching process. + +Sequence of messages and states: + +- Initial state: Both A and Z send $NR(r = 0, b = 1)$ . Traffic is selected from working transport entity. +- Node A detects **Failure $W(A \leftarrow Z)$** and sends $SF(r = 1, b = 1)$ . Traffic is selected from protection transport entity. +- Node Z detects **Degrade $W(A \rightarrow Z)$** and sends $SD(r = 1, b = 1)$ . Traffic is selected from protection transport entity. +- Node A receives $SD$ and enters **Recovery $W(A \leftarrow Z)$** , sending $DNR(r = 1, b = 1)$ . +- Node Z receives $DNR$ and enters **Recovery $W(A \rightarrow Z)$** , sending $WTR(r = 1, b = 1)$ . A **WTR timer** starts. +- After timer expires, Node Z sends $NR(r = 0, b = 1)$ . Traffic is selected from working transport entity. + +G.808.4(24) + +Sequence diagram illustrating 1+1 unidirectional switching operation between nodes A and Z. + +Figure I.1 – Operation example of 1+1 unidirectional switching + +### I.2 1+1 bidirectional switching + +Figure I.2 shows an example of 1+1 bidirectional, non-revertive switching operation. + +![Sequence diagram of 1+1 bidirectional switching between nodes A and Z.](2cde062fd82833415971a8bd1a2cafab_img.jpg) + +The diagram illustrates the operation of 1+1 bidirectional switching between two nodes, A and Z. It shows the selection of traffic from working and protection transport entities under different failure and recovery conditions. + +- Initial State:** Both nodes A and Z select traffic from the working transport entity. The state is labeled $NR(r = 0, b = 1)$ at both ends. +- Failure Event:** A failure occurs on the working path from A to Z, labeled **Failure $W(A \leftarrow Z)$** . Node A detects the failure and switches to the protection transport entity, labeled $SF(r = 1, b = 1)$ . Node Z continues to select traffic from the working transport entity. +- Revertive Request:** Node A sends a revertive request to Node Z, labeled $RR(r = 1, b = 1)$ . Node Z responds by switching to the protection transport entity, labeled $RR(r = 1, b = 1)$ . Both nodes now select traffic from the protection transport entity. +- Recovery Event:** The working path is restored, labeled **Recovery $W(A \leftarrow Z)$** . Node A switches back to the working transport entity, labeled $DNR(r = 1, b = 1)$ . Node Z continues to select traffic from the protection transport entity. +- Final State:** Node Z receives the $DNR(r = 1, b = 1)$ message and switches back to the working transport entity. Both nodes A and Z now select traffic from the working transport entity, returning to the initial state $NR(r = 0, b = 1)$ . + +G.808.4(24) + +Sequence diagram of 1+1 bidirectional switching between nodes A and Z. + +Figure I.2 – Operation example of 1+1 bidirectional switching + + + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series 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Telecommunication Union (ITU) features a globe with a lightning bolt superimposed on it, and the letters 'ITU' in a bold, sans-serif font. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.812** + +(06/2004) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital networks – Design objectives for digital networks + +--- + +**Timing requirements of slave clocks suitable for +use as node clocks in synchronization networks** + +ITU-T Recommendation G.812 + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | G.500–G.599 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| QUALITY OF SERVICE AND PERFORMANCE - GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DIGITAL TERMINAL EQUIPMENTS | G.7000–G.7999 | +| DIGITAL NETWORKS | G.8000–G.8999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# **Timing requirements of slave clocks suitable for use as node clocks in synchronization networks** + +## **Summary** + +This Recommendation outlines minimum requirements for timing devices used as node clocks in synchronization networks. The requirements relate to frequency deviation; pull-in, hold-in and pull-out range; noise generation, tolerance and transfer; transient response and holdover performances. The node clocks are suitable for use in SDH and PSTN network applications. + +This Recommendation includes specifications for three types of clocks. The Type I clock is primarily intended for use in networks optimized for the 2048 kbit/s hierarchy. The Types II and III clocks are primarily intended for use in networks optimized for the particular 1544 kbit/s hierarchy that includes the rates 1544 kbit/s, 6312 kbit/s and 44 736 kbit/s. + +Additionally, this Recommendation includes specifications for three other clocks in Annex A. Type IV is typically deployed in existing networks that support the 1544 kbit/s. The Types V and VI clocks were defined for transit and local node applications in the 1988 version of this Recommendation. + +## **Source** + +ITU-T Recommendation G.812 was approved on 13 June 2004 by ITU-T Study Group 15 (2001-2004) under the ITU-T Recommendation A.8 procedure. The typo corrected by G.812 (2004) Erratum 1 is included in the electronic version of this Recommendation. + +## **Keywords** + +Clock performance objectives, clock performance parameters, jitter performance, node clock, wander performance. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2004 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## CONTENTS + +| | | Page | +|------|------------------------------------------------------------------------|------| +| 1 | Scope ..... | 1 | +| 2 | Node clock types and applications ..... | 1 | +| 2.1 | Synchronization network considerations..... | 1 | +| 2.2 | Node clock types and applications ..... | 2 | +| 3 | References..... | 3 | +| 4 | Definitions ..... | 3 | +| 5 | Abbreviations..... | 3 | +| 6 | Frequency accuracy ..... | 4 | +| 7 | Pull-in, hold-in, and pull-out ranges ..... | 4 | +| 8 | Noise generation ..... | 4 | +| 8.1 | Wander in locked mode ..... | 5 | +| 8.2 | Non-locked wander ..... | 7 | +| 8.3 | Jitter ..... | 7 | +| 9 | Noise tolerance ..... | 8 | +| 9.1 | Wander tolerance..... | 9 | +| 9.2 | Jitter tolerance ..... | 12 | +| 10 | Noise transfer..... | 14 | +| 11 | Transient response and hold-over performance..... | 16 | +| 11.1 | Short-term phase transient response ..... | 16 | +| 11.2 | Long-term phase transient response (hold-over) ..... | 17 | +| 11.3 | Phase response to input signal interruptions ..... | 19 | +| 11.4 | Phase discontinuity ..... | 20 | +| 12 | Interfaces..... | 21 | +| | Annex A – Specifications for Types IV, V and VI clocks..... | 21 | +| A.1 | Frequency accuracy ..... | 21 | +| A.2 | Pull-in, hold-in and pull-out ranges ..... | 21 | +| A.3 | Noise generation ..... | 22 | +| A.4 | Noise tolerance ..... | 25 | +| A.5 | Noise transfer..... | 29 | +| A.6 | Transient response and hold-over performance ..... | 30 | +| A.7 | Interfaces ..... | 34 | +| | Appendix I – Relationship between TDEV and power spectral density..... | 35 | +| | Appendix II – Measurement method for noise transfer ..... | 37 | +| II.1 | Measurement set-up..... | 37 | +| II.2 | Functional model of TDEV noise generator ..... | 38 | + + + +# **Timing requirements of slave clocks suitable for use as node clocks in synchronization networks** + +# **1 Scope** + +This Recommendation outlines minimum requirements for timing devices used as node clocks in synchronization networks. The function of a node clock is to select one of the external synchronization links coming into a telecommunication station as the active synchronization reference, to attenuate its jitter and wander and subsequently to distribute the reference to the telecommunication equipment in the station. The requirements in this Recommendation apply under the normal environmental conditions specified for telecommunications equipment. + +This Recommendation specifies node clocks suitable for use in SDH and PSTN network applications. They may provide acceptable performance for other applications, but that has to be investigated for each case individually. + +In normal operation, a node clock is operating as a slave clock, traceable to a primary reference clock. For purposes of redundancy, a node clock will in general have multiple reference inputs. In the event that all links between the master(s) and the node clock fail, the node clock should be capable of maintaining operation within prescribed performance limits (the hold-over mode of operation). + +A node clock can be a separate piece of equipment called a Stand Alone Synchronization Equipment (SASE) or it can be a part of another equipment such as a telephony exchange or an SDH cross-connect. + +This Recommendation defines six Types of clocks. Applications for each clock Type are described in clause 2. + +# **2 Node clock types and applications** + +## **2.1 Synchronization network considerations** + +Design of synchronization networks in general is not standardized. Principles for synchronization of SDH networks are outlined in ITU-T Rec. G.803. Some of these principles can be taken as general design rules for synchronization networks. + +Synchronization requirements for node clocks in a PSTN environment can in principle be derived from the controlled slip rate objectives in ITU-T Rec. G.822. There are three elements that determine whether G.822 objectives can be achieved: + +- the hold-over stability of the clocks; +- the network topology (i.e., length, routing and redundancy of the references); and +- the operational practices of the operator (i.e., mean time to repair). + +Only the first element is covered in this Recommendation. Network providers can choose to use particular clock Types in their synchronization planning in order to match their network topology and operational practices. + +Synchronization requirements for node clocks in an SDH environment are mainly driven by the jitter and wander specifications in ITU-T Recs G.823, G.824 and G.825. Given that SDH equipment clocks (as specified in ITU-T Rec. G.813) have only limited filtering capabilities and at the same time need to maintain their STM-N and PDH outputs in conformance with ITU-T Recs G.823, + +G.824 and G.825, the phase transients at the output of node clocks must meet specifications that are more stringent than what is strictly needed for pure PDH transport equipment. + +NOTE – Since the bandwidths of SDH equipment clocks are wider in networks based on the 2048 kbit/s hierarchy compared to those based on the 1544 kbit/s hierarchy (as described in ITU-T Rec. G.813 option 1 and option 2, respectively), the output phase transient requirements are correspondingly more stringent for node clocks deployed in 2048 kbit/s hierarchy environments. + +## 2.2 Node clock types and applications + +This Recommendation includes specifications for three clocks. The Type I clock is primarily intended for use in networks optimized for the 2048 kbit/s hierarchy. The Types II and III clocks are primarily intended for use in networks optimized for the particular 1544 kbit/s hierarchy that includes the rates 1544 kbit/s, 6312 kbit/s and 44 736 kbit/s. + +The Type I clock can be used at all levels of the synchronization hierarchy in 2048 kbit/s based networks. The wander generation and bandwidth of Type I clocks are limited to values that allow the deployment of the maximum number of node clocks according to the synchronization network reference chain as defined in ITU-T Rec. G.803. Although a Type I clock is primarily intended for use in networks supporting the 2048 kbit/s hierarchy, a Type I clock can also be deployed in 1544 kbit/s based networks as long as at least its pull-in range, noise generation and noise tolerance (see clauses 7, 8 and 9) comply with the more stringent requirements that apply to Types II and III clocks in order to be compatible with SDH equipment clocks built according to ITU-T Rec. G.813 option 2. + +The Type II clock has a more stringent hold-over stability specification than a Type I clock. It is typically deployed at distribution hubs in networks that support the 1544 kbit/s hierarchy mentioned above. Type II clocks have a hold-over stability specification sufficient to operate with a single reference at the highest levels of the synchronization hierarchy. Although a Type II clock is primarily intended for use in networks supporting the 1544 kbit/s hierarchy, a clock with Type II hold-over specifications can also be deployed in 2048 kbit/s based networks as long as at least its noise generation, noise tolerance and transient behaviour (see clauses 8, 9, 11.1 and 11.4) comply with the more stringent requirements that apply to Type I clocks in order to be compatible with SDH equipment clocks built according to ITU-T Rec. G.813 option 1. + +The Type III clock has a less stringent hold-over stability requirement than Type I and Type II. It is typically deployed in end offices in networks that support the 1544 kbit/s hierarchy mentioned above. Like a Type II clock, a clock with Type III hold-over stability may also be deployed in 2048 kbit/s based networks as long as at least its noise generation, noise tolerance and transient behaviour (see clauses 8, 9, 11.1 and 11.4) comply to the more stringent requirements that apply to Type I when it is used to synchronize SDH equipment. + +Additionally, this Recommendation includes specifications for three clocks in Annex A. + +The Type IV clock is typically deployed in existing networks that support the 1544 kbit/s hierarchy mentioned above. If clocks with Type IV hold-over performance are embedded in SDH equipment in this hierarchy, the requirements in ITU-T Rec. G.813 option 2 should be met as well. + +The Type V clock is typically deployed in existing transit nodes of networks based on both 1544 kbit/s and 2048 kbit/s hierarchies according to the specifications of the 1988 version of this Recommendation. It should be noted that these clocks are perfectly suitable for the synchronization of 2048 kbit/s based SDH networks provided they conform at least to the noise generation and short-term stability requirements (clauses 8, 11.1 and 11.4) of Type I clocks. + +The Type VI clock is typically deployed in existing local nodes of networks based on the 2048 kbit/s hierarchy according to the specifications of the 1988 version of this Recommendation. Like Type V, clocks with Type VI hold-over stability characteristics may be used for the + +synchronization of SDH networks as long as the clock at least meets the noise generation and short-term stability requirements (clauses 8, 11.1 and 11.4) of the Type I clock. + +# 3 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [1] ITU-T Recommendation G.703 (2001), *Physical/electrical characteristics of hierarchical digital interfaces*. +- [2] ITU-T Recommendation G.783 (2004), *Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks*. +- [3] ITU-T Recommendation G.801 (1988), *Digital transmission models*. +- [4] ITU-T Recommendation G.803 (2000), *Architecture of transport networks based on the synchronous digital hierarchy (SDH)*. +- [5] ITU-T Recommendation G.810 (1996), *Definitions and terminology for synchronization networks*. +- [6] ITU-T Recommendation G.811 (1997), *Timing requirements of primary reference clocks*. +- [7] ITU-T Recommendation G.813 (2003), *Timing requirements of SDH equipment slave clocks (SEC)*. +- [8] ITU-T Recommendation G.822 (1988), *Controlled slip rate objectives on an international digital connection*. +- [9] ITU-T Recommendation G.823 (2000), *The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy*. +- [10] ITU-T Recommendation G.824 (2000), *The control of jitter and wander within digital networks which are based on the 1544 kbit/s hierarchy*. +- [11] ITU-T Recommendation G.825 (2000), *The control of jitter and wander within digital networks which are based on the synchronous digital hierarchy (SDH)*. +- [12] ITU-T Recommendation Q.551 (2002), *Transmission characteristics of digital exchanges*. + +# 4 Definitions + +The terms and definitions used in this Recommendation are contained in ITU-T Rec. G.810. + +# 5 Abbreviations + +This Recommendation uses the following abbreviations. + +| | | +|------|----------------------------------| +| CMI | Coded Mark Inversion | +| MTIE | Maximum Time Interval Error | +| NE | Network Element | +| PDH | Plesiochronous Digital Hierarchy | +| ppm | parts per million | + +| | | +|------|---------------------------------------| +| PRBS | Pseudo Random Binary Sequence | +| PRC | Primary Reference Clock | +| PSD | Power Spectral Density | +| PSTN | Public Switched Telephone Network | +| SASE | Stand Alone Synchronization Equipment | +| SDH | Synchronous Digital Hierarchy | +| SEC | SDH Equipment Clock | +| SSU | Synchronization Supply Unit | +| STM | Synchronous Transport Module | +| TDEV | Time Deviation | +| UI | Unit Interval | + +# 6 Frequency accuracy + +Under prolonged hold-over conditions, the output frequency accuracy of the different Types of node clocks should not exceed the values in Table 1 with regard to a reference traceable to a primary reference clock, over a time period T as reported in the same Table. + +**Table 1/G.812 – Output frequency accuracy requirements** + +| | Type I | Type II | Type III | +|-----------------------------------------------------------------------------------------------------------|--------|----------------------|----------------------| +| Accuracy | NA | $1.6 \times 10^{-8}$ | $4.6 \times 10^{-6}$ | +| Period T | NA | 1 year | 1 year | +| NA Not applicable
NOTE – The time period T applies after 30 days of continuous synchronized operation. | | | | + +# 7 Pull-in, hold-in, and pull-out ranges + +The minimum pull-in, hold-in and pull-out ranges for the different Types of node clocks should be according to Table 2, whatever the internal oscillator frequency offset may be. + +**Table 2/G.812 – Pull-in, hold-in, and pull-out requirements** + +| | Type I | Type II | Type III | +|----------------------------------------|--------------------|----------------------|----------------------| +| Pull-in | $1 \times 10^{-8}$ | $1.6 \times 10^{-8}$ | $4.6 \times 10^{-6}$ | +| Hold-in | NA | $1.6 \times 10^{-8}$ | $4.6 \times 10^{-6}$ | +| Pull-out | TBD | NA | NA | +| NA Not applicable
TBD To be defined | | | | + +# 8 Noise generation + +The noise generation of a slave clock represents the amount of phase noise produced at the output when there is an ideal input reference signal or the clock is in hold-over state (see 11.2). A suitable reference, for practical testing purposes, implies a performance level at least 10 times more stable than the output requirements. The ability of the clock to limit this noise is described by its + +frequency stability. The measures MTIE and Time Deviation (TDEV) are useful for characterization of noise generation performance. + +MTIE and TDEV are measured through an equivalent 10 Hz, first-order, low-pass measurement filter, at a maximum sampling time $\tau_0$ of 1/30 second. The minimum measurement period for TDEV is twelve times the integration period ( $T = 12 \tau$ ). + +## 8.1 Wander in locked mode + +When the slave clock is in the locked mode of operation, the MTIE at constant temperature (within $\pm 1$ K) measured using the synchronized clock configuration defined in Figure 1-a/G.810 should have the limits in Tables 3 and 4 for the different Types of node clocks. + +**Table 3/G.812 – Wander generation (MTIE) for Type I node clock at constant temperature (within $\pm 1$ K)** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|-----------------------|---------------------------------| +| 24 | $0.1 < \tau \leq 9$ | +| $8 \times \tau^{0.5}$ | $9 < \tau \leq 400$ | +| 160 | $400 < \tau \leq 10\,000$ | + +**Table 4/G.812 – Wander generation (MTIE) for Types II and III node clocks at constant temperature (within $\pm 1$ K)** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|------------------------|---------------------------------| +| 40 | $0.1 < \tau \leq 1$ | +| $40 \times \tau^{0.4}$ | $1 < \tau \leq 10$ | +| 100 | $\tau > 10$ | + +When temperature effects are included of which the limits and rate of change are to be defined, the allowance for the total MTIE contribution of a single Type I node clock is given by the values in Table 5. + +**Table 5/G.812 – Total wander generation (MTIE) for Type I node clock for variable temperature** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|------------------|---------------------------------| +| $3.2 \tau^{0.5}$ | $2500 < \tau \leq 10\,000$ | + +NOTE – For observation periods greater than 10 000 s, the MTIE is expected not to exceed 1 $\mu\text{s}$ . + +The resultant requirements are shown in Figure 1. + +![Figure 1/G.812 – Wander generation (MTIE) graph. The y-axis is MTIE (ns) on a log scale from 10 to 10 K. The x-axis is Observation interval τ (s) on a log scale from 0.1 to 10 K. The graph shows two main curves: Type I and Types II, III. Type I is a solid line that is constant at 24 ns until τ = 9 s, then increases linearly to 160 ns at τ = 400 s, and then increases to 320 ns at τ = 10 K. Types II, III is a dashed line that is constant at 40 ns until τ = 1 s, then increases linearly to 100 ns at τ = 9 s, and then remains constant at 100 ns until τ = 10 K. A label 'Variable temperature' points to the Type I curve at τ = 2.5 K.](398674b42e3466add6d47f420c136494_img.jpg) + +Figure 1/G.812 – Wander generation (MTIE) graph. The y-axis is MTIE (ns) on a log scale from 10 to 10 K. The x-axis is Observation interval τ (s) on a log scale from 0.1 to 10 K. The graph shows two main curves: Type I and Types II, III. Type I is a solid line that is constant at 24 ns until τ = 9 s, then increases linearly to 160 ns at τ = 400 s, and then increases to 320 ns at τ = 10 K. Types II, III is a dashed line that is constant at 40 ns until τ = 1 s, then increases linearly to 100 ns at τ = 9 s, and then remains constant at 100 ns until τ = 10 K. A label 'Variable temperature' points to the Type I curve at τ = 2.5 K. + +G.812\_F1 + +**Figure 1/G.812 – Wander generation (MTIE)** + +When the node clock is in the locked mode of operation, the TDEV at constant temperature (within $\pm 1$ K) measured using the synchronized clock configuration defined in Figure 1-a/G.810 should have the limits in Tables 6 and 7 for the different Types of node clock. + +**Table 6/G.812 – Wander generation (TDEV) for Type I node clock at constant temperature (within $\pm 1$ K)** + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|-----------------|---------------------------------| +| 3 | $0.1 < \tau \leq 25$ | +| $0.12 \tau$ | $25 < \tau \leq 100$ | +| 12 | $100 < \tau \leq 10\,000$ | + +**Table 7/G.812 – Wander generation (TDEV) for Types II and III node clocks at constant temperature (within $\pm 1$ K)** + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|--------------------------|---------------------------------| +| $3.2 \times \tau^{-0.5}$ | $0.1 < \tau \leq 2.5$ | +| 2 | $2.5 < \tau \leq 40$ | +| $0.32 \times \tau^{0.5}$ | $40 < \tau \leq 1000$ | +| 10 | $\tau > 1000$ | + +The resultant requirements are shown in Figure 2. + +![Figure 2/G.812 – Wander generation (TDEV) for constant temperature. This is a log-log plot showing TDEV (ns) on the y-axis versus Observation interval τ (s) on the x-axis. The y-axis has major ticks at 1, 2, 3, 10, 12, and 100. The x-axis has major ticks at 0.1, 1.0, 2.5, 10, 25, 40, 100, 1 K, and 10 K. Two curves are shown: Type I (solid line) and Types II, III (dashed line). Type I starts at 3 ns for τ = 0.1 s, remains constant until τ = 25 s, then rises to 12 ns at τ = 100 s and remains constant. Types II, III starts at 10 ns for τ = 0.1 s, decreases to 3 ns at τ = 1.0 s, then to 2 ns at τ = 2.5 s, remains constant until τ = 25 s, then rises to 10 ns at τ = 100 s and remains constant.](2236272d3b3db6e6363337f5a8db72f6_img.jpg) + +Figure 2/G.812 – Wander generation (TDEV) for constant temperature. This is a log-log plot showing TDEV (ns) on the y-axis versus Observation interval τ (s) on the x-axis. The y-axis has major ticks at 1, 2, 3, 10, 12, and 100. The x-axis has major ticks at 0.1, 1.0, 2.5, 10, 25, 40, 100, 1 K, and 10 K. Two curves are shown: Type I (solid line) and Types II, III (dashed line). Type I starts at 3 ns for τ = 0.1 s, remains constant until τ = 25 s, then rises to 12 ns at τ = 100 s and remains constant. Types II, III starts at 10 ns for τ = 0.1 s, decreases to 3 ns at τ = 1.0 s, then to 2 ns at τ = 2.5 s, remains constant until τ = 25 s, then rises to 10 ns at τ = 100 s and remains constant. + +Figure 2/G.812 – Wander generation (TDEV) for constant temperature + +## 8.2 Non-locked wander + +When a clock is not locked to a synchronization reference, the random noise components are negligible compared to deterministic effects like initial frequency offset. Consequently, the non-locked wander effects are included in 11.2. + +## 8.3 Jitter + +While most requirements in this Recommendation are independent of the output interface at which they are measured, this is not the case for jitter production; jitter generation requirements utilize existing Recommendations that have different limits for different interface rates. These requirements are stated separately for the interfaces identified in clause 12. To be consistent with other jitter requirements, the values are in UI peak-peak, where the UI corresponds to the reciprocal of the bit rate of the interface. + +Note that all filter values for STM-N interfaces specified in this clause have been harmonized with the filter values for the network limit as specified in ITU-T Rec. G.825. + +NOTE – Due to the stochastic nature of jitter, the peak-peak values given in this clause eventually are exceeded. The requirements should therefore be fulfilled in at least 99% of all measurements made. + +#### 8.3.1 Output jitter at 2048 kHz and 2048 kbit/s interfaces + +In the absence of input jitter, the intrinsic jitter at 2048 kHz and 2048 kbit/s output interfaces as measured over a 60-second interval should not exceed 0.05 UI peak-peak when measured through a single pole band-pass filter with corner frequencies at 20 Hz and 100 kHz. + +### 8.3.2 Output jitter at a 1544 kbit/s interface + +In the absence of input jitter, the intrinsic jitter at a 1544 kbit/s output interface should not exceed 0.05 UI peak-peak when measured through a single pole band-pass filter with corner frequencies at 10 Hz and 40 kHz. The measurement interval is for further study. + +### 8.3.3 Output jitter at an STM-N interface + +In the absence of input jitter at the synchronization interface, the intrinsic jitter at optical STM-N output interfaces as measured over a 60-second interval should not exceed the limits given in Table 8 below. The allowed jitter on an STM-1 electrical (CMI) interface is also given in Table 8 below. + +The measurement filter roll-off at the lower cut-off frequency shall be 20 dB/decade and the roll-off at the upper cut-off frequency shall be 60 dB/decade. The characteristic of the upper cut-off filter roll-off is for further study. + +**Table 8/G.812 – STM-N jitter generation** + +| Interface | Measuring filter
(-3 dB frequencies) | Peak-peak amplitude
(UI) | +|-----------------------------------------------------------------------------------------|-----------------------------------------|-----------------------------| +| STM-1
electrical | 500 Hz to 1.3 MHz | 0.50 | +| | 65 kHz to 1.3 MHz | 0.075 | +| STM-1
optical | 500 Hz to 1.3 MHz | 0.50 | +| | 65 kHz to 1.3 MHz | 0.10 | +| STM-4 | 1000 Hz to 5 MHz | 0.50 | +| | 250 kHz to 5 MHz | 0.10 | +| STM-16 | 5000 Hz to 20 MHz | 0.50 | +| | 1 MHz to 20 MHz | 0.10 | +| For STM-1: 1 UI = 6.43 ns.
For STM-4: 1 UI = 1.61 ns.
For STM-16: 1 UI = 0.40 ns. | | | + +# 9 Noise tolerance + +The noise tolerance of a G.812 clock indicates the lower limit of the maximum phase noise level at the input of the clock that should be accommodated while: + +- Maintaining the clock within prescribed performance limits. The exact performance limits are for further study. +- Not causing any alarms. +- Not causing the clock to switch reference. +- Not causing the clock to go into hold-over. + +In general, the noise tolerance of a G.812 clock is the same as the network limit for the synchronization interface in order to maintain acceptable performance. However, the synchronization interface network limit may be different according to the application. Therefore, in order to determine the slave clock noise tolerance, the worst-case network limit should be used. An explanation of the different network limits for acceptable payload performance is given in Appendix I/G.813 for information. + +The wander and jitter tolerances given in 9.1 and 9.2 represent the worst levels that a synchronization carrying interface should exhibit. The TDEV signal used for a conformance test should be generated by adding white, gaussian noise sources, each of which has been filtered to obtain the proper type of noise process with the proper amplitude. Guidance is provided in Appendix II. + +MTIE and TDEV are measured through an equivalent 10 Hz, first-order, low-pass measurement filter, at a maximum sampling time $\tau_0$ of 1/30 second. The minimum measurement period for TDEV is twelve times the integration period ( $T = 12 \tau$ ). + +## 9.1 Wander tolerance + +#### 9.1.1 MTIE wander tolerance + +The G.812 clock input wander tolerance expressed as an MTIE limit is given in Table 9 for Type I node clocks and in Table 10 for Types II and III node clocks. + +**Table 9/G.812 – Input wander tolerance (MTIE) +for Type I node clock** + +| MTIE limit
( $\mu\text{s}$ ) | Observation interval $\tau$
(s) | +|---------------------------------|------------------------------------| +| 0.75 | $0.1 < \tau \leq 7.5$ | +| $0.1 \tau$ | $7.5 < \tau \leq 20$ | +| 2 | $20 < \tau \leq 400$ | +| $0.005 \tau$ | $400 < \tau \leq 1000$ | +| 5 | $1000 < \tau \leq 10\,000$ | + +**Table 10/G.812 – Input wander tolerance (MTIE) +for Types II and III node clocks** + +| MTIE limit
( $\mu\text{s}$ ) | Observation interval $\tau$
(s) | +|---------------------------------|------------------------------------| +| $0.3 + 0.002\,5 \tau$ | $0.05 < \tau \leq 280$ | +| $0.997 + 0.000\,01 \tau$ | $\tau > 280$ | + +The resultant requirements are shown in Figure 3. + +![Figure 3/G.812 – Input wander tolerance (MTIE). A log-log plot showing MTIE (μs) on the y-axis (0.1 to 100) versus Observation interval τ (s) on the x-axis (10 m to 10 K). The plot shows two curves: Type I (solid line) and Types II, III (dashed line). Type I starts at 0.3 μs for τ < 0.1 s, rises to 0.75 μs at τ = 0.1 s, then to 2 μs at τ = 10 s, and finally to 5 μs at τ = 1000 s. Types II, III starts at 0.3 μs for τ < 0.1 s, rises to 0.75 μs at τ = 0.1 s, then to 1 μs at τ = 100 s, and remains at 1 μs for τ > 1000 s.](b05fbb6a015ea153c1e25245772b1a1b_img.jpg) + +Figure 3/G.812 – Input wander tolerance (MTIE). A log-log plot showing MTIE (μs) on the y-axis (0.1 to 100) versus Observation interval τ (s) on the x-axis (10 m to 10 K). The plot shows two curves: Type I (solid line) and Types II, III (dashed line). Type I starts at 0.3 μs for τ < 0.1 s, rises to 0.75 μs at τ = 0.1 s, then to 2 μs at τ = 10 s, and finally to 5 μs at τ = 1000 s. Types II, III starts at 0.3 μs for τ < 0.1 s, rises to 0.75 μs at τ = 0.1 s, then to 1 μs at τ = 100 s, and remains at 1 μs for τ > 1000 s. + +Figure 3/G.812 – Input wander tolerance (MTIE) + +#### 9.1.2 TDEV wander tolerance + +The G.812 clock input wander tolerance expressed as a TDEV limit is given in Table 11 for Type I node clocks and in Table 12 for Types II and III node clocks. + +Table 11/G.812 – Input wander tolerance (TDEV) +for Type I node clock + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|-------------------------|---------------------------------| +| 34 | $0.1 < \tau \leq 20$ | +| $1.7 \times \tau$ | $20 < \tau \leq 100$ | +| 170 | $100 < \tau \leq 1000$ | +| $5.4 \times \tau^{0.5}$ | $1000 < \tau \leq 10\,000$ | + +Table 12/G.812 – Input wander tolerance (TDEV) +for Types II and III node clocks + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|-----------------------|---------------------------------| +| FFS | $\tau \leq 0.05$ | +| 100 | $0.05 < \tau \leq 10$ | +| $31.6 \tau^{0.5}$ | $10 < \tau \leq 1000$ | +| FFS | $\tau > 1000$ | +| FFS For further study | | + +The resultant requirements are shown in Figure 4. + +![Figure 4/G.812 – Input wander tolerance (TDEV). A log-log plot showing TDEV (ns) on the y-axis versus Observation interval τ (s) on the x-axis. The y-axis ranges from 10 to 10 K with major ticks at 10, 34, 100, 170, 540, 1 K, and 10 K. The x-axis ranges from 0.01 to 10 K with major ticks at 0.01, 0.05, 0.1, 1, 10, 20, 100, 1 K, and 10 K. Two curves are shown: 'Types II, III' (dashed line) and 'Type I' (solid line). The 'Types II, III' curve is horizontal at 100 ns from 0.05 s to 10 s, then rises with a slope of 1. The 'Type I' curve is horizontal at 34 ns from 0.1 s to 20 s, then rises with a slope of 1. The two curves intersect at 100 ns and 10 s.](af06598cfb31b517e79b50d74f72a0ca_img.jpg) + +Figure 4/G.812 – Input wander tolerance (TDEV). A log-log plot showing TDEV (ns) on the y-axis versus Observation interval τ (s) on the x-axis. The y-axis ranges from 10 to 10 K with major ticks at 10, 34, 100, 170, 540, 1 K, and 10 K. The x-axis ranges from 0.01 to 10 K with major ticks at 0.01, 0.05, 0.1, 1, 10, 20, 100, 1 K, and 10 K. Two curves are shown: 'Types II, III' (dashed line) and 'Type I' (solid line). The 'Types II, III' curve is horizontal at 100 ns from 0.05 s to 10 s, then rises with a slope of 1. The 'Type I' curve is horizontal at 34 ns from 0.1 s to 20 s, then rises with a slope of 1. The two curves intersect at 100 ns and 10 s. + +**Figure 4/G.812 – Input wander tolerance (TDEV)** + +#### 9.1.3 Sinusoidal wander tolerance + +While suitable test signals that check conformance to the mask in Figure 3 are being studied, test signals with a sinusoidal phase variation can be used. The requirements for Type I node clocks are shown in Table 13. The requirements for Types II and III are shown in Table 14. + +**Table 13/G.812 – Lower limit of maximum tolerable sinusoidal input wander for Type I node clocks** + +| Peak-peak wander amplitude (μs) | Frequency f (Hz) | +|---------------------------------|---------------------------------| +| 5 | $0.000\ 012 < f \leq 0.000\ 32$ | +| $0.001\ 6 \times f^{-1}$ | $0.000\ 32 < f \leq 0.000\ 8$ | +| 2 | $0.000\ 8 < f \leq 0.016$ | +| $0.032 \times f^{-1}$ | $0.016 < f \leq 0.043$ | +| 0.75 | $0.043 < f \leq 1$ | + +**Table 14/G.812 – Lower limit of maximum tolerable sinusoidal input wander for Types II and III node clocks** + +| Peak-peak wander amplitude (μs) | Frequency f (Hz) | +|---------------------------------|------------------------------------| +| $0.997 + [4 \times 10^{-6}/f]$ | $0.000\ 031\ 8 < f \leq 0.001\ 43$ | +| $0.3 + [0.001/f]$ | $0.001\ 43 < f \leq 10$ | + +The resultant requirements are shown in Figure 5. + +![Figure 5/G.812 – Lower limit of maximum tolerable sinusoidal input wander. A log-log plot showing peak-peak wander amplitude (μs) versus wander frequency (Hz). The plot includes a solid line for Type I and a dashed line for Types II, III. The Type I line has segments at 5 μs, 2 μs, and 0.75 μs. The Types II, III line has segments at 1 μs and 0.3 μs. Frequency markers include 10 μ, 12 μ, 31.8 μ, 0.1 m, 0.32 m, 0.8 m, 1.43 m, 10 m, 16 m, 43 m, 0.1, 1, and 10 Hz. A '1 m' marker is also present.](8ccbc9fa77bf60ba0ca0b79dec8681b8_img.jpg) + +Peak-peak wander amplitude ( $\mu\text{s}$ ) (Log scale) + +Wander frequency (Hz) (Log scale) + +G.812\_F5 + +Figure 5/G.812 – Lower limit of maximum tolerable sinusoidal input wander. A log-log plot showing peak-peak wander amplitude (μs) versus wander frequency (Hz). The plot includes a solid line for Type I and a dashed line for Types II, III. The Type I line has segments at 5 μs, 2 μs, and 0.75 μs. The Types II, III line has segments at 1 μs and 0.3 μs. Frequency markers include 10 μ, 12 μ, 31.8 μ, 0.1 m, 0.32 m, 0.8 m, 1.43 m, 10 m, 16 m, 43 m, 0.1, 1, and 10 Hz. A '1 m' marker is also present. + +**Figure 5/G.812 – Lower limit of maximum tolerable sinusoidal input wander** + +## 9.2 Jitter tolerance + +#### 9.2.1 Jitter tolerance at 2048 kHz and 2048 kbit/s interfaces + +The lower limit of maximum tolerable sinusoidal input jitter for a Type I node clock is given in Table 15 and Figure 6 for both 2048 kHz and 2048 kbit/s input ports. + +**Table 15/G.812 – Lower limit of maximum tolerable sinusoidal input jitter for Type I node clock** + +| Peak-peak jitter amplitude (ns) | Frequency $f$ (Hz) | +|---------------------------------|--------------------------| +| 750 | $1 < f \leq 2400$ | +| $1.8 \times 10^6 f^{-1}$ | $2400 < f \leq 18\,000$ | +| 100 | $18\,000 < f < 100\,000$ | + +![Figure 6/G.812: Lower limit of maximum tolerable sinusoidal input jitter for Type I node clocks. The graph shows peak-peak jitter amplitude (ns) on a log scale (100 to 1 K) versus jitter frequency (Hz) on a log scale (1 to 100 K). The curve is constant at 750 ns from 10 Hz to 2.4 K Hz, then decreases linearly to 100 ns at 18 K Hz, and remains constant at 100 ns up to 100 K Hz. The region between 10 Hz and 100 Hz is labeled 'Type I'.](b2d16e07bfa79d67a8adabf7e26c7764_img.jpg) + +| Jitter frequency (Hz) | Peak-peak jitter amplitude (ns) | +|-----------------------|---------------------------------| +| 10 | 750 | +| 2.4 K | 750 | +| 18 K | 100 | +| 100 K | 100 | + +Figure 6/G.812: Lower limit of maximum tolerable sinusoidal input jitter for Type I node clocks. The graph shows peak-peak jitter amplitude (ns) on a log scale (100 to 1 K) versus jitter frequency (Hz) on a log scale (1 to 100 K). The curve is constant at 750 ns from 10 Hz to 2.4 K Hz, then decreases linearly to 100 ns at 18 K Hz, and remains constant at 100 ns up to 100 K Hz. The region between 10 Hz and 100 Hz is labeled 'Type I'. + +**Figure 6/G.812 – Lower limit of maximum tolerable sinusoidal input jitter for Type I node clocks** + +#### 9.2.2 Jitter tolerance at a 1544 kbit/s interface + +The lower limit of maximum tolerable sinusoidal input jitter for Types II and III node clocks is given in Table 16 and Figure 7 for 1544 kbit/s input ports. + +**Table 16/G.812 – Lower limit of maximum tolerable sinusoidal input jitter for Types II and III node clocks** + +| Peak-peak jitter amplitude (UI) | Frequency f (Hz) | +|---------------------------------|-------------------------| +| 5 | $10 < f \leq 500$ | +| $5 \times [500/f]^{1.411}$ | $500 < f \leq 8000$ | +| 0.1 | $8000 < f \leq 40\,000$ | + +![Figure 7/G.812: Lower limit of maximum tolerable sinusoidal input jitter for Types II and III node clocks. The graph shows peak-peak jitter amplitude (UI) on a logarithmic y-axis (0.01 to 10) versus jitter frequency f (Hz) on a logarithmic x-axis (1 to 100 K). The curve for Types II and III is constant at 5 UI from 10 Hz to 500 Hz, then decreases with a slope of -20 dB/decade until it reaches 0.1 UI at 10 KHz, where it remains constant up to 40 KHz.](3102c32204f998dba666e1e915d5babf_img.jpg) + +| Jitter frequency f (Hz) | Peak-peak jitter amplitude (UI) | +|-------------------------|---------------------------------| +| 10 | 5 | +| 500 | 5 | +| 10,000 | 0.1 | +| 40,000 | 0.1 | + +Figure 7/G.812: Lower limit of maximum tolerable sinusoidal input jitter for Types II and III node clocks. The graph shows peak-peak jitter amplitude (UI) on a logarithmic y-axis (0.01 to 10) versus jitter frequency f (Hz) on a logarithmic x-axis (1 to 100 K). The curve for Types II and III is constant at 5 UI from 10 Hz to 500 Hz, then decreases with a slope of -20 dB/decade until it reaches 0.1 UI at 10 KHz, where it remains constant up to 40 KHz. + +**Figure 7/G.812 – Lower limit of maximum tolerable sinusoidal input jitter for Types II and III node clocks** + +### 9.2.3 Jitter tolerance at an STM-N interface + +Jitter tolerance for STM-N interfaces is given in ITU-T Rec. G.825. + +# 10 Noise transfer + +The transfer characteristic of a slave clock determines its properties with regard to the transfer of excursions of the input phase relative to the phase modulation. Noise transfer can be described in two ways: + +- a) The slave clock can be viewed as a low-pass filter for the differences between the actual input phase and the ideal input phase of the reference. The maximum allowed bandwidth for this low-pass filter behaviour is defined in Table 17 below, along with the maximum allowed gain in the passband. + +**Table 17/G.812 – Noise transfer requirements** + +| | Type I | Type II | Type III | +|-------------------------|--------|---------|----------| +| Maximum bandwidth (mHz) | 3 | 1 | 1 | +| Maximum gain (dB) | 0.2 | 0.2 | 0.2 | + +The above applies to a linear G.812 clock model. However, this model should not restrict implementations. + +- b) Noise transfer describes the amount of noise observed at the output, as a result of noise introduced at the input of the clock. The slave clock, when subjected to a wideband noise signal shaped as described in 9.1 (i.e., the TDEV input tolerance specification) shall produce an output signal lying below the limit specified in Table 18 for Type I node clocks and in Table 19 for Types II and III node clocks. The resultant requirements are shown in Figure 8. These masks should not be used to verify phase gain peaking. + +**Table 18/G.812 – Output wander mask (TDEV) +for Type I node clock** + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|-------------------|---------------------------------| +| 3 | $0.1 < \tau \leq 13.1$ | +| $0.017 6 \tau^2$ | $13.1 < \tau \leq 100$ | +| 176 | $100 < \tau \leq 1000$ | +| $5.58 \tau^{0.5}$ | $1000 < \tau \leq 10\,000$ | + +NOTE – The values in Table 18 include the effects of gain peaking and intrinsic noise. + +**Table 19/G.812 – Output wander mask (TDEV) +for Types II and III node clocks** + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|-------------------|---------------------------------| +| $3.2 \tau^{-0.5}$ | $0.1 < \tau \leq 1.44$ | +| $1.86 \tau$ | $1.44 < \tau \leq 300$ | +| $32.2 \tau^{0.5}$ | $300 < \tau \leq 1000$ | + +![Figure 8/G.812 – Output wander mask (TDEV) graph. The Y-axis is TDEV (ns) on a log scale from 1 to 1000. The X-axis is Observation interval tau (s) on a log scale from 0.01 to 10,000. The graph shows two masks: Type I (solid line) and Types II, III (dashed line). Type I mask is constant at 3 ns from 0.1 s to 13.1 s, then increases linearly to 176 ns at 100 s, remains constant at 176 ns until 1000 s, and then increases linearly to 558 ns at 10,000 s. Types II, III mask starts at 10 ns at 0.1 s, decreases to 2.67 ns at 1.44 s, increases linearly to 10 ns at 10 s, increases linearly to 176 ns at 100 s, increases linearly to 558 ns at 1000 s, and continues to increase linearly to 1000 ns at 10,000 s.](723827e0738d2743c3b3423760a5c48e_img.jpg) + +Figure 8/G.812 – Output wander mask (TDEV) graph. The Y-axis is TDEV (ns) on a log scale from 1 to 1000. The X-axis is Observation interval tau (s) on a log scale from 0.01 to 10,000. The graph shows two masks: Type I (solid line) and Types II, III (dashed line). Type I mask is constant at 3 ns from 0.1 s to 13.1 s, then increases linearly to 176 ns at 100 s, remains constant at 176 ns until 1000 s, and then increases linearly to 558 ns at 10,000 s. Types II, III mask starts at 10 ns at 0.1 s, decreases to 2.67 ns at 1.44 s, increases linearly to 10 ns at 10 s, increases linearly to 176 ns at 100 s, increases linearly to 558 ns at 1000 s, and continues to increase linearly to 1000 ns at 10,000 s. + +**Figure 8/G.812 – Output wander mask (TDEV)** + +Guidance on the measurement techniques for these requirements is given in Appendix II. + +MTIE and TDEV are measured through an equivalent 10 Hz, first-order, low-pass measurement filter, at a maximum sampling time $\tau_0$ of 1/30 second. The minimum measurement period for TDEV is twelve times the integration period ( $T = 12 \tau$ ). + +# 11 Transient response and hold-over performance + +The requirements in this clause apply to situations where the input signal is affected by disturbances or transmission failures (e.g., short interruptions, switching between different synchronization signals, loss of reference, etc.) that result in phase transients at the G.812 output (see clause 12). The ability to withstand disturbances is necessary to avoid transmission defects or failures. Transmission failures and disturbances are common stress conditions in the transmission environment. + +To ensure transmission integrity, it is recommended that all the phase movements at the output of the G.812 clock stay within the level described in the following subclauses. + +## 11.1 Short-term phase transient response + +This requirement reflects the performance of the clock in cases when the (selected) input reference is lost due to a failure in the reference path and a second reference input signal, traceable to the same reference clock, is available simultaneously or shortly after the detection of the failure (e.g., in cases of autonomous restoration). + +The output jitter limit in 8.3 should be met. + +### 11.1.1 Transient for Type I node clocks (2048 kHz and 2048 kbit/s interfaces) + +The MTIE of the phase error should not exceed the limits given in Table 20 and illustrated by the dashed curve in Figure 9. + +**Table 20/G.812 – Transient for Type I node clocks +(2048 kHz and 2048 kbit/s interfaces)** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|-------------------|---------------------------------| +| 25 | $0.001 < \tau \leq 0.003\ 3$ | +| $7500\ \tau$ | $0.003\ 3 < \tau \leq 0.016$ | +| $120 + 0.5\ \tau$ | $0.016 < \tau \leq 240$ | +| 240 | $240 < \tau \leq 1000$ | + +### 11.1.2 Transient for Type I node clocks (STM-N interfaces) + +The MTIE of the phase error should not exceed the limits given in Table 21 and illustrated by the solid curve in Figure 9. + +**Table 21/G.812 – Transient for Type I node clocks +(STM-N interfaces)** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|-------------------|---------------------------------| +| $7500\ \tau$ | $0.001 < \tau \leq 0.016$ | +| $120 + 0.5\ \tau$ | $0.016 < \tau \leq 240$ | +| 240 | $240 < \tau \leq 10\ 000$ | + +### 11.1.3 Transient for Types II and III node clocks (1544 kbit/s interfaces) + +The MTIE of the phase error should not exceed the limits given in Table 22 and illustrated by the dashed curve in Figure 9. + +**Table 22/G.812 – Transient for Types II and III node clocks +(1544 kbit/s interfaces)** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|-----------------|---------------------------------| +| $40 + 885 \tau$ | $0.014 < \tau \leq 0.16$ | +| 182 | $0.16 < \tau \leq 280$ | + +### 11.1.4 Transient for Types II and III node clocks (STM-N interfaces) + +The MTIE of the phase error should not exceed the limits given in Table 23 and illustrated by the solid curve in Figure 9. + +**Table 23/G.812 – Transient for Types II and III node clocks +(STM-N interfaces)** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|------------------|---------------------------------| +| $7.6 + 885 \tau$ | $0.014 < \tau \leq 0.16$ | +| 150 | $0.16 < \tau \leq 280$ | + +![Figure 9/G.812 – Short-term phase transient mask (MTIE). A log-log plot showing MTIE (ns) on the y-axis (1 to 1000) versus Observation interval tau (s) on the x-axis (1 m to 10 K). Four curves are shown: Type I at 2048 kHz and 2048 kbit/s (dashed line), Type I at STM-N (solid line), Types II and III at 1544 kbit/s (dotted line), and Types II and III at STM-N (solid line). The STM-N curves are lower than the 1544 kbit/s curves. The plot includes grid lines and labels for specific intervals like 16 m, 14 m, 280, and 240.](65a9654ccb3d0d452378b0f4c0c392f7_img.jpg) + +Legend: + +- Type I at 2048 kHz and 2048 kbit/s +- Type I at STM-N +- ... Types II and III at 1544 kbit/s +- Types II and III at STM-N + +Figure 9/G.812 – Short-term phase transient mask (MTIE). A log-log plot showing MTIE (ns) on the y-axis (1 to 1000) versus Observation interval tau (s) on the x-axis (1 m to 10 K). Four curves are shown: Type I at 2048 kHz and 2048 kbit/s (dashed line), Type I at STM-N (solid line), Types II and III at 1544 kbit/s (dotted line), and Types II and III at STM-N (solid line). The STM-N curves are lower than the 1544 kbit/s curves. The plot includes grid lines and labels for specific intervals like 16 m, 14 m, 280, and 240. + +**Figure 9/G.812 – Short-term phase transient mask (MTIE)** + +## 11.2 Long-term phase transient response (hold-over) + +When a G.812 clock loses all its references, it enters the hold-over state. This requirement bounds the maximum excursions in the output timing signal. Additionally, it restricts the accumulation of the phase movement during input signal impairments or internal disturbances. + +### 11.2.1 Clock Types I and III + +The Phase Error, $\Delta x$ , at the output of the slave clock from the moment of loss of reference should, over any period of $S$ seconds, meet the following: + +$$|\Delta x(S)| \leq \{(a_1 + a_2)S + 0.5 b S^2 + c\} \text{ [ns]}$$ + +The derivative of $\Delta x(S)$ , the fractional frequency offset, should, over any period of $S$ seconds, meet the following: + +$$|d(\Delta x(S))/dS| \leq \{a_1 + a_2 + bS\} \text{ [ns/s]}$$ + +The second derivative of $\Delta x(S)$ , the fractional frequency drift, should, over any period of $S$ seconds, meet the following: + +$$|d^2(\Delta x(S))/dS^2| \leq d \text{ [ns/s}^2\text{]}$$ + +In applying the above requirements for the derivative of $\Delta x(S)$ and the second derivative of $\Delta x(S)$ , the period $S$ must begin after any transient associated with entry into hold-over is over. During this transient period, the transient requirements of 11.1 apply. + +NOTE 1 – $a_1$ represents an initial frequency offset under constant temperature conditions ( $\pm 1$ K). + +NOTE 2 – $a_2$ accounts for temperature variations after the clock went into hold-over. If there are no temperature variations, the term $a_2 S$ should not contribute to the phase error. + +NOTE 3 – $b$ represents the average frequency drift caused by aging. This value is derived from typical aging characteristics after 60 days of continuous operation. It is not intended to measure this value on a per day basis, as the temperature effect will dominate. + +NOTE 4 – The phase offset $c$ takes care of any additional phase shift that may arise during the transition at the entry of the hold-over state. + +NOTE 5 – $d$ represents the maximum temporary frequency drift rate at constant temperature allowed during hold-over. However, it is not required that $d$ and $b$ be equal. + +The permissible phase error specifications for different G.812 clock Types are shown in Table 24. + +**Table 24/G.812 – Transient response specifications during hold-over** + +| | Type I | Type III | +|--------------------------|----------------------|-----------------------| +| $a_1$ (ns/s) | 0.5 | 1.0 | +| $a_2$ (ns/s) | 2 | 10 | +| $b$ (ns/s 2 ) | $2.3 \times 10^{-6}$ | $1.16 \times 10^{-5}$ | +| $c$ (ns) | 60 | 150 | +| $d$ (ns/s 2 ) | NA | $1.16 \times 10^{-5}$ | +| NA Not applicable | | | + +During the transition at the entry of hold-over state, the temporary frequency offset on SDH output interfaces of Type I node clocks should not exceed 7.5 ppm. + +### 11.2.2 Clock Type II + +The derivative of the phase $\Delta x(S)$ , the fractional frequency offset, should, over any period of S seconds, meet the following: + +$$|d(\Delta x(S))/dS| \leq Y(S)$$ + +where $Y(S)$ is the maximum fractional frequency offset as given in Table 25 and shown in Figure 10 below. $Y(S)$ begins 5000 s after entry into hold-over, i.e., $Y(S)$ is not defined for S less than 5000 s, to ensure that any transient associated with entry into hold-over is over. During the first 5000 s, the transient requirements of 11.1 (Table 22 and Figure 9) apply. + +**Table 25/G.812 – Maximum fractional frequency offset $Y(S)$ for Type II hold-over** + +| Maximum fractional frequency offset $Y(S)$ (ns/s) | Time S (s) | +|---------------------------------------------------|---------------------------------------------| +| ND | $0 < S \leq 5000$ | +| 0.1 | $5000 < S \leq 86\,400$ | +| $1.16 \times 10^{-6} S$ | $86\,400 < S \leq 1.38 \times 10^7$ | +| 16 | $1.38 \times 10^7 < S \leq 3.2 \times 10^7$ | +| ND | Not defined | + +![Figure 10/G.812 – Maximum fractional frequency offset Y(S) for Type II hold-over. This is a log-log plot showing the maximum fractional frequency offset Y(S) in ns/s on the y-axis against time S in seconds on the x-axis. The y-axis has major ticks at 0.1, 1, 10, 16, and 100. The x-axis has major ticks at 10^3, 10^4, 10^5, 10^6, 10^7, and 10^8, with specific labels at 5 x 10^3, 8.64 x 10^4, 1.38 x 10^7, and 3.2 x 10^7. The plot shows a piecewise linear function: it is constant at 0.1 ns/s from 5 x 10^3 s to 8.64 x 10^4 s, then increases linearly on the log-log scale to 16 ns/s at 1.38 x 10^7 s, and remains constant at 16 ns/s until 3.2 x 10^7 s.](0245dc88c1db93181871e732bc0655dd_img.jpg) + +Figure 10/G.812 – Maximum fractional frequency offset Y(S) for Type II hold-over. This is a log-log plot showing the maximum fractional frequency offset Y(S) in ns/s on the y-axis against time S in seconds on the x-axis. The y-axis has major ticks at 0.1, 1, 10, 16, and 100. The x-axis has major ticks at 10^3, 10^4, 10^5, 10^6, 10^7, and 10^8, with specific labels at 5 x 10^3, 8.64 x 10^4, 1.38 x 10^7, and 3.2 x 10^7. The plot shows a piecewise linear function: it is constant at 0.1 ns/s from 5 x 10^3 s to 8.64 x 10^4 s, then increases linearly on the log-log scale to 16 ns/s at 1.38 x 10^7 s, and remains constant at 16 ns/s until 3.2 x 10^7 s. + +**Figure 10/G.812 – Maximum fractional frequency offset $Y(S)$ for Type II hold-over** + +## 11.3 Phase response to input signal interruptions + +For short-term interruptions on synchronization input signals, that do not cause reference switching, the output phase variation is for further study. + +## 11.4 Phase discontinuity + +In cases of infrequent internal testing or rearrangement operations within the slave clock, the phase transient at the output of G.812 clocks should meet the MTIE specifications in Table 26 for Type I node clock and Table 27 for Types II and III node clocks. + +**Table 26/G.812 – Output phase transient (MTIE) for Type I node clock** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|-----------------|---------------------------------| +| 60 | $\tau \leq 0.001$ | +| 120 | $0.001 < \tau \leq 4$ | +| 240 | $\tau > 4$ | + +In case the G.812 Type I clock is built-in into an SDH equipment, the temporary frequency offset at any STM-N output interface should never exceed 7.5 ppm. + +**Table 27/G.812 – Output phase transient (MTIE) for Types II and III node clocks** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|-----------------|----------------------------------| +| $61\,000 \tau$ | $0.001\,33 < \tau \leq 0.016\,4$ | +| 1000 | $0.016\,4 < \tau$ | + +The resultant requirements are shown in Figure 11. + +![Figure 11/G.812 – Output phase transient requirements (MTIE). A log-log plot showing MTIE (ns) on the y-axis (1 to 10,000) versus Observation interval τ (s) on the x-axis (1 ms to 1,000 s). Two curves are shown: Type I (solid line) and Types II, III (dashed line). Type I has limits of 60 ns for τ ≤ 1 ms, 120 ns for 1 ms < τ ≤ 4 s, and 240 ns for τ > 4 s. Types II, III have a limit of 61,000 τ ns for 1.33 ms < τ ≤ 16.4 ms, and 1,000 ns for τ > 16.4 ms.](cdba53bb2fb4d459f37515ee7fab3418_img.jpg) + +Figure 11 is a log-log plot showing the MTIE (ns) on the y-axis (ranging from 1 to 10,000) versus the Observation interval $\tau$ (s) on the x-axis (ranging from 1 ms to 1,000 s). The plot illustrates the MTIE requirements for Type I and Types II, III node clocks. The Type I curve (solid line) shows a step function with limits of 60 ns for $\tau \leq 1$ ms, 120 ns for $1$ ms $< \tau \leq 4$ s, and 240 ns for $\tau > 4$ s. The Types II, III curve (dashed line) shows a step function with limits of $61\,000 \tau$ ns for $1.33$ ms $< \tau \leq 16.4$ ms, and 1,000 ns for $\tau > 16.4$ ms. The x-axis also includes markers for 1.33 ms, 16.4 ms, and 4 s. + +Figure 11/G.812 – Output phase transient requirements (MTIE). A log-log plot showing MTIE (ns) on the y-axis (1 to 10,000) versus Observation interval τ (s) on the x-axis (1 ms to 1,000 s). Two curves are shown: Type I (solid line) and Types II, III (dashed line). Type I has limits of 60 ns for τ ≤ 1 ms, 120 ns for 1 ms < τ ≤ 4 s, and 240 ns for τ > 4 s. Types II, III have a limit of 61,000 τ ns for 1.33 ms < τ ≤ 16.4 ms, and 1,000 ns for τ > 16.4 ms. + +**Figure 11/G.812 – Output phase transient requirements (MTIE)** + +# 12 Interfaces + +The requirements in this Recommendation are related to reference points internal to the Network Elements (NEs) in which the clock is embedded and are therefore not necessarily available for measurement or analysis by the user. Therefore the performance of the G.812 clock is not defined at these internal reference points, but rather at the external interfaces of the equipment. The external input and output are: + +- 1544 kbit/s interfaces according to ITU-T Rec. G.703. +- 2048 kHz external interfaces according to ITU-T Rec. G.703. +- 2048 kbit/s interfaces according to ITU-T Rec. G.703. +- STM-N traffic interfaces according to ITU-T Recs G.703 and G.957. + +Note that all of the above interfaces may not be implemented on all equipment. These interfaces should comply with the additional jitter and wander requirements as defined in this Recommendation. + +# Annex A + +## Specifications for Types IV, V and VI clocks + +The Type V clock is the transit node clock from the 1988 version of this Recommendation; the Type VI clock is the local node clock from the 1988 version of this Recommendation. + +### A.1 Frequency accuracy + +Under prolonged hold-over conditions, the output frequency accuracy of the different Types of node clocks should not exceed the values in Table A.1 with regard to a reference traceable to a primary reference clock, over a time period T as reported in the same Table. + +**Table A.1/G.812 – Output frequency accuracy requirements** + +| | Type IV | Type V | Type VI | +|-----------------------------------------------------------------------------------------------------------|----------------------|--------|---------| +| Accuracy | $4.6 \times 10^{-6}$ | NA | NA | +| Period T | 1 year | NA | NA | +| NA Not applicable
NOTE – The time period T applies after 30 days of continuous synchronized operation. | | | | + +### A.2 Pull-in, hold-in and pull-out ranges + +The minimum pull-in, hold-in and pull-out ranges for the different Types of node clocks should be according to Table A.2, whatever the internal oscillator frequency offset may be. + +**Table A.2/G.812 – Pull-in, hold-in, and pull-out requirements** + +| | Type IV | Type V | Type VI | +|-------------------|----------------------|--------|---------| +| Pull-in | $4.6 \times 10^{-6}$ | ND | ND | +| Hold-in | $4.6 \times 10^{-6}$ | ND | ND | +| Pull-out | NA | ND | ND | +| NA Not applicable | | | | +| ND Not defined | | | | + +### A.3 Noise generation + +The noise generation of a slave clock represents the amount of phase noise produced at the output when there is an ideal input reference signal or the clock is in hold-over state (see A.6.2). A suitable reference, for practical testing purposes, implies a performance level at least 10 times more stable than the output requirements. The ability of the clock to limit this noise is described by its frequency stability. The measures MTIE and Time Deviation (TDEV) are useful for characterization of noise generation performance. + +MTIE and TDEV are measured through an equivalent 10 Hz, first-order, low-pass measurement filter, at a maximum sampling time $\tau_0$ of 1/30 second. The minimum measurement period for TDEV is twelve times the integration period ( $T = 12 \tau$ ). + +#### A.3.1 Wander in locked mode + +When the slave clock is in the locked mode of operation, the MTIE at constant temperature (within $\pm 1$ K) measured using the synchronized clock configuration defined in Figure 1-a/G.810 should have the limits given in Tables A.3 and A.4 for the different Types of node clocks. + +**Table A.3/G.812 – Wander generation (MTIE) for Type IV node clock at constant temperature (within $\pm 1$ K)** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|------------------------|---------------------------------| +| 40 | $0.1 < \tau \leq 1$ | +| $40 \times \tau^{0.4}$ | $1 < \tau \leq 10$ | +| 100 | $\tau > 10$ | + +**Table A.4/G.812 – Wander generation (MTIE) for Types V and VI node clocks at constant temperature (within $\pm 1$ K)** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|-----------------------|---------------------------------| +| FFS | $0.05 < \tau \leq 100$ | +| 1000 | $\tau > 100$ | +| FFS For further study | | + +The resultant requirements are shown in Figure A.1. + +![Figure A.1/G.812: Wander generation (MTIE) at constant temperature (within ±1 K). The graph shows MTIE (ns) on a log scale (10 to 10 K) versus Observation interval τ (s) on a log scale (0.1 to 10 K). Two curves are shown: Type IV (solid line) and Types V, VI (dashed line). Type IV starts at 40 ns for τ = 0.1 s, increases to 100 ns at τ = 10 s, and remains constant at 100 ns for τ > 10 s. Types V, VI start at 1 K ns for τ = 100 s and remain constant at 1 K ns for τ > 100 s.](920eeb131e71a5b81535239f1c838c68_img.jpg) + +Figure A.1/G.812: Wander generation (MTIE) at constant temperature (within ±1 K). The graph shows MTIE (ns) on a log scale (10 to 10 K) versus Observation interval τ (s) on a log scale (0.1 to 10 K). Two curves are shown: Type IV (solid line) and Types V, VI (dashed line). Type IV starts at 40 ns for τ = 0.1 s, increases to 100 ns at τ = 10 s, and remains constant at 100 ns for τ > 10 s. Types V, VI start at 1 K ns for τ = 100 s and remain constant at 1 K ns for τ > 100 s. + +**Figure A.1/G.812 – Wander generation (MTIE) at constant temperature (within $\pm 1$ K)** + +When the node clock is in the locked mode of operation, the TDEV at constant temperature (within $\pm 1$ K) measured using the synchronized clock configuration defined in Figure 1-a/G.810 should have the limits given in Tables A.5 and A.6 for the different Types of node clock. + +**Table A.5/G.812 – Wander generation (TDEV) for Type IV node clock at constant temperature (within $\pm 1$ K)** + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|-------------------|---------------------------------| +| $3.2 \tau^{-0.5}$ | $0.1 < \tau \leq 2.5$ | +| 2 | $2.5 < \tau \leq 40$ | +| $0.32 \tau^{0.5}$ | $40 < \tau \leq 1000$ | +| 10 | $\tau > 1000$ | + +**Table A.6/G.812 – Wander generation (TDEV) for Types V and VI node clocks at constant temperature (within $\pm 1$ K)** + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|-----------------------|---------------------------------| +| FFS | $0.1 < \tau < 10\,000$ | +| FFS For further study | | + +The resultant requirements are shown in Figure A.2. + +![Figure A.2/G.812 – Wander generation (TDEV) for constant temperature. A log-log plot showing TDEV (ns) on the y-axis versus Observation interval τ (s) on the x-axis. The curve for Type IV shows a decrease from 10 ns at 0.1 s to 2 ns at 2.5 s, a constant value of 2 ns until 40 s, and then an increase to 10 ns at 1 K, remaining constant at 10 ns up to 10 K.](19f5ea8afbf380781eb0645831a88987_img.jpg) + +| Observation interval $\tau$ (s) | TDEV (ns) | +|---------------------------------|-----------| +| 0.1 | 10 | +| 2.5 | 2 | +| 40 | 2 | +| 1 K | 10 | +| 10 K | 10 | + +Figure A.2/G.812 – Wander generation (TDEV) for constant temperature. A log-log plot showing TDEV (ns) on the y-axis versus Observation interval τ (s) on the x-axis. The curve for Type IV shows a decrease from 10 ns at 0.1 s to 2 ns at 2.5 s, a constant value of 2 ns until 40 s, and then an increase to 10 ns at 1 K, remaining constant at 10 ns up to 10 K. + +Figure A.2/G.812 – Wander generation (TDEV) for constant temperature + +#### A.3.2 Non-locked wander + +When a clock is not locked to a synchronization reference, the random noise components are negligible compared to deterministic effects like initial frequency offset. Consequently the non-locked wander effects are included in A.6.2. + +#### A.3.3 Jitter + +While most requirements in this Recommendation are independent of the output interface at which they are measured, this is not the case for jitter production; jitter generation requirements utilize existing Recommendations that have different limits for different interface rates. These requirements are stated separately for the interfaces identified in A.7. To be consistent with other jitter requirements, the values are in UI peak-peak, where the UI corresponds to the reciprocal of the bit rate of the interface. + +Note that all filter values specified in this generation clause for STM-N interfaces have been harmonized with the filter values for the network limit as specified in ITU-T Rec. G.825. + +NOTE – Due to the stochastic nature of jitter, the peak-peak values given in this clause eventually are exceeded. The requirements should therefore be fulfilled in at least 99% of all measurements made. + +##### A.3.3.1 Output jitter at 2048 kHz and 2048 kbit/s interfaces + +In the absence of input jitter, the intrinsic jitter at 2048 kHz and 2048 kbit/s output interfaces as measured over a 60-second interval should not exceed 0.05 UI peak-peak when measured through a single pole band-pass filter with corner frequencies at 20 Hz and 100 kHz. + +##### A.3.3.2 Output jitter at a 1544 kbit/s interface + +In the absence of input jitter, the intrinsic jitter at a 1544 kbit/s output interface should not exceed 0.05 UI peak-peak when measured through a single pole band-pass filter with corner frequencies at 10 Hz and 40 kHz (the measurement interval is for further study). + +##### A.3.3.3 Output jitter at an STM-N interface + +In the absence of input jitter at the synchronization interface, the intrinsic jitter at optical STM-N output interfaces as measured over a 60-second interval should not exceed the limits given in Table A.7 below. The allowed jitter on an STM-1 electrical (CMI) interface is also given in Table A.7 below. + +The measurement filter roll-off at the lower cut-off frequency shall be 20 dB/decade and the roll-off at the upper cut-off frequency shall be 60 dB/decade. The characteristic of the upper cut-off filter roll-off is for further study. + +**Table A.7/G.812 – STM-N jitter generation** + +| Interface | Measuring filter
(-3 dB frequencies) | Peak-peak amplitude
(UI) | +|-----------------------------------------------------------------------------------------|-----------------------------------------|-----------------------------| +| STM-1 electrical | 500 Hz to 1.3 MHz | 0.50 | +| | 65 kHz to 1.3 MHz | 0.075 | +| STM-1 optical | 500 Hz to 1.3 MHz | 0.50 | +| | 65 kHz to 1.3 MHz | 0.10 | +| STM-4 | 1000 Hz to 5 MHz | 0.50 | +| | 250 kHz to 5 MHz | 0.10 | +| STM-16 | 5000 Hz to 20 MHz | 0.50 | +| | 1 MHz to 20 MHz | 0.10 | +| For STM-1: 1 UI = 6.43 ns.
For STM-4: 1 UI = 1.61 ns.
For STM-16: 1 UI = 0.40 ns. | | | + +### A.4 Noise tolerance + +The noise tolerance of a G.812 clock indicates the lower limit of the maximum phase noise level at the input of the clock that should be accommodated while: + +- Maintaining the clock within prescribed performance limits. The exact performance limits are for further study. +- Not causing any alarms. +- Not causing the clock to switch reference. +- Not causing the clock to go into hold-over. + +In general, the noise tolerance of a G.812 clock is the same as the network limit for the synchronization interface in order to maintain acceptable performance. However, the synchronization interface network limit may be different according to the application. Therefore, in order to determine the slave clock noise tolerance, the worst-case network limit should be used. An explanation of the different network limits for acceptable payload performance is given in Appendix I/G.813 for information. + +The wander and jitter tolerances given in A.4.1 and A.4.2 represent the worst levels that a synchronization carrying interface should exhibit. The TDEV signal used for a conformance test should be generated by adding white, gaussian noise sources, each of which has been filtered to obtain the proper type of noise process with the proper amplitude. Guidance is provided in Appendix II. + +MTIE and TDEV are measured through an equivalent 10 Hz, first-order, low-pass measurement filter, at a maximum sampling time $\tau_0$ of 1/30 second. The minimum measurement period for TDEV is twelve times the integration period ( $T = 12 \tau$ ). + +#### A.4.1 Wander tolerance + +The G.812 clock input wander tolerance expressed as an MTIE limit is given in Table A.8 for Type IV node clocks. + +**Table A.8/G.812 – Input wander tolerance (MTIE) for Type IV node clocks** + +| MTIE limit ( $\mu\text{s}$ ) | Observation interval $\tau$ (s) | +|------------------------------|---------------------------------| +| $0.3 + 0.002 5 \tau$ | $0.05 < \tau \leq 280$ | +| $0.997 + 0.000 01 \tau$ | $\tau > 280$ | + +The resultant requirement is shown in Figure A.3. + +![Figure A.3/G.812 – Input wander tolerance (MTIE) for Type IV node clocks. This is a log-log plot showing the MTIE limit in microseconds versus the observation interval in seconds. The y-axis (MTIE (μs) (Log scale)) ranges from 0.1 to 100. The x-axis (Observation interval τ (s) (Log scale)) ranges from 0.01 to 10,000. The curve starts at 0.3 μs for τ = 0.05 s, rises slightly to about 0.4 μs at τ = 100 s, then rises sharply to 1 μs at τ = 280 s, and remains constant at 1 μs for τ > 280 s. The label 'Type IV' is placed near the horizontal part of the curve.](a01a138884c0b7c6e4c5a0a8cd5a41ce_img.jpg) + +Figure A.3/G.812 – Input wander tolerance (MTIE) for Type IV node clocks. This is a log-log plot showing the MTIE limit in microseconds versus the observation interval in seconds. The y-axis (MTIE (μs) (Log scale)) ranges from 0.1 to 100. The x-axis (Observation interval τ (s) (Log scale)) ranges from 0.01 to 10,000. The curve starts at 0.3 μs for τ = 0.05 s, rises slightly to about 0.4 μs at τ = 100 s, then rises sharply to 1 μs at τ = 280 s, and remains constant at 1 μs for τ > 280 s. The label 'Type IV' is placed near the horizontal part of the curve. + +**Figure A.3/G.812 – Input wander tolerance (MTIE) for Type IV node clocks** + +Input wander tolerance in terms of MTIE for Types V and VI is not defined. + +The G.812 clock input wander tolerance expressed as a TDEV limit is given in Table A.9 for Type IV node clocks. + +**Table A.9/G.812 – Input wander tolerance (TDEV) for Type IV node clocks** + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|-----------------------|---------------------------------| +| FFS | $\tau \leq 0.05$ | +| 100 | $0.05 < \tau \leq 10$ | +| $31.6 \tau^{0.5}$ | $10 < \tau \leq 1000$ | +| FFS | $\tau > 1000$ | +| FFS For further study | | + +The resultant requirements are also shown in Figure A.4. + +![Figure A.4/G.812 – Input wander tolerance for Type IV node clocks (TDEV). This is a log-log plot showing TDEV (ns) on the y-axis versus Observation interval tau (s) on the x-axis. The y-axis ranges from 10 to 10,000 ns, and the x-axis ranges from 0.01 to 10,000 s. The plot shows a horizontal line at 100 ns for observation intervals between 0.05 s and 10 s, labeled 'Type IV'. For intervals between 10 s and 1,000 s, the tolerance increases linearly on the log-log scale, following the formula 31.6 * tau^0.5. For intervals below 0.05 s and above 1,000 s, the tolerance is 'FFS' (For Further Study).](051638d871c75230edb3d005fa668810_img.jpg) + +Figure A.4/G.812 – Input wander tolerance for Type IV node clocks (TDEV). This is a log-log plot showing TDEV (ns) on the y-axis versus Observation interval tau (s) on the x-axis. The y-axis ranges from 10 to 10,000 ns, and the x-axis ranges from 0.01 to 10,000 s. The plot shows a horizontal line at 100 ns for observation intervals between 0.05 s and 10 s, labeled 'Type IV'. For intervals between 10 s and 1,000 s, the tolerance increases linearly on the log-log scale, following the formula 31.6 \* tau^0.5. For intervals below 0.05 s and above 1,000 s, the tolerance is 'FFS' (For Further Study). + +**Figure A.4/G.812 – Input wander tolerance for Type IV node clocks (TDEV)** + +Input wander tolerance in terms of TDEV for Types V and VI is not defined. + +While suitable test signals that check conformance to the mask in Figure A.3 are being studied, test signals with a sinusoidal phase variation can be used. The requirements for Type IV node clocks are shown in Table A.10. + +**Table A.10/G.812 – Lower limit of maximum tolerable sinusoidal input wander for Type IV node clocks** + +| Peak-peak wander amplitude ( $\mu\text{s}$ ) | Frequency $f$ (Hz) | +|----------------------------------------------|------------------------------------| +| $0.997 + [4 \times 10^{-6}/f]$ | $0.000\,031\,8 < f \leq 0.001\,43$ | +| $0.3 + [0.001/f]$ | $0.001\,43 < f \leq 10$ | + +The resultant requirements are also shown in Figure A.5. + +![Figure A.5/G.812 – Lower limits of maximum tolerable sinusoidal input wander for Type IV node clocks. The graph shows peak-to-peak wander amplitude (μs) on a log scale (0.1 to 10) versus wander frequency (Hz) on a log scale (10⁻⁵ to 10¹). The curve for Type IV node clocks is constant at 1 μs from 10⁻⁵ Hz to 10⁻³ Hz, then decreases to approximately 0.3 μs at 10⁻² Hz, and remains constant at 0.3 μs from 10⁻¹ Hz to 10¹ Hz.](9ac04bd96ff7aa9e60639b5f5a63ed40_img.jpg) + +| Wander frequency (Hz) | Peak-to-peak wander amplitude (μs) | +|-----------------------|------------------------------------| +| $10^{-5}$ | 1 | +| $10^{-4}$ | 1 | +| $10^{-3}$ | 1 | +| $10^{-2}$ | 0.3 | +| $10^{-1}$ | 0.3 | +| $10^0$ | 0.3 | +| $10^1$ | 0.3 | + +Figure A.5/G.812 – Lower limits of maximum tolerable sinusoidal input wander for Type IV node clocks. The graph shows peak-to-peak wander amplitude (μs) on a log scale (0.1 to 10) versus wander frequency (Hz) on a log scale (10⁻⁵ to 10¹). The curve for Type IV node clocks is constant at 1 μs from 10⁻⁵ Hz to 10⁻³ Hz, then decreases to approximately 0.3 μs at 10⁻² Hz, and remains constant at 0.3 μs from 10⁻¹ Hz to 10¹ Hz. + +**Figure A.5/G.812 – Lower limits of maximum tolerable sinusoidal input wander for Type IV node clocks** + +Lower limits of maximum tolerable sinusoidal input wander for Types V and VI are not defined. + +#### A.4.2 Jitter tolerance + +The lower limit of maximum tolerable sinusoidal input jitter for a Type IV node clock is given in Table A.11 and Figure A.6, for 1544 kbit/s input ports. + +**Table A.11/G.812 – Lower limit of maximum tolerable sinusoidal input jitter for Type IV node clocks** + +| Peak-peak jitter amplitude (UI) | Frequency f (Hz) | +|---------------------------------|-------------------------| +| 5 | $10 < f \leq 500$ | +| $5 \times [500/f]^{1.411}$ | $500 < f \leq 8000$ | +| 0.1 | $8000 < f \leq 40\,000$ | + +![Figure A.6/G.812: Lower limits of maximum tolerable sinusoidal input jitter for Type IV node clocks. The graph plots Peak-to-peak jitter amplitude (UI) on a logarithmic y-axis (0.01 to 10) against Jitter frequency f (Hz) on a logarithmic x-axis (1 to 100 K). The curve for Type IV shows a constant 5 UI limit from 10 Hz to 100 Hz, then a 20 dB/decade roll-off until it reaches 0.1 UI at 10 K Hz, where it remains constant up to 100 K Hz.](24b549c0c4b79c515b244625cf4f4978_img.jpg) + +Figure A.6/G.812: Lower limits of maximum tolerable sinusoidal input jitter for Type IV node clocks. The graph plots Peak-to-peak jitter amplitude (UI) on a logarithmic y-axis (0.01 to 10) against Jitter frequency f (Hz) on a logarithmic x-axis (1 to 100 K). The curve for Type IV shows a constant 5 UI limit from 10 Hz to 100 Hz, then a 20 dB/decade roll-off until it reaches 0.1 UI at 10 K Hz, where it remains constant up to 100 K Hz. + +**Figure A.6/G.812 – Lower limits of maximum tolerable sinusoidal input jitter for Type IV node clocks** + +The lower limits of maximum tolerable sinusoidal input jitter for Types V and VI node clocks are not defined. + +### A.5 Noise transfer + +The transfer characteristic of a slave clock determines its properties with regard to the transfer of excursions of the input phase relative to the phase modulation. Noise transfer can be described in two ways: + +- a) The slave clock can be viewed as a low-pass filter for the differences between the actual input phase and the ideal input phase of the reference. The maximum allowed bandwidth for this low-pass filter behaviour is defined in Table A.12 below, along with the maximum allowed gain in the passband. + +**Table A.12/G.812 – Noise transfer requirements** + +| | Type IV | Type V | Type VI | +|------------------------------------------------------|---------|------------|------------| +| Maximum bandwidth (Hz) | 3 | 0.1 (Note) | 0.1 (Note) | +| Maximum gain (dB) | 0.2 | 0.2 (Note) | 0.2 (Note) | +| NOTE – These values are taken from ITU-T Rec. Q.551. | | | | + +The above applies to a linear G.812 clock model. However, this model should not restrict implementations. + +- b) Noise transfer describes the amount of noise observed at the output, as a result of noise introduced at the input of the clock. The slave clock, when subjected to a wideband noise signal shaped as described in A.4 (i.e., the TDEV input tolerance specification), shall produce an output signal lying below the limit specified in Table A.13 for Type IV node clocks. Wander transfer in terms of TDEV for Types V and VI node clocks is not defined. The resultant requirements are shown in Figure A.7. This mask should not be used to verify phase gain peaking. + +**Table A.13/G.812 – Output wander mask (TDEV) +for Type IV node clocks** + +| TDEV limit (ns) | Observation interval $\tau$ (s) | +|-------------------|---------------------------------| +| 1020 $\tau$ | $0.05 < \tau \leq 0.1$ | +| 102 | $0.1 < \tau \leq 10$ | +| $32.2 \tau^{0.5}$ | $10 < \tau \leq 1000$ | + +![Figure A.7/G.812 – Output wander mask (TDEV) graph. The y-axis is TDEV (ns) on a log scale from 1 to 1 K. The x-axis is Observation interval τ (s) on a log scale from 0.01 to 10 K. The graph shows a piecewise linear mask with three segments: a horizontal line at 51 ns from 0.01 s to 0.05 s, a horizontal line at 102 ns from 0.05 s to 10 s (labeled 'Type IV'), and a dashed line with a positive slope starting at 102 ns at 10 s and ending at 1 K ns at 1 K s.](fe655d77258397f7242c2df72b965b56_img.jpg) + +Figure A.7/G.812 – Output wander mask (TDEV) graph. The y-axis is TDEV (ns) on a log scale from 1 to 1 K. The x-axis is Observation interval τ (s) on a log scale from 0.01 to 10 K. The graph shows a piecewise linear mask with three segments: a horizontal line at 51 ns from 0.01 s to 0.05 s, a horizontal line at 102 ns from 0.05 s to 10 s (labeled 'Type IV'), and a dashed line with a positive slope starting at 102 ns at 10 s and ending at 1 K ns at 1 K s. + +G.812\_FA.7 + +**Figure A.7/G.812 – Output wander mask (TDEV)** + +Guidance on the measurement techniques for these requirements is given in Appendix II. + +MTIE and TDEV are measured through an equivalent 10 Hz, first-order, low-pass measurement filter, at a maximum sampling time $\tau_0$ of 1/30 second. The minimum measurement period for TDEV is twelve times the integration period ( $T = 12 \tau$ ). + +### A.6 Transient response and hold-over performance + +The requirements in this clause apply to situations where the input signal is affected by disturbances or transmission failures (e.g., short interruptions, switching between different synchronization signals, loss of reference, etc.) that result in phase transients at the G.812 output (see A.7). The ability to withstand disturbances is necessary to avoid transmission defects or failures. Transmission failures and disturbances are common stress conditions in the transmission environment. + +To ensure transmission integrity, it is recommended that all the phase movements at the output of the G.812 clock stay within the level described in the following subclauses. + +#### A.6.1 Short-term phase transient response + +This requirement reflects the performance of the clock in cases when the (selected) input reference is lost due to a failure in the reference path and a second reference input signal, traceable to the same reference clock, is available simultaneously or shortly after the detection of the failure (e.g., in cases of autonomous restoration). + +The output jitter limit in A.3.3 should be met. + +##### A.6.1.1 Transient for Type IV node clocks (1544 kbit/s interfaces) + +The MTIE of the phase error should not exceed the limits given in Table A.14 and illustrated by the dashed curve in Figure A.8. + +**Table A.14/G.812 – Transient for Type IV node clocks +(1544 kbit/s interfaces)** + +| MTIE limit
(ns) | Observation interval $\tau$
(s) | +|--------------------|-------------------------------------| +| 61 000 $\tau$ | $0.001\ 33 \leq \tau \leq 0.016\ 4$ | +| 1000 | $\tau > 0.016\ 4$ | + +##### A.6.1.2 Transient for Type IV node clocks (STM-N interfaces) + +The MTIE of the phase error should not exceed the limits given in Table A.15 and illustrated by the solid curve in Figure A.8. + +**Table A.15/G.812 – Transient for Type IV node clocks +(STM-N interfaces)** + +| MTIE limit
(ns) | Observation interval $\tau$
(s) | +|--------------------|------------------------------------| +| $7.6 + 885\ \tau$ | $0.014 < \tau \leq 0.5$ | +| $300 + 300\ \tau$ | $0.5 < \tau \leq 2.33$ | +| 1000 | $2.33 < \tau \leq 280$ | + +##### A.6.1.3 Transient for Types V and VI node clocks (2048 kHz and 2048 kbit/s interfaces) + +The MTIE of the phase error should not exceed the limits given in Table A.16 and illustrated by the dashed curve in Figure A.8. + +**Table A.16/G.812 – Transient for Types V and VI node clocks +(2048 kHz and 2048 kbit/s interfaces)** + +| MTIE limit
(ns) | Observation interval $\tau$
(s) | +|--------------------|------------------------------------| +| 25 | $0.001 < \tau \leq 0.003\ 3$ | +| 7500 $\tau$ | $0.003\ 3 < \tau \leq 0.016$ | +| $120 + 0.5\ \tau$ | $0.016 < \tau \leq 240$ | +| 240 | $240 < \tau \leq 10\ 000$ | + +##### A.6.1.4 Transient for Types V and VI node clocks (STM-N interfaces) + +The MTIE of the phase error should not exceed the limits given in Table A.17 and illustrated by the solid curve in Figure A.8. + +**Table A.17/G.812 – Transient for Types V and VI node clocks (STM-N interfaces)** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|------------------|---------------------------------| +| 7500 $\tau$ | $0.001 < \tau \leq 0.016$ | +| $120 + 0.5 \tau$ | $0.016 < \tau \leq 240$ | +| 240 | $240 < \tau \leq 10\,000$ | + +![Figure A.8/G.812 – Short-term phase transient mask (MTIE). A log-log plot showing MTIE (ns) on the y-axis versus Observation interval tau (s) on the x-axis. The y-axis ranges from 7.5 to 10 K, with major ticks at 7.5, 10, 20, 25, 81, 100, 120, 240, 450, 1 K, and 10 K. The x-axis ranges from 1 m to 1 K, with major ticks at 1 m, 1.33 m, 3.3 m, 10 m, 0.1, 0.16, 0.5, 1, 2.33, 10, 100, 240, 280, and 1 K. Four curves are shown: Type IV 1544 kbit/s (dashed line), Type IV STM-N (solid line), Types V and VI 2048 kHz and 2048 kbit/s (dotted line), and Types V and VI STM-N (solid line). The Type IV 1544 kbit/s curve is the highest, starting at 7500 ns at 1 m and rising to 1 K ns at 10 m. The Type IV STM-N curve starts at 7.5 ns at 1 m and rises to 1 K ns at 10 m. The Types V and VI 2048 kHz and 2048 kbit/s curve starts at 25 ns at 1 m and rises to 240 ns at 10 m. The Types V and VI STM-N curve starts at 7.5 ns at 1 m and rises to 240 ns at 10 m. Two vertical lines are labeled 14 m and 16.4 m.](efbdff107f5a5aade487cf4ea0eae150_img.jpg) + +Figure A.8/G.812 – Short-term phase transient mask (MTIE). A log-log plot showing MTIE (ns) on the y-axis versus Observation interval tau (s) on the x-axis. The y-axis ranges from 7.5 to 10 K, with major ticks at 7.5, 10, 20, 25, 81, 100, 120, 240, 450, 1 K, and 10 K. The x-axis ranges from 1 m to 1 K, with major ticks at 1 m, 1.33 m, 3.3 m, 10 m, 0.1, 0.16, 0.5, 1, 2.33, 10, 100, 240, 280, and 1 K. Four curves are shown: Type IV 1544 kbit/s (dashed line), Type IV STM-N (solid line), Types V and VI 2048 kHz and 2048 kbit/s (dotted line), and Types V and VI STM-N (solid line). The Type IV 1544 kbit/s curve is the highest, starting at 7500 ns at 1 m and rising to 1 K ns at 10 m. The Type IV STM-N curve starts at 7.5 ns at 1 m and rises to 1 K ns at 10 m. The Types V and VI 2048 kHz and 2048 kbit/s curve starts at 25 ns at 1 m and rises to 240 ns at 10 m. The Types V and VI STM-N curve starts at 7.5 ns at 1 m and rises to 240 ns at 10 m. Two vertical lines are labeled 14 m and 16.4 m. + +**Figure A.8/G.812 – Short-term phase transient mask (MTIE)** + +#### A.6.2 Long-term phase transient response (hold-over) + +This requirement bounds the maximum excursions in the output timing signal. Additionally, it restricts the accumulation of the phase movement during input signal impairments or internal disturbances. + +When a G.812 clock loses all its references, it enters the hold-over state. The Phase Error, $\Delta x$ , at the output of the slave clock from the moment of loss of reference, should, over any period of S seconds, meet the following: + +$$|\Delta x(S)| \leq \{(a_1 + a_2)S + 0.5 b S^2 + c\} \text{ [ns]}$$ + +The derivative of $\Delta x(S)$ , the fractional frequency offset, should, over any period of S seconds, meet the following: + +$$|d(\Delta x(S))/dS| \leq \{a_1 + a_2 + bS\} \text{ [ns/s]}$$ + +The second derivative of $\Delta x(S)$ , the fractional frequency drift, should, over any period of S seconds, meet the following: + +$$|d^2(\Delta x(S))/dS^2| \leq d \text{ [ns/s}^2\text{]}$$ + +In applying the above requirements for the derivative of $\Delta x(S)$ and the second derivative of $\Delta x(S)$ , the period S must begin after any transient associated with entry into hold-over is over. During this transient period, the transient requirements of A.6.1 apply. + +NOTE 1 – $a_1$ represents an initial frequency offset under constant temperature conditions ( $\pm 1$ K). + +NOTE 2 – $a_2$ accounts for temperature variations after the clock went into hold-over. If there are no temperature variations, the term $a_2$ S should not contribute to the phase error. + +NOTE 3 – $b$ represents the average frequency drift caused by aging. This value is derived from typical aging characteristics after 60 days of continuous operation. It is not intended to measure this value on a per day basis, as the temperature effect will dominate. + +NOTE 4 – The phase offset $c$ takes care of any additional phase shift that may arise during the transition at the entry of the hold-over state. + +NOTE 5 – $d$ represents the maximum temporary frequency drift rate at constant temperature allowed during hold-over. However, it is not required that $d$ and $b$ be equal. + +The permissible phase error specifications for different G.812 clock Types are shown in Table A.18. + +**Table A.18/G.812 – Transient response specifications during hold-over** + +| | Type IV | Type V | Type VI | +|--------------------------|-----------------------|-----------------------|----------------------| +| Applies for | TBD | $S > 100$ s | $S > 100$ s | +| $a_1$ (ns/s) | 50 | 0.5 | 10 | +| $a_2$ (ns/s) | 300 | NA | NA | +| $b$ (ns/s 2 ) | $4.63 \times 10^{-4}$ | $1.16 \times 10^{-5}$ | $2.3 \times 10^{-4}$ | +| $c$ (ns) | 1000 | 1000 | 1000 | +| $d$ (ns/s 2 ) | $4.63 \times 10^{-4}$ | NA | NA | +| NA Not applicable | | | | +| TBD To be defined | | | | + +#### A.6.3 Phase response to input signal interruptions + +For short-term interruptions on synchronization input signals, that do not cause reference switching, the output phase variation is for further study. + +#### A.6.4 Phase discontinuity + +In cases of infrequent internal testing or rearrangement operations within the slave clock, the phase transient at the output of G.812 clocks should meet the MTIE specifications in Table A.19 for Type IV node clock and in Table A.20 for Types V and VI clocks and illustrated for all these clocks in Figure A.9. + +**Table A.19/G.812 – Output phase transient (MTIE) for Type IV node clocks** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|-------------------|----------------------------------| +| NA | $\tau \leq 0.001\ 33$ | +| 61 000 $\tau$ | $0.001\ 33 < \tau \leq 0.016\ 4$ | +| 1000 | $\tau > 0.016\ 4$ | +| NA Not applicable | | + +**Table A.20/G.812 – Output phase transient (MTIE) for Types V and VI node clocks** + +| MTIE limit (ns) | Observation interval $\tau$ (s) | +|-----------------|---------------------------------| +| 61 | $\tau \leq 0.001$ | +| 61 000 $\tau$ | $0.001 < \tau \leq 0.016\ 4$ | +| 1000 | $\tau > 0.016\ 4$ | + +The resultant requirements are shown in Figure A.9. + +![Figure A.9/G.812 – Output phase transient requirements (MTIE). A log-log plot showing MTIE (ns) on the y-axis (1 to 10,000) versus Observation interval tau (s) on the x-axis (1 ms to 1 K). Two curves are shown: Type IV (dashed line) and Types V, VI (solid line). Both curves start at 61 ns for 1 ms, rise to 1,000 ns at 10 ms, and then remain constant at 1,000 ns for longer intervals. Annotations below the x-axis indicate 1.33 m and 16.4 m.](809eec371620084c4b949c66d5d7bae0_img.jpg) + +Figure A.9/G.812 – Output phase transient requirements (MTIE). The graph plots MTIE (ns) on a logarithmic y-axis (1 to 10,000) against Observation interval $\tau$ (s) on a logarithmic x-axis (1 ms to 1 K). Two curves are shown: Type IV (dashed line) and Types V, VI (solid line). Both curves start at 61 ns for 1 ms, rise to 1,000 ns at 10 ms, and then remain constant at 1,000 ns for longer intervals. Annotations below the x-axis indicate 1.33 m and 16.4 m. + +Figure A.9/G.812 – Output phase transient requirements (MTIE). A log-log plot showing MTIE (ns) on the y-axis (1 to 10,000) versus Observation interval tau (s) on the x-axis (1 ms to 1 K). Two curves are shown: Type IV (dashed line) and Types V, VI (solid line). Both curves start at 61 ns for 1 ms, rise to 1,000 ns at 10 ms, and then remain constant at 1,000 ns for longer intervals. Annotations below the x-axis indicate 1.33 m and 16.4 m. + +**Figure A.9/G.812 – Output phase transient requirements (MTIE)** + +### A.7 Interfaces + +The requirements in this Recommendation are related to reference points internal to the Network Elements (NEs) in which the clock is embedded and are therefore not necessarily available for measurement or analysis by the user. Therefore the performance of the G.812 clock is not defined at these internal reference points, but rather at the external interfaces of the equipment. The external input and output are: + +- 1544 kbit/s interfaces according to ITU-T Rec. G.703. +- 2048 kHz external interfaces according to ITU-T Rec. G.703. + +- 2048 kbit/s interfaces according to ITU-T Rec. G.703. +- STM-N traffic interfaces according to ITU-T Recs G.703 and G.957. + +Note that all of the above interfaces may not be implemented on all equipment. These interfaces should comply with the additional jitter and wander requirements as defined in this Recommendation. + +# Appendix I + +## Relationship between TDEV and power spectral density + +This appendix is provided for information and shows that the power spectral density of phase is given approximately in terms of the TDEV of the phase by $S_x(f) \approx \frac{0.75}{f} \left( \text{TDEV} \left( \frac{0.3}{f} \right) \right)^2$ + +From II.3/G.810: + +$$\text{TDEV}(\tau) = \sqrt{\frac{2}{3(\pi v_{nom} n)^2} \int_0^{f_h} S_\phi(f) \frac{\sin^6(\pi n \tau_0 f)}{\sin^2(\pi \tau_0 f)} df}$$ + +where $v_{nom}$ is the nominal frequency (in Hz) of the reference with wander, and $n\tau_0 = \tau$ , and $S_\phi(f)$ is the Power Spectral Density (PSD) of phase $\phi(t)$ in radians. Let: + +$$S_x(f) = \frac{1}{(2\pi v_{nom})^2} S_\phi(f)$$ + +be the power spectral density of the time interval error $x(t) = \phi(t) / (2\pi v_{nom})$ in seconds. If the largest $f$ is $f = 10$ Hz and the largest $\tau_0$ is $\tau_0 = 20$ ms, then $\pi \tau_0 f < 0.628$ , and $n \cdot \sin(\pi \tau_0 f) \approx n \cdot \pi \tau_0 f = \pi \tau f$ , and: + +$$\text{TDEV}(\tau) = \sqrt{\frac{8}{3} \int_0^{f_h} S_x(f) \frac{\sin^6(\pi \tau f)}{(\pi \tau f)^2} df} = \sqrt{\int_0^{f_h} S_x(f) H^2(\tau, f) df} \quad (\text{I-1})$$ + +where: + +$$H(\tau, f) = \sqrt{\frac{8}{3} \frac{\sin^3(\pi \tau f)}{\pi \tau f}}$$ + +The term $S_x(f) H^2(\tau, f)$ is the power spectral density of the phase $x(t)$ . Therefore, TDEV can be seen as the rms of the phase filtered by a band-bass filter $H(\tau, f)$ . Figure I.1 shows $H(\tau, f)^2$ for the values $\tau = 0.5$ s and $\tau = 1.0$ s. Since $H(\tau, f)^2$ has only 0.85% of its area beyond $20/\tau$ in practice, one can use $f_h = 20/\tau$ with little effect on the calculated value of TDEV. + +![Figure I.1/G.812 shows two plots of the frequency response H^2(tau, f) versus frequency f. The left plot is for tau = 0.5 and the right plot is for tau = 1.0. Both plots show a sharp peak at f = 0.42/tau, with the area under the curve approximately equal to 1/(2*tau). The x-axis ranges from 0 to 8, and the y-axis ranges from 0 to 1.5. The peak is marked with a vertical dashed line and an arrow pointing to the area under the curve. The label G.812_FI.1 is present in the bottom right corner of the right plot.](103781b498cc6846ffc11a041e14dc3e_img.jpg) + +Figure I.1/G.812 shows two plots of the frequency response H^2(tau, f) versus frequency f. The left plot is for tau = 0.5 and the right plot is for tau = 1.0. Both plots show a sharp peak at f = 0.42/tau, with the area under the curve approximately equal to 1/(2\*tau). The x-axis ranges from 0 to 8, and the y-axis ranges from 0 to 1.5. The peak is marked with a vertical dashed line and an arrow pointing to the area under the curve. The label G.812\_FI.1 is present in the bottom right corner of the right plot. + +**Figure I.1/G.812 – Frequency response of filter $H(\tau, f)$ that is part of TDEV calculation** + +Note that the response peaks at $f = 0.42/\tau$ , and the area under the curve is $1/(2\tau)$ . If the passband were very narrow, we would expect $\int_0^\infty S_x(f)H(\tau, f)^2 df \approx (1/2\tau)S_x(0.42/\tau)$ . But because the filter has substantial bandwidth, and because phase tends to have stronger spectral components at low frequencies, a better approximation is: + +$$\int_0^\infty S_x(f)H(\tau, f)^2 df \approx (1/2.5\tau)S_x(0.3/\tau)$$ + +Then TDEV is approximated by: + +$$\text{TDEV}(\tau) \approx \sqrt{\frac{1}{2.5\tau} S_x\left(\frac{0.3}{\tau}\right)} \quad (\text{I-2})$$ + +We can get the inverse relationship – the PSD from TDEV – by substituting $0.3/f$ for $\tau$ and solving for $S_x(f)$ : + +$$S_x(f) \approx \frac{0.75}{f} \left( \text{TDEV}\left(\frac{0.3}{f}\right) \right)^2 \quad (\text{I-3})$$ + +In particular, if TDEV( $\tau$ ) has a break at $\tau = \tau_{\text{break}}$ , then $S_x(f)$ has a break at $f = f_{\text{break}}$ , where $f_{\text{break}} \approx 0.3/\tau_{\text{break}}$ . + +# Appendix II + +## Measurement method for noise transfer + +The measurement method recommended here directly tests conformance with the noise transfer specification of clause 10 part b) by applying the TDEV input noise tolerance limit, Figure 4, as the test signal. The output TDEV characteristic is then directly compared against the specification limit, Figure 8. + +### II.1 Measurement set-up + +The measurement set-up is shown in Figure II.1. + +![Figure II.1/G.812 – Measurement set-up for TDEV noise transfer characteristics](9a14684f8ae1345c6efea6f5994c730c_img.jpg) + +The diagram illustrates the measurement set-up. A 'Ref. clock' (represented by a circle) provides a signal to a mixer (a circle with an 'X'). A 'TDEV noise gen.' block also feeds into this mixer. The output of the mixer, labeled 'Ref. input', goes into the 'SSU under test' block. A dashed line box labeled '(Calibration)' encloses the path from 'Ref. input' to the 'SSU under test'. The output of the 'SSU under test' is labeled 'SSU output' and goes into a 'TDEV meas.' block. Additionally, a 'Sync.' line connects the 'Ref. clock' directly to the 'TDEV meas.' block. The diagram is labeled 'G.812\_FII.1' at the bottom right. + +``` + +graph LR + RefClock((Ref. clock)) --> Mixer((X)) + TDEVNoiseGen[TDEV noise gen.] --> Mixer + Mixer -- "Ref. input" --> SSU[SSU under test] + RefClock -- "Sync." --> TDEVMeas[TDEV meas.] + SSU -- "SSU output" --> TDEVMeas + subgraph Calibration + direction LR + C1[ ] -.- SSU + end + style C1 fill:none,stroke:none + +``` + +Figure II.1/G.812 – Measurement set-up for TDEV noise transfer characteristics + +**Figure II.1/G.812 – Measurement set-up +for TDEV noise transfer characteristics** + +To ensure sufficiently accurate, robust and consistent measurements, the following principles should be applied: + +- 1) The test signal should be deterministic, yet sufficiently noise-like over a short observation interval. +- 2) The noise generator should produce a test signal within $\pm 20\%$ of the input noise tolerance specification – clause 9, Figure 4. +- 3) At large values of $\tau$ , the TDEV results should match the TDEV output mask within $\pm 2\%$ of the specification – clause 10, Figure 8. + +In order to achieve the above levels of accuracy, normalization and calibration techniques should be applied. In general, the following procedure is recommended: + +- 1) Perform a calibration measurement sequence, without the slave clock under test – TDEV(cal). This obtains the raw test signal characteristics. +- 2) Calculate a correction factor with respect to the required input wander tolerance specification – TDEV(ref). This now represents the ideal test signal. +- 3) Measure TDEV(dat) of the slave clock under test under the same conditions as the calibration sequence. +- 4) Normalize TDEV(dat) using TDEV(ref) – obtaining TDEV(meas). +- 5) TDEV(meas) may now be directly compared with the noise transfer specification limit. + +### II.2 Functional model of TDEV noise generator + +The noise generator shown in Figure II.1 can be described by the functional diagram in Figure II.2. It does not imply a specific implementation, but defines the key characteristics that should be observed in order to meet the measurement objectives above. A suitable noise generator can, for example, be constructed with a PRBS sequence of $2^{31} - 1$ , generated at 6.4 kHz. + +![Functional model of TDEV noise generator block diagram](f5a5f52bc25d95a7f616290c99e88ae6_img.jpg) + +The diagram illustrates the functional model of a TDEV noise generator. It consists of a sequence of four blocks connected in series, followed by a final output stage. The first block is labeled 'PRBS generator' with a sub-label 'Period > 150 hrs'. The second block is labeled 'Invert every other bit'. The third block is labeled 'Low-pass filter' and contains a small graph of a low-pass filter response. The fourth block is labeled 'TDEV weighting filter' and contains a small graph of a weighting filter response. The output of the fourth block is labeled 'Clock phase modulation'. Below the third block, there is a label 'Frequency spectrum' with a sub-label '0-10 Hz ± 1 dB'. Below the output of the fourth block, there is a label 'Phase characteristic' with a sub-label 'TDEV(t) ± 20%'. A small vertical line connects the output of the third block to the input of the fourth block. + +Functional model of TDEV noise generator block diagram + +G.812\_FII.2 + +Figure II.2/G.812 – Functional model of TDEV noise generator + + + +# SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure, Internet protocol aspects and Next Generation Networks | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.821-200212-I_PDF-E/007b053fe94a8348f75128a584503fd0_img.jpg b/marked/G/T-REC-G.821-200212-I_PDF-E/007b053fe94a8348f75128a584503fd0_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..dc494d65bfd269b7dc8076bc83194e9f5a4d06a7 --- /dev/null +++ b/marked/G/T-REC-G.821-200212-I_PDF-E/007b053fe94a8348f75128a584503fd0_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:17b486c2d02afffc92fdb73bcc0c43be8b6c3865a3b84fc31ed682932f4ff039 +size 42318 diff --git a/marked/G/T-REC-G.821-200212-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.821-200212-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 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UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.821** + +(12/2002) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital networks – Quality and availability targets + +--- + +**Error performance of an international digital +connection operating at a bit rate below the +primary rate and forming part of an Integrated +Services Digital Network** + +ITU-T Recommendation G.821 + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | G.500–G.599 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| QUALITY OF SERVICE AND PERFORMANCE | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DIGITAL TERMINAL EQUIPMENTS | G.7000–G.7999 | +| DIGITAL NETWORKS | G.8000–G.8999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# **ITU-T Recommendation G.821** + +## **Error performance of an international digital connection operating at a bit rate below the primary rate and forming part of an Integrated Services Digital Network** + +## **Summary** + +This Recommendation defines error performance parameters and objectives for international digital connections operating below the primary rate of the digital hierarchy, using equipment designed prior to the adoption of revised ITU-T Rec. G.826 on 14 December 2002. The objectives given are independent of the physical network supporting the connection. This Recommendation is based upon bit error and bit error ratio measurements. The events, parameters and objectives are defined accordingly. + +Annex A deals with the definition of availability of the connection. + +## **Source** + +ITU-T Recommendation G.821 was revised by ITU-T Study Group 13 (2001-2004) and approved under the WTSA Resolution 1 procedure on 14 December 2002. + +## **Keywords** + +Error Performance Objectives, Error Performance Parameters, Errored Second, Severely Errored Second. + +# FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2003 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +# CONTENTS + +###### Page + +| | | | +|---------|--------------------------------------------------------------------------|---| +| 1 | Scope ..... | 1 | +| 2 | References..... | 1 | +| 3 | Abbreviations..... | 1 | +| 4 | Definitions ..... | 2 | +| 4.1 | Digital connections ..... | 2 | +| 4.2 | Error performance events and parameters ..... | 2 | +| 4.2.1 | Events ..... | 2 | +| 4.2.2 | Parameters ..... | 2 | +| 4.3 | Functions of error performance objectives..... | 2 | +| 5 | Performance objectives..... | 3 | +| 6 | Apportionment of overall objectives ..... | 3 | +| 6.1 | Basic apportionment principles ..... | 3 | +| 6.2 | Apportionment strategy for the errored seconds requirement..... | 5 | +| 6.3 | Apportionment strategy for the severely errored seconds requirement..... | 6 | +| Annex A | – Criteria for entry and exit for the unavailable state..... | 7 | +| A.1 | Criteria for a single direction..... | 7 | +| A.2 | Criterion for a bidirectional connection ..... | 7 | +| A.3 | Criterion for a unidirectional connection ..... | 7 | +| A.4 | Consequences on error performance measurements ..... | 7 | + +# Introduction + +This Recommendation takes into account that services are based on the concept of an Integrated Services Digital Network (ISDN). + +In digital networks, errors are a major source of degradation in that they affect voice services in terms of distortion of voice, and data type services in terms of lost or inaccurate information or reduced throughput. + +In spite of the fact that voice services are likely to predominate the narrow-band ISDN, it is required to transport a wide range of service types and it is therefore desirable to have a unified specification. + +An explanation of network performance objectives and their relationship with design objectives is given in ITU-T Rec. G.102. [1] + +NOTE – The application of this Recommendation is limited to international digital connections, operating below the primary rate of the digital hierarchy, that use equipment designed prior to the adoption of revised ITU-T Rec. G.826 on 14 December 2002. + +## Background + +This Recommendation was adopted in 1980 and defined error performance parameters and objectives for ISDN connections operating at a bit rate of 64 kbit/s. Because it was the first Recommendation giving error performance objectives, it found wide application even in areas it was not developed for. One of these applications was error performance evaluation at bit rates higher than 64 kbit/s. + +In 1988, an Annex D was added to this Recommendation, which indicated how to derive error performance data of 64 kbit/s connections taking into account measurements performed at higher bit rates. Practical experience showed, however, that Annex D/G.821 lead in many cases to doubtful results. It became obvious that a Recommendation was needed which dealt with error performance parameters and objectives for higher bit rates. + +To fill this gap, ITU-T Rec. G.826 [3] was developed and was adopted in 1993. It gives error performance parameters and objectives for constant bit rate digital paths operating at bit rates at and above the primary rate. ITU-T Rec. G.826 contains the statement that it "*... is the only Recommendation specifying error performance parameters and objectives at bit rates at or above the primary rate.*" Considering this statement, this Recommendation had to be restricted to bit rates below the primary rate and Annex D/G.821 had to be deleted. On the other hand, the bit rate range between 64 kbit/s and the primary rate was to be covered by this Recommendation. + +Another problem discovered in the practical use of this Recommendation was the applicability of the Degraded Minute parameter (DM). In practice, this event was hardly detected and it was therefore decided to delete it from this Recommendation. + +In summary, the following modifications are now included in this Recommendation: + +- this Recommendation has been restructured in accordance with ITU-T Rec. A.15; +- this Recommendation is applicable to bit rates below the primary rate of the digital hierarchy; +- the Degraded Minute parameter is deleted; +- Annex D/G.821 (1988) is deleted; +- otherwise, there are no technical changes to this Recommendation. + +After ITU-T Rec. G.826 [3] was adopted, work on this Recommendation continued and comparisons between the performance objectives for digital connections in this Recommendation and digital paths in ITU-T Rec. G.826 were made. From these comparisons it became apparent that inconsistencies existed between the two Recommendations. + +The performance of $N \times 64$ kbit/s ( $1 \leq N \leq 24$ or $\leq 31$ respectively) international digital connections using equipment designed after the adoption of revised ITU-T Rec. G.826 on 14 December 2002 shall be governed by revised ITU-T Rec. G.826. + + + +# ITU-T Recommendation G.821 + +## Error performance of an international digital connection operating at a bit rate below the primary rate and forming part of an Integrated Services Digital Network + +# 1 Scope + +This Recommendation specifies error performance events, parameters and objectives of a $N \times 64$ kbit/s circuit-switched digital connection ( $1 \leq N \leq 24$ or $\leq 31$ respectively) used for voice traffic or as a "Bearer Channel" for data-type services. The application of this Recommendation is limited to international digital connections, operating below the primary rate of the digital hierarchy, that use equipment designed prior to the adoption of revised ITU-T Rec. G.826 on 14 December 2002. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [1] ITU-T Recommendation G.102 (1988), *Transmission performance objectives and Recommendations*. +- [2] ITU-T Recommendation G.801 (1988), *Digital transmission models*. +- [3] ITU-T Recommendation G.826 (2002), *End-to-end error performance parameters and objectives for international, constant bit-rate digital paths and connections*. +- [4] ITU-T Recommendation I.325 (1993), *Reference configurations for ISDN connection types*. +- [5] ITU-T Recommendation I.340 (1988), *ISDN connection types*. +- [6] ITU-T Recommendation G.921 (1988), *Digital sections based on the 2048 kbit/s hierarchy*. + +# 3 Abbreviations + +This Recommendation uses the following abbreviations: + +| | | +|------|-------------------------------------| +| BER | Bit Error Ratio | +| ES | Errored Second | +| ESR | Errored Second Ratio | +| HRDP | Hypothetical Reference Digital Path | +| HRX | Hypothetical Reference Connection | +| ISDN | Integrated Services Digital Network | +| SES | Severely Errored Second | +| SESR | Severely Errored Second Ratio | + +# 4 Definitions + +This Recommendation defines the following terms: + +## 4.1 Digital connections + +The performance objectives are stated for each direction of a $N \times 64$ kbit/s circuit-switched connection ( $1 \leq N \leq 24$ or $\leq 31$ respectively) used for voice traffic or as a "Bearer Channel" for data-type services. + +ITU-T Rec. I.325 [4] gives reference configurations for the ISDN connection types listed in ITU-T Rec. I.340 [5]. In the context of error performance of 64 kbit/s circuit-switched connection types and the allocation of performance to the connection elements, an all digital hypothetical reference configuration (HRX) is given in Figure 1. It encompasses a total length of 27 500 km and is a derivative of the standard hypothetical reference configuration given in Figure 1/G.801 [2] and of the reference configuration given in Figure 3/I.325. + +## 4.2 Error performance events and parameters + +### 4.2.1 Events + +Error performance parameters are derived from the following events: + +**4.2.1.1 errored second (ES):** It is a one-second period in which one or more bits are in error or during which Loss of Signal (LOS) or Alarm Indication Signal (AIS) is detected. + +**4.2.1.2 severely errored second (SES):** It is a one-second period which has a bit error ratio $\geq 1 \cdot 10^{-3}$ or during which Loss of Signal (LOS) or Alarm Indication Signal (AIS) is detected. + +### 4.2.2 Parameters + +It should be noted that total observation time ( $S_{\text{total}}$ ) is split into two parts, namely, time for which the connection is deemed to be available ( $S_{\text{avail}}$ ) and that time when it is unavailable ( $S_{\text{unavail}}$ ). Error performance should only be evaluated whilst the connection is in the available state. See Annex A. + +Parameters are: + +**4.2.2.1 errored second ratio (ESR):** The ratio of ES to total seconds in available time during a fixed measurement interval. + +**4.2.2.2 severely errored second ratio (SESR):** The ratio of SES to total seconds in available time during a fixed measurement interval. + +## 4.3 Functions of error performance objectives + +The performance objectives aim to serve two main functions: + +- a) to give the user of national and international digital networks an indication as to the expected error performance under real operating conditions, thus facilitating service planning and terminal equipment design; +- b) to form the basis upon which performance standards are derived for transmission equipment and systems in an ISDN connection. + +The performance objectives represent a compromise between a desire to meet service needs and a need to realize transmission systems taking into account economic and technical constraints. The performance objectives, although expressed to suit the needs of different services are intended to represent a single level of transmission quality. + +Since the performance objectives are intended to satisfy the needs of the digital network, it must be recognized that such objectives cannot be readily achieved by all of today's digital equipment and systems. The intent, however, is to establish equipment design objectives that are compatible with the objectives in this Recommendation. + +It is further urged that all technologies, wherever they appear in the network, should preferably be designed to better standards than those indicated here in order to minimize the possibility of exceeding the end-to-end objectives on significant numbers of real connections. + +The objectives relate to a very long connection and recognizing that a large proportion of real international connections will be shorter, it is expected that a significant proportion of real connections will offer a better performance than the limiting value given in clause 5. On the other hand, a small percentage of the connections will be longer and in this case may exceed the allowances outlined in this Recommendation. + +NOTE – Controlled slips, which may be perceived as short bursts of errors, are not included in the calculations of the error performance objectives in this Recommendation. Therefore, users should be aware that error performance measurements which include controlled slip effects may produce poorer performance than would be indicated by this Recommendation. Users are directed to ITU-T Rec. G.822, which specifies the controlled slip rate objectives, for guidance in estimating the possible effects on their applications. + +The error performance objectives detailed in clauses 5 and 6 apply to a $N \times 64$ kbit/s circuit switched connection (as defined in 4.1). + +However, it is recognized that in practical situations objectives of this Recommendation will need to be evaluated from measurements made on paths operating at higher bit rates. For that purpose, ITU-T Rec. G.826 [3] – which specifies error performance objectives for international constant bit rate digital paths at or above the primary rate – shall be used. + +# 5 Performance objectives + +The performance objectives for an international ISDN connection as identified in 4.1 are shown in Table 1. It is intended that international ISDN connections should meet all of the requirements of Table 1 and of clause 6. The connection fails to satisfy the objective if any of the requirements is not met. + +**Table 1/G.821 – Error performance objectives for international ISDN connections** + +| Performance classification | Objective (Note) | +|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------| +| Severely Errored Second Ratio | <0.002 | +| Errored Second Ratio | <0.08 | +| NOTE – The ratios are calculated over the available time. The observation time has not been specified since the period may depend upon the application. A period of the order of any one month is suggested as a reference. | | + +# 6 Apportionment of overall objectives + +Since the objectives given in clause 5 relate to an overall connection, it is necessary to subdivide this to constituent parts. This clause outlines the basic principles and strategy for apportioning the performance objectives. + +The overall apportionment philosophy involves the use of two slightly different strategies, one applicable to the errored seconds requirement and the other applicable to the severely errored seconds requirement. + +## 6.1 Basic apportionment principles + +Apportionment is based on the assumed use of transmission systems having qualities falling into one of a limited number of different classifications. + +Three distinct quality classifications have been identified representative of practical digital transmission circuits and are independent of the transmission systems used. These classifications are termed local grade, medium grade and high grade and their usage generally tends to be dependent on their location within a network (see Figure 1). + +![Figure 1/G.821 – Circuit quality demarcation of longest HRX. The diagram shows a transmission path between two T-reference points. The total length is 27 500 km. It is divided into segments: 1250 km (Local grade), 25 000 km (High grade), and 1250 km (Local grade). Along the path, there are four boxes representing exchanges: LE (Note 2), (Note 1), (Note 1), and LE (Note 2). The quality grades are demarcated as follows: Local grade (ends), Medium grade (adjacent to ends), High grade (middle), Medium grade (adjacent to middle), and Local grade (ends).](007b053fe94a8348f75128a584503fd0_img.jpg) + +Figure 1/G.821 – Circuit quality demarcation of longest HRX. The diagram shows a transmission path between two T-reference points. The total length is 27 500 km. It is divided into segments: 1250 km (Local grade), 25 000 km (High grade), and 1250 km (Local grade). Along the path, there are four boxes representing exchanges: LE (Note 2), (Note 1), (Note 1), and LE (Note 2). The quality grades are demarcated as follows: Local grade (ends), Medium grade (adjacent to ends), High grade (middle), Medium grade (adjacent to middle), and Local grade (ends). + +NOTE 1 – It is not possible to provide a definition of the location of the boundary between the medium and the high grade portions HRX. Note 4 to Table 2 provides further clarification of this point. + +NOTE 2 – LE denotes the local exchange or equivalent point. + +**Figure 1/G.821 – Circuit quality demarcation of longest HRX** + +The apportionment of the permitted degradation is given in Table 2. The derived network performance objectives are given in subsequent clauses. + +**Table 2/G.821 – Allocation of the objectives for the three-circuit classifications (Note 1)** + +| Circuit classification | Allocation of the objectives given in Table 1 | +|--------------------------|----------------------------------------------------------------------------------------------| +| Local grade
(2 ends) | 15% block allowance to each end
(Notes 2, 5 and 6) | +| Medium grade
(2 ends) | 15% block allowance to each end
(Notes 3, 5 and 6) | +| High grade | 40% (equivalent to conceptual quality of 0.0016% per km for 25 000 km)
(Notes 4, 7 and 8) | + +NOTE 1 – The allocation principle given in this table is applicable to ESR and half of the SESR according to 6.3a). + +NOTE 2 – The local grade apportionment is considered to be a block allowance, i.e. an allowance to that part of the connection regardless of length. + +NOTE 3 – The medium grade apportionment is considered to be a block allowance, i.e. an allowance to that part of the connection regardless of length. The actual length covered by the medium grade part of the connection will vary considerably from one country to another. Transmission systems in this classification exhibit a variation in quality falling between the other classifications. + +NOTE 4 – The high-grade apportionment is divided on the basis of length resulting in a conceptual per kilometre allocation which can be used to derive a block allowance for a defined network model (e.g. Hypothetical Reference Digital Link). For practical planning purposes of links in network models, link allowances based on the number of 280 km sections nominally 280 km (as specified in Table 2/G.921 [6]) can be used in place of the per kilometre allocation specified in this Recommendation. For longer sections which are not an exact integer multiple of 280 km, the next highest integer multiple is used. + +**Table 2/G.821 – Allocation of the objectives for the three-circuit classifications (Note 1)** + +NOTE 5 – The local-grade and medium-grade portions are permitted to cover up the first 1250 km of the circuit from the T-reference point (see Figure 1) extending into the network. For example, in large countries this portion of the circuit may only reach the Primary Centre whilst in small countries it may go as far as the Secondary Centre, Tertiary Centre or the International Switching Centre (see Figure 1). + +NOTE 6 – Administrations may allocate the block allowances for the local- and medium-grade portions of the connection as necessary within the total allowance of 30% for any one end of the connection. + +NOTE 7 – Based on the understanding that satellite error performance is largely independent of distance, a block allowance of 20% of the permitted errored second objectives is allocated to a single satellite HRDP employed in the high-grade portion of the HRX. + +NOTE 8 – If the high-grade portion of a connection includes a satellite system and the remaining distance included in this category exceeds 12 500 km or if the high-grade portion of a non-satellite connection exceeds 25 000 km, then the objectives of this Recommendation may be exceeded. The occurrence of such connections is thought to be relatively rare and studies are continuing in order to investigate this. The concept of satellite equivalent distance (the length of an equivalent terrestrial path) is useful in this respect and it has been noted that a value in the range 10 000 to 13 000 km might be expected. + +NOTE 9 – For subscriber premises installation, between the T-reference point and terminal equipment, no specific requirements are given. However careful attention should be paid to the choice of the subscriber equipment since the overall performance of the connection depends heavily, not only on the network performance, but also on the quality of the terminal installation. + +The following general assumptions apply to the apportionment strategy that follows: + +- In apportioning the objectives to the constituent elements of a connection, it is the Ratios ESR and SESR that are subdivided. +- The error ratio threshold is not subdivided. +- An equal apportionment of the objectives applies for the errored seconds requirement. +- No account is taken of the error contribution from either digital switching elements or digital multiplex equipments on the basis that it is negligible in comparison with the contribution from transmission systems. + +These quality classifications for different parts of the connection are considered to represent the situation for a large proportion of real international connections. Administrations are free to use whatever transmission systems they wish within their own networks and these other arrangements are considered as being completely acceptable provided that the overall performance of the national portion is no worse than it would have been if the standard ITU-T arrangements had been employed. + +It should be noted that a small percentage of connections will be longer than the 27 500 km HRX. By definition the extra connection length will be carried over high-grade circuits and hence the amount by which such connections exceed the total allowance envisaged in this Recommendation will be proportional to the amount by which the 25 000 km section is exceeded. Administrations should note that if the performance limits in the various classifications could be improved in practical implementations, the occurrence of these situations could be significantly reduced. + +## **6.2 Apportionment strategy for the errored seconds requirement** + +The apportionment of the permitted degradation, i.e. 0.08 ESR, is given in Table 2. The derived network performance objectives are given in Table 3. + +**Table 3/G.821 – Allocation of Errored Second Ratio objective** + +| Circuit classification (see Figure 1) | Network performance objectives ESR | +|---------------------------------------|------------------------------------| +| Local grade | 0.012 | +| Medium grade | 0.012 | +| High grade | 0.032 | + +## 6.3 Apportionment strategy for the severely errored seconds requirement + +The total allocation of 0.002 SESR is subdivided into each circuit classification (i.e. local, medium, high grades) in the following manner: + +- a) 0.001 SESR is divided between the three circuit classifications in the same proportions as adopted for the other objective. This results in the allocation as shown in Table 4. + +**Table 4/G.821 – Allocation of Severely Errored Second Ratio objective** + +| Circuit classification | Allocation of SESR objectives | +|------------------------|---------------------------------------------------------| +| Local grade | 0.00015 block allowance to each end (Note 6 to Table 2) | +| Medium grade | 0.00015 block allowance to each end (Note 6 to Table 2) | +| High grade | 0.0004 (Notes 1, 2) | + +NOTE 1– For transmission systems covered by the high grade classification each 2500 km portion may contribute not more than 0.00004 SESR. +NOTE 2– For a satellite HRDP operating in the high grade portion there is a block allowance of 0.0002 SESR (see also Note 7 to Table 2). + +- b) The remaining 0.001 SESR is a block allowance to the medium and high grade classifications to accommodate the occurrence of adverse network conditions occasionally experienced (intended to mean the worst month of the year) on transmission systems. Because of the statistical nature of the occurrence of worst month effects in a worldwide connection, it is considered that the following allowances are consistent with the total 0.001 SESR figure: +- 0.0005 SESR to a 2500 km HRDP for radio relay systems which can be used in the high-grade and the medium-grade portion of the connection; + - 0.0001 SESR to a satellite HRDP. + +# Annex A + +## Criteria for entry and exit for the unavailable state + +## A.1 Criteria for a single direction + +A period of unavailable time begins at the onset of ten consecutive SES events. These ten seconds are considered to be part of unavailable time. A new period of available time begins at the onset of ten consecutive non-SES events. These ten seconds are considered to be part of available time. Figure A.1 illustrates this definition. + +![Figure A.1/G.821 – Example of unavailability determination. A timeline diagram showing a sequence of seconds categorized as Severely Errored Second (SES), Errored Second (non-SES), or Error-free. A period of 10 consecutive SES seconds marks the start of an 'Unavailable period'. A subsequent period of less than 10 seconds containing non-SES events marks the start of an 'Available period'. The diagram shows the detection of unavailability and availability based on these consecutive event counts.](fe753d01ad5fe6cf150018c958173c6d_img.jpg) + +Legend: + +- Severely Errored Second +- ⊠ Errored Second (non-SES) +- Error-free Second + +G.821\_FA.1 + +Figure A.1/G.821 – Example of unavailability determination. A timeline diagram showing a sequence of seconds categorized as Severely Errored Second (SES), Errored Second (non-SES), or Error-free. A period of 10 consecutive SES seconds marks the start of an 'Unavailable period'. A subsequent period of less than 10 seconds containing non-SES events marks the start of an 'Available period'. The diagram shows the detection of unavailability and availability based on these consecutive event counts. + +Figure A.1/G.821 – Example of unavailability determination + +### A.2 Criterion for a bidirectional connection + +A bidirectional connection is in the unavailable state if either one or both directions are in the unavailable state. This is shown in Figure A.2. + +![Figure A.2/G.821 – Example of the unavailable state of a connection. A diagram showing three horizontal lines representing 'Forward direction', 'Backward direction', and 'Connection'. Vertical dashed lines indicate periods where one or both directions are in the 'Unavailable state' (shaded gray). The 'Connection' line is shaded whenever either the 'Forward direction' or 'Backward direction' is shaded.](4a8166688ed7276efb173f550ba47eb4_img.jpg) + +Legend: + +- Unavailable state + +G.821\_FA.2 + +Figure A.2/G.821 – Example of the unavailable state of a connection. A diagram showing three horizontal lines representing 'Forward direction', 'Backward direction', and 'Connection'. Vertical dashed lines indicate periods where one or both directions are in the 'Unavailable state' (shaded gray). The 'Connection' line is shaded whenever either the 'Forward direction' or 'Backward direction' is shaded. + +Figure A.2/G.821 – Example of the unavailable state of a connection + +### A.3 Criterion for a unidirectional connection + +The criterion for a unidirectional connection is defined in A.1 above. + +### A.4 Consequences on error performance measurements + +When a bidirectional connection is in the unavailable state, ES and SES counts may be collected in both directions and may be helpful in the analysis of the trouble. However, it is recommended that these ES and SES counts are not included in estimates of performance. + +Some existing systems cannot support this requirement to exclude ES and SES counts. For these systems, the performance of a bidirectional connection can be approximated by evaluating the parameters in each direction, independently of the state of availability of the other direction. It should be noted that this approximation method may result in a worse estimate of performance in the event that only one direction of a bidirectional connection becomes unavailable. + +NOTE – This is not an issue for unidirectional connections. + + + +# SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure and Internet protocol aspects | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.826-200212-I_PDF-E/raw.md b/marked/G/T-REC-G.826-200212-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..c611f0d1091af397a2f85ae1ea60c3d1fb1b536f --- /dev/null +++ b/marked/G/T-REC-G.826-200212-I_PDF-E/raw.md @@ -0,0 +1,1075 @@ + + +![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with a lightning bolt and the letters ITU. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.826** + +(12/2002) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital networks – Quality and availability targets + +--- + +**End-to-end error performance parameters and +objectives for international, constant bit-rate +digital paths and connections** + +ITU-T Recommendation G.826 + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | G.500–G.599 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| QUALITY OF SERVICE AND PERFORMANCE | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DIGITAL TERMINAL EQUIPMENTS | G.7000–G.7999 | +| DIGITAL NETWORKS | G.8000–G.8999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## **ITU-T Recommendation G.826** + +# **End-to-end error performance parameters and objectives for international, constant bit-rate digital paths and connections** + +## **Summary** + +This Recommendation defines end-to-end error performance parameters and objectives for international digital paths which operate at or above the primary rate and for international digital connections which operate below the primary rate of the digital hierarchy. The objectives given are independent of the physical network supporting the path or connection. + +For digital paths which operate at or above the primary rate, this Recommendation is based upon a block-based measurement concept using error detection codes inherent to the path under test. This supports in-service measurements. + +For digital connections which operate below the primary rate of the digital hierarchy, this Recommendation is based upon bit error and bit error ratio measurements. This approach does not support in-service measurements. + +Annex A deals with the definition of availability of the path or connection. Annexes B, C and D give specific information concerning PDH, SDH and cell-based transmission paths. + +It is not required to apply this Recommendation to connections which operate below the primary rate using equipment designed prior to the adoption of this Recommendation in December 2002. + +This Recommendation deals with the performance of PDH paths, and of those SDH paths using equipment designed prior to the adoption of ITU-T Rec. G.828 in March 2000. ITU-T Rec. G.828 deals with the performance of SDH paths using equipment designed as of or after the adoption of ITU-T Rec. G.828 in March 2000. New Recommendation G.8201 deals with performance of ODUk paths of the OTN. + +## **Source** + +ITU-T Recommendation G.826 was revised by ITU-T Study Group 13 (2001-2004) and approved under the WTSA Resolution 1 procedure on 14 December 2002. + +## **Keywords** + +Background block error, background block error ratio, bit error, bit error ratio, block-based concept, digital connection, digital path, error detection codes, error performance objectives, error performance parameters, errored second, in-service measurements, severely errored second. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2003 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## CONTENTS + +###### Page + +| | | | +|---------|--------------------------------------------------------------------------------------------|----| +| 1 | Scope ..... | 1 | +| 1.1 | Application of this Recommendation ..... | 1 | +| 1.2 | Transport network layers ..... | 2 | +| 1.2.1 | PDH and SDH transport networks ..... | 2 | +| 1.2.2 | ATM connections ..... | 2 | +| 1.3 | Allocation of end-to-end performance ..... | 3 | +| 2 | References..... | 3 | +| 3 | Abbreviations..... | 4 | +| 4 | Terms and definitions ..... | 6 | +| 4.5 | Error performance events for paths ..... | 6 | +| 4.6 | Error performance events for connections ..... | 7 | +| 4.7 | Error performance parameters ..... | 7 | +| 5 | The measurement of the block..... | 7 | +| 5.1 | In-service monitoring of blocks..... | 7 | +| 5.2 | Out-of-service measurements of blocks ..... | 8 | +| 6 | Performance assessment ..... | 8 | +| 6.1 | Implications for error performance measuring devices..... | 8 | +| 6.2 | Performance monitoring at the near end and far end of a path ..... | 8 | +| 7 | Error performance objectives ..... | 8 | +| 7.1 | End-to-end objectives..... | 8 | +| 7.2 | Apportionment of end-to-end objectives..... | 10 | +| 7.2.1 | Allocation to the national portion of the end-to-end path or connection ..... | 10 | +| 7.2.2 | Allocation to the international portion of the end-to-end path or connection..... | 11 | +| Annex A | – Criteria for entry and exit for the unavailable state ..... | 11 | +| A.1 | Criteria for a single direction..... | 11 | +| A.2 | Criterion for a bidirectional path or connection ..... | 12 | +| A.3 | Criterion for a unidirectional path or connection ..... | 12 | +| A.4 | Consequences on error performance measurements ..... | 12 | +| Annex B | – Relationship between PDH path performance monitoring and the block-based parameters..... | 13 | +| B.1 | General ..... | 13 | +| B.1.1 | Block size for monitoring PDH paths ..... | 13 | +| B.1.2 | Anomalies..... | 13 | +| B.1.3 | Defects..... | 13 | + +| | Page | | +|--------------|--------------------------------------------------------------------------------------------------------------------|----| +| B.2 | Types of paths..... | 14 | +| B.3 | Estimation of the performance parameters..... | 14 | +| B.4 | In-service monitoring capabilities and criteria for declaration of the performance parameters ..... | 15 | +| B.5 | Estimation of performance events at the far end of a path..... | 16 | +| B.6 | Differences between this Recommendation and ITU-T Rec. M.2100 concerning path performance ..... | 16 | +| B.6.1 | General ..... | 16 | +| B.6.2 | Allocation methodology ..... | 16 | +| Annex C | – Relationship between SDH path performance monitoring and the block-based parameters..... | 17 | +| C.1 | General ..... | 17 | +| C.1.1 | Converting BIP measurements into errored blocks..... | 17 | +| C.1.2 | Block size for monitoring SDH paths ..... | 17 | +| C.1.3 | Anomalies..... | 17 | +| C.1.4 | Defects..... | 17 | +| C.1.5 | Measurement of performance events using aggregate parity error counts..... | 18 | +| C.2 | Estimation of the performance parameters..... | 19 | +| C.3 | Estimation of performance events at the far end of a path..... | 19 | +| Annex D | – Relationship between cell-based network performance monitoring and the block-based parameters ..... | 19 | +| D.1 | General ..... | 19 | +| D.1.1 | Block size for monitoring cell-based paths ..... | 19 | +| D.1.2 | Anomalies..... | 20 | +| D.1.3 | Defects..... | 20 | +| D.2 | Types of paths..... | 21 | +| D.3 | Estimation of the performance parameters..... | 21 | +| D.4 | Estimation of performance events at the far end of the path..... | 21 | +| Appendix I | – Flow chart illustrating for digital paths the recognition of anomalies, defects, errored blocks, ES and SES..... | 22 | +| Appendix II | – Bit errors and block errors, merits and limitations ..... | 23 | +| Appendix III | – Applicability of this Recommendation to non-public networks ..... | 24 | + +# **End-to-end error performance parameters and objectives for international, constant bit-rate digital paths and connections** + +# **1 Scope** + +This Recommendation specifies end-to-end error performance events, parameters and objectives for: + +- 1) digital paths operating at bit rates at or above the primary rate; and +- 2) $N \times 64$ kbit/s circuit-switched digital connection ( $1 \leq N \leq 24$ or 31 respectively). + +This Recommendation also specifies allocations of the end-to-end performance objectives. + +## **1.1 Application of this Recommendation** + +This Recommendation is applicable to international, constant bit-rate digital paths which operate at or above the primary rate and to international $N \times 64$ kbit/s ( $1 \leq N \leq 24$ or 31 respectively) digital connections. + +NOTE – It is not required to apply this Recommendation to connections which operate below the primary rate using equipment designed prior to the adoption of this Recommendation in December 2002. Performance events and objectives for connections using equipment designed prior to this date are given in ITU-T Rec. G.821 [14]. + +The constant bit-rate digital paths may be based on a Plesiochronous Digital Hierarchy, Synchronous Digital Hierarchy or some other transport network such as cell-based. This Recommendation is generic in that it defines the parameters and objectives for the paths and connections independent of the physical transport network. Compliance with the path performance specification of this Recommendation will, in most cases, also ensure that a client 64 kbit/s connection will meet its requirements. Therefore, this Recommendation and ITU-T Rec. G.828 [24] are currently the only Recommendations required for designing the error performance of digital paths at or above the primary rate1. In accordance with the definition of a digital path, path end points may be located at user's premises. + +Paths are used to support services such as circuit switched, packet switched and leased circuit services. The quality of such services, as well as the performance of the network elements belonging to the service layer, is outside of the scope of this Recommendation. + +The performance objectives are applicable to a single direction of the path or connection. The values apply end-to-end over a 27 500 km Hypothetical Reference Path or Connection (see Figure 3), which may include optical fibre, digital radio relay, metallic cable and satellite transmission systems. The performance of multiplex and cross-connect functions employing ATM techniques is not included in these values. + +The parameter definitions for digital paths which operate at or above the primary rate are block-based, making in-service measurement convenient. In some cases, the network fabric is not able to provide the basic events necessary to directly obtain the performance parameters. In these cases, compliance with this Recommendation can be assessed using out-of-service measurements or estimated by measures compatible with this Recommendation, such as those specified in + +--- + +1 This Recommendation deals with the performance of PDH paths, and of those SDH paths using equipment designed prior to the adoption of ITU-T Rec. G.828 in March 2000. ITU-T Rec. G.828 deals with the performance of SDH paths using equipment designed as of or after the adoption of ITU-T Rec. G.828 in March 2000. New ITU-T Rec. G.8201 deals with the performance of ODUk paths of the OTN. + +Annexes B, C and D. The parameter definitions for digital connections which operate below the primary rate of the digital hierarchy are not block-based; rather, they are based upon bit error and bit-error ratio measurements. + +## 1.2 Transport network layers + +For paths, this Recommendation specifies the error performance in a given transport network layer. Two cases have to be considered: + +### 1.2.1 PDH and SDH transport networks + +Figure 1 gives the intended scope where ATM does not form part of the end-to-end path. It should be noted that end-to-end performance monitoring is only possible if the monitored blocks together with the accompanying overhead are transmitted transparently to the path end points. + +![Diagram of a non-ATM end-to-end transmission path. It shows two square boxes labeled 'A' and 'B' connected by a central oval labeled 'Network fabric, e.g., PDH, SDH'. Above the oval is a double-headed arrow labeled 'Application of this Recommendation'. The label 'G.826_F01' is at the bottom right.](c0e88e4bd3a209b66ee7cb67e1cec2be_img.jpg) + +Diagram of a non-ATM end-to-end transmission path. It shows two square boxes labeled 'A' and 'B' connected by a central oval labeled 'Network fabric, e.g., PDH, SDH'. Above the oval is a double-headed arrow labeled 'Application of this Recommendation'. The label 'G.826\_F01' is at the bottom right. + +NOTE – A and B are path end points located at physical interfaces, e.g. in accordance with ITU-T Rec. G.703 [1]. + +**Figure 1/G.826 – Application of this Recommendation for a non-ATM end-to-end transmission path** + +### 1.2.2 ATM connections + +Where the path forms the physical part of an ATM connection (see Figure 2), the overall end-to-end performance of the ATM connection is defined by ITU-T Rec. I.356 [16]. In this case, this Recommendation can be applied with an appropriate allocation to the performance between the path end points where the physical layer of the ATM protocol reference model (see ITU-T Rec. I.321 [15]) is terminated by ATM cross-connects or switches. ATM transmission paths in the physical layer correspond to a stream of cells mapped either into a cell-based format or into SDH or PDH-based frame structures. + +![Diagram showing the architectural relationship between G.826 and ITU-T Rec. I.356 for ATM connections. It features three main components: a stack of AAL, ATM, and PL layers on the left, a central ATM switch with two PL layers, and another stack of AAL, ATM, and PL layers on the right. Arrows labeled 'G.826 allocated' point from the PL layers of the end systems to the PL layers of the switch. Arrows labeled 'ITU-T Rec. I.356' point from the AAL layers of the end systems to the ATM layer of the switch. The label 'G.826_F02' is at the bottom right.](7affafe7362a2d2d072e9d4bf515f0bb_img.jpg) + +Diagram showing the architectural relationship between G.826 and ITU-T Rec. I.356 for ATM connections. It features three main components: a stack of AAL, ATM, and PL layers on the left, a central ATM switch with two PL layers, and another stack of AAL, ATM, and PL layers on the right. Arrows labeled 'G.826 allocated' point from the PL layers of the end systems to the PL layers of the switch. Arrows labeled 'ITU-T Rec. I.356' point from the AAL layers of the end systems to the ATM layer of the switch. The label 'G.826\_F02' is at the bottom right. + +AAL ATM Adaptation Layer + ATM ATM Layer + PL Physical Layer + +**Figure 2/G.826 – Architectural relationship between this Recommendation G.826 and ITU-T Rec. I.356 [16]** + +## 1.3 Allocation of end-to-end performance + +Allocations of end-to-end performance of CBR paths and connections are derived using the rules laid out in 7.2 which are length- and complexity-based. Detailed allocations of G.826 performance to the individual components (lines, sections, multiplexers and cross-connects, etc.) are outside the scope of this Recommendation, but when such allocations are performed, the national and international allocations as given in 7.2 shall be achieved. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation + +- [1] ITU-T Recommendation G.703 (2001), *Physical/electrical characteristics of hierarchical digital interfaces*. +- [2] ITU-T Recommendation G.704 (1998), *Synchronous frame structures used at 1544, 6312, 2048, 8448 and 44 736 kbit/s hierarchical levels*. +- [3] ITU-T Recommendation G.707/Y.1322 (2000), *Network node interface for the synchronous digital hierarchy (SDH)*, plus Corrigendum 1 (2001), Corrigendum 2 (2001), and Amendment 1 (2001). +- [4] ITU-T Recommendation G.732 (1988), *Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s*. +- [5] ITU-T Recommendation G.733 (1988), *Characteristics of primary PCM multiplex equipment operating at 1544 kbit/s*. +- [6] ITU-T Recommendation G.734 (1988), *Characteristics of synchronous digital multiplex equipment operating at 1544 kbit/s*. +- [7] ITU-T Recommendation G.742 (1988), *Second order digital multiplex equipment operating at 8448 kbit/s and using positive justification*. +- [8] ITU-T Recommendation G.743 (1988), *Second order digital multiplex equipment operating at 6312 kbit/s and using positive justification*. +- [9] ITU-T Recommendation G.751 (1988), *Digital multiplex equipments operating at the third order bit rate of 34 368 kbit/s and the fourth order bit rate of 139 264 kbit/s and using positive justification*. +- [10] ITU-T Recommendation G.752 (1988), *Characteristics of digital multiplex equipments based on a second order bit rate of 6312 kbit/s and using positive justification*. +- [11] ITU-T Recommendation G.755 (1988), *Digital multiplex equipment operating at 139 264 kbit/s and multiplexing three tributaries at 44 736 kbit/s*. +- [12] ITU-T Recommendation G.775 (1998), *Loss of Signal (LOS), Alarm Indication Signal (AIS) and Remote Defect Indication (RDI) defect detection and clearance criteria for PDH signals*. +- [13] ITU-T Recommendation G.783 (2000), *Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks*, plus Corrigendum 1 (2001). + +- [14] ITU-T Recommendation G.821 (2002), *Error performance of an international digital connection operating at a bit rate below the primary rate and forming part of an Integrated Services Digital Network.* +- [15] ITU-T Recommendation I.321 (1991), *B-ISDN protocol reference model and its application.* +- [16] ITU-T Recommendation I.356 (2000), *B-ISDN ATM layer cell transfer performance.* +- [17] ITU-T Recommendation I.3622, *B-ISDN ATM adaptation layer (AAL) functional description.* +- [18] ITU-T Recommendations I.432.x series, *B-ISDN user-network interface – Physical layer specification.* +- [19] ITU-T Recommendation I.610 (1999), *B-ISDN operation and maintenance principles and functions*, plus Corrigendum 1 (2000). +- [20] ITU-T Recommendation M.60 (1993), *Maintenance terminology and definitions.* +- [21] ITU-T Recommendation M.2100 (1995), *Performance limits for bringing-into-service and maintenance of international PDH paths, sections and transmission systems.* +- [22] ITU-T Recommendation M.2101 (2000), *Performance limits and objectives for bringing-into-service and maintenance of international SDH paths and multiplex sections.* +- [23] ITU-T Recommendation M.2101.1 (1997), *Performance limits for bringing-into-service and maintenance of international SDH paths and multiplex sections.* +- [24] ITU-T Recommendation G.828 (2000), *Error performance parameters and objectives for international, constant bit-rate synchronous digital paths.* +- [25] ITU-T Recommendation I.325 (1993), *Reference configurations for ISDN connection types.* +- [26] ITU-T Recommendation I.340 (1988), *ISDN connection types.* +- [27] ITU-T Recommendation G.801 (1988), *Digital transmission models.* + +# 3 Abbreviations + +This Recommendation uses the following abbreviations: + +| | | +|--------|-----------------------------------------------| +| AAL | ATM Adaptation Layer | +| AIS | Alarm Indication Signal | +| ATM | Asynchronous Transfer Mode | +| AU | Administrative Unit | +| BBE | Background Block Error | +| BBER | Background Block Error Ratio | +| BIP | Bit Interleaved Parity | +| B-ISDN | Broadband Integrated Services Digital Network | +| CBR | Constant Bit Rate | +| CEC | Cell Error Control | +| CRC | Cyclic Redundancy Check | + +--- + +2 Withdrawn in June 1997. + +| | | +|--------|-------------------------------------------------| +| EB | Errored Block | +| EDC | Error Detection Code | +| ES | Errored Second | +| ESR | Errored Second Ratio | +| FAS | Frame Alignment Signal | +| HEC | Header Error Check | +| HP | Higher order Path | +| HRP | Hypothetical Reference Path | +| HRX | Hypothetical Reference Connection | +| IG | International Gateway | +| ISDN | Integrated Services Digital Network | +| ISM | In-Service Monitoring | +| LOF | Loss of Frame Alignment | +| LOM | Loss of Multiframe Alignment | +| LOP | Loss Of Pointer | +| LOS | Loss Of Signal | +| LP | Lower order Path | +| MS | Multiplex Section | +| N-ISDN | Narrow-band Integrated Services Digital Network | +| NTE | Network Terminal Equipment | +| OAM | Operation and Maintenance | +| ODUk | Optical Channel Data Unit-k | +| OOS | Out-of-Service | +| OTN | Optical Transport Network | +| PDH | Plesiochronous Digital Hierarchy | +| PEP | Path End Point | +| PL | Physical Layer | +| RDI | Remote Defect Indication | +| REI | Remote Error Indication | +| SDH | Synchronous Digital Hierarchy | +| SES | Severely Errored Second | +| SESR | Severely Errored Second Ratio | +| STM | Synchronous Transport Module | +| TE | Terminal Equipment | +| TIM | Trace Identifier Mismatch | +| TP | Transmission Path | +| TU | Tributary Unit | + +| | | +|------|---------------------| +| UAS | Unavailable Second | +| UNEQ | Unequipped (defect) | +| VC | Virtual Container | + +# 4 Terms and definitions + +This Recommendation defines the following terms: + +**4.1 hypothetical reference path:** A Hypothetical Reference Path (HRP) is defined as the whole means of digital transmission of a digital signal of specified rate including the path overhead (where it exists) between equipment at which the signal originates and terminates. An end-to-end Hypothetical Reference Path spans a distance of 27 500 km. + +**4.2 digital paths:** A digital path may be bidirectional or unidirectional and may comprise both customer-owned portions and network operator-owned portions. + +**4.2.1 PDH digital paths:** With regard to PDH digital paths, ITU-T Rec. M.60 [20] applies. + +**4.2.2 SDH digital paths:** An SDH digital path is a trail carrying the SDH payload and associated overhead through the layered transport network between the terminating equipment. + +**4.2.3 cell-based digital paths:** Under study. + +**4.3 digital connections:** The performance objectives for digital connections are stated for each direction of a $N \times 64$ kbit/s circuit-switched connection ( $1 \leq N \leq 24$ or $\leq 31$ respectively). + +ITU-T Rec. I.325 [25] gives reference configurations for the ISDN connection types listed in ITU-T Rec. I.340 [26]. In the context of error performance of 64 kbit/s circuit-switched connection types and the allocation of performance to the connection elements, an all-digital hypothetical reference configuration (HRX) is given in Figure 3. It encompasses a total length of 27 500 km and is a derivative of the standard hypothetical reference configuration given in Figure 1/G.801 [27] and of the reference configuration given in Figure 3/I.325. + +**4.4 generic definition of the block:** The error performance of digital paths in this Recommendation is based upon the error performance measurement of blocks. This clause offers a generic definition of the term "block" as follows3: + +A block is a set of consecutive bits associated with the path; each bit belongs to one and only one block. Consecutive bits may not be contiguous in time. + +Table 1 specifies the recommended range of the number of bits within each block for the various bit rate ranges. Annexes B, C and D contain information on block sizes of existing system designs. + +## 4.5 Error performance events for paths4 + +**4.5.1 errored block (EB):** A block in which one or more bits are in error. + +**4.5.2 errored second (ES):** A one-second period with one or more errored blocks or at least one defect. + +**4.5.3 severely errored second (SES):** A one-second period which contains $\geq 30\%$ errored blocks or at least one defect. SES is a subset of ES. + +Consecutive Severely Errored Seconds may be precursors to periods of unavailability, especially when there are no restoration/protection procedures in use. Periods of consecutive Severely Errored + +3 Appendix II contains information on block error versus bit-error measurements. + +4 See Appendix I, which contains a flow chart illustrating for digital paths the recognition of anomalies, defects, errored blocks, ES and SES. + +Seconds persisting for T seconds, where $2 \leq T < 10$ (some Network Operators refer to these events as "failures"), can have a severe impact on service, such as the disconnection of switched services. The only way this Recommendation limits the frequency of these events is through the limit for the SESR. (See Notes 1 and 2.) + +NOTE 1 – The defects and related performance criteria are listed in the relevant Annexes (B, C or D) for the different network fabrics PDH, SDH or cell-based. + +NOTE 2 – To simplify measurement processes, the defect is used in the definition of SES instead of defining SES directly in terms of severe errors affecting the path. While this approach simplifies the measurement of SES, it should be noted that there may exist error patterns of severe intensity that would not trigger a defect as defined in Annexes B, C and D. Thus, these would not be considered as an SES under this definition. If in the future such severe user-affecting events were found, this definition will have to be studied again. + +**4.5.4 background block error (BBE):** An errored block not occurring as part of an SES. + +## **4.6 Error performance events for connections** + +**4.6.1 errored second (ES):** It is a one-second period in which one or more bits are in error or during which Loss of Signal (LOS) or Alarm Indication Signal (AIS) is detected. + +**4.6.2 severely errored second (SES):** It is a one-second period which has a bit-error ratio $\geq 1 \cdot 10^{-3}$ or during which Loss of Signal (LOS) or Alarm Indication Signal (AIS) is detected. + +## **4.7 Error performance parameters** + +Error performance should only be evaluated whilst the path is in the available state. For a definition of the entry/exit criteria for the unavailable state, see Annex A. + +**4.7.1 errored second ratio (ESR):** The ratio of ES to total seconds in available time during a fixed measurement interval. This parameter is applicable to both paths and connections. + +**4.7.2 severely errored second ratio (SESR):** The ratio of SES to total seconds in available time during a fixed measurement interval. This parameter is applicable to both paths and connections. + +**4.7.3 background block error ratio (BBER):** The ratio of Background Block Errors (BBE) to total blocks in available time during a fixed measurement interval. The count of total blocks excludes all blocks during SESs. This parameter is applicable only to paths. + +# **5 The measurement of the block** + +Clause 5 is applicable only to paths. + +## **5.1 In-service monitoring of blocks** + +Each block is monitored by means of an inherent Error Detection Code (EDC), e.g., Bit Interleaved Parity or Cyclic Redundancy Check. The EDC bits are physically separated from the block to which they apply. It is not normally possible to determine whether a block or its controlling EDC bits are in error. If there is a discrepancy between the EDC and its controlled block, it is always assumed that the controlled block is in error. + +No specific EDC is given in this generic definition but it is recommended that for in-service monitoring purposes, future designs should be equipped with an EDC capability such that the probability to detect an error event is $\geq 90\%$ , assuming Poisson error distribution. CRC-4 and BIP-8 are examples of EDCs currently used which fulfil this requirement. + +Estimation of errored blocks on an in-service basis is dependent upon the network fabric employed and the type of EDC available. Annexes B, C and D offer guidance on how in-service estimates of errored blocks can be obtained from the ISM facilities of the PDH, SDH and cell-based network fabrics respectively. + +## **5.2 Out-of-service measurements of blocks** + +Out-of-service measurements shall also be block-based. It is expected that the out-of-service error detection capability will be superior to the in-service capability described in 5.1. + +# **6 Performance assessment** + +## **6.1 Implications for error performance measuring devices** + +There is a large number of devices (test equipment, transmission systems, collecting devices, operating systems, software applications) currently designed to estimate the connection parameters ESR and SESR at bit rates up to the fourth level of the PDH. For such devices, the path parameters ESR and SESR may be approximated using the criteria for connections, but an approximation of BBER is not possible from measurements based on connection events and parameters. As the block-based concept and the BBER parameter are not defined for connections, converting those devices to measure the path parameters of this Recommendation is not required. + +Maintenance on specific systems and transport paths may require other parameters. Parameters and values can be found in the M-series Recommendations. See, for example, ITU-T Recs M.2100 [21] and M.2101 [22]. + +## **6.2 Performance monitoring at the near end and far end of a path** + +By monitoring SES events for both directions at a single path end point, a network provider is able to determine the unavailable state of the path (see Annex A). In some cases, it is also possible to monitor the full set of error performance parameters in both directions from one end of the path. Specific in-service indicators for deriving far end performance of a path are listed in Annexes B, C and D. + +# **7 Error performance objectives** + +## **7.1 End-to-end objectives** + +Table 1 specifies the end-to-end objectives for a 27 500 km HRX or HRP in terms of the parameters defined in 4.7. The actual objectives applicable to a real path or connection are derived from Table 1 using the allocation principles detailed in 7.2. Each direction of the path or connection shall concurrently satisfy the allocated objectives for all relevant parameters. In other words, a path or connection fails to satisfy this Recommendation if any relevant parameter exceeds the allocated objective in either direction at the end of the given evaluation period. The suggested evaluation period is one month. + +NOTE 1 – For the purpose of this Recommendation, a month is understood to be any period of 28 to 31 consecutive 24-hour intervals. To be able to compare measurement results taken by different parties on the same path, start time and duration of the performance evaluation period need to be agreed between the parties concerned. + +**Table 1/G.826 – End-to-end error performance objectives for a 27 500 km international digital HRX or HRP** + +| Rate | Connections | Paths | | | | | +|------------|------------------------------------|-----------------------------|--------------------|---------------------|----------------------|------------------------| +| | 64 kbit/s to primary rate (Note 4) | 1.5 to 5 (Mbit/s) | > 5 to 15 (Mbit/s) | > 15 to 55 (Mbit/s) | > 55 to 160 (Mbit/s) | > 160 to 3500 (Mbit/s) | +| Bits/block | Not applicable | 800-5000 | 2000-8000 | 4000-20 000 | 6000-20 000 | 15 000-30 000 (Note 2) | +| ESR | 0.04 | 0.04 | 0.05 | 0.075 | 0.16 | (Note 3) | +| SESR | 0.002 | 0.002 | 0.002 | 0.002 | 0.002 | 0.002 | +| BBER | Not applicable | $2 \times 10^{-4}$ (Note 1) | $2 \times 10^{-4}$ | $2 \times 10^{-4}$ | $2 \times 10^{-4}$ | $10^{-4}$ | + +NOTE 1 – For systems designed prior to 1996, the BBER objective is $3 \times 10^{-4}$ . + +NOTE 2 – As currently defined, VC-4-4c (ITU-T Rec. G.707/Y.1322 [3]) is a 601 Mbit/s path with a block size of 75 168 bits/block. Since this is outside the recommended range for 160-3500 Mbit/s paths, performance on VC-4-4c paths should not be estimated in-service using this table. The BBER objective for VC-4-4c using the 75 168 bit block size is taken to be $4 \times 10^{-4}$ . + +Digital sections are defined for higher bit rates and guidance on evaluating the performance of digital sections can be found in 7.1 and in a Recommendation dealing with multiplex section error performance. + +NOTE 3 – ESR objectives tend to lose significance for applications at high bit rates and are therefore not specified for paths operating at bit rates above 160 Mbit/s. Nevertheless, it is recognised that the observed performance of SDH paths is essentially error-free for long periods of time, even at Gigabit rates. Significant ESR indicates a degraded transmission system. Therefore, for maintenance purposes, ES monitoring should be implemented within any error performance measuring devices operating at these rates. + +NOTE 4 – It is not required to apply this Recommendation to connections which operate below the primary rate using equipment designed prior to the adoption of this Recommendation in December 2002. Performance events and objectives for connections using equipment designed prior to this date are given in ITU-T Rec. G.821 [14]. + +It is noted that SES events may occur in clusters, not always as isolated events. A sequence of "n" contiguous SES may have a very different impact on performance from "n" isolated SES events. + +Digital paths and connections operating at bit rates covered by this Recommendation are carried by transmission systems (digital sections) operating at equal or higher bit rates. Such systems must meet their allocations of the end-to-end objectives for the most demanding paths or connections which are foreseen to be carried. For example, in SDH, an STM-1 section may carry a VC-11/VC-12 path and therefore the STM-1 section should be designed such that it will ensure that the objectives as specified in this Recommendation for the bit rate corresponding to a VC-11/VC-12 path are met. Under the assumption of random error distribution, meeting the allocated objectives in Table 1 for the highest bit rate should be sufficient to ensure that all paths or connections through the system are achieving their objectives. + +NOTE 2 – Objectives are allocated in this Recommendation to the national and international portions of a path or connection. In the above example, if the STM-1 section does not form a complete national or international portion, the corresponding national/international allocation must be subdivided to determine the appropriate allocation for the digital section. This is outside the scope of this Recommendation and is covered in a separate Recommendation. + +## 7.2 Apportionment of end-to-end objectives + +The following apportionment methodology specifies the levels of performance expected from the national and international portions of an HRX or HRP. Further subdivision of these objectives is beyond the scope of this Recommendation. (See Figure 3.) + +![Diagram of a Hypothetical Reference Path or Connection (Figure 3/G.826). The path is shown as a horizontal line with several components: PEP (Note 1) at the far left, followed by an IG (International Gateway). This is followed by a 'National portion' leading to another IG (Note 2). The path then enters an 'International portion' which includes 'Intermediate countries (Note 3)' and two more IGs. A dashed line segment represents an 'Inter-country (e.g., Connection or Path carried over a submarine cable)'. The path then enters another 'National portion' leading to a final IG, and finally a PEP (Note 1) at the far right. The total length of the path is labeled as '27 000 km'. The diagram is labeled 'G.826_F03' at the bottom right.](0f985b39edc1d52ba3600c438bc8f0a5_img.jpg) + +Diagram of a Hypothetical Reference Path or Connection (Figure 3/G.826). The path is shown as a horizontal line with several components: PEP (Note 1) at the far left, followed by an IG (International Gateway). This is followed by a 'National portion' leading to another IG (Note 2). The path then enters an 'International portion' which includes 'Intermediate countries (Note 3)' and two more IGs. A dashed line segment represents an 'Inter-country (e.g., Connection or Path carried over a submarine cable)'. The path then enters another 'National portion' leading to a final IG, and finally a PEP (Note 1) at the far right. The total length of the path is labeled as '27 000 km'. The diagram is labeled 'G.826\_F03' at the bottom right. + +NOTE 1 – If a path is considered to terminate at the IG, only the international portion allocation applies. + +NOTE 2 – One or two International Gateways (entry or exit) may be defined per intermediate country. + +NOTE 3 – Four intermediate countries are assumed. + +**Figure 3/G.826 – Hypothetical Reference Path or Connection** + +For the purposes of this Recommendation, the boundary between the national and international portions is defined to be at an International Gateway which usually corresponds to a cross-connect, a higher-order multiplexer or a switch (N-ISDN or B-ISDN). IGs are always terrestrially based equipment physically resident in the terminating (or intermediate) country. Higher-order paths (relative to the HRP or HRX under consideration) may be used between IGs. Such paths receive only the allocation corresponding to the international portion between the IGs. In intermediate countries, the IGs are only located in order to calculate the overall length of the international portion of the path in order to deduce the overall allocation. + +The following allocation methodology applies to each parameter defined in 4.7 and takes into account both the length and complexity of the international path. All paths should be engineered to meet their allocated objectives as described in 7.2.1 and 7.2.2. If the overall allocation exceeds 100%, then the performance of the path may not fulfil the objectives of Table 1. Network Operators should note that if performance could be improved in practical implementations to be superior to allocated objectives, the occurrence of paths exceeding the objectives of Table 1 can be minimised. + +### 7.2.1 Allocation to the national portion of the end-to-end path or connection + +Each national portion is allocated a fixed block allowance of 17.5% of the end-to-end objective. Furthermore, a distance-based allocation is added to the block allowance. The actual route length between the PEP and IG should first be calculated if known. The air route distance between the PEP and IG should also be determined and multiplied by an appropriate routing factor. This routing factor is specified as follows: + +- if the air route distance is <1000 km, the routing factor is 1.5; +- if the air route distance is $\geq 1000$ km and <1200 km, the calculated route length is taken to be 1500 km; +- if the air route distance is $\geq 1200$ km, the routing factor is 1.25. + +When both actual and calculated route lengths are known, the smaller value is retained. This distance should be rounded up to the nearest 500 km (i.e., the two national portions comprise at least 500 km each). An allocation of 0.2% per 100 km is then applied to the resulting distance. + +When a national portion includes a satellite hop, a total allowance of 42% of the end-to-end objectives in Table 1 is allocated to this national portion. The 42% allowance completely replaces both the distance-based allowance and the 17.5% block allowance otherwise given to national portions. + +NOTE – If a path or connection comprises portions that are privately owned (private in this context means that the network portion is customer owned and not available to the public), end-to-end performance objectives apply to the portion situated between the two Network Terminal Equipment (NTE). Between the NTE and the Terminal Equipment (TE), no specific requirements are given. However, careful attention should be paid concerning this portion because overall performance depends on it. Appendix III contains details for the case of Leased Circuits. + +### **7.2.2 Allocation to the international portion of the end-to-end path or connection** + +The international portion is allocated a block allowance of 2% per intermediate country plus 1% for each terminating country. Furthermore, a distance-based allocation is added to the block allowance. As the international path or connection may pass through intermediate countries, the actual route length between consecutive IGs (one or two for each intermediate country) should be added to calculate the overall length of the international portion. The air route distance between consecutive IGs should also be determined and multiplied by an appropriate routing factor. This routing factor is specified as follows for each element between IGs: + +- if the air route distance between two IGs is <1000 km, the routing factor is 1.5; +- if the air route distance is $\geq 1000$ km and <1200 km, the calculated route length is taken to be 1500 km; +- if the air route distance between two IGs is $\geq 1200$ km, the routing factor is 1.25. + +When both actual and calculated route lengths are known, the smaller value is retained for each element between IGs for the calculation of the overall length of the international portion. This overall distance should be rounded up to the nearest 500 km but shall not exceed 26 500 km. An allocation of 0.2% per 100 km is then applied to the resulting distance. + +In the case where the allocation to the international portion is less than 6%, then 6% shall be used as the allocation. + +Independent of the distance spanned, any satellite hop in the international portion receives a 35% allocation of the objectives in Table 1. The 35% allowance completely replaces all distance-based and block allowances otherwise given to parts of the international portion spanned by the satellite hop. + +# **Annex A** + +## **Criteria for entry and exit for the unavailable state** + +## **A.1 Criteria for a single direction** + +A period of unavailable time begins at the onset of ten consecutive SES events. These ten seconds are considered to be part of unavailable time. A new period of available time begins at the onset of ten consecutive non-SES events. These ten seconds are considered to be part of available time. Figure A.1 illustrates this definition. + +![Figure A.1/G.826 – Example of unavailability determination. A timeline diagram showing a sequence of seconds categorized as Severely Errored Second (SES), Errored Second (non-SES), or Error-free Second. It defines the 'Unavailability detected' and 'Availability detected' thresholds based on consecutive seconds of error.](b53846f262c6904a1b45abef2e95fbd8_img.jpg) + +The diagram shows a horizontal timeline labeled 'Time' at the top right, divided into 24 individual seconds. Below the timeline, three categories are defined in a legend: + +- Severely Errored Second +- ⊠ Errored Second (non-SES) +- Error-free Second + +The timeline is divided into three main periods by vertical dashed lines: + +- Unavailability detected:** The first period, lasting 10 seconds, where the first 15 seconds are SES and the next 5 are non-SES. +- Unavailable period:** A shorter period, lasting less than 10 seconds (<10 s), where the first 5 seconds are SES and the next 4 are non-SES. +- Availability detected:** The final period, lasting 10 seconds, where the first 5 seconds are SES and the next 5 are non-SES. + +The label 'G.826\_FA.1' is located in the bottom right corner. + +Figure A.1/G.826 – Example of unavailability determination. A timeline diagram showing a sequence of seconds categorized as Severely Errored Second (SES), Errored Second (non-SES), or Error-free Second. It defines the 'Unavailability detected' and 'Availability detected' thresholds based on consecutive seconds of error. + +**Figure A.1/G.826 – Example of unavailability determination** + +## A.2 Criterion for a bidirectional path or connection + +A bidirectional path or connection is in the unavailable state if either one or both directions are in the unavailable state. This is shown in Figure A.2. + +![Figure A.2/G.826 – Example of the unavailable state of a path or connection. A diagram showing three horizontal lines representing 'Forward direction', 'Backward direction', and 'Path'. Shaded blocks indicate periods of unavailability for each. The 'Path' line is shaded if either the 'Forward direction' or 'Backward direction' is shaded at that time.](ef25c3cf1fdb334fc8679e85ab5265ca_img.jpg) + +The diagram shows three horizontal lines representing different states over time: + +- Forward direction:** Shows two shaded blocks representing unavailability. +- Backward direction:** Shows two shaded blocks representing unavailability, offset from the forward direction. +- Path:** Shows a shaded block that spans the duration of both the forward and backward unavailability periods. + +The label 'G.826\_FA.2' is located in the bottom right corner. A legend at the bottom left shows a shaded rectangle labeled 'Unavailable state'. + +Figure A.2/G.826 – Example of the unavailable state of a path or connection. A diagram showing three horizontal lines representing 'Forward direction', 'Backward direction', and 'Path'. Shaded blocks indicate periods of unavailability for each. The 'Path' line is shaded if either the 'Forward direction' or 'Backward direction' is shaded at that time. + +**Figure A.2/G.826 – Example of the unavailable state of a path or connection** + +## A.3 Criterion for a unidirectional path or connection + +The criterion for a unidirectional path or connection is defined in A.1 above. + +## A.4 Consequences on error performance measurements + +When a bidirectional path or connection is in the unavailable state, ES, SES and BBE counts may be collected in both directions and may be helpful in the analysis of the trouble. However, it is recommended that these ES, SES and BBE counts are not included in estimates of ESR, SESR and BBER performance (see 4.5). + +Some existing systems cannot support this requirement to exclude ES, SES and BBE counts. For these systems, the performance of a bidirectional path can be approximated by evaluating the parameters in each direction, independently of the state of availability of the other direction. It should be noted that this approximation method may result in a worse estimate of performance in the event that only one direction of a bidirectional path becomes unavailable. + +NOTE – This is not an issue for unidirectional paths or connections. + +# Annex B + +## Relationship between PDH path performance monitoring and the block-based parameters + +## B.1 General + +### B.1.1 Block size for monitoring PDH paths + +The block sizes for in-service performance monitoring of PDH paths are given in Table B.1. + +**Table B.1/G.826 – Block sizes for PDH path performance monitoring** + +| Bit rate of PDH path | Block size according to Table 1 | PDH block size used in this Recommendation | EDC | Reference | +|----------------------|---------------------------------|--------------------------------------------|--------------------------------|----------------| +| 1 544 kbit/s | 800-5000 bits | 4632 bits | CRC-6 | 2.1/G.704 [2] | +| 2 048 kbit/s | 800-5000 bits | 2048 bits | CRC-4 | 2.3/G.704 | +| 6 312 kbit/s | 2000-8000 bits | 3156 bits | CRC-5 | 2.2/G.704 | +| 44 736 kbit/s | 4000-20 000 bits | 4760 bits | Single bit parity check (Note) | 1.3/G.752 [10] | + +NOTE – It shall be noted that single bit parity check does not satisfy the error detection probability of $\geq 90\%$ . + +### B.1.2 Anomalies + +In-service anomaly conditions are used to determine the error performance of a PDH path when the path is not in a defect state. The two following categories of anomalies related to the incoming signal are defined: + +- a1 an errored frame alignment signal; +- a2 an EB as indicated by an EDC. + +### B.1.3 Defects + +In-service defect conditions are used in the G.730 to G.750 series of Recommendations relevant to PDH multiplex equipment to determine the change of performance state which may occur on a path. The three following categories of defects related to the incoming signal are defined: + +- d1 loss of signal; +- d2 alarm indication signal; +- d3 loss of frame alignment. + +For the 2 Mbit/s hierarchy, the definition of the LOF defect condition is given in the G.730 to G.750 series of Recommendations. + +For some formats of the 1.5 Mbit/s hierarchy, the definition of the LOF defect condition requires further study + +For both hierarchies, the definitions of LOS and AIS defect detection criteria are given in ITU-T Rec. G.775 [12]. + +## **B.2 Types of paths** + +Depending on the type of in-service monitoring "ISM" facility associated with the PDH path under consideration, it may not be possible to derive the full set of performance parameters. Four types of paths are identified: + +### **Type 1: Frame and block structured paths** + +The full set of defect indications $d_1$ to $d_3$ and anomaly indications $a_1$ and $a_2$ are provided by the ISM facilities. Examples of this type of path are: + +- primary rate and second order paths with CRC (4 to 6) as defined in ITU-T Rec. G.704 [2]; +- fourth order paths with a parity bit per frame as defined in ITU-T Rec. G.755 [11]. + +### **Type 2: Frame structured paths** + +The full set of defect indications $d_1$ to $d_3$ and the anomaly indication $a_1$ are provided by the ISM facilities. Examples of this type of path are: + +- primary rate up to the fourth order paths in the 2 Mbit/s hierarchy as defined in ITU-T Recs G.732 [4], G.742 [7] and G.751 [9]; +- primary rate paths in the 1.5 Mbit/s hierarchy as defined in Recs G.733 [5] and G.734 [6]. + +### **Type 3: Other frame structured paths** + +A limited set of defect indications $d_1$ and $d_2$ and the anomaly indication $a_1$ are provided by the ISM facilities. In addition, the number of consecutive errored FAS per second is available. An example of this type of path is: + +- second up to the fourth order paths in the 1.5 Mbit/s hierarchy as defined in Recs G.743 [8] and G.752 [10]. + +### **Type 4: Unframed paths** + +A limited set of defect indications $d_1$ and $d_2$ is provided by the ISM facilities which do not include any error check. No FAS control is available. An example of this type of path is: + +- end-to-end path (e.g., for a leased circuit) carried over several higher order paths placed in tandem. + +## **B.3 Estimation of the performance parameters** + +Table B.2 gives information on which set of parameters should be estimated and the related measurement criteria according to the type of path considered. + +**Table B.2/G.826 – Set of parameters and measurement criteria** + +| Type | Set of parameters | Measurement criteria | +|------|-------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| 1 | ESR | An ES is observed when, during one second, at least one anomaly a 1 or a 2 , or one defect d 1 to d 3 occurs. | +| | SESR | An SES is observed when, during one second, at least "x" anomalies a 1 or a 2 , or one defect d 1 to d 3 occurs (Notes 1 and 2). | +| | BBER | A BBE is observed when an anomaly a 1 or a 2 occurs in a block not being part of an SES. | +| 2 | ESR | An ES is observed when, during one second, at least one anomaly a 1 or one defect d 1 to d 3 occurs. | +| | SESR | An SES is observed when, during one second, at least "x" anomalies a 1 or one defect d 1 to d 3 occurs (Note 2). | +| 3 | ESR | An ES is observed when, during one second, at least one anomaly a 1 or one defect d 1 or d 2 occurs. | +| | SESR | An SES is observed when, during one second, at least "x" anomalies a 1 or one defect d 1 or d 2 occurs (Note 2). | +| 4 | SESR | An SES is observed when, during one second, at least one defect d 1 or d 2 occurs (Note 3). | + +NOTE 1 – If more than one anomaly a1 or a2 occur during the block interval, then only one anomaly has to be counted. + +NOTE 2 – Values of "x" can be found in B.4. + +NOTE 3 – The estimates of the ESR and SESR will be identical since the SES event is a subset of the ES event. + +## **B.4 In-service monitoring capabilities and criteria for declaration of the performance parameters** + +Table B.3 is provided for guidance on the criteria for declaration of an SES event on PDH paths. + +The capabilities for the detection of anomalies and defects for the various PDH signal formats are described in Tables B.2/M.2100 to B.6/M.2100 [21]. These tables also indicate the criteria for declaring the occurrence of an ES or a SES condition in accordance with ITU-T Rec. G.821 [14] criteria. + +While it is recommended that ISM capabilities of future systems be designed to permit performance measurements in accordance with this Recommendation, it is recognised that it may not be practical to change equipment already installed and/or designed in accordance with ITU-T Rec. G.821 [14] or the 1996 version of this Recommendation. + +Table B.3 lists examples of the ISM SES criteria x, for signal formats with EDC capabilities, implemented prior to this Recommendation. + +**Table B.3/G.826 – Criteria for declaration of an SES event on PDH paths** + +| Bit rate (kbit/s) | 1544 | 2048 | 44 736 | +|------------------------------------------------------------------------------------------|-----------------------|-----------------------|------------------------------------------------------------------------| +| Recommendation | G.704 [2] | G.704 [2] | G.752 [10] | +| EDC type | CRC-6 | CRC-4 | Single bit parity check | +| Blocks/second | 333 | 1000 | 9398 | +| Bits/block | 4632 | 2048 | 4760 | +| SES threshold used on equipment developed prior to the acceptance of this Recommendation | $x = 320$
(Note 2) | $x = 805$
(Note 2) | $x = 45$ or $x = 2444$
as suggested in
ITU-T
Rec. M.2100 [21] | +| ISM threshold based on G.826 SES (30% errored blocks) | $x = 100$
(Note 3) | $x = 300$
(Note 3) | $x = 2444$
(Note 4) | + +NOTE 1 – It is recognised that there are discrepancies between the figures above and those given in Table B.1. This requires further study. + +NOTE 2 – Applicable to installations in accordance with ITU-T Rec. G.821 [14] or the 1996 version of this Recommendation and where compatibility with these installations is required. + +NOTE 3 – Preferred option for new installations. + +NOTE 4 – This figure takes into account the fact that, although 30% of the blocks could contain errors, a smaller value will be detected by the EDC due to the inability of the simple parity code to detect even numbers of errors in a block. It should be noted that such a simple EDC is non-compliant with the intent of this Recommendation. + +NOTE 5 – Completion of this table for other bit rates is for further study. + +## **B.5 Estimation of performance events at the far end of a path** + +The available remote in-service indications such as RDI or, if provided, REI are used at the near end to estimate the number of SES occurring at the far end. + +## **B.6 Differences between this Recommendation and ITU-T Rec. M.2100 concerning path performance** + +### **B.6.1 General** + +When looking at the differences between this Recommendation and ITU-T Rec. M.2100 [21], it shall be taken into account that the two Recommendations serve a different purpose and can therefore not be compatible in all respects. ITU-T Rec. M.2100 [21] is a maintenance Recommendation which also allows short-term measurements. It can be used to indicate that the long-term requirements of this Recommendation are met. + +### **B.6.2 Allocation methodology** + +The allocation methodology used in this Recommendation differs from the methods applied in ITU-T Rec. M.2100 [21]. Though there are differences, in most cases the requirements of this Recommendation are satisfied if the objectives of ITU-T Rec. M.2100 [21] are met. + +With regard to the purpose of the intermediate IGs depicted in Figure 3, it shall be noted that they are required to calculate route length. + +# Annex C + +## Relationship between SDH path performance monitoring and the block-based parameters + +## C.1 General + +### C.1.1 Converting BIP measurements into errored blocks + +Clause 4.4 describes error performance events used in defining performance parameters. The method of converting BIP measurements into errored blocks is described below. + +Since this Recommendation defines a block as consecutive bits associated with a path, each BIP-n (Bit Interleaved Parity, order "n") in the SDH path overhead pertains to a single defined block. For the purpose of this Annex, a BIP-n corresponds to a G.826 block. The BIP-n is NOT interpreted as checking "n" separate interleaved parity check blocks. If any of the "n" separate parity checks fails, the block is assumed to be in error. + +NOTE – It shall be noted that BIP-2 does not satisfy the error detection probability of $\geq 90\%$ . + +### C.1.2 Block size for monitoring SDH paths + +The block sizes for in-service performance monitoring of SDH paths as specified in ITU-T Rec. G.707/Y.1322 [3] are given in Table C.1. + +**Table C.1/G.826 – Block sizes for SDH path performance monitoring** + +| Bit rate of SDH path | Path type | Block size according to Table 1 | SDH block size used in this Recommendation | EDC | +|-----------------------------------------------|------------------|---------------------------------|--------------------------------------------|------------------| +| 1664 kbit/s | VC-11 | 800-5000 bits | 832 bits | BIP-2 | +| 2240 kbit/s | VC-12 | 800-5000 bits | 1120 bits | BIP-2 | +| 6848 kbit/s | VC-2 | 2000-8000 bits | 3424 bits | BIP-2 | +| 48 960 kbit/s | VC-3 | 4000-20 000 bits | 6120 bits | BIP-8 | +| 150 336 kbit/s | VC-4 | 6000-20 000 bits | 18 792 bits | BIP-8 | +| $m \times 6848$ kbit/s | VC-2-mc (Note 1) | | 3424 bits | $m \times$ BIP-2 | +| 34 240 kbit/s | VC-2-5c (Note 2) | 6000-20 000 bits | 17 120 bits | BIP-2 | +| 601 344 kbit/s | VC-4-4c | 15 000-30 000 bits | 75 168 bits | BIP-8 | +| NOTE 1 – Applies to virtual concatenation. | | | | | +| NOTE 2 – Applies to contiguous concatenation. | | | | | + +### C.1.3 Anomalies + +In-service anomaly conditions are used to determine the error performance of an SDH path when the path is not in a defect state. The following anomaly is defined: + +a1 an EB as indicated by an EDC (see C.1.1). + +### C.1.4 Defects + +In-service defect conditions are used in ITU-T Recs G.707/Y.1322 [3] and G.783 [13] relevant to SDH equipment to determine the change of performance state which may occur on a path. Tables C.2 and C.3 show the defects used in this Recommendation. + +**Table C.2/G.826 – Defects resulting in a near-end severely errored second** + +| Near-end defects | Kind of path | +|-------------------------|----------------------------------| +| LP UNEQ | Applicable to lower-order paths | +| LP TIM | | +| TU LOP | | +| TU AIS | | +| HP LOM (Note 1) | | +| HP PLM | | +| HP UNEQ | Applicable to higher-order paths | +| HP TIM | | +| AU LOP | | +| AU AIS | | + +NOTE 1 – This defect is not related to VC-3. + +NOTE 2 – VC AIS defect is not included above as it only applies to a segment of a path. + +NOTE 3 – The above defects are path defects only. Section defects such as MS AIS, RS TIM, STM LOF and STM LOS give rise to an AIS defect in the path layers. + +NOTE 4 – When a near-end SES is caused by a near-end defect as defined above, the far-end performance event counters are not incremented, i.e., an error-free period is assumed. When a near-end SES is resulting from $\geq 30\%$ errored blocks, the far-end performance evaluation continues during the near-end SES. + +This approach does not allow reliable evaluation of far-end data if the near-end SES is caused by a defect. It should be noted in particular, that the evaluation of far-end events (such as SES or Unavailability) can be inaccurate in the case where far-end SESs occur in coincidence with near-end SESs caused by a defect. Such inaccuracies cannot be avoided, but are negligible in practice because of the low probability of the occurrence of such phenomena. + +**Table C.3/G.826 – Defects resulting in a far-end severely errored second** + +| Far-end defects | Kind of path | +|------------------------|----------------------------------| +| LP RDI | Applicable to lower-order paths | +| HP RDI | Applicable to higher-order paths | + +### C.1.5 Measurement of performance events using aggregate parity error counts + +This clause offers guidance for equipment designed to sum individual Bit Interleaved Parity violations over the entire second instead of using the BIP-n block to detect and count errored blocks as recommended in C.1.1. The following text should not be interpreted as a basis for future equipment design. + +Aggregate counts of Bit Interleaved Parity (BIP) violations can be used to estimate the number of G.826 errored blocks. As a simplifying assumption, the aggregate count of individual Bit Interleaved Parity violations in a second can be taken to be roughly equivalent to the number of G.826 errored blocks in that second. The following relationship is recommended for both BIP-2 and BIP-8, even though it may tend to overestimate errored blocks in case of BIP-8: + +$$E \approx P$$ + +where: + +E number of errored blocks in the measurement period + +P number of individual parity violations in the measurement period + +## C.2 Estimation of the performance parameters + +For SDH transmission paths, the full set of performance parameters shall be estimated using the following events: + +ES: An ES is observed when, during one second, at least one anomaly $a_1$ , or one defect according to Tables C.2 and C.3 occurs. For the ES event, the actual count of EBs is irrelevant; it is only the fact that an EB has occurred in a second which is significant. + +SES: An SES is observed when, during one second, at least 30% EBs; derived from anomaly $a_1$ or one defect according to Tables C.2 and C.3, occur (see Note). + +BBE: A BBE is observed when an anomaly $a_1$ occurs in a block not being part of an SES. + +NOTE – The errored block threshold resulting in an SES is shown in Table C.4 for each SDH path type. + +**Table C.4/G.826 – Threshold for the declaration of a severely errored second** + +| Path type | Threshold for SES
(Number of errored blocks in one second) | +|-----------|---------------------------------------------------------------| +| VC-11 | 600 | +| VC-12 | 600 | +| VC-2 | 600 | +| VC-3 | 2400 | +| VC-4 | 2400 | +| VC-2-5c | 600 | +| VC-4-4c | 2400 | + +NOTE – It is recognised that there are discrepancies between the figures above and those given in Table B.3. This requires further study. + +## C.3 Estimation of performance events at the far end of a path + +The following indications available at the near end are used to estimate the performance events (occurring at the far end) for the reverse direction: + +Higher and lower order path RDI and REI (ITU-T Rec. G.707/Y.1322 [3]). + +Higher- or lower-order path REIs are anomalies which are used to determine the occurrence of ES, BBE and SES at the far end. + +Higher or lower order path RDIs are defects which estimate the occurrence of SES at the far end. + +# Annex D + +## Relationship between cell-based network performance monitoring and the block-based parameters + +## D.1 General + +### D.1.1 Block size for monitoring cell-based paths + +The block sizes for in-service performance monitoring of cell-based paths are given in Table D.1. + +**Table D.1/G.826 – Block sizes for cell-based path performance monitoring** + +| Bit rate for cell-based path | Block size according to Table 1 | Number of cells/block (as defined in ITU-T Rec. I.432) [18] | Cell-based block size used in this Recommendation | +|-------------------------------------|----------------------------------------|--------------------------------------------------------------------|----------------------------------------------------------| +| 51 Mbit/s | 4 000-20 000 | 15 | 6 360 bits | +| 155 Mbit/s | 6 000-20 000 | 27 | 11 448 bits | +| 622 Mbit/s | 15 000-30 000 | 54 | 22 896 bits | + +The operation and maintenance function for the transmission path is provided by the F3 flow as defined in ITU-T Rec. I.610 [19] which deals with the general OAM principles for B-ISDN. + +The F3 maintenance flow corresponds to the ISM facilities and is defined in ITU-T Rec. I.432 [18]. For the 51 Mbit/s cell-based path, each F3 OAM cell monitors 15 cells. For the 155 Mbit/s and the 622 Mbit/s cell-based paths, each F3 OAM cell monitors 8 blocks of 27 (or 54) contiguous cells. The block – as defined in this Recommendation – corresponds to a set of contiguous cells monitored by a BIP-8 EDC. For the purpose of this Recommendation, the BIP-8 is not interpreted as checking 8 separate interleaved parity check blocks. One BIP-8 interleaved parity check cannot lead to more than one errored block. Within one BIP-8 check, if any of the 8 separate parity checks fails, the overall block is assumed to be in error. + +### **D.1.2 Anomalies** + +The following categories of anomalies related to the incoming signal on an ATM transmission path are defined: + +- a1 errored payload of an idle or ATM cell (detected by an EDC in the F3 OAM cell) (see Note 1); +- a2 errored or corrected header of an idle or ATM cell; +- a3 corrected F3 cell header; +- a4 loss of a single F3 cell (Note 2) or error detected by the cell error control of a valid F3 cell. + +NOTE 1 – An ATM cell is provided by the ATM layer. + +NOTE 2 – Loss of a single F3 cell is declared when no valid F3 OAM cell is received x cells after the last valid F3 OAM cells. The value of x is given below. + +| Applicable bit rate | Value of x | +|----------------------------|-------------------| +| 51.840 Mbit/s | 14 | +| 155.520 Mbit/s | 215 | +| 622.080 Mbit/s | 431 | + +When at least one anomaly a1 to a3 occurs in a given block, an Errored Block should be counted. If more than one anomaly occurs for a given block, only one EB is counted. When an a4 anomaly occurs, all blocks monitored by the F3 OAM cell are errored (1 block for 51 Mbit/s and 8 blocks for the bit rates of 155 and 622 Mbit/s respectively). + +### **D.1.3 Defects** + +The following categories of defects related to the incoming signal on an ATM transmission path are defined: + +- d1 loss of two consecutive OAM cells, in accordance with ITU-T Rec. I.432 [18]; + +- d2 transmission path alarm indication signal (TP-AIS); +- d3 loss of cell delineation; +- d4 loss of signal. + +## **D.2 Types of paths** + +Two types of ATM transmission paths are identified: + +- Type 1: Paths corresponding to a stream of cells mapped in a cell-based format. +- Type 2: Paths corresponding to a stream of cells mapped into SDH or PDH-based frame structures. + +The full set of performance parameters of this Recommendation and corresponding objectives is applicable to the ATM transmission path of type 1. + +The performance parameters and corresponding objectives are applied to underlying SDH or PDH paths which support ATM transmission paths of type 2. + +The applicability of the performance parameters for type 2 ATM transmission paths requires further study. + +## **D.3 Estimation of the performance parameters** + +For type 1 ATM transmission paths, the full set of G.826 performance parameters should be estimated using the following events: + +- ES: An ES is observed when, during one second, at least one anomaly a1 to a4, or one defect d1 to d4 occurs. +- SES: An SES is observed when, during one second, at least 30% EBs, derived from anomalies a1 to a4, or one defect d1 to d4 occur. +- BBE: A BBE is observed when one anomaly a1 to a4 occurs in a block not being part of an SES. + +## **D.4 Estimation of performance events at the far end of the path** + +The TP-RDI defect (see ITU-T Rec. I.432 [18]) and REI indications are used at the near end to estimate the G.826 performance events occurring at the far end. + +REIs are anomalies which are used to determine the occurrence of ES, BBE and SES at the far end of the path. + +TP-RDIs are defects which estimate the occurrence of SES at the far end of the path. + +# Appendix I + +## Flow chart illustrating for digital paths the recognition of anomalies, defects, errored blocks, ES and SES + +![Flow chart illustrating the recognition of anomalies, defects, errored blocks, ES, SES and BBE.](b235edb1dbe659e2782c9a0e47775ca4_img.jpg) + +``` + +graph TD + Start([Monitored second]) --> D{Defects?} + D -- Yes --> SES_Label[SES +(and therefore an ES)] + D -- No --> A{Anomalies?} + A -- No --> End([End]) + A -- Yes --> EB{ $\%EB \geq 30?$ } + EB -- Yes --> SES_Label + EB -- No --> ES_Label[ES +(but not a SES)] + + ES_Label --> P1{Path in +available +State?} + P1 -- No --> End + P1 -- Yes --> cES1[cES = cES + 1] + cES1 --> cBBE[cBBE = cBBE + EB(s)] + cBBE --> End + + SES_Label --> P2{Path in +available +State?} + P2 -- No --> End + P2 -- Yes --> cES2[cES = cES + 1] + cES2 --> cSES[cSES = cSES + 1] + cSES --> End + +``` + +G.826\_FI.1 + +Flow chart illustrating the recognition of anomalies, defects, errored blocks, ES, SES and BBE. + +**Figure I.1/G.826 – Flow chart illustrating the recognition of anomalies, defects, errored blocks, ES, SES and BBE** + +### Notes to Figure I.1 + +NOTE 1 – The determination of unavailability time introduces a delay of ten seconds. This delay should be considered when counting BBE, ES and SES. + +NOTE 2 – cES, cSES and cBBE represent counts of ES, SES, BBE respectively. These counts are reset at the start of a measurement period. + +NOTE 3 – EB is the count of errored blocks within an ES whilst %EB represents the proportion of errored blocks within an ES compared to the number of blocks per second. + +NOTE 4 – G.826 parameters can be evaluated during, or at the end of, a measurement period P as follows, taking into account Unavailable Seconds (UAS): + +$$\text{BBER} = \text{cBBE} / [(P - \text{UAS} - \text{cSES}) \times \text{blocks per second}]$$ + +$$\text{ESR} = \text{cES} / (P - \text{UAS})$$ + +$$\text{SESR} = \text{cSES} / (P - \text{UAS})$$ + +NOTE 5 – In the simplified diagram, no action is taken if the path is in the unavailable state. This is because the diagram does not consider the transition between availability states when, in fact, event counters must be modified retrospectively. In practice, the status of a second (i.e., error-free, ES or SES) must always be determined before a test is made on the status of path availability. In other words, error events are always detected regardless of whether the path is available or not – only the *counting* of events is inhibited during unavailability periods for the purposes of long-term performance monitoring. This process is reflected in the flow chart although consequent actions on changes of availability state are not. + +# Appendix II + +## Bit errors and block errors, merits and limitations + +In digital transmission technology, any bit received in error – a Bit Error – may deteriorate transmission quality. It is obvious that quality will decrease with an increasing number of erroneous bits. Therefore, the ratio of the number of errored bits referred to the total number of bits transmitted in a given time interval is a quantity which can be used to describe digital transmission performance. + +The quantity is called Bit-Error Ratio (BER) and is a well-known error performance parameter (see definition in Fascicle I.3 of the CCITT *Blue Book*). + +Bit-Error Ratio can only be measured if the bit structure of the evaluated sequence is known. For this reason, bit error ratio measurements are mostly carried out using well-defined Pseudo-Random Bit Sequences (PRBSs). In practice, the PRBS replaces the information sent in-service. This means that BER can only be measured correctly out-of-service because the bit structure of an arbitrary message is normally unknown. + +It was one of the prime objectives of this Recommendation to define all performance parameters for digital paths in such a way that in-service estimation is possible. Thus, parameter definitions for digital paths based upon Bit Error Ratios were not chosen in spite of their merits. + +In-service detection of errors in digital transmission is possible, however, using special error detection mechanisms (Error Detection Code, EDC) which are inherent to certain transmission systems. + +Examples of those inherent EDCs are Cyclic Redundancy Check (CRC), Parity Check and observation of Bit Interleaved Parity (BIP). EDCs are capable to detect whether one or more errors + +have occurred in a given sequence of bits – the block. It is normally not possible to determine the exact number of errored bits within the block. + +Block Errors are processed in a similar way as Bit Errors, i.e., the term "Block-Error Ratio" is defined as the ratio of the number of errored blocks referred to the total number of blocks transmitted in a given time interval. + +The basic philosophy of this Recommendation is based upon the measurement of errored blocks for digital paths, thus making in-service error estimation possible for paths. + +It should be noted that the measurement of Bit-Error Ratio and Block-Error Ratio yields comparable results for small Bit-Error Ratios. + +It should also be noted that for some specific error models it is possible to calculate Bit-Error Ratio from a Block-Error Ratio. It is the drawback of this procedure that error models describe the situation found in practice only imperfectly and may be strongly media-dependent. Therefore, the result of such a calculation is not very reliable + +# Appendix III + +## Applicability of this Recommendation to non-public networks + +Figure III.1 depicts a typical leased circuit situation where a path is composed of three independent networks: two private networks at both path ends and a public network connecting them. + +![Diagram of a digital path or connection composed of two private networks and a leased circuit provided by a public network operator.](5b6e139e89c6ce90107ea7d7d77620a0_img.jpg) + +The diagram illustrates a digital path across two terminating countries, labeled 'Terminating country 1' and 'Terminating country 2', separated by 'Intermediate countries (Terrestrial link)'. The path consists of several components: 'TE' (Terminal Equipment) at both ends, connected to 'NTE' (Network Terminal Equipment), which is connected to a 'Private network'. The 'Private network' connects to an 'IG' (International Gateway). The 'IG' connects to another 'IG' in the intermediate countries, which then connects to a third 'IG' in the second terminating country. This third 'IG' connects to an 'NTE', which is connected to another 'Private network', which finally connects to the 'TE' at the other end. The diagram is divided into three main horizontal segments: 'National portion' (from the first IG to the first NTE, and from the last NTE to the last IG), 'International portion' (between the first and last IG), and 'Leased circuit' (between the first and last IG). The entire path from the first TE to the last TE is labeled 'End-to-end path'. A legend at the bottom left defines the abbreviations: IG International Gateway, NTE Network Terminal Equipment, TE Terminal Equipment. The diagram is labeled 'G.826\_FIII.1' at the bottom right. + +Diagram of a digital path or connection composed of two private networks and a leased circuit provided by a public network operator. + +**Figure III.1/G.826 – Digital path or connection composed of two private networks and a leased circuit provided by a public network operator** + +The public network provides a leased circuit to connect the two private networks. However, the problem is not restricted to the case shown in Figure III.1 but is of more general nature. For + +instance, similar considerations are applicable if only one side of the path or connection ends in a private network. + +Taking into account that a public operator can only control the public network from NTE to NTE (Network Terminal Equipment), no performance objectives can be given for the portion between NTE and TE. + +It may also be that the public network operator provides the connection by other means than a leased circuit. + + + + + +# SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure and Internet protocol aspects | +| Series Z | Languages and general software aspects for telecommunication systems | + +![Barcode with the number 23371 between two asterisks.](eadd8abb2c85161842bcd823881cbe5f_img.jpg) + +A barcode consisting of vertical black lines of varying widths. 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in packet networks** + +![ITU logo](0538daaa5583c23e17db3a12f2281a55_img.jpg) + +The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with white lines representing latitude and longitude, and the letters 'ITU' in a bold, blue, sans-serif font overlaid on the globe. + +ITU logo + +## ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| Ethernet over Transport aspects | G.8000–G.8099 | +| MPLS over Transport aspects | G.8100–G.8199 | +| Synchronization, quality and availability targets | G.8200–G.8299 | +| Mobile network transport aspects | G.8300–G.8399 | +| Service Management | G.8600–G.8699 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.8260 + +# Definitions and terminology for synchronization in packet networks + +## Summary + +Recommendation ITU-T G.8260 provides the definitions, terminology and abbreviations used in ITU-T Recommendations on timing and synchronization in packet networks. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.8260 | 2010-08-12 | 15 | 11.1002/1000/10907 | +| 2.0 | ITU-T G.8260 | 2012-02-13 | 15 | 11.1002/1000/11521 | +| 2.1 | ITU-T G.8260 (2012) Amd. 1 | 2013-08-29 | 15 | 11.1002/1000/12016 | +| 2.2 | ITU-T G.8260 (2012) Amd. 2 | 2014-05-14 | 15 | 11.1002/1000/12189 | +| 3.0 | ITU-T G.8260 | 2015-08-13 | 15 | 11.1002/1000/12545 | +| 3.1 | ITU-T G.8260 (2015) Amd. 1 | 2016-04-13 | 15 | 11.1002/1000/12808 | +| 3.2 | ITU-T G.8260 (2015) Amd. 2 | 2018-11-29 | 15 | 11.1002/1000/13765 | +| 4.0 | ITU-T G.8260 | 2020-03-15 | 15 | 11.1002/1000/14206 | +| 5.0 | ITU-T G.8260 | 2022-11-13 | 15 | 11.1002/1000/15127 | + +## Keywords + +Frequency, phase and time, packet delay variation, synchronization definitions. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents/software copyrights, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the appropriate ITU-T databases available via the ITU-T website at . + +© ITU 2023 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|------------------------------------------------------------------------------|------| +| 1 Scope ..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 1 | +| 3.1 Terms defined in this Recommendation..... | 1 | +| 4 Abbreviations and acronyms ..... | 7 | +| 5 Conventions ..... | 8 | +| 6 Description of packet timing concepts ..... | 8 | +| 6.1 The nature of packet timing..... | 8 | +| 6.2 Differences between packet-based and physical layer timing systems ..... | 9 | +| 6.3 Classes of packet clocks ..... | 10 | +| 6.4 Two-way timing protocols ..... | 10 | +| 6.5 Packet delay sequence measurement..... | 11 | +| 6.6 Packet timing signal equipment interface characterization ..... | 13 | +| Appendix I – Definitions and properties of packet measurement metrics..... | 14 | +| I.1 Introduction ..... | 14 | +| I.2 Definition of the time error sequence ..... | 15 | +| I.3 Packet selection and filtering..... | 17 | +| I.4 PDV metrics estimating the performance of a packet slave clock ..... | 25 | +| I.5 PDV metrics studying floor delay packet population..... | 40 | +| Bibliography..... | 47 | + + + +# Recommendation ITU-T G.8260 + +## Definitions and terminology for synchronization in packet networks + +# 1 Scope + +This Recommendation provides the definitions, terminology and abbreviations used in Recommendations on frequency, phase and time synchronization in packet networks. It includes mathematical definitions for various synchronization stability and quality metrics for packet networks, and also provides background information on the nature of packet timing systems and the impairments created by packet networks. + +Ethernet physical layer methods for synchronization are based on traditional time division multiplexing (TDM) physical layer synchronization and therefore most of the definitions related to these methods are covered by [ITU-T G.810]. Additional definitions are included in this Recommendation. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.810] Recommendation ITU-T G.810 (1996), *Definitions and terminology for synchronization networks*. +- [ITU-T G.811] Recommendation ITU-T G.811 (1997), *Timing characteristics of primary reference clocks*. +- [ITU-T G.8261] Recommendation ITU-T G.8261/Y.1361 (2019), *Timing and synchronization aspects in packet networks*. +- [ITU-T Y.1413] Recommendation ITU-T Y.1413 (2004), *TDM-MPLS network interworking – User plane interworking*. +- [IEEE 1588] IEEE Standard 1588-2019, *IEEE standard for a precision clock synchronization protocol for networked measurement and control systems*. + +# 3 Definitions + +## 3.1 Terms defined in this Recommendation + +This Recommendation defines the following terms: + +**3.1.1 adaptive clock recovery:** Clock recovery technique that does not require the support of a network-wide synchronization signal to regenerate the timing. In this case, the timing recovery process is based on the (inter-)arrival time of the packets, e.g., timestamps or circuit emulation service (CES) packets. The information carried by the packets could be used to support this operation. Two-way or one-way protocols can be used. + +**3.1.2 arbitrary reference time clock (ARTC):** A reference time generator that provides a reference time signal, or simply a reference phase signal, whose frequency has the accuracy of a + +primary reference clock (PRC) as specified in [ITU-T G.811], while the epoch does not necessarily have a relationship with an internationally recognized time standard. + +**3.1.3 coherent time and frequency:** The condition where the timing signal-carrying frequency and the timing signal-carrying time-of-day or phase are traceable back to the same primary source. + +**3.1.4 floor delay:** The notion of "floor delay" is derived from the notion of minimum possible transit delay of packets over a network. It may be useful to distinguish the notions of "*absolute floor delay*" and "*observed floor delay*": + +- **absolute floor delay:** Absolute minimum possible transit delay of packets of a given size over a network. This may generally be described as the transit delay experienced by a packet that has experienced the minimum possible delay through each network element along a specified path. Depending on loading and other considerations, it is possible that in any given finite window of observation interval a packet with delay equal to this absolute minimum may not be observed. Full knowledge of the packet network, network elements, and routing path must be known in order to perform a theoretical analysis of the minimum transit delay. +- **observed floor delay (OFD):** Minimum transit delay of packets of a given size over a network observed over a given observation interval [for instance, during a packet delay variation (PDV) measurement]. + +NOTE – As mentioned above, the observed floor delay during a PDV measurement may differ from the absolute floor delay. + +**3.1.5 floor delay step:** The difference between the observed floor delays of two consecutive, non-overlapping observation intervals, see Figure 1: + +![Figure 1: Illustration of observed floor delays and floor delay step. The figure shows a scatter plot of packet delays over two consecutive observation intervals. The x-axis is labeled 'Observation interval 1' for both the first and second intervals. The y-axis represents delay. The first interval shows a dense cloud of points with a lower bound (floor delay) indicated by a horizontal line. The second interval shows a similar cloud of points, but shifted upwards. The vertical difference between the two floor delays is labeled 'Floor delay step (over observation intervals 1 and 2)'. The floor delay for the second interval is also indicated by a horizontal line and labeled 'Floor delay (over observation interval 2)'.](27b22513fc27a0ff5f230b062ad3112f_img.jpg) + +The figure is a scatter plot on a grid. The horizontal axis represents time, divided into two 'Observation interval 1' segments. The vertical axis represents delay. In the first interval, there is a dense cloud of blue points with a clear lower boundary. In the second interval, the cloud of points is shifted vertically upwards. A horizontal line marks the lower boundary of the first cloud, and another horizontal line marks the lower boundary of the second cloud. A vertical double-headed arrow between these two lines is labeled 'Floor delay step (over observation intervals 1 and 2)'. An arrow points to the lower boundary of the second cloud with the label 'Floor delay (over observation interval 2)'. The text 'G.8260(12)\_F01' is in the bottom right corner. + +Figure 1: Illustration of observed floor delays and floor delay step. The figure shows a scatter plot of packet delays over two consecutive observation intervals. The x-axis is labeled 'Observation interval 1' for both the first and second intervals. The y-axis represents delay. The first interval shows a dense cloud of points with a lower bound (floor delay) indicated by a horizontal line. The second interval shows a similar cloud of points, but shifted upwards. The vertical difference between the two floor delays is labeled 'Floor delay step (over observation intervals 1 and 2)'. The floor delay for the second interval is also indicated by a horizontal line and labeled 'Floor delay (over observation interval 2)'. + +**Figure 1 – Illustration of observed floor delays and floor delay step** + +**3.1.6 packet-based method:** Timing distribution method (for frequency or time or phase) where the timing information is associated with packets. + +- The frequency can be recovered using two-way or one-way protocols. +- Time and phase information is recovered with a two-way protocol in order to compensate for the transfer delay from packet master clock to packet slave clock. + +**3.1.7 packet-based method with full timing support to the protocol level from the network:** Packet-based method (frequency or time and/or phase synchronization) requiring that all the network nodes on the path of the synchronization flow implement one of the two following types of timing support: + +- termination and regeneration of the timing [e.g., network time protocol (NTP) stratum clocks, precision time protocol (PTP) boundary clock]; +- a mechanism to correct for the delay introduced by the network node or the connected links (e.g., PTP transparent clock). + +**3.1.8 packet-based method with partial timing support to the protocol level from the network:** Packet-based method (frequency or time and/or phase synchronization) where not all of the network nodes on the path of the synchronization flow implement timing support. + +**3.1.9 packet-based method with physical frequency support from the network:** Packet-based method for time and phase synchronization using frequency support from a traceable network reference clock carried by a physical layer timing trail. + +NOTE – For instance, it can correspond to telecom boundary clocks syntonized by a frequency reference carried at the physical layer. This type of support is expected to provide "phase and/or time holdover" capacities, enabling phase and/or time local reference to be maintained during periods of failure of the phase and/or time distribution protocol. + +**3.1.10 packet-based method without timing support from the network:** Packet-based method (frequency or time and/or phase synchronization) where the timing packets are transported over a timing transport agnostic network. + +**3.1.11 packet master clock:** A clock that measures the precise times at which the significant instants of a packet timing signal pass the master's timing reference point (e.g., as they enter the network from the packet master clock or as they enter the packet master clock from the network). These measurements are done relative to the master clock's local time scale. They are forwarded to, and used to control, one or more packet slave clocks. + +NOTE – In the case of a periodic packet timing signal (used for one-way frequency distribution), the event packets enter the network from the packet master clock at regular intervals, such that the master's timing information is implied from the nominal frequency of the packets. + +**3.1.12 packet network timing function (PNT-F):** The set of functions within the inter-working function (IWF) that supports the synchronization network clock domain (see Figure B.2 of [ITU-T G.8261]). This includes the function to recover and distribute the timing carried by the synchronization network. The PNT-F clocks may be part of the IWF or may be part of any other network element in the packet network. + +When the PNT-Fs are part of the IWF, they may support the CES IWF or change the layer over which timing is carried (i.e., from packet to physical layer and vice versa). + +**3.1.13 packet slave clock:** A clock whose timing output is frequency locked or phase aligned or time aligned to one or more reference packet timing signals exchanged with a higher quality clock. + +**3.1.14 packet timing monitor:** A device capable of analysing the packet flow [e.g., precision time protocol (PTP)] including precise measurement of the sending times and arrival times of timing event messages utilizing an accurate, stable clock. A tapped monitor does not substantively impact the transmission of packets between the communicating clocks; an in-line monitor introduces a fixed, symmetric, delay for packets in the two directions of transmission and thereby does not substantively impact the transfer of timing between the communicating clocks. + +**3.1.15 packet timing signal:** A signal, consisting of a series of event packets or frames, that is used to convey timing information from a packet master clock to a packet slave clock. + +Event packets in a packet timing signal may travel from a packet master clock to a packet slave clock or vice versa, but the flow of timing information is always in the direction from master to slave. + +The significant instants of the packet timing signal are measured relative to the master's local time scale as they pass the master's timing reference point, and these measurements are communicated to the packet slave clock. + +The significant instants of the packet timing signal are also measured relative to the slave's local time scale as they pass the slave's timing reference point. + +NOTE 1 – The significant instants of the signal are the set of times that a defined location in each event packet or frame passes a given reference point in the network (e.g., the interface between the packet master clock and the network). Conventionally the defined location is the end of the start-of-frame delimiter, but it may be defined differently in any given packet timing protocol provided the definition is consistent. + +NOTE 2 – In the case of a periodic packet timing signal, the master's timing information is implied from the nominal frequency of the packets. + +**3.1.16 phase synchronization:** This term implies that all associated nodes have access to reference timing signals whose significant events occur at the same instant (within the relevant phase accuracy requirement). In other words, the term refers to the process of aligning clocks with respect to phase (phase alignment). This is shown in Figure 2. + +NOTE 1 – Phase synchronization includes compensation for delay between the (common) source and the associated nodes. + +NOTE 2 – This term might also include the notion of frame timing (i.e., the point in time when the timeslot of an outgoing frame is to be generated). + +NOTE 3 – The concept of phase synchronization (phase alignment) should not be confused with the concept of phase locking, where a fixed phase offset is allowed to be arbitrary and unknown. Phase alignment implies that this phase offset is nominally zero. Two signals which are phase locked are implicitly frequency synchronized. Phase alignment and phase lock both imply that the time error between any pair of associated nodes is bounded. + +![Diagram illustrating phase synchronization between two systems, A and B. System A receives a reference timing signal and generates a timing signal recovered by system A. System B receives a reference timing signal and generates a timing signal recovered by system B. The recovered signals are shown as periodic waveforms over time (t).](c2fc2621e8206d24427b56bcb2398fc0_img.jpg) + +The diagram illustrates phase synchronization between two systems, A and B. At the top, two boxes represent 'System A' and 'System B'. Each box contains a phase symbol ( $\phi_A$ and $\phi_B$ respectively) and a sine wave symbol. Arrows labeled 'Reference timing signal to system A' and 'Reference timing signal to system B' point into these boxes. Below the boxes, two horizontal axes represent time ( $t$ ). The top axis is labeled 'Timing signal recovered by system A' and the bottom axis is labeled 'Timing signal recovered by system B'. Both axes show a series of vertical dashed lines representing the recovered timing signals. The signals are perfectly aligned, showing that the phase difference is zero. The text 'G.8260(15)\_F02' is located at the bottom right of the diagram. + +Diagram illustrating phase synchronization between two systems, A and B. System A receives a reference timing signal and generates a timing signal recovered by system A. System B receives a reference timing signal and generates a timing signal recovered by system B. The recovered signals are shown as periodic waveforms over time (t). + +Figure 2 – Phase synchronization + +**3.1.17 primary reference time clock (PRTC):** A reference time generator that provides a reference timing signal traceable to an internationally recognized time standard [e.g., Co-ordinated Universal Time (UTC)]. + +**3.1.18 time clock:** A device that provides the elapsed time from a reference epoch. + +**3.1.19 time synchronization:** The distribution of a time reference to the real-time clocks of a telecommunication network. All the associated nodes have access to information about time (in other words, each period of the reference timing signal is marked and dated) and share a common time scale and related epoch (within the relevant time accuracy requirement), as shown in Figure 3. + +Examples of time scales are: + +- UTC +- International Atomic Time (TAI) +- UTC + offset (e.g., local time) +- Global Positioning System (GPS) +- PTP +- local arbitrary time + +Note that distributing time synchronization is one way of achieving phase synchronization. + +![Figure 3 – Time synchronization. The diagram shows two systems, System A and System B, each with a clock icon. Below each system is a graph of 'Timing signal recovered by system A' and 'Timing signal recovered by system B' respectively. Both graphs show a series of pulses at 00:01:00, 00:01:01, and 00:01:02. The 00:01:02 pulses are circled. Arrows from these circled pulses point to a common label: 'Ex.: UTC, UTC + n x hours, GPS time, local arbitrary time'. The x-axis is labeled 't'. A small code 'G.8260(15)_F03' is in the bottom right corner of the figure area.](ff2492be4fa814905acbad18f261b8a5_img.jpg) + +Figure 3 – Time synchronization. The diagram shows two systems, System A and System B, each with a clock icon. Below each system is a graph of 'Timing signal recovered by system A' and 'Timing signal recovered by system B' respectively. Both graphs show a series of pulses at 00:01:00, 00:01:01, and 00:01:02. The 00:01:02 pulses are circled. Arrows from these circled pulses point to a common label: 'Ex.: UTC, UTC + n x hours, GPS time, local arbitrary time'. The x-axis is labeled 't'. A small code 'G.8260(15)\_F03' is in the bottom right corner of the figure area. + +Figure 3 – Time synchronization + +**3.1.20 time error:** The difference between the time of a clock and the time indicated by the time standard. A model for expressing the time error of a clock is described in clause I.3 of [ITU-T G.810]. + +- **constant time error:** With reference to the time error model provided in clause I.3 of [ITU-T G.810], the constant time error (cTE) of a synchronized clock is the term $x_0$ . +- **constant time error estimate:** Given a time error sequence $\{x(n); n = 0, 1 \dots (N - 1)\}$ measured at constant temperature, an estimate of the constant time error is the average of the first $M$ samples of the time error sequence. $M$ is obtained from the observation interval providing the minimum value for TDEV as computed for the given time error sequence. If a frequency offset is present, then a linear regression method in accordance with Appendix II of [ITU-T G.823] can be applied. Considerations for measurement data containing transients is for further study. + +NOTE – In some cases, due to the frequency components of the noise of the signal being measured, it might be difficult to identify a stable, consistent observation interval. These cases must be addressed case by case. + +- **dynamic time error:** With reference to the time error model provided in clause I.3 of [ITU-T G.810], the dynamic time error (dTE) of a synchronized clock is the random noise component, i.e., + +$$\frac{\varphi(t) - \varphi_{\text{ref}}(t)}{2\pi\nu_{\text{nom}}}.$$ + +The shape of the dTE component may be expressed using the time interval error function TIE( $t, \tau$ ), and characterized using the related metrics, maximum time interval error (MTIE) + +and time deviation (TDEV), although the offset from zero of the TIE function may vary depending on the time $t$ when the measurement starts. + +- **maximum absolute time error:** The $(\max|TE|)$ : maximum absolute value of the time error function of a synchronized clock. + +**3.1.21 message timestamp point:** See definition in [IEEE 1588], clause 3.1.33. + +**3.1.22 reference plane:** The boundary between a port of a PTP clock and the network physical medium. Timestamp events occur as messages cross this interface. + +**3.1.23 timestamp measurement plane:** The plane at which timestamps are captured. If the timestamp measurement plane is different from the reference plane, the timestamp is corrected for ingress latency and/or egress latency. + +**3.1.24 relative time error ( $TE_R$ ):** The difference between two timing signals carrying time. The timing signals may be from different interfaces of the same clock or from different clocks. + +A model for expressing the time error is described in clause I.3 of [ITU-T G.810]. + +The relative time error between timing signal A and timing signal B can be expressed as: + +- either a difference between the two timing signals: + +$$TE_R(t)_{(A,B)} = T(t)_{(A)} - T(t)_{(B)}$$ + +- or the difference between the time errors of each timing signal with respect to a common reference timing signal, where each timing signal is separately but simultaneously measured: + +$$TE_R(t)_{(A,B)} = TE_R(t)_{(A, Ref)} - TE_R(t)_{(B, Ref)}$$ + +As with time error, relative time error $TE_R(t)$ may be characterised by: + +- the constant relative time error $cTE_R$ +- the dynamic relative time error $dTE_R(t)$ +- and the maximum absolute relative time error: $\max|TE_R|$ + +The definition above shows that the comparison of the two signals should be made at the same instant in time. + +When dealing with sampled data, such as PTP time signals, it is possible that either their sample rates will be the same, but the sampling instants are not aligned, or that the sampling rates may be different. In both of these cases, the computed relative time error will be wrong, especially if there is any variation of time error at frequencies close to the Nyquist frequency. + +As a principle, when measuring relative time error, the two time error sequences to be compared should be smoothed before comparison to remove high-frequency components of the time error, and then re-sampled such that the sampling rates and instants of the two signals are aligned. The smoothing process should be defined in the relevant recommendations. + +**3.1.25 synchronization network segment:** Part of a synchronization network using the same synchronization distribution method (e.g., PTP clocks communicating within the same PTP domain). + +**3.1.26 synchronization interworking function (synchronization IWF):** A node function, interworking between synchronization network segments using different synchronization methods. + +NOTE – For example, if PTP is being used, there might be a different PTP profile in use in each segment. The two profiles are connected via the synchronization IWF node. + +**3.1.27 recognized time standard:** See definition of recognized standard time source in [IEEE 1588], clause 3.1.62. + +**3.1.28 traceability:** See definition in [IEEE 1588], clause 3.1.81. + +**3.1.29 traceable:** See definition in [IEEE 1588], clause 3.1.82. + +# 4 Abbreviations and acronyms + +For the purposes of Recommendations on timing and synchronization in packet networks, the following abbreviations and acronyms apply: + +| | | +|-------|-------------------------------------| +| ADEV | Allan Deviation | +| ARTC | Arbitrary Reference Time Clock | +| CES | Circuit Emulation Service | +| cTE | constant Time Error | +| dTE | dynamic Time Error | +| FFO | Fractional Frequency Offset | +| FFM | Flicker Frequency Modulation | +| FM | Frequency Modulation | +| FPC | Floor Packet Count | +| FPP | Floor Packet Per cent | +| FPR | Floor Packet Rate | +| GPS | Global Positioning System | +| IWF | Inter-Working Function | +| MAFE | Maximum Average Frequency Error | +| MATIE | Maximum Average Time Interval Error | +| MDEV | Modified Allan Deviation | +| MTIE | Maximum Time Interval Error | +| NTP | Network Time Protocol | +| OFD | Observed Floor Delay | +| PDV | Packet Delay Variation | +| PEC-M | Packet-based Equipment Clock Master | +| PEC-S | Packet-based Equipment Clock Slave | +| PM | Phase Modulation | +| PNT-F | Packet Network Timing Function | +| PRC | Primary Reference Clock | +| PRTC | Primary Reference Time Clock | +| PTP | Precision Time Protocol | +| RWFM | Random Walk Frequency Modulation | +| TAI | International Atomic Time | +| TDEV | Time DEVIation | +| TDM | Time Division Multiplexing | +| TE | Time Error | +| TIE | Time Interval Error | +| UTC | Coordinated Universal Time | + +# 5 Conventions + +No conventions are used in this Recommendation. + +# 6 Description of packet timing concepts + +## 6.1 The nature of packet timing + +A simplistic view of a generic slave clock is that it takes frequency information in, and puts frequency information out, as shown in Figure 4. + +![Figure 4: Generic slave clock block diagram](1b5a812c8aa20fd5cba28e97001d32de_img.jpg) + +A block diagram of a generic slave clock. It consists of a central rectangular block labeled "clock". An arrow labeled "Frequency information in" points into the block from the left. An arrow labeled "Frequency information out" points out of the block to the right. Below the output arrow is the text "G.8260(15)\_F04". + +Figure 4: Generic slave clock block diagram + +**Figure 4 – Generic slave clock** + +Conventionally, this frequency information is encoded as a timing signal. This is typically implemented as a periodic digital signal, where the edges of the signal are reference points in time known as the "significant instants" of the signal. Timing jitter and wander causes these significant instants to vary slightly from their ideal position in time, i.e., they may not occur at precisely equally spaced points in time. A physical layer timing signal is shown in Figure 5. + +![Figure 5: Physical layer timing signal waveform](c036e2540a94b31357ceb0002f0cacab_img.jpg) + +A waveform diagram of a physical layer timing signal. The signal is a periodic digital signal with a series of pulses. A label "Timing signal" points to one of the pulses. Four vertical arrows point to specific edges of the pulses, labeled "Significant instants". A horizontal double-headed arrow between two of these instants is labeled "Timing jitter and wander". A horizontal arrow at the bottom right is labeled "Time". Below the time arrow is the text "G.8260(15)\_F05". + +Figure 5: Physical layer timing signal waveform + +**Figure 5 – Physical layer timing signal** + +A packet timing signal is similar in concept. The frequency is encoded as a series of time-critical packets in a network, known as event packets. While the transmission medium is different (packets on a network as opposed to signals on a wire), the packets still contain significant instants (normally the front edge of the packet), with a defined ideal position in time. The variation of the significant instants around their ideal position is termed packet delay variation (PDV). This is shown in Figure 6. + +![Figure 6 – Packet timing signal. The diagram shows four packets transmitted over time, each consisting of a footer (F), a payload, and a header (H). Above the packets, the label 'Significant instants' has dashed lines pointing to the start of each packet. Below the first packet, the label 'Event packets (header, payload and footer)' has dashed lines pointing to the start and end of the packet. Between the second and third packets, a double-headed arrow labeled 'Packet delay variation' indicates the time difference between the start of the third packet and the end of the second. A horizontal arrow at the bottom right is labeled 'Time'. The text 'G.8260(15)_F06' is in the bottom right corner.](33ed1f9b27c7c21c797aa928b0f06851_img.jpg) + +Figure 6 – Packet timing signal. The diagram shows four packets transmitted over time, each consisting of a footer (F), a payload, and a header (H). Above the packets, the label 'Significant instants' has dashed lines pointing to the start of each packet. Below the first packet, the label 'Event packets (header, payload and footer)' has dashed lines pointing to the start and end of the packet. Between the second and third packets, a double-headed arrow labeled 'Packet delay variation' indicates the time difference between the start of the third packet and the end of the second. A horizontal arrow at the bottom right is labeled 'Time'. The text 'G.8260(15)\_F06' is in the bottom right corner. + +**Figure 6 – Packet timing signal** + +Some of the causes and characteristics of PDV and other impairments that may be introduced by the packet network are discussed in clause 10 of [ITU-T G.8261]. + +Some packet timing signals may be periodic (e.g., circuit emulation packets containing constant bit rate data), and for these the ideal position in time is implicitly given by the packet rate. Other packet timing signals are not periodic (e.g., PTP or NTP), and for these the ideal position in time is given by a timestamp embedded in the packet data. It is important to note that both periodic and non-periodic packet timing signals are still time domain signals. It is the position in time of the packets that is significant, not the contents of the packets. + +## 6.2 Differences between packet-based and physical layer timing systems + +Packet-based timing systems are not fundamentally different from physical layer timing systems. Conceptually, both utilize timing signals that are sequences of periodic or timed events, termed significant instants, where there is a notion of the ideal position in time for each event. Similarly, after transmission of these timing signals through the network, there will be some phase noise component, corrupting this ideal position in time. The recovery of the original timing signal is achieved by filtering the incoming timing signal to remove the transport-related phase noise and generate a clean output. + +However, there are some differences that lead to packet timing signals having different characteristics to physical layer timing signals: + +- Rate of significant instants: + +The packet rate in a packet timing signal is much lower than the frequency of most physical layer timing signals. For example, in PTP (defined in [IEEE 1588]), the sync message rate will normally be in the range 1-128 Hz, while a conventional E1 timing signal has a frequency of 2.048 MHz. + +Secondly, the packets that form the significant instants need not be sent at precisely regular intervals. While the mean rate is specified, the intervals between packets may vary. Timestamps are used to identify the precise sending time, relative to a pre-determined epoch. + +- Amplitude and nature of noise processes: + +The principal cause of noise in a packet timing system is PDV. The amplitude and distribution of PDV is much larger than jitter and wander in physical layer timing systems, and it may contain very low frequency components such as diurnal wander due to network loading variations. + +Unlike physical layer noise, the PDV depends not only on the physics of components but also on the architecture and implementation of network elements. Therefore, the noise is more complex and harder to model. + +## 6.3 Classes of packet clocks + +There can be several classes of packet-based clocks, depending on the combination of input and output timing signal classes. Table 1 shows the different classes, with real-world examples of each case. + +**Table 1 – Classes of packet-based clocks** + +| Packet-based clock class | Input timing signal | Output timing signal | Examples | +|-----------------------------------------------------|------------------------------|------------------------------|----------------------------------------------------------| +| Packet master clock
PEC-M | Physical layer timing signal | Packet timing signal | PTP master,
NTP server
Ingress CES IWF (Note 1) | +| Packet slave clock
PEC-S | Packet timing signal | Physical layer timing signal | PTP slave,
NTP client
Egress CES IWF (Note 2) | +| Combined packet slave clock and packet master clock | Packet timing signal | Packet timing signal | PTP boundary clock
NTP stratum $n$ server ( $n > 1$ ) | + +NOTE 1 – i.e., TDM to packet direction, see term "ingress IWF" in [ITU-T Y.1413]. +NOTE 2 – i.e., packet to TDM direction, see term "egress IWF" in [ITU-T Y.1413]. + +## 6.4 Two-way timing protocols + +Packet timing signals may flow from packet master clock to packet slave clock or vice versa. However, in each case, the flow of timing and synchronization is always from master to slave. + +In the case of a packet timing signal flowing from a packet master clock to a packet slave clock (e.g., the PTP *sync* messages), the time of exit of each event packet from the packet master clock is measured (to be precise, the time relative to the master's time scale at which the significant instant of each event packet passes the master's timing reference point). This information is sent to the packet slave clock either in a timestamp embedded in the event packet, or in a subsequent information packet (e.g., the PTP *follow\_up* message). + +On reception at the packet slave clock, the arrival time of the event packet is measured (to be precise, the time relative to the slave's local time scale at which the significant instant of each event packet passes the slave's timing reference point). The two times are compared, creating a series of time differences. These time differences are then filtered, and may be used to control the frequency of the output timing signal. + +In the case of a packet timing signal flowing from a packet slave clock to a packet master clock (e.g., the PTP *delay\_request* messages), the time of exit of each event packet from the packet slave clock is measured. On reception at the packet master clock, the arrival time of each event packet is measured, and this information is sent to the packet slave clock in a subsequent information packet (e.g., the PTP *delay\_response* message). + +The use of a two-way timing protocol (such as PTP or NTP) makes it possible to align the local time scale to the master time scale. The four times may be used to calculate the round-trip delay of the message exchange, and hence to calculate the time offset between the local and master time scales. + +The timing message exchange is shown in Figure 7. + +![Figure 7: Packet timing signal flow and timing reference points. The diagram shows a 'Packet master clock' on the left and a 'Packet slave clock' on the right, connected by a 'Network' cloud. Two packet structures are shown: one with fields 'F', 'Payload', 'H' and another with 'H', 'Payload', 'F'. Arrows indicate 'Master to slave packet timing signal' (e.g., PTP sync messages) and 'Slave to master packet timing signal' (e.g., PTP delay_request packets). Below the diagram, three text blocks define the timing reference points: 'Master timing reference point' (local time at master when packet exits), 'Slave to master packet timing signal' (local time at slave when packet exits), and 'Slave timing reference point' (local time at slave when packet enters). A reference code G.8260(15)_F07 is in the bottom right.](8fbdfc3d17fb1dae7b2d8f5a287fa9fc_img.jpg) + +**Master to slave packet timing signal** + – Local time recorded as event packets exit the master and enter the slave + – Example: PTP *sync* messages + +**Packet master clock** + +**Packet slave clock** + +**Network** + +**Master timing reference point** + – Local time recorded as the significant instant of each event packet passes this point, in either direction + – Measurements communicated to packet slave clock in an information flow + +**Slave to master packet timing signal** + – Local time recorded as event packets exit the slave and enter the master + – Example: PTP *delay\_request* packets + +**Slave timing reference point** + – Local time recorded as the significant instant of each event packet passes this point, in either direction + +G.8260(15)\_F07 + +Figure 7: Packet timing signal flow and timing reference points. The diagram shows a 'Packet master clock' on the left and a 'Packet slave clock' on the right, connected by a 'Network' cloud. Two packet structures are shown: one with fields 'F', 'Payload', 'H' and another with 'H', 'Payload', 'F'. Arrows indicate 'Master to slave packet timing signal' (e.g., PTP sync messages) and 'Slave to master packet timing signal' (e.g., PTP delay\_request packets). Below the diagram, three text blocks define the timing reference points: 'Master timing reference point' (local time at master when packet exits), 'Slave to master packet timing signal' (local time at slave when packet exits), and 'Slave timing reference point' (local time at slave when packet enters). A reference code G.8260(15)\_F07 is in the bottom right. + +**Figure 7 – Packet timing signal flow and timing reference points** + +## 6.5 Packet delay sequence measurement + +In general, a packet delay sequence measurement involves comparing time instants on a sequence of packets, such as those of a packet timing signal, as they pass two points in the network. A configuration for performing such a measurement is shown in Figure 8. For each packet, a difference is computed between the time instant taken at the point of origin and the time instant taken at the point of destination. + +![Figure 8: Configuration for packet delay sequence measurement. The diagram shows two nodes, each with a 'Time or frequency reference' (R) and a 'Packet timestamper' (PT), connected via a 'Network' cloud. The left node is labeled 'Master' and the right 'Probe'. Timestamps T1(t), T2(t), T3(t), and T4(t) are shown at the PTs. Forward delay d_fwd is calculated as T2(t) - T1(t), and reverse delay d_rev as T4(t) - T3(t). A reference code G.8260(15)_F08 is in the bottom right.](df82d77a0d2637cbf2da9ea920a554fa_img.jpg) + +R Time or frequency reference + PT Packet timestamper + +G.8260(15)\_F08 + +Figure 8: Configuration for packet delay sequence measurement. The diagram shows two nodes, each with a 'Time or frequency reference' (R) and a 'Packet timestamper' (PT), connected via a 'Network' cloud. The left node is labeled 'Master' and the right 'Probe'. Timestamps T1(t), T2(t), T3(t), and T4(t) are shown at the PTs. Forward delay d\_fwd is calculated as T2(t) - T1(t), and reverse delay d\_rev as T4(t) - T3(t). A reference code G.8260(15)\_F08 is in the bottom right. + +**Figure 8 – Configuration for packet delay sequence measurement** + +The forward and reverse delay sequences are calculated from timestamp sequences. + +The forward delays are: + +$$d_{\text{fwd}}(i) = T_2(i) - T_1(i) \quad (1)$$ + +Similarly, the reverse delays are: + +$$d_{\text{rev}}(j) = T_4(j) - T_3(j) \quad (2)$$ + +An ideal configuration for making this measurement places two references traceable to a common time standard at each of the two measurement points. Such a configuration assesses not only the variation of packet delay, but also the packet transit time. + +In many circumstances, such as packet-based frequency synchronization, the focus is on variation of packet delay rather than absolute packet delay. In such a case, frequency references can be employed + +for the references $R$ and a common time reference is not required. In this case there will be an arbitrary but constant time error in the resulting delay values, and the metrics used to qualify frequency synchronization cancel this constant time error out. + +In many circumstances, such as packet-based frequency synchronization, the focus may be in either forward or reverse delay. However, in time synchronization, usually both directions are of equal importance. + +The use of unstable or inaccurate references directly impacts the packet delay measurement, and may lead to limitations regarding the length of the packet delay measurement. If the references are frequency standards, packet delay can be studied with the same precision as for the case where the references are time standards. If practical, a common frequency standard should be used for both $R$ references. In other cases, separate primary reference clocks could be used. + +The probe function could be implemented as separate equipment or in the case where the first measurement point is at the source of the packet timing signal of interest, integrated into that equipment. In this case, the time instant could be delivered within the packet in the form of a timestamp. Similarly, in the case where the second measurement point is at the destination equipment, the probe function may be integrated into that equipment. Any inaccuracy of the timestamping function in the probes directly impacts the precision of the packet delay measurement. + +In the case where packets are sent according to a schedule that is known in advance, such as packets spaced by a uniform interval of time (e.g., CES), the relative origin timestamps are implicit, and the PDV measurement can be performed with timestamping at the destination node. + +If the network contains boundary clocks (BC), see Figure 9, the measurement device on the right communicates, instead of with the source device on the left, with an intermediate BC that has time error. The timestamps created by the BC are $T_1' = T_1 + Err_{BC}$ and $T_4' = T_4 + Err_{BC}$ where $Err_{BC}$ is the time error of the BC. Due to the time error of the BC the differences between the times stamps: + +$$d_{afwd}(i) = T_2(i) - T_1'(i) \quad (3)$$ + +and + +$$d_{arev}(j) = T_4'(j) - T_3(j) \quad (4)$$ + +represent apparent delays $d_{afwd}$ and $d_{arev}$ rather than actual delays. + +![Figure 9: Configuration for packet delay sequence measurement in a network including BCs. The diagram shows a sequence of components: a Time or frequency reference (R) connected to a Packet timestamper (PT) labeled 'Master'; a Network cloud; a Boundary Clock (BC); another Network cloud; a Packet timestamper (PT) labeled 'Probe' connected to a Time or frequency reference (R). Timestamps are indicated at various points: T1'(t) and T2(t) at the right PT; T3(t) and T4'(t) at the BC. Arrows and plus/minus signs show the calculation of delays d_afwd and d_arev. A dashed line connects the BC and the right PT. A legend at the bottom left defines R and PT. A code G.8260(15)_F09 is at the bottom right.](124c6108c63173818afb8ed49521e22d_img.jpg) + +R Time or frequency reference +PT Packet timestamper + +G.8260(15)\_F09 + +Figure 9: Configuration for packet delay sequence measurement in a network including BCs. The diagram shows a sequence of components: a Time or frequency reference (R) connected to a Packet timestamper (PT) labeled 'Master'; a Network cloud; a Boundary Clock (BC); another Network cloud; a Packet timestamper (PT) labeled 'Probe' connected to a Time or frequency reference (R). Timestamps are indicated at various points: T1'(t) and T2(t) at the right PT; T3(t) and T4'(t) at the BC. Arrows and plus/minus signs show the calculation of delays d\_afwd and d\_arev. A dashed line connects the BC and the right PT. A legend at the bottom left defines R and PT. A code G.8260(15)\_F09 is at the bottom right. + +**Figure 9 – Configuration for packet delay sequence measurement in a network including BCs** + +It can be shown that $d_{afwd}$ and $d_{arev}$ can be used interchangeably with $d_{fwd}$ and $d_{rev}$ in the formulas that derive time error from delay measurements. + +## 6.6 Packet timing signal equipment interface characterization + +The configuration described in clause 6.5 for measuring packet delay variation can be extended to measurement of the packet timing signal at an equipment interface. In this case, the packet timestamper with reference is connected directly to the packet timing signal interface with no intervening network. + +A configuration for performing such a measurement is shown in Figure 10. The packet time-error signals resemble the time error function $x(t)$ described in clause 4.5.13 of [ITU-TG.810]. For each packet, a difference is computed between the timestamp from the device and the timestamp taken on that same packet from the packet timestamper (PT) with reference (R). This is true for the streams in both directions with the details of the difference operations indicated in the figure. + +![Figure 10: Configuration for packet timing signal equipment interface measurement. The diagram shows a 'Packet timing signal equipment interface' connected to a 'PT' (Packet timestamper), which is connected to a reference 'R' (Time or frequency reference). The interface outputs two signals: 'Reserve packet time error signal' and 'Forward packet time error signal'. The 'Reserve packet time error signal' is calculated as T4(t) - T3(t). The 'Forward packet time error signal' is calculated as T2(t) - T1(t). The legend indicates R is 'Time or frequency reference' and PT is 'Packet timestamper'. The diagram is labeled G.8260(15)-Amd.1(16)_F10.](8fa679f79a1bb1f527cba9f29e784e89_img.jpg) + +The diagram illustrates the configuration for packet timing signal equipment interface measurement. It features a 'Packet timing signal equipment interface' connected to a 'PT' (Packet timestamper), which is in turn connected to a reference 'R' (Time or frequency reference). The interface outputs two signals: 'Reserve packet time error signal' and 'Forward packet time error signal'. The 'Reserve packet time error signal' is calculated as $T_4(t) - T_3(t)$ . The 'Forward packet time error signal' is calculated as $T_2(t) - T_1(t)$ . The legend indicates R is 'Time or frequency reference' and PT is 'Packet timestamper'. The diagram is labeled G.8260(15)-Amd.1(16)\_F10. + +R Time or frequency reference +PT Packet timestamper + +G.8260(15)-Amd.1(16)\_F10 + +Figure 10: Configuration for packet timing signal equipment interface measurement. The diagram shows a 'Packet timing signal equipment interface' connected to a 'PT' (Packet timestamper), which is connected to a reference 'R' (Time or frequency reference). The interface outputs two signals: 'Reserve packet time error signal' and 'Forward packet time error signal'. The 'Reserve packet time error signal' is calculated as T4(t) - T3(t). The 'Forward packet time error signal' is calculated as T2(t) - T1(t). The legend indicates R is 'Time or frequency reference' and PT is 'Packet timestamper'. The diagram is labeled G.8260(15)-Amd.1(16)\_F10. + +**Figure 10 – Configuration for packet timing signal equipment interface measurement** + +Requirements on the accuracy of the reference (R) are driven by the characteristics of the packet timing signal, and in many cases might exceed those for studying network PDV. If the packet timing signal is derived directly from a primary reference, reference (R) would need to be a primary reference, ideally one with greater stability. Further, in cases where the device under study takes an external reference directly or is traceable to an external reference, the optimal configuration is for both the device and the packet timestamper (PT) in Figure 10 to share the same reference (R). + +# Appendix I + +## Definitions and properties of packet measurement metrics + +(This appendix does not form an integral part of this Recommendation.) + +NOTE – This appendix contains information related to ongoing studies on the definition of suitable PDV metrics. The text below is for information only, and may be revised in a future version of the Recommendation. It must not be used as normative text, nor as an implied specification of a packet slave clock. + +## I.1 Introduction + +With the telecommunications industry evolving and rapidly adopting packet technology, much emphasis has been placed on addressing packet synchronization and timing, including the use of measurement data to assist in specifying the performance of packet-based clocks. + +Physical layer timing signal stability quantities, including metrics such as maximum time interval error (MTIE) and time deviation (TDEV), have been used extensively and are central to synchronization measurement analysis. For a packet clock, the level of stability at the clock's packet network input has a direct bearing on the stability of the clock output. + +In terms of the packet metrics, the goal of a first category of PDV metrics, introduced in clause I.4, is to formulate packet-based stability quantities (metrics) that will provide a means of estimating the physical-based stability quantities for the packet clock output. This is illustrated in Figure I.1. + +![Diagram of packet equipment clock interfaces showing a Packet network connected to a PEC slave via a Packet interface, and a PEC slave connected to a Physical layer timing interface via a Clock stability quantities output. The diagram includes labels for PDV stability quantities and Clock stability quantities, and a formula for Clock stability quantities estimation.](1a85642ed2356d183ce598f2c8b3ee8b_img.jpg) + +The diagram illustrates the flow of stability quantities in a packet equipment clock. A 'Packet network' (represented by an orange cloud) is connected to a 'PEC slave' (represented by a grey rectangle) via a 'Packet interface'. Below this connection, 'PDV stability quantities' are indicated. The 'PEC slave' is connected to a 'Physical layer timing interface' (represented by a grey rectangle) via a 'Clock stability quantities' output. Below this connection, 'Clock stability quantities' are indicated. Below the diagram, the following formula is provided: + +$$[\text{Clock stability quantities estimation}] = \text{function}(\text{PDV stability quantities})$$ + +G.8260(10)\_Fl.1 + +Diagram of packet equipment clock interfaces showing a Packet network connected to a PEC slave via a Packet interface, and a PEC slave connected to a Physical layer timing interface via a Clock stability quantities output. The diagram includes labels for PDV stability quantities and Clock stability quantities, and a formula for Clock stability quantities estimation. + +**Figure I.1 – Packet equipment clock interfaces** + +A second category of PDV metrics is also introduced in clause I.5. The goal of this second category is not directly to provide an estimation of the physical-based stability quantities for the packet clock output, but simply to study the population of timing packets within a certain delay window range. + +PDV measurement guidelines are provided in clause 6.5. + +For packet measurement data analysis, packet selection is added as an important component to the analysis. Indeed, in order to reduce the input PDV noise, the packet slave clock implementations generally use only a subset of the received timing packets. + +Therefore, a first simple approach to analyse the PDV as received by a packet slave clock can be to display the measured PDV in the form of a histogram. It generally provides useful information about the population of packets in different delay regions, and is in some cases sufficient to analyse the network conditions. Figure I.2 shows an example plot of the measured PDV and the corresponding histogram. + +![Figure I.2 consists of two plots. The left plot shows a scatter plot of packet delay variation (PDV) over time. The y-axis is labeled 'ms' and has major ticks at 1.17, 90.0, and 180. The x-axis is labeled 'hours' and has major ticks at 0.000, 1.00 hours/div, and 10.36. The data points are clustered around a horizontal line at approximately 180 µs. The right plot is a histogram of the PDV measurements. The y-axis is logarithmic, ranging from 1 to 10 k. The x-axis is labeled 'µs' and has major ticks at 180.00 and 1.1700. The histogram shows a sharp peak at approximately 180 µs, with a long tail extending to higher values. Both plots are titled 'PDV phase; Samples: 596919; Initial phase offset: 270.020 µs'. The right plot also includes the text 'bins = 2048 Measurements = 596919' and 'G.8260(10)_Fl.2'.](5ed9189841659dfb01f809b8e3b21f74_img.jpg) + +Figure I.2 consists of two plots. The left plot shows a scatter plot of packet delay variation (PDV) over time. The y-axis is labeled 'ms' and has major ticks at 1.17, 90.0, and 180. The x-axis is labeled 'hours' and has major ticks at 0.000, 1.00 hours/div, and 10.36. The data points are clustered around a horizontal line at approximately 180 µs. The right plot is a histogram of the PDV measurements. The y-axis is logarithmic, ranging from 1 to 10 k. The x-axis is labeled 'µs' and has major ticks at 180.00 and 1.1700. The histogram shows a sharp peak at approximately 180 µs, with a long tail extending to higher values. Both plots are titled 'PDV phase; Samples: 596919; Initial phase offset: 270.020 µs'. The right plot also includes the text 'bins = 2048 Measurements = 596919' and 'G.8260(10)\_Fl.2'. + +**Figure I.2 – Measured packet delay and corresponding PDV histogram** + +In a second approach, mathematical tools (called "metrics" in this appendix) can be applied on a given PDV measurement to analyse it more in detail. Those metrics generally use only a subset of the packets. The packet selection can be either integrated into the calculation or performed as a pre-processing step. For example, the packet selection can focus on the minimum packet delay floor or more generally on some other region of packet delays. + +With regard to the packet selection just discussed, it is important to point out the link between the methods of packet measurement data analysis described here and packet clock algorithms as they exist in actual equipment. For both, packet selection is important for optimization given the realities of packet delay variation. + +However, it is important to mention that due to the proprietary nature of most of the packet slave clock implementations today, especially regarding the packet selection criteria, the packet selection used by a given PDV metric may not correspond to the criteria used in the packet slave clock of interest. Therefore, there can be some discrepancies between the information provided by a given PDV metric and the real performances achieved by a packet slave clock. + +Methods for alignment of the results provided by the PDV metrics with the performance of the packet slave clock are still under study. Alignment may involve the specification of some minimum common behaviour in the packet selection criteria in the packet slave clock implementations. + +Moreover, it is important to mention that PDV metrics compute an estimate of achievable performance through the use of PDV sample information only, and do not consider the effects of internal oscillator noise in a packet slave clock. Non-negligible differences between the estimate and the actual performance of a packet slave clock may sometimes be observed because of this effect. In order to take oscillator noise into account, the noise generation components of a packet slave clock are considered in [b-ITU-T G.8263]. + +While metrics can provide the basis for setting equipment requirements and network limits, their value as general analysis tools leading to insight into particular sets of measurement data should not be overlooked. For time division multiplexing (TDM) synchronization measurements, normative limits have been applied to the MTIE and TDEV calculations, but other metrics such as Allan deviation (ADEV) and modified Allan deviation (MDEV), while not associated with normative telecom limits, have great utility as analysis tools. + +## I.2 Definition of the time error sequence + +For packet timing signals the packet time error sequence can be established in the following way. For specificity, consider the transfer of timing packets originating at the packet master clock and terminating at the packet slave clock. In the case of PTP (see [IEEE 1588]) the rate of packets is determined via negotiation between master and slave and can be as high as 128 packets/s. PTP packets may not be equally spaced, but will meet this nominal rate over the long term. The ideal position in + +time for these packets is given by a timestamp embedded in the packet data. The rate of packets in the reverse direction, from slave to master, can be different from the rate in the forward direction, from master to slave. + +Packets leave the master with a long-term mean spacing of $\tau_F = 1/f_F$ where $f_F$ is the average forward packet rate. From a signal processing perspective, the sampling rate is $f_F$ and an arbitrary mathematical-time origin for describing the times of departure from the master can be chosen. With this choice of time origin, the $i$ th packet departs the master at time $t = i\tau_F$ . In practice the $i$ th packet will depart at time $T_1(i)$ which is but approximately equal to $i\tau_F$ . Note that in the case of circuit emulation, the times of departure are considered to be exactly spaced by $\tau_F$ . The $i$ th packet then arrives at the slave at time $T_2(i)$ where: + +$$d_{\text{fwd}}(i) = T_2(i) - T_1(i) \quad (\text{I-1})$$ + +is the forward transit delay and $T_2(i)$ is expressed relative to the master clock. Assuming the time instants are determined by synchronized clocks, this forward transit delay is composed of a fixed, albeit unknown, delay and a random delay component that is the result of queuing delays in the intermediate network elements. If the application is frequency synchronization, the fixed (unknown) delay is not relevant and can be ignored, leaving the random delay component as the principal cause of time error. + +The same principle applies for packets that traverse the network from the slave to the master. Denoting the packet rate in the reverse direction by $f_R = 1/\tau_R$ , the $j$ th packet will depart at time $T_3(j)$ which is approximately equal to $j\tau_R$ . + +$$d_{\text{rev}}(j) = T_4(j) - T_3(j) \quad (\text{I-2})$$ + +is the reverse packet delay that is composed of a fixed, unknown, delay and a random delay component. $T_3(j)$ and $T_4(j)$ are expressed relative to the same clock. + +If the forward delay were known *a priori*, then the master and slave clock could be time synchronized using Equation I-1. However, if the delay is not known *a priori*, and the slave takes the master time to be $T_1(i)$ at the instant it receives the forward packet, the (hypothetical) time-error at this instant will be $T_1(i) - T_2(i) = -d_{\text{fwd}}(i)$ (i.e., the slave's estimate of the master time minus the actual master time), because the actual time relative to the master clock that the forward packet is received at the slave is $T_2(i)$ . Then, if the (hypothetical) forward packet time-error signal $x_F(t)$ is considered, the sample of the forward packet time-error signal taken at the sampling instant $T_1(i)$ is: + +$$x_F(t) = -d_{\text{fwd}}(i) \quad (\text{I-3})$$ + +Similarly, if the reverse packet time-error signal $x_R(t)$ is considered, then the sample of the reverse packet time-error signal taken at the sampling instant $T_3(j)$ is: + +$$x_R(t) = d_{\text{rev}}(j) \quad (\text{I-4})$$ + +The sign is reversed compared to the forward time error signal, because now the slave takes the master time to be $T_4(j)$ when it is actually $T_3(j)$ ; the time error is $T_4(j) - T_3(j) = d_{\text{rev}}(j)$ . + +This means that increasing forward delay corresponds to increasingly negative time error in the slave, whereas increasing reverse delay corresponds to increasingly positive time error. That is, the sequences $\{-d_{\text{fwd}}(i)\}$ and $\{d_{\text{rev}}(j)\}$ are equivalent to packet time error sequences, but on a non-uniform time grid. Note that delay measures the difference between two time instants, while time error measures the difference between two clocks at the same instant if the packet were used to set or + +estimate the time of the slave clock without any filtering. The normal packet time error sequences, $\{-d_{\text{fwd}}(i)\}$ and $\{d_{\text{rev}}(j)\}$ are actually sequences generated by sampling the packet time-error signal $x_{\text{F}}(t)$ and $x_{\text{R}}(t)$ on a uniform grid with sampling interval $\tau_{\text{F}}$ and $\tau_{\text{R}}$ in the forward and reverse directions creating time error sequences $x_{\text{F}}(i\tau_{\text{F}})$ and $x_{\text{R}}(j\tau_{\text{R}})$ . In the following sections $x(t)$ corresponds to either $x_{\text{F}}(t)$ or $x_{\text{R}}(t)$ depending on which one-way sequence is of interest. Also, if the packet rates in the two directions are equal, then we set $\tau_{\text{F}} = \tau_{\text{R}} = \tau_0$ . + +## I.3 Packet selection and filtering + +Physical layer timing signals are stationary and Gaussian in nature. Therefore, the relevant applied stability quantities (i.e., MTIE and TDEV) will usually use every noise sample point (significant instant) in the stability quantification process in order to filter out as much noise as possible and achieve the best stability quantification possible. + +Packet-based timing signals, on the other hand, are not always stationary or Gaussian in nature. Hence, methods of quantifying them (thus attaining a better estimation of their ability to carry timing information) would usually require the selection of only a subset of their entire population or in general performing some pre-filtering before applying the specific stability quantification analysis. + +The following discussion focuses on the approach that involves a selection of packets. + +#### I.3.1 Packet selection types + +As mentioned in clause I.1, when applying some PDV metrics, packet selection and filtering can be incorporated into the calculation or into separate pre-processing steps. + +- The packet selection and filtering techniques integrated into the calculation are useful in metrics that are intended to determine the characteristics of the packet network in terms of the PDV behavior. The main benefit of this approach is to provide a generic tool independent of the characteristics of a specific packet slave clock implementation (e.g., time interval used to select packets). The main purpose of this approach is therefore to support vendors with progressing packet timing recovery techniques (class B metrics). +- On the other hand, pre-processing selects packets from suitable, pre-defined time window lengths. Therefore, the selection process resembles that of a practical packet clock in steady-state operation. This approach is therefore more suitable for the definition of metrics used to specify network limits (i.e., class A metrics) as an assumption is made on a "minimum" implementation of a packet slave clock as specified in [b-ITU-T G.8263]. + +##### I.3.1.1 Pre-processed packet selection + +With pre-processed packet selection, quantifying packet timing signals is carried in two steps: + +- 1) Applying a specific packet selection procedure to select a specific subset of packet delay samples, having similar delay properties, among the entire population of packet delay samples. +- 2) Applying the required stability quantification algorithm (metric) over the selected group of samples to get an estimation of the achievable output clock quality estimation. + +NOTE – As mentioned earlier, there can be discrepancies between the information provided by a given PDV metric and the real performances achieved by a packet slave clock. + +This is shown in Figure I.4: + +![Figure I.4 – Pre-processed packet selection flow diagram](73b5cce955ba9415a98791db7b0080ad_img.jpg) + +``` + + graph LR + A("x(t) +Entire PDV +population") -- "Packet time +error sequence" --> B[Packet +selection] + B -- "x'(t) +Selected subset +with common +delay properties" --> C[Stability +metric] + C --> D("Estimated +achievable +performance") + style B fill:#fff,stroke:#000 + style C fill:#fff,stroke:#000 + +``` + +The diagram illustrates the pre-processed packet selection flow. It starts with an input labeled 'Packet time error sequence' and $x(t)$ entering a 'Packet selection' block. The input is also labeled 'Entire PDV population'. The output of the 'Packet selection' block is labeled 'Selected-packet time error sequence' and $x'(t)$ . This output is also labeled 'Selected subset with common delay properties'. The output of the 'Packet selection' block enters a 'Stability metric' block. The output of the 'Stability metric' block is labeled 'Estimated achievable performance'. The diagram is labeled 'G.8260(15)\_FI.4'. + +Figure I.4 – Pre-processed packet selection flow diagram + +**Figure I.4 – Pre-processed packet selection** + +In essence, an input packet time error sequence $x(t) = x(i\tau_0)$ is subject to packet selection, which produces a new packet time error sequence. The input packet time error sequence is divided into time windows of equal length $m\tau_0$ where $m$ is the number of samples in the selection window. A fraction of packets is selected from each window in a similar manner and the information is combined so that each window produces a single value to the new packet time error sequence $x'(t) = x'(i\tau_s)$ . The sample interval of the selected-packet time error sequence is $\tau_s = m\tau_0$ . Unless otherwise specified, the time errors of the selected packets in each selection window are averaged to produce a single delay value. + +When a metric is computed using pre-processed packet selection, the name of the metric is prepended by the term *pktselected*, e.g., *pktselectedTDEV* (see clause I.4.2.1). + +In the case of pre-processed packet selection, the preliminary packet selection process is independent of the applied stability quantification. Thus, different combinations of the two might yield interesting properties that require investigation. Both need to be fully defined as each has significant influence on the resulting performance measurement. + +##### I.3.1.2 Pre-processed packet filtering + +As described above, an input packet time error sequence $x(t)$ that is subject to packet selection, produces a new selected-packet time error sequence $x'(t)$ . Additionally, that new packet time error sequence $x'(t)$ may be subsequently filtered to create a filtered-packet time error sequence $y(t)$ . This flow is shown below in Figure I.5. + +![Figure I.5 – Packet selection and filtering flow diagram](19a5f0db57a21a0e82a7f326083e96fd_img.jpg) + +``` + + graph LR + A("x(t)") -- "Packet time +error sequence" --> B[Packet +selection] + B -- "x'(t) +Selected-packet +time error sequence" --> C[Bandwidth +filtering] + C -- "y(t) +Filtered-packet +time error sequence" --> D[Stability +metric] + D --> E("Estimated +achievable +performance") + style B fill:#fff,stroke:#000 + style C fill:#fff,stroke:#000 + style D fill:#fff,stroke:#000 + +``` + +The diagram illustrates the packet selection and filtering flow. It starts with an input labeled 'Packet time error sequence' and $x(t)$ entering a 'Packet selection' block. The output of the 'Packet selection' block is labeled 'Selected-packet time error sequence' and $x'(t)$ . This output enters a 'Bandwidth filtering' block. The output of the 'Bandwidth filtering' block is labeled 'Filtered-packet time error sequence' and $y(t)$ . This output enters a 'Stability metric' block. The output of the 'Stability metric' block is labeled 'Estimated achievable performance'. The diagram is labeled 'G.8260(15)\_FI.5'. + +Figure I.5 – Packet selection and filtering flow diagram + +**Figure I.5 – Packet selection and filtering flow** + +The selected-packet time error sequence $x'(t)$ may be filtered by applying an averaging function in line with the clock bandwidth, with averaging time related to the window length of the packet selection process. In particular, 1:10 is as an example of a suitable ratio of the window length of the packet selection block to the time constant of the bandwidth filtering block in Figure I.5.1 + +The parameters of the selection process must be chosen to ensure that sufficient packet information is available to allow the filtering process to operate. As an example, assuming a packet rate of 1 packet/s and a selection window of 100 s, the minimum possible selection percentage is 1%, resulting in the selection of 1 packet in every window. + +In many cases a higher packet rate would be used for these measurements in order to get a higher number of samples. + +The following applies a sliding window averaging function with length $b$ (the number of windows, where each window has $K$ samples): + +$$y(n\tau_0) = \frac{1}{b} \sum_{i=n}^{n+b-1} (x'_i), i = 1, 2, \dots, N - b + 1 \quad (\text{I-7})$$ + +The filtered-packet time error sequence $y(t)$ may be used to compute TIE and applied to traditional synchronization metrics defined in [ITU-T G.810] such as MTIE and TDEV. When TIE or a metric are computed using $y(t)$ , the term *pktfiltered* is prepended to TIE or the name of the metric, respectively. As illustrated in Figure I.5, the *pktfiltered* operation includes both packet selection and bandwidth filtering. + +##### I.3.1.3 Integrated packet selection + +With integrated packet selection, the packet selection and sometimes also the filtering steps are integrated into the metric calculation, as shown in Figure I.6. Generally, this involves replacing a full population averaging calculation with a selection process that may or may not itself include averaging. + +![Figure I.6 – Integrated packet selection. A block diagram showing the flow from 'Entire PDV population' to a box labeled 'Stability metric with packet selection', which then outputs to 'Estimated achievable performance'. The diagram is labeled G.8260(15)_FI.6.](e7c6a6e4c3047dac05a3b92e396e9794_img.jpg) + +``` + +graph LR + A[Entire PDV population] --> B[Stability metric with packet selection] + B --> C[Estimated achievable performance] + style B fill:#d3d3d3,stroke:#333,stroke-width:1px + style C fill:#d3d3d3,stroke:#333,stroke-width:1px + style A fill:#d3d3d3,stroke:#333,stroke-width:1px + style G[G.8260(15)_FI.6] fill:none,stroke:none + G -.-> C + +``` + +Figure I.6 – Integrated packet selection. A block diagram showing the flow from 'Entire PDV population' to a box labeled 'Stability metric with packet selection', which then outputs to 'Estimated achievable performance'. The diagram is labeled G.8260(15)\_FI.6. + +**Figure I.6 – Integrated packet selection** + +NOTE – As mentioned earlier, there can be some discrepancies between the information provided by a given PDV metric and the real performances achieved by a packet slave clock. + +##### I.3.1.4 Packet selection windows + +For the packet selection described in the previous clauses, packet selection is carried out in a sequence of time windows applied to the entire set of data. There is a variety of possible approaches to this progression of windows. The windows could be non-overlapping but contiguous (also known as "jumping windows"), overlapping by some number of samples (known as "step-overlapping"), or overlapping by sliding the window sample by sample. Figure I.6bis illustrates these three approaches: + +1 The time constant of a PLL, also known as its characteristic response time, provides an indication of the duration of the effects on the output of the PLL due to a given input. This is why it is important that the selection window is properly chosen in order to get a significant number of samples during this period of time. Note that the time constant $\tau_c$ is related to the 3 dB bandwidth of the PLL $f_{3\text{ dB}}$ , by the following relationship: $\tau_c = 1/(2\pi f_{3\text{ dB}})$ . + +![Figure I.6bis – Packet selection windowing. The diagram illustrates three types of windowing: Non-overlapping windows, Step-overlapping windows, and Sliding windows. Each type is shown with three windows (1, 2, 3) on a timeline with tick marks. Non-overlapping windows have no gaps or overlaps. Step-overlapping windows have a gap between the end of one window and the start of the next. Sliding windows overlap by one sample.](cbdfdade780e677eb1c1aef3081ce9ef_img.jpg) + +**Non-overlapping windows** +(next window starts at prior window stop) + +**Step-overlapping windows** +(windows overlap but starting points skip over N samples) + +**Sliding windows** +(overlapping windows slide sample by sample) + +G.8260(15)-Amd.2(18)\_FI.6bis + +Figure I.6bis – Packet selection windowing. The diagram illustrates three types of windowing: Non-overlapping windows, Step-overlapping windows, and Sliding windows. Each type is shown with three windows (1, 2, 3) on a timeline with tick marks. Non-overlapping windows have no gaps or overlaps. Step-overlapping windows have a gap between the end of one window and the start of the next. Sliding windows overlap by one sample. + +**Figure I.6bis – Packet selection windowing** + +To illustrate applying windowing to a set of data, consider the following specific case of step-overlapping windows. If the duration of the packet selection window is 200 seconds, a suitable window step size is 10% of 200 seconds, or 20 seconds. The first window would span 0 to 200 seconds, the second window 20 to 220 seconds, the third window 40 to 240 seconds, and so on. If the duration of the entire set of data is 10 000 seconds, this process would continue until reaching the final window, which spans 9800 seconds to 10 000 seconds. + +#### I.3.2 Packet selection methods + +Four examples of packet selection methods are described in the clauses that follow. The first two, minimum packet selection and percentile average packet selection, focus on packet data at the floor delay. The second two, band average packet selection and cluster range packet selection, can be applied either at the floor delay or at some other region. + +Equation I-4 defines that the reverse time errors are the same as the reverse delays. Thus, the minimum time error values correspond to the floor delays. However, Equation I-3 defines that the forward time errors are the inverse of forward delays. Thus, the maximum time error values correspond to floor delays. + +##### I.3.2.1 Minimum packet selection method + +The minimum packet selection method involves selecting the minimum delayed packet, i.e., the maximum or minimum value within a section of forward or reverse time error data, correspondingly. This can be represented as. + +$$x_{\min}(i) = -\min[-x_F(j)] \text{ for } (i \leq j \leq i+n-1) \quad (\text{I-8})$$ + +when using the forward time error sequence and. + +$$x_{\min}(i) = \min[x_R(j)] \text{ for } (i \leq j \leq i+n-1) \quad (\text{I-8a})$$ + +when using the reverse time error sequence. + +##### I.3.2.2 Percentile average packet selection method + +The percentile average packet selection method is related to the minimum packet selection method, except that instead of selecting the minimum, some number (or some percentage) of minimum values + +are chosen and averaged together. It is a special case of the band average packet selection method described in clause I.3.2.3 with the lower limit set to zero. + +##### I.3.2.3 Band average packet selection method + +The band average packet selection method can be used to select a section of packet data at the floor or from some other region such as the ceiling or somewhere else above the floor. The band is defined by two percentile values representing the upper and lower selection bounds. To perform the band average packet selection, it is first necessary to represent the sorted packet time-error sequence. Let $x''$ represent this sorted phase sequence from minimum to maximum for the reverse time error sequence, and maximum to minimum for the forward time error sequence, over the range $i \leq j \leq i + n - 1$ . Next, it is necessary to represent the indices that are themselves set based on the selection of the two percentile values. + +Let $a$ and $b$ represent indices for the two selected percentile values. The averaging is then applied to the $x''$ variable indexed by $a$ and $b$ . The number of averaged points $m$ is related to $a$ and $b$ : $m = b - a + 1$ . + +$$x'_{band\_avg}(i) = \frac{1}{m} \sum_{j=a}^b x''_{j+i} \quad (I-9)$$ + +Each of the indices $a$ and $b$ is determined by rounding to find the closest index to the desired percentile value. The additional constraint is that both indices have a minimum value of the first index and a maximum value of the last index. Further, at least one point within the data set must be selected. Thus, for example, a set of ten points with the percentile values set to 0% and 2% (0.02), both $a$ and $b$ would be set to the minimum index so that at least a single point would be selected. + +##### I.3.2.4 Cluster range packet selection method + +The cluster range packet selection method uses a time- and/or phase-bounded range rather than indices based on percentiles (probabilities) to perform the packet selection. This selection method involves the selection of a group of one or more packets that are closely related with respect to their transit time. The location of the cluster may be made based on various criteria, for example, packets at the floor or from some other region observed in the window interval, or the location of the cluster may be based on other criteria or information outside the interval. The cluster of packets could then be processed in a variety of ways to generate a single value for that interval, such as the mean transit time of all packets within the cluster. + +Figure I.7 shows an example of a packet delay sequence, zooming in on an example of a packet cluster for a single window interval. + +![Figure I.7: Example of concept of cluster range packet selection. The plot shows packet transit times (in μs) on the y-axis (0 to 1.5) versus Time (s) on the x-axis (1750 to 2200). A rectangular box highlights a cluster of points. The horizontal dimension of the box is labeled 'Window interval' and the vertical dimension is labeled 'Cluster range'. The text 'G.8260(15)_FI.7' is in the bottom right corner.](2a23751710f7827065d2b99b6df588df_img.jpg) + +Figure I.7: Example of concept of cluster range packet selection. The plot shows packet transit times (in μs) on the y-axis (0 to 1.5) versus Time (s) on the x-axis (1750 to 2200). A rectangular box highlights a cluster of points. The horizontal dimension of the box is labeled 'Window interval' and the vertical dimension is labeled 'Cluster range'. The text 'G.8260(15)\_FI.7' is in the bottom right corner. + +**Figure I.7 – Example of concept of cluster range packet selection** + +The cluster selection method involves the following pre-determined choices: + +- First, the range of the packet transit times accepted within a cluster is set and is related to the target performance. That is, the range can be chosen to best serve the application for which the clock is intended. This is the *cluster range*, $\delta$ , and is specified in units of time. +- Second, the selection window interval for the cluster is set. +- Third, the *cluster location* or *cluster anchor value*, $a(n)$ , within the overall distribution of packet delays is variable and can be programmed to best characterize the type(s) of noise introduced by the packet network. That is, the optimal time error is obtained when the cluster selection method identifies the packets that represent the most stable transit delay. The specific cluster anchor type may be considered as the cluster rule, denoted as $clusterType = rule$ or $clusterType_{rule}$ . + +Denote the time error sequence of the packet timing signal at the slave clock packet interface by $\{x(k\tau_p)\}$ . That is, the underlying sampling interval (nominal packet interval) is $\tau_p$ . The cluster selection method considers $K$ samples (packets) using a fixed-window processing architecture and generates a new time error sequence $\{x'(n\tau_0)\}$ where $\tau_0 = K\tau_p$ . Note that the sample value $x'(n\tau_0)$ is based on the $K$ input samples $\{x(m\tau_p); m = nK, (nK+1), \dots, ((n+1)K-1)\}$ . This sample value can be expressed as: + +$$x'(n\tau_0) = \frac{\sum_{i=0}^{(K-1)} x((nK + i)\tau_p) \cdot \phi(n, i)}{\sum_{i=0}^{(K-1)} \phi(n, i)} \quad (I-10)$$ + +where in Equation I-10, $\phi(\cdot)$ is the indicator function that expresses the selection mechanism in a mathematical manner and is given by: + +$$\phi(n, i) = \begin{cases} 1 & \text{for } |x((nK + i)\tau_p) - a(n)| \leq \frac{\delta}{2} \\ 0 & \text{otherwise} \end{cases} \quad (I-11)$$ + +In Equation I-11, $\delta$ is the cluster range and $a(n)$ is the anchor value for the particular window of $K$ samples. Note that Equation I-11 generates the new time error sequence by computing the average over those packets that satisfy the selection rule. + +The anchor value can be interpreted as a nominal value for the window and is established according to a pre-determined cluster type. For example, the selection rule for this anchor value could be: + +- Minimum transit delay over the $K$ packets in the window, represented as $clusterType = min$ or $clusterType_{min}$ . +- Average (mean) transit delay over the $K$ packets in the window, represented as $clusterType = mean$ or $clusterType_{mean}$ . +- An absolute minimum value that may be determined before, during or after the sample window, represented as $clusterType = min\_absolute$ or $clusterType_{min\_absolute}$ . +- When using an absolute value, it is possible that no packets may be selected within the window (similar to a total packet loss situation). Note that the determination of an absolute minimum value after the sample window (as opposed to before or during) would only be used in post-analysis situations, as the information regarding the future packet delay transit times is not available to the client in a real-time system. + +It is common to refer to the anchor value as the transit delay of a particular packet that is then called the anchor packet. This is generally true, except when the anchor value is not associated with a particular packet (e.g., mean value or absolute minimum value). + +It may be helpful to use the representation $cluster(\delta, clusterType)$ where $\delta$ is the cluster range, and the $clusterType$ is an indication of the rule used to generate the anchor value. + +#### I.3.3 Consideration of non-stationary network conditions + +As the packet selection can focus on a particular statistical region, it is important to consider the case where network packet delay statistics are not stationary, but rather change over time. For example, if a floor-based metric is applied to packet measurement data where the floor shifts, the application of the floor-based metric would perhaps be best applied to sections of the data separately (see Figures I.8 and I.9). In many cases, segregating the data into sections might not be so straightforward, such as the case of an increasing load ramp. Such a situation is for further study. + +![Figure I.8: A scatter plot showing phase deviation in units of time (μs) over a period of 1.114 hours. The y-axis ranges from 0.00 to 18.0 μs, with major ticks at 0.00, 2.00, and 18.0. The x-axis ranges from 0.000 to 1.114 hours, with major ticks at 0.000, 5.00 minutes/div, and 1.114 hours. The plot shows three distinct sections of data points: a dense cluster near 0.00 μs from 0.000 to approximately 0.5 hours, a sparse cluster between 0.5 and 1.0 hours, and a dense cluster between 1.0 and 1.114 hours.](a2dcc4a0703102026ec86e82caa4985e_img.jpg) + +Phase deviation in units of time; $F_s = 63.97$ Hz; $F_o = 10.000000$ MHz; 2009/11/06; 10:55:06 + Phase minimum; Overlap; $T_{au} = 1.56$ s; $A = 100$ ; $N = 256418$ + +G.8260(15)\_FI.8 + +Figure I.8: A scatter plot showing phase deviation in units of time (μs) over a period of 1.114 hours. The y-axis ranges from 0.00 to 18.0 μs, with major ticks at 0.00, 2.00, and 18.0. The x-axis ranges from 0.000 to 1.114 hours, with major ticks at 0.000, 5.00 minutes/div, and 1.114 hours. The plot shows three distinct sections of data points: a dense cluster near 0.00 μs from 0.000 to approximately 0.5 hours, a sparse cluster between 0.5 and 1.0 hours, and a dense cluster between 1.0 and 1.114 hours. + +**Figure I.8 – Minimum tracking statistic shows three distinct sections** + +![Figure I.9: A histogram (PDF) of phase deviation in units of time (μs) on a logarithmic scale. The y-axis ranges from 10 m to 1 k, with major ticks at 10 m, 100 m, 1, 10, 100, and 1 k. The x-axis ranges from -10.000 to 150.00 μs, with major ticks at -10.000 and 150.00 μs. The histogram shows three distinct sections corresponding to the data in Figure I.8: a sharp peak at approximately -10 μs, a broad peak at approximately 10 μs, and a broad peak at approximately 100 μs.](7119b28e39fa3784606bf8b8f44e4f9d_img.jpg) + +Phase deviation histogram; $F_s = 63.99$ Hz; $F_o = 10.00$ MHz; 2009/11/06; 10:55:06 + +G.8260(15)\_FI.9 + +Figure I.9: A histogram (PDF) of phase deviation in units of time (μs) on a logarithmic scale. The y-axis ranges from 10 m to 1 k, with major ticks at 10 m, 100 m, 1, 10, 100, and 1 k. The x-axis ranges from -10.000 to 150.00 μs, with major ticks at -10.000 and 150.00 μs. The histogram shows three distinct sections corresponding to the data in Figure I.8: a sharp peak at approximately -10 μs, a broad peak at approximately 10 μs, and a broad peak at approximately 100 μs. + +**Figure I.9 – Histograms (PDFs) for the three sections** + +#### I.3.4 Two-way time error calculation + +The two-way time error sequence $x_C$ is calculated from the forward time error sequence $x_F$ and reverse time error sequence $x_R$ according to the following equation: + +$$x_C(n\tau_0) = \frac{x_R(n\tau_0) + x_F(n\tau_0)}{2} \quad (\text{I-12a})$$ + +where $\tau_0$ is the mean packet spacing. + +Figure I.9a shows the combination operation producing the two-way time error. + +![Block diagram of a combination operation. Two input signals, x_F(t) and x_R(t), enter a block labeled 'Combination'. The output signal is x_C(t).](c494cd874a082a97b50b3c4d3938f467_img.jpg) + +Block diagram of a combination operation. Two input signals, x\_F(t) and x\_R(t), enter a block labeled 'Combination'. The output signal is x\_C(t). + +G.8260(15)-Amd.1(16)\_Fl.9a + +**Figure I.9a – Two-way offset** + +When combined with packet selection, which is performed on the forward and reverse sequences independently, the packet-selected time-error sequence of the forward path, $x_F'(t)$ , is combined with the packet-selected time-error sequence of the reverse path, $x_R'(t)$ , to create the packet-selected two-way time error sequence $x_C'(t)$ . + +$$x_C'(n\tau_s) = \frac{x_R'(n\tau_s) + x_F'(n\tau_s)}{2} \quad (I-12b)$$ + +where $\tau_s$ is the packet selection window width. + +Figure I.10 shows that when the combination operation is preceded by packet selection, the packet-selected two-way time error sequence is produced. This can itself be optionally combined with bandwidth filtering and/or stability metrics. The sequence $x_C'(t)$ is referred to as packet-selected two-way time error (pktSelected2wayTE). + +![Block diagram showing the process of two-way time error calculation including packet selection and filtering. Two input signals, x_F(t) and x_R(t), enter 'Packet selection' blocks. The outputs, x_F'(t) and x_R'(t), enter a 'Combination' block. The output of the 'Combination' block, x_C'(t), is split into two paths: one goes to a 'Stability metric' block, and the other goes to a 'Bandwidth filtering' block. The output of the 'Bandwidth filtering' block, y(t), enters another 'Stability metric' block. All three output signals (from the first stability metric, the second stability metric, and the bandwidth filtering output) are shown as outputs to the right.](fc0735d325f0ebd9214171975c68a888_img.jpg) + +Block diagram showing the process of two-way time error calculation including packet selection and filtering. Two input signals, x\_F(t) and x\_R(t), enter 'Packet selection' blocks. The outputs, x\_F'(t) and x\_R'(t), enter a 'Combination' block. The output of the 'Combination' block, x\_C'(t), is split into two paths: one goes to a 'Stability metric' block, and the other goes to a 'Bandwidth filtering' block. The output of the 'Bandwidth filtering' block, y(t), enters another 'Stability metric' block. All three output signals (from the first stability metric, the second stability metric, and the bandwidth filtering output) are shown as outputs to the right. + +G.8260(15)-Amd.1(16)\_Fl.10 + +**Figure I.10 – Two-way time error including packet selection and filtering** + +Note that the combination operation could be performed after bandwidth filtering as applied to each packet selection output separately, with the same results. + +Subsequently, $x_C'(t)$ for two-way flows (or $x_C(t)$ if there is no packet selection) may be substituted into the various metrics in the same manner as $x'(t)$ for one-way flows. When used in this way, the prefix "2way" denotes the fact that the metric is computed on a two-way flow, e.g., "2wayTDEV", "pktSelected2wayMAFE", or "pktFiltered2wayMTIE". + +## I.4 PDV metrics estimating the performance of a packet slave clock + +Clauses I.4.1 to I.4.4 describe the stability metrics and a few specific associations with packet selection that have been studied for quantifying packet network timing signals. + +The metrics are divided into four main classifications: + +### 1) Metrics estimating phase wander + +These include TIE and MTIE based metrics, similar to the use of TIE and MTIE to characterize the phase wander of conventional timing signals. + +### 2) Metrics estimating frequency stability + +These include TDEV based metrics, analysing the stability of the clock over different observation intervals. + +### 3) Metrics estimating frequency accuracy + +These include metrics based on maximum average frequency error (MAFE) and fractional frequency offset (FFO). + +#### 4) Metrics estimating time error + +#### I.4.1 Metrics estimating phase wander + +##### I.4.1.1 Maximum average time interval error + +Maximum average time interval error (MATIE) and its related metric maximum average frequency error (MAFE) describe maximum phase or frequency deviations over an observation interval. MATIE and MAFE include a noise-averaging function similar to TDEV. + +###### Definition + +Two adjacent sliding observation windows are used to analyse the time error of a clock or selected packet delay data. The width of the observation windows ( $\tau$ ) is used as the independent variable ( $x$ -axis of the resulting curve) like in TDEV. + +The average time error value is computed in the two adjacent windows. The averaging establishes the filtering capability that resembles the one used in TDEV. The unsigned difference between two consecutive windows is determined by subtracting the average of one window from the other and calculating the absolute value. + +The sliding window averaging process described above is a low-pass filtering process approximately corresponding to the one applied by a PLL filter to a timing signal. The difference calculation compares the estimation of the phase of the clock output at two time instances, which are a distance of $n\tau_0$ apart, see the MATIE formula (Equation I-13). + +The two adjacent sliding windows are swept over the whole time error data and the maximum value is taken to express the worst-case occurrence expected from the data. + +For the MATIE analysis of packet data, the same calculation is done for different values of the window size ( $\tau$ ), similar to TDEV. + +The function applied to discrete data samples is described in Equation I-14. + +MATIE( $n\tau_0$ ) is defined as a specified percentile, $\beta$ , of the random variable: + +$$X_n = \max_{1 \leq k \leq N - 2n + 1} \frac{1}{n} \left| \sum_{i=k}^{n+k-1} (x_{i+n} - x_i) \right| \quad (\text{I-13})$$ + +for $n = 1, 2, \dots$ , integer part ( $N/2$ ) + +where $x_i$ is the packet time error sequence (and is a random sequence), $n\tau_0$ is the observation window length, $n$ is the number of samples in the window, $\tau_0$ is the sample interval, $N$ is the number of samples in the data set, and $k$ is incremented to slide the window. MATIE describes the maximum of average time changes between adjacent windows of length $n\tau_0$ . + +###### Estimator formula + +MATIE( $n\tau_0$ ) may be estimated by: + +$$\text{MATIE}(n\tau_0) \cong \max_{1 \leq k \leq N - 2n + 1} \frac{1}{n} \left| \sum_{i=k}^{n+k-1} (x_{i+n} - x_i) \right| \quad (\text{I-14})$$ + +for $n = 1, 2, \dots$ , integer part ( $N/2$ ) + +Equation I-14 gives a point estimate, obtained from measurements (i.e., samples $x_i$ of the packet time error sequence or physical clock signal time error sequence, which represents the data values) over a single measurement period (see Figure II.1 of [ITU-T G.810]). Estimates of MATIE (for specified $N$ , $\tau = n\tau_0$ , and $\beta$ ), and their respective degrees of statistical confidence, may be obtained from measured data if measurements are made for multiple measurement periods (see clause II.5 of [ITU-T G.810]). + +###### Usage + +The recommended usage for determining the applicability of a network for packet synchronization is to apply the metric to pre-processed delay data, corresponding to the selected subset in Figure I.4. MATIE predicts the largest difference in averaged time interval error that occurs between adjacent averaging windows of width $n\tau_s$ : + +$$\text{MATIE}(n\tau_s) \cong \max_{1 \leq k \leq N-2n+1} \frac{1}{n} \left| \sum_{i=k}^{n+k-1} (x'_{i+n} - x'_i) \right| \quad (\text{I-15})$$ + +for $n = 1, 2, \dots$ , integer part ( $N/2$ ) + +Figure I.11 shows some example MATIE data. The black curve represents MATIE applied to pre-processed delay data. The red curve depicts pktfilteredMTIE (see clause I.4.1.4) with a 960 s averaging function. + +![Figure I.11: Example MATIE and pktfilteredMTIE data. The graph plots MATIE and pktfilteredMTIE in seconds on a logarithmic y-axis (1E-5 to 1E-3) against Tau in seconds on a logarithmic x-axis (1 to 100,000). The black curve (MATIE) starts at approximately 1E-3 s at Tau=1, decreases to a minimum of about 1E-4 s at Tau=1000, then rises to a peak of about 1.5E-4 s at Tau=10,000, before dropping sharply to about 3E-5 s at Tau=100,000. The red curve (pktfilteredMTIE) starts at approximately 1E-5 s at Tau=1, increases steadily to about 1.5E-4 s at Tau=10,000, and then remains relatively flat, ending at about 2E-4 s at Tau=100,000. The graph is labeled G.8260(15)_Fl.11.](645cfdb7a7e02c3b04b20d83aed890c3_img.jpg) + +Figure I.11: Example MATIE and pktfilteredMTIE data. The graph plots MATIE and pktfilteredMTIE in seconds on a logarithmic y-axis (1E-5 to 1E-3) against Tau in seconds on a logarithmic x-axis (1 to 100,000). The black curve (MATIE) starts at approximately 1E-3 s at Tau=1, decreases to a minimum of about 1E-4 s at Tau=1000, then rises to a peak of about 1.5E-4 s at Tau=10,000, before dropping sharply to about 3E-5 s at Tau=100,000. The red curve (pktfilteredMTIE) starts at approximately 1E-5 s at Tau=1, increases steadily to about 1.5E-4 s at Tau=10,000, and then remains relatively flat, ending at about 2E-4 s at Tau=100,000. The graph is labeled G.8260(15)\_Fl.11. + +Figure I.11 – Example MATIE and pktfilteredMTIE data + +##### I.4.1.2 minMATIE + +The packet selection operation can also be integrated in the MATIE calculation. The definitions and estimator formulas for minMATIE are given as follows: + +###### Definition + +minMATIE( $n\tau_0$ ) is defined as a specified percentile, $\beta$ , of the random variable: + +$$U_n = \max_{1 \leq k \leq N-2n+1} |x_{\min}(k+n) - x_{\min}(k)| \quad (\text{I-16})$$ + +where $x_{\min}(k)$ is as defined in equation (I-8) for the forward time error sequence, or (I-8a) for the reverse time error sequence, $n\tau_0$ is the observation window length, $n$ is the number of samples in the window, $\tau_0$ is the sample interval, $N$ is the number of samples in the data set, and $k$ is incremented for sliding the window. + +###### Estimator formula + +minMATIE( $n\tau_0$ ) may be estimated by: + +$$\text{minMATIE}(n\tau_0) \cong \max_{1 \leq k \leq N-2n+1} |x_{\min}(k+n) - x_{\min}(k)| \quad (\text{I-17})$$ + +for $n = 1, 2, \dots$ , integer part ( $N/2$ ) + +The above is a point estimate, and is obtained for measurements (i.e., samples $x_i$ of the packet time error sequence, which represent the data values) over a single measurement period (see Figure II.1 of [ITU-T G.810]). Estimates of minMATIE (for specified $N$ , $\tau = n\tau_0$ , and $\beta$ ), and their respective degrees of statistical confidence, may be obtained from measured data if measurements are made for multiple measurement periods (see clause II.5 of [ITU-T G.810]). + +##### I.4.1.3 pktfilteredTIE + +pktfilteredTIE is the TIE of the filtered-packet time error sequence, substituted into the formula defined in [ITU-T G.810]. + +$$\text{pktfilteredTIE}(t, \tau) = y(t + \tau) - y(t) \quad (\text{I-18})$$ + +##### I.4.1.4 pktfilteredMTIE + +pktfilteredMTIE is the MTIE of the filtered-packet time error sequence, obtained from the appropriate formula given in [ITU-T G.810] for the definition or estimator. + +###### Definition + +pktfilteredMTIE( $\tau$ ) is defined as a specified percentile, $\beta$ , of the random variable: + +$$Y = \max_{0 \leq t_0 \leq T-\tau} \left( \max_{t_0 \leq t \leq t_0+\tau} [y(t)] - \min_{t_0 \leq t \leq t_0+\tau} [y(t)] \right), \quad (\text{I-19})$$ + +where $T$ is the measurement interval and $\tau$ is the observation interval. + +###### Estimator formula + +pktfilteredMTIE( $n\tau_0$ ) may be estimated by: + +$$\text{pktfilteredMTIE}(n\tau_0) \cong \max_{1 \leq k \leq N-n} \left[ \max_{k \leq i \leq k+n} y_i - \min_{k \leq i \leq k+n} y_i \right], \quad n = 1, 2, \dots, N-1 \quad (\text{I-20})$$ + +The above is a point estimate, and is obtained for measurements over a single measurement period (see Figure II.1 of [ITU-T G.810]). Estimates of pktfilteredMTIE (for specified $T$ , $\tau = n\tau_0$ and $\beta$ ), and their respective degrees of statistical confidence, may be obtained from measured data, if measurements are made for multiple measurement periods (see clause II.5 of [ITU-T G.810]). + +#### I.4.2 Metrics estimating frequency stability + +##### I.4.2.1 TDEV-based metrics + +TDEV has been specified in [ITU-T G.810] and used in other Recommendations to specify network wander limits for physical timing signals. TDEV is also applicable to packet timing data. In relation to packet timing data, TDEV can be applied to pre-processed PDV data or integrated into the calculation. The case where TDEV is applied to pre-processed PDV data, which can be referred to as pktselectedTDEV, is depicted by Figure I.4 with TDEV as the stability metric. + +The integrated methods based on TDEV include minTDEV, percentileTDEV, and bandTDEV. The minTDEV and percentileTDEV metrics focus the packet selection on the minimum packet delay floor and the more general bandTDEV metric can select packet delays from any region, for example, the floor, just above the floor, in the middle, or the ceiling. The integrated methods can be applied for MATIE and MAFE metrics described further below but are described in depth only in the TDEV clause. + +Like the TDEV metric, the TDEV-based packet measurement metrics study the noise processes in the packet measurement data – white phase modulation (PM), flicker PM, random walk PM, flicker frequency modulation (FM), and random walk FM. With the incorporation of packet selection it is often possible that one or more of these noise processes can be reduced as compared to analysis incorporating no selection. + +###### I.4.2.1.1 MinTDEV + +###### Definition + +The minTDEV operator has been defined based on the TDEV metric. The TDEV metric is shown below in equation (I-21): + +$$\sigma_x(\tau) = \text{TDEV}(\tau) = \sqrt{\frac{1}{6n^2} \left\langle \left[ \sum_{i=1}^n (x_{i+2n} - 2x_{i+n} + x_i) \right]^2 \right\rangle} \quad (\text{I-21})$$ + +The TDEV operator is based on the mean of the sample window (Equation I-22): + +$$x_{\text{mean}}(i) = \frac{1}{n} \sum_{j=0}^{n-1} x_{j+i} \quad (\text{I-22})$$ + +Compared with the TDEV operator, in the minTDEV operation the mean of the sample window is replaced by $x_{\min}(i)$ as defined in Equation I-8 for the forward time error sequence, or I-8a for the reverse time error sequence. Substituting $x_{\min}(i)$ back into original TDEV definition yields the definition of minTDEV( $\tau$ ) (with $\tau = n\tau_0$ ): + +$$\sigma_{x\_min}(n\tau_0) = \text{minTDEV}(n\tau_0) = \sqrt{\frac{1}{6} \left\langle [x_{\min}(i+2n) - 2x_{\min}(i+n) + x_{\min}(i)]^2 \right\rangle}, \quad (\text{I-24})$$ + +$$\text{for } n = 1, 2, \dots, \text{ integer part } \left( \frac{N}{3} \right)$$ + +where the angle brackets denote ensemble average. + +###### Estimator formula + +minTDEV( $n\tau_0$ ) may be estimated by: + +$$\text{minTDEV}(n\tau_0) \cong \sqrt{\frac{1}{6(N-3n+1)} \sum_{i=1}^{N-3n+1} [x_{\min}(i+2n) - 2x_{\min}(i+n) + x_{\min}(i)]^2} \quad (\text{I-25})$$ + +$$\text{for } n = 1, 2, \dots, \text{ integer part } \left( \frac{N}{3} \right)$$ + +###### Usage + +The minTDEV operator has been indicated as a useful tool in combination with packet networks that exhibit a PDV behavior, where it is possible to identify a suitable set of packets with packet delay variation close to a minimum delay. + +In fact, these packets are less impacted by the queuing delays, and therefore are more representative of the original timing. Because of its definition, the minTDEV may not fully address all network scenarios (e.g., those with two-sided PDV distributions for which minimum selection can show large variations and hence increased TDEV noise) and further study is needed. + +###### Pros and cons + +The minTDEV calculation gives information on network packet delay noise processes but is not suitable for frequency offset characterization. + +Like TDEV, minTDEV is sensitive to systematic effects which could mask noise components. + +Unlike TDEV, minTDEV is sensitive to a small number of outliers (low-lying in this case). + +The definition of the precise aspects that create the potential sensitivities listed above and the subsequent method of handling these when applying this metric are for further study. + +###### I.4.2.1.2 PercentileTDEV + +###### Definition and estimator formula + +The percentileTDEV calculation is a special case of bandTDEV where the lower index $a$ is assigned to 0 (see the bandTDEV definition below). Therefore, the definition and estimator formula are given by the definition and estimator formula, respectively, for bandTDEV (see clause I.4.2.1.3) with $a = 0$ . Like the minTDEV metric, percentileTDEV focuses on the minimum packet delay floor. Instead of selecting a single minimum point, a (typically) small set of points at the floor are averaged together. + +###### Usage + +The percentileTDEV metric is applied much like the minTDEV metric. See clause I.4.2.1.1 on minTDEV usage. The percentile TDEV metric has the advantage that in some circumstances, noise is reduced when a number of floor packet delay measurements are selected and averaged together as opposed to the selection of a single point (see Figure I.12). + +![Figure I.12: A log-log plot comparing minTDEV and percentileTDEV (1%) over time. The y-axis represents time deviation in seconds, ranging from 10 ns to 100 μs. The x-axis represents time in seconds, ranging from 1.000 s to 100.0 s. The minTDEV curve (blue) starts at approximately 10 μs at 1.000 s and decreases to about 1 μs at 100.0 s. The percentileTDEV curve (black) starts at approximately 10 μs at 1.000 s and decreases more sharply, reaching about 100 ns at 100.0 s. The percentileTDEV curve is consistently below the minTDEV curve after the initial point.](4250329d33792315bc0d0940f256a2ea_img.jpg) + +| Time (s) | min TDEV (s) | percentile TDEV (s) | +|----------|-------------------|---------------------| +| 1.000 | 10 -5 | 10 -5 | +| 10.00 | 2.5 -6 | 10 -6 | +| 100.0 | 10 -6 | 10 -7 | + +Figure I.12: A log-log plot comparing minTDEV and percentileTDEV (1%) over time. The y-axis represents time deviation in seconds, ranging from 10 ns to 100 μs. The x-axis represents time in seconds, ranging from 1.000 s to 100.0 s. The minTDEV curve (blue) starts at approximately 10 μs at 1.000 s and decreases to about 1 μs at 100.0 s. The percentileTDEV curve (black) starts at approximately 10 μs at 1.000 s and decreases more sharply, reaching about 100 ns at 100.0 s. The percentileTDEV curve is consistently below the minTDEV curve after the initial point. + +Figure I.12 – minTDEV vs. percentileTDEV (1%) + +###### Pros and cons + +Like minTDEV, percentileTDEV gives information on network packet delay noise processes but is not optimal for frequency offset characterization. + +Like TDEV and minTDEV, percentileTDEV is sensitive to systematic effects which could mask noise components. + +Unlike TDEV and like minTDEV, percentileTDEV is sensitive to a small number of low-lying outliers (though less sensitive than minTDEV). + +An additional parameter, the percentile index, must be selected for percentileTDEV. + +The definition of the precise aspects that create the potential sensitivities listed above and the subsequent method of handling these when applying this metric are for further study. + +##### I.4.2.1.3 BandTDEV + +###### Definition + +BandTDEV represents the TDEV calculation where the band average selection operator (see clause I.3.2.3) is used to replace the mean of the sample window. The selected band is defined by two percentile values representing the upper and lower selection bounds, as shown in Equation I-9. + +bandTDEV can then be defined as: + +$$\sigma_{x\_band}(\tau) = \text{bandTDEV}(\tau) = \sqrt{\frac{1}{6} \left\langle \left[ x'_{\text{band\_avg}}(i+2n) - 2x'_{\text{band\_avg}}(i+n) + x'_{\text{band\_avg}}(i) \right]^2 \right\rangle} \quad (\text{I-27})$$ + +where the angle brackets denote ensemble average. + +###### Estimator formula + +bandTDEV( $n\tau_0$ ) may be estimated by: + +$$\text{bandTDEV}(n\tau_0) \cong \sqrt{\frac{1}{6(N-3n+1)} \sum_{i=1}^{N-3n+1} \left[ x'_{\text{band\_avg}}(i+2n) - 2x'_{\text{band\_avg}}(i+n) + x'_{\text{band\_avg}}(i) \right]^2} \quad (\text{I-28})$$ + +for $n = 1, 2, \dots$ , integer part $\left( \frac{N}{3} \right)$ + +###### Usage + +The bandTDEV calculation has the flexibility, in comparison to minTDEV and percentileTDEV, of being able to select a region of packet delay values away from the floor. Thus, if the population of packet delay values at the floor is noisier than the population immediately above, bandTDEV indices could be selected to focus analysis on that region. + +Some of the comments on minTDEV usage apply here, but bandTDEV can apply effectively to distributions other than one-sided distributions slanted towards the packet with the minimum delay. It is particularly effective for packet delay distributions with a well-populated mode somewhere in the packet delay distribution. + +###### Pros and cons + +Like minTDEV and percentileTDEV, bandTDEV gives information on network packet delay noise processes but is not optimal for frequency offset characterization. + +Like TDEV, minTDEV, and percentileTDEV, bandTDEV is sensitive to systematic effects which could mask noise components. + +The definition of the precise aspects that create the potential sensitivities listed above and the subsequent method of handling these when applying this metric are for further study. + +###### I.4.2.1.4 ClusterTDEV + +###### Definition + +To define clusterTDEV, it is first necessary to represent the sorted phase data. Let $x'$ represent this sorted phase sequence from minimum to maximum over the range $i \leq j \leq i + n - 1$ . Next it is necessary to represent the cluster type that determines the cluster anchor $a(n)$ and the cluster range $\delta$ . Let $a$ and $b$ represent indices for the packets that fit within cluster range $\delta$ . The averaging is then applied to the $x'$ variable for the cluster range $\delta$ . The number of averaged points is $m$ , where $m = b - a + 1$ for that cluster. + +$$x'_{\text{cluster}}(i) = \frac{1}{m} \sum_{j=a}^b x'_{j+i} \quad (\text{I-29})$$ + +For clusterTDEV the average of the values in the cluster range as per Equation I-29 is substituted for the mean value in the defining equation for TDEV. ClusterTDEV( $n\tau_0$ ) can then be defined as: + +$$\sigma_{x\_ \text{cluster}}(\tau) = \text{clusterTDEV}(\tau) = \sqrt{\frac{1}{6} \langle [x'_{\text{cluster}}(i + 2n) - 2x'_{\text{cluster}}(i + n) + x'_{\text{cluster}}(i)]^2 \rangle} \quad (\text{I-30})$$ + +where the angle brackets denote ensemble average. + +###### Estimator formula + +clusterTDEV( $n\tau_0$ ) may be estimated by: + +$$\text{clusterTDEV}(n\tau_0) \cong \sqrt{\frac{1}{6(N - 3n + 1)} \sum_{j=1}^{N-3n+1} [x'_{\text{cluster}}(i + 2n) - 2x'_{\text{cluster}}(i + n) + x'_{\text{cluster}}(i)]^2}, \quad (\text{I-31})$$ + +for $n = 1, 2, \dots$ , integer part $\left(\frac{N}{3}\right)$ + +###### Usage + +The clusterTDEV calculation has the flexibility of being able to select a region of packet delay values away from the floor. Thus, if the population of packet delay values at the floor is noisier than the population immediately above, clusterTDEV indices could be selected to focus analysis on that region. Generally speaking, clusterTDEV provides a quantitative measure of stability of transit delays that are in a pre-determined band based on a phase and/or time range centred at a value that is determined by a chosen selection rule. + +Some of the comments on minTDEV usage apply to clusterTDEV as well, but clusterTDEV can apply effectively to distributions other than one-sided distributions slanted towards the minimum delayed packet. It is particularly effective for packet delay distributions with a well-populated mode somewhere in the packet delay distribution. + +###### Pros and cons + +Like minTDEV, clusterTDEV gives information on network packet delay noise processes but is not suitable for frequency offset characterization. + +Like TDEV and minTDEV, clusterTDEV is sensitive to systematic effects which could mask noise components. + +Unlike TDEV and like minTDEV, clusterTDEV is sensitive to frequency offsets. Frequency offsets may be more difficult to ascertain precisely when neither a well-populated floor nor ceiling exists. + +Two additional parameters, the cluster range and the cluster rule, must be selected for clusterTDEV. + +The definition of the precise aspects that create the potential sensitivities listed above and the subsequent method of handling these when applying this metric are for further study. + +It may be helpful to use the representation $\text{clusterTDEV}(\tau, \delta, \text{clusterType})$ where $\tau$ is the observation interval, $\delta$ the cluster range, and the *clusterType* provides the rule used to generate the *anchor value*. Generally the rule is available from context and in that case need not be included in the representation. + +For example: + +$$\text{minTDEV}(\tau) = \text{clusterTDEV}(\tau, 0, \text{clusterType}_{\min}) \quad (\text{I-32})$$ + +###### I.4.2.1.5 pktfilteredTDEV + +pktfilteredTDEV is the TDEV of the filtered-packet time error sequence, obtained from the appropriate formula given in [ITU-T G.810] for the definition or estimator. + +###### Definition + +pktfilteredTDEV( $n\tau_0$ ) is defined as: + +$$\text{pktfilteredTDEV}(n\tau_0) = \sqrt{\frac{1}{6n^2} \left\langle \left[ \sum_{i=1}^n (y_{i+2n} - 2y_{i+n} + y_i) \right]^2 \right\rangle}, \quad (\text{I-33})$$ + +where the angle brackets denote an ensemble average. + +###### Estimator formula + +pktfilteredTDEV( $n\tau_0$ ) may be estimated by: + +$$\text{pktfilteredTDEV}(n\tau_0) \cong \sqrt{\frac{1}{6n^2(N-3n+1)} \sum_{j=1}^{N-3n+1} \left[ \sum_{i=j}^{n+j-1} (y_{i+2n} - 2y_{i+n} + y_i) \right]^2} \quad (\text{I-34})$$ + +$$\text{for } n = 1, 2, \dots, \text{ integer part } \left( \frac{N}{3} \right)$$ + +#### I.4.3 Metrics estimating frequency accuracy + +##### I.4.3.1 Maximum average frequency error + +###### Definition + +There is a simple relationship between MAFE and the MATIE metric defined above. + +$$\text{MAFE}(n\tau_0) = \frac{\text{MATIE}(n\tau_0)}{n\tau_0} \quad (\text{I-35})$$ + +Thus, $\text{MAFE}(n\tau_0)$ is defined as a specified percentile, $\beta$ , of the random variable: + +$$Z_n = \frac{\max_{1 \leq k \leq N-2n+1} \frac{1}{n} \left| \sum_{i=k}^{n+k-1} (x_{i+n} - x_i) \right|}{n\tau_0} \quad (\text{I-36})$$ + +$$\text{for } n = 1, 2, \dots, \text{ integer part } (N/2)$$ + +where $x_i$ is the packet time error sequence (and is a random sequence), $n\tau_0$ is the observation window length, $n$ is the number of samples in the window, $\tau_0$ is the sample interval, $N$ is the number of samples in the data set, and $k$ is incremented for sliding the window. MAFE is a dimensionless, normalized frequency ( $\Delta f/f$ ). + +###### Estimator formula + +MAFE( $n\tau_0$ ) may be estimated by: + +$$\text{MAFE}(n\tau_0) \cong \frac{\max_{1 \leq k \leq N-2n+1} \frac{1}{n} \left| \sum_{i=k}^{n+k-1} (x_{i+n} - x_i) \right|}{n\tau_0} \quad (\text{I-37})$$ + +for $n = 1, 2, \dots$ , integer part ( $N/2$ ) + +The above is a point estimate, and is obtained for measurements (i.e., samples $x_i$ of the packet time error sequence or physical clock signal time error sequence, which represents the data values) over a single measurement period (see Figure II.1 of [ITU-T G.810]). Estimates of MAFE (for specified $N$ , $\tau = n\tau_0$ , and $\beta$ ), and their respective degrees of statistical confidence, may be obtained from measured data if measurements are made for multiple measurement periods (see clause II.5 of [ITU-T G.810]). + +###### Usage + +When applied to the time error sequence of a physical clock signal data corresponding to the clock output in Figure I.1, at small $\tau$ values where the MAFE calculation does not do any further filtering to the clock signal, MAFE expresses the peak frequency error of the clock, see Figure I.13. At larger $\tau$ values where MAFE represents narrower bandwidth than in the clock servo producing the signal, MAFE presents how the maximum frequency error could be reduced by further averaging of the clock signal. + +The recommended usage for determining the applicability of a network for packet synchronization is to apply the metric to pre-processed delay data, corresponding to the selected subset in Figure I.4, MAFE predicts the maximum frequency error calculated from the largest difference in averaged time interval error observed between adjacent averaging windows of width $n\tau_s$ , see Figure I.13. + +$$\text{MAFE}(n\tau_s) \cong \frac{\max_{1 \leq k \leq N-2n+1} \frac{1}{n} \left| \sum_{i=k}^{n+k-1} (x'_{i+n} - x'_i) \right|}{n\tau_s} \quad (\text{I-38})$$ + +for $n = 1, 2, \dots$ , integer part ( $N/2$ ) + +Figure I.13 shows an example of the effect of MAFE applied to pre-processed delay data and to the time error data of one particular physical clock that uses an averaging period of the order of 1 000 s. The definition of averaging period is for further study. + +![Figure I.13: A log-log plot showing MAFE [relative] on the y-axis (ranging from 1E-9 to 1E-4) versus Tau [s] on the x-axis (ranging from 1 to 10000). Two curves are plotted: a black curve labeled 'MAFE applied to pre-processed delay data' and a red curve labeled 'MAFE applied to time error data of a physical clock signal'. The black curve starts at approximately 1E-4 at Tau=1 and decreases steadily to about 1E-9 at Tau=10000. The red curve starts at approximately 1E-7 at Tau=1 and remains relatively flat until Tau=100, then decreases to about 1E-9 at Tau=10000. A horizontal line at 1.6 x 10^-7 is labeled 'Maximum frequency error of a clock, 1.6 x 10^-7'. The plot is labeled 'G.8260(15)_FI.13' in the bottom right corner.](32f80b2d70752613b6577797811f3a95_img.jpg) + +Figure I.13: A log-log plot showing MAFE [relative] on the y-axis (ranging from 1E-9 to 1E-4) versus Tau [s] on the x-axis (ranging from 1 to 10000). Two curves are plotted: a black curve labeled 'MAFE applied to pre-processed delay data' and a red curve labeled 'MAFE applied to time error data of a physical clock signal'. The black curve starts at approximately 1E-4 at Tau=1 and decreases steadily to about 1E-9 at Tau=10000. The red curve starts at approximately 1E-7 at Tau=1 and remains relatively flat until Tau=100, then decreases to about 1E-9 at Tau=10000. A horizontal line at 1.6 x 10^-7 is labeled 'Maximum frequency error of a clock, 1.6 x 10^-7'. The plot is labeled 'G.8260(15)\_FI.13' in the bottom right corner. + +**Figure I.13 – MAFE applied to pre-processed delay data and to time error data of physical clock** + +###### I.4.3.1.1 Pros and cons of MAFE and MATIE + +MAFE is well suited to the characterization of frequency error. + +The behavior of MAFE and MATIE as a function of the nature of the time error is examined below. Note that MAFE and MATIE do not converge for noise types of higher order than WFM, e.g., FFM and RWFM. + +Like the minTDEV and percentileTDEV metrics, MAFE and MATIE with floor-based selection is sensitive to a small number of low-lying outliers. + +The definition of the precise aspects that create the potential sensitivities listed above and the subsequent method of handling these when applying this metric are for further study. + +###### Properties of MAFE and MATIE + +Suppose that the time error sequence for which the MAFE (or MATIE) is computed is described by the sequence $\{x(n\tau_0)\}$ or (to simplify notation), $\{x(n)\}$ . The coefficient $\mu$ below is the *constant time error*. Consider the cases where the dominant component of the time error is: + +- Simple frequency offset + +In this case the time error can be written as (frequency offset = $b$ ): + +$$x(k) = \mu + b \cdot k \cdot \tau_0 \quad (\text{I-39})$$ + +and it can be shown that: + +$$\text{MATIE}(\tau = n \cdot \tau_0) = b \cdot \tau_0 \cdot n \quad (\text{I-40})$$ + +Note that the frequency offset is related to MATIE in this case via the relationship: + +$$b = \frac{\text{MATIE}(\tau = n \cdot \tau_0)}{n \cdot \tau_0} = \text{MAFE}(\tau = n \cdot \tau_0) \quad (\text{I-41})$$ + +That is, when the time error is dominated by a frequency offset, the value of MAFE will be a constant, equal to the frequency offset (fractional frequency units). + +###### b. White phase noise + +In this case: + +$$x(k) = \mu + \varphi_{\text{WPM}}(k) \quad (\text{I-42})$$ + +where $\varphi_{\text{WPM}}(k)$ is a white noise sequence with power (variance) $\sigma_{\varphi}^2$ . It can be shown that whereas a closed form expression for MATIE does not exist it can be approximated by: + +$$\text{MATIE}(\tau = n \cdot \tau_0) \approx \left(4 \cdot \sqrt{2 \cdot \tau_0} \cdot \sigma_{\varphi}\right) \cdot \left(\frac{1}{\sqrt{n \cdot \tau_0}}\right) \quad (\text{I-43})$$ + +Equation I-43 assumes that the noise distribution is approximately Gaussian, based on the central limit theorem. The maximum value is approximated as four times the standard deviation. This is represented by the factor of 4 in Equation I-43. For a Gaussian distribution, four standard deviations correspond to the upper $6.33 \times 10^{-5}$ quantile (2-sided). + +In terms of MAFE: + +$$\text{MAFE}(\tau = n \cdot \tau_0) = \frac{\text{MATIE}(\tau)}{\tau} \approx \left(4 \cdot \sigma_{\varphi} \cdot \sqrt{2 \cdot \tau_0}\right) \cdot \tau^{-\frac{3}{2}} \quad (\text{I-44})$$ + +Thus, the impact of white PM on values of MATIE/MAFE becomes less important for large values of the observation interval $\tau$ . When plotted on a log-log scale, the graph of MATIE appears as a straight line of slope $-0.5$ ( $-1.5$ for MAFE). + +###### c. Flicker phase noise + +In this case: + +$$x(k) = \mu + \varphi_{\text{FPM}}(k) \quad (\text{I-45})$$ + +Generally speaking, flicker lies between white noise and random walk. If $C$ is a constant that is related to the strength of the flicker random process, then we can write (note that this is not a formal proof.): + +$$\text{MATIE}(\tau = n \cdot \tau_0) \approx 4 \cdot C \quad (\text{I-46})$$ + +$$\text{MAFE}(\tau = n \cdot \tau_0) \approx 4 \cdot C \cdot \tau^{(-1)}$$ + +The factor of 4 represents four standard deviations as described in the white phase noise description above. + +###### d. Random walk phase noise + +In this case: + +$$x(k) = \mu + \varphi_{\text{WFM}}(k) \quad (\text{I-47})$$ + +and it can be shown that for large $n$ , we can write + +$$\text{MATIE}(\tau = n \cdot \tau_0) \approx 4 \cdot \sigma_{\varepsilon} \cdot \left(\sqrt{\frac{2}{3 \cdot \tau_0}}\right) \cdot (n \cdot \tau_0)^{0.5} \quad (\text{I-48})$$ + +$$\text{MAFE}(\tau = n \cdot \tau_0) \approx 4 \cdot \sigma_{\varepsilon} \cdot \left(\sqrt{\frac{2}{3 \cdot \tau_0}}\right) \cdot (n \cdot \tau_0)^{-0.5}$$ + +The factor of 4 represents four standard deviations as described in the white phase noise description above. + +Thus the impact of random walk PM on values of MATIE/MAFE becomes very important for large values of the observation interval $\tau$ . When plotted on a log-log scale, the graph of MATIE appears as a straight line of slope +0.5 (−0.5 for MAFE). The term $\sigma_\epsilon$ represents the standard deviation of the white-noise sequence underlying the generation of the random walk sequence. + +##### I.4.3.2 minMAFE + +The packet selection operation can also be integrated in the MAFE calculation. The definitions and estimator formulas for minMAFE are given as follows: + +###### Definition + +minMAFE( $n\tau_0$ ) is defined as a specified percentile, $\beta$ , of the random variable: + +$$V_n = \frac{\max_{1 \leq k \leq N-2n+1} |x_{\min}(k+n) - x_{\min}(k)|}{n\tau_0} \quad (\text{I-49})$$ + +for $n = 1, 2, \dots$ , integer part ( $N/2$ ) + +where $x_{\min}(k) = \min[x_j]$ for $(k \leq j \leq k+n-1)$ , where $x_i$ is the packet time error sequence (and is a random sequence), $n\tau_0$ is the observation window length, $n$ is the number of samples in the window, $\tau_0$ is the sample interval, $N$ is the number of samples in the data set, and $k$ is incremented for sliding the window. + +###### Estimator formula + +minMAFE( $n\tau_0$ ) may be estimated by: + +$$\text{minMAFE}(n\tau_0) \cong \frac{\text{minMATIE}(n\tau_0)}{n\tau_0} = \frac{\max_{1 \leq k \leq N-2n+1} |x_{\min}(k+n) - x_{\min}(k)|}{n\tau_0}, \quad (\text{I-50})$$ + +for $n = 1, 2, \dots$ integer part ( $N/2$ ) + +The above is a point estimate, and is obtained for measurements (i.e., samples $x_i$ of the packet time error sequence, which represent the data values) over a single measurement period (see Figure II.1 of [ITU-T G.810]). Estimates of minMATIE (for specified $N$ , $\tau = n\tau_0$ , and $\beta$ ), and their respective degrees of statistical confidence, may be obtained from measured data, if measurements are made for multiple measurement periods (see clause II.5 of [ITU-T G.810]). + +##### I.4.3.3 pktfilteredFFO + +pktfilteredFFO is the fractional frequency offset of the filtered-packet time error sequence, $y(t)$ , substituted into the formula defined in [b-GR-1244-CORE]. Refer to clauses 4.5.2 and I.2 of [ITU-T G.810] for the definition and a description of FFO. + +###### Estimator formula + +pktfilteredFFO( $t; M\tau_s$ ), a dimensionless quantity, may be estimated by: + +$$\text{pktfilteredFFO}(t; M\tau_s) \cong \frac{6}{M\tau_s} \sum_{i=1}^M y_{i+m-1} \left( \frac{2i}{(M^2-1)} - \frac{1}{M-1} \right), m=1,2,3, \dots, N-M+1 \quad (\text{I-51})$$ + +where: + +$$t = m \cdot \tau_s$$ + +$\tau_s$ is the sampling period in seconds of the time samples after preselection and filtering. + +$M$ is the number of samples in the calculation interval. + +$M \cdot \tau_s$ is the calculation interval. + +$N$ is the total number of samples of the time data. + +$y_m$ are samples of time data in units of seconds, after preselection and filtering. + +#### I.4.4 Metrics estimating time error + +##### I.4.4.1 Packet-selected two-way time error (pktSelected2wayTE) + +The packet-selected two-way time error sequence, $x_c'(t)$ in Figure I.11 of clause I.3.4, is a sequence that can be used directly as a metric estimating time error. It is referred to as pktSelected2wayTE. A graphical representation of the packet-selected two-way time error sequence is shown in Figure I.13a: + +![Figure I.13a: Packet-selected two-way time error sequence and derived values. The graph shows a curve labeled x_c'(t) representing the packet-selected two-way time error over time (t). The y-axis is labeled 'Packet-selected two-way time error' and the x-axis is labeled 'Time (t)'. The curve has a local maximum and a local minimum. The maximum value is labeled 'max x_c'(t)' and the minimum value is labeled 'min x_c'(t)'. The peak-to-peak value is labeled 'p-p x_c'(t)'.](0cda1f4c603972dc23aefc2cc3cbd135_img.jpg) + +The figure is a line graph showing the packet-selected two-way time error sequence, $x_c'(t)$ , over time $t$ . The vertical axis represents the time error, and the horizontal axis represents time. The curve starts at the origin (0,0) and rises to a local maximum, then falls to a local minimum, and then rises again. The maximum value of the curve is labeled $\max x_c'(t)$ with a vertical double-headed arrow. The minimum value is labeled $\min x_c'(t)$ with a vertical double-headed arrow. The peak-to-peak value, which is the difference between the maximum and minimum values, is labeled $p-p x_c'(t)$ with a vertical double-headed arrow. A horizontal dashed line extends from the maximum value to the right. Another horizontal dashed line extends from the minimum value to the right. The graph is labeled 'G.8260(15)-Amd.1(16)\_FI.13a' at the bottom right. + +Figure I.13a: Packet-selected two-way time error sequence and derived values. The graph shows a curve labeled x\_c'(t) representing the packet-selected two-way time error over time (t). The y-axis is labeled 'Packet-selected two-way time error' and the x-axis is labeled 'Time (t)'. The curve has a local maximum and a local minimum. The maximum value is labeled 'max x\_c'(t)' and the minimum value is labeled 'min x\_c'(t)'. The peak-to-peak value is labeled 'p-p x\_c'(t)'. + +Figure I.13a – Packet-selected two-way time error sequence and derived values + +Peak-to-peak packet-selected two-way time error: + +$$\text{peak-to-peak}(\text{pktSelected2wayTE}) = \max(\text{pktSelected2wayTE}) - \min(\text{pktSelected2wayTE}) \quad (\text{I-51a})$$ + +Maximum absolute packet-selected two-way time error: + +$$\max|\text{pktSelected2wayTE}| = \max(|\max(\text{pktSelected2wayTE})|, |\min(\text{pktSelected2wayTE})|) \quad (\text{I-51b})$$ + +##### I.4.4.2 Packet filtered two-way time error (pktFiltered2wayTE) + +The packet-filtered two-way time error sequence, $y(t)$ in Figure I.11 of clause I.3.4, is a sequence that can be used directly as a metric estimating time error. It is referred to as pktFiltered2wayTE. + +Maximum absolute packet-filtered two-way time error: + +$$\max|\text{pktFiltered2wayTE}| = \max(|\max(\text{pktFiltered2wayTE})|, |\min(\text{pktFiltered2wayTE})|) \quad (\text{I-51c})$$ + +##### I.4.4.3 Maximum/Minimum/Peak-to-peak average time error (maxATE, minATE, ppATE) + +###### Definitions + +For estimating how a time clock could further filter the noise in the two-way time error sequence, an averaging function can be slid over the data in a similar manner as in the bandwidth filtering function (clause I.3.1.2) used for pktTIE (clause I.4.1.3) and other metrics. + +maxATE( $n\tau_s$ ) ("Maximum Average Time Error") is defined as a specified percentile, $\beta$ , of the random variable: + +$$X_n^{\max} = \max_{1 \leq k \leq N-n+1} \frac{1}{n} \sum_{i=k}^{n+k-1} (x_c'(i)) \quad (\text{I-52})$$ + +for $n = 1, 2, \dots, N$ + +where $x_c'(i)$ is the packet-selected two-way time error (which represents time error and is a random sequence), $n\tau_s$ is the observation window length, $n$ is the number of packet selection windows in the observation window and consequently the number of pre-processed samples in the observation window, $\tau_s$ is the packet selection window length and consequently the time interval between delay samples after the pre-processing step of packet selection, $N$ is the total number of pre-processed samples, and $k$ is incremented for sliding the observation window. maxATE describes the maximum value of average packet-selected two-way time error over an observation interval of length $n\tau_s$ . + +Similarly, minATE( $n\tau_s$ ) ("Minimum Average Time Error") is defined as a specified percentile, $\beta$ , of the random variable: + +$$X_n^{\min} = \min_{1 \leq k \leq N-n+1} \frac{1}{n} \sum_{i=k}^{n+k-1} (x_c'(i)) \quad (\text{I-53})$$ + +for $n = 1, 2, \dots, N$ + +where the variables are defined as above. minATE describes the minimum value of average packet-selected two-way time error over an observation interval of length $n\tau_s$ . + +Finally, ppATE( $n\tau_s$ ) ("Peak-to-peak Average Time Error") is defined as a specified percentile, $\beta$ , of the random variable: + +$$X_n^{pp} = X_n^{\max} - X_n^{\min} = \max_{1 \leq k \leq N-n+1} \frac{1}{n} \sum_{i=k}^{n+k-1} (x_c'(i)) - \min_{1 \leq k \leq N-n+1} \frac{1}{n} \sum_{i=k}^{n+k-1} (x_c'(i)) \quad (\text{I-54})$$ + +for $n = 1, 2, \dots, N$ + +where the variables are defined as above. ppATE describes the peak-to-peak value of average packet-selected two-way time error over an observation interval of length $n\tau_s$ . + +###### Estimator formulas + +For calculating maxATE the sliding window size is varied by sequencing $n$ and determining the maximum two-way time error for each value of $n$ , thus creating maxATE as a function of sliding averaging window width. In a similar fashion, minATE is calculated by determining the minimum two-way time error as a function of sliding averaging window width. ppATE is calculated through a point-by-point subtraction of maxATE minus minATE elements. + +$$\text{maxATE}(n\tau_s) \cong \max_{1 \leq k \leq N-n+1} \frac{1}{n} \sum_{i=k}^{n+k-1} (x_c'(i)), \quad (\text{I-55})$$ + +$$\text{minATE}(n\tau_s) \cong \min_{1 \leq k \leq N-n+1} \frac{1}{n} \sum_{i=k}^{n+k-1} (x_c'(i)), \quad (\text{I-56})$$ + +$$\text{ppATE}(n\tau_s) = \text{maxATE}(n\tau_s) - \text{minATE}(n\tau_s) \quad (\text{I-57})$$ + +for $n = 1, 2, \dots, N$ + +where $\tau_s$ is the time interval between delay samples after packet selection. Thus $\tau_s$ is the same as the selection window size. $N$ is the total number of samples and $x_c'(i)$ is the packet-selected two-way + +time error after packet selection. The resulting maxATE and minATE curves are shown in Figure I.14 along with the value of ppATE for $n = 1$ . + +![Figure I.14: Example of average time error calculation. A line graph showing mATE [ns] on the y-axis (from -500 to 0) versus τ [s] on the x-axis (from 200 to 1200). Two curves are plotted: maxATE(mτs) and minATE(mτs). The maxATE curve is nearly horizontal at 0 ns. The minATE curve starts at -520 ns at τ=200, rises to -420 ns at τ=400, and continues to rise to approximately -280 ns at τ=1200. A vertical double-headed arrow between the two curves at τ=400 is labeled 521 ns. A small horizontal segment at the top left is labeled 1 ns. The graph is labeled G.8260(15)-Amd.1(16)_FI.14.](734487b0336ba703328f4484af34e77d_img.jpg) + +Figure I.14: Example of average time error calculation. A line graph showing mATE [ns] on the y-axis (from -500 to 0) versus τ [s] on the x-axis (from 200 to 1200). Two curves are plotted: maxATE(mτs) and minATE(mτs). The maxATE curve is nearly horizontal at 0 ns. The minATE curve starts at -520 ns at τ=200, rises to -420 ns at τ=400, and continues to rise to approximately -280 ns at τ=1200. A vertical double-headed arrow between the two curves at τ=400 is labeled 521 ns. A small horizontal segment at the top left is labeled 1 ns. The graph is labeled G.8260(15)-Amd.1(16)\_FI.14. + +**Figure I.14 – Example of average time error calculation** + +## I.5 PDV metrics studying floor delay packet population + +The objective of this category of PDV metrics is to study the population of timing packets within a certain fixed cluster range starting at the observed floor delay. The population of timing packets can then be compared with acceptance or rejection thresholds. The main idea here is to ensure that at least a minimum number of packets, or alternately a minimum percentage of packets, always remains within the specified fixed cluster range starting at the observed floor delay. + +As an example, consider Figure I.15. The packet delay values are shown as a function of time. Some packets arrive within a certain range of the smallest observed delay (those below the red line) and others arrive outside that range. In each window interval, those packets arriving within the range are counted. This count is compared against an acceptance criterion for each window interval. If all window intervals meet the acceptance criterion, then the network has met the PDV network limit. + +The windows depicted in Figure I.15 are shown as non-overlapping, but contiguous. This is also referred to as a "jumping window" approach. The "sliding window" approach considers windows that are shifted by 1 packet (sample). Intermediate approaches consider different levels of overlap, where the degree of overlap is known as the step size. Thus, overlapping windows include both sliding windows and step-overlapping windows. Using sliding windows detects all non-stationary and short transient failure events. Implementations may choose to use a jumping window or an overlapping window approach (including both sliding and step-overlapping). + +![Figure I.15: A scatter plot showing timing packet latencies over time. The y-axis represents latency in microseconds (µs), ranging from 0.00 s to 99.0 µs, with a scale of 3.00 µs/div. The x-axis represents time in minutes, ranging from 0.00 minute to 37.93 minutes, with a scale of 3.00 minutes/div. The plot shows two main clusters of data points. A horizontal red line at the bottom of the first cluster is labeled 'Fixed cluster range'. Vertical red dashed lines divide the time into 'Window interval' segments. Brackets on the right indicate that 'Timing packets outside the range are not counted' and 'Timing packets within the range are counted'. The figure is labeled G.8260(15)_FI.15.](25fab88fda841d5eec316c440656187e_img.jpg) + +Figure I.15: A scatter plot showing timing packet latencies over time. The y-axis represents latency in microseconds (µs), ranging from 0.00 s to 99.0 µs, with a scale of 3.00 µs/div. The x-axis represents time in minutes, ranging from 0.00 minute to 37.93 minutes, with a scale of 3.00 minutes/div. The plot shows two main clusters of data points. A horizontal red line at the bottom of the first cluster is labeled 'Fixed cluster range'. Vertical red dashed lines divide the time into 'Window interval' segments. Brackets on the right indicate that 'Timing packets outside the range are not counted' and 'Timing packets within the range are counted'. The figure is labeled G.8260(15)\_FI.15. + +**Figure I.15 – Example of PDV metric studying the population of packets within a fixed cluster range starting at the observed floor delay** + +PDV limits specified in terms of these metrics are considered as met if at least $m$ packets, or alternately at least $p\%$ of packets, are observed for any window interval of $t$ s within a fixed cluster range starting at the observed floor delay and having a size $\delta$ . If fewer than $m$ packets are observed, or alternately less than $p\%$ of packets, then the PDV limit is considered as not met. + +This process can be described in the following way: + +Let $x[i]$ represent the measured latency of timing packet $i$ , where $0 \leq i < N$ . That is, there are $N$ packets in the measurement data set. Let the nominal time between timing packets be represented by $\tau_P$ . Let $\delta$ represent the cluster range and let $W$ represent the window interval in units of time, which can also be expressed as $K$ samples, where $K = W/\tau_P$ . $K$ represents the (nominal) number of packets transmitted in the window interval. + +NOTE – It is assumed that the packet rate of the timing flow is nominally constant. The case for a variable rate of packet transmission is for further study. + +Define the minimum observed delay as: + +$$d_{\min} = \min_{0 \leq i < N} x[i] \quad (\text{I-59})$$ + +The observed $d_{\min}$ given by Equation I-59 is an estimate of the absolute minimum latency that a packet may experience. If a better estimate of the absolute minimum latency is available, for example from previous measurement data, that alternate value may be used. In all cases, Equations I-60 to I-65 are valid for choices of minimum delay less than or equal to the observed $d_{\min}$ . + +Then, define the indicator function which performs floor packet selection: + +$$\phi_F(i, \delta) = \begin{cases} 1; & \text{if } x[i] \leq d_{\min} + \delta \\ 0; & \text{otherwise} \end{cases} \quad \text{for } 0 \leq i < N \quad (\text{I-60})$$ + +Note that Equation I-60 assumes that packet delay is always greater than $d_{\min}$ . + +The convention followed in Equations I-61, I-62 and I-63 is that sample index $n$ is associated with the end of the window. That is, the floor packet metrics are based on complete windows and consequently values of $n$ less than $(K - 1)$ are not defined. + +Then define the *Floor Packet Count* (FPC) sequence with parameters $n$ , $W$ ( $W = K \cdot \tau_P$ ) and $\delta$ : + +$$\text{FPC}(n, W, \delta) = \sum_{j=n-(K-1)}^n \phi_F(j, \delta) \text{ for } (K-1) \leq n < N \quad (\text{I-61})$$ + +Define the *Floor Packet Rate* (FPR) sequence with parameters $n$ , $W$ and $\delta$ : + +$$\text{FPR}(n, W, \delta) = \frac{\text{FPC}(n, W, \delta)}{W} \text{ for } (K-1) \leq n < N \quad (\text{I-62})$$ + +Define the *Floor Packet Per cent* (FPP) sequence with parameters $n$ , $W$ and $\delta$ : + +$$\text{FPP}(n, W, \delta) = \left( \frac{\tau_P}{W} \right) \times \text{FPC}(n, W, \delta) \times 100 \% \text{ for } (K-1) \leq n < N \quad (\text{I-63})$$ + +The *floor packet per cent* is applicable to defining network limits. That is, the network performance is acceptable if + +$$\min_{(K-1) \leq n < N} \{\text{FPP}(n, W, \delta)\} \geq p \% \quad (\text{I-64})$$ + +where the network acceptance criterion is $p\%$ , and the parameters $W$ and $\delta$ are provided in the appropriate Recommendation, for example [b-ITU-T G.8261.1]. + +The *floor packet rate* (equivalently *floor packet count*) is a suitable metric for identifying the slave clock tolerance limit. That is, the slave clock must meet its specified output performance if + +$$\min_{(K-1) \leq n < N} \{\text{FPC}(n, W, \delta)\} \geq m \quad (\text{I-65})$$ + +where the parameters $m$ , $W$ and $\delta$ are provided in the appropriate recommendation as applicable. + +Equations I-62, I-63, I-64, and I-65 are general and appropriate for sliding window approaches. Jumping and overlapping window calculations can be obtained by sub-sampling the sliding window samples. + +For the jumping window case, estimates are derived every $K$ samples. That is, the jumping window samples are simply the sliding window estimates under-sampled by a factor of $K$ . Over the full measurement interval, there are $M = (N/K)$ jumping window samples and consequently the index for the jumping window sequence ranges from 0 through $(M - 1)$ . + +The jumping window approach is suitable when network conditions are stationary and spectral, and probability density parameters do not change rapidly. The sliding windows may be more appropriate, for example, for short term transient or rapidly changing events. + +NOTE 1 – This category of PDV metrics requires a long enough measurement period such that the observed floor delay would give a good enough estimation of the absolute floor delay. The minimum measurement period depends on the type of network considered. Long measurement periods, for instance over one or several days, should be favored in order to study diurnal PDV effects. + +NOTE 2 – Like minTDEV and MAFE, these metrics may be sensitive to a small number of low-lying outliers. The definition of the precise aspect that creates the potential sensitivity and the subsequent method of handling this when applying this metric is for further study. + +NOTE 3 – This category of PDV metrics is sensitive to non-stationary network conditions as described in clause I.3.3 that produce floor delay steps of significant amplitude, which may occur for instance during network re-routing events. The handling of floor delay steps is for further study. + +NOTE 4 – These metrics are mainly intended to be used as post-processing metrics. The use of these metrics for real-time processing is for further study. + +NOTE 5 – These metrics can be used to study the PDV noise produced independently by the forward or the reverse direction of a packet timing flow. Consideration of the combined effect of both directions is for further study. + +#### I.5.1 Determination of observed floor delay + +When calculating the Floor Population metrics, it is first necessary to determine the value of the observed floor delay. Whereas it is permissible for the user to specify a suitable value for the floor delay, two data-driven methods of determining this value are described here. The first method, called the *overall minimum* method, is to use the minimum delay observed over the entire measurement period. The second method, called the *progressive minimum* method, is to use the minimum observed delay in the measurement period up to the time window over which the individual Floor Population metric value is calculated. Refer to clause I.5.1.3 for information concerning the impact of packet network re-route events on the determination of observed floor delay. + +##### I.5.1.1 Minimum floor delay over the entire measurement + +In the overall minimum method, the observed floor delay used in computing the Floor Population metrics is the minimum delay value over the entire measurement data set following Equation I-59. + +As the overall minimum delay for a measurement period may not be known until the end of the period, calculation of Floor Population metric values over a given time window may depend upon delay values that have not yet been observed. This dependency upon future observations makes it more difficult to provide an early indication of Floor Population conformance for long-term tests. + +##### I.5.1.2 Progressive determination of floor delay + +In applications where it is not practical to wait till the end of the measurement period to determine the observed floor delay, the following causal estimation procedure can be used. At each Floor Population metric computation point $n$ , the observed floor delay is estimated as the smallest delay value in the measurement period up to (and including) the window over which the metric is computed. This running estimate of floor delay is then used when calculating the Floor Population metric. This enables calculation of the Floor Population metric value at any given time, depending only upon delay values that have already been observed. + +To accommodate the dynamic notion of observed floor delay, the floor population metrics defined in clause I.5 are modified to use the current retrospective estimate of the floor delay rather than the minimum over the whole data set. The terminology used is $FP_{xM}[n, W, \delta, d_{\min}(n)]$ where $x$ represents the metric ("count", "rate", "per cent"), the subscript M indicates that the formula used is a modified form of the ITU-T G.8260 definition, and $d_{\min}(n)$ is the current running estimate of the floor delay. + +In terms of Equation I-59, the observed floor delay at time $n$ (where $n$ is always a sample index at the end of an observation window) can be estimated as: + +$$d_{\min}(n) = \min_{0 \leq i < n} x[i] \quad (\text{I-66})$$ + +The value of the floor packet metrics in Equations I-61 to I-63 at time $n$ are then calculated using $d_{\min}(n)$ instead of $d_{\min}$ , as shown in Equation I-66. + +As an example for a specific implementation, the floor delay at time $n$ can be iteratively estimated according to the following algorithm: + +1. Denote $d(n)$ as the minimum packet delay of the most recent observation window; +2. Compare $d(n)$ to the current estimate of the observed floor delay $d_{\min}(n)$ + - a. If $d(n) < d_{\min}(n) \Rightarrow d_{\min}(n) = d(n)$ + - b. Otherwise $\Rightarrow d_{\min}(n)$ remains unchanged + +$$(\text{I-67})$$ + +The progressive floor determination method continually refines the estimate of the observed floor delay value during the measurement period. At each Floor Population metric computation point $n$ , the observed floor delay is estimated as the smallest delay value, $d_{\min}(n)$ , in the measurement period up to (and including) the window over which the metric is computed. The running value of this + +estimate is then used when calculating the (estimated) Floor Population metric. The windows could be sliding, overlapping, or jumping. + +Starting from the first observation window and for each subsequent window, the Floor population metrics are computed as $FP_{XM}[n, W, \delta, d_{\min}(n)]$ . + +An initial *settling-time* ( $S$ s) should be allowed to ensure a good estimate of the floor has been established, resulting in valid calculations only occurring after this time has elapsed. The objective is to select a value of $S$ after which the estimation of the observed floor delay would be close enough to the true delay floor, allowing for reliable $FP_x$ conformance tests to be calculated for the subsequent observation windows. The settling time can be either based on a predefined fixed value (for example, on some worst-case assumption) or calculated in real time based on the specific properties of the packet delay. The specific method and value are for further study. It has been demonstrated that for [ITU-T G.8261] Appendix VI test cases, a value of $S = 600$ s should suffice. + +##### **I.5.1.3 Re-route events and impact on observed floor delay** + +###### **I.5.1.3.1 Re-route events** + +Re-route events are defined as a change in the path taken by packets through a network. Such a re-route event can result in a change to the observed floor delay of a given PTP flow. + +Significant re-route events that occur in a given network are expected to have the following attributes: + +- These are infrequent events. In a well-engineered telecom network, such re-route events (usually as a result of some equipment malfunction or routine maintenance) should be quite rare. +- A single re-route event may cause multiple floor delay changes over a short time period (e.g., a network maintenance activity that results in a short-term network re-route event that is restored through a second re-route event after a relatively short period of time). Such a series of proximate re-route events should be regarded as a single event. It is typically assumed that such network route instability can last between a few minutes (due to software upgrade of the routers) up to a few hours (as a result of some failure in the network). +- The consequent floor delay changes are abrupt. The floor delay changes occur within only a few packet interval durations (as it is very short, the specific duration is not critical). + +###### **I.5.1.3.2 Re-route event impact on packet network limit** + +Unlike network loading variations, congestion and other extreme conditions, observed floor delay changes due to re-route events are not part of the packet network limit and do not consume part of the packet network limit budget. + +When a re-route event occurs, the packet network is considered to not comply with the packet network limit. The packet network limit measurement should be re-started and a new observed floor delay computed. It should be noted that between re-route events, the network observed floor delay is considered to be fixed and thus, the FPP calculation procedures described in clause I.5.1 apply. + +###### **I.5.1.3.3 Determination of re-route event** + +The methods of determination of re-route event occurrences and related observed floor delay change are for further study. These methods are applicable to network analysis equipment and are not applicable to packet slave clocks. + +Generally speaking such methods could be classified into the following: + +- Based on information sent to the probe from the network management entity alerting that a reroute event took place. Such an alert would derive the probe to search for a new observed floor delay (OFD) based on one of the methods described in clause I.5.1. + +- Based on information sent to the probe from an active network OAM mechanism (whether that is part of PTP or relying on external OAM techniques) alerting that a reroute event took place. As in the previous case, such an alert would derive the probe to search for a new OFD based on one of the methods described in clause I.5.1. +- In the absence of the above methods, the use of an automatic OFD classification estimation method is an efficient way to allow for meaningful OFD computation in network with re-route events. + +A mixture of all or part of these approaches could also be beneficial. + +###### **I.5.1.3.4 Determination of re-route events using an OFD estimation method** + +This section describes an observed floor delay estimation method that automates the location of re-routes events by post-processing packet capture data and compute the in-between observed floor delay. This approach is suggested for use when an existing network management entity is not available to make such a determination. + +Being an estimation for re-route detection, this method may not fully conform to the requirements in clause I.5.1.3.2 that requires the observed floor delay to be re-calculated every re-route event. Specifically, this approach may be subject to both false alarms (incorrectly determining that a re-route event occurred when one did not actually take place) and mis-detections (failing to notice a re-route event occurrence). Since an OFD section determination is made only after a stable minimum floor is observed for a long enough time (the *S* parameter), false alarms should be quite rare. Mis-detections of small magnitude re-route events may still occur from time to time. A typical reason for mis-detecting a re-route may be that that the magnitude was too small compared with the data set noise; in such a case, such a failure may not have a material impact on the network analysis when the target network or synchronization performance is very relaxed. + +An observed floor delay estimation method for finding the observed floor delay between re-route occurrences may comprise of the following recursive steps: + +- 1) A full packet capture is performed, with minimum capture duration, creating the entire packet section. The capture must be based on an accurate time reference (e.g., GPS). +- 2) The packet section is analysed to find the overall floor delay, and is then divided into sliding or jumping windows. +- 3) The floor delay of the first window of the packet section must be close to the overall floor delay. +- 4) The floor delay of the last window of the packet section must be close to the overall floor delay. +- 5) There must not be another packet sub-section between the first and last window of the original packet section that itself: + - a) meets above criteria 2, 3 & 4 and + - b) where the overall floor delay of this sub-set packet sequence is not close to the original overall floor delay. +- 6) If such a sub-section is not detected, the original packet section comprises a single OFD section and its delay minimum is the OFD. +- 7) On the other hand, if such sub-section(s) (one or more) are detected, the entire original section is then divided down to its sub-sections and the entire process [1) to 7)] is then repeated for every subsection independently. + +This procedure is based on the following mathematical characterization of a legitimate OFD section: + +A group of observation windows that share the same observed floor delay property can be defined as the *largest* group of $N$ consecutive windows (jumping or overlapping to some degree) $W^{(1)}$ to $W^{(N)}$ that meet the following requirements: + +- The overall group duration is not shorter than $S$ s AND not longer than 86 400 s. +- Given $j = \underset{k}{\operatorname{argmin}}(d_{\min}^{(k)})$ , $1 \leq k \leq N$ , ( $W^{(j)}$ is the window, within the group, having the lowest delay) the following conditions must be met: + +$$\begin{aligned} |d_{\min}^{(1)} - d_{\min}^{(j)}| &\leq \varepsilon \\ |d_{\min}^{(N)} - d_{\min}^{(j)}| &\leq \varepsilon \end{aligned} \quad (\text{I-68})$$ + +Where $\varepsilon$ , in seconds, is the degree of tightness in classifying groups of distinct OFDs that we require. + +- There is no subgroup of $M$ consecutive windows $W^{(l)}$ to $W^{(l+M-1)}$ contained within $W^{(1)}$ to $W^{(N)}$ ( $1 < l < l + M - 1 < N$ ) that meets the following requirement: + - The overall subgroup duration is not shorter than $S$ s AND not longer than 86 400 s. + - Given $i = \underset{k}{\operatorname{argmin}}(d_{\min}^{(k)})$ , $l \leq k \leq l + M - 1$ , ( $W^{(i)}$ is the window, within the subgroup, having the lowest delay) the following conditions are met: + +$$\begin{aligned} |d_{\min}^{(l)} - d_{\min}^{(i)}| &\leq \varepsilon \\ |d_{\min}^{(l+M-1)} - d_{\min}^{(i)}| &\leq \varepsilon \\ |d_{\min}^{(j)} - d_{\min}^{(i)}| &> \delta \end{aligned} \quad (\text{I-69})$$ + +$W^{(k)}$ , $1 \leq k \leq N$ can be either non-overlapping or overlapping (to whatever degree) 200 s windows. + +The determination of the parameters $S$ , $\varepsilon$ , $\delta$ is for further study. + +#### 1.5.2 Use of floor delay packet population PDV metrics for two-way protocol flows + +The floor delay packet population PDV metrics may be used with two-way protocol flows. + +One usage, following Equation I-59, would establish a unique minimum path delay, $d_{\min}$ , for each direction of a two-way protocol flow, resulting in the forward path delay, $d_{\min\text{-fwd}}$ and the reverse path delay, $d_{\min\text{-rev}}$ . These minimum path delays may then be processed to compute the path delay asymmetry, based on minimum path delay: + +$$\text{path\_delay\_asymmetry} = (d_{\min\text{-rev}} - d_{\min\text{-fwd}})/2 \quad (\text{I-70})$$ + +These minimum path delays, $d_{\min\text{-fwd}}$ and $d_{\min\text{-rev}}$ may also be used to compute FPP according to Equation I-63 for the forward path, $\text{FPP}_{\text{fwd}}(n, W, \delta)$ , and the reverse path, $\text{FPP}_{\text{rev}}(n, W, \delta)$ . The $\text{FPP}_{\text{fwd}}(n, W, \delta)$ and $\text{FPP}_{\text{rev}}(n, W, \delta)$ may then be applied against defined performance limits. + +#### 1.5.3 Exceptional events and impact on packet network limit + +Exceptional events and other severe, unexpected network phenomena may occur from time to time in a packet network. These events may reduce the number of packets that arrive within the defined cluster range, thereby causing a temporary failure of the packet network to comply with the defined FPP network limit. To accommodate such exceptional events, a small number of non-overlapping failing windows ( $X$ ) may be allowed over a measurement period ( $Y$ ). To ensure that such exceptional events have limited time duration, the maximum number of consecutive non-overlapping failing windows may also be specified ( $Z$ ). The values of $X$ , $Y$ and $Z$ are defined in the relevant recommendations. + +## Bibliography + +- [b-ITU-T G.8261.1] Recommendation ITU-T G.8261.1/Y.1361.1 (2012), *Packet delay variation network limits applicable to packet-based methods (Frequency synchronization)*. +- [b-ITU-T G.8263] Recommendation ITU-T G.8263/Y.1363 (2017), *Timing characteristics of packet-based equipment clocks*. +- [b-GR-1244-CORE] GR-1244-CORE (2009), *Clocks for the synchronized network: Common generic criteria*, Telcordia Technologies Generic Requirements, (Issue 4, October 2009). + + + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, 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protocol aspects – Transport + +--- + +**Packet delay variation network limits applicable +to packet-based methods (Frequency +synchronization)** + +Recommendation ITU-T G.826.1/Y.1361.1 + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| Ethernet over Transport aspects | G.8000–G.8099 | +| MPLS over Transport aspects | G.8100–G.8199 | +| Quality and availability targets | G.8200–G.8299 | +| Service Management | G.8600–G.8699 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## Recommendation ITU-T G.826.1/Y.1361.1 + +# Packet delay variation network limits applicable to packet-based methods (Frequency synchronization) + +## Summary + +Recommendation ITU-T G.826.1/Y.1361.1 depicts synchronization aspects in packet networks. In particular, it specifies the hypothetical reference model and the PDV network limits applicable when frequency synchronization is carried via packets and is recovered according to an adaptive clock recovery method as defined in Recommendations ITU-T G.826.1 and ITU-T G.826.0. It specifies the minimum equipment tolerance to packet delay variation in terms of the metrics defined in Recommendation ITU-T G.826.0 at the boundary of these packet networks. + +## History + +| Edition | Recommendation | Approval | Study Group | +|---------|------------------------|------------|-------------| +| 1.0 | ITU-T G.826.1/Y.1361.1 | 2012-02-13 | 15 | + +## Keywords + +PDV, synchronization. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2012 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|------------------------------------------------------------------|------| +| 1 Scope ..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 2 | +| 4 Abbreviations and acronyms ..... | 2 | +| 5 Conventions ..... | 3 | +| 6 General..... | 3 | +| 7 Network reference model ..... | 3 | +| 7.1 Hypothetical reference models ..... | 3 | +| 7.2 Reference points for network limits in packet networks ..... | 6 | +| 8 PDV network limit..... | 8 | +| Bibliography..... | 10 | + + + +## Recommendation ITU-T G.826.1/Y.1361.1 + +# Packet delay variation network limits applicable to packet-based methods (Frequency synchronization) + +# 1 Scope + +This Recommendation relays synchronization aspects in packet networks. In particular, it specifies the hypothetical reference model (HRM) and the PDV network limits applicable when frequency synchronization is carried via packets and is recovered according to the adaptive clock recovery method as defined in Recommendations ITU-T G.826.1 and ITU-T G.826.0. It specifies the minimum equipment tolerance to packet delay variation in terms of the metrics defined in Recommendation ITU-T G.826.0 at the boundary of these packet networks. + +Two main applications are addressed in this Recommendation: the distribution of a synchronization network clock signal via a packet based method (e.g., using PTP or NTP packets and using an adaptive approach), and the distribution of a service clock signal over a packet network according to an adaptive clock recovery method (e.g., clock recovery of a circuit emulation service (CES) using an adaptive method), however the details on the CES network limits are for further study. + +Both one-way and two-way methods are considered. + +The packet networks that are in the scope of this Recommendation are currently limited to the following scenarios: + +- Ethernet ([IEEE 802.3], [IEEE 802.1D], [IEEE 802.1 ad], [IEEE 802.1Q], [IEEE 802.1Qay]) +- MPLS ([IETF RFC 3031], [ITU-T G.8110]) +- IP ([IETF RFC 791] and [IETF RFC 2460]) + +The physical layer that is relevant to this specification is the Ethernet media types as defined in IEEE Standard 802.3™–2008. Other physical layers can be relevant and may be addressed in future versions of this Recommendation. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.803] Recommendation ITU-T G.803 (2000), *Architecture of transport networks based on the synchronous digital hierarchy (SDH)*. +- [ITU-T G.810] Recommendation ITU-T G.810 (1996), *Definitions and terminology for synchronization networks*. +- [ITU-T G.823] Recommendation ITU-T G.823 (2000), *The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy*. +- [ITU-T G.824] Recommendation ITU-T G.824 (2000), *The control of jitter and wander within digital networks which are based on the 1544 kbit/s hierarchy*. + +- [ITU-T G.8110] Recommendation ITU-T G.8110/Y.1370 (2005), *MPLS layer network architecture*. +- [ITU-T G.8260] Recommendation ITU-T G.8260 (2012), *Definitions and terminology for synchronization in packet networks*. +- [ITU-T G.8261] Recommendation ITU-T G.8261/Y.1361 (2008), *Timing and synchronization aspects in packet networks*. +- [ITU-T G.8263] Recommendation ITU-T G.8263/Y.1363 (2012), *Timing characteristics of packet-based equipment clocks*. +- [ITU-T G.8265] Recommendation ITU-T G.8265/Y.1365 (2010), *Architecture and requirements for packet-based frequency delivery*. +- [ITU-T G.8265.1] Recommendation ITU-T G.8265.1/Y.1365.1 (2010), *Precision time protocol telecom profile for frequency synchronization*. +- [ITU-T O.172] Recommendation ITU-T O.172 (2005), *Jitter and wander measuring equipment for digital systems which are based on the synchronous digital hierarchy (SDH)*. +- [IEEE 802] IEEE 802-2001, *IEEE standard for local and metropolitan area networks: Overview and architecture*. +<> +- [IEEE 802.1ad] IEEE 802.1adTM-2005, *IEEE Standard for local and metropolitan area networks: Virtual bridged local area networks – Amendment 4: Provider Bridges*. <> +- [IEEE 802.1D] IEEE 802.1DTM-2004, *IEEE Standard for local and metropolitan area networks: Media Access Control (MAC) Bridges*. +<> +- [IEEE 802.1Q] IEEE 802.1QTM-2005, *IEEE Standard for local and metropolitan area networks: Virtual bridged local area networks*. +<> +- [IEEE 802.3] IEEE 802.3-2008, *Part 3: Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specifications*. +<> +- [IETF RFC 791] IETF RFC 791 (1981), *Internet Protocol*. +<> +- [IETF RFC 2460] IETF RFC 2460 (1998), *Internet Protocol, Version 6 (IPv6) Specification*. +<> +- [IETF RFC 3031] IETF RFC 3031 (2001), *Multiprotocol Label Switching Architecture*. +<> + +# 3 Definitions + +The terms and definitions used in this Recommendation are found in [ITU-T G.810] and [ITU-T G.8260]. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|-----|---------------------------| +| CES | Circuit Emulation Service | +| DSL | Digital Subscriber Line | + +| | | +|---------|----------------------------------------------| +| DSLAM | Digital Subscriber Line Access Multiplexer | +| EEC | Ethernet Equipment Clock | +| HRM | Hypothetical Reference Model | +| MW | Microwave | +| OLT | Optical Line Terminal | +| ONU | Optical Network Unit | +| OTN | Optical Transport Network | +| PDV | Packet Delay Variation | +| PEC-M | Packet-based Equipment Clock Master | +| PEC-S-F | Packet based Equipment Clock Slave Frequency | +| PNT-F | Packet Network Timing Function | +| PON | Passive Optical Network | +| PRC | Primary Reference Clock | +| PTP | Precision Time Protocol | +| SEC | SDH Equipment Clock | +| SSU | Synchronization Supply Unit | + +# 5 Conventions + +None. + +# 6 General + +The use of packet-based methods as described in [ITU-T G.8261] to deliver reference timing signals for the purpose of frequency synchronization, requires the control of the PDV generated in the network in order to meet acceptable performance requirements when using a packet clock with characteristics as specified in [ITU-T G.8263]. + +This Recommendation defines the applicable network limits at all relevant points in a network. + +The network reference models and the related target performance requirements that are considered relevant for this application are described in clause 7. The related PDV limits are specified in clause 8. + +# 7 Network reference model + +## 7.1 Hypothetical reference models + +This clause provides hypothetical reference models which are assumed to correspond to the worst-case models for most of the mobile backhaul networks. + +NOTE – The hypothetical reference models defined in this clause are assumed to be composed with network equipment generating a controlled amount of PDV, compatible with the network limits defined in clause 8. It is known that some network equipment may generate excessive PDV, leading potentially to exceed these PDV network limits. What constitutes a controlled amount of PDV, how to determine if particular network equipment are suitable for being considered in these hypothetical reference models, or in a reduced hypothetical reference model, as well as, how to evaluate the level of PDV generated by a network equipment, is for further study. + +### 7.1.1 HRM-1: network using only 1 Gbit/s and 10 Gbit/s connections + +The HRM-1 is shown in Figure 1 below; it is composed of a 1 Gbit/s link to connect the packet master clock to the first node, $3 \times 10$ Gbit/s fibre optical links and $7 \times 1$ Gbit/s fibre optical links. It is assumed to correspond to the worst case model for most of the mobile backhaul networks using only optical fibre connections. + +The packet delay variation network limits for the HRM-1 are specified in clause 8 of this Recommendation. + +![Diagram of HRM-1 network topology showing a packet master clock connected to a packet network with 10 nodes (N=10) and a packet slave clock. The network consists of 1 Gbit/s and 10 Gbit/s fibre optical links.](e6df2733626a85205c1db682e6259c46_img.jpg) + +The diagram illustrates the HRM-1 network topology. On the left, a 'Packet master clock' is connected to a 'Packet network' via a 1 Gbit/s fibre optical link (blue line). The packet network contains 10 packet nodes (yellow circles), labeled 'N = 10'. The first node is connected to the master clock. The links between nodes are a mix of 10 Gbit/s fibre optical links (green lines) and 1 Gbit/s fibre optical links (blue lines). The last node is connected to a 'Packet slave clock' on the right via a 1 Gbit/s fibre optical link (blue line). A legend below the diagram identifies the symbols: a yellow circle for a 'Packet node (e.g., ethernet switch, IP router, MPLS router)', a green line for a '10 Gbit/s fibre optical link', and a blue line for a '1 Gbit/s fibre optical link'. The text 'G.8261.1-Y1361.1(12)\_F01' is in the bottom right corner. + +Diagram of HRM-1 network topology showing a packet master clock connected to a packet network with 10 nodes (N=10) and a packet slave clock. The network consists of 1 Gbit/s and 10 Gbit/s fibre optical links. + +**Figure 1 – HRM-1 for packet delay variation network limits** + +NOTE 1 – The link between the packet master clock and the first packet node may be 100 Mbit/s instead of 1 Gbit/s. + +NOTE 2 – The link between the last packet node and the packet slave clock may be 100 Mbit/s instead of 1 Gbit/s in case it is only carrying PTPv2 messages and no data traffic. + +NOTE 3 – The 1 Gbit/s links can be replaced by 10 Gbit/s links in a real deployment, but not the opposite. + +NOTE 4 – The distribution of the links connecting the packet nodes has no importance (e.g., the 10 Gbit/s links may not always be at the beginning of the packet network); in general however, the 10 Gbit/s links are located in the core network. + +NOTE 5 – Some of the links connecting the packet nodes may be carried over an OTN network, assuming that the PDV generated by these transmission techniques is negligible compared to the PDV generated by the packet nodes of the HRM. + +Some of the links connecting the packet nodes may also be carried over an SDH network, this is for further study. + +NOTE 6 – It is assumed that no frames larger than 2000 bytes are carried over the links of the packet network carrying the PTPv2 messages. + +NOTE 7 – The PTPv2 messages are assumed to be carried with the highest priority, and placed in a strict priority queue in the packet nodes; the other flows using this queue are for further study (it might be assumed that this queue either only contains PTPv2 messages, or that the other data traffic packets going also in this queue are small packets, and that the amount of data in the queue is much smaller than the output interface capacity). + +NOTE 8 – The traffic models carried over this network are for further study; they may include both mobile and fixed data traffic. + +### 7.1.2 HRM-2: network using specific access technologies + +In many mobile backhaul networks, a base station is connected to the network using specific access technologies, such as digital subscriber line (DSL), passive optical network (PON), or microwave links (MW). + +The HRM-2 is shown in Figure 2 below; it is composed of a reduced HRM-1 (1 Gbit/s link to connect the packet master clock to the first node, $1 \times 10$ Gbit/s fibre optical link and $4 \times 1$ Gbit/s fibre optical links), followed by either a DSL link (HRM-2a), or a PON link (HRM-2b), or a few MW links (HRM-2c), followed by a 1 Gbit/s link to connect the access portion to the packet slave clock. It is assumed to correspond to the worst case model for most of the mobile backhaul networks using specific access technologies. + +The packet delay variation network limits for the HRM-2 are specified in clause 8 of this Recommendation. + +![Diagram of HRM-2 network architecture showing packet master clock, packet network with 5 nodes, and three access paths (HRM-2a: DSL, HRM-2b: PON, HRM-2c: Microwave) leading to a packet slave clock.](d26959f4514c26ca19c3d6f00da85956_img.jpg) + +The diagram illustrates the HRM-2 network architecture. On the left, a 'Packet master clock' box is connected to a 'Packet network' containing $N = 5$ packet nodes (represented by yellow circles). The first node is connected to the master clock via a 1 Gbit/s fibre optical link (blue line). The nodes are interconnected by a mix of 10 Gbit/s (green line) and 1 Gbit/s (blue line) fibre optical links. The last node in the packet network connects to three alternative access technology paths: + +- HRM-2a (Blue box):** A DSL link consisting of a DSLAM and a DSL modem. +- HRM-2b (Red box):** A PON link consisting of an OLT and an ONU. +- HRM-2c (Green box):** Multiple microwave links (represented by three pairs of antenna icons). + +All three access paths converge to a single 'Packet slave clock' box on the right, connected by a 1 Gbit/s fibre optical link (blue line). + +Legend: + +- Yellow circle: Packet node (e.g., Ethernet switch, IP router, MPLS router) +- Green line: 10 Gbit/s fibre optical link +- Blue line: 1 Gbit/s fibre optical link +- Antenna icon: Microwave link + +G.8261.1-Y.1361.1(12)\_F02 + +Diagram of HRM-2 network architecture showing packet master clock, packet network with 5 nodes, and three access paths (HRM-2a: DSL, HRM-2b: PON, HRM-2c: Microwave) leading to a packet slave clock. + +**Figure 2 – HRM-2 for packet delay variation network limits** + +NOTE 1 – The link between the packet master clock and the first packet node may be 100 Mbit/s instead of 1 Gbit/s. + +NOTE 2 – The link between the last access node and the packet slave clock may be 100 Mbit/s instead of 1 Gbit/s in case it is only carrying PTPv2 messages and no data traffic. + +NOTE 3 – The 1 Gbit/s links can be replaced by 10 Gbit/s links in a real deployment, but not the opposite. + +NOTE 4 – The distribution of the links connecting the packet nodes has no importance (e.g., the 10 Gbit/s link may not always be at the beginning of the packet network); in general however, the 10 Gbit/s links are located in the core network. + +NOTE 5 – Some of the links connecting the packet nodes may be carried over an OTN network, assuming that the PDV generated by these transmission techniques is negligible compared to the PDV generated by the packet nodes of the HRM. + +Some of the links connecting the packet nodes may also be carried over an SDH network, this is for further study. + +NOTE 6 – It is assumed that no frames larger than 2000 bytes are carried over the links of the packet network carrying the PTPv2 messages. + +NOTE 7 – The PTPv2 messages are assumed to be carried with the highest priority, and placed in a strict priority queue in the packet nodes and in the access equipment; the other flows using this queue are for further study (it might be assumed that this queue either only contains PTPv2 messages, or that the other data traffic packets going also in this queue are small packets, and that the amount of data in the queue is much smaller than the output interface capacity). + +NOTE 8 – The traffic models carried over this network are for further study; they may include both mobile and fixed data traffic. + +NOTE 9 – The DSL technologies in the HRM-2a to be considered are SHDSL and VDSL2; the PDV noise generated by these technologies is for further study, and may differ significantly from other technologies. + +NOTE 10 – The HRM-2c may involve adaptive microwave equipment, adapting their bandwidth to the weather conditions. + +NOTE 11 – The number of microwave hops in the HRM-2c is for further study. + +NOTE 12 – The bandwidth of the links connecting the DSLAM to the modem in the HRM-2a, the OLT to the ONU in the HRM-2b, and two microwave sites in the HRM-2c is for further study. + +NOTE 13 – The traffic carried over the microwave links in the HRM-2c is for further study (microwave links may aggregate traffic coming from other sites than the packet slave clock site). + +## 7.2 Reference points for network limits in packet networks + +Figure 3 shows all the network limits reference points applicable to a generalization of the PNT deployment case 2 as shown in Figure 18 of [ITU-T G.8261] (e.g., between the PRC and the packet master clock, the timing reference signal is distributed via a physical layer based synchronization network). + +The use case described by PNT deployment case 1 as shown in Figure 17 of [ITU-T G.8261] where the PEC-S-F provides an external synchronization interface to the connected synchronization network is for further study. + +Details on the CES network limits are also for further study. + +![Diagram illustrating reference points for network limits in packet networks. A PRC (Physical Reference Clock) is connected to a 'Physical layer based synchronization network'. This network connects to a 'Packet master clock' block containing a 'PNT-F' (Packet Network Timing Function) and a 'PEC-M' (Packet Equipment Master). The 'Packet master clock' is connected to a 'Packet network' which carries 'Timing packets'. Reference point 'A' is at the input of the 'Packet master clock' (PRC, EEC, SSU or SEC network limits). Reference point 'B' is at the output of the 'Packet master clock' (PEC-M output packet network limits). Reference point 'C' is at the input of the 'Packet network' (PEC-S-F input packet network limits). The 'Packet network' connects to a 'PNT-F' block containing a 'PEC-S-F' (Packet Equipment Slave Function). Reference point 'C1' is at the input of the 'PNT-F' (PEC-S-F input packet network limits). Reference point 'C2' is at the output of the 'PNT-F' (PEC-S-F output packet network limits). The 'PNT-F' block is connected to an 'End application clock'. Reference point 'E' is at the output of the 'PNT-F' (End application requirements, e.g., frequency accuracy). Reference point 'D' is at the output of the 'PNT-F' (PEC-S-F output network limits, deployment case 2).](63e0c22852c26699d0bd095a2d796bab_img.jpg) + +Diagram illustrating reference points for network limits in packet networks. A PRC (Physical Reference Clock) is connected to a 'Physical layer based synchronization network'. This network connects to a 'Packet master clock' block containing a 'PNT-F' (Packet Network Timing Function) and a 'PEC-M' (Packet Equipment Master). The 'Packet master clock' is connected to a 'Packet network' which carries 'Timing packets'. Reference point 'A' is at the input of the 'Packet master clock' (PRC, EEC, SSU or SEC network limits). Reference point 'B' is at the output of the 'Packet master clock' (PEC-M output packet network limits). Reference point 'C' is at the input of the 'Packet network' (PEC-S-F input packet network limits). The 'Packet network' connects to a 'PNT-F' block containing a 'PEC-S-F' (Packet Equipment Slave Function). Reference point 'C1' is at the input of the 'PNT-F' (PEC-S-F input packet network limits). Reference point 'C2' is at the output of the 'PNT-F' (PEC-S-F output packet network limits). The 'PNT-F' block is connected to an 'End application clock'. Reference point 'E' is at the output of the 'PNT-F' (End application requirements, e.g., frequency accuracy). Reference point 'D' is at the output of the 'PNT-F' (PEC-S-F output network limits, deployment case 2). + +G.8261.1-Y.1361.1(12)\_F03 + +Figure 3 – Reference points for network limits + +### 7.2.1 Packet master clock (PEC-M) network limits + +This clause addresses the case of the PEC-M network limits. + +In this case the network limits are applicable at the input of the PEC-M (interface A). Depending on the details of the synchronization network connected to the PEC-M, these are: + +- EEC network limits (in case of a synchronous Ethernet), see clause 9.2.1 of [ITU-T G.8261] +- SEC/SSU network limits (in case of an SDH based synchronization network), see clauses 6.2.2 and 6.2.3 of [ITU-T G.823] +- the PRC interface limits (in case a PRC is directly connected to the PEC), see clause 6.2.1 of [ITU-T G.823]. + +The most general case that is considered in this Recommendation is when the reference timing signal is distributed to the PEC-M via a full synchronization network reference chain as described in Figure 8-5 of [ITU-T G.803] (note that the PEC-M clock itself must be considered as part of the chain), see [ITU-T G.803]. Therefore the EEC or SEC network limits as defined in clauses 9.2.1 of [ITU-T G.8261] and 6.2.3 of [ITU-T G.823], respectively, are considered. + +The packet network limits at the output of the PEC-M (reference point B in Figure 3) are defined on the packet timing signal in terms of the relevant metric. This is for further study. + +NOTE 1 – The PDV at the output of the packet master clock is expected to be relatively low, that means that the metric to be used in this case does not need to include particular packet pre-processing (e.g., packet selection). + +NOTE 2 – The PEC-M can also be modelled by the PEC included in the PNT-F (see Figure B.5 of [ITU-T G.8261]; Note 1) where the PNT-F translates the timing carrier from the physical layer to the packet layer. + +### 7.2.2 PEC-S-F network limits + +This section addresses the case of the PEC-S-F network limits. + +With reference to Figure 3, over the C1 connection, the PEC-S-F provides an external synchronization interface to the end application (i.e., PNT deployment case 2 shown in Figure 18 of [ITU-T G.8261]). + +In these cases, the network limits are specified by [ITU-T G.8261] (clause 9.2.2) on the recovered reference timing signal. + +In particular as described in clause 9.2.2 and Appendix IV of [ITU-T G.8261], the following three main cases can be identified for the network limits applicable at interface D: + +- Case 1: EEC network limits (see clause 9.2.2.1 of [ITU-T G.8261]). This case is for further study. +- Case 2: network limits for traffic interfaces (see clause 5 of [ITU-T G.823] or clause 5 of [ITU-T G.824]). +- Case 3: limits on the short term are set by [ITU-T G.823] and [ITU-T G.824] clause 5 and on the long term by an $n$ ppb line (where $n$ shall be below the applicable requirement on the radio interface). + +With respect to case 3, and assuming $n = 16$ ppb, the output wander network limit applicable at reference point D is provided by Table 1 and Figure 4. + +NOTE – The equivalent mask in case of ITU-T G.824 is for further study. + +**Table 1 – Output wander network limit for case 3 based on [ITU-T G.823]** + +| Observation interval
$\tau$ (s) | MTIE requirement
( $\mu\text{s}$ ) | +|------------------------------------|---------------------------------------| +| $0.05 < \tau \leq 0.2$ | $46 \tau$ | +| $0.2 < \tau \leq 32$ | 9 | +| $32 < \tau \leq 64$ | $0.28 \tau$ | +| $64 < \tau \leq 1\,125$ | 18 | +| $\tau > 1\,125$ | $0.016 \tau$ | + +![Graph of MTIE requirement vs Observation interval tau (s). The y-axis is MTIE in microseconds, with markers at 9 and 18. The x-axis is Observation interval tau in seconds, with markers at 0.05, 0.2, 32, 64, and 1125. The graph shows a piecewise linear function: from 0.05 to 0.2 s, it rises from 4.6 to 9 microseconds; from 0.2 to 32 s, it is constant at 9 microseconds; from 32 to 64 s, it rises from 9 to 18 microseconds; from 64 to 1125 s, it is constant at 18 microseconds; for tau > 1125 s, it rises with a slope of 16 ppb.](c2b98986bdf45e15707f6b2bd7ade2bd_img.jpg) + +G.8261.1-Y.1361.1(12)\_F04 + +Graph of MTIE requirement vs Observation interval tau (s). The y-axis is MTIE in microseconds, with markers at 9 and 18. The x-axis is Observation interval tau in seconds, with markers at 0.05, 0.2, 32, 64, and 1125. The graph shows a piecewise linear function: from 0.05 to 0.2 s, it rises from 4.6 to 9 microseconds; from 0.2 to 32 s, it is constant at 9 microseconds; from 32 to 64 s, it rises from 9 to 18 microseconds; from 64 to 1125 s, it is constant at 18 microseconds; for tau > 1125 s, it rises with a slope of 16 ppb. + +**Figure 4 – Output wander network limit for case 3 based on [ITU-T G.823]** + +The wander measurement requirements (e.g., sampling time and measurement interval) for the MTIE parameters, the 10 Hz wander measurement filter characteristic and the functional description for measuring output wander are described in [ITU-T O.172]. Instrumentation in accordance with [ITU-T O.172] is appropriate for measurement of wander parameters. + +The packet network limits are expressed in terms of the relevant PDV based metric at interface C (in fact in this case the timing recovery is based on the adaptive method) as defined in clause 8 of this Recommendation. + +The connection over C2 in Figure 3 describes the case when the PNT-F and the related PEC-S-F are integrated in the end application. + +In this case, the packet network interface (e.g., Ethernet interface) is directly connected to the end application (e.g., base station with Ethernet interface) and the network limits can only be expressed at the interface C. In fact, the PNT-F output (the equivalent of the interface D of the connection C1 in Figure 3) is not generally accessible for measurement for the connection over C2. + +The network limits at the output of the end equipment depends on the end application requirement (reference point E). This is for further study. + +# 8 PDV network limit + +The packet delay variation network limit given in this clause represents the maximum permissible levels of packet delay variation at the interface C shown in Figure 3. + +The limits given in this section shall be met for all operating conditions. In general, these network limits are compatible with the minimum tolerance to packet delay variation that all PEC-S-F equipment are required to provide. + +NOTE – The PEC embedded within the end application, as shown after the connection C2 in Figure 3 is for further study in [ITU-T G.8263]. + +Note that the PDV network limit specified in this clause assumes that the network equipment composing the hypothetical reference model generates a controlled amount of PDV. It is known that some network equipment may generate excessive PDV and potentially exceed these PDV network limits. What constitutes a controlled amount of PDV, how to determine if network equipment is suitable for being considered in the hypothetical reference models defined in this Recommendation, or in a reduced hypothetical reference model, as well as how to evaluate the level of PDV generated by network equipment, is for further study. + +The packet delay variation network limit at point C of Figure 3 for the HRM-1 shown in Figure 1 is defined as follows: + +With window interval $W = 200$ s and fixed cluster range $\delta = 150$ $\mu\text{s}$ starting at the floor delay, the network transfer characteristic quantifying the proportion of delivered packets that meet the delay criterion should satisfy + +$$\text{FPP}(n, W, \delta) \geq 1\%$$ + +That is, the floor packet percentage must exceed 1%. + +This means that for any window interval of 200 s at least 1% of transmitted timing packets will be received within a fixed cluster, starting at the observed floor delay, and having a range of 150 $\mu\text{s}$ . + +NOTE 1– The selection method (using sliding, overlapping or jumping windows) applicable to the network limit specified in this Recommendation is for further study. + +NOTE 2 – The number of packets received within the fixed cluster range depends on the nominal packet rate. For example, with a nominal packet rate of one packet per second, $\text{FPP} > 1\%$ implies that two or more packets will be received within the fixed cluster range in each 200 s interval. The number of packets in a selection window is important for considering the tolerance limit of a slave clock. + +For more details on the measurement methodology refer to clause I.5 of [ITU-T G.8260]. + +This network limit can be applied independently on the forward or the reverse direction of a packet timing flow. Consideration of the combined effect of both directions is for further study. + +NOTE 3 – This network limit only applies for HRM-1. Many HRM-1 networks may exhibit much lower packet delay variation than indicated by this limit, and therefore this limit is considered very conservative. It does not describe the distribution of packet delays within the cluster range. + +Other PDV metrics emulating the behaviour of a packet slave clock are currently under study and might be used in the future for specifying the PDV network limits in a less conservative way. Some information can be found in clause I.4 of [ITU-T G.8260]. + +The packet delay variation network limits for the HRM-2 are for further study. For HRM-2, different limits may apply, and may use different metrics. + +# Bibliography + +[b-IEEE 802.1Qay] IEEE 802.1QayTM-2009, *IEEE Standard for Local and metropolitan area networks – Virtual Bridged Local Area Networks Amendment 10: Provider Backbone Bridge Traffic Engineering.* + +# ITU-T Y-SERIES RECOMMENDATIONS + +## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS + +## GLOBAL INFORMATION INFRASTRUCTURE + +| | | +|-------------------------------------------|-------------| +| General | Y.100–Y.199 | +| Services, applications and middleware | Y.200–Y.299 | +| Network aspects | Y.300–Y.399 | +| Interfaces and protocols | Y.400–Y.499 | +| Numbering, addressing and naming | Y.500–Y.599 | +| Operation, administration and maintenance | Y.600–Y.699 | +| Security | Y.700–Y.799 | +| Performances | Y.800–Y.899 | + +## INTERNET PROTOCOL ASPECTS + +| | | +|--------------------------------------------------------------------|----------------------| +| General | Y.1000–Y.1099 | +| Services and applications | Y.1100–Y.1199 | +| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 | +| Transport | Y.1300–Y.1399 | +| Interworking | Y.1400–Y.1499 | +| Quality of service and network performance | Y.1500–Y.1599 | +| Signalling | Y.1600–Y.1699 | +| Operation, administration and maintenance | Y.1700–Y.1799 | +| Charging | Y.1800–Y.1899 | +| IPTV over NGN | Y.1900–Y.1999 | + +## NEXT GENERATION NETWORKS + +| | | +|-------------------------------------------------------------------|---------------| +| Frameworks and functional architecture models | Y.2000–Y.2099 | +| Quality of Service and performance | Y.2100–Y.2199 | +| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 | +| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 | +| Numbering, naming and addressing | Y.2300–Y.2399 | +| Network management | Y.2400–Y.2499 | +| Network control architectures and protocols | Y.2500–Y.2599 | +| Smart ubiquitous networks | Y.2600–Y.2699 | +| Security | Y.2700–Y.2799 | +| Generalized mobility | Y.2800–Y.2899 | +| Carrier grade open environment | Y.2900–Y.2999 | +| Future networks | Y.3000–Y.3099 | + +For further details, please refer to the list of ITU-T Recommendations. + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|--------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Terminals and subjective and objective assessment methods | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects and next-generation networks | +| Series Z | Languages and general software aspects for 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+Packet over Transport aspects – Quality and availability +targets + +SERIES Y: GLOBAL INFORMATION +INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS +AND NEXT-GENERATION NETWORKS + +Internet protocol aspects – Transport + +# --- **Architecture and requirements for packet-based frequency delivery** + +Recommendation ITU-T G.8265/Y.1365 + +![ITU logo](d3294dc879b451b369c0b06f42e9b39f_img.jpg) + +The logo of the International Telecommunication Union (ITU) features a stylized globe with a red lightning bolt striking through it, symbolizing global connectivity and telecommunications. To the right of the globe, the text "International Telecommunication Union" is written in a blue, sans-serif font. + +ITU logo + +## ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| Ethernet over Transport aspects | G.8000–G.8099 | +| MPLS over Transport aspects | G.8100–G.8199 | +| Quality and availability targets | G.8200–G.8299 | +| Service Management | G.8600–G.8699 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## **Recommendation ITU-T G.8265/Y.1365** + +# **Architecture and requirements for packet-based frequency delivery** + +# **Summary** + +Recommendation ITU-T G.8265/Y.1365 describes the architecture and requirements for packet-based frequency distribution in telecom networks. Examples of packet-based frequency distribution include the network time protocol (NTP) and IEEE-1588-2008, briefly described here. Details necessary to utilize IEEE-1588-2008 in a manner consistent with the architecture are defined in other Recommendations. + +## **History** + +| Edition | Recommendation | Approval | Study Group | +|---------|---------------------|------------|-------------| +| 1.0 | ITU-T G.8265/Y.1365 | 2010-10-07 | 15 | + +# FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +# INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2011 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +# Table of Contents + +| | Page | +|--------------------------------------------------------------------|------| +| 1 Scope ..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 1 | +| 3.1 Terms defined elsewhere ..... | 1 | +| 4 Abbreviations and acronyms ..... | 2 | +| 5 Conventions ..... | 2 | +| 6 General introduction to packet-based frequency distribution..... | 2 | +| 6.1 Requirements for packet timing ..... | 3 | +| 7 Architecture of packet-based frequency distribution..... | 3 | +| 7.1 Packet-based frequency distribution..... | 3 | +| 7.2 Timing protection ..... | 4 | +| 7.3 Packet network partitioning..... | 7 | +| 7.4 Mixed technologies ..... | 8 | +| 8 Packet-based protocols for frequency distribution ..... | 8 | +| 8.1 Packet-based protocols ..... | 8 | +| 8.2 PTP [IEEE 1588] general description ..... | 8 | +| 8.3 NTP – General description ..... | 9 | +| 9 Security aspects ..... | 9 | +| Appendix I – Bibliography ..... | 11 | + + + +## Recommendation ITU-T G.8265/Y.1365 + +# Architecture and requirements for packet-based frequency delivery + +# 1 Scope + +This Recommendation describes the general architecture of frequency distribution using packet-based methods. This version of the Recommendation focuses on the delivery of frequency using methods such as NTP or the precision time protocol (PTP) [IEEE 1588]. The requirements and architecture form a base for the specification of other functionality needed to achieve packet-based frequency distribution in a carrier environment. The architecture described covers the case where protocol interaction is at the end points of the network only, between a packet master clock and a packet slave clock. Details of requirements for other architectures involving devices that participate between the packet master and packet slave clocks are for further study. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.8260] Recommendation ITU-T G.8260 (2010), *Definitions and terminology for synchronization in packet networks*. +- [ITU-T G.8261] Recommendation ITU-T G.8261/Y.1361 (2008), *Timing and synchronization aspects in packet networks*. +- [ITU-T G.8264] Recommendation ITU-T G.8264 (2008), *Distribution of timing information through packet networks*, plus Amendment 1 (2010). +- [IEEE 1588] IEEE STD 1588-2008, *Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems*. +- [IETF RFC 5905] IETF RFC 5905 (2010), *Network Time Protocol Version 4: Protocol And Algorithms Specification*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined elsewhere: + +- 3.1.1 **packet master clock** [ITU-T G.8260]. +- 3.1.2 **packet slave clock** [ITU-T G.8260]. +- 3.1.3 **packet timing signal** [ITU-T G.8260]. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|---------|-------------------------------------------------| +| CDMA | Code Division Multiple Access | +| DSL | Digital Subscriber Line | +| EEC | Ethernet Equipment Clock | +| GM | Grand Master | +| GNSS | Global Navigation Satellite System | +| LSP | Label Switched Path | +| LTE | Long Term Evolution | +| MINPOLL | Minimum Poll interval | +| NTP | Network Time Protocol | +| PDV | Packet Delay Variation | +| PON | Passive Optical Network | +| PRC | Primary Reference Clock | +| PTP | Precision Time Protocol | +| QL | Quality Level | +| RTP | Real Time Protocol | +| SDH | Synchronous Digital Hierarchy | +| SEC | SDH Equipment Clock | +| SSM | Synchronization Status Message | +| TDM | Time Division Multiplexing | +| VLAN | Virtual Local Area Network | +| WIMAX | Worldwide Interoperability for Microwave Access | + +# 5 Conventions + +Within this Recommendation, the term PTP refers to the PTP version 2 protocol defined in [IEEE 1588]. NTP refers to network time protocol as defined in [IETF RFC 5905]. + +# 6 General introduction to packet-based frequency distribution + +The modern telecom network has relied on accurate distribution of frequency in order to optimize transmission and TDM cross-connection. In contrast, packet networks and packet services are highly buffered by their nature and, as a result, do not require accurate timing for their operation. The migration towards converged packet networks on the surface leads to the belief that frequency distribution will not be required as packet network technology becomes more prevalent in the network. + +While this may be true for certain services (Internet is one example), the underlying transport mechanisms that deliver these timing agnostic services may require stringent timing requirements that must be provided in the new converged network paradigm. For example, in some cases, support of circuit emulation services over a packet-based infrastructure requires the presence of a stable + +frequency reference to enable the service. Likewise, in wireless access technologies (e.g., GSM, LTE, WIMAX, CDMA, etc.) the air interface requirements have stringent synchronization requirements that need to be met, even though the end-user service (e.g., mobile Internet) may seemingly not require timing. + +In order to enable timing distribution in packet-based networks, ITU-T has developed specification for synchronous Ethernet [ITU-T G.8261], [b-ITU-T G.8262], [ITU-T G.8264] for the physical layer frequency distribution, which is similar to what was provided by SDH. This Recommendation describes the use of packet-based mechanisms that are intended to be used to transport frequency over a packet network in the absence of physical layer timing. + +## 6.1 Requirements for packet timing + +Packet-based mechanisms for frequency distribution must meet the following requirements: + +- 1) Mechanisms must be specified to allow interoperability between master and slave devices (clocks). +- 2) Mechanisms must permit consistent operation over managed wide area telecom networks. +- 3) Packet-based mechanisms must allow interoperation with existing SDH and synchronous Ethernet-based frequency synchronization networks. +- 4) Packet-based mechanisms must allow the synchronization network to be designed and configured in a fixed arrangement. +- 5) Protection schemes used by packet-based systems must be based on standard telecom operational practice and allow slave clocks the ability to take timing from multiple geographically separate master clocks. +- 6) Source (clock) selection should be consistent with existing practices for physical layer synchronization and permit source selection based on received QL and priority. +- 7) Packet-based mechanisms must permit the operation of existing, standards-based, security techniques to help ensure the integrity of the synchronization. + +# 7 Architecture of packet-based frequency distribution + +In contrast to physical layer synchronization, where the significant edges of a data signal define the timing content of the signal, packet-based methods rely on the transmission of dedicated "event packets". These "event packets" form the significant instants of a packet timing signal. The timing of these significant instances is precisely measured relative to a master time source, and this timing information is encoded in the form of a time-stamp which is a machine-readable representation of a specific instance of time1. The time-stamp is generated at a packet master function and is carried over a packet network to a packet slave clock. As time is the integral of frequency, the time-stamps can therefore be used to derive frequency. + +## 7.1 Packet-based frequency distribution + +The three main components are the packet master clock, the packet slave clock and the packet network. A packet timing signal generated by the packet master clock is transported over the packet network so that the packet slave clock can generate a clock frequency traceable to the input timing + +--- + +1 In some cases frequency may be derived from the arrival rate of incoming packets that do not contain a time-stamp, but that rather are generated at precise intervals. As this Recommendation deals with the use of time-based protocols, methods to derive frequency from the arrival rate of packets are outside the scope of this Recommendation. + +signal available at the packet master clock. The packet master clock is presented with a timing signal traceable to a PRC. The clock produced at the packet slave clock represents the clock traceable to the PRC plus some degradation ( $\delta$ ) due to the packet network. The general architectural topology is shown in Figure 1. The synchronization flow is from master to slave. In cases where the reference to the master is provided over a synchronization distribution network, additional degradation of the frequency signal may be present at the input to the master and therefore also at the output of the slave. + +![Figure 1: General packet network timing architecture diagram. A central 'Packet network' cloud is connected to a 'Packet master clock' at the top and three 'Packet slave clock' units. The master clock receives a 'Reference' signal (labeled with frequency F_i) and exchanges 'Packet timing signals' (orange arrows) with the network. The network distributes these signals to the slave clocks (black arrows). Each slave clock outputs a signal labeled F_out + delta_i, where i represents the slave number (1, 2, or 3).](f4fdd410cdb84df81274da55721e56fb_img.jpg) + +Figure 1: General packet network timing architecture diagram. A central 'Packet network' cloud is connected to a 'Packet master clock' at the top and three 'Packet slave clock' units. The master clock receives a 'Reference' signal (labeled with frequency F\_i) and exchanges 'Packet timing signals' (orange arrows) with the network. The network distributes these signals to the slave clocks (black arrows). Each slave clock outputs a signal labeled F\_out + delta\_i, where i represents the slave number (1, 2, or 3). + +a) The reference may be from a PRC directly, from a GNSS or via a synchronization network + +G.8265/Y.1365(10)\_F01 + +**Figure 1 – General packet network timing architecture** + +## 7.2 Timing protection + +### 7.2.1 Packet master protection + +In traditional synchronization networks, timing availability is enhanced by the use of timing protection whereby the timing to a slave clock (e.g., SEC, or EEC) may be provided over one or more alternative network paths. In the case of the packet-based timing architecture, slave clocks may have visibility to two or more master clocks, as shown in Figure 2. + +In contrast to physical layer timing, where the selection of the clock is performed at the slave clock, selection of a secondary master clock may involve some communication and negotiation between the master and the slave, and the secondary master and slave. + +![Diagram of packet network timing (frequency) protection. A central cloud represents the 'Packet network'. Above it, a box labeled 'Packet master clock (primary)' is connected to the network via two red arrows labeled '"Working" packet timing signals'. To the left, a box labeled 'Packet master clock (secondary)' is also connected to the network via two red arrows. To the right, a box labeled 'Packet slave clock' is connected to the network via two red arrows. A grey arrow labeled '"Protection" packet timing signals' points from the primary master clock to the secondary master clock. A NOTE below the diagram states: 'NOTE – For clarity, the network reference signals to masters are not shown.'](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg) + +Diagram of packet network timing (frequency) protection. A central cloud represents the 'Packet network'. Above it, a box labeled 'Packet master clock (primary)' is connected to the network via two red arrows labeled '"Working" packet timing signals'. To the left, a box labeled 'Packet master clock (secondary)' is also connected to the network via two red arrows. To the right, a box labeled 'Packet slave clock' is connected to the network via two red arrows. A grey arrow labeled '"Protection" packet timing signals' points from the primary master clock to the secondary master clock. A NOTE below the diagram states: 'NOTE – For clarity, the network reference signals to masters are not shown.' + +NOTE – For clarity, the network reference signals to masters are not shown. + +G.8265/Y.1365(10)\_F02 + +**Figure 2 – Packet network timing (frequency) protection** + +### 7.2.2 Packet master/slave selection functions + +Functions required in order to support packet reference selection are described in the following clauses. + +#### 7.2.2.1 Temporary master exclusion – Lock-out function + +To protect the downstream architecture, it must be possible in the slaves to exclude temporarily a master from a list of candidate masters (lock-out functionality). + +#### 7.2.2.2 Slave wait-to-restore time function + +To protect the downstream architecture, a wait-to-restore time must be implemented in the slave. If a master fails or is unreachable, a slave will switch to a backup master. However, upon the recovery of the primary master, the slave will not switch back to the primary master until the wait-to-restore time expires. + +#### 7.2.2.3 Slave non-reversion function + +To protect the downstream architecture, a slave non-reversion function may be implemented to protect against slaves "flipping" between masters. + +This will ensure that if a master fails or is not reachable anymore, a slave will switch to a backup master but will not switch back to the primary master if the non-revertive mode is implemented and activated. + +#### 7.2.2.4 Forced traceability of master function + +It must be possible to force the QL traceability value at the input of the packet master clock. + +Network implementations and scenarios making use of this functionality will need to be defined by the operator on a case by case basis and will depend on the operator's architecture. + +This function is illustrated in Figure 3. + +![Figure 3: Diagram showing the use case where forcing the QL value at the input of the PTPv2 master is needed. An external input reference (no QL) is provided to a Packet master clock. The master clock outputs a QL value associated with the external input reference by the master. This signal is transmitted through a Packet network (represented by a cloud) to a Packet slave clock.](d4af765160d04ecef538e5066006dc77_img.jpg) + +The diagram illustrates a 'Packet master clock' block receiving an 'External input reference (no QL)'. An arrow points from the master clock to a cloud labeled 'Packet network'. Above this arrow is a callout box stating 'QL value associated to the external input reference by the master'. From the cloud, an arrow points to a 'Packet slave clock' block. + +Figure 3: Diagram showing the use case where forcing the QL value at the input of the PTPv2 master is needed. An external input reference (no QL) is provided to a Packet master clock. The master clock outputs a QL value associated with the external input reference by the master. This signal is transmitted through a Packet network (represented by a cloud) to a Packet slave clock. + +G.8265/Y.1365(10)\_F03 + +**Figure 3 – Example of use case where forcing the QL value at the input of the PTPv2 master is needed** + +#### 7.2.2.5 Packet slave clock QL hold off function + +In the case where sufficient holdover performance exists within the packet slave clock, it must be possible to delay the transition of the QL value at the output of the slaves. This will allow the operator to limit downstream switching of the architecture under certain network implementations when traceability to the packet master is lost. + +NOTE – The QL hold off is highly dependent on the quality of the clock implemented in the slave and is for further study. + +These network implementations and scenarios will need to be defined by the operator on a case by case basis. + +This function is illustrated in Figure 4. + +![Figure 4: Diagram showing the use case where the QL hold off at the output of the packet slave clock is needed. A Packet master clock is connected to a Packet network (cloud). The signal is lost at the input of the Packet slave clock, indicated by a red X. The Packet slave clock then outputs a Hold off QL value and a Physical timing signal (e.g., 2 Mbit/s, or synchronous Ethernet).](78ffccd66df9bafd96e3e081110d09dd_img.jpg) + +The diagram shows a 'Packet master clock' block connected to a 'Packet network' cloud. A dashed line with an arrow points from the cloud to a 'Packet slave clock' block, but this path is blocked by a large red 'X'. Above the 'X' is the text 'Loss of input references'. From the 'Packet slave clock' block, an arrow points to the right, labeled 'Hold off QL value' and 'Physical timing signal (e.g., 2 Mbit/s, or synchronous Ethernet)'. + +Figure 4: Diagram showing the use case where the QL hold off at the output of the packet slave clock is needed. A Packet master clock is connected to a Packet network (cloud). The signal is lost at the input of the Packet slave clock, indicated by a red X. The Packet slave clock then outputs a Hold off QL value and a Physical timing signal (e.g., 2 Mbit/s, or synchronous Ethernet). + +G.8265/Y.1365(10)\_F04 + +**Figure 4 – Example of use case where the QL hold off at the output of the packet slave clock** + +#### 7.2.2.6 Slave output squelch function + +In case the packet slave provides an external output synchronization interface (e.g., 2 MHz), a squelch function must be implemented in order to protect the downstream architecture and certain end applications. + +This function is used under certain upstream packet timing signal failure conditions between the packet master and the packet slave. + +These network implementations and scenarios will need to be defined by the operator on a case by case basis. For example, one application will be the case of a packet slave external to the end equipment, such as a base station, which may implement better holdover conditions compared to the packet slave. In this case, it is recommended to squelch the signal at the output of the packet slave in packet timing failure conditions, so that the end equipment will switch into holdover rather than synchronizing the end equipment with the holdover of the packet slave. + +Architectural implementations using this function are for further study. The function is illustrated in Figure 5. + +![Diagram illustrating squelching at the output of a packet slave.](ff0952ef692c9d960ce5f6708bcc9711_img.jpg) + +The diagram shows a 'Packet master clock' box on the left with a solid arrow pointing to a cloud labeled 'Packet network'. A dashed line with an arrow points from the cloud to a 'Packet slave clock' box. Above this dashed line is a red 'X' and the text 'Failure of all input references'. From the 'Packet slave clock' box, another dashed line with an arrow points to an 'End equipment (e.g., base station)' box. This second dashed line also has a red 'X' over it, with the text 'Squelch of the output of the packet slave' below it. In the bottom right corner of the diagram area, the text 'G.8265/Y.1365(10)\_F05' is present. + +Diagram illustrating squelching at the output of a packet slave. + +**Figure 5 – Squelching at output of packet slave** + +## 7.3 Packet network partitioning + +Packet networks may be partitioned into a number of different administrative domains. The transport of timing across the packet network must consider the partitioning of networks into different administration domains, as illustrated in Figure 6. This could mean, for example, that packet master clocks may be located in different administrative domains. Operation in this configuration may be limited due to the protocol capabilities and is for further study. + +![Diagram illustrating packet timing flow over a partitioned network.](3ad00ce93ad9dea9ee0f47535e5355e6_img.jpg) + +The diagram shows three clouds, each labeled 'Network operator'. The first cloud contains a 'Packet master clock' box. A dashed line with an arrow, labeled 'Timing flow', originates from this box and points into the second cloud. The second cloud contains a 'Packet slave clock' box. The third cloud is empty. In the bottom right corner of the diagram area, the text 'G.8265/Y.1365(10)\_F06' is present. + +Diagram illustrating packet timing flow over a partitioned network. + +**Figure 6 – Packet timing flow over partitioned network** + +Passing packet-based timing between administrative domains is not currently specified in this version of the Recommendation and is for further study. There are issues surrounding the demarcation of the packet timing flow and the transferred performance between operators. + +Due to the operation of packet-based networks and their impact on packet-based timing recovery, especially under stress conditions, derived performance is difficult to characterize. Concerning the end-to-end recovery of timing from the packet timing flow, situations can exist where it is difficult to determine the location of performance problems, especially if the packet timing is passing through multiple administrative domains. + +When multiple administrative domains are involved, other methods that are based on physical layer synchronization (for example, synchronous Ethernet over OTN) may be applicable for frequency distribution. The details are outside the scope of this Recommendation. Further information can be found in clause 11 of [ITU-T G.8264]. + +## **7.4 Mixed technologies** + +Packet services may be carried over a packet switching network where the core and access are carried over different technologies. This may impact packet delay variation performance and the ability of the slave clock to derive frequency. For example, within the core, packets containing time-stamps may traverse routers, switches or bridges interconnected by Ethernet links, while the access portion interconnect may be xDSL or PON. + +A connection through a network may consist of a concatenation of different technologies. The PDV performance may be different based on these technologies. The aggregate PDV may therefore differ when mixes of different technologies are deployed. A slave clock may need to accommodate the impact of using different technologies. + +Details of the PDV contributions of individual transport technologies and the performance of slave clocks are for further study. + +# **8 Packet-based protocols for frequency distribution** + +## **8.1 Packet-based protocols** + +As noted in clause 6, frequency transfer over packet networks is not inherent in the packet layer. In cases where frequency transfer is required, methods such as circuit emulation, which utilize either differential or adaptive clock recovery methods may be employed [ITU-T G.8261]. + +Protocols for distribution of time exist such as NTP and PTP [IEEE 1588]. Although the protocols are primarily intended for the distribution of time, it is also possible to derive frequency. A general description on the protocols as well as clarifications on the need to define further details when using these protocols for the purpose of frequency distribution is provided below. Note that the performance achievable may also depend on factors outside of the protocol definitions. + +## **8.2 PTP [IEEE 1588] general description** + +[IEEE 1588] describes the "precision time protocol", commonly referred to as PTP. The PTP protocol enables the accurate time-transfer between two entities (clocks) by the transmission of messages containing accurate timestamps representing an estimate of the time at which the packet is sent. The repeated transmission of messages also allows the derivation of frequency. + +The PTP protocol supports unicast and multicast operation. Additionally, the protocol provides the support for two clock modes, a one-step mode and a two-step mode, which involves the transmission of an additional Follow-up message. Additional messages are also defined for other purposes, such as signalling and management. + +While the first version of [IEEE 1588] was developed for industrial automation, the second version was extended to be applicable to other applications such as telecom. The protocol may be tailored to + +specific applications by the creation of "profiles" which specify which subset of functionality may be required, together with any related configuration settings, to satisfy a specific application. ITU-T is concerned with application to telecom environments. + +[IEEE 1588] defines several types of clocks: ordinary, boundary and transparent clocks. While the standard defines clocks, these are only high level constructs. The performance achievable by the PTP protocol is based on factors that are outside the scope of [IEEE 1588]. + +[b-ITU-T G.8265.1] contains a PTP profile applicable to telecom applications using ordinary clocks in an unicast environment. Profiles developed by ITU-T are intended to meet all the high-level requirements specified in this Recommendation. + +## 8.3 NTP – General description + +NTPv4 is defined in [IETF RFC 5905], which obsoletes both [b-IETF RFC 1305] (NTP v3), and [b-IETF RFC 4330] (SNTP). + +[IETF RFC 5905] defines both a protocol and an algorithm to distribute time synchronization, however the NTP on-wire protocol can also be used to distribute a frequency reference. In this case, however, a specific algorithm to recover frequency has to be developed, and only the packet format and protocol aspects need to be considered. The specific implementation in the client for the purpose of frequency synchronization clock recovery can be considered similar to an implementation using other packet protocols. + +According to [IETF RFC 5905], an SNTP client is not required to implement the NTP algorithms specified in [IETF RFC 5905]. In particular, [IETF RFC 5905] notes that primary servers and clients complying with a subset of NTP, called the simple network time protocol (SNTP), do not need to implement the mitigation algorithms described in the relevant sections of [IETF RFC 5905]. The SNTP client can operate with any subset of the NTP on-wire protocol through the simplest approach, using only the transmit timestamp of the server packet and ignoring all other fields. + +Among the aspects to consider is that in some applications the required packet rate may need to be higher (lower MINPOLL value) than the limit currently suggested for the time synchronization algorithm specified in [IETF RFC 5905]. In relation to this, [IETF RFC 5905] indicates, with respect to the MINPOLL parameter, that "These are in 8-bit signed integer format in log2 (log base 2) seconds... [and] suggested default limits for minimum and maximum Poll intervals are 6 and 10, respectively". + +NOTE – The detailed way of using NTP for the specific application e.g., including the method to support SSM according to the requirements of clause 6, is for further study. + +More details on the use of timing packets (such as NTP) for the purpose of frequency transfer are provided in Appendix XII (Basic principles of timing over packet networks) of [ITU-T G.8261]. + +# 9 Security aspects + +Unlike traditional timing streams where frequency is carried over the physical layer, packet-based timing streams may be observed at different points in the network. There may be cases where timing packets flow across multiple network domains which may introduce specific security requirements. There may also be aspects of security that may be related to both the network (e.g., authentication and/or authorization) and to the PTP protocol itself. + +It is important to permit the operation with existing, standards-based security techniques to help ensure the integrity of the synchronization. Examples may include encryption and/or authentication techniques, or network techniques for separating traffic, such as VLANs or LSPs. Specifically, + +- slaves should be prevented from connecting to rogue masters (this could be either by an authentication process or by using network separation to prevent rogue masters from accessing slaves); +- masters should be prevented from providing service to unauthorized slaves. + +It may not be possible to implement some of these requirements without actually degrading the overall level of timing or system performance. + +Security aspects are for further study. + +# Appendix I + +## Bibliography + +- [b-ITU-T G.8262] Recommendation ITU-T G.8262/Y.1362 (2010), *Timing characteristics of a synchronous Ethernet equipment slave clock.* +- [b-ITU-T G.8265.1] Recommendation ITU-T G.8265.1/Y.1365.1 (2010), *Precision time protocol telecom profile for frequency synchronization.* +- [b-IETF RFC 1305] IETF RFC 1305 (1992), *Network Time Protocol (Version 3) Specification, Implementation and Analysis.* +- [b-IETF RFC 4330] IETF RFC 4330 (2006), *Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI.* + + + +## ITU-T Y-SERIES RECOMMENDATIONS + +## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS + +## GLOBAL INFORMATION INFRASTRUCTURE + +| | | +|-------------------------------------------|-------------| +| General | Y.100–Y.199 | +| Services, applications and middleware | Y.200–Y.299 | +| Network aspects | Y.300–Y.399 | +| Interfaces and protocols | Y.400–Y.499 | +| Numbering, addressing and naming | Y.500–Y.599 | +| Operation, administration and maintenance | Y.600–Y.699 | +| Security | Y.700–Y.799 | +| Performances | Y.800–Y.899 | + +## INTERNET PROTOCOL ASPECTS + +| | | +|--------------------------------------------------------------------|----------------------| +| General | Y.1000–Y.1099 | +| Services and applications | Y.1100–Y.1199 | +| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 | +| Transport | Y.1300–Y.1399 | +| Interworking | Y.1400–Y.1499 | +| Quality of service and network performance | Y.1500–Y.1599 | +| Signalling | Y.1600–Y.1699 | +| Operation, administration and maintenance | Y.1700–Y.1799 | +| Charging | Y.1800–Y.1899 | +| IPTV over NGN | Y.1900–Y.1999 | + +## NEXT GENERATION NETWORKS + +| | | +|-------------------------------------------------------------------|---------------| +| Frameworks and functional architecture models | Y.2000–Y.2099 | +| Quality of Service and performance | Y.2100–Y.2199 | +| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 | +| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 | +| Numbering, naming and addressing | Y.2300–Y.2399 | +| Network management | Y.2400–Y.2499 | +| Network control architectures and protocols | Y.2500–Y.2599 | +| Future networks | Y.2600–Y.2699 | +| Security | Y.2700–Y.2799 | +| Generalized mobility | Y.2800–Y.2899 | +| Carrier grade open environment | Y.2900–Y.2999 | + +For further details, please refer to the list of ITU-T Recommendations. + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|--------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Terminals and subjective and objective assessment methods | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects and next-generation networks | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.829-200212-I_PDF-E/raw.md b/marked/G/T-REC-G.829-200212-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..a3599c8f72e4ef0affb1be59edb2fe10ecc254a8 --- /dev/null +++ b/marked/G/T-REC-G.829-200212-I_PDF-E/raw.md @@ -0,0 +1,489 @@ + + +![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with a lightning bolt and the letters ITU. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.829** + +(12/2002) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital networks – Quality and availability targets + +--- + +**Error performance events for SDH multiplex and +regenerator sections** + +ITU-T Recommendation G.829 + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | G.500–G.599 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| QUALITY OF SERVICE AND PERFORMANCE | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DIGITAL TERMINAL EQUIPMENTS | G.7000–G.7999 | +| DIGITAL NETWORKS | G.8000–G.8999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## **ITU-T Recommendation G.829** + +# **Error performance events for SDH multiplex and regenerator sections** + +## **Summary** + +ITU-T Rec. G.828 [6] specifies error performance parameters and objectives of international, constant bit rate synchronous digital paths. Error performance objectives of ITU-T Rec. G.828 refer to the hypothetical reference path (HRP) of a length of 27 500 km. ITU-T Rec. G.828 does not contain information on path elements. + +NOTE – Performance objectives for SDH paths using equipment designed prior to the adoption of ITU-T Rec. G.828 in March 2000 are given in ITU-T Rec. G.826 [5]. + +This Recommendation defines error performance events and block structures for SDH multiplex and regenerator sections (see ITU-T Recs G.707/Y.1322 [1] and G.708 [2] for reference). SDH equipment functional blocks and SDH management are defined in ITU-T Recs G.783 [3] and G.784 [4]. Observing the definitions given in this Recommendation shall ensure that error performance assessment on SDH multiplex and regenerator sections yields compatible results. Definition of events in this Recommendation is based on the same basic concept as in ITU-T Rec. G.828 [6]. + +The events defined for regenerator sections apply to microwave radio and satellite systems only. + +Performance monitoring of SDH sections is not mandatory. If implemented, the specifications of this Recommendation apply. + +## **Source** + +ITU-T Recommendation G.829 was revised by ITU-T Study Group 13 (2001-2004) and approved under the WTSA Resolution 1 procedure on 14 December 2002. + +## **Keywords** + +Background Block Error, Block-based measurement concept, Error Detection Code (EDC), Error performance events, Errored Second (ES), In-Service Monitoring (ISM), SDH multiplex section, SDH regenerator section, SES threshold, Severely Errored Second (SES), Synchronous Digital Hierarchy (SDH). + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2003 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## CONTENTS + +###### Page + +| | | | +|---------|--------------------------------------------------------------------------------------------------|---| +| 1 | Scope ..... | 1 | +| 2 | References..... | 1 | +| 3 | Abbreviations..... | 2 | +| 4 | The definition and measurement of the block for SDH multiplex sections ..... | 2 | +| 4.1 | Definition of the block for an SDH multiplex section ..... | 2 | +| 4.2 | Block sizes..... | 3 | +| 4.2.1 | In-service monitoring of blocks..... | 3 | +| 4.3 | Out-of-service measurements of blocks ..... | 3 | +| 5 | Error performance events for SDH multiplex sections..... | 4 | +| 5.1 | Definitions ..... | 4 | +| 5.2 | Events determination for multiplex sections ..... | 4 | +| 5.2.1 | Anomalies..... | 4 | +| 5.2.2 | Defects..... | 4 | +| 5.2.3 | Estimation of the performance events ..... | 4 | +| 6 | The definition and measurement of the block for SDH regenerator sections..... | 5 | +| 6.1 | Definition of the block for an SDH regenerator section..... | 5 | +| 6.2 | Block sizes..... | 5 | +| 6.3 | In-service monitoring of blocks..... | 6 | +| 6.4 | Out-of-service measurements of blocks ..... | 6 | +| 7 | Error performance events for SDH regenerator sections..... | 6 | +| 7.1 | Definitions ..... | 6 | +| 7.2 | Events determination for regenerator sections ..... | 7 | +| 7.2.1 | Anomalies..... | 7 | +| 7.2.2 | Defects..... | 7 | +| 7.2.3 | Estimation of the performance events ..... | 7 | +| Annex A | – Entry and exit criteria for the unavailable state of a single direction of an SDH section..... | 8 | +| A.1 | Criteria for a single direction..... | 8 | + + + +# Error performance events for SDH multiplex and regenerator sections + +# 1 Scope + +This Recommendation is applicable to multiplex and regenerator sections employing Synchronous Digital Hierarchy (SDH) technology. This Recommendation is generic in that it defines the events for multiplex sections independent of the physical transport medium supporting the sections. + +The performance events are applicable to each kind of multiplex section, based on optical fibre, digital radio relay, metallic cable and satellite transmission systems or on a combination of them. + +The events defined for regenerator sections apply to microwave radio and satellite systems only. + +In accordance with ITU-T Rec. G.828 [6], the event definitions are block-based, making in-service error evaluation convenient. + +Out-of-service measurements shall be based on the same principles. + +This Recommendation does not address error performance objectives and allocations. Performance limits for bringing-into-service and maintenance of international SDH multiplex and regenerator sections can be found in ITU-T Rec. M.2101 [7]. + +This Recommendation only specifies the unavailability of a single direction of a section, but not the unavailability of a section as such. This concept is different to the one used in ITU-T Rec. G.828 [6] which contains a specification for the unavailability of a path taking into account both directions of that path (see Annex A). + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [1] ITU-T Recommendation G.707/Y.1322 (2000), *Network node interface for the synchronous digital hierarchy (SDH)*, plus Corrigendum 1 (2001), Corrigendum 2 (2001) and Amendment 1 (2001). +- [2] ITU-T Recommendation G.708 (1999), *Sub STM-0 network node interface for the synchronous digital hierarchy (SDH)*. +- [3] ITU-T Recommendation G.783 (2000), *Characteristics of synchronous digital hierarchy (SDH) equipment functional blocks*, plus Corrigendum 1 (2001). +- [4] ITU-T Recommendation G.784 (1999), *Synchronous digital hierarchy (SDH) management*. +- [5] ITU-T Recommendation G.826 (2002), *End-to-end error performance parameters and objectives for international, constant bit-rate digital paths and connections*. +- [6] ITU-T Recommendation G.828 (2000), *Error performance parameters and objectives for international, constant bit-rate synchronous digital paths*, plus Corrigendum 1 (2001). +- [7] ITU-T Recommendation M.2101 (2000), *Performance limits and objectives for bringing-into-service and maintenance of international SDH paths and multiplex sections*. + +- [8] ITU-T Recommendation M.2101.1 (1997), *Performance limits for bringing-into-service and maintenance of international SDH paths and multiplex sections*. + +# 3 Abbreviations + +This Recommendation uses the following abbreviations: + +| | | +|--------|-----------------------------------------------| +| AIS | Alarm Indication Signal | +| BBE | Background Block Error | +| BIP | Bit Interleaved Parity | +| EB | Errored Block | +| EDC | Error Detection Code | +| ES | Errored Second | +| HRP | Hypothetical Reference Path | +| ISM | In-Service Monitoring | +| LOF | Loss of Frame Alignment | +| LOS | Loss of Signal | +| OOS | Out-of-Service | +| RDI | Remote Defect Indication | +| REI | Remote Error Indication | +| RS-TIM | Regenerator Section Trace Identifier Mismatch | +| SDH | Synchronous Digital Hierarchy | +| SES | Severely Errored Second | +| STM | Synchronous Transport Module | + +# 4 The definition and measurement of the block for SDH multiplex sections + +## 4.1 Definition of the block for an SDH multiplex section + +In accordance with ITU-T Rec. G.828 [6], this Recommendation is based upon the error performance measurement of blocks. This clause gives definitions of the term "block" as follows: + +**4.1.1 generic definition:** A block is a set of consecutive bits associated with the section; each bit belongs to one and only one block. "Consecutive" bits may not be contiguous in time. + +**4.1.2 block definition applicable to sub-STM-0 bit rates:** The 8 BIP-1s contained in the B2 byte of an SDH multiplex section in an sSTM-2n ( $n = 1, 2, 4$ ) and sSTM-1k ( $k = 1, 2, 4, 8, 16$ ) pertain to 8 different blocks. Thus, the signal structure of a generic multiplex section in an sSTM-2n and sSTM-1k comprises 8 blocks within a 125 $\mu$ s frame. + +The generic i-th block ( $1 \leq i \leq 8$ ) is equivalent to the i-th bit of the B2 byte and the corresponding monitored bits in the same frame as defined in ITU-T Rec. G.708 [2]. + +**4.1.3 block definition applicable to STM-0:** The 8 BIP-1s contained in the B2 byte of an SDH multiplex section in an STM-0 pertain to 8 different blocks. Thus, the signal structure of a generic multiplex section in an STM-0 comprises 8 blocks within a 125 $\mu$ s frame. + +The generic i-th block ( $1 \leq i \leq 8$ ) is equivalent to the i-th bit of the B2 byte and the corresponding monitored bits in the same frame as defined in ITU-T Rec. G.707/Y.1322 [1]. + +**4.1.4 block definition applicable to STM-N (N = 1, 4, 16, 64):** The $N \times 24$ BIP-1s contained in the B2 bytes of an SDH multiplex section in an STM-N (N = 1, 4, 16, 64) pertain to $N \times 24$ different blocks. Thus, the signal structure of a generic multiplex section in an STM-N comprises $N \times 24$ blocks within a 125 $\mu$ s frame. + +The generic i-th block ( $1 \leq i \leq N \times 24$ ) is equivalent to the i-th bit of the B2 bytes and the corresponding monitored bits in the same frame as defined in ITU-T Rec. G.707/Y.1322 [1]. + +## 4.2 Block sizes + +Table 1 defines, for each type of multiplex section, the block size (number of bits per block), the number of blocks per second (blocks/s), the associated error detection code (EDC) and the blocks per frame. + +**Table 1/G.829 – Block sizes, blocks per frame, blocks per second and EDCs for SDH multiplex sections** + +| STM-N | Block size | Blocks per frame | Blocks per second | EDC | +|------------------------------------------------------------------------------------------------|----------------------------------------|------------------|---------------------|----------------------------| +| sSTM-1k
(Note 2) | $k \times 36$ bits
(Notes 2 and 4) | 8 | 64 000 (Note 5) | $8 \times \text{BIP-1}$ | +| sSTM-2n
(Note 1) | $n \times 108$ bits
(Notes 1 and 3) | 8 | 64 000 (Note 5) | $8 \times \text{BIP-1}$ | +| STM-0 | 801 bits | 8 | 64 000 (Note 5) | $8 \times \text{BIP-1}$ | +| STM-1 | 801 bits | 24 | 192 000 (Note 5) | $24 \times \text{BIP-1}$ | +| STM-4 | 801 bits | 96 | 768 000 (Note 5) | $96 \times \text{BIP-1}$ | +| STM-16 | 801 bits | 384 | 3 072 000 (Note 5) | $384 \times \text{BIP-1}$ | +| STM-64 | 801 bits | 1536 | 12 288 000 (Note 5) | $1536 \times \text{BIP-1}$ | +| NOTE 1 – $n = 1, 2$ and $4$ according to ITU-T Rec. G.708 [2]. | | | | | +| NOTE 2 – $k = 1, 2, 4, 8, 16$ according to ITU-T Rec. G.708 [2]. | | | | | +| NOTE 3 – Bits per frame composed by payload bytes $864 \times n$ . The SOH bytes are excluded. | | | | | +| NOTE 4 – Bits per frame composed by payload bytes $288 \times k$ . The SOH bytes are excluded. | | | | | +| NOTE 5 – Blocks per second = Blocks per frame $\times 8000$ . | | | | | + +### 4.2.1 In-service monitoring of blocks + +Each block is monitored by means of an inherent Error Detection Code, e.g. Bit Interleaved Parity. The EDC bits are physically separated from the block to which they apply. It is not normally possible to determine whether a block or its controlling EDC bits are in error. If there is a discrepancy between the EDC and its controlled block, it is always assumed that the controlled block is in error. + +## 4.3 Out-of-service measurements of blocks + +Out-of-service (OOS) measurements shall also be block-based and shall make use of the same blocks as defined for in-service monitoring (ISM). This will allow an easy comparison of OOS measurements and ISM. It is expected that the out-of-service error detection capability will be superior to the in-service capability described in 4.2.1. + +# 5 Error performance events for SDH multiplex sections + +## 5.1 Definitions + +**5.1.1 errored block (EB):** A block in which one or more bits are in error. + +**5.1.2 errored second (ES):** A one-second period with one or more errored blocks or at least one defect (see Note 1). + +**5.1.3 severely errored second (SES):** A one-second period which contains $\geq X\%$ errored blocks or at least one defect. SES is a subset of ES (see Notes 1 and 2). + +NOTE 1 – The anomalies, defects and related performance criteria are listed in 5.2.1 and 5.2.2. + +NOTE 2 – The threshold value of $X\%$ errored blocks has been chosen to improve consistency between SESs declared at the section and the path layer. It should be noted, however, that this consistency depends on the error distribution observed at the section under test and may also be influenced by the characteristics of the equipment under test (e.g. the modulation scheme used). Because of this dependency, full SES consistency at section and path layer cannot be expected. For maintenance purposes, consistency may be obtained, i.e., by applying media-dependent thresholds. The values of $X$ for the various bit rates are given in Table 2. + +**Table 2/G.829 – SES thresholds for SDH multiplex sections** + +| Bit rate | sSTM-21
sSTM-11 | sSTM-22
sSTM-12 | sSTM-24
sSTM-14 | sSTM-18 | sSTM-116 | +|-----------------|--------------------|--------------------|--------------------|---------|----------| +| SES threshold X | 10% EBs | 15% EBs | 25% EBs | 35% EBs | 40% EBs | + +| Bit rate | STM-0 | STM-1 | STM-4 | STM-16 | STM-64 | +|-----------------|---------|---------|---------|---------|---------| +| SES threshold X | 15% EBs | 15% EBs | 25% EBs | 30% EBs | 30% EBs | + +**5.1.4 background block error (BBE):** An errored block not occurring as part of an SES. + +## 5.2 Events determination for multiplex sections + +### 5.2.1 Anomalies + +In-service anomaly conditions are used in ITU-T Recs G.707/Y.1322 [1] and G.783 [3] to determine the error performance of an SDH section when the section is not in a defect state. The following anomalies are defined for a multiplex section: + +- a1 An error as indicated by the EDC; +- a2 Multiplex section remote error indication (MS-REI). + +### 5.2.2 Defects + +In-service defect conditions are used in ITU-T Recs G.707/Y.1322 [1] and G.783 [3] relevant to SDH equipment to determine the change of performance state which may occur on a section. The following categories of defects are defined for multiplex sections: + +- d1 Multiplex section AIS (MS-AIS) (See Note); +- d2 Multiplex section remote defect indication (MS-RDI). + +NOTE – This defect is an SDH multiplex section defect. Regenerator section defects such as LOS, LOF and RS-TIM give rise to an AIS defect in the multiplex section layer. + +### 5.2.3 Estimation of the performance events + +For SDH multiplex sections, the full set of performance events shall be estimated as follows: + +ES: A near-end ES is observed when, during one second, at least one anomaly $a_1$ , or one defect $d_1$ occurs. + +A far-end ES is observed when, during one second, at least one anomaly $a_2$ , or one defect $d_2$ occurs. + +For the ES event, the actual count of EBs is irrelevant; it is only the fact that an EB has occurred in a second which is significant. + +SES: A near-end SES is observed when, during one second, at least "Y" EBs, derived from anomaly $a_1$ or defect $d_1$ , occur (see Note). + +A far-end SES is observed when, during one second, at least "Y" EBs, derived from anomaly $a_2$ or defect $d_2$ , occur (see Note). + +BBE: A near-end BBE is observed when an anomaly $a_1$ occurs in a block not being part of an SES. + +A far-end BBE is observed when an anomaly $a_2$ occurs in a block not being part of an SES. + +NOTE – The value of "Y" is obtained by multiplying the number of blocks per second by X% (from the SES definition). + +# 6 The definition and measurement of the block for SDH regenerator sections + +Clauses 6 and 7 apply to radio-relay and satellite transmission systems. + +## 6.1 Definition of the block for an SDH regenerator section + +In accordance with ITU-T Rec. G.828 [6], this Recommendation is based upon the error performance measurement of blocks. This clause gives definitions of the term "block" as follows: + +**6.1.1 generic definition:** A block is a set of consecutive bits associated with the section; each bit belongs to one and only one block. "Consecutive" bits may not be contiguous in time. + +**6.1.2 block definition applicable to sub-STM-0 bit rates:** The signal structure of a regenerator section sSTM-2n ( $n = 1, 2, 4$ ) and sSTM-1k ( $k = 1, 2, 4, 8, 16$ ) comprises 1 block within a 125 $\mu$ s frame. + +**6.1.3 block definition applicable to STM-0:** The BIP-8 contained in the B1 byte of an SDH regenerator section in an STM-0 pertains to 1 block. Thus, the signal structure of a regenerator section in an STM-0 comprises 1 block within a 125 $\mu$ s frame. + +The BIP-8 code and the corresponding monitored bits are defined in ITU-T Rec. G.707/Y.1322 [1]. + +**6.1.4 block definition applicable to STM-N ( $N = 1, 4, 16$ ):** The $N \times$ BIP-8 contained in the B1 byte and in relevant media-dependent bytes of an SDH regenerator section in an STM-N ( $N \geq 1$ ) pertains to N blocks. Thus, the signal structure of a regenerator section in an STM-N comprises N blocks within a 125 $\mu$ s frame. + +The i-th block ( $1 \leq i \leq N$ ) is equivalent to the i-th BIP-8 byte and the corresponding monitored bits in the same frame. + +## 6.2 Block sizes + +Table 3 defines, for each type of regenerator section, the block size (number of bits per block), the number of blocks per second (blocks/s), the associated error detection code (EDC) and the blocks per frame. + +**Table 3/G.829 – Block sizes, blocks per frame, blocks per second +and EDCs for SDH regenerator sections** + +| STM-N | Block size | Blocks per frame | Blocks/s | EDC
(Note 3) | +|------------------|---------------------|------------------|--------------------|-------------------------------| +| sSTM-2n (Note 1) | $n \times 864$ bits | 1 | 8 000 | Media-specific; to be defined | +| sSTM-1k (Note 2) | $k \times 288$ bits | 1 | 8 000 | Media-specific; to be defined | +| STM-0 | 6 480 bits | 1 | 8 000 | BIP-8 | +| STM-1 | 19 440 bits | 1 | 8 000 | BIP-8 | +| STM-4 | 19 440 bits | 4 | $4 \times 8\,000$ | $4 \times \text{BIP-8}$ | +| STM-16 | 19 440 bits | 16 | $16 \times 8\,000$ | $16 \times \text{BIP-8}$ | + +NOTE 1 – $n = 1, 2$ and 4 according to ITU-T Rec. G.708 [2]. + +NOTE 2 – $k = 1, 2, 4, 8$ and 16 according to ITU-T Rec. G.708 [2]. + +NOTE 3 – The EDC is a media-specific indicator which is under study in other ITU Study Groups for media-specific error performance purposes. (See 6.3 for more details.) + +## 6.3 In-service monitoring of blocks + +Each block is monitored by means of an inherent Error Detection Code, e.g. Bit Interleaved Parity. The EDC bits are physically separated from the block to which they apply. It is not normally possible to determine whether a block or its controlling EDC bits are in error. If there is a discrepancy between the EDC and its controlled block, it is always assumed that the controlled block is in error. + +For sub-STM-0 rates no specific EDC is given, since ITU-T Rec. G.708 defines it for media-specific application. In this generic definition, it is recommended that for in-service monitoring purposes the EDC capability be such that the probability to detect an error event be $\geq 90\%$ , assuming Poisson error distribution. An example of an EDC which fulfils the monitoring requirements is the BIP-8 code. + +## 6.4 Out-of-service measurements of blocks + +On condition that a suitable interface is available, Out-of-Service (OOS) measurements shall also be block-based and shall make use of the same blocks as defined for in-service monitoring (ISM). This will allow an easy comparison of OOS measurements and ISM. It is expected that the out-of-service error detection capability will be superior to the in-service capability described in 6.3. + +# 7 Error performance events for SDH regenerator sections + +Clauses 6 and 7 of this Recommendation apply to radio-relay and satellite transmission systems. + +## 7.1 Definitions + +**7.1.1 errored block (EB):** A block in which one or more bits are in error. + +**7.1.2 errored second (ES):** A one-second period with one or more errored blocks or at least one defect (see Note 1). + +**7.1.3 severely errored second (SES):** A one-second period which contains $\geq X\%$ errored blocks or at least one defect. SES is a subset of ES, where the value of X is defined in Table 4 (see Notes 1 and 2). + +NOTE 1 – The anomalies, defects and related performance criteria are listed in 7.2.1 and 7.2.2. + +NOTE 2 – The SES threshold for sSTM-2n ( $n = 1, 2, 4$ ) and sSTM-1k ( $k = 1, 2, 4, 8, 16$ ) rates are evaluated considering an EDC with a detection probability greater than 90%. + +**Table 4/G.829 – SES thresholds for SDH regenerator sections** + +| Bit rate | sSTM-21
sSTM-11 | sSTM-22
sSTM-12 | sSTM-24
sSTM-14 | sSTM-18
sSTM-116 | +|------------------------|--------------------|--------------------|--------------------|---------------------| +| SES threshold X | 10% EBs | 25% EBs | 45% EBs | 60% EBs | + +| Bit rate | STM-0 | STM-1 | STM-4 | STM-16 | +|------------------------|---------|---------|---------|---------| +| SES threshold X | 10% EBs | 30% EBs | 30% EBs | 30% EBs | + +**7.1.4 background block error (BBE):** An errored block not occurring as part of an SES. + +## **7.2 Events determination for regenerator sections** + +### **7.2.1 Anomalies** + +In-service anomaly conditions are used in ITU-T Recs G.707/Y.1322 [1] and G.783 [3] to determine the error performance of an SDH section when the section is not in a defect state. The following anomaly is defined for a regenerator section: + +$a_1$ An error on the whole block as indicated by the EDC. + +### **7.2.2 Defects** + +In-service defect conditions are used in ITU-T Recs G.707/Y.1322 [1] and G.783 [3] relevant to SDH equipment to determine the change of performance state which may occur on a section. The following categories of defects are defined for regenerator sections: + +$d_1$ LOS; + +$d_2$ LOF; + +$d_3$ RS-TIM. + +### **7.2.3 Estimation of the performance events** + +For SDH regenerator sections, the full set of near-end performance events shall be estimated as follows: + +**ES:** A near-end ES is observed when, during one second, at least one anomaly $a_1$ , or one defect $d_1$ occurs. + +For the ES event, the actual count of EBs is irrelevant; it is only the fact that an EB has occurred in a second which is significant. + +**SES:** A near-end SES is observed when, during one second, at least "Y" EBs, derived from anomaly $a_1$ or defect $d_1$ , occur (see Note). + +**BBE:** A near-end BBE is observed when an anomaly $a_1$ occurs in a block not being part of an SES. + +**NOTE** – The value of "Y" is obtained by multiplying the number of blocks per second by X% (from the SES definition). + +# Annex A + +## Entry and exit criteria for the unavailable state of a single direction of an SDH section + +## A.1 Criteria for a single direction + +A period of unavailable time begins at the onset of ten consecutive SES events. These ten seconds are considered to be part of unavailable time. A new period of available time begins at the onset of ten consecutive non-SES events. These ten seconds are considered to be part of available time. The availability criterion is defined for a single direction. To determine the entry to/exit from the unavailable state, the continuous collection of SESs is necessary. + +Figure A.1 illustrates this definition. + +![Figure A.1/G.829 – Example of unavailability determination. The diagram shows a timeline of seconds categorized as Severely Errored Second (SES), Errored Second (non-SES), or Error-free Second. A period of 10 consecutive SESs marks the start of unavailability. A subsequent period of less than 10 seconds containing non-SES events does not restore availability. Once 10 consecutive non-SES events occur, availability is restored.](a26e142d3df5bef41a84a9dd099d7825_img.jpg) + +The diagram illustrates the determination of unavailability and availability over time. The timeline is divided into three main segments: a 10-second period of unavailability, a short period of less than 10 seconds, and a 10-second period of availability. The first 10-second period consists of 10 consecutive Severely Errored Seconds (SES), marked by grey squares. The onset of this period is labeled 'Unavailability detected'. The next segment, lasting less than 10 seconds, contains a mix of SESs and Errored Seconds (non-SES), marked by squares with an 'X'. The final 10-second period consists of 10 consecutive non-SES events (white squares), and its onset is labeled 'Availability detected'. The entire timeline is labeled 'Time' at the top right and 'G.829\_F.A.1' at the bottom right. A legend at the bottom left defines the symbols: a grey square for 'Severely Errored Second', a square with an 'X' for 'Errored Second (non-SES)', and a white square for 'Error-free Second'. + +Figure A.1/G.829 – Example of unavailability determination. The diagram shows a timeline of seconds categorized as Severely Errored Second (SES), Errored Second (non-SES), or Error-free Second. A period of 10 consecutive SESs marks the start of unavailability. A subsequent period of less than 10 seconds containing non-SES events does not restore availability. Once 10 consecutive non-SES events occur, availability is restored. + +Figure A.1/G.829 – Example of unavailability determination + +This Recommendation only specifies the unavailability of a single direction of a section, but not the unavailability of a section as such. This concept is different to the one used in ITU-T Rec. G.828 [6] which contains a specification for the unavailability of a path taking into account both directions of that path. (An obvious exception are unidirectional paths where unavailability is only related to the relevant direction.) + +The reasons for using different concepts in both Recommendations are as follows: + +This Recommendation deals with sections and is therefore not directly related to a service. It is network-oriented and treats each direction independently. ITU-T Recs G.826 and G.828, however, specify end-to-end error performance objectives for a path and thus are service-oriented. As most services are bidirectional, it follows that a path must be available in both directions to provide a meaningful service. + +With regard to regenerator sections it should be noted that REI and RDI indications are not available at this level. Therefore, bidirectional monitoring of availability on a single signal is not possible and each direction has to be monitored separately. + + + +# SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure and Internet protocol aspects | +| Series Z | Languages and general software aspects for telecommunication systems | + +![Barcode with the number 23338](83926108dd52e3998fda7a99a91cdf3b_img.jpg) + +A barcode consisting of vertical black bars of varying widths. 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+STANDARDIZATION SECTOR +OF ITU + +(04/97) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital transmission systems – Digital networks – SDH +network characteristics + +--- + +**Interworking of SDH network protection +architectures** + +ITU-T Recommendation G.842 + +(Previously CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| INTERNATIONAL ANALOGUE CARRIER SYSTEM | | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA CHARACTERISTICS | | +| DIGITAL TRANSMISSION SYSTEMS | | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Telecommunications management network | G.850–G.859 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| General | G.900–G.909 | +| Parameters for optical fibre cable systems | G.910–G.919 | +| Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s | G.920–G.929 | +| Digital line transmission systems on cable at non-hierarchical bit rates | G.930–G.939 | +| Digital line systems provided by FDM transmission bearers | G.940–G.949 | +| Digital line systems | G.950–G.959 | +| Digital section and digital transmission systems for customer access to ISDN | G.960–G.969 | +| Optical fibre submarine cable systems | G.970–G.979 | +| Optical line systems for local and access networks | G.980–G.999 | + +For further details, please refer to ITU-T List of Recommendations. + +# **ITU-T RECOMMENDATION G.842** + +# **INTERWORKING OF SDH NETWORK PROTECTION ARCHITECTURES** + +## **Summary** + +This Recommendation provides specifications for the interworking of network protection architectures. Specifically covered are single and dual node interconnection between MS-shared protection rings and SNCP rings of like or unlike types. + +### **Source** + +ITU-T Recommendation G.842 was prepared by ITU-T Study Group 15 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 8th of April 1997. + +## FOREWORD + +ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, the ITU had/had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 1997 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +## CONTENTS + +| | Page | +|---------------------------------------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Terms and definitions ..... | 1 | +| 4 Abbreviations..... | 3 | +| 5 Interworking criteria/objectives..... | 4 | +| 5.1 Criteria for ring interworking with an MS-shared protection ring..... | 4 | +| 6 Interworking architectures ..... | 5 | +| 6.1 Single node interconnection..... | 5 | +| 6.2 Dual node interconnection ..... | 5 | +| 6.2.1 Generalized architecture ..... | 5 | +| 6.2.2 Ring interworking with an MS-shared protection ring..... | 7 | +| 6.2.3 Ring interworking with an SNCP ring..... | 21 | +| 6.2.4 Multiple rings ..... | 32 | +| 7 Interworking among network layers ..... | 32 | +| 8 Switch contention ..... | 32 | + + + +# **INTERWORKING OF SDH NETWORK PROTECTION ARCHITECTURES** + +*(Geneva, 1997)* + +# **1 Scope** + +This Recommendation describes mechanisms for interworking between network protection architectures. The network protection architectures are described in Recommendation G.841. Interworking is described for single and dual node interconnection for exchanging traffic between rings. Each ring may be configured for MS-shared protection or for SNCP protection. + +# **2 References** + +The following ITU-T Recommendations, and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- ITU-T Recommendation G.803 (1997), *Architecture of transport networks based on the Synchronous Digital Hierarchy (SDH)*. +- ITU-T Recommendation G.841 (1995), *Types and characteristics of SDH network protection architectures*. +- ITU-T Recommendation G.783 (1997), *Characteristics of Synchronous Digital Hierarchy (SDH) equipment functional blocks*. + +# **3 Terms and definitions** + +NOTE – These definitions need to be reviewed with respect to the emerging Recommendation on SDH vocabulary. + +This Recommendation defines the following terms. + +**3.1 drop-and-continue:** A function within a ring node where traffic is both extracted from the working channels on the ring (drop), and transmitted onwards on the ring (continue). + +**3.2 dual hubbed:** Dual hubbed traffic can be routed to either or both of two central offices (or similar sites). Dual hubbed traffic is survivable under a failure of one of the two hubs. + +**3.3 dual node interconnection:** An architecture between two rings where two nodes in each ring are interconnected. + +**3.4 hold-off time:** The time that a protection switch controller waits after detecting a failure before initiating the switch. + +**3.5 path selector:** Within an SNCP architecture, the node function that selects a tributary which is extracted from the working channels arriving from one side of the node or from the other side of the node, according to path level criteria. + +**3.6 primary node:** Within an MS-shared protection ring interworking architecture, the node which provides the service selection and drop-and-continue functions for a tributary. Different tributaries may have different designated primary nodes. + +- 3.7 propagation of switching:** One protection switch leading to another. Propagation of switching is often, though not always, undesirable from a maintenance point of view. +- 3.8 ring interconnection:** An architecture between two rings where one or more nodes in each ring are interconnected. +- 3.9 ring interworking:** A network topology whereby two rings are interconnected at two nodes on each ring, and the topology operates such that a failure at either of these two nodes will not cause loss of any working traffic. This is illustrated in Figure 1. +- 3.10 secondary circuit:** Within an MS-shared protection ring interworking architecture, this is the alternate routing that traffic travelling from one ring to another follows. This alternate additional routing is used when the service circuit is interrupted. +- 3.11 secondary node:** Within an MS-shared protection ring interworking architecture, the node which provides the alternate interworking route for a tributary. +- 3.12 service circuit:** Within an MS-shared protection ring interworking architecture, this is the preferred original routing that traffic travelling from one ring to another normally follows. +- 3.13 service selector:** Within an MS-shared protection ring architecture, the node function used for ring interworking. It selects traffic from either the channels arriving from one side of the node, or from traffic entering the ring, according to some criteria. +- 3.14 single node interconnection:** An architecture between two rings where one node in each ring is interconnected. +- 3.15 termination node:** The node (other than a primary or secondary node) where a tributary enters or exits the ring. + +![Diagram of Generalized ring interworking showing two rings connected by four ADM nodes. The top ring has an external connection at node A with signals RA (up) and TA (down). The bottom ring has a termination at node Z. The four ADM nodes between the rings have signals labeled RI1, TI1 on the left and RI2, TI2 on the right. Arrows indicate signal flow: TA down into the top ring, RA up from the top ring, RI1 down from the top ring to the bottom ring, TI1 up from the bottom ring to the top ring, RI2 down from the top ring to the bottom ring, and TI2 up from the bottom ring to the top ring.](ebff22fb5dd6f50a90e44dca0f82f285_img.jpg) + +Diagram of Generalized ring interworking showing two rings connected by four ADM nodes. The top ring has an external connection at node A with signals RA (up) and TA (down). The bottom ring has a termination at node Z. The four ADM nodes between the rings have signals labeled RI1, TI1 on the left and RI2, TI2 on the right. Arrows indicate signal flow: TA down into the top ring, RA up from the top ring, RI1 down from the top ring to the bottom ring, TI1 up from the bottom ring to the top ring, RI2 down from the top ring to the bottom ring, and TI2 up from the bottom ring to the top ring. + +T1524330-96 + +Failure free state (from perspective of top ring) + +$$\begin{aligned} + R_{I1} &= R_{I2} = T_A \\ + R_A &= T_{I1} \text{ or } T_{I2} \\ + T_{I1} &= T_{I2} + \end{aligned}$$ + +**Figure 1/G.842 – Generalized ring interworking** + +# 4 Abbreviations + +This Recommendation uses the following abbreviations: + +| | | +|------|------------------------------------| +| ADM | Add/Drop Multiplexer | +| AIS | Alarm Indication Signal | +| AU | Administrative Unit | +| HO | Higher Order | +| HP | Higher order Path | +| HPC | Higher order Path Connection | +| HPOM | Higher order Path Overhead Monitor | +| LO | Lower Order | +| LOF | Loss of Frame | +| LOP | Loss of Pointer | +| LOS | Loss of Signal | +| LPC | Lower order Path Connection | +| LPOM | Lower order Path Overhead Monitor | + +| | | +|---------|----------------------------------------------------------------| +| MS | Multiplex Section | +| SDH | Synchronous Digital Hierarchy | +| SNC | SubNetwork Connection | +| SNCP | SubNetwork Connection Protection | +| SNC/I | SubNetwork Connection Protection with Inherent Monitoring | +| SNC/N | SubNetwork Connection Protection with Non-Intrusive Monitoring | +| STM(-N) | Synchronous Transport Module (-N) | +| TIM | Trace Identifier Mismatch | +| UNEQ | Unequipped | +| VC | Virtual Container | + +# 5 Interworking criteria/objectives + +Interworking SDH protection architectures are meant to provide an even greater degree of protection within a network. Some considerations for interworking criteria are as follows: + +- end-to-end availability requirements; +- robustness against various failure events; +- implementation complexity and costs. + +The following is a list of interworking objectives: + +- 1) Ring interworking shall be accommodated in such a way that if two rings are connected at more than one node each, a failure at one of these node shall not cause loss of any service. +- 2) It should be possible to avoid propagation of switching between interworking rings. +- 3) The ring shall be able to drop traffic at multiple nodes, i.e. working traffic can be dropped at two, or more, nodes on a ring without compromising the ability to restore traffic that is dual hubbed (or any other traffic). +- 4) Ring interconnection may occur among multiple rings. Interconnection boundaries should be the same for all similar instances of interworking between two ring types. + +## 5.1 Criteria for ring interworking with an MS-shared protection ring + +The following objectives apply to the particular case of ring interworking with an MS-shared protection ring: + +- MS-shared protection ring nodes should support the capability to interconnect with another architecture at two nodes. In particular, MS-shared protection ring nodes should support the capability to interconnect with another ring at two nodes, regardless of the type of protection switching employed by the other ring (e.g. SNCP or MS-shared protection rings). +- For a tributary being protected against ring interconnection failures, the interconnection architecture should be capable of protecting against the failure of one interconnecting node, two interconnecting nodes (each on different rings, but on the same interconnect), or the connection between the two interconnecting nodes. +- The two interconnecting nodes should not need to be adjacent. +- The ring interconnect architecture should support STM-1 electrical or STM-N optical interconnection (where STM-N signals may contain concatenated payloads). +- The ring interconnection architecture should not require inter-ring signalling. Providing protection for the interconnecting line is not considered inter-ring signalling. + +- Protection for ring interconnection failures should be based on detecting path defects. +- To avoid propagation of failures when possible, a hold-off time should be allowed. +- Ring interworking using protection bandwidth between ring interworking nodes will be accommodated. The details of ring interworking using protection bandwidth are for further study. + +# 6 Interworking architectures + +This clause describes the interworking between multiple instances of protection architectures within the same network layer intersecting at one or more network nodes (e.g. two or more SNC rings exchanging traffic within a single office). + +## 6.1 Single node interconnection + +Single node interconnection is an architecture between two rings where one node in each ring is interconnected. + +This architecture (shown in Figure 2) has a single point of failure at the point where the rings are interconnected. Interconnection protection can be provided by multiplex section protection of the interconnecting span, but no protection is available due to failure of either interconnecting node. + +![Diagram of single node interconnection between two rings, Ring 1 and Ring 2. Ring 1 contains nodes A, B, C, and D. Ring 2 contains nodes W, X, Y, and Z. Node D in Ring 1 is connected to node W in Ring 2 via four parallel arrows representing multiple traffic paths. The diagram is labeled T1524340-96.](5e92d9e8e9ce204e405bff2367f88176_img.jpg) + +The diagram illustrates a single node interconnection between two rings. Ring 1 (top) consists of nodes A, B, C, and D connected in a clockwise loop. Ring 2 (bottom) consists of nodes W, X, Y, and Z connected in a clockwise loop. Node D in Ring 1 is connected to node W in Ring 2 via four parallel vertical arrows, representing multiple traffic paths between the two rings. The diagram is labeled T1524340-96. + +Diagram of single node interconnection between two rings, Ring 1 and Ring 2. Ring 1 contains nodes A, B, C, and D. Ring 2 contains nodes W, X, Y, and Z. Node D in Ring 1 is connected to node W in Ring 2 via four parallel arrows representing multiple traffic paths. The diagram is labeled T1524340-96. + +Figure 2/G.842 – Example of single node interconnection + +## 6.2 Dual node interconnection + +### 6.2.1 Generalized architecture + +Dual node interconnection is an architecture between two rings where two nodes in each ring are interconnected. This is illustrated in Figure 3. The two interconnections between the two rings can be arranged to provide protection of the traffic crossing from one ring to the other. A special form of + +dual node interconnection is given the term ring interworking. Ring interworking is a network topology whereby two rings are interconnected at two nodes on each ring, and the topology operates such that a failure at either of these two nodes will not cause loss of any working traffic. This is illustrated in Figure 1. In this figure, there is a tributary that enters and exits the top ring from Node A, and also enters and exits the bottom ring from Node Z. Using the following notation: + +- $T_A$ = the transmit signal at Node A; +- $R_A$ = the receive signal at Node A; +- $T_{I1}$ = the transmit signal at one of the interconnection nodes; +- $R_{I1}$ = the receive signal at one of the interconnection nodes; +- $T_{I2}$ = the transmit signal at the other interconnection node; +- $R_{I2}$ = the receive signal at the other interconnection node. + +In ring interworking, the interfaces between the two set of interconnecting nodes is such that: + +- $R_{I1} = R_{I2} = T_A$ ; +- $T_{I1} = T_{I2}$ ; and +- $R_A = T_{I1}$ or $T_{I2}$ . + +In other words, the signal transmitted from Node A towards Node Z is present at both interconnection interfaces. Similarly, the signal transmitted from Node Z back to Node A is also present at both interconnection interfaces. Eventually only one copy of the duplicated signals at the interconnection interfaces is chosen at either Node A or Node Z. Specific examples of ring interworking architectures are described below. + +![Diagram of dual node interconnection between two rings. Ring 1 (top) contains nodes A, B, C, and D. Ring 2 (bottom) contains nodes W, X, Y, and Z. Node D is connected to Node W, and Node C is connected to Node X, forming the dual interconnection. Arrows indicate signal flow between the rings at these interfaces. Nodes A and Z are shown as tributary nodes.](7f17c430b9598e4d748a8041457810b3_img.jpg) + +The diagram illustrates two rings, Ring 1 and Ring 2, interconnected at two nodes. Ring 1 (top) consists of nodes A, B, C, and D. Ring 2 (bottom) consists of nodes W, X, Y, and Z. Node D in Ring 1 is connected to Node W in Ring 2. Node C in Ring 1 is connected to Node X in Ring 2. These two connections represent the dual interconnection points. Arrows indicate signal flow: from Node D to Node W and from Node W to Node D, and from Node C to Node X and from Node X to Node C. Node A is shown as a tributary node on Ring 1, and Node Z is shown as a tributary node on Ring 2. + +Diagram of dual node interconnection between two rings. Ring 1 (top) contains nodes A, B, C, and D. Ring 2 (bottom) contains nodes W, X, Y, and Z. Node D is connected to Node W, and Node C is connected to Node X, forming the dual interconnection. Arrows indicate signal flow between the rings at these interfaces. Nodes A and Z are shown as tributary nodes. + +T1524350-96 + +**Figure 3/G.842 – Example of dual node interconnection** + +### 6.2.2 Ring interworking with an MS-shared protection ring + +#### 6.2.2.1 Architecture + +Figure 4 shows the nominal failure free state of a simple MS-shared protection ring and illustrates a particular tributary handed-off at two ring interconnection nodes and to be terminated at the node A. The two ring interconnection nodes are referred to as the primary node and the secondary node. These interconnection nodes need not be adjacent. Starting from the top in Figure 4, a bidirectional tributary from the (uppermost) termination node A is assigned counter-clockwise towards the bottom on the ring. Although there is symmetry in the hand-off to the other ring, the primary node would normally be the one "closest" to the terminating node without respect to ring orientation. Primary and secondary nodes are defined on a per tributary basis. The MS-shared protection ring nodes can interface with any architecture at the interconnection nodes so long as the interface requirements illustrated in Figure 4 are met. + +This architecture includes recovery from the following failure scenarios: + +- 1) Within the MS-shared protection ring, any failure outside of the termination, primary, or secondary nodes are handled in standard fashion. The MS-shared protection ring is assumed to behave as described in Recommendation G.841. The nature of the failure – whether an electronics failure, a cable cut, or even a node failure – has no impact on the configuration of the termination, primary, or secondary nodes. A cable cut failure is illustrated in Figure 5. +- 2) A failure of the primary node in the MS-shared protection ring results in a secondary connection of the tributary. Normally such a tributary would be squelched, but for this architecture this particular tributary remains unsquelched. All other (undesired) crossed traffic is squelched. Failure of the primary node is illustrated in Figure 6. The ring interworking behavior for this case remains the same even if a disaster is large enough (e.g. central office lost) to cause a failure of both the primary node on one ring and its interconnected node on the other ring. +- 3) For a failure of the secondary node, the tributary at the terminating node (see Node A in Figure 7) is unaffected, since it receives its tributary from the primary node. Because of the ring signalling, the primary node knows that the secondary node has failed. The primary node chooses its tributary from the traffic entering it from the other ring. The secondary node has a failed tributary $R_S$ sent to the second ring. The failure of this signal may unavoidably lead to a switch in the second ring depending on its ring type. +- 4) For a failure of either of the signals coming in from the other ring (i.e. $T_{I1}$ or $T_{I2}$ ), the primary node in the MS-shared protection ring chooses the signal that is not failed. Figure 8 illustrates a failure of the hand-off to the secondary node. Here the primary node remains switched to its own good hand-off. Figure 9 illustrates a failure of the hand-off to the primary node. In this case, the primary node switches to choose a good tributary from the secondary node. +- 5) This architecture also protects against a single failure in each of the two rings (i.e. the MS-shared protection ring and the other ring), provided that these failures are not terminating node failures, or these failures do not combine to affect both interconnections between the rings. + +![Diagram of ring interworking with an MS-shared protection ring. The diagram shows a central 'MS-shared protection ring' with two concentric loops. The outer loop is labeled 'Working' and the inner loop is labeled 'Protection'. At the top, a tributary node 'A' is connected to the ring, with arrows labeled R_A and T_A. At the bottom, two nodes labeled 'Primary' and 'Secondary' are connected. The 'Primary' node has arrows labeled T_P and R_P. The 'Secondary' node has arrows labeled T_S and R_S. A switch symbol is shown on the line between the Primary and Secondary nodes. The diagram is labeled 'T1524360-96' in the bottom right corner.](4801720824e4b5e2361a5564f91cfb70_img.jpg) + +Diagram of ring interworking with an MS-shared protection ring. The diagram shows a central 'MS-shared protection ring' with two concentric loops. The outer loop is labeled 'Working' and the inner loop is labeled 'Protection'. At the top, a tributary node 'A' is connected to the ring, with arrows labeled R\_A and T\_A. At the bottom, two nodes labeled 'Primary' and 'Secondary' are connected. The 'Primary' node has arrows labeled T\_P and R\_P. The 'Secondary' node has arrows labeled T\_S and R\_S. A switch symbol is shown on the line between the Primary and Secondary nodes. The diagram is labeled 'T1524360-96' in the bottom right corner. + +Nominal failure free state of A-Z tributary in MS-shared protection ring: + +$$R_P = R_S = T_A$$ + +$$R_A = T_P = (T_S)$$ + +**Figure 4/G.842 – Ring interworking with an MS-shared protection ring** + +![Diagram of an MS-shared protection ring showing signal response to a failure. The ring consists of a 'Working' path (solid line) and a 'Protection' path (dashed line). Nodes are labeled 'A' (top), 'Primary' (bottom left), and 'Secondary' (bottom right). A cable cut is shown between the Primary node and Node A, marked with a large 'X'. Signal paths are shown entering and leaving the nodes. At Node A, signals are labeled RA and TA. At the Primary node, signals are labeled TP and RP. At the Secondary node, signals are labeled TS and RS. The text 'MS-shared protection ring' is in the center. A reference code 'T1524370-96' is at the bottom right. Below the diagram are two equations: RP = RS = TA and RA = TP = (TS).](33ed1f9b27c7c21c797aa928b0f06851_img.jpg) + +$$R_P = R_S = T_A$$ + +$$R_A = T_P = (T_S)$$ + +Diagram of an MS-shared protection ring showing signal response to a failure. The ring consists of a 'Working' path (solid line) and a 'Protection' path (dashed line). Nodes are labeled 'A' (top), 'Primary' (bottom left), and 'Secondary' (bottom right). A cable cut is shown between the Primary node and Node A, marked with a large 'X'. Signal paths are shown entering and leaving the nodes. At Node A, signals are labeled RA and TA. At the Primary node, signals are labeled TP and RP. At the Secondary node, signals are labeled TS and RS. The text 'MS-shared protection ring' is in the center. A reference code 'T1524370-96' is at the bottom right. Below the diagram are two equations: RP = RS = TA and RA = TP = (TS). + +**Figure 5/G.842 – Signal response to any ring failure outside of termination, primary, or secondary nodes (cable cut between primary and Node A shown)** + +![Diagram of an MS-shared protection ring showing signal response to a complete primary node failure. The diagram includes a 'Working' ring and a 'Protection' ring. Node A at the top has transmit (TA) and receive (RA) ports. Node 'Primary' at the bottom left is crossed out with an 'X', indicating failure, with transmit (Tp) and receive (Rp) ports. Node 'Secondary' at the bottom right has transmit (Ts) and receive (Rs) ports. Arrows show signal paths: from TA to RA, from RA into the protection ring, from the protection ring to Ts, from Ts to Rs, and from Rs back into the protection ring. The label 'MS-shared protection ring' is in the center. A reference code 'T1524380-96' is at the bottom right of the diagram.](fa859e4e468bfb2710a94527f2c504af_img.jpg) + +$R_A = T_S$ + $R_S = T_A$ + $R_p = T_p = 0$ + +Diagram of an MS-shared protection ring showing signal response to a complete primary node failure. The diagram includes a 'Working' ring and a 'Protection' ring. Node A at the top has transmit (TA) and receive (RA) ports. Node 'Primary' at the bottom left is crossed out with an 'X', indicating failure, with transmit (Tp) and receive (Rp) ports. Node 'Secondary' at the bottom right has transmit (Ts) and receive (Rs) ports. Arrows show signal paths: from TA to RA, from RA into the protection ring, from the protection ring to Ts, from Ts to Rs, and from Rs back into the protection ring. The label 'MS-shared protection ring' is in the center. A reference code 'T1524380-96' is at the bottom right of the diagram. + +**Figure 6/G.842 – Signal response to complete primary node failure** + +![Diagram of an MS-shared protection ring showing signal response to a complete secondary node failure. The diagram includes a 'Working' path and a 'Protection' path. Nodes are labeled 'A', 'Primary', and 'Secondary' (which is crossed out). Signal paths are labeled with RA, TA, TP, RP, TS, and RS. The text 'MS-shared protection ring' is in the center. A reference code 'T1524390-96' is in the bottom right.](8fbdfc3d17fb1dae7b2d8f5a287fa9fc_img.jpg) + +MS-shared protection ring + +T1524390-96 + +$$R_A = T_P$$ +$$R_P = T_A$$ +$$R_S = T_S = 0$$ + +Diagram of an MS-shared protection ring showing signal response to a complete secondary node failure. The diagram includes a 'Working' path and a 'Protection' path. Nodes are labeled 'A', 'Primary', and 'Secondary' (which is crossed out). Signal paths are labeled with RA, TA, TP, RP, TS, and RS. The text 'MS-shared protection ring' is in the center. A reference code 'T1524390-96' is in the bottom right. + +**Figure 7/G.842 – Signal response to complete secondary node failure** + +![Diagram of an MS-shared protection ring showing a failure at the secondary node. The ring consists of a 'Working' path and a 'Protection' path. Node A is at the top, with transmit (TA) and receive (RA) ports. Node Primary is at the bottom left, with transmit (Tp) and receive (Rp) ports. Node Secondary is at the bottom right, with transmit (Ts) and receive (Rs) ports. A failure is indicated by an 'X' on the transmit line at the Secondary node. Arrows show the flow of signals around the ring. The label 'MS-shared protection ring' is in the center. A reference code 'T1524400-96' is in the bottom right corner of the diagram area.](76b0cd79baaedd942af4dc42f2e764b8_img.jpg) + +Diagram of an MS-shared protection ring showing a failure at the secondary node. The ring consists of a 'Working' path and a 'Protection' path. Node A is at the top, with transmit (TA) and receive (RA) ports. Node Primary is at the bottom left, with transmit (Tp) and receive (Rp) ports. Node Secondary is at the bottom right, with transmit (Ts) and receive (Rs) ports. A failure is indicated by an 'X' on the transmit line at the Secondary node. Arrows show the flow of signals around the ring. The label 'MS-shared protection ring' is in the center. A reference code 'T1524400-96' is in the bottom right corner of the diagram area. + +$$\begin{aligned} + R_A &= T_P \\ + R_P &= R_S = T_A \\ + T_S &= 0 + \end{aligned}$$ + +**Figure 8/G.842 – Failure of the transmit hand-off at the secondary node** + +![Diagram of an MS-shared protection ring showing a failure at the primary node. Node A is at the top, connected to a 'Working' channel (outer ring) and a 'Protection' channel (inner ring). Below it are 'Primary' and 'Secondary' nodes. At the Primary node, the transmit hand-off from the working channel to the protection channel is failed, indicated by a crossed-out switch symbol. Arrows show signal flow: from A to Primary, from Primary to Secondary, and from Secondary back to A. At node A, signals RA and TA are shown. At the Primary node, TP is failed, and RP is the received signal. At the Secondary node, TS and RS are shown. The diagram is labeled 'MS-shared protection ring' and 'T1524410-96'.](9c6461e1e94afae4dec455e69a2ce152_img.jpg) + +$R_A = T_P$ + $R_P = R_S = T_A$ + $T_S = 0$ + +Diagram of an MS-shared protection ring showing a failure at the primary node. Node A is at the top, connected to a 'Working' channel (outer ring) and a 'Protection' channel (inner ring). Below it are 'Primary' and 'Secondary' nodes. At the Primary node, the transmit hand-off from the working channel to the protection channel is failed, indicated by a crossed-out switch symbol. Arrows show signal flow: from A to Primary, from Primary to Secondary, and from Secondary back to A. At node A, signals RA and TA are shown. At the Primary node, TP is failed, and RP is the received signal. At the Secondary node, TS and RS are shown. The diagram is labeled 'MS-shared protection ring' and 'T1524410-96'. + +**Figure 9/G.842 – Failure of the transmit hand-off at the primary node** + +##### 6.2.2.1.1 Routing with all traffic on working channels + +For the unidirectional signal transmitted from the node A, the primary node dual feeds that signal both towards its own interface and towards the multiplex section to the secondary node. This function is often referred to as drop-and-continue. In the other direction, the primary node selects, via a service selector, between the hand-offs to the primary and secondary nodes from the other ring, and transmits that selection to the upper terminating node. The interconnections are at the STM-1 electrical or STM-N optical level. The same channel assignment on the multiplex section used between the secondary and primary nodes is the same as that used between the primary and terminating nodes. Figures 10 and 11 give two ring interworking examples. Interworking of an MS-shared protection ring with a lower order SNCP ring may require further study. With the switching criteria from 6.2.2.3 and squelching logic from 6.2.2.4, this interconnection architecture provides protection against the failure of one or both interconnecting nodes (each on different rings, but on the same interconnect), or the connection between the two interconnecting nodes. Furthermore, the interconnection architecture does not require inter-ring signalling. + +![Diagram of ring interworking between two MS-shared protection rings. The diagram shows two stacked rings, each labeled 'MS-shared protection ring'. Each ring has a Primary node (P) and a Secondary node (S). The nodes are connected by a Service Selector (SS). Arrows indicate the flow of traffic within and between the rings. A legend at the bottom left defines the symbols: P for Primary node, S for Secondary node, and SS for Service Selector. The text 'T1524420-96' is in the bottom right.](b6671cfafda3820aafe9a24fa7a4d8c7_img.jpg) + +P Primary node + S Secondary node + SS Service Selector + +T1524420-96 + +Diagram of ring interworking between two MS-shared protection rings. The diagram shows two stacked rings, each labeled 'MS-shared protection ring'. Each ring has a Primary node (P) and a Secondary node (S). The nodes are connected by a Service Selector (SS). Arrows indicate the flow of traffic within and between the rings. A legend at the bottom left defines the symbols: P for Primary node, S for Secondary node, and SS for Service Selector. The text 'T1524420-96' is in the bottom right. + +**Figure 10/G.842 – Ring interworking between two MS-shared protection rings** + +![Diagram of ring interworking between an MS-shared protection ring and a HO SNCP ring. The diagram shows two concentric rings. The outer ring is labeled 'MS-shared protection ring' and the inner ring is labeled 'SNC protection ring'. Nodes are represented by rectangles. On the left, a node contains a 'PS' (Path Selector). In the center, a node contains an 'SS' (Service Selector) and a 'PS'. On the right, a node contains a 'PS'. Arrows indicate traffic flow. Labels 'P' (Primary node) and 'S' (Secondary node) are above the central node. A reference code 'T1524430-96' is in the bottom right. A legend at the bottom left defines the symbols: P Primary node, S Secondary node, SS Service Selector, PS Path Selector.](5b8a756d9a71c35f17db8bcb90b438a3_img.jpg) + +P Primary node +S Secondary node +SS Service Selector +PS Path Selector + +T1524430-96 + +Diagram of ring interworking between an MS-shared protection ring and a HO SNCP ring. The diagram shows two concentric rings. The outer ring is labeled 'MS-shared protection ring' and the inner ring is labeled 'SNC protection ring'. Nodes are represented by rectangles. On the left, a node contains a 'PS' (Path Selector). In the center, a node contains an 'SS' (Service Selector) and a 'PS'. On the right, a node contains a 'PS'. Arrows indicate traffic flow. Labels 'P' (Primary node) and 'S' (Secondary node) are above the central node. A reference code 'T1524430-96' is in the bottom right. A legend at the bottom left defines the symbols: P Primary node, S Secondary node, SS Service Selector, PS Path Selector. + +**Figure 11/G.842 – Ring interworking between an MS-shared protection ring and a HO SNCP ring** + +##### **6.2.2.1.2 Routing with continue traffic on protection channels between primary and secondary nodes** + +This describes general considerations associated with using protection bandwidth for ring interconnection. Further details of ring interworking using protection bandwidth are under study. + +This alternative method to ring interworking takes advantage of the protection bandwidth between primary and secondary ring interworking nodes to address the capacity issue that arises when drop-and-continue in conjunction with a service selector is used for ring interconnection on an MS-shared protection ring. This is illustrated in Figure 12. The issue is one of early bandwidth exhaust between primary and secondary nodes when using only working bandwidth for drop-and-continue in conjunction with a service selector. + +The problem can be illustrated by referring to Figure 10, which shows two interconnected MS-shared protection rings. The two interconnecting ring nodes in each MS-shared protection ring use the working bandwidth for the extra circuit between them that allows for dual node ring interworking, i.e. the combination of the "continue" portion of the drop-and-continue (from the primary to the secondary node), along with the duplicate feed from the other ring (from the secondary node to the service selector in the primary node). This extra circuit is called the secondary circuit. + +By taking advantage of the protection bandwidth between the interconnection nodes on the MS-shared protection ring, less working bandwidth would be consumed as compared to the method of using only working bandwidth for ring interconnection. For example, either one, or both, of the secondary circuits in Figure 10 can use the protection bandwidth between the primary and secondary nodes, instead of using the working bandwidth. The protection bandwidth between the primary and secondary nodes on an MS-shared protection ring can be used even if the other interconnected ring is an SNCP ring (see Figure 11). + +The following options for ring interworking using combinations of working and protection bandwidth between interconnecting ring nodes (i.e. between primary and secondary nodes) are possible: + +- a) ring interconnection using working bandwidth only; +- b) ring interconnection using working bandwidth in one ring and protection bandwidth in the other; and +- c) ring interconnection using protection bandwidth in both rings. + +These ring interworking options may be used on interconnected rings with either same-side or opposite-side routing. Same-side routing is illustrated in Figure 10, while opposite-side routing is illustrated in Figure 6. Note that same-side routing requires two extra, or secondary circuits, i.e. one per ring, for dual node interworking (see Figure 10), while opposite-side routing requires only one extra, or secondary circuit (see Figure 13). In the bottom ring of Figure 13, the traffic already passes through both the primary and secondary nodes for opposite-side ring interworking; this is known as the service circuit. For opposite-side routing, extra bandwidth for a secondary circuit is only used in one ring (e.g. the top ring in Figure 13). + +The option of using only working bandwidth provides the highest level of survivability. If less survivability can be tolerated, certain options that take advantage of protection bandwidth between interconnecting ring nodes may be used, including: + +- a) same-side ring interworking with one secondary circuit on working and one secondary circuit on protection; +- b) same-side ring interworking with both secondary circuits on protection; +- c) opposite-side ring interworking with the service circuit on working and the secondary circuit on protection. + +Assigning the service circuit to protection bandwidth in opposite-side ring interworking is not recommended. + +![Diagram of ring interworking using protection capacity. It shows a dual-ring system (Working and Protection) with three nodes: A, Primary, and Secondary. Node A is at the top, connected to the Working ring via TA and RA. Node Primary is at the bottom left, connected to the Protection ring via TP and RP. Node Secondary is at the bottom right, connected to the Protection ring via TS and RS. Arrows indicate the flow of data between the rings and the nodes. The diagram is labeled 'MS-shared protection ring' and 'T1524440-96'.](c914f51f4427bc672dd0526cfc90ebe9_img.jpg) + +Diagram of ring interworking using protection capacity. It shows a dual-ring system (Working and Protection) with three nodes: A, Primary, and Secondary. Node A is at the top, connected to the Working ring via TA and RA. Node Primary is at the bottom left, connected to the Protection ring via TP and RP. Node Secondary is at the bottom right, connected to the Protection ring via TS and RS. Arrows indicate the flow of data between the rings and the nodes. The diagram is labeled 'MS-shared protection ring' and 'T1524440-96'. + +Nominal failure free state of A-Z tributary in MS-shared protection ring: + +$$R_P = R_S = T_A$$ + +$$R_A = T_P = (T_S)$$ + +Tributary assignment for secondary connection = Protection tributary for working path + +**Figure 12/G.842 – Ring interworking using protection capacity** + +![Diagram of ring interworking between two MS-shared protection rings with opposite-side routing. The diagram shows two rings connected by four nodes: P1, S1, S2, and P2. A 'Service circuit' is shown between P1 and S2, and a 'Secondary circuit' is shown between S1 and P2. Nodes P1 and S2 contain 'SS' (Service Selector) blocks. Arrows indicate signal flow, including 'Drop and continue' points at nodes A and the bottom node. A legend defines P as Primary node, S as Secondary node, SS as Service Selector, and the arrow symbol as Drop and continue. Reference T1524450-96 is noted in the bottom right.](c5452f95f3b28f1bfe29e84fbc2e1267_img.jpg) + +P Primary node + S Secondary node + [SS] Service Selector + ⬆ Drop and continue + +T1524450-96 + +Diagram of ring interworking between two MS-shared protection rings with opposite-side routing. The diagram shows two rings connected by four nodes: P1, S1, S2, and P2. A 'Service circuit' is shown between P1 and S2, and a 'Secondary circuit' is shown between S1 and P2. Nodes P1 and S2 contain 'SS' (Service Selector) blocks. Arrows indicate signal flow, including 'Drop and continue' points at nodes A and the bottom node. A legend defines P as Primary node, S as Secondary node, SS as Service Selector, and the arrow symbol as Drop and continue. Reference T1524450-96 is noted in the bottom right. + +**Figure 13/G.842 – Ring interworking between two MS-shared protection rings, with opposite-side routing** + +#### 6.2.2.2 Functional model + +Figures 14 and 15 illustrate the functional model associated with a primary node in an MS-shared protection ring. In this example, an electrical STM-1 signal is connected at the tributary side of the ADM equipment and two STM-N optical signals are connected at both west and east line sides. + +A HOVC out of the STM-1 signal has a 1 + 1 SNC protection relation with a HOVC out of the west STM-N signal; the selected HOVC signal is connected to the east STM-N signal. In the other direction the associated HOVC at the east STM-N signal is dual-fed to both the STM-1 and west STM-N signals. + +For the case of SNC/N protection (Figure 15), the HOVC out of the STM-1 is also connected to the interface with a HPOM function. Similarly, the HOVC out of the west STM-N is connected also to a HPOM function. + +Figure 16 illustrates the matrix connections within the HPC that realise the "service selector". For the case of SNC/I three matrix connections are required: (1) .. (3). For the case of SNC/N five matrix connections are required: (1) .. (5). + +NOTE – The HPC interfaces A, B, C, D, E in Figure 16 represent the same interfaces in Figures 14 and 15. + +![Functional model diagram for a network element with a service selector of type SNC/I. The diagram shows signal paths from external interfaces (Trib, West, East) through various processing stages (MS1, RSI, ES1, MSn, RSn, OSn) into a central HPC (High Path Controller) and MSnP (Multiplex Section Protection) matrix. The HPC is connected to an 'SNC/I type service selector' which includes interfaces A, B, and C. Signal paths are shown entering the HPC from the left (Trib path) and right (West and East paths), passing through the MSnP matrix, and then being directed by the HPC to the appropriate output interfaces.](e354b57563dae469c00b412b2abdf765_img.jpg) + +The diagram illustrates the functional model for a network element with a service selector of type SNC/I. At the top, an oval labeled 'HPC' (High Path Controller) is shown. To its left, a shaded area labeled 'SNC/I type service selector' contains three interfaces: A, B, and C. Interface A is connected to a 'MS1/HP' block, which is part of a path coming from 'Trib' (Tributary) through 'ES1', 'RS1', and 'MS1' blocks. Interface B is connected to a 'MSn/HP' block, which is part of a path coming from 'West' through 'OSn', 'RSn', 'MSn', and 'MSn/MSnP' blocks. Interface C is connected to another 'MSn/HP' block, which is part of a path coming from 'East' through 'OSn', 'RSn', 'MSn', and 'MSn/MSnP' blocks. Below the HPC, there is a large oval labeled 'MSnP' (Multiplex Section Protection). The 'MSn/HP' blocks from interfaces B and C connect to the 'MSnP' matrix. The 'MSnP' matrix has four output ports labeled 'W' (West) and 'P' (Protection) on both the left and right sides. These ports connect to 'MSn/MSnP' blocks, which then connect to 'MSn' blocks, 'RSn' blocks, and finally 'OSn' blocks, leading to the 'West' and 'East' interfaces. Dashed arrows labeled 'SSF' (Service Selector Function) point from the HPC to the 'MS1/HP' and 'MSn/HP' blocks. + +Functional model diagram for a network element with a service selector of type SNC/I. The diagram shows signal paths from external interfaces (Trib, West, East) through various processing stages (MS1, RSI, ES1, MSn, RSn, OSn) into a central HPC (High Path Controller) and MSnP (Multiplex Section Protection) matrix. The HPC is connected to an 'SNC/I type service selector' which includes interfaces A, B, and C. Signal paths are shown entering the HPC from the left (Trib path) and right (West and East paths), passing through the MSnP matrix, and then being directed by the HPC to the appropriate output interfaces. + +**Figure 14/G.842 – Example of functional model for network element with service selector of type SNC/I** + +![Functional model for network element with service selector of type SNC/N. The diagram shows a hierarchy of network elements. At the top, an 'SNC/N type service selector' box contains two 'HPOM' (High Performance Optical Module) units. These are connected to a central 'HPC' (High Performance Controller) oval. Below the HPC is an 'SSF' (Service Switching Function) oval. Below the SSF are five 'MSn/HP' (Multi-Service High Performance) units. The first is labeled 'MS1/HP' and the others 'MSn/HP'. Each 'MSn/HP' is connected to an 'MSnP' (Multi-Service Packet) unit. All five 'MSnP' units are connected to a central 'MSnP' oval. Below this oval are two 'MSn/MSnP' (Multi-Service Multi-Packet) units, labeled 'W P' and 'P W'. The left 'MSn/MSnP' is connected to a vertical stack: 'MSn', 'RSn', 'OSn', and finally 'West'. The right 'MSn/MSnP' is connected to a similar stack: 'MSn', 'RSn', 'OSn', and finally 'East'. The 'MS1/HP' unit is connected to a vertical stack: 'MS1', 'RS1', 'ES1', and finally 'Trib'. Arrows labeled A, B, C, D, and E indicate various signal paths. A small box with a switch symbol is shown on the HPC oval. The text 'T1524280-96' is in the bottom right corner.](cbdfdade780e677eb1c1aef3081ce9ef_img.jpg) + +Functional model for network element with service selector of type SNC/N. The diagram shows a hierarchy of network elements. At the top, an 'SNC/N type service selector' box contains two 'HPOM' (High Performance Optical Module) units. These are connected to a central 'HPC' (High Performance Controller) oval. Below the HPC is an 'SSF' (Service Switching Function) oval. Below the SSF are five 'MSn/HP' (Multi-Service High Performance) units. The first is labeled 'MS1/HP' and the others 'MSn/HP'. Each 'MSn/HP' is connected to an 'MSnP' (Multi-Service Packet) unit. All five 'MSnP' units are connected to a central 'MSnP' oval. Below this oval are two 'MSn/MSnP' (Multi-Service Multi-Packet) units, labeled 'W P' and 'P W'. The left 'MSn/MSnP' is connected to a vertical stack: 'MSn', 'RSn', 'OSn', and finally 'West'. The right 'MSn/MSnP' is connected to a similar stack: 'MSn', 'RSn', 'OSn', and finally 'East'. The 'MS1/HP' unit is connected to a vertical stack: 'MS1', 'RS1', 'ES1', and finally 'Trib'. Arrows labeled A, B, C, D, and E indicate various signal paths. A small box with a switch symbol is shown on the HPC oval. The text 'T1524280-96' is in the bottom right corner. + +**Figure 15/G.842 – Example of functional model for network element with service selector of type SNC/N** + +![Service selector's HPC connectivity diagrams. The left diagram shows a 'Selector (1+1 SNC)' within a dashed box. It has three input/output points: 'A' at the bottom, 'B' on the right, and 'C' on the left. Path (1) is a direct line from A to C. Path (2) is a line from A to B. Path (3) is a line from C to B. The right diagram shows the same 'Selector (1+1 SNC)' but with additional connections. It has four input/output points: 'A' at the bottom, 'B' on the right, 'C' on the left, and 'D' and 'E' at the top. Path (1) is from A to C. Path (2) is from A to B. Path (3) is from C to B. Path (4) is from A to D. Path (5) is from A to E. The text 'T1524290-96' is in the bottom right corner.](5a1abd59a95fa47ae192807de151e9eb_img.jpg) + +Service selector's HPC connectivity diagrams. The left diagram shows a 'Selector (1+1 SNC)' within a dashed box. It has three input/output points: 'A' at the bottom, 'B' on the right, and 'C' on the left. Path (1) is a direct line from A to C. Path (2) is a line from A to B. Path (3) is a line from C to B. The right diagram shows the same 'Selector (1+1 SNC)' but with additional connections. It has four input/output points: 'A' at the bottom, 'B' on the right, 'C' on the left, and 'D' and 'E' at the top. Path (1) is from A to C. Path (2) is from A to B. Path (3) is from C to B. Path (4) is from A to D. Path (5) is from A to E. The text 'T1524290-96' is in the bottom right corner. + +**Figure 16/G.842 – Service selector's HPC connectivity** + +#### 6.2.2.3 Switching criteria and operation + +At the primary node, a service selector is used to select the better of two incoming tributaries, i.e. the tributary from the interconnecting line or the tributary from the secondary node. The service selectors trigger on path layer criteria. The hierarchy of conditions for MS-shared protection ring service selection switch initiation is listed in Table 1. The switching hierarchy must select the least impacted signal under multiple failures occurring at different levels on the same path. + +**Table 1/G.842 – Hierarchy of conditions for service selector (see Note 3)** + +| Condition | Priority (see Note 1) | +|-----------------------------------------------------------------------------------------------------------------------------------------|-----------------------| +| AIS, LOP, UNEQ defect, TIM (optional), or server signal fail (see Note 2) | 1 (hard failure) | +| Excessive error defect (optional) | 2 (hard failure) | +| Signal degrade | 3 | +| NOTE 1 – The highest priority (1) corresponds to the worst impairment, and the lowest priority (3) corresponds to the least impairment. | | +| NOTE 2 – Server signal fail arises as a result of section defects; e.g. LOS, LOF. | | +| NOTE 3 – For the case of SNC/I, only AIS, LOP, or server signal fail are applicable. | | + +The service selector shall be capable of revertive or non-revertive operation. To have a known failure-free state, it may be desirable to have the service selector be revertive. In the case of conditions of identical severity arriving on both incoming tributaries, the service selector shall select the preferred route in the case of revertive operation, or the current (i.e. active or currently selected) route in the case of non-revertive operation. This may be subject to a hold-off time. + +In a future revision, when Recommendations G.841, G.783, and this Recommendation are aligned, Table 1 can be replaced by a reference to Recommendations G.841 and G.783. + +#### 6.2.2.4 Squelching logic + +For the case of the failure of the primary node, the connection of the signal between the termination A and the secondary node is maintained. This is called a secondary connection. + +An MS-shared protection ring providing the sort of ring interworking described here must be provisionable on a per channel basis to allow a secondary connection or to squelch the traffic in the case of a node failure as required for the particular application and circuit. The squelching for a ring interworking circuit is simply based on the failure of either of the endpoints for the interconnected circuit, because a switching node should squelch the channel in Figure 4 if and only if node A fails or the secondary node fails. If the secondary node fails and the primary node is the switching node, observe that the primary squelches bidirectionally with respect to the signal towards the secondary node, but that the bidirectional connection from the primary node to node A is maintained. + +The rules for squelching logic when interworking using protection capacity are for further study. + +### 6.2.3 Ring interworking with an SNCP ring + +#### 6.2.3.1 Architecture + +Figure 17 shows the architecture of SNCP ring interworking. For each direction of transmission, the signal is dual-fed from the source node around both sides of the ring. When each of the dual-fed signals hits an interconnection node, it is dropped at that node and continued onto the other interconnection node using the drop-and-continue feature. Thus, each interconnection node can select + +from two signals sent on a different way around the ring. The output of the selector in each interconnection node is then transmitted to the second ring. Each of the interconnection nodes in the second ring takes its respective signal and transmits it towards the sink node, away from the other interconnection node. Finally, the sink node makes the selection between the two signals from the two directions around the ring. + +Due to the symmetry of this scheme, the two interconnection nodes are completely equivalent. + +Interworking between higher order SNCP rings and lower order SNCP rings may require further study. + +Some examples of reconfiguration in case of failure are shown in Figures 18 through 23: + +- Figure 18 shows a bidirectional span failure in one ring; +- Figure 19 shows a bidirectional failure of one interconnection link; +- Figure 20 shows a nodal failure at one interconnection point; +- Figure 21 shows a bidirectional failure between interconnecting nodes on the same ring; +- Figures 22 and 23 show unidirectional failures in each direction assuming unidirectional working of SNCP. + +In each figure, the nodes where switching should occur to restore the interworking traffic are shadowed. Due to different switching time of network elements, different final configurations are possible (see clause 8). + +![Diagram of SNCP ring interworking architecture showing two interconnected rings with path selectors and external connections.](69b7bd65e85cdef6fdd7fb0a8194257c_img.jpg) + +The diagram illustrates the SNCP ring interworking architecture. It features two rectangular rings, each labeled "SNC protection ring". The rings are interconnected by two horizontal lines. Each ring has four corner nodes, each represented by a square box. At each corner node, there is a path selector symbol, which is a switch-like icon with two selectable paths. The top ring has an external connection at its top center, and the bottom ring has an external connection at its bottom center. Arrows indicate the direction of signal flow within the rings and at the external connections. A small text label "T1524460-96" is located in the bottom right corner of the diagram area. + +Path selector + +T1524460-96 + +Diagram of SNCP ring interworking architecture showing two interconnected rings with path selectors and external connections. + +Figure 17/G.842 – SNCP ring interworking architecture + +![Diagram illustrating interworking between two SNCP protection rings with a bidirectional failure in one ring. The diagram shows two stacked rectangular rings. The top ring is labeled 'SNC protection ring' and has a bidirectional failure on its left vertical segment, marked with an 'X'. The bottom ring is also labeled 'SNC protection ring'. Both rings have four corner nodes and two central nodes. The central nodes in the top ring are shaded gray, while those in the bottom ring are white. Arrows indicate the direction of signal flow. A legend at the bottom left shows a 'Path selector' symbol. A reference code 'T1524470-96' is in the bottom right of the diagram area. Path selector symbol](11edb7fcedf09ac6a817f8d7b8c61eec_img.jpg) + +SNC protection ring + +SNC protection ring + +T1524470-96 + +Path selector + +Diagram illustrating interworking between two SNCP protection rings with a bidirectional failure in one ring. The diagram shows two stacked rectangular rings. The top ring is labeled 'SNC protection ring' and has a bidirectional failure on its left vertical segment, marked with an 'X'. The bottom ring is also labeled 'SNC protection ring'. Both rings have four corner nodes and two central nodes. The central nodes in the top ring are shaded gray, while those in the bottom ring are white. Arrows indicate the direction of signal flow. A legend at the bottom left shows a 'Path selector' symbol. A reference code 'T1524470-96' is in the bottom right of the diagram area. Path selector symbol + +**Figure 18/G.842 – Interworking between SNCP rings: bidirectional failure in one ring** + +![Diagram showing interworking between two SNCP protection rings with a bidirectional failure at one interconnection point. The diagram includes two rings, each with two path selectors at the top and bottom. The rings are interconnected by four nodes in the center. One of these interconnection nodes is marked with an 'X', indicating a failure. Arrows show the flow of signals within the rings and through the interconnection points. A legend at the bottom left shows a path selector symbol and the text 'Path selector'. A small code 'T1524480-96' is in the bottom right of the diagram area.](c494cd874a082a97b50b3c4d3938f467_img.jpg) + +SNC protection ring + +SNC protection ring + +T1524480-96 + +Path selector + +Diagram showing interworking between two SNCP protection rings with a bidirectional failure at one interconnection point. The diagram includes two rings, each with two path selectors at the top and bottom. The rings are interconnected by four nodes in the center. One of these interconnection nodes is marked with an 'X', indicating a failure. Arrows show the flow of signals within the rings and through the interconnection points. A legend at the bottom left shows a path selector symbol and the text 'Path selector'. A small code 'T1524480-96' is in the bottom right of the diagram area. + +**Figure 19/G.842 – Interworking between SNCP rings: +bidirectional failure of one interconnection point** + +![Diagram showing the interconnection between two SNCP protection rings with a failure of one interconnection node.](692541e65db4dc852988ce77ebb60ce5_img.jpg) + +The diagram illustrates two SNCP protection rings, each represented by a rectangular loop of two parallel lines with arrows indicating bidirectional traffic. The rings are interconnected by several nodes, which are depicted as rectangular boxes containing switching symbols. One of these interconnection nodes is marked with a large 'X', indicating a failure. The text 'SNCP protection ring' is placed inside each loop. At the top and bottom of the diagram, external lines enter the rings through nodes. A label 'T1524490-96' is located in the bottom right corner of the diagram area. + +Diagram showing the interconnection between two SNCP protection rings with a failure of one interconnection node. + +![Path selector symbol](a5781e6cd2b5189286866604dfad6f5d_img.jpg) + +A symbol consisting of a vertical line with three horizontal branches at the top, and two vertical branches at the bottom, each ending in a small circle. This represents a path selector component. + +Path selector symbol + +Path selector + +**Figure 20/G.842 – Interconnection between SNCP rings: +failure of one interconnection node** + +![Diagram of interworking between two SNCP protection rings with a bidirectional failure between interconnecting nodes.](08dce7ad4c512fdf0c0cde60415fade6_img.jpg) + +The diagram illustrates the interworking of two SNCP protection rings. Each ring is represented by a rectangular loop of two parallel lines, with the label "SNC protection ring" centered within each loop. The rings are connected at two points. At the top connection point, a failure is indicated by a large 'X' over the lines. The nodes at this connection are shown as boxes containing path selector symbols (a switch-like icon with multiple contacts). The bottom connection point also features path selector symbols. External connections are shown at the top and bottom of the diagram, entering the rings through path selector symbols. A small label "T1524500-96" is located in the bottom right corner of the diagram area. + +Path selector + +Diagram of interworking between two SNCP protection rings with a bidirectional failure between interconnecting nodes. + +**Figure 21/G.842 – Interworking between SNCP rings: +bidirectional failure between interconnecting nodes on the same ring** + +![Diagram of interworking between two SNCP protection rings. The top ring is labeled 'SNC protection ring' and contains 'Node A'. The bottom ring is also labeled 'SNC protection ring' and contains 'Node B'. A unidirectional failure is indicated by an 'X' on the left side of the top ring. The diagram shows signal paths and path selectors at various nodes. A legend at the bottom left shows a path selector symbol and the text 'Path selector'. A reference code 'T1524510-96' is in the bottom right.](7ae836e598020d937ed1478c2ef13025_img.jpg) + +Node A + +SNC protection ring + +SNC protection ring + +Node B + +T1524510-96 + +Path selector + +Diagram of interworking between two SNCP protection rings. The top ring is labeled 'SNC protection ring' and contains 'Node A'. The bottom ring is also labeled 'SNC protection ring' and contains 'Node B'. A unidirectional failure is indicated by an 'X' on the left side of the top ring. The diagram shows signal paths and path selectors at various nodes. A legend at the bottom left shows a path selector symbol and the text 'Path selector'. A reference code 'T1524510-96' is in the bottom right. + +**Figure 22/G.842 – Interworking between SNCP rings: +unidirectional failure from Node B to Node A** + +![Diagram illustrating the interworking between two SNCP protection rings. The top ring is labeled 'SNC protection ring' and contains 'Node A'. The bottom ring is also labeled 'SNC protection ring' and contains 'Node B'. The rings are interconnected by two intermediate nodes. A failure is indicated by an 'X' on the left side of the top ring. Arrows show the signal flow, which is rerouted around the failure. A legend at the bottom left shows a switch symbol labeled 'Path selector'. A reference code 'T1524520-96' is in the bottom right of the diagram area.](f9c64800d9bace9b4315646d1057be3c_img.jpg) + +Diagram illustrating the interworking between two SNCP protection rings. The top ring is labeled 'SNC protection ring' and contains 'Node A'. The bottom ring is also labeled 'SNC protection ring' and contains 'Node B'. The rings are interconnected by two intermediate nodes. A failure is indicated by an 'X' on the left side of the top ring. Arrows show the signal flow, which is rerouted around the failure. A legend at the bottom left shows a switch symbol labeled 'Path selector'. A reference code 'T1524520-96' is in the bottom right of the diagram area. + +**Figure 23/G.842 – Interworking between SNCP rings: +unidirectional failure from Node A to Node B** + +#### **6.2.3.2 Functional model** + +Figures 24 and 25 illustrate the functional model associated with an interconnecting node in an LO SNC protected ring. In this example, an electrical STM-1 signal is connected at the tributary side of the ADM equipment and two STM-N optical signals are connected at both west and east line sides. + +A LOVC out of the east STM-N signal has a 1+1 SNC protection relation with a LOVC out of the west STM-N signal; the selected LOVC signal is connected to the STM-1 signal. In the other direction the associated LOVC in the STM-1 signal is connected to the east STM-N signal. The received LOVC in the east STM-N signal is also connected to the west STM-N signal. + +For the case of SNC/N protection (Figure 25), the LOVC signals out of the east and west STM-N signals are also connected to interfaces with a LPOM function. + +Figure 26 illustrates the matrix connections within the LPC that realise the "path selector". For the case of SNC/I three matrix connections are required: (1) .. (3). For the case of SNC/N five matrix connections are required: (1) .. (5). + +NOTE – The LPC interfaces A, B, C, D, E in Figure 26 represent the same interfaces in Figures 16 and 24. + +![Functional model diagram for a network element with a path selector of type SNC/I. The diagram shows three vertical signal paths. The left path (Trib) consists of ES1, RS1, MS1, MS1/HP, HP, HP/LP, and SSF interfaces. The middle path (West) consists of OSn, RSn, MSn, MSn/HP, HP, HP/LP, and SSF interfaces. The right path (East) consists of OSn, RSn, MSn, MSn/HP, HP, HP/LP, and SSF interfaces. All three paths connect to a central 'SNC/I type path selector' (LPC) block. The LPC has three output interfaces labeled A, B, and C. Interface A connects to the left path's HP/LP. Interface B connects to the middle path's HP/LP. Interface C connects to the right path's HP/LP. The LPC also has internal connections between these interfaces, represented by lines within the shaded LPC block.](1cac1845cf99a3f64ae00cd2bb4f9ed7_img.jpg) + +Functional model diagram for a network element with a path selector of type SNC/I. The diagram shows three vertical signal paths. The left path (Trib) consists of ES1, RS1, MS1, MS1/HP, HP, HP/LP, and SSF interfaces. The middle path (West) consists of OSn, RSn, MSn, MSn/HP, HP, HP/LP, and SSF interfaces. The right path (East) consists of OSn, RSn, MSn, MSn/HP, HP, HP/LP, and SSF interfaces. All three paths connect to a central 'SNC/I type path selector' (LPC) block. The LPC has three output interfaces labeled A, B, and C. Interface A connects to the left path's HP/LP. Interface B connects to the middle path's HP/LP. Interface C connects to the right path's HP/LP. The LPC also has internal connections between these interfaces, represented by lines within the shaded LPC block. + +**Figure 24/G.842 – Example of functional model for network element with path selector of type SNC/I** + +![Functional model for network element with path selector of type SNC/N. The diagram shows a central LPC (Linear Path Controller) connected to three vertical paths: Trib (left), West (middle), and East (right). Each path consists of a stack of functional blocks: ES1/RS1/MS1/HP/HP/LP (Trib), OSn/RSn/MSn/HP/HP/LP (West), and OSn/RSn/MSn/HP/HP/LP (East). The LPC is connected to the HP/LP blocks via points A, B, and C. Above the LPC, a shaded area labeled 'SNC/N type path selector' contains LPOM and TSF/TSD blocks, connected to the LPC via points D and E. A small switch symbol is shown on the LPC line between points A and B. Reference T1524310-96 is noted at the bottom right.](f57c7b37d7a05a99618104f390089f03_img.jpg) + +Functional model for network element with path selector of type SNC/N. The diagram shows a central LPC (Linear Path Controller) connected to three vertical paths: Trib (left), West (middle), and East (right). Each path consists of a stack of functional blocks: ES1/RS1/MS1/HP/HP/LP (Trib), OSn/RSn/MSn/HP/HP/LP (West), and OSn/RSn/MSn/HP/HP/LP (East). The LPC is connected to the HP/LP blocks via points A, B, and C. Above the LPC, a shaded area labeled 'SNC/N type path selector' contains LPOM and TSF/TSD blocks, connected to the LPC via points D and E. A small switch symbol is shown on the LPC line between points A and B. Reference T1524310-96 is noted at the bottom right. + +Figure 25/G.842 – Example of functional model for network element with path selector of type SNC/N + +![Path selector's LPC connectivity diagrams. The left diagram shows a single path selector with inputs A and C, and outputs B and D. It includes a 'selector (1+1 SNC)' block and numbered arrows (1) through (4) indicating signal flow. The right diagram shows a more complex connectivity with multiple inputs (A, C, E) and outputs (B, D, E), also featuring a 'selector (1+1 SNC)' block and numbered arrows (1) through (5). Reference T1524320-96 is noted at the bottom right.](145d00f59802048185303f15937ea65c_img.jpg) + +Path selector's LPC connectivity diagrams. The left diagram shows a single path selector with inputs A and C, and outputs B and D. It includes a 'selector (1+1 SNC)' block and numbered arrows (1) through (4) indicating signal flow. The right diagram shows a more complex connectivity with multiple inputs (A, C, E) and outputs (B, D, E), also featuring a 'selector (1+1 SNC)' block and numbered arrows (1) through (5). Reference T1524320-96 is noted at the bottom right. + +Figure 26/G.842 – Path selector's LPC connectivity + +#### **6.2.3.3 Switching criteria and operation** + +The switching criteria for the path selector in SNCP protection interworking is the same as for the service selector in MS-shared protection ring interworking. See 6.2.2.3. + +### **6.2.4 Multiple rings** + +(One issue that may be described here is the mixing of traffic that is dual-node coupled with traffic that is only single-node coupled. Another is the interworking of rings that hand off LO VC traffic onto rings that incorporate this traffic into either HO SNC architectures, or MS-shared protection rings). + +# **7 Interworking among network layers** + +[This clause describes the interworking between protection applications within different layers of the network (e.g. between MS-shared protection rings and VC trail protection).] + +# **8 Switch contention** + +It is recognized that problems may occur due to contention between protection switch operation in interworking protection architectures. The contention may be inter-layer or intra-layer. This contention may result in multiple hits being introduced and may leave the switches in an indeterminate state. The outcome of the switching actions which are in contention is dependent upon the relative speed of operation of the protection switches and on the relative transmission delay on alternative routes. These problems may be solved by the use of hold-off times or by defining default positions for the switches (which would require revertive operation) in the absence of failures. + +The detailed definition of these problems and the exploration of possible solutions are left for further study. + +# ITU-T RECOMMENDATIONS SERIES + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of the ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communication | +| Series Z | Programming languages | \ No newline at end of file diff --git a/marked/G/T-REC-G.852.2-199903-I_PDF-E/raw.md b/marked/G/T-REC-G.852.2-199903-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..f1481d279ade2b34af53a81d87861beb2cf1c87d --- /dev/null +++ b/marked/G/T-REC-G.852.2-199903-I_PDF-E/raw.md @@ -0,0 +1,978 @@ + + +![ITU logo: A globe with the letters ITU and a lightning bolt.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with the letters ITU and a lightning bolt. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.852.2** + +(03/99) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital transmission systems – Digital networks – +Management of transport network + +--- + +**Enterprise viewpoint description of transport +network resource model** + +ITU-T Recommendation G.852.2 + +(Previously CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| INTERNATIONAL ANALOGUE CARRIER SYSTEM | | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TRANSMISSION SYSTEMS | | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | + +For further details, please refer to ITU-T List of Recommendations. + +# **ENTERPRISE VIEWPOINT DESCRIPTION OF TRANSPORT NETWORK RESOURCE MODEL** + +## **Source** + +ITU-T Recommendation G.852.2 was prepared by ITU-T Study Group 4 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 26th of March 1999. + +## FOREWORD + +ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation the term *recognized operating agency (ROA)* includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms *Administration*, *ROA* and *public correspondence* are defined in the *Constitution of the ITU (Geneva, 1992)*. + +## INTELLECTUAL PROPERTY RIGHTS + +The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 1999 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +## CONTENTS + +| | Page | +|--------------------------------------------------------------|------| +| 1 Scope ..... | 1 | +| 2 References ..... | 1 | +| 3 Definitions ..... | 2 | +| 4 Abbreviations ..... | 2 | +| 5 Conventions ..... | 2 | +| 6 Transport network resource model ..... | 3 | +| 6.1 Community TEM "transport network enterprise model" ..... | 3 | +| 6.1.1 Purpose ..... | 3 | +| 6.2 Resources ..... | 5 | +| 6.2.1 Access group ..... | 5 | +| 6.2.2 Administrative domain ..... | 6 | +| 6.2.3 Connection termination point ..... | 6 | +| 6.2.4 Equipment ..... | 9 | +| 6.2.5 Layer network domain ..... | 10 | +| 6.2.6 Link ..... | 10 | +| 6.2.7 Link connection ..... | 12 | +| 6.2.8 Link end ..... | 14 | +| 6.2.9 Node ..... | 16 | +| 6.2.10 Physical port ..... | 16 | +| 6.2.11 Subnetwork ..... | 16 | +| 6.2.12 Subnetwork connection ..... | 17 | +| 6.2.13 Tandem connection ..... | 19 | +| 6.2.15 Topological link end ..... | 21 | +| 6.2.16 Trail ..... | 22 | +| 6.2.17 Trail termination point ..... | 23 | +| 6.3 Policy ..... | 24 | +| Annex A – Illustration of a tandem connection ..... | 25 | +| Annex B – Examples of use of TEM resources ..... | 26 | + + + +# **ENTERPRISE VIEWPOINT DESCRIPTION OF TRANSPORT NETWORK RESOURCE MODEL** + +*(Geneva, 1999)* + +# **1 Scope** + +The objective of this Recommendation is to provide a set of definitions of management abstractions of G.805 transport networks architectural components. The resources defined in this community provide a basis for the description of enterprise specifications of transport network-level management services. A resource can be defined as what is to be managed at the network level, something which is used by a transport network-level management service. + +# **2 References** + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- [1] ITU-T Recommendation G.851.1 (1996), *Management of the transport network – Application of the RM-ODP framework.* +- [2] ITU-T Recommendation G.852.1 (1996), *Enterprise viewpoint for simple subnetwork connection management.* +- [3] ITU-T Recommendation G.852.3 (1999), *Enterprise viewpoint for topology management.* +- [4] ITU-T Recommendation G.852.6 (1999), *Enterprise viewpoint for trail management.* +- [5] ITU-T Recommendation G.852.8 (1999), *Enterprise viewpoint for pre-provisioned adaptation management.* +- [6] ITU-T Recommendation G.852.10 (1999), *Enterprise viewpoint for pre-provisioned link connection management.* +- [7] ITU-T Recommendation G.852.12 (1999), *Enterprise viewpoint for pre-provisioned link management.* +- [8] ITU-T Recommendation G.853.1 (1999), *Common information elements of the information viewpoint for the management of a transport network.* +- [9] ITU-T Recommendation G.853.2 (1996), *Subnetwork connection management information viewpoint.* +- [10] ITU-T Recommendation G.853.3 (1999), *Information viewpoint for topology management.* +- [11] ITU-T Recommendation G.853.6 (1999), *Information viewpoint for trail management.* +- [12] ITU-T Recommendation G.853.8 (1999), *Information viewpoint for pre-provisioned adaptation management.* + +- [13] ITU-T Recommendation G.853.10 (1999), *Information viewpoint for pre-provisioned link connection management.* +- [14] ITU-T Recommendation G.853.12 (1999), *Information viewpoint for pre-provisioned link management.* +- [15] ITU-T Recommendation G.854.1 (1996), *Computational interfaces for basic transport network model.* +- [16] ITU-T Recommendation G.854.3 (1999), *Computational viewpoint for topology management.* +- [17] ITU-T Recommendation G.854.6 (1999), *Computational viewpoint for trail management.* +- [18] ITU-T Recommendation G.854.8 (1999), *Computational viewpoint for pre-provisioned adaptation management.* +- [19] ITU-T Recommendation G.854.10 (1999), *Computational viewpoint for pre-provisioned link connection management.* +- [20] ITU-T Recommendation G.854.12 (1999), *Computational viewpoint for pre-provisioned link management.* +- [21] ITU-T Recommendation G.855.1 (1999), *Management information generic network level model.* +- [22] ITU-T Recommendation M.3100/Amd.1 (1999), *Generic Network Information Model – Amendment 1.* + +# 3 Definitions + +None. + +# 4 Abbreviations + +This Recommendation uses the following abbreviations: + +| | | +|-----|------------------------------| +| AP | Access Point | +| CP | Connection point | +| CTP | Connection Termination Point | +| LC | Link Connection | +| SNC | Subnetwork Connection | +| TCP | Trail Connection point | +| TTP | Trail Termination Point | + +# 5 Conventions + +None. + +# 6 Transport network resource model + +## 6.1 Community TEM "transport network enterprise model" + +### 6.1.1 Purpose + +The objective of this community is to provide a set of definitions of management abstractions of G.805 transport networks architectural components. The resources defined in this community provide a basis for the description of enterprise specifications of transport network-level management services. A resource can be defined as what is to be managed at the network level, something which is used by a transport network-level management service. + +#### 6.1.1.1 General policy + +Resource Identifier general permission: Each TEM resource has a *Resource Identifier* that needs to be unique, in the domain in which it is used. A user responsible to create a resource, may use a *User Identifier* that may be attached to the resource at creation time and gives the value for the Resource Identifier. This user identifier (if it is defined) has then to be used by the user in all operations attached to the resource as the resource identifier. The User Identifier may change during the life of the resource and all change shall be reported. + +User label general permission: As a general policy, user labels may be associated with TEM entities. For a given community, these names are assigned by the caller and may be changed. They are not guaranteed to be unique. They carry no semantic information, but are used to "label" the physical or logic resource for purposes understood by the caller and perhaps by other potential callers who have a common understanding of the semantics carried by the user label. The User Label is an optional string attached to a resource which may be defined at creation time or later. This string (if it is defined) must not be used by the caller to identify the resource in an operation. + +#### 6.1.1.2 Relationships between specifications + +All resources defined in this Recommendation will be used by the management components described in other specifications (as in Recommendations G.852.3, G.852.4, G.852.5, ...). These resources will be used as roles in each community. That can be explained by the fact that the TEM concept represents the actual resource, independently of all management action. Each resource may play a role in the description of a management component. For example, looking at Figure 1, it can be seen that a TEM connection termination point that represents the managed view of G.805 functions (adaptation and trail termination) will play the role of port in the simple subnetwork connection configuration service (G.852.1) and the role of connection termination point in the adaptation management service. A set of management components will be defined in Recommendations to allow the management of a transport network. Each organization will be able to use the components it wishes, independently from the others. An activity may be defined that relates all these management components in order to construct a management application, but it is not a standardization process to describe this overall activity. The components studied so far are: + +- simple subnetwork connection configuration (G.852.1): allows to connect or release a subnetwork connection across a subnetwork; +- trail management: allows to connect or release a trail across a layer network domain; +- topology management: allows to create, delete and modify the topology resources (subnetworks, links, link ends, access groups); +- pre-provisioned link management: allows to manage the capacity of a link by adding or removing link connections; + +- pre-provisioned link connection management: allows to assign the link connections inside a link to several users; +- pre-provisioned adaptation management: allows to manage the adaptation between a client layer network and a server layer network by creating the link connections served by a trail. + +![Diagram illustrating the management and resource structure for G.852.2. It shows two communities: 'simple subnetwork connection configuration' and 'adaptation management'. Each community contains 'Caller role', 'Provider role', and 'Resource role' (Port or CTP). These roles connect to 'TEM resources' (Trail termination point, Connection termination point, Trail termination point). Below a dashed line are 'G.805 resources' including 'trail termination function', 'connection point', and 'adaptation function'. Arrows indicate 'Use of resources' and 'Management abstraction'.](f4fdd410cdb84df81274da55721e56fb_img.jpg) + +The diagram illustrates the management and resource structure for G.852.2. It is divided into two main communities: "simple subnetwork connection configuration" and "adaptation management". + +- Management services enterprise:** The top level, containing the two communities. +- Communities:** + - "simple subnetwork connection configuration":** Contains "Caller role", "Provider role", and two "Resource role 'Port'". + - "adaptation management":** Contains "Caller role", "Provider role", a "Resource role 'CTP'", and a "Resource role 'Port'". +- TEM resources:** Below the communities, connected via arrows. It includes "Trail termination point", "Connection termination point", and another "Trail termination point". +- G.805 resources:** Below a dashed line, including "trail termination function", "connection point" (represented by a series of nodes), and "adaptation function". +- Arrows:** + - "Use of resources" points from the G.805 resources up towards the TEM resources. + - "Management abstraction" points from the TEM resources up towards the Communities. + +T0410230-98 + +Diagram illustrating the management and resource structure for G.852.2. It shows two communities: 'simple subnetwork connection configuration' and 'adaptation management'. Each community contains 'Caller role', 'Provider role', and 'Resource role' (Port or CTP). These roles connect to 'TEM resources' (Trail termination point, Connection termination point, Trail termination point). Below a dashed line are 'G.805 resources' including 'trail termination function', 'connection point', and 'adaptation function'. Arrows indicate 'Use of resources' and 'Management abstraction'. + +Figure 1/G.852.2 + +The resources are: + +- access group; +- administrative domain; +- connection termination point; +- equipment; +- layer network domain; +- link; +- link connection; +- link end; +- node; +- physical port; +- subnetwork; +- subnetwork connection; + +- tandem connection; +- topological link; +- topological link end; +- trail; +- trail termination point. + +They appear in Figure 2: + +![Figure 2/G.852.2: Protocol stack diagram showing Client layer, Client to server adaptation, and Server layer. The diagram illustrates the flow of data through various network components including AP, Trail termination, TCP, Subnetwork (SNC), CP, Link (LC), and Connection termination points. A legend at the bottom left indicates that a hatched circle represents a 'Port defined in Recommendation G.805'. The diagram is labeled T0410250-98 in the bottom right corner.](e9314c83043183351ed74908e9bf2f90_img.jpg) + +The diagram illustrates a three-layer protocol stack. The top layer is the 'Client layer', containing components: AP, Trail termination, TCP, Subnetwork (SNC), CP, Link (LC), TCP, Trail termination, and AP. The middle layer is 'Client to server adaptation', featuring 'Connection termination point' blocks and a 'Trail' label. The bottom layer is the 'Server layer', which mirrors the Client layer's components: AP, Trail termination, TCP, Subnetwork (SNC), CP, Link (LC), TCP, Trail termination, and AP. Dashed lines connect the Client layer components to the Server layer components via the 'Connection termination point' blocks in the adaptation layer. A hatched circle symbol is used to mark specific ports. The text 'T0410250-98' is in the bottom right. + +Figure 2/G.852.2: Protocol stack diagram showing Client layer, Client to server adaptation, and Server layer. The diagram illustrates the flow of data through various network components including AP, Trail termination, TCP, Subnetwork (SNC), CP, Link (LC), and Connection termination points. A legend at the bottom left indicates that a hatched circle represents a 'Port defined in Recommendation G.805'. The diagram is labeled T0410250-98 in the bottom right corner. + +⊘ Port defined in Recommendation G.805 + +Figure 2/G.852.2 + +## 6.2 Resources + +### 6.2.1 Access group + +An access group represents a group of co-located trail termination points that are bound to one subnetwork or link. + +#### Properties + +**SIGNAL\_IDENTIFICATION:** An access group has a signal identification which represents the specific signal format that the resource carries. The specific format values will be defined in the technology specific extensions. + +**GROUPING:** An access group is a set (possibly empty) of trail termination points. + +**GROUPING\_CONSTRAINT:** The trail termination points of a given access group have all the same signal identification as the access group. + +**GROUPING\_CRITERIA:** Criterion to group trail termination points in an access group may be multiple, including: same client subnetwork or link, same routing, etc. As a consequence, a given trail termination point may be part of zero, one or more access groups. + +For example, an access group may contain a number of trail termination points that are equivalent for routing purposes, i.e. from this access group originates a unique link towards a unique subnetwork in the same layer network. Or the group may be made according to the client layer network: all trail termination points of this access group serve connection termination points at the boundary of a unique subnetwork in the client layer. + +**TOPOLOGICAL\_END\_DIRECTION:** An access group has a directionality that characterizes its ability to originate or/and terminate the traffic to be carried. It may be source, sink, bidirectional or undefined. An access group sink shall contain trail termination points sink. An access group source shall contain trail termination points source. An access group bidirectional shall contain trail termination points bidirectional. An access group undefined shall contain trail termination points sink, source or/and bidirectional. + +### **6.2.2 Administrative domain** + +An administrative domain is a domain in which the resources are grouped for a management purpose by an administrator. A transport administrative domain contains only transport network resources, excluding service-level resources. + +The administrative domain defines the allocation of responsibility for managing a collection of resources between operators, or between different parts of an operator's organization. A transport network resource may pertain to several transport administrative domains, according to the management function considered. An administrative domain may contain resources belonging to several layer network domains. + +Typical applications are the allocation of individual operators' responsibilities in a multi-operator (e.g. international) network context, or regional responsibilities within one operator's organization, or the allocation of access rights (responsibilities) to customers for managing the resources available within e.g. a Virtual Private Network. + +### **6.2.3 Connection termination point** + +A connection termination point represents the potential extremity of a link connection. It relates to the G.805 port and its associated part of the adaptation function that is in the server layer (Figure 3). + +![Figure 3/G.852.2: A schematic diagram of a G.805 node. At the top, a 'G.805 port' is shown as a small circle. Below it, a 'connection termination point' is indicated by an arrow pointing to the top of a rectangular box. Inside this box, a 'G.805 adaptation function' is represented by a trapezoidal shape. Below the box, a 'G.805 access point' is shown as two small circles. Further down, a 'G.805 trail termination function' is represented by a large inverted triangle. At the bottom of the box, a 'trail termination point' is indicated by an arrow pointing to the bottom of the triangle. A 'G.805 port' is shown at the bottom of the box. The reference code 'T0410260-98' is located at the bottom right of the diagram.](af7916c89a458fdab6c3f443217388ae_img.jpg) + +Figure 3/G.852.2: A schematic diagram of a G.805 node. At the top, a 'G.805 port' is shown as a small circle. Below it, a 'connection termination point' is indicated by an arrow pointing to the top of a rectangular box. Inside this box, a 'G.805 adaptation function' is represented by a trapezoidal shape. Below the box, a 'G.805 access point' is shown as two small circles. Further down, a 'G.805 trail termination function' is represented by a large inverted triangle. At the bottom of the box, a 'trail termination point' is indicated by an arrow pointing to the bottom of the triangle. A 'G.805 port' is shown at the bottom of the box. The reference code 'T0410260-98' is located at the bottom right of the diagram. + +**Figure 3/G.852.2** + +#### **Properties** + +**POINT\_DIRECTIONALITY:** A connection termination point has a directionality that characterizes the ability of a connection termination point to originate and/or terminate the traffic to be carried. It may be source, sink or bidirectional. A connection termination point source originates a unidirectional link connection. A connection termination point terminates a unidirectional link connection. A connection termination point bidirectional originates and terminates the same bidirectional link connection. + +**SIGNAL\_IDENTIFICATION:** A connection termination point is characterized by a signal identification that describes the signal transferred at the connection termination point. + +**CONNECTIVITY\_CONSTRAINTS:** At a given moment in time, a connection termination point A\_end, which sends the signal through the link connection, or a connection termination point Z\_end, which receives the signal through the link connection, may be bound either to: + +- a subnetwork connection (Figure 4); + +![Figure 4/G.852.2: A diagram showing a 'Connection termination point A_end' as a solid black circle on a horizontal line. To the left of the circle, a dashed line represents a 'Subnetwork connection', with an arrow pointing to it from below. To the right of the circle, a solid line represents a 'Link connection', with an arrow pointing to it from above. The reference code 'T0410270-98' is located at the bottom right of the diagram.](3ad00ce93ad9dea9ee0f47535e5355e6_img.jpg) + +Figure 4/G.852.2: A diagram showing a 'Connection termination point A\_end' as a solid black circle on a horizontal line. To the left of the circle, a dashed line represents a 'Subnetwork connection', with an arrow pointing to it from below. To the right of the circle, a solid line represents a 'Link connection', with an arrow pointing to it from above. The reference code 'T0410270-98' is located at the bottom right of the diagram. + +**Figure 4/G.852.2** + +- a link connection (it is the arc view and it means that the subnetwork connection that should be there is not manageable) (Figure 5); + +![Figure 5/G.852.2: A diagram showing a horizontal line representing a network path. On the left, a dashed line segment is labeled 'Link connection'. This segment ends at a solid black circle labeled 'Connection termination point A_end'. From this circle, a solid line continues to the right, labeled 'Link connection'. Below the solid line segment, there is a label 'Degenerated subnetwork connection' with an arrow pointing to the line. In the bottom right corner, the text 'T0410280-98' is present.](b9ecbc3baefab13719e000faa6e0c7eb_img.jpg) + +Figure 5/G.852.2: A diagram showing a horizontal line representing a network path. On the left, a dashed line segment is labeled 'Link connection'. This segment ends at a solid black circle labeled 'Connection termination point A\_end'. From this circle, a solid line continues to the right, labeled 'Link connection'. Below the solid line segment, there is a label 'Degenerated subnetwork connection' with an arrow pointing to the line. In the bottom right corner, the text 'T0410280-98' is present. + +**Figure 5/G.852.2** + +- a connection termination point (it is the point view and it means that the subnetwork connection that should be there is not manageable) (Figure 6); + +![Figure 6/G.852.2: A diagram showing a horizontal line representing a network path. On the left, a dashed line segment is labeled 'Connection termination point'. This segment ends at a solid black circle. To the right of this circle is another solid black circle labeled 'Connection termination point A_end'. A solid line continues from the second circle to the right, labeled 'Link connection'. Below the solid line segment, there is a label 'Degenerated subnetwork connection' with an arrow pointing to the line. In the bottom right corner, the text 'T0410290-98' is present.](bd671b21db63e6fdb2196e9b18502aac_img.jpg) + +Figure 6/G.852.2: A diagram showing a horizontal line representing a network path. On the left, a dashed line segment is labeled 'Connection termination point'. This segment ends at a solid black circle. To the right of this circle is another solid black circle labeled 'Connection termination point A\_end'. A solid line continues from the second circle to the right, labeled 'Link connection'. Below the solid line segment, there is a label 'Degenerated subnetwork connection' with an arrow pointing to the line. In the bottom right corner, the text 'T0410290-98' is present. + +**Figure 6/G.852.2** + +- or a trail termination point (if at the border of the layer network) (Figure 7); + +![Figure 7/G.852.2: A diagram showing a horizontal line representing a network path. On the left, a dashed line segment is labeled 'trail termination point (at the border of a network layer)'. This segment ends at a solid black circle. To the right of this circle is another solid black circle labeled 'Connection termination point A_end'. A solid line continues from the second circle to the right, labeled 'link connection'. Below the solid line segment, there is a label 'Degenerated subnetwork connection' with an arrow pointing to the line. In the bottom right corner, the text 'T0410300-98' is present.](16c1175b5f05a4b55e6d396fc51b15b3_img.jpg) + +Figure 7/G.852.2: A diagram showing a horizontal line representing a network path. On the left, a dashed line segment is labeled 'trail termination point (at the border of a network layer)'. This segment ends at a solid black circle. To the right of this circle is another solid black circle labeled 'Connection termination point A\_end'. A solid line continues from the second circle to the right, labeled 'link connection'. Below the solid line segment, there is a label 'Degenerated subnetwork connection' with an arrow pointing to the line. In the bottom right corner, the text 'T0410300-98' is present. + +**Figure 7/G.852.2** + +- or nothing (nothing has been provisioned yet). + +**TOPOLOGICAL\_CONSTRAINTS:** A connection termination point may be bound to one subnetwork, (or a set of subnetworks related by partitioning), or one access group (Figure 8). + +![Figure 8/G.852.2: A diagram showing a 'link connection' between two 'Connection termination point' nodes, labeled 'A_end' and 'Z_end'. The 'A_end' node is associated with an 'Access group', and the 'Z_end' node is associated with a 'Subnetwork'. The diagram is labeled T0410310-98.](724c7777b608e53be38b12b6fb3c43bc_img.jpg) + +Figure 8/G.852.2: A diagram showing a 'link connection' between two 'Connection termination point' nodes, labeled 'A\_end' and 'Z\_end'. The 'A\_end' node is associated with an 'Access group', and the 'Z\_end' node is associated with a 'Subnetwork'. The diagram is labeled T0410310-98. + +**Figure 8/G.852.2** + +**ADAPTATION\_RELATION:** Connection termination points may be supported by a trail termination point. In such a case, the connection termination points pertain to a given layer network (known as the client layer network) and the trail termination point that supports them pertain to a server layer network, as shown in Figure 9. + +![Figure 9/G.852.2: A diagram illustrating an adaptation relation. A central 'trail termination point' (black circle) in the 'server layer' is connected to four 'Connection termination point' nodes (white circles) in the 'client layer'. The diagram is labeled T0410320-98.](9b6b5924b48bf2fd5f347f88f06f45b3_img.jpg) + +Figure 9/G.852.2: A diagram illustrating an adaptation relation. A central 'trail termination point' (black circle) in the 'server layer' is connected to four 'Connection termination point' nodes (white circles) in the 'client layer'. The diagram is labeled T0410320-98. + +**Figure 9/G.852.2** + +**BUNDLING:** A connection termination point may bundle other connection termination points. In the context of SDH, bundling of connection termination points may be used for contiguous or virtual concatenation, but is not restricted to these. In the context of ATM, it may be used to group a connection termination point carrying end-user information and a connection termination point carrying OAM cells. + +### 6.2.4 Equipment + +An equipment represents physical components of a managed element, including replaceable components. It may be nested within another equipment. (see M.3100 definition). Examples of equipment are multiplexers, cards, fibres, switches, etc. + +#### Properties + +**LOCATION:** An equipment has a location that permits to locate where transport functions are. + +### 6.2.5 Layer network domain + +A layer network domain is a transport administrative domain in which all resources pertain to the same G.805 layer. It represents the network entities which together provide communication services with one signal identification. + +#### Properties + +**RELATIONS:** A layer network domain may be related to other layer network domains as server or client. The corresponding signal identifications shall have an adaptation relationship. For example, an SDH VC4 layer network domain may serve SDH VC11, VC12, VC3 or ATM VP layer network domains or an ATM VP layer network domain may serve an ATM VC layer network domain. + +### 6.2.6 Link + +A link represents capacity between two subnetworks, two access groups or one subnetwork and one access group (Figure 10). This capacity will be defined in accordance with the technology. + +![Diagram of a link between an access group and a subnetwork.](41a438d7e4adc17c3a4005e7c9500091_img.jpg) + +A diagram showing a link between two entities. On the left is a shaded circle labeled 'access group'. On the right is an oval labeled 'Subnetwork'. They are connected by a horizontal cylinder labeled 'link'. Arrows point from the labels to the corresponding elements. A small code 'T0410330-98' is in the bottom right corner. + +Diagram of a link between an access group and a subnetwork. + +Figure 10/G.852.2 + +#### Properties + +**SIGNAL\_IDENTIFICATION:** A link has a signal identification that describes the signal transferred across the link. + +**LINK\_DIRECTIONALITY:** A link has a directionality that characterizes its ability to carry traffic in one, two or undefined directions. In case of a unidirectional link, traffic goes from A\_end to Z\_end. In case of a bidirectional link, traffic goes from A\_end to Z\_end and from Z\_end to A\_end. In case of an undefined link, nothing can be said. + +**EXTREMITIES:** A link is terminated by two extremities referred to as link\_ends. The link\_ends have the same signal identification as the link. In case of a unidirectional link, the link\_end A shall be source and the link\_end Z shall be sink. In case of a bidirectional link, the link\_ends A and Z shall be bidirectional. In case of an undefined link, the link\_ends A and Z shall be undefined. + +**PRE-PROVISIONED CAPACITY:** For some technologies (e.g. SDH), capacity can be expressed by a certain number of link connections (Figure 11). The link connections have all the same signal identification. These link connections do not have to be served by the same trail. + +![Diagram of a link with multiple link connections.](2de714cedbbdd36f901f71bafa78f75a_img.jpg) + +A diagram showing a link with multiple connections. A horizontal cylinder is labeled 'link'. To its left, three parallel lines are labeled 'link connections'. Arrows point from the labels to the corresponding elements. A small code 'T0410340-98' is in the bottom right corner. + +Diagram of a link with multiple link connections. + +Figure 11/G.852.2 + +**DYNAMIC CAPACITY:** For some technologies (e.g. ATM), capacity can be characterized by name space and bandwidths. + +**DIRECTIONALITY AND CAPACITY:** In case of a unidirectional link, the link connections pertaining to it shall be unidirectional and from A\_end to Z\_end. In case of a bidirectional link, the link connections pertaining to it shall be bidirectional. In case of an undefined link, the link connections pertaining to it may be unidirectional (from one side or the other) and/or bidirectional. + +**PARALLEL\_COMPOSITION:** A compound link is made of component links (Figure 12). The container and the elements must have both the same signal identification and the same directionality. Decomposition of links may be recursive, i.e. component links may be themselves composed of component links, and so on. All links (compound and component) must have the same extremities. + +![Diagram of parallel composition showing a compound link made of two component links between two subnetworks.](8307f6b04df072c9332f9987e034272c_img.jpg) + +The diagram illustrates parallel composition. Two dashed ovals, each labeled 'Subnetwork', are positioned on the left and right. Between them are two parallel, shaded horizontal cylinders. An arrow labeled 'compound link' points to the top cylinder, and an arrow labeled 'component link' points to the bottom cylinder. A small code 'T0410350-98' is visible in the bottom right corner of the diagram area. + +Diagram of parallel composition showing a compound link made of two component links between two subnetworks. + +**Figure 12/G.852.2** + +**COMPOUND CAPACITY:** The capacity of the compound link shall be equal to the sum of the capacities of all the component links. + +**SERIAL\_COMPOSITION:** A serial-compound link is made of component links that are contiguous. The container and the components must have the same signal identification and the same directionality. Although only the component links are captured by this relationship, a serial-compound link is made of not only links but also subnetworks, as shown in Figure 13. + +![Diagram of serial composition showing a serial-compound link made of two component links and a subnetwork between two subnetworks.](36117e9cb27c58484cd8d3e5f9dc7ac3_img.jpg) + +The diagram illustrates serial composition. At the top, two dashed ovals labeled 'Subnetwork A' and 'Subnetwork B' are connected by a single white cylinder labeled 'Serial-compound link'. Below this, the same 'Subnetwork A' and 'Subnetwork B' ovals are shown, but they are connected by a sequence of a shaded cylinder, a white oval, and another shaded cylinder. This sequence is labeled 'Component links'. A small code 'T0410360-98' is visible in the bottom right corner of the diagram area. + +Diagram of serial composition showing a serial-compound link made of two component links and a subnetwork between two subnetworks. + +**Figure 13/G.852.2** + +**SERIAL\_COMPOSITION CAPACITY:** The capacity of the serial-compound link shall be lower than the lowest capacity of the component links. + +### 6.2.7 Link connection + +A link connection represents the transparent capacity of transfer of information characterized by a given signal identification between two fixed points. + +#### Properties + +**EXTREMITIES:** A link connection is terminated by two and only two extremities, the connection termination points which are its A\_end and Z\_end. Through a unidirectional link connection, traffic goes only from the A\_end to the Z\_end; through a bidirectional one, traffic goes from A to Z and from Z to A. + +**SIGNAL\_IDENTIFICATION:** A link connection is characterized by a signal identification. The signal identification describes the signal that is transferred across the link connection. + +**DIRECTIONALITY:** A link connection is characterized by a directionality. The directionality characterizes the ability of a link connection to carry traffic in one (for unidirectional link connection) or two directions (for bidirectional link connection). + +**CONNECTIVITY\_CONSTRAINTS:** A link connection may be bound at one extremity either to + +- a subnetwork connection (Figure 14); + +![Diagram of a link connection connected to a subnetwork connection.](51db757d054ce1ce83c436a3578b56ca_img.jpg) + +The diagram shows a horizontal line representing a connection. On the left, a dashed line segment is labeled 'Subnetwork connection' with an upward-pointing arrow. This dashed line meets a solid line segment at a point marked by a small black dot. The solid line segment is labeled 'link connection' with a downward-pointing arrow. The identifier 'T0410370-98' is located at the bottom right of the solid line. + +Diagram of a link connection connected to a subnetwork connection. + +**Figure 14/G.852.2** + +- a link connection (if the subnetwork is not managed) (Figure 15); + +![Diagram of a link connection connected to a degenerated subnetwork connection.](e928f4874ed492d3ad4c6fa2d29aedbc_img.jpg) + +The diagram shows a horizontal line. On the left, a dashed line segment is labeled 'link connection' with an upward-pointing arrow. This dashed line meets a solid line segment at a point marked by a small black dot. The solid line segment is labeled 'link connection' with a downward-pointing arrow. A curved arrow points from the label 'Degenerated subnetwork connection' to the junction point. The identifier 'T0410380-98' is located at the bottom right of the solid line. + +Diagram of a link connection connected to a degenerated subnetwork connection. + +**Figure 15/G.852.2** + +- a connection termination point (it is the point view and it means that the subnetwork connection that should be there is not manageable) (Figure 16); + +![Diagram of a link connection connected to a connection termination point.](dc23d430e878eb71b8cd589984113940_img.jpg) + +The diagram shows a horizontal line. On the left, a dashed line segment ends at a solid black circle labeled 'Connection termination point' with a downward-pointing arrow. This circle is at the junction with a solid line segment labeled 'link connection' with a downward-pointing arrow. A curved arrow points from the label 'Degenerated subnetwork connection' to this junction. The identifier 'T0410390-98' is located at the bottom right of the solid line. + +Diagram of a link connection connected to a connection termination point. + +**Figure 16/G.852.2** + +- or to a trail termination point (at the border of a layer network) (Figure 17). + +![Figure 17/G.852.2: A diagram showing a trail termination point, a link connection, and a degenerated subnetwork connection. The trail termination point is a solid black circle. A dashed line connects it to a solid line labeled 'link connection'. A curved arrow points from the solid line to a point labeled 'Degenerated subnetwork connection'. The text 'T0410400-98' is in the top right.](7f25db95ce3916c0e09803b861a2f7bc_img.jpg) + +Figure 17/G.852.2: A diagram showing a trail termination point, a link connection, and a degenerated subnetwork connection. The trail termination point is a solid black circle. A dashed line connects it to a solid line labeled 'link connection'. A curved arrow points from the solid line to a point labeled 'Degenerated subnetwork connection'. The text 'T0410400-98' is in the top right. + +**Figure 17/G.852.2** + +**TOPOLOGICAL\_CONSTRAINTS:** A link connection may be managed without having to manage a link and may be bound to a subnetwork (or a set of partitioned subnetworks), or an access group (Figure 18). + +![Figure 18/G.852.2: A diagram showing a subnetwork and an access group connected by a link connection. On the left is a dashed oval labeled 'Subnetwork'. On the right is a solid circle labeled 'Access group'. A solid line labeled 'link connection' connects them. The text 'T0410410-98' is in the bottom right.](10781f43062bf3e9601a1e086710556c_img.jpg) + +Figure 18/G.852.2: A diagram showing a subnetwork and an access group connected by a link connection. On the left is a dashed oval labeled 'Subnetwork'. On the right is a solid circle labeled 'Access group'. A solid line labeled 'link connection' connects them. The text 'T0410410-98' is in the bottom right. + +**Figure 18/G.852.2** + +**ADAPTATION\_RELATION:** Link connections may be supported by a trail. In such a case, the link connections pertain to a given layer network (known as the client layer network) and the trail that supports them pertain to a server layer network, as shown in Figure 19. + +![Figure 19/G.852.2: A diagram showing the adaptation relation between client layer link connections and a server layer trail. The top section is labeled 'Client layer' and contains five horizontal lines labeled 'link connections'. The bottom section is labeled 'Server layer' and contains a single thick horizontal line labeled 'trail'. Arrows from the link connections point down to the trail, passing through a dashed line labeled 'adaptation function'. The text 'T0410420-98' is in the bottom right.](12de9b926df0384ec07702671827c9cd_img.jpg) + +Figure 19/G.852.2: A diagram showing the adaptation relation between client layer link connections and a server layer trail. The top section is labeled 'Client layer' and contains five horizontal lines labeled 'link connections'. The bottom section is labeled 'Server layer' and contains a single thick horizontal line labeled 'trail'. Arrows from the link connections point down to the trail, passing through a dashed line labeled 'adaptation function'. The text 'T0410420-98' is in the bottom right. + +**Figure 19/G.852.2** + +**SERIAL\_COMPOSITION:** A serial-composed link connection is made of other link connections and possibly subnetwork connections as shown in Figure 20. + +![Diagram of serial composition showing a 'serial-composed link connection' at the top, indicated by a downward arrow. Below it, a dashed line separates the top level from the bottom level. The bottom level contains 'component link connections' on the left and 'component subnetwork connections' on the right. Arrows show a sequence of connections: starting with a link connection, followed by a subnetwork connection, then another link connection, then another subnetwork connection, and finally a link connection. The diagram is labeled T0410430-98.](83852ec55d4802521a727926336bedab_img.jpg) + +Diagram of serial composition showing a 'serial-composed link connection' at the top, indicated by a downward arrow. Below it, a dashed line separates the top level from the bottom level. The bottom level contains 'component link connections' on the left and 'component subnetwork connections' on the right. Arrows show a sequence of connections: starting with a link connection, followed by a subnetwork connection, then another link connection, then another subnetwork connection, and finally a link connection. The diagram is labeled T0410430-98. + +**Figure 20/G.852.2** + +**SERIAL\_COMPOSITION\_CONSTRAINT:** In the case where a link connection is serial composed, the component connections have to be contiguous. As a link connection "represents a pair of adaptation functions", both the first and the last one of that series must be link connections (not subnetwork connections). The serial-composed link connection is not served directly by a trail though all the component link connections may be. + +**BUNDLING:** A link connection may bundle other link connections, as shown in Figure 21. In the context of SDH, bundling of link connections may be used for contiguous or virtual concatenation, but is not restricted to. In the context of ATM, it may be used to group a link connection carrying end-user information and a link connection carrying OAM cells. Bundled link connections may be considered as parallel to each others. + +![Diagram of bundling showing a thick horizontal line at the top labeled 'Link connection with an y (y > x) bandwidth'. Below it are four parallel horizontal lines, each labeled 'Link connections with an x bandwidth'. Arrows point from the top thick line down to each of the four parallel lines, indicating that the top line is a bundle of the four lines below. The diagram is labeled T0410440-98.](3da1a07cb87051bf616c9876db958cf0_img.jpg) + +Diagram of bundling showing a thick horizontal line at the top labeled 'Link connection with an y (y > x) bandwidth'. Below it are four parallel horizontal lines, each labeled 'Link connections with an x bandwidth'. Arrows point from the top thick line down to each of the four parallel lines, indicating that the top line is a bundle of the four lines below. The diagram is labeled T0410440-98. + +**Figure 21/G.852.2** + +### 6.2.8 Link end + +A link end represents the extremity of a link. + +#### Properties + +**SIGNAL\_IDENTIFICATION:** A link end has a signal identification that characterizes all signals transferred at the link end. + +**EXTREMITIES:** A link end terminates one link. The link has the same signal identification as the link end. + +**PRE-PROVISIONED CAPACITY:** For some technologies (e.g. SDH), a link end is a (possibly empty) set of connection termination points (Figure 22). The connection termination points shall have the same signal identification. These connection termination points do not have to be adapted from the same trail termination point. + +![Figure 22/G.852.2: A diagram showing a 'link end' represented by a circle containing four small circles (connection termination points). A dashed line extends from the circle to the right, representing the link. The label 'connection termination points' is below the circle, and 'T0410450-98' is at the end of the dashed line.](812e188283162af0b54fb3e30ffee51b_img.jpg) + +Figure 22/G.852.2: A diagram showing a 'link end' represented by a circle containing four small circles (connection termination points). A dashed line extends from the circle to the right, representing the link. The label 'connection termination points' is below the circle, and 'T0410450-98' is at the end of the dashed line. + +**Figure 22/G.852.2** + +**DYNAMIC CAPACITY:** For some technologies (e.g. ATM), a link end can be characterized by name space and bandwidth. + +**TOPOLOGICAL\_END\_DIRECTION:** A link end has a directionality that characterizes its ability to originate or/and terminate the traffic to be carried. It may be source, sink, bidirectional or undefined. A link end source or sink is intended to be bound to a unidirectional link. A link end bidirectional is intended to be bound to a bidirectional link. A link end undefined is intended to be bound to an undefined link. A link end source shall contain connection termination points source. A link end sink shall contain connection termination points sink. A link end bidirectional shall contain connection termination points bidirectional. A link end undefined shall contain connection termination points sink, source or/and bidirectional. + +**PARALLEL\_COMPOSITION:** A compound link end is made of component link ends if the corresponding link is made of component links (Figure 23). The container and the components must have both the same signal identification and the same directionality. Decomposition of link ends may be recursive, i.e. component link ends may be themselves composed of component link ends, and so on. + +![Figure 23/G.852.2: A diagram showing a 'compound link end' represented by a circle containing two smaller circles (component link ends). Two parallel horizontal lines extend from the circle to the right, representing the component links. The label 'component link end' is above the circle, and 'T0410460-98' is at the end of the lines.](4cc7cdce3d498d8b0ba033a9be24ade5_img.jpg) + +Figure 23/G.852.2: A diagram showing a 'compound link end' represented by a circle containing two smaller circles (component link ends). Two parallel horizontal lines extend from the circle to the right, representing the component links. The label 'component link end' is above the circle, and 'T0410460-98' is at the end of the lines. + +**Figure 23/G.852.2** + +**BOUNDING:** One link end is bound to one topological component that can be one subnetwork or one access group (if at the border of the layer network). + +### 6.2.9 Node + +A node is an administrative domain that represents a collection of G.852.2 (TEM) resources that are grouped in a single geographical location, and could pertain to several layer network domains. It can for example, be one town, one building or an equipment. + +#### Properties + +GROUPING: The policy to group the resources is up to the network administrator. + +### 6.2.10 Physical port + +A physical port represents the potential capacity provided by a physical access. + +#### Properties + +CAPACITY: A physical port will always be characterized by a given capacity. For example, a 2-Mbit/s physical port represents the fact that a capacity of 2 Mbit/s is available. + +### 6.2.11 Subnetwork + +A subnetwork represents a topological component used to effect routing of a specific signal identification (see G.805 definition). It may be characterized by a set of related extremities, which can be link connections, connection termination points or trail termination points, and which shall be connectable. + +#### Properties + +SIGNAL\_IDENTIFICATION: A subnetwork carries a signal identification. The signal identification will be defined in the technology specific extensions. + +COMPOSITION: A subnetwork may be composed of smaller subnetworks that are part of its decomposition, due to partitioning, as shown in Figure 24. Decomposition of subnetworks may be recursive, i.e. component subnetworks may be themselves composed of inner subnetworks, and so on. The smaller component subnetwork is associated to a G.805 matrix. + +![Diagram illustrating the composition of subnetworks. A large oval labeled 'composite subnetworks' contains five smaller circles. Two of these circles are labeled 'component subnetworks'. Each component subnetwork contains two small ovals. The diagram is labeled T0410470-98.](8ed7f57cc317f6574bec781d01ae6ad2_img.jpg) + +The diagram shows a large oval representing a 'composite subnetwork'. Inside this oval are five smaller circles, which represent 'component subnetworks'. Two of these component subnetworks are highlighted with arrows and labels. Each of these two component subnetworks contains two small ovals. The other three component subnetworks are shown as single circles without internal ovals. The label 'T0410470-98' is located at the bottom right of the diagram. + +Diagram illustrating the composition of subnetworks. A large oval labeled 'composite subnetworks' contains five smaller circles. Two of these circles are labeled 'component subnetworks'. Each component subnetwork contains two small ovals. The diagram is labeled T0410470-98. + +**Figure 24/G.852.2** + +COMPOSITION\_CONSTRAINT: The component subnetworks must have the same signal identification as the composite one. + +**CONNECTIVITY:** A subnetwork may be crossed by subnetwork connections, as shown in Figure 25. At some point in time, the number of subnetwork connections crossing a given subnetwork may be zero. + +![Figure 25/G.852.2: A diagram showing a subnetwork as an oval. Three dashed lines, labeled 'Subnetwork connections', cross the oval. An arrow labeled 'Subnetwork' points to the oval's boundary. The text 'T0410480-98' is in the bottom right corner.](365b54f616aff249b4e6c0edafdcb9b3_img.jpg) + +Figure 25/G.852.2: A diagram showing a subnetwork as an oval. Three dashed lines, labeled 'Subnetwork connections', cross the oval. An arrow labeled 'Subnetwork' points to the oval's boundary. The text 'T0410480-98' is in the bottom right corner. + +**Figure 25/G.852.2** + +**RELATED\_EXTREMITIES:** A subnetwork can be defined by a set of related extremities (e.g. connection termination point, trail termination, link connection) (Figure 26). This set represents the potential connectivity of the subnetwork. + +![Figure 26/G.852.2: A diagram showing a subnetwork as an oval. Three dashed lines, labeled 'Subnetwork connections', cross the oval. A solid line, labeled 'link connections', enters the oval from the top right. Three black dots on the oval's boundary are labeled: 'trail termination point' (left), 'Connection termination point' (bottom), and 'Subnetwork' (inside the oval). The text 'T0410490-98' is in the bottom right corner.](844077b3034f0030b404207db0ad76b4_img.jpg) + +Figure 26/G.852.2: A diagram showing a subnetwork as an oval. Three dashed lines, labeled 'Subnetwork connections', cross the oval. A solid line, labeled 'link connections', enters the oval from the top right. Three black dots on the oval's boundary are labeled: 'trail termination point' (left), 'Connection termination point' (bottom), and 'Subnetwork' (inside the oval). The text 'T0410490-98' is in the bottom right corner. + +**Figure 26/G.852.2** + +**PROTECTED SUBNETWORK:** A subnetwork may be considered as protected if all its subnetwork connections are protected. + +### 6.2.12 Subnetwork connection + +A subnetwork connection represents a transport entity that transfers information across a subnetwork. + +#### Properties + +**SIGNAL\_IDENTIFICATION:** A subnetwork connection is characterized by a signal identification. The signal identification describes the signal that is transferred across the subnetwork connection. + +**DIRECTIONALITY:** Any subnetwork connection is characterized by a directionality. The directionality characterizes the ability of a subnetwork connection to carry traffic in one or two directions. + +**CONNECTIVITY\_CONSTRAINTS:** The A\_end, which sends the signal through the subnetwork connection, shall be associated to a sink connection termination point. The Z\_end, which receives the signal through the subnetwork connection, shall be associated to a source connection termination point. + +**BIDIRECTIONAL\_CHARACTERISTIC:** A bidirectional subnetwork connection may be supported by two unidirectional (one of which being codirectional and the other one contradirectional with regard to an orientation reference) subnetwork connections that together provide bidirectionality (e.g. case of a unidirectional SDH ring), as shown in Figure 27. + +![Diagram of a bidirectional subnetwork connection supported by two unidirectional subnetwork connections.](73b5cce955ba9415a98791db7b0080ad_img.jpg) + +The diagram illustrates a bidirectional subnetwork connection. It features two Add-Drop Multiplexors (ADM) represented by rectangular boxes. The left ADM has a solid black dot on its left side labeled 'ADM'. The right ADM has a solid black dot on its right side labeled 'physical access'. Between them, a central wavy line represents the 'bidirectional subnetwork connection'. Above this, two dashed lines represent 'two uni- and contradirectional subnetwork connections'. An arrow from the top points to the top dashed line, labeled 'Add-Drop Multiplexor (ADM)'. Another arrow points to the bottom dashed line. The text 'T0410500-98' is located near the bottom right ADM. + +Diagram of a bidirectional subnetwork connection supported by two unidirectional subnetwork connections. + +**Figure 27/G.852.2** + +**BUNDLING:** A subnetwork connection may bundle other subnetwork connections. In the context of SDH, bundling of subnetwork connections may be used for, but not restricted to, contiguous or virtual concatenation. In the context of ATM, it may be used to group a subnetwork connection carrying end-user information and a subnetwork connection carrying OAM cells. Bundled subnetwork connections may be considered as paralleled to each other. + +**SERIAL\_COMPOSITION:** A serial composite subnetwork connection may be made of other subnetwork connections and link connections. The components being contiguous, both the first and the last one must be subnetwork connections, as shown in Figure 28. The component subnetwork connections may be considered as arranged in a series. + +![Diagram of a serial composite subnetwork connection.](7e1c9b51e067a48cd0fcc9748d8bd8d8_img.jpg) + +The diagram shows a 'serial composite subnetwork connection' represented by a long dashed line at the top. Below it, a solid line represents the physical path, composed of alternating 'link connections' (dashed segments) and 'Subnetwork connections' (solid segments). Arrows indicate the direction of flow from left to right. The text 'T0410510-98' is located near the bottom right. + +Diagram of a serial composite subnetwork connection. + +**Figure 28/G.852.2** + +**DEGENERATED SNC:** A subnetwork connection may be considered as degenerated, and so not managed, if it is a fixed transfer capacity. In this case, the associated subnetwork is also degenerated. + +PROTECTED SNC: A subnetwork connection is considered as protected if it can be replaced by a protecting subnetwork connection if the working subnetwork connection fails or if the performance falls below the required level. It is a protection switching method applied in the client layer network when a defect condition is detected in a server layer network, sub-layer or other transport layer network. + +### 6.2.13 Tandem connection + +A tandem connection represents an arbitrary series of contiguous link connections and/or subnetwork connections (for definition, see Recommendation G.805). A tandem connection is created for monitoring purposes. + +#### Properties + +SIGNAL\_IDENTIFICATION: A tandem connection is characterized by a signal identification. The signal identification describes the signal that is transferred across the tandem connection. + +DIRECTIONALITY: Any tandem connection is characterized by a directionality. The directionality characterizes the ability of a tandem connection to carry traffic in one or two directions. + +CONNECTIVITY\_CONSTRAINT: A tandem connection being a series of contiguous link connections and/or subnetwork connections, both the first and the last one of such a series may be either a link connection or a subnetwork connection, as shown in Figure 29. + +![Diagram illustrating a tandem connection as a series of contiguous link connections and subnetwork connections.](8d325fc12b494e42c9ea7ed2a7f327a6_img.jpg) + +The diagram shows a horizontal line representing a network path. It is divided into segments by vertical tick marks. The first segment is a dashed line with a right-pointing arrow. The second segment is a solid line with a right-pointing arrow. The third segment is a dashed line with a right-pointing arrow. The fourth segment is a solid line with a right-pointing arrow. The fifth segment is a dashed line with a right-pointing arrow. The sixth segment is a solid line with a right-pointing arrow. The seventh segment is a dashed line with a right-pointing arrow. The eighth segment is a solid line with a right-pointing arrow. The ninth segment is a dashed line with a right-pointing arrow. The tenth segment is a solid line with a right-pointing arrow. The eleventh segment is a dashed line with a right-pointing arrow. The twelfth segment is a solid line with a right-pointing arrow. The thirteenth segment is a dashed line with a right-pointing arrow. The fourteenth segment is a solid line with a right-pointing arrow. The fifteenth segment is a dashed line with a right-pointing arrow. The sixteenth segment is a solid line with a right-pointing arrow. The seventeenth segment is a dashed line with a right-pointing arrow. The eighteenth segment is a solid line with a right-pointing arrow. The nineteenth segment is a dashed line with a right-pointing arrow. The twentieth segment is a solid line with a right-pointing arrow. The twenty-first segment is a dashed line with a right-pointing arrow. The twenty-second segment is a solid line with a right-pointing arrow. The twenty-third segment is a dashed line with a right-pointing arrow. The twenty-fourth segment is a solid line with a right-pointing arrow. The twenty-fifth segment is a dashed line with a right-pointing arrow. The twenty-sixth segment is a solid line with a right-pointing arrow. The twenty-seventh segment is a dashed line with a right-pointing arrow. The twenty-eighth segment is a solid line with a right-pointing arrow. The twenty-ninth segment is a dashed line with a right-pointing arrow. The thirtieth segment is a solid line with a right-pointing arrow. The thirty-first segment is a dashed line with a right-pointing arrow. The thirty-second segment is a solid line with a right-pointing arrow. The thirty-third segment is a dashed line with a right-pointing arrow. The thirty-fourth segment is a solid line with a right-pointing arrow. The thirty-fifth segment is a dashed line with a right-pointing arrow. The thirty-sixth segment is a solid line with a right-pointing arrow. The thirty-seventh segment is a dashed line with a right-pointing arrow. The thirty-eighth segment is a solid line with a right-pointing arrow. The thirty-ninth segment is a dashed line with a right-pointing arrow. The fortieth segment is a solid line with a right-pointing arrow. The forty-first segment is a dashed line with a right-pointing arrow. The forty-second segment is a solid line with a right-pointing arrow. The forty-third segment is a dashed line with a right-pointing arrow. The forty-fourth segment is a solid line with a right-pointing arrow. The forty-fifth segment is a dashed line with a right-pointing arrow. The forty-sixth segment is a solid line with a right-pointing arrow. The forty-seventh segment is a dashed line with a right-pointing arrow. The forty-eighth segment is a solid line with a right-pointing arrow. The forty-ninth segment is a dashed line with a right-pointing arrow. The fiftieth segment is a solid line with a right-pointing arrow. The fifty-first segment is a dashed line with a right-pointing arrow. The fifty-second segment is a solid line with a right-pointing arrow. The fifty-third segment is a dashed line with a right-pointing arrow. The fifty-fourth segment is a solid line with a right-pointing arrow. The fifty-fifth segment is a dashed line with a right-pointing arrow. The fifty-sixth segment is a solid line with a right-pointing arrow. The fifty-seventh segment is a dashed line with a right-pointing arrow. The fifty-eighth segment is a solid line with a right-pointing arrow. The fifty-ninth segment is a dashed line with a right-pointing arrow. The sixtieth segment is a solid line with a right-pointing arrow. The sixty-first segment is a dashed line with a right-pointing arrow. The sixty-second segment is a solid line with a right-pointing arrow. The sixty-third segment is a dashed line with a right-pointing arrow. The sixty-fourth segment is a solid line with a right-pointing arrow. The sixty-fifth segment is a dashed line with a right-pointing arrow. The sixty-sixth segment is a solid line with a right-pointing arrow. The sixty-seventh segment is a dashed line with a right-pointing arrow. The sixty-eighth segment is a solid line with a right-pointing arrow. The sixty-ninth segment is a dashed line with a right-pointing arrow. The seventieth segment is a solid line with a right-pointing arrow. The seventy-first segment is a dashed line with a right-pointing arrow. The seventy-second segment is a solid line with a right-pointing arrow. The seventy-third segment is a dashed line with a right-pointing arrow. The seventy-fourth segment is a solid line with a right-pointing arrow. The seventy-fifth segment is a dashed line with a right-pointing arrow. The seventy-sixth segment is a solid line with a right-pointing arrow. The seventy-seventh segment is a dashed line with a right-pointing arrow. The seventy-eighth segment is a solid line with a right-pointing arrow. The seventy-ninth segment is a dashed line with a right-pointing arrow. The eightieth segment is a solid line with a right-pointing arrow. The eighty-first segment is a dashed line with a right-pointing arrow. The eighty-second segment is a solid line with a right-pointing arrow. The eighty-third segment is a dashed line with a right-pointing arrow. The eighty-fourth segment is a solid line with a right-pointing arrow. The eighty-fifth segment is a dashed line with a right-pointing arrow. The eighty-sixth segment is a solid line with a right-pointing arrow. The eighty-seventh segment is a dashed line with a right-pointing arrow. The eighty-eighth segment is a solid line with a right-pointing arrow. The eighty-ninth segment is a dashed line with a right-pointing arrow. The ninetieth segment is a solid line with a right-pointing arrow. The ninety-first segment is a dashed line with a right-pointing arrow. The ninety-second segment is a solid line with a right-pointing arrow. The ninety-third segment is a dashed line with a right-pointing arrow. The ninety-fourth segment is a solid line with a right-pointing arrow. The ninety-fifth segment is a dashed line with a right-pointing arrow. The ninety-sixth segment is a solid line with a right-pointing arrow. The ninety-seventh segment is a dashed line with a right-pointing arrow. The ninety-eighth segment is a solid line with a right-pointing arrow. The ninety-ninth segment is a dashed line with a right-pointing arrow. The hundredth segment is a solid line with a right-pointing arrow. A bracket labeled 'tandem connection' spans the entire sequence of segments. A bracket labeled 'link connections' spans the first four segments. A bracket labeled 'subnetwork connections' spans the last four segments. The text 'T0410520-98' is located at the bottom right of the diagram. + +Diagram illustrating a tandem connection as a series of contiguous link connections and subnetwork connections. + +Figure 29/G.852.2 + +### 6.2.14 Topological link + +A topological link is a link provided by one and only one server trail, in a client layer. + +#### Properties + +SIGNAL\_IDENTIFICATION: A topological link has a signal identification that describes the signal transferred across the topological link. + +DIRECTIONALITY: A link has a directionality that characterizes its ability to carry traffic in one or two directions. The directionality is the same as the directionality of the server trail. In case of a unidirectional topological link, traffic goes from A\_end to Z\_end. In case of a bidirectional topological link, traffic goes from A\_end to Z\_end and from Z\_end to A\_end. + +EXTREMITIES: A topological link is terminated by two extremities referred to as topological link\_ends. The topological link\_ends have the same signal identification as the topological link. In case of a unidirectional topological link, the topological link\_end A shall be source and the topological link\_end Z shall be sink. In case of a bidirectional topological link, the topological link\_ends A and Z shall be bidirectional. + +ADAPTATION\_RELATION: A topological link is supported by one and only one trail. In such a case, the topological link end pertains to a given layer network (known as the client layer network) and the trail that supports it pertains to a server layer network, as shown in Figure 30. + +![Figure 30/G.852.2: Diagram illustrating the adaptation relation between a client layer and a server layer. A dashed horizontal line separates the 'client layer' (top) and 'server layer' (bottom). In the client layer, a 'Topological link' is shown as a 3D cylinder. An arrow labeled 'adaptation function' points from the server layer up to the topological link. In the server layer, a 'trail' is shown as a solid horizontal line, with an arrow pointing up to the topological link. The reference code T0410530-98 is in the bottom right.](0c08e48c08f96934cd6bc6911f3069dc_img.jpg) + +Figure 30/G.852.2: Diagram illustrating the adaptation relation between a client layer and a server layer. A dashed horizontal line separates the 'client layer' (top) and 'server layer' (bottom). In the client layer, a 'Topological link' is shown as a 3D cylinder. An arrow labeled 'adaptation function' points from the server layer up to the topological link. In the server layer, a 'trail' is shown as a solid horizontal line, with an arrow pointing up to the topological link. The reference code T0410530-98 is in the bottom right. + +Figure 30/G.852.2 + +PRE-PROVISIONED CAPACITY: For some technologies (e.g. SDH), capacity can be expressed by a certain number of link connections (Figure 31). The link connections have all the same signal identification. These link connections must be served by the same trail. + +![Figure 31/G.852.2: Diagram illustrating pre-provisioned capacity. A 'link' is shown as a 3D cylinder. On the left, multiple parallel lines representing 'link connections' enter the link. The reference code T0410540-98 is in the bottom right.](58f4167687de8d7339594e5f6fbe0bc6_img.jpg) + +Figure 31/G.852.2: Diagram illustrating pre-provisioned capacity. A 'link' is shown as a 3D cylinder. On the left, multiple parallel lines representing 'link connections' enter the link. The reference code T0410540-98 is in the bottom right. + +Figure 31/G.852.2 + +DYNAMIC CAPACITY: For some technologies (e.g. ATM), capacity can be characterized by name space and bandwidths. + +DIRECTIONALITY\_AND\_CAPACITY: In case of a unidirectional topological link, the link connections pertaining to it shall be unidirectional and from A\_end to Z\_end. In case of a bidirectional topological link, the link connections pertaining to it shall be bidirectional. + +PARALLEL\_COMPOSITION: A compound topological link is made of component links (Figure 32). The container and the elements must have both the same signal identification and the same directionality. + +![Figure 32/G.852.2: Diagram illustrating parallel composition. A 'compound topological link' is shown as a shaded 3D cylinder composed of two 'component link' cylinders. It is connected between two 'Subnetwork' nodes, which are represented by dashed ovals. The reference code T0410550-98 is in the bottom right.](bb3354f497635d15bef873577125c48d_img.jpg) + +Figure 32/G.852.2: Diagram illustrating parallel composition. A 'compound topological link' is shown as a shaded 3D cylinder composed of two 'component link' cylinders. It is connected between two 'Subnetwork' nodes, which are represented by dashed ovals. The reference code T0410550-98 is in the bottom right. + +Figure 32/G.852.2 + +### 6.2.15 Topological link end + +A topological link end represents the extremity of a topological link. + +#### Properties + +**SIGNAL\_IDENTIFICATION:** A topological link end has a signal identification that characterizes all signals transferred at the topological link end. + +**EXTREMITIES:** A topological link end terminates one topological link. The topological link has the same signal identification as the topological link end. + +**ADAPTATION\_RELATION:** A topological link end is supported by one and only one trail termination point (Figure 33). In such a case, the topological link end pertains to a given layer network (known as the client layer network) and the trail termination point that supports it pertains to a server layer network, as shown below. + +![Diagram illustrating the adaptation relation between a topological link end and a trail termination point.](088921fa3f5a44c8551815122517eefd_img.jpg) + +The diagram shows a horizontal line separating two layers: 'client layer' above and 'server layer' below. In the client layer, there is a white circle labeled 'Topological link end'. In the server layer, there is a black circle labeled 'trail termination point'. A vertical double-headed arrow connects the two circles, indicating a mutual relationship. The text 'T0410560-98' is in the bottom right corner. + +Diagram illustrating the adaptation relation between a topological link end and a trail termination point. + +**Figure 33/G.852.2** + +**PRE-PROVISIONED CAPACITY:** For some technologies (e.g. SDH), a link end is a (possibly empty) set of connection termination points (Figure 34). The connection termination points shall have the same signal identification. These connection termination points must be adapted from the same trail termination point. + +![Diagram illustrating a link end as a set of connection termination points.](15e4a144a88176b71ea3eff2722253b0_img.jpg) + +The diagram shows a 'link end' represented by a black circle containing four white dots. An arrow points from the label 'link end' to this circle. Below the circle, the label 'connection termination points' has an arrow pointing to the dots. To the right of the circle is a dashed rectangular box. The text 'T0410570-98' is in the bottom right corner. + +Diagram illustrating a link end as a set of connection termination points. + +**Figure 34/G.852.2** + +**DYNAMIC CAPACITY:** For some technologies (e.g. ATM), a topological link end can be characterized by name space and bandwidth. + +**TOPOLOGICAL\_END\_DIRECTION:** A topological link end has a directionality that characterizes its ability to originate and/or terminate the traffic to be carried. It may be source, sink or bidirectional. A topological link end source and sink originate and terminate a unidirectional link, respectively. A topological link end bidirectional originates and terminates a bidirectional link. A topological link end source shall contain connection termination points source. A topological link end sink shall contain connection termination points sink. A topological link end bidirectional shall contain connection termination points bidirectional. + +PARALLEL\_COMPOSITION: A compound topological link end is made of component link ends if the corresponding topological link is made of component links (Figure 35). The container and the components must have both the same signal identification and the same direction. + +![Figure 35/G.852.2: Diagram illustrating Parallel Composition. A 'compound link end' is shown as a shaded rectangular block. Inside this block, two 'component link ends' are depicted as smaller circles with arrows pointing to the right, indicating signal direction. The label 'T0410580-98' is present in the bottom right corner of the diagram.](d17aa1fcc3b86503ad1dd0717a6c34c2_img.jpg) + +Figure 35/G.852.2: Diagram illustrating Parallel Composition. A 'compound link end' is shown as a shaded rectangular block. Inside this block, two 'component link ends' are depicted as smaller circles with arrows pointing to the right, indicating signal direction. The label 'T0410580-98' is present in the bottom right corner of the diagram. + +Figure 35/G.852.2 + +BOUNDING: One topological link end is bound to one topological component that can be one subnetwork or one access group (if at the border of the layer network). + +### 6.2.16 Trail + +A trail represents a transport entity which is responsible for the transfer and integrity of information between two trail termination points (for definition, see Recommendation G.805). + +#### Properties + +EXTREMITIES: A trail is terminated by two extremities, the trail termination points which are its A\_end and Z\_end. Through a unidirectional trail, traffic goes only from the A\_end to the Z\_end; through a bidirectional one, traffic may go from A\_end to Z\_end and from Z\_end to A\_end. + +SIGNAL\_IDENTIFICATION: A trail is characterized by a signal identification. The signal identification describes the signal that is transferred across the trail. + +DIRECTIONALITY: Any trail is characterized by a directionality. The directionality characterizes the ability of a trail to carry traffic in one (unidirectional) or two directions (bidirectional). + +COMPOSITION: A trail is made of contiguous link connections and/or subnetwork connections, as shown in Figure 36. Both the first and the last one of such a series may be either a link connection or a subnetwork connection. + +![Figure 36/G.852.2: Diagram illustrating Trail Composition. A dashed line labeled 'trail' is shown. Below it, a solid line represents the path of the trail. The trail is composed of two segments: a 'link connection' on the left and a 'subnetwork connection' on the right. Arrows point from the trail line to these two segments. The label 'T0410590-98' is present in the bottom right corner of the diagram.](68ea9310fb829dd6007635a6cd4ea2ad_img.jpg) + +Figure 36/G.852.2: Diagram illustrating Trail Composition. A dashed line labeled 'trail' is shown. Below it, a solid line represents the path of the trail. The trail is composed of two segments: a 'link connection' on the left and a 'subnetwork connection' on the right. Arrows point from the trail line to these two segments. The label 'T0410590-98' is present in the bottom right corner of the diagram. + +Figure 36/G.852.2 + +ADAPTATION\_RELATION: A trail may support link connections (case of pre-provisioned link, e.g. in SDH, where link connections exist when the equipment is installed) or a topological link (case of dynamic link, e.g. in ATM where link connections will exist only when a connection is required). In such a case, the trail pertains to a given layer network (known as the server layer network) and the + +link connections or topological link that are supported pertain to one (or more) client layer network, as shown in Figure 37. + +![Figure 37/G.852.2: Diagram illustrating two cases of trail adaptation. The top case, 'pre-provisioned case', shows multiple 'link connections' in the 'client layer(s)' being adapted by an 'adaptation function' into a single 'trail' in the 'server layer'. The bottom case, 'dynamic case', shows a 'Topological link' in the 'client layer' being adapted by an 'adaptation function' into a single 'trail' in the 'server layer'. A dashed line separates the client layer(s) from the server layer in both cases. The diagram is labeled T0410600-98.](2bacc162a73d75c43a7f90715832bd13_img.jpg) + +The diagram illustrates two scenarios of trail adaptation. In the 'pre-provisioned case', multiple 'link connections' in the 'client layer(s)' are shown converging through an 'adaptation function' to form a single 'trail' in the 'server layer'. In the 'dynamic case', a 'Topological link' in the 'client layer' is shown converging through an 'adaptation function' to form a single 'trail' in the 'server layer'. A dashed horizontal line separates the client layer(s) from the server layer in both cases. The diagram is labeled T0410600-98. + +Figure 37/G.852.2: Diagram illustrating two cases of trail adaptation. The top case, 'pre-provisioned case', shows multiple 'link connections' in the 'client layer(s)' being adapted by an 'adaptation function' into a single 'trail' in the 'server layer'. The bottom case, 'dynamic case', shows a 'Topological link' in the 'client layer' being adapted by an 'adaptation function' into a single 'trail' in the 'server layer'. A dashed line separates the client layer(s) from the server layer in both cases. The diagram is labeled T0410600-98. + +**Figure 37/G.852.2** + +**BUNDLING:** A trail may bundle other trails. In the context of SDH, bundling of trails may be used for, but not restricted to, contiguous or virtual concatenation. In the context of ATM, it may be used to group a trail carrying end-user information and a trail carrying signal information. Bundled trails may be considered as paralleled to each other. + +### 6.2.17 Trail termination point + +The trail termination point represents an extremity of a trail. It is the combination of a part of the adaptation function, the access point and the trail termination function (see Figure 3). + +#### Properties + +**SIGNAL\_IDENTIFICATION:** A trail termination point has a signal identification which describes the signal that is transferred across the trail termination point. + +**POINT\_DIRECTIONALITY:** A trail termination point has a directionality. The direction characterizes its ability to originate and/or terminate the traffic to be carried. It may be source, sink or bidirectional. A trail termination point source originates a trail. A trail termination point sink terminates a trail. A trail termination point bidirectional may either originate or terminate a trail, or both. + +**ADAPTATION:** A trail termination point source takes as input adapted signal identification from a number of client connection termination points or from a client topological link end (Figure 38). A trail termination point sink delivers adapted signal identification to a number of client connection termination points or to a client topological link end. In such a case, the connection termination points or the topological link end pertain to one (or more) given layer network (known as the client layer network) and the trail termination point that supports them pertain to another layer network (known as the server layer network). + +![Diagram illustrating network layers and termination points. A horizontal line separates the 'client layer' (top) and 'server layer' (bottom). On the left, four white circles labeled 'connection termination points' are in the client layer, with arrows pointing down to a black circle labeled 'trail termination point' in the server layer. On the right, a white circle labeled 'Topological link end' is in the client layer, with an arrow pointing down to another black circle labeled 'trail termination point' in the server layer. The text 'T0410610-98' is in the bottom right corner.](11edb7fcedf09ac6a817f8d7b8c61eec_img.jpg) + +Diagram illustrating network layers and termination points. A horizontal line separates the 'client layer' (top) and 'server layer' (bottom). On the left, four white circles labeled 'connection termination points' are in the client layer, with arrows pointing down to a black circle labeled 'trail termination point' in the server layer. On the right, a white circle labeled 'Topological link end' is in the client layer, with an arrow pointing down to another black circle labeled 'trail termination point' in the server layer. The text 'T0410610-98' is in the bottom right corner. + +**Figure 38/G.852.2** + +## 6.3 Policy + +## OBLIGATION RESOURCES\_USE + +The resources defined in this community provide a basis for the description of enterprise specifications of transport network-level management services. + +## OBLIGATION RETRIEVAL + +For any service operating on resources defined in this specification, the provider shall provide retrieval facilities of the following resource properties: identity of the resource, directionality (if any) and signal identification. + +# ANNEX A + +### Illustration of a tandem connection + +Figure A.1 illustrates that a tandem connection is any series of contiguous link connections and/or subnetwork connections. It differs from link connections and subnetwork connections in that in order to be able to set up a tandem connection, monitoring capabilities must be available in the equipment that support its terminations (e.g. HCS function for SDH Higher-Order Path Layer). + +![Diagram illustrating the hierarchy of network connections across management levels N+1, N, and N-1. It shows SNC, subnetwork, TC, LC, and DSNC components and their relationships.](00504fc688ebcf131ccbeff94dfc9939_img.jpg) + +The diagram illustrates the relationship between different types of network connections across three management levels: + +- management level N + 1:** Shows a single **SNC** (Subnetwork Connection) spanning the entire width. +- management level N:** Shows a **subnetwork** containing four nodes connected in series. Below this, a **TC** (Tandem Connection) is shown spanning the first two nodes. Further down, a sequence of **SNC**, **LC**, **SNC**, **LC**, **SNC**, **LC**, **DSNC**, **LC**, **DSNC**, **LC**, **SNC** is shown. Arrows indicate that the **LC** segments between the first three **SNC** segments are part of the **subnetwork** above. +- management level N - 1:** Shows a sequence of **SNC**, **LC**, **SNC**, **LC**, **SNC**, **LC**, **SNC**, **LC**, **DSNC**, **LC**, **DSNC**, **LC**, **SNC**. Below this, another **subnetwork** is shown, containing four nodes. The third node is a dashed oval and is labeled "not manageable in level N". The fourth node is followed by two boxes labeled "e.g. regen". Arrows indicate that the **LC** segments between the first three **SNC** segments of level N-1 are part of the **subnetwork** below. + +T0410620-98 + +Diagram illustrating the hierarchy of network connections across management levels N+1, N, and N-1. It shows SNC, subnetwork, TC, LC, and DSNC components and their relationships. + +DSNC Degenerate Subnetwork Connection + SNC Subnetwork Connection + LC Link Connection + TC Tandem Connection + +Figure A.1/G.852.2 + +## ANNEX B + +### Examples of use of TEM resources + +The aim of this annex is to give examples of how and by which services all the resources we have been describing will be used in their management life. It is a non-normative part of this Recommendation. The services which are referred later are all described in standards which are independent each from the other; their use in such or such way is let to the discretion of the provider of applications who will use them. All that is described later on is only given as example in order to help to understand the reason of being of each G.852.2 (TEM) resource. + +An activity may be defined that relates all these management components in order to construct a management application, but it is not a standardization process to describe this overall activity. The components studied so far are: + +- simple subnetwork connection configuration (G.852.1): allows to connect or release a subnetwork connection across a subnetwork; +- trail management (tm): allows to connect or release a trail across a layer network domain; +- topology management (topman): allows to create, delete and modify the topology resources (subnetworks, links, link ends, access groups); +- pre-provisioned link management (plm): allows to manage the capacity of a link by adding or removing link connections; +- pre-provisioned link connection management (plcm): allows to assign the link connections inside a link to several users; +- pre-provisioned adaptation management (pam): allows to manage the adaptation between a client layer network and a server layer network by creating the link connections served by a trail. + +The following principles on arc-oriented and point-oriented resources are applied: + +- i) Linking entity and client transport entity can be played by either an arc-oriented resource (link, topological link, link connection) or a point-oriented resource (link end, topological link end, CTP). Note that only point-oriented resource can be at the edge of the network. +- ii) On the other hand, both arc-oriented resource (trail) and point-oriented resource (TTP) can play a role of server transport entity simultaneously in one community. + +A typical management scenario is described in Figures B.1 through B.4 with the corresponding explanatory text below. Note that this management scenario is assuming that arc-oriented resources are within the client layer network and that point-oriented resources are at the edge of the client layer network. + +- 1) Creation of network topology of a client layer network (Figure B.1) + +Topman Caller creates network topology resources of one client layer network domain as follows. Note that this network topology represents a typical non-partitioning case. + +- (a-1) Create access group. +- (a-2) Create subnetwork. +- (a-3) Create link: This action creates topological link #1 between access group and subnetwork, which are previously created. The value of each attribute of topological link #1, such as pamMaxProvisionableCapacity, is zero. +- (a-4) Create link: This action creates a link between access group and subnetwork, which are previously created. + +- (a-5) Create link end: This action creates a topological link end bound to a subnetwork at the edge of a network. The value of each attribute of the topological link end, such as pamMaxProvisionableCapacity, is zero. +- (a-6) Create link end: This action creates a link end bound to a subnetwork at the edge of a network. + +![Diagram illustrating the creation of network topology. A 'topman Caller' box at the top has arrows pointing to various network components. (a-5) points to a 'Link end' (dashed oval) which is part of a 'Topological link end' (solid oval). (a-6) points to the same 'Link end'. (a-2) points to a 'Subnetwork' (large rounded rectangle). (a-3) points to a 'Topological link #1' (rectangle) which contains a 'Link' (dashed rectangle). (a-4) points to the 'Link'. (a-1) points to an 'Access group' (oval). All components are within a 'Client Layer Network' (large rectangle).](c76da2d73c064464051d1583fd80bb6b_img.jpg) + +T0410630-98 + +Diagram illustrating the creation of network topology. A 'topman Caller' box at the top has arrows pointing to various network components. (a-5) points to a 'Link end' (dashed oval) which is part of a 'Topological link end' (solid oval). (a-6) points to the same 'Link end'. (a-2) points to a 'Subnetwork' (large rounded rectangle). (a-3) points to a 'Topological link #1' (rectangle) which contains a 'Link' (dashed rectangle). (a-4) points to the 'Link'. (a-1) points to an 'Access group' (oval). All components are within a 'Client Layer Network' (large rectangle). + +**Figure B.1/G.852.2 – Creation of network topology** + +- 2) Creation of trail and TTP of a server layer network (Figure B.2) + Tm Caller creates TTPs and a trail of one server layer network domain as follows. + - (b-1) Create TTP: This action creates TTP#1. + - (b-2) Create TTP: This action creates TTP#2. + - (b-3) Set up point-to-point trail: This action creates a trail between TTP#1 and #2. + - (b-4) Create TTP: This action creates TTP#3. + +![Diagram illustrating the creation of a trail and TTPs in a server layer network. A 'tm Caller' box at the top has four arrows pointing down to a 'Server Layer Network' box. The arrows are labeled: (b-4) Create TTP pointing to TTP#3, (b-1) Create TTP pointing to TTP#1, (b-3) Set up point-to-point Trail pointing to the Trail, and (b-2) Create TTP pointing to TTP#2. The 'Server Layer Network' box contains a horizontal line labeled 'Trail' with arrows at both ends pointing to TTP#1 and TTP#2. TTP#3 is shown as a small circle below TTP#1.](7ae836e598020d937ed1478c2ef13025_img.jpg) + +T0410640-98 + +Diagram illustrating the creation of a trail and TTPs in a server layer network. A 'tm Caller' box at the top has four arrows pointing down to a 'Server Layer Network' box. The arrows are labeled: (b-4) Create TTP pointing to TTP#3, (b-1) Create TTP pointing to TTP#1, (b-3) Set up point-to-point Trail pointing to the Trail, and (b-2) Create TTP pointing to TTP#2. The 'Server Layer Network' box contains a horizontal line labeled 'Trail' with arrows at both ends pointing to TTP#1 and TTP#2. TTP#3 is shown as a small circle below TTP#1. + +**Figure B.2/G.852.2 – Creation of a trail and TTPs of a server layer network** + +#### 3) Association between server layer and client layer network (Figure B.3) + +As mentioned before, this management scenario is assuming that arc-oriented resources are within the client layer network and that while point-oriented resources are at the edge of the client layer network. pam Caller associates a trail and a TTP with a topological link and a topological link end, respectively. The former is called Scenario #A, while the latter is called Scenario #B in this Recommendation. + +There are two cases for adaptation function: one case where the adaptation is fixed and all the client transport entities have been already provisioned during the creation of the server transport entity, the other where the adaptation is flexible. Scenario #A addresses the latter, while Scenario #B addresses the former. + +#### Scenario #A + +Two client topological linking entities, topological links #1 and #2, share one server trail. The following management scenario addresses this situation. + +- (c1-11) Assign server transport entity to client linking entity (pam): This action is used to assign a server trail to a client topological link #1. In this case, client link connections are not provisioned yet. +- (c1-12) Provision capacity to client linking entity (pam): This action provides a capacity in terms of a number of client link connections from the server trail to a client topological link #1. The value of pamMaxProvisionableCapacity is equal to the maximum number of client link connections from the server trail. The pamProvisionedLinkCapacity is equal to the number of client link connections that the caller requested to provision. +- (c1-2) Add transport entities to linking entities (plm): This action adds client link connections of client topological link #1 to the link. Note that a topological link is not a role of plm community. The link connections contained in the link shall be changed in terms of linkHasLinkConnections, while pamAvailableLinkCapacity shall increase accordingly. + +- (c1-3) Assign transport entity (plcm): This action assigns client link connections inside the link. Note that a topological link is not a role of plcm community. pamAvailableLinkCapacity shall decrease accordingly. +- (c2-11) Assign server transport entity to client linking entity (pam): This action is used to assign a server trail to a client topological link #2. In this case, client link connections are not provisioned yet. +- (c2-12) Provision capacity to client linking entity (pam): This action provides a capacity in terms of a number of client link connections from the server trail to a client topological link #2. As the trail is shared by client topological links #1 and #2, the number of link connections that the caller can request to provision in client topological link #1 will be affected by the number of provisioned link connections in client topological link #2. pamPotentialLinkCapacity represent this capacity. + +#### Scenario #B + +- (d-1) Assign server transport entity to client linking entity (pam): This action is also used to cover the case where the adaptation is fixed and all the client transport entities have been already provisioned during the creation of the server transport entity. All the CTPs are provisioned in the client topological link end. +- (d-2) Add transport entities to linking entities (plm): This action adds client CTPs to the link end. +- (d-3) Assign transport entity (plcm): This action assigns CTPs inside the link end. Note that a topological link end is not a role of plcm community. + +![Diagram illustrating the association between server layer and client layer network. It shows various components like plm Caller, plcm Caller, CTP, Link end, Topological link end, Link, Topological link #1, Topological link #2, Trail, TTP, Server Layer Network, and pam Caller. Arrows indicate actions such as (d-2) Add transport entities to linking entities, (c1-2) Add transport entities to linking entities, (d-3) Assign transport entity, (c1-3) Assign transport entity, (c1-11) Assign server transport entity to client linking entity, (c1-12) Provision capacity to client linking entity, (d-1) Assign server transport entity to client linking entity, (c2-11) Assign server transport entity to client linking entity, and (c2-12) Provision capacity to client linking entity. Capacity labels include pamMaxProvisionableCapacity, link connection, pamPotentialLinkCapacity, pamProvisionedLinkCapacity, pamAvailableLinkCapacity, __linkHasLinkConnections, and __pamAvailableLinkCapacity.](6e15fc9ea763541c5913d26f85072ae1_img.jpg) + +The diagram illustrates the interaction between a client layer network and a server layer network. On the left, a 'CTP' (Client Transport Packet) is shown as a vertical oval containing several small circles. An arrow labeled '(d-2) Add transport entities to linking entities' points from a 'plm Caller' box to the CTP. Another arrow labeled '(d-3) Assign transport entity' points from the plm Caller to a 'Link end' circle. Below the CTP is a 'Topological link end' label. In the center, 'Topological link #1' is represented by a stack of horizontal bars labeled 'link connection'. Arrows labeled '(c1-2) Add transport entities to linking entities' and '(c1-3) Assign transport entity' point from a 'plcm Caller' box to this stack. To the right of the stack are labels for 'pamPotentialLinkCapacity', 'pamProvisionedLinkCapacity', and 'pamAvailableLinkCapacity'. Below the stack is a 'Topological link #1' label. At the bottom center, a 'Trail' is shown as a horizontal double-headed arrow between a 'TTP' (Transport Transport Packet) box and a 'Server Layer Network' box. Arrows labeled '(c1-11) Assign server transport entity to client linking entity' and '(c1-12) Provision capacity to client linking entity' point from the TTP to the stack. Below the TTP is a '(d-1) Assign server transport entity to client linking entity' label. On the far right, 'Topological link #2' is shown as a vertical stack of horizontal bars labeled 'link connection'. Arrows labeled '(c2-11) Assign server transport entity to client linking entity' and '(c2-12) Provision capacity to client linking entity' point from a 'pam Caller' box to this stack. To the left of this stack are labels for 'pamMaxProvisionableCapacity', 'link connection', and 'pamPotentialLinkCapacity'. At the bottom left, labels for '\_\_linkHasLinkConnections' and '\_\_pamAvailableLinkCapacity' are present. + +Diagram illustrating the association between server layer and client layer network. It shows various components like plm Caller, plcm Caller, CTP, Link end, Topological link end, Link, Topological link #1, Topological link #2, Trail, TTP, Server Layer Network, and pam Caller. Arrows indicate actions such as (d-2) Add transport entities to linking entities, (c1-2) Add transport entities to linking entities, (d-3) Assign transport entity, (c1-3) Assign transport entity, (c1-11) Assign server transport entity to client linking entity, (c1-12) Provision capacity to client linking entity, (d-1) Assign server transport entity to client linking entity, (c2-11) Assign server transport entity to client linking entity, and (c2-12) Provision capacity to client linking entity. Capacity labels include pamMaxProvisionableCapacity, link connection, pamPotentialLinkCapacity, pamProvisionedLinkCapacity, pamAvailableLinkCapacity, \_\_linkHasLinkConnections, and \_\_pamAvailableLinkCapacity. + +Figure B.3/G.852.2 – Association between server layer and client layer network + +- 4) Creation of transport entities in client layer network (Figure B.4) +- (e) Set up point-to-point SNC (sscc): This action sets up subnetwork connection between CTP and link connection. + - (f-1) Create TTP (tm): This action creates a TTP, associating this TTP with a link connection. + - (f-2) Associate TTP with access group (tm): This action associates TTP with access group. + +![Diagram illustrating the creation of transport entities in a client layer network. It shows two callers, 'sscc Caller' and 'tm Caller', interacting with a 'Client Layer Network' which contains a 'Subnetwork' and a 'Link'. The 'sscc Caller' initiates action (e) 'Set up point-to-point SNC' to establish a 'subnetwork connection' between a 'CTP Link end' and a 'link connection'. The 'tm Caller' initiates actions (f-1) 'Create TTP' and (f-2) 'Associate TTP with access group' to associate a TTP with the 'link connection' and an 'Access group'.](339be989b91d5b1e73e5ecdc8401ca75_img.jpg) + +The diagram shows the following components and actions: + +- sscc Caller**: Initiates action (e) "Set up point-to-point SNC". +- tm Caller**: Initiates actions (f-1) "Create TTP" and (f-2) "Associate TTP with access group". +- Client Layer Network**: Contains a **Subnetwork** and a **Link**. +- Subnetwork**: Contains a **CTP Link end** and a **subnetwork connection**. +- Link**: Contains a **link connection** and an **Access group**. +- Action (e)**: A line from the sscc Caller points to the subnetwork connection. +- Actions (f-1) and (f-2)**: A line from the tm Caller points to the link connection. + +T0410660-98 + +Diagram illustrating the creation of transport entities in a client layer network. It shows two callers, 'sscc Caller' and 'tm Caller', interacting with a 'Client Layer Network' which contains a 'Subnetwork' and a 'Link'. The 'sscc Caller' initiates action (e) 'Set up point-to-point SNC' to establish a 'subnetwork connection' between a 'CTP Link end' and a 'link connection'. The 'tm Caller' initiates actions (f-1) 'Create TTP' and (f-2) 'Associate TTP with access group' to associate a TTP with the 'link connection' and an 'Access group'. + +**Figure B.4/G.852.2 – Creation of transport entities in client layer** + +# ITU-T RECOMMENDATIONS SERIES + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of the ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure and Internet protocol aspects | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.852.3-199903-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.852.3-199903-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..a7da83ecb82b51a4cef7694858eef2c35f1986ff --- /dev/null +++ b/marked/G/T-REC-G.852.3-199903-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:d77a478c5b78d330a2a6abbd32e7d0ac053d8b9c1ffe8a96476214afa6ddf7ae +size 8196 diff --git a/marked/G/T-REC-G.853.1-199903-I_PDF-E/raw.md b/marked/G/T-REC-G.853.1-199903-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..98c70edbb9e861c2e25b26c10b2adca7929046ce --- /dev/null +++ b/marked/G/T-REC-G.853.1-199903-I_PDF-E/raw.md @@ -0,0 +1,3915 @@ + + +![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.853.1** + +(03/99) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital transmission systems – Digital networks – +Management of transport network + +--- + +**Common elements of the information viewpoint +for the management of a transport network** + +ITU-T Recommendation G.853.1 + +(Previously CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| INTERNATIONAL ANALOGUE CARRIER SYSTEM | | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TRANSMISSION SYSTEMS | | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | + +*For further details, please refer to ITU-T List of Recommendations.* + +# **COMMON ELEMENTS OF THE INFORMATION VIEWPOINT FOR THE MANAGEMENT OF A TRANSPORT NETWORK** + +## **Summary** + +The objective of this Recommendation is to provide the information viewpoint specification for management abstractions of G.805 transport network architectural components. The resources defined in this Recommendation provide a basis for the description of transport network level management services. + +## **Source** + +ITU-T Recommendation G.853.1 was prepared by ITU-T Study Group 4 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 26th of March 1999. + +## FOREWORD + +ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +### NOTE + +In this Recommendation the term *recognized operating agency (ROA)* includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms *Administration*, *ROA* and *public correspondence* are defined in the *Constitution of the ITU (Geneva, 1992)*. + +## INTELLECTUAL PROPERTY RIGHTS + +The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 1999 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +## CONTENTS + +###### Page + +| | | | +|------|-------------------------------------------|----| +| 1 | Scope ..... | 1 | +| 2 | References ..... | 1 | +| 3 | Definitions ..... | 1 | +| 4 | Abbreviations ..... | 1 | +| 5 | Conventions ..... | 2 | +| 6 | Information object type definitions ..... | 2 | +| 6.1 | accessGroup ..... | 6 | +| 6.2 | administrativeDomain ..... | 6 | +| 6.3 | circuitPack ..... | 6 | +| 6.4 | equipment ..... | 6 | +| 6.5 | layerNetworkDomain ..... | 7 | +| 6.6 | link ..... | 7 | +| 6.7 | linkConnection ..... | 7 | +| 6.8 | linkEnd ..... | 8 | +| 6.9 | networkCTP ..... | 8 | +| 6.10 | networkCTPBidirectional ..... | 9 | +| 6.11 | networkCTPSink ..... | 9 | +| 6.12 | networkCTPSource ..... | 9 | +| 6.13 | networkElementCTP ..... | 9 | +| 6.14 | networkElementFabric ..... | 10 | +| 6.15 | networkElementTP ..... | 10 | +| 6.16 | networkElementTTP ..... | 10 | +| 6.17 | networkInformationTop ..... | 10 | +| 6.18 | networkTTP ..... | 10 | +| 6.19 | networkTTPBidirectional ..... | 11 | +| 6.20 | networkTTPSink ..... | 11 | +| 6.21 | networkTTPSource ..... | 11 | +| 6.22 | node ..... | 12 | +| 6.23 | physicalMedium ..... | 12 | +| 6.24 | physicalPort ..... | 12 | +| 6.25 | subnetwork ..... | 12 | +| 6.26 | subnetworkConnection ..... | 13 | +| 6.27 | subnetworkTP ..... | 13 | + +| | Page | +|---------------------------------------------------|-------------| +| 6.28 subnetworkTPBidirectional..... | 13 | +| 6.29 subnetworkTPPool ..... | 14 | +| 6.30 subnetworkTPSink ..... | 14 | +| 6.31 subnetworkTPSource..... | 14 | +| 6.32 tandemConnection..... | 14 | +| 6.33 topologicalLink ..... | 15 | +| 6.34 topologicalLinkEnd ..... | 15 | +| 6.35 trail ..... | 16 | +| 6.36 transportConnection ..... | 16 | +| 7 Attribute type definition ..... | 16 | +| 7.1 directionality..... | 16 | +| 7.2 linkDirectionality..... | 17 | +| 7.3 locationName..... | 17 | +| 7.4 pointDirectionality..... | 17 | +| 7.5 resourceId ..... | 17 | +| 7.6 signalIdentification..... | 17 | +| 7.7 topologicalEndDirection ..... | 18 | +| 7.8 userLabel ..... | 18 | +| 8 Information relationship type definitions ..... | 18 | +| 8.1 accessGroupIsMadeOfNetworkTTPs..... | 18 | +| 8.2 accessGroupIsRelatedToSntpPool ..... | 19 | +| 8.3 administrativeDomainIsMadeOf..... | 19 | +| 8.4 circuitPackSupportsPhysicalPorts ..... | 20 | +| 8.5 compoundLinkEndHasLinkEnds ..... | 20 | +| 8.6 compoundLinkHasLinks ..... | 20 | +| 8.7 concatenatedLinkHasLinks ..... | 21 | +| 8.8 equipmentImplements ..... | 22 | +| 8.9 equipmentIsMadeOfEquipments..... | 22 | +| 8.10 extremitiesTerminatePhysicalMedium..... | 23 | +| 8.11 isConnectedTo..... | 23 | +| 8.12 layerNetworkDomainCanServeLnds..... | 23 | +| 8.13 layerNetworkDomainIsMadeOf..... | 24 | +| 8.14 linkBinds ..... | 24 | +| 8.15 linkConnectionIsBoundTo ..... | 25 | + +| | Page | +|----------------------------------------------------------------|-------------| +| 8.16 linkConnectionIsBundleOfLinkConnections ..... | 26 | +| 8.17 linkConnectionIsMadeOfTransportEntities ..... | 26 | +| 8.18 linkConnectionIsSupportedByTrail..... | 27 | +| 8.19 linkConnectionIsTerminatedByPointToPoint ..... | 28 | +| 8.20 linkConnectionIsTerminatedByTopologicalEntities..... | 28 | +| 8.21 linkEndIsBoundTo ..... | 29 | +| 8.22 linkEndHasNetworkCTPs ..... | 29 | +| 8.23 linkHasLinkConnections ..... | 30 | +| 8.24 linkIsTerminatedByLinkEnds ..... | 31 | +| 8.25 networkCTPIsBundleOfNetworkCTPs ..... | 31 | +| 8.26 networkTTPAdaptsNetworkCTP ..... | 32 | +| 8.27 representSameResourceAs ..... | 33 | +| 8.28 sncBidIsSupportedByUnis..... | 33 | +| 8.29 snIsPartitionedByLinks ..... | 34 | +| 8.30 snIsPartitionedBySn ..... | 34 | +| 8.31 subnetworkConnectionIsBundleOfSubnetworkConnections ..... | 35 | +| 8.32 subnetworkConnectionIsMadeOfTransportEntities ..... | 36 | +| 8.33 subnetworkConnectionIsTerminatedByPointToPoint..... | 37 | +| 8.34 subnetworkHasSubnetworkConnections..... | 37 | +| 8.35 subnetworkIsDelimitedBy ..... | 38 | +| 8.36 subnetworkIsDelimitedBySnTpPools ..... | 39 | +| 8.37 subnetworkTPIsBundleOfSubnetworkTPs..... | 39 | +| 8.38 subnetworkTPIsRelatedToExtremity ..... | 40 | +| 8.39 subnetworkTPPoolIsMadeOfSubnetworkTP ..... | 41 | +| 8.40 subnetworkTPPoolIsRelatedToExtremity ..... | 42 | +| 8.41 tandemConnectionIsMadeOfTransportEntities..... | 42 | +| 8.42 topologicalLinkEndIsSupportedByNetworkTTP ..... | 43 | +| 8.43 topologicalLinkIsSupportedByTrail..... | 44 | +| 8.44 trailIsBundleOfTrails..... | 44 | +| 8.45 trailIsMadeOfTransportEntities..... | 45 | +| 8.46 trailIsTerminatedByPointToPoint ..... | 46 | +| Annex A – UML relationships diagrams..... | 47 | +| A.1 Topology..... | 47 | +| A.2 Partitioning relationships..... | 48 | +| A.3 Connection extremities..... | 49 | + +| | Page | +|-------------------------------------------|-------------| +| A.4 Connection composition..... | 50 | +| A.5 Inter-layering relationships..... | 51 | +| A.6 Bundle relationships ..... | 52 | +| A.7 Physical entities relationships ..... | 53 | + +# Recommendation G.853.1 + +# COMMON ELEMENTS OF THE INFORMATION VIEWPOINT FOR THE MANAGEMENT OF A TRANSPORT NETWORK + +(Geneva, 1999) + +## 1 Scope + +This information viewpoint specification is related to the enterprise specification of the transport network resource model defined in Recommendation G.852.2. + +## 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- [1] ITU-T Recommendation G.851.1 (1996), *Management of the transport network – Application of the RM-ODP framework*. +- [2] ITU-T Recommendation G.852.2 (1999), *Enterprise viewpoint description of transport network resource model*. +- [3] ITU-T Recommendation G.805 (1995), *Generic functional architecture of transport networks*. +- [4] ITU-T Recommendation M.3100 (1995), *Generic network information model*. + +## 3 Definitions + +None. + +## 4 Abbreviations + +This Recommendation uses the following abbreviations: + +| | | +|-----|------------------------------| +| AD | Administrative Domain | +| AG | Access Group | +| bid | bidirectional | +| CTP | Connection Termination Point | +| gtp | Group Termination Point | +| Id | Identifier | +| inv | invariant | +| LC | Link Connection | +| LE | Link End | + +| | | +|------------|--------------------------------------------------------------------| +| LEnd | Link End | +| LND | Layer Network Domain | +| NE | Network Element | +| NTTP | Network Trail Termination Point | +| PhysMed | Physical Medium | +| PhysPort | Physical Port | +| SDH | Synchronous Digital Hierarchy | +| SN | Subnetwork | +| SNC | Subnetwork Connection | +| SNTP | Subnetwork Termination Point | +| TC | Tandem Connection | +| tem | Transport Network Resource Model – Enterprise Viewpoint (G.852.2) | +| TEntity | Transport Entity | +| tim | Transport Network Resource Model – Information Viewpoint (G.853.1) | +| TL | Topological Link | +| TLE | Topological Link End | +| TP | Termination Point | +| TransportC | Transport Connection | +| TTP | Trail Termination Point | +| uni | unidirectional | +| UML | Unified Modelling Language | + +## 5 Conventions + +None. + +## 6 Information object type definitions + +See Figures 1 a) to 1 e). + +![UML class diagram showing network-related information object types. At the top is 'networkInformationTop' with attribute 'resourceId'. Below it, a horizontal line connects several classes: 'accessGroup' (attributes: topologicalEndDirection, signalIdentification), 'administrativeDomain', 'layerNetworkdomain' (attribute: signalIdentification), 'link' (attributes: signalIdentification, linkDirectionality), 'linkEnd' (attributes: signalIdentification, topologicalEndDirection), 'subnetwork' (attribute: signalIdentification), and 'subnetworkTPPool' (attributes: signalIdentification, topologicalEndDirection). Below 'accessGroup' is 'topologicalLink'. Below 'administrativeDomain' is 'node' (attribute: locationName), with an arrow pointing up to 'administrativeDomain'. Below 'subnetworkTPPool' is 'topologicalLinkEnd'. Arrows point from 'topologicalLink', 'node', and 'topologicalLinkEnd' up to the horizontal line connecting the main classes. An arrow also points from the horizontal line up to 'networkInformationTop'.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg) + +``` + +classDiagram + class networkInformationTop { + resourceId + } + class accessGroup { + topologicalEndDirection + signalIdentification + } + class administrativeDomain + class layerNetworkdomain { + signalIdentification + } + class link { + signalIdentification + linkDirectionality + } + class linkEnd { + signalIdentification + topologicalEndDirection + } + class subnetwork { + signalIdentification + } + class subnetworkTPPool { + signalIdentification + topologicalEndDirection + } + class topologicalLink + class node { + locationName + } + class topologicalLinkEnd + + networkInformationTop <|-- accessGroup + networkInformationTop <|-- administrativeDomain + networkInformationTop <|-- layerNetworkdomain + networkInformationTop <|-- link + networkInformationTop <|-- linkEnd + networkInformationTop <|-- subnetwork + networkInformationTop <|-- subnetworkTPPool + + topologicalLink <|-- accessGroup + node <|-- administrativeDomain + topologicalLinkEnd <|-- subnetworkTPPool + +``` + +UML class diagram showing network-related information object types. At the top is 'networkInformationTop' with attribute 'resourceId'. Below it, a horizontal line connects several classes: 'accessGroup' (attributes: topologicalEndDirection, signalIdentification), 'administrativeDomain', 'layerNetworkdomain' (attribute: signalIdentification), 'link' (attributes: signalIdentification, linkDirectionality), 'linkEnd' (attributes: signalIdentification, topologicalEndDirection), 'subnetwork' (attribute: signalIdentification), and 'subnetworkTPPool' (attributes: signalIdentification, topologicalEndDirection). Below 'accessGroup' is 'topologicalLink'. Below 'administrativeDomain' is 'node' (attribute: locationName), with an arrow pointing up to 'administrativeDomain'. Below 'subnetworkTPPool' is 'topologicalLinkEnd'. Arrows point from 'topologicalLink', 'node', and 'topologicalLinkEnd' up to the horizontal line connecting the main classes. An arrow also points from the horizontal line up to 'networkInformationTop'. + +T0410800-99 + +Figure 1 a)/G.853.1 – Network-related information object types diagram (topological entities) + +![UML class diagram for network-related information object types (topological entities).](d4af765160d04ecef538e5066006dc77_img.jpg) + +``` + +classDiagram + networkInformationTop <|-- transportConnection + transportConnection <|-- linkConnection + transportConnection <|-- subnetworkConnection + transportConnection <|-- tandemConnection + transportConnection <|-- trail + class networkInformationTop { + resourceId + } + class transportConnection { + signalIdentification + directionality + } + class linkConnection + class subnetworkConnection + class tandemConnection + class trail + +``` + +The diagram shows a hierarchy of classes. At the top is **networkInformationTop** with attribute **resourceId**. Below it is **transportConnection** with attributes **signalIdentification** and **directionality**. An arrow points from **transportConnection** to **networkInformationTop**. Below **transportConnection** are four classes: **linkConnection**, **subnetworkConnection**, **tandemConnection**, and **trail**. Arrows point from each of these four classes to **transportConnection**. + +UML class diagram for network-related information object types (topological entities). + +T0410810-99 + +Figure 1 b)/G.853.1 – Network-related information object types diagram (topological entities) + +![UML class diagram for network-related information object types (point entities).](27b06ec9f42b5d727a2630f61a5f1861_img.jpg) + +``` + +classDiagram + networkInformationTop <|-- networkTTP + networkInformationTop <|-- networkCTP + networkTTP <|-- networkTTPSource + networkTTP <|-- networkTTPSink + networkCTP <|-- networkCTPSink + networkCTP <|-- networkCTPSource + networkTTPSource <|-- networkTTPBidirectional + networkTTPSink <|-- networkTTPBidirectional + networkCTPSink <|-- networkCTPBidirectional + networkCTPSource <|-- networkCTPBidirectional + class networkInformationTop { + resourceId + } + class networkTTP { + signalIdentification + pointDirectionality + } + class networkCTP { + signalIdentification + pointDirectionality + } + class networkTTPSource + class networkTTPSink + class networkCTPSink + class networkCTPSource + class networkTTPBidirectional + class networkCTPBidirectional + +``` + +The diagram shows a hierarchy of classes. At the top is **networkInformationTop** with attribute **resourceId**. Below it are **networkTTP** and **networkCTP**, both with attributes **signalIdentification** and **pointDirectionality**. Arrows point from **networkTTP** and **networkCTP** to **networkInformationTop**. Below **networkTTP** are **networkTTPSource** and **networkTTPSink**. Below **networkCTP** are **networkCTPSink** and **networkCTPSource**. Arrows point from these four classes to **networkTTP** and **networkCTP** respectively. Below **networkTTPSource** and **networkTTPSink** is **networkTTPBidirectional**. Below **networkCTPSink** and **networkCTPSource** is **networkCTPBidirectional**. Arrows point from **networkTTPBidirectional** to both **networkTTPSource** and **networkTTPSink**. Similarly, arrows point from **networkCTPBidirectional** to both **networkCTPSink** and **networkCTPSource**. + +UML class diagram for network-related information object types (point entities). + +T0410820-99 + +Figure 1 c)/G.853.1 – Network-related information object types diagram (point entities) + +![UML class diagram for network element-related information object types. The hierarchy starts with networkInformationTop at the top, which has a resourceId attribute. Below it are networkElementTP and networkElementFabric. networkElementTP is further divided into networkElementCTP and networkElementTTP, both of which have a pointDirectionality attribute. A small code T0410830-99 is present at the bottom right of the diagram.](af7916c89a458fdab6c3f443217388ae_img.jpg) + +``` + +classDiagram + networkInformationTop <|-- networkElementTP + networkInformationTop <|-- networkElementFabric + networkElementTP <|-- networkElementCTP + networkElementTP <|-- networkElementTTP + class networkInformationTop { + resourceId + } + class networkElementTP + class networkElementFabric + class networkElementCTP { + pointDirectionality + } + class networkElementTTP { + pointDirectionality + } + +``` + +T0410830-99 + +UML class diagram for network element-related information object types. The hierarchy starts with networkInformationTop at the top, which has a resourceId attribute. Below it are networkElementTP and networkElementFabric. networkElementTP is further divided into networkElementCTP and networkElementTTP, both of which have a pointDirectionality attribute. A small code T0410830-99 is present at the bottom right of the diagram. + +Figure 1 d)/G.853.1 – Network element-related information object types diagram + +![UML class diagram for physical-related information object types. The hierarchy starts with networkInformationTop at the top, which has a resourceId attribute. Below it is equipment, which has a locationName attribute. Below equipment are circuitPack, physicalPort, and physicalMedium. A small code T0410840-99 is present at the bottom right of the diagram.](eefe19c5e14dc4d6c316b7f7fbb7d7d7_img.jpg) + +``` + +classDiagram + networkInformationTop <|-- equipment + equipment <|-- circuitPack + equipment <|-- physicalPort + equipment <|-- physicalMedium + class networkInformationTop { + resourceId + } + class equipment { + locationName + } + class circuitPack + class physicalPort + class physicalMedium + +``` + +T0410840-99 + +UML class diagram for physical-related information object types. The hierarchy starts with networkInformationTop at the top, which has a resourceId attribute. Below it is equipment, which has a locationName attribute. Below equipment are circuitPack, physicalPort, and physicalMedium. A small code T0410840-99 is present at the bottom right of the diagram. + +Figure 1 e)/G.853.1 – Physical-related information object types diagram + +### 6.1 accessGroup + +This information type is related to the following enterprise entity: + +. + +#### DEFINITION + +"An accessGroup information object represents *'a group of co-located networkTTPs that are connected to the same subnetwork or link'* (G.852.2 definition). + +The accessGroup information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +topologicalEndDirection + +"The topologicalEndDirection attribute characterizes the ability of the accessGroup to originate and/or terminate the traffic to be carried." + +signalIdentification + +"An accessGroup has a characteristic information which represents the specific format of signal that the resource carries. The specific format values will be defined in the technology-specific extensions." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + + + + +### 6.2 administrativeDomain + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"An administrativeDomain information object represents *'a domain in which the resources are grouped for a management purpose by an administrator'* (G.852.2 definition). + +The administrativeDomain information object type is a subtype of the networkInformationTop information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + +### 6.3 circuitPack + +#### DEFINITION + +"A circuitPack information object is a particular equipment that represents a physical circuitPack. + +The circuitPack information object type is a subtype of the equipment information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + +### 6.4 equipment + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"An equipment information object represents *'physical components of a managed element, including replaceable components'* (G.852.2 definition). + +The equipment information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +locationName + +"The locationName attribute identifies the location of an equipment that permits to locate where transport functions are." + +#### POTENTIAL\_RELATIONSHIPS + + + + +### 6.5 layerNetworkDomain + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A layerNetworkDomain information object represents *'a transport administrative domain in which all resources pertain to the same G.805 layer' (G.852.2 definition)*. + +The layerNetworkDomain information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +signalIdentification + +"The signalIdentification describes the signal that is transferred across the layer network domain." + +#### POTENTIAL\_RELATIONSHIPS + + + + +### 6.6 link + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A link information object represents *'the capacity between two subnetworks, two access groups or one subnetwork and one access group' (G.852.2 definition)*. + +The link information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +signalIdentification + +"The signalIdentification describes the signal that is transferred across the link." + +linkDirectionality + +"The linkDirectionality attribute characterizes the ability of the associated resource to carry traffic in one, two, or undefined direction." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + +### 6.7 linkConnection + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A linkConnection information object represents *'the transparent capacity of transfer of information characterized by a given signal identification between two fixed points' (G.852.2 definition)*." + +The linkConnection information object type is a subtype of the transportConnection information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + + + + + + + +### 6.8 linkEnd + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A linkEnd information object represents the extremity of a link. It can contain a set (possibly empty) of networkCTPs. + +The linkEnd information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +topologicalEndDirection + +"The topologicalEndDirection attribute characterizes the ability of the linkEnd resource to originate and/or terminate the traffic to be carried." + +signalIdentification + +"A linkEnd carries a specific format. The specific formats will be defined in the technology-specific extensions." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + +### 6.9 networkCTP + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"The networkCTP information object represents *'the potential extremity of a link connection. It relates to the G.805 port and its associated part of the adaptation function that is in the server layer'* (G.852.2 definition). + +The networkCTP information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +pointDirectionality + +"The pointDirectionality attribute characterizes the ability of the networkCTP to terminate or/and originate the signal to be carried." + +signalIdentification + +"A networkCTP has a characteristic information which represents the specific format of signal that the resource carries. The specific format values will be defined in the technology-specific extensions." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + +### 6.10 networkCTPBidirectional + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"The networkCTPBidirectional information object represents *'the extremity of a link connection and is intended to be bound to the output of an unidirectional link connection or to the input of an unidirectional link connection or to the input and output of a bidirectional link connection (G.852.2 definition) .*" + +The networkCTPBidirectional information object type is a subtype of the networkCTPSink and networkCTPSource information object types." + +#### INVARIANT + +inv\_directionality + +"The pointDirectionality attribute value is set to bidirectional." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.11 networkCTPSink + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"The networkCTPSink information object represents *'the extremity of a link connection and is intended to be bound to the output of an unidirectional link connection (G.852.2 definition) .*" + +The networkCTPSink information object type is a subtype of the networkCTP information object type." + +#### INVARIANT + +inv\_directionality + +"The pointDirectionality attribute value is set to sink." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.12 networkCTPSource + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"The networkCTPSource information object represents *'the extremity of a link connection and is intended to be bound to the input of a unidirectional link connection (G.852.2 definition) .*" + +The networkCTPSource information object type is a subtype of the networkCTP information object type." + +#### INVARIANT + +inv\_directionality + +"The pointDirectionality attribute value is set to source." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.13 networkElementCTP + +#### DEFINITION + +"A networkElementCTP information object represents a M.3100 connection termination point source, sink or bidirectional. + +The networkElementCTP information object type is a subtype of the networkElementTP information object type." + +#### ATTRIBUTE + +pointDirectionality + +"The pointDirectionality attribute characterizes the ability of the networkElementCTP to terminate or/and originate the signal to be carried." + +#### POTENTIAL\_RELATIONSHIPS + + + +### 6.14 networkElementFabric + +#### DEFINITION + +"A networkElementFabric information object class represents a M.3100 fabric. + +The networkElementFabric information object type is a subtype of the networkInformationTop information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + + +### 6.15 networkElementTP + +#### DEFINITION + +"The networkElementTP information object represents a M.3100 termination point. + +The networkElementTP information object type is a subtype of the networkInformationTop information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + + +### 6.16 networkElementTTP + +#### DEFINITION + +"A networkElementTTP information object class represents a M.3100 trail termination point source, sink or bidirectional. + +The networkElementTTP information object type is a subtype of the networkElementTP information object type." + +#### ATTRIBUTE + +pointDirectionality + +"The pointDirectionality attribute characterizes the ability of the networkElementTTP to terminate or/and originate the signal to be carried." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.17 networkInformationTop + +#### DEFINITION + +"The networkInformationTop information object type is the root of the inheritance diagram of TIM. All the other information object types are subtypes of networkInformationTop, either directly or indirectly." + +#### ATTRIBUTE + +resourceId + +"Each resource has a unique identification" + +#### POTENTIAL\_RELATIONSHIPS + + + + + +### 6.18 networkTTP + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"The networkTTP information object represents *'an extremity of a trail. It represents the combination of a part of the adaptation function, the access point and the trail termination function' (G.852.2 definition)*. + +The networkTTP information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +pointDirectionality + +"The pointDirectionality attribute characterizes the ability of the networkTTP to terminate or/and originate the signal to be carried." + +signalIdentification + +"A networkTTP has a characteristic information which represents the specific format of signal that the resource carries. The specific format values will be defined in the technology-specific extensions." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + + + + + + +### 6.19 networkTTPBidirectional + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"The networkTTPBidirectional information object represents a particular networkTTP that *'may either originate or terminate a trail, or both'* (G.852.2 definition)." + +The networkTTPBidirectional information object type is a subtype of the information object types networkTTPSink and networkTTPSource." + +#### INVARIANT + +inv\_directionality + +"The pointDirectionality attribute value is set to bidirectional." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.20 networkTTPSink + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"The networkTTPSink information object represents a particular networkTTP that *'terminates a trail'* (G.852.2 definition)." + +The networkTTPSink information object type is a subtype of the networkTTP information object type." + +#### INVARIANT + +inv\_directionality + +"The pointDirectionality attribute value is set to sink." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.21 networkTTPSource + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"The networkTTPSource information object represents a particular networkTTP that *'originates a trail'* (G.852.2 definition)." + +The networkTTPSource information object type is a subtype of the networkTTP information object type." + +#### INVARIANT + +inv\_directionality + +"The pointDirectionality attribute value is set to source." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.22 node + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A node information object represents *'a collection of resources grouped in a single geographical location. It is a kind of administrative domain (for example, it can be one town or one building)' (G.852.2 definition)*. + +The node information object type is a subtype of the administrativeDomain information object type." + +#### ATTRIBUTE + +locationName + +"The locationName attribute identifies the location of a node." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.23 physicalMedium + +#### DEFINITION + +"A physicalMedium information object represents a physical medium that can transfer a signal (i.e. optical fibre). + +The physicalMedium information object type is a subtype of the equipment information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + +### 6.24 physicalPort + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A physicalPort information object represents a physical port. + +The physicalPort information object type is a subtype of the equipment information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + + + +### 6.25 subnetwork + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A subnetwork information object represents *'a topological component used to effect routing of a specific characteristic information' (G.852.2 definition)*. + +The subnetwork information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +signalIdentification + +"A subnetwork carries a specific format. The specific formats will be defined in the technology-specific extensions." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + + + + + + + + + + +### 6.26 subnetworkConnection + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A subnetworkConnection information object represents *'a transport entity that transfers information across a subnetwork.'* (G.852.2 definition). + +The subnetworkConnection information object type is a subtype of the transportConnection information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + + + +### 6.27 subnetworkTP + +#### DEFINITION + +"The subnetworkTP information object class is an abstraction that represents the potential termination of a transport entity and the associated port (see G.805 definition). + +It also represents the potential for connection across subnetworks. + +The subnetworkTP information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +pointDirectionality + +"The pointDirectionality attribute characterizes the ability of the subnetworkTP to terminate or/and originate the signal to be carried." + +signalIdentification + +"A subnetworkTP has a characteristic information which represents the specific format of signal that the resource carries. The specific format values will be defined in the technology-specific extensions." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + +### 6.28 subnetworkTPBidirectional + +#### DEFINITION + +"The subnetworkTPBidirectional information object type is a subtype of the subnetworkTPSink and subnetworkTPSource information object types." + +#### INVARIANT + +inv\_directionality + +"The pointDirectionality attribute value is set to bidirectional." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.29 subnetworkTPPool + +#### DEFINITION + +"A subnetworkTPPool information object is an abstraction that represents a set (possibly empty) of subnetworkTPs at the frontier of a given subnetwork. + +The subnetworkTPPool information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +signalIdentification + +"A subnetwork carries a specific format. The specific formats will be defined in the technology-specific extensions." + +topologicalEndDirection + +"The topologicalEndDirection attribute characterizes the ability of the subnetworkTpPool to originate and/or terminate the traffic to be carried." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + + + + +### 6.30 subnetworkTPSink + +#### DEFINITION + +"The subnetworkTPSink information object class is an abstraction that represents the potential termination of a transport entity and the associated unidirectional port (see G.805 definition). + +It also represents the potential for connection across subnetworks. + +The subnetworkTPSink information object type is a subtype of the subnetworkTP information object type." + +#### INVARIANT + +inv\_directionality + +"The pointDirectionality attribute value is set to sink." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.31 subnetworkTPSource + +#### DEFINITION + +"The subnetworkTPSource information object class is an abstraction that represents the potential origin of a transport entity and the associated unidirectional port (see G.805 definition). + +It also represents the potential for connection across subnetworks. + +The subnetworkTPSource information object type is a subtype of the subnetworkTP information object type." + +#### INVARIANT + +inv\_directionality + +"The pointDirectionality attribute value is set to source." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +### 6.32 tandemConnection + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A tandemConnection information object represents *'an arbitrary series of contiguous link connections and/or subnetwork connections. A tandem connection is created for monitoring purposes' (G.852.2 definition)*. + +The tandemConnection information object type is a subtype of the transportConnection information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + +### 6.33 topologicalLink + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A topologicalLink information object represents *'a link provided by one and only one server trail, in a client layer'* (G.852.2 definition). + +This topologicalLink information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +signalIdentification + +"The signalIdentification describes the signal that is transferred across the link." + +linkDirectionality + +"The linkDirectionality attribute characterizes the ability of the associated resource to carry traffic in one, two, or undefined direction." + +#### INVARIANT + +signalIdentification + +"The signalIdentification describes the signal that is transferred across the topological link." + +linkDirectionality + +"The linkDirectionality attribute characterizes the ability of the associated resource to carry traffic in one or two direction." + +inv\_directionality + +"The linkDirectionality attribute value can not be set to undefined." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + + + + + + +### 6.34 topologicalLinkEnd + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A topologicalLinkEnd information object represents the extremity of a topologicalLink. + +The topologicalLinkEnd information object type is a subtype of the networkInformation Top information object type." + +#### ATTRIBUTE + +topologicalEndDirection + +"The topologicalEndDirection attribute characterizes the ability of the linkEnd resource to originate and/or terminate the traffic to be carried." + +signalIdentification + +"A linkEnd carries a specific format. The specific formats will be defined in the technology-specific extensions." + +#### INVARIANT + +inv\_directionality + +"The topologicalEndDirection attribute value can not be set to undefined." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + + +### 6.35 trail + +This information type is related to the following enterprise entity: + + + +#### DEFINITION + +"A trail information object represents a *'transport entity which is responsible for the transfer and integrity of information between two trail termination points'* (G.852.2 definition). + +The trail information object type is a subtype of the transportConnection information object type." + +#### POTENTIAL\_RELATIONSHIPS + + + + + + + +### 6.36 transportConnection + +#### DEFINITION + +"A transportConnection information object represents a G.805 connection, or a G.805 trail (see G.805 definition). The information transfer can be unidirectional or bidirectional, qualifying the directionality of the transportConnection. + +This transportConnection information object type is a subtype of the networkInformationTop information object type." + +#### ATTRIBUTE + +signalIdentification + +"The signalIdentification describes the signal that is transferred across the transportConnection." + +directionality + +"The directionality characterizes the ability of a transportConnection to carry traffic in one or two directions." + +#### POTENTIAL\_RELATIONSHIPS + +No additional relationship. + +## 7 Attribute type definition + +### 7.1 directionality + +#### DEFINITION + +"The directionality attribute characterizes the ability of the associated resource to carry traffic in one or two directions. The semantic of this attribute is imported from M.3100 directionality attribute." + +#### INVARIANT + +inv\_lifetime + +"The directionality associated with an information object must not change during its whole lifetime." + +#### STATE + +unidirectional + +"The resource is able to carry the signal in only one direction." + +bidirectional + +"The resource is able to carry the signal in two directions." + +### 7.2 linkDirectionality + +#### DEFINITION + +"The directionality attribute characterizes the ability of the associated resource to carry traffic in one, two or undefined direction." + +#### STATE + +undefined + +"There is no indication on the ability of the resource to carry the signal in one or two directions." + +unidirectional + +"The resource is able to carry the signal in only one direction from A\_end to Z\_end." + +bidirectional + +"The resource is able to carry the signal in two directions." + +### 7.3 locationName + +#### DEFINITION + +"The locationName attribute identifies the location of a resource. The semantic of this attribute is imported from M.3100 locationName attribute." + +### 7.4 pointDirectionality + +#### DEFINITION + +"The pointDirectionality attribute characterizes the ability of the associated resource to terminate or/and originate the signal to be carried." + +#### INVARIANT + +inv\_lifetime + +"The directionality associated with an information object must not change during its whole lifetime." + +#### STATE + +sink + +"The resource terminates the signal to be carried." + +source + +"The resource originates the signal to be carried." + +bidirectional + +"The resource is able to originate and terminate the signal to be carried." + +### 7.5 resourceId + +#### DEFINITION + +"The resourceId attribute represents the unique identification of a resource." + +NOTE – This attribute can be implemented as an attribute in a GDMO-based specification or as an object reference in a CORBA environment. It does not represent a user label." + +#### INVARIANT + +inv\_unique + +"The resourceId associated with an information object must be unique for its associated class." + +### 7.6 signalIdentification + +#### DEFINITION + +The signalIdentification attribute represents the specific format of signal that the resource carries. The specific formats will be defined in the technology-specific extensions. + +#### INVARIANT + +Invariants depend on transmission technology. + +#### STATE + +States depend on transmission technology. + +#### TRANSITION + +Transitions depend on transmission technology. + +### 7.7 **topologicalEndDirection** + +#### DEFINITION + +"The topologicalEndDirection attribute characterizes the ability of the associated resource to originate and/or terminate the traffic to be carried." + +#### STATE + +undefined + +"There is no information about the capability of the resource to terminate or originate the signal transport processing." + +sink + +"The resource is able to terminate the signal transport processing." + +source + +"The resource is able to originate the signal transport processing." + +bidirectional + +"The resource is able to originate and terminate the signal transport processing." + +### 7.8 **userLabel** + +#### DEFINITION + +"The userLabel attribute represents a label given by an user to a resource." + +## 8 **Information relationship type definitions** + +### 8.1 **accessGroupIsMadeOfNetworkTTPs** + +This relationship type is related to the following enterprise entities: + +, + + + +#### DEFINITION + +"The accessGroupIsMadeOfNetworkTTPs relationship class describes the relationship that exists between an accessGroup and the networkTTPs that are part of it." + +![Diagram illustrating the accessGroupIsMadeOfNetworkTTPs relationship. An oval labeled 'accessGroup' contains seven black dots. One dot is labeled 'T0410850-99' and 'networkTTP' via a leader line.](5a13c28486ba6b19f59d7a9a7a1c3f28_img.jpg) + +The diagram shows an oval labeled 'accessGroup' on the left. Inside the oval are seven black dots. One dot at the bottom right is connected by a leader line to the text 'T0410850-99' and 'networkTTP' on the right. + +Diagram illustrating the accessGroupIsMadeOfNetworkTTPs relationship. An oval labeled 'accessGroup' contains seven black dots. One dot is labeled 'T0410850-99' and 'networkTTP' via a leader line. + +" + +#### ROLE + +containerAG + +"Played by an instance of the information object type or subtype." + +elementTTP + +"Played by an instance of a sub-type of the information object type." + +#### INVARIANT + +inv\_containerAGRoleCardinality + "One and only one instance of the role *containerAG* must participate in the relationship." + inv\_elementAGRoleCardinality + "One or more instances of the role *elementTTP* must participate in the relationship." + inv\_signalIdentification + "The *containerAG* and the *elementTTPs* must contain the same signalIdentification information." + inv\_directionality + "The objects involved in the relationship must have a compatible directionality: + +| containerAG | elementTTP | +|--------------------|-----------------------------------| +| sink | sink | +| source | source | +| bidirectional | bidirectional | +| undefined | sink, source or/and bidirectional | + +" + +### 8.2 accessGroupIsRelatedToSntpPool + +This relationship type is related to the following enterprise entities: + + + +#### DEFINITION + +"The accessGroupIsRelatedToSntpPool relationship class describes the relationship that exists between an accessGroup and a subnetworkTpPool." + +#### ROLE + +extremityAG + +"Played by instances of the information object type or subtype." + +abstractionPool + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_extremityAGRoleCardinality + "One and only one instance of the role *extremityAG* must participate in the relationship." + inv\_abstractionPoolRoleCardinality + "One and only one instance of the role *extremityAG* must participate in the relationship." + inv\_signalIdentification + "The *abstractionPool* and the *extremityAG* must contain the same signalIdentification information." + +### 8.3 administrativeDomainIsMadeOf + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The administrativeDomainIsMadeOf relationship class describes the relationship that exists between an administrativeDomain and the information objects that are part of it. + +![Diagram illustrating the administrativeDomainIsMadeOf relationship. A large oval labeled 'administrativeDomain' contains several smaller shapes (circles and rectangles) representing components. A line points from the label 'component of the administrativeDomain' to one of these shapes. The text 'T0410860-99' is also present near the components.](c4312d6d416e683271db3162a4f009fc_img.jpg) + +Diagram illustrating the administrativeDomainIsMadeOf relationship. A large oval labeled 'administrativeDomain' contains several smaller shapes (circles and rectangles) representing components. A line points from the label 'component of the administrativeDomain' to one of these shapes. The text 'T0410860-99' is also present near the components. + +" + +#### ROLE + +containerAD + +"Played by an instance of the information object type." + +element + +"Played by an instance of a subtype of the information object type." + +#### INVARIANT + +inv\_containerADRoleCardinality + +"One and only one instance of the role *containerAD* must participate in the relationship." + +inv\_elementADRoleCardinality + +"One or more instances of the role *element* must participate in the relationship." + +### 8.4 circuitPackSupportsPhysicalPorts + +#### DEFINITION + +"The circuitPackSupportsPhysicalPorts relationship class describes the relationship that exists between a circuitPack and the ports that are supported by a circuitPack." + +#### ROLE + +containerPack + +"Played by an instance of the information object type or subtype." + +elementPort + +"Played by instances of the information object type or subtype." + +#### INVARIANT + +inv\_containerPackRoleCardinality + +"One and only one instance of the role *containerPack* must participate in the relationship." + +inv\_elementPackRoleCardinality + +"One or more instances of the role *elementPort* must participate in the relationship." + +### 8.5 compoundLinkEndHasLinkEnds + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The compoundLinkEndHasLinkEnds relationship class describes the group of linkEnds to form a compound linkEnd." + +#### ROLE + +compoundLEnd + +"Played by an instance of the information object type or subtype." + +componentLEnd + +"Played by instances of the information object type or subtype." + +#### INVARIANT + +inv\_compoundRoleCardinality + +"One and only one instance of the role *compoundLEnd* must participate in the relationship." + +inv\_componentRoleCardinality + +"One or more instances of the role *componentLEnd* must participate in the relationship." + +inv\_signalIdentification + +"The *compoundLEnd* and the *componentLEnd* must contain the same signalIdentification information." + +inv\_directionality + +"The *compoundLEnd* and the *componentLEnd* must have the same topologicalEndDirection." + +inv\_roles + +"In an instance of the relationship, an instance can not play both roles: *compoundLEnd* and *componentLEnd*." + +### 8.6 compoundLinkHasLinks + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The compoundLinkHasLinks relationship class describes the group of links to form a compound link." + +![Diagram of a compound link relationship. A central 'compound link' (represented by two stacked grey rectangles) is connected to two 'subnetwork' nodes (dashed ovals). Each 'component link' (a line from the compound link) connects to one subnetwork node. The diagram is labeled 'T0410870-99'.](69b7bd65e85cdef6fdd7fb0a8194257c_img.jpg) + +Diagram of a compound link relationship. A central 'compound link' (represented by two stacked grey rectangles) is connected to two 'subnetwork' nodes (dashed ovals). Each 'component link' (a line from the compound link) connects to one subnetwork node. The diagram is labeled 'T0410870-99'. + +" + +#### **ROLE** + +*compoundLink* + +"Played by an instance of the information object type or subtype." + +*componentLink* + +"Played by instances of the information object type or subtype." + +#### **INVARIANT** + +*inv\_compoundRoleCardinality* + +"One and only one instance of the role *compoundLink* must participate in the relationship." + +*inv\_componentRoleCardinality* + +"One or more instances of the role *componentLink* must participate in the relationship." + +*inv\_signalIdentification* + +"The *compoundLink* and the *componentLink* must contain the same signalIdentification information." + +*inv\_directionality* + +"The *compoundLink* and the *componentLink* must have the same linkDirectionality." + +*inv\_extremities* + +"All the objects involved in the relationship must have the same extremities." + +*inv\_roles* + +"In an instance of the relationship, an instance can not play both roles: *compoundLink* and *componentLink*." + +*inv\_capacity* + +"The capacity of the object playing the role *compoundLink* must be equal to the sum of the capacities of all the objects playing the role *componentLink*." + +### **8.7 concatenatedLinkHasLinks** + +This relationship type is related to the following enterprise entity: + + + +#### **DEFINITION** + +"The concatenatedLinkHasLinks relationship class describes the group of links to form a concatenated link." + +![Diagram of a concatenated link relationship. A central 'Serial-compound' (a white rounded rectangle) is connected to two 'subnetwork' nodes (dashed ovals), labeled 'subnetwork A' and 'subnetwork B'. Below it, two 'component link' segments (grey rectangles) are shown, each connected to one of the subnetwork nodes. The diagram is labeled 'T0410880-99'.](22f69a5473360beb672a10970dbcfa30_img.jpg) + +Diagram of a concatenated link relationship. A central 'Serial-compound' (a white rounded rectangle) is connected to two 'subnetwork' nodes (dashed ovals), labeled 'subnetwork A' and 'subnetwork B'. Below it, two 'component link' segments (grey rectangles) are shown, each connected to one of the subnetwork nodes. The diagram is labeled 'T0410880-99'. + +" + +#### ROLE + +serialLink + +"Played by an instance of the information object type and subtype." + +serieLink + +"Played by instances of the information object type and subtype or by an instance of the information object type." + +#### INVARIANT + +inv\_serialRoleCardinality + +"One and only one instance of the role *serialLink* must participate in the relationship." + +inv\_serieRoleCardinality + +"One or more instances of the role *serieLink* must participate in the relationship." + +inv\_signalIdentification + +"The *serialLink* and the *serieLink* must contain the same signalIdentification information." + +inv\_directionality + +"The *serialLink* and the *serieLink* must have a compatible linkDirectionality." + +inv\_contiguityAend + +"One and only one *serieLink* must have a a\_end equal to the a\_end of the *serialLink*." + +inv\_contiguityZend + +"One and only one *serieLink* must have a z\_end equal to the z\_end of the *serialLink*." + +inv\_capacity + +"The capacity of the *serialLink* must be lower or equal than the lowest capacity of the *serieLink*." + +inv\_roles + +"In an instance of the relationship, an instance can not play both roles: *serialLink* and *serieLink*." + +### 8.8 equipmentImplements + +#### DEFINITION + +"The equipmentImplements relationship class describes the relationship that exists between an equipment and the network element resources." + +#### ROLE + +containerEquipment + +"Played by an instance of the information object type or subtype." + +NEImplemented + +"Played by instances of the , information object type or subtype." + +#### INVARIANT + +inv\_containerEquipmentRoleCardinality + +"One and only one instance of the role *containerEquipment* must participate in the relationship." + +inv\_elementEquipmentRoleCardinality + +"One or more instances of the role *NEImplemented* must participate in the relationship." + +### 8.9 equipmentIsMadeOfEquipments + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The equipmentIsMadeOfEquipments relationship class describes the relationship that exists between an equipment and its components." + +#### ROLE + +containerEquipment + +"Played by an instance of the information object type or subtype." + +elementEquipment + +"Played by instances of the information object type or subtype." + +#### INVARIANT + +inv\_containerRoleCardinality + +"One and only one instance of the role *containerEquipment* must participate in the relationship." + +inv\_elementRoleCardinality + +"One or more instances of the role *elementEquipment* must participate in the relationship." + +### 8.10 extremitiesTerminatePhysicalMedium + +#### DEFINITION + +"The extremitiesTerminatePhysicalMedium relationship class describes the relationship that exists between a physicalMedium and its extremities." + +#### ROLE + +transportPhysMed + +"Played by an instance of the information object type or subtype." + +a\_endPhysPort + +"Played by an instance of the information object type or subtype." + +z\_endPhysPort + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_transportRoleCardinality + +"One and only one instance of the role *transportPhysMed* must participate in the relationship." + +inv\_aendRoleCardinality + +"One and only one instance of the role *a\_endPhysPort* must participate in the relationship." + +inv\_zendRoleCardinality + +"One and only one instance of the role *z\_endPhysPort* must participate in the relationship." + +### 8.11 isConnectedTo + +#### DEFINITION + +"The isConnectedTo relationship class describes the relationship that exists between subnetworkTPs through which the signal transfers." + +![Diagram of the isConnectedTo relationship class. It shows two black circular nodes representing subnetworkTPs, enclosed within a dashed oval labeled 'subnetwork'. A double-headed arrow connects the two nodes, labeled 'isConnectedTo'. A label 'subnetworkTp' points to the left node. The identifier 'T0410890-99' is located near the bottom right of the oval.](bc9152f59fdf75ea4835a8a60f08bef4_img.jpg) + +The diagram illustrates the *isConnectedTo* relationship class. It features two black circular nodes, each representing a *subnetworkTp* information object. These nodes are positioned within a dashed oval boundary labeled *subnetwork*. A horizontal double-headed arrow connects the two nodes, with the label *isConnectedTo* positioned above it. A line points from the label *subnetworkTp* to the left node. The identifier *T0410890-99* is placed near the bottom right of the oval. + +Diagram of the isConnectedTo relationship class. It shows two black circular nodes representing subnetworkTPs, enclosed within a dashed oval labeled 'subnetwork'. A double-headed arrow connects the two nodes, labeled 'isConnectedTo'. A label 'subnetworkTp' points to the left node. The identifier 'T0410890-99' is located near the bottom right of the oval. + +" + +#### ROLE + +peerSNTP + +"Played by two instances of the information object type or subtype." + +#### INVARIANT + +inv\_peerRoleCardinality + +"One instance must be of the object type or subtype and the other must be of the object type or subtype." + +inv\_signalIdentification + +"In a given relationship instance of *isConnectedTo*, the information objects playing the role *peerSNTP* must have all the same *signalIdentification* value." + +### 8.12 layerNetworkDomainCanServeLnds + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The layerNetworkDomainCanServeLnds relationship class describes the relationship that exists between a server layerNetworkDomain and the client layerNetworkDomain." + +#### ROLE + +clientLND + +"Played by instances of the information object type or subtype." + +serverLND + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_clientRoleCardinality + +"One or more instances of the role *clientLND* must participate in the relationship." + +inv\_serverRoleCardinality + +"One and only one instance of the role *serverLND* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of layerNetworkDomainCanServeLnds, the information object playing the role *serverLND* must have a different signalIdentification value than the information object playing the role *clientLND* as defined in Recommendation G.805 (compliant values are technologies dependent and defined in the corresponding Recommendations, e.g. Recommendation G.783 for SDH)." + +### 8.13 layerNetworkDomainIsMadeOf + +#### DEFINITION + +"The layerNetworkDomainIsMadeOf relationship class describes the relationship that exists between a layerNetworkDomain and the objects that compose it." + +#### ROLE + +containerLND + +"Played by an instance of the information object type or subtype." + +element + +"Played by an instance of the subtype of the information object type." + +#### INVARIANT + +inv\_containerLNDRoleCardinality + +"One and only one instance of the role *containerLND* must participate in the relationship." + +inv\_elementLNDRoleCardinality + +"One or more instances of the role *element* must participate in the relationship." + +inv\_signalIdentification + +"The *containerLND* and the *element* must contain the same signalIdentification information." + +### 8.14 linkBinds + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The linkBinds relationship class describes the relationship that exists between a link and its two extremities. These can be any of the following: subnetwork/accessGroup/subnetworkTPPool. The two associated extremities are referred to as the a\_end and the z\_end." + +![Diagram of a linkBinds relationship. A central horizontal cylinder is labeled 'link'. To its left, a shaded circle labeled 'accessGroup' is connected to the cylinder. To its right, an oval labeled 'subnetwork' is connected to the cylinder. A small circle at the left junction of the cylinder is labeled 'a_end'. A small circle at the right junction of the cylinder is labeled 'z_end'. The diagram is labeled 'T0410900-99' in the bottom right corner.](85cd27423acb6a60da23ab5bf9086bd2_img.jpg) + +Diagram of a linkBinds relationship. A central horizontal cylinder is labeled 'link'. To its left, a shaded circle labeled 'accessGroup' is connected to the cylinder. To its right, an oval labeled 'subnetwork' is connected to the cylinder. A small circle at the left junction of the cylinder is labeled 'a\_end'. A small circle at the right junction of the cylinder is labeled 'z\_end'. The diagram is labeled 'T0410900-99' in the bottom right corner. + +#### ROLE + +transferCapacityLink + +"Played by an instance of the information object type or subtype." + +a\_endTopological + +"Played by an instance of the information object type or subtype or by an instance of the information object type or subtype or by an instance of the information object type or subtype." + +z\_endTopological + +"Played by an instance of the information object type or subtype or by an instance of the information object type or subtype or by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_transferCapacityRoleCardinality + +"One and only one instance of the role *transferCapacityLink* must participate in the relationship." + +inv\_aendRoleCardinality + +"One and only one instance of the role *a\_endTopological* must participate in the relationship." + +inv\_zendRoleCardinality + +"One and only one instance of the role *z\_endTopological* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of *linkBinds*, the information objects playing the role *transferCapacityLink*, *a\_endTopological* and *z\_endTopological* must have all the same *signalIdentification* value." + +inv\_directionality + +"If the role *a\_endTopological* or *z\_endTopological* is played by an *accessGroup*, then the objects involved in the relationship must have a compatible directionality." + +### 8.15 linkConnectionIsBoundTo + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The *linkConnectionIsBoundTo* relationship class describes the relationship that exists between a link connection the extremities that can be bound to." + +![Diagram of the linkConnectionIsBoundTo relationship. A solid line on the left connects a black circle to a horizontal line. Above this solid line is the label 'linkConnection'. Below the solid line is the label 'NetworkCTP or networkTTP'. The horizontal line transitions from solid to dashed. Above the dashed line is the label 'subnetworkConnection or linkConnection'. To the right of the dashed line is the code 'T0410910-99'.](bf32ff2a1af507083217ccc56c515a50_img.jpg) + +The diagram illustrates the *linkConnectionIsBoundTo* relationship. On the left, a solid line connects a black circle (representing an extremity) to a horizontal line. Above this solid line is the label *linkConnection*. Below the solid line is the label *NetworkCTP or networkTTP*. The horizontal line transitions from solid to dashed. Above the dashed line is the label *subnetworkConnection or linkConnection*. To the right of the dashed line is the code *T0410910-99*. + +Diagram of the linkConnectionIsBoundTo relationship. A solid line on the left connects a black circle to a horizontal line. Above this solid line is the label 'linkConnection'. Below the solid line is the label 'NetworkCTP or networkTTP'. The horizontal line transitions from solid to dashed. Above the dashed line is the label 'subnetworkConnection or linkConnection'. To the right of the dashed line is the code 'T0410910-99'. + +" + +#### ROLE + +boundLC + +"Played by an instance of the information object type or subtype." + +boundA\_end + +"Played by instances of the , , or information object type or subtype." + +boundZ\_end + +"Played by instances of the , , or information object type or subtype." + +#### INVARIANT + +inv\_cardinalityTransportEntity + +"One and only one instance of the role *boundLC* must participate in the relationship." + +inv\_cardinalityAend + +"One and only one instance of the role *boundA\_end* must participate in the relationship." + +inv\_cardinalityZend + +"One and only one instance of the role *boundZ\_end* must participate in the relationship." + +inv\_directionality + +"If the information object playing the role *boundLC* is bidirectional, then the information objects playing the roles *boundA\_end* and *boundZ\_end* must be bidirectional." + +inv\_signalIdentification + +"In a given relationship instance of *trailIsTerminatedByPointToPoint*, the information objects playing the role *boundLC*, *boundA\_end* and *boundZ\_end* must have all the same *signalIdentification* value." + +### 8.16 linkConnectionIsBundleOfLinkConnections + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The linkConnectionIsBundleOfLinkConnections relationship class describes the relationship that exists between a bundled link connection and its component link connections." + +![Diagram illustrating the linkConnectionIsBundleOfLinkConnections relationship. A thick horizontal line at the top represents a 'linkConnection with an n*x bandwith'. Below it, five parallel horizontal lines represent 'linkConnection with an x bandwith'. Arrows point from the top line to each of the five bottom lines, indicating that the top line is a bundle of the bottom lines.](a4b963a07cc368283154762c4b156fe7_img.jpg) + +Diagram illustrating the linkConnectionIsBundleOfLinkConnections relationship. A thick horizontal line at the top represents a 'linkConnection with an n\*x bandwith'. Below it, five parallel horizontal lines represent 'linkConnection with an x bandwith'. Arrows point from the top line to each of the five bottom lines, indicating that the top line is a bundle of the bottom lines. + +T0410920-99 + +" + +#### ROLE + +bundleLC + +"Played by an instance of the information object type or subtype." + +bundledLC + +"Played by an instance of a subtype of the information object type or subtype." + +#### INVARIANT + +inv\_bundleRoleCardinality + +"One and only one instance of the role *bundleLC* must participate in the relationship." + +inv\_bundledRoleCardinality + +"One or more instances of the role *bundledLC* must participate in the relationship." + +inv\_signalIdentification + +"The *bundledLC* and the *bundleLC* must contain the same signalIdentification information." + +inv\_directionality + +"The *bundledLC* and the *bundleLC* must have the same directionality." + +inv\_roles + +"In an instance of the relationship, an instance can not play both roles: *bundledLC* and *bundleLC*." + +### 8.17 linkConnectionIsMadeOfTransportEntities + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The linkConnectionIsMadeOfTransportEntities relationship class describes the relationship that exists between a composite link connection and its component transport entities." + +![Diagram illustrating the linkConnectionIsMadeOfTransportEntities relationship. A long horizontal line at the top is labeled 'abstract linkConnection'. Below it, a dashed horizontal line is labeled 'component subnetworkConnection'. At the bottom, two horizontal lines are labeled 'component linkConnection'. Arrows point from the top line to the dashed line, and from the dashed line to the two bottom lines, indicating a hierarchical composition.](f82372c6a14ee48b0d00b0e591f8c05b_img.jpg) + +Diagram illustrating the linkConnectionIsMadeOfTransportEntities relationship. A long horizontal line at the top is labeled 'abstract linkConnection'. Below it, a dashed horizontal line is labeled 'component subnetworkConnection'. At the bottom, two horizontal lines are labeled 'component linkConnection'. Arrows point from the top line to the dashed line, and from the dashed line to the two bottom lines, indicating a hierarchical composition. + +T0410930-99 + +" + +#### ROLE + +compositeLC + +"Played by an instance of the information object type or subtype." + +componentTEntity + +"Played by an instance of the information object type or subtype, or information object type or subtype." + +#### INVARIANT + +inv\_compositeLCRoleCardinality + +"One and only one instance of the role *compositeLC* must participate in the relationship." + +inv\_componentLCRoleCardinality + +"At least one instance of the role *componentTEntity* must participate in the relationship." + +inv\_directionality + +"If the information object playing the role *compositeLC* is bidirectional, then all the information objects playing the role *componentTEntity* must be bidirectional." + +inv\_signalIdentification + +"In a given relationship instance of linkConnectionIsMadeOfTransportEntities, the information objects playing the role *compositeLC* and *componentTEntity* must have all the same signalIdentification value." + +inv\_contiguity + +"The *componentTEntity* connections being contiguous, both the first and the last one must be instances of the linkConnection information object type or subtype." + +inv\_roles + +"In an instance of the relationship, an instance can not play both roles: *compositeLC* and *componentTEntity*." + +### 8.18 linkConnectionIsSupportedByTrail + +This relationship type is related to the following enterprise entities: + +, + + + +#### DEFINITION + +"The linkConnectionIsSupportedByTrail relationship class describes the relationship that exists between linkConnections of a given layer network (known as the client layer network) and the trail that supports them in a server layer network." + +![Diagram illustrating the linkConnectionIsSupportedByTrail relationship. A thick horizontal line represents the 'trail'. Above it, five parallel horizontal lines represent 'linkConnections'. Arrows point from each linkConnection down to the trail line. A label 'adaptation function' points to one of these arrows. A label 'linkConnection' points to one of the parallel lines. A label 'trail' points to the thick horizontal line. The diagram is labeled T0410940-99.](1d7843cba3689033fb3d36d56984cf38_img.jpg) + +Diagram illustrating the linkConnectionIsSupportedByTrail relationship. A thick horizontal line represents the 'trail'. Above it, five parallel horizontal lines represent 'linkConnections'. Arrows point from each linkConnection down to the trail line. A label 'adaptation function' points to one of these arrows. A label 'linkConnection' points to one of the parallel lines. A label 'trail' points to the thick horizontal line. The diagram is labeled T0410940-99. + +#### ROLE + +clientLC + +"Played by instances of the information object type or subtype." + +serverTrail + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_serverTrailRoleCardinality + +"One and only one instance of the role *serverTrail* must participate in the relationship." + +inv\_clientLCRoleCardinality + +"At least one instance of the role *clientLC* must participate in the relationship." + +inv\_directionality + +"If the information object playing the role *serverTrail* is bidirectional, then the information objects playing the role *clientLC* must be bidirectional." + +inv\_signalIdentification + +"In a given relationship instance of linkConnectionIsSupportedByTrail, the information object playing the role *serverTrail* must have a different signalIdentification value than the information object playing the role *clientLC* as defined in Recommendation G.805 (compliant values are technologies dependent and defined in the corresponding Recommendations, e.g. Recommendation G.783 for SDH)." + +### 8.19 linkConnectionIsTerminatedByPointToPoint + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The linkConnectionIsTerminatedByPointToPoint relationship class describes the relationship that exists between a link connection and its two extremities." + +![Diagram of a link connection terminated by two networkCTP objects.](315bdbeafb39026e19b77c26b19d9d1f_img.jpg) + +The diagram shows a horizontal line representing a 'linkConnection'. At each end of this line is a solid black circle. From the left circle, a line extends downwards and to the left to the label 'networkCTP'. From the right circle, a line extends downwards and to the right to the label 'networkCTP'. Below the right 'networkCTP' label is the text 'T0410950-99'. + +Diagram of a link connection terminated by two networkCTP objects. + +" + +#### ROLE + +transportEntityLC + +"Played by an instance of the information object type or subtype." + +a\_endCTP + +"Played by instances of the information object type or subtype." + +z\_endCTP + +"Played by instances of the information object type or subtype." + +#### INVARIANT + +inv\_transportEntityLCRoleCardinality + +"One and only one instance of the role *transportEntityLC* must participate in the relationship." + +inv\_aendCTPRoleCardinality + +"One and only one instance of the role *a\_endCTP* must participate in the relationship." + +inv\_zendCTPRoleCardinality + +"One and only one instance of the role *z\_endCTP* must participate in the relationship." + +inv\_directionAend + +"The object playing the role *a\_endCTP* must have a pointDirectionality set to source or bidirectional." + +inv\_directionZend + +"The object playing the role *z\_endCTP* must have a pointDirectionality set to sink or bidirectional." + +inv\_directionality + +"If the information object playing the role *transportEntityLC* is bidirectional, then the information objects playing the roles *a\_endCTP* and *z\_endCTP* must be bidirectional." + +inv\_signalIdentification + +"In a given relationship instance of linkConnectionIsTerminatedByPointToPoint, the information objects playing the role *transportEntityLC*, *a\_endCTP* and *z\_endCTP* must have all the same signalIdentification value." + +### 8.20 linkConnectionIsTerminatedByTopologicalEntities + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The linkConnectionIsTerminatedByTopologicalEntities relationship class describes the relationship that exists between the resources represented by a pair of subnetwork or access group and the link connection that may bind them. The two associated information objects are referred to as the A\_end and the Z\_end. Through a unidirectional link connection, traffic goes only from the A\_end to the Z\_end; through a bidirectional one, traffic may go from A\_end to Z\_end and from Z\_end to A\_end." + +![Diagram of the linkConnection relationship. A horizontal line represents the relationship. Above the line, a label 'linkConnection' is connected by a line. Below the line, two labels, 'subnetwork' and 'accessGroup', are connected by lines to the left and right ends of the relationship line, respectively. At the left end, an oval represents an entity. At the right end, another oval represents an entity. To the right of the right oval, the text 'T0410960-99' is present.](f57c7b37d7a05a99618104f390089f03_img.jpg) + +Diagram of the linkConnection relationship. A horizontal line represents the relationship. Above the line, a label 'linkConnection' is connected by a line. Below the line, two labels, 'subnetwork' and 'accessGroup', are connected by lines to the left and right ends of the relationship line, respectively. At the left end, an oval represents an entity. At the right end, another oval represents an entity. To the right of the right oval, the text 'T0410960-99' is present. + +" + +#### ROLE + +transportEntityLC + +"Played by an instance of the information object type or subtype." + +a\_endTopologicalEntity + +"Played by an instance of the or information object type or subtype." + +z\_endTopologicalEntity + +"Played by an instance of the or information object type or subtype." + +#### INVARIANT + +inv\_transportEntityRoleCardinality + +"One and only one instance playing the role *transportEntityLC* must participate in the relationship." + +inv\_aendTopologicalEntityRoleCardinality + +"One and only one instance playing the role *a\_endTopologicalEntity* must participate in the relationship." + +inv\_zendTopologicalEntityRoleCardinality + +"One and only one instance playing the role *z\_endTopologicalEntity* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of *linkConnectionIsTerminatedByTopologicalEntities*, the information objects must have all the same *signalIdentification* value." + +### 8.21 linkEndIsBoundTo + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The *linkEndIsBoundTo* relationship class describes the relationship that exists between a link end and a subnetwork or an access group." + +#### ROLE + +transferCapacityLE + +"Played by an instance of the information object type or subtype." + +topologicalEntity + +"Played by an instance of the information object type or subtype or information object type." + +#### INVARIANT + +inv\_transferCapacityRoleCardinality + +"One and only one instance of the role *transferCapacityLE* must participate in the relationship." + +inv\_extremityRoleCardinality + +"One and only one instance of the role *topologicalEntity* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of *linkEndIsBoundTo*, the information objects playing the role *transferCapacityLE* and *topologicalEntity* must have all the same *signalIdentification* value." + +### 8.22 linkEndHasNetworkCTPs + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The *linkEndHasNetworkCTPs* relationship class describes the relationship that exists between a linkEnd and the networkCTPs that are part of it." + +#### ROLE + +containerLE + +"Played by an instance of the information object type or subtype." + +elementCTP + +"Played by instances of the information object type or subtype." + +#### INVARIANT + +inv\_containerLERoleCardinality + "One and only one instance of the role *containerLE* must participate in the relationship." + inv\_elementLERoleCardinality + "One or more instances of the role *elementCTP* must participate in the relationship." + inv\_signalIdentification + "In a given relationship instance of linkEndHasNetworkCTPs, the information objects playing the role *elementCTP* and *containerLE* must have all the same signalIdentification value." + inv\_directionality + "The objects involved in the relationship must have a compatible directionality: + +| role: containerLE | role: elementCTP | +|-------------------|-------------------------------| +| source | source | +| sink | sink | +| bidirectional | bidirectional | +| undefined | source, sink or bidirectional | + +" + +### **8.23 linkHasLinkConnections** + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The linkHasLinkConnections relationship class describes the relationship that exists between a link and the linkConnections that are part of it. + +![Diagram of linkHasLinkConnections relationship. A central horizontal cylinder represents a 'link'. On its left end, three parallel lines (representing 'linkConnections') enter through an oval. A leader line from the label 'linkConnection' points to these lines. Another leader line from the label 'link' points to the main cylinder body. On the right end, the three parallel lines exit the cylinder.](a8050baf48cc2c8e25d5ea2d1a67ef39_img.jpg) + +Diagram of linkHasLinkConnections relationship. A central horizontal cylinder represents a 'link'. On its left end, three parallel lines (representing 'linkConnections') enter through an oval. A leader line from the label 'linkConnection' points to these lines. Another leader line from the label 'link' points to the main cylinder body. On the right end, the three parallel lines exit the cylinder. + +T0410970-99 + +" + +#### ROLE + +containerLink + "Played by an instance of the information object type or subtype." + elementLC + "Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_containerLinkRoleCardinality + "One and only one instance of the role *containerLink* must participate in the relationship." + inv\_elementLinkRoleCardinality + "One or more instances of the role *elementLC* must participate in the relationship." + inv\_signalIdentification + "In a given relationship instance of linkHasLinkConnections, the information objects playing the role *containerLink* and *elementLC* must have all the same signalIdentification value." + inv\_directionality + "The objects involved in the relationship must have a compatible directionality: + +| containerLink | elementLC | +|----------------------|-------------------------------------| +| unidirectional | unidirectional | +| bidirectional | bidirectional | +| undefined | unidirectional or/and bidirectional | + +" + +### 8.24 linkIsTerminatedByLinkEnds + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The linkIsTerminatedByLinkEnds relationship class describes the relationship that exists between a link and its two extremities." + +#### ROLE + +transferCapacityLink + +"Played by an instance of the information object type or subtype." + +a\_endLE + +"Played by an instance of the information object type or subtype." + +z\_endLE + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_transferCapacityRoleCardinality + +"One and only one instance of the role *transferCapacityLink* must participate in the relationship." + +inv\_aendLERoleCardinality + +"One and only one instance of the role *a\_endLE* must participate in the relationship." + +inv\_zendLERoleCardinality + +"One and only one instance of the role *z\_endLE* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of linkIsTerminatedByLinkEnds, the information objects playing the role *transferCapacityLink*, *a\_endLE* and *z\_endLE* must have all the same signalIdentification value." + +inv\_directionality + +"The objects involved in the relationship must have a compatible directionality: + +| role: transferCapacityLink | role: a_endLE | role: z_endLE | +|-----------------------------------|-----------------------------------|-----------------------------------| +| unidirectional | source | sink | +| bidirectional | bidirectional | bidirectional | +| undefined | source, sink or/and bidirectional | source, sink or/and bidirectional | + +" + +### 8.25 networkCTPisBundleOfNetworkCTPs + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The networkCTPisBundleOfNetworkCTPs relationship class describes the relationship that exists between a networkCTP and the networkCTPs that are part of it." + +#### ROLE + +*bundleCTP* + +"Played by an instance of the information object type or subtype." + +*bundledCTP* + +"Played by an instance of a subtype of the information object type or subtype." + +#### INVARIANT + +*inv\_bundleRoleCardinality* + +"One and only one instance of the role *bundleCTP* must participate in the relationship." + +*inv\_bundledRoleCardinality* + +"One or more instances of the role *bundledCTP* must participate in the relationship." + +*inv\_signalIdentification* + +"In a given relationship instance of networkCTPisBundleOfNetworkCTPs, the information objects playing the role *bundleCTP* and *bundledCTP* must have all the same signalIdentification value." + +*inv\_directionality* + +"The objects involved in the relationship must have a compatible directionality." + +*inv\_roles* + +"In an instance of the relationship, an instance can not play both roles: *bundleCTP* and *bundledCTP*." + +### 8.26 networkTTPAdaptsNetworkCTP + +This relationship type is related to the following enterprise entities: +, + + +#### DEFINITION + +"The networkTTPAdaptsNetworkCTP relationship class describes the relationship that exists between networkCTPs of a given layer network (known as the client layer network) and the networkTTP that supports them in a server layer network." + +![Diagram illustrating the networkTTPAdaptsNetworkCTP relationship. A central black circle represents the networkTTP. Four white circles represent networkCTPs. Arrows point from the networkTTP to each networkCTP. A label 'adaptation function' points to one of the arrows. A label 'networkCTP' points to one of the white circles. A label 'networkTTP' points to the central black circle.](583e14835ddabad1d8b92a07b82fc31b_img.jpg) + +``` +graph TD + TTP((networkTTP)) -- adaptation function --> CTP1((networkCTP)) + TTP -- adaptation function --> CTP2((networkCTP)) + TTP -- adaptation function --> CTP3((networkCTP)) + TTP -- adaptation function --> CTP4((networkCTP)) +``` + +The diagram shows a central black circle labeled 'networkTTP'. Four white circles, each labeled 'networkCTP', are arranged around it. Arrows point from the central 'networkTTP' circle to each of the four 'networkCTP' circles. A label 'adaptation function' points to one of these arrows. The diagram is labeled 'T0410980-99' at the bottom right. + +Diagram illustrating the networkTTPAdaptsNetworkCTP relationship. A central black circle represents the networkTTP. Four white circles represent networkCTPs. Arrows point from the networkTTP to each networkCTP. A label 'adaptation function' points to one of the arrows. A label 'networkCTP' points to one of the white circles. A label 'networkTTP' points to the central black circle. + +" + +#### ROLE + +*clientCTP* + +"Played by instances of the information object type or subtype." + +*serverTTP* + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +*inv\_serverTTPRoleCardinality* + +"One and only one instance of the role *serverTTP* must participate in the relationship." + +*inv\_clientCTPRoleCardinality* + +"At least one instance of the role *clientCTP* must participate in the relationship." + +*inv\_directionality* + +"If the information object playing the role *serverTTP* is bidirectional, then the information objects playing the role *clientCTP* must be bidirectional." + +*inv\_signalIdentification* + +"In a given relationship instance of topologicalLinkEndIsSupportedByNetworkTTP, the information object playing the role *serverTTP* must have a different signalIdentification value than the information object playing the role *clientCTP* as defined in Recommendation G.805 (compliant values are technologies dependent and defined in the corresponding Recommendations, e.g. Recommendation G.783 for SDH)." + +### 8.27 representSameResourceAs + +#### DEFINITION + +"The representSameResourceAs relationship class describes the relationship that exists between two object that represent the same resource." + +#### ROLE + +resourceInfo + +"Played by instances of the subtype of information object type." + +#### INVARIANT + +inv\_resourceInfoRoleCardinality + +"At least two instances of the role *resourceInfo* must participate in the relationship." + +### 8.28 sncBidIsSupportedByUnis + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The sncBidIsSupportedByUnis relationship class describes the relationship that exists between a bidirectional subnetworkConnection instance and the two unidirectional (co- and contra-directional with regard to an orientation reference) subnetworkConnection instances that together provide bidirectionality (e.g. case of a unidirectional SDH ring). + +![Diagram illustrating the sncBidIsSupportedByUnis relationship. A thick horizontal line with arrows at both ends represents a 'bidirectional subnetwork connection'. Below it, two thinner horizontal lines with arrows at both ends represent 'unidirectional subnetwork connections'. The top unidirectional connection is co-directional with the bidirectional connection, and the bottom one is contra-directional. The diagram is enclosed in a dashed oval. A label 'T0410990-99' is present in the bottom right corner of the diagram area.](2dfd7b53bd3c518fc1f68921ed2bf441_img.jpg) + +Diagram illustrating the sncBidIsSupportedByUnis relationship. A thick horizontal line with arrows at both ends represents a 'bidirectional subnetwork connection'. Below it, two thinner horizontal lines with arrows at both ends represent 'unidirectional subnetwork connections'. The top unidirectional connection is co-directional with the bidirectional connection, and the bottom one is contra-directional. The diagram is enclosed in a dashed oval. A label 'T0410990-99' is present in the bottom right corner of the diagram area. + +" + +#### ROLE + +bidSNC + +"Played by an instance of the information object type or subtype." + +uni1SNC + +"Played by an instance of the information object type or subtype." + +uni2SNC + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_uni1RoleCardinality + +"One and only one instance of the role *uni1SNC* must participate in the relationship." + +inv\_uni2RoleCardinality + +"One and only one instance of the role *uni2SNC* must participate in the relationship." + +inv\_bidRoleCardinality + +"One and only one instance of the role *bidSNC* must participate in the relationship." + +inv\_directionality + +"The instance of the role *uni1SNC* and the instance of the role *uni2SNC* must be both unidirectional, the first one co-directional and the second one contra-directional with regard to an orientation reference." + +inv\_signalIdentification + +"In a given relationship instance of sncBidIsSupportedByUnis, the information objects playing the role *bidSNC*, *uni1SNC* and *uni2SNC* must have all the same signalIdentification value." + +inv\_roles + +"In an instance of the relationship, an instance can not play two roles." + +### 8.29 snIsPartitionedByLinks + +This relationship type is related to the following enterprise entity: + + +DEFINITION + +"The snIsPartitionedByLinks relationship class describes the relationship that exists between a subnetwork and the links that are part of it." + +![Diagram showing a subnetwork containing nodes and links.](50214d232017279410e9c9db8eb75119_img.jpg) + +The diagram illustrates the snIsPartitionedByLinks relationship. A large outer oval represents a subnetwork. Inside this oval are three smaller circles representing nodes or smaller subnetworks. Two pairs of these circles are connected by double-line segments representing links. A leader line points from the text "link" to one of these double-line segments. Another leader line points from the text "subnetwork" to the large outer oval. The label "T0411000-99" is located at the bottom right of the diagram. + +Diagram showing a subnetwork containing nodes and links. + +" + +ROLE + +compositeSN + +"Played by an instance of the information object type or subtype." + +componentLink + +"Played by an instance of the information object type or subtype." + +INVARIANT + +inv\_compositeSNRoleCardinality + +"One and only one instance of the role *compositeSN* must participate in the relationship." + +inv\_componentLinkRoleCardinality + +"One or more instances of the role *componentLink* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of linkHasLinkConnections, the information objects playing the role *compositeSN* and *componentLink* must have all the same signalIdentification value." + +### 8.30 snIsPartitionedBySn + +This relationship type is related to the following enterprise entity: + + +DEFINITION + +"The snIsPartitionedBySn relationship class describes the relationship that exists between a subnetwork and the smaller subnetwork (or subclasses) instances that are part of its decomposition due to partitioning." + +![Diagram T0411010-99 showing a large oval labeled 'composite subnetwork' containing five smaller circles labeled 'component subnetwork'.](798679874d1c29f8343506a156c79d7e_img.jpg) + +A diagram showing a large oval labeled "composite subnetwork" containing five smaller circles labeled "component subnetwork". + +Diagram T0411010-99 showing a large oval labeled 'composite subnetwork' containing five smaller circles labeled 'component subnetwork'. + +T0411010-99 + +" + +#### ROLE + +compositeSN + +"Played by an instance of the information object type or subtype." + +componentSN + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_compositeSNRoleCardinality + +"One and only one instance of the role *compositeSN* must participate in the relationship." + +inv\_componentSNRoleCardinality + +"At least one instance of the role *componentSN* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of snIsPartitionedBySn, the information objects playing the role *compositeSN* and *componentSN* must have all the same signalIdentification value." + +inv\_roles + +"In an instance of the relationship, an instance can not play both roles: *compositeSN* and *componentSN*." + +### **8.31 subnetworkConnectionIsBundleOfSubnetworkConnections** + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The subnetworkConnectionIsBundleOfSubnetworkConnections relationship class describes the relationship that exists between a subnetworkConnection and the subnetworkConnections that are part of it." + +![Diagram T0411020-99 showing a thick horizontal line labeled 'subnetwork Connection with an n*x bandwith' with five arrows pointing down to five thinner horizontal lines labeled 'subnetwork Connection with an x bandwith'.](b2fb400fc9b21b9a4449b6460911b8b4_img.jpg) + +A diagram showing a thick horizontal line labeled "subnetwork Connection with an n\*x bandwith" with five arrows pointing down to five thinner horizontal lines labeled "subnetwork Connection with an x bandwith". + +Diagram T0411020-99 showing a thick horizontal line labeled 'subnetwork Connection with an n\*x bandwith' with five arrows pointing down to five thinner horizontal lines labeled 'subnetwork Connection with an x bandwith'. + +T0411020-99 + +" + +#### ROLE + +bundleSNC + +"Played by an instance of the information object type or subtype." + +bundledSNC + +"Played by an instance of a subtype of the information object type or subtype." + +#### INVARIANT + +inv\_bundleRoleCardinality +"One and only one instance of the role *bundleSNC* must participate in the relationship." +inv\_bundledRoleCardinality +"One or more instances of the role *bundledSNC* must participate in the relationship." +inv\_signalIdentification +"In a given relationship instance of *linkHasLinkConnections*, the information objects playing the role *bundleSNC* and *bundledSNC* must have all the same *signalIdentification* value." +inv\_directionality +"The objects involved in the relationship must have a compatible directionality." +inv\_roles +"In an instance of the relationship, an instance can not play both roles: *bundleSNC* and *bundledSNC*." + +### 8.32 subnetworkConnectionIsMadeOfTransportEntities + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The *subnetworkConnectionIsMadeOfTransportEntities* relationship class describes the relationship that exists between a composite subnetwork connection and its component transport entities." + +![UML diagram showing the relationship between a subnetwork Connection and its components. A dashed line labeled 'link Connection' is at the top, with a solid line labeled 'subnetwork Connection' branching off it. Below the dashed line, two solid lines labeled 'subnetwork Connection' point to the left and right ends of the dashed line. The diagram is labeled T0411030-99.](24a89bcaba787f2bc1721356480a4a01_img.jpg) + +The diagram illustrates the relationship between a composite subnetwork connection and its component transport entities. A dashed line labeled 'link Connection' is at the top. A solid line labeled 'subnetwork Connection' branches off from the top of the dashed line. Below the dashed line, two solid lines labeled 'subnetwork Connection' point to the left and right ends of the dashed line. The diagram is labeled T0411030-99. + +UML diagram showing the relationship between a subnetwork Connection and its components. A dashed line labeled 'link Connection' is at the top, with a solid line labeled 'subnetwork Connection' branching off it. Below the dashed line, two solid lines labeled 'subnetwork Connection' point to the left and right ends of the dashed line. The diagram is labeled T0411030-99. + +" + +#### ROLE + +compositeSNC +"Played by an instance of the information object type or subtype." +componentTEntity +"Played by instances of the information object type or subtype, or information object type or subtype." + +#### INVARIANT + +inv\_compositeSNCRoleCardinality +"One and only one instance of the role *compositeSNC* must participate in the relationship." +inv\_componentSNCRoleCardinality +"At least one instance of the role *componentTEntity* must participate in the relationship." +inv\_directionality +"If the information object playing the role *compositeSNC* is bidirectional, then all the information objects playing the role *componentTEntity* must be bidirectional." +inv\_signalIdentification +"In a given relationship instance of *subnetworkConnectionIsMadeOfTransportEntities*, the information objects playing the role *compositeSNC* and *componentTEntity* must have all the same *signalIdentification* value." +inv\_contiguity +"The component transport entities being contiguous, both the first and the last one must be instances of the subnetworkConnection information object type or of one of its subtypes." +inv\_roles +"In an instance of the relationship, an instance can not play both roles: *compositeSNC* and *componentTEntity*." + +### 8.33 subnetworkConnectionIsTerminatedByPointToPoint + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The subnetworkConnectionIsTerminatedByPointToPoint relationship class describes the relationship that exists between a subnetwork connection and its two terminations." + +![Diagram of the subnetworkConnectionIsTerminatedByPointToPoint relationship. A dashed line labeled 'subnetwork Connection' connects two black circular nodes. The left node is labeled 'subnetworkTP' and the right node is labeled 'subnetworkTP' and 'T0411040-99'.](67d03c9e89620d73e3786c869e559752_img.jpg) + +The diagram illustrates the relationship between a subnetwork connection and its two terminations. A central dashed line represents the 'subnetwork Connection'. At each end of this line is a black circular node. The left node is labeled 'subnetworkTP' and the right node is labeled 'subnetworkTP' and 'T0411040-99'. + +Diagram of the subnetworkConnectionIsTerminatedByPointToPoint relationship. A dashed line labeled 'subnetwork Connection' connects two black circular nodes. The left node is labeled 'subnetworkTP' and the right node is labeled 'subnetworkTP' and 'T0411040-99'. + +" + +#### ROLE + +transportEntitySNC + +"Played by an instance of the information object type or subtype." + +a\_endSNTP + +"Played by instances of the information object type or subtype." + +z\_endSNTP + +"Played by instances of the information object type or subtype." + +#### INVARIANT + +inv\_cardinalityTransportEntity + +"One and only one instance of the role *transportEntitySNC* must participate in the relationship." + +inv\_aendRoleCardinality + +"One and only one instance of the role *a\_endSNTP* must participate in the relationship." + +inv\_zendRoleCardinality + +"One and only one instance of the role *z\_endSNTP* must participate in the relationship." + +inv\_directionAend + +"The object playing the role *a\_endSNTP* must have a pointDirectionality set to source or bidirectional." + +inv\_directionZend + +"The object playing the role *z\_endSNTP* must have a pointDirectionality set to sink or bidirectional." + +inv\_directionality + +"If the information object playing the role *transportEntitySNC* is bidirectional, then the information objects playing the roles *a\_endSNTP* and *z\_endSNTP* must be bidirectional." + +inv\_signalIdentification + +"In a given relationship instance of subnetworkConnectionIsTerminatedByPointToPoint, the information objects playing the role *transportEntitySNC*, *a\_endSNTP* and *z\_endSNTP* must have all the same signalIdentification value." + +### 8.34 subnetworkHasSubnetworkConnections + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The subnetworkHasSubnetworkConnections relationship class describes the relationship that exists between a subnetwork and the subnetworkConnections that are part of it." + +![Diagram of subnetworkHasSubnetworkConnections relationship](0a42e05c07941450f34e4f7117725834_img.jpg) + +A diagram illustrating a subnetwork relationship. It features a large ellipse representing a `subnetwork`. Inside this ellipse, several dashed lines intersect, representing `subnetwork connections`. A solid line labeled "subnetwork connection" points to one of these dashed lines. Another solid line labeled "subnetwork" points to the outer boundary of the ellipse. The identifier "T0411050-99" is located to the right of the ellipse. + +Diagram of subnetworkHasSubnetworkConnections relationship + +" + +#### **ROLE** + +`containerSN` + +"Played by an instance of the information object type or subtype." + +`elementSNC` + +"Played by an instance of the information object type or subtype." + +#### **INVARIANT** + +`inv_containerSNRoleCardinality` + +"One and only one instance of the role *containerSNC* must participate in the relationship." + +`inv_elementSNCRoleCardinality` + +"One or more instances of the role *elementSNC* must participate in the relationship." + +`inv_signalIdentification` + +"In a given relationship instance of `subnetworkHasSubnetworkConnections`, the information objects playing the role *containerSNC* and *elementSNC* must have all the same `signalIdentification` value." + +### 8.35 subnetworkIsDelimitedBy + +This relationship type is related to the following enterprise entity: + + +#### **DEFINITION** + +"The `subnetworkIsDelimitedBy` relationship class describes the relationship that exists between a subnetwork and the subnetworkTPs that delimit it." + +![Diagram of subnetworkIsDelimitedBy relationship](d99a54a2d327cbeae6f5a3abd0c978ad_img.jpg) + +A diagram illustrating the `subnetworkIsDelimitedBy` relationship. It shows a series of black dots, representing `subnetworkTPs`, arranged in an oval shape. A solid line, representing a `subnetwork`, connects these dots. A label "subnetworkTP" points to one of the dots, and a label "subnetwork" points to the line connecting them. The identifier "T0411060-99" is located below the diagram. + +Diagram of subnetworkIsDelimitedBy relationship + +" + +#### **ROLE** + +`containerSN` + +"Played by an instance of the information object type or a subtype." + +`elementSNTP` + +"Played by an instance of the information object type or subtype." + +#### **INVARIANT** + +`inv_containerSNRoleCardinality` + +"One and only one instance of the role *containerSN* must participate in the relationship." + +`inv_elementSNTPRoleCardinality` + +"One or more instances of the role *elementSNTP* must participate in the relationship." + +`inv_signalIdentification` + +"In a given relationship instance of `subnetworkIsDelimitedBy`, the information objects playing the role *containerSN* and *elementSNTP* must have all the same `signalIdentification` value." + +### 8.36 subnetworkIsDelimitedBySnTpPools + +#### DEFINITION + +"The subnetworkIsDelimitedBySnTpPools relationship class describes the relationship that exists between a subnetwork and the subnetworkTpPools that delimit it." + +![Diagram of subnetworkIsDelimitedBySnTpPools relationship](be3e5fe8be7cc5a74f67a4b8ac93193d_img.jpg) + +A diagram showing a large oval labeled 'subnetwork' at the bottom left. Inside the oval, there are five gray circular nodes. One node at the top right is labeled 'subnetworkTpPool' with a line pointing to it. The identifier 'T0411070-99' is located below the oval. + +Diagram of subnetworkIsDelimitedBySnTpPools relationship + +" + +#### ROLE + +containerSN + +"Played by an instance of the information object type or a subtype." + +elementPool + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_containeSNRoleCardinality + +"One and only one instance of the role *containerSN* must participate in the relationship." + +inv\_elementPoolRoleCardinality + +"One or more instances of the role *elementPool* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of subnetworkIsDelimitedBySnTpPools, the information objects playing the role *containerSN* and *elementPool* must have all the same signalIdentification value." + +### 8.37 subnetworkTPIsBundleOfSubnetworkTPs + +#### DEFINITION + +"The subnetworkTPIsBundleOfSubnetworkTPs relationship class describes the relationship that exists between a subnetworkTP and the subnetworkTPs that are part of it. (This relationship is similar to the information specification of the M.3100 gtp managed object class.)" + +![Diagram of subnetworkTPIsBundleOfSubnetworkTPs relationship](bdd19e1aefc189598ab515f8f12518dd_img.jpg) + +A diagram showing a large gray circle labeled 'bundled subnetworkTp' at the bottom left. Inside the circle, there are 12 small black circular nodes. One node at the bottom right is labeled 'bundled subNetworkTp' with a line pointing to it. The identifier 'T0411080-99' is located below the circle. + +Diagram of subnetworkTPIsBundleOfSubnetworkTPs relationship + +" + +#### ROLE + +bundleSNTP + +"Played by an instance of the information object type or subtype." + +bundledSNTP + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_bundleRoleCardinality + +"One and only one instance of the role *bundleSNTP* must participate in the relationship." + +inv\_bundledRoleCardinality + +"One or more instances of the role *bundledSNTP* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of *subnetworkIsDelimitedBySnTpPools*, the information objects playing the role *bundleSNTP* and *bundledSNTP* must have all the same *signalIdentification* value." + +inv\_roles + +"In an instance of the relationship, an instance can not play both roles: *bundleSNTP* and *bundledSNTP*." + +### 8.38 subnetworkTPIsRelatedToExtremity + +#### DEFINITION + +"The *subnetworkTPIsRelatedToExtremity* relationship class describes the relationship that exists between *subnetworkTPs* at a different level of partitioning and the extremity to which they are related." + +![Diagram showing the relationship between an extremity and subnetworkTps at different levels. A single circle on the left represents the extremity (networkCTP, networkTTP, or linkConnection). Three arrows point from this circle to three ovals on the right. The top oval is labeled 'subnetworkTp level 1' and is associated with 'subnetwork level 1'. The middle oval is labeled 'subnetworkTp level 2' and is associated with 'subnetwork level 2'. The bottom oval is labeled 'subnetworkTp level 3' and is associated with 'subnetwork level 3'.](a89d151b67109378baed0c117830cf78_img.jpg) + +The diagram illustrates the *subnetworkTPIsRelatedToExtremity* relationship. On the left, a node labeled "networkCTP or networkTTP or linkConnection" is connected by three arrows to three ovals on the right. Each oval represents a *subnetworkTp* at a different level of partitioning: "subnetworkTp level 1", "subnetworkTp level 2", and "subnetworkTp level 3". Each oval is also associated with a "subnetwork level" label (1, 2, or 3). The diagram is labeled "T0411090-99" in the bottom right corner. + +Diagram showing the relationship between an extremity and subnetworkTps at different levels. A single circle on the left represents the extremity (networkCTP, networkTTP, or linkConnection). Three arrows point from this circle to three ovals on the right. The top oval is labeled 'subnetworkTp level 1' and is associated with 'subnetwork level 1'. The middle oval is labeled 'subnetworkTp level 2' and is associated with 'subnetwork level 2'. The bottom oval is labeled 'subnetworkTp level 3' and is associated with 'subnetwork level 3'. + +" + +#### ROLE + +extremity + +"Played by one and only one instance of the , sub-types or type or subtype." + +abstractionSNTP + +"Played by instances of the sub-types." + +#### INVARIANT + +inv\_extremityRoleCardinality + +"One and only one instance of the role *extremity* must participate in the relationship." + +inv\_abstractionRoleCardinality + +"One or more instances of the role *abstractionSNTP* must participate in the relationship." + +inv\_constraints + +"The following constraints on the types of related object have to be respected:" + +| role: extremity | role: abstractionSNTP | +|-----------------------------------------------------|---------------------------| +| networkCTPwith pointDirectionality = sink | subnetworkTPSource | +| networkTTPwith pointDirectionality = source | subnetworkTPSource | +| linkConnection with directionality = uni | subnetworkTPSource | +| networkCTP with pointDirectionality = source | subnetworkTPSink | +| networkTTP with pointDirectionality = sink | subnetworkTPSink | +| linkConnectionwith directionality = uni | subnetworkTPSink | +| networkCTP with pointDirectionality = bidirectional | subnetworkTPBidirectional | +| networkTTPwith pointDirectionality = bidirectional | subnetworkTPBidirectional | +| linkConnectionwith directionality = bid | subnetworkTPBidirectional | + +" + +inv\_signalIdentification + +"In a given relationship instance of subnetworkTPIsRelatedToExtremity, the information objects playing the role *extremity* and *abstractionSNTP* must have all the same signalIdentification value." + +### 8.39 subnetworkTPPoolIsMadeOfSubnetworkTP + +#### DEFINITION + +"The subnetworkTPPoolIsMadeOfSubnetworkTP relationship class describes the relationship that exists between a subnetworkTPPool and the SubnetworkTPs that are part of it." + +![Diagram illustrating the relationship between a subnetworkTPPool and subNetworkTp. A large circle represents the subnetworkTPPool, and several smaller circles inside it represent subNetworkTp. A line labeled 'subnetworkTpPool' points to the large circle, and a line labeled 'subNetworkTp' points to one of the smaller circles.](a3b3abbf6d0b18f3dd4a83680b5e3e42_img.jpg) + +Diagram illustrating the relationship between a subnetworkTPPool and subNetworkTp. A large circle represents the subnetworkTPPool, and several smaller circles inside it represent subNetworkTp. A line labeled 'subnetworkTpPool' points to the large circle, and a line labeled 'subNetworkTp' points to one of the smaller circles. + +T0411100-99 + +" + +#### ROLE + +containerPool + +"Played by an instance the information object type or subtype." + +elementSNTP + +"Played by instances of the information object type or subtype." + +#### INVARIANT + +inv\_containerPoolRoleCardinality + +"One and only one instance of the role *containerPool* must participate in the relationship." + +inv\_elementPoolRoleCardinality + +"One or more instances of the role *elementSNTP* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of subnetworkTPPoolIsMadeOfSubnetworkTP, the information objects playing the role *containerPool* and *elementSNTP* must have all the same signalIdentification value." + +### 8.40 subnetworkTPPoolsRelatedToExtremity + +#### DEFINITION + +"The subnetworkTPPoolsRelatedToExtremity relationship class describes the relationship that exists between subnetworkTPPools at a different level of partitioning and the extremity to which they are related." + +![Diagram for subnetworkTPPoolsRelatedToExtremity relationship. A central circle on the left is labeled 'linkEnd'. Three arrows point from this circle to three ovals on the right. The ovals are labeled 'subnetworkTpPool level 1', 'subnetworkTpPool level 2', and 'subnetworkTpPool level 3'. To the right of each oval is a label: 'subnetwork level 1', 'subnetwork level 2', and 'subnetwork level 3'. The diagram is labeled 'T0411110-99'.](3442f31a562d1ef45bfa18b18a6a1ddc_img.jpg) + +Diagram for subnetworkTPPoolsRelatedToExtremity relationship. A central circle on the left is labeled 'linkEnd'. Three arrows point from this circle to three ovals on the right. The ovals are labeled 'subnetworkTpPool level 1', 'subnetworkTpPool level 2', and 'subnetworkTpPool level 3'. To the right of each oval is a label: 'subnetwork level 1', 'subnetwork level 2', and 'subnetwork level 3'. The diagram is labeled 'T0411110-99'. + +" + +#### ROLE + +extremityGroup + +"Played by an instance of the , , or or subtypes." + +abstractionSNTPPool + +"Played by instances of the or subtypes." + +#### INVARIANT + +inv\_extremityEndRoleCardinality + +"One and only one instance of the role *extremityGroup* must participate in the relationship." + +inv\_abstractionRoleCardinality + +"At least one instance of the role *abstractionSNTPPool* must participate in the relationship." + +inv\_directionality + +"If the information object playing the role *extremityGroup* is bidirectional, then all the information objects playing the role *abstractionSNTPPool* must be bidirectional." + +inv\_signalIdentification + +"In a given relationship instance of subnetworkTPPoolsRelatedToExtremity, the information objects playing the role *extremityGroup* and *abstractionSNTPPool* must have all the same signalIdentification value." + +### 8.41 tandemConnectionIsMadeOfTransportEntities + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The tandemConnectionIsMadeOfTransportEntities relationship class describes the relationship that exists between a tandem connection and its component transport entities." + +![Diagram for tandemConnectionIsMadeOfTransportEntities relationship. A dashed line forms a wide inverted V shape. The top vertex is labeled 'tandem Connection'. The left downward-pointing arrow is labeled 'link Connection'. The right downward-pointing arrow is labeled 'subnetwork Connection'. The diagram is labeled 'T0411120-99'.](db42f27db117c6e8ac41dbbb67722021_img.jpg) + +Diagram for tandemConnectionIsMadeOfTransportEntities relationship. A dashed line forms a wide inverted V shape. The top vertex is labeled 'tandem Connection'. The left downward-pointing arrow is labeled 'link Connection'. The right downward-pointing arrow is labeled 'subnetwork Connection'. The diagram is labeled 'T0411120-99'. + +" + +#### **ROLE** + +*compositeTC* + +"Played by an instance of the information object type or subtype." + +*componentTransportC* + +"Played by an instance of the information object type or subtype, or information object type or subtype." + +#### **INVARIANT** + +*inv\_compositeTCRoleCardinality* + +"One and only one instance of the role *compositeTC* must participate in the relationship." + +*inv\_componentTCRoleCardinality* + +"At least one instance of the role *componentTransportC* must participate in the relationship." + +*inv\_directionality* + +"If the information object playing the role *compositeTC* is bidirectional, then all the information objects playing the role *componentTransportC* must be bidirectional." + +*inv\_signalIdentification* + +"In a given relationship instance of tandemConnectionIsMadeOfTransportEntities, the information objects playing the role *compositeTC* and *componentTransportC* must have all the same signalIdentification value." + +### 8.42 topologicalLinkEndIsSupportedByNetworkTTP + +This relationship type is related to the following enterprise entities: + + <"ITU-T Rec. G.852.2", COMMUNITY:tem, ROLE:trail termination point, PROPERTY:adaptation>." + +#### **DEFINITION** + +"The *topologicalLinkEndIsSupportedByNetworkTTP* relationship class describes the relationship that exists between a *topologicalLinkEnd* of a given layer network (known as the client layer network) and the *networkTTP* that supports them in a server layer network." + +![Diagram showing the relationship between topologicalLinkEnd and networkTTP. A white circle at the top is labeled topologicalLinkEnd. A black circle below it is labeled networkTTP. An arrow points from the black circle to the white circle. A line from the left points to the arrow/connection area and is labeled adaptation function. The diagram is labeled T0411130-99.](a461c3fbcb754ea34add62bb4bd25751_img.jpg) + +``` + +graph TD + TLE(( )) -- adaptation function --- nTTP(( )) + style TLE fill:#fff,stroke:#000 + style nTTP fill:#000,stroke:#000 + nTTP --> TLE + TLE --- label1[topologicalLinkEnd] + nTTP --- label2[networkTTP] + +``` + +Diagram showing the relationship between topologicalLinkEnd and networkTTP. A white circle at the top is labeled topologicalLinkEnd. A black circle below it is labeled networkTTP. An arrow points from the black circle to the white circle. A line from the left points to the arrow/connection area and is labeled adaptation function. The diagram is labeled T0411130-99. + +" + +#### **ROLE** + +*clientTLE* + +"Played by instances of the information object type or subtype." + +*serverTTP* + +"Played by an instance of the information object type or subtype." + +#### **INVARIANT** + +*inv\_serverTTPRoleCardinality* + +"One and only one instance of the role *serverTTP* must participate in the relationship." + +*inv\_clientTLERoleCardinality* + +"At least one instance of the role *clientTLE* must participate in the relationship." + +*inv\_directionality* + +"If the information object playing the role *serverTTP* is bidirectional, then the information objects playing the role *clientTLE* must be bidirectional." + +*inv\_signalIdentification* + +"In a given relationship instance of *topologicalLinkEndIsSupportedByNetworkTTP*, the information object playing the role *serverTTP* must have a different *signalIdentification* value than the information object playing the role *clientTLE* as defined in Recommendation G.805 (compliant values are technologies dependent and defined in the corresponding Recommendations, e.g. G.783 for SDH)." + +### 8.43 topologicalLinkIsSupportedByTrail + +This relationship type is related to the following enterprise entity: + +, + + + +#### DEFINITION + +"The topologicalLinkIsSupportedByTrail relationship class describes the relationship that exists between topologicalLinks of a given layer network (known as the client layer network) and the trail that supports them in a server layer network. + +![Diagram illustrating the topologicalLinkIsSupportedByTrail relationship. A thick horizontal line represents the 'trail'. Above it, a thinner horizontal line represents the 'topologicalLink'. An arrow labeled 'adaptation function' points from the trail to the topologicalLink. The diagram is labeled T0411140-99.](3493d7ba4c86f944e159de1bf45ff03d_img.jpg) + +The diagram shows a thick horizontal line at the bottom labeled 'trail'. Above it is a thinner horizontal line labeled 'topologicalLink'. An arrow labeled 'adaptation function' points from the trail to the topologicalLink. The diagram is labeled T0411140-99. + +Diagram illustrating the topologicalLinkIsSupportedByTrail relationship. A thick horizontal line represents the 'trail'. Above it, a thinner horizontal line represents the 'topologicalLink'. An arrow labeled 'adaptation function' points from the trail to the topologicalLink. The diagram is labeled T0411140-99. + +" + +#### ROLE + +clientTL + +"Played by instances of the information object type or subtype." + +serverTrail + +"Played by an instance of the information object type or subtype." + +#### INVARIANT + +inv\_serverTrailRoleCardinality + +"One and only one instance of the role *serverTrail* must participate in the relationship." + +inv\_clientTLRoleCardinality + +"At least one instance of the role *clientTL* must participate in the relationship." + +inv\_directionality + +"If the information object playing the role *serverTrail* is bidirectional, then the information objects playing the role *clientTL* must be bidirectional." + +inv\_signalIdentification + +"In a given relationship instance of topologicalLinkEndIsSupportedByNetworkTTP, the information object playing the role *serverTrail* must have a different signalIdentification value than the information object playing the role *clientTL* as defined in Recommendation G.805 (compliant values are technologies dependent and defined in the corresponding Recommendations, e.g. G.783 for SDH)." + +### 8.44 trailIsBundleOfTrails + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The trailIsBundleOfTrails relationship class describes the relationship that exists between a trail and the trails that are part of it. + +![Diagram illustrating the trailIsBundleOfTrails relationship. A thick horizontal line at the top represents a 'trail with an n*x bandwidth'. Below it, five thinner horizontal lines represent 'trails with an x bandwidth'. Arrows point from the top trail down to each of the five bottom trails. The diagram is labeled T0411150-99.](155cdc51eb4f6a3e9f032459d85a2f77_img.jpg) + +The diagram shows a thick horizontal line at the top labeled 'trail with an n\*x bandwidth'. Below it are five thinner horizontal lines, each labeled 'trail with an x bandwidth'. Arrows point from the top trail down to each of the five bottom trails. The diagram is labeled T0411150-99. + +Diagram illustrating the trailIsBundleOfTrails relationship. A thick horizontal line at the top represents a 'trail with an n\*x bandwidth'. Below it, five thinner horizontal lines represent 'trails with an x bandwidth'. Arrows point from the top trail down to each of the five bottom trails. The diagram is labeled T0411150-99. + +" + +#### ROLE + +bundleTrail + +"Played by an instance of the information object type or subtype." + +bundledTrail + +"Played by an instance of a subtype of the information object type or subtype." + +#### INVARIANT + +inv\_bundleRoleCardinality + +"One and only one instance of the *bundleTrail* container must participate in the relationship." + +inv\_bundledRoleCardinality + +"One or more instances of the role *bundledTrail* must participate in the relationship." + +inv\_signalIdentification + +"In a given relationship instance of *trailsIsBundleOfTrails*, the information objects playing the role *bundleTrail* and *bundledTrail* must have all the same *signalIdentification* value." + +inv\_directionality + +"The objects involved in the relationship must have a compatible directionality." + +inv\_roles + +"In an instance of the relationship, an instance can not play both roles: *bundleTrail* and *bundledTrail*." + +### **8.45 trailsIsMadeOfTransportEntities** + +This relationship type is related to the following enterprise entity: + + +#### DEFINITION + +"The *trailsIsMadeOfTransportEntities* relationship class describes the relationship that exists between a trail and its component transport entities." + +![Diagram showing the relationship between a trail and its component transport entities (link Connection and subnetwork Connection).](7ef15a55963eccd86906be784f1d75c4_img.jpg) + +``` + +graph TD + Trail[trail] --- LinkC[link Connection] + LinkC --- SubnetC[subnetwork Connection] + style Trail fill:none,stroke:none + style LinkC fill:none,stroke:none + style SubnetC fill:none,stroke:none + +``` + +The diagram illustrates the relationship between a trail and its component transport entities. A top line is labeled 'trail'. Below it, a dashed box contains 'link Connection'. Further down, a line is labeled 'subnetwork Connection'. Arrows on the left and right connect these levels, indicating a hierarchical or compositional relationship. The diagram is indexed as T0411160-99. + +Diagram showing the relationship between a trail and its component transport entities (link Connection and subnetwork Connection). + +" + +#### ROLE + +compositeTrail + +"Played by an instance of the information object type or subtype." + +componentTransportC + +"Played by an instance of the information object type or subtype, or information object type or subtype." + +#### INVARIANT + +inv\_compositeTrailRoleCardinality + +"One and only one instance of the role *compositeTrail* must participate in the relationship." + +inv\_componentTrailRoleCardinality + +"At least one instance of the role *componentTransportC* must participate in the relationship." + +inv\_directionality + +"If the information object playing the role *compositeTrail* is bidirectional, then all the information objects playing the role *componentTransportC* must be bidirectional." + +inv\_signalIdentification + +"In a given relationship instance of *trailsIsMadeOfTransportEntities*, the information objects playing the role *compositeTrail* and *componentTransportC* must have all the same *signalIdentification* value." + +### 8.46 **trailIsTerminatedByPointToPoint** + +This relationship type is related to the following enterprise entity: + + + +#### DEFINITION + +"The *trailIsTerminatedByPointToPoint* relationship class describes the relationship that exists between a trail and its two extremities." + +![Diagram of the trailIsTerminatedByPointToPoint relationship. A dashed line labeled 'trail' connects two black circular nodes. The left node is labeled 'networkTTP' and the right node is labeled 'networkTTP' and 'T0411170-99'.](508bc574df81fa8d3027a374f6d155fc_img.jpg) + +The diagram illustrates the *trailIsTerminatedByPointToPoint* relationship. A horizontal dashed line, labeled *trail* above it, connects two solid black circular nodes. The left node has a line pointing to it from the label *networkTTP*. The right node has a line pointing to it from the label *networkTTP*, and another line pointing to it from the value *T0411170-99*. + +Diagram of the trailIsTerminatedByPointToPoint relationship. A dashed line labeled 'trail' connects two black circular nodes. The left node is labeled 'networkTTP' and the right node is labeled 'networkTTP' and 'T0411170-99'. + +" + +#### ROLE + +*transportEntityTrail* + +"Played by an instance of the information object type or subtype." + +*a\_endNTTP* + +"Played by instances of the information object type or subtype." + +*z\_endNTTP* + +"Played by instances of the information object type or subtype." + +#### INVARIANT + +*inv\_transportEntityRoleCardinality* + +"One and only one instance of the role *transportEntityTrail* must participate in the relationship." + +*inv\_aendRoleCardinality* + +"One and only one instance of the role *a\_endNTTP* must participate in the relationship." + +*inv\_zendRoleCardinality* + +"One and only one instance of the role *z\_endNTTP* must participate in the relationship." + +*inv\_directionAend* + +"The object playing the role *a\_endNTTP* must have a *pointDirectionality* set to *source* or *bidirectional*." + +*inv\_directionZend* + +"The object playing the role *z\_endNTTP* must have a *pointDirectionality* set to *sink* or *bidirectional*." + +*inv\_directionality* + +"If the information object playing the role of *transportEntityTrail* is *bidirectional*, then the information objects playing the roles *a\_endNTTP* and *z\_endNTTP* must be *bidirectional*." + +*inv\_signalIdentification* + +"In a given relationship instance of *trailIsTerminatedByPointToPoint*, the information objects playing the role *transportEntityTrail*, *a\_endNTTP* and *z\_endNTTP* must have all the same *signalIdentification* value." + +# ANNEX A + +## UML relationships diagrams + +### A.1 Topology + +![UML class diagram for network topology showing relationships between layerNetworkdomain, networkInformationTop, subnetwork, link, subnetworkTPPool, accessGroup, subnetworkTP, networkTTP, linkEnd, and networkCTP.](9e8ebf03cae78f4f81b697548c2d7250_img.jpg) + +``` + +classDiagram + class layerNetworkdomain + class networkInformationTop + class subnetwork + class LinkExtremity { + <> + subnetwork + accessGroup + subnetworkTPPool + } + class link + class subnetworkTPPool + class accessGroup + class subnetworkTP + class networkTTP + class linkEnd + class networkCTP + + layerNetworkdomain "0..1" -- "0..*" networkInformationTop : layerNetworkDomainIsMadeOf + subnetwork "0..*" -- "0..1" subnetworkTPPool : subnetworkIsDelimitedBySntpPools + subnetwork "0..*" -- "0..1" subnetworkTP : subnetworkIsDelimitedBy + LinkExtremity "0..1" -- "0..*" link : linkBinds + link "0..*" -- "0..1" linkEnd : linkEndIsTerminatedByLinkEnds + linkEnd "0..1" -- "0..*" networkCTP : linkEndIsHasNetworkCTPs + subnetworkTPPool "0..1" -- "0..*" subnetworkTP : subnetworkTPPoolIsMadeOfSubnetworkTP + accessGroup "0..1" -- "0..*" networkTTP : accessGroupIsMadeOfNetworkTTPs + +``` + +UML class diagram for network topology. The diagram shows the following classes and relationships: + +- layerNetworkdomain** (0..1) is associated with **networkInformationTop** (0..\*) via the relationship *layerNetworkDomainIsMadeOf*. The association is labeled with **+containerLND** and **+elementLND**. +- subnetwork** (0..\*) is associated with **subnetworkTPPool** (0..1) via the relationship *subnetworkIsDelimitedBySntpPools*. The association is labeled with **+containerSN** and **+elementPool**. +- subnetwork** (0..\*) is associated with **subnetworkTP** (0..1) via the relationship *subnetworkIsDelimitedBy*. The association is labeled with **+containerSN** and **+elementSNTP**. +- LinkExtremity** (a *<>* of subnetwork, accessGroup, or subnetworkTPPool) (0..1) is associated with **link** (0..\*) via the relationship *linkBinds*. The association is labeled with **+a\_end**, **+z\_en**, and **+transferCapacity**. +- link** (0..\*) is associated with **linkEnd** (0..1) via the relationship *linkEndIsTerminatedByLinkEnds*. The association is labeled with **+transferCapacity**, **+z\_end**, and **+a\_end**. +- linkEnd** (0..1) is associated with **networkCTP** (0..\*) via the relationship *linkEndIsHasNetworkCTPs*. The association is labeled with **+containerLE** and **+elementLE**. +- subnetworkTPPool** (0..1) is associated with **subnetworkTP** (0..\*) via the relationship *subnetworkTPPoolIsMadeOfSubnetworkTP*. The association is labeled with **+containerPool** and **+elementPool**. +- accessGroup** (0..1) is associated with **networkTTP** (0..\*) via the relationship *accessGroupIsMadeOfNetworkTTPs*. The association is labeled with **+containerAG** and **+elementAG**. + +UML class diagram for network topology showing relationships between layerNetworkdomain, networkInformationTop, subnetwork, link, subnetworkTPPool, accessGroup, subnetworkTP, networkTTP, linkEnd, and networkCTP. + +T0411180-99 + +![UML class diagram for link relationships showing relationships between link, linkConnection, and concatenatedLinkHasLinks.](18e519d1f91133e080347562f681dfb5_img.jpg) + +``` + +classDiagram + class link + class linkConnection + + link "0..*" -- "0..*" link : concatenatedLinkHasLinks + link "0..*" -- "0..*" link : compoundLinkHasLinks + link "0..*" -- "0..*" linkConnection : linkHasLinkConnections + +``` + +UML class diagram for link relationships. The diagram shows the following classes and relationships: + +- link** (0..\*) is associated with itself (0..\*) via the relationship *concatenatedLinkHasLinks*. The association is labeled with **+serie** and **+serial**. +- link** (0..\*) is associated with itself (0..\*) via the relationship *compoundLinkHasLinks*. The association is labeled with **+compound** and **+component**. +- link** (0..\*) is associated with **linkConnection** (0..\*) via the relationship *linkHasLinkConnections*. The association is labeled with **+elementLink** and **+containerLink**. + +UML class diagram for link relationships showing relationships between link, linkConnection, and concatenatedLinkHasLinks. + +T0411190-99 + +### A.2 Partitioning relationships + +![UML Class Diagram showing a recursive relationship on the subnetwork class and a relationship between subnetwork and link.](b2cc37ae1974ec7b87b91f54963b855d_img.jpg) + +UML Class Diagram illustrating partitioning relationships: + +- subnetwork** (Class): + - Association: *snIsPartitionedBySn* (Self-association). Multiplicity 0..1 at the **+compositeSN** end and 0..\* at the **+componentSN** end. + - Association: *snIsPartitionedByLinks* with **link**. Multiplicity 0..1 at the **+compositeSN** end and 0..\* at the **+componentLink** end. +- link** (Class): + - Association: *snIsPartitionedByLinks* with **subnetwork**. Multiplicity 0..\* at the **+componentLink** end. + +UML Class Diagram showing a recursive relationship on the subnetwork class and a relationship between subnetwork and link. + +![UML Class Diagram showing a relationship between subnetworkTPPool and linkEnd.](675af5bb2357ce5b510e613d04f66bdc_img.jpg) + +UML Class Diagram illustrating a relationship: + +- subnetworkTPPool** (Class): + - Association: *subnetworkTPPool IsRelatedToExtremity* with **linkEnd**. Multiplicity 0..\* at the **+abstraction** end and 0..1 at the **+extremity** end. +- linkEnd** (Class): + - Association: *subnetworkTPPool IsRelatedToExtremity* with **subnetworkTPPool**. Multiplicity 0..1 at the **+extremity** end. + +UML Class Diagram showing a relationship between subnetworkTPPool and linkEnd. + +![UML Class Diagram showing a relationship between subnetworkTP and a choice class.](2cf3896394a2342a2b46c504ab9a8830_img.jpg) + +UML Class Diagram illustrating a relationship with a choice class: + +- subnetworkTP** (Class): + - Association: *subnetworkIsRelatedToExtremity* with **extremityChoice**. Multiplicity 0..\* at the **+abstraction** end and 0..1 at the **+extremity** end. +- extremityChoice** (Choice Class): + - Options: networkTTP, networkCTP, linkConnection. + - Association: *subnetworkIsRelatedToExtremity* with **subnetworkTP**. Multiplicity 0..1 at the **+extremity** end. + +UML Class Diagram showing a relationship between subnetworkTP and a choice class. + +T0411200-99 + +### A.3 Connection extremities + +![UML Class Diagram showing linkConnectionIsTerminatedByPointToPoint association between linkConnection and networkCTP.](8a9f4764511ce90622893ec65c065eeb_img.jpg) + +*linkConnectionIsTerminatedByPointToPoint* + +``` + +classDiagram + class linkConnection + class networkCTP + linkConnection "0..1" -- "0..1" networkCTP : +transportEntityLC + linkConnection "0..1" -- "0..1" networkCTP : +transportEntityLC + networkCTP "0..1" -- "0..1" linkConnection : +a_endCTP + networkCTP "0..1" -- "0..1" linkConnection : +z_endCTP + +``` + +This diagram illustrates the association between **linkConnection** and **networkCTP**. The association is named *linkConnectionIsTerminatedByPointToPoint*. On the **linkConnection** side, there are two associations, both labeled `+transportEntityLC`, with multiplicities of `0..1`. On the **networkCTP** side, there are two associations: one labeled `+a_endCTP` and the other `+z_endCTP`, both with multiplicities of `0..1`. A dashed vertical line bisects the association, indicating a bidirectional relationship. + +UML Class Diagram showing linkConnectionIsTerminatedByPointToPoint association between linkConnection and networkCTP. + +![UML Class Diagram showing subnetworkConnectionIsTerminatedByPointToPoint association between subnetworkConnection and subnetworkTP.](255efa1d461fc79b4ed367aaec11637f_img.jpg) + +*subnetworkConnectionIsTerminatedByPointToPoint* + +``` + +classDiagram + class subnetworkConnection + class subnetworkTP + subnetworkConnection "0..1" -- "0..1" subnetworkTP : +transportEntity + subnetworkConnection "0..1" -- "0..1" subnetworkTP : +transportEntity + subnetworkTP "0..1" -- "0..1" subnetworkConnection : +a_end + subnetworkTP "0..1" -- "0..1" subnetworkConnection : +z_end + +``` + +This diagram illustrates the association between **subnetworkConnection** and **subnetworkTP**. The association is named *subnetworkConnectionIsTerminatedByPointToPoint*. On the **subnetworkConnection** side, there are two associations, both labeled `+transportEntity`, with multiplicities of `0..1`. On the **subnetworkTP** side, there are two associations: one labeled `+a_end` and the other `+z_end`, both with multiplicities of `0..1`. The association is bidirectional, indicated by a dashed vertical line. + +UML Class Diagram showing subnetworkConnectionIsTerminatedByPointToPoint association between subnetworkConnection and subnetworkTP. + +![UML Class Diagram showing trailIsTerminatedByPointToPoint association between trail and networkTTP.](7ed5d5770331f31ade15439a21c31425_img.jpg) + +*trailIsTerminatedByPointToPoint* + +``` + +classDiagram + class trail + class networkTTP + trail "0..1" -- "0..1" networkTTP : +transportEntity + trail "0..1" -- "0..1" networkTTP : +transportEntity + networkTTP "0..1" -- "0..1" trail : +a_end + networkTTP "0..1" -- "0..1" trail : +z_end + +``` + +This diagram illustrates the association between **trail** and **networkTTP**. The association is named *trailIsTerminatedByPointToPoint*. On the **trail** side, there are two associations, both labeled `+transportEntity`, with multiplicities of `0..1`. On the **networkTTP** side, there are two associations: one labeled `+a_end` and the other `+z_end`, both with multiplicities of `0..1`. The association is bidirectional, indicated by a dashed vertical line. + +UML Class Diagram showing trailIsTerminatedByPointToPoint association between trail and networkTTP. + +T0411210-99 + +### A.4 Connection composition + +![UML Class Diagram showing connection composition relationships between linkConnection, subnetworkConnection, tandemConnection, and trail classes.](7d929ba1b7d09ea8e00b9e7abbbe50c9_img.jpg) + +``` + +classDiagram + class linkConnection + class subnetworkConnection + class tandemConnection + class trail + class componentConnection { + <> + subnetworkConnection + linkConnection + } + + linkConnection "0..1" -- "0..*" componentConnection : +compositeLC + subnetworkConnection "0..1" -- "0..*" componentConnection : +compositeSNC + tandemConnection "0..1" -- "0..*" componentConnection : +compositeTC + trail "0..*" -- "0..*" componentConnection : +compositeTrail + + linkConnection --> componentConnection : linkConnection IsMadeOfTransportEntities + subnetworkConnection --> componentConnection : subnetworkConnection IsMadeOfTransportEntities + tandemConnection --> componentConnection : tandemConnection IsMadeOfTransportEntities + trail --> componentConnection : trailIsMadeOfTransportEntities + + componentConnection --> linkConnection : +componentLC + componentConnection --> subnetworkConnection : +componentSNC + componentConnection --> tandemConnection : +componentTC + componentConnection --> trail : +componentTrail + +``` + +The diagram illustrates the composition relationships for connection entities. At the top, **linkConnection** and **subnetworkConnection** are shown. Below them, **tandemConnection** and **trail** are shown. A central **<> componentConnection** class contains **subnetworkConnection** and **linkConnection**. Associations with multiplicities (0..1, 0..\*) and role names (+compositeLC, +compositeSNC, +compositeTC, +compositeTrail) connect the top-level classes to the componentConnection class. Stereotypes like *IsMadeOfTransportEntities* and *trailIsMadeOfTransportEntities* are also present. The diagram is identified by the code T0411220-99. + +UML Class Diagram showing connection composition relationships between linkConnection, subnetworkConnection, tandemConnection, and trail classes. + +### A.5 Inter-layering relationships + +![UML class diagram showing inter-layering relationships between topologicalLinkEnd, networkCTP, topologicalLink, linkConnection, networkTTP, trail, and layerNetworkdomain.](9cd85f266cdb1fb3ad544eb3dd3bd5e4_img.jpg) + +``` + +classDiagram + class topologicalLinkEnd + class networkCTP + class topologicalLink + class linkConnection + class networkTTP + class trail + class layerNetworkdomain + + topologicalLinkEnd "0..*" -- "0..*" networkCTP : +clientTLE + networkCTP "0..*" -- "0..*" topologicalLinkEnd : +clientCTP + topologicalLinkEnd "0..*" -- "0..1" networkTTP : +serverTTP + networkTTP "0..1" -- "0..*" topologicalLinkEnd : +serverTTP + topologicalLink "0..*" -- "0..1" trail : +clientTL + trail "0..1" -- "0..*" topologicalLink : +serverTrail + linkConnection "0..*" -- "0..1" trail : +clientLC + trail "0..1" -- "0..*" linkConnection : +serverTrail + layerNetworkdomain "0..*" -- "0..1" networkTTP : +client + networkTTP "0..1" -- "0..*" layerNetworkdomain : +server + +``` + +The diagram illustrates the following relationships: + +- topologicalLinkEnd** and **networkCTP** have a bidirectional association. The multiplicity at **topologicalLinkEnd** is 0..\* and at **networkCTP** is 0..\*. The role **+clientTLE** is associated with **topologicalLinkEnd** and **+clientCTP** with **networkCTP**. The relationship is labeled *networkTTPAdaptsNetworkCTPS*. +- topologicalLinkEnd** and **networkTTP** have a bidirectional association. The multiplicity at **topologicalLinkEnd** is 0..\* and at **networkTTP** is 0..1. The role **+serverTTP** is associated with **networkTTP** and **+clientTLE** with **topologicalLinkEnd**. The relationship is labeled *topologicalLinkEndIsSupportedByNetworkTTP*. +- topologicalLink** and **trail** have a bidirectional association. The multiplicity at **topologicalLink** is 0..\* and at **trail** is 0..1. The role **+clientTL** is associated with **topologicalLink** and **+serverTrail** with **trail**. The relationship is labeled *topologicalLinkIsSupportedByTrail*. +- linkConnection** and **trail** have a bidirectional association. The multiplicity at **linkConnection** is 0..\* and at **trail** is 0..1. The role **+clientLC** is associated with **linkConnection** and **+serverTrail** with **trail**. The relationship is labeled *linkConnectionIsSupportedByTrail*. +- layerNetworkdomain** and **networkTTP** have a bidirectional association. The multiplicity at **layerNetworkdomain** is 0..\* and at **networkTTP** is 0..1. The role **+client** is associated with **layerNetworkdomain** and **+server** with **networkTTP**. The relationship is labeled *layerNetworkDomainCanServeLnds*. + +T0411230-99 + +UML class diagram showing inter-layering relationships between topologicalLinkEnd, networkCTP, topologicalLink, linkConnection, networkTTP, trail, and layerNetworkdomain. + +### A.6 Bundle relationships + +![UML class diagram for linkConnectionIsBundleOfLinkConnections](0ccaa59b5bc46884777e728ee3dadaa7_img.jpg) + +``` + +classDiagram + class linkConnection + linkConnection "0..1" -- "0..*" linkConnection : +bundle / +bundled + +``` + +A UML class diagram for the class *linkConnection*. It shows a self-association where the multiplicity at the top right is 0..1 and the multiplicity at the bottom left is 0..\*. The association is labeled with '+bundle' at the top right and '+bundled' at the bottom left. + +UML class diagram for linkConnectionIsBundleOfLinkConnections + +*linkConnectionIsBundleOfLinkConnections* + +![UML class diagram for networkCTPIsBundledOfNetworkCTPs](b34c69e1ec326b01c3a485b27b1df5f6_img.jpg) + +``` + +classDiagram + class networkCTP + networkCTP "0..*" -- "0..1" networkCTP : +bundled / +bundle + +``` + +A UML class diagram for the class *networkCTP*. It shows a self-association where the multiplicity at the top right is 0..\* and the multiplicity at the bottom left is 0..1. The association is labeled with '+bundled' at the top right and '+bundle' at the bottom left. + +UML class diagram for networkCTPIsBundledOfNetworkCTPs + +*networkCTPIsBundledOfNetworkCTPs* + +![UML class diagram for subnetworkTPIsBundleOfSubnetworkTPs](848073118eebfdbfdb9a60e3923fe0b3_img.jpg) + +``` + +classDiagram + class subnetworkTP + subnetworkTP "0..*" -- "0..1" subnetworkTP : +bundled / +bundle + +``` + +A UML class diagram for the class *subnetworkTP*. It shows a self-association where the multiplicity at the top right is 0..\* and the multiplicity at the bottom left is 0..1. The association is labeled with '+bundled' at the top right and '+bundle' at the bottom left. + +UML class diagram for subnetworkTPIsBundleOfSubnetworkTPs + +*subnetworkTPIsBundleOfSubnetworkTPs* + +![UML class diagram for subnetworkConnectionIsBundleOfSubnetworkConnections](802707b774f2d2973b49cea2020e8453_img.jpg) + +``` + +classDiagram + class subnetworkConnection + subnetworkConnection "0..*" -- "0..1" subnetworkConnection : +bundled / +bundle + +``` + +A UML class diagram for the class *subnetworkConnection*. It shows a self-association where the multiplicity at the top right is 0..\* and the multiplicity at the bottom left is 0..1. The association is labeled with '+bundled' at the top right and '+bundle' at the bottom left. + +UML class diagram for subnetworkConnectionIsBundleOfSubnetworkConnections + +*subnetworkConnectionIsBundleOfSubnetworkConnections* + +![UML class diagram for trailIsBundleOfTrails](b5987d63203a5fa601921039922ac520_img.jpg) + +``` + +classDiagram + class trail + trail "0..*" -- "0..1" trail : +bundled / +bundle + +``` + +A UML class diagram for the class *trail*. It shows a self-association where the multiplicity at the top right is 0..\* and the multiplicity at the bottom left is 0..1. The association is labeled with '+bundled' at the top right and '+bundle' at the bottom left. + +UML class diagram for trailIsBundleOfTrails + +*trailIsBundleOfTrails* + +T0411240-99 + +### A.7 Physical entities relationships + +![UML Class Diagram showing physical entities relationships: equipment, circuitPack, ImplementedNE, physicalPort, and physicalMedium.](3766b291e69420b0437ae278b057b5ee_img.jpg) + +``` + +classDiagram + class equipment { + <> + } + class circuitPack { + <> + } + class ImplementedNE { + networkElementTP + networkElementFabric + } + class physicalPort { + <> + } + class physicalMedium { + <> + } + + equipment "0..1" -- "0..1" equipment : equipmentIsMadeOfEquipments + equipment "0..*" -- "0..1" circuitPack : equipmentImplements + circuitPack "0..1" -- "0..*" physicalPort : circuitPackSupportsPhysicalPorts + physicalPort "0..1" -- "0..1" physicalMedium : extremitiesTerminatePhysicalMedium + +``` + +The diagram illustrates the relationships between five physical entities: + +- equipment**: The base entity for all physical equipment. It has a self-association labeled *equipmentIsMadeOfEquipments* with a multiplicity of 0..1 at both ends, role name **+container**. +- circuitPack**: A subclass of **equipment**. The association is labeled *equipmentImplements* with a multiplicity of 0..\* at the equipment end (role name **+element**) and 0..1 at the circuitPack end. +- ImplementedNE**: A subclass of **circuitPack**. The association is labeled *equipmentImplements* with a multiplicity of 0..\* at the circuitPack end (role name **+containerEquipment**) and 0..1 at the ImplementedNE end (role name **+elementEquipment**). +- physicalPort**: A subclass of **circuitPack**. The association is labeled *circuitPackSupportsPhysicalPorts* with a multiplicity of 0..1 at the circuitPack end (role name **+containerPack**) and 0..\* at the physicalPort end (role name **+elementPack**). +- physicalMedium**: A subclass of **physicalPort**. The association is labeled *extremitiesTerminatePhysicalMedium* with a multiplicity of 0..1 at the physicalPort end (role name **+a\_end**) and 0..1 at the physicalMedium end (role name **+transport**). + +UML Class Diagram showing physical entities relationships: equipment, circuitPack, ImplementedNE, physicalPort, and physicalMedium. + +T0411250-99 + + + +# ITU-T RECOMMENDATIONS SERIES + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of the ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure and Internet protocol aspects | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.853.6-199903-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.853.6-199903-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..a7da83ecb82b51a4cef7694858eef2c35f1986ff --- /dev/null +++ b/marked/G/T-REC-G.853.6-199903-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:d77a478c5b78d330a2a6abbd32e7d0ac053d8b9c1ffe8a96476214afa6ddf7ae +size 8196 diff --git a/marked/G/T-REC-G.853.6-199903-I_PDF-E/35a7554182eb055209552843f341a1ae_img.jpg b/marked/G/T-REC-G.853.6-199903-I_PDF-E/35a7554182eb055209552843f341a1ae_img.jpg new file mode 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100644 index 0000000000000000000000000000000000000000..0e091885a85118306c4948234549a9fb01110158 --- /dev/null +++ b/marked/G/T-REC-G.853.6-199903-I_PDF-E/raw.md @@ -0,0 +1,588 @@ + + +![ITU logo: A globe with the letters ITU and a lightning bolt.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with the letters ITU and a lightning bolt. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.853.6** + +(03/99) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital transmission systems – Digital networks – +Management of transport network + +--- + +**Information viewpoint for trail management** + +ITU-T Recommendation G.853.6 + +(Previously CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| INTERNATIONAL ANALOGUE CARRIER SYSTEM | | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TRANSMISSION SYSTEMS | | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | + +For further details, please refer to ITU-T List of Recommendations. + +## **INFORMATION VIEWPOINT FOR TRAIL MANAGEMENT** + +## **Summary** + +The trail management service provides functionality for: + +- creation/deletion of trail termination points; +- association/disassociation of trail termination points with/from subnetworks or access groups; +- set-up/release and modification of trails between a specified set of endpoints and/or access groups at the boundary of a layer network. + +### **Source** + +ITU-T Recommendation G.853.6 was prepared by ITU-T Study Group 4 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 26th of March 1999. + +## FOREWORD + +ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +### NOTE + +In this Recommendation the term *recognized operating agency (ROA)* includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms *Administration*, *ROA* and *public correspondence* are defined in the *Constitution of the ITU (Geneva, 1992)*. + +### INTELLECTUAL PROPERTY RIGHTS + +The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, the ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 1999 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +## CONTENTS + +###### Page + +| | | | +|-----|--------------------------------------------------------------------|---| +| 1 | Scope ..... | 1 | +| 2 | References ..... | 1 | +| 3 | Definitions ..... | 1 | +| 4 | Abbreviations ..... | 1 | +| 5 | Conventions ..... | 2 | +| 6 | Class diagrams ..... | 2 | +| 6.1 | UML class diagram representing relationships between classes ..... | 2 | +| 6.2 | UML class diagram representing the inheritance hierarchy ..... | 3 | +| 7 | Label references ..... | 4 | +| 8 | Information object class definitions ..... | 4 | +| 8.1 | tmAccessGroup ..... | 4 | +| 8.2 | tmLayerNetworkDomain ..... | 4 | +| 8.3 | tmNetworkTTP ..... | 5 | +| 8.4 | tmSubnetwork ..... | 5 | +| 8.5 | tmSubnetworkConnection ..... | 5 | +| 8.6 | tmSubnetworkTP ..... | 6 | +| 8.7 | tmTrail ..... | 6 | +| 8.8 | tmTrafficDescriptor ..... | 6 | +| 8.9 | tmTrailServiceCharacteristics ..... | 7 | +| 9 | Information relationship definitions ..... | 7 | +| 9.1 | tmTrailHasImmediateTrafficDescriptor ..... | 7 | +| 9.2 | tmTrailHasTSC ..... | 7 | +| 10 | Static schemas ..... | 8 | +| 11 | Dynamic schemas ..... | 8 | +| 12 | Attributes ..... | 8 | + + + +## Recommendation G.853.6 + +## INFORMATION VIEWPOINT FOR TRAIL MANAGEMENT + +(Geneva, 1999) + +# 1 Scope + +This information viewpoint specification is related to the trail management enterprise specification defined in Recommendation G.852.6. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- [1] ITU-T Recommendation G.851.1 (1996), *Management of the transport network – Application of the RM-ODP framework.* +- [2] ITU-T Recommendation G.853.1 (1999), *Common elements of the information viewpoint for the management of a transport network.* +- [3] ITU-T Recommendation G.853.2 (1996), *Subnetwork connection management information viewpoint.* +- [4] ITU-T Recommendation G.852.6 (1999), *Enterprise viewpoint for trail management.* +- [5] ITU-T Recommendation G.854.6 (1999), *Computational viewpoint for trail management.* + +# 3 Definitions + +None. + +# 4 Abbreviations + +This Recommendation uses the following abbreviations: + +| | | +|--------|-------------------------------------------------| +| Id | Identifier | +| imp | imported | +| inh | inherited | +| RM-ODP | Reference Model for Open Distributed Processing | +| tm | Trail Management | +| TTP | Trail Termination Point | +| UML | Unified Modelling Language | + +# 5 Conventions + +For further study. + +# 6 Class diagrams + +## 6.1 UML class diagram representing relationships between classes + +![UML class diagram for tmLayerNetworkDomain showing relationships between tmSubnetwork, tmSubnetworkConnection, tmAccessGroup, tmTrail, tmSubnetworkTP, tmNetworkTP, tmTrailServiceCharacteristics, and tmTrafficDescriptor. The diagram includes associations with multiplicities and role names like 'layerNetworkDomain IsMadeOf' and 'trailIsTerminated ByPointToPoint'.](35a7554182eb055209552843f341a1ae_img.jpg) + +The diagram illustrates the following classes and their relationships: + +- tmLayerNetworkDomain**: The root class for network domains. + - tmSubnetwork**: Associated with **tmLayerNetworkDomain** via *layerNetworkDomain IsMadeOf*. Multiplicity (1..1) to (1..N). + - tmSubnetworkConnection**: Associated with **tmLayerNetworkDomain** via *layerNetworkDomain IsMadeOf*. Multiplicity (1..1) to (1..N). + - tmAccessGroup**: Associated with **tmLayerNetworkDomain** via *layerNetworkDomain IsMadeOf*. Multiplicity (1..1) to (1..N). + - tmTrail**: Associated with **tmLayerNetworkDomain** via *layerNetworkDomain IsMadeOf*. Multiplicity (1..1) to (1..N). This class is highlighted in a shaded oval. +- tmSubnetwork** and **tmSubnetworkTP**: + - Associated via *subnetworkIsDelimitedBy*. Multiplicity (1..1) to (1..N). +- tmSubnetworkConnection** and **tmSubnetworkTP**: + - Associated via *subnetworkConnectionIsTerminatedByPointToPoint*. Multiplicity (1..1) to (1..1). +- tmSubnetworkTP** and **tmNetworkTP**: + - Associated via *subnetworkTPs RelatedToExtremity*. Multiplicity (1..N) to (1..1). +- tmAccessGroup** and **tmNetworkTP**: + - Associated via *accessGroupIsMadeOfNetworkTPs*. Multiplicity (1..1) to (1..N). +- tmTrail** (shaded oval) and **tmNetworkTP**: + - Associated via *trailIsTerminatedByPointToPoint*. Multiplicity (1..1) to (1..1). +- tmTrail** (shaded oval) and **tmTrailServiceCharacteristics**: + - Associated via *tmTrailHasTSC*. Multiplicity (1..N) to (1..1). +- tmTrail** (shaded oval) and **tmTrafficDescriptor**: + - Associated via *tmTrailHasImmediateTrafficDescriptor*. Multiplicity (1..N) to (1..1). + +UML class diagram for tmLayerNetworkDomain showing relationships between tmSubnetwork, tmSubnetworkConnection, tmAccessGroup, tmTrail, tmSubnetworkTP, tmNetworkTP, tmTrailServiceCharacteristics, and tmTrafficDescriptor. The diagram includes associations with multiplicities and role names like 'layerNetworkDomain IsMadeOf' and 'trailIsTerminated ByPointToPoint'. + +Figure 1/G.853.6 – UML class diagram representing relationships between classes + +## 6.2 UML class diagram representing the inheritance hierarchy + +![UML class diagram showing the inheritance hierarchy for information object classes. The root class is G.853.1:networkInformationTop. It has four direct subclasses: G.853.1:layerNetworkDomain, G.853.1:subnetwork, G.853.1:subnetworkTP, and G.853.1:accessGroup. Below these are further subclasses: plmLayerNetworkDomain, tmSubnetwork, tmSubnetworkTP, and tmAccessGroup. Another branch from the root includes G.853.1:transportConnection, tmTrafficDescriptor, G.853.1:networkTTP, and G.853.2:serviceCharacteristics. Further subclasses include G.853.1:subnetworkConnection, G.853.1:trail, tmNetworkTTP, and tmTrailServiceCharacteristics. The lowest level includes tmSubnetworkConnection and tmTrail. Attributes like resourceId, signalIdentification, pointDirectionality, directionality, topologicalEndDirection, and userLabel (imp) are shown in various classes.](acfc53eca625d62b38aa2563efa95c3e_img.jpg) + +``` + +classDiagram + class G853_1_networkInformationTop["G.853.1:networkInformationTop"] { + resourceId + } + class G853_1_layerNetworkDomain["G.853.1:layerNetworkDomain"] { + signalIdentification + } + class G853_1_subnetwork["G.853.1:subnetwork"] { + signalIdentification + } + class G853_1_subnetworkTP["G.853.1:subnetworkTP"] { + signalIdentification + pointDirectionality + } + class G853_1_accessGroup["G.853.1:accessGroup"] { + signalIdentification + topologicalEndDirection + } + class plmLayerNetworkDomain["plmLayerNetworkDomain"] + class tmSubnetwork["tmSubnetwork"] + class tmSubnetworkTP["tmSubnetworkTP"] + class tmAccessGroup["tmAccessGroup"] + class G853_1_transportConnection["G.853.1:transportConnection"] { + signalIdentification + directionality + } + class tmTrafficDescriptor["tmTrafficDescriptor"] { + signalIdentification + } + class G853_1_networkTTP["G.853.1:networkTTP"] { + signalIdentification + pointDirectionality + } + class G853_2_serviceCharacteristics["G.853.2:serviceCharacteristics"] + class G853_1_subnetworkConnection["G.853.1:subnetworkConnection"] + class G853_1_trail["G.853.1:trail"] + class tmNetworkTTP["tmNetworkTTP"] { + userLabel (imp) + } + class tmTrailServiceCharacteristics["tmTrailServiceCharacteristics"] { + signalIdentification + } + class tmSubnetworkConnection["tmSubnetworkConnection"] + class tmTrail["tmTrail"] { + userLabel (imp) + } + + G853_1_networkInformationTop <|-- G853_1_layerNetworkDomain + G853_1_networkInformationTop <|-- G853_1_subnetwork + G853_1_networkInformationTop <|-- G853_1_subnetworkTP + G853_1_networkInformationTop <|-- G853_1_accessGroup + G853_1_networkInformationTop <|-- G853_1_transportConnection + G853_1_networkInformationTop <|-- tmTrafficDescriptor + G853_1_networkInformationTop <|-- G853_1_networkTTP + G853_1_networkInformationTop <|-- G853_2_serviceCharacteristics + + plmLayerNetworkDomain <|-- G853_1_layerNetworkDomain + tmSubnetwork <|-- G853_1_subnetwork + tmSubnetworkTP <|-- G853_1_subnetworkTP + tmAccessGroup <|-- G853_1_accessGroup + + G853_1_subnetworkConnection <|-- G853_1_transportConnection + G853_1_trail <|-- G853_1_transportConnection + tmNetworkTTP <|-- G853_1_networkTTP + tmTrailServiceCharacteristics <|-- G853_2_serviceCharacteristics + + tmSubnetworkConnection <|-- G853_1_subnetworkConnection + tmTrail <|-- G853_1_trail + +``` + +UML class diagram showing the inheritance hierarchy for information object classes. The root class is G.853.1:networkInformationTop. It has four direct subclasses: G.853.1:layerNetworkDomain, G.853.1:subnetwork, G.853.1:subnetworkTP, and G.853.1:accessGroup. Below these are further subclasses: plmLayerNetworkDomain, tmSubnetwork, tmSubnetworkTP, and tmAccessGroup. Another branch from the root includes G.853.1:transportConnection, tmTrafficDescriptor, G.853.1:networkTTP, and G.853.2:serviceCharacteristics. Further subclasses include G.853.1:subnetworkConnection, G.853.1:trail, tmNetworkTTP, and tmTrailServiceCharacteristics. The lowest level includes tmSubnetworkConnection and tmTrail. Attributes like resourceId, signalIdentification, pointDirectionality, directionality, topologicalEndDirection, and userLabel (imp) are shown in various classes. + +Figure 2/G.853.6 – Information object class inheritance diagram + +# 7 Label references + +| Full label reference | Local label reference | +|-------------------------------------------------------------------------------------------|------------------------------------------------| +| <"Rec. G.853.1", INFORMATION_OBJECT: accessGroup> | accessGroup | +| <"Rec. G.853.1", INFORMATION_OBJECT: layerNetworkDomain> | layerNetworkDomain | +| <"Rec. G.853.1", INFORMATION_OBJECT: networkTTP> | networkTTP | +| <"Rec. G.853.2", INFORMATION_OBJECT: serviceCharacteristics> | serviceCharacteristics | +| <"Rec. G.853.1", INFORMATION_OBJECT: subnetwork> | subnetwork | +| <"Rec. G.853.1", INFORMATION_OBJECT: subnetworkConnection> | subnetworkConnection | +| <"Rec. G.853.1", INFORMATION_OBJECT: subnetworkTP> | subnetworkTP | +| <"Rec. G.853.1", INFORMATION_OBJECT: trail> | trail | +| <"Rec.G.853.1", INFORMATION_RELATIONSHIP: accessGroupIsMadeOfNetworkTTPs> | accessGroupIsMadeOfNetworkTTPs | +| <"Rec. G.853.1", INFORMATION_RELATIONSHIP: layerNetworkDomainIsMadeOf> | layerNetworkDomainIsMadeOf | +| <"Rec.G.853.1", INFORMATION_RELATIONSHIP: subnetworkIsDelimitedBy> | subnetworkIsDelimitedBy | +| <"Rec.G.853.1", INFORMATION_RELATIONSHIP: subnetworkConnectionIsTerminatedByPointToPoint> | subnetworkConnectionIsTerminatedByPointToPoint | +| <"Rec.G.853.1", INFORMATION_RELATIONSHIP: subnetworkTPIsRelatedToExtremity> | subnetworkTPIsRelatedToExtremity | +| <"Rec.G.853.1", INFORMATION_RELATIONSHIP: trailIsTerminatedByPointToPoint> | trailIsTerminatedByPointToPoint | +| <"Rec.G.853.1", INFORMATION_ATTRIBUTE: signalIdentification> | signalIdentification | +| <"Rec.G.853.1", INFORMATION_ATTRIBUTE: userLabel> | userLabel | + +# 8 Information object class definitions + +## 8.1 tmAccessGroup + + + +#### DEFINITION + +"This object class is derived from ." + +#### ATTRIBUTE + +-- none additional + +#### RELATIONSHIP + + + + +## 8.2 tmLayerNetworkDomain + + + +#### DEFINITION + +"This object class is derived from ." + +#### ATTRIBUTE + +-- none additional + +#### RELATIONSHIP + + + +## 8.3 **tmNetworkTTP** + + + +#### DEFINITION + +"This object class is derived from ." + +#### ATTRIBUTE + + + +" + +This attribute is imported from G.853.1 and is used as a user friendly label for the networkTTP." + +#### RELATIONSHIP + + + + + + + + + +## 8.4 **tmSubnetwork** + + + +#### DEFINITION + +"This object class is derived from ." + +#### ATTRIBUTE + +-- none additional + +#### RELATIONSHIP + + + + + +## 8.5 **tmSubnetworkConnection** + + + +#### DEFINITION + +"This object class is derived from ." + +#### ATTRIBUTE + +-- none additional + +#### RELATIONSHIP + + + + + +## 8.6 **tmSubnetworkTP** + + + + + + + +#### DEFINITION + +"This object class is derived from ." + +#### ATTRIBUTE + +-- none additional + +#### RELATIONSHIP + + + + + + +## 8.7 **tmTrail** + + + +#### DEFINITION + +"This object class is derived from ." + +#### ATTRIBUTE + + +" +This attribute is imported from G.853.1 and is used as a user-friendly name for the trail." + +#### RELATIONSHIP + + + + + + +## 8.8 **tmTrafficDescriptor** + + + +#### DEFINITION + +"This object class reflects all the characteristics associated with the requested transport service. This class will be refined based on technology-dependent characteristics." + +#### ATTRIBUTE + + +"This attribute is imported from G.853.1 and it specifies the signal format of the resources whose traffic descriptors are determined by the information object. The specific format values will be defined in technology-specific extensions." + +#### RELATIONSHIP + + + +## 8.9 **tmTrailServiceCharacteristics** + + + + + +#### DEFINITION + +"This object class is derived from . + +This object class will be refined due to the technological-dependent characteristics." + +#### ATTRIBUTE + + + +"This attribute is imported from G.853.1 and it specifies the signal format of the resources whose service characteristics are determined by the tmTrailServiceCharacteristics information object. The specific format values will be defined in technology-specific extensions." + +#### RELATIONSHIP + + + +# 9 **Information relationship definitions** + +## 9.1 **tmTrailHasImmediateTrafficDescriptor** + + + +#### DEFINITION + +"This information relationship represents the relationship which exists between a trail and a traffic descriptor." + +#### ROLE + +trailTD + +"Played by instances of the information object class and subclasses." + +immediateTrafficDescriptorTrail + +"Played by an instance of the object class." + +#### INVARIANT + +inv\_1 + +"Several objects playing the trailTD role may be involved in the relationship." + +inv\_2 + +"Only one object playing the immediateTrafficDescriptorTrail role may be involved in the relationship." + +## 9.2 **tmTrailHasTSC** + + + +#### DEFINITION + +"The tmTrailHasTSC relationship describes the association between a trail and the related quality of transport service characteristics." + +#### ROLE + +transportQualifiedTrail + +"Played by instances of the information object class and subclasses." + +transportQualifierTSC + +"Played by an instance of the object class." + +#### **INVARIANT** + +inv\_1 + +"Several objects playing the transportQualifiedTrail role may be involved in the relationship." + +inv\_2 + +"Only one object playing the transportQualifierTSC role may be involved in the relationship." + +## **10 Static schemas** + +None. + +## **11 Dynamic schemas** + +None. + +## **12 Attributes** + +None additional. + +# ITU-T RECOMMENDATIONS SERIES + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of the ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | 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with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with a lightning bolt and the letters ITU. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +**G.854.1** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +(11/96) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital transmission systems – Digital networks – SDH +network characteristics + +--- + +**Management of the transport network – +Computational interfaces for basic transport +network model** + +ITU-T Recommendation G.854.1 + +(Previously CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| INTERNATIONAL ANALOGUE CARRIER SYSTEM | | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TRANSMISSION SYSTEMS | | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| General | G.700–G.709 | +| Coding of analogue signals by pulse code modulation | G.710–G.719 | +| Coding of analogue signals by methods other than PCM | G.720–G.729 | +| Principal characteristics of primary multiplex equipment | G.730–G.739 | +| Principal characteristics of second order multiplex equipment | G.740–G.749 | +| Principal characteristics of higher order multiplex equipment | G.750–G.759 | +| Principal characteristics of transcoder and digital multiplication equipment | G.760–G.769 | +| Operations, administration and maintenance features of transmission equipment | G.770–G.779 | +| Principal characteristics of multiplexing equipment for the synchronous digital hierarchy | G.780–G.789 | +| Other terminal equipment | G.790–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| General | G.900–G.909 | +| Parameters for optical fibre cable systems | G.910–G.919 | +| Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s | G.920–G.929 | +| Digital line transmission systems on cable at non-hierarchical bit rates | G.930–G.939 | +| Digital line systems provided by FDM transmission bearers | G.940–G.949 | +| Digital line systems | G.950–G.959 | +| Digital section and digital transmission systems for customer access to ISDN | G.960–G.969 | +| Optical fibre submarine cable systems | G.970–G.979 | +| Optical line systems for local and access networks | G.980–G.999 | + +For further details, please refer to ITU-T List of Recommendations. + +## **ITU-T RECOMMENDATION G.854.1** + +# **MANAGEMENT OF THE TRANSPORT NETWORK – COMPUTATIONAL INTERFACES FOR BASIC TRANSPORT NETWORK MODEL** + +## **Summary** + +This Recommendation contains the computational viewpoint specification for managing a transport network from a network viewpoint. In particular, this Recommendation details the computational viewpoint for subnetwork connection management. This Recommendation was written in accordance with G.851.1 Management of the transport network – Application of the RM-ODP framework. + +### **Source** + +ITU-T Recommendation G.854.1 was prepared by ITU-T Study Group 15 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 8th of November 1996. + +## FOREWORD + +ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +### NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, the ITU had/had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 1997 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +## CONTENTS + +| | | Page | +|-------|----------------------------------------------------------------------------------------------------------------------------------|------| +| 1 | Scope..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions ..... | 1 | +| 4 | Abbreviations..... | 1 | +| 5 | Computational interfaces for basic transport network model..... | 2 | +| | Annex A – Computational interfaces for simple subnetwork connection configuration..... | 2 | +| A.0 | Computational interfaces to satisfy simple subnetwork connection configuration community enterprise requirements..... | 2 | +| A.1 | Label references..... | 2 | +| A.2 | simple SNC performer interface..... | 3 | +| A.2.1 | sscc set-up SNC..... | 3 | +| A.2.2 | sscc release SNC..... | 5 | +| A.3 | sscc SN interface..... | 6 | +| A.3.1 | query SN for snTPs..... | 7 | +| A.3.2 | query SN for SNCs..... | 7 | +| A.4 | snTP interface ..... | 8 | +| A.4.1 | query snTP for SNC..... | 8 | +| A.4.2 | query snTP for subnetwork the point delimits..... | 9 | +| A.4.3 | query snTP for nTP..... | 9 | +| A.5 | Service characteristics interface..... | 10 | +| A.6 | nTP interface..... | 11 | +| A.6.1 | query nTP for SnTPs ..... | 11 | +| A.7 | SNC interface..... | 12 | +| A.7.1 | get user label..... | 12 | +| A.7.2 | query SNC terminating points ..... | 13 | +| A.7.3 | get directionality ..... | 14 | +| A.7.4 | query SNC for Transport Service Characteristics..... | 15 | +| | Annex B – Computational interfaces for simple monitored subnetwork connection configuration..... | 16 | +| B.0 | Computational interfaces to satisfy simple monitored subnetwork connection configuration community enterprise requirements ..... | 16 | +| B.1 | Label references..... | 16 | +| B.2 | monitored SNC performer interface – derived from simpleSncPerformerIfce..... | 16 | + +| | Page | +|---------------------------------------------|-------------| +| B.2.1 suspend SNC monitor reporting ..... | 16 | +| B.2.2 resume SNC monitor reporting..... | 17 | +| B.3 SNC monitor interface ..... | 18 | +| B.3.1 Get SNC operational State..... | 18 | +| B.3.2 Get reportFailureStatus..... | 19 | +| B.4 SNC monitor reporting interface ..... | 20 | +| B.4.1 report SNC failure notification ..... | 20 | +| B.4.2 report SNC recovery notification..... | 20 | + +## Recommendation G.854.1 + +# MANAGEMENT OF THE TRANSPORT NETWORK – COMPUTATIONAL INTERFACES FOR BASIC TRANSPORT NETWORK MODEL + +(Geneva, 1996) + +## 1 Scope + +This Recommendation describes the computational viewpoint specification for computational interfaces for basic transport network model. + +## 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations. A list of the currently valid ITU-T Recommendations is regularly published. + +- ITU-T Recommendation G.805 (1995), *Generic functional architecture of transport networks*. +- ITU-T Recommendation G.851.1 (1996), *Management of the transport network – Application of the RM-ODP framework*. +- ITU-T Recommendation G.852.1 (1996), *Management of the transport network – Enterprise viewpoint for simple subnetwork connection management*. +- ITU-T Recommendation G.853.1 (1996), *Common elements of the information viewpoint for the management of a transport network*. +- ITU-T Recommendation G.853.2 (1996), *Subnetwork connection management information viewpoint*. +- ITU-T Recommendation M.3100 (1995), *Generic network information model*. + +## 3 Definitions + +None. + +## 4 Abbreviations + +This Recommendation uses the following abbreviations. + +| | | +|--------|----------------------------------------------------------------------------------| +| Ifce | Interface | +| ITU-T | International Telecommunication Union – Telecommunication Standardization Sector | +| RM-ODP | Reference Model for Open Distributed Processing | + +## 5 Computational interfaces for basic transport network model + +Computational interfaces are specified using engineering neutral computational templates, defined in Recommendation G.851.1. These computational interface templates may be translated to templates associated with more than one engineering realization for use in particular communication domains. + +A complete computational specification requires the definition of computational objects and the scenarios which describe how the computational objects are used. The specification of computational objects is for further study. + +This is not the complete computational viewpoint for transport networks, and these interfaces may be satisfied by a profile or subset of a more comprehensive interface description. + +An implementation which claims support of an interface in this Recommendation, as a server, shall implement all of the operations of that interface. + +The inheritance structure of the computational viewpoint is not necessarily the same as the inheritance structure of the engineering viewpoint. + +## ANNEX A + +### Computational interfaces for simple subnetwork connection configuration + +### A.0 Computational interfaces to satisfy simple subnetwork connection configuration community enterprise requirements + +The simple subnetwork connection community enterprise requirements are met by the interfaces specified in this Annex. + +A reference to a snTP interface type is equivalent to a reference to a nTP interface type. + +#### A.1 Label references + +The following information relationships, static schema, and ASN.1 productions are referenced in this Annex: + +| Fully-qualified label reference | Local reference used | +|--------------------------------------------------------------------------------|---------------------------------------| +| <"Rec. G.853.1", INFORMATION_RELATIONSHIP:subnetworkIsDelimitedBy> | | +| <"Rec. G.853.1", INFORMATION_RELATIONSHIP:subnetworkHasSubnetworkConnections> | | +| <"Rec. G.853.1", INFORMATION_RELATIONSHIP:extremitiesTerminateTransportEntity> | | +| <"Rec. G.853.1", INFORMATION_RELATIONSHIP:subnetworkTPIsRelatedToExtremity> | | +| <"Rec. G.853.2", INFORMATION_RELATIONSHIP:subnetworkConnectionHasTSC> | | +| <"Rec. G.853.2", STATIC_SCHEMA:ssccNotConnected> | | +| <"Rec. G.853.2", STATIC_SCHEMA:ssccConnected> | | +| | | +| Fully-qualified ASN.1 production reference | Local reference used | +| "M.3100 : 199x : ASN1DefinedTypesModule"::Failed | Failed | +| "M.3100 : 199x : ASN1DefinedTypesModule"::Directionality | Directionality | +| "M.3100 : 199x : ASN1DefinedTypesModule"::UserLabel | UserLabel | + +#### A.2 simple SNC performer interface + +The simple subnetwork performer manages the set-up and release of subnetwork connections. + +The simple SNC performer interface is required to satisfy the enterprise requirements stated in: + +<"Rec. G.852.1", COMMUNITY:sscc, ACTION:sscc1 > , +<"Rec. G.852.1", COMMUNITY:sscc, ACTION:sscc2 > . + +The simple subnetwork connection performer interface provides basic connection set-up functionality. The operation ssccSetupSubnetworkConnection sets up a subnetwork connection, and the operation ssccReleaseSubnetworkConnection removes the subnetwork connection. + +``` +COMPUTATIONAL_INTERFACE simpleSncPerformerIfce { + OPERATION ; + OPERATION ; +} +``` + +##### A.2.1 sscc set-up SNC + +This operation sets up a simple subnetwork connection between a single A-End snTP or nTP, and a single Z-End snTP or nTP. + +``` +OPERATION ssccSetupSubnetworkConnection { + + INPUT_PARAMETERS + subnetwork : SubnetworkId ::= (ssccSnIfce); + -- The subnetwork parameter is used to indicate the subnetwork across which the performer is setting + -- up the SNCs. This parameter is used, for example, when a given performer can set up SNCs in + -- many subnetworks. If the performer is associated with a single subnetwork, the subnetwork + -- parameter of this operation is redundant, and may be removed as an engineering optimization. + snpa : SnTPId ::= (snTPIfce); + snpz : SnTPId ::= (snTPIfce); + dir : Directionality; + suppliedUserLabel : UserLabel ; + -- zero length string implies none supplied + serviceCharacteristics: CharacteristicsId ::= (serviceCharacteristicsIfce) ; + -- reference can be used to determine any QOS or routing characteristics ; + + OUTPUT_PARAMETERS + newSNC : SNCId ::= (sncIfce) ; + agreedUserLabel : UserLabel ; + + RAISED_EXCEPTIONS + invalidTransportServiceCharacteristics: NULL; + incorrectSubnetworkTerminationPoints : SEQUENCE OF SnTPId; + -- the list contains one element when only point is incorrect. + subnetworkTerminationPointsConnected : SEQUENCE OF SnTPId; + -- the list contains one element when only one subnetworkTerminationPoint remains + -- connected + failure : Failed; + wrongDirectionality : Directionality; + userLabelInUse : UserLabel; + + BEHAVIOUR + INFORMAL + ! +``` + +This operation sets up a subnetwork connection between a given A-End snTP or nTP and a given Z-End snTP or nTP. The subnetwork termination points or network termination points to be + +connected are specified by explicitly identifying the subnetwork network termination points or network termination points. + +The client may supply a unique user label. If not supplied (i.e. string length zero) the provider assigns a user label for the connection. + +A single point-to-point unidirectional, or point-to-point bidirectional, unpartitioned subnetwork connection object will be created. The subnetwork connection object will have one A-End and one Z-End. + +The subnetwork connection will have a directionality (unidirectional or bidirectional) as specified in the operation parameters. + +If used, the service characteristics specify one predetermined set of transport parameters which the server may offer. + +The operation replies for set-up includes full information about the reasons in case the request could not be satisfied. + +##### PRE\_CONDITIONS + +This operation will fail if any of the subnetwork termination points or network termination points specified is already involved in a subnetwork connection. The exception "subnetworkTerminationPointsConnected" will be generated. + +This operation will fail if the subnetwork termination points or network termination points are not contained within the domain of the subnetwork. The exception "incorrectSubnetworkTerminationPoints" will be generated. + +This operation will fail if the serviceCharacteristics requested is not supported by the computational object which executes the operation. The exception "invalidTransportServiceCharacteristics" will be generated. + +##### POST\_CONDITIONS + +If any subnetwork connection input parameters cannot be met by the server, the operation will fail. + +This operation will fail if the value of the userLabel of the SubnetworkConnection is zero or is not unique within the domain of the containing subnetwork. The exception "userLabelInUse" will be generated. + +! + +##### SEMI\_FORMAL + +##### PARAMETER\_MATCHING + +subnetwork: < sscNotConnected , ROLE:involvedSubnetwork > AND +< sscConnected , ROLE:involvedSubnetwork > ; +snpa : < sscNotConnected , ROLE:potentialAEnd > AND +< sscConnected , ROLE:connectedAEnd > ; +snpz : < sscNotConnected , ROLE: potentialZEnd > AND +< sscConnected , ROLE:connectedZEnd > ; +dir : < sscConnected, ROLE: involvedSubnetwork , ATTRIBUTE: directionality > ; +newSNC : ; +suppliedUserLabel : +OR <> ; -- The user does not have to supply a user label value +agreedUserLabel : ; +serviceCharacteristics : < sscConnected , ROLE:involvedServiceCharacteristics > ; + +##### PRE\_CONDITIONS < sscNotConnected > ; + +-- The sscNotConnected schema defines a schema type with two non-connected + +-- networkTP information objects subtypes candidates to the point-to-point connection + +-- management service. + +**POST\_CONDITIONS** ; +*--The ssccConnected schema defines the schema type of two connected networkTP* +*-- information objects candidates to the point-to-point connection management service.* + +##### **EXCEPTIONS** + +**IF PRE\_CONDITION** **NOT\_VERIFIED RAISE\_EXCEPTION** +    incorrectSubnetworkTerminationPoints ; +**IF PRE\_CONDITION** **NOT\_VERIFIED RAISE\_EXCEPTION** +    subnetworkTerminationPointsConnected ; +**IF PRE\_CONDITION** **NOT\_VERIFIED RAISE\_EXCEPTION** +    subnetworkTerminationPointsConnected ; +**IF POST\_CONDITION** **NOT\_VERIFIED RAISE\_EXCEPTION** failure ; +**IF POST\_CONDITION** **NOT\_VERIFIED RAISE\_EXCEPTION** failure ; +**IF POST\_CONDITION** **NOT\_VERIFIED RAISE\_EXCEPTION** failure ; +**IF POST\_CONDITION** **NOT\_VERIFIED RAISE\_EXCEPTION** userLabelInUse ; +; + +} + +#### **A.2.2 sscc release SNC** + +This operation releases a given subnetwork connection. + +**OPERATION**     ssccReleaseSubnetworkConnection { + +##### **INPUT\_PARAMETERS** + +**subnetwork : SubnetworkId := (ssccSnIfce)** ; +*-- The subnetwork parameter is used to indicate the subnetwork across which the performer is* +*-- releasing the SNCs. This parameter is used, for example, when a given performer can release SNCs* +*-- in many subnetworks. If the performer is associated with a single subnetwork, the subnetwork* +*-- parameter of this operation is redundant, and may be removed as an engineering optimization.* +**connection: ConnectionId := CHOICE { userLabel UserLabel , sncId SNCId }** ; + +##### **OUTPUT\_PARAMETERS** + +**userLabel : UserLabel** ; + +##### **RAISED\_EXCEPTIONS** + +**noSuchConnection : ConnectionId** ; +**subnetworkTerminationPointsConnected : SEQUENCE OF SnTPId** ; +*-- the list contains one element when only one subnetworkTerminationPoint remains* +*-- connected* +**failure : Failed** ; +**invalidUserLabel : UserLabel** ; + +##### **BEHAVIOUR** + +##### **INFORMAL** + +! +This operation releases a given point-to-point subnetwork connection. This subnetwork connection is between two existing snTP or nTPs and is not partitioned. + +##### **PRE\_CONDITIONS** + +This operation will fail if the subnetwork connection is not terminated by valid network termination points. The exception "failure" will be generated. + +This operation will fail if the subnetwork connection id is not within the domain of the object which executes this operation. The exception "noSuchConnection" will be generated. Note that this exception is raised on a computational identifier, sncid, and is thus not defined in the EXCEPTION clause. + +This operation will fail if the value of the userLabel supplied for the subnetwork connection is zero or is not within the domain of the containing subnetwork. The exception "invalidUserLabel" will be generated. + +##### POST\_CONDITIONS + +This operation will fail if the userLabel returned does not match the userLabel supplied or is not within the domain of the object which executes this operation. The exception "failure" with a value "logical problem" will be generated. + +If the requested subnetwork connection is still connected to a subnetwork termination point, the exception "subnetworkTerminationPointConnected" is raised. + +! + +##### SEMI\_FORMAL + +##### PARAMETER\_MATCHING + +subnetwork: < ssccNotConnected , ROLE:involvedSubnetwork > AND +< ssccConnected, ROLE:involvedSubnetwork > ; + +connection : < ssccConnected, ROLE: involvedPointToPointSubnetworkConnection, + +ATTRIBUTE:userLabel > OR < ssccConnected, ROLE: involvedPointToPointSubnetworkConnection> ; + +##### PRE\_CONDITIONS ; + +- The ssccConnected schema defines the schema type of two connected snTP or nTP +- information object candidates to the point-to-point connection management service. + +##### POST\_CONDITIONS ; + +- The ssccNotConnected schema defines a schema type with two non-connected +- nTP information objects subtypes candidates to the point-to-point connection + +##### EXCEPTIONS + +- The exception "noSuchConnection" is raised on a computational identifier and is thus not defined +- in the EXCEPTION clause. + +``` +IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION failure ; +IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION failure ; +IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION failure ; +IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION invalidUserLabel ; +IF POST_CONDITION NOT_VERIFIED RAISE_EXCEPTION failure ; +IF POST_CONDITION NOT_VERIFIED RAISE_EXCEPTION +subnetworkTerminationPointsConnected ; +IF POST_CONDITION NOT_VERIFIED RAISE_EXCEPTION +subnetworkTerminationPointsConnected ; +``` + +; + +} + +#### A.3 sscc SN interface + +The sscc SN interface is required to satisfy the enterprise requirements stated in: + +<"Rec. G.852.1", COMMUNITY:sscc, OBLIGATION:OBLG\_1> + +The subnetwork represents logical collections of subnetwork termination points or network termination points. + +``` +COMPUTATIONAL_INTERFACE ssccSnIfce { + OPERATION ; + ; +} +``` + +##### A.3.1 query SN for snTPs + +This operation retrieves the list of snTP or nTPs that are associated with the given subnetwork. + +**OPERATION** querySnForSnTPs { + +**INPUT\_PARAMETERS** + +        subnetwork : SubnetworkId ::= (ssccSnIfce) + +-- The subnetwork parameter is used to indicate which interface serves queries for that subnetwork. + +-- This parameter is used, for example, when a given interface can serve queries for many + +-- subnetworks. If the interface is associated with a single subnetwork, the subnetwork parameter of + +-- this operation is redundant, and may be removed as an engineering optimization. + +**OUTPUT\_PARAMETERS** + +        delimitingSNTPs : SnTPIds ::= SEQUENCE OF (snTPIfce) + +        -- list may be empty for an unprovisioned subnetwork + +**BEHAVIOUR** + +**INFORMAL** + +! + +This operation retrieves the list of snTP or nTPs that delimit the given subnetwork. + +! + +**SEMI\_FORMAL** + +**PARAMETER\_MATCHING** + +                subnetwork : ; + +                delimitingSNTPs ELEMENTS : < subnetworkIsDelimitedBy,ROLE: element> ; + +; + +} + +##### A.3.2 query SN for SNCs + +This operation retrieves the list of subnetwork connections that are contained within the given subnetwork. + +**OPERATION** querySnForSNCs { + +**INPUT\_PARAMETERS** + +        subnetwork : SubnetworkId ::= (ssccSnIfce); + +-- The subnetwork parameter is used to indicate which interface serves queries for that subnetwork. + +-- This parameter is used, for example, when a given interface can serve queries for many + +-- subnetworks. If the interface is associated with a single subnetwork, the subnetwork parameter of + +-- this operation is redundant, and may be removed as an engineering optimization. + +**OUTPUT\_PARAMETERS** + +        containedSNCs : SNCs ::= SEQUENCE OF (SNCIfce); -- list may be empty + +**BEHAVIOUR** + +**INFORMAL** + +! + +This operation retrieves the list of subnetwork connections that are contained within the given subnetwork. + +! + +**SEMI\_FORMAL** + +**PARAMETER\_MATCHING** + +                subnetwork : < subnetworkHasSubnetworkConnections , ROLE:container > ; + +                containedSNCs ELEMENTS : < subnetworkHasSubnetworkConnections , ROLE:element > ; + +; + +} + +#### A.4 snTP interface + +The snTP query interface is required to satisfy the enterprise requirements stated in: + +<"Rec. G.852.1", COMMUNITY:sscc, OBLIGATION:OBLG\_1 > . + +The snTP delimits a subnetwork and provides an association to a nTP. + +``` +COMPUTATIONAL_INTERFACE snTPIfce { + OPERATION ; + ; + : +} +``` + +##### A.4.1 query snTP for SNC + +This operation retrieves the subnetwork connection, if any, that is associated with the given subnetwork termination point. + +``` +OPERATION querySNTPforSNC { + INPUT_PARAMETERS + snTP : SnTPId := (snTPIfce); + -- The snTP parameter is used to indicate which interface serves queries for that snTP. This + -- parameter is used, for example, when a given interface can serve queries for many snTPs. If the + -- interface is associated with a single snTP, the snTP parameter of this operation is redundant, and + -- may be removed as an engineering optimization. + + OUTPUT_PARAMETERS + associatedSNC : SNCId := (sncIfce); + + RAISED_EXCEPTIONS + unconnectedSNTP : SnTPId; + + BEHAVIOUR + INFORMAL + ! + This operation retrieves the subnetwork connection that is associated with the given subnetwork + termination point. + The subnetwork termination point must terminate at most one subnetwork connection. + An exception is generated if this operation fails. + ! + + SEMI_FORMAL + PARAMETER_MATCHING + + associatedSNC : < extremitiesTerminateTransportEntity, ROLE: transportEntity>; + + snTP : < extremitiesTerminateTransportEntity, ROLE: A_end> + OR < extremitiesTerminateTransportEntity , ROLE: Z_end> ; + + PRE_CONDITIONS + "inv1: "; + POST_CONDITIONS + ; + + EXCEPTIONS + IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION unconnectedSNTP; + ; +} +``` + +##### A.4.2 query snTP for subnetwork the point delimits + +This operation retrieves the subnetwork that is associated with the given subnetwork termination point. + +**OPERATION** querySNTPforSN { + +**INPUT\_PARAMETERS** + +snTP : SnTPId ::= (snTPIfce); + +-- The snTP parameter is used to indicate which interface serves queries for that snTP. This +-- parameter is used, for example, when a given interface can serve queries for many snTPs. If the +-- interface is associated with a single snTP, the snTP parameter of this operation is redundant, and +-- may be removed as an engineering optimization. + +**OUTPUT\_PARAMETERS** + +containingSN : SubnetworkId ::= (ssccSnIfce); + +**RAISED\_EXCEPTIONS** + +invalidSNTP : SnTPId ; + +**BEHAVIOUR** + +**INFORMAL** + +! + +This operation retrieves the subnetwork that is delimited by the given subnetwork termination point. + +The subnetwork termination point is contained in exactly one subnetwork. + +An exception is generated if this operation fails. + +! + +**SEMI\_FORMAL** + +**PARAMETER\_MATCHING** + +containingSN : < subnetworkIsDelimitedBy , ROLE:container> ; + +snTP : < subnetworkIsDelimitedBy , ROLE:element> ; + +**PRE\_CONDITIONS** + +"inv1: " ; + +**POST\_CONDITIONS** + + ; + +**EXCEPTIONS** + +IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION invalidSNTP ; + +; + +} + +##### A.4.3 query snTP for nTP + +This operation retrieves the network termination point that the subnetwork termination point is representing. + +If the snTP is at the lowest level of partitioning, and is also an nTP, then engineering optimizations may eliminate this operation. + +**OPERATION** querySNTPforNTP { + +**INPUT\_PARAMETERS** + +snTP : SnTPId ::= (snTPIfce) ; + +-- The snTP parameter is used to indicate which interface serves queries for that snTP. This +-- parameter is used, for example, when a given interface can serve queries for many snTPs. If the +-- interface is associated with a single snTP, the snTP parameter of this operation is redundant, and +-- may be removed as an engineering optimization. + +##### **OUTPUT\_PARAMETERS** + +**nTP : NtpId ::= (nTPIfce) ;** + +##### **RAISED\_EXCEPTIONS** + +**invalidSnTP : snTPId ;** + +##### **BEHAVIOUR** + +##### **INFORMAL** + +! + +This operation retrieves the networkTTP, networkCTP, or link connection that is associated with a subnetwork termination point. + +A bidirectional subnetwork termination point is associated with a bidirectional networkTTP, networkCTP, or link connection. + +A subnetwork termination point source is associated with a networkTTP source, networkCTP sink, or unidirectional link connection. + +A subnetwork termination point sink is associated with a networkTTP sink, networkCTP source, or unidirectional link connection. + +An exception is generated if this operation fails. + +! + +##### **SEMI\_FORMAL** + +##### **PARAMETER\_MATCHING** + +**snTP : < subnetworkTPIsRelatedToExtremity , ROLE: abstraction > ;** + +**nTP : < subnetworkTPIsRelatedToExtremity , ROLE: extremity > ;** + +##### **PRE\_CONDITIONS** + +**inv1: ;** + +##### **POST\_CONDITIONS** + +** ;** + +##### **EXCEPTIONS** + +**IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION invalidSnTP ;** + +; + +} + +#### **A.5 Service characteristics interface** + +The service characteristics query interface is required to satisfy the enterprise requirements stated in: + +**<"Rec. G.852.1", COMMUNITY:sscc, ACTION:sscc1, PERMISSION:PERM\_3> .** + +This interface is a superclass for technology specific interface subclasses, which can be used to allow the client to pass, by reference, an interface identifier which can be queried to determine the client service characteristic requirements for a requested subnetwork connection, e.g. transport QOS and route restriction characteristics. + +This interface may be specialized through inheritance to add operations to conveying service characteristics appropriate for a specific technology. Subclasses of this interface type may also have technology specific modify operations, allowing the client to modify the requested service characteristics. + +NOTE – Transport technology specific subclasses of this interface are for further study. + +``` + +COMPUTATIONAL_INTERFACE serviceCharacteristicsIfce { + OPERATION --none defined +} + +``` + +#### A.6 nTP interface + +The common nTP interface is required to satisfy the enterprise requirements stated in: + +<"Rec. G.852.1", COMMUNITY:sscc, OBLIGATION:OBLG\_1 > . + +The common nTP interface represents the termination of a transport entity. + +This interface type is intended to be subclassed to add operations for particular TP specializations (e.g. nTTP, nCTP). + +``` + +COMPUTATIONAL_INTERFACE nTPIfce { + OPERATION ; +} + +``` + +##### A.6.1 query nTP for SnTPs + +This operation retrieves the list of subnetwork termination points that are associated with a networkTTP, networkCTP, or link connection at different levels of partitioning. + +``` + +OPERATION queryNTPForSnTPs { + INPUT_PARAMETERS + ntp : NTPId := (nTPIfce) ; + -- The nTP parameter is used to indicate which interface serves queries for that nTP. This parameter + -- is used, for example, when a given interface can serve queries for many nTPs. If the interface is + -- associated with a single nTP, the nTP parameter of this operation is redundant, and may be + -- removed as an engineering optimization. +} + + OUTPUT_PARAMETERS + snTPs : SnTPids := SEQUENCE OF (snTPIfce) ; + + RAISED_EXCEPTIONS + uncomposedNTP : NTPId ; + +``` + +##### BEHAVIOUR INFORMAL + +! + +A bidirectional subnetwork termination point is associated with a bidirectional networkTTP, networkCTP, or link connection. + +A subnetwork termination point source is associated with a networkTTP source, networkCTP sink, or unidirectional link connection. + +A subnetwork termination point sink is associated with a networkTTP sink, networkCTP source, or unidirectional link connection. + +An exception is generated if this operation fails. + +! + +##### SEMI\_FORMAL PARAMETER\_MATCHING + +``` + +nTP : < subnetworkTPsRelatedToExtremity , ROLE: extremity > ; +snTPs ELEMENTS : < subnetworkTPsRelatedToExtremity , ROLE: abstraction > + AND NOT ; + +``` + +``` + + PRE_CONDITIONS + "inv1: " ; + + POST_CONDITIONS + ; + + EXCEPTIONS + IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION uncomposedNTP ; + ; +} + +``` + +#### A.7 SNC interface + +The SNC interface is required to satisfy the enterprise requirements stated in: + +<"Rec. G.852.1", COMMUNITY:sscc, OBLIGATION:OBLG\_1 > . + +The Subnetwork Connection associates the Network CTP(s), Network TP(s), or subnetworkTPs identified in the A-End and the Network CTP(s), Network TP(s), or subNetwork TP(s) identified in the Z-End. For all types of subnetwork connection, the network termination points at the A-End are related to the network termination points at the Z-End in such a way that traffic can flow between the network termination points in a unidirectional or bidirectional manner as indicated by the directionality attribute. + +``` + +COMPUTATIONAL_INTERFACE sncIfce { + OPERATION ; + ; + ; + ; +} + +``` + +#### A.7.1 get user label + +This operation retrieves the user label attribute value associated with the subnetwork connection. This operation may be implemented by direct manipulation of an attribute if the engineering viewpoint language supports attributes. + +``` + +OPERATION get_userLabel { + INPUT_PARAMETERS -- none + OUTPUT_PARAMETERS + userLabel_val : UserLabel ; + + RAISED_EXCEPTIONS + cannotDetermineValue : NULL; + +``` + +``` + + BEHAVIOUR + INFORMAL + +``` + +! + +This operation retrieves the value of a user label for the subnetwork connection. + +An exception is generated if this operation fails. + +! + +``` + + SEMI_FORMAL + PARAMETER_MATCHING + + userLabel_val : ; + +``` + +##### **PRE\_CONDITIONS** + +"inv\_1 - value of userLabel attribute of SNC is obtainable and valid "; + +##### **POST\_CONDITIONS** *--none* + +##### **EXCEPTIONS** + +**IF PRE\_CONDITION** **NOT\_VERIFIED RAISE\_EXCEPTION** +cannotDetermineValue ; + +; + +} + +#### **A.7.2 query SNC terminating points** + +This operation returns the subnetwork termination points or network termination points that terminate the given subnetwork connection. + +##### **OPERATION** querySncTerminatingPoints { + +##### **INPUT\_PARAMETERS** + +subnetworkConnection : SNCId := (sncIfce) ; + +*-- The subnetworkConnection parameter is used to indicate which interface serves queries for that* + +*-- subnetworkConnection. This parameter is used, for example, when a given interface can serve* + +*-- queries for many subnetworkConnection. If the interface is associated with a single* + +*-- subnetworkConnection, the subnetworkConnection parameter of this operation is redundant, and* + +*-- may be removed as an engineering optimization .* + +##### **OUTPUT\_PARAMETERS** + +aEndTP : SnTP := (snTPIfce) ; +zEndTP : SnTP := (snTPIfce) ; + +##### **RAISED\_EXCEPTIONS** + +unterminatedSNC : SNCId ; + +##### **BEHAVIOUR** + +###### **INFORMAL** + +! + +This operation returns the subnetwork termination points or network termination points that terminate the A-End and the Z-End of a given subnetwork connection. + +An A-End may be a subnetworkTP source, or subnetworkTP bidirectional. + +A Z-End may be a subnetworkTP sink, or subnetworkTP bidirectional. + +A point-to-point unidirectional subnetwork connection can be established between one of snTP (or nTP) source and snTP (or nTP) sink. + +If the SNC is bidirectional, A-End snTP or nTP and Z-End snTP or nTP are bidirectional. + +For all types of subnetwork connection, the subnetwork network termination point which terminates the A-End is related to the subnetwork termination point which terminates the Z-End attribute in such a way that traffic can flow between these subnetwork terminations in a unidirectional or bidirectional manner as indicated by the directionality attribute. + +An exception is raised if the subnetwork connection has no A-End subnetwork termination point or no Z-End subnetwork termination point. + +An exception is generated if this operation fails. + +! + +##### **SEMI\_FORMAL** + +##### **PARAMETER\_MATCHING** + +subnetworkConnection: < extremitiesTerminateTransportEntity , ROLE: transportEntity> ; +aEndTPs ELEMENTS: < extremitiesTerminateTransportEntity , ROLE:A\_end > ; +zEndTPs ELEMENTS : < extremitiesTerminateTransportEntity , ROLE:Z\_end > ; + +##### **PRE\_CONDITIONS** + +"inv1: " ; + +###### **POST\_CONDITIONS** + + ; + +##### **EXCEPTIONS** + +IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION unterminatedSNC ; + +###### **INFORMAL** + +"." ; + +} + +#### A.7.3 get directionality + +This operation retrieves the directionality attribute value associated with the subnetwork connection. This operation may be implemented by direct manipulation of an attribute if the engineering viewpoint language supports attributes. + +**OPERATION** get\_directionality { + +**INPUT\_PARAMETERS** -- none + +##### **OUTPUT\_PARAMETERS** + +directionality\_val : Directionality ; + +##### **RAISED\_EXCEPTIONS** + +cannotDetermineValue : NULL ; + +##### **BEHAVIOUR** + +##### **INFORMAL** + +! + +This operation retrieves the directionality attribute value associated with a transport connection. The value of the directionality is fixed during the lifetime of the transport connection. + +An exception is generated if this operation fails. + +! + +##### **SEMI\_FORMAL** + +##### **PARAMETER\_MATCHING** + +directionality\_val : ; + +##### **PRE\_CONDITIONS** + +"inv\_1 - value of directionality attribute of SNC is obtainable and valid " ; + +###### **POST\_CONDITIONS** --none + +###### **EXCEPTIONS** + +IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION +cannotDetermineValue ; + +; + +} + +#### A.7.4 query SNC for Transport Service Characteristics + +##### OPERATION querySncForTSC { + +##### INPUT\_PARAMETERS + +**subnetworkConnection : SNCId := (sncIfce) ;** + +*-- The subnetworkConnection parameter is used to indicate which interface serves queries for that* + +*-- subnetworkConnection. This parameter is used, for example, when a given interface can serve* + +*-- queries for many subnetworkConnections. If the interface is associated with a single* + +*-- subnetworkConnection, the subnetworkConnection parameter of this operation is redundant, and* + +*-- may be removed as an engineering optimization.* + +##### OUTPUT\_PARAMETERS + +**tsc : TSCId := (serviceCharacteristicsIfce) ;** + +##### RAISED\_EXCEPTIONS + +**uncharacterizedSNC : SNCId ;** + +**invalidTSC : NULL ;** + +##### BEHAVIOUR + +###### INFORMAL + +! + +This operation returns the transport service characteristics that qualify the given subnetwork connection. + +Several subnetwork connections may share the same transport service characteristics but a given subnetwork connection may only have one set of transport service characteristics. + +An "uncharacterizedSNC" exception will be generated if this operation is directed towards a subnetwork connection which has no transport service characteristics. + +An "invalidTSC" exception is generated if this operation fails. + +! + +###### SEMI\_FORMAL + +##### PARAMETER\_MATCHING + +**subnetworkConnection : < subnetworkConnectionHasTSC , ROLE: transportQualified > ;** + +**tsc: < subnetworkConnectionHasTSC , ROLE: transportQualifier > ;** + +###### PRE\_CONDITIONS + +**" inv1: ,** + +**inv2: " ;** + +###### POST\_CONDITIONS + +** ;** + +** ;** + +###### EXCEPTIONS + +**IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION uncharacterizedSNC ;** + +**IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION invalidTSC ;** + +; + +} + +## ANNEX B + +### Computational interfaces for simple monitored subnetwork connection configuration + +### B.0 Computational interfaces to satisfy simple monitored subnetwork connection configuration community enterprise requirements + +The simple monitored subnetwork connection community enterprise requirements are met by the interfaces specified in Annex A, along with the additional interfaces specified in this Annex. + +#### B.1 Label references + +This Annex uses the same label references as those used in Annex A together with the following: + +| Fully-qualified ASN.1 production reference | Local reference used | +|------------------------------------------------------------|----------------------| +| "M.3100 : 199x : ASN1DefinedTypesModule"::OperationalState | OperationalState | + +#### B.2 monitored SNC performer interface – derived from simpleSncPerformerIfce + +The monitored SNC performer interface is required to satisfy the enterprise requirements stated in: + +<"Rec. G.852.1", COMMUNITY:smscc, OBLIGATION:OBLG\_6> , +<"Rec. G.852.1", COMMUNITY:smscc, ACTION:sfm3> , +<"Rec. G.852.1", COMMUNITY:smscc, ACTION:sfm4> . + +This interface suspends and resumes failure monitoring for a given subnetwork connection. + +``` +COMPUTATIONAL_INTERFACE monitoredSncPerformerIfce { + DERIVED FROM ; + OPERATION ; + ; +} +``` + +#### B.2.1 suspend SNC monitor reporting + +``` +OPERATION suspendSNCMonitorReporting { + INPUT_PARAMETERS + subnetwork : SubnetworkId ::= (ssecSnIfce); + -- The subnetwork parameter is used to indicate which subnetwork the performer is monitoring. This + -- parameter is used, for example, when a given performer can monitor SNCs in many subnetworks. If + -- the performer is associated with a single subnetwork, the subnetwork parameter of this operation is + -- redundant, and may be removed as an engineering optimization. + + userLabel : UserLabel ; + + OUTPUT_PARAMETERS + --none + + RAISED_EXCEPTIONS + suspendFailure : NULL ; + notConnected : NULL ; + + BEHAVIOUR + INFORMAL +``` + +This operation suspends failure reporting for a given subnetwork connection. + +##### PRE\_CONDITIONS + +An exception will not be generated if the reportFailureStatus attribute has the value "off". + +The user label which is supplied as part of this notification must identify a subnetwork connection which has a unique Id in the domain of the containing subnetwork. + +If the SNC does not exist, the exception "notConnected" is generated. If any other pre-condition is not satisfied, the exception "suspendFailure" is generated. + +##### POST\_CONDITIONS + +The reportFailureStatus attribute has the value "Off", otherwise the exception "suspendFailure" is generated. + +##### SEMI\_FORMAL + +##### PARAMETER\_MATCHING + +subnetwork : ; +userLabel : ; + +PRE\_CONDITIONS ; +POST\_CONDITIONS +"inv\_1: < ATTRIBUTE:reportFailureStatus, STATE: reportFailureOff>" ; + +##### EXCEPTIONS + +IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION notConnected ; +IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION suspendFailure ; +IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION suspendFailure ; +IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION suspendFailure ; +IF POST\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION +suspendFailure ;; +} + +#### B.2.2 resume SNC monitor reporting + +##### OPERATION resumeSNCMonitorReporting { + +##### INPUT\_PARAMETERS + +subnetwork : SubnetworkId ::= (ssccSnIfce); + +-- The subnetwork parameter is used to indicate which subnetwork the performer is monitoring. This +-- parameter is used, for example, when a given performer can monitor SNCs in many subnetworks. If +-- the performer is associated with a single subnetwork, the subnetwork parameter of this operation is +-- redundant, and may be removed as an engineering optimization. + +userLabel : UserLabel ; + +##### OUTPUT\_PARAMETERS + +--none + +##### RAISED\_EXCEPTIONS + +resumeFailure : NULL ; +notConnected : NULL ; + +##### BEHAVIOUR + +###### INFORMAL + +This operation resumes failure reporting for a given subnetwork connection. + +##### PRE\_CONDITIONS + +An exception will not be generated if the reportFailureStatus attribute has the value "on". + +The user label which is supplied as part of this notification must identify a subnetwork connection which has a unique Id in the domain of the containing subnetwork. + +If the SNC does not exist, the exception "notConnected" is generated. If any other pre-condition is not satisfied, the exception "suspendFailure" is generated. + +###### POST\_CONDITIONS + +The reportFailureStatus attribute has the value "On", otherwise the exception "suspendFailure" is generated". + +``` + +SEMI_FORMAL + PARAMETER_MATCHING + subnetwork : ; + userLabel : ; + + PRE_CONDITIONS ; + POST_CONDITIONS + "inv_1: < ATTRIBUTE:reportFailureStatus, STATE: reportFailureOn>" ; + + EXCEPTIONS + IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION notConnected ; + IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION resumeFailure ; + IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION resumeFailure ; + IF PRE_CONDITION NOT_VERIFIED RAISE_EXCEPTION resumeFailure ; + IF POST_CONDITION NOT_VERIFIED RAISE_EXCEPTION resumeFailure ;; +} +``` + +#### B.3 SNC monitor interface + +The SNC monitor control interface is required to satisfy the enterprise requirements stated in + +<"Rec. G.852.1", COMMUNITY:smsec, OBLIGATION:OBLG\_6> , + +``` + +COMPUTATIONAL_INTERFACE sncMonitorIfce { + DERIVED FROM ; + OPERATION ; + ; +} +``` + +##### B.3.1 Get SNC operational State + +This operation may be implemented by direct manipulation of an attribute if the engineering viewpoint language supports attributes. + +``` + +OPERATION get_snc_operationalState { + INPUT_PARAMETERS -- none + OUTPUT_PARAMETERS + operationalState_val : OperationalState ; + RAISED_EXCEPTIONS + cannotDetermineValue : NULL ; +``` + +##### BEHAVIOUR + +##### INFORMAL + +"This operation retrieves the value of the OperationalState attribute value of a given subnetwork connection. + +An exception is generated if this operation fails." + +##### **SEMI\_FORMAL** + +##### **PARAMETER\_MATCHING** + +**operationalState\_val : ;** + +##### **PRE\_CONDITIONS** + +**"inv\_1: value of operationalState of SNC is obtainable and valid";** + +##### **POST\_CONDITIONS -- none** + +##### **EXCEPTIONS** + +**IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION +cannotDetermineValue ;** + +**; +}** + +#### **B.3.2 Get reportFailureStatus** + +This operation may be implemented by direct manipulation of an attribute if the engineering viewpoint language supports attributes. + +##### **OPERATION get\_reportFailureStatus {** + +###### **INPUT\_PARAMETERS -- none** + +##### **OUTPUT\_PARAMETERS** + +**reportFailureStatus\_val : ReportFailureStatusType ::= +ENUMERATED { +reportFailureOn (0), +reportFailureOff (1) } ;** + +##### **RAISED\_EXCEPTIONS** + +**cannotDetermineValue : NULL ;** + +##### **BEHAVIOUR** + +###### **INFORMAL** + +**"This operation retrieves the value of the report failure status attribute.** + +**If this value is one, there is no failure reporting for the entity, if this value is zero then failure reporting for the entity is enabled.** + +**An exception is generated if this operation fails."** + +###### **SEMI\_FORMAL** + +##### **PARAMETER\_MATCHING** + +**reportFailureStatus\_val : ;** + +###### **PRE\_CONDITIONS** + +**"inv 1: value of reportFailureStatus of SNC is obtainable and valid " ;** + +###### **POST\_CONDITIONS -- none** + +###### **EXCEPTIONS** + +**IF PRE\_CONDITION NOT\_VERIFIED RAISE\_EXCEPTION +cannotDetermineValue ;** + +**; +}** + +#### B.4 SNC monitor reporting interface + +SNC client notification interface. This interface generates notifications when the operational state of the SNC changes. + +The SNC monitor reporting interface is required to satisfy the enterprise requirements stated in + +<"Rec. G.852.1", COMMUNITY:smsec, ACTIONS:sfm1 > , +<"Rec. G.852.1", COMMUNITY:smsec, ACTIONS:sfm2 > . + +COMPUTATIONAL\_INTERFACE sncMonitorReportingIfce { +    OPERATION        ; +                       ; +} + +##### B.4.1 report SNC failure notification + +OPERATION       reportSNCFailureNotification { +    INPUT\_PARAMETERS +        existingSNCLabel : UserLabel ; +    OUTPUT\_PARAMETERS -- none +    RAISED\_EXCEPTIONS -- none +    BEHAVIOUR +        INFORMAL "If the operational state of the SNC changes from enabled to disabled, a notification is generated. The user label which is supplied as part of this notification must identify a subnetwork connection which has a unique Id in the domain of the containing subnetwork." +        SEMI\_FORMAL +            PARAMETER\_MATCHING +            existingSNCLabel: ; + +        TRIGGERING\_CONDITIONS <"Rec. G.853.2", DYNAMIC\_SCHEMA: +    reportFailureOnEnabledToDisabled > ; + +        EXCEPTIONS -- none; +} + +#### B.4.2 report SNC recovery notification + +OPERATION       reportSNCRecoveryNotification { +    INPUT\_PARAMETERS +        existingSNCLabel : UserLabel ; +    OUTPUT\_PARAMETERS -- none +    RAISED\_EXCEPTIONS -- none +    BEHAVIOUR + +        INFORMAL "If the operational state of the SNC changes from disabled to enabled, a notification is generated. The user label which is supplied as part of this notification must identify a subnetwork connection which has a unique Id in the domain of the containing subnetwork." +        SEMI\_FORMAL +            PARAMETER\_MATCHING +            existingSNCLabel : ; +            TRIGGERING\_CONDITIONS <"Rec. G.853.2", DYNAMIC\_SCHEMA: +    reportFailureOnDisabledToEnabled > ; +            EXCEPTIONS -- none; +} + +# ITU-T RECOMMENDATIONS SERIES + +| | | +|-----------------|----------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of the ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | Maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communication | +| Series Z | Programming languages | \ No newline at end of file diff --git a/marked/G/T-REC-G.854.16-200101-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.854.16-200101-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..104a57fbd03964ffd2520508b2be42e03343d20f --- /dev/null +++ b/marked/G/T-REC-G.854.16-200101-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:f2468dfa77e8d32611a5fe8a2ebb904676994eeb54463226fd865698560c960c +size 8232 diff --git a/marked/G/T-REC-G.854.16-200101-I_PDF-E/raw.md b/marked/G/T-REC-G.854.16-200101-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..2cb1ebce8b0d75e37b35f27a8c0f0cd9a13db928 --- /dev/null +++ b/marked/G/T-REC-G.854.16-200101-I_PDF-E/raw.md @@ -0,0 +1,614 @@ + + +![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with intersecting lines. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.854.16** + +(01/2001) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital networks – Management of transport network + +--- + +**Computational viewpoint for pre-provisioned +route discovery** + +ITU-T Recommendation G.854.16 + +(Formerly CCITT Recommendation) + +--- + +## ITU-T G-SERIES RECOMMENDATIONS + +## TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | G.500–G.599 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | + +For further details, please refer to the list of ITU-T Recommendations. + +**Computational viewpoint for pre-provisioned route discovery** + +**Summary** + +This computational viewpoint specification is related to the pre-provisioned route discovery enterprise and information specification. The objective of the community is to identify appropriate routes for setting up, or reserving the route components for (by using other communities), a trail, a tandem connection or a subnetwork connection. It is possible to request conditions that have to be met by the identified route. In addition to proposing routes, information is provided to help in the selection among the candidate route on the basis of a set of properties. In case of protection, the number of routes corresponds to the protection scheme chosen. + +**Source** + +ITU-T Recommendation G.854.16 was prepared by ITU-T Study Group 4 (2001-2004) and approved under the WTSA Resolution 1 procedure on 19 January 2001. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2001 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. + +## CONTENTS + +### Page + +| | | | +|-------|-------------------------------------------|---| +| 1 | Scope..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions ..... | 1 | +| 4 | Abbreviations..... | 1 | +| 5 | Conventions ..... | 2 | +| 6 | Label references..... | 2 | +| 7 | Interfaces..... | 3 | +| 7.1 | Query interfaces..... | 3 | +| 7.2 | Operational interfaces ..... | 5 | +| 7.2.1 | Route discovery interface ..... | 5 | +| 7.3 | Reporting interfaces..... | 7 | +| 7.3.1 | Route discovery reporting interface ..... | 7 | +| 7.4 | ASN.1 supporting productions ..... | 8 | + +## **Computational viewpoint for pre-provisioned route discovery** + +### **1 Scope** + +This computational viewpoint specification is related to the pre-provisioned route discovery enterprise specification defined in ITU-T G.852.16 and the pre-provisioned route discovery information specification defined in ITU-T G.853.16. + +### **2 References** + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- [1] ITU-T G.851.1 (1996), *Management of the transport network – Application of the RM-ODP framework.* +- [2] ITU-T G.853.1 (1999), *Common elements of the information viewpoint for the management of a transport network.* +- [3] ITU-T G.852.16 (2001), *Enterprise viewpoint for pre-provisioned route discovery.* +- [4] ITU-T G.853.16 (2001), *Information viewpoint for pre-provisioned route discovery.* +- [5] ITU-T G.853.10 (1999), *Information viewpoint for pre-provisioned link connection management.* +- [6] ITU-T G.854.3 (1999), *Computational viewpoint for topology management.* + +### **3 Definitions** + +No new term is defined in this Recommendation. + +### **4 Abbreviations** + +This Recommendation uses the following abbreviations: + +| | | +|---------|----------------------------------------------------------------------------------| +| ASN.1 | Abstract Syntax Notation One | +| CTP | Connection Termination Point | +| Id | Identifier | +| Ifce | Interface | +| inv | invariant | +| ITU-T | International Telecommunication Union – Telecommunication Standardization Sector | +| layerND | layerNetwork Domain | +| LC | LinkConnection | +| plem | pre-provisioned link connection management | + +| | | +|--------|-------------------------------------------------| +| prd | pre-provisioned route discovery | +| Rec. | Recommendation | +| RM-ODP | Reference Model for Open Distributed Processing | +| TTP | Trail Termination Point | + +## 5 Conventions + +In order to increase the readability of the behaviour in the operations: + +- parameters are written in **bold**; +- elements defined in the information viewpoint specification are written in *italic*. + +## 6 Label references + +| Full label reference | Local label reference | +|--------------------------------------------------------------------------------|--------------------------------------| +| <"Rec. G.853.16", INFORMATION_OBJECT: prdAccessGroup> | prdAccessGroup | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdLayerNetworkDomain> | prdLayerNetworkDomain | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdLink> | prdLink | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdLinkConnection> | prdLinkConnection | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdLinkEnd> | prdLinkEnd | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdNetworkTTP> | prdNetworkTTP | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdNetworkCTP> | prdNetworkCTP | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdRoutingConditions> | prdRoutingConditions | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdRoute> | prdRoute | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdRouteSet> | prdRouteSet | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdSubnetwork> | prdSubnetwork | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdTopologicalLink> | prdTopologicalLink | +| <"Rec. G.853.16", INFORMATION_OBJECT: prdTopologicalLinkEnd> | prdTopologicalLinkEnd | +| <"Rec. G.853.1", INFORMATION_RELATIONSHIP: layerNetworkDomainIsMadeOf> | layerNetworkDomainIs MadeOf | +| <"Rec. G.853.16", INFORMATION_RELATIONSHIP: prdRouteFulfillsRoutingConditions> | prdRouteFulfillsRouting Conditions | +| <"Rec. G.853.16", INFORMATION_RELATIONSHIP: prdRouteSetHasRoutes> | prdRouteSetHasRoutes | +| <"Rec. G.853.1", INFORMATION_ATTRIBUTE: directionality> | directionality | +| <"Rec. G.853.1", INFORMATION_ATTRIBUTE: linkDirectionality> | linkDirectionality | +| <"Rec.G.853.10", INFORMATION_ATTRIBUTE: plcMCallerId> | plcmCallerId | +| <"Rec. G.853.1", INFORMATION_ATTRIBUTE: pointDirectionality> | pointDirectionality | +| <"Rec.G.853.16", INFORMATION_ATTRIBUTE: prdArc-Point-orientedRouteComponents> | prdArc-Point-orientedRouteComponents | + +| Full label reference | Local label reference | +|---------------------------------------------------------------------------|----------------------------------| +| <"Rec.G.853.16", INFORMATION_ATTRIBUTE: prdReturnedProperties> | prdReturnedProperties | +| <"Rec.G.853.16", INFORMATION_ATTRIBUTE: prdRouteEnds> | prdRouteEnds | +| <"Rec.G.853.16", INFORMATION_ATTRIBUTE: prdIndividualRouteComponentsList> | prdIndividualRouteComponentsList | +| <"Rec. G.853.1", INFORMATION_ATTRIBUTE: resourceId> | resourceId | +| <"Rec.G.853.1", INFORMATION_ATTRIBUTE: signalIdentification> | signalIdentification | +| <"Rec.G.853.1", INFORMATION_ATTRIBUTE: topologicalEndDirection> | topologicalEndDirection | +| <"Rec. G.853.1", INFORMATION_ATTRIBUTE: userLabel> | userLabel | +| <"Rec. G.854.3", INTERFACE: commonReportResourceIdChangeIfce> | commonReportResourceIdChangeIfce | +| <"Rec. G.854.3", INTERFACE: commonResourceIfce> | commonResourceIfce | + +| Full ASN.1 production reference | Local label reference | +|-------------------------------------------------------------|------------------------------| +| <"Rec. X.721:1992: Attribute-ASN.1 Module": SimpleNameType> | SimpleNameType | +| <"Rec. X.680:1997: GraphicString"> | GraphicString | + +## 7 Interfaces + +This Recommendation does not define operations which change the userLabel of the resources or report this change to the notification receiver (these operations are defined in the superclass interfaces defined in ITU-T G.854.3 and used in this Recommendation) because they do not change the state of the system. Their exact signature will be developed as part of the engineering viewpoint specification with the concerned technology. + +### 7.1 Query interfaces + +This Recommendation refers to interfaces that allow access to identification and properties of resources involved in the "pre-provisioned route discovery" community. As the invocation of contained operations does not modify any state, there is no interest in developing them explicitly. Their exact signature will be developed as part of the engineering viewpoint, with the concerned technology. These interfaces are listed in the following table with the information they allow access to. + +| Interface name | Information object | Attributes and relationships | +|--------------------------------|-------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| prdAccessGroupQueryIfce | |


| +| prdLayerNetworkDomainQueryIfce | |

| +| prdLinkConnectionQueryIfce | |




| +| prdLinkEndQueryIfce | |


| +| prdLinkQueryIfce | |


| +| prdNetworkCTPQueryIfce | |




| +| prdNetworkTTPQueryIfce | |


| +| prdRouteSetQueryIfce | |




| + +| Interface name | Information object | Attributes and relationships | +|--------------------------------|-------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| prdRouteQueryIfce | |



| +| prdRoutingConditionsQueryIfce | |

| +| prdSubnetworkQueryIfce | |

| +| prdTopologicalLinkEndQueryIfce | |


| +| prdTopologicalLinkQueryIfce | |


| + +## 7.2 Operational interfaces + +### 7.2.1 Route discovery interface + +The route discovery interface provides functionality for retrieving potential routes that can be used when setting up trails, tandem connections or subnetwork connections as defined in <"Rec. G.852.16", COMMUNITY: pre-provisioned route discovery>. + +``` + +COMPUTATIONAL INTERFACE routeDiscoveryIfce{ + DERIVED FROM + OPERATION { + ; + } +} + +``` + +## Discover routes + + + +OPERATION discoverRoutes { + +INPUT\_PARAMETERS + +routeEnds: RouteEnds ::= SEQUENCE OF { + +aEndAEndChoice, +zEndZEndChoice}; + +*-- one aEnd/zEnd pair is sufficient to represent the ends of all the routes* + +suppliedRoutingConditions: SuppliedRoutingConditions + +*-- the ASN.1 type for suppliedRoutingConditions will be developed in technology* + +*-- specific extensions of the route discovery community* + +arcOrPointOrientedRouteComponents: ArcPointOriented; + +layerND: LayerNetworkDomainChoice; + +routeDir: RouteDirChoice ::= CHOICE { + +dir                        Directionality, +linkDir                  LinkDirectionality, +pointDir                PointDirectionality, +topologicalEndDir    TopologicalEndDirectionality}; + +suppliedUserIdentifier: UserIdentifier; + +OUTPUT\_PARAMETERS + +routeSet: ReturnedRouteSet ::= SET OF ReturnedRoute; + +routeEnds: RouteEnds + +*-- the ASN.1 type for ReturnedRoute will be developed in technology* + +*-- specific extensions of the pre-provisioned route discovery community* + +RAISED\_EXCEPTIONS + +invalidRouteEnds: routeEnds; + +routingConditionsNotAssociated: SuppliedRoutingConditions; + +newRouteComponentsNotPartOfLND: SET OF RouteComponents; + +newRouteComponentsNotFree: SET OF RouteComponents; + +routeComponentsNotConsistent: NULL; + +BEHAVIOUR + +SEMI\_FORMAL + +PARAMETER\_MATCHING + +accessGroup: < INFORMATION OBJECT: prdAccessGroup>; + +link: < INFORMATION OBJECT: prdLink>; + +linkConnection: < INFORMATION OBJECT: prdLinkConnection>; + +linkEnd : < INFORMATION OBJECT: prdLinkEnd>; + +networkCTP: < INFORMATION OBJECT: prdNetworkCTP>; + +networkTTP: < INFORMATION OBJECT: prdNetworkTTP>; + +subnetwork: ; + +topologicalLink: < INFORMATION OBJECT: prdTopologicalLink>; + +topologicalLinkEnd: < INFORMATION OBJECT: prdTopologicalLinkEnd>; + +suppliedRoutingConditions: < INFORMATION OBJECT: prdRoutingConditions>; + +arcOrPointOrientedRouteComponents: ; + +layerND: ; + +suppliedUserIdentifier: ; + +routeSet: ; + +routeEnds: ; + +dir : < INFORMATION ATTRIBUTE: directionality > ; + +linkDir: < INFORMATION ATTRIBUTE: linkDirectionality>; + +topologicalEndDir: ; + +pointDir : < INFORMATION ATTRIBUTE: pointDirectionality > ; + +#### PRE\_CONDITIONS + +inv\_routeEndsLNDContainment +"The elements representing the aEnd and zEnd of the routeEnds are referring to *element* in the relationship where layerND refers to *containerLND*." + +#### POST\_CONDITIONS + +inv\_associatedWithSuppliedRoutingConditions +"The suppliedRoutingConditions have to participate in the relationship taking the *fulfilledConditions* role while routeSet is taking on the *routeSet* role." +inv\_newRouteComponentsLNDContainment +"All route components of routeSet must refer to *element* in the relationship where layerND refers to *containerLND*." +inv\_freeNewRouteComponents +" of all route components contained in routeSet must be equal to NULL." +inv\_consistentRouteComponents +"Only linkConnections are allowed as route components in routeSet when arcOrPointOrientedRouteComponents is equal to arc-oriented. Only networkCTPs are allowed as route components in routeSet when arcOrPointOrientedRouteComponents is equal to point-oriented." + +#### EXCEPTIONS + +IF PRE\_CONDITION inv\_routeEndsLNDContainment NOT\_VERIFIED RAISE\_EXCEPTION +invalidRouteEnds; +IF POST\_CONDITION inv\_associatedWithSuppliedRoutingConditions NOT\_VERIFIED +RAISE\_EXCEPTION routingConditionsNotAssociated; +IF POST\_CONDITION inv\_newRouteComponentsLNDContainment NOT\_VERIFIED +RAISE\_EXCEPTION newRouteComponentsNotPartOfLND; +IF POST\_CONDITION inv\_freeNewRouteComponents NOT\_VERIFIED RAISE\_EXCEPTION +newRouteComponentsNotFree; +IF POST\_CONDITION inv\_consistentRouteComponents NOT\_VERIFIED RAISE\_EXCEPTION +routeComponentsNotConsistent; +;} + +### 7.3 Reporting interfaces + +#### 7.3.1 Route discovery reporting interface + +The route discovery reporting interface provides functionality for the reporting of the retrieving of potential routes that can be used for setting up trails, tandem connections or subnetwork connections as defined in <"Rec. G.852.16", COMMUNITY: pre-provisioned route discovery>. + +COMPUTATIONAL INTERFACE routeDiscoveryReportingIfce{ +DERIVED FROM +OPERATION { +; +} +} + +#### Route discovery reporting + + +OPERATION reportRouteDiscovery { +INPUT\_PARAMETERS +layerND: LayerNetworkDomainChoice; +routeSet: ReturnedRouteSet ::= SET OF ReturnedRoute; +routeEnds: RouteEnds +-- the ASN.1 type for ReturnedRoute will be developed in technology +-- specific extensions of the pre-provisioned route discovery community +OUTPUT\_PARAMETERS +-- none + +#### RAISED\_EXCEPTIONS + +-- none + +#### BEHAVIOUR + +##### SEMI\_FORMAL + +###### PARAMETER\_MATCHING + +layerND: ; + +routeSet: ; + +routeEnds: ; + +###### TRIGGERING\_CONDITIONS + +###### PRE\_CONDITIONS + +inv\_noRouteSet + +" routeSet does not refer to any *element* in the the relationship where layerND refers to *containerLND*." + +###### POST\_CONDITIONS + +inv\_existingRouteSet + +" routeSet does refer to *element* in the the relationship where layerND refers to *containerLND*." + +###### EXCEPTIONS + +-- none + +;} + +#### 7.4 ASN.1 supporting productions + +In this Recommendation, when an interface name is used within an ASN.1 production, the same label will be used, starting with a capital letter. The complete ASN.1 type definition for this query interface (e.g. use of ObjectIdentifier, INTEGER, ...) will be developed as part of the engineering viewpoint, with the concerned technology. + +##### AccessGroupChoice ::= CHOICE { + +| | | +|-------------------------|--------------------------| +| prdAccessGroupQueryIfce | PrdAccessGroupQueryIfce, | +| userIdentifier | UserIdentifier }; | + +##### AEndChoice ::= CHOICE { + +| | | +|--------------------------|---------------------------| +| networkTTPChoice | NetworkTTPChoice, | +| networkCTPChoice | NetworkCTPChoice, | +| linkConnectionChoice | LinkConnectionChoice, | +| accessGroupChoice | AccessGroupChoice, | +| linkChoice | LinkChoice, | +| linkEndChoice | LinkEndChoice, | +| topologicalLinkChoice | TopologicalLinkChoice, | +| topologicalLinkEndChoice | TopologicalLinkEndChoice, | +| subnetworkChoice | SubnetworkChoice}; | + +##### ArcPointOriented ::= CHOICE { + +| | | +|-------|--------| +| arc | NULL, | +| point | NULL}; | + +##### LayerNetworkDomainChoice ::= CHOICE { + +| | | +|--------------------------------|---------------------------------| +| prdLayerNetworkDomainQueryIfce | PrdLayerNetworkDomainQueryIfce, | +| userIdentifier | UserIdentifier}; | + +##### LinkChoice ::= CHOICE { + +| | | +|------------------|-------------------| +| prdLinkQueryIfce | PrdLinkQueryIfce, | +| userIdentifier | UserIdentifier}; | + +``` + +LinkConnectionChoice ::= CHOICE { + prdLinkConnectionQueryIfce PrdLinkConnectionQueryIfce, + userIdentifier UserIdentifier}; + +LinkEndChoice ::= CHOICE { + prdLinkEndQueryIfce PrdLinkEndQueryIfce, + userIdentifier UserIdentifier}; + +NetworkCTPChoice ::= CHOICE { + prdNetworkCTPQueryIfce PrdNetworkCTPQueryIfce, + userIdentifier UserIdentifier}; + +NetworkTTPChoice ::= CHOICE { + prdNetworkTTPQueryIfce PrdNetworkTTPQueryIfce, + userIdentifier UserIdentifier}; + +ProtectionScheme ::= CHOICE { + noProtection NULL, + 1+1_Protection NULL, + 1:n_Protection NULL, + m:n_Protection NULL}; + +ReturnedProperties ::= SET OF { + property1 Property1 + .... + propertyN PropertyN}; + -- the ASN.1 type for ReturnedProperties will be developed in technology + -- specific extensions of the pre-provisioned route discovery community + +ReturnedRoute ::= SEQUENCE OF { + route PrdRouteQueryIfce; + + routeProperties ReturnedProperties, + -- 0 implies none supplied + routeComponents SEQUENCE OF RouteComponents}; + -- the number of the SEQUENCE OF in routeComponents corresponds to the protection scheme requested + -- the final ASN.1 type for ReturnedRoute will be developed in technology specific extensions + +RouteComponents ::= CHOICE { + arcView SEQUENCE OF LinkConnectionChoice, + pointView SEQUENCE OF NetworkCTPChoice}; + +SubnetworkChoice ::= CHOICE { + prdSubnetworkQueryIfce PrdSubnetworkQueryIfce + userIdentifier UserIdentifier}; + +SuppliedRoutingConditions ::= SET OF { + topologyCriteria TopologyComponentCriteria, + maximumNumberOfNodes INTEGER, + bandwidthConstraints INTEGER, + protectionScheme ProtectionScheme, + .... +}; + -- bandwidth constraints requests the maximum average spare capacity and shall be expressed in % + -- the ASN.1 type for suppliedRoutingConditions will be developed in technology specific extensions + +TopologicalLinkChoice ::= CHOICE { + prdTopologicalLinkQueryIfce PrdTopologicalLinkQueryIfce, + userIdentifier UserIdentifier}; + +``` + +``` + +TopologicalLinkEndChoice ::= CHOICE { + prdTopologicalLinkEndQueryIfce PrdTopologicalLinkEndQueryIfce, + userIdentifier UserIdentifier}; + +TopologyComponentCriteria ::= SET OF { + criteria1 Criteria1 + .... + criteriaN CriteriaN}; + -- the ASN.1 type for TopologyComponentCriteria will be developed in technology + -- specific extensions of the pre-provisioned route discovery community + +UserIdentifier ::= SimpleNameType; + +ZEndChoice ::= CHOICE { + networkTTPChoice NetworkTTPChoice, + networkCTPChoice NetworkCTPChoice, + linkConnectionChoice LinkConnectionChoice, + accessGroupChoice AccessGroupChoice, + linkChoice LinkChoice, + linkEndChoice LinkEndChoice, + topologicalLinkChoice TopologicalLinkChoice, + topologicalLinkEndChoice TopologicalLinkEndChoice, + subnetworkChoice SubnetworkChoice }; + +``` + +## **SERIES OF ITU-T RECOMMENDATIONS** + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure and Internet protocol aspects | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.8601-200606-I_PDF-E/raw.md b/marked/G/T-REC-G.8601-200606-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..d8dc148360f1114657140f9d6e795484fa8802e5 --- /dev/null +++ b/marked/G/T-REC-G.8601-200606-I_PDF-E/raw.md @@ -0,0 +1,1084 @@ + + +**ITU-T** + +**G.8601/Y.1391** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +(06/2006) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Packet over Transport aspects – Service management + +SERIES Y: GLOBAL INFORMATION +INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS +AND NEXT-GENERATION NETWORKS + +Internet protocol aspects – Transport + +# --- **Architecture of service management in multi-bearer, multi-carrier environment** + +ITU-T Recommendation G.8601/Y.1391 + +## ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| Ethernet over Transport aspects | G.8000–G.8099 | +| MPLS over Transport aspects | G.8100–G.8199 | +| Quality and availability targets (continuation of G.82x series) | G.8200–G.8299 | +| Service Management | G.8600–G.8699 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## **ITU-T Recommendation G.8601/Y.1391** + +# **Architecture of service management in multi-bearer, multi-carrier environment** + +## **Summary** + +This Recommendation defines a set of requirements that are applicable to Client Service Management in multi-carrier, multi-transport-technology networks. + +###### **Source** + +ITU-T Recommendation G.8601/Y.1391 was approved on 6 June 2006 by ITU-T Study Group 15 (2005-2008) under the ITU-T Recommendation A.8 procedure. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2007 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +# CONTENTS + +###### Page + +| | | | +|------|----------------------------------------------------------------------|----| +| 1 | Scope ..... | 1 | +| 2 | References..... | 1 | +| 3 | Terms and definitions ..... | 1 | +| 4 | Acronyms and abbreviations ..... | 3 | +| 5 | Conventions ..... | 4 | +| 5.1 | Nomenclature ..... | 4 | +| 6 | Introduction ..... | 4 | +| 7 | General description of client service management..... | 5 | +| 7.1 | General management areas..... | 5 | +| 7.2 | OAM flow categories ..... | 7 | +| 8 | Business relationship models: Service provider to end customer ..... | 7 | +| 8.1 | Single carrier: Ownership Model 0 (OM-0)..... | 8 | +| 8.2 | Multiple carriers ..... | 10 | +| 8.3 | Composite carrier scenarios ..... | 16 | +| 9 | Network transport technology ..... | 18 | +| 9.1 | Drawing conventions..... | 18 | +| 9.2 | Candidate technologies..... | 19 | +| 9.3 | Technology models ..... | 19 | +| 9.4 | Applicability of technology models to ownership models ..... | 22 | +| 10 | Applicable client service types ..... | 24 | +| 11 | Management communication functions..... | 24 | +| 11.1 | Performance information..... | 25 | +| 11.2 | Commands and responses..... | 26 | +| 11.3 | Autonomous notification..... | 26 | +| 11.4 | Remotely located NE (CLE) software upgrades ..... | 27 | +| 12 | Testing requirements ..... | 27 | + + + +# **Architecture of service management in multi-bearer, multi-carrier environment** + +# **1 Scope** + +This Recommendation defines architectural requirements for the edge-to-edge management and/or control of client services transported over various transport network topologies and technologies. The services for which such management capabilities are required are included. + +The requirements for the transference of the management and/or control data between the edge points is described along with the requirements for accessibility to management and/or control information at some point in the network, other than the end point. + +The provision of such management services is also considered in the context of business relationships that may be involved in the delivery of a service to, for example, the Service Provider, Network Operator(s) and the Enterprise End customer. Consideration is also given to the management and/or control of Customer Located Equipment which is owned by the Service Provider and carrying said services. + +Although the client service management detail is not within the scope of this Recommendation, consideration is given to three generic management and/or control functions: performance reporting, status reporting and client service control (e.g., loopback, end node configuration, etc). + +This Recommendation describes the architecture for service management and/or control, and includes the reference points of the architecture. It does not define the implementation methodology or any of the interfaces that may need to be specified. + +# **2 References** + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- ITU-T Recommendation G.707/Y.1322 (2007), *Network node interface for the synchronous digital hierarchy (SDH)*. +- ITU-T Recommendation G.709/Y.1331 (2003), *Interfaces for the Optical Transport Network (OTN)*. +- ITU-T Recommendation G.806 (2006), *Characteristics of transport equipment – Description methodology and generic functionality*. + +# **3 Terms and definitions** + +This Recommendation defines the following terms: + +**3.1 anomaly:** (See ITU-T Rec. G.806) The smallest discrepancy which can be observed between the actual and desired characteristics of an item. The occurrence of a single anomaly does not constitute an interruption in the ability to perform a required function. Anomalies are used as the input for the Performance Monitoring (PM) process and for the detection of defects. + +- 3.2 defect:** (See ITU-T Rec. G.806) The density of anomalies has reached a level where the ability to perform a required function has been interrupted. Defects are used as input for PM, the control of consequent actions, and the determination of fault cause. +- 3.3 degrade:** A degrade is the presence of a defect for a sufficient period of time that impairs the ability of a resource to perform the desired function. +- 3.4 edge service:** The service from the perspective of a single SOF. +- 3.5 edge-to-edge:** The path serving the service that sources at a local SOF (Service Origination Function) and sinks at a remote SOF. +- 3.6 end-to-end:** The complete path that the customer/client signal takes that sources at a local Customer Equipment (CE) and sinks at the remote CE. +- 3.7 failure:** (See ITU-T Rec. G.806) The fault cause persisted long enough to consider the ability of an item to perform a required function to be terminated. The item may be considered as failed; a fault has now been detected. +- 3.8 fault:** (See ITU-T Rec. G.806) A fault is the inability of a function to perform a required action. This does not include an inability due to preventive maintenance, lack of external resources, or planned actions. +- 3.9 management access point (MAP):** The Management Access Point is the point in the transport network where the Management System has its point of contact for purposes of management and/or control. This MAP may be at any point in the transport network including at the edge of the transport network. +- 3.10 network resource:** Resources that are owned and managed by the SP in support of the offered customer service. +- 3.11 service status:** Service status indicates that the service is in one of four states. +- 1) Operational: Service is operating within the bounds of the established SLA. + - 2) Degraded: Service is operational; however, its performance is degraded in reference to the SLA. + - 3) Failure: Service failure has occurred and is not operational. + - 4) In-test: Service is under control of service/network operator for maintenance actions. +- Service failure may be attributed to path level defects, service failures at the client link, or significant disparity in achieving adherence to the SLA. +- The Service Status is generated by each SOF. The Service Status is generated by comparing local edge-service PMs and remote edge-service PMs (conveyed between edges) to formulate edge-to-edge service PMs. These edge-to-edge service PMs are then compared to SLA thresholds to determine the operational disposition of the service. +- 3.12 service management function (SMF):** A logical entity found within a service-aware NE that performs Management Access Point (MAP) and/or Test Access Point (TAP) functions. +- 3.13 service origination function (SOF):** The Network Element (NE) function, managed by the Service Provider (SP) which represents the edge optical service point. It performs customer frame/signal mapping to the SP optical network. Typically incorporates a SMF. +- 3.14 user network interface (UNI):** The UNI is the bearer between the CPE and the Network. + +# 4 Acronyms and abbreviations + +This Recommendation uses the following abbreviations: + +| | | +|--------|--------------------------------------------| +| C/R | Command Response | +| CE | Customer Equipment | +| CLE_NE | Customer Located Equipment Network Element | +| CPE | Customer Premises Equipment | +| CSM | Client Service Management | +| EM | Element Management | +| ETH | Ethernet MAC layer network | +| ETY | Ethernet Physical interface | +| FD | Flow Domain | +| MAP | Management Access Point | +| NE | Network Element | +| NM | Network Manager | +| NMS | Network Management System | +| NNI | Network to Network Interface | +| NO | Network Operator | +| OAM | Operations, Administration and Maintenance | +| OAMiF | OAM in Frame | +| OM-n | Ownership Model n | +| OSS | Operations Support System | +| OTN | Optical Transport Network | +| PDH | Plesiochronous Digital Hierarchy | +| PE | Provider Edge | +| PL | Private Line | +| PM | Performance Monitoring | +| PTE | Path Terminating Equipment | +| SDH | Synchronous Digital Hierarchy | +| SLA | Service Level Agreement | +| SM | Service Management | +| SMF | Service Management Function | +| SNC | SubNetwork Connection | +| SOF | Service Origination Function | +| SP | Service Provider | +| SS | Service Status | +| TAP | Test Access Point | +| UNI | User Network Interface | + +# 5 Conventions + +## 5.1 Nomenclature + +For purposes of signal identification, the following nomenclature will be used in this Recommendation. + +Signal Names will have the format: Letter.number.number + +Where: Letter represents the Service Provider (SP): + +(e.g., R = Red SP; B = Blue SP; G = Green SP; P = Purple SP). + +Number represents the individual signal number belonging to the SP. + +Number represents the Ownership Model (OM). + +Examples: + +R.3.1 is Owned by Red SP (SP\_R), and is SP\_R's 3rd signal and is configured as OM-1. + +B.1.0 is Owned by Blue SP (SP\_B), and is SP\_B's 1st signal and is configured as OM-0. + +P.2.2 is Owned by Purple SP (SP\_P), and is SP\_P's 2nd signal and is configured as OM-2. + +NOTE – The ownership model at each edge of a client signal connection may be different; this is dependant on the location of the MAP and whether the SP owns the edge device. + +# 6 Introduction + +Service providers are demanding a simple service model for transport of Client Data Services over networks that fits their existing operational model. That is, the Client Data private line service must be analogous to existing private line services, and more importantly must interface into existing management systems. + +This Recommendation is structured with **numbered requirements** integrated into the descriptive normative clauses. In some instances where a requirement is applicable to more than one clause, there will be a reference to the original instance of that requirement. All requirements will appear on a separate line in **Bold**. + +NOTE – The numbering is not always contiguous to allow for insertion of requirements if and when this Recommendation is updated. + +**R1 Management of the Client Private Line Service should interface to existing management systems.** + +**R2 A defect or failure in a given layer network should not cause multiple alarm events to be raised, nor cause unnecessary corrective actions to be taken, in any higher level client layer networks. This applies to all client layer network types that the Private Line service is required to carry.** + +**R3 If a network defect or failure occurs in an interface, mapping function, or path, it is necessary to detect it, diagnose it, localize it, notify the NMS/OSS and take corrective actions appropriate to the type of defect. The primary objective is to reduce operating costs by minimizing service interruptions, operational repair times and operational resource.** + +The business drivers for managed Client Services are: + +- Manageability of the network. +- Management of the service offered to the customer. +- Interconnection of billing/management data to carrier OSS systems. +- Accessibility of performance data for confirmation of service level agreement (SLA) conformance. + +Also of importance is the manageability of remotely located Customer Located Equipment (CLE). Several business models are used to define the requirements for Client Service Management (CSM). The Network Technologies and combinations thereof are defined, as are the applicable Client Service types. + +**R4 To confirm SLA compliance with the customer, the Service Provider (SP) must have visibility of the performance of the Client Interface at the edge of the transport network.** + +- a) The edge NE must support the ability of a remote device to query service configuration information (i.e., Service or Circuit ID, service PM, thresholds, etc.). + +**R5 To confirm SLA compliance with the customer, the SP must have visibility of the mapping function performance at the edge of the transport network.** + +- a) The edge NE must support the ability of a remote device to query the edge devices mapping function performance. + +# **7 General description of client service management** + +Client Service Management (CSM) is the management and/or control of the client services by the Service Provider (SP), regardless of the location of the SP (within the topology of the transport network) and consists of the following general management and/or control functions: + +- a) Performance Monitoring at the edge of the transport network. +- b) Monitoring of the status of the edge-to-edge transport connection. +- c) Control of the 'edge' device (commands and responses to/from the edge device). +- d) Generation and reception of anomalous conditions of the service and the NE at the edge. + +The components of CSM will be dependant on: + +- 1) Business relationships between SP and enterprise customer. + - i) Single Carrier configuration. + - ii) Multiple Carrier configuration. +- 2) Network transport technologies (and combinations thereof). +- 3) Communications between SP and edge device necessary for a – d above. + +## **7.1 General management areas** + +While more complex network diagrams are possible, a simple model of a Client Data network to show the management areas would only show the endpoints of a single carrier's network. This is based on the relationship shown in Figure 1. + +The simple Client Data network management areas shown in Figure 1 are: + +- A End-to-End: CE – CE (i.e., service – customer to customer): Customer OAM. +- B Access Link: CE – PE (i.e., facility – carrier to customer): Access OAM. +- C Edge-to-Edge: PE – PE (i.e., service – intra carrier): Service OAM. +- D Transport (i.e., facility – intra carrier): Path OAM. + +FCAPS (fault, configuration, accounting, performance, and security) is an acronym for a categorical model of the working objectives of network management. The carriage of management information is often dependant on the network or service that is being managed. Each of these four areas would have a carriage and FCAPS component. + +- R6** The OAM functionality of optical PL service should not be dependant on any specific server or client-layer network. This is architecturally critical to ensure that layer networks can evolve (or new/old layer networks be added/removed) without impacting other layer networks. +- R7** The use of Service OAM functions should be optional for the operator. Network operators should be able to choose which OAM functions to use and which connections they apply them to. +- R8** In the case of failures, OAM mechanisms provided should ensure (as far as reasonably practicable) that customers should not have to detect failures. It is therefore necessary that service faults be detected and notifications sent to the SP. +- R9** In the case of degraded performance, OAM mechanisms provided should ensure (as far as reasonably practicable) that customers should not have to detect service degrades. It is therefore necessary that service degrade conditions be detected and notifications sent to the SP. + +![Figure 1/G.8601/Y.1391 – Simple view of general management areas. The diagram illustrates a network architecture with two Customer units connected via a Transport operator network. The Transport operator network is connected to an SNC (Service Network Connection) which is further connected to ETY (Enterprise Transporter) units. The diagram shows various management areas: UNI-C (User Network Interface - Customer), demarc (demarcation point), UNI-N (User Network Interface - Network), NNI (Network Network Interface), and ETY (Enterprise Transporter). The management areas are labeled A, B, C, and D. Area A is the end-to-end management between the two Customer units. Area B is the access link management between the Customer unit and the demarc. Area C is the management between the demarc and the UNI-N. Area D is the management between the UNI-N and the NNI. The diagram also shows UNI attributes and Ethernet connection attributes.](007b053fe94a8348f75128a584503fd0_img.jpg) + +The diagram shows a network architecture with the following components and management areas: + +- Customer:** Two customer units at the ends of the network. +- UNI-C:** User Network Interface - Customer, located at the customer units. +- demarc:** Demarcation point, located between the customer unit and the transport operator network. +- UNI-N:** User Network Interface - Network, located at the transport operator network. +- NNI:** Network Network Interface, located at the transport operator network. +- Transport operator network:** The central network cloud. +- FD:** Forwarding device, located at the ETY unit. +- ETY:** Enterprise Transporter, located at the ends of the network. +- SNC:** Service Network Connection, located in the center of the diagram. +- Management Areas:** + - A:** End-to-end management between the two Customer units. + - B:** Access link management between the Customer unit and the demarc. + - C:** Management between the demarc and the UNI-N. + - D:** Management between the UNI-N and the NNI. +- Attributes:** + - UNI attributes:** Indicated by a red double-headed arrow between the two UNI-C interfaces. + - Ethernet connection attributes:** Indicated by a blue double-headed arrow between the two UNI-N interfaces. + +Figure 1/G.8601/Y.1391 – Simple view of general management areas. The diagram illustrates a network architecture with two Customer units connected via a Transport operator network. The Transport operator network is connected to an SNC (Service Network Connection) which is further connected to ETY (Enterprise Transporter) units. The diagram shows various management areas: UNI-C (User Network Interface - Customer), demarc (demarcation point), UNI-N (User Network Interface - Network), NNI (Network Network Interface), and ETY (Enterprise Transporter). The management areas are labeled A, B, C, and D. Area A is the end-to-end management between the two Customer units. Area B is the access link management between the Customer unit and the demarc. Area C is the management between the demarc and the UNI-N. Area D is the management between the UNI-N and the NNI. The diagram also shows UNI attributes and Ethernet connection attributes. + +**Figure 1/G.8601/Y.1391 – Simple view of general management areas** + +### 7.1.1 End-to-end management + +This is the management performed by the Enterprise customer between clients at both ends (A in Figure 1). This service management of live traffic assumes the Client Data link through the transport network to be transparent. + +### 7.1.2 Access link management + +This is the enterprise customer to transport portion of the Client Data connection (B in Figure 1). + +### **7.1.3 Edge-to-edge management** + +This is the management of Client Data Services over the transport network (C in Figure 1). This will carry data relating to the service edge function/process and also relevant information from the terminated link management. + +### **7.1.4 Transport management** + +This is the network management of the carrier's facilities, for example, fault isolation within the carrier's network (D in Figure 1). It is performed using well-defined transport network management techniques. + +## **7.2 OAM flow categories** + +### **7.2.1 Customer OAM** + +- This OAM flow identifies the OAM operations associated with the connection between the CPE source and CPE sink devices. This flow identifies the OAM functionality supported between two customer sites. + +### **7.2.2 UNI OAM** + +- This OAM flow identifies the OAM operations associated with the connection between the SOF and the CE. For example in the case of Ethernet service, the OAM operations are based on IEEE 802.3ah (i.e., Ethernet Link OAM). + +### **7.2.3 Path OAM** + +- Path OAM flows are between PTEs. +- These flows identify OAM operations associated with network resource (e.g., equipment) management functions. + +### **7.2.4 Service OAM** + +- This OAM flow identifies the OAM operations associated with the edge-to-edge service. OAM information conveyed in the Service OAM flow can include network path level OAM and UNI link OAM information. +- Service OAM flows follow the network path flows serving the service being offered. It can be optionally monitored at intermediate optical service NEs. + +# **8 Business relationship models: Service provider to end customer** + +It is important to understand who is buying what and from whom when Broadband Services are being transported over a transport network. In the following models, it is assumed that the Client Data Private Line service is being sold by a Service Provider to an Enterprise end customer. + +In all business relationship models, the Management Access Point (MAP) could be at any NE along the transport path. + +A Client Service Management scheme is required that will be consistent and compatible with several business relationship models. + +#### **R10 The ability of the Management Access Point (MAP) located at any point along the transport path to perform service/network/equipment management functions on the edge/remote or CLE/NE devices is required.** + +- a) If the end-to-end PL service is being transported over networks belonging to different operators, the operator that offers the service to the customer should be aware of a service fault even if the fault and detection point are located in the network of another operator.** + +- R11** The SP requires a management connection to the Edge NE for PM reporting purposes. +- a)** This performance monitoring will be governed by the technology of the native customer signal. +- R12** The SP needs to be notified of anomalous service conditions at the edge of the transport network. This notification needs to be done in a timely manner. +- R13** The SP needs to be able to do rudimentary intrusive control at the Edge NE for purposes of Management of the Client Service. The edge NE must support the ability of a remote device to modify, add, or set service configuration information. For example: +- a)** To query Service or Circuit ID (service PM, thresholds, etc.). + - b)** To activate/deactivate the service. + - c)** To interrogate the client interface status. + - d)** To apply loopback(s) in test & commission phase. + +## **8.1 Single carrier: Ownership Model 0 (OM-0)** + +The simplest ownership model is the single carrier model, shown in Figure 1. The customer – supplier relationship is between the enterprise customer and the service provider. That is, payment for service is from enterprise customer to service provider only. This is a retail only model. For OM-0 the SP owns the entire transport network across which the Client Signal is to be transported. The SP therefore provides connectivity and mapping to transport the Client Signal. Since there are performance guarantees per a contract, there is a resulting SLA between the demarcation points (demarc or UNI) as noted in Figure 1. + +The network connection and transport facility path are virtually identical – the transport path starts just after service encapsulation. + +In this single-carrier case, it is desirable to have an operational model that is consistent with the multi-carrier case. (See clause 8.2.) + +Single Carrier Model (Ownership Model 0) is depicted in Figure 2: + +- NO\_R and SP\_R are synonymous. +- NO\_R provides transport connection for the edge-to-edge service. +- NO\_R provides transport PTE functions. +- NO\_R performs client frame adaptation (mapping) into transport. +- SP\_R is the Service Provider (SP) and has a SLA with the enterprise customer (shown as CPE). +- To confirm SLA compliance with the customer, SP\_R needs to have visibility of the performance of the Client Interface and the mapping function. +- SP\_R requires a management connection to NO\_R's Edge NE for PM reporting purposes. +- SP\_R needs to be able to do rudimentary intrusive control at NO\_R's Edge NE for purposes of Management of the Client Service. + - For example to activate/deactivate the service; interrogate the client interface status; apply loopback(s) in test & commission phase. + +Figure 2 also shows that in the Single Carrier network Scenario: + +- Each Network 'edge' device can have several service instances (example: R.1.0 & R.2.0 connected to edge device E-R1). +- There can be several Network edge devices in the network (example: E-R1 & E-R2) each carrying multiple services. +- In the single carrier case, there is only one SP that requires access to the edge device(s). + +![Diagram of a Single Carrier network – Ownership Model 0. The diagram shows a central cloud labeled 'SP_R' containing four edge devices: TNE E-R1, TNE E-R2, TNE E-R3, and TNE E-R4. Each edge device is connected to one or more Customer Premises Equipment (CPE) units. E-R1 is connected to CPEs R.1.0 and R.2.0. E-R2 is connected to CPEs R.3.0 and R.4.0. E-R3 is connected to CPEs R.1.0 and R.2.0. E-R4 is connected to CPEs R.3.0 and R.4.0. Inside the SP_R cloud, the edge devices are connected to a central node labeled 'EM-SM-NM'. Below the SP_R cloud is another cloud labeled 'NO_R'.](724c7777b608e53be38b12b6fb3c43bc_img.jpg) + +Diagram of a Single Carrier network – Ownership Model 0. The diagram shows a central cloud labeled 'SP\_R' containing four edge devices: TNE E-R1, TNE E-R2, TNE E-R3, and TNE E-R4. Each edge device is connected to one or more Customer Premises Equipment (CPE) units. E-R1 is connected to CPEs R.1.0 and R.2.0. E-R2 is connected to CPEs R.3.0 and R.4.0. E-R3 is connected to CPEs R.1.0 and R.2.0. E-R4 is connected to CPEs R.3.0 and R.4.0. Inside the SP\_R cloud, the edge devices are connected to a central node labeled 'EM-SM-NM'. Below the SP\_R cloud is another cloud labeled 'NO\_R'. + +G.8601-Y.1391(06)\_F02 + +Figure 2/G.8601/Y.1391 – Single carrier network – Ownership Model 0 + +**R14** The CSM operational model for Single Carrier network (OM-0) must be consistent with that for the Multi-Carrier (OM-1 and OM-2) network(s); see 8.2. + +**R15** Each Network 'edge' device can have several service instances (example Figure 2: R.1.0 & R.2.0 connected to edge device E-R1). + +**R16** There can be several Network edge devices in the network (example Figure 2: E-R1 & E-R2) and each edge device can carry multiple services. + +Requirements 10, 11, 12 and 13 also apply to the OM-0 case. + +### 8.1.1 Single carrier dark fibre connection + +An alternative Single Carrier scenario is depicted in Figure 3. Here the SP could offer a managed connection, which is provided by two equipments directly interconnected via a fibre (or a wavelength). The signal carried would be the customer's native signal and would be different from the NO's network transport technology (for example NO is SDH while customer's native signal is OTN or GbE). + +In this case: + +- NO\_R and SP\_R are synonymous. +- NO\_R provides only dark fibre for the edge-to-edge native customer signal. +- NO\_R performs adaptation of customer's native signal onto dark fibre/wavelength. +- SP\_R is the Service Provider (SP) and has a SLA with the enterprise customer (shown as CPEs connected to E-R5 and E-R6 in Figure 3). +- To confirm SLA compliance with the customer, SP\_R needs to have visibility of the performance of the Client Interface and the adaptation function. + - This performance monitoring will be governed by the technology of the native customer signal. + +- SP\_R requires a management connection to NO\_R's Edge NE for PM reporting purposes. +- SP\_R needs to be able to do rudimentary intrusive control at NO\_R's Edge NE for purposes of Management of the Client Signal. + - For example to activate/deactivate the service; interrogate the client interface status; apply loopback(s) in test & commission phase. + +In the Single Carrier dark fibre Scenario (similarly to the Single Carrier case above but not depicted): + +- Each Network 'edge' device can have several native customer signal instances. +- There can be several Network edge devices in the network each carrying multiple native customer signals. +- In the single carrier case, there is only one SP that requires access to the edge device(s). + +![Diagram of a single carrier dark fibre connection. A central orange cloud represents the network, containing SP_R and NO_R nodes. SP_R is connected to six TNE (E-R1 to E-R6) devices. Each TNE is connected to one or more CPEs labeled R.1.0, R.2.0, R.3.0, and R.4.0. The TNEs are interconnected by a 'Dark fibre' link. The NO_R node is also connected to the TNEs. A small text 'G.8601-Y.1391(06)_F03' is visible in the bottom right corner of the diagram area.](1a827b10290f33d4fec04d0e8ef7a897_img.jpg) + +Diagram of a single carrier dark fibre connection. A central orange cloud represents the network, containing SP\_R and NO\_R nodes. SP\_R is connected to six TNE (E-R1 to E-R6) devices. Each TNE is connected to one or more CPEs labeled R.1.0, R.2.0, R.3.0, and R.4.0. The TNEs are interconnected by a 'Dark fibre' link. The NO\_R node is also connected to the TNEs. A small text 'G.8601-Y.1391(06)\_F03' is visible in the bottom right corner of the diagram area. + +Figure 3/G.8601/Y.1391 – Single carrier (Dark fibre connection) + +- R17** In the case where transport network edges are connected via a wavelength or dark fibre, each Network 'edge' device can have several native customer signal instances. +- R18** There can be several Network edge devices pairs in the network (each pair interconnected by wavelength or dark fibre) and each edge device can carry multiple native customer signals. +- R19** There shall be no requirement to have client signals belonging to different Service providers carried over this scenario where an edge pair is interconnected by wavelength or dark fibre scenario. + +## 8.2 Multiple carriers + +The reality is that several carriers may be involved in the edge-to-edge transport of a Client Data private line service between two end points. + +The multiple-carrier model is one where the SP owns part of the transport path but does not have management and/or control access to the edge(s) of the transport network. + +This wholesale multiple-carrier scenario results in two pertinent ownership models. These are: + +- Ownership Model-1 (OM-1) shown in Figure 4; and +- Ownership Model-2 (OM-2) shown in Figure 5. + +In both cases, the customer – supplier relationship is still between the enterprise and service provider. However, in both OM-1 and OM-2, the service provider does not have physical management connectivity to the transport network edges. However, the service provider *is* the retailer and holds the edge-to-edge contract with the enterprise customer. As in the OM-0 case, a SLA guarantees provider edge to provider edge performance (UNI to UNI). + +In order to complete the service offering, the service provider buys transport connectivity, and may also buy mapping/de-mapping functionality from a carrier with physical presence near the enterprise customer. The presence carriers wholesale their service to the service provider. This relationship requires another level of agreements at the interface between carriers. + +Each network owner monitors transport performance across its own transport network. The service provider needs to monitor service performance edge-to-edge. As a result, the service provider needs a mechanism to gather actual service performance parameters from the edge NEs. It is important to note at this point that transport section overhead originating at the edge NE will terminate at the NNI, so it cannot be used to convey performance service data. Only the path overhead traverses all networks. + +**R20** The CSM operational model for Multiple Carrier networks (OM-1 and OM-2) must be consistent with that for the Single-Carrier (OM- 0) network. + +**R21** Each network owner shall monitor transport performance across its own transport network. + +**R22** The service provider needs to monitor service performance edge-to-edge. + +a) As a result, the service provider needs a mechanism to gather actual service performance parameters from the edge NEs. + +**R23** The service provider needs to have access to the edge NE for service control purposes. + +**R24** The service provider needs to have access to the edge NE for the purposes of receiving anomalous condition reports. + +### **8.2.1 Ownership Model 1 (OM-1)** + +Ownership Model 1 is depicted in Figure 4: SP\_R is isolated from the edge owned by NO\_B: + +- NO\_B provides transport connection from the service edge to the handoff between NO\_B & NO\_R. +- NO\_B provides transport PTE functions. +- NO\_B performs client frame adaptation (mapping) into transport. +- SP\_R is the Service Provider (SP) and has a SLA with the enterprise customer (shown as CPE). +- SP\_R buys connectivity from NO\_B. +- SP\_R also buys mapping from NO\_B. +- To confirm SLA compliance with the customer, SP\_R needs to have visibility of the performance of the Client Interface and the mapping function. +- The minimum that SP\_R requires is a management connection to NO\_B's Edge NE for PM reporting purposes. +- SP\_R needs to be able to do rudimentary intrusive control at NO\_B's Edge NE for purposes of Management of the Client Service. + - For example to activate/deactivate the service; interrogate the client interface status; apply loopback(s) in test & commission phase. + +Figure 4 also shows that in the Ownership Model 1: + +- The Network 'edge' device can have several service instances (example: R.5.1 & R.6.1 connected to edge device E-B1). +- There can be several Network edge devices in the 'local' network (example: E-B1 & E-B2) each carrying multiple services (example: E-B1 carrying R.5.1 & R.6.1 and E-B2 carrying R.7.1 & R.8.1). +- A network edge device can have service instances belonging to multiple SPs (example: E-B1 carrying R.5.1, R.6.1 & P.1.1). + +![Diagram of a multi-carrier network showing four Service Providers (SPs) connected to a central network. SP_R (orange) is connected to NO_R (red). SP_B (blue) is connected to NO_B (blue). SP_P (purple) is connected to NO_P (purple). SP_G (green) is connected to NO_G (green). Each NO is connected to a central TNE. SP_B is connected to two edge devices, E-B1 and E-B2. E-B1 is connected to CPEs R.5.1, R.6.1, and P.1.1. E-B2 is connected to CPEs R.7.1 and R.8.1. SP_G is connected to two edge devices, E-G1 and E-G2. E-G1 is connected to CPEs R.5.1, R.6.1, and P.1.1. E-G2 is connected to CPEs R.7.1 and R.8.1. Each SP contains an EM, SM, and NM component. Each NO contains a TNE component. The central TNE is connected to all four NOs.](dfe556fea00682b09a59427aaf72051c_img.jpg) + +Diagram of a multi-carrier network showing four Service Providers (SPs) connected to a central network. SP\_R (orange) is connected to NO\_R (red). SP\_B (blue) is connected to NO\_B (blue). SP\_P (purple) is connected to NO\_P (purple). SP\_G (green) is connected to NO\_G (green). Each NO is connected to a central TNE. SP\_B is connected to two edge devices, E-B1 and E-B2. E-B1 is connected to CPEs R.5.1, R.6.1, and P.1.1. E-B2 is connected to CPEs R.7.1 and R.8.1. SP\_G is connected to two edge devices, E-G1 and E-G2. E-G1 is connected to CPEs R.5.1, R.6.1, and P.1.1. E-G2 is connected to CPEs R.7.1 and R.8.1. Each SP contains an EM, SM, and NM component. Each NO contains a TNE component. The central TNE is connected to all four NOs. + +G.8601-Y.1391(06)\_F04 + +Figure 4/G.8601/Y.1391 – Multi-carrier network – Ownership Model 1 + +- R25** The isolated SP requires a management connection to the Edge NE for PM reporting purposes. +- R26** The isolated SP requires a management connection to the edge NE for edge event reporting. +- R27** The isolated SP requires a management connection to the Edge NE to enable rudimentary intrusive control at the Edge NE for purposes of Management of the Client Services. +- a) For example to activate/deactivate the service; interrogate the client interface status; apply loopback(s) in test & commission phase. +- R28** The Network 'edge' device can have several service instances (example Figure 4: R.5.1 & R.6.1 connected to edge device E-B1). +- R29** There can be several Network edge devices in the 'local' network (example Figure 4: E-B1 & E-B2) each carrying multiple services (example Figure 4: E-B1 carrying R.5.1 & R.6.1 and E-B2 carrying R.7.1 & R.8.1). + +- R30** A network edge device can have service instances belonging to multiple SPs (example Figure 4: E-B1 carrying R.5.1, R.6.1 & P.1.1). +- R31** Where a single or small number of services is supported by a service provider over a third party network operator's element, the service provider does not need to support network element management, but could provide service management at a service level. Where a group of services might be more efficiently managed as a bundle, they might be managed together. + +### 8.2.2 Ownership Model 2 + +Ownership Model 2 is depicted in Figure 5: SP\_R is isolated from the edge owned by SP\_B. + +In this model, SP\_R's customer-located NE (CLE\_NE) is remotely located beyond NO\_B's network. SP\_R therefore needs a way to manage both its services and this remotely located NE. + +- NO\_B provides part of the transport connection between the service edge and the handoff between NO\_B & NO\_R. +- SP\_R is the Service Provider and has a SLA with the enterprise customer (shown as CPE). +- SP\_R has an NE (located beyond NO\_B's network) which does the mapping into transport. The transport signal(s) are then transported over NO\_B's network to NO\_R's network. +- SP\_R buys only connectivity from NO\_B. +- SP\_R needs visibility of client I/F PMs, mapping PMs and also Path PMs at the edge of the transport network. In OM-2, this is at the CLE\_NE. +- SP\_R needs management communication to the remotely located NE at the edge of the transport network for purposes of Service management. +- SP\_R needs management communication to the remotely located NE at the edge of the transport network for purposes of NE management. + +Figure 5 also shows that in the Ownership Model 2: + +- The remotely located CLE-NE can have several service instances (example: R.9.2 & R.10.2 connected to CLE-R1). +- There can be several CLE-NEs connected to a 'local' network edge device (example: CLE-R1 & CLE-R2 connected to E-B3) each carrying multiple services (example: CLE-R1 carrying R.9.2 & R.10.2 and CLE-R2 carrying R.11.2 & R.12.2). +- CLE\_NEs belonging to different SPs may be connected to a 'local' network edge device (example: CLE-P1 & CLE-G1 connected to E-B4). + +NOTE – Only services belonging to one SP can be connected to a CLE. + +![Figure 5/G.8601/Y.1391 – Multi-carrier network – Ownership Model 2. The diagram illustrates a network architecture with four Service Providers (SPs): SP_R (orange), SP_B (blue), SP_G (green), and SP_P (purple). Each SP has a central node (EM-SM-NM) connected to a Transport Network Element (TNE). These TNEs are interconnected via a central 'NO' (Network Operator) node. SP_R is connected to NO_R, which is connected to SP_B, SP_G, and SP_P. SP_B is connected to NO_B, which is connected to SP_P. SP_G is connected to NO_G, which is connected to SP_P. SP_P is connected to NO_P. Various Customer Premises Equipment (CPE) and Customer Located Edge (CLE) devices are connected to the SP nodes. For example, SP_B has CPEs R.9.2, R.10.2, R.11.2, R.12.2, P.2.2, G.1.2, and B.2.0 connected to CLE-R1, CLE-R2, CLE-P1, and CLE-G1. SP_G has CPEs R.9.2, R.11.2, P.2.2, P.3.2, R.12.1, R.10.1, B.2.2, and G.1.0 connected to CLE-R3, CLE-P2, and CLE-B1. SP_P has CPEs P.3.0 and P.2.0 connected to CLE-P1 and CLE-G1. SP_R has CPEs R.9.2, R.10.2, R.11.2, R.12.2, P.2.2, G.1.2, and B.2.0 connected to CLE-R1, CLE-R2, CLE-P1, and CLE-G1. The diagram also shows various TNEs (E-B3, E-B4, E-P1, E-G3, E-G4) and their connections to the SP nodes and CLE devices. A label 'G.8601-Y.1391(06)_F05' is present in the bottom right corner.](b6671cfafda3820aafe9a24fa7a4d8c7_img.jpg) + +Figure 5/G.8601/Y.1391 – Multi-carrier network – Ownership Model 2. The diagram illustrates a network architecture with four Service Providers (SPs): SP\_R (orange), SP\_B (blue), SP\_G (green), and SP\_P (purple). Each SP has a central node (EM-SM-NM) connected to a Transport Network Element (TNE). These TNEs are interconnected via a central 'NO' (Network Operator) node. SP\_R is connected to NO\_R, which is connected to SP\_B, SP\_G, and SP\_P. SP\_B is connected to NO\_B, which is connected to SP\_P. SP\_G is connected to NO\_G, which is connected to SP\_P. SP\_P is connected to NO\_P. Various Customer Premises Equipment (CPE) and Customer Located Edge (CLE) devices are connected to the SP nodes. For example, SP\_B has CPEs R.9.2, R.10.2, R.11.2, R.12.2, P.2.2, G.1.2, and B.2.0 connected to CLE-R1, CLE-R2, CLE-P1, and CLE-G1. SP\_G has CPEs R.9.2, R.11.2, P.2.2, P.3.2, R.12.1, R.10.1, B.2.2, and G.1.0 connected to CLE-R3, CLE-P2, and CLE-B1. SP\_P has CPEs P.3.0 and P.2.0 connected to CLE-P1 and CLE-G1. SP\_R has CPEs R.9.2, R.10.2, R.11.2, R.12.2, P.2.2, G.1.2, and B.2.0 connected to CLE-R1, CLE-R2, CLE-P1, and CLE-G1. The diagram also shows various TNEs (E-B3, E-B4, E-P1, E-G3, E-G4) and their connections to the SP nodes and CLE devices. A label 'G.8601-Y.1391(06)\_F05' is present in the bottom right corner. + +Figure 5/G.8601/Y.1391 – Multi-carrier network – Ownership Model 2 + +- R32** The isolated SP needs management connection to the remotely located NE at the edge of the transport network for purposes of Service management. +- The isolated SP requires a management connection to the Customer Located Edge NE (CLE) for PM reporting purposes. +- R33** The isolated SP requires a management connection to the Customer Located Edge NE for edge anomalous service condition reporting. +- R34** The isolated SP requires management communication to the remotely located NE at the edge of the transport network for purposes of NE management. +- The isolated SP requires a management connection to the Customer Located Edge NE (CLE\_NE) for control purposes. + - The isolated SP requires a management connection to the Customer Located Edge NE for the purposes of equipment management. + - This includes Software Download. +- R35** The remotely located CLE device can have several service instances (example Figure 5: R.9.2 & R.10.2 connected to CLE-R1). +- R36** There can be several CLE devices connected to a 'local' network edge device (example Figure 5: CLE-R1 & CLE-R2 connected to E-B3) each carrying multiple services (example Figure 5: CLE-R1 carrying R.9.2 & R.10.2 and CLE-R2 carrying R.11.2 & R.12.2). +- R37** Where the service edge device is a remote element (CLE\_NE) owned and operated by the service provider, the service management function may be considered along with management of the remotely located network element itself. + +**R38** CLEs belonging to different SPs may be connected to a 'local' network edge device (example Figure 5: CLE-P1 & CLE-G1 connected to E-B4). + +**R39** Only services belonging to one SP can be connected to a CLE. + +### 8.2.3 Incompatible edge device + +When the edge equipment is from a vendor other than the equipment of the management domain and the edge equipment is incompatible with regard to management communications, it mimics an OM-2 model. + +In this case: + +- NO\_R and SP\_R are synonymous. +- NO\_R provides the transport connection for the edge-to-edge service (including the edge device). +- SP\_R is the Service Provider and has a SLA with the enterprise customer (shown as CPE connected to E-R7 and E-R8 in Figure 6). +- The NEs (E-R7 and E-R8 in Figure 6) located beyond NO\_R's main network do the mapping into transport. +- SP\_R needs visibility of client I/F PMs, mapping PMs and Path PMs at the edge. +- SP\_R needs management communication to the NE located at the edge of the transport network for purposes of Service management. +- SP\_R needs management communication to the NE located at the edge of the transport network for purposes of NE management. + +**R40** In the case where an edge device is incompatible with the NO's management communication, each Network 'edge' device can have several native customer signal instances. + +**R41** In the case where an edge device is incompatible with the NO's management communication, there can be several edge devices with each edge device carrying multiple native customer signals. + +![Diagram of a single carrier scenario where an edge device is incompatible with NO management systems. The diagram shows a central cloud labeled 'SP_R' and 'NO_R'. Inside the cloud are three boxes: 'EM', 'SM', and 'NM'. Surrounding the cloud are eight 'TNE' (Transport Network Element) boxes, labeled E-R1 through E-R8. Each TNE is connected to one or more 'CPE' (Customer Premises Equipment) boxes. The CPEs are labeled with version numbers: R.1.0, R.2.0, R.3.0, and R.4.0. The connections are as follows: E-R1 connects to CPE R.1.0 and CPE R.2.0; E-R2 connects to CPE R.3.0 and CPE R.4.0; E-R3 connects to CPE R.1.0 and CPE R.2.0; E-R4 connects to CPE R.3.0 and CPE R.4.0; E-R5 connects to CPE R.4.0; E-R6 connects to CPE R.3.0; E-R7 connects to CPE R.4.0; E-R8 connects to CPE R.4.0. The diagram is labeled 'G.8601-Y.1391(06)_F06' in the bottom right corner.](75e4b78ee25f885d73120e3066a5253e_img.jpg) + +Diagram of a single carrier scenario where an edge device is incompatible with NO management systems. The diagram shows a central cloud labeled 'SP\_R' and 'NO\_R'. Inside the cloud are three boxes: 'EM', 'SM', and 'NM'. Surrounding the cloud are eight 'TNE' (Transport Network Element) boxes, labeled E-R1 through E-R8. Each TNE is connected to one or more 'CPE' (Customer Premises Equipment) boxes. The CPEs are labeled with version numbers: R.1.0, R.2.0, R.3.0, and R.4.0. The connections are as follows: E-R1 connects to CPE R.1.0 and CPE R.2.0; E-R2 connects to CPE R.3.0 and CPE R.4.0; E-R3 connects to CPE R.1.0 and CPE R.2.0; E-R4 connects to CPE R.3.0 and CPE R.4.0; E-R5 connects to CPE R.4.0; E-R6 connects to CPE R.3.0; E-R7 connects to CPE R.4.0; E-R8 connects to CPE R.4.0. The diagram is labeled 'G.8601-Y.1391(06)\_F06' in the bottom right corner. + +**Figure 6/G.8601/Y.1391 – Single carrier scenario – Edge device is incompatible with NO management systems** + +## 8.3 Composite carrier scenarios + +It is possible that services may be transported over a network where more than a single Ownership Model applies. + +The composite network diagram shown in Figure 7 shows that any combination of the Ownership Models (OM-0, OM-1, and OM-2) may be present on a typical Client Service connection in a multi-carrier network. A service may have the following Ownership Model combinations: + +- OM-0 to OM-0 + - Example Figure 7: R.1.0 (E-R1) to R.1.0 (E-R3). +- OM-0 to OM-1 + - Example Figure 7: B.1.0 (E-B2) to B.1.1 (E-R3). +- OM-0 to OM-2 + - Example Figure 7: B.2.0 (E-B4) to B.2.2 (CLE-B1). +- OM-1 to OM-1 + - Example Figure 7: R.5.1 (E-B1) to R.5.1 (E-G1). +- OM-1 to OM-2 + - Example Figure 7: R.10.1 (E-G4) to R.10.2 (CLE-R1). +- OM-2 to OM-2 + - Example Figure 7: R.9.2 (E-B3) to R.9.2 (E-G3). + +Figure 7 also demonstrates that a 'local' network edge device may carry service of any/all ownership models. + +Figure 7 demonstrates that a SP may be 'isolated' from its service end-point by multiple 'intervening' networks. + +Figure 7 demonstrates that an 'intervening' NOs edge device can support transport signals in both OM-1 and OM-2 modes; furthermore the signal may belong to different SPs. + +**R42 The following Ownership Model combinations at the edges of a service connection shall be possible:** + +**OM-0 to/from OM-0** + +**OM-0 to/from OM-1** + +**OM-0 to/from OM-2** + +**OM-1 to/from OM-1** + +**OM-1 to/from OM-2** + +**OM-2 to/from OM-2** + +**R43 A 'local' network edge device may carry service of any/all ownership models.** + +**R44 A SP may be 'isolated' from its service edge-point by multiple intervening networks.** + +**R45 An 'intervening' NOs edge device can support transport signals in both OM-1 and OM-2 modes.** + +**R46 Services at an edge device may 'belong' to different SPs.** + +![Figure 7/G.8601/Y.1391 – Composite network scenario (OM-0, OM-1 and OM-2). This diagram shows a network topology with four main service domains: SP_R (orange), SP_B (blue), SP_G (green), and SP_P (purple). Each domain contains NO (Network Operator) and TNE (Terminal Network Element) components. SP_R has NO_R and TNE E-R1, E-R2, E-R3, E-R4. SP_B has NO_B and TNE E-B2, E-B3, E-B4. SP_G has NO_G and TNE E-G1, E-G2, E-G3, E-G4. SP_P has NO_P and TNE E-P1. CPE (Customer Premises Equipment) units are connected to these TNEs and are labeled with various alphanumeric codes such as R.1.0, R.2.0, R.3.0, R.4.0, R.5.1, R.6.1, P.1.1, R.7.1, R.8.1, B.1.0, R.9.2, R.10.2, R.11.2, R.12.2, P.2.2, G.1.2, B.2.0, P.3.0, R.1.0, R.2.0, R.3.0, R.4.0, R.5.1, R.6.1, P.1.1, R.7.1, R.8.1, R.9.2, R.11.2, P.2.2, P.3.2, R.12.1, R.10.1, B.2.2, G.1.0. The diagram is labeled G.8601-Y.1391(06)_F07 at the bottom right.](c914f51f4427bc672dd0526cfc90ebe9_img.jpg) + +Figure 7/G.8601/Y.1391 – Composite network scenario (OM-0, OM-1 and OM-2). This diagram shows a network topology with four main service domains: SP\_R (orange), SP\_B (blue), SP\_G (green), and SP\_P (purple). Each domain contains NO (Network Operator) and TNE (Terminal Network Element) components. SP\_R has NO\_R and TNE E-R1, E-R2, E-R3, E-R4. SP\_B has NO\_B and TNE E-B2, E-B3, E-B4. SP\_G has NO\_G and TNE E-G1, E-G2, E-G3, E-G4. SP\_P has NO\_P and TNE E-P1. CPE (Customer Premises Equipment) units are connected to these TNEs and are labeled with various alphanumeric codes such as R.1.0, R.2.0, R.3.0, R.4.0, R.5.1, R.6.1, P.1.1, R.7.1, R.8.1, B.1.0, R.9.2, R.10.2, R.11.2, R.12.2, P.2.2, G.1.2, B.2.0, P.3.0, R.1.0, R.2.0, R.3.0, R.4.0, R.5.1, R.6.1, P.1.1, R.7.1, R.8.1, R.9.2, R.11.2, P.2.2, P.3.2, R.12.1, R.10.1, B.2.2, G.1.0. The diagram is labeled G.8601-Y.1391(06)\_F07 at the bottom right. + +Figure 7/G.8601/Y.1391 – Composite network scenario (OM-0, OM-1 and OM-2) + +![Figure 8/G.8601/Y.1391 – Composite network scenario showing service management signal flows. This diagram is identical to Figure 7 but includes additional dashed lines of various colors (red, blue, green, purple) representing service management signal flows between the different SP and NO components. The signal flows originate from the SP domains and connect to the NO domains and TNEs. The diagram is labeled G.8601-Y.1391(06)_F08 at the bottom right.](d734a6ea1b381280f043fcf70391b6db_img.jpg) + +Figure 8/G.8601/Y.1391 – Composite network scenario showing service management signal flows. This diagram is identical to Figure 7 but includes additional dashed lines of various colors (red, blue, green, purple) representing service management signal flows between the different SP and NO components. The signal flows originate from the SP domains and connect to the NO domains and TNEs. The diagram is labeled G.8601-Y.1391(06)\_F08 at the bottom right. + +Figure 8/G.8601/Y.1391 – Composite network scenario showing service management signal flows + +![Figure 9/G.8601/Y.1391 – Composite network scenarios showing CLE management signal flows. The diagram illustrates five Service Provider (SP) domains: SP_R (orange), SP_B (blue), SP_G (green), SP_P (purple), and NO_R (red). Each SP domain contains internal components like TNE, EM, SM, and NM. SP_R is connected to SP_B, SP_G, and SP_P. SP_B is connected to SP_R, SP_G, and SP_P. SP_G is connected to SP_R, SP_B, and SP_P. SP_P is connected to SP_R, SP_B, and SP_G. NO_R is connected to SP_R. NO_B (blue) is connected to SP_B and SP_P. NO_G (green) is connected to SP_G and SP_P. NO_P (purple) is connected to SP_P and SP_G. Various CPE (Customer Premises Equipment) and CLE (Central Line Equipment) units are connected to the SP and NO domains. Signal flows are indicated by solid lines (Service Management), dotted lines (Service Management Communications), and dot-dashed lines (CLE_NE management).](c5452f95f3b28f1bfe29e84fbc2e1267_img.jpg) + +Figure 9/G.8601/Y.1391 – Composite network scenarios showing CLE management signal flows. The diagram illustrates five Service Provider (SP) domains: SP\_R (orange), SP\_B (blue), SP\_G (green), SP\_P (purple), and NO\_R (red). Each SP domain contains internal components like TNE, EM, SM, and NM. SP\_R is connected to SP\_B, SP\_G, and SP\_P. SP\_B is connected to SP\_R, SP\_G, and SP\_P. SP\_G is connected to SP\_R, SP\_B, and SP\_P. SP\_P is connected to SP\_R, SP\_B, and SP\_G. NO\_R is connected to SP\_R. NO\_B (blue) is connected to SP\_B and SP\_P. NO\_G (green) is connected to SP\_G and SP\_P. NO\_P (purple) is connected to SP\_P and SP\_G. Various CPE (Customer Premises Equipment) and CLE (Central Line Equipment) units are connected to the SP and NO domains. Signal flows are indicated by solid lines (Service Management), dotted lines (Service Management Communications), and dot-dashed lines (CLE\_NE management). + +**Figure 9/G.8601/Y.1391 – Composite network scenarios showing CLE management signal flows** + +Figure 7 shows a composite view of OM-0, OM-1 and OM-2. + +Each SP has to be able to communicate all Service Management functions to its relevant end points. + +Figure 8 shows the composite view with the necessary Service Management Communications shown as dotted lines. + +Each SP has to be able to communicate all Network Element Management functions to its relevant remotely located CLE. + +Figure 9 shows this composite view with the necessary CLE\_NE management communications shown as dot-dashed lines. This includes the download of NE Software up-grades. + +The requirements of the Service and CLE\_NE management communication functions are in 8.2.2. + +# 9 Network transport technology + +This clause describes "transport technology models" and makes certain starting assumptions based on current existing standards and the management requirements. Emphasis is placed on the need to manage both single technology and multi-technology networks in a similar manner. The application of Multi-technology models to the various Ownership Models described in clause 8 is discussed in 9.4. + +## 9.1 Drawing conventions + +To assist clarity and legibility, the drawing conventions in Figure 10 are used in this clause. + +![Figure 10/G.8601/Y.1391 – Drawing conventions. The diagram illustrates two sets of protocol stack conventions. The top set shows a generic stack (A, B, B/Cv, Cv, Cv/C-x, C-x, X) being equated to a specific example stack (ETH/Enc, Enc, Enc/Sn-Xv, Sn-Xv, Sn-Xv/Sn-X, Sn-X, X). A legend indicates that a heavy line represents X separate signals. The bottom set shows another generic stack (R, S, T) being equated to a specific example stack (R/S, S, S/T, T) which is further detailed as (Sn-X/STM-n, STM-n, STM-n/ODUk-X, ODUk-X).](7133ccf78043568ca62ecbcd43628a4a_img.jpg) + +The diagram illustrates drawing conventions for protocol stacks. It is divided into two horizontal sections by a dash-dot line. + +**Top Section:** + +- Left:** A generic stack of seven layers. From top to bottom, they are labeled: A, B, B/Cv, Cv, Cv/C-x, C-x, and X. The bottom two layers, C-x and X, are separated by a heavy vertical line. To the right of the stack is an equals sign (=). +- Middle:** An expanded view of the generic stack. The layers are A/B, B, B/Cv, Cv, Cv/C-x, C-x, and X. The C-x and X layers are shown with multiple parallel lines, indicating multiple signals. A callout box points to these lines with the text: "Heavy line represents X separate signals". To the right of this stack is an equals sign (=). +- Right:** An example stack. From top to bottom, the layers are: ETH/Enc, Enc, Enc/Sn-Xv, Sn-Xv, Sn-Xv/Sn-X, Sn-X, and X. The Sn-X and X layers are separated by a heavy vertical line. To the left of this stack is the text "Example =". + +**Bottom Section:** + +- Left:** A generic stack of three layers: R, S, and T. To the right of the stack is an equals sign (=). +- Middle:** An expanded view of the generic stack. The layers are R/S, S, S/T, and T. To the right of this stack is an equals sign (=). +- Right:** An example stack. From top to bottom, the layers are: Sn-X/STM-n, STM-n, STM-n/ODUk-X, and ODUk-X. To the left of this stack is the text "Example =". + +G.8601-Y1319(06)\_F10 + +Figure 10/G.8601/Y.1391 – Drawing conventions. The diagram illustrates two sets of protocol stack conventions. The top set shows a generic stack (A, B, B/Cv, Cv, Cv/C-x, C-x, X) being equated to a specific example stack (ETH/Enc, Enc, Enc/Sn-Xv, Sn-Xv, Sn-Xv/Sn-X, Sn-X, X). A legend indicates that a heavy line represents X separate signals. The bottom set shows another generic stack (R, S, T) being equated to a specific example stack (R/S, S, S/T, T) which is further detailed as (Sn-X/STM-n, STM-n, STM-n/ODUk-X, ODUk-X). + +**Figure 10/G.8601/Y.1391 – Drawing conventions** + +## 9.2 Candidate technologies + +SONET/SDH, OTN and PDH transport technologies are considered applicable for Client Service Management. + +It is considered highly improbable that the OTN transport technology will be used to interface to Client Data signals at the Edge of the transport network. Therefore, OTN technology at the edge is not considered in this Recommendation. + +Furthermore, it is highly improbable that the MAP will be within the OTN transport technology. + +**R47 The valid transport technologies for Client Service Management (CSM) shall be:** + +- a) SONET/SDH +- b) OTN +- c) PDH + +**R48 The use of OTN transport technology at the edge shall not be applicable to CSM.** + +**R49 The sitting of the MAP within an OTN transport portion of the network is not applicable to Client Service Management.** + +## 9.3 Technology models + +Also please see clause 9.4 regarding the applicability of Technology Models to the Ownership models. + +### 9.3.1 Single technology model + +This is the simplest of the technology models since there is no hand-off between different transport technologies along the path, and therefore the signal will not be de-encapsulated within the single transport technology path. + +**R50** It shall be assumed, for Client Service Management purposes, that the client signal is encapsulated into the network transport technology at the 'edge' of the single transport technology network and transported across the entire network without being de-encapsulated until delivery at the other edge. + +### 9.3.2 Multiple technology models + +This is defined as a network where the transport path transcends two or more of the transport technology types listed in 9.2. While the minimum number of transport technology spans is two, the assumption that OTN will not be used at the edge of the transport network means that if OTN is part of the path then there will be at least three transport technology portions.1 + +Furthermore, the only standardized mappings under consideration are: + +- 1) PDH into SDH: Refer to ITU-T Rec. G.707/Y.1322. +- 2) SDH into OTN: Refer to ITU-T Rec. G.709/Y.1331. + +It is also possible that a client signal will be transported across a path where the edges are of different transport technologies. Considering the unlikely use of OTN at the edge, the only edge combinations are: + +- a) SDH:SDH +- b) PDH:PDH +- c) PDH:SDH + +The intervening transport technologies between the 'edge' networks can be of any combination provided that the standardized mappings above are adhered to. + +In the case of a and b above, it is permissible to de-encapsulate/re-encapsulate at any point along the transport path. + +In the case of c above, it is necessary to de-encapsulate the client signal from the 'receiving' transport technology and re-encapsulate it into the 'delivery' transport technology at some point along the transport path. The details of this de-encapsulation/re-encapsulation are outside the scope of this Recommendation. + +Furthermore, the MAP may be at any legitimate point within the SONET/SDH or PDH transport technologies. + +**R51** The only standardized mappings to be considered are: + +- a) PDH into SDH: Refer to ITU-T Rec. G.707/Y.1322. +- b) SDH into OTN: Refer to ITU-T Rec. G.709/Y.1331. + +**R52** Therefore, combinations of these technologies that can be considered are: + +- a) SDH:SDH +- b) PDH:PDH +- c) PDH:SDH + +--- + +1 SDH edge with OTN in the path: SDH:OTN:SDH results in three technology spans. + +- R53** In the case of 'same-edge' transport technologies (Req 52a and 52b), it is permissible for the client signal to be de-encapsulated/re-encapsulated at any point within the transport path. +- R54** In the case of 'different-edge' transport technologies (Req 52c), the client signal must be de-encapsulated from the 'receiving' edge transport technology and re-encapsulated into the 'delivery' edge transport technology. This can be at any suitable point in the path where these two technologies interface. +- R55** The MAP may be within any of the SONET/SDH or PDH transport technology portions of the overall transport network. +- R56** The management of client services transported in concatenated technologies (either contiguous or virtual concatenation) is required. This is applicable to both SONET/SDH and PDH transport technologies. + +NOTE – There is no limit to the number of 'transport technology' islands within any one transport path, provided that the combinations above in Req 51 are adhered to. + +A functional model of an example SDH:OTN:SDH network is shown in Figure 11. This shows an Ethernet Client signal being transported across a network consisting of two SDH networks separated by an OTN 'island'. The hand-off between the SDH and the OTN network technologies is shown in the functional layer diagram. Note that in this case, the SDH signal is carried over the OTN island. Other combinations of standardized technologies are of course possible. + +![Functional model of SDH:OTN:SDH network diagram showing signal flow from CPE through SDH, OTN, and SDH networks with detailed layer breakdowns.](2ae3eae1bd80a90f192f568ae246a9a6_img.jpg) + +The diagram illustrates the functional model of an SDH:OTN:SDH network. At the top, a signal flows from a CPE (Client Equipment) through three network islands: SDH (blue), OTN (red), and SDH (green). Below each island is a management node: NO\_Bu for the first SDH, NO\_Rd for the OTN, and NO\_Gn for the second SDH. The signal path is shown in detail below the islands. On the left (SDH side), the signal passes through layers labeled ETH, ETY, Enc, Sn-Xv, Sn-X, and a series of X interfaces (1, 2, ..., X). It then enters the SNC Bu (Service Network Connection) island, which contains STM-n and ODUk-n layers. The signal then passes through the OTN island (NO\_Rd), which contains STM-n and ODUk-n layers. Finally, it enters the second SDH island (NO\_Gn), which contains layers labeled Sn-X, Sn-Xv, Enc, ETY, and ETH, before reaching the destination CPE. The diagram also includes labels for G.8601-Y.1391(06)\_F11. + +Functional model of SDH:OTN:SDH network diagram showing signal flow from CPE through SDH, OTN, and SDH networks with detailed layer breakdowns. + +**Figure 11/G.8601/Y.1391 – Functional model of SDH:OTN:SDH network** + +## 9.4 Applicability of technology models to ownership models + +The technology models described above are directly applicable to all Ownership Models. + +In a multi-technology network, the hand-off combinations in 9.3.2 above must be adhered to, and as per requirement 55 the MAP may be within any of the SONET/SDH or PDH sections of the transport network. + +**R57** The boundary between NOs along the path of such a multi-technology network path can be at any of the technology interfaces. The boundary between NOs may also be within a technology span. + +Figure 12 below shows an example transport path consisting of several transport technology spans. Each of the interfaces is supported by the list in 9.3.2. Two multi-carrier example combinations for the same multi-technology path are shown in Figures 12 and 13: + +Example #1 (Figure 12) shows four carriers: + +- NO\_R (Red): PDH-SDH-PDH interfacing to +- NO\_B (Blue): SDH-OTN-SDH-PDH interfacing to +- NO\_G (Green): SDH-OTN-SDH interfacing to +- NO\_P (Purple): PDH (Single Technology) + +Example #2 (Figure 13) shows four carriers with the transport technology straddling on of the NO boundaries (between Red and Blue). This is equivalent to a same technology hand-off between the Red and Blue NOs. + +![Figure 12/G.8601/Y.1391 – Multi-technology, multi-carrier transport path combinations showing dithering technology I/F at carrier boundary. The diagram illustrates two versions of a transport path. The top version shows a continuous path with alternating segments labeled P (PDH), S (SDH), and O (OTN). The bottom version breaks this path into four distinct Network Ownership (NO) segments: NO_R (Red, containing P-S-P), NO_B (Blue, containing S-O-S-P), NO_G (Green, containing S-O-S), and NO_P (Purple, containing P). Below these segments, a series of trapezoidal icons represent technology interfaces: Eth/PDH, PDH/SDH, SDH/OTN, and OTN. The diagram is labeled 'Multi-technology path – no NO boundaries shown' and 'Multi-technology path – Example #1: four NOs, each with multi-technology spans'. A reference code 'G.8601-Y.1391(06)_F12' is in the bottom right.](4af57aad638888edf2062306f8a54a6c_img.jpg) + +Figure 12/G.8601/Y.1391 – Multi-technology, multi-carrier transport path combinations showing dithering technology I/F at carrier boundary. The diagram illustrates two versions of a transport path. The top version shows a continuous path with alternating segments labeled P (PDH), S (SDH), and O (OTN). The bottom version breaks this path into four distinct Network Ownership (NO) segments: NO\_R (Red, containing P-S-P), NO\_B (Blue, containing S-O-S-P), NO\_G (Green, containing S-O-S), and NO\_P (Purple, containing P). Below these segments, a series of trapezoidal icons represent technology interfaces: Eth/PDH, PDH/SDH, SDH/OTN, and OTN. The diagram is labeled 'Multi-technology path – no NO boundaries shown' and 'Multi-technology path – Example #1: four NOs, each with multi-technology spans'. A reference code 'G.8601-Y.1391(06)\_F12' is in the bottom right. + +**Figure 12/G.8601/Y.1391 – Multi-technology, multi-carrier transport path combinations showing dithering technology I/F at carrier boundary** + +![Diagram showing two examples of multi-technology transport paths. The top path shows four Network Operator (NO) boundaries: NO_R, NO_B, NO_G, and NO_P. Each NO contains a sequence of nodes (P, S, O, S, P) and interfaces (S, P). The bottom path shows the same sequence of nodes and interfaces, but with different technology boundaries: Eth, PDH, SDH, and OTN. The diagram illustrates how technology can straddle NO boundaries.](69b7bd65e85cdef6fdd7fb0a8194257c_img.jpg) + +Multi-technology path – Example #2: technology straddles NO boundary + +Eth +Eth/PDH +PDH +PDH/SDH +SDH +SDH/OTN +OTN + +G.8601-Y.1391(06)\_F13 + +Diagram showing two examples of multi-technology transport paths. The top path shows four Network Operator (NO) boundaries: NO\_R, NO\_B, NO\_G, and NO\_P. Each NO contains a sequence of nodes (P, S, O, S, P) and interfaces (S, P). The bottom path shows the same sequence of nodes and interfaces, but with different technology boundaries: Eth, PDH, SDH, and OTN. The diagram illustrates how technology can straddle NO boundaries. + +**Figure 13/G.8601/Y.1391 – Multi-technology, multi-carrier transport path combinations showing same technology I/F at carrier boundary** + +Based on these examples of multi-technology and multi-carrier transport network paths, it is clear that: + +- 1) The Multi-technology Models place no restriction on the Ownership Models. +- 2) Similarly, the Ownership Models place no restriction on the Multi-technology models. +- 3) The boundary between neighbouring NOs can be at any point along the transport path. + - a) A boundary occurring in the 'mid-span' of a given technology is the same as having that technology on both sides of the NO handoff. See Figure 12. + +Figure 14 shows an example transport path consisting of several transport technology spans. Each of the interfaces are supported by the list in 9.3.2. + +NOTE – In this example the start and end of the path have DIFFERENT transport technologies. + +In this simple scenario, the client signal MUST be de-encapsulated at a point in the path where it can be re-encapsulated into the transport technology of the delivery edge. This is at point A in Figure 14. + +![Diagram showing a transport path with different transport technology edges. The path consists of nodes P, S, O, S, and a client node C. Point A is marked on the P node. The path shows various interfaces: C/PDH, P, C/SDH, S, SDH/OTN, O, and C/SDH. The diagram illustrates the need for de-encapsulation and re-encapsulation at point A.](55136bc716146672fc680fa05989f1d2_img.jpg) + +C +C/PDH +P +C/SDH +S +SDH/OTN +O +C/SDH + +G.8601-Y.1391(06)\_F14 + +Diagram showing a transport path with different transport technology edges. The path consists of nodes P, S, O, S, and a client node C. Point A is marked on the P node. The path shows various interfaces: C/PDH, P, C/SDH, S, SDH/OTN, O, and C/SDH. The diagram illustrates the need for de-encapsulation and re-encapsulation at point A. + +**Figure 14/G.8601/Y.1391 – Example of 'Different-transport-technology' edges** + +# **10 Applicable client service types** + +**R58 The following Point-to-point Client Service types are required to be managed:** + +- a) Ethernet (Private Line)** +- b) Fibre Channel (Private Line)** +- c) PDH (Private Line)** + - 1) DS1** + - 2) DS3** + - 3) E1** + - 4) E3** + +# **11 Management communication functions** + +The CSM system will have communication functions to perform Client Service, and remotely located CLE management. These communication functions will be between the transport network edge(s) and the Management Access Point (MAP). This clause outlines these communication functions but does not define the actual management function or the content of such communications. This is outside the scope of this Recommendation. + +The CSM system will be required to perform two distinct management functions: + +- Management of the Service at the Service Edge: + - Applies to Ownership Model 1 (OM-1), Ownership Model 2 (OM-2) and the single carrier case (OM-0). +- Management of the remotely located CLE\_NE: + - Applies only to Ownership Model 2. + +The CSM system will be required to convey three types of management information: + +- Performance information. +- Commands and responses. +- Autonomous notification. + +Inspection of the basic requirements and the Ownership Models clearly shows that there are several distinct management communication functions for effective Client Service/CLE\_NE Management. + +- a) Performance Monitoring (Service) Edge to MAP +- b) Performance Monitoring (Service) Edge to Edge +- c) Service Status Edge to Edge +- d) Service Status Edge to MAP +- e) C/R (Service) MAP to Edge (command); Edge to MAP (response) +- f) C/R (Equipment) MAP to Edge (command); Edge to MAP (response) +- g) Autonomous Notification (service) Edge to MAP +- h) Autonomous Notification (equip) Edge to MAP + +To ensure consistent operational methods, the information flows in the following clauses and depicted in Figures 8 and 9 are applicable to both the multiple-carrier and the single carrier model. + +All mentions of MAP in the following refer to the Management Access Point within the Service Providers network which may be isolated from either end of the Edge-to-edge SONET/SDH path. + +## 11.1 Performance information + +Performance monitoring messages convey (single-ended) service metrics computed at an Edge device. These messages inform the MAP of the Edge service metrics. They also inform near-end Edge of far-end Edge service metrics. + +Performance monitoring signals are sent periodically by the Edge device. These messages are therefore considered as scheduled. + +The performance messages from the edge will include: + +- a) Monitoring and reporting of Access Link Termination: + - i) This will monitor and report metrics from the termination function performed at the Access Link Interface. +Examples are: Frames Received, Frames Transmitted, Frames Dropped, Frame throughput. +- b) Monitoring and reporting of Mapping Function: + - i) This will monitor and report metrics from the encapsulation of the service into transport. +Examples are: Framing statistics, mapping errors, code violations. +- c) Monitoring and reporting of Path related functions: + - i) This will monitor and report metrics from the path termination function. +Examples are: remote defects, error counts. +- d) Monitoring and reporting of Service Status: + - i) This will be an indication of the health of the service. Service status indicates that the service is in one of four states. + - 1) Operational: Service is operating within the bounds of the established SLA. + - 2) Degraded: Service is operational; however, its performance is degraded in reference to the SLA. + - 3) Failure: Service failure has occurred and is not operational. + - 4) In-test: Service is under control of service/network operator for maintenance actions. + +The Service Status is generated by each Edge on a service by service basis. The Service Status is generated by comparing local edge-service PMs and remote edge-service PMs (conveyed between edges) to formulate edge-to-edge service PMs. These edge-to-edge service PMs are then compared to SLA thresholds to determine the operational disposition of the service. + +Service failure may be attributed to path level defects, service failures at the client link, or significant disparity in achieving adherence to the SLA. + +**R59 It is required to regularly report Performance Metrics from Edge-to-Edge for each Service instance and for all Ownership Models.** + +**R60 It is required to regularly report Performance Metrics from the Edge to the MAP for each Service instance and for all Ownership Models.** + +**R61 The regularity of the Performance reports is TBD.** + +**R62 It is required to regularly report Service Status (SS) from Edge-to-Edge for each Service instance and for all Ownership Models.** + +**R63 It is required to regularly report Service Status (SS) from Edge to MAP for each Service instance and for all Ownership Models.** + +**R64** The regularity of SS reports is TBD. + +## **11.2 Commands and responses** + +### **Command signals** + +- Convey a request for an action. +- Originate at only the MAP. +- Are processed only by Edge Device. They are not processed at the MAP. +- Are unscheduled messages. They can occur at any time. + +Examples of command signals include service configuration query. + +### **Response signals** + +- Result from a received command. +- Originate only at the Edge Device. +- Are unscheduled messages. They can occur at any time. + +**R65** It is required to convey Command signals from MAP to Edge for purposes of Service Management. This shall apply to each service instance and all Ownership Models. + +**R66** It is required to convey Command signals from MAP to Edge CLE for purposes of CLE\_NE management. This shall apply to each CLE\_NE and shall apply to Ownership Model 2. + +**R67** It is required to convey Response signals from Edge to MAP for purposes of service Management. This shall apply to each Service instance and for all Ownership Models. + +**R68** It is required to convey Response signals from Edge to MAP for purposes of CLE management. This shall apply to each CLE\_NE and shall apply to Ownership Model 2. + +## **11.3 Autonomous notification** + +Autonomous Notification: + +- Provides a mechanism for reporting anomalous service conditions. +- Provides a mechanism for reporting non-service affecting conditions. + - i) Examples include equipment alarms such as 'fan failure', 'cabinet open', 'environmental alarm', etc. +- Typically indicates a service affecting condition (e.g., service alarm indications). +- Are unscheduled messages. They can occur at any time. + +Examples of service affecting conditions are a client signal failure or service remote fault. Other examples include service activation status, and loopback invocations. + +**R69** It is required to convey Autonomous Notifications from Edge to MAP for purposes of Service management. This shall apply to each Service instance and all Ownership Models. + +**R70** It is required to convey Autonomous Notifications from Edge to MAP for purposes of CLE management. This shall apply to each CLE\_NE and shall apply to Ownership Model 2. + +## **11.4 Remotely located NE (CLE) software upgrades** + +Because in the Ownership Model 2 scenario, the SP does not have direct management connectivity to the Edge NE, the CSM needs to be able to perform software upgrades to this CLE\_NE. + +#### **R71 The CSM shall be capable of communicating to the remotely located (CLE) NE for purposes of software upgrades.** + +NOTE – In OM-1 and in the single carrier case (OM-0), management of the 'edge' NE will be performed by the NO in whose network the edge NE resides, and therefore software updates from the MAP will not be required. + +# **12 Testing requirements** + +There is a need by some carriers to be able to perform certain remote testing procedures in order to streamline the deployment and delivery of broadband services. The current service model that is expected to be employed for the delivery of Ethernet private line (EPL) services is that used to manage, test and deploy DS-1 private line services today. + +#### **R72 It is required that Service testing be performed from a centralized location.** + +#### **R73 It is required that testing requests and testing result collection be performed under the control of a centralized test operation system.** + +#### **R74 For certain tests it is required that the test set, under the control OS, may issue commands to a far-end system to, for example, initiate a loopback.** + +Further testing requirements are for further study. + + + +## ITU-T Y-SERIES RECOMMENDATIONS + +## GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS + +## GLOBAL INFORMATION INFRASTRUCTURE + +| | | +|-------------------------------------------|-------------| +| General | Y.100–Y.199 | +| Services, applications and middleware | Y.200–Y.299 | +| Network aspects | Y.300–Y.399 | +| Interfaces and protocols | Y.400–Y.499 | +| Numbering, addressing and naming | Y.500–Y.599 | +| Operation, administration and maintenance | Y.600–Y.699 | +| Security | Y.700–Y.799 | +| Performances | Y.800–Y.899 | + +## INTERNET PROTOCOL ASPECTS + +| | | +|--------------------------------------------------------------------|----------------------| +| General | Y.1000–Y.1099 | +| Services and applications | Y.1100–Y.1199 | +| Architecture, access, network capabilities and resource management | Y.1200–Y.1299 | +| Transport | Y.1300–Y.1399 | +| Interworking | Y.1400–Y.1499 | +| Quality of service and network performance | Y.1500–Y.1599 | +| Signalling | Y.1600–Y.1699 | +| Operation, administration and maintenance | Y.1700–Y.1799 | +| Charging | Y.1800–Y.1899 | + +## NEXT GENERATION NETWORKS + +| | | +|-------------------------------------------------------------------|---------------| +| Frameworks and functional architecture models | Y.2000–Y.2099 | +| Quality of Service and performance | Y.2100–Y.2199 | +| Service aspects: Service capabilities and service architecture | Y.2200–Y.2249 | +| Service aspects: Interoperability of services and networks in NGN | Y.2250–Y.2299 | +| Numbering, naming and addressing | Y.2300–Y.2399 | +| Network management | Y.2400–Y.2499 | +| Network control architectures and protocols | Y.2500–Y.2599 | +| Security | Y.2700–Y.2799 | +| Generalized mobility | Y.2800–Y.2899 | + +For further details, please refer to the list of ITU-T Recommendations. + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|--------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | 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b/marked/G/T-REC-G.874-202010-I_PDF-E/raw.md @@ -0,0 +1,2426 @@ + + +International Telecommunication Union + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.874** + +(10/2020) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital networks – Optical transport networks + +# --- **Management aspects of optical transport network elements** + +Recommendation ITU-T G.874 + +![ITU logo: A globe with a red lightning bolt and the text 'ITU International Telecommunication Union'.](84a1d09fb489061482111515543b60dc_img.jpg) + +The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a blue globe with a red lightning bolt striking across it. To the right of the globe, the text "ITU" is written in a large, bold, blue font, with "International Telecommunication Union" in a smaller, blue font underneath. + +ITU logo: A globe with a red lightning bolt and the text 'ITU International Telecommunication Union'. + +## ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| General aspects | G.800–G.809 | +| Design objectives for digital networks | G.810–G.819 | +| Synchronization, quality and availability targets | G.820–G.829 | +| Network capabilities and functions | G.830–G.839 | +| SDH network characteristics | G.840–G.849 | +| Management of transport network | G.850–G.859 | +| SDH radio and satellite systems integration | G.860–G.869 | +| Optical transport networks | G.870–G.879 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## Recommendation ITU-T G.874 + +# Management aspects of optical transport network elements + +# Summary + +Recommendation ITU-T G.874 addresses management aspects of optical transport network (OTN) elements containing transport functions of one or more of the layer networks of the OTN. The management of optical layer networks is separable from that of its client layer networks so that the same means of management can be used regardless of the client. The management functions for fault management, configuration management (CM) and performance monitoring are specified. + +Recommendation ITU-T G.874 (2008) updated the management information (MI) to align with Recommendation ITU-T G.798, reorganized the sections to align with the structure of Recommendation ITU-T G.7710/Y.1701, and replaced the generic text with pointers to Recommendation ITU-T G.7710/Y.1701. + +Recommendation ITU-T G.874 (2010) added the management of new transport functions that were introduced in ITU-T G.798 (2010), including OPSMnk\_TT, OPSM/OTUk a\_A, and ODUk for k=0, 2e, 4, and flex. + +Recommendation ITU-T G.874 (2013) added the management of hitless adjustment of ODUflex(GFP) (HAO), automatic protection switching (APS), application codes and performance management (PM) data collection. + +Recommendation ITU-T G.874 (2017) added a description to cover OTUCn GCC0, added the application code related MI signals, updated the MI signals for ODU2eP/FC-1200\_A, OSM256.4/CBRx\_A, OSx/CBRx-b\_A\_Sk and OSx/CBRx-c\_A\_Sk, removed the nDelay, nES, and fES primitives, moved the description of O.MN, O.MSN, and O.NE to the convention clause, updated the default values of DEGThr and DEGM, updated Appendix III to align with Table 15-9 of ITU-T G.709/Y.1331 (2016), and removed the adaptation function activation and MI\_Active to align with ITU-T G.798. + +Recommendation ITU-T G.874 (2020) aligns with the latest editions of ITU-T G.709 and ITU-T G.798, and harmonizes generic requirements with clauses 8 and 10 of ITU-T G.7710/Y.1701 . + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|---------------------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.874 | 2001-11-29 | 15 | 11.1002/1000/5607 | +| 2.0 | ITU-T G.874 | 2008-03-29 | 15 | 11.1002/1000/9376 | +| 3.0 | ITU-T G.874 | 2010-07-29 | 15 | 11.1002/1000/10881 | +| 3.1 | ITU-T G.874 (2010) Cor. 1 | 2011-06-06 | 15 | 11.1002/1000/11121 | +| 3.2 | ITU-T G.874 (2010) Amd. 1 | 2012-04-06 | 15 | 11.1002/1000/11493 | +| 3.3 | ITU-T G.874 (2010) Amd. 2 | 2012-10-29 | 15 | 11.1002/1000/11792 | +| 4.0 | ITU-T G.874 | 2013-08-29 | 15 | 11.1002/1000/11987 | +| 4.1 | ITU-T G.874 (2013) Amd. 1 | 2015-08-13 | 15 | 11.1002/1000/12559 | +| 5.0 | ITU-T G.874 | 2017-08-13 | 15 | 11.1002/1000/13304 | +| 6.0 | ITU-T G.874 | 2020-10-29 | 15 | 11.1002/1000/14500 | + +## Keywords + +Optical transport network, OTN. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +# FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +# INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2021 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +# Table of Contents + +###### Page + +| | | | +|------|------------------------------------------------------------------------|----| +| 1 | Scope ..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions ..... | 3 | +| 3.1 | Terms defined elsewhere ..... | 3 | +| 3.2 | Terms defined in this Recommendation..... | 4 | +| 4 | Abbreviations and acronyms ..... | 4 | +| 5 | Conventions ..... | 9 | +| 6 | Optical transport network management architecture..... | 10 | +| 6.1 | OTN management network architecture ..... | 10 | +| 6.2 | Optical transport network equipment management architecture..... | 15 | +| 6.3 | Information flows over management points..... | 16 | +| 7 | Fault management..... | 16 | +| 7.1 | Fault management applications ..... | 16 | +| 7.2 | Fault management functions..... | 17 | +| 8 | Configuration management ..... | 31 | +| 8.1 | Hardware ..... | 31 | +| 8.2 | Software..... | 32 | +| 8.3 | Protection switching ..... | 32 | +| 8.4 | Trail termination..... | 32 | +| 8.5 | Adaptation ..... | 36 | +| 8.6 | Connection..... | 49 | +| 8.7 | DEG thresholds ..... | 50 | +| 8.8 | ZZZ_Reported ..... | 50 | +| 8.9 | Alarm severity ..... | 50 | +| 8.10 | Alarm reporting control..... | 51 | +| 8.11 | Performance management thresholds..... | 51 | +| 8.12 | Tandem connection monitoring activations ..... | 51 | +| 8.13 | Date and time..... | 51 | +| 8.14 | Control function..... | 52 | +| 8.15 | Application identifier management ..... | 52 | +| 8.16 | Media element management..... | 53 | +| 9 | Account management ..... | 54 | +| 10 | Performance management ..... | 54 | +| 10.1 | Performance management applications ..... | 54 | +| 10.2 | Performance management functions ..... | 57 | +| 11 | Security management..... | 60 | +| | Appendix I – Management information for configuration management ..... | 61 | + +| | | +|---------------------------------------------------------------------------------------|----| +| Appendix II – Management information for performance management ..... | 63 | +| Appendix III – Mapping between OPUk payload type and adaptation atomic function ..... | 64 | + +## Recommendation ITU-T G.874 + +# Management aspects of optical transport network elements + +# 1 Scope + +This Recommendation addresses management aspects of optical transport network (OTN) elements containing transport functions of one or more layer networks of the OTN as described in [ITU-T G.709]. The management of optical layer networks is separable from that of its client layer networks; therefore the same means of management can be used regardless of the client. This Recommendation specifies the management functions for fault management, configuration management (CM), account management, performance management (PM) and security management. + +This Recommendation describes the management network organizational model for communication between an element management layer (EML) operations system (OS) and the optical equipment management function (EMF) within an OTN network element (O.NE). + +The architecture described in this Recommendation for the management of OTNs is based upon the following considerations. + +- The management view of network element (NE) functional elements should be uniform whether those elements form part of an inter-domain interface (IrDI) or part of an intra-domain interface (IaDI). Those properties necessary to form such a uniform management view are to be included in this Recommendation. +- OTN layer network entities (OLNEs) include trail termination (TT), adaptation and connection functions as described in [ITU-T G.872] for the OTN digital layer. +- An NE may only contain OLNEs. +- An NE may contain both OLNEs and client layer network entities (CLNEs). +- CLNEs are managed as part of their own logical domain [e.g., a synchronous digital hierarchy (SDH) management network]. +- CLNEs and OLNEs may or may not share a common message communication function (MCF) and management application function (MAF) depending on application. +- CLNEs and OLNEs may or may not share the same agent. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.695] Recommendation ITU-T G.695 (2018), *Optical interfaces for coarse wavelength division multiplexing applications*. +- [ITU-T G.698.2] Recommendation ITU-T G.698.2 (2018), *Amplified multichannel dense wavelength division multiplexing applications with single channel optical interfaces*. +- [ITU-T G.7041] Recommendation ITU-T G.7041/Y.1303 (2016), *Generic framing procedure*. +- [ITU-T G.7044] Recommendation ITU-T G.7044/Y.1347 (2011), *Hitless adjustment of ODUflex(GFP)*. + +- [ITU-T G.709] Recommendation ITU-T G.709/Y.1331 (2020), *Interfaces for the optical transport network.* +- [ITU-T G.709.1] Recommendation ITU-T G.709.1/Y.1331.1 (2018), *Flexible OTN short-reach interfaces.* +- [ITU-T G.784] Recommendation ITU-T G.784 (2008), *Management aspects of synchronous digital hierarchy (SDH) transport network elements.* +- [ITU-T G.798] Recommendation ITU-T G.798 (2017), *Characteristics of optical transport network hierarchy equipment functional blocks.* +- [ITU-T G.806] Recommendation ITU-T G.806 (2012), *Characteristics of transport equipment – Description methodology and generic functionality.* +- [ITU-T G.826] Recommendation ITU-T G.826 (2002), *End-to-end error performance parameters and objectives for international, constant bit-rate digital paths and connections.* +- [ITU-T G.870] Recommendation ITU-T G.870/Y.1352 (2016), *Terms and definitions for optical transport networks.* +- [ITU-T G.872] Recommendation ITU-T G.872 (2019), *Architecture of optical transport networks.* +- [ITU-T G.873.1] Recommendation ITU-T G.873.1 (2017), *Optical transport network: Linear protection.* +- [ITU-T G.875] Recommendation ITU-T G.875 (2020), *Optical transport network: Protocol-neutral management information model for the network element view.* +- [ITU-T G.959.1] Recommendation ITU-T G.959.1 (2018), *Optical transport network physical layer interfaces.* +- [ITU-T G.7710] Recommendation ITU-T G.7710/Y.1701 (2020), *Common equipment management function requirements.* +- [ITU-T G.7712] Recommendation ITU-T G.7712/Y.1703 (2019), *Architecture and specification of data communication network.* +- [ITU-T G.8121] Recommendation ITU-T G.8121/Y.1381 (2018), *Characteristics of MPLS-TP equipment functional blocks.* +- [ITU-T M.20] Recommendation ITU-T M.20 (1992), *Maintenance philosophy for telecommunication networks.* +- [ITU-T M.60] Recommendation ITU-T M.60 (1993), *Maintenance terminology and definitions.* +- [ITU-T M.2120] Recommendation ITU-T M.2120 (2002), *International multi-operator paths, sections and transmission systems fault detection and localization procedures.* +- [ITU-T M.3010] Recommendation ITU-T M.3010 (2000), *Principles for a telecommunications management network.* +- [ITU-T M.3100] Recommendation ITU-T M.3100 (2005), *Generic network information model.* +- [ITU-T X.700] Recommendation ITU-T X.700 (1992), *Management framework for Open Systems Interconnection (OSI) for CCITT applications.* +- [ITU-T X.701] Recommendation ITU-T X.701 (1997) | ISO/IEC 10040:1998, *Information technology – Open Systems Interconnection – Systems management overview.* + +# **3 Definitions** + +## **3.1 Terms defined elsewhere** + +This Recommendation uses the following terms defined elsewhere: + +### **3.1.1 Terms defined in [ITU-T G.784]** + +#### **3.1.1.1 Data communication channel (DCC).** + +### **3.1.2 Terms defined in [ITU-T G.806]** + +#### **3.1.2.1 Atomic function.** + +#### **3.1.2.2 Management point (MP).** + +### **3.1.3 Terms defined in [ITU-T G.870]** + +#### **3.1.3.1 Intra-domain interface (IaDI).** + +#### **3.1.3.2 Inter-domain interface (IrDI).** + +### **3.1.4 Terms defined in [ITU-T G.7710]** + +#### **3.1.4.1 Local craft terminal (LCT).** + +#### **3.1.4.2 Management application function (MAF).** + +### **3.1.5 Terms defined in [ITU-T G.7712]** + +#### **3.1.5.1 Data communication network (DCN).** + +#### **3.1.5.2 Embedded communication channel (ECC).** + +### **3.1.6 Terms defined in [ITU-T M.60]** + +#### **3.1.6.1 Message communication function (MCF).** + +### **3.1.7 Terms defined in [ITU-T M.3010]** + +#### **3.1.7.1 Network element.** + +#### **3.1.7.2 Network element function.** + +#### **3.1.7.3 Operations system (OS).** + +#### **3.1.7.4 Q interface.** + +#### **3.1.7.5 Workstation function.** + +### **3.1.8 Terms defined in [ITU-T M.3100]** + +- 3.1.8.1** Aggregate audible/visual indicators. +- 3.1.8.2** Alarm reporting. +- 3.1.8.3** Alarm reporting control. +- 3.1.8.4** Inhibited. +- 3.1.8.5** Managed entity. +- 3.1.8.6** Managed resource. +- 3.1.8.7** Managed resource-specific/unit audible/visual indicator. +- 3.1.8.8** Management interface. +- 3.1.8.9** Persistence interval. +- 3.1.8.10** Qualified problem. +- 3.1.8.11** Timed interval. +- 3.1.9** Terms defined in [ITU-T X.700] + - 3.1.9.1** Managed object. +- 3.1.10** Terms defined in [ITU-T X.701] + - 3.1.10.1** Agent. + - 3.1.10.2** Managed object class. + - 3.1.10.3** Manager. + +## **3.2 Terms defined in this Recommendation** + +None. + +# **4 Abbreviations and acronyms** + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|------------|-----------------------------------| +| AcPT | Accepted Payload Type | +| AcSTAT | Accepted Status | +| AcTI | Accepted Trace Identifier | +| AdminState | Administrative State | +| AIS | Alarm Indication Signal | +| ALM | Alarm | +| AP | Access Point | +| APR | Automatic Power Reduction | +| APRCntrl | Automatic Power Reduction Control | +| APS | Automatic Protection Switching | +| ARC | Alarm Reporting Control | +| AST | Alarm Status | +| ASY | Alarm Synchronization | + +| | | +|----------|-------------------------------------------------------------------------| +| AutoMS | Automatic configuration of the Multiplex Structure | +| BDI-O | Backward Defect Indicator Overhead | +| BDI-P | Backward Defect Indicator Payload | +| BIAE | Backward Incoming Alignment Error | +| BIP | Bit Interleaved Parity | +| CBRx | Constant Bit Rate signal of bit rate [range] x | +| CBRx-a | Constant Bit Rate signal of bit rate [range] x -Asynchronous mapping | +| CBRx-b | Constant Bit Rate signal of bit rate [range] x -Bit synchronous mapping | +| CLNE | Client Layer Network Entity | +| CM | Configuration Management | +| COMMS | Communications | +| COMMS OH | Communications Overhead | +| CP | Connection Point | +| CPL | Current Problem List | +| CSACM | Calendar Slot Availability Count Mismatch | +| CSF | Client Signal Failure | +| CTP | Connection Termination Point | +| CWDM | Coarse Wavelength Division Multiplexing | +| DCC | Data Communication Channel | +| DCN | Data Communication Network | +| DS | Defect Second | +| DS-O | Defect Second Overhead | +| DS-P | Defect Second Payload | +| DEG | Degraded | +| DEGM | DEG consecutive 1 s Monitoring intervals | +| DEGThr | DEG 1 s EBC Threshold | +| DTDL | Defect Type and Defect Location | +| DWDM | Dense Wavelength Division Multiplexing | +| EBC | Errored Block Count | +| ECC | Embedded Communication Channel | +| EMF | Equipment Management Function | +| EML | Element Management Layer | +| ETH | Ethernet | +| ETH-C | Ethernet connection | +| ExDAPI | Expected Destination Access Point Identifier | +| ExMSI | Expected Multiplex Structure Identifier | +| ExSAPI | Expected Source Access Point Identifier | + +| | | +|-----------|------------------------------------------------------------| +| ExtCMD | External Command | +| F | Far end | +| FCAPS | Fault, Configuration, Accounting, Performance and Security | +| FEC | Forward Error Correction | +| FECEn | Forward Error Correction Enabled | +| FFS | For Further Study | +| FlexO | Flexible Optical transport network | +| FOP-PM | Failure of Protocol; Provisioning Mismatch | +| FOP-NR | Failure of Protocol; No Response | +| GCC | General Communication Channel | +| GCCAccess | General Communication Channel Access | +| GCCCont | General Communication Channel Continue | +| GetAcTI | Get Accepted trail Trace Identifier | +| GFC | Generic Flow Control | +| GIDM | Group Identification Mismatch | +| HAO | Hitless Adjustment of ODUflex(GFP) | +| HEC | Header Error Control | +| HO | High Order | +| HoTime | Hold-off Time | +| IaDI | Intra-Domain Interface | +| IAE | Incoming Alignment Error | +| IrDI | Inter-Domain Interface | +| LAN | Local Area Network | +| LCK | Locked | +| LCS | Loss of Character Synchronization | +| LCT | Local Craft Terminal | +| LFD | Loss of Frame Delineation | +| LOA | Loss of Alignment | +| LOF | Loss of Frame | +| LOFLOM | Loss of Frame and Loss of Multiframe | +| LOG | Logging | +| LOL | Loss Of Lane | +| LOM | Loss Of Multiframe | +| LOOMFI | Loss of OPU Multiframe Indication | +| LOS | Loss Of Signal | +| LOS-O | Loss Of Signal Overhead | +| LOS-P | Loss Of Signal Payload | + +| | | +|---------|--------------------------------------------------------------------------------------| +| LSS | Loss of pseudo-random bit Sequence lock | +| LTC | Loss of Tandem Connection | +| MAF | Management Application Function | +| MCC | Maintenance Communication Channel | +| MCF | Message Communication Function | +| MCN | Management Communication Network | +| MI | Management Information | +| MIB | Management Information Base | +| MO | Managed Object | +| MP | Management Point | +| MPI-R | Main Path Interface-Reference point | +| MPI-S | Main Path Interface-S interface | +| MS | Multiplex Session | +| MSIM | Multiplex Structure Identifier Mismatch | +| NE | Network Element | +| NEA | Network Element Alarm | +| NEF | Network Element Function | +| NT | Network Termination | +| OCh | Optical Channel | +| OCI | Open Connection Indication | +| ODTUjk | Optical Data Tributary Unit j into k | +| ODU | Optical Data Unit | +| ODUCn | Optical Data Unit-Cn | +| ODUCnP | Optical Data Unit-Cn, Path | +| ODUi | Optical Data Unit of level i | +| ODU[i]j | Optical Data Unit of level j and i (i is optional; i < j) | +| ODUj | Optical Data Unit of level j | +| ODUk | Optical Data Unit of level k, k=0, 1, 2, 2e, 3, 4, flex | +| ODUkP | Optical Data Unit of level k, Path, k=0, 1, 2, 2e, 3, 4, flex | +| ODUkT | Optical Data Unit of level k, Tandem connection sub-layer, k=0, 1, 2, 2e, 3, 4, flex | +| ODUkTm | ODUkT non-intrusive monitoring function, k=0, 1, 2, 2e, 3, 4, flex | +| ODUT | Optical Data Unit, Tandem | +| OLNE | OTN Layer Network Entity | +| O.MN | OTN Management Network | +| OMS-O | Optical Multiplex Section – Overhead | +| O.MSN | OTN Management Subnetwork | + +| | | +|----------|-----------------------------------------------------------------------------| +| O.NE | OTN Network Element | +| OOS | Overhead Signal | +| OPS | Operational State | +| OS | Operations System | +| OSC | Optical Supervisory Channel | +| OSI | Open Systems Interconnection | +| OTH | Open Transport Hierarchy | +| OTM | Optical Transport Module | +| OTN | Optical Transport Network | +| OTS | Optical Transmission Section | +| OTSi | Optical Tributary Signal | +| OTSiG | Optical Tributary Signal Group | +| OTUCn | Optical Transport Unit-Cn | +| OTUk | Optical Transport Unit-k | +| OTU | Optical Transmission Unit | +| OTUk | Optical Transmission Unit of level k, k=1, 2, 3, 4 | +| OTUkV | Optical Transmission Unit of level k, functional standardized, k=1, 2, 3, 4 | +| PCS | Physical Coding Sublayer | +| PLM | Payload Mismatch | +| PM | Performance Management | +| PMC | Performance Monitoring Clock | +| PMM | Physical layer Map Mismatch | +| PPP | Point-to-Point Protocol | +| ProtType | Protection Type | +| PRBS | Pseudo-Random Bit Sequence | +| PRS | Persistency | +| PT | Payload Type | +| REP | Reportable failure | +| RSn | Regenerator Section of level n | +| RTC | Real-Time Clock | +| RTR | Reset Threshold Report | +| SCC | Signalling Communication Channel | +| SCN | Signalling Communication Network | +| SDH | Synchronous Digital Hierarchy | +| SEV | Severity assignment | +| Sk | Sink | +| So | Source | + +| | | +|-------------|-------------------------------------------------------| +| SSF-O | Server Signal Fail Overhead | +| SSF-P | Server Signal Fail Payload | +| STA | Station Alarm | +| STAT | Status | +| STM-N | Synchronous Transfer Mode-N | +| TAN | TMN Alarm event Notification | +| TCM | Tandem Connection Monitoring | +| TCMCP | TCM Control Point | +| TCP | Termination Connection Point | +| TEP | TMN Event Pre-processing alarm | +| TIM | Trail trace Identifier Mismatch | +| TIMActDis | Trace Identifier Mismatch consequent Actions Disabled | +| TIMDetMo | Trace Identifier Mismatch Detection Mode | +| TMN | Telecommunications Management Network | +| TP | Termination Point | +| TPusgActive | TP usage measurement Active | +| TR | Threshold Report | +| TSE | Test Sequence Error | +| TT | Trail Termination | +| TTI | Trail Trace Identifier | +| TTP | Trail Termination Point | +| TxMSI | Transmitted Multiplex Structure Identifier | +| TxTI | Transmitted trail Trace Identifier | +| UNA | Unit Alarm | +| VPI | Virtual Path Identifier | +| WDM | Wavelength Division Multiplexing | + +# 5 Conventions + +An O.MN is a subset of a telecommunications management network (TMN) that is responsible for managing those parts of an NE that contain OLNEs. An O.MN may be subdivided into a set of O.MSNs. + +An O.MSN consists of a set of separate OTN ECCs and associated intra-site data communication links that have been interconnected to form a DCN within any given OTN transport topology. + +An O.NE is that part of an NE that contains entities from one or more OTN layer networks. An O.NE may therefore be a standalone physical entity or a subset of an NE. It supports at least network element functions (NEFs) and may also support an OS function or a mediation function. It contains managed objects (MOs), an MCF and an MAF. The functions of an O.NE may be contained within an NE that also supports other layer networks. These layer network entities are considered to be managed separately from OTN entities. As such, they are not part of the O.MSN or O.MN. + +# 6 Optical transport network management architecture + +See clause 6 of [ITU-T G.7710] for the generic architecture for managing transport equipment. + +The transport layer networks of the OTN are described in [ITU-T G.872], [ITU-T G.798] and [ITU-T G.709]. The management of the OTN layer networks is separable from that of its client layer networks so that the same means of management can be used regardless of the client. + +## 6.1 OTN management network architecture + +### 6.1.1 Relationship between telecommunications management network, O.MN and O.MSN + +The inter-relationship between a management network, its subnetworks and a TMN as generically described in clause 6.1.1 of [ITU-T G.7710] is applicable to OTN. + +This Recommendation specifies the O.MN and O.MSNs. + +### 6.1.2 Access to the O.MSN + +See clause 6.1.2 of [ITU-T G.7710] for the generic requirements. + +### 6.1.3 O.MSN requirements + +See clause 6.1.3 of [ITU-T G.7710] for the generic requirements. + +The main ECC for OTN is considered to be the communications overhead (COMMS OH) in the optical supervisory channel (OSC), see clause 15.1.7 of [ITU-T G.709]. The COMMS OH is carried in the OSC in OTN optical networking interfaces, type I. This COMMS-based ECC is equivalent to the SDH synchronous transfer mode-N (STM-N) multiplex session-data communication channel (MS-DCC). A general communication channel (GCC) is typically used as an ECC when a remote CPE or a remote subnetwork has to be reached, and on OTN point-to-point interfaces of type I and type II only. + +In addition, the O.MSN allows for the support of the following: + +- 1) The OTN allows the ECC options of using the general management COMMS OH or the GCCs. + - All O.NEs, which are not connected through an Ethernet local area network (LAN) with a co-located NE, are required to terminate the COMMS OH. + - All O.NEs, which are not connected through an Ethernet LAN with a co-located NE, are required to terminate the optical transmission unit of level k (OTUk; k=1, 2, 3, 4) GCC0 to connect to O.NEs [e.g., open transport hierarchy (OTH) network terminations (NTs)] that are equipped with OTN point-to-point interfaces of type I and type II only. +- 2) OTN inter-site communications. The inter-site or inter-office communications link between O.NEs will normally be formed from the COMMS OH. +- 3) OTN intra-site communications. Within a particular site, O.NEs may communicate via an intra-site COMMS OH or via an LAN. + +The use of GCCs and COMMS OH for management communications is described in clauses 6.1.3.1 and 6.1.3.2. + +#### 6.1.3.1 General communication channels + +The OTN supports three GCCs: + +- 1) GCC0; +- 2) GCC1; +- 3) GCC2. + +Figure 6-1 illustrates a network scenario consisting of two operators. Operator B provides an optical data unit of level k (ODUk; k=0, 1, 2, 2e, 3, 4, flex) service to operator A (i.e., operator B transports the ODUk frame that begins and ends in operator A's domain). According to [ITU-T G.709], only a subset of the ODUk overhead (e.g., path monitoring) is guaranteed to be passed through operator B's network. Other overheads, such as tandem connection monitoring (TCM) overhead, as well as GCC1 and GCC2 are subject to the service level agreement made between operator A and operator B. + +![](c85ded401105f62f2d6ff26b3b5eb4af_img.jpg) + +| Operator A                      Operator B                      Operator A | | | +|-----------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------| +| | 3R    3R    3R | 3R    3R    3R | +| | OTU k [V]/
OTUC n OTU k /
OTUC n OTU k [V]/
OTUC n OTU k /
OTUC n OTU k [V]/
OTUC n | | +| | ODU k /ODUC n | | +| GCC0 Channel never crosses administrative domains since it operates between OTU k termination points | GCC0    GCC0    GCC0    GCC0    GCC0 | | +| Example a)
Contract allows GCC1 to pass-through Operator B but not GCC2 | GCC1 | or | +| | GCC2 | | +| Example b)
Contract allows GCC2 to pass-through Operator B but not GCC1 | GCC1 | | +| | GCC2 | or | +| Example c)
Contract allows GCC1 and GCC2 to pass-through Operator B | GCC1 | or | +| | GCC2 | or | +| Example d)
Neither GCC1 nor GCC2 are allowed to pass-through Operator B | GCC1 | | +| | GCC2 | | + +G.874(20)\_F6-1 + +**Figure 6-1 – GCC contract scenarios** +OTUk[V]: OTUk or OTUkV + +GCC0 is a channel between OTUk/OTUCn termination points (TPs) and therefore does not cross administrative domains, since an IrDI interface supports 3R points on either end of the interface. Example a) illustrates a scenario where the contract between operators A and B only allows GCC1 to pass through operator B's network. In such a scenario, operator B may use GCC2 within its own network. Example b) illustrates a scenario where the contract between operators A and B only allows GCC2 to pass through operator B's network. In this scenario, operator B may use GCC1 within its own network. Example c) illustrates a scenario where the contract between operators A and B allows both GCC1 and GCC2 to pass through operator B's network. In this scenario, operator B cannot use GCC1 or GCC2. Example d) illustrates a scenario where the contract between operators A and B does not allow GCC1 or GCC2 to pass through operator B's network. In this scenario, operator B can use both GCC1 and GCC2 within its own network. + +##### 6.1.3.1.1 General communication channel physical characteristics + +The OTUk GCC0 shall operate as a single message channel between OTUk TPs using the OTUk overhead bytes located in row 1, columns 11 and 12 of the OTUk overhead. The bit rate of the GCC0 depends on the rate of the OTUk. For an OTU1, the GCC0 channel shall operate at 326.723 kbit/s. For an OTU2, the GCC0 channel shall operate at 1 312.405 kbit/s. For an OTU3, the GCC0 channel shall operate at 5 271.864 kbit/s. For an OTU4, the GCC0 channel shall operate at 13 702.203 kbit/s. The OTUCn GCC0 shall operate as a single message channel between OTUCn TPs using the OTUC overhead bytes located in row 1, columns 11 and 12 of the OTUC overhead. The OTUCn contains n instances of the OTUC GCC0 overhead, numbered 1 to n (GCC0 #1 to GCC0 #n). The bit rate of the OTUCn GCC0 depends on the value of n. The GCC0 #1 to #n overhead instances are combined to provide one communication channel as illustrated in Figure 15-15 of [ITU-T G.709] with an approximated bandwidth of $n \times 13.762\ 8$ Mbit/s. According to [ITU-T G.709], vendor specific interfaces could use the first GCC0 only. + +The ODUk GCC1 shall operate as a single message channel between any two NEs with access to the ODUk frame structure using the optical data unit (ODU) overhead bytes located in row 4, columns 1 and 2 of the ODUk overhead. The bit rate of the GCC1 depends on the rate of the ODUk. For an ODU1, the GCC1 channel shall operate at 326.723 kbit/s. For an ODU2, the GCC1 channel shall operate at 1 312.405 kbit/s. For an ODU2e, the GCC1 channel shall operate at 1 359 kbit/s. For an ODU3, the GCC1 channel shall operate at 5 271.864 kbit/s. For an ODU4, the GCC1 channel shall operate at 13 702.203 kbit/s. For an ODU flex (packet) of n timeslots, the GCC1 channel shall operate at ODUflex rate/7 648 kbit/s. For an ODU flex (CBR), the GCC1 channel shall operate at $(239/238)/7\ 648 \times \text{client bit rate}$ kbit/s. The completely standardized optical data unit/Cn (ODUCn) GCC1 shall operate as a single message channel between any two NEs with access to the ODUCn frame structure using the ODUC overhead bytes located in row 4, columns 1 and 2 of the ODUC overhead. The bit rate of the GCC1 depends on the rate of the ODUCn. The OTUCn contains n instances of the ODUC GCC1 overhead, numbered 1 to n (GCC1 #1 to GCC1#n). The GCC1 #1 to #n overhead instances are combined to provide one communication channel as illustrated in Figure 15-25 of [ITU-T G.709] with an approximated bandwidth of $n \times 13.768$ Mbit/s. + +The ODUk GCC2 shall operate as a single message channel between any two NEs with access to the ODUk frame structure using the ODU overhead bytes located in row 4, columns 3 and 4 of the ODUk overhead. The bit rate of the GCC2 depends on the rate of the ODUk. For an ODU1, the GCC1 channel shall operate at 326.723 kbit/s. For an ODU2, the GCC2 channel shall operate at 1 312.405 kbit/s. For an ODU2e, the GCC2 channel shall operate at 1 359 kbit/s. For an ODU3, the GCC2 channel shall operate at 5 271.864 kbit/s. For an ODU4, the GCC2 channel shall operate at 13 702.203 kbit/s. For an ODU flex (packet) of n timeslots, the GCC2 channel shall operate at ODUflex rate/7 648 kbit/s. For an ODU flex (CBR), the GCC2 channel shall operate at $(239/238)/7\ 648 \times \text{client bit rate}$ kbit/s. The ODUCn GCC2 shall operate as a single message channel between any two NEs with access to the ODUCn frame structure using the ODUC overhead bytes located in row 4, columns 1 and 2 of the ODUC overhead. The bit rate of the GCC2 depends on the rate of the ODUCn. The OTUCn contains n instances of the ODUC GCC2 overhead, numbered 1 to n (GCC2 #1 to GCC2 #n). The GCC2 #1 to #n overhead instances are combined to provide one communication channel as illustrated in Figure 15-25 of [ITU-T G.709] with an approximated bandwidth of $n \times 13.768$ Mbit/s. + +The GCC1 #1 to #n plus GCC2 #1 to #n overhead may be combined to provide one communication channel as illustrated in Figure 15-25 of [ITU-T G.709] with an approximated bandwidth of $n \times 27.525$ Mbit/s. + +NOTE 1 – The GCC0/1/2 rates specified in this clause are nominal rates with $\pm 20$ ppm rate tolerance. + +NOTE 2 – The GCC0 rates is based on Table 13-10 of [ITU-T G.798], The GCC1 and GCC2 rates is based on Table 14-49 of [ITU-T G.798]. + +##### 6.1.3.1.2 GCC data link layer protocol + +When used for management applications, the data link point-to-point protocol (PPP) provides connections between nodes of the underlying transmission network. Mapping of an OTN data-link layer frame into the GCC is specified in [ITU-T G.7712]. + +##### 6.1.3.1.3 Support of the management communication network and signalling communication network separation + +In some network deployment scenarios, it might be desirable to have separation of the management communication network (MCN) and signalling communication network (SCN), such as separately enabling or disabling the MCN and SCN traffic on each DCN interface. This might include scenarios where the SCN spans multiple network domains. The following mechanisms can be used to meet such an application requirement. + +- GCC1 and GCC2 can be used simultaneously and separately via two parallel independent instances of the ODUP/COMMS\_A function or via two parallel independent instances of the ODUCnP/COMMS\_A function. For these two instances, one must be configured as GCC1 (MI\_GCCAccess = "GCC1") while the other instance must be configured as GCC2 (MI\_GCCAccess = "GCC2"). The two COMMS\_CPs can then be assigned to the MCN and SCN, respectively. See Figure 6-2. + +![Figure 6-2 shows two diagrams illustrating COMMS (GCC1 and GCC2) access at an access point. Diagram (a) shows access at an ODUP access point (AP), and Diagram (b) shows access at an ODUCnP access point (AP). Both diagrams show three client functions (COMMS_CP for GCC1, COMMS_CP for GCC2, and a client) connected to an access point (AP) which is connected to a transport layer (ODUP or ODUCnP) and a TCP layer.](898fb89a50d9ec1dfb4e425c816976a7_img.jpg) + +The diagram consists of two parts, (a) and (b), illustrating the architecture for COMMS (GCC1 and GCC2) access at an access point. + +**a) For ODUP access point (AP)** + +Three client functions are shown at the top: COMMS\_CP (for GCC1), COMMS\_CP (for GCC2), and a client. Each client function is connected to an ODUP/COMMS block. These blocks are connected to an ODUP\_AP block. The ODUP\_AP block is connected to an ODUP block, which is in turn connected to an ODUP\_TCP block. + +**b) For ODUCnP access point (AP)** + +Three client functions are shown at the top: COMMS\_CP (for GCC1), COMMS\_CP (for GCC2), and a client. Each client function is connected to an ODUCnP/COMMS block. These blocks are connected to an ODUCnP\_AP block. The ODUCnP\_AP block is connected to an ODUCnP block, which is in turn connected to an ODUCnP\_TCP block. A small note "G.874(20)\_F6-2" is present next to the ODUCnP\_TCP block. + +Figure 6-2 shows two diagrams illustrating COMMS (GCC1 and GCC2) access at an access point. Diagram (a) shows access at an ODUP access point (AP), and Diagram (b) shows access at an ODUCnP access point (AP). Both diagrams show three client functions (COMMS\_CP for GCC1, COMMS\_CP for GCC2, and a client) connected to an access point (AP) which is connected to a transport layer (ODUP or ODUCnP) and a TCP layer. + +**Figure 6-2 – COMMS (GCC1 and GCC2) access at ODUP access point** +(Updated from Figure 14-104 and Figure 14-106 of [ITU-T G.798]) +ODUP: optical data unit of level k, Path (k=0, 1, 2, 2e, 3, 4, flex) + +- GCC1 and GCC2 can be used simultaneously and separately via two cascaded independent instances of the ODUP/COMMS\_AC atomic function or via two parallel independent + +instances of the ODUCnP/COMMS\_AC function. For these two instances, one must be configured as GCC1 (MI\_GCCAccess = "GCC1") while the other instance must be configured as GCC2 (MI\_GCCAccess = "GCC2"). The two COMMS\_CPs can then be assigned to the MCN and SCN, respectively. See Figure 6-3. + +![Figure 6-3: ODUk_CP expansion for COMMS access for GCC1 and GCC2. The diagram consists of two parts, (a) and (b). Part (a) shows an ODUk_CP connected to two ODUk/COMMS blocks, which are then connected to COMMS_CPs for GCC1 and GCC2. Part (b) shows a more detailed expansion of the ODUk/COMMS blocks into ODUCnP/COMMS and ODUCnP/client blocks, which are connected to ODUCnP_AP blocks, which are then connected to an ODUCnP block, which is finally connected to an ODUCnP_TCP block.](83852ec55d4802521a727926336bedab_img.jpg) + +a) ODUk\_CP expansion for COMMS access + +b) ODUCn\_CP expansion for COMMS access + +G.874(20)\_F6-3 + +Figure 6-3: ODUk\_CP expansion for COMMS access for GCC1 and GCC2. The diagram consists of two parts, (a) and (b). Part (a) shows an ODUk\_CP connected to two ODUk/COMMS blocks, which are then connected to COMMS\_CPs for GCC1 and GCC2. Part (b) shows a more detailed expansion of the ODUk/COMMS blocks into ODUCnP/COMMS and ODUCnP/client blocks, which are connected to ODUCnP\_AP blocks, which are then connected to an ODUCnP block, which is finally connected to an ODUCnP\_TCP block. + +**Figure 6-3 – ODUk\_CP expansion for COMMS access for GCC1 and GCC2** +(Updated version of Figure 14-108 of [ITU-T G.798]) + +- If there is limitation in the ODUk layer network deployment, such that GCC1 and GCC2 cannot be used separately and simultaneously, it is necessary to have at least two ODUk connections between the two NEs (if possible) such that the GCC of one high-order (HO) ODUk connection can be used as the maintenance communication channel (MCC) and the GCC of the other ODUk connection can be used as the signalling communication channel (SCC). +- If there is limitation in the ODUCn layer network deployment, such that GCC1 and GCC2 cannot be used separately and simultaneously, it is necessary to have at least two other ODUCn connections between the two NEs (if possible) such that the GCC of one ODUCn connection can be used as the MCC and the GCC of the other ODUCn connection can be used as the SCC. + +- If there is limitation in the ODUk/ ODUCn layer network deployment, such that GCC1 and GCC2 cannot be used separately and simultaneously and it is also not possible to have two ODUk connections between the two NEs, mechanisms such as deep packet inspection would be needed if the MCC and the SCC share that single GCC. This would, however, mean that the MCC or SCC messages need to be analysed beyond open systems interconnection (OSI) layer 3. + +#### **6.1.3.2 General management communications overhead** + +The general management COMMS OH is specified in [ITU-T G.709]. + +##### **6.1.3.2.1 COMMS OH physical characteristics** + +The COMMS OH is a logical element within the optical transport module (OTM) overhead signal (OOS). It provides general management communications between two optical NEs with access to the OOS. As such, the COMMS OH supports the ECC of the OTN OSC. The OOS is transported via the OSC. + +The specific physical frame structure and coding for the COMMS OH lies outside the scope of [ITU-T G.709] and is therefore not standardized. + +##### **6.1.3.2.2 COMMS OH data link layer protocol** + +The adaptation of COMMS OH data link layer into the physical layer is FFS. + +### **6.1.4 O.MSN data communications network** + +See clause 6.1.4 of [ITU-T G.7710] for the generic requirements. + +### **6.1.5 Management of data communication network** + +See clause 6.1.5 of [ITU-T G.7710] for the generic requirements. + +### **6.1.6 Remote log-in** + +See clause 6.1.6 of [ITU-T G.7710] for the generic requirements. + +### **6.1.7 Relationship between technology domains** + +See clause 6.1.7 of [ITU-T G.7710] for the generic requirements. + +## **6.2 Optical transport network equipment management architecture** + +See clause 6.2 of [ITU-T G.7710] for a generic description of the equipment management architecture. + +Protocol-neutral specifications of the OTN MAFs, in terms of MO classes, attributes and message specification are provided in [ITU-T G.875]. + +The OTN EMF interacts with the other atomic functions specified in [ITU-T G.798]. See [ITU-T G.806] and [ITU-T G.798] for more information on atomic functions and on MP reference points. + +See Figure 6-4. + +![Figure 6-4 – Optical equipment management architecture. The diagram shows the internal structure of a Network Element Function (NEF). On the left, 'Transport plane atomic functions' are shown with a vertical stack of icons. An arrow labeled 'Management information' points from these functions to an 'MP reference point'. From the MP reference point, the architecture is divided into two main vertical sections. The left section is the 'Equipment management function (EMF)'. It contains a vertical stack of boxes: 'Date and time functions', 'Fault management', 'Configuration management', 'Account management', 'Performance management', 'Security management', and 'Control plane function'. The 'Control plane function' box contains three small icons and an arrow pointing to an 'Agent' box. Below the EMF stack is a 'Management application function (MAF)' box, which contains 'Date and time interface', 'Management plane interface', 'Control plane interface', and 'Local alarm interface'. At the bottom of the EMF section is a 'MIB' (Management information base) represented by a cylinder icon containing six 'MO' (Managed object) circles. The right section is the 'Message communication function (MCF)'. It contains a vertical stack of boxes: 'Date and time communication', 'Management plane communication', 'Control plane communication', a vertical ellipsis, and 'Local alarm communication'. Arrows show information flows between the EMF and MCF: 'Date and time information' between 'Date and time functions' and 'Date and time communication'; 'Management plane information' between 'Configuration management' and 'Management plane communication'; 'Control plane information' between 'Performance management' and 'Control plane communication'; and 'Local alarm information' between 'Local alarm interface' and 'Local alarm communication'. External connections are shown on the far right: 'from external time source' to 'Date and time communication'; 'to/from management plane (e.g., EMS, peer NE)' to 'Management plane communication'; 'to/from control plane (e.g., EMS, peer NE)' to 'Control plane communication'; 'to/from local craft terminal' to the ellipsis; and 'to local alarms' from 'Local alarm communication'. A legend at the bottom shows a blue cylinder for 'Management information base' and a circle with 'MO' for 'Managed object'. The text 'G.874(13)_F6-4' is in the bottom right corner.](e69b9188aa2c14ec6b21c83f711fef65_img.jpg) + +Figure 6-4 – Optical equipment management architecture. The diagram shows the internal structure of a Network Element Function (NEF). On the left, 'Transport plane atomic functions' are shown with a vertical stack of icons. An arrow labeled 'Management information' points from these functions to an 'MP reference point'. From the MP reference point, the architecture is divided into two main vertical sections. The left section is the 'Equipment management function (EMF)'. It contains a vertical stack of boxes: 'Date and time functions', 'Fault management', 'Configuration management', 'Account management', 'Performance management', 'Security management', and 'Control plane function'. The 'Control plane function' box contains three small icons and an arrow pointing to an 'Agent' box. Below the EMF stack is a 'Management application function (MAF)' box, which contains 'Date and time interface', 'Management plane interface', 'Control plane interface', and 'Local alarm interface'. At the bottom of the EMF section is a 'MIB' (Management information base) represented by a cylinder icon containing six 'MO' (Managed object) circles. The right section is the 'Message communication function (MCF)'. It contains a vertical stack of boxes: 'Date and time communication', 'Management plane communication', 'Control plane communication', a vertical ellipsis, and 'Local alarm communication'. Arrows show information flows between the EMF and MCF: 'Date and time information' between 'Date and time functions' and 'Date and time communication'; 'Management plane information' between 'Configuration management' and 'Management plane communication'; 'Control plane information' between 'Performance management' and 'Control plane communication'; and 'Local alarm information' between 'Local alarm interface' and 'Local alarm communication'. External connections are shown on the far right: 'from external time source' to 'Date and time communication'; 'to/from management plane (e.g., EMS, peer NE)' to 'Management plane communication'; 'to/from control plane (e.g., EMS, peer NE)' to 'Control plane communication'; 'to/from local craft terminal' to the ellipsis; and 'to local alarms' from 'Local alarm communication'. A legend at the bottom shows a blue cylinder for 'Management information base' and a circle with 'MO' for 'Managed object'. The text 'G.874(13)\_F6-4' is in the bottom right corner. + +**Figure 6-4 – Optical equipment management architecture (Figure 5 of [ITU-T G.7710])** + +## 6.3 Information flows over management points + +See clause 6.3 of [ITU-T G.7710] for a generic description of information flows over MPs. + +The information flow over the MP reference points is described in specific detail for each atomic function in [ITU-T G.798]. Note that these information flows and associated functions apply equally to both the client and supervisory channel due to the independent nature of these signals. This implies neither that the supervisory channel shall provide all the functions described, nor that [ITU-T G.798] will provide the details of which functions are available. + +# 7 Fault management + +See clause 7 of [ITU-T G.7710] for generic requirements for fault management. OTN-specific specifications, if needed, are explicitly described. + +## 7.1 Fault management applications + +See clause 7.1 of [ITU-T G.7710] for a description of basic fault management applications. + +### 7.1.1 Supervision + +See clause 7.1.1 of [ITU-T G.7710] for a generic description of supervision applications. + +The supervision philosophy for OTN is also based on the concepts underlying the OTN functional model of [ITU-T G.872]. + +#### **7.1.1.1 Transmission supervision** + +See clause 7.1.1.1 of [ITU-T G.7710] for a description of transmission supervision. + +#### **7.1.1.2 Quality of service supervision** + +See clause 7.1.1.2 of [ITU-T G.7710] for a description of quality of service supervision. + +#### **7.1.1.3 Processing supervision** + +See clause 7.1.1.3 of [ITU-T G.7710] for a description of processing supervision. + +#### **7.1.1.4 Hardware supervision** + +See clause 7.1.1.4 of [ITU-T G.7710] for a description of hardware supervision. + +#### **7.1.1.5 Environment supervision** + +See clause 7.1.1.5 of [ITU-T G.7710] for a description of environment supervision. + +### **7.1.2 Fault cause validation** + +See clause 7.1.2 of [ITU-T G.7710] for a description of fault cause validation. + +### **7.1.3 Alarm handling** + +#### **7.1.3.1 Severity assignment** + +See clause 7.1.3.1 of [ITU-T G.7710] for a description of severity categories. + +#### **7.1.3.2 Alarm reporting control** + +See clause 7.1.3.2 of [ITU-T G.7710] for a description of alarm reporting control (ARC). + +#### **7.1.3.3 Reportable failures** + +See clause 7.1.3.3 of [ITU-T G.7710] for a description of reportable failures. + +#### **7.1.3.4 Alarm surveillance** + +See clause 7.1.3.4 of [ITU-T G.7710] for a description of alarm surveillance. + +##### **7.1.3.4.1 Local reporting** + +See clause 7.1.3.4.1 of [ITU-T G.7710] for a description of local reporting. + +##### **7.1.3.4.2 Telecommunications management network reporting** + +See clause 7.1.3.4.2 of [ITU-T G.7710] for a description of TMN reporting. + +## **7.2 Fault management functions** + +See clause 7.2 of [ITU-T G.7710] for a description of fault management inside the EMF. + +Figure 7-1 shows the functional model of fault management inside the OTN EMF. + +![Figure 7-1: Fault management within the optical transport network network element function. This block diagram shows the flow of information between various atomic functions (PRS, SEV, ARC, REP, TEP, UNA, NEA, STA, ASY, LOG, TAN, CPL, AST, OPS) and management applications. Inputs include 'Fault cause' and 'Failure'. PRS outputs 'MI_cZZZ'. SEV outputs 'fZZZ-value'. ARC outputs 'fZZZ-value', 'fZZZ-severity', and 'fZZZ-arc'. REP outputs 'rZZZ-value' and 'rZZZ-severity'. TEP outputs 'rZZZ-value' and 'rZZZ-severity'. Management applications receive 'Unit alarms', 'Network element alarms', 'Station alarms', 'Alarm synchronization', 'Query', 'Report', 'TMN alarm event notifications', 'Current problem list', 'Alarm status', and 'Operational state'. External inputs include 'Alarm severity assignment profile', 'ARC information', and 'NE-RTC' (from Date and time functions).](c5452f95f3b28f1bfe29e84fbc2e1267_img.jpg) + +Figure 7-1: Fault management within the optical transport network network element function. This block diagram shows the flow of information between various atomic functions (PRS, SEV, ARC, REP, TEP, UNA, NEA, STA, ASY, LOG, TAN, CPL, AST, OPS) and management applications. Inputs include 'Fault cause' and 'Failure'. PRS outputs 'MI\_cZZZ'. SEV outputs 'fZZZ-value'. ARC outputs 'fZZZ-value', 'fZZZ-severity', and 'fZZZ-arc'. REP outputs 'rZZZ-value' and 'rZZZ-severity'. TEP outputs 'rZZZ-value' and 'rZZZ-severity'. Management applications receive 'Unit alarms', 'Network element alarms', 'Station alarms', 'Alarm synchronization', 'Query', 'Report', 'TMN alarm event notifications', 'Current problem list', 'Alarm status', and 'Operational state'. External inputs include 'Alarm severity assignment profile', 'ARC information', and 'NE-RTC' (from Date and time functions). + +G.874(20)\_F7-1 + +**Figure 7-1 – Fault management within the optical transport network network element function (Figure 7 of [ITU-T G.7710])** + +### **7.2.1 Fault cause persistency function** + +See clause 7.2.1 of [ITU-T G.7710] for a description of the fault cause persistency (PRS) function. + +For an O.NE that supports the atomic functions listed in Table 7-1, the EMF PRS process shall support the persistency check for the associated fault causes. + +**Table 7-1 – Inputs and outputs for the fault cause persistency function** + +| Atomic functions | Input (fault cause) | Output (failure) | +|--------------------|----------------------------------------------------|----------------------------------------------------| +| OSM256.4/CBRx_A_So | cLOF | fLOF | +| OTS-O_TT_Sk | cTIM
cBDI
cBDI-O
cBDI-P
cLOS-P
cLOS | fTIM
fBDI
fBDI-O
fBDI-P
fLOS-P
fLOS | +| OMS-O_TT_Sk | cBDI
cBDI-O
cBDI-P
cSSF
cSSF-O | fBDI
fBDI-O
fBDI-P
fSSF
fSSF-O | + +**Table 7-1 – Inputs and outputs for the fault cause persistency function** + +| Atomic functions | Input (fault cause) | Output (failure) | +|---------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------| +| | cSSF-P
cLOS-P | fSSF-P
fLOS-P | +| OMS-O/OTSiG OCh-O_A_Sk | cMSIM[1..(n+m)] | fMSIM[1..(n+m)] | +| OCh-O_TT_Sk | cLOS-P
cOCI
cSSF
cSSF-P
cSSF-O | fLOS-P
fOCI
fSSF
fSSF-P
fSSF-O | +| OTSiG-O_TT_Sk | cOCI
cSSF
cSSF-P
cSSF-O
cTIM
cBDI
cBDI-P
cBDI-O | fOCI
fSSF
fSSF-P
fSSF-O
fTIM
fBDI
fBDI-P
fBDI-O | +| OTSi/OTUkV_A_Sk | cLOS-P
cLOF
cLOM (if the optical transmission unit of level k, functional standardized (OTUkV; k=1, 2, 3, 4) has a multiframe) | fLOS-P
fLOF
fLOM | +| OTSi/OTUCn_A_Sk | cLOS-P
cLOL
cLOF
cLOM | fLOS-P
fLOL
fLOF
fLOM | +| OTSi/FlexO-1-SC_A_Sk | cLOS-P
cLOL
cLOM | fLOS-P
fLOL
fLOM | +| OTSi/OTUk_A_Sk
See Table 16-1 in [ITU-T G.798] for the function types | cLOS-P
cLOF
cLOM | fLOS-P
fLOF
fLOM | +| OTSiG/OTUkV_A_Sk | cLOS-P
cLOF
cLOM (if OTUkV has a multiframe) | fLOS-P
fLOF
fLOM | +| OTSiG/OTUk_A_Sk
See Table 16-6 of [ITU-T G.798] for the function types | cLOS-P
cLOL
cLOF
cLOM | fLOS-P
fLOL
fLOF
fLOM | +| OTSiG/OTUCn_A_Sk | cLOS-P
cLOL
cLOF
cLOM | fLOS-P
fLOL
fLOF
fLOM | +| OTSiG/FlexO_A_Sk | cLOS-P | fLOS-P | + +**Table 7-1 – Inputs and outputs for the fault cause persistency function** + +| Atomic functions | Input (fault cause) | Output (failure) | +|-------------------------------------------------------------------------------------------|-----------------------------------------------------------|-----------------------------------------------------------| +| | cLOL
cLOM | fLOL
fLOM | +| OTSi/OSC_A_Sk | cLOS-O | fLOS-O | +| OTU_TT_Sk | cTIM
cDEG
cBDI
cSSF | fTIM
fDEG
fBDI
fSSF | +| OTUkV_TT_Sk | cTIM
cDEG
cBDI
cSSF | fTIM
fDEG
fBDI
fSSF | +| OTUkV/ODU_A_Sk (if loss of alignment supervision is performed) | cLOA | fLOA | +| ODUk_C | cFOP-PM
cFOP-NR | fFOP-PM
fFOP-NR | +| ODUP_TT_Sk | cOCI
cTIM
cDEG
cBDI
cSSF
cLCK | fOCI
fTIM
fDEG
fBDI
fSSF
fLCK | +| ODUkP/CBRx_A_Sk | cPLM
cCSF | fPLM
fCSF | +| ODUP/NULL_A_Sk | cPLM | fPLM | +| ODUP/PRBS_A_Sk | cPLM
cLSS | fPLM
fLSS | +| ODUkP/RSn_A_Sk | cPLM
cLOF | fPLM
fLOF | +| ODUkP/CBRx-g_A_SkFor the value of k and x in ODUkP/CBRx, see Table 14-18 of [ITU-T G.798] | cPLM
cCSF
cLCS (Note) | fPLM
fCSF
fLCS (Note) | +| ODUkP/ODU[i]j_A_Sk | cPLM
cMSIM[ 1..n+m]
cLOFLOM[1..(n+m)] | fPLM
fMSIM[1..n+m]
fLOFLOM[1..(n+m)] | +| ODUkP/ODUj-21_A_Sk | cPLM
cLOOMFI
cMSIM[p]
cLOFLOM[1..n] | fPLM
fLOOMFI
fMSIM[p]
fLOFLOM[1..n] | +| ODUkP-h/ODUj-21_A_Sk | cPLM
cLOOMFI
cMSIM[1..n]
cLOFLOM[1..n]
cRCOHM | fPLM
fLOOMFI
fMSIM[1..n]
fLOFLOM[1..n]
fRCOHM | +| ODUkP/ETH_A_Sk | cPLM
cLFD | fPLM
fLFD | + +**Table 7-1 – Inputs and outputs for the fault cause persistency function** + +| Atomic functions | Input (fault cause) | Output (failure) | +|--------------------------------------------------------------------------------|------------------------------------------------------|------------------------------------------------------| +| | cUPM
cEXM
cCSF | fUPM
fEXM
fCSF | +| ODUkP-h/ETH_A_Sk | cPLM
cLFD
cUPM
cEXM
cCSF | fPLM
fLFD
fUPM
fEXM
fCSF | +| ODU2P/ERS10G_A_Sk | cPLM
cLFD
cUPM
cEXM
cCSF | fPLM
fLFD
fUPM
fEXM
fCSF | +| ODU2eP/FC-1200_A_Sk | cPLM
cCSF
cLFD | fPLM
fCSF
fLFD | +| ODUCnP/ODUk_A_Sk | cPLM
cLOOMFI
cMSIM[1..m]
cLOFLOM[1..m] | fPLM
fLOOMFI
fMSIM[1..m]
fLOFLOM[1..m] | +| ODUflexP/FlexEC_A_Sk | cPLM
cCSF
cLCS | fPLM
fCSF
fLCS | +| ODUflexP/FlexESG_A_So | cPMM
cGIDM
cLOL
cCSACM | fPMM
fGIDM
fLOL
fCSACM | +| ODUflexP/FlexESG_A_Sk | cPLM
cCSF
cCSACM
cLCS
cLOF
cLOM | fPLM
fCSF
fCSACM
fLCS
fLOF
fLOM | +| ODUflexP/ETCy_A_Sk
See Table 14-47.1 of [ITU-T G.798]
for the value of y | cPLM
cCSF
cLCS
cLRC | fPLM
fCSF
fLCS
fLRC | +| ODUT_TT_Sk | cOCI
cTIM
cDEG
cBDI
cSSF
cLCK
cLTC | fOCI
fTIM
fDEG
fBDI
fSSF
fLCK
fLTC | + +**Table 7-1 – Inputs and outputs for the fault cause persistency function** + +| Atomic functions | Input (fault cause) | Output (failure) | +|--------------------------------------------------------------------------|---------------------|------------------| +| ODUTm_TT_Sk | cOCI | fOCI | +| | cTIM | fTIM | +| | cDEG | fDEG | +| | cBDI | fBDI | +| | cSSF | fSSF | +| | cLCK | fLCK | +| | cLTC | fLTC | +| FlexO_TT_Sk | cRDI | fRDO | +| | cSSF | fSSF | +| FlexO-n/OTUCn_A_Sk | cLOFLOM[1..n] | fLOFLOM[1..n] | +| | cGIDM | fGIDM | +| | cPMM | fPMM | +| | cLOL | fLOL | +| ME_MI | cLOS[i] | fLOS | +| OSx_TT_Sk, x=2G5, 10G, 40G | cLOS | fLOS | +| OSx/CBRx-b_A_Sk | cLFA | fLFA | +| OSx/CBRx-c_A_Sk | cLFA | fLFA | +| NOTE – Applicable only when (k=3, CBRx=ETC40GR) or (k=4, CBRx=ETC100GR). | | | + +### 7.2.2 Severity assignment function + +See clause 7.2.2 of [ITU-T G.7710] for a description of the severity assignment (SEV) function. + +### 7.2.3 Alarm reporting control function + +See clause 7.2.3 of [ITU-T G.7710] for a description of the severity alarm reporting control (ARC) function. + +The alarms that can be controlled with this function are specified for each atomic function in [ITU-T G.798]. + +In Table 7-2, for each atomic function, a subset of the plausible failures (specified in Table 7-1) is selected, consisting of qualified problems. These qualified problems are recommended as they are deemed essential to the operability of the subject managed entity. Note that for each managed entity, one or more of the qualified problems could then be further selected by the management system to be included in the ARC list for controlling alarm reporting for the entity. + +The default ARC state is also specified for each managed entity. If the ARC function is supported by the O.NE and an ARC state is not explicitly provisioned from the management system for the managed entity, then the default ARC specified in Table 7-2 should be in effect. + +For an O.NE that supports the atomic functions listed in Table 7-2, the EMF ARC process shall support ARC for the associated fault causes. + +**Table 7-2 – Alarm reporting control specifications for the optical transport network** + +| Atomic function | Qualified problems | QoS reporting | Default ARC state value constraints | +|---------------------------------------------------------------------------|----------------------------------------------------------------------|---------------|-------------------------------------| +| OSM256.4/CBRx_A_So | fLOF | FFS | Alarm (ALM) | +| OTS-O_TT_Sk | fTIM
fBDI
fBDI-P
fLOS-P
fLOS | FFS | ALM | +| OMS-O_TT_Sk | fBDI
fBDI-O
fBDI-P
fSSF
fSSF-O
fSSF-P
fLOS-P | FFS | ALM | +| OMS-O/OTSiG OCh-O_A_Sk | fMSIM[1..(n+m)] | FFS | ALM | +| OCh-O_TT_Sk | fLOS-P
fOCI
fSSF
fSSF-O
fSSF-P | FFS | ALM | +| OTSiG-O_TT_Sk | fOCI
fSSF
fSSF-P
fSSF-O
fTIM
fBDI
fBDI-P
fBDI-O | FFS | ALM | +| OTSi/OTUk_A_Sk
See Table 16-1 of [ITU-T G.798] for the function types | fLOS-P
fLOF
fLOM | FFS | ALM | +| OTSiG/OTUk_A_Sk
See Table 16-6 of [ITU-T G.798] for the function types | fLOS-P
fLOL
fLOF
fLOM | FFS | ALM | +| OTSi/OTUkV_A_Sk | fLOS-P
fLOF
fLOM | FFS | ALM | +| OTSiG/OTUkV_A_Sk | fLOS-P
fLOF
fLOM | FFS | ALM | +| OTSi/OTUCn_A_Sk | fLOS-P
fLOL
fLOF
fLOM | FFS | ALM | +| OTSiG/OTUCn_A_Sk | fLOS-P | FFS | ALM | + +**Table 7-2 – Alarm reporting control specifications for the optical transport network** + +| Atomic function | Qualified problems | QoS reporting | Default ARC state value constraints | +|-----------------------------------------------------------------------------------------|----------------------------------------------|---------------|-------------------------------------| +| | fLOL
fLOF
fLOM | | | +| OTSiG/FlexO_A_Sk | fLOS-P
fLOL
fLOM | FFS | ALM | +| OTSi/FlexO-1-SC_A_Sk | fLOS-P
fLOL
fLOM | FFS | ALM | +| OTSi/OSC_A_Sk | fLOS-O | FFS | ALM | +| OTU_TT_Sk | fTIM
fDEG
fBDI
fSSF | FFS | ALM | +| OTUkV_TT_Sk | fTIM
fDEG
fBDI
fSSF | FFS | ALM | +| OTUkV/ODU_A_Sk | fLOA | FFS | ALM | +| ODUk_C | fFOP-PM
fFOP-NR | FFS | ALM | +| ODUP_TT_Sk | fOCI
fTIM
fDEG
fBDI
fSSF
fLCK | FFS | ALM | +| ODUkP/CBRx_A_Sk | fPLM
fCSF | FFS | ALM | +| ODUP/NULL_A_Sk | fPLM | FFS | ALM | +| ODUP/PRBS_A_Sk | fPLM
fLSS | FFS | ALM | +| ODUkP/RSn_A_Sk | fPLM
fLOF | FFS | ALM | +| ODUkP/CBRx-g_A_Sk
For the value of k and x in CBRx, see Table 14-18 of [ITU-T G.798] | fPLM
fCSF
fLCS (Note) | FFS | ALM | +| ODUkP/ODU[i]j_A_Sk | fPLM
fMSIM[1..(n+m)]
fLOFLOM[1..(n+m)] | FFS | ALM | +| ODUkP/ODUj-21_A_Sk | fPLM
fLOOMFI | FFS | ALM | + +**Table 7-2 – Alarm reporting control specifications for the optical transport network** + +| Atomic function | Qualified problems | QoS reporting | Default ARC state value constraints | +|--------------------------|-----------------------------------------------------------|---------------|-------------------------------------| +| | fMSIM[1..n]
fLOFLOM[1..n] | | | +| ODUkP-h/ODUj-21_A_Sk | fPLM
fLOOMFI
fMSIM[1..n]
fLOFLOM[1..n]
fRCOHM | FFS | ALM | +| ODUkP/ETH_A_Sk | fPLM
fLFD
fUPM
fEXM
fCSF | FFS | ALM | +| ODUkP-h/ETH_A_Sk(k=flex) | fPLM
fLFD
fUPM
fEXM
fCSF | FFS | ALM | +| ODU2P/ERS10G_A_Sk | fPLM
fLFD
fUPM
fEXM
fCSF | FFS | ALM | + +**Table 7-2 – Alarm reporting control specifications for the optical transport network** + +| Atomic function | Qualified problems | QoS reporting | Default ARC state value constraints | +|--------------------------------------------------------------------------------|------------------------------------------------------|---------------|-------------------------------------| +| ODU2eP/FC-1200_A_Sk | fPLM
fCSF
fLFD | FFS | ALM | +| ODUCnP/ODUk_A_Sk | fPLM
fLOOMFI
fMSIM[1..m]
fLOFLOM[1..m] | FFS | ALM | +| ODUflexP/FlexEC_A_Sk | fPLM
fCSF
fLCS | FFS | ALM | +| ODUflexP/FlexESG_A_So | fPMM
fGIDM
fLOL
fCSACM | FFS | ALM | +| ODUflexP/FlexESG_A_Sk | fPLM
fCSF
fCSACM
fLCS
fLOF
fLOM | FFS | ALM | +| ODUflexP/ETCy_A_Sk
See Table 14-47.1 of [ITU-T G.798]
for the value of y | fPLM
fCSF
fLCS
fLRC | FFS | ALM | +| ODUT_TT_Sk | fOCI
fTIM
fDEG
fBDI
fSSF
fLCK
fLTC | FFS | ALM | +| ODUTm_TT_Sk | fOCI
fTIM
fDEG
fBDI
fSSF
fLCK
fLTC | FFS | ALM | +| FlexO_TT_Sk | fRDI
fSSF | FFS | ALM | +| FlexO-n/OTUCn_A_Sk | fLOFLOM[1..n]
fGIDM
fPMM
fLOL | FFS | ALM | + +**Table 7-2 – Alarm reporting control specifications for the optical transport network** + +| Atomic function | Qualified problems | QoS reporting | Default ARC state value constraints | +|--------------------------------------------------------------------------|--------------------|---------------|-------------------------------------| +| ME_MI | fLOS[i] | FFS | ALM | +| OSx_TT_Sk | fLOS | FFS | ALM | +| OSx/CBRx-b_A_Sk | fLFA | FFS | ALM | +| OSx/CBRx-c_A_Sk | fLFA | FFS | ALM | +| NOTE – Applicable only when (k=3, CBRx=ETC40GR) or (k=4, CBRx=ETC100GR). | | | | + +### **7.2.4 Reportable failure function** + +See clause 7.2.4 of [ITU-T G.7710] for a description of the reportable failure (REP) function. + +### **7.2.5 Unit alarm function** + +See clause 7.2.5 of [ITU-T G.7710] for a description of the unit alarm (UNA) function. + +### **7.2.6 Network element alarm function** + +See clause 7.2.6 of [ITU-T G.7710] for a description of the network element alarm (NEA) function. + +### **7.2.7 Station alarm function** + +See clause 7.2.7 of [ITU-T G.7710] for a description of the station alarm (STA) function. + +### **7.2.8 Telecommunications management network event pre-processing function** + +See clause 7.2.8 of [ITU-T G.7710] for a description of the TMN event pre-processing alarm (TEP) function. + +### **7.2.9 Alarm synchronization function** + +See clause 7.2.9 of [ITU-T G.7710] for a description of the alarm synchronization (ASY) function. + +### **7.2.10 Logging function** + +See clause 7.2.10 of [ITU-T G.7710] for a description of the logging (LOG) function. + +### **7.2.11 Telecommunications management network alarm event notification function** + +See clause 7.2.11 of [ITU-T G.7710] for a description of the TMN alarm event notification (TAN) function. + +### **7.2.12 Current problem list function** + +See clause 7.2.12 of [ITU-T G.7710] for a description of the current problem list (CPL) function. + +### **7.2.13 Alarm status function** + +See clause 7.2.13 of [ITU-T G.7710] for a description of the alarm status (AST) function. + +### **7.2.14 Operational state function – OPS** + +See clause 7.2.14 of [ITU-T G.7710] for a description of the operational state function. + +Table 7-3 lists the failures that could influence the operational state of the related objects. + +For an O.NE that supports the atomic functions listed in Table 7-3, the EMF OPS process shall support the operational state for the associated fault causes. + +**Table 7-3 – Input and output signals of the operational state function +for the optical transport network** + +| Atomic function | Failure input
(fZZZ-value) | Operational state output
(enabled/disabled)
of the trail object class | +|------------------------------------------------------------------------------|----------------------------------------------------------------------|--------------------------------------------------------------------------------------| +| OSM256.4/CBRx_A_So | fLOF | Disabled | +| OTS-O_TT_Sk | fTIM
fBDI
fBDI-P
fBDI-O
fLOS-P
fLOS | Enabled
Enabled
Enabled
Enabled
Disabled
Disabled | +| OMS-O_TT_Sk | fBDI
fBDI-O
fBDI-P
fSSF
fSSF-O
fSSF-P
fLOS-P | Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Disabled | +| OMS-O/OTSiG OCh-O_A_Sk | fMSIM[1..(n+m)] | Enabled | +| OCh-O_TT_Sk | fLOS-P
fOCI
fSSF
fSSF-P
fSSF-O | Disabled
Enabled
Enabled
Enabled
Enabled | +| OTSiG-O_TT_Sk | fOCI
fSSF
fSSF-P
fSSF-O
fTIM
fBDI
fBDI-P
fBDI-O | Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled
Enabled | +| OTSi/OTUkV_A_Sk | fLOS-P
fLOF
fLOM | Disabled
Disabled
Disabled | +| OTSiG/OTUkV_A_Sk | fLOS-P
fLOF
fLOM | Disabled
Disabled
Disabled | +| OTSi/OTUk_A_Sk
See Table 16-1 of [ITU-T G.798] for the
function types | fLOS-P
fLOF
fLOM | Disabled
Disabled
Disabled | +| OTSiG/OTUk_A_Sk
See Table 16-6 of [ITU-T G.798] for the
function types | fLOS
fLOL
fLOF
fLOM | Disabled
Disabled
Disabled
Disabled | +| OTSi/FlexO-1-SC_A_Sk | fLOS-P
fLOL | Disabled
Disabled | + +**Table 7-3 – Input and output signals of the operational state function +for the optical transport network** + +| Atomic function | Failure input
(fZZZ-value) | Operational state output
(enabled/disabled)
of the trail object class | +|------------------------------------------------------------------------------------------------|---------------------------------------|--------------------------------------------------------------------------------------| +| | fLOM | Disabled | +| OTSi/OTUCn_A_Sk | fLOS-P | Disabled | +| | fLOL | Disabled | +| | fLOF | Disabled | +| | fLOM | Disabled | +| OTSiG/OTUCn_A_Sk | fLOS-P | Disabled | +| | fLOL | Disabled | +| | fLOF | Disabled | +| | fLOM | Disabled | +| OTSiG/FlexO_A_Sk | fLOS-P | Disabled | +| | fLOL | Disabled | +| | fLOM | Disabled | +| OTSi/OSC_A_Sk | fLOS-O | Disabled | +| OTU_TT_Sk | fTIM | Enabled | +| | fDEG | Enabled | +| | fBDI | Enabled | +| | fSSF | Enabled | +| OTUkV_TT_Sk | fTIM | Enabled | +| | fDEG | Enabled | +| | fBDI | Enabled | +| | fSSF | Enabled | +| OTUkV/ODU_A_Sk | fLOA | Disabled | +| ODUk_C | fFOP-PM | Disabled | +| | fFOP-NR | Disabled | +| ODUP_TT_Sk | fOCI | Enabled | +| | fTIM | Enabled | +| | fDEG | Enabled | +| | fBDI | Enabled | +| | fSSF | Enabled | +| | fLOCK | Enabled | +| | | | +| ODUkP/CBRx_A_Sk | fPLM | Disabled | +| | fCSF | Enabled | +| ODUP/NULL_A_Sk | fPLM | Disabled | +| ODUkP/PRBS_A_Sk | fPLM | Disabled | +| | fLSS | Disabled | +| ODUkP/RSn_A_Sk | fPLM | Disabled | +| | fLOF | Disabled | +| ODUkP/CBRx-g_A_Sk
For the values of k
and x in CBRx, see Table 14-18 of
[ITU-T G.798] | fPLM | Disabled | +| | fCSF | Enabled | +| | fLCS (Note) | Disabled | +| ODUkP/ETH_A_Sk | fPLMfLFD | Disabled | +| | fUPM | | + +**Table 7-3 – Input and output signals of the operational state function +for the optical transport network** + +| Atomic function | Failure input
(fZZZ-value) | Operational state output
(enabled/disabled)
of the trail object class | +|------------------------|-----------------------------------------------------------|--------------------------------------------------------------------------------------| +| | fEXM
fCSF | Disabled
Disabled
Enabled | +| ODUkP/ODU[i]j_A_Sk | fPLM
fMSIM[1..(n+m)]
fLOFLOM[1..(n+m)] | Disabled
Disabled
Disabled | +| ODUkP/ODUj-21_A_Sk | fPLM
fLOOMFI
fMSIM[1..n]
fLOFLOM[1..n] | FFS
FFS
FFS
Disabled | +| ODUkP-h/ETH_A_Sk | fPLM
fLFD
fUPM
fEXM
fCSF | Disabled
Disabled
Disabled
Disabled
Enabled | +| ODUkP-h/ODUj-21_A_Sk | fPLM
fLOOMFI
fMSIM[1..n]
fLOFLOM[1..n]
fRCOHM | Disabled
Disabled
Disabled
Disabled
FFS | +| ODU2P/ERS10G_A_Sk | fPLM
fLFD
fUPM
fEXM
fCSF | Disabled
Disabled
Disabled
Disabled
Enabled | +| ODU2eP/FC-1200_A_Sk | fPLM
fCSF
fLFD | Disabled
Enabled
Disabled | +| ODUCnP/ODUk_A_Sk | cPLM
cLOOMFI
cMSIM[1..m]
cLOFLOM[1..m] | Disabled
Disabled
Disabled
Disabled | +| ODUflexP/FlexEC_A_Sk | fPLM
fCSF
fLCS | Disabled
Disabled
Disabled | +| ODUflexP/FlexESG_A_So | fPMM
fGIDM
fLOL
fCSACM | Disabled
Disabled
Disabled
Disabled | + +**Table 7-3 – Input and output signals of the operational state function +for the optical transport network** + +| Atomic function | Failure input
(fZZZ-value) | Operational state output
(enabled/disabled)
of the trail object class | +|--------------------------------------------------------------------------------|-------------------------------|-----------------------------------------------------------------------------| +| ODUflexP/FlexESG_A_Sk | fPLM | Disabled | +| | fCSF | Disabled | +| | fCSACM | Disabled | +| | fLCS | Disabled | +| | fLOF | Disabled | +| | fLOM | Disabled | +| ODUflexP/ETCy_A_Sk
See Table 14-47.1 of [ITU-T G.798] for the
value of y | fPLM | Disabled | +| | fCSF | Disabled | +| | fLCS | Disabled | +| | fLRC | Disabled | +| ODUT_TT_Sk | fOCI | Enabled | +| | fTIM | Enabled | +| | fDEG | Enabled | +| | fBDI | Enabled | +| | fSSF | Enabled | +| | fLCK | Enabled | +| | fLTC | FFS | +| | | | +| ODUTm_TT_Sk | fOCI | Enabled | +| | fTIM | Enabled | +| | fDEG | Enabled | +| | fBDI | Enabled | +| | fSSF | Enabled | +| | fLCK | Enabled | +| | fLTC | FFS | +| | | | +| FlexO_TT_Sk | fRDI | Enabled | +| | fSSF | Enabled | +| FlexO-n/OTUCn_A_Sk | fLOFLOM[1..n] | Disabled | +| | fGIDM | Disabled | +| | fPMM | Disabled | +| | fLOL | Disabled | +| ME_MI | fLOS[i] | Disabled | +| OSx_TT_Sk | fLOS | Disabled | +| OSx/CBRx-b_A_Sk | fPLM | Disabled | +| OSx/CBRx-c_A_Sk | fPLM | Disabled | + +NOTE – Applicable only when (k=3, CBRx=ETC40GR) or (k=4, CBRx=ETC100GR). + +# 8 Configuration management + +See clause 8 of [ITU-T G.7710] for the generic requirements for CM. OTN-specific specifications, if needed, are explicitly described. + +## 8.1 Hardware + +See clause 8.1 of [ITU-T G.7710] for a description of hardware management. + +## 8.2 Software + +See clause 8.2 of [ITU-T G.7710] for a description of software management. + +## 8.3 Protection switching + +See clause 8.3 of [ITU-T G.7710] for a description of protection switching management. + +This function allows a user to provision and monitor the operation of protection processes deployed in an Ethernet (ETH) connection (ETH-C) process. + +Management information (MI) signals concerning the protection processes are listed in Table 8-3 and communicated between the EMF and the protection process through the MP. According to these MI signals, the EMF generates a corresponding event notification and state report signals to the MAF. + +For the protection processes supported by an O.NE, the O.NE EMF shall support the following management functions: + +- provisioning the protection switching MI; +- retrieving the protection switching MI; +- notifying the changes of the protection switching MI; +- receiving the monitored protection switching MI. + +## 8.4 Trail termination + +See clause 8.4 of [ITU-T G.7710] for a description of TT management. + +This function allows a user to provision and monitor the operation of the OTN TT process. + +A trail trace identifier (TTI) at the optical transmission section (OTS) layer is useful to ensure proper fibre connection between NEs, in particular in meshed network topology with optical cross-connections that have several line input ports and several line output ports. + +TTIs are also a means for the OS to deduce the network topology at the OTS layer first, and then at the OMS and optical channel (OCh) level. Specifically, the OS gets the list of source and sink (Sk) TTIs of all NEs and can automatically deduce the trails at the OTS layer by a comparison of the expected TTIs of the Sk objects and the TTIs sent from the source objects. Then, as there is only one instance of an OMS connection point (CP) and one instance of an OMS trail termination point (TTP), the OS can deduce automatically the topology at the OMS layer. A similar method may be applied at the OCh level from the list of existing ochCTP (which are named by omsTTP). + +The TTIs received are used at the NE level to detect wrong fibre connection and generate an OTS trail trace identifier mismatch (TIM) alarm if the accepted value is different from the expected value. + +The TTI at the OCh layer is necessary to check that the signal received by an Sk originates from the intended source. To be able to localize the cross-connection responsible for a TIM, the expected and the received OCh TTIs are needed at the Sk. + +The received OCh TTI is used at the NE level to detect incorrect OCh connections and to generate an OCH TIM alarm. + +The MI signals listed in Table 8-1 are communicated between the EMF and the OTN TT process across the MP within the O.NE. + +For the TT functions supported by an O.NE, the O.NE EMF shall support the following management functions: + +- provisioning the TT MI; +- retrieving the TT MI; +- notifying the changes of the TT MI; + +– receiving the monitored TT MI. + +**Table 8-1 – Trail termination-related provisioning and reporting** + +| MI signal | Value range | Default value | +|---------------------------------------------------|-------------------------------------------------------|----------------| +| OTS-O_TT_So Provisioning | | | +| OTS-O_TT_So_MI_TxTI | According to [ITU-T G.709] | Not applicable | +| OTS-O_TT_Sk Provisioning | | | +| OTS-O_TT_Sk_MI_ExSAPI | According to [ITU-T G.709] | Not applicable | +| OTS-O_TT_Sk_MI_ExDAPI | According to [ITU-T G.709] | Not applicable | +| OTS-O_TT_Sk_MI_GetActTI | According to [ITU-T G.798] | Not applicable | +| OTS-O_TT_Sk_MI_TIMDetMo | According to [ITU-T G.798] | OFF | +| OTS-O_TT_Sk_MI_TIMActDis | True, false | True | +| OTS-O_TT_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTS-O_TT_Sk Reporting | | | +| OTS-O_TT_Sk_MI_ActTI | According to [ITU-T G.709] | Not applicable | +| OTSiG-O_TT_So Provisioning | | | +| OTSiG-O_TT_So_MI_TxTI | According to [ITU-T G.709] | Not applicable | +| OTSiG-O_TT_Sk Provisioning | | | +| OTSiG-O_TT_Sk_MI_ExSAPI | According to [ITU-T G.709] | Not applicable | +| OTSiG-O_TT_Sk_MI_ExDAPI | According to [ITU-T G.709] | Not applicable | +| OTSiG-O_TT_Sk_MI_GetActTI | According to [ITU-T G.798] | Not applicable | +| OTSiG-O_TT_Sk_MI_TIMDetMo | According to [ITU-T G.798] | OFF | +| OTSiG-O_TT_Sk_MI_TIMActDis | True, false | True | +| OTSiG-O_TT_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTSiG-O_TT_Sk Reporting | | | +| OTSiG-O_TT_Sk_MI_ActTI | According to [ITU-T G.709] | Not applicable | +| OMS-O_TT_Sk Provisioning | | | +| OMS-O_TT_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OCh_TT_So Provisioning (Note 1) | | | +| OCh_TT_So_MI_nominalCentralFrequencyOrWavelength | See [ITU-T G.875] for the object OCh_TerminationPoint | – | +| OCh_TT_So_MI_selectedApplicationIdentifier | See [ITU-T G.875] for the object OCh_TerminationPoint | – | +| OCh_TT_So Reporting (Note 1) | | | +| OCh_TT_So_MI_nominalCentralFrequencyOrWavelength | See [ITU-T G.875] for the object OCh_TerminationPoint | – | +| OCh_TT_So_MI_supportableApplicationIdentifierList | See [ITU-T G.875] for the object OCh_TerminationPoint | – | +| OCh_TT_Sk Reporting (Note 1) | | | +| OCh_TT_Sk_MI_supportableApplicationIdentifierList | See [ITU-T G.875] for the object OCh_TerminationPoint | – | +| OTU_TT_So Provisioning | | | +| OTU_TT_So_MI_TxTI | According to [ITU-T G.709] | Not applicable | + +**Table 8-1 – Trail termination-related provisioning and reporting** + +| MI signal | Value range | Default value | +|--------------------------|----------------------------------------------------------------------------------------------------|------------------------| +| OTU_TT_Sk Provisioning | | | +| OTU_TT_Sk_MI_ExSAPI | According to [ITU-T G.709] | Not applicable | +| OTU_TT_Sk_MI_ExDAPI | According to [ITU-T G.709] | Not applicable | +| OTU_TT_Sk_MI_GetAcTI | According to [ITU-T G.798] | Not applicable | +| OTU_TT_Sk_MI_TIMDetMo | According to [ITU-T G.798] | OFF | +| OTU_TT_Sk_MI_TIMActDis | True, false | True | +| OTU_TT_Sk_MI_DEGThr | In number of errored blocks or as a percentage between 0% and 100%; see Table 7-1 of [ITU-T G.806] | SES Threshold (Note 2) | +| OTU_TT_Sk_MI_DEGM | 2-10; see Table 7-1 of [ITU-T G.806] | (Note 2) | +| OTU_TT_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTU_TT_Sk Reporting | | | +| OTU_TT_Sk_MI_AcTI | According to [ITU-T G.709] | Not applicable | +| OTUkV_TT_So Provisioning | | | +| OTUkV_TT_So_MI_TxTI | According to [ITU-T G.709] | Not applicable | +| OTUkV_TT_Sk Provisioning | | | +| OTUkV_TT_Sk_MI_ExSAPI | According to [ITU-T G.709] | Not applicable | +| OTUkV_TT_Sk_MI_ExDAPI | According to [ITU-T G.709] | Not applicable | +| OTUkV_TT_Sk_MI_GetAcTI | According to [ITU-T G.798] | Not applicable | +| OTUkV_TT_Sk_MI_TIMDetMo | According to [ITU-T G.798] | OFF | +| OTUkV_TT_Sk_MI_TIMActDis | Enabled, disabled | Disabled | +| OTUkV_TT_Sk_MI_DEGThr | In number of errored blocks or as a percentage between 0% and 100%; see Table 7-1 of [ITU-T G.806] | SES Threshold (Note 2) | +| OTUkV_TT_Sk_MI_DEGM | 2-10; see Table 7-1 of [ITU-T G.806] | (Note 2) | +| OTUkV_TT_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTUkV_TT_Sk Reporting | | | +| OTUkV_TT_Sk_MI_AcTI | According to [ITU-T G.709] | Not applicable | +| ODUP_TT_So Provisioning | | | +| ODUP_TT_So_MI_TxTI | According to [ITU-T G.709] | Not applicable | +| ODUP_TT_So_MI_DM_Source | true, false | false | +| ODUP_TT_So_MI_DMValue | Not applicable.
See [ITU-T G.798] | Not applicable | +| ODUP_TT_Sk Provisioning | | | +| ODUP_TT_Sk_MI_ExSAPI | According to [ITU-T G.709] | Not applicable | +| ODUP_TT_Sk_MI_ExDAPI | According to [ITU-T G.709] | Not applicable | +| ODUP_TT_Sk_MI_GetAcTI | According to [ITU-T G.798] | Not applicable | + +**Table 8-1 – Trail termination-related provisioning and reporting** + +| MI signal | Value range | Default value | +|-----------------------------|----------------------------------------------------------------------------------------------------|------------------------| +| ODUP_TT_Sk_MI_TIMDetMo | According to [ITU-T G.798] | OFF | +| ODUP_TT_Sk_MI_TIMActDis | Enabled, disabled | Disabled | +| ODUP_TT_Sk_MI_DEGThr | In number of errored blocks or as a percentage between 0% and 100%; see Table 7-1 of [ITU-T G.806] | SES Threshold (Note 2) | +| ODUP_TT_Sk_MI_DEGM | 2-10; see Table 7-1 of [ITU-T G.806] | (Note 2) | +| ODUP_TT_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| ODUP_TT_Sk_MI_DM_Source | true, false | false | +| ODUP_TT_Sk_MI_DMValue | Not applicable.
See [ITU-T G.798] | Not applicable. | +| ODUP_TT_Sk Reporting | | | +| ODUP_TT_Sk_MI_AcTI | According to [ITU-T G.709] | Not applicable | +| ODUT_TT_So Provisioning | | | +| ODUT_TT_So_MI_TxTI | According to [ITU-T G.709] | Not applicable | +| ODUT_TT_So_MI_DM_Source | true, false | false | +| ODUT_TT_So_MI_DMValue | Not applicable.
See [ITU-T G.798] | Not applicable. | +| ODUT_TT_Sk Provisioning | | | +| ODUT_TT_Sk_MI_ExSAPI | According to [ITU-T G.709] | Not applicable | +| ODUT_TT_Sk_MI_ExDAPI | According to [ITU-T G.709] | Not applicable | +| ODUT_TT_Sk_MI_GetAcTI | According to [ITU-T G.798] | Not applicable | +| ODUT_TT_Sk_MI_TIMDetMo | According to [ITU-T G.798] | FFS | +| ODUT_TT_Sk_MI_TIMActDis | Enabled, disabled | Disabled | +| ODUT_TT_Sk_MI_DEGThr | In number of errored blocks or as a percentage between 0% and 100%; See Table 7-1 of [ITU-T G.806] | SES Threshold (Note 2) | +| ODUT_TT_Sk_MI_DEGM | 2-10; see Table 7-1 of [ITU-T G.806] | (Note 2) | +| ODUT_TT_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| ODUT_TT_Sk_MI_DM_Source | true, false | true | +| ODUT_TT_Sk_MI_DMValue | Not applicable.
See [ITU-T G.798] | Not applicable. | +| ODUT_TT_Sk_MI_LTCAct_Enable | true, false | false | +| ODUT_TT_Sk Reporting | | | +| ODUT_TT_Sk_MI_AcTI | According to [ITU-T G.709] | Not applicable | +| ODUTm_TT_Sk Provisioning | | | +| ODUTm_TT_Sk_MI_Level | 1..6 | Not applicable | +| ODUTm_TT_Sk_MI_ExSAPI | According to [ITU-T G.709] | Not applicable | + +**Table 8-1 – Trail termination-related provisioning and reporting** + +| MI signal | Value range | Default value | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------|------------------------| +| ODUTm_TT_Sk_MI_ExDAPI | According to [ITU-T G.709] | Not applicable | +| ODUTm_TT_Sk_MI_GetAcTI | According to [ITU-T G.798] | Not applicable | +| ODUTm_TT_Sk_MI_TIMDectMo | According to [ITU-T G.798] | FFS | +| ODUTm_TT_Sk_MI_TIMActDis | Enabled, disabled | Disabled | +| ODUTm_TT_Sk_MI_DEGThr | In number of errored blocks or as a percentage between 0% and 100%; see Table 7-1 of [ITU-T G.806] | SES Threshold (Note 2) | +| ODUTm_TT_Sk_MI_DEGM | 2-10; see Table 7-1 of [ITU-T G.806] | (Note 2) | +| ODUTm_TT_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| ODUTm_TT_Sk Reporting | | | +| ODUTm_TT_Sk_MI_AcTI | According to [ITU-T G.709] | Not applicable | +| OSx_TT_So Provisioning | | | +| OSx_TT_So_MI_APRCntrl (Notes 3 and 4) | Enable, disable | Enable | +| NOTE 1 – These MIs are specified in [ITU-T G.798].
NOTE 2 – Equipment designed prior to the 2017 edition of this Recommendation may use a default MI_DEGTHR value of 30% and of MI_DEGM of 10.
NOTE 3 – If automatic power reduction (APR) is required.
NOTE 4 – The automatic power reduction control (APRCntrl) commands depend on the specific APR process. | | | + +For the management of the connectivity at the OTS layer, the following TTI attributes are recommended: + +- 1) otsTTIsent attribute in every otsTTPsource (get – replace); +- 2) otsTTIexpected attribute in every otsTTPsink (get – replace); +- 3) otsTTIreceived attribute in every otsTTPsink (get – replace). + +For the management of the connectivity at the OCH layer, the following TTI attributes are recommended: + +- 1) ochTTIsent attribute in every ochTTPsource (get – replace); +- 2) ochTTIexpected attribute in every ochTTPsink and ochCTPsink (get – replace); +- 3) ochTTIreceived attribute in every ochTTPsink and ochCTPsink (get only). + +## 8.5 Adaptation + +See clause 8.5 of [ITU-T G.7710] for a description of adaptation management. + +An access point (AP) that has multiple adaptation functions connected to it, thereby allowing different clients to be transported via the server signal, requires a mechanism for the selection of the active client. + +The adaptation function allows a user to provision and monitor the operation of the OTN adaptation processes. + +Both OMS/OCh\_A and OCh/Application\_A will report on request from the OTN EMF the value of the received and accepted payload type (PT) indication signal via the MI\_AcPTI. + +The MI signals listed in Table 8-2 are communicated between the EMF and the adaptation processes across the MP within the OTN NE. + +NOTE – ODUkP/ETH\_A and ODU2P/ETHPP-OS\_A are specified in [ITU-T G.798]. + +For the adaptation functions supported by an O.NE, the O.NE EMF shall support the following management functions: + +- provisioning the adaptation MI; +- retrieving the adaptation MI; +- notifying the changes of the adaptation MI. + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|---------------------------------------------------------------------------------|-------------------------------------------------------------------------------------|----------------| +| OMS-O/OTSiG OCh-O_A_So Provisioning | | | +| OMS-O/OTSiG OCh-O_A_So_MI_TxMSI | The value range is implementation specific.
See clause 8.7.2.3 of [ITU-T G.798]. | Not applicable | +| OMS-O/OTSiG OCh-O_A_Sk Provisioning | | | +| OMS-O/OTSiG OCh-O_A_Sk_MI_ExMSI[1..(n+m)] for the n OTSiG-O_CPs and m OCh-O_CPs | The value range is implementation specific.
See clause 8.7.2.3 of [ITU-T G.798]. | Not applicable | +| OMS-O/OTSiG OCh-O_A_Sk Reporting | | | +| OMS-O/OTSiG OCh-O_A_Sk_MI_AcMSI[1..(n+m)] for the n OTSiG-O_CPs and m OCh-O_CPs | The value range is implementation specific.
See clause 8.7.2.3 of [ITU-T G.798]. | Not applicable | +| OSC/COMMS_A_So Provisioning | | | +| None | | | +| OSC/COMMS_A_Sk Provisioning | | | +| None | | | +| OSM256.4/CBRx_So Provisioning | | | +| None | | | +| OTSi/OTUkV_A_So Provisioning | | | +| None | | | +| OTSi/OTUkV_A_Sk Provisioning | | | +| OTSi/OTUkV_A_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTSi/OTUk_A_So Provisioning | | | +| None | | | +| OTSi/OTUk_A_Sk Provisioning | | | +| See Table 16-1 of [ITU-T G.798] for the function types | | | +| OTSi/OTUk_A_Sk_MI_FECEn | True, false | True | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|-----------------------------------------------------------------------------------------|----------------------------|----------------| +| OTSi/OTUk_A_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTSiG/OTUk_A_So Provisioning
See Table 16-6 of [ITU-T G.798] for the function types | | | +| None | | | +| OTSiG/OTUk_A_Sk Provisioning
See Table 16-6 of [ITU-T G.798] for the function types | | | +| OTSiG/OTUk_A_Sk_MI_FECEn | True, false | True | +| OTSiG/OTUk_A_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTSiG/OTUkV_A_So Provisioning | | | +| None | | | +| OTSiG/OTUkV_A_Sk Provisioning
See Table 16-6 of [ITU-T G.798] for the function types | | | +| OTSiG/OTUkV_A_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTSi/FlexO-1-SC_A_So Provisioning | | | +| None | | | +| OTSi/FlexO-1-SC_A_Sk Provisioning | | | +| OTSi/FlexO-1-SC_A_Sk_MI_FECEn | True, false | True | +| OTSi/FlexO-1-SC_A_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTSiG/OTUCn_A_So Provisioning | | | +| OTSiA/OTUCn_A_So_MI_Active | True, false | False | +| OTSiG/OTUCn_A_Sk Provisioning | | | +| OTSiG/OTUCn_A_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTSiG/FlexO_A_So Provisioning | | | +| None | | | +| OTSiG/FlexO_A_Sk Provisioning | | | +| OTSiG/FlexO_A_Sk_MI_FECEn | | | +| OTSiG/FlexO_A_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTSiG/OTUk-SC_A_Sk_MI_1second | | | +| OTSi/OSC_A_So Provisioning | | | +| None | | | +| OTSi/OSC_A_Sk Provisioning | | | +| OTSi/OSC_A_Sk_MI_1second | According to [ITU-T G.798] | Not applicable | +| OTU/ODU_A_So_Provisioning | | | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|--------------------------------|-----------------------------------------|---------------| +| OTU/ODU_A_So_MI_AdminState | LOCKED, Not LOCKED | Not LOCKED | +| OTU/ODU_A_So_MI_APS_EN | true, false | true | +| OTU/ODU_A_So_MI_APS_LVL | 0..6,
0 for path and 1..6
for TCM | – | +| OTU/ODU_A_Sk_Provisioning | | | +| OTU/ODU_A_Sk_MI_AdminState | LOCKED, Not LOCKED | Not LOCKED | +| OTU/ODU_A_Sk_MI_APS_EN | true, false | true | +| OTU/ODU_A_Sk_MI_APS_LVL | 0..6,
0 for path and 1..6
for TCM | – | +| OTUkV/ODU_A_So_Provisioning | | | +| OTUkV/ODU_A_So_MI_AdminState | LOCKED, Not LOCKED | Not LOCKED | +| OTUkV/ODU_A_So_MI_APS_EN | true, false | true | +| OTUkV/ODU_A_So_MI_APS_LVL | 0..6,
0 for path and 1..6
for TCM | – | +| OTUkV/ODU_A_Sk_Provisioning | | | +| OTUkV/ODU_A_Sk_MI_AdminState | LOCKED, Not LOCKED | Not LOCKED | +| OTUkV/ODU_A_Sk_MI_APS_EN | true, false | true | +| OTUkV/ODU_A_Sk_MI_APS_LVL | 0..6,
0 for path and 1..6
for TCM | – | +| OTU/COMMS_A_So_Provisioning | | | +| None | | | +| OTU/COMMS_A_Sk_Provisioning | | | +| None | | | +| OTUkV/COMMS_A_So_Provisioning | | | +| None | | | +| OTUkV/COMMS_A_Sk_Provisioning | | | +| None | | | +| ODUkP/CBRx-a_A_So_Provisioning | | | +| None | | | +| ODUkP/CBRx-b_A_So_Provisioning | | | +| None | | | +| ODUkP/CBRx_A_Sk_Provisioning | | | +| ODUkP/CBRx_A_Sk_MI_CSF_Enable | True, False | False | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|-------------------------------------------------------------------------------------------------|-------------------------------|----------------| +| ODUkP/CBRx_A_Sk Reporting | | | +| ODUkP/CBRx_A_Sk_MI_AcPT,
(Note 1) | According to
[ITU-T G.798] | Not applicable | +| ODUkP/CBRx-g_A_So Provisioning | | | +| None | | | +| ODUkP/CBRx-g_A_Sk Provisioning | | | +| None | | | +| ODUkP/ CBRx-g_A_Sk Reporting | | | +| ODUkP/CBRx_A_Sk_MI_AcPT
(For the values of k and x in CBRx, see Table 15-8 of [ITU-T G.709]) | 0 to 255 | Not applicable | +| ODUP/NULL_A_So Provisioning | | | +| ODUP/NULL_A_So_MI_Nominal_Bitrate_and_Tolerance | According to
[ITU-T G.798] | Not applicable | +| ODUP/NULL_A_Sk Provisioning | | | +| None | | | +| ODUP/NULL_A_Sk Reporting | | | +| ODUP/NULL_A_Sk_MI_AcPT, k=0, 1, 2, 2e, 3, 4, flex | According to
[ITU-T G.798] | Not applicable | +| ODUP/PRBS_A_So Provisioning | | | +| ODUP/PRBS_A_So_MI_Nominal_Bitrate_and_Tolerance | According to
[ITU-T G.798] | Not applicable | +| ODUP/PRBS_A_Sk Provisioning | | | +| ODUP/PRBS_A_Sk_MI_1second | According to
[ITU-T G.798] | Not applicable | +| ODUP/PRBS_A_Sk Reporting | | | +| ODUP/PRBS_A_Sk_MI_AcPT, k=0, 1, 2, 2e, 3, 4, flex | According to
[ITU-T G.798] | Not applicable | +| ODUkP/RSn_A_So Provisioning
See clause 14.3.6 of [ITU-T G.798] | | | +| None | | | +| ODUkP/RSn_A_Sk Provisioning
See clause 14.3.6 of [ITU-T G.798] | | | +| None | | | +| ODUkP/RSn_A_Sk Reporting
See clause 14.3.6 of [ITU-T G.798] | | | +| ODUkP/RSn_A_Sk_MI_AcPT | According to
[ITU-T G.709] | Not applicable | +| ODUkP/ODU[i]j_A_So Provisioning | | | +| ODUkP/ODU[i]j_A_So_MI_AdminState[1..(n+m)] | LOCKED, Not
LOCKED | Not LOCKED | +| ODUkP/ODU[i]j_A_So_MI_APS_EN[1..(n+m)] | true, false | true | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|--------------------------------------------------------------------------------|-------------------------------------------------|----------------| +| ODUkP/ODU[i]j_A_So_MI_APS_LVL[1..(n+m)] | 0..6,
0 for path and 1..6
for TCM | – | +| ODU3P/ODU12_A_So Provisioning | | | +| ODU3P/ODU12_A_So_MI_TxMSI | According to
Table 14-30 of
[ITU-T G.798] | Not applicable | +| ODUkP/ODU[i]j_A_Sk Provisioning | | | +| ODUkP/ODU[i]j_A_Sk_MI_AdminState[1..(n+m)] | LOCKED, Not
LOCKED | Not LOCKED | +| ODUkP/ODU[i]j_A_Sk_MI_APS_EN[1..(n+m)]
when doing m x ODUi_CP respectively. | true, false | true | +| ODUkP/ODU[i]j_A_Sk_MI_APS_LVL[1..(n+m)] | 0..6,
0 for path and 1..6
for TCM | – | +| ODU3P/ODU12_A_Sk Provisioning | | | +| ODU3P/ODU12_A_Sk_MI_ExMSI[1..(n+m)] | According to
Table 14-32 of
[ITU-T G.798] | Not applicable | +| ODUkP/ODU[i]j_A_Sk Reporting | | | +| ODUkP/ODU[i]j_A_Sk_MI_AcPT | According to
[ITU-T G.709] | Not applicable | +| ODUkP/ODU[i]j_A_Sk_MI_AcMSI[1..(n+m)] | According to
[ITU-T G.709] | Not applicable | +| ODUkP/ODUj-21_A_So Provisioning | | | +| ODUkP/ODUj-21_A_So_MI_TxMSI | According to
[ITU-T G.798] | Not applicable | +| ODUkP/ODUj-21_A_So_MI_AUTOpayloadtype | According to
[ITU-T G.798] | Not applicable | +| ODUkP/ODUj-21_A_So_MI_ODUType_Rate[1..n] | According to
clause 19.6 of
[ITU-T G.709] | Not applicable | +| ODUkP/ODUj_A_So_MI_AdminState[1..n] | LOCKED, Not
LOCKED | Not LOCKED | +| ODUkP/ODUj-21_A_So_MI_APS_EN[1..n] | true, false | true | +| ODUkP/ODUj-21_A_So_MI_APS_LVL[1..n] | 0..6,
0 for path and 1..6
for TCM | – | +| ODUkP/ODUj-21_A_So Reporting | | | +| ODUkP/ODUj-21_A_So_MI_TrPT | According to
[ITU-T G.709] | Not applicable | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|-----------------------------------------------------------|-----------------------------------------------|----------------| +| ODUkP/ODUj-21_A_Sk Provisioning | | | +| ODUkP/ODUj-21_A_Sk_MI_ExMSI[1..n] | According to [ITU-T G.798] | Not applicable | +| ODUkP/ODUj-21_A_Sk_MI_AdminState[1..n] | LOCKED, Not LOCKED | Not LOCKED | +| ODUkP/ODUj-21_A_Sk_MI_Nominal_Bitrate_and_Tolerance[1..n] | According to [ITU-T G.798] | Not applicable | +| ODUkP/ODUj-21_A_Sk_MI_ODUType[1..n] | According to clause 19.6 of [ITU-T G.709] | Not applicable | +| ODUkP/ODUj-21_A_Sk_MI_APS_EN[1..n] | true, false | true | +| ODUkP/ODUj-21_A_Sk_MI_APS_LVL[1..n] | 0..6,
0 for path and 1..6 for TCM | – | +| ODUkP/ODUj-21_A_Sk Reporting | | | +| ODUkP/ODUj-21_A_Sk_MI_AcPT | According to [ITU-T G.709] | Not applicable | +| ODUkP/ODUj-21_A_Sk_MI_AcMSI[1..n] | According to [ITU-T G.709] | Not applicable | +| ODU2P/ERS10G_A_So Provisioning | | | +| ODU2P/ERS10G_A_So_MI_CSFEnable | True, False | True | +| ODU2P/ERS10G_A_So Reporting | | | +| None | | | +| ODU2P/ERS10G_A_Sk Provisioning | | | +| ODU2P/ERS10G_A_Sk_MI_CSF_Reported | True, False | False | +| ODU2P/ERS10G_A_Sk Reporting | | | +| ODU2P/ERS10G_A_Sk_MI_AcPT | 0 to 255
(See Table 15-8 of [ITU-T G.709]) | Not applicable | +| ODU2P/ERS10G_A_Sk_MI_AcEXI | 0 to 255
(See Table 6-2 of [ITU-T G.7041]) | Not applicable | +| ODU2P/ERS10G_A_Sk_MI_AcUPI | 0 to 255
(See Table 6-3 of [ITU-T G.7041]) | Not applicable | +| ODUkP/ETH_A_So Provisioning, in G.798 | | | +| ODUkP/ETH_A_So_MI_CSFEnable | True, False | True | +| ODUkP/ETH_A_So_MI_CSFrdifdiEnable (Note 2) | True, False | True | +| ODUkP/ETH_A_Sk Provisioning, | | | +| ODUkP/ETH_A_Sk_MI_FilterConfig | (Note 3) | (Note 3) | +| ODUkP/ETH_A_Sk_MI_CSF_Reported | True, False | False | +| ODUkP/ETH_A_Sk_MI_CSFrdifdiEnable (Note 2) | True, False | True | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|---------------------------------------------|-----------------------------------------------|----------------| +| ODUkP/ETH_A_Sk_MI_MAC_Length | 1518, 1522, 2000 | 2000 | +| ODUkP/ETH_A_Sk Reporting | | | +| ODUkP/ETH_A_So_MI_MI_AcPT | 0 to 255
(See Table 15-8 of [ITU-T G.709]) | Not applicable | +| ODUkP/ETH_A_So_MI_MI_AcEXI | 0 to 255
(See Table 6-2 of [ITU-T G.7041]) | Not applicable | +| ODUkP/ETH_A_So_MI_MI_AcUPI | 0 to 255
(See Table 6-3 of [ITU-T G.7041]) | Not applicable | +| ODUkP-h/ETH_A_So Provisioning | | | +| ODUkP-h/ETH_A_So_MI_CSFEnable | True, False | True | +| ODUkP-h/ETH_A_So_MI_CSFrdfidEnable (Note 2) | True, False | True | +| ODUkP-h/ETH_A_So_MI_INCREASE | True, False | False | +| ODUkP-h/ETH_A_So_MI_DECREASE | True, False | False | +| ODUkP-h/ETH_A_So_MI_TSNUM | According to [ITU-T G.7044] | Not applicable | +| ODUkP-h/ETH_A_So_MI_ODUflexRate | FlexCBR, FlexGFP | Not applicable | +| ODUkP-h/ETH_A_So Reporting | | | +| ODUkP-h/ETH-m_A_So_MI_ADJSTATE | According to [ITU-T G.7044] | Not applicable | +| ODUkP-h/ETH_A_Sk Provisioning | | | +| ODUkP-h/ETH-h_A_Sk_MI_FilterConfig | (Note 3) | (Note 3) | +| ODUkP-h/ETH-h_A_Sk_MI_CSF_ Reported | True, False | False | +| ODUkP-h/ETH_A_Sk_MI_CSFrdfidEnable (Note 2) | True, False | True | +| ODUkP-h/ETH-h_A_Sk_MI_MAC_Length | 1518, 1522, 2000 | 2000 | +| ODUkP-h/ETH_A_Sk_MI_INCREASE | True, False | False | +| ODUkP-h/ETH_A_Sk_MI_DECREASE | True, False | False | +| ODUkP-h/ETH_A_Sk Reporting | | | +| ODUkP-h/ETH_A_Sk_MI_AcPT | 0 to 255
(See Table 15-8 of [ITU-T G.709]) | Not applicable | +| ODUkP-h/ETH_A_Sk_MI_AcEXI | 0 to 255
(See Table 6-2 of [ITU-T G.7041]) | Not applicable | +| ODUkP-h/ETH_A_Sk_MI_AcUPI | 0 to 255
(See Table 6-3 of [ITU-T G.7041]) | Not applicable | +| ODUkP-h/ODUj-21_A_So Provisioning; | | | +| ODUkP-h/ODUj-21_A_So_MI_TxMSI | According to [ITU-T G.798] | Not applicable | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|--------------------------------------------------------------|-------------------------------------------|----------------| +| ODUkP-h/ODUj-21_A_So_MI_Autopayloadtype mapping. | According to [ITU-T G.798] | Not applicable | +| ODUkP-h/ODUj-21_A_So_MI_ODUType_Rate[1..n] | According to clause 19.6 of [ITU-T G.709] | Not applicable | +| ODUkP-h/ODUj-21_A_So_MI_AdminState[1..n] | According to [ITU-T G.798] | Not applicable | +| ODUkP-h/ODUj-21_A_So_MI_APS_EN[1..n] | true, false | true | +| ODUkP-h/ODUj-21_A_So_MI_APS_LVL[1..n] | 0..6,
0 for path and 1..6 for TCM | – | +| ODUkP-h/ODUj-21_A_So_MI_INCREASE | True, false | False | +| ODUkP-h/ODUj-21_A_So_MI_DECREASE | True, false | False | +| ODUkP-h/ODUj-21_A_So_MI_TSMAP | According to [ITU-T G.7044] | Not applicable | +| ODUkP-h/ODUj-21_A_So_MI_TPID | According to [ITU-T G.7044] | Not applicable | +| ODUkP-h/ODUj-21_A_So Reporting | | | +| ODUkP-h/ODUj-21_A_So_MI_TRPT | According to [ITU-T G.7044] | Not applicable | +| ODUkP-h/ODUj-21_A_So_MI_ADJSTATE | According to [ITU-T G.7044] | Not applicable | +| ODUkP-h/ODUj-21_A_Sk Provisioning | | | +| ODU3P-h /ODUj21_A_Sk_MI_ExMSI[1..n] | According to [ITU-T G.798] | Not applicable | +| ODUkP-h /ODUj-21_A_Sk_MI_AdminState[1..n] | According to [ITU-T G.798] | Not applicable | +| ODUkP-h /ODUj-21_A_Sk_MI_Nominal_Bitrate_and_Tolerance[1..n] | According to [ITU-T G.709] | Not applicable | +| ODUkP-h/ODUj-21_A_Sk_MI_APS_EN[1..n] | true, false | true | +| ODUkP-h/ODUj-21_A_Sk_MI_APS_LVL[1..n] | 0..6,
0 for path and 1..6 for TCM | – | +| ODUkP-h/ODUj-21_A_Sk_MI_ODUType[1..n] | According to clause 19.6 of [ITU-T G.709] | Not applicable | +| ODUkP-h/ODUj-21_A_Sk_MI_INCREASE | True, false | False | +| ODUkP-h/ODUj-21_A_Sk_MI_DECREASE | True, false | False | +| ODUkP-h/ODUj-21_A_Sk_MI_TSMAP | According to [ITU-T G.7044] | Not applicable | +| ODUkP-h/ODUj-21_A_Sk_MI_TPID | According to [ITU-T G.7044] | Not applicable | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|---------------------------------------------------------|-----------------------------------------------|----------------| +| ODUkP-h/ODUj-21_A_Sk Reporting | | | +| ODUkP-h/ODUj-21_A_Sk_MI_AcPT | According to [ITU-T G.709] | Not applicable | +| ODUkP-h/ODUj-21_A_Sk_MI_AcMSI[1..n]. | According to [ITU-T G.709] | Not applicable | +| ODU2eP/FC-1200_A_So Provisioning | | | +| None | | | +| ODU2eP/FC-1200_A_Sk Provisioning | | | +| None | | | +| ODU2eP/FC-1200_A_Sk Reporting | | | +| ODU2eP/FC-1200_A_Sk_MI_AcPT | 0 to 255
(See Table 15-8 of [ITU-T G.709]) | Not applicable | +| ODUCnP/ODUk_A_So Provisioning | | | +| ODUCnP/ODUk_A_So_MI_TxMSI | According to [ITU-T G.798] | Not applicable | +| ODUCnP/ODUk_A_So_MI_Nominal_Bitrate_and_Tolerance[1..m] | According to [ITU-T G.709] | Not applicable | +| ODUCnP/ODUk_A_So_MI_AdminState[1..m] | LOCKED, Not LOCKED | Not LOCKED | +| ODUCnP/ODUk_A_So_MI_APS_EN[1..m] | true, false | true | +| ODUCnP/ODUk_A_SoMI_APS_LVL[1..m] | 0..6,
0 for path and 1..6 for TCM | – | +| ODUCnP/ODUk_A_Sk Provisioning | | | +| ODUCnP/ODUk_A_Sk_MI_ExMSI | According to [ITU-T G.798] | Not applicable | +| ODUCnP/ODUk_A_Sk_MI_Nominal_Bitrate_and_Tolerance[1..m] | According to [ITU-T G.709] | Not applicable | +| ODUCnP/ODUk_A_Sk_MI_AdminState[1..m] | LOCKED, Not LOCKED | Not LOCKED | +| ODUCnP/ODUk_A_Sk_MI_APS_EN[1..m] | true, false | true | +| ODUCnP/ODUk_A_SkMI_APS_LVL[1..m] | 0..6,
0 for path and 1..6 for TCM | – | +| ODUCnP/ODUk_A_Sk Reporting | | | +| ODUCnP/ODUk_A_Sk_MI_AcPT | According to [ITU-T G.709] | Not applicable | +| ODUCnP/ODUk_A_Sk_MI_AcMSI | According to [ITU-T G.709] | Not applicable | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|--------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------|----------------| +| ODUflexP/FlexEC_A_So Provisioning | | | +| None | | | +| ODUflexP/FlexEC_A_Sk Provisioning | | | +| None | | | +| ODUflexP/FlexEC_A_Sk Reporting | | | +| ODUflexP/FlexEC_A_Sk_MI_AcPT | According to [ITU-T G.709] | Not applicable | +| ODUflexP/FlexESG_A_So Provisioning | | | +| ODUflexP/FlexESG_A_So_MI_ExGID | See clause 9.2.2 of [ITU-T G.709.1]. | Not applicable | +| ODUflexP/FlexESG_A_So_MI_ExPhyMAP | A 256 bit (8 byte) Bit Map. A bit is set to "1" indicating a member/PHY is part of the FlexO Group.
See clause 9.2.4 of [ITU-T G.709.1]. | Not applicable | +| ODUflexP/FlexESG_A_So_MI_CS_n[1..p] | Integer from 1 to 254.
See clause 9.2.2 of [ITU-T G.709.1]. | Not applicable | +| ODUflexP/FlexESG_A_So Reporting | | | +| ODUflexP/FlexESG_A_So_MI_AcCC[1..p] | According to [ITU-T G.709.1] | Not applicable | +| ODUflexP/FlexESG_A_So_MI_AcCCA[1..p] | According to [ITU-T G.709.1] | Not applicable | +| ODUflexP/FlexESG_A_So_MI_AcCCB[1..p] | According to [ITU-T G.709.1] | Not applicable | +| ODUflexP/FlexESG_A_Sk Provisioning | | | +| ODUflexP/FlexESG_A_Sk_MI_CS_n[1..p] | According to [ITU-T G.709.1] | Not applicable | +| ODUflexP/FlexESG_A_Sk Reporting | | | +| ODUflexP/FlexESG_A_Sk_MI_AcPT | According to [ITU-T G.709.1] | Not applicable | +| ODUflexP/ETCy_A_So Provisioning | | | +| None | | | +| ODUflexP/ETCy_A_So Reporting | | | +| None | | | +| ODUflexP/ETCy_A_Sk Provisioning
(See Table 14-47.1 of [ITU-T G.798] for the value of y) | | | +| ODUflexP/ETCy_A_Sk_MI_CSF_Enable | True, False | False | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|-----------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------|----------------| +| ODUflexP/ETCy_A_Sk Reporting
(See Table 14-47.1 of [ITU-T G.798] for the value of y) | | | +| ODUflexP/ETCy_A_Sk_MI_AcPT | According to [ITU-T G.709] | Not applicable | +| ODUP/COMMS_A_So Provisioning | | | +| ODUP/COMMS_A_So_MI_GCCAccess, k=0, 1, 2, 2e, 3, 4, flex | GCC1, GCC2, GCC1+GCC2 | Not applicable | +| ODUP/COMMS_A_Sk Provisioning | | | +| ODUP/COMMS_A_Sk_MI_GCCAccess, k=0, 1, 2, 2e, 3, 4, flex | GCC1, GCC2, GCC1+GCC2 | Not applicable | +| ODU/COMMS_AC_So Provisioning | | | +| ODU/COMMS_AC_So_MI_GCCAccess, k=0, 1, 2, 2e, 3, 4, flex | GCC1, GCC2, GCC1+GCC2 | Not applicable | +| ODU/COMMS_AC_Sk Provisioning | | | +| ODU/COMMS_AC_Sk_MI_GCCAccess, k=0, 1, 2, 2e, 3, 4, flex | GCC1, GCC2, GCC1+GCC2 | Not applicable | +| ODU/COMMS_AC_Sk_MI_GCCCont, k=0, 1, 2, 2e, 3, 4, flex | True, false | True | +| ODUT/ODU_A_So Provisioning | | | +| ODUT/ODU_A_So_MI_AdminState, k=0, 1, 2, 2e, 3, 4, flex | LOCKED, Not LOCKED | Not LOCKED | +| ODUT/ODU_A_Sk Provisioning | | | +| ODUT/ODU_A_Sk_MI_AdminState, k=0, 1, 2, 2e, 3, 4, flex | LOCKED, Not LOCKED | Not LOCKED | +| FlexO-n/OTUCn_A_So Provisioning | | | +| FlexO-n/OTUCn_A_So_MI_TxGID(Note 4) | Integer >=0
encoded in 20-bit.
See clause 9.2.2 of [ITU-T G.709.1]. | None | +| FlexO-n/OTUCn_A_So_MI_TxPID[1..n] (Note 5 and Note 6) | Integer from 1 to 254.
See clause 9.2.3 of [ITU-T G.709.1]. | None | +| FlexO-n/OTUCn_A_So_MI_TxPhyMAP (Note 5 and Note 8) | A 256 bit (8 byte) Bit Map. A bit is set to "1" indicating a member/PHY is part of the FlexO Group.
See clause 9.2.4 of [ITU-T G.709.1]. | None | +| FlexO-n/OTUCn_A_Sk Provisioning | | | +| FlexO/OTUCn_A_Sk_MI_ExGID (Note 4) | Integer >=0
encoded in 20-bit. | None | + +**Table 8-2 – Provisioning and reporting for adaptation functions** + +| MI signal | Value range | Default value | +|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------|---------------| +| | See clause 9.2.2 of [ITU-T G.709.1]. | | +| FlexO/OTUCn_A_Sk_MI_ExPhyMAP (Note 7 and Note 8) | A 256-bit (8 bytes) Bit Map. A bit is set to "1" indicating a member/PHY is part of the FlexO Group.
See clause 9.2.4 of [ITU-T G.709.1]. | None | +| FlexO/OTUCn_A_Sk_MI_ExPID[1..n] (Note 6 and Note 7) | Integer from 1 to 254.
See clause 9.2.2 of [ITU-T G.709.1]. | None | +| FlexO/FCC_A_So Provisioning | | | +| None defined in [ITU-T G.798] | | | +| FlexO/FCC_A_Sk Provisioning | | | +| None defined in [ITU-T G.798] | | | +| OSx/CBRx_A_So_Provisioning | | | +| None defined in [ITU-T G.798] | | | +| OSx/CBRx_A_Sk Provisioning | | | +| None defined in [ITU-T G.798] | | | +| OSx/CBRx-b_A_So_Provisioning | | | +| None defined in [ITU-T G.798] | | | +| OSx/CBRx-b_A_Sk Provisioning | | | +| OSx/CBRx-b_A_Sk_MI_FECEn | True, false | False | +| OSx/CBRx-b_A_Sk_MI_1second | True, false | False | +| OSx/CBRx-c_A_Sk Provisioning | | | +| OSx/CBRx-c_A_Sk_MI_1second | True, false | False | +| NOTE 1 – x = 2G5, 10G, 10G3, 40G. | | | +| NOTE 2 – The EMF shall configure the same value for the MI_CSFrdifdiEnable signals of the paired source and Sk functions. | | | +| NOTE 3 – According to clause 8.3 of [ITU-T G.8021]. | | | +| NOTE 4 – The EMF shall configure the same value for the MI_TxGID and MI_ExGID signals of the paired FlexO-n/OTUCn_A_So and FlexO-n/OTUCn_A_Sk functions. | | | +| NOTE 5 – The EMF shall configure consistent values between the MI_TxPID[1..n] and MI_TxPhyMAP of the same FlexO-n/OTUCn_A_So function, as described in clause 9.2.4 of [ITU-T G.709.1]. | | | +| NOTE 6 – The EMF shall configure the same values for the MI_TxPID[1..n] and MI_ExPID[1..n] signals of the paired FlexO-n/OTUCn_A_So and FlexO-n/OTUCn_A_Sk functions. | | | +| NOTE 7 – The EMF shall configure consistent values between the MI_ExPID[1..n] and MI_ExPhyMAP of the same FlexO-n/OTUCn_A_Sk function, as described in clause 9.2.4 of [ITU-T G.709.1]. | | | +| NOTE 8 – The EMF shall configure the same values for the MI_TxPhyMAP and MI_ExPhyMAP signals of the paired FlexO-n/OTUCn_A_So and FlexO-n/OTUCn_A_Sk functions. | | | + +## 8.6 Connection + +See clause 8.6 of [ITU-T G.7710] for a description of connection management. + +This function allows a user to provision the operation of an OTN connection process. + +The MI signals listed in Table 8-3 are communicated from the EMF to the connection process through the MP. + +For the connection functions supported by an O.NE, the O.NE EMF shall support the following management functions: + +- provisioning the connection MI; +- retrieving the connection MI; +- notifying the changes of the connection MI. + +**Table 8-3 – Provisioning and reporting for connection functions** + +| MI signal | Value range | Default value | +|----------------------------------------------------------------------------------|---------------------------------------------|----------------| +| OMSnP_C Provisioning | | | +| OMSnP_C_MI_OperType | Revertive, non-revertive | Revertive | +| OMSnP_C_MI_WTR | 5..12 min | FFS | +| OMSnP_C_MI_HoTime | 0..10 s in steps of 100 ms | FFS | +| OMSnP_C_MI_ExtCMD | – (Command) | Not applicable | +| OMSnP_C_MI_SSF-ODis | True, false | False | +| OTSiA OCh_C Provisioning | | | +| OTSiA OCh_C_MI_MatrixControl | Connect, disconnect | Not applicable | +| Per protection group: | Revertive, non-revertive | Revertive | +| OTSiA OCh_C_MI_OperType | 5..12 min | FFS | +| OTSiA OCh_C_MI_WTR | 0..10 s in steps of 100 ms | FFS | +| OTSiA OCh_C_MI_HoTime | – (Command) | Not applicable | +| OTSiA OCh_C_MI_ExtCMD | True, false | False | +| OTSiA OCh_C_MI_TSF-ODis | | | +| ODUk_C Provisioning | | | +| ODUk_C_MI_MatrixControl | Connect, disconnect | Not applicable | +| Per protection group: | According to clause 8.4 of [ITU-T G.873.1]. | 000x | +| ODUk_C_MI_ProtType | Revertive, non-revertive | | +| ODUk_C_MI_OperType | 5..12 min | Revertive | +| ODUk_C_MI_WTR | 0..10 s in steps of 100 ms | FFS | +| ODUk_C_MI_HoTime | – (Command) | FFS | +| ODUk_C_MI_ExtCMD | 0..7 (for Path, TCM1..6, Section) | Not applicable | +| ODUk_C_MI_APSChannel (Note) | True, false | Not applicable | +| ODUk_C_MI_SDEnable | | True | +| NOTE – According to 14.1.1 in G.798, ODUCn is excluded from ODU_C. | | | +| NOTE – For SNC protection with an automatic protection switching (APS) protocol. | | | + +Reconfigurable NEs provide connection capabilities at the OCh layer. Cross-connections can be configured between client add ports and line output ports or between line input ports and client drop ports or between line input ports and line output ports (straight through matrix connections). + +NOTE 1 – A matrix connection between a client add port and a client drop port is not useful from a network provisioning point of view, as it does not carry a signal through the optical core network, but it can be useful for loop back test purposes. + +The following management functions are identified. + +### 1) *Get connectivity capabilities* + +Because reconfigurable NEs may have static cross-connection restrictions, the OS should be aware of these restrictions. + +This function gives an overview of the fabric's static capability to connect TPs. This is done by identifying one or more sets of TPs that can be interconnected. + +Restrictions of connectivity may be caused by principal design of the switch matrix or by the fact that not all Sk TPs are fully reachable from all source TPs. One example for restricted connectivity capability is a missing frequency conversion function in an all-optical network. + +This function should not take limited processing capacity, usage or current problems into account. These additional restrictions have to be considered dynamically by the OS. + +### 2) *Report connectivity changes of an optical cross-connect* + +The availability of frequency converters in a cross-connect may change. As a consequence, the connectivity sets (sets of TPs that can be connected by the fabric) may change. The NE has to send a report when the connectivity of the fabric changes. + +NOTE 2 – After receiving a report about connectivity changes, the OS may again get all connectivity sets to update its connectivity topology. + +### 3) *Create a unidirectional point-to-point cross-connection* + +A unidirectional point-to-point cross-connection can be created between: + +- a) one ochCTPsink and one ochCTPsource (straight through); in case of connection monitoring via och adapter; +- b) one ochCTPsink and one ochTTPsink (drop); +- c) one ochTTPsource and one ochCTPsource (add); +- d) one ochTTPsource and one ochTTPsink (for loop back test purposes). + +A cross-connection object is created and a report on this creation has to be sent to the OS. + +### 4) *Remove a unidirectional point-to-point cross-connection* + +This action disconnects the ochXTPs connected together. The cross-connection object is deleted and a report on this deletion has to be sent to the OS. + +### 5) *Suspend/resume traffic on a point-to-point cross-connection* + +This function provides the possibility to suspend and resume traffic on a point-to-point cross-connection to put it out of service (suspend) or to put it in service (resume). This change has to be reported to the OS. + +### 6) *Get all point-to-point cross-connections* + +This action returns the list of all point-to-point cross-connections created. + +## 8.7 DEG thresholds + +See clause 8.7 of [ITU-T G.7710] for a description of degraded (DEG) thresholds configuration. + +## 8.8 **ZZZ\_ Reported** + +ZZZ\_ Reported is not applicable to O.NEs. + +## 8.9 Alarm severity + +See clause 8.9 of [ITU-T G.7710] for a description of alarm severity configuration functions. + +## **8.10 Alarm reporting control** + +See clause 8.10 of [ITU-T G.7710] for a description of ARC configuration functions. + +## **8.11 Performance management thresholds** + +See clause 8.11 of [ITU-T G.7710] for a description of PM threshold configuration functions. + +## **8.12 Tandem connection monitoring activations** + +See clause 8.12 of [ITU-T G.7710] for a description of TCM activation configuration functions. + +## **8.13 Date and time** + +The date and time functions within the OTN EMF comprise the local real-time clock (RTC) function and the performance monitoring clock (PMC) function. The MCF within the OTN NEF shall be capable of setting the local RTC function. + +The date and time values are incremented by a free-running local clock, or by an external timing source. The fault, configuration, accounting, performance and security (FCAPS) management functions need date and time information, e.g., to time stamp event reports. They obtain this information from the date and time function. + +### **8.13.1 Date and time applications** + +Clause 8.13.1 of [ITU-T G.7710] identifies three date and time applications. These are: + +- time-stamping; +- PMC signals; +- activity scheduling. + +The OTN NEF functional requirements for these applications are specified in clauses 8.13.1.1 to 8.13.1.3. + +#### **8.13.1.1 Time stamping** + +See clause 8.13.1.1 of [ITU-T G.7710] for a description of the time-stamping application. + +#### **8.13.1.2 Performance monitoring clock signals** + +See clause 8.13.1.2 of [ITU-T G.7710] for a description of the PMC signals. + +#### **8.13.1.3 Activity scheduling** + +See clause 8.13.1.3 of [ITU-T G.7710] for a description of the activity scheduling. + +### **8.13.2 Date and time functions** + +See clause 8.13.2 of [ITU-T G.7710] for a description of the date and time application. + +#### **8.13.2.1 Local real-time clock function** + +The local RTC function is specified in clause 8.13.2.1 of [ITU-T G.7710]. + +#### **8.13.2.2 Local real-time clock alignment function with external time reference** + +The local RTC alignment function with an external time reference is specified in clause 8.13.2.2 of [ITU-T G.7710]. + +#### **8.13.2.3 Performance monitoring clock function** + +The PMC function is specified in clause 8.13.2.3 of [ITU-T G.7710]. + +## 8.14 Control function + +The ODUT\_TCMC function (i.e., ODUKT\_TCMC or ODUCnT\_TCMC functions) are responsible for the activation or deactivation of a TCM trail. An ODUT\_TCMC function is connected to the ODUT\_TT and ODUT/ODUK\_A functions at the TCM control points (TCMCPs) as shown in Figure 14-93 of [ITU-T G.798]. + +Currently only an ODUT\_TCMC function for manual activation or deactivation via the management is defined. ODUT\_TCMC functions for automatic activation are FFS. + +The MI signals listed in Table 8-4 are communicated from the EMF to the connection process through the MP. + +For the control functions supported by an O.NE, the O.NE EMF shall support the following management functions: + +- provisioning the control MI; +- retrieving the control MI; +- notifying the changes of the control MI. + +**Table 8-4 – Provisioning and reporting for control functions** + +| MI signal | Value range | Default value | +|------------------------------|-------------------------------------------------|----------------| +| ODUT_TCMCm Provisioning | | | +| ODUT_TCMCm_MI_Level | 1..6 | Not applicable | +| ODUT_TCMCm_MI_ModeSo | OPERATIONAL, MONITOR, TRANSPARENT | FFS | +| ODUT_TCMCm_MI_ModeSk | OPERATIONAL, MONITOR, TRANSPARENT | FFS | +| ODUT_TCMCm_MI_TCM_Extension | Normal, Pass-through, Erase | Normal | +| ODUT_TCMCm Reporting | | | +| ODUT_TCMCm_MI_AcSTATSo[1..6] | According to clause 15.8.2.2.5 of [ITU-T G.709] | Not applicable | +| ODUT_TCMCm_MI_AcSTATSk[1..6] | According to clause 15.8.2.2.5 of [ITU-T G.709] | Not applicable | + +## 8.15 Application identifier management + +This clause specifies management requirements for the OTN NE having OChs that support optical system standard applications (specified in ITU-T Recommendations, e.g., [ITU-T G.695], [ITU-T G.698.2] and [ITU-T G.959.1]) and proprietary applications. + +[ITU-T G.695], [ITU-T G.698.2] and [ITU-T G.959.1] provide optical parameter values of physical layer interfaces for the coarse wavelength division multiplexing (CWDM) system, dense wavelength division multiplexing (DWDM) system, and non-wavelength division multiplexing (non-WDM) system, respectively. The applications specified in these Recommendations are determined using optical interface parameters at the main path interface S (or MPI-S) reference point, at the R (or MPI-R) reference point, as well as for the optical link between the reference points. + +The specifications of the optical interface parameters in [ITU-T G.695], [ITU-T G.698.2] and [ITU-T G.959.1] are organized according to sets of application codes. The current edition of [ITU-T G.872] has generalized the application code to application identifier so that proprietary (i.e., non-standard) applications can be handled. + +For the OTN NE having OChs that support standards or proprietary applications, there is a need to provision or report on the supported set of application identifiers and to select a specific one from the set to ensure application identifier compatibility among the transmitter, receiver and link. + +Note that an application identifier does not specify the actual nominal central frequency or actual nominal central wavelength, though it does specify the range of the nominal central frequency or wavelength. In the cases of DWDM and CWDM, in addition to the application identifier, the nominal central frequency or nominal central wavelength needs also to be specified. + +[ITU-T G.872] has introduced some new terms to better describe the media aspects of optical networking. In particular, the media path that interconnects an OCh source (So) with an OCh Sk is called a network media channel. A black link is an instance of a network media channel. + +For the OCh TT in an OTN-compliant NE supporting standard or proprietary application identifiers, the OTN NE EMF shall support the following management functions: + +- provisioning the supportable application identifiers for the OCh TT; +- retrieving the supportable application identifiers from the OCh TT; +- notifying the changes of the supportable application identifiers of the OCh TT; +- selecting the application identifier to be used for the OCh TT; +- retrieving the selected application identifier from the OCh TT; +- notifying the changes of the selected application identifier of the OCh TT; +- if the selected application identifier defines a tributary to a DWDM system, provisioning the nominal central frequency of the OCh\_TT; +- if the selected application identifier defines a tributary to a DWDM system, retrieving the nominal central frequency of the OCh\_TT; +- if the selected application identifier defines a tributary to a DWDM system, notifying the changes in the nominal central frequency of the OCh\_TT; +- if the selected application identifier defines a tributary to a CWDM system, provisioning the nominal central wavelength of the OCh\_TT; +- if the selected application identifier defines a tributary to a CWDM system, retrieving the nominal central wavelength of the OCh\_TT; +- if the selected application identifier defines a tributary to a CWDM system, notifying the changes in the nominal central wavelength of the OCh\_TT. + +Valid ITU-T standard application identifiers are specified in ITU-T Recommendations, e.g., [ITU-T G.695], [ITU-T G.698.2] and [ITU-T G.959.1]. In the management interface, when an ITU-T standard application code is referred to, the values and value ranges of the optical parameters as specified in the corresponding ITU-T Recommendation for that application code are assumed. + +Note that an operable OCh trail is formed from an OCh\_TT So, a network media channel and an OCh\_TT Sk, all of which share a common application identifier. + +Note that OCh\_TT had been specified in [ITU-T G.798]. The specification of OCh\_TT was integrated into the optical tributary signal (OTSi) modulation and demodulator processes in the 2017 edition of [ITU-T G.798]. + +## 8.16 Media element management + +This clause specifies the management requirements for the media element, in particular the input provisioning information to and the output information from the media element, of which the equipment functionality is specified in clause 16 of [ITU-T G.798]. See Table 8-5. + +**Table 8-5 – Media element-related provisioning and reporting** + +| MI signal | Value range | Default value | +|-----------------------------------------------------------------------|-------------|---------------| +| Media element provisioning | | | +| ME_MI_configureMediaChannel(port j, port k, freqSlot, signalTransfer) | FFS | FFS | +| ME_MI_configureNOM(port j, freqSlot, threshold) | FFS | FFS | +| Media element reporting | | | +| ME_MI_queryMediaChannel(port j, port k, freqSlot, signalTransfer) | FFS | FFS | +| ME_MI_NOM(port j, freqSlot, value) | FFS | FFS | + +# 9 Account management + +Account management is FFS. + +# 10 Performance management + +See clause 10 of [ITU-T G.7710] for the generic requirements for PM. OTN-specific management requirements are described as follows. + +Note that, due to the frame synchronous mapping between an optical data unit of level k, path (ODUkP, k=0, 1, 2, 2e, 3, 4, flex) and an optical data unit of level k, tandem connection sub-layer, (ODUkT; k=0, 1, 2, 2e, 3, 4, flex) and between an ODUk and an OTUk, a frame slip that already exists at the source of the ODUkT or the OTUk trail is also detected at the Sk of the ODUkT and the OTUk trail. This frame slip will result in bit error detection at the TT Sk, even if the trail contains no errors. In order to suppress these bit errors, incoming alignment error (IAE) and backward incoming alignment error (BIAE) signalling is supported in the OTN. IAE is generated at the trail source if a frame slip is detected. It is transmitted to the trail Sk to suppress the bit errors. BIAE is the signalling for the reverse direction and is used to suppress the backward error indication. Due to the detection, propagation and signalling delay, no fixed time relation between the occurrence of bit errors and the detection of the IAE exists. Therefore, bit errors detected in the current or previous second are wrong and must be suppressed if an IAE is detected. + +The following rules apply: + +- if pBIAE is active, the F\_DS and the F\_EBC values of the previous and the current second must be discarded; +- if pIAE is active, the N\_DS, the F\_DS, the N\_EBC and the F\_EBC values for the previous and the current second must be discarded. + +Note that the previous second must be discarded due to the delay of the IAE information coming from the remote source. + +## 10.1 Performance management applications + +See clause 10.1 of [ITU-T G.7710] for the generic description for PM applications. + +### 10.1.1 Concepts of near-end and far-end + +See clause 10.1.1 of [ITU-T G.7710] for a description of near-end and far-end concepts. + +### **10.1.2 Maintenance** + +See clause 10.1.2 of [ITU-T G.7710] for a description of PM for maintenance. + +### **10.1.3 Bringing-into-service** + +See clause 10.1.3 of [ITU-T G.7710] for a description of bringing-into-service. + +### **10.1.4 Quality of service** + +See clause 10.1.4 of [ITU-T G.7710] for a description of quality of service. + +### **10.1.5 Availability** + +See clause 10.1.5 of [ITU-T G.7710] for a description of availability. + +### **10.1.6 Reporting** + +See clause 10.1.6 of [ITU-T G.7710] for a description of reporting. + +As soon as a threshold is reached or crossed in a 15 min/24 h period for a given performance measurement, a threshold report (TR) is generated. + +As an option for 15 min periods, an alternative method of threshold reporting can be used. When, for the first time, a threshold is reached or crossed for a given performance measurement, a TR is generated. No TRs will be generated in subsequent 15 min periods until the value of the performance measurement falls below a specific threshold. Then, a reset threshold report (RTR) is generated. + +Performance data shall be reportable across the NE/OS interface automatically upon reaching or crossing a performance-monitoring threshold. + +#### **10.1.6.1 Performance data collection** + +See clause 10.1.6.1 of [ITU-T G.7710] for the generic description of performance data collection. + +Counter-based performance data collection refers to the measurement counting associated with each of the performance measurements and any additional performance parameter specified in this Recommendation. + +Two types of performance data collection are possible. + +- A collection as specified in [ITU-T M.2120], i.e., based on information of each direction of transport independently. This type is also referred to as performance data collection for maintenance purposes. +- The collection as specified in [ITU-T G.826], i.e., based on information of both directions of transport together. This type is also referred to as performance data collection for error performance assessment purposes. + +Counts are taken over fixed time periods of 15 min and 24 h. Counting is stopped during unavailable time. + +Gauge-based performance data collection refers to the measurement gauge crossings associated with each of the performance measurements and any additional performance parameter specified in this Recommendation. + +Performance history data is necessary to assess the recent performance of transmission systems. Such information can be used to sectionalize faults and to locate the source of intermittent errors. + +Historical data, in the form of performance measurement, may be stored in registers in the NE or in mediation devices associated with the NE. For specific applications, e.g., when only quality of service alarms are used, historical data may not be stored. + +All the history registers shall be time-stamped. + +The history registers operate as follows. + +##### – 15 min registers + +The history of the 15 min monitoring is contained in a stack of 16 registers per monitored measurement. These registers are called the recent registers. + +Every 15 min, the contents of the current registers are moved to the first of the recent registers. When all 15 min registers are used, the oldest information will be discarded. + +##### – 24 h registers + +The history of the 24 h monitoring is contained in a single register per monitored measurement. This register is called the recent register. + +Every 24 h, the contents of the current register are moved to the recent register. + +#### **10.1.6.2 History storage suppression** + +See clause 10.1.6.2 of [ITU-T G.7710] for a description of history storage suppression. + +### **10.1.7 Thresholding** + +A thresholding mechanism can be used to generate an autonomous measurement report when the performance of a transport entity falls below a predetermined level. The general strategy for the use of thresholds is described in [ITU-T M.20]. Specific information for optical networks is FFS. The thresholding mechanism is applicable only for the maintenance-based collection. + +See clause 10.1.7 of [ITU-T G.7710] for a description of thresholding. + +#### **10.1.7.1 Threshold setting** + +The thresholds may be set in the NE via the OS. The OS shall be able to retrieve and change the settings of the 15 min and 24 h thresholds. + +The threshold values for measurements evaluated over the 15 min period should be programmable within the specified range. + +#### **10.1.7.2 Threshold reporting** + +As soon as a threshold is reached or crossed in a 15 min/24 h period for a given performance measurement, a TR is generated. + +As an option for 15 min periods, an alternative method of threshold reporting can be used. When, for the first time, a threshold is reached or crossed for a given performance measurement, a TR is generated. No TRs will be generated in subsequent 15 min periods until the value of the performance measurement falls below a specific threshold. Then, an RTR is generated. + +The detailed functioning of the threshold mechanisms is FFS. + +Performance data shall be reportable across the NE/OS interface automatically upon reaching or crossing a performance-monitoring threshold. + +#### **10.1.7.3 Evaluation for counters** + +See clause 10.1.7.3 of [ITU-T G.7710] for a generic description. + +#### **10.1.7.4 Evaluation for gauges** + +See clause 10.1.7.4 of [ITU-T G.7710] for a generic description. + +### **10.1.8 Delay measurement requirements** + +- 1) OTN delay measurement is defined as a "round trip" measurement; i.e., it can only be used in bidirectional connections. + +- 2) The toggling of the DMValue has to be synchronized between the source and Sk atomic functions. +- 3) DM\_Source in the So and Sk atomic functions always has the same value. +- 4) DM\_Source should be set to false in all involved atomic functions when no delay measurement is required. +- 5) On-demand delay measurement must be supported. +- 6) Proactive delay measurement is FFS. + +## 10.2 Performance management functions + +See clause 10.2 of [ITU-T G.7710] for generic requirements of PM functions. + +OTN NE provides the PM MI in Table 10-1. + +**Table 10-1 – Performance management information** + +| Performance management information | OTN function | PM current data and history data collected in EMF | +|------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------| +| OTS-O_TT_Sk_MI_pN_DS-P
OTS-O_TT_Sk_MI_pN_DS-O
OTS-O_TT_Sk_MI_pF_DS-P
OTS-O_TT_Sk_MI_pF_DS-O | OT-On_TT_Sk | OTS-O_TTP_Sk:
nSES, fSES,
{UAS nUAS,
fUAS}(Note 1) | +| OMS-O_TT_Sk_MI_pN_DS-P
OMS-O_TT_Sk_MI_pN_DS-O
OMS-O_TT_Sk_MI_pF_DS-P
OMS-O_TT_Sk_MI_pF_DS-O | OMS-O_TT_Sk | OMS-n_TTP_Sk:
nSES, fSES,
{UAS nUAS, fUAS} | +| OTSi/OTUk_A_Sk_MI_pFECcorrErr (Note 2) | OTSi/OTUk-a_A_Sk
See Table 16-1 of [ITU-T G.798] for the function types | OTU_CTP_Sk:
CD/HD: #FECcorrErr
OTSi_TTP_Sk:
CD/HD: #FECcorrErr
where #FECcorrErr =
count of FEC-corrected
Errors | +| OTSi/OTUkV_A_Sk_MI_pFECcorrErr (Note 2) | OTSi/OTUkV_A_Sk | | +| OTSiG/OTUkV_A_Sk_MI_pFECcorrErr (Note 2) | OTSiG/OTUkV_A_Sk | | +| OTSi/FlexO-1-SC_A_Sk_MI_pFECcorrErr | OTSi/FlexO-1-SC_A_Sk | | +| OTSiG/OTUk_A_Sk_MI_pFECcorrErr | OTSiG/OTUk_A_Sk
See Table 16-6 of [ITU-T G.798] for the function types | OTSiG_TTP_Sk:
CD/HD: #FECcorrErr
where #FECcorrErr =
count of FEC-corrected
Errors | +| OTSiG/OTUCn_A_Sk_MI_pFECcorrErr | OTSiG/OTUCn_A_Sk | | +| OTSiG/FlexO_A_Sk_MI_pFECcorrErr | OTSiG/FlexO_A_Sk | | +| OTSi/OSC_A_MI_pN_DS-O | OTSi/OSC_A_Sk | OTSi/OSC_A_Sk:
nSES, fSES,
{UAS nUAS, fUAS}
(Note 1)
pN_DS-O is missing this
primitive in Table 16-18 of
[ITU-T G.798]. | + +**Table 10-1 – Performance management information** + +| Performance management information | OTN function | PM current data and history data collected in EMF | +|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------| +| OTU_TT_Sk_MI_pN_EBC
OTU_TT_Sk_MI_pN_DS
OTU_TT_Sk_MI_pF_EBC
OTU_TT_Sk_MI_pF_DS
OTU_TT_Sk_MI_pBIAE
OTU_TT_Sk_MI_pIAE | OTU_TT_Sk | OTU_TTP_Sk:
nSES, fSES,
{UAS nUAS, fUAS},
nBBE, fBBE,
(Note 4) | +| OTUkV_TT_Sk_MI_pN_EBC
OTUkV_TT_Sk_MI_pN_DS
OTUkV_TT_Sk_MI_pF_EBC
OTUkV_TT_Sk_MI_pF_DS
OTUkV_TT_Sk_MI_pBIAE (Note 3)
OTUkV_TT_Sk_MI_pIAE (Note 3) | OTUkV_TT_Sk | | +| OTSiG-O_TT_Sk_MI_pN_DS-P
OTSiG-O_TT_Sk_MI_pN_DS-O
OTSiG-O_TT_Sk_MI_pF_DS-P
OTSiG-O_TT_Sk_MI_pF_DS-O | OTSiG-O_TT_Sk | OTSiG-O_TTP_Sk:
nSES, fSES,
{UAS nUAS, fUAS},
nBBE, fBBE, | +| ODUP_TT_Sk_MI_pN_EBC
ODUP_TT_Sk_MI_pN_DS
ODUP_TT_Sk_MI_pF_EBC
ODUP_TT_Sk_MI_pF_DS
ODUP_TT_Sk_MI_pN_delay | ODUP_TT_Sk | ODUkP_TTP_Sk:
nSES, fSES,
{UAS nUAS, fUAS},
nBBE, fBBE,
Proactive DM is FFS.
See clause 14.2.1 of
[ITU-T G.798] for
pN_Delay | +| ODUkP/PRBS_A_Sk_MI_pN_TSE | ODUkP/PRBS_A_Sk | PRBS or generic client
layer CTP_Sk:
Sum of pN_TSE | +| ODUkP/CBRx-g_A_So_MI_pN_PCS_BIP
(Note 5) | ODUkP/CBRx-g_A_So
For the value of k and x
in ODUkP/CBRx, see
Table 14-18 of [ITU-T
G.798] | generic client layer
CTP_So:
Sum of pN_PCS_BIP | +| ODUkP/CBRx-g_A_Sk_MI_pN_PCS_BIP
(Note 5) | ODUkP/CBRx-g_A_Sk
For the value of k and x
in ODUkP/CBRx, see
Table 14-18 of [ITU-T
G.798] | generic client layer
CTP_Sk:
Sum of pN_PCS_BIP | +| ODUkP/ETH_A_Sk_MI_pFCSErrors | ODUkP/ETH_A_Sk | ETH or generic client
layer CTP_Sk:
Sum of pFCSErrors | +| ODUkP-h/ETH_A_Sk_MI_pFCSErrors | ODUkP-h/ETH_A_Sk | ETH or generic client
layer CTP_Sk:
Sum of pFCSErrors | + +**Table 10-1 – Performance management information** + +| Performance management information | OTN function | PM current data and history data collected in EMF | | +|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|--| +| ODUT_TT_Sk_MI_pN_EBC
ODUT_TT_Sk_MI_pN_DS
ODUT_TT_Sk_MI_pF_EBC
ODUT_TT_Sk_MI_pF_DS
ODUT_TT_Sk_MI_pN_delay
ODUT_TT_Sk_MI_pBIAE
ODUT_TT_Sk_MI_pIAE | ODUT_TT_Sk
See clause 14.5.1.1.2 of [ITU-T G.798] | ODUK_TTP_Sk:
nSES, fSES,
{UAS nUAS, fUAS},
nBBE, fBBE,
Proactive DM is FFS.
See clause 14.2.1 of [ITU-T G.798] for
pN_Delay
(Note 4) | | +| ODUTm_TT_Sk_MI_pN_EBC
ODUTm_TT_Sk_MI_pN_DS
ODUTm_TT_Sk_MI_pF_EBC
ODUTm_TT_Sk_MI_pF_DS
ODUTm_TT_Sk_MI_pBIAE
ODUTm_TT_Sk_MI_pIAE | ODUTm_TT_Sk
See clause 14.5.1.1.3 of [ITU-T G.798] | ODUkTm_TTP_Sk:
nSES, fSES,
{UAS nUAS, fUAS},
nBBE, fBBE,
(Note 4) | | +| OSx_TT_Sk_MI_pN_DS | OSx_TT_Sk | OSx_TTP_Sk:
nSES, nUAS | | +| OSx/CBRx-b_A_Sk_MI_pFECcorrErr | OSx/CBRx-b_A_Sk | OSx/CBRx_Sk:
CD/HD: #FECcorrErr
where #FECcorrErr =
count of FEC-corrected
Errors | | +| OSx/CBRx-c_A_Sk_MI_FECcorrErr | OSx/CBRx-c_A_Sk | | | +| OSx/CBRx-b_A_Sk_MI_pFECuncorrErr | OSx/CBRx-b_A_Sk | OSx/CBRx_Sk:
CD/HD: #FECuncorrErr
where #FECuncorrErr =
FEC-uncorrected Errors | | +| OSx/CBRx-c_A_Sk_MI_pFECuncorrErr | OSx/CBRx-c_A_Sk | | | +| NOTE 1 – {UAS nUAS, fUAS} means bidirectional UAS or Unidirectional "nUAS and fUAS". | | | | +| NOTE 2 – If the function performs forward error correction (FEC). | | | | +| NOTE 3 – In case of frame-synchronous mapping of ODUk client signal. | | | | +| NOTE 4 – pIAE and pBIAE are used for the suppression of the PM data in the EMFs. If pBIAE is active, the F_DS and F_EBC values of the previous and current second have to be discarded (errored block count (EBC) = 0 and defect second (DS) = false). If pIAE is active, the N/F_DS and N/F_EBC and N_delay values of the previous and current second have to be discarded (EBC = 0 and DS = false). The previous second has to be included due to the delay of the IAE information coming from the remote source. | | | | +| NOTE 5 – Applicable only when (k=3, CBRx=ETC40GR) or (k=4, CBRx=ETC100GR). | | | | + +The EMF shall support the following functions: + +- collecting OTN layer-specific current PM data as specified in Table 10-1; +- collecting OTN layer-specific history PM data as specified in Table 10-1; +- resetting of the OTN layer-specific current PM data registers; +- reporting OTN layer-specific current PM data at the maturity of the monitoring time interval; +- on-demand retrieval of the collected OTN layer-specific PM data; +- setting of the threshold of the monitored OTN layer-specific PM data collection; + +- reporting of threshold crossing for the collected OTN layer-specific current PM data; +- notifying the change of the threshold of the monitored OTN layer-specific PM data collection. + +# **11 Security management** + +FFS. + +# Appendix I + +## Management information for configuration management + +(This appendix does not form an integral part of this Recommendation.) + +Regarding CM, the OTN NEs can be configured via the following MI signals that are specified per atomic function in [ITU-T G.798]: + +- \_MI\_AutoMS +- \_MI\_AdminState +- \_MI\_APRCtrl +- \_MI\_APSChannel +- \_MI\_CellDiscardActive +- \_MI\_DTDLuseEnabled +- \_MI\_ExtCMD +- \_MI\_ExDAPI +- \_MI\_ExMSI +- \_MI\_ExSAPI +- \_MI\_FECEn +- \_MI\_GCCAccess +- \_MI\_GCCCont +- \_MI\_GetAcTI +- \_MI\_GFCActive +- \_MI\_HECActive +- \_MI\_HoTime +- \_MI\_Level +- \_MI\_MatrixControl +- \_MI\_ModeSk +- \_MI\_ModeSo +- \_MI\_OperType +- \_MI\_ProtType +- \_MI\_SDEnable +- \_MI\_TIMActDis +- \_MI\_TIMDetMo +- \_MI\_TPusgActive +- \_MI\_TSF-ODis +- \_MI\_TxMSI +- \_MI\_TxTI +- \_MI\_VPIrange +- \_MI\_VPI-KActive +- \_MI\_VPIK\_SAISActive +- \_MI\_WTR + +Regarding CM, the OTN NEs can provide the configuration data via the following MI signals that are specified per atomic function in [ITU-T G.798]: + +- \_MI\_AcMSI +- \_MI\_AcPT +- \_MI\_AcPT[1..XMR] +- \_MI\_AcTI +- \_MI\_AcSTATSk[1..6] +- \_MI\_AcSTATSo[1..6] +- \_MI\_AcVcPT + +# Appendix II + +## Management information for performance management + +(This appendix does not form an integral part of this Recommendation.) + +Regarding PM, the OTN NEs can be configured via the following MI signals that are specified per atomic function in [ITU-T G.798]: + +- \_MI\_1second +- \_MI\_DEGM +- \_MI\_DEGThr + +Regarding PM, the OTN NEs can provide the performance data via the following MI signals that are specified per atomic function in [ITU-T G.798]: + +- \_MI\_pBIAE +- \_MI\_pF\_DS-O +- \_MI\_pF\_DS-P +- \_MI\_pFECcorrErr +- \_MI\_pF\_EBC +- \_MI\_pF\_DS +- \_MI\_pIAE +- \_MI\_pN\_DS-O +- \_MI\_pN\_DS-P +- \_MI\_pN\_EBC +- \_MI\_pN\_DS +- \_MI\_pN\_delay +- \_MI\_pN\_TSE +- \_MI\_pN\_PCS\_BIP + +# Appendix III + +## Mapping between OPuk payload type and adaptation atomic function + +(This appendix does not form an integral part of this Recommendation.) + +Table III.1 maps the OPuk PTs specified in Table 15-9 of [ITU-T G.709] to the corresponding adaptation atomic functions. + +**Table III.1 – Payload type and atomic functions** + +| Payload types
Table 15-9 of [ITU-T G.709]
(clause numbers in this column are those of [ITU-T G.709]) | | Atomic functions
[ITU-T G.798] | | | +|--------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------|--| +| PT in Hex code | Interpretation | Adaptation atomic function | | | +| 01 | Experimental mapping | – | | | +| 02 | Asynchronous CBR mapping, see clause 17.2 | ODUkP/
CBRx-a_A_so | ODUkP/
CBRx_A_Sk | | +| 03 | Bit synchronous CBR mapping, see clause 17.2 | ODUkP/
CBRx-b_A_So | | | +| 04 | Not available | None | | | +| 05 | GFP mapping, see clause 17.4 | ODUkP/ETH_A
ODUkP-X-L/ETH_A;
k = 1, 2, 3
NOTE – Since GFP is not an adaptation, i.e., only a mapping, the adaptation function depends on the client signal. | | | +| 06 | Not available | None | | | +| 07 | Physical coding sublayer (PCS) codeword transparent Ethernet mapping:
1000BASE-X into OPU0 mapping, see clauses 17.7.1 and 17.7.1.1
40GBASE-R into OPU3, see clauses 17.7.4 and 17.7.4.1
100GBASE-R into OPU4, see clauses 17.7.5 and 17.7.5.1 | ODU0P/CBRx_A
(0≤x≤1.25G) | | | +| 08 | FC-1200 into OPU2e mapping, see clause 17.8.2 | ODUkP/CBRx-g_A | | | +| 09 | GFP mapping into Extended OPU2 payload, see clause 17.4.1 | ODU2P/EthPP-OS_A | | | +| 0A | STM-1 mapping into ODU0, see clause 17.7.1 | ODUkP/RSn_A | | | +| 0B | STM-4 mapping into ODU0, see clause 17.7.1 | | | | +| 0C | FC-100 mapping into ODU0, see clause 17.7.1 | ODUkP/CBRx-g_A | | | +| 0D | FC-200 mapping into ODU1, see clause 17.7.2 | | | | +| 0E | FC-400 mapping into ODUFlex, see clause 17.9 | | | | +| 0F | FC-800 mapping into ODUFlex, see clause 17.9 | | | | +| 10 | Bit stream with octet timing mapping, see clause 17.6.1 | | | | + +| Payload types
Table 15-9 of [ITU-T G.709]
(clause numbers in this column are those of [ITU-T G.709]) | | Atomic functions
[ITU-T G.798] | +|--------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------|-------------------------------------------------| +| PT in Hex code | Interpretation | Adaptation atomic function | +| 11 | Bit stream without octet timing mapping, see clause 17.6.2 | | +| 12 | IB SDR mapping into OPUflex, see clause 17.9 | | +| 13 | IB DDR mapping into OPUflex, see clause 17.9 | | +| 14 | IB QDR mapping into OPUflex, see clause 17.9 | | +| 15 | SDI mapping into OPU0, see clause 17.7.1 | | +| 16 | (1.485/1.001) Gbit/s SDI mapping into OPU1, see clause 17.7.2 | | +| 17 | 1.485 Gbit/s SDI mapping into OPU1, see clause 17.7.2 | | +| 18 | (2.970/1.001) Gbit/s SDI mapping into OPUflex, see clause 17.9 | | +| 19 | 2.970 Gbit/s SDI mapping into OPUflex, see clause 17.9 | | +| 1A | SBCON/ESCON mapping into OPU0, see clause 17.7.1 | | +| 1B | DVB_ASI mapping into OPU0, see clause 17.7.1 | | +| 1C | FC-1600 mapping into OPUflex, see clause 17.9 | | +| 1D | FlexE Client mapping into OPUflex, see clause 17.11 | OPUflexP/FlexEC | +| 1E | FlexE aware (partial rate) mapping into OPUflex, see clause 17.12 | OPUflexP/FlexESG | +| 1F | FC-3200 mapping into OPUflex, see clause 17.9 | ODUkP/CBRx-g_A | +| 20 | ODU multiplex structure supporting optical data tributary unit j into k (ODTUjk) only, see clause 19 (AMP only) | ODUkP/ODU[i]j_A | +| 21 | ODU multiplex structure supporting ODTUk.ts or ODTUk.ts and ODTUjk, see clause 19 (GMP capable) | ODUkP/ODUj-21_A | +| 22 | ODU multiplex structure supporting ODTUCn.ts, see clause 20 (GMP capable) | ODUCnP/ODUk | +| 30 | 25GBASE-R mapping into OPUflex, see clause 17.13 | OPUflexP/xGBASE-R | +| 31 | 200GBASE-R mapping into OPUflex, see clause 17.13 | | +| 32 | 400GBASE-R mapping into OPUflex, see clause 17.13 | | +| 33 | 50GBASE-R mapping into OPUflex, see clause 17.13 | | +| 55 | Not available | None | +| 66 | Not available | None | +| 80-8F | Reserved codes for proprietary use | None | +| FD | NULL test signal mapping, see clause 17.5.1 | ODUkP/NULL_A | +| FE | PRBS test signal mapping, see clause 17.5.2 | ODkP/PRBS_A | +| FF | Not available | None | + +NOTE – The PT does not have a unique value for every adaptation function. Multiple adaptation functions share the same PT value. An overview is presented as follows. + +- 14.3.1/G.798 ODUkP/CBRx\_A, bit sync: = <1,2G5>, <2,10G>, <2e,10G3>, <3,40G>, , async: <1,2G5> (20 ppm), <1,2G5> (32 ppm), <2,10G>, <3,40G>; no need to manage 2G5 ppm differences +PT of these adaptation functions; +PT=0x02 for async mapping of CBR2G5, CBR10G, CBR40G +PT=0x03 for bitsync mapping of CBR2G5, CBR10G, CBR10G3, CBR40G +PT=0x0E for bitsync mapping of FC400 +PT=0x0F for bitsync mapping of FC800 +PT=0x12 for bitsync mapping of IB QDR +PT=0x13 for bitsync mapping of IB QDR +PT=0x14 for bitsync mapping of IB QDR +PT=0x18 for bitsync mapping of (2.970/1.001)G SDI +PT=0x19 for bitsync mapping of 2.970G SDI +PT=0x1C for bitsync mapping of FC1600 +- 14.3.3/G.798 ODU2P/EthPP\_OS\_A => 11.5.3/G.8021 ODU2P/EthOS\_A +PT=0x05 +- 14.3.4/G.798 ODUkP/NULL\_A +PT=0xFD. +Additional control here is for ODUk, k=flex the nominal bit rate. +- 14.3.5/G.798 ODUkP/PRBS\_A +PT=0xFE. +Additional control here is for ODUk, k=flex the nominal bit rate. +- 14.3.6/G.798 ODUkP/RSn\_A, = <1,16>, <2,64>, <3,256> +PT=0x02 for async mapping of RS16, RS64, RS256, +PT=0x03 for bitsync mapping of RS16, RS64, RS256.14.3.7 ODU0P/CBRx\_A, x = 155M, 622M, ETC3, FC100, SBCON, DVB\_ASI +PT=0x0A for STM-1 (155M) mapping into OPU0 +PT=0x0B for STM-4 (622M) mapping into OPU0 +PT=0x0C for FC100 +PT=0x07 for 1000BASE-X (ETC3) +PT=0x1A for SBCON/ESCON +PT=0x1B for DVB\_ASI +Table III.2 maps PT values of SDHs to ODUs. + +**Table III.2 – PT of SDH to ODU mapping** + +| ODUk | SDH | PT | | | +|------|-------------|------|------|------| +| | | BMP | AMP | GMP | +| ODU0 | STM-1(155M) | – | – | 0x0A | +| ODU0 | STM-4(622M) | – | – | 0x0B | +| ODU1 | STM – 4 | 0x03 | 0x02 | – | +| ODU2 | STM - 16 | 0x03 | 0x02 | – | +| ODU3 | STM – 64 | 0x03 | 0x02 | – | + +- 14.3.8/G.798 ODUkP/CBRx-g\_A, CBRx-g = ETC5, ETC6, FC200 + PT=0x07 for 40GBASE-R (ETC5) + PT=0x07 for 100GBASE-R (ETC6) + PT=0x0D for FC200 +- 14.3.9/G.798 ODUkP/ODU[i]j\_A + PT=0x20. + Additional control here is on a per LO optical data unit of level j (ODUj) basis, which can be performed as part of LO ODU connection management: + MI\_TxMSI, MI\_ExMSI[p], MI\_AdminState[p], MI\_APS\_EN[p], MI\_APS\_LVL [p] +- 14.3.10/G.798 ODUkP/ODUj-21\_A + PT=0x21 + Additional control here is MI\_AUTOpayloadtype. + Further additional control is on a per LO ODUj basis, which can be performed as part of LO ODU connection management: + MI\_TxMSI, MI\_ExMSI[p], MI\_ODUType\_Rate[i], MI\_AdminState[n], MI\_APS\_EN [n], MI\_APS\_LVL [n] +- 14.3.11/G.798 ODUkP/ETH\_A, see 11.5.1/G.8021 ODUkP/ETH\_A + PT=0x06. + vcPT=0x05. + Additional control here is MI\_CSFEnable and MI\_CSFrdifdiEnable, MI\_FilterConfig, MI\_CSF\_Reported, MI\_MAC\_Length. +- 14.3.12/G.798 ODUkP-h/ETH\_A, k=flex + PT=0x05. The same PT value is used for this hitless adjustment of ODUflex(GFP) (HAO) capable function as for the regular, non-HAO capable function. + Additional control here is MI\_ODUflexRate, MI\_CSFEnable, MI\_CSFrdifdiEnable, MI\_FilterConfig, MI\_CSF\_Reported, MI\_MAC\_Length. + Further additional control here is for HAO; i.e., MI\_INCREASE, MI\_DECREASE, MI\_TSNUM. +- 14.3.13/G.798 ODUkP-h/ODUj-21\_A + PT=0x21. The same PT value is used for this HAO capable function as for the regular, non-HAO capable function. + Additional control here is MI\_AUTOpayloadtype. + +Further additional control is on a per LO ODUj basis, which can be performed as part of LO ODU connection management: + +MI\_TxMSI[p], MI\_ExMSI[p], MI\_ODUType\_Rate[i], MI\_AdminState[n], MI\_APS\_EN[n], MI\_APS\_LVL[n] + +Further additional control here is for HAO of a LO ODUflex; i.e., MI\_INCREASE, MI\_DECREASE, MI\_TSMAP, MI\_TPID. + +- [14.3.v/G.798 ODU2eP/FC1200\_A] to be added + +PT=0x08. + +- [14.3.x/G.798 ODUkP/MT\_A] see 11.2.1/G.8121 ODUkP/MT\_A + +PT=0x05. This PT value is the same as for ODUkP/ETH\_A functions. + +Additional control here is MI\_SCCType. + +Further additional control is on a per PW/LSP basis, which can be performed as part of LO ODU connection management: + +MI\_Label[1...M], MI\_LSPTYPE[1...M], MI\_CoS[1...M], MI\_PHB2TCMapping[1...M], MI\_QoSEncodingMode[1...M], MI\_TC2PHBMapping[1...M], MI\_QoSDecodingMode[1...M], MI\_LCK\_Period[1...M], MI\_LCK\_CoS[1...M], MI\_Admin\_State, MI\_AIS\_Period[1...M], MI\_AIS\_CoS[1...M], MI\_GAL\_Enable[1...M] + +- [14.3.z/G.798 ODUkP-h/MT\_A] to be added to e.g., 11.2.3/G.8121 or 14.3.z/G.798 + +Not specified yet. + +- [17.13/G.709] Mapping a 64b/66b PCS coded signal into OPUflex using BMP and 2-bit alignment of 66b code words + +PT=0x30, 25GBASE-R mapping into OPUflex + +PT=0x31, 200GBASE-R mapping into OPUflex + +PT=0x32, 400GBASE-R mapping into OPUflex + +PT=0x33, 50GBASE-R mapping into OPUflex + +- [17.11/G.709] OPUflexP/FlexE + +*Mapping of FlexE Client signals into OPUflex using IMP* + +*FlexE Client signal bit rates are $s \times 5,156,250.000$ kbit/s $\pm 100$ ppm, with $s = 2, 8, n*5$ ( $n \geq 1$ ).* + +*Refer to [OIF FlexE IA].* + + + + + + + +# SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.967.3-200003-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/G/T-REC-G.967.3-200003-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..ab2cbdd4af6bc1ea9ffa8cca87f9d455eb147008 --- /dev/null +++ b/marked/G/T-REC-G.967.3-200003-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:94ee226724314e8b36ac3c73e99f9ed2a4fbb4786e0c7f3f43c1debd5966aa00 +size 8239 diff --git a/marked/G/T-REC-G.967.3-200003-I_PDF-E/raw.md b/marked/G/T-REC-G.967.3-200003-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..71b89d691093a363b35f88664edbc842aa8d997d --- /dev/null +++ b/marked/G/T-REC-G.967.3-200003-I_PDF-E/raw.md @@ -0,0 +1,227 @@ + + +![ITU logo: A globe with a lightning bolt and the letters ITU.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: A globe with a lightning bolt and the letters ITU. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +**G.967.3** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +(03/2000) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital transmission systems – Digital sections and digital +line system – Digital section and digital transmission +systems for customer access to ISDN + +--- + +**V-interfaces at the service node (SN): Protocol +implementation conformance statements for +interfaces at VB5 reference points** + +ITU-T Recommendation G.967.3 + +(Formerly CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|-----------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| General | G.900–G.909 | +| Parameters for optical fibre cable systems | G.910–G.919 | +| Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s | G.920–G.929 | +| Digital line transmission systems on cable at non-hierarchical bit rates | G.930–G.939 | +| Digital line systems provided by FDM transmission bearers | G.940–G.949 | +| Digital line systems | G.950–G.959 | +| Digital section and digital transmission systems for customer access to ISDN | G.960–G.969 | +| Optical fibre submarine cable systems | G.970–G.979 | +| Optical line systems for local and access networks | G.980–G.989 | +| Access networks | G.990–G.999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## **V-interfaces at the service node (SN) – Protocol implementation conformance statements for interfaces at VB5 reference points** + +## **Summary** + +This ITU-T Recommendation defines the Protocol Implementation Conformance Statements (PICS) for protocols across the VB5 reference point as a supporting tool to ensure the interoperability of Access Networks and Service Nodes connected via interfaces at the VB5 reference points. It covers both the Real-Time Management Coordination (RTMC) protocol which applies to the VB5.1 and the VB5.2 reference point and the Broadband Bearer Connection Control (B-BCC) protocol which exclusively applies to the VB5.2 reference point. To evaluate conformance of a particular implementation, it is necessary to have a statement of which capabilities and options have been implemented for a telecommunication specification. Such a statement is called a Protocol Implementation Conformance Statement (PICS). + +### **Source** + +ITU-T Recommendation G.967.3 was prepared by ITU-T Study Group 13 (1997-2000) and approved under the WTSC Resolution 1 procedure on 10 March 2000. + +### **Keywords** + +Access Network, PICS, Service Node, VB5 reference points. + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSC Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +### NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +### INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2001 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +## CONTENTS + +###### Page + +| | | | +|-----|-------------------------------------------------------|---| +| 1 | Scope..... | 1 | +| 2 | References..... | 1 | +| 3 | Definitions and abbreviations ..... | 2 | +| 3.1 | Definitions ..... | 2 | +| 3.2 | Abbreviations..... | 2 | +| 4 | PICS for interfaces at the VB5.1 reference point..... | 2 | +| 5 | PICS for interfaces at the VB5.2 reference point..... | 3 | +| 6 | Differences from the ETSI PICS documents ..... | 3 | +| 6.1 | Differences from EN 301 005-2 [3]..... | 3 | +| 6.2 | Differences from EN 301 217-2 [5]..... | 3 | + +## **V-interfaces at the service node (SN) – Protocol implementation conformance statements for interfaces at VB5 reference points** + +## **1 Scope** + +This ITU-T Recommendation defines the Protocol Implementation Conformance Statements (PICS) for protocols across the VB5 reference point as a supporting tool to ensure the interoperability of Access Network and Service Nodes connected via interface(s) at the VB5 reference point. It covers both the Real-Time Management Coordination (RTMC) protocol which applies to the VB5.1 and the VB5.2 reference point and the Broadband Bearer Connection Control (B-BCC) protocol which exclusively applies to the VB5.2 reference point. To evaluate conformance of a particular implementation, it is necessary to have a statement of which capabilities and options have been implemented for a telecommunication specification. Such a statement is called a Protocol Implementation Conformance Statement (PICS). + +## **2 References** + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- [1] ITU-T Recommendation G.967.1 (1998), *V-interfaces at the service node (SN) – VB5.1 reference point specification*. +- [2] ITU-T Recommendation G.967.2 (1999), *V-interfaces at the service node (SN) – VB5.2 reference point specification*. +- [3] ETSI EN 301 005-2 (1998), *V-interfaces at the digital Service Node (SN); Interfaces at the VB5.1 reference point for the support of broadband or combined narrowband and broadband Access Networks (ANs); Part 2: Protocol Implementation Conformance Statement (PICS) proforma specification*. +- [4] ETSI EN 301 005-1 (1998), *V interfaces at the digital Service Node (SN); Interfaces at the VB5.1 reference point for the support of broadband or combined narrowband and broadband Access Networks (ANs); Part 1: Interface specification*. +- [5] ETSI EN 301 217-2 (1999), *V interfaces at the digital Service Node (SN); Interfaces at the VB5.2 reference point for the support of broadband or combined narrowband and broadband Access Networks (ANs); Part 2: Protocol Implementation Conformance Statement (PICS) proforma specification*. +- [6] ETSI EN 301 217-1(1999), *V interfaces at the digital Service Node (SN); Interfaces at the VB5.2 reference point for the support of broadband or combined narrowband and broadband Access Networks (ANs); Part 1: Interface specification*. +- [7] ISO/IEC 9646-1:1994 *Information technology – Open Systems Interconnection – Conformance testing methodology and framework – Part 1: General concepts*. + +## 3 Definitions and abbreviations + +### 3.1 Definitions + +For the purposes of this ITU-T Recommendation, the following terms defined in ISO/IEC 9646-1 [7] apply: + +**3.1.1 Implementation Conformance Statement (ICS):** A statement made by the supplier of an implementation or system claimed to conform to a given specification, stating which capabilities have been implemented. + +**3.1.2 Protocol Implementation Conformance Statement (PICS):** An ICS for an implementation or system claimed to conform to a given protocol specification. + +**3.1.3 ICS pro forma:** Document, in the form of a questionnaire, which when completed for an implementation or system becomes an ICS. + +**3.1.4 static conformance review:** Review of the extent to which the static conformance requirements are met by the Implementation Under Test (IUT), accomplished by comparing the PICS with the static conformance requirements expressed in the relevant standard(s) (see ISO/IEC9646-1 [7] ). + +### 3.2 Abbreviations + +This Recommendation uses the following abbreviations: + +| | | +|-------|------------------------------------------------| +| AN | Access Network | +| B-BCC | Broadband Bearer Connection Control | +| ETSI | European Telecommunication Standards Institute | +| ICS | Implementation Conformance Statement | +| IUT | Implementation Under Test | +| PICS | Protocol Implementation Conformance Statement | +| RTMC | Real Time Management Coordination | +| SAAL | Signalling ATM Adaptation Layer | +| SN | Service Node | +| VCL | Virtual Channel Link | +| VPCI | Virtual Path Connection Identifier | +| VPL | Virtual Path Link | + +## 4 PICS for interfaces at the VB5.1 reference point + +ITU-T Recommendation G.967.1 [1] specifies the physical, procedural and protocol requirements for interfaces at the VB5.1 reference point between an Access Network (AN) and a Service Node (SN) with flexible (provisioned) Virtual Path Link (VPL) allocation and flexible (provisioned) Virtual Channel Link (VCL) allocation (controlled by the Q3 interfaces) at the VB5.1 reference point. + +The detailed PICS which conforms to the VB5.1 reference point shall be as shown in ETSI EN 301 005-2 – "VB5.1 Protocol Implementation Conformance Statement (PICS) proforma specification" [3]. + +NOTE – In the ETSI EN 301 005-2 [3], reference is made to EN 301 005-1 [4] for the detailed VB5.1 specification and subclauses. All such references should be understood to refer also to the corresponding subclauses of ITU-T Recommendation G.967.1 [1]. (Subclause numbering is the same in both documents.) + +## 5 PICS for interfaces at the VB5.2 reference point + +ITU-T Recommendation G.967.2 [2] specifies the physical, procedural and protocol requirements for interfaces at the VB5.2 reference point between an Access Network (AN) and a Service Node (SN). The VB5.2 reference point provides flexible (provisioned) Virtual Path Link (VPL) allocation and flexible (provisioned) Virtual Channel Link (VCL) allocation (controlled by the Q3 interfaces) as well as on-demand VCL allocation controlled by the SN via the broadband bearer connection control (B-BCC) protocol. + +The VB5.2 reference point is a superset of the VB5.1 reference point, enabling on-demand VCL allocation in the AN and across the VB5 reference point via the additional B-BCC function. That is the PICS for interfaces at the VB5.2 reference point comprise the PICS defined for the VB5.1 reference point and those which are specific for the B-BCC protocol. + +The detailed PICS which conforms to the VB5.2 reference point shall be as shown in ETSI EN 301 217-2 – "VB5.2 Protocol Implementation Conformance Statement (PICS) proforma specification" [5]. + +NOTE – In ETSI EN 301 217-2 [5], reference is made to EN 301 005-1 [4] for the detailed VB5.1 specification and subclauses, and to EN 301 217-1 [6] for the detailed VB5.2 specification and subclauses. All such references should be understood to refer also to the corresponding subclauses of ITU-T Recommendations G.967.1 [1] and G.967.2 [2] respectively. (In both cases, subclause numbering is the same in the corresponding ITU-T and ETSI documents.) + +## 6 Differences from the ETSI PICS documents + +### 6.1 Differences from EN 301 005-2 [3] + +- "13.6.1.5.2" in the column "Reference" for item 9 of Table A.11 should be replaced by "13.3.1.5.2". +- "13.6.1.5.2" in the column "Reference" for item 9 of Table A.29 should be replaced by "13.3.1.5.2". + +### 6.2 Differences from EN 301 217-2 [5] + +- "13.6.1.5.2" in the column "Reference" for item 9 of Table A.12 should be replaced by "13.3.1.5.2". +- "13.6.1.5.2" in the column "Reference" for item 9 of Table A.49 should be replaced by "13.3.1.5.2". +- "AM\_FAULT\_ACC" in the column "message" for item 9 of Table A.55 should be replaced by "AN\_FAULT\_ACC". + +## **SERIES OF ITU-T RECOMMENDATIONS** + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure and Internet protocol aspects | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.975-200010-I_PDF-E/raw.md b/marked/G/T-REC-G.975-200010-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..67552122464e0873860e8255687c4a6abe4f128c --- /dev/null +++ b/marked/G/T-REC-G.975-200010-I_PDF-E/raw.md @@ -0,0 +1,696 @@ + + +![ITU logo](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +The logo of the International Telecommunication Union (ITU) features the letters 'ITU' in a bold, sans-serif font, superimposed on a stylized globe with latitude and longitude lines. A lightning bolt symbol is positioned to the right of the globe. + +ITU logo + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.975** + +(10/2000) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital sections and digital line system – Optical fibre +submarine cable systems + +--- + +**Forward error correction for submarine systems** + +ITU-T Recommendation G.975 + +(Formerly CCITT Recommendation) + +--- + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TESTING EQUIPMENTS | G.500–G.599 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| General | G.900–G.909 | +| Parameters for optical fibre cable systems | G.910–G.919 | +| Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s | G.920–G.929 | +| Digital line transmission systems on cable at non-hierarchical bit rates | G.930–G.939 | +| Digital line systems provided by FDM transmission bearers | G.940–G.949 | +| Digital line systems | G.950–G.959 | +| Digital section and digital transmission systems for customer access to ISDN | G.960–G.969 | +| Optical fibre submarine cable systems | G.970–G.979 | +| Optical line systems for local and access networks | G.980–G.989 | +| Access networks | G.990–G.999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# **Forward error correction for submarine systems** + +## **Summary** + +The present Recommendation is primarily concerned with the implementation of a Forward Error Correction (FEC) function in the multigigabit-per-second optical fibre submarine cable systems. The applications being addressed in this Recommendation are both optically amplified repeated systems and repeaterless optical systems (described in ITU-T G.973 [3]). The use of this FEC function in submarine terminal transmission equipment is not mandatory. + +###### **Source** + +ITU-T Recommendation G.975 was revised by ITU-T Study Group 15 (1997-2000) and approved under the World Telecommunication Standardization Assembly (Montreal, 27 September – 6 October 2000). + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. + +© ITU 2001 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. + +## CONTENTS + +| | Page | +|-------------------------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Terms and definitions ..... | 1 | +| 4 Abbreviations..... | 2 | +| 5 FEC features ..... | 2 | +| 5.1 General principles of the FEC function ..... | 2 | +| 5.2 Error monitoring capability ..... | 3 | +| 5.3 Interest of the FEC function for submarine systems..... | 4 | +| 5.4 Inter-terminal channels ..... | 4 | +| 6 Definition of the FEC function ..... | 4 | +| 6.1 Definitions ..... | 4 | +| 6.2 Forward Error Correction algorithm..... | 4 | +| 6.3 Properties of the RS(255,239) code..... | 5 | +| 6.4 FEC frame structure..... | 5 | +| 6.4.1 FEC encoder and FEC decoder architectures ..... | 5 | +| 6.4.2 Framing structure..... | 8 | +| 6.4.3 Scrambling..... | 8 | +| 6.4.4 Redundancy ratio ..... | 8 | +| 7 FEC function performance..... | 9 | +| 7.1 Theoretical FEC function performance ..... | 9 | +| 7.2 Coding gain..... | 10 | +| Appendix I – FEC frame structure (optional) ..... | 11 | +| I.1 FEC encoder and FEC decoder architecture..... | 11 | +| I.2 Framing structure ..... | 14 | +| I.3 Scrambling ..... | 14 | +| I.4 Redundancy ratio ..... | 15 | + +## **Forward error correction for submarine systems** + +# **1 Scope** + +The present Recommendation is primarily concerned with the implementation of a Forward Error Correction (FEC) function in the multigigabit-per-second optical fibre submarine cable systems. The applications being addressed in this Recommendation are both optically amplified repeated systems and repeaterless optical systems (ITU-T G.973 [3]). The use of this FEC function in submarine terminal transmission equipments (TTEs) should not be considered as mandatory. + +It is not the intention of this Recommendation to pursue the transverse compatibility of the system. Therefore the selection of the FEC frame structures described in this Recommendation is a matter of joint engineering. + +The transmission data rates under consideration in this Recommendation are 2.5 Gbit/s STM-16 (ITU-T G.707 [1]) and integer multiples of 2.5 Gbit/s (interleaved STM-16 tributaries). + +Clause 5 presents the main features of the FEC function implemented in the submarine systems, and in particular the error monitoring facility. + +Clause 6 provides the definition of the forward error correction algorithm to be used, which is a Reed-Solomon code, and gives guidelines for the implementation of this algorithm in the submarine Terminal Transmission Equipments (TTEs). + +Clause 7 is dedicated to the measurement of the performance of this Reed-Solomon code and the expected gain on the optical transmission power budget. + +# **2 References** + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- [1] ITU-T G.707 (1996), *Network node interface for the synchronous digital hierarchy (SDH)*. +- [2] ITU-T G.972 (1997), *Definition of terms relevant to optical fibre submarine cable systems*. +- [3] ITU-T G.973 (1996), *Characteristics of repeaterless optical fibre submarine cable systems*. + +# **3 Terms and definitions** + +This Recommendation uses the following terms defined in other Recommendations: + +- Synchronous Digital Hierarchy (SDH): See ITU-T G.707 [1]. +- Synchronous Transport Module (STM): See ITU-T G.707 [1]. +- Optical fibre submarine cable system: See ITU-T G.972 [2]. +- Terminal Transmission Equipment (TTE): See ITU-T G.972 [2]. +- Optical power budget: See ITU-T G.972 [2]. +- Service channel: See ITU-T G.972 [2]. + +- Order wire channel: See ITU-T G.972 [2]. +- Line error ratio: See ITU-T G.972 [2]. +- Forward Error Correction (FEC): See ITU-T G.972 [2]. +- FEC frame: See ITU-T G.972 [2]. +- FEC encoder: See ITU-T G.972 [2]. +- FEC decoder: See ITU-T G.972 [2]. + +# 4 Abbreviations + +This Recommendation uses the following abbreviations: + +BER Bit Error Ratio + +EDFA Erbium-Doped Fibre Amplifier + +FEC Forward Error Correction + +GF Galois Field + +RS Reed-Solomon + +# 5 FEC features + +## 5.1 General principles of the FEC function + +The FEC function defined in this Recommendation works on the STM-16 basis. When $M$ ( $M$ integer different from 0) STM-16 signals are interleaved to achieve $M \times 2.5$ Gbit/s transmission data rates, the encoding is performed before the interleaving of the $M$ STM-16 tributaries and the decoding is performed after the de-interleaving of the optical line signal. + +The FEC function essentially comprises: + +- a FEC encoder in the transmit Terminal Transmission Equipment (TTE) that accepts information bits and adds computed redundant symbols, producing encoded data at a higher bit rate; +- a FEC decoder in the receive Terminal Transmission Equipment (TTE) that performs the error correction while extracting the redundancy to regenerate the data that was encoded by the FEC encoder. + +Figure 1 outlines the fact that the encoding and decoding procedures are performed at the Terminal Transmission Equipment (TTE) level only, on electrical signals, and benefit the overall optical fibre submarine cable system, which comprises the optical fibre and possibly optical modules such as optical amplifiers using EDFA technology. + +![Block diagram of a submarine system using FEC. The diagram shows two main sections: TRANSMIT TTE and RECEIVE TTE, connected by an Optical section. The TRANSMIT TTE takes STM-16 inputs (x M) through Optical Receivers and FEC encoders into an Interleaver & Transmit optical terminal interface, which outputs signal S. The RECEIVE TTE takes signal I from the Optical section through a De-interleaver & Receive optical terminal interface into FEC decoders and Optical Transmitters, which output STM-16 signals (x M). Noise is shown entering the Optical section.](3121ebddccf183ca63bb9781be440a7e_img.jpg) + +The diagram illustrates a submarine system architecture using Forward Error Correction (FEC). It is divided into two main functional blocks: TRANSMIT TTE and RECEIVE TTE, connected by an Optical section. + +- TRANSMIT TTE:** This block takes multiple STM-16 inputs (labeled x M) as input. Each input passes through an Optical Receiver and then an FEC encoder. The outputs of the FEC encoders are then processed by an Interleaver & Transmit optical terminal interface, which produces the signal S for transmission. +- Optical section:** This is the physical transmission medium. It receives signal S from the transmit side and outputs signal I to the receive side. Noise is shown as an external input to this section. +- RECEIVE TTE:** This block receives signal I from the optical section through a De-interleaver & Receive optical terminal interface. The signal then passes through an FEC decoder and an Optical Transmitter to produce the final STM-16 outputs (labeled x M). + +Block diagram of a submarine system using FEC. The diagram shows two main sections: TRANSMIT TTE and RECEIVE TTE, connected by an Optical section. The TRANSMIT TTE takes STM-16 inputs (x M) through Optical Receivers and FEC encoders into an Interleaver & Transmit optical terminal interface, which outputs signal S. The RECEIVE TTE takes signal I from the Optical section through a De-interleaver & Receive optical terminal interface into FEC decoders and Optical Transmitters, which output STM-16 signals (x M). Noise is shown entering the Optical section. + +T1520650-96 + +**Figure 1/G.975 – Block diagram of a submarine system which uses a FEC function** + +## 5.2 Error monitoring capability + +The implementation of a FEC function allows the in-line monitoring of the line Bit Error Ratio before correction ( $BER_{Input}$ ) through the knowledge of the exact number of corrected bits ( $BER_C$ ). The errors that remain uncorrected after forward error correction ( $BER_{Output}$ ) (these errors remain when the number of line errors is beyond the decoder's ability to correct) can be considered negligible in the computation of $BER_{Input}$ ( $BER_{Input} = BER_C + BER_{Output} \approx BER_C$ ), for low error rates. + +The conditions that could make the previous statement inaccurate ( $BER_{Input} > 10^{-3}$ ) would lead the system into an intermittent loss of FEC frame alignment state (see 5.4 for the FEC frame definition). In fact, the $10^{-3}$ bit error rate represents the limit beyond which the FEC function becomes inefficient. + +The forward error correction code reports the evolution of the line errors (the measurable values of the $BER_{Input}$ are comprised of between $10^{-3}$ and $10^{-15}$ ) while keeping the system faultless by correcting these errors. Consequently, the FEC function can dynamically provide an evaluation of the system margins relative to the required level of performance. If a maintenance of the line appears to be necessary, it can then be planned before any effective degradation of the transmission. + +## 5.3 Interest of the FEC function for submarine systems + +The implementation of a Forward Error Correction (FEC) function in optical fibre submarine cable systems provides significant gains over the overall optical power budget of the link, and lowers at the same time the line BER floor of the system (see 7.2). + +The resulting gain over the optical power budget obtained with the FEC technique can then be used to improve either: + +- the line parameters: + +For repeaterless submarine applications, the FEC function will possibly be used to increase the maximum span length. + +For optically amplified submarine applications, the FEC function will possibly be used to either increase the inter-repeater distances or relax optical component and line fibre specifications. + +- the overall quality of communication for protection against unwanted degraded operating conditions (component or cable failure, due to ageing for instance). + +In counterpart, the use of the FEC function in the submarine Terminal Transmission Equipments (TTEs) introduces an increase of the line bit rate. + +## 5.4 Inter-terminal channels + +Provided that a framing structure is included in the FEC frame (see 6.4.2), it is possible to transmit tributary markers for systems carrying several interleaved STM-16 signals, or to transmit order wire channels or service channels through the unused bits of the framing structure. + +# 6 Definition of the FEC function + +## 6.1 Definitions + +**6.1.1 block code:** Such codes are characterized by the fact that the encoder accepts K information symbols from the information source and appends a set of R redundant symbols derived from the information symbols, in accordance with the code algorithm. + +**6.1.2 cyclic code:** A linear code is said to be cyclic when any cyclic shift of a codeword is also a codeword. + +**6.1.3 systematic code:** With such codes, the information word is not disturbed in any way in the encoder and the redundant symbols are added separately to each block. + +**6.1.4 information word:** The information word contains K information symbols. + +**6.1.5 codeword:** The block of N symbols that carries the K information symbols and the R redundant symbols ( $N = K + R$ ). + +## 6.2 Forward Error Correction algorithm + +The Forward Error Correction code used to protect the STM-16 information against in-line errors in the optical fibre submarine cable systems is a Reed-Solomon code, already specified in the CMTT Recommendation CCIR 723: the RS(255,239) code. The RS(255,239) code is a non-binary code (the FEC algorithm operates on 8-bit symbols) and belongs to the family of systematic linear cyclic block codes. + +The generator polynomial of the code is given by: + +$$G(z) = \prod_{i=0}^{15} (z - \alpha^i)$$ + +where $\alpha$ is a root of the binary primitive polynomial $x^8 + x^4 + x^3 + x^2 + 1$ . A data byte ( $d_7, d_6, \dots, d_1, d_0$ ) is identified with the element $d_7 \cdot \alpha^7 + d_6 \cdot \alpha^6 + \dots + d_1 \cdot \alpha^1 + d_0$ in GF(256), the finite field with 256 elements. + +## 6.3 Properties of the RS(255,239) code + +With regard to the wide variety of forward error correction codes, the selection of a particular forward error correction code consists in part of matching the features of a coding technique with the system objectives being addressed. + +The choice of the Reed-Solomon code for optical fibre submarine cable systems is essentially motivated by the following properties: + +- an important error correcting capacity with respect to the redundancy ratio applied to the information word: the RS(255,239) algorithm can correct up to 8 erroneous byte-symbols in a single codeword of length 255; +- a low complexity of both the FEC encoder and the FEC decoder; +- a coding structure compatible with binary transmissions, providing that a demultiplexing operation is performed; +- an important correcting capacity of burst errors. This intrinsic property of the Reed-Solomon codes is even enhanced by the interleaving of elementary RS(255,239) codecs. This technique, implemented on the 2.5 Gbit/s optical fibre submarine cable systems, puts the error correcting capacity to bursts of 1024 bits maximal length, for 16 interleaved codecs. + +In addition, the Reed-Solomon codes remain among the most efficient codes which can be implemented using the state-of-the-art hardware and software technology. + +## 6.4 FEC frame structure + +Another FEC frame structure (Optional) is given in Appendix I for information. + +### 6.4.1 FEC encoder and FEC decoder architectures + +In order to enhance the immunity of the optical fibre submarine cable system to burst errors, several RS(255,239) codes can be interleaved. In Figures 2 and 3, ( $n$ ) denotes the interleaving order ( $n$ is a non-zero integer). + +Given the interleaving to depth " $n$ " of RS(255,239) codes, the architectures of both the FEC encoder and the FEC decoder are detailed in Figures 2 and 3 respectively. + +![Figure 2/G.975 – FEC encoder architecture diagram. An STM-16 signal at 2.5 Gbit/s enters a demultiplexer (1/n). The output is split into n parallel RS(255,239) encoders. Each encoder takes an 8-bit subframe and produces an 8-bit subframe with a framing structure inserted. These subframes are then multiplexed back together (n/1) to produce an FEC frame at 2.66 Gbit/s. The diagram shows encoders #1, #2, and #n, with subframe 1 and subframe (8 x n) indicated. A note at the bottom left states 'n Number of interleaved codecs'.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg) + +STM-16 at 2.5 Gbit/s + +1/n + +Demultiplexer + +1/8 + +8 + +Framing structure (insertion) + +subframe 1 + +RS(255,239) encoder #1 + +8 + +8 + +RS(255,239) encoder #2 + +8 + +8 + +RS(255,239) encoder #n + +subframe (8 × n) + +8 + +8 + +8/1 + +8/1 + +8/1 + +n/1 + +Multiplexer + +FEC frame at 2.66 Gbit/s + +n Number of interleaved codecs + +T1520660-96 + +Figure 2/G.975 – FEC encoder architecture diagram. An STM-16 signal at 2.5 Gbit/s enters a demultiplexer (1/n). The output is split into n parallel RS(255,239) encoders. Each encoder takes an 8-bit subframe and produces an 8-bit subframe with a framing structure inserted. These subframes are then multiplexed back together (n/1) to produce an FEC frame at 2.66 Gbit/s. The diagram shows encoders #1, #2, and #n, with subframe 1 and subframe (8 x n) indicated. A note at the bottom left states 'n Number of interleaved codecs'. + +**Figure 2/G.975 – FEC encoder architecture** + +![Figure 3/G.975 – FEC decoder architecture diagram. An FEC frame at 2.66 Gbit/s enters a demultiplexer (1/n). The output is split into n parallel RS(255,239) decoders. Each decoder takes an 8-bit subframe with a framing structure and produces an 8-bit subframe. These subframes are then multiplexed back together (n/1) to produce an STM-16 signal at 2.5 Gbit/s. The diagram shows decoders #1, #2, and #n, with subframe 1 and subframe (8 x n) indicated. A note at the bottom left states 'n Number of interleaved codecs'.](e9314c83043183351ed74908e9bf2f90_img.jpg) + +FEC frame at 2.66 Gbit/s + +1/n + +Demultiplexer + +1/8 + +8 + +subframe 1 + +RS(255,239) decoder #1 + +8 + +8 + +RS(255,239) decoder #2 + +8 + +8 + +RS(255,239) decoder #n + +subframe (8 × n) + +8 + +8 + +8/1 + +8/1 + +8/1 + +n/1 + +Multiplexer + +STM-16 at 2.5 Gbit/s + +n Number of interleaved codecs + +T1520670-96 + +Figure 3/G.975 – FEC decoder architecture diagram. An FEC frame at 2.66 Gbit/s enters a demultiplexer (1/n). The output is split into n parallel RS(255,239) decoders. Each decoder takes an 8-bit subframe with a framing structure and produces an 8-bit subframe. These subframes are then multiplexed back together (n/1) to produce an STM-16 signal at 2.5 Gbit/s. The diagram shows decoders #1, #2, and #n, with subframe 1 and subframe (8 x n) indicated. A note at the bottom left states 'n Number of interleaved codecs'. + +**Figure 3/G.975 – FEC decoder architecture** + +For data integrity, the digital multiplexer and the digital demultiplexer represented in Figures 2 and 3 are strictly symmetrical. In addition, the same digital multiplexers and the same digital demultiplexers are used for both the FEC encoder and the FEC decoder. + +Due to the fact that each elementary Reed-Solomon algorithm process byte information and therefore works on 8 parallel data stream, the demultiplexers deliver $(8 \times n)$ data stream to the $(n)$ interleaved codecs while the multiplexers do the reverse operation. + +Provided the FEC encoder and the FEC decoder architectures, the FEC frame construction is described in Figure 4. + +![Diagram of FEC frame construction showing subframes, columns, and data types (Framing Structure, STM-16 Data, Redundant Data).](27b06ec9f42b5d727a2630f61a5f1861_img.jpg) + +The diagram illustrates the construction of an FEC frame. At the top, a horizontal double-headed arrow indicates a 'subframe length = 255 bits'. Below this, a grid shows 'subframe 1' through 'subframe 9', followed by a gap, and then 'subframe 8 × n'. The grid is divided into columns, with 'column 1', 'column 240', and 'column 255' explicitly labeled. On the left, two data byte streams are shown: 'Data byte from FEC encoder #1' and 'Data byte from FEC encoder #n', each with MSB and LSB indicators. Below the grid, the 'FEC frame' is shown as a sequence of columns. Column 1 is labeled 'FRAMING STRUCTURE' and contains bits 1 to $8 \times n$ . Column 2 contains bits $8 \times n + 1$ to $16 \times n$ . Column 239 contains bits $1912 \times n$ to $1920 \times n$ . Column 240 contains bits $1920 \times n$ to $2040 \times n$ and is labeled 'REDUNDANT DATA'. Column 255 contains bits $2040 \times n$ to $2160 \times n$ and is also labeled 'REDUNDANT DATA'. The middle section (columns 2 to 239) is labeled 'STM-16 DATA'. At the bottom left, 'n Number of interleaved codecs' is noted. At the bottom right, the code 'T1520680-96' is present. + +Diagram of FEC frame construction showing subframes, columns, and data types (Framing Structure, STM-16 Data, Redundant Data). + +**Figure 4/G.975 – FEC frame construction** + +Due to the interleaving of RS(255,239) codes to depth $n$ , the FEC frame is $(2040 \times n)$ bits long and is made of $(8 \times n)$ bit interleaved subframes. + +And, as a consequence of the symmetry of the digital demultiplexers and the digital multiplexers on each side of the Reed-Solomon algorithms, the sequence of STM-16 data bits within the FEC frame is identical to that within the STM-16 input signal. + +### 6.4.2 Framing structure + +A framing structure is added in the FEC frame to possibly insert a FEC frame alignment word, which is required to perform the synchronization of the FEC frame with the FEC decoder structure at the receive Terminal Transmission Equipment (TTE). + +The remaining spare bits can be used for carrying tributary markers, order wire channels or service channels. + +The FEC frame presented in 6.4.1 can be divided into $(8 \times n)$ 255 bits long subframe. Each subframe (see Figure 5) contains the following information: + +- bit 1 of each subframe carries the framing structure [either the FEC Frame Alignment Word, the tributary markers for STM-16 data stream identification in systems carrying multiples of STM-16 (if required) or order wire channels or service channels for inter-terminal communication]; +- bits 2 to 239 of each subframe carry the STM-16 information; +- bits 240 to 255 of each subframe carry the redundant bits, computed by the RS(255,239) algorithm. + +![Diagram of a subframe structure showing 255 bits total length, divided into 1 bit framing structure, 238 bits STM-16 data, and 16 bits redundant codes.](410562339ce067fdc6fa41940c118658_img.jpg) + +The diagram illustrates the internal structure of a subframe. At the top, a horizontal line with arrows at both ends is labeled "subframe length = 255 bits". Below this, the subframe is divided into three segments by vertical dashed lines. The first segment is labeled "1 bit" and has an arrow pointing down to a box labeled "framing structure". The second segment is labeled "238 bits" and contains a large hatched rectangle labeled "STM-16 data". The third segment is labeled "16 bits" and contains a box labeled "redundant codes". In the bottom right corner of the diagram area, the text "T1520690-96" is present. + +Diagram of a subframe structure showing 255 bits total length, divided into 1 bit framing structure, 238 bits STM-16 data, and 16 bits redundant codes. + +**Figure 5/G.975 – Content of the subframes of the FEC frame** + +### 6.4.3 Scrambling + +STM-16 data in the FEC frame are already scrambled as shown in ITU-T G.707 [1]. Hence, rescrambling of the FEC frame is not generally required. + +However, when implemented in the submarine Terminal Transmission Equipment (TTE), the scrambling facility should possibly be inhibited. + +The scrambling of the FEC frame may be carried out in the following procedure: the FEC frame is scrambled, with the exception of the framing structure bits of the FEC frame, by a $x^7 + x + 1$ polynomial initiated at each frame on the first bit which follows the framing structure in the FEC frame. + +The first bits of the scrambler sequence are 1111111. Thereafter, the scrambler runs continuously throughout the complete FEC frame. + +### 6.4.4 Redundancy ratio + +The redundancy ratio of the FEC function defined in ITU-T G.975 is equal to 1/14. Consequently, the line bit rates of optical fibre submarine cable systems using the forward error correction feature are as follows: + +- one STM-16 tributary carried: $2\,488.320 \times 15/14$ Mbit/s; +- two STM-16 tributaries carried: 2 multiplexed signals at $2\,488.320 \times 15/14$ Mbit/s; +- $M$ STM-16 tributaries carried ( $M$ is a non-zero integer): $M$ multiplexed signals at $2\,488.320 \times 15/14$ Mbit/s. + +# 7 FEC function performance + +## 7.1 Theoretical FEC function performance + +A criterion for the evaluation of the intrinsic correcting performance of the RS(255,239) code is the theoretical relationship between the line BER after FEC function correction ( $BER_{Output}$ ) and the line BER before FEC function correction ( $BER_{Input}$ ). + +For the RS codes, this criterion can be mathematically computed with the assumptions that errors occur independently from each other and that the decoder never fails (probability of incorrect decoding equal to zero): + +$$\begin{cases} P_{UE} = \sum_{i=9}^N \frac{i}{N} \cdot \binom{N}{i} \cdot P_{SE}^i \cdot (1 - P_{SE})^{N-i} \text{ with } N = 255 \\ BER_{Input} = 1 - (1 - P_{SE})^{1/8} \\ BER_{Output} = 1 - (1 - P_{UE})^{1/8} \end{cases}$$ + +with: + +$P_{UE}$ Probability of an Uncorrectable Error + +$P_{SE}$ Probability of a Symbol (byte) Error + +$N$ Codeword length (255) + +Figure 6 and Table 1 give an indication of the theoretical intrinsic performance of the RS(255,239) code. + +![Figure 6/G.975 – Theoretical output versus input BER. A line graph showing BER Output (-log BER) on the y-axis (0 to 60) versus BER Input (-log BER) on the x-axis (3 to 9). Two curves are plotted: 'with FEC' (solid line) and 'without FEC' (dotted line). The 'with FEC' curve starts at approximately (3, 8) and rises steeply to (9, 58). The 'without FEC' curve starts at approximately (3, 4) and rises very gradually to (9, 10).](70f5f44cb855bbb0c203c00187b2113e_img.jpg) + +| BER Input (-log BER) | BER Output (-log BER) with FEC | BER Output (-log BER) without FEC | +|----------------------|--------------------------------|-----------------------------------| +| 3 | 8 | 4 | +| 4 | 15 | 5 | +| 5 | 25 | 6 | +| 6 | 35 | 7 | +| 7 | 45 | 8 | +| 8 | 52 | 9 | +| 9 | 58 | 10 | + +Figure 6/G.975 – Theoretical output versus input BER. A line graph showing BER Output (-log BER) on the y-axis (0 to 60) versus BER Input (-log BER) on the x-axis (3 to 9). Two curves are plotted: 'with FEC' (solid line) and 'without FEC' (dotted line). The 'with FEC' curve starts at approximately (3, 8) and rises steeply to (9, 58). The 'without FEC' curve starts at approximately (3, 4) and rises very gradually to (9, 10). + +Figure 6/G.975 – Theoretical output versus input BER + +**Table 1/G.975 – Theoretical output versus input BER** + +| BERInput | BEROutput | +|----------------------------|-----------------------------| +| $10^{-4}$ | $5 \cdot 10^{-15}$ | +| $10^{-5}$ | $6.3 \cdot 10^{-24}$ | +| $10^{-6}$ | $6.4 \cdot 10^{-33}$ | + +The statistical independence between consecutive errors is generally considered to be relevant with the Reed-Solomon interleaving technique: with this approach, a bursty channel is transformed into several independent error channels. + +For BERInput above $10^{-3}$ , the probability of incorrect decoding (an incorrect decoding occurs when the decoder attempts correction but acts incorrectly because the error pattern is beyond its ability to correct) becomes un-negligible and makes the previous calculation of BEROutput inaccurate. In such cases, the BEROutput versus BERInput curves are even located below the "without FEC" curve in Figure 6. + +This calculation remains identical whatever the optical fibre submarine cable system, but gives no indication on the degradation brought by the in-line bit rate increase over the optical transmission channel performances. + +## 7.2 Coding gain + +The FEC function performance can also be evaluated through the coding gain, that is, the difference in the input optical power of the receiver required for coded and uncoded operation to provide a specified level of communication performance (BER = $10^{-10}$ in Figure 7). + +![Figure 7/G.975 – Coding gain (D) evaluation scheme. A log-linear plot showing BER versus Received power (dB). The y-axis (BER) ranges from 10^-100 to 1. The x-axis (Received power (dB)) ranges from -40 to -32. Three curves are shown: BER_Input (without FEC) as a dotted line, BER_Input (with FEC) as a dashed line, and BER_Output as a solid line. The BER_Input (without FEC) curve drops steeply and then floors at a higher BER. The BER_Input (with FEC) curve follows the without FEC curve initially but then drops more steeply before flooring at a lower BER. The BER_Output curve is the lowest, showing the best performance. A horizontal line at BER = 10^-10 intersects the curves, and the horizontal distance between the 'without FEC' and 'with FEC' curves at this BER is labeled 'D', representing the coding gain.](cc8bec39d25eb0aafb5382c05f0d5deb_img.jpg) + +Figure 7/G.975 – Coding gain (D) evaluation scheme. A log-linear plot showing BER versus Received power (dB). The y-axis (BER) ranges from 10^-100 to 1. The x-axis (Received power (dB)) ranges from -40 to -32. Three curves are shown: BER\_Input (without FEC) as a dotted line, BER\_Input (with FEC) as a dashed line, and BER\_Output as a solid line. The BER\_Input (without FEC) curve drops steeply and then floors at a higher BER. The BER\_Input (with FEC) curve follows the without FEC curve initially but then drops more steeply before flooring at a lower BER. The BER\_Output curve is the lowest, showing the best performance. A horizontal line at BER = 10^-10 intersects the curves, and the horizontal distance between the 'without FEC' and 'with FEC' curves at this BER is labeled 'D', representing the coding gain. + +T1520710-96 + +**Figure 7/G.975 – Coding gain (D) evaluation scheme** + +While correcting the BERInput, the FEC function brings a positive coding gain to the system. This coding gain is slightly attenuated by the effect of the signal bandwidth increase brought by the redundant symbols. + +The coding gain value intrinsically depends on the overall structure of the optical fibre submarine cable system (inter-repeater distances, photodetection parameters and optical amplifier output power in particular). + +When a line BER floor penalizes the optical fibre submarine cable system, one of the most valuable effects of the FEC function is to translate these line BER floors down to acceptable levels which the physical system could never achieve without FEC, regardless of the receiver input power. + +The expected coding gain for optical fibre submarine cable systems is 4 to 5 dB per fibre span. + +# APPENDIX I + +## FEC frame structure (optional) + +## I.1 FEC encoder and FEC decoder architecture + +In contrast to the subframe length of 255 bits described in the main body, 256 bits can be used where one dummy bit is added to the 255-bit subframe. The resultant 256-bit subframe can be then divided by four. This allows four-parallel calculation thus making it possible to use an FEC IC with a 2.667 Gbit/s throughput. + +The architecture of FEC encoder and the FEC decoder for STM-16 is shown in Figures I.1 and I.2, where the entire signal is calculated by using a single FEC IC. For STM-64 systems, signals are demultiplexed into four signal groups, and each demultiplexed signal is processed with a single FEC IC. The architecture of FEC encoder and the FEC decoder for STM-64 is shown in Figures I.3 and I.4. + +![Figure I.1/G.975 – FEC encoder architecture for STM-16 systems. The diagram shows an STM-16 signal at 2.5 Gbit/s entering a 1/8 Demultiplexer. The output is an 8-bit wide signal that enters an RS(256,239) encoder #1 block. A 'Framing structure (insertion)' is added to the input of the encoder. The encoder outputs 8 subframes (subframe 1 to subframe 8), which are then recombined by an 8/1 Multiplexer to produce an FEC frame at 2.7 Gbit/s. A reference code T1540500-00 is shown at the bottom right.](b90144cfbb81a2d610d920240fda689d_img.jpg) + +STM-16 at 2.5 Gbit/s → [1/8 Demultiplexer] → 8 → [RS(256,239) encoder #1] (Framing structure (insertion) added) → subframe 1, subframe 8 → [8/1 Multiplexer] → FEC frame at 2.7 Gbit/s + +T1540500-00 + +Figure I.1/G.975 – FEC encoder architecture for STM-16 systems. The diagram shows an STM-16 signal at 2.5 Gbit/s entering a 1/8 Demultiplexer. The output is an 8-bit wide signal that enters an RS(256,239) encoder #1 block. A 'Framing structure (insertion)' is added to the input of the encoder. The encoder outputs 8 subframes (subframe 1 to subframe 8), which are then recombined by an 8/1 Multiplexer to produce an FEC frame at 2.7 Gbit/s. A reference code T1540500-00 is shown at the bottom right. + +Figure I.1/G.975 – FEC encoder architecture for STM-16 systems + +![Figure I.2/G.975 – FEC decoder architecture for STM-64 systems. The diagram shows an FEC frame at 2.7 Gbit/s entering a 1/8 Demultiplexer. The output is an 8-bit wide signal that enters an RS(256,239) decoder #1 block. A 'Framing structure (extraction)' is shown as an output from the decoder. The decoder outputs 8 subframes (subframe 1 to subframe 8), which are then recombined by an 8/1 Multiplexer to produce an STM-16 signal at 2.5 Gbit/s. A reference code T1540510-00 is shown at the bottom right.](f57a881fcbcaf494a7dedc4f61224991_img.jpg) + +FEC frame at 2.7 Gbit/s → [1/8 Demultiplexer] → subframe 1, subframe 8 → [RS(256,239) decoder #1] (Framing structure (extraction) output) → 8 → [8/1 Multiplexer] → STM-16 at 2.5 Gbit/s + +T1540510-00 + +Figure I.2/G.975 – FEC decoder architecture for STM-64 systems. The diagram shows an FEC frame at 2.7 Gbit/s entering a 1/8 Demultiplexer. The output is an 8-bit wide signal that enters an RS(256,239) decoder #1 block. A 'Framing structure (extraction)' is shown as an output from the decoder. The decoder outputs 8 subframes (subframe 1 to subframe 8), which are then recombined by an 8/1 Multiplexer to produce an STM-16 signal at 2.5 Gbit/s. A reference code T1540510-00 is shown at the bottom right. + +Figure I.2/G.975 – FEC decoder architecture for STM-64 systems + +![FEC encoder architecture for STM-64 systems. The diagram shows an STM-64 signal at 10.0 Gbit/s entering a 1/4 demultiplexer. The output is split into four 1/8 demultiplexers. Each 1/8 demultiplexer feeds into an RS(256,239) encoder (labeled #1, #2, and #4, with a dashed box indicating four encoders). The encoders output subframes (8 x 4) which are then processed by 8/1 multiplexers. These are followed by a 4/1 multiplexer that outputs the final FEC frame at 10.8 Gbit/s. A 'Framing structure (insertion)' is shown entering the encoders. Reference T1540520-00 is noted.](8fbdfc3d17fb1dae7b2d8f5a287fa9fc_img.jpg) + +FEC encoder architecture for STM-64 systems. The diagram shows an STM-64 signal at 10.0 Gbit/s entering a 1/4 demultiplexer. The output is split into four 1/8 demultiplexers. Each 1/8 demultiplexer feeds into an RS(256,239) encoder (labeled #1, #2, and #4, with a dashed box indicating four encoders). The encoders output subframes (8 x 4) which are then processed by 8/1 multiplexers. These are followed by a 4/1 multiplexer that outputs the final FEC frame at 10.8 Gbit/s. A 'Framing structure (insertion)' is shown entering the encoders. Reference T1540520-00 is noted. + +**Figure I.3/G.975 – FEC encoder architecture for STM-64 systems** + +![FEC decoder architecture for STM-64 systems. The diagram shows an FEC frame at 10.8 Gbit/s entering a 1/4 demultiplexer. The output is split into four 1/8 demultiplexers. Each 1/8 demultiplexer feeds into an RS(256,239) decoder (labeled #1, #2, and #4, with a dashed box indicating four decoders). The decoders output subframes (8 x 4) which are then processed by 8/1 multiplexers. These are followed by a 4/1 multiplexer that outputs the final STM-64 signal at 10.0 Gbit/s. A 'Framing structure (extraction)' is shown exiting the decoders. Reference T1540530-00 is noted.](2cde062fd82833415971a8bd1a2cafab_img.jpg) + +FEC decoder architecture for STM-64 systems. The diagram shows an FEC frame at 10.8 Gbit/s entering a 1/4 demultiplexer. The output is split into four 1/8 demultiplexers. Each 1/8 demultiplexer feeds into an RS(256,239) decoder (labeled #1, #2, and #4, with a dashed box indicating four decoders). The decoders output subframes (8 x 4) which are then processed by 8/1 multiplexers. These are followed by a 4/1 multiplexer that outputs the final STM-64 signal at 10.0 Gbit/s. A 'Framing structure (extraction)' is shown exiting the decoders. Reference T1540530-00 is noted. + +**Figure I.4/G.975 – FEC decoder architecture for STM-64 systems** + +Based on the above FEC encoder/decoder architecture applied to STM-16 signals and STM-64 signals, the FEC frame constructions are respectively described in Figures I.5 and I.6. + +![Diagram of FEC frame construction for STM-16 systems. It shows a grid of 8 subframes, each 256 bits long. Below the grid, the FEC frame structure is shown with columns 1, 2, 5, 241, and 256. Column 1 contains 1 dummy data byte. Column 2 contains 8 framing structure bytes. Column 5 contains 32 STM-16 data bytes. Column 241 contains 1920 STM-16 data bytes. Column 256 contains 2048 redundant data bytes. Arrows point from the subframe grid to the FEC frame structure, indicating the mapping of data bytes.](76b0cd79baaedd942af4dc42f2e764b8_img.jpg) + +subframe length = 256 bits + +MSB +Data byte from FEC encoder +LSB + +subframe 1 +subframe 2 +subframe 3 +subframe 4 +subframe 5 +subframe 6 +subframe 7 +subframe 8 + +column 1 column 2 column 5 column 241 column 256 + +FEC frame { 1 8 9 32 33 1920 1928 2048 + +DUMMY DATA FRAMING STRUCTURE STM-16 DATA REDUNDANT DATA + +T1540540-00 + +Diagram of FEC frame construction for STM-16 systems. It shows a grid of 8 subframes, each 256 bits long. Below the grid, the FEC frame structure is shown with columns 1, 2, 5, 241, and 256. Column 1 contains 1 dummy data byte. Column 2 contains 8 framing structure bytes. Column 5 contains 32 STM-16 data bytes. Column 241 contains 1920 STM-16 data bytes. Column 256 contains 2048 redundant data bytes. Arrows point from the subframe grid to the FEC frame structure, indicating the mapping of data bytes. + +Figure I.5/G.975 – FEC frame construction for STM-16 systems + +![Diagram of FEC frame construction for STM-64 systems. It shows a grid of 32 subframes, each 256 bits long. Below the grid, the FEC frame structure is shown with columns 1, 2, 5, 241, and 256. Column 1 contains 1 dummy data byte. Column 2 contains 8x4+1 framing structure bytes. Column 5 contains 32x4 STM-64 data bytes. Column 241 contains 1920x4 STM-64 data bytes. Column 256 contains 2048x4 redundant data bytes. Arrows point from the subframe grid to the FEC frame structure, indicating the mapping of data bytes from four FEC encoders.](dfe556fea00682b09a59427aaf72051c_img.jpg) + +subframe length = 256 bits + +MSB +Data byte from FEC encoder #1 +LSB +Data byte from FEC encoder #2 +Data byte from FEC encoder #3 +Data byte from FEC encoder #4 + +subframe 1 +subframe 2 +subframe 3 +subframe 4 +subframe 5 +subframe 6 +subframe 7 +subframe 8 +subframe 9 +⋮ +subframe 31 +subframe 32 + +column 1 column 2 column 5 column 241 column 256 + +FEC frame { 1 8x4 8x4+1 32x4 1920x4 1928x4 2048x4 + +DUMMY DATA FRAMING STRUCTURE STM-64 DATA REDUNDANT DATA + +T1540550-00 + +Diagram of FEC frame construction for STM-64 systems. It shows a grid of 32 subframes, each 256 bits long. Below the grid, the FEC frame structure is shown with columns 1, 2, 5, 241, and 256. Column 1 contains 1 dummy data byte. Column 2 contains 8x4+1 framing structure bytes. Column 5 contains 32x4 STM-64 data bytes. Column 241 contains 1920x4 STM-64 data bytes. Column 256 contains 2048x4 redundant data bytes. Arrows point from the subframe grid to the FEC frame structure, indicating the mapping of data bytes from four FEC encoders. + +Figure I.6/G.975 – FEC frame construction for STM-64 systems + +The FEC frames for STM-16 and STM-64 are 2048 bits long and $2048 \times 4$ bits long, and are respectively made of single-bit and four-bit interleaved subframes. The sequences of STM-16 data bits and STM-64 data bits within the FEC frame are respectively identical to those within the STM-16 and STM-64 input signal. + +### I.2 Framing structure + +To achieve four-parallel calculation that allows to use a high-throughput FEC IC, one bit is added to the 255-bit subframe described in 6.4.2. Each of the resultant 256-bit subframe contains the following information: + +- bit 1 is a dummy bit; +- bits 2-4 carry the framing structure (either the FEC Frame Alignment Word, the tributary markers for STM-16 data stream identification in systems carrying multiples of STM-16 (if required) or order wire channels or service channels for inter-terminal communication); +- bits 5 to 240 of each subframe carry the STM-16 information; +- bits 241 to 256 of each subframe carry the redundant bits, computed by the RS(255,239) algorithm. + +![Diagram of a 256-bit subframe format. The total length is 256 bits. It is divided into four sections: 1 bit (dummy), 3 bits (framing structure), 236 bits (STM-16 data), and 16 bits (redundant codes).](10781f43062bf3e9601a1e086710556c_img.jpg) + +The diagram illustrates the structure of a 256-bit subframe. At the top, a horizontal line with arrows at both ends is labeled "subframe length = 256 bits". Below this, the subframe is divided into four segments by vertical dashed lines. The first segment is labeled "1 bit" and "dummy" (with an arrow pointing to it). The second segment is labeled "3 bits" and "framing structure" (with an arrow pointing to it). The third segment is labeled "236 bits" and "STM-16 data" (with a hatched pattern). The fourth segment is labeled "16 bits" and "redundant codes". The identifier "T1540560-00" is located at the bottom right of the diagram. + +Diagram of a 256-bit subframe format. The total length is 256 bits. It is divided into four sections: 1 bit (dummy), 3 bits (framing structure), 236 bits (STM-16 data), and 16 bits (redundant codes). + +**Figure I.7/G.975 – 256-bit subframe format that allows the parallel calculation** + +## I.3 Scrambling + +STM-16 data in the FEC frame are already scrambled as shown in ITU-T G.707 [1]. Hence, rescrambling of the FEC frame is not generally required. + +However, when implemented in the submarine Terminal Transmission Equipment (TTE), the scrambling facility should possibly be inhibited. + +The scrambling of the FEC frame may be carried out in the following procedure: the FEC frame is scrambled, with the exception of the framing structure bits of the FEC frame, by a $x^7 + x + 1$ polynomial initiated at each frame on the first bit which follows the framing structure in the FEC frame. + +The first bits of the scrambler sequence are 1111111. Thereafter, the scrambler runs continuously throughout the complete FEC frame. + +## **I.4 Redundancy ratio** + +The redundancy ratio of the FEC function described in Appendix I is equal to 5/59. Consequently, the line bit rates of optical fibre submarine cable systems using the forward error correction feature described in Appendix I are as follows: + +- one STM-16 tributary carried: $2\,488.320 \times 64/59$ Mbit/s; +- one STM-64 tributary carried: $9\,953.280 \times 64/59$ Mbit/s. + +# **SERIES OF ITU-T RECOMMENDATIONS** + +| | | +|-----------------|--------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series B | Means of expression: definitions, symbols, classification | +| Series C | General telecommunication statistics | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks and open system communications | +| Series Y | Global information infrastructure and Internet protocol aspects | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.977-201501-I_PDF-E/raw.md b/marked/G/T-REC-G.977-201501-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..bf389068bc8b7b9f65ed1acf4dd0a6e76757564b --- /dev/null +++ b/marked/G/T-REC-G.977-201501-I_PDF-E/raw.md @@ -0,0 +1,1294 @@ + + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.977** + +(01/2015) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Digital sections and digital line system – Optical fibre +submarine cable systems + +# --- **Characteristics of optically amplified optical fibre submarine cable systems** + +Recommendation ITU-T G.977 + +## ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| General | G.900–G.909 | +| Parameters for optical fibre cable systems | G.910–G.919 | +| Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s | G.920–G.929 | +| Digital line transmission systems on cable at non-hierarchical bit rates | G.930–G.939 | +| Digital line systems provided by FDM transmission bearers | G.940–G.949 | +| Digital line systems | G.950–G.959 | +| Digital section and digital transmission systems for customer access to ISDN | G.960–G.969 | +| Optical fibre submarine cable systems | G.970–G.979 | +| Optical line systems for local and access networks | G.980–G.989 | +| Metallic access networks | G.990–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.977 + +# Characteristics of optically amplified optical fibre submarine cable systems + +## Summary + +Recommendation ITU-T G.977 is concerned with the system performance and interface requirements of repeated optical submarine systems using optical fibre amplifiers (OFAs) as line repeaters. It covers the aspects related to single wavelength systems (SWS), wavelength division multiplexing systems (WDMS) and dense wavelength division multiplexing systems (DWDMs). The physical implementation of optically amplified fibre submarine systems is considered in Annex A. + +This edition of the Recommendation introduces a new power budget template for the implementation of coherent systems. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.977 | 2000-04-04 | 15 | 11.1002/1000/5060 | +| 2.0 | ITU-T G.977 | 2004-03-08 | 15 | 11.1002/1000/7070 | +| 3.0 | ITU-T G.977 | 2006-12-14 | 15 | 11.1002/1000/8984 | +| 4.0 | ITU-T G.977 | 2011-04-13 | 15 | 11.1002/1000/11125 | +| 5.0 | ITU-T G.977 | 2015-01-13 | 15 | 11.1002/1000/12369 | + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2015 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|-----------------------------------------------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 3 | +| 3.1 Terms defined elsewhere ..... | 3 | +| 3.2 Terms defined in this Recommendation..... | 4 | +| 4 Abbreviations and acronyms ..... | 8 | +| 5 Conventions ..... | 10 | +| 6 Characteristics and performances of the system..... | 10 | +| 6.1 Characteristics and performance of the digital line sections (DLSs) ..... | 10 | +| 6.2 Optical power budget ..... | 12 | +| 6.3 System reliability performance..... | 14 | +| 6.4 System capacity upgradeability..... | 14 | +| 7 Characteristics and performance of the TTE ..... | 15 | +| 7.1 General ..... | 15 | +| 7.2 Transmission performance ..... | 16 | +| 7.3 Actions consequent to an alarm..... | 16 | +| 7.4 Automatic switching..... | 16 | +| 8 Characteristics and performance of the optical submarine repeaters (OSRs) ..... | 16 | +| 8.1 Mechanical characteristics..... | 16 | +| 8.2 Electrical characteristics ..... | 17 | +| 8.3 Optical characteristics ..... | 17 | +| 8.4 Supervisory facilities ..... | 18 | +| 8.5 Fault location ..... | 18 | +| 8.6 Reliability ..... | 19 | +| 9 Characteristics and performance of the in-line branching unit (BU) ..... | 19 | +| 9.1 General ..... | 19 | +| 9.2 Mechanical characteristics..... | 20 | +| 9.3 Electrical characteristics ..... | 21 | +| 9.4 Optical characteristics ..... | 21 | +| 9.5 Supervisory facilities ..... | 21 | +| 9.6 Fault location ..... | 21 | +| 9.7 Reliability ..... | 22 | +| 10 Characteristics and performance of the optical submarine equalizer (OSE) ..... | 22 | +| 10.1 Mechanical characteristics..... | 22 | +| 10.2 Electrical characteristics (for adjustable OSEs only) ..... | 23 | +| 10.3 Optical characteristics ..... | 23 | +| 10.4 Supervisory facilities ..... | 23 | + +| | Page | +|----------------------------------------------------------------------------------------------------------------------|------| +| 10.5 Reliability ..... | 23 | +| 11 Characteristics and performance of the submarine cable ..... | 23 | +| 11.1 Dispersion mapping..... | 23 | +| 11.2 Dispersion management implementation ..... | 24 | +| Annex A – Implementation of repeated optical fibre submarine cable systems using optical fibre amplifiers..... | 25 | +| A.1 Introduction ..... | 25 | +| A.2 System configuration..... | 25 | +| A.3 System performance ..... | 28 | +| A.4 System operation ..... | 32 | +| A.5 Optical submarine repeater (OSR), branching unit (BU) and optical submarine equalizer (OSE) characteristics..... | 33 | +| Bibliography..... | 34 | + +## Recommendation ITU-T G.977 + +# Characteristics of optically amplified optical fibre submarine cable systems + +# 1 Scope + +This Recommendation is concerned with the system performances and interface requirements of repeated optical fibre submarine cable systems using optical line amplifiers (OLAs) as line repeaters. It covers the aspects related to single wavelength systems (SWS), wavelength division multiplexing systems (WDMS) and dense wavelength division multiplexing systems (DWDMs). Depending on the system specifications, such as the number of terminations, the connectivity, the total capacity, the maximum end-to-end distance, and/or the system cost, one of these three types of systems may be more appropriate to guarantee the system requirements. A high data capacity may be carried by one wavelength using a high data bit-rate, or by several wavelengths using a smaller one. + +From a general point of view, the characteristics, performance specifications and requirements of the submerged equipment are mostly identical for SWS, WDMS and DWDMs. Indeed, SWS appears as a specific case of WDMS using one wavelength and, in turn, WDMS can be considered as a specific case of DWDMs with a small number of wavelengths. As a consequence, general statements mentioned in this Recommendation can be applied to SWS, WDMS and DWDMs. However, when necessary, more detailed Recommendations will highlight the specificity of these three types of systems. + +Common implementation aspects of optical submarine cable systems for manufacturing, installing and maintenance are described in [ITU-T G.971]. [ITU-T G.978] contains common aspects of the characteristics of the optical fibre submarine cables. [ITU-T G.979] is also concerned with the characteristics of monitoring systems for optical fibre submarine cable systems with repeaters. + +The physical implementation of optically amplified fibre submarine systems is considered in Annex A. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.661] Recommendation ITU-T G.661 (2007), *Definitions and test methods for the relevant generic parameters of optical amplifier devices and subsystems*. +- [ITU-T G.662] Recommendation ITU-T G.662 (2005), *Generic characteristics of optical amplifier devices and subsystems*. +- [ITU-T G.664] Recommendation ITU-T G.664 (2012), *Optical safety procedures and requirements for optical transmission systems*. +- [ITU-T G.692] Recommendation ITU-T G.692 (1998), *Optical interfaces for multichannel systems with optical amplifiers*. + +- [ITU-T G.701] Recommendation ITU-T G.701 (1993), *Vocabulary of digital transmission and multiplexing, and pulse code modulation (PCM) terms.* +- [ITU-T G.702] Recommendation ITU-T G.702 (1988), *Digital hierarchy bit rates.* +- [ITU-T G.703] Recommendation ITU-T G.703 (2001), *Physical/electrical characteristics of hierarchical digital interfaces.* +- [ITU-T G.707] Recommendation ITU-T G.707/Y.1322 (2007), *Network node interface for the synchronous digital hierarchy (SDH).* +- [ITU-T G.709] Recommendation ITU-T G.709/Y.1331 (2012), *Interfaces for the optical transport network.* +- [ITU-T G.780] Recommendation ITU-T G.780/Y.1351 (2010), *Terms and definitions for synchronous digital hierarchy (SDH) networks.* +- [ITU-T G.821] Recommendation ITU-T G.821 (2002), *Error performance of an international digital connection operating at a bit rate below the primary rate and forming part of an Integrated Services Digital Network.* +- [ITU-T G.823] Recommendation ITU-T G.823 (2000), *The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy.* +- [ITU-T G.825] Recommendation ITU-T G.825 (2000), *The control of jitter and wander within digital networks which are based on the synchronous digital hierarchy (SDH).* +- [ITU-T G.826] Recommendation ITU-T G.826 (2002), *End-to-end error performance parameters and objectives for international, constant bit-rate digital paths and connections.* +- [ITU-T G.828] Recommendation ITU-T G.828 (2000), *Error performance parameters and objectives for international, constant bit-rate synchronous digital paths.* +- [ITU-T G.870] Recommendation ITU-T G.870/Y.1352 (2012), *Terms and definitions for optical transport networks.* +- [ITU-T G.921] Recommendation ITU-T G.921 (1988), *Digital sections based on the 2048 kbit/s hierarchy.* +- [ITU-T G.955] Recommendation ITU-T G.955 (1996), *Digital line systems based on the 1544 kbit/s and the 2048 kbit/s hierarchy on optical fibre cables.* +- [ITU-T G.957] Recommendation ITU-T G.957 (2006), *Optical interfaces for equipments and systems relating to the synchronous digital hierarchy.* +- [ITU-T G.959.1] Recommendation ITU-T G.959.1 (2012), *Optical transport network physical layer interfaces.* +- [ITU-T G.971] Recommendation ITU-T G.971 (2010), *General features of optical fibre submarine cable systems.* +- [ITU-T G.972] Recommendation ITU-T G.972 (2011), *Definition of terms relevant to optical fibre submarine cable systems.* +- [ITU-T G.975] Recommendation ITU-T G.975 (2000), *Forward error correction for submarine systems.* + +- [ITU-T G.975.1] Recommendation ITU-T G.975.1 (2004), *Forward error correction for high bit-rate DWDM submarine systems*. +- [ITU-T G.976] Recommendation ITU-T G.976 (2014), *Tests methods applicable to optical fibre submarine cable systems*. +- [ITU-T G.978] Recommendation ITU-T G.978 (2010), *Characteristics of optical fibre submarine cables*. +- [ITU-T G.979] Recommendation ITU-T G.979 (2012), *Characteristics of monitoring systems for optical submarine cables*. +- [ITU-T G.8201] Recommendation ITU-T G.8201 (2011), *Error performance parameters and objectives for multi-operator international paths within optical transport networks*. +- [ITU-T G.8251] Recommendation ITU-T G.8251 (2010), *The control of jitter and wander within the optical transport network (OTN)*. +- [IEC 60825-1] IEC 60825-1 (2007), *Safety of laser products – Part 1: Equipment classification and requirements*. +- [IEC 60825-2] IEC 60825-2 (2007), *Safety of laser products – Part 2: Safety of optical fibre communication systems (OFCS)*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined elsewhere: + +- 3.1.1 **compression factor**: See [ITU-T G.976]. +- 3.1.2 **digital line section (DLS)**: See [ITU-T G.701]. +- 3.1.3 **forward error correction (FEC)**: See [ITU-T G.972], [ITU-T G.975] and [ITU-T G.975.1]. +- 3.1.4 **gain flatness**: See [ITU-T G.976]. +- 3.1.5 **maximum channel power difference**: See [ITU-T G.692]. +- 3.1.6 **noise figure**: See [ITU-T G.661]. +- 3.1.7 **nominal gain**: See [ITU-T G.976]. +- 3.1.8 **nominal signal input power**: See [ITU-T G.976]. +- 3.1.9 **nominal signal output power**: See [ITU-T G.976]. +- 3.1.10 **optical fibre amplifier (OFA)**: See [ITU-T G.661]. +- 3.1.11 **optical transport network (OTN)**: See [ITU-T G.870]. +- 3.1.12 **polarization-dependent gain**: See [ITU-T G.661]. +- 3.1.13 **polarization-dependent loss**: See [ITU-T G.661]. +- 3.1.14 **polarization hole burning**: See [ITU-T G.661]. +- 3.1.15 **polarization mode dispersion**: See [ITU-T G.661]. +- 3.1.16 **S, R reference points**: See [ITU-T G.955]. +- 3.1.17 **S', R' reference points**: See [ITU-T G.661] and [ITU-T G.662]. + +- 3.1.18 small signal gain:** See [ITU-T G.661]. +- 3.1.19 synchronous digital hierarchy (SDH):** See [ITU-T G.780]. +- 3.1.20 synchronous transport module (STM):** See [ITU-T G.780]. + +## **3.2 Terms defined in this Recommendation** + +This Recommendation defines the following terms. Figures 3-1, 3-2, 3-3 and 3-4, which illustrate these definitions, describe terminal equipment for wavelength division multiplexing system (WDMS) and dense wavelength division multiplexing system (DWDM). In case of a single wavelength system (SWS), the optical multiplexer/demultiplexer interface should be removed so that only one wavelength should be concerned as shown in Figures 3-3 and 3-4. + +**3.2.1 branching unit (BU):** A piece of optical submarine equipment inserted into the submarine portion of an optical fibre submarine cable network where the electrical and optical interconnection of three cable sections is necessary. + +**3.2.2 dense wavelength division multiplexing (DWDM):** An aggregate of a large number of line optical channel (LOCs) to be carried through part or the whole of the submarine line on the same line fibre. + +**3.2.3 dense wavelength division multiplexing system (DWDM):** A bidirectional optical system carried on a large number of line optical channels (LOCs). + +**3.2.4 fixed optical add/drop multiplexing-branching unit (FOADM-BU):** A branching unit (BU) with optical add/drop multiplex (OADM) function where the wavelengths that are added, dropped and passed through are fixed. + +**3.2.5 full fibre drop-BU (FFD-BU):** A branching unit (BU) where the optical interconnection between the three submarine cables is made by physically connecting fibre pairs between any two cables. + +**3.2.6 gain equalizer:** Gain equalizer is the means used to adapt the submerged plant gain profile characteristics suitable for transmission. + +**3.2.7 intermediate terrestrial interface (ITI):** It is to be noted that the terminal transmission equipment (TTE) can be composed of two distinct pieces of equipment interfaced together, the first piece called submarine cable transmission terminal equipment (SCTTE), on the submarine cable side, and the second piece, called terrestrial network transmission terminal equipment (TNTTE), on the terrestrial network side. In this case, an intermediate interface is required which links the two pieces of equipment. This interface is composed of bidirectional data interfaces and, where applicable, of an extra link used to exchange information between the two pieces of terminal transmission equipment (TTE). + +**3.2.8 line optical channel (LOC):** A bidirectional optical data channel carried on a specific optical frequency/wavelength for each transmission direction. + +**3.2.9 LOC-TTE:** A terminal transmission equipment (TTE) whose submarine cable optical interface (SCOI) is composed of only one line optical channel (LOC). + +**3.2.10 N-WDM:** A wavelength division multiplexing (WDM) or dense wavelength division multiplexing (DWDM) of N line optical channel (LOCs) (N being an integer). + +**3.2.11 optical submarine equalizer (OSE):** Optical submarine equalizer is the submerged equipment used to compensate for, or to handle, the accumulative gain ripple and tilt along a submarine digital line section (SDLS) in order to be compliant with the pre-emphasis capability of + +the terminal transmission equipment (TTE) at the transmitter side, and with the corresponding impairment allocated in the power budget table. + +**3.2.12 reconfigurable optical add/drop multiplexing-branching unit (ROADM-BU):** A branching unit (BU) with optical add/drop multiplexing (OADM) function where the wavelengths that are added, dropped and passed through can be dynamically modified. + +**3.2.13 shunt fault:** A shunt fault is a current leakage path between the power conductor and the sea water without a break in the power conductor. + +**3.2.14 single wavelength system (SWS):** A bidirectional optical system carried on only one line optical channel (LOC). + +**3.2.15 slope equalizer:** Slope equalizer is the means used for wavelength division multiplexing system (WDMS) to provide the equalization of the residual gain/wavelength slope which accumulates when the signal is transmitted through a chain of submerged repeaters. + +**3.2.16 submarine cable optical interface (SCOI):** The bidirectional optical interface between the submarine cable (including the terrestrial cable section) and the terminal transmission equipment (TTE). This signal is composed of a line optical channel (LOC) or a wavelength division multiplexing (WDM). + +**3.2.17 submarine cable transmission terminal equipment (SCTTE):** See definition on intermediate terrestrial interface (ITI). + +**3.2.18 submarine digital line section (SDLS):** A bidirectional continuous optical path along which one line optical channel (LOC) links two terminal transmission equipments (TTEs) at the submarine electro-optic interface (SEOI) level. + +**3.2.19 submarine electro-optic interface (SEOI):** The bidirectional interface inside the terminal transmission equipment (TTE) where an electro-optic conversion and an electrical regeneration are performed between a line optical channel (LOC) and an electrical channel. + +**3.2.20 terminal transmission equipment (TTE):** The equipment included in the terrestrial portion of an optical fibre submarine cable system for terminal transmission multiplexing and demultiplexing operations, coding and converting the incoming tributaries into optical line signal, converting and decoding the received optical line signal in the outgoing tributaries, ensuring submarine protection switching, submarine plant supervision and performing cable optical termination. + +**3.2.21 terrestrial interface (TI):** The interface between the submarine system and the terrestrial network. + +**3.2.22 terrestrial network transmission terminal equipment (TNTTE):** See definition on intermediate terrestrial interface. + +**3.2.23 tilt equalizer:** Tilt equalizer is the means used for wavelength division multiplexing system (WDMS) to provide the equalization of the residual gain/wavelength tilt, which accumulates when the signal is transmitted through a chain of submerged repeaters. + +**3.2.24 umbilical:** The extra link used at intermediate terrestrial interface (ITI) to exchange information between the two pieces of terminal transmission equipment (TTE), which are the submarine cable transmission terminal equipment (SCTTE) and the terrestrial network transmission terminal equipment (TNTTE). + +**3.2.25 wavelength demultiplexer (WD):** The equipment required to split a wavelength division multiplexing (WDM) into several line optical channels (LOCs) and/or WDM to be carried on different fibres. + +**3.2.26 wavelength division multiplexing (WDM):** An aggregate of several line optical channels (LOCs) to be carried through part or the whole of the submarine line on the same line fibre. + +**3.2.27 wavelength division multiplexing system (WDMS):** A bidirectional optical system carried on several line optical channels (LOCs). + +**3.2.28 wavelength multiplexer (WM):** The equipment required to combine several line optical channels (LOCs) and/or wavelength division multiplexing (WDM) coming from different fibres into a common WDM composed of all the combined LOCs. + +**3.2.29 wavelength division multiplexing-branching unit (WDM-BU):** A branching unit (BU) where the optical interconnection between the three submarine cables is made through wavelength multiplexer (WM) and wavelength demultiplexer (WD), that is, adding and dropping one or more line optical channels (LOCs) out of the N-WDM. + +**3.2.30 wavelength division multiplexing-terminal transmission equipment (WDM-TTE):** A terminal transmission equipment (TTE) equipped with wavelength multiplexer (WM) and wavelength demultiplexer (WD), whose submarine cable optical interface (SCOI) is a wavelength division multiplexing (WDM) or dense wavelength division multiplexing (DWDM). + +![Diagram illustrating the terms and definitions for SWS (Submarine Wavelength Division Multiplexing System). The diagram shows the signal flow from a Line Optical Channel (LOC) through various components including SCOI, SDLS, SEOI, Normal/Protection, ITI, and TI, connecting SCTTE and TNTTE units.](7f17c430b9598e4d748a8041457810b3_img.jpg) + +The diagram illustrates the signal flow in a submarine wavelength division multiplexing system. It is divided into two main sections: SCTTE (Submarine Cable Terminal Transmission Equipment) and TNTTE (Terrestrial Network Terminal Transmission Equipment), connected by a 'Possible umbilical'. + +- SCTTE (Submarine Cable Terminal Transmission Equipment):** This section is represented by a large grey box. It contains the following components in sequence from left to right: + - LOC (Line Optical Channel):** The input signal enters from the left. + - SCOI (Submarine Cable Optical Interface):** The first component the LOC encounters. + - SDLS (Submarine Data Link System):** The signal passes through SDLS. + - SEOI (Submarine Equipment Optical Interface):** There are two parallel paths: one labeled 'Normal' and another labeled 'Protection'. Both paths include an SEOI component. + - ITI (Inter-Transmission Interface):** The signal from both the Normal and Protection paths passes through an ITI component. +- Connection:** A line labeled 'Possible umbilical' connects the ITI components in the SCTTE to the ITI components in the TNTTE. +- TNTTE (Terrestrial Network Terminal Transmission Equipment):** This section is represented by a white box. It contains: + - ITI (Inter-Transmission Interface):** Two ITI components receive signals from the SCTTE. + - .... (省略号):** An ellipsis indicates additional internal components or multiple parallel paths. + - TI (Terrestrial Interface):** The final output component on the right side of the diagram. + +Diagram illustrating the terms and definitions for SWS (Submarine Wavelength Division Multiplexing System). The diagram shows the signal flow from a Line Optical Channel (LOC) through various components including SCOI, SDLS, SEOI, Normal/Protection, ITI, and TI, connecting SCTTE and TNTTE units. + +**Figure 3-1 – Terms and definitions for SWS** + +![Figure 3-2: Terms and definitions for WDMS. This block diagram shows the internal architecture of a Wavelength Division Multiplexing System (WDMS). On the left, multiple input wavelengths (λ1, λ2, λ3, ..., λN) enter a block labeled 'LOC'. These pass through an 'SCOI' (Signal Control Interface) and then into an 'Optical Mux/Demux' block. The output of the mux is labeled 'N'. From the mux, multiple paths emerge, each consisting of an 'SDLS' (Signal Detection and Loss Sensing) block, an 'SEOI' (Signal End Office Interface) block, and a 'Normal' or 'Protection' block. These blocks are part of a larger 'SCTTE' (Signal Control and Transport Terminal Equipment) block. The 'Normal' blocks are connected to 'ITI' (Inter-Terminal Interface) blocks, which in turn connect to 'TI' (Terminal Interface) blocks. A 'Switch box' is also connected to the 'Protection' block. A 'Possible umbilical' connection is shown between the 'ITI' blocks and the 'TI' blocks. The entire system is labeled 'G.977(11)_F3-2'.](af7916c89a458fdab6c3f443217388ae_img.jpg) + +Figure 3-2: Terms and definitions for WDMS. This block diagram shows the internal architecture of a Wavelength Division Multiplexing System (WDMS). On the left, multiple input wavelengths (λ1, λ2, λ3, ..., λN) enter a block labeled 'LOC'. These pass through an 'SCOI' (Signal Control Interface) and then into an 'Optical Mux/Demux' block. The output of the mux is labeled 'N'. From the mux, multiple paths emerge, each consisting of an 'SDLS' (Signal Detection and Loss Sensing) block, an 'SEOI' (Signal End Office Interface) block, and a 'Normal' or 'Protection' block. These blocks are part of a larger 'SCTTE' (Signal Control and Transport Terminal Equipment) block. The 'Normal' blocks are connected to 'ITI' (Inter-Terminal Interface) blocks, which in turn connect to 'TI' (Terminal Interface) blocks. A 'Switch box' is also connected to the 'Protection' block. A 'Possible umbilical' connection is shown between the 'ITI' blocks and the 'TI' blocks. The entire system is labeled 'G.977(11)\_F3-2'. + +Figure 3-2 – Terms and definitions for WDMS + +![Figure 3-3: Transmit side. This diagram illustrates the transmit side of a WDMS. It shows multiple transmitters (TX1 to TXn) connected to a common bus. The bus is labeled with 'ITU-T G.703' and 'ITU-T G.709'. The transmitters are connected to the bus via 'S' (Signal) interfaces, which are defined by 'ITU-T G.957', 'ITU-T G.691', and 'ITU-T G.959.1'. The bus is also connected to 'O/E/O' (Optical/Electrical/Optical) converters (O/E/O1 to O/E/O_n). These converters are connected to 'SEOI' (Signal End Office Interface) blocks. The 'SEOI' blocks are connected to 'RM' (Rate Match) blocks (RM1 to RM_n). The 'RM' blocks are connected to an 'OM/OA' (Optical Multiplexer/Optical Amplifier) block. The 'OM/OA' block is connected to an 'SCOI' (Signal Control Interface) block, which is further connected to an 'MPI-S' (Multi-Protocol Interface - S) block. The entire system is labeled 'G.977(11)_F3-3'.](eefe19c5e14dc4d6c316b7f7fbb7d7d7_img.jpg) + +Figure 3-3: Transmit side. This diagram illustrates the transmit side of a WDMS. It shows multiple transmitters (TX1 to TXn) connected to a common bus. The bus is labeled with 'ITU-T G.703' and 'ITU-T G.709'. The transmitters are connected to the bus via 'S' (Signal) interfaces, which are defined by 'ITU-T G.957', 'ITU-T G.691', and 'ITU-T G.959.1'. The bus is also connected to 'O/E/O' (Optical/Electrical/Optical) converters (O/E/O1 to O/E/O\_n). These converters are connected to 'SEOI' (Signal End Office Interface) blocks. The 'SEOI' blocks are connected to 'RM' (Rate Match) blocks (RM1 to RM\_n). The 'RM' blocks are connected to an 'OM/OA' (Optical Multiplexer/Optical Amplifier) block. The 'OM/OA' block is connected to an 'SCOI' (Signal Control Interface) block, which is further connected to an 'MPI-S' (Multi-Protocol Interface - S) block. The entire system is labeled 'G.977(11)\_F3-3'. + +Figure 3-3 – Transmit side + +![Figure 3-4 – Receive side. A block diagram showing the receive side of an optical system. On the left, an MPI-R connects to an OA/OD unit. The OA/OD unit has multiple output ports labeled SD1, SDn, and SEOI. These connect to a series of O/E/O units labeled O/E/O1 and O/E/O_n. Each O/E/O unit has an input port labeled R1, Rn and an output port labeled S. The S ports of all O/E/O units are connected to a common bus. Above the bus, the signal types are listed as S (ITU-T G.957), S (ITU-T G.691), and S (ITU-T G.959.1). The bus is labeled ITI. To the right of the bus, there is a series of RX units labeled RX1 and RX_n. Each RX unit has an input port labeled R and an output port labeled TI. The R ports of all RX units are connected to the bus. Above the bus, the signal types are listed as R (ITU-T G.957), R (ITU-T G.691), and R (ITU-T G.959.1). The TI ports of all RX units are connected to a common bus. Above this bus, the signal types are listed as ITU-T G.703 and ITU-T G.709. The entire diagram is labeled G.377(1')_F3-4 at the bottom right.](4801720824e4b5e2361a5564f91cfb70_img.jpg) + +Figure 3-4 – Receive side. A block diagram showing the receive side of an optical system. On the left, an MPI-R connects to an OA/OD unit. The OA/OD unit has multiple output ports labeled SD1, SDn, and SEOI. These connect to a series of O/E/O units labeled O/E/O1 and O/E/O\_n. Each O/E/O unit has an input port labeled R1, Rn and an output port labeled S. The S ports of all O/E/O units are connected to a common bus. Above the bus, the signal types are listed as S (ITU-T G.957), S (ITU-T G.691), and S (ITU-T G.959.1). The bus is labeled ITI. To the right of the bus, there is a series of RX units labeled RX1 and RX\_n. Each RX unit has an input port labeled R and an output port labeled TI. The R ports of all RX units are connected to the bus. Above the bus, the signal types are listed as R (ITU-T G.957), R (ITU-T G.691), and R (ITU-T G.959.1). The TI ports of all RX units are connected to a common bus. Above this bus, the signal types are listed as ITU-T G.703 and ITU-T G.709. The entire diagram is labeled G.377(1')\_F3-4 at the bottom right. + +**Figure 3-4 – Receive side** + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|------------|----------------------------------------------------------------------------| +| APC | Automatic Power Control | +| BER | Bit Error Ratio | +| BOL | Beginning Of Life | +| BU | Branching Unit | +| CF | Compression Factor | +| COTDR | Coherent Optical Time Domain Reflectometry | +| CRZ | Chirped Return to Zero | +| CS-RZ | Carrier Suppressed Return to Zero | +| CS-RZ-DPSK | Carrier Suppressed Return to Zero Differential Phase Shift Keying | +| CTE | Cable Terminating Equipment | +| DLS | Digital Line Section | +| DP-BPSK | Dual Polarization - Binary Phase Shift Keying | +| DP-nQAM | Dual Polarization - n Quadrature Amplitude Modulation (where n=8, 16 etc.) | +| DP-QPSK | Dual Polarization - Quadrature Phase Shift Keying | +| DPSK | Differential Phase Shift Keying | +| DWDM | Dense Wavelength Division Multiplexing | +| DWDMS | Dense Wavelength Division Multiplexing System | +| EDF | Erbium Doped Fibre | +| EOL | End Of Life | +| FFD-BU | Full Fibre Drop-Branching Unit | +| FOADM-BU | Fixed Optical Add/Drop Multiplexing-Branching Unit | +| FWM | Four-Wave Mixing | +| GF | Gain Flatness | + +| | | +|----------|-------------------------------------------------------------| +| ITI | Intermediate Terrestrial Interface | +| LOC | Line Optical Channel | +| LOC-TTE | Line Optical Channel-Terminal Transmission Equipment | +| MPI | Main Path Interface | +| MPI-R | Receive Main Path Interface Reference Point | +| MPI-S | Source Main Path Interface Reference Point | +| NF | Noise Figure | +| NG | Nominal Gain | +| NRZ | Non Return to Zero | +| NRZ-DPSK | Non Return to Zero Differential Phase Shift Keying | +| NSIP | Nominal Signal Input Power | +| NSOP | Nominal Signal Output Power | +| N-WDM | N-Wavelength Division Multiplexing | +| OADM | Optical Add/Drop Multiplexing | +| OFA | Optical Fibre Amplifier | +| OSE | Optical Submarine Equalizer | +| OSR | Optical Submarine Repeater | +| OTDR | Optical Time Domain Reflectometry | +| OTN | Optical Transport Network | +| PDG | Polarization-Dependent Gain | +| PDH | Plesiochronous Digital Hierarchy | +| PDL | Polarization-Dependent Loss | +| PFE | Power Feeding Equipment | +| PHB | Polarization Hole Burning | +| PMD | Polarization Mode Dispersion | +| ROADM-BU | Reconfigurable Optical Add/Drop Multiplexing-Branching Unit | +| RZ | Return to Zero | +| RZ-DPSK | Return to Zero Differential Phase Shift Keying | +| SCOI | Submarine Cable Output Interface | +| SCTTE | Submarine Cable Transmission Terminal Equipment | +| SDH | Synchronous Digital Hierarchy | +| SDLS | Submarine Digital Line Section | +| SEOI | Submarine Electro-Optic Interface | +| SNR | Signal-to-Noise Ratio | +| SSG | Small Signal Gain | + +| | | +|---------|------------------------------------------------------------------| +| STM | Synchronous Transport Module | +| SWS | Single Wavelength System | +| TI | Terrestrial Interface | +| TNTTE | Terrestrial Network Transmission Terminal Equipment | +| TTE | Terminal Transmission Equipment | +| TVSP | Time-Varying System Penalty | +| VSB | Vestigial Side Band | +| WD | Wavelength Demultiplexer | +| WDM | Wavelength Division Multiplexing | +| WDMS | Wavelength Division Multiplexing System | +| WDM-BU | Wavelength Division Multiplexing-Branching Unit | +| WDM-TTE | Wavelength Division Multiplexing-Terminal Transmission Equipment | +| WM | Wavelength Multiplexer | + +# 5 Conventions + +None. + +# 6 Characteristics and performances of the system + +## 6.1 Characteristics and performance of the digital line sections (DLSs) + +The digital line sections (DLSs) provided by the system should be in accordance with the relevant ITU-T Recommendations. + +### 6.1.1 Characteristics of the digital signals at intermediate terrestrial interface (ITI) and terrestrial interface (TI) + +For the terrestrial interface (TI), the digital signals should comply, as applicable, with [ITU-T G.702], [ITU-T G.703], [ITU-T G.707], [ITU-T G.709], [ITU-T G.957] and [ITU-T G.959.1]. + +At the intermediate terrestrial interface (ITI), it is recommended that the digital signals be compliant with the physical parameters described in [ITU-T G.957] and [ITU-T G.959.1]. + +Several interfaces with different bit-rates may co-exist for one single optical fibre submarine cable system. + +### 6.1.2 Overall error performance at TI + +The error performances of an optical fibre submarine cable system should conform to the relevant ITU-T Recommendations for the system's designed lifetime for: + +- pleisochronous digital hierarchy (PDH) interfaces: [ITU-T G.821] for systems designed prior to December 2002 and [ITU-T G.826] for later systems; +- synchronous digital hierarchy (SDH) interfaces: [ITU-T G.826] for systems designed prior to March 2000 and [ITU-T G.828] for later systems; +- optical transport network (OTN) interfaces: [ITU-T G.8201]. + +For PDH systems, the relevant parameters are errored seconds and severely errored seconds. They are derived from [ITU-T G.821] and [ITU-T G.826] in conjunction with the performances at the 64 kbit/s level on a per km basis. Information on the mapping of system performances at the 64 kbit/s level is given in Annex D of [ITU-T G.821]. + +For SDH systems, the relevant parameters are errored seconds and severely errored seconds. They are derived from [ITU-T G.826] and [ITU-T G.828]. + +For OTN systems, the relevant parameters are severely errored seconds, background block errors and errored blocks. They are derived from [ITU-T G.8201]. + +### 6.1.3 System availability at TI + +For PDH interfaces: + +- the unavailable time definition is derived from Annex A of [ITU-T G.821] and Annex A of [ITU-T G.826]; +- as per Annex A of [ITU-T G.821] and Annex A of [ITU-T G.826], a period of unavailable time begins when the bit error ratio (BER) in each second is worse than $1 \times 10^{-3}$ for a period of ten consecutive seconds. These ten seconds are considered to be unavailable time. The period of unavailable time terminates when the BER in each second is better than $1 \times 10^{-3}$ for a period of ten consecutive seconds. These ten seconds are to be considered available time. + +For SDH interfaces: + +- the unavailable time definition is derived from [ITU-T G.826] (for systems designed prior to March 2000) and [ITU-T G.828] (for systems designed after March 2000). + +For OTN interfaces: + +- the unavailable time definition is derived from [ITU-T G.8201]. + +The system availability obviously depends on the availability at the various TIs. It is recommended that system unavailability in any period be defined as the time cumulation of all unavailability of any TI in this period (several TI unavailabilities occurring in the same time-frame should not be cumulated). + +The unavailability specification applies to unavailable time caused by system component failure and includes, for example, any switching action, terminal faults and supervisory and maintenance operation leading to interruptions of ten seconds or longer. It does not include faults caused by external factors such as trawlers, anchoring, terminal transmission equipment (TTE) power feeding or any period during which the system is de-powered for repair. Similarly, faults requiring ship intervention are not included in the unavailable time calculation. + +### 6.1.4 Jitter performance at ITI and TI + +The jitter performances of an optical fibre submarine cable system should follow [ITU-T G.823], [ITU-T G.825] and [ITU-T G.8251], as well as other relevant Recommendations at ITI and TI for the system's designed lifetime. + +### 6.1.5 Performance allocation between portions of the system + +The end-to-end performance for a given DLS is obtained by multiplying the specified per km allocation by the DLS length. When it is necessary to allocate performance degradation to various portions in the DLS, an amount corresponding to a fixed length (to be determined) is allocated to each station terminal equipment, and the submarine portion is allocated, on a per km basis, an amount equal to the difference between the DLS specification and the terminal allocation. + +### 6.1.6 DLS independence + +It is recommended that any failure, maintenance operation, supervisory operation, etc., on any DLS should have no impact on the specified performances of any other DLS in the system. In particular: + +- a) *for WDMs and DWDMs* + - 1) any failure of up to half the LOCs inside a WDM should have no effect on any of the remaining LOCs of the WDM. +- b) *for SWS, WDMs and DWDMs* + - 1) any failure on one fibre pair should have no effect on the other fibre pairs in the system; + - 2) any failure on any tributary at any level of multiplexing or demultiplexing (optical or electrical) in the system should have no effect on the remaining parts of the system. + +The short-term effects of transients, in their unlikely event, should normally be considered tolerable. + +## 6.2 Optical power budget + +Optical power budget tables should describe how the system performance will be met in regards to the error performance. + +In submarine systems with in-line optical amplifiers, regeneration occurs only in the TTE at the submarine electro-optic interface (SEOI) level. In between, the channels will suffer impairments due, for example, to optical noise accumulation, or propagation (fibre non-linearities, chromatic dispersion, etc.). It is, therefore, recommended that an optical power budget be established at the submarine digital line section (SDLS) level. As some systems may accommodate several SDLSs with different impairments, it is further recommended that an optical power budget be established for each of those SDLS. + +A further consideration is that, in some cases (WDM networks with wavelength division multiplex-branching unit (WDM-BU), for example), the two directions may suffer different impairments: in this case, different power budgets can be established for each direction of the concerned SDLS, and the one with the largest impairments should be considered the SDLS power budget. + +Additionally, in case the design of a multi-landing points system has been optimized for the longest SDLS in terms of optical signal-to-noise degradation and repeater spacing, extra margins may be available on the shorter ones. Those extra margins, usually called unallocated supplier margins, should be clearly reported in the power budget tables. + +For each SDLS, it is recommended that the power budget be established such that beginning of life (BOL) and the end of life (EOL) performance expectations are clearly specified: + +- BOL is representative of the SDLS performances when the system is put into service and is used as a benchmark for test results at this time. It is recommended that this power budget include a guaranteed margin ensuring compliance with EOL conditions. The commissioning limit should define the required BOL compliance to EOL operating conditions. +- EOL is representative of the system performances at the end of the design life and should include the impairments due to component ageing and failure, cable ageing and specified repair margins. +- If the expected performance exceeds the commissioning limit, the extra margins should be used to communicate the amount by which the commissioning limit is exceeded. + +The supplier should provide sufficient information in order to support the validity of the power budget tables, in particular, but not limited to the: + +- a) nominal repeater output power value; + +- b) nominal noise figure (NF) value; and +- c) optical and electrical bandwidth values at the receiver side, used to calculate the power budget. + +A detailed description of a typical power budget is given in [b-ITU-T G-Sup.41]. An example of a 10 Gbit/s or similar power budget table is provided in Annex A.3.1.1 (Example 1). To accurately reference modem behaviour for higher bit-rate coherent systems, the power budget table provided in Annex A.3.1.2 (Example 2) can be used. + +The supplier should also clarify if any device located either at the transmitter/receiver end side, such as polarization scramblers and/or dummy channels, or within the submerged plant, such as gain equalization filters, tilt equalizers and/or slope equalizers, is supposed to improve the transmission performances. + +### **6.2.1 Quality factor (Q factor)** + +It is recommended that the power budget of each SDLS be based on the use of the Q factor as described in Annex A of [ITU-T G.976] and the impairments shown in terms of Q factor degradation. + +The performance of an SDLS should be characterized by the measurement of its Q factor, or by a direct BER measurement that should allow the reconciliation of the contractual Q factor commissioning limits indicated in the power budget. + +### **6.2.2 Relevant parameters for power budget** + +It is recommended that the power budget take into account, as a minimum, the impairments resulting from the following effects and considerations: + +- optical noise accumulation; +- propagation impairments due to the combined effects of chromatic dispersion and non-linear effects (self-phase modulation, cross-phase modulation, four-wave mixing (FWM) effects between the LOCs, stimulated Raman scattering, etc.); +- propagation impairments due to optical polarization effects such as polarization mode dispersion (PMD), polarization-dependent loss (PDL), and polarization-dependent gain (PDG). As these impairments fluctuate with time, a distinct provision should be made for performance variations over time; +- impairments due to the non-flatness of the cumulative gain curve on the whole segment; +- impairments due to the misadjustment of the wavelength(s) of the SDLS; +- impairments due to the misadjustment of the relative optical powers of the LOC inside a WDM. This impairment applies to submarine systems using WDM or DWDM. It has to be taken into account each time wavelength multiplexing (WM) is performed; +- impairments due to the supervision and fault location functions; +- impairments due to the TTE imperfections (related to back-to-back Q factor performances of the TTE). + +Cross-phase modulation and FWM between the LOCs, stimulated Raman scattering, non-flatness of the cumulative gain curve, and misadjustment of the relative optical powers of LOCs, are impairments, especially applicable to WDMS and DWDMS as they are due to the propagation of several optical signals on the same fibre. + +Specifically for the EOL power budget, the following impairments should be considered. Impairments due to: + +- repair operations (repair splices, additional loss and change in dispersion map due to extra cable length after repair, etc.); +- cable and component ageing; +- TTE ageing (the decrease of the back-to-back Q factor value of the TTE); +- the foreseen faults of some components, such as pump laser faults. + +Regarding impairments due to repair operations, the different cable type repair scenarios should be taken into consideration since impairments could be different for cables located in shallow waters, deep waters and the on-land part (from the beach to the terrestrial station). + +In addition, the power budget should clearly show the minimum Q factor required to obtain the specified error performances of the system and include margin improvement provided by the use of FEC (if applicable). + +## 6.3 System reliability performance + +The reliability of the submarine portion of an optical fibre submarine cable system is generally characterized by: + +- The expected number of repairs requiring intervention by a cable ship due to system component failures during the system's designed lifetime: + +The usual requirement for system reliability is less than three failures requiring cable ship intervention during the system's designed lifetime. + +- The system's designed lifetime. The period of time over which the submarine optical fibre cable system is designed to be operational in conformance with its performance specifications. Usually, a system's designed lifetime is a period of 25 years starting at the provisional acceptance date of the system, i.e., the date following installation when the system is compliant with the performance specifications. + +## 6.4 System capacity upgradeability + +Since optical fibre amplifiers (OFAs) have wide gain bandwidth and bit-rate flexibility, it may be advantageous to increase transmission capacity by increasing the signal bit-rate and/or the number of transmission channels (WDM or DWDM). Such upgrading can be beneficial because the reuse of long cables, many in-line amplifiers, and power-feed equipment can be achieved cost-effectively over the equipment's long life, typically 25 years. + +Bit-rate upgradeability demands that systems be constructed with cables and in-line amplifiers optimized for the higher bit-rate, while the lower bit-rate TTE may be initially used. Even after upgrading, the bit-rate of TTE output must comply with SDH or OTN specifications to ensure compatibility with standard terrestrial equipment. Upgradeability through WDM or DWDM also demands that the initially installed cable and in-line amplifiers be applicable to the system with the maximum number of channels expected in the future. Upgrading by increasing signal bit-rate, or by using WDM or DWDM, is very different from many viewpoints of system design. These include fibre-amplifier design and control, power budget, signal-to-noise ratio (SNR), fibre chromatic dispersion and fibre non-linearities. It is, therefore, recommended that the systems be designed appropriately considering the possibility of future upgrades. + +# 7 Characteristics and performance of the TTE + +## 7.1 General + +The TTE is designed to assemble the tributaries for transmission over the optical fibre submarine cable system and to provide monitoring and maintenance facilities. + +### 7.1.1 Definition of reference points of the relevant signals at the ITI, TI, SEOI and SCOI + +With reference to Figures 3-3 and 3-4, the following minimum list of parameters should be specified with regard to the E/O reference interfaces: + +- a) The TI and ITI are in accordance with [ITU-T G.703], [ITU-T G.709], [ITU-T G.957] and [ITU-T G.959.1]. +- b) The transmit side of SEOI (points $S_1$ , $S_n$ at the outputs of O/E/Os) should be specified at least in terms of: + - 1) spectral characteristics; + - 2) mean launched power; + - 3) extinction ratio, if applicable; + - 4) channel frequency; + - 5) channel spacing; + - 6) channel frequency deviation; + - 7) modulation format (return to zero (RZ), non-return to zero (NRZ), chirped return to zero (CRZ), carrier suppressed return to zero (CS-RZ), vestigial side band (VSB), non-return to zero differential phase shift keying (NRZ-DPSK), return to zero differential phase shift keying (RZ-DPSK), carrier suppressed return to zero differential phase shift keying (CS-RZ-DPSK), dual polarization - binary phase shift keying (DP-BPSK), dual polarization - quadrature phase shift keying (DP-QPSK), dual polarization - n quadrature amplitude modulation (DP-nQAM), etc.); + - 8) baud rate and bit-rate; + - 9) use of phase modulation (if applicable); + - 10) use of polarization scrambler (and the type, if applicable); + - 11) pre-dispersion compensation value; + - 12) post-dispersion compensation value. +- c) The transmit side of SCOI (point - source main path interface reference point (MPI-S)) should be specified at least in terms of: + - 1) maximum channel power difference; + - 2) channel output power; + - 3) channel signal-to-noise ratio. +- d) The receive side of SCOI (point - receive main path interface reference point (MPI-R)) should be specified at least in terms of: + - 1) channel signal-to-noise ratio (according to bit-rate and FEC implementation); + - 2) maximum channel power difference. +- e) The receive side of SEOI (points $R_1$ , $R_n$ at the inputs of the O/E/Os) should be specified at least in terms of: + - 1) receiver sensitivity (if FEC is excluded); + +- 2) receiver overload; +- 3) receiver wavelength range; +- 4) optical signal-to-noise ratio. + +## **7.2 Transmission performance** + +### **7.2.1 Characteristics of the digital signal at TI** + +The digital signal at TI should be in accordance with the relevant ITU-T Recommendations. + +### **7.2.2 Characteristics of the signal at SCOI** + +For further study. + +### **7.2.3 Jitter performance at TI** + +The jitter performance of the TTE of an optical fibre submarine cable system should be in compliance with [ITU-T G.823], [ITU-T G.825], [ITU-T G.8251] and other relevant Recommendations throughout the system's designed lifetime. + +## **7.3 Actions consequent to an alarm** + +The terminal equipment should detect fault conditions and perform consequent actions as detailed in the relevant Recommendations (see, in particular, Table 4 of [ITU-T G.921]). Alarm indications which could be taken into consideration for optical amplifiers utilized in the system should be limited to the critical parameters (e.g., input and output signal optical power, operating conditions of the pump laser such as bias current and temperature). The laser safety aspects should be in accordance with [ITU-T G.664], [IEC 60825-1] and [IEC 60825-2]. + +## **7.4 Automatic switching** + +Where automatic switching is used to meet the overall availability requirement: + +- the traffic degradation due to switching should be minimized and compatible with the overall system performance; +- indication should be given of the in-service equipment; +- manual override of the automatic switching should be feasible with a minimal degradation of system performance. + +Depending on the TTE architecture, the stand-by equipment is recommended to be kept operating and monitored as per the service equipment. + +# **8 Characteristics and performance of the optical submarine repeaters (OSRs)** + +## **8.1 Mechanical characteristics** + +### **8.1.1 Repeater housing** + +Repeater housing must be designed to allow operation, laying, recovery, and re-laying of optical repeaters in large depths with no degradation in mechanical, electrical or optical performance. The joint housing must support large load transfer from the submarine cable through a flexible coupling. + +### **8.1.2 The internal unit** + +Inside the repeater housing, the internal unit can contain several power feed modules and OFA pairs to amplify, in both directions, optical signal from one or several fibre pairs. + +### **8.1.3 Corrosion protection** + +The external housing of OSR should be designed so as not to suffer from corrosion due to sea water. + +### **8.1.4 Water pressure resistance** + +The OSR must be designed to support large pressure strengths in deep sea water. + +### **8.1.5 High voltage insulation** + +High voltage insulation is required between the repeater housing and the internal unit to ensure repeater operations. + +### **8.1.6 Thermal management** + +Heat generated by the electronic components inside the OSR may be dissipated sufficiently via thermal conduction within the repeater housing. + +### **8.1.7 Repeater housing sealing** + +The repeater must be provided with protection against water and gas ingress, both directly from the surrounding sea and from axial cable leakage resulting from a cable break close to the repeater. + +### **8.1.8 Ambient atmosphere control** + +Reliability and good operating of components may require a controlled internal atmosphere regarding relative humidity or any expected gas that may be generated inside the repeater. + +## **8.2 Electrical characteristics** + +### **8.2.1 Power modules** + +OSRs are powered from the terminal end station at a constant current via the electrical conductor on the cable. Power modules feed the OFA pairs to ensure the optical amplification. OSRs may accept both electrical polarities. + +### **8.2.2 Surge protection** + +OSRs must be protected against power surges, which may result from sudden interruption of the high voltage supply on the cable (cable break, shunt fault or power feeding equipment (PFE) short circuit). + +## **8.3 Optical characteristics** + +### **8.3.1 OFA design** + +OFA s use erbium doped fibre (EDF) to achieve amplification of the optical signal. The EDF may be pumped in a co-propagating way and/or in a contra-propagating way by one or several redundant pump lasers. Optical isolators may be included to ensure good characteristics regarding the filtering of optical reflections. Automatic power control (APC) may be used to regulate the output optical power or pump power level. + +Supervisory facilities must be provided to remotely monitor the status and performance of the OFAs. + +### **8.3.2 Relevant parameters** + +[ITU-T G.661] deals with definition and test methods for the relevant generic parameters of OFAs. More specifically, for a long haul SWS, WDMS or DWDMS amplified optical link, it is necessary to take into account the following parameters: + +- small signal gain (SSG); +- nominal gain (NG); + +- noise figure (NF); +- nominal signal output power (NSOP); +- nominal signal input power (NSIP); +- compression factor (CF). + +Moreover, especially for WDMS and DWDMS, it is also necessary to take into account: + +- gain flatness (GF). + +### 8.3.3 Polarization effects + +The individual optical components of an OFA may be chosen to ensure that its performance is reasonably insensitive to polarization effects such as PDL and PMD, depending on the system requirements. Some other polarization effects such as PDG and polarization hole burning (PHB) are intrinsic effects and can only be avoided or limited by the use of external means such as signal polarization scrambling in the TTE transmitter. + +## 8.4 Supervisory facilities + +A supervisory system is required to monitor, from the land station, the status and performance of the OFAs. This supervisory system must be able to operate when the link is in service without disturbing system performance. The characteristics of monitoring systems for optical fibre submarine cable systems with repeaters are described in [ITU-T G.979]. + +## 8.5 Fault location + +A cable-break point is usually located in an out-of-service condition. Generally, an optical time domain reflectometry (OTDR) is employed for this purpose, a coherent optical time domain reflectometry (COTDR) is used especially in a long distance OFA system fault location because of its higher sensitivity and higher frequency selectivity. + +If optical isolators are used within each OFA, the back-scattered optical pulse, which is indispensable for OTDR measurement, is blocked. One solution for solving this problem is the use of a return path (COTDR path) that should not disturb the in-service traffic as shown in Figures 8-1, 8-2 and 8-3. The transmission penalty induced by the COTDR path should be taken into account in the power budget. By using such a solution, COTDR facilities may be implemented in OFA systems to monitor the fibre span status. Moreover, if COTDR is employed in an in-service condition in the OFA systems via a return path, this method will have the potential to monitor the gain status of each OFA. + +Two different ways may be chosen to implement a COTDR path inside a repeater: + +- The first consists of connecting both outputs of one amplifier pair through optical couplers (refer to Figure 8-1). +- The second consists of connecting the output of one optical amplifier (OA) to the input of the OA located in the reverse direction (refer to Figures 8-2 and 8-3). + +Both solutions allow a bidirectional monitoring. + +The definitions and parameters for OTDR and COTDR and related test methods are described in [ITU-T G.976]. + +![Diagram of fault location using COTDR for OFA with output-to-output loopback coupling. It shows three in-line amplifiers. The first amplifier has a loopback from its output to its input. The second amplifier has a fault (X) on its output line. The third amplifier is also present. Reflected light is shown returning from the fault in the second amplifier. Reference G.977(15)_F8-2 is noted.](7133ccf78043568ca62ecbcd43628a4a_img.jpg) + +Diagram of fault location using COTDR for OFA with output-to-output loopback coupling. It shows three in-line amplifiers. The first amplifier has a loopback from its output to its input. The second amplifier has a fault (X) on its output line. The third amplifier is also present. Reflected light is shown returning from the fault in the second amplifier. Reference G.977(15)\_F8-2 is noted. + +**Figure 8-1 – Example of fault location using COTDR for OFA with output-to-output loopback coupling** + +![Diagram of fault location in the first fibre using COTDR for OFA systems using output-to-input coupler. It shows three in-line amplifiers. The first amplifier has a loopback from its output to the input of the second amplifier. The second amplifier has a fault (X) on its output line. The third amplifier is also present. Reflected light is shown returning from the fault in the second amplifier. Reference G.977(15)_F8-3 is noted.](552265bdbcf6d43d341fd018a9076269_img.jpg) + +Diagram of fault location in the first fibre using COTDR for OFA systems using output-to-input coupler. It shows three in-line amplifiers. The first amplifier has a loopback from its output to the input of the second amplifier. The second amplifier has a fault (X) on its output line. The third amplifier is also present. Reflected light is shown returning from the fault in the second amplifier. Reference G.977(15)\_F8-3 is noted. + +**Figure 8-2 – Example of fault location in the first fibre using COTDR for OFA systems using output-to-input coupler** + +![Diagram of fault location in the second fibre using COTDR for OFA systems using output-to-input coupler. It shows three in-line amplifiers. The first amplifier has a loopback from its output to the input of the second amplifier. The second amplifier has a fault (X) on its input line. The third amplifier is also present. Reflected light is shown returning from the fault in the second amplifier. Reference G.977(11)_F8-4 is noted.](e354b57563dae469c00b412b2abdf765_img.jpg) + +Diagram of fault location in the second fibre using COTDR for OFA systems using output-to-input coupler. It shows three in-line amplifiers. The first amplifier has a loopback from its output to the input of the second amplifier. The second amplifier has a fault (X) on its input line. The third amplifier is also present. Reflected light is shown returning from the fault in the second amplifier. Reference G.977(11)\_F8-4 is noted. + +**Figure 8-3 – Example of fault location in the second fibre using COTDR for OFA systems using output-to-input coupler** + +## 8.6 Reliability + +All of the repeater components must be qualified and life tested to ensure the reliability requirements. + +# 9 Characteristics and performance of the in-line branching unit (BU) + +## 9.1 General + +Optical submarine cable systems may use branching units (BUs) where multiple landing points are required. A BU is designed to terminate three line cables. One of them, the branch termination, permits the extraction of a part of the traffic coming from the two other terminations called the trunk + +terminations. Different BU designs may exist to answer particular requirements, depending of the specific system configuration. + +In that way, a BU may offer: + +1. full fibre drop functions for SWS; +2. full fibre drop functions and/or WDM add/drop functions for WDMS and DWDMS; +3. fixed (fixed optical add/drop multiplexing-branching unit (FOADM-BU)) or reconfigurable optical add/drop multiplexing-branching unit (ROADM-BU) add/drop functions for WDMS and DWDMS. + +Optical amplification, as well as other facilities, such as the power switching function, supervisory system, automatic gain control, optical filtering and coupling for COTDR, may be provided. + +## **9.2 Mechanical characteristics** + +### **9.2.1 BU housing** + +The BU mechanical housing is terminated by three cable entries and an attached sea earth. It must be designed to allow operation, laying, recovery and re-laying of BU at great depths with no degradation in mechanical, electrical and optical performances. The joint housings must support large load transfer from the submarine cable through a flexible coupling. + +Inside the BU housing, the internal unit can contain power switching circuitry and OFAs to amplify optical signals from one or several fibre pairs. It may also contain add/drop modules to ensure the WM and WD functions. + +### **9.2.2 Corrosion protection** + +Protection must prevent the BU from corrosion due to sea water. + +### **9.2.3 Water pressure resistance** + +The BU must be designed to support large pressure strengths. + +### **9.2.4 High voltage insulation** + +High voltage insulation is required between the BU housing and the internal unit to ensure BU operations. + +### **9.2.5 Thermal management** + +Heat generated by the electronic components inside the BU should be dissipated sufficiently via thermal conduction within the BU housing. + +### **9.2.6 BU housing sealing** + +The BU must be provided with a protection against water and gas ingress, both directly from the surrounding sea, and from axial cable leakage resulting from a cable break close to the BU. + +### **9.2.7 Ambient atmosphere control** + +Reliability and good operating of components may require a controlled internal atmosphere regarding relative humidity or any expected gas that may be generated inside the BU. + +## **9.3 Electrical characteristics** + +### **9.3.1 Sea electrode** + +A sea electrode connection will permit the connection of one or several of the three cable terminations to the sea potential. + +### **9.3.2 Power switching** + +Any two incoming cables with power feed conductors may be connected together and isolated from the BU sea electrode on which the third cable is connected. Different possible configurations may exist to ensure traffic recovery in some cases of PFE failure or cable break. + +In case of a faulty segment within a submarine network using BUs, the system, and in particular the BU electrical power switching circuitry, should provide the capability to restore the traffic in all the other segments, either in the presence of this fault, or during the repair operation. + +### **9.3.3 Power modules** + +A BU is powered from the terminal end station at a constant current via the electrical conductor on the cable. If applicable, power modules feed the OFA pairs to ensure the optical amplification. BUs may accept both electrical polarities. + +### **9.3.4 Surge protection** + +The BU must be protected against power surges, which may result from sudden interruption of the high voltage supply on the cable (cable break or PFE short circuit). + +## **9.4 Optical characteristics** + +### **9.4.1 Functionalities** + +A BU may be a full fibre drop-branching unit (FFD-BU), a WDM-BU or an aggregate of both. In all cases, the BU functionalities may guarantee, as far as possible, the DLS independence to ensure that any failure of a LOC will not disturb the remaining ones. In the case of a WDM-BU, specific optical components may ensure the multiplexer and demultiplexer functions. + +### **9.4.2 Relevant parameters** + +When a BU contains optical amplifiers, the relevant optical parameters defined for the OSR should be applied. Moreover, the whole characterization of the add/drop modules should be completed. + +### **9.4.3 Polarization effects** + +The individual optical components of a BU may be chosen to ensure that its performance is reasonably insensitive to polarization effects such as PDL and PMD. Some other polarization effects, such as PDG and PHB, are intrinsic effects to OFAs, possibly contained in the BU, and can only be avoided or limited by the use of external means such as signal polarization scrambling in the TTE transmitter. + +## **9.5 Supervisory facilities** + +A supervisory system is required to monitor, from the land station, the status and performance of the BU. This supervisory system must be able to operate when the link is in service without disturbing system performances. + +## **9.6 Fault location** + +Fault location in the systems, including a BU, can generally be performed using COTDR. When a BU offers a full fibre drop function, COTDR can directly locate a fault inside and beyond the BU. When + +a BU offers WDM add/drop functions, COTDR with a wavelength-tunable source can monitor a main line and a branched line independently by setting the source wavelength at the transmission wavelength of each line. If an OFA is included in the BU, a return path, as described in clause 8.5, can be applied for fault location beyond the OFA. + +The definitions and parameters for COTDR and related test methods are described in [ITU-T G.976]. + +## **9.7 Reliability** + +All the BU components must be qualified and life-tested to ensure the reliability requirement. + +# **10 Characteristics and performance of the optical submarine equalizer (OSE)** + +WDM and DWDM optical submarine cable systems may use optical submarine equalizers (OSEs) in the system DLS to reach the performance requirements for all channels. The equalization module's design is specific to each submarine cable system. It mainly depends on the SDLS characteristics and the sea temperature. + +Two distinct types of OSE may exist: + +- a) gain shape equalizer; +- b) tilt or slope equalizer. + +Adjustable equalizations, as well as other facilities such as the power monitoring function and supervisory system, may be also provided. + +## **10.1 Mechanical characteristics** + +### **10.1.1 Submarine gain equalizer housing** + +OSE housing must be designed to allow operation, laying, recovery, and re-laying in large depths with no degradation in mechanical, electrical and optical performance. + +### **10.1.2 The internal unit** + +Inside the OSE housing, the internal unit can contain several equalization modules dedicated to the optical signal from one or several fibre pairs related to each direction. + +### **10.1.3 Corrosion protection** + +The external housing of OSE should be designed so as not to suffer from corrosion due to sea water. + +### **10.1.4 Water pressure resistance** + +The OSE must be designed to support large pressure strengths in deep sea water. + +### **10.1.5 High voltage insulation** + +High voltage insulation is required between the OSE housing and the internal unit to ensure OSE operations. + +### **10.1.6 Thermal management** + +Heat generated by the electronic components inside the OSE (particularly in the case of an adjustable equalizer) may be dissipated sufficiently via thermal conduction within the OSE housing. + +### **10.1.7 OSE housing sealing** + +The OSE must be provided with a protection against water and gas ingress, both directly from the surrounding sea and from axial cable leakage resulting from a cable break close to the OSE. + +### **10.1.8 Ambient atmosphere control** + +Reliability and good operating of components may require a controlled internal atmosphere regarding relative humidity or any expected gas that may be generated inside the OSE. + +## **10.2 Electrical characteristics (for adjustable OSEs only)** + +### **10.2.1 Power modules** + +Adjustable OSEs are powered from the terminal end station at a constant current via the electrical conductor on the cable. Power modules feed the adjustable equalization modules to obtain the optical gain profile required. OSE may accept both electrical polarities. + +### **10.2.2 Surge protection** + +Adjustable OSEs must be protected against power surges, which may result from sudden interruption of the high voltage supply on the cable (cable break, shunt fault or PFE short circuit). + +## **10.3 Optical characteristics** + +### **10.3.1 Functionalities** + +Each equalization module realizes an optical filtering function on the WDM spectrum to provide the equalization of the residual gain/wavelength ripple and/or tilt which accumulates when the optical signal is transmitted through a chain of optical submarine repeaters. Adjustable functionalities may be added to adjust the response of the filtering function of the equalization module. In that case, supervisory facilities must be provided to remotely monitor the status of such adjustable OSEs. + +### **10.3.2 Relevant parameters** + +The optical specification of the submarine equalization modules should be completed by further studies. + +### **10.3.3 Polarization effects** + +The individual optical components of an OSE may be chosen to ensure that its performance is reasonably insensitive to polarization effects such as PDL and PMD. + +## **10.4 Supervisory facilities** + +A supervisory system is required to monitor, from the land station, the status of adjustable OSEs. This supervisory system must be able to operate when the link is in service without impacting the performance of the systems. + +## **10.5 Reliability** + +All of the OSE components must be qualified and life tested to guarantee the reliability requirements. + +# **11 Characteristics and performance of the submarine cable** + +The recommended characteristics and performance of the submarine cable are given in [ITU-T G.978]. + +## **11.1 Dispersion mapping** + +The dispersion map is the principal tool for describing the chromatic dispersion characteristics of a system. Cumulative dispersion is defined as the dispersion measured between the output of the terminal transmitter and any other point in the optical path. The dispersion map is the plot of local + +chromatic dispersion, for a given operating wavelength, as a function of distance from the optical transmitter to the optical receiver. The dispersion map will depend mainly on the type of system (SWS, WDMS or DWDMS). + +For a SWS, typically the fibres with low negative chromatic dispersion close to zero but not zero are used along the link corresponding to main sections, and the fibres with higher positive chromatic dispersion are used for the link corresponding to a few sections of dispersion compensation. The aim of this management is to keep a cumulative dispersion close to zero for the whole link, while keeping local chromatic dispersion at non-zero. + +For a WDMS, fibres with low negative chromatic dispersion but far from zero (around $-2$ ps/nm.km) are typically used for most sections (sometimes two types of fibre can be used, at the beginning of the section with a large effective area fibre and at the end with low slope fibre), while fibres with higher positive chromatic dispersion are regularly used for dispersion compensation sections. The aim of this management is to keep the cumulative dispersion of the whole link close to zero, while keeping local chromatic dispersion higher and non-zero, to limit the FWM and cross-phase modulation. + +For a DWDMS at 10 Gbit/s, fibres with large chromatic dispersion are typically used along the link for all the sections. One portion of the section is typically positive dispersion with positive slope (normally with a very large effective area) and the remaining portion is negative dispersion with negative slope (normally a very small effective area). The aim of this management is to keep the cumulative dispersion in each section for all the wavelengths close to zero, while keeping local chromatic dispersion very high to limit the cross-phase modulation. + +## 11.2 Dispersion management implementation + +The design of the dispersion map for each optical section must be in accordance with the transmission requirements (limitation of non-linear effects, pulse broadening, etc.). + +Residual cumulative dispersion for each wavelength may be compensated to zero by using a length of equalization fibre or other passive dispersion compensation devices at the transmit (pre-compensation) and/or receive (post-compensation) side in TTE. Typically, the compensation is made at the receive end only for a SWS, and at the transmit and receive ends for a WDMS and DWDMS. In transmission systems designed for coherent detection, dispersion may not need to be compensated. + +The system design should take into consideration all causes of variation from the planned dispersion map, both random and systematic, including, but not limited to: + +- uncertainty in the measurements of zero dispersion wavelength, dispersion, and dispersion slope of constituent single mode fibres and EDF, etc.; +- uncertainty in temperature, pressure and strain coefficients of these fibres in the cable and pressure vessels; +- uncertainty of the exact temperature and strain of these fibres during dispersion measurements; +- uncertainty of the temperature of the installed fibre; +- uncertainty resulting from reordering and "random" selection of portions of fibre sets in the assembly of elementary cable sections; +- ageing; and +- repair operations. + +# Annex A + +## Implementation of repeated optical fibre submarine cable systems using optical fibre amplifiers + +(This annex forms an integral part of this Recommendation.) + +## A.1 Introduction + +This annex outlines various aspects of submarine cable system practice as commonly employed on optical amplifier systems. It covers SWS, WDMS and DWDMS implementation. + +The information provided in this annex is intended as a guide to current practice and is not intended as a recommendation relating to existing or future systems. + +## A.2 System configuration + +### A.2.1 Constituents of repeated optical fibre submarine cable systems + +The purpose of an optical fibre submarine cable system is to establish transmission links between two or more terminal stations. Where only two terminal stations are connected by the cable system, it may be termed an optical fibre submarine cable link. If more than two are connected, then it may be termed an optical fibre submarine cable network. + +Figure A.1 shows the basic concept of optical fibre submarine cable systems and boundaries. OSRs and/or optical submarine branching units and/or OSEs could be included, depending on each system's requirements. + +In Figure A.1, A denotes the system interfaces at the terminal station (where the system can be interfaced to terrestrial digital links or to other submarine cable systems), and B denotes beach joints or landing points. Letters (in brackets) in the following clauses refer to Figure A.1. + +An optical fibre submarine cable system consists of: + +- a land portion, between the system interface in the terminal station (A) and the beach joint or landing point (B), which includes the optical fibre land cable, land joints, and the system terminal equipment; +- a submarine portion on the sea bed, between the beach joints or landing points (B), which includes the optical fibre submarine cable and, where necessary, submarine equipment, i.e., OSR(s), BU(s), OSE (s) and cable jointing box(es). + +The cable contains one or more optical fibre pairs (an optical fibre pair is used to establish transmission in both directions). + +The optical fibre submarine cable is protected where appropriate. There are several different types of cable characterized by their mechanical structure, such as lightweight cable, lightweight protected cable, light-armoured cable, single-armoured cable, double-armoured cable, and rock-armoured cable. + +The optical fibre land cable also requires protection. In particular, the optical fibre land cable carries the OSR and BU power feeding current and, in these conditions, a high potential difference may exist between the cable conductor and the ground, so that personnel protection is necessary. + +The OSRs include optical amplifiers, which are designed to accept an incoming optical signal constrained within certain limits and to amplify it so that the optical output signal is constrained within certain limits. The repeaters also include units to provide supervisory, protection and power feeding functions. These circuits constitute the repeater electronic unit and are contained within the watertight and pressure-resistant repeater housing. + +![Schematic diagram of a repeated optical fibre submarine cable system showing land and submarine portions with various components like TTE, CTE, OSR, OSE, BU, PFE, and maintenance controllers. Includes a legend for cable types and interface symbols, and a list of 10 notes explaining the components and interfaces.](692541e65db4dc852988ce77ebb60ce5_img.jpg) + +The diagram illustrates a repeated optical fibre submarine cable system. It is divided into three main sections: Land portion (1004) at the left, Submarine portion (1005) in the center, and Land portion (1004) at the right. The system starts with a system interface (A) connected to a TTE (1010) which has an optical source output (O). This is connected via an optical fibre station cable to a CTE (1014) which has a transmit terminal optical interface (S). The CTE is connected to a maintenance controller (1012) and a PFE (1013). The signal then enters the submarine portion at a landing point (B). The submarine portion contains a sequence of components: OSR (1020), OSR, OSE, BU (1022), OSR, and OSR. An 'Elementary cable section (1028)' is indicated between the first and second OSR. A branch from the BU (1022) leads to an OSR, which is connected to a cable jointing box (5013) marked with an 'X'. From the jointing box, the path continues through another OSR to a landing point (B) on the right. The right land portion includes a CTE (1014) with a receive terminal optical interface (R) connected to a TTE (1010) with an optical detector input (I). This TTE is connected to a maintenance controller and a PFE (1013). The system ends at another system interface (A). A legend defines the line types: solid for optical fibre submarine cable, double for optical fibre land cable, triple for optical fibre station cable, and single for electrical. Symbols include a circle for optical interface and a circle with a dot for system interface. Ten notes provide further details on the interfaces and component numbering. + +Legend: + +- Optical fibre submarine cable +- Optical fibre land cable +- Optical fibre station cable +- Electrical +- Optical interface +- System interface + +NOTE 1 – A denotes system interface (2008) + NOTE 2 – B denotes landing points or beach joints (1006) + NOTE 3 – A-B represents land portion (1004) + NOTE 4 – B-B represents submarine portion (1005) + NOTE 5 – X denotes cable jointing box (5013) + NOTE 6 – Numbers in brackets relate to Rec. ITU-T G.972 + NOTE 7 – O denotes optical source output (2005) + NOTE 8 – I denotes optical detector input (2006) + NOTE 9 – S denotes transmit terminal optical interface (2010) + NOTE 10 – R denotes receive terminal optical interface (2011) + +G.977(15)\_FA-1 + +Schematic diagram of a repeated optical fibre submarine cable system showing land and submarine portions with various components like TTE, CTE, OSR, OSE, BU, PFE, and maintenance controllers. Includes a legend for cable types and interface symbols, and a list of 10 notes explaining the components and interfaces. + +**Figure A.1 – Example of repeated optical fibre submarine cable system** + +An optical submarine BU is inserted into the submarine portion of an optical fibre submarine cable network where it is necessary to interconnect more than two cable sections. According to the network requirement, this equipment may include some or all of the following sub-assemblies: direct fibre connection, a fibre switching unit, optical amplifier for each fibre and a power feeding path switching unit. Moreover, the BU can provide WDMS and DWDMS with signal interchange functionality between optical signal paths; it is then termed a WDM-BU. + +An OSE may be inserted into the submarine portion of an optical submarine cable to mitigate the cumulated gain inhomogeneity when the pre-emphasis capability of the TTE at the transmitter side is not sufficient to guarantee the performance requirements for all WDM channels. This equipment may include different schemes of equalization units according to the shape of the input WDM signal spectrum: shape equalizer for spectral ripple correction and/or tilt (or slope) equalizer for tilt compensation. Adjustable equalizations as well as other facilities such as power monitoring functions and supervisory systems may be also provided. + +### **A.2.2 Transmission configuration** + +The transmission configuration characterizes the flow of information between the terminal stations across the optical fibre submarine cable system. + +The line frame and the line bit-rate result from the multiplexing and coding operations performed by the TTE, taking into account the inclusion of the service and supervisory channels. The line code is chosen so as to optimally meet the system requirements. + +An optical fibre cable section may contain a number of optical fibre pairs, and an optical fibre pair may support a number of DLSs. The number of DLSs carried by an optical fibre cable section is given by the product of these two numbers. + +The DLSs supported by the same optical fibre pair follow the fibre pair across the repeaters and the BUs. They may be separated between different fibre pairs when crossing an undersea branching multiplexer. + +### **A.2.3 Supervision and remote maintenance of the system** + +A supervisory and maintenance controller located in the terminal, in association with the repeater (or BU) supervisory unit, normally provides for fault localization, repeater performance monitoring and remote controlled redundancy switching. + +The supervisory facilities commonly include one or more of the following: + +- provision, on an in-service basis, of sufficient information to enable preventive maintenance, particularly if switchable redundancy is provided; +- provision for further out-of-service fault location or system monitoring through loopback remotely controlled from appropriate terminals; +- indication of approaching failure of the in-service equipment, so that preventive action may be undertaken or planned; and +- the means to locate hard faults and intermittent faults of duration and frequency that cause the system to fail, to ensure the performance requirement is met. + +Other means, such as COTDR, if OSRs and BUs are loopback equipped, and electrical measurement using equipment installed in the terminal stations or on board the cable ship, may permit the accuracy of fault localization to be increased. + +Supervision of the system may be facilitated by computerized equipment located at one or both ends. + +### A.2.4 System integration + +A submarine optical fibre cable link or network may be constructed using two or more submarine optical fibre systems (i.e., sets of equipment including cable, repeater, terminal equipment, BU, OSE, etc.) designed independently by different suppliers. + +To integrate the submarine optical fibre network, it is necessary to ensure the compatibility of these designs. This is the purpose of the integration specification. + +## A.3 System performance + +### A.3.1 Power budget + +#### A.3.1.1 Example 1 + +The power budget tables should compute margins that should be considered as a minimum requirement for the system at BOL. These margins should be expressed in terms of a Q factor value. The contractors should provide, as a minimum, the values of the parameters used to compute the power budget and specify all necessary complementary relevant information, for instance, the use of any optical polarization scrambling or phase modulation to minimize the polarization effects or non-linear effects. + +An example of a possible power budget template is shown in Table A.1. + +**Table A.1 – An example of a possible power budget template** + +| | Parameter | BOL Q
in dB | EOL Q
in dB | +|-----|-----------------------------------------------------------------------------------------------------------------------------------------------------|------------------------|------------------------| +| 1 | Mean Q value (from a simple SNR calculation) | | | +| 1.1 | Propagation impairments due to combined effects of chromatic dispersion, non-linear effects, FWM effects, stimulated Raman scattering effects, etc. | | | +| 1.2 | Gain flatness impairments | | | +| 1.3 | Non-optimal optical pre-emphasis impairment | | | +| 1.4 | Wavelength tolerance impairment | | | +| 1.5 | Mean PDL penalty | | | +| 1.6 | Mean PDG penalty | | | +| 1.7 | Mean PMD penalty | | | +| 1.8 | Supervisory impairment | | | +| 1.9 | Manufacturing and environmental impairment | | | +| 2 | Time-varying system penalty (5 sigma rule) | | | +| 3 | Line Q value (1-1.1 to 1.9-2) | | | +| 4 | Specified TTE Q value (back-to-back) | | | +| 5 | Segment Q value (computed from 3 and 4) | | | +| 5.1 | BER corresponding to segment Q without FEC | | | +| 5.2 | BER corresponding to segment Q with FEC | | | +| 5.3 | Effective segment Q value with FEC | | | +| 6 | Q limit compliance with [ITU-T G.826] or [ITU-T G.8201] after FEC | | | + +**Table A.1 – An example of a possible power budget template** + +| | Parameter | BOL Q
in dB | EOL Q
in dB | +|----|-------------------------------------------------------------------------------------------------------------|----------------|----------------| +| 7 | Repair margin, component- and fibre-ageing penalty, pump(s) failure penalty, non-optimal decision threshold | | | +| 8 | Segment margins | | | +| 9 | Unallocated supplier margin | | | +| 10 | Commissioning limits | | | + +Table A.1 should be completed as follows: + +- Line 1: Mean Q value (simple SNR calculation). (There exist different formulas: simple noise accumulation with constant signal power or total output power with/without extinction ratio, etc. Some calculation examples are given in [b-ITU-T G-Sup.41].) +- Lines 1.1 to 1.9: Give a non-exhaustive list of impairment sources that impact system performances. Those impairments have to be deduced from line 1. +- Line 2: Time-varying system performance. This defines an additional impairment due to polarization fluctuation phenomena that decrease the mean performances. +- Line 3: Line Q value. This line gives the line Q factor. It is the result of this operation: + +$$\text{line } 3 = \text{line } 1 - (\text{line } 1.1 \text{ to line } 1.9) - \text{line } 2$$ + +- Line 4: Specified TTE Q value. This line gives the SLTE back Q factor at BOL and EOL. +- Line 5: Segment Q value. This line gives the segment Q factor calculated from lines 3 and 4 using the following formula: + +$$\frac{1}{Q^2_{\text{segment}}} = \frac{1}{Q^2_{\text{line}}} + \frac{1}{Q^2_{\text{TTEbacktoback}}}$$ + +- Line 5.1: BER corresponding to segment Q without FEC. Line 5 converted into BER before forward error correction. +- Line 5.2: BER corresponding to segment Q with FEC. BER after FEC. +- Line 5.3: Effective segment Q value with FEC. Line 5.2 converted into Q factor. +- Line 6: Q limit for compliance with [ITU-T G.826] or [ITU-T G.8201] after FEC. Q factor corresponding to the worst allowable BER before correction by FEC. For example, 11.2 dB corresponds to a BER of $2.4 \times 10^{-4}$ . A BER of $2.4 \times 10^{-4}$ is converted by the first generation FEC defined in [ITU-T G.975] to a BER better than $10^{-11}$ . Therefore, a Q factor of all 11.2 dB covers all DLS lengths for the first generation FECs. With advanced FEC schemes defined in [ITU-T G.975.1] a BER of $10^{-3}$ is converted to a BER better than $10^{-13}$ after correction. +- Line 7: Repairs, ageing and pump failures. Line 7 is given by line 5 (BOL) minus line 5 (EOL). +- Line 8: Segment margins. Line 8 (EOL), the segment margins are usually 1 dB contractually at EOL. Line 8 (BOL), is given by line 7 plus line 8 (EOL). +- Line 9: Unallocated supplier margins. Margin for other and unknown impairments. +- Line 10: Commissioning limits. This line gives the contractual commissioned Q limit for each DLS. + +#### A.3.1.2 Example 2 + +The power budget tables should compute margins that should be considered as a minimum requirement for the system at BOL. These margins should be expressed in terms of a Q factor value. The suppliers should provide, as a minimum, the values of the parameters used to compute the power budget and specify all necessary complementary relevant information such as channel power, optical SNR and method for obtaining TTE Q factor as function of OSNR. + +An example of a possible power budget template is shown in Table A.2. + +**Table A.2 – An example of a possible coherent power budget template** + +| Item | Description | dB/0.1 nm | +|------|--------------------------------------------------------------|-----------| +| A | BOL OSNR at full loading 1 (XX dBm channel power) | | +| B | EOL OSNR at full loading 1 (XX dBm channel power) | | +| Item | Description | Q (dB) | +| 1 | Back-to-back Q at BOL OSNR | | +| 2 | Propagation impairments | | +| 3 | Other impairments | | +| 3.1 | Non-optimal optical pre-emphasis | | +| 3.2 | Wavelength tolerance impairment | | +| 3.3 | Mean penalty due to polarization-dependent effects | | +| 3.4 | Supervisory impairment | | +| 3.5 | Manufacturing and environmental impairment | | +| 3.6 | Unspecified impairment | | +| 4 | Margin for Q time variations (5 $\sigma$ ) | | +| 5 | BOL segment Q | | +| 6 | Repair and ageing Impairments | | +| 6.1 | Cable repair and ageing | | +| 6.2 | TTE ageing | | +| 7 | EOL segment Q | | +| 8 | FEC limit | | +| 9 | Customer segment EOL margin | | +| 10 | Extra margin | | +| 11 | Commissioning limit | | + +Table A.2 should be completed as follows: + +- Line A: The BOL OSNR is given for the full loading condition with a specified channel power. The supplier should provide key parameters for the system that would allow estimation of OSNR for the given channel power. For new system builds, this OSNR value is given as a reference only. +- Line B: The EOL OSNR is given for the full loading condition with a specified channel power. The supplier should provide key parameters for the system that would allow estimation of OSNR for the given channel power. For new system builds, this OSNR value is given as a reference only. + +1 Full loading implies design capacity. + +- Line 1: The back-to-back (i.e. no fibre propagation) Q factor, should be specified at the OSNR given in line A, for a TTE with average performance. The supplier should provide the method for obtaining TTE Q as function of OSNR. +- Line 2: The propagation impairment is specified as follows: + - Through measurement or simulation, of a transmission representative of the SDLS, obtain the expected Q factor after propagation (including all modem implementation penalties), at the OSNR listed in line A for a TTE with average performance. If line 1 lists TTE Q for a single channel loading, then line 2 should include the penalty due to the cross-talk between WDM channels. + - Subtract the propagated Q factor from the back-to-back Q factor in line 1. +- Line 3: The supplier margin allocations are specified as follows: + - Line 3.1: The non-optimal pre-emphasis impairment corresponds to the imperfect Q factor equalization over the full spectral range. + - Line 3.2: The wavelength tolerance impairment corresponds to the degradation due to the non-optimal wavelength setting. + - Line 3.3: Mean penalty due to polarization-dependent effects such as PDL, PDG, and PMD. + - Line 3.4: The supervisory impairment accounts for system degradation due to the presence of a supervisory system. + - Line 3.5: The manufacturing and environmental impairment provides margin for normal product fluctuations due to the manufacturing process and environmental conditions. For new system builds, this parameter includes impairments both from the DLS transmission path and the TTE. For system upgrades, this parameter includes only impairments from the TTE. + - Line 3.6: Unspecified impairment is allocated for any other impairment not listed in lines 3.1 to 3.5. +- Line 4: The Q-time variations margin (or time-varying system penalty (TVSP)) defines an additional impairment due to performance fluctuations around the mean performance. Five standard deviations of Q factor should be allocated. +- Line 5: The BOL segment Q is defined as: + +$$\text{line 5} = \text{line 1} - (\text{sum of line 2 to lines 3.1-3.6}) - \text{line 4}$$ +- Lines 6.1 and 6.2: Allocation for repairs and ageing in Q (dB). The supplier should detail the method of estimating this penalty and how it relates to the OSNR degradation defined as the difference between line A and line B. +- Line 7: EOL segment Q is defined as: + +$$\text{line 7} = \text{line 5} - (\text{sum of lines 6.1 and 6.2})$$ +- Line 8: FEC Limit in Q (dB) for compliance with [ITU-T G.826] or [ITU-T G.8201] after FEC. +- Line 9: Customer margin is the specified margin required at EOL by the cables' customer. +- Line 10: Extra margin is the margin available after all repair, ageing, and customer required margins are allocated, and is calculated as the difference between the BOL segment Q and the commissioning limit. +- Line 11: This line gives the contractual commissioned Q limit for each DLS. If performance of each channel is measured to be above the commissioning limit, then adequate margin for repair, ageing and customer provisions have been demonstrated. + +### **A.3.2 Digital line section performance** + +The performance of each DLS should at least conform to [ITU-T G.826] or [ITU-T G.8201]. + +## **A.4 System operation** + +### **A.4.1 Terminal-to-terminal communication** + +Generally, at least two service channels are established between two terminal stations: one through the optical fibre submarine cable system for the purpose of operating and maintaining the system; the other through either external means or other route for ring network systems, for the purpose of maintaining the communication between the two terminal stations in case of system fault. + +In particular, a service channel is normally provided to: + +- permit transmission of terminal-to-terminal messages between the supervisory equipment of corresponding terminal stations; +- provide information on the status of the system and of the DLSs; +- provide information on the ongoing supervisory activity so as to help in overall system monitoring; and +- provide information for supervisory or fault location purposes. + +One order wire channel may be established between terminal stations exchanging traffic for communication between the staff of the terminal stations. + +### **A.4.2 Function and characteristics of the power feeding equipment (PFE)** + +#### **A.4.2.1 PFE normal operating condition** + +The PFE provides, through the cable power conductor with return through the sea, a stabilized electric current to power the electrical circuits of the OSR(s) and/or optical submarine branching unit(s). This current is generally adjustable and is a slightly decreasing function of the PFE resistive load. + +The variations in time of the PFE current, which may be caused by ambient temperature changes within a specified range, variations and transients in the power source voltage, or redundancy switching in the PFE, are maintained between specific limits. The PFE current stability is defined so as to meet the overall stability requirement of the optical fibre submarine cable system. The PFE current stability is usually expressed as a percentage of the PFE nominal current. + +The PFE output voltage is automatically adjusted to keep the PFE current constant in the presence of naturally induced voltages. It is usually considered that these naturally induced voltages, which accumulate along a link, may reach a value of 0.3 V/km (east-west) and that they vary slowly with time (less than 10 V/s). + +#### **A.4.2.2 System protection** + +The PFE is normally equipped with facilities designed to protect the PFE itself and the submarine portion from excessive current or excessive voltage in case of electrical fault in the PFE itself or anywhere in the system. + +In particular, a PFE earth protection is provided to automatically route the power feeding current to the earth station if the system power feed electrode becomes disconnected or changes to an excessive potential difference from the earth potential. The operation of this device is designed to avoid interruption of the optical fibre submarine cable system and to prevent a rise in the power equipment earth potential sufficient to damage the equipment or endanger personnel. + +#### **A.4.2.3 PFE personnel protection** + +PFE personnel protection is provided to prevent personnel from gaining access to dangerous voltages, whether generated at the near end or at the far end of the optical fibre submarine cable system. + +The protection equipment includes, in particular, interlocks at the cable terminating equipment (CTE), emergency shut-down at the PFE, and earthing devices enabling the cable power conductor to be discharged to earth before handling. + +## **A.5 Optical submarine repeater (OSR), branching unit (BU) and optical submarine equalizer (OSE) characteristics** + +### **A.5.1 General** + +OSRs, BUs and OSEs are capable of being operated in accordance with the system performance specifications during the system's designed lifetime and in the sea depth environmental conditions (temperature, pressure, etc.). + +OSRs, BUs and OSEs are designed to be handled, i.e., laid, recovered and re-layed, without impairment of the performance of the cable, cable jointing boxes, repeaters, BUs, and cable terminations, provided that handling specifications are respected. + +OSRs, BUs and OSEs are designed to be transported and stored under specified temperature conditions without affecting the system's designed lifetime, provided that storage and transport specifications are respected. + +OSRs, BUs and OSEs are capable of being operated on board a cable ship during laying and repair operations without affecting the system's designed lifetime. + +The size of OSRs, BUs and OSEs is such that they can be handled by appropriate cable ship equipment. + +The repeater optical input interface (point R) on each incoming fibre is defined where the repeater fibre is spliced to the cable fibre. + +The repeater optical output interface (point S) on each outgoing fibre is defined where the repeater fibre is spliced to the cable fibre. + +### **A.5.2 OSR (or BU or OSE) constituents** + +The main OSR (or BU or OSE) constituents are: + +- the OSR (or BU or OSE) housing: is designed to provide resistance to the sea depth pressure, water-tightness, high mechanical strength, electrical and optical connection to the cable sections on each side of the OSR (or BU or OSE), high voltage insulation and low thermal impedance between the OSR (or BU or adjustable OSE) electronic unit and the sea. +- the OSR (or BU or adjustable OSE) electronic/optical unit: +the piece part, made of the optical amplifier(s), and/or the supervisory circuit(s), and/or the power supply and protection circuit(s), and/or optical multiplexer(s) and demultiplexer(s), and/or redundancy switch(es). + +### **A.5.3 Supervisory and monitoring** + +In association with the maintenance controller in the terminal, the OSR (or BU or adjustable OSE) supervisory unit permits repeater performance monitoring. Optical loopbacks may provide facilities to monitor the cable sections between two OSRs with the use of COTDR. + +# Bibliography + +- [b-ITU-T G-Sup.41] ITU-T G-series Recommendations – Supplement 41 (2010), *Design guidelines for optical fibre submarine cable systems*. + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|---------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Terminals and subjective and objective assessment methods | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects and next-generation networks | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of 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+version https://git-lfs.github.com/spec/v1 +oid sha256:d16230babe125f6f0e4d13adf67513b09f44446d1c2748655ac9750f4b1152da +size 83289 diff --git a/marked/G/T-REC-G.9802-201504-I_PDF-E/raw.md b/marked/G/T-REC-G.9802-201504-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..e80926cdee08ab867ee0c26a193bfc07742088f9 --- /dev/null +++ b/marked/G/T-REC-G.9802-201504-I_PDF-E/raw.md @@ -0,0 +1,645 @@ + + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**G.9802** + +(04/2015) + +SERIES G: TRANSMISSION SYSTEMS AND MEDIA, +DIGITAL SYSTEMS AND NETWORKS + +Access networks – Optical line systems for local and +access networks + +--- + +**Multiple-wavelength passive optical networks +(MW-PONs)** + +Recommendation ITU-T G.9802 + +ITU-T G-SERIES RECOMMENDATIONS +**TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | +| Metallic access networks | G.9700–G.9799 | +| Optical line systems for local and access networks | G.9800–G.9899 | +| In premises networks | G.9900–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## Recommendation ITU-T G.9802 + +### Multiple-wavelength passive optical networks (MW-PONs) + +#### Summary + +Recommendation ITU-T G.9802 describes the general requirements and architecture of multiple-wavelength passive optical network (PON) systems. It specifies the mechanism of wavelength assignment, wavelength tuning and wavelength maintenance in multiple-wavelength PON systems. The functionalities of wavelength resource management and wavelength channel performance monitoring and supervision are also included within the scope of this Recommendation. The specifications in this Recommendation can be applied to various types of multiple-wavelength PON systems. + +#### History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.9802 | 2015-04-06 | 15 | 11.1002/1000/12398 | + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2015 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|-----------------------------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 2 | +| 3.1 Terms defined elsewhere ..... | 2 | +| 3.2 Terms defined in this Recommendation..... | 2 | +| 4 Abbreviations and acronyms ..... | 2 | +| 5 Conventions ..... | 3 | +| 6 Multiple-wavelength PON architecture..... | 3 | +| 6.1 Network architecture ..... | 3 | +| 6.2 Reference configuration ..... | 4 | +| 7 General requirements on multiple-wavelength PON systems ..... | 12 | +| 8 Specifications for multiple-wavelength PON systems ..... | 13 | +| 8.1 Wavelength assignment..... | 13 | +| 8.2 Wavelength tuning..... | 14 | +| 8.3 Wavelength resource administration ..... | 16 | +| 8.4 Wavelength channel performance supervision..... | 16 | +| Annex A – Multiple-wavelength XG-PON enhancement ..... | 17 | +| A.1 Wavelength assignment..... | 17 | +| A.2 Wavelength tuning..... | 17 | +| A.3 Wavelength resource administration ..... | 17 | +| A.4 Wavelength channel performance supervision..... | 17 | +| Appendix I – Multiple-wavelength 10G-EPON enhancement ..... | 18 | +| I.1 Wavelength assignment..... | 18 | +| I.2 Wavelength tuning..... | 18 | +| I.3 Wavelength resource administration ..... | 18 | +| I.4 Wavelength channel performance supervision..... | 19 | + + + +## Recommendation ITU-T G.9802 + +### Multiple-wavelength passive optical networks (MW-PONs) + +#### 1 Scope + +This Recommendation describes the general requirements and architecture of multiple-wavelength passive optical network (PON) systems. It specifies the mechanism of wavelength assignment, wavelength tuning and wavelength maintenance in multiple-wavelength PON systems. The functionalities of wavelength resource management and wavelength channel performance monitoring and supervision are also included within the scope of this Recommendation. + +The specifications in this Recommendation can be applied to various types of multiple-wavelength PON systems such as: + +- a stack of several TDM PON systems in a single ODN, realized by assigning different wavelengths to each TDM PON system, where wavelength tunable devices may be employed in the transceivers, +- a TDM PON enhanced by dynamic or semi-dynamic wavelength tuning to allow traffic load balancing, selective OLT-port sleep, etc., +- a WDM PON in which ONUs do not share wavelengths for offering logical point to point connectivity, +- a hybrid scheme that combines these or other options. + +This Recommendation considers the following three classes as the tunability of ONU: fixed, electrically controlled and optically controlled. + +This Recommendation considers the following three classes as the wavelength tuning speed: + +- slow ( 25 ms to 1 s), +- middle (10 $\mu$ s to 25 ms), +- fast (< 10 $\mu$ s). + +This Recommendation includes specification of the functions necessary: + +- to initiate the ONU discovery process, and recognize new ONUs on the PON and their tunability in a way that does not disrupt existing traffic, +- to assign a newly recognized ONU to an initial operating wavelength set, both upstream and downstream, +- to reassign an ONU's operating wavelength set during operation. + +Not every OLT, nor every ONU, need to implement all of these functions. The annex and appendix of this Recommendation provide specific implementations of MW-PON technologies in several systems. + +#### 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.984.2] Recommendation ITU-T G.984.2 (2003), *Gigabit-capable Passive Optical Networks (G-PON): Physical Media Dependent (PMD) layer specification.* +- [ITU-T G.987] Recommendation ITU-T G.987 (2010), *10-Gigabit-capable passive optical network (XG PON) systems: Definitions, abbreviations and acronyms.* +- [ITU-T G.989.3] Recommendation ITU-T G.989.3 (2015), *40-Gigabit-capable passive optical networks (NG-PON2): Transmission convergence layer specification.* + +### 3 Definitions + +#### 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined in [ITU-T G.987]: + +**3.1.1 optical distribution network (ODN):** A point-to-multipoint optical fibre infrastructure. A *simple* ODN is entirely passive and is represented by a single-rooted point-to-multipoint tree of optical fibres with splitters, combiners, filters, and possibly other passive optical components. A *composite* ODN consists of two or more passive *segments* interconnected by active devices, each of the segments being either an optical trunk line segment or an optical distribution segment. A passive optical distribution segment is a simple ODN itself. Two ODNs with distinct roots can share a common subtree. + +**3.1.2 optical line termination (OLT):** A network element in an ODN-based optical access network that terminates the root of at least one ODN and provides an OAN SNI. + +**3.1.3 optical network unit (ONU):** A network element in an ODN-based optical access network that terminates a leaf of the ODN and provides an OAN UNI. + +**3.1.4 passive optical network (PON) system:** A combination of network elements in an ODN-based optical access network that includes an OLT and multiple ONUs and implements a particular coordinated suite of physical medium dependent layer, transmission convergence layer, and management protocols. + +#### 3.2 Terms defined in this Recommendation + +This Recommendation defines the following term: + +**3.2.1 OLT port:** Each of the physical ports in the optical line terminal (OLT) that connects to/from a fibre of the optical distribution network (ODN). + +### 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|-------|----------------------------------------| +| CT | Channel Termination | +| demux | demultiplexer | +| DWDM | Dense Wavelength Division Multiplexing | +| EPON | Ethernet Passive Optical Network | +| LLID | Logical Link Identifier | +| MAC | Media Access Control | +| mux | multiplexer | +| MPCP | Multi-Point Control Protocol | +| MW | Multiple Wavelength | + +| | | +|-------|----------------------------------------------------------| +| ODN | Optical Distribution Network | +| OLT | Optical Line Terminal | +| OMCC | ONU Management and Control Channel | +| ONU | Optical Network Unit | +| PLOAM | Physical Layer Operation, Administration and Maintenance | +| PON | Passive Optical Network | +| PS | Power Splitter | +| R/S | R/S Reference point | +| Rx | Receiver | +| SNI | Service Node Interface | +| S/R | S/R Reference point | +| TDM | Time Division Multiplexing | +| TWDM | Time and Wavelength Division Multiplexing | +| Tx | Transmitter | +| UNI | User-Network Interface | +| WC | WDM Coupler | +| WDM | Wavelength Division Multiplexing | +| WM | Wavelength Multiplexer | + +## 5 Conventions + +This Recommendation uses conventions defined in [ITU-T G.987]. + +## 6 Multiple-wavelength PON architecture + +### 6.1 Network architecture + +Figures 6-1 and 6-2 show an MW-PON architecture with a single OLT and multiple OLTs, respectively. The architecture includes an OLT or OLTs, ONUs and an ODN between them. + +In the downstream direction, the OLT or OLTs transmit multiple-wavelength signals to the ONUs. The ODN distributes signals via a point-to-multipoint optical fibre infrastructure. Depending on the deployment scenario, the ODN could be single or multiple stages. + +In the upstream direction, an ONU transmits one of the upstream wavelength signals during its transmission time. The ODN combines multiple upstream wavelengths. The OLT or OLTs receive and process more than one upstream wavelength. + +![Figure 6-1: MW-PON architecture with a single OLT. The diagram shows a single OLT connected to an Optical Distribution Network (ODN) via a Single-Mode Fiber (S/M). The ODN consists of two stages of splitters or wavelength multiplexers (WM). The first stage splits the signal into multiple branches, and the second stage further splits each branch. Each branch connects to an Optical Network Unit (ONU) via a Remote Station (R/S). Each ONU contains a Wavelength function and Logic. The OLT contains Logic and a Multiple wavelength function. Upstream signals are labeled as λ_a, λ_{a+1}, ..., λ_{a+n} and downstream signals as λ_b, λ_{b+1}, ..., λ_{b+m}. The diagram is labeled G.9802(15)_F6-1.](a5ee5c23b6dc52ec1d724b76d5a5f58f_img.jpg) + +Figure 6-1: MW-PON architecture with a single OLT. The diagram shows a single OLT connected to an Optical Distribution Network (ODN) via a Single-Mode Fiber (S/M). The ODN consists of two stages of splitters or wavelength multiplexers (WM). The first stage splits the signal into multiple branches, and the second stage further splits each branch. Each branch connects to an Optical Network Unit (ONU) via a Remote Station (R/S). Each ONU contains a Wavelength function and Logic. The OLT contains Logic and a Multiple wavelength function. Upstream signals are labeled as λ\_a, λ\_{a+1}, ..., λ\_{a+n} and downstream signals as λ\_b, λ\_{b+1}, ..., λ\_{b+m}. The diagram is labeled G.9802(15)\_F6-1. + +Figure 6-1 – MW-PON architecture with a single OLT + +![Figure 6-2: MW-PON architecture with multiple OLTs. The diagram shows multiple OLTs connected to a common Wavelength Multiplexer (WM) and/or splitter. This WM and/or splitter is connected to the ODN via a Single-Mode Fiber (S/M). The ODN consists of two stages of splitters or wavelength multiplexers (WM). The first stage splits the signal into multiple branches, and the second stage further splits each branch. Each branch connects to an Optical Network Unit (ONU) via a Remote Station (R/S). Each ONU contains a Wavelength function and Logic. Each OLT contains Logic and a Multiple wavelength function. Upstream signals are labeled as λ_a, λ_{a+1}, ..., λ_{a+n} and downstream signals as λ_b, λ_{b+1}, ..., λ_{b+m}. The diagram is labeled G.9802(15)_F6-2.](cfda9df1319e04207eb28bcefd1dab7b_img.jpg) + +Figure 6-2: MW-PON architecture with multiple OLTs. The diagram shows multiple OLTs connected to a common Wavelength Multiplexer (WM) and/or splitter. This WM and/or splitter is connected to the ODN via a Single-Mode Fiber (S/M). The ODN consists of two stages of splitters or wavelength multiplexers (WM). The first stage splits the signal into multiple branches, and the second stage further splits each branch. Each branch connects to an Optical Network Unit (ONU) via a Remote Station (R/S). Each ONU contains a Wavelength function and Logic. Each OLT contains Logic and a Multiple wavelength function. Upstream signals are labeled as λ\_a, λ\_{a+1}, ..., λ\_{a+n} and downstream signals as λ\_b, λ\_{b+1}, ..., λ\_{b+m}. The diagram is labeled G.9802(15)\_F6-2. + +Figure 6-2 – MW-PON architecture with multiple OLTs + +## 6.2 Reference configuration + +### 6.2.1 ODN + +There can be several types of ODN architecture to achieve service distribution in MW-PONs. Figures 6-3 and 6-4 show examples of MW-PON with power-splitter-based ODN. Figures 6-5 and 6-6 are examples of MW-PON with wavelength-mux (demux)-based ODN, where "mux" denotes "multiplexer". Figure 6-7 is an example of an MW-PON with an ODN consisting of power splitters and multiple feeder fibres. Figure 6-8 is an example of MW-PON with an ODN consisting of an NxM wavelength mux (demux) and multiple power splitters. Figure 6-9 is a reference diagram of an MW-PON with Type C protection and an ODN of one-stage power or wavelength mux (demux). Figure 6-10 is a reference diagram of the MW-PON in Figure 6-9 with a two-stage splitter ODN. Figure 6-11 is an example of an MW-PON with wavelength muxes (demuxs) at the OLT and at the ODN. + +Note that Figures 6-3 to 6-11 simply provide reference examples of the ODN architectures. They are not intended to limit designs and implementations of OLTs and ONUs. In addition, the designs and implementations of MW-PON OLT and ONU are outside the scope of this Recommendation. + +Also note that this Recommendation recognizes ODN architectures with multiple stages. Each stage can be a different type of ODN configuration depending on the chosen technology. + +![Diagram of MW-PON configuration showing CT, Tunable ONU, OLT, and ODN components with signal paths and logical connectivity.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg) + +The diagram illustrates the configuration of a Multi-Wavelength Passive Optical Network (MW-PON). On the left, the Optical Line Terminal (OLT) contains multiple Channel Terminations (CT 1 to CT M), each connected to a transmitter (Tx) and a receiver (Rx). These are connected to a 1xM Power Splitter (PS). The OLT is connected to the Service Network Interface (SNI) and the System Reference (S/R) point. The Optical Distribution Network (ODN) consists of a 1xN PS followed by N PON segments (PON 1 to PON N). Each PON segment contains a 1xN PS and multiple Optical Network Units (ONUs). For example, PON 1 includes ONUs 1-1, 1-2, and 1-n. Each ONU is connected to a Tunable ONU block containing a Tunable Tx, Tunable Rx, and Logic, which is further connected to the User Network Interface (UNI) and the Remote System (R/S) point. Signal paths are shown for downstream (λd1, λd2, ..., λdm) and upstream (λu1, λu2, ..., λum) traffic. A yellow box indicates that each ONU can access all CTs. + +CT: Channel termination + WC: WDM coupler + Tx: Transmitter, Rx: Receiver + PS: Power splitter + +SNI S/R ODN R/S UNI + +Logical connectivity: each ONU can access all CTs. + +G.9802(15)\_F6-3 + +Diagram of MW-PON configuration showing CT, Tunable ONU, OLT, and ODN components with signal paths and logical connectivity. + +**Figure 6-3 – Configuration example of MW-PON with a 1xM power splitter at the OLT and 1xN power splitters at the ODN** + +![Diagram of MW-PON configuration with an 1xM wavelength mux at the OLT and 1xN power splitters at the ODN. The diagram shows the flow of multiple wavelengths (λ_d1 to λ_dm for downlink, λ_u1 to λ_um for uplink) from multiple Channel Terminations (CTs) through a Wavelength Mux (WM) at the OLT, then through a 1xN Power Splitter (PS) in the ODN to multiple PONs (PON 1 to PON N). Each PON then splits to multiple ONUs (e.g., ONU 1-1 to ONU 1-n). Each ONU contains a Tunable WDM Coupler (WC), a Tunable Transceiver (Tx/Rx), and Logic. A separate box shows the internal structure of a CT and a Tunable ONU.](d4af765160d04ecef538e5066006dc77_img.jpg) + +Detailed diagram components: + +- CT (Channel Termination) Detail:** Contains Logic, Rx, and Fixed- $\lambda$ Tx connected via a WC (WDM Coupler). +- Tunable ONU Detail:** Contains Logic, Tunable Rx, and Tunable Tx connected via a WC (WDM Coupler). +- OLT:** Contains CT 1 to CT M. CT 1 uses $\lambda_{d1}$ , CT 2 uses $\lambda_{d2}$ , and CT M uses $\lambda_{dm}$ . These are multiplexed by a 1×M WM. +- ODN:** Features a 1×N PS (Power Splitter) distributing signals to PON 1, PON 2, ..., PON N. +- PON 1:** Serves ONU 1-1, ONU 1-2, ..., ONU 1-n. Downstream wavelengths are $\lambda_{d1}, \lambda_{d2}, ..., \lambda_{dm}$ . Upstream wavelengths are $\lambda_{u1}, \lambda_{u2}, ..., \lambda_{um}$ . +- PON 2:** Serves ONU 2-1, ONU 2-2, ..., ONU 3-n. +- PON N:** Serves ONU x-1, ONU x-2, ..., ONU x-n. + +Diagram of MW-PON configuration with an 1xM wavelength mux at the OLT and 1xN power splitters at the ODN. The diagram shows the flow of multiple wavelengths (λ\_d1 to λ\_dm for downlink, λ\_u1 to λ\_um for uplink) from multiple Channel Terminations (CTs) through a Wavelength Mux (WM) at the OLT, then through a 1xN Power Splitter (PS) in the ODN to multiple PONs (PON 1 to PON N). Each PON then splits to multiple ONUs (e.g., ONU 1-1 to ONU 1-n). Each ONU contains a Tunable WDM Coupler (WC), a Tunable Transceiver (Tx/Rx), and Logic. A separate box shows the internal structure of a CT and a Tunable ONU. + +Tx: Transmitter, Rx: Receiver + PS: Power splitter, WM: Wavelength Mux (Demux) + CT: Channel termination + WC: WDM coupler + +Logical connectivity: each ONU can access all CTs. + +G.9802(15)\_F6-4 + +**Figure 6-4 – Configuration example of MW-PON with an 1xM wavelength mux (demux) at the OLT and 1xN power splitters at the ODN** + +![Diagram of MW-PON configuration showing OLT with multiple CTs and a power splitter, connected via ODN with a wavelength mux to multiple PONs, each serving several tunable ONUs. Downstream wavelengths are labeled lambda_d and upstream lambda_u.](af7916c89a458fdab6c3f443217388ae_img.jpg) + +The diagram illustrates the configuration of a Multi-Wavelength Passive Optical Network (MW-PON). On the left, the Optical Line Terminal (OLT) contains multiple Channel Terminations (CTs), labeled CT 1 through CT M. Each CT consists of a Logic unit, a Tunable Transmitter (Tx), a Receiver (Rx), and a Tunable filter. These CTs are connected to a 1×M Power Splitter (PS). The PS outputs multiple wavelengths, labeled $\lambda_{d1}, \lambda_{d2}, \dots, \lambda_{dm}$ for downstream and $\lambda_{u1}, \lambda_{u2}, \dots, \lambda_{um}$ for upstream, to a 1×N Wavelength Mux (Demux) in the Optical Distribution Network (ODN). The ODN then splits these into N PONs (PON 1, PON 2, ..., PON N). Each PON serves a group of Optical Network Units (ONUs). For example, PON 1 serves ONUs 1-1, 1-2, and 1-n. Each ONU contains a Wavelength Coupler (WC), a Tunable Tx, a Tunable Rx, and a Logic unit. The ONUs are connected to the ODN via R/S interfaces, and the ODN is connected to the OLT via S/R interfaces. The OLT is connected to the Service Network Interface (SNI) and the ONUs are connected to the User Network Interface (UNI). + +Diagram of MW-PON configuration showing OLT with multiple CTs and a power splitter, connected via ODN with a wavelength mux to multiple PONs, each serving several tunable ONUs. Downstream wavelengths are labeled lambda\_d and upstream lambda\_u. + +Tx: Transmitter, Rx: Receiver +PS: Power splitter, WM: Wavelength Mux (Demux) +CT: Channel termination +WC: WDM coupler + +Logical connectivity: each ONU can access all CTs. +Needs the tunable components in CTs. + +G.9802(15)\_F6-5 + +**Figure 6-5 – Configuration example of MW-PON with an 1×N power splitter at the OLT and a 1×N wavelength mux (demux) at the ODN** + +![Diagram of MW-PON configuration showing OLT, ODN, and UNIs with multiple PONs and CTs.](4801720824e4b5e2361a5564f91cfb70_img.jpg) + +The diagram illustrates a Multi-Wavelength Passive Optical Network (MW-PON) architecture. On the left, the Optical Line Terminal (OLT) is connected to the Service Network Interface (SNI). It contains multiple Channel Terminations (CTs), labeled CT 1 through CT M. Each CT is associated with a specific wavelength: $\lambda_{d1}$ (red), $\lambda_{d2}$ (yellow), ..., $\lambda_{dm}$ (blue). Each CT consists of a Transmitter (Tx) and a Receiver (Rx) connected to a Logic unit. The OLT also includes a Wavelength Mux (Demux) labeled 1xM. Downstream signals ( $\lambda_{d1}, \lambda_{d2}, \dots, \lambda_{dm}$ ) are multiplexed and sent towards the Optical Distribution Network (ODN). Upstream signals ( $\lambda_{u1}, \lambda_{u2}, \dots, \lambda_{um}$ ) are demultiplexed and sent to the corresponding CTs. The ODN contains an 1xN Wavelength Mux (Demux). This device splits the downstream signals into N separate PONs (PON 1, PON 2, ..., PON N) and combines upstream signals from these PONs. Each PON i serves a group of Optical Network Units (ONUs): ONU i-1, ONU i-2, ..., ONU i-n. Each ONU is connected to a User Network Interface (UNI) and contains a Wavelength Coupler (WC), a Tunable Transmitter (Tx), a Tunable Receiver (Rx), and a Logic unit. The ONUs are configured to receive the specific wavelength assigned to their PON (e.g., $\lambda_{di}$ for PON i) and transmit on a wavelength assigned to the ONU (e.g., $\lambda_{ui}$ for ONU i-j). A yellow box at the bottom states: "Logical connectivity: each ONU can only access the specified CT." The diagram also includes labels for interfaces: SNI, S/R (Service/Receiver), ODN, R/S (Receiver/Service), and UNI. + +CT: Channel termination + WC: WDM coupler + WM: Wavelength Mux (Demux) + Tx: Transmitter, Rx: Receiver + +Logical connectivity: each ONU can only access the specified CT. + +G.9802(15)\_F6-6 + +Diagram of MW-PON configuration showing OLT, ODN, and UNIs with multiple PONs and CTs. + +**Figure 6-6 – Configuration example of MW-PON with an 1xM wavelength mux (demux) at the OLT and an 1xN wavelength mux (demux) at the ODN** + +![Diagram of MW-PON configuration with an NxM wavelength mux at the OLT and 1xN power splitters at the ODN. The OLT contains CT 1 through CT M, each with a Tunable Tx and Rx. These connect to an NxM (N) WM. The ODN consists of PON 1 through PON N, each with a 1xN splitter. PON 1 serves ONU 1-1 to ONU 1-n; PON 2 serves ONU 2-1 to ONU 2-n; PON N serves ONU x-1 to ONU x-n. Downstream wavelengths λd1, λd2, λdm and upstream wavelengths λu1, λu2, λum are shown. A detailed view of a CT and a Tunable ONU is provided at the top.](33ed1f9b27c7c21c797aa928b0f06851_img.jpg) + +Diagram of MW-PON configuration with an NxM wavelength mux at the OLT and 1xN power splitters at the ODN. The OLT contains CT 1 through CT M, each with a Tunable Tx and Rx. These connect to an NxM (N) WM. The ODN consists of PON 1 through PON N, each with a 1xN splitter. PON 1 serves ONU 1-1 to ONU 1-n; PON 2 serves ONU 2-1 to ONU 2-n; PON N serves ONU x-1 to ONU x-n. Downstream wavelengths λd1, λd2, λdm and upstream wavelengths λu1, λu2, λum are shown. A detailed view of a CT and a Tunable ONU is provided at the top. + +Tx: Transmitter, Rx: Receiver +WM: Wavelength Mux (Demux) +CT: Channel termination +WC: WDM coupler + +Logical connectivity: each ONU can access all CTs. +Needs the tunable components in CTs. + +G.9802(15)\_F6-7 + +**Figure 6-7 – Configuration example of MW-PON with an NxM wavelength mux (demux) at the OLT and 1xN power splitters at the ODN** + +![Figure 6-8: Configuration example of MW-PON with an 1xM wavelength mux (demux) at the OLT and an NxM wavelength splitter at the ODN. The diagram shows an OLT with multiple CT (Channel Termination) units connected to a 1xM WM (Wavelength Mux/Demux). The OLT is connected to an SNI on the left and an ODN on the right. The ODN contains an NxM WM (Wavelength Splitter) that branches into multiple PONs (PON 1, PON 2, ..., PON N). Each PON is connected to multiple ONUs (ONU 1-1 to 1-n, 2-1 to 2-n, ..., x-1 to x-n). Each ONU is connected to a Tunable ONU unit containing a Tunable Tx, Tunable Rx, and Logic. The Tunable ONU is connected to a UNI on the right. Wavelengths are indicated: λ_d1, λ_d2, ..., λ_dm for downstream from OLT; λ_u1, λ_u2, ..., λ_um for upstream from ONUs. A legend defines Tx (Transmitter), Rx (Receiver), WM (Wavelength Mux/Demux), CT (Channel termination), and WC (WDM coupler).](fa859e4e468bfb2710a94527f2c504af_img.jpg) + +Figure 6-8: Configuration example of MW-PON with an 1xM wavelength mux (demux) at the OLT and an NxM wavelength splitter at the ODN. The diagram shows an OLT with multiple CT (Channel Termination) units connected to a 1xM WM (Wavelength Mux/Demux). The OLT is connected to an SNI on the left and an ODN on the right. The ODN contains an NxM WM (Wavelength Splitter) that branches into multiple PONs (PON 1, PON 2, ..., PON N). Each PON is connected to multiple ONUs (ONU 1-1 to 1-n, 2-1 to 2-n, ..., x-1 to x-n). Each ONU is connected to a Tunable ONU unit containing a Tunable Tx, Tunable Rx, and Logic. The Tunable ONU is connected to a UNI on the right. Wavelengths are indicated: λ\_d1, λ\_d2, ..., λ\_dm for downstream from OLT; λ\_u1, λ\_u2, ..., λ\_um for upstream from ONUs. A legend defines Tx (Transmitter), Rx (Receiver), WM (Wavelength Mux/Demux), CT (Channel termination), and WC (WDM coupler). + +Tx: Transmitter, Rx: Receiver + WM: Wavelength Mux (Demux) + CT: Channel termination + WC: WDM coupler + +G.9802(15)\_F6-8 + +**Figure 6-8 – Configuration example of MW-PON with an 1xM wavelength mux (demux) at the OLT and an NxM wavelength splitter at the ODN** + +![Figure 6-9: Reference configuration of Type C protection with one stage splitter at the ODN. The diagram shows an OLT with two Logic units, each connected to a Multiple wavelength function. These functions are connected to two Splitter or WDM mux/demux units in the ODN. Each Splitter or WDM mux/demux is connected to two ONUs. Each ONU contains a Wavelength function and a Logic unit, and is connected to a UNI on the right. Wavelengths are indicated: λ_a, λ_{a+1}, ..., λ_{a+m} for downstream from OLT; λ_b, λ_{b+1}, ..., λ_{b+m} for upstream from ONUs. A legend defines Tx (Transmitter), Rx (Receiver), WM (Wavelength Mux/Demux), CT (Channel termination), and WC (WDM coupler).](16152cf1d84aea10848758f51a91ff6a_img.jpg) + +Figure 6-9: Reference configuration of Type C protection with one stage splitter at the ODN. The diagram shows an OLT with two Logic units, each connected to a Multiple wavelength function. These functions are connected to two Splitter or WDM mux/demux units in the ODN. Each Splitter or WDM mux/demux is connected to two ONUs. Each ONU contains a Wavelength function and a Logic unit, and is connected to a UNI on the right. Wavelengths are indicated: λ\_a, λ\_{a+1}, ..., λ\_{a+m} for downstream from OLT; λ\_b, λ\_{b+1}, ..., λ\_{b+m} for upstream from ONUs. A legend defines Tx (Transmitter), Rx (Receiver), WM (Wavelength Mux/Demux), CT (Channel termination), and WC (WDM coupler). + +G.9802(15)\_F6-9 + +**Figure 6-9 – Reference configuration of Type C protection with one stage splitter at the ODN** + +![Figure 6-10: Reference configuration of Type C protection with two stages of splitters at the ODN. The diagram shows an OLT on the left connected to an ODN (Optical Distribution Network) via S/R (Service Reference) and R/S (Reseller Reference) points. The ODN consists of two stages of splitters. The first stage has two splitters, each receiving two inputs from the OLT's 'Multiple wavelength function' blocks. The second stage has two 'Splitter or WDM mux/demux' blocks, each receiving one input from each first-stage splitter. These then connect to two ONUs on the right. Each ONU contains a 'Wavelength function' block and a 'Logic' block. The OLT also contains 'Logic' blocks. Arrows indicate wavelength paths: λ_a, λ_{a+1}, ..., λ_{a+n} and λ_b, λ_{b+1}, ..., λ_{b+m} from the OLT to the first stage, and then to the second stage, and finally to the ONUs. The diagram is labeled G.9802(15)_F6-10.](8fbdfc3d17fb1dae7b2d8f5a287fa9fc_img.jpg) + +Figure 6-10: Reference configuration of Type C protection with two stages of splitters at the ODN. The diagram shows an OLT on the left connected to an ODN (Optical Distribution Network) via S/R (Service Reference) and R/S (Reseller Reference) points. The ODN consists of two stages of splitters. The first stage has two splitters, each receiving two inputs from the OLT's 'Multiple wavelength function' blocks. The second stage has two 'Splitter or WDM mux/demux' blocks, each receiving one input from each first-stage splitter. These then connect to two ONUs on the right. Each ONU contains a 'Wavelength function' block and a 'Logic' block. The OLT also contains 'Logic' blocks. Arrows indicate wavelength paths: λ\_a, λ\_{a+1}, ..., λ\_{a+n} and λ\_b, λ\_{b+1}, ..., λ\_{b+m} from the OLT to the first stage, and then to the second stage, and finally to the ONUs. The diagram is labeled G.9802(15)\_F6-10. + +Figure 6-10 – Reference configuration of Type C protection with two stages of splitters at the ODN + +![Figure 6-11: Configuration example of MW-PON with wavelength mux (demux) at the OLT and at the ODN. The diagram shows an OLT on the left with multiple 'CT' (Channel Termination) blocks, each connected to a 'Fixed-λ Tx' and 'Rx' block. These are connected to a '1×M WM' (Wavelength mux) block. The OLT is connected to an ODN via S/R and R/S points. The ODN contains another '1×M WM' block that splits into multiple PONs (PON 1, PON 2, ..., PON N). Each PON is connected to an ONU (ONU 1, ONU 2, ..., ONU x). Each ONU contains a 'Tunable Tx' and 'Rx' block, connected to a 'Logic' block. Arrows indicate wavelength paths: λ_{d1}, λ_{d2}, ..., λ_{dm} from the OLT to the ODN, and then to the ONUs; and λ_{u1}, λ_{u2}, ..., λ_{um} from the ONUs back to the OLT. A yellow box states 'Logical connectivity: each ONU can access the specified CT'. The diagram is labeled G.9802(15)_F6-11.](2cde062fd82833415971a8bd1a2cafab_img.jpg) + +Tx: Transmitter, Rx: Receiver + CT: Channel termination + WC: WDM coupler + WM: Wavelength mux (demux) + +Logical connectivity: each ONU can access the specified CT + +Figure 6-11: Configuration example of MW-PON with wavelength mux (demux) at the OLT and at the ODN. The diagram shows an OLT on the left with multiple 'CT' (Channel Termination) blocks, each connected to a 'Fixed-λ Tx' and 'Rx' block. These are connected to a '1×M WM' (Wavelength mux) block. The OLT is connected to an ODN via S/R and R/S points. The ODN contains another '1×M WM' block that splits into multiple PONs (PON 1, PON 2, ..., PON N). Each PON is connected to an ONU (ONU 1, ONU 2, ..., ONU x). Each ONU contains a 'Tunable Tx' and 'Rx' block, connected to a 'Logic' block. Arrows indicate wavelength paths: λ\_{d1}, λ\_{d2}, ..., λ\_{dm} from the OLT to the ODN, and then to the ONUs; and λ\_{u1}, λ\_{u2}, ..., λ\_{um} from the ONUs back to the OLT. A yellow box states 'Logical connectivity: each ONU can access the specified CT'. The diagram is labeled G.9802(15)\_F6-11. + +Figure 6-11 – Configuration example of MW-PON with wavelength mux (demux) at the OLT and at the ODN + +## 6.2.2 ONU + +This recommendation recognizes several types of ONUs with respect to the transmitter and receiver implementation. The first type of ONU is with fixed wavelength configuration. The ONU receiving + +and transmitting wavelengths are not tunable. The second type of ONU is with a fixed receiver and a tunable transmitter. The third type of ONU is with a tunable receiver and a tunable transmitter. + +Note that the ONU tunable receiver and/or transmitter can be electrically controlled or optically controlled depending on the chosen technology. + +## 7 General requirements on multiple-wavelength PON systems + +MW-PON general requirements are defined as four logical function requirements, including wavelength assignment, wavelength tuning, wavelength resource administration and wavelength channel performance supervision. They are elaborated in the following. + +- **Wavelength assignment:** In an MW-PON system with a splitter-based ODN, wavelength assignment is critical to bring an inactive ONU into operation. When a new ONU is installed on the ODN, the initial downstream and upstream wavelengths have to be automatically and remotely assigned between the OLT and the new ONU. This wavelength assignment process has to be carried out as a part of the ONU activation. To properly communicate with the OLT, the ONU downstream and upstream wavelengths should be designated as early as possible, and wavelength tuning may be needed during activation. In an MW-PON system with a wavelength mux-based ODN, only a single wavelength can pass in the ODN from the OLT to an ONU or from an ONU to the OLT. In this case, wavelength assignment is done during the physical installation process. +- **Wavelength tuning:** If ONUs are capable of wavelength tuning, during the process of ONU activation, a newly activated ONU may need to tune its wavelengths by following an OLT command. During the operation of an MW-PON system with wavelength tunability, the assigned wavelengths may need further change. For example, in an MW-PON system, ONUs could be equipped with tunable transceivers; if some wavelengths are heavily loaded while there are idle wavelengths, a good practice might be tuning some ONUs from the heavily loaded wavelengths into the idle ones. This would balance traffic among the available wavelengths, maintaining the stable status of the PON. Alternatively, OLT power savings could be realized by turning off certain OLT ports under light load conditions (e.g., midnight to 6 AM), while tuning the ONUs to a subset of the available wavelengths. In addition, dynamic wavelength changes with fast wavelength tuning may be necessary for some MW-PON systems for the purpose of efficient wavelength resource utilization. This can be also used in case of troubleshooting and maintenance to temporarily move a channel to a spare resource. +- **Wavelength resource administration:** In an MW-PON system, wavelength becomes a key resource to arbitrate medium access. In both splitter-based and wavelength mux-based MW-PON systems, the OLT should be able to confirm the ONU wavelength assignment in the MAC layer. This supports regular wavelength maintenance. Information such as wavelength resource availability and wavelength assignment should be provided for resource administration. Traditional PON administration mechanisms are conducted in the TDM channel. Proper extension and enhancement should be investigated to address the issue of wavelength resource administration. Available timeslots and wavelengths should be used for dynamic wavelength and bandwidth assignment/allocation (DWBA), which manages both wavelength resources and timeslots in MW-PON. In an MW-PON system with a wavelength mux-based ODN, ONU wavelengths are determined by the physical infrastructure, and MW-PON should inventory all working wavelengths. +- **Wavelength channel performance supervision:** Each wavelength channel should be monitored to maintain system health. Failures and defects related to wavelengths should be detected to facilitate troubleshooting. Two major issues associated with the use of wavelength are wavelength drift monitoring and wavelength stabilization supervision. + +- *Wavelength drift monitoring*: Drift from the desired wavelength grid should be monitored. This function is especially important in the splitter-based MW-PON systems because wavelength drift may interfere with communications of other ONUs. +- *Wavelength stabilization supervision*: All working wavelengths should be stabilized around the desired wavelength grid. This function is especially important in the MW-PON systems with DWDM technologies. + +## 8 Specifications for multiple-wavelength PON systems + +### 8.1 Wavelength assignment + +Wavelength assignment is an integral procedure of the ONU activation in an MW-PON system. The OLT makes the wavelength assignment decision and controls the ONU wavelengths by means of issuing function-specific bandwidth grants and/or exchanging wavelength management and control messages. The general ONU activation in PON consists of three phases: synchronization to the downstream signal, ONU identification and adaptation to the multiplexing technique. Wavelength assignment in MW-PON can be during, before or after any of the three phases depending on the implementation. This Recommendation specifies the general mechanism of wavelength assignment. + +The wavelength assignment procedure consists of the steps given below: + +- Step 1: Communication on wavelength tuning capability (optional) +- Step 2: Wavelength assignment decision +- Step 3: OLT command ONU of the downstream and/or upstream wavelength +- Step 4: ONU wavelength adjustment (optional) +- Step 5: ONU response (optional) + +The OLT optionally conducts Step 1 by issuing function-specific bandwidth grants or wavelength management and control messages to acquire the ONU tunability information. The ONU scans the downstream wavelength channel and responds with a wavelength management and control message. The ONU tunability information would include elements such as transmitter or receiver wavelength tuning range, tuning granularity, tuning time, channel spacing, calibrated or uncalibrated transmitter type. + +The wavelength assignment decision in Step 2 can be made when connecting an ONU to the ODN, before an ONU activation or during an ONU activation, depending on the ODN architecture. In an MW-PON system with wavelength-splitter-based ODN, the ONU wavelength is determined by the connection between the ONU and ODN, and no further wavelength assignment is needed. In an MW-PON system with power-splitter-based ODN, the OLT makes wavelength assignment decisions either before or during an ONU activation, depending on factors such as ONU design, OLT design, PON traffic load, etc. + +After deciding the wavelength assignment of a newly activated ONU, the OLT issues a wavelength management and control message to the ONU in Step 3. This message contains information to instruct the ONU of the wavelength assignment decision. The information elements include upstream wavelength ID, downstream wavelength ID, destination wavelength in nanometers or the corresponding frequency, wavelength tuning direction (longer or shorter wavelength), wavelength tuning start time. Note that there are several ways to issue the wavelength assignment message. The OLT can broadcast it to all downstream wavelengths, send it in a wavelength selected for system control and management, or issue it in the downstream wavelength of the new ONU. The new ONU scans the downstream wavelength channel and detects the wavelength assignment message if there is any. + +Depending on the initial wavelengths, the ONU may or may not change its wavelengths in Step 4. Once the ONU confirms the downstream and upstream wavelengths following the OLT command, it optionally responds with a wavelength management and control message in Step 5. + +An ONU joins MW-PON operations by the ONU activation process. Various types of ONUs can be employed. In the activation process, the working wavelengths of an inactive ONU (one for downstream, the other for upstream) can be a random pair of wavelengths or a default pair of wavelengths, depending on the ONU transceiver design and the protocol specification. + +![Sequence diagram showing the wavelength assignment message exchange between an OLT and an ONU. The sequence starts with PHY Sync, followed by a Request wavelength and tunability from OLT to ONU, an ONU wavelength and tunability report from ONU to OLT, a Wavelength assignment command from OLT to ONU, and an optional ONU response from ONU to OLT. The OLT side is labeled 'Wavelength assignment decision making procedure' and the ONU side is labeled 'Wavelength tuning procedure'. The diagram is labeled G.9802(15)_F8-1.](5445597cceefaca1ac89e710fe339325_img.jpg) + +``` + +sequenceDiagram + participant OLT + participant ONU + Note right of ONU: PHY Sync + OLT->>ONU: Request wavelength and tunability + ONU-->>OLT: ONU wavelength and tunability report + Note left of OLT: Wavelength assignment decision making procedure + OLT->>ONU: Wavelength assignment command + Note right of ONU: Wavelength tuning procedure + ONU-->>OLT: ONU response (optional) + +``` + +G.9802(15)\_F8-1 + +Sequence diagram showing the wavelength assignment message exchange between an OLT and an ONU. The sequence starts with PHY Sync, followed by a Request wavelength and tunability from OLT to ONU, an ONU wavelength and tunability report from ONU to OLT, a Wavelength assignment command from OLT to ONU, and an optional ONU response from ONU to OLT. The OLT side is labeled 'Wavelength assignment decision making procedure' and the ONU side is labeled 'Wavelength tuning procedure'. The diagram is labeled G.9802(15)\_F8-1. + +**Figure 8-1 – Wavelength assignment message exchange in ONU activation** + +The OLT acquires the information of ONU working wavelengths and wavelength tunability after the ONU conducts PHY synchronization. Such information helps the OLT to make wavelength assignment. Once making the wavelength assignment decision, the OLT instructs the ONU to either maintain the current wavelengths or switch to the target wavelengths. Figure 8-1 shows the main information exchange between the OLT and an ONU in the activation process. + +## 8.2 Wavelength tuning + +Wavelength tuning is the procedure of changing the ONU wavelengths during regular operation. In the regular operation, due to purposes such as load balance or power saving, the OLT may direct ONUs to change wavelengths. + +Note that wavelength tuning does not apply to the MW-PON system with a fixed wavelength configuration restricted by the ODN architecture. + +The wavelength tuning procedure consists of the steps given below: + +- Step 1 Communication on wavelength tuning capability (optional) +- Step 2 Wavelength tuning decision +- Step 3 OLT command ONU of the downstream and/or upstream wavelength +- Step 4 ONU wavelength adjustment +- Step 5 ONU response (optional) + +The OLT optionally conducts Step 1 by issuing a wavelength management and control message to acquire the ONU tunability information. The ONU sends a response message. Note that the wavelength management and control message can either broadcast to all ONUs or unicast to an ONU. The ONU tunability information would include elements such as transmitter or receiver wavelength tuning range, tuning granularity, tuning time, channel spacing, calibrated or uncalibrated transmitter type. + +In Step 2 the OLT makes wavelength tuning decision based on requirements such as load balance or power saving. + +The OLT issues a wavelength management and control message to the ONU in Step 3. This message contains information to instruct the ONU of the wavelength tuning decision. The information elements include upstream wavelength ID, downstream wavelength ID, destination wavelength in nanometers or the corresponding frequency, wavelength tuning direction (longer or shorter wavelength), wavelength tuning start time. + +The ONU adjusts wavelengths in Step 4. + +Once the ONU confirms its downstream and upstream wavelengths following the OLT command, it optionally sends a response message in Step 5. + +A major reason of changing ONU wavelengths in operation is to balance MW-PON traffic among the available wavelengths. Another reason is to potentially facilitate power savings at the OLT by reducing the number of required "active" ports. Figures 8-2 and 8-3 show the message exchange between the OLT and an ONU to support wavelength tuning. + +![Sequence diagram showing message exchange between OLT and ONU for wavelength tunability request.](a24e89a6fe9bb70c83f8bf5202baba95_img.jpg) + +``` + +sequenceDiagram + participant OLT + participant ONU + OLT->>ONU: Wavelength request + ONU-->>OLT: ONU wavelength and tunability report + +``` + +A sequence diagram illustrating the message exchange between an OLT and an ONU for a wavelength tunability request. The OLT sends a 'Wavelength request' message to the ONU. The ONU responds with an 'ONU wavelength and tunability report' message. The diagram is labeled G.9802(15)\_F8-2. + +Sequence diagram showing message exchange between OLT and ONU for wavelength tunability request. + +**Figure 8-2 – Example of message exchange in wavelength tunability request** + +Figure 8-2 shows the OLT transmits a wavelength request to an ONU. The ONU reports its working wavelengths and its tunability. Such information helps the OLT to make the wavelength tuning decision. + +![Sequence diagram showing message exchange between OLT and ONU for wavelength tuning.](75e4b78ee25f885d73120e3066a5253e_img.jpg) + +``` + +sequenceDiagram + participant OLT + participant ONU + Note over OLT: OLT makes the wavelength +tuning decision + OLT->>ONU: Wavelength change command + Note over ONU: ONU finishes its wavelength +tuning procedure + ONU-->>OLT: ONU response + +``` + +A sequence diagram illustrating the message exchange between an OLT and an ONU for wavelength tuning. The OLT makes the wavelength tuning decision and sends a 'Wavelength change command' to the ONU. The ONU finishes its wavelength tuning procedure and sends an 'ONU response' message. The diagram is labeled G.9802(15)\_F8-3. + +Sequence diagram showing message exchange between OLT and ONU for wavelength tuning. + +**Figure 8-3 – Message exchange in wavelength tuning** + +When the OLT decides to change the ONU wavelengths, it instructs the assigned wavelengths to the ONU by transmitting a wavelength change command as shown in Figure 8-3. The ONU converts its wavelengths to the target wavelengths by following the command. After tuning its transceiver, the ONU transmits a response to confirm the completion of wavelength change. + +The wavelength change command includes the destination wavelength. This command may include a start time when the ONU should start the wavelength tuning procedure to flush out the OLT-port's accumulated downstream buffer or to avoid the collision at the ONU between the period of wavelength tuning and the previously granted period of sending upstream data. + +After sending the wavelength change command, the OLT waits for the ONU response. The OLT may periodically assign upstream grants to let ONUs to send responses. The ONU sends its response when completing the wavelength tuning procedure. + +### **8.3 Wavelength resource administration** + +#### **8.3.1 Channel ID** + +The channel ID is the wavelength connection indication in MW-PON. It is the logic ID of the MW-PON wavelength resource. + +In an MW-PON system, the downstream wavelength received by an ONU is decided either by the ODN configuration or by the ONU receiver tunability. The channel ID of the downstream wavelength indicates the wavelength connection between an OLT port and its associated ONUs. + +The channel ID of the upstream wavelength has several applications in MW-PON. For example, when the downstream and upstream wavelength channels have a fixed relationship, the OLT needs the upstream wavelength information to correlate the upstream transmission from the ONU with the downstream wavelength that the ONU receives. In this case, the ONU can feedback its downstream wavelength up through the upstream, and the OLT makes the key association. Another example is when the ONU transmits its upstream wavelength channel indication in the upstream frames. The OLT uses this as a confirmation to check the ONU upstream working wavelength. + +### **8.4 Wavelength channel performance supervision** + +Wavelength channel performance supervision supports the management and troubleshooting of an MW-PON system. Traditional optical layer supervision, described in Appendix IV of [ITU-T G.984.2], is expected to be supported via an ONU management and control interface. + +In an MW-PON system with the capability of channel calibration, the OLT obtains the channel calibration information from the ONUs. This information is for wavelength tuning in the process of ONU activation and/or system operation. The OLT may implement methods such as dithering for wavelength channel supervision. The OLT assigns an optical power value to each upstream wavelength channel. The dithering alarm is on when the difference between the measured optical signal power and the pre-configured value exceeds a threshold. + +## **Annex A** + +### **Multiple-wavelength XG-PON enhancement** + +(This annex forms an integral part of this Recommendation.) + +#### **A.1 Wavelength assignment** + +For wavelength assignment, exchange of management and control messages is required. For this purpose, PLOAMs in XG-PON are extended for TWDM channels in NG-PON2 as described in [ITU-T G.989.3]. + +For enhancing multiple-wavelength system, downstream channel scanning process is required for a colourless ONU to decide initial downstream wavelength selection for ONU activation. The ONU activation process extended for TWDM channels in NG-PON2 is described in [ITU-T G.989.3]. + +#### **A.2 Wavelength tuning** + +The wavelength tuning procedure is implemented in TWDM channels in NG-PON2 as described in [ITU-T G.989.3]. + +#### **A.3 Wavelength resource administration** + +A logic ID that represents the wavelength connection indication is required in MW-PON systems. [ITU-T G.989.3] includes the description of TWDM downstream and upstream identifiers as well as other indicators. + +#### **A.4 Wavelength channel performance supervision** + +This requirement is implemented in TWDM channels of NG-PON2 as described in [ITU-T G.989.3]. + +## Appendix I + +### Multiple-wavelength 10G-EPON enhancement + +(This appendix does not form an integral part of this Recommendation.) + +#### I.1 Wavelength assignment + +For wavelength assignment, exchange of management and control messages is required. In EPON, MAC control extension is available for the ONU control. Another way is to add the wavelength information to the current MAC control messages (e.g., GATE message and REPORT message). + +For colourless ONUs, a downstream channel scanning process is required to select the initial downstream wavelength in the ONU discovery process. The enhanced ONU discovery process for multiple-wavelength 10G-EPON is shown in Figure I.1. + +![Diagram of the ONU discovery process for multiple-wavelength 10G-EPON. It shows an OLT and an ONU. The OLT sends a 'Discovery gate' message to the ONU. The ONU performs 'Downstream channel scanning'. The process is labeled as ''. A double-headed arrow indicates the 'Single wavelength 10G-EPON ONU discovery sequence'. The diagram is labeled G.9802(15)_FI.1.](171115f072e42b379238ed0dd438e9d7_img.jpg) + +The diagram illustrates the interaction between an OLT and an ONU for wavelength assignment. The OLT sends a 'Discovery gate' message to the ONU. The ONU performs 'Downstream channel scanning'. The process is labeled as ''. A double-headed arrow indicates the 'Single wavelength 10G-EPON ONU discovery sequence'. The diagram is labeled G.9802(15)\_FI.1. + +Diagram of the ONU discovery process for multiple-wavelength 10G-EPON. It shows an OLT and an ONU. The OLT sends a 'Discovery gate' message to the ONU. The ONU performs 'Downstream channel scanning'. The process is labeled as ''. A double-headed arrow indicates the 'Single wavelength 10G-EPON ONU discovery sequence'. The diagram is labeled G.9802(15)\_FI.1. + +Figure I.1 – ONU discovery process for multiple-wavelength 10G-EPON + +#### I.2 Wavelength tuning + +A wavelength tuning procedure is implemented with the following mechanisms. + +- 1) A mechanism to command the designation of the destination wavelength to ONUs and the tuning start timing – It may need to modify the Gate message of the MPCP or to utilize a MAC control extension to command wavelength change. The command may include a local time to schedule the start timing of the wavelength tuning procedure. +- 2) A mechanism to allow each ONU to have a different tuning time and to recover connection as fast as possible – It may be realized by sending a grant of Report message periodically right after commanding a wavelength change from the OLT and by sending a modified Report message as ONU responses at the grant right after completing the wavelength tuning procedure of the ONU. It may also be realized by utilizing a MAC control extension. + +The wavelength tuning capability of the ONU can be transferred to the OLT via the OMCC. + +#### I.3 Wavelength resource administration + +A logic ID that represents the wavelength connection indication is required in MW-PON systems. In EPON, the ONU is able to recognize the OLT ports in the MAC layer by checking the OLT MAC address that is populated in the MAC control message received from the OLT. The ONU is also able to recognize the point-to-point connection between the OLT and the ONU by checking the LLID that is populated in the preamble of Ethernet frames. This information can be used for identifying the wavelength connection. + +#### **I.4 Wavelength channel performance supervision** + +This requirement is implemented as a physical layer function. In a multiple-wavelength EPON system, physical layer specification can be in common with TWDM-PON. + + + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|---------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Terminals and subjective and objective assessment methods | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects and next-generation networks | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.9805-202202-I_PDF-E/02bb4edc0dbdf4f0749ffd3e0ea2805c_img.jpg 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digital line system – Optical line +systems for local and access networks + +# --- **40-Gigabit-capable passive optical networks (NG-PON2): Definitions, abbreviations and acronyms** + +Recommendation ITU-T G.989 + +## ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|--------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| General | G.900–G.909 | +| Parameters for optical fibre cable systems | G.910–G.919 | +| Digital sections at hierarchical bit rates based on a bit rate of 2048 kbit/s | G.920–G.929 | +| Digital line transmission systems on cable at non-hierarchical bit rates | G.930–G.939 | +| Digital line systems provided by FDM transmission bearers | G.940–G.949 | +| Digital line systems | G.950–G.959 | +| Digital section and digital transmission systems for customer access to ISDN | G.960–G.969 | +| Optical fibre submarine cable systems | G.970–G.979 | +| Optical line systems for local and access networks | G.980–G.989 | +| Metallic access networks | G.990–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +# Recommendation ITU-T G.989 + +# 40-Gigabit-capable passive optical networks (NG-PON2): Definitions, abbreviations and acronyms + +## Summary + +Recommendation ITU-T G.989 contains the common definitions, acronyms, abbreviations and conventions of the ITU-T G.989-series of Recommendations. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.989 | 2015-10-22 | 15 | 11.1002/1000/12561 | + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2015 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|---------------------------------------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 1 | +| 3.1 Terms defined elsewhere ..... | 1 | +| 3.2 Terms defined in this Recommendation..... | 2 | +| 4 Abbreviations and acronyms ..... | 10 | +| 5 Conventions ..... | 16 | +| 5.1 Optical access concepts ..... | 16 | +| 5.2 Multi-wavelength PON system reference points..... | 17 | +| 5.3 Optical power and loss parameters..... | 18 | +| 5.4 Dynamic range, sensitivity and overload ..... | 18 | +| 5.5 Sensitivity and overload in the presence of FEC..... | 19 | +| 5.6 Reach and distance ..... | 19 | +| 5.7 Use of the term PON ..... | 20 | +| 5.8 Use of the term ODN..... | 20 | +| 5.9 Use of the terms ONU and ONT ..... | 21 | +| 5.10 Use of the terms T-CONT and Alloc-ID ..... | 21 | +| 5.11 Use of the terms bandwidth assignment and bandwidth allocation ..... | 22 | +| 5.12 Use of the terms band and range ..... | 22 | +| 5.13 Transmitter enable control and associated transient times ..... | 22 | +| Bibliography..... | 24 | + + + +## Recommendation ITU-T G.989 + +# 40-Gigabit-capable passive optical networks (NG-PON2): Definitions, abbreviations and acronyms + +# 1 Scope + +This Recommendation contains the common definitions, acronyms, abbreviations and conventions of the ITU-T G.989-series of Recommendations. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T J.185] Recommendation ITU-T J.185 (2012), *Transmission equipment for transferring multi-channel television signals over optical access networks by frequency modulation conversion*. +- [ITU-T J.186] Recommendation ITU-T J.186 (2008), *Transmission equipment for multi-channel television signals over optical access networks by sub-carrier multiplexing (SCM)*. + +# 3 Definitions + +## 3.1 Terms defined elsewhere + +This Recommendation uses the following terms defined elsewhere: + +- 3.1.1 access network (AN)** [b-ITU-T G.902]: An implementation comprising those entities (such as cable plant, transmission facilities, etc.) which provide the required transport bearer capabilities for the provision of telecommunications services between a service node interface (SNI) and each of the associated user-network interfaces (UNIs). +- 3.1.2 Ethernet LAN service (E-LAN)** [b-MEF 6.1]: An Ethernet service type that is based on a Multipoint-to-Multipoint Ethernet virtual connection. +- 3.1.3 Ethernet line service (E-Line)** [b-MEF 6.1]: An Ethernet service type that is based on a Point-to-Point Ethernet virtual connection. +- 3.1.4 Ethernet tree service (E-Tree)** [b-MEF 6.1]: An Ethernet service type that is based on a Rooted-Multipoint Ethernet virtual connection. +- 3.1.5 Ethernet virtual connection (EVC)** [b-MEF 6.1]: An association of UNIs to which the exchange of service frames is limited. +- 3.1.6 jitter (timing jitter)** [b-ITU-T G.810]: The short-term variations of the significant instances of a digital signal from their ideal positions in time (where "short-term" implies that these variations are of a frequency greater than or equal to 10 Hz). + +**3.1.7 service node (SN)** [b-ITU-T G.902]: A network element that provides access to various switched and/or permanent telecommunication services. + +**3.1.8 service node interface (SNI)** [b-ITU-T G.902]: An interface which provides customer access to a service node. + +**3.1.9 user-network interface (UNI)** [b-ITU-T I.112]: The interface between the terminal equipment and a network termination at which interface the access protocols apply. + +**3.1.10 1:1 VLAN** [b-BBF TR-101]: A VLAN forwarding paradigm involving a one-to-one mapping between user port and VLAN. The uniqueness of the mapping is maintained in the Access Node and across the Aggregation Network. + +**3.1.11 N:1 VLAN** [b-BBF TR-101]: A VLAN forwarding paradigm involving many-to-one mapping between user ports and VLAN. The user ports may be located in the same or different Access Nodes. + +## **3.2 Terms defined in this Recommendation** + +This Recommendation defines the following terms: + +### **3.2.1 Optical access architecture terms** + +**3.2.1.1 channel group:** A set of channel pairs carried over a common fibre. + +**3.2.1.2 channel pair:** A set of one downstream wavelength channel and one upstream wavelength channel that provides connectivity between an OLT and one or more ONUs. + +**3.2.1.3 channel partition:** Any of the operator-specified non-overlapping subsets of TWDM or PtP WDM channels in an NG-PON2 system. + +**3.2.1.4 channel partition index:** An identity of an operator-specified TWDM or PtP WDM channel subset in an NG-PON2 system. + +**3.2.1.5 channel termination (CT):** See OLT PtP WDM channel termination, OLT TWDM channel termination. + +**3.2.1.6 coexistence element:** A bidirectional functional element used to connect PON systems defined in different Recommendation series to the same ODN. + +**3.2.1.7 domain:** A collection of all NG-PON2 network elements under a common and unique operational administration. + +**3.2.1.8 gigabit-capable passive optical network (G-PON):** A PON system supporting transmission rates in excess of 1.0 Gbit/s in at least one direction, and which implements the suite of protocols specified in the ITU-T G.984-series of Recommendations. + +**3.2.1.9 next generation PON (NG-PON):** In the context of ITU-T standards development activity, a generic term referencing the PON system evolution beyond G-PON. The concept of NG-PON currently includes NG-PON1, where the ODN is maintained from B-PON and G-PON, and NG-PON2, where a redefinition of the ODN is allowed from that defined in B-PON and G-PON. + +**3.2.1.10 NG-PON1:** A PON system with a nominal aggregate capacity of 10 Gbit/s in the downstream direction. The NG-PON1 system is represented by XG-PON. + +**3.2.1.11 NG-PON2:** A PON system with a nominal aggregate capacity of 40 Gbit/s in the downstream direction and 10 Gbit/s in the upstream direction, and implementing the suite of protocols specified in the ITU-T G.989-series of Recommendations. An NG-PON2 system is composed of a set of TWDM channels and/or a set of PtP WDM channels. + +- 3.2.1.12 OLT PtP WDM channel termination:** A logical function that resides at the OLT network element and terminates a single PtP WDM channel in a PtP WDM system. +- 3.2.1.13 OLT TWDM channel termination:** A logical function that resides at the OLT network element and that terminates a single TWDM channel in a TWDM system. +- 3.2.1.14 optical access network (OAN):** A part of an access network whose network elements are interconnected by optical communication channels. Note that an OAN may or may not extend all the way to the UNI, so that the user-side interface of the OAN does not necessarily coincide with the UNIs of the AN. +- 3.2.1.15 optical distribution network (ODN):** A point-to-multipoint optical fibre infrastructure. A simple ODN is entirely passive and is represented by a single-rooted point-to-multipoint tree of optical fibres with splitters, combiners, filters and possibly other passive optical components. A composite ODN consists of two or more passive segments interconnected by active devices, each of the segments being either an optical trunk line segment or an optical distribution segment. A passive optical distribution segment is a simple ODN itself. Two ODNs with distinct roots can share a common subtree. +- 3.2.1.16 optical distribution segment (ODS):** A simple ODN, that is, a point-to-multipoint optical fibre infrastructure that is entirely passive and is represented by a single-rooted tree of optical fibres with splitters, combiners, filters and possibly other passive optical components. +- 3.2.1.17 optical line termination (OLT):** A network element in an ODN-based optical access network that terminates the root of at least one ODN and provides an OAN SNI. +- 3.2.1.18 optical network terminal (ONT):** An ONU supporting a single subscriber. +- 3.2.1.19 optical network unit (ONU):** A network element in an ODN-based optical access network that terminates a leaf of the ODN and provides an OAN UNI. +- 3.2.1.20 optical trunk line (OTL):** A passive point-to-point segment of a composite ODN. +- 3.2.1.21 parenting:** A passive optical network protection configuration where ONUs are connected to two CTs hosted in different OLT chassis. Typically, the OLT chassis in dual parenting are geographically remote from each other. +- 3.2.1.22 passive optical network (PON) system:** A combination of network elements in an ODN-based optical access network that includes an OLT and one or more ONUs and implements a particular coordinated suite of physical medium dependent layer, transmission convergence layer and management protocols. +- 3.2.1.23 PtP WDM channel:** In an NG-PON2 system, PtP WDM channel refers to the pair of one downstream wavelength channel and one upstream wavelength channel providing point-to-point connectivity. +- 3.2.1.24 PtP WDM PON:** A multiple wavelength PON system that enables point-to-point connectivity using a dedicated wavelength channel per ONU for the downstream direction and a dedicated wavelength channel per ONU for the upstream direction. +- 3.2.1.25 RF video overlay:** A method for video transmission in the downstream direction in a wavelength band between 1550 nm and 1560 nm according to [ITU-T J.185] and [ITU-T J.186]. +- 3.2.1.26 TWDM channel:** In an NG-PON2 system, TWDM channel refers to the pair of one downstream wavelength channel and one upstream wavelength channel providing point-to-multipoint connectivity by using, respectively, time division multiplexing and multiple access mechanisms. + +**3.2.1.27 TWDM PON:** A multiple wavelength PON system in which each wavelength channel may be shared among multiple ONUs by employing time division multiplexing and multiple access mechanisms. + +**3.2.1.28 wavelength channel:** A unidirectional (downstream or upstream) optical communications channel characterized by a single unique central frequency or a set of unique central frequencies mapped to one WM tributary port. + +**3.2.1.29 wavelength multiplexer (WM):** A bidirectional functional element used to multiplex / demultiplex between NG-PON2 wavelength channel pairs and channel groups. + +**3.2.1.30 10-gigabit-capable passive optical network (XG-PON):** A PON system supporting nominal transmission rates on the order of 10 Gbit/s in at least one direction, and implementing the suite of protocols specified in the ITU-T G.987-series of Recommendations. XG-PON is the realization of NG-PON1. + +**3.2.1.31 XG-PON1:** A variant of an XG-PON system that operates at a nominal line rate of 10 Gbit/s downstream and 2.5 Gbit/s upstream. + +**3.2.1.32 XG-PON2:** A variant of an XG-PON system that operates at a nominal line rate of 10 Gbit/s downstream and upstream. + +### **3.2.2 Optical parameters, optical power, losses and penalties1** + +**3.2.2.1 attenuation:** See optical path loss. + +**3.2.2.2 channel spacing:** The absolute difference between the nominal central frequencies of two adjacent wavelength channels in a given reference grid. + +**3.2.2.3 consecutive identical digit (CID) immunity:** The longest continuous sequence of identical bits, that can be present in a digital signal without causing degradation so that the system specifications are no longer met. + +**3.2.2.4 differential fibre distance:** The absolute difference between the fibre distances of any two given paths between the R/S and S/R-CG reference points in the same ODN. + +**3.2.2.5 differential optical path loss:** The absolute difference between the optical losses, expressed in decibel units, of any two given paths between the R/S and S/R-CG reference points in the same ODN. + +**3.2.2.6 dispersion:** A physical phenomenon comprising the dependence of the phase or group velocity of a light wave in the medium, on its propagation characteristics such as optical frequency (wavelength) or polarization mode. + +**3.2.2.7 dynamic range:** An optical receiver characteristic that is equal to the ratio of the receiver overload to the receiver sensitivity. + +**3.2.2.8 extinction ratio (ER):** With respect to a digital On-Off keying signal generated by an optical transmitter, the ratio of the average optical power level at the centre of the binary digit corresponding to the high intensity of light to the average optical power level at the centre of a binary digit corresponding to the low intensity of light. + +--- + +1 For the definition of the NG-PON2 architectural reference points mentioned within this clause, please see clause 5.2. For the relationship between optical power and loss parameters, see clause 5.3. For the definition of the burst-mode transmitter enabled/disabled periods and the associated transient times, see clause 5.13. + +For the burst-mode signal, averaging is performed over the time periods when the transmitter is enabled, but excluding the associated transient times (see clause 5.13). For the continuous mode signal, averaging is performed over the entire signal string. + +**3.2.2.9 fibre distance:** The overall length of fibre (and, if applicable, equivalent fibre runs representing delay-inducing components) between the R/S and S/R-CG reference points. + +**3.2.2.10 in-band crosstalk tolerance:** The minimum value of signal-to-crosstalk ratio at the S/R-CG (upstream direction) or R/S (downstream direction) reference point that maintains the receiver compliance with the sensitivity requirements. The crosstalk is assumed to be polarized and aligned with the signal polarization. + +**3.2.2.11 line code:** In the NG-PON2 context, a code which transforms a binary digital signal into an amplitude- and time-discrete waveform for transmission over a physical channel. + +**3.2.2.12 mask of transmitter eye diagram:** A general method of transmitter pulse shape characterization that allows the combined specification of rise time, fall time, pulse overshoot/undershoot, ringing and jitter to ensure satisfactory operation with a compliant receiver. Transmitter mask compliance is required at the appropriate reference point (S/R-CG for downstream, R/S for upstream). + +**3.2.2.13 mean launch optical power:** An optical transmitter characteristic expressing the average optical power of an optical signal transmitted into the fibre and carrying a given digital sequence, referring to the optical power of an individual wavelength channel at the appropriate reference point (S/R-CG for downstream direction, R/S for upstream direction). When specified as a range, the minimum mean launch optical power provides the power level that the transmitter should guarantee at all times, and the maximum mean launch optical power provides the power level that the transmitter should never exceed. When applied to burst-mode transmission, the term pertains to the time interval during which the transmitter is enabled, and excludes possible starting and ending transient behaviour. + +**3.2.2.14 nominal central frequency:** The specified frequency of a wavelength channel. + +**3.2.2.15 nominal line rate:** The total number of bits that can be physically transferred per unit of time over a communication link. Nominal line rate accounts for useful data as well as for all possible protocol overheads and necessarily exceeds the effective data rate on any given protocol level. + +**3.2.2.16 ODN fibre distance class:** A categorization of an ODN based on the predefined values of minimum and maximum fibre distance between the S/R-CG and any of R/S reference points. + +**3.2.2.17 ODN optical path loss class (ODN Class):** A categorization of an ODN based on the predefined values of minimum and maximum optical path loss over all possible paths between the S/R-CG and any of the R/S reference points and over all possible operating wavelengths of a specific PON system. + +**3.2.2.18 operating wavelength band:** The spectral interval defined by its boundaries $\lambda_{\min}$ and $\lambda_{\max}$ which includes all possible central operating wavelengths for a particular application. + +**3.2.2.19 optical path loss:** The reduction in the optical power of light having traversed the ODN expressed as a ratio in decibel units. This loss may be caused by the fibre, connectors, splices, splitters, wavelength couplers, attenuators and other passive optical components. + +**3.2.2.20 optical path penalty (OPP):** The apparent degradation of receiver sensitivity due to impairments from fibre transmission and an apparent increase in ODN loss due to Raman depletion. The optical path penalty accounts for the effects of reflections, intersymbol interference, mode partition noise, fibre dispersion, and fibre non-linearities. + +**3.2.2.21 optical power spectral density when not enabled (WNE-PSD):** The optical power spectral density per transmitter, at any wavelength inside or outside the operating wavelength band, measured when the transmitter is not enabled and the allocated transient time has elapsed, at the appropriate reference point (S/R-CG for downstream direction, R/S for upstream direction). Measurements are averaged over time and are expressed as the total integrated power within a sliding spectral window of known width. + +**3.2.2.22 optical return loss (ORL):** The total reflection at the source reference point of the optical signal propagation path, measured as a ratio of the transmitted optical power to the reflected optical power. + +**3.2.2.23 overload:** A receiver parameter equal to the maximum average received optical power that produces the specified BER reference level, referring to the optical power of an individual wavelength channel at the appropriate reference point (S/R-CG for upstream direction, R/S for downstream direction) measured with the worst case signal, but without the optical path impairments. + +**3.2.2.24 per channel out-of-band optical power spectral density (OOB-PSD):** The optical PSD outside the operating wavelength band measured at the appropriate reference point (S/R-CG for downstream direction, R/S for upstream direction). Measurements are averaged over the time periods when the transmitter is enabled, or when the transmitter is not enabled but the allocated transient time has not yet elapsed, and these are expressed as the total integrated power within a sliding spectral window of known width. + +**3.2.2.25 per channel out-of-channel optical power spectral density (OOC-PSD):** For a transmitter in a stationary wavelength channel state, the optical PSD outside the spectral interval corresponding to the operating wavelength channel, measured at the appropriate reference point (S/R-CG for downstream direction, R/S for upstream direction). Measurements are averaged over the time periods when the transmitter is enabled, or when the transmitter is not enabled but the allocated transient time has not yet elapsed, and these are expressed as the total integrated power within a sliding spectral window of known width. + +**3.2.2.26 reflectance:** The reflection from any single discrete reflection point in the optical signal propagation path, which is defined to be the ratio of the reflected optical power present at a point, to the optical power incident to that point. + +**3.2.2.27 sensitivity:** A receiver parameter equal to the minimum average received optical power that produces the specified BER reference level, referring to the optical power of an individual wavelength channel at the appropriate reference point (S/R-CG for upstream direction, R/S for downstream direction) measured with the worst case signal, but without the optical path impairments. + +**3.2.2.28 side mode suppression ratio (SMSR):** The ratio of the power of the largest peak of the transmitter spectrum to that of the second largest peak. The second largest peak may be next to the main peak, or far removed from it. Within this definition, spectral peaks that are separated from the largest peak by the clock frequency are not considered to be side modes. + +**3.2.2.29 spectral excursion:** For a transmitter in a stationary wavelength channel state, the absolute difference between the nominal central frequency of the channel and the –15 dB points of the transmitter spectrum furthest from the nominal central frequency measured at the transmitter output at the appropriate reference point (S/R-CG for downstream direction, R/S for upstream direction). + +**3.2.2.30 spectral width:** The full width of the largest spectral peak, measured 15 dB down from the maximum amplitude of the peak. + +**3.2.2.31 stationary wavelength channel state:** An optical transmitter or receiver is said to be *in a stationary wavelength channel state*, if 1) it is fixed wavelength, or 2) it is wavelength-tunable and its transient processes associated with the execution of a wavelength channel tuning control command have completed. + +**3.2.2.32 tolerance to reflected optical power:** A transmitter parameter that characterizes the maximum admissible ratio of the average reflected optical transmit power incident at the transmitter to the average optical transmit power. + +**3.2.2.33 transmitter calibration:** An optical transmitter is *calibrated with accuracy* $\delta$ , if given a target transmission frequency $f_0$ within its tuning range, it is capable of transmitting with the spectral excursion not exceeding $\delta$ (in other words, its transmission spectrum between the $-15$ dB cutoff points lays entirely within the spectral interval $(f_0 - \delta, f_0 + \delta)$ ). + +**3.2.2.34 transmitter power wavelength dependency:** For a tunable transmitter under wavelength control, the variation of the mean launch optical power when tuning within MSE. + +**3.2.2.35 transmitter disable transient time:** For a burst-mode transmitter, the allocated transient time on de-assertion of the TxEnable signal, measured in bit periods with respect to the transmitter nominal line rate. + +**3.2.2.36 transmitter enable transient time:** For a burst-mode transmitter, the allocated transient time on assertion of the TxEnable signal, measured in bit periods with respect to the transmitter nominal line rate. + +**3.2.2.37 tuning granularity:** The smallest step by which a tunable device is able to adjust the operating frequency/wavelength within the tuning range of the device. This Recommendation specifies the tuning granularity by its maximum allowable value. + +**3.2.2.38 tuning range:** The spectral interval either in frequency ( $f_{\min}, f_{\max}$ ) or wavelength ( $\lambda_{\min}, \lambda_{\max}$ ) over which the operating frequency/wavelength of a tunable device can be adjusted by means of tuning control. + +**3.2.2.39 tuning time:** The elapsed time from the moment the tunable device leaves the source wavelength channel to the moment the tunable device reaches the target wavelength channel. + +**3.2.2.40 tuning window:** The difference between the highest and lowest operating frequencies/wavelengths of a tunable device, attainable by means of tuning control. + +**3.2.2.41 wavelength channel spacing:** See channel spacing. + +### **3.2.3 Transmission convergence layer terms** + +**3.2.3.1 activation:** A set of distributed procedures executed by the OLT and the ONUs that allows an inactive ONU to join or resume operations on the PON. The activation process includes three phases: parameter learning, serial number acquisition, and ranging. + +**3.2.3.2 activation cycle:** An interval of continuous ONU operation between two consecutive re-entries of the ONU state machine into the initial state. + +**3.2.3.3 attenuation level:** A controlled attenuation applied to the output of an ONU transmitter to shift its mean launch optical power range down. + +**3.2.3.4 bandwidth allocation:** An upstream transmission opportunity granted by the OLT for a specified time interval to a specified traffic-bearing entity within an ONU. + +**3.2.3.5 calibration record:** A data structure which establishes an association between the wavelength channels and the corresponding values of the tuning control parameters. + +- 3.2.3.6 calibration record status:** A linear array which contains a calibration record accuracy indication for every available wavelength channel. +- 3.2.3.7 dynamic bandwidth assignment (DBA):** A process by which the OLT distributes upstream PON capacity between the traffic-bearing entities within ONUs, based on dynamic indication of their traffic activity and their configured traffic contracts. +- 3.2.3.8 effective key length:** The number of randomly generated bits of a cryptographic key. The effective key length may be less than the nominal key length of a particular cryptosystem, if a part of the key is replaced by a well-known bit pattern. +- 3.2.3.9 embedded OAM:** An operation and management channel between the OLT and the ONUs that utilizes the structured overhead fields of the downstream XGTC frame and upstream XGTC burst and supports time-sensitive functions. +- 3.2.3.10 equalization delay (EqD):** The requisite delay assigned by the OLT to an individual ONU in order to ensure that the ONU's transmissions are precisely aligned on a common OLT-based upstream frame reference. The ONU's equalization delay is assigned as a result of ranging and is subject to in-service updates in the course of burst arrival phase monitoring. +- 3.2.3.11 loose calibration:** An accuracy characterization of an ONU's calibration record with respect to a given upstream wavelength channel which allows the ONU to avoid interference with the any other upstream wavelength channels. +- 3.2.3.12 loose calibration bound:** An upper limit for the permitted transmitter spectral excursion of ONUs, connected to an NG-PON2 system, to be considered as loosely calibrated. This is determined by the physical properties of any particular implementation of an NG-PON2 system. +- 3.2.3.13 one-step tuning time:** The time it takes an ONU to tune its transmitter over the spectral distance equal to its tuning granularity value. +- 3.2.3.14 ONU management and control interface (OMCI):** An operation and management channel between the OLT and an ONU that is message-based and employs an extendable management information base. +- 3.2.3.15 physical layer OAM (PLOAM):** An operation and management channel between the OLT and the ONUs that is close to real time and is based on a fixed set of messages. +- 3.2.3.16 power levelling:** A mechanism that allows an ONU to change its mean launch optical power. +- 3.2.3.17 profile:** A collection of parameters describing a particular object. Within the context of the NG-PON2 TC layer, profile can pertain to a NG-PON2 system as a whole, a TWDM or PtP channel, or an upstream burst in TWDM PON system. +- 3.2.3.18 quiet window:** A time interval during which the OLT suppresses all bandwidth allocations to in-service ONUs in order to avoid collisions between their upstream transmissions and the transmissions from ONUs whose burst arrival time is uncertain. The OLT opens a quiet window to allow new ONUs to join the PON and to perform ranging of specific ONUs. +- 3.2.3.19 ranging:** A procedure of measuring the round-trip delay between the OLT and any of its subtending ONUs with the objective to determine and assign the appropriate equalization delay, which is necessary to align the ONU's upstream transmissions on a common OLT CT based upstream frame reference. Ranging is performed during ONU activation and may be performed while the ONU is in service. + +**3.2.3.20 ranging grant:** An allocation structure that is addressed to the default Alloc-ID of the ONU and has the PLOAMu flag set. A ranging grant does not specify a data allocation and has the GrantSize of zero. + +**3.2.3.21 requisite delay:** A general term denoting the total extra delay the OLT may require an ONU to apply to the upstream transmission beyond the ONU's regular response time. The purpose of requisite delay is to compensate for variation of propagation and processing delays of individual ONUs, and to avoid or reduce the probability of collisions between upstream transmissions. + +**3.2.3.22 root frequency:** The nominal central frequency representing a cyclic set of frequencies that forms an upstream wavelength channel. + +**3.2.3.23 round-trip delay:** A sum of round-trip propagation delay, ONU response time, and any ONU requisite delay. + +**3.2.3.24 round-trip propagation delay:** The total amount of time it takes an optical signal to travel from the OLT transmitter to the ONU receiver and from the ONU transmitter to the OLT receiver. + +**3.2.3.25 round-trip time:** The time interval, as observed by the OLT CT, between the start of a downstream PHY frame carrying a certain bandwidth map and the start of an upstream PHY burst specified by that bandwidth map. + +**3.2.3.26 serial number grant:** A type of allocation structure, addressed to a broadcast Alloc-ID and having the PLOAMu flag set, that invites the ONUs in Serial Number state to transmit a Serial\_Number\_ONU PLOAM message either in band or via AMCC. A serial number grant does not specify a data allocation. + +**3.2.3.27 service adapter:** A functional entity responsible for encapsulating/de-encapsulating of the SDUs belonging to the specific service type to/from the XGEM frames. + +**3.2.3.28 status reporting DBA (SR-DBA):** A method of dynamic bandwidth assignment that infers the dynamic activity status of the traffic-bearing entities within ONUs based on explicit buffer occupancy reports communicated over the embedded OAM channel. + +**3.2.3.29 sufficient calibration:** An accuracy characterization of an ONU's calibration record with respect to a given upstream wavelength channel which allows the ONU to guarantee transmission within the specified maximum spectral excursion (MSE) interval of that channel. + +**3.2.3.30 time quantum:** A line-rate-invariant unit of time which is equal to 32 bit periods at the line rate of 2.48832 Gbit/s. + +**3.2.3.31 traffic-monitoring DBA (TM-DBA):** A method of dynamic bandwidth assignment that infers the dynamic activity status of the traffic-bearing entities within ONUs based on observation of idle XGEM frame transmissions during upstream bursts. + +**3.2.3.32 transmission container (T-CONT):** A traffic-bearing object within an ONU that represents a group of logical connections, is managed via the ONU management and control channel (OMCC), and, through its TC layer Alloc-ID, is treated as a single entity for the purpose of upstream bandwidth assignment on the PON. + +**3.2.3.33 tunability:** In the NG-PON2 context, a property of an ONU to change its wavelength. + +**3.2.3.34 TWDM PON transmission convergence (TWDM TC) layer:** A protocol layer of the TWDM PON protocol suite that is positioned between the physical medium dependent (PMD) layer and the TWDM PON clients. The TWDM TC layer is composed of the TWDM TC service adaptation sublayer, the TWDM TC framing sublayer, and the TWDM TC PHY adaptation sublayer. + +**3.2.3.35 TWDM TC framing sublayer:** A sublayer of the TWDM PON transmission convergence layer that supports the functions of frame/burst encapsulation and delineation, embedded OAM processing, and Alloc-ID filtering. + +**3.2.3.36 TWDM TC PHY adaptation sublayer:** A sublayer of the TWDM PON transmission convergence layer that supports the functions of physical synchronization and delineation, forward error correction (FEC), and scrambling. + +**3.2.3.37 TWDM TC service adaptation sublayer:** A sublayer of the TWDM PON transmission convergence layer that supports the functions of SDU (user data and OMCI traffic) fragmentation and reassembly, XGEM encapsulation, XGEM frame delineation, and XGEM Port-ID filtering. + +**3.2.3.38 uncalibrated ONU:** An ONU is said to be *uncalibrated* with respect to a given upstream wavelength channel if its calibration record accuracy does not satisfy the criterion for loose calibration. + +**3.2.3.39 XGEM port:** An abstraction in the TWDM TC service adaptation sublayer representing a logical connection associated with a specific client packet flow. + +**3.2.3.40 10-gigabit-capable PON encapsulation method (XGEM):** A data frame transport scheme used in XG-PON and XG-PON-based systems that is connection-oriented and that supports fragmentation of user data frames into variable sized transmission fragments. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|----------|----------------------------------------------------| +| ACK | Acknowledgment | +| AES | Advanced Encryption Standard | +| Alloc-ID | Allocation Identifier | +| ALRF | Attenuation Level Request Failure | +| AMCC | Auxiliary Management and Control Channel | +| AN | Access Network | +| ANI | Access Node Interface | +| AO | Allocation Overhead | +| APC | Angled Physical Contact | +| ASCII | American Standard Code for Information Interchange | +| AVC | Attribute Value Change | +| AWG | Arrayed Waveguide Grating | +| BBU | Baseband Unit | +| BCH | Bose-Chaudhuri-Hocquenghem (code) | +| BE | Best Effort (service category) | +| BER | Bit Error Ratio | +| BIP | Bit-Interleaved Parity | +| BITS | Building Integrated Timing Source | + +| | | +|-----------------|--------------------------------------------------------| +| BN | Branching Node | +| B-PON | Broadband Passive Optical Network (ITU-T G.983-series) | +| BufOcc | Buffer Occupancy | +| BWmap | Bandwidth Map | +| CAWG | Cyclic Arrayed Waveguide Grating | +| CD | Chromatic Dispersion | +| CE | Coexistence Element | +| CE x | Coexistence Element Type x (x = 1, 2, etc.) | +| CG | Channel Group | +| CID | Consecutive Identical Digits | +| Clob | Count of the loss of burst events | +| CMAC | Cipher-based Message Authentication Code | +| CP | Channel Pair | +| CPE | Customer Premises Equipment | +| CPI | Channel Partition Index | +| CPRI | Common Public Radio Interface | +| CRC | Cyclic Redundancy Check | +| CS | Channel Spacing | +| CT | Channel Termination | +| CTP | Connection Termination Point | +| CTR | Counter (block cipher mode) | +| DA | Destination Address | +| DBA | Dynamic Bandwidth Assignment | +| DBRu | Dynamic Bandwidth Report, upstream | +| DF | Disable Failure | +| DG | Dying Gasp | +| DOTX | Drift of Transmitter Wavelength | +| DOW | Drift Of Window | +| DS | DownStream (transmission direction) | +| DWLCH | Downstream WaveLength CHannel | +| ECB | Electronic Code Book (block cipher mode) | +| EDC | Electronic Dispersion Compensation | +| EDFA | Erbium-Doped Fibre Amplifier | +| EMS | Element Management System | +| EWMA | Exponentially Weighted Moving Average | + +| | | +|---------|----------------------------------------------------------------------| +| eNode B | evolved Node B | +| EqD | Equalization Delay | +| ER | Extinction Ratio | +| EVC | Ethernet Virtual Connection | +| FCS | Frame Check Sequence | +| FEC | Forward Error Correction | +| FFS | For Further Study | +| FS | Framing Sublayer | +| FSR | Free Spectral Range | +| FTTx | Fibre To The x (B – building, business; H – home; C – cabinet, curb) | +| FWI | Forced Wake-up Indication | +| G-PON | Gigabit-capable Passive Optical Network (ITU-T G.984-series) | +| HEC | Hybrid Error Correction | +| HLend | Header Length, downstream | +| ICTP | Inter-Channel-Termination Protocol | +| ID | Identifier | +| IFC | Intra-Frame Counter | +| IK | Integrity Key | +| ILODS | Intermittent Loss Of Downstream Synchronization (ONU state) | +| Ind | Indication (format field) | +| KEK | Key Encryption Key | +| LCB | Loose Calibration Bound | +| LF | Last Fragment (format flag) | +| LOB | Loss Of Burst | +| LODS | Loss Of Downstream Synchronization | +| LOF | Loss Of Frame | +| LOMC | Loss Of Management Channel | +| LOOC | Loss Of OMCI Channel | +| LOPC | Loss Of PLOAM Channel | +| LOS | Loss Of Signal | +| LSB | Least Significant Bit | +| LSI | Local Sleep Indication | +| LTE | Long Term Evolution | +| LWI | Local Wake-up Indication | +| MAC | Media Access Control | + +| | | +|---------|----------------------------------------------------------------| +| MDU | Management Data Unit | +| MDU/SFU | Multi-Dwelling Unit/Single-Family Unit | +| MEF | Metro Ethernet Forum | +| MIB | Management Information Base | +| MIC | Message Integrity Check | +| MPLS | Multi-Protocol Label Switching | +| MSB | Most Significant Bit | +| MSE | Maximum Spectral Excursion | +| MSK | Master Session Key | +| MTE | Maximum Tuning Error | +| NA | Non-Assured (service category) | +| NACK | Negative Acknowledgment | +| NG-PON1 | Next Generation Passive Optical Network 1 (ITU-T G.987-series) | +| NG-PON2 | Next Generation Passive Optical Network 2 (ITU-T G.989-series) | +| NRZ | Non-Return to Zero | +| OAM | Operation, Administration and Maintenance | +| OAN | Optical Access Network | +| OC | Operation Control | +| OCS | Operation Control Structure | +| ODF | Optical Distribution Frame | +| ODN | Optical Distribution Network | +| ODN-ID | Optical Distribution Network Identifier | +| ODS | Optical Distribution Segment | +| OLT | Optical Line Terminal | +| OMCC | ONU Management and Control Channel | +| OMCI | ONU Management and Control Interface | +| OMCI_IK | OMCI Integrity Key | +| ONU | Optical Network Unit | +| ONU-ID | Optical Network Unit Identifier | +| OOB | Out-Of-Band | +| OOB-PSD | Out-Of-Band Power Spectral Density | +| OOC | Out-Of-Channel | +| OOC-PSD | Out-Of-Channel Power Spectral Density | +| OPL | Optical Path Loss | +| OPP | Optical Path Penalty | + +| | | +|----------|---------------------------------------------------------------------| +| ORL | Optical Return Loss | +| OSNR | Optical Signal-to-Noise Ratio | +| OSS | Operations Support System | +| OTDR | Optical Time Domain Reflectometer | +| OTL | Optical Trunk Line | +| PDU | Protocol Data Unit | +| PHY | Physical interface | +| PIT | PON-ID Type | +| PL | Power Levelling | +| PLI | Payload Length Indication | +| PLOAM | Physical Layer Operation, Administration and Maintenance | +| PLOAMd | PLOAM downstream | +| PLOAMu | PLOAM upstream | +| PLOAM_IK | PLOAM Integrity Key | +| PM | Performance Monitoring | +| PMD | Physical Medium Dependent | +| PON | Passive Optical Network | +| PSBd | Physical Synchronization Block downstream | +| PSBu | Physical Synchronization Block upstream | +| PSD | Power Spectral Density | +| PSK | Pre-shared Secret Key | +| PSync | Physical Synchronization sequence | +| PtP | Point-to-Point | +| PtP WDM | Point-to-Point Wavelength Division Multiplexing | +| QAM | Quadrature Amplitude Modulation | +| QoS | Quality of Service | +| RE | Reach Extender | +| RF | Radio Frequency | +| RNG | Ranging | +| RRT | Round-trip Response Time | +| RRU | Remote Radio Unit | +| RS | Reed-Solomon (code) | +| RSSI | Received Signal Strength Indication | +| R/S | Receive/Send reference point at the interface of the ONU to the ODN | +| R'S' | Reach extender interface to optical trunk line | + +| | | +|--------|----------------------------------------------------------| +| RTD | Round Trip Delay | +| RTT | Round Trip Time | +| Rx | Receiver | +| SA | Sleep Allow (PLOAM message type) | +| SA | Source Address | +| SDU | Service Data Unit | +| SeqNo | Sequence Number | +| SFC | Superframe Counter | +| SFD | Start Frame Delimiter | +| SK | Session Key | +| SLM | Single Longitudinal Mode (laser type) | +| SMA | Secure Mutual Association | +| SMF | Single Mode Fibre | +| SMSR | Side Mode Suppression Ratio | +| SN | Serial Number | +| SN | Service Node | +| SNI | Service Node Interface | +| SOA | Semiconductor Optical Amplifier | +| S/R | Send/Receive reference point at the OLT side | +| S/R-CP | S/R for Channel Pair | +| S/R-CG | S/R for Channel Group | +| S'R' | Reach extender interface to optical distribution network | +| SR | Status Reporting (DBA method) | +| SR | Sleep Request (PLOAM message type) | +| SUF | Start-Up Failure | +| TBD | To Be Defined | +| T-CONT | Transmission Container | +| TC | Transmission Convergence | +| TDM | Time Division Multiplexing | +| TDMA | Time Division Multiple Access | +| TIW | Transmission Interference Warning | +| TM | Traffic Monitoring (DBA method) | +| ToD | Time of Day | +| TOL | Transmit Optical Level | +| TOx | Timeout (x = Z, 1, 2, 3, 4, 5) | + +| | | +|---------|---------------------------------------------------------| +| TuCtrl | Tuning Control (PLOAM message type) | +| TuResp | Tuning Response (PLOAM message type) | +| Tx | Transmitter | +| TWDM | Time and Wavelength Division Multiplexing | +| UI | Unit Interval | +| UNI | User-Network Interface | +| UPC | Ultra Physical Contact | +| US | Upstream (transmission direction) | +| UWLCH | Upstream Wavelength Channel | +| VOA | Variable Optical Attenuator | +| VSSN | Vendor-Specific Serial Number | +| WBF | Wavelength Blocking Filter | +| WDM | Wavelength Division Multiplexing | +| WLCP | Wavelength Channel Protection | +| WM | Wavelength Multiplexer | +| WNE-PSD | When Not Enabled Power Spectral Density | +| WR | Wavelength-Routed (PtP WDM PON architecture class) | +| WS | Wavelength-Selected (PtP WDM PON architecture class) | +| XG-PON | 10-Gigabit Passive Optical Network (ITU-T G.987-series) | +| XGEM | 10-Gigabit-capable PON Encapsulation Method | +| XML | Extensible Markup Language | +| XOR | Exclusive OR | +| X/S | Crosstalk-to-Signal ratio | + +# 5 Conventions + +## 5.1 Optical access concepts + +This Recommendation reuses the optical access network terminology and definitions system adopted by [b-ITU-T G.987]. An example of an access network architecture satisfying the definition system is shown in Figure 5-1. + +![Figure 5-1 – Reference access network architecture](2ccb8de18aa551f1fa9919b410cf662b_img.jpg) + +The diagram shows a 'PON system' containing an OLT (Optical Line Terminal) connected to a 'Composite ODN' (Optical Distribution Network). The Composite ODN includes OTL (Optical Trunk Line) and ODS (Optical Distribution Segment) components. It features RE (Reach Extender) units and Splitters. The network branches out to multiple ONU (Optical Network Unit) blocks, which then connect to UNI (User Network Interface) points. The entire span from the SNI (Service Node Interface) to the UNI is labeled as 'Access network (AN) [b-ITU-T G.902]'. + +**Figure 5-1 – Reference access network architecture** + +### 5.2 Multi-wavelength PON system reference points + +In a multiple wavelength passive optical network (PON) system, such as next generation passive optical network 2 (NG-PON2), the optical line terminal (OLT) is conceptually composed of multiple OLT channel terminations (CTs) connected via a wavelength multiplexer (WM). The associated reference logical architecture and its reference points are presented in Figure 5-2. + +![Figure 5-2 – NG-PON2 reference logical architecture](26debdd08de6dadb3b1430770cea622d_img.jpg) + +This logical architecture diagram illustrates the connection between OLT CTs and ONUs. On the left, multiple blocks labeled 'NG-PON2 OLT CT 1' through 'NG-PON2 OLT CT n' are shown. These connect at reference points S/R-CP1 through S/R-CPn to a Wavelength Multiplexer (WM). The WM output passes through reference point S/R-CG into the ODN. Within the ODN, a splitter distributes the signal (IFNG-PON2) to multiple 'NG-PON2 ONU' units at the R/S reference point. The diagram also marks the SNI on the far left and UNI on the far right. Below the OLT blocks, definitions are provided: CG – channel group, CP – channel pair, CT – channel termination, WM – wavelength mux. + +**Figure 5-2 – NG-PON2 reference logical architecture** + +Rec. ITU-T G.989 (10/2015)      17 + +## 5.3 Optical power and loss parameters + +The relationships between optical power and loss parameters are captured in Figure 5-3. + +![Figure 5-3: Relationship between the optical power and loss parameters. The diagram is split into two halves by a vertical dashed line. The left half, 'Allotment of optical path losses and penalties', shows 'Maximum OPL' as the vertical distance from 'Rx sensitivity' to 'Maximum OPP', and 'Minimum OPL' as the vertical distance from 'Rx sensitivity' to 'Min OPP = 0'. The right half, 'Available transceiver optical power', shows 'Max Tx launch power' and 'Min Tx launch power' as horizontal lines. 'Rx overload' is a horizontal line between them. Vertical distances are labeled: Δ1 from 'Rx sensitivity' to 'Rx overload', Δ2 from 'Rx overload' to 'Max Tx launch power', and Δ3 from 'Rx sensitivity' to 'Min Tx launch power'. The 'Rx dynamic range' is the vertical span between 'Rx sensitivity' and 'Rx overload'.](485c57a6add7e0bd7898009db1179ee6_img.jpg) + +Figure 5-3: Relationship between the optical power and loss parameters. The diagram is split into two halves by a vertical dashed line. The left half, 'Allotment of optical path losses and penalties', shows 'Maximum OPL' as the vertical distance from 'Rx sensitivity' to 'Maximum OPP', and 'Minimum OPL' as the vertical distance from 'Rx sensitivity' to 'Min OPP = 0'. The right half, 'Available transceiver optical power', shows 'Max Tx launch power' and 'Min Tx launch power' as horizontal lines. 'Rx overload' is a horizontal line between them. Vertical distances are labeled: Δ1 from 'Rx sensitivity' to 'Rx overload', Δ2 from 'Rx overload' to 'Max Tx launch power', and Δ3 from 'Rx sensitivity' to 'Min Tx launch power'. The 'Rx dynamic range' is the vertical span between 'Rx sensitivity' and 'Rx overload'. + +**Figure 5-3 – Relationship between the optical power and loss parameters** + +Given an optical distribution network (ODN) characterized by the maximum and minimum optical path loss and the maximum optical path penalty, the optical links are balanced if and only if the following two constraints are met (assuming logarithmic representation of the parameters): + +1. The difference between the minimum transmitter mean channel launch power and the receiver sensitivity is greater than or equal to the sum of the maximum optical path loss and the maximum optical path penalty. +2. The difference between maximum transmitter mean channel launch power and the receiver overload does not exceed the minimum optical path loss. + +## 5.4 Dynamic range, sensitivity and overload + +The concept of the dynamic range definition is illustrated in Figure 5-4. The receiver sensitivity and overload are generally understood respectively, as the minimum and maximum average received optical power at which the bit error ratio (BER) at the receiver output remains at the specified reference level. The observed values of receiver sensitivity and overload may vary as the operating temperature and signal quality change, and the system ages. The signal quality characteristics that affect receiver sensitivity and overload may include: the transmitter extinction ratio, parameters of the eye diagram, in-band crosstalk. In the present Recommendation series, receiver sensitivity and receiver overload are formally specified by their respective worst-case values, i.e., maximum sensitivity and minimum overload over the range of operating temperature and signal quality parameters, and under the end-of-life conditions. + +![Figure 5-4: Rx output BER as a function of received optical power and the definition of dynamic range. The graph shows BER on the y-axis and Power on the x-axis. A U-shaped curve represents the BER performance. A horizontal line indicates the 'Reference BER level'. The curve intersects this line at two points, defining the 'Dynamic range: worst-case sensitivity and worst-case overload'. The area between the curve and the reference line is shaded. The left shaded region is labeled 'Sensitivity variation' and the right shaded region is labeled 'Overload variation'. The text 'G.989(15)_F5-4' is in the bottom right corner.](645bea0b27d63e4a9a300af5793ae7d2_img.jpg) + +Figure 5-4: Rx output BER as a function of received optical power and the definition of dynamic range. The graph shows BER on the y-axis and Power on the x-axis. A U-shaped curve represents the BER performance. A horizontal line indicates the 'Reference BER level'. The curve intersects this line at two points, defining the 'Dynamic range: worst-case sensitivity and worst-case overload'. The area between the curve and the reference line is shaded. The left shaded region is labeled 'Sensitivity variation' and the right shaded region is labeled 'Overload variation'. The text 'G.989(15)\_F5-4' is in the bottom right corner. + +**Figure 5-4 – Rx output BER as a function of received optical power and the definition of dynamic range** + +## 5.5 Sensitivity and overload in the presence of FEC + +To simplify time and wavelength division multiplexing (TWDM) PON optical component verification, this Recommendation, as [b-ITU-T G.987.2] prior to it, specifies the sensitivity and overload at the reference BER level, which corresponds to the Rx output and the forward error correction (FEC) decoder input. It is assumed that the FEC algorithms specified, respectively, for continuous mode downstream and burst-mode upstream transmission are sufficiently strong to achieve the BER level of $10^{-12}$ or better at the FEC decoder output. See [b-ITU-T G-Sup.39] for further discussion. + +## 5.6 Reach and distance + +Like the ITU-T G.987-series of Recommendations before it, the ITU-T G.989-series addresses the linear extent parameters of NG-PON2 using the single concept of fibre distance. An optical network unit (ONU) is characterized by its fibre distance, and for each pair of ONUs on the same OLT PON interface, the differential fibre distance is the difference between the two individual fibre distances. Each specific physical medium dependent (PMD) layer parameter set contains a provision to support a specific maximum fibre distance. The NG-PON2 transmission convergence (TC) layer specification contains a provision to support specific ranges of maximum fibre distance and maximum differential fibre distance. These ranges can be configurable for a given system. It can be expected that for each NG-PON2 deployment, the configured TC layer maximum fibre distance will match the maximum fibre distance supported by the selected PMD layer parameter set. Fibre distance concepts are illustrated in Figure 5-5. + +![Diagram illustrating fibre distance concepts in a PON. A central OLT is shown at the center of two concentric circles. The inner circle represents the 'Maximum differential fibre distance' and the outer circle represents the 'Maximum fibre distance'. An ONU_min is located on the inner circle, and an ONU_max is located on the outer circle. The diagram is labeled G.989(15)_F5-5.](cbdfdade780e677eb1c1aef3081ce9ef_img.jpg) + +The diagram shows a central OLT (Optical Line Terminal) at the center of two concentric circles. The inner circle is labeled 'Maximum differential fibre distance' and the outer circle is labeled 'Maximum fibre distance'. An ONUmin (Optical Network Unit) is located on the inner circle, and an ONUmax is located on the outer circle. The diagram is labeled G.989(15)\_F5-5. + +Diagram illustrating fibre distance concepts in a PON. A central OLT is shown at the center of two concentric circles. The inner circle represents the 'Maximum differential fibre distance' and the outer circle represents the 'Maximum fibre distance'. An ONU\_min is located on the inner circle, and an ONU\_max is located on the outer circle. The diagram is labeled G.989(15)\_F5-5. + +**Figure 5-5 – Fibre distance concepts** + +## 5.7 Use of the term PON + +Historically, the term PON was introduced to describe a point-to-multipoint fibre infrastructure composed exclusively of passive optical components. This strict-sense usage was soon naturally extended to include a fibre-in-the-loop communication system employing such an infrastructure and using time division multiplexing (TDM) to share the available digital bandwidth among many subscribers (TDM-PON). As new types of PON-based systems were introduced, leveraging various TDM transport mechanisms (B-PON, G-PON, EPON) or alternative multi-access methods (WDM-PON), it became common to use the word PON with appropriate qualification in reference to the specific architectural variations. While the term remained overloaded, referring in different contexts to a network, a system, architecture or technology, all the referenced entities shared a common attribute of containing, using or relying upon a fibre infrastructure with no active (electronic) components between the central office interface and the user equipment interface. More recently, the introduction of active reach extenders within the optical distribution network as defined in [b-ITU-T G.984.6] created a paradoxical situation when an infrastructural component of a G-PON system may not be entirely passive, that is, nominally, no longer a PON. Thus, it became apparent that the excessive overloading of what was once meant to be a precise term may adversely impact the clarity of a technical presentation. + +This current series of Recommendations deliberately restricts the usage of the term PON to the contexts where it denotes a system, that is, a combination of network elements including at least one OLT and multiple ONUs interconnected by an ODN that implements a particular coordinated suite of physical medium dependent layer, transmission convergence layer and management protocols. It also strives to provide a consistent, unambiguous and extensible definition system that allows supporting efficient communication on the subject. + +## 5.8 Use of the term ODN + +In the ITU-T G.983 B-PON and ITU-T G.984 G-PON series of Recommendations (prior to [b-ITU-T G.984.6]), the term optical distribution network refers to a passive point-to-multipoint distribution means extending from the user-facing interface of the OLT to the network-facing interfaces of the ONUs. The introduction of active reach extenders and the concept of dual-homing + +call for a revision of the term's scope and usage, as the fibre-based distribution network extending between the OLT and ONU interfaces may be neither point-to-multipoint nor strictly passive. + +This current series of Recommendations follows the ITU-T G.987-series, endorsing a generalized usage of the term ODN to denote a point-to-multipoint fibre infrastructure, which is not required to be entirely passive. In the contexts where the internal structure of the ODN is not a concern, it is the ODN that interconnects the OLT and the ONUs to form a PON system. In the contexts where the internal structure of the ODN is relevant, two types of ODNs can be distinguished. A *simple* ODN is entirely passive and is represented by a single-rooted point-to-multipoint tree of optical fibres with splitters, combiners, filters, and possibly other passive optical components. A *composite* ODN consists of two or more *segments* interconnected by active devices, each of the segments being either an optical trunk line segment or an optical distribution segment. A passive optical distribution segment in is a simple ODN itself. The definition allows two ODNs with distinct roots to share a common subtree, thus supporting the notions of dual-homing and protection within the definition system. + +## 5.9 Use of the terms ONU and ONT + +Throughout the ITU-T G.989-series of Recommendations, as in the earlier ITU-T G.987-series, the network element interfacing the end-user access facilities and the ODN is referred to as an ONU, or an optical network unit, irrespective of the number and type of user interfaces or the depth of fibre deployment. Historically, the term ONT, or optical network terminal/termination, has been used either interchangeably with ONU or with the particular semantics of "an ONU that is used for fibre to the home (FTTH) and includes the user port function" (see [b-ITU-T G.983.1]), or "a single-subscriber ONU" (see [b-ITU-T G.984.1] and other documents of the ITU-T G.984-series). This Recommendation follows the latter approach in defining ONT. Note, however, that while this definition captures one established trade interpretation of the term, the concept itself is not used as a part of the ITU-T G.989 reference access architecture. + +Outside of the scope of the ITU-T G.987-series and ITU-T G.989-series of Recommendations, alternative interpretations may apply, and therefore the reader is advised to clarify the exact meaning of the term in each specific context. In particular, in some external contexts, the term ONT may be used generically to refer to any device terminating a leaf of the ODN. + +## 5.10 Use of the terms T-CONT and Alloc-ID + +A transmission container (T-CONT) is an ONU management and control interface (OMCI) managed entity representing a group of logical connections that appear as a single entity for the purpose of upstream bandwidth assignment in a PON system. + +For a given ONU, the number of supported T-CONTs is fixed. The ONU autonomously creates all the supported T-CONT instances during ONU activation or upon OMCI management information base (MIB) reset. The OLT uses the ONU management and control channel (OMCC) to discover the number of T-CONT instances supported by a given ONU and to manage those instances. + +The *allocation identifier* (*Alloc-ID*) is a 14 bit number that the OLT assigns to an ONU to identify a traffic-bearing entity that is a recipient of upstream bandwidth allocations within that ONU. Such a traffic-bearing entity is usually represented by a T-CONT, but may also be represented by an internal non-managed structure. + +Each ONU is assigned at least its default Alloc-ID and may be explicitly assigned additional Alloc-IDs per OLT's discretion. + +To activate a T-CONT instance for carrying the upstream user traffic, the OLT has to map that T-CONT instance to an Alloc-ID which was previously assigned to the given ONU via the physical + +layer operations, administration and maintenance (PLOAM) messaging channel. Mapping of T-CONTs to Alloc-IDs is performed via the OMCC. The OMCC itself is mapped, in the upstream direction, to the default Alloc-ID. This mapping is fixed; it cannot be managed via the OMCI MIB and it should survive OMCI MIB reset. + +Although in many cases there exists a one-to-one correspondence between T-CONTs and Alloc-IDs, it is the Alloc-ID, not a T-CONT, which is visible at the TC layer of the system. + +## 5.11 Use of the terms bandwidth assignment and bandwidth allocation + +The term "bandwidth assignment" refers to the distribution of the upstream PON capacity between the ONUs' traffic-bearing entities using certain isolation and fairness criteria. In static bandwidth assignment, the said criteria are based exclusively on the provisioned parameters of the traffic contracts, and the bandwidth is assigned on the timescale of the individual service provisioning. In dynamic bandwidth assignment, the activity status of the traffic-bearing entities is taken into consideration along with the parameters of the traffic contracts, and the bandwidth assignment is periodically refined. + +The term "bandwidth allocation", on the other hand, denotes the process of granting individual transmission opportunities to the ONUs' traffic-bearing entities on the timescale of a single physical interface (PHY) frame. The process of bandwidth allocation uses the assigned bandwidth values as an input and produces the per-frame bandwidth maps as an output. It also accounts for PLOAM messaging and DBRu overhead requirements and the short-term disturbances associated with the creation of quiet windows for serial number acquisition and ranging purposes. + +## 5.12 Use of the terms band and range + +When used in the context of optical spectrum, both terms "band" and "range" generally denote a spectral interval in terms of frequency ( $f_{\min}$ , $f_{\max}$ ) or wavelength ( $\lambda_{\min}$ , $\lambda_{\max}$ ). Within the NG-PON2 context, the term "band" applies specifically to a spectral interval which covers all wavelength channels of a specific application (e.g., TWDM PON upstream band, narrow band option, shared spectrum band, G-PON downstream band), whereas the term "range" usually applies to a spectral interval corresponding to a single wavelength channel. + +The operating bands are specified in wavelength terms as a matter of convenience for classification and reference purposes. The actual minimum and maximum wavelengths for an operating band should be calculated from the maximum and minimum wavelengths of the two outmost wavelength channels. + +## 5.13 Transmitter enable control and associated transient times + +Conceptually, TxEnable is a binary signal that controls a burst-mode ONU transmitter. The TxEnable signal must be asserted (active) for the ONU to transmit an assigned burst. The TxEnable signal is expected to be de-asserted (inactive) whenever no burst is assigned to the ONU. The Transmitter Enable transient time and Transmitter Disable transient time are the allocated time intervals which serve to accommodate any transient physical processes that may be associated, respectively, with assertion and de-assertion of the TxEnable signal. The maximum number of bits allocated for Transmitter Enable transient time and Transmitter Disable transient time are parameters of the ONU optical interface specification. Figure 5-6 shows the relationship between the level of the TxEnable signal (without loss of generality, active-high logic is assumed) and the associated transient times of the burst-mode transmitter. Within the scope of the ITU-T G.989-series of Recommendations, the definitions of the optical-power-related PMD parameters applicable to the burst-mode transmitters (mean launch optical power, extinction ratio, OOC-PSD, + +WNE-PSD) are referenced to the corresponding averaging intervals which are specified in terms of a transmitter's enabled/disabled periods and the associated transient times. + +![Timing diagram showing Transmitter optical power and TxEnable signal over time for a burst-mode transmitter.](920eeb131e71a5b81535239f1c838c68_img.jpg) + +The diagram illustrates the timing relationship between a control signal (TxEnable) and the resulting optical output power of a burst-mode transmitter. The horizontal axis represents time $t$ . + +The top waveform represents 'Transmitter optical power'. It starts at a zero level, then ramps up linearly during a period labeled 'Transmitter enable transient time'. Following this, it enters a 'Burst transmission' phase, depicted as a rectangular block with vertical hatching, representing modulated data. Finally, the power ramps down linearly to zero during a period labeled 'Transmitter disable transient time'. + +The bottom waveform represents the 'TxEnable signal'. It is a binary signal that transitions from low to high at the exact moment the optical power begins its enable transient ramp. It remains high throughout the enable transient and the burst transmission phases. It transitions from high back to low at the exact moment the optical power begins its disable transient ramp. + +Vertical blue lines align the transitions of the TxEnable signal with the start of the power ramps, and separate the transient phases from the burst transmission phase. A reference label 'G.989(15)\_F5-6' is present at the bottom right of the diagram. + +Timing diagram showing Transmitter optical power and TxEnable signal over time for a burst-mode transmitter. + +**Figure 5-6 – The TxEnable signal and the associated transient times of a burst-mode transmitter** + +## Bibliography + +- [b-ITU-T G.810] Recommendation ITU-T G.810 (1996), *Definitions and terminology for synchronization networks*. +- [b-ITU-T G.902] Recommendation ITU-T G.902 (1995), *Framework Recommendation on functional access networks (AN) – Architecture and functions, access types, management and service node aspects*. +- [b-ITU-T G.983.1] Recommendation ITU-T G.983.1 (2005), *Broadband optical access systems based on Passive Optical Networks (PON)*. +- [b-ITU-T G.984.1] Recommendation ITU-T G.984.1 (2008), *Gigabit-capable passive optical networks (GPON): General characteristics*. +- [b-ITU-T G.984.6] Recommendation ITU-T G.984.6 (2008), *Gigabit-capable passive optical networks (GPON): Reach extension*. +- [b-ITU-T G.987] Recommendation ITU-T G.987 (2010), *10-Gigabit-capable passive optical network (XG-PON) systems: Definitions, abbreviations and acronyms*. +- [b-ITU-T G.987.2] Recommendation ITU-T G.987.2 (2010), *10-Gigabit-capable passive optical networks (XG-PON): Physical media dependent (PMD) layer specification*. +- [b-ITU-T G-Sup.39] ITU-T G-series Recommendations – Supplement 39 (2008), *Optical system design and engineering considerations*. +- [b-ITU-T I.112] ITU-T Recommendation I.112 (1993), *Vocabulary of terms for ISDNs*. +- [b-BBF TR-101] Broadband Forum, Technical Report TR-101, Issue 2 (2011), *Migration to Ethernet-Based Broadband Aggregation*. +- [b-MEF 6.1] MEF Technical Specification MEF 6.1 (2008), *Ethernet Services Definitions – Phase 2*. + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | General tariff principles | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Terminals and subjective and objective assessment methods | +| Series Q | Switching and signalling | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git a/marked/G/T-REC-G.9903-201708-I_PDF-E/02bb4edc0dbdf4f0749ffd3e0ea2805c_img.jpg 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CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | +| Metallic access networks | G.9700–G.9799 | +| Optical line systems for local and access networks | G.9800–G.9899 | +| In premises networks | G.9900–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## Recommendation ITU-T G.9903 + +# Narrowband orthogonal frequency division multiplexing power line communication transceivers for G3-PLC networks + +# Summary + +Recommendation ITU-T G.9903 contains the physical layer (PHY) and data link layer (DLL) specification for the G3-PLC narrowband orthogonal frequency division multiplexing (OFDM) power line communication transceivers, for communications via alternating current and direct current electric power lines over frequencies below 500 kHz. + +The control parameters that determine spectral content, power spectral density (PSD) mask requirements, and the set of tools and procedures to support the measurement and reduction of the transmit PSD can be found in Recommendation ITU-T G.9901. + +This Recommendation adds several corrections of and improvements to the PHY, the DLL, and the routing parts of the specification. It also integrates Amendment 1 to Recommendation ITU-T G.9903 (2014), adding support for coexistence with other narrowband PLC technologies via the preamble-based coexistence mechanism specified in clause 10 of IEEE 1901.2. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.9903 | 2012-10-29 | 15 | 11.1002/1000/11823 | +| 1.1 | ITU-T G.9903 (2012) Amd. 1 | 2013-05-07 | 15 | 11.1002/1000/11897 | +| 2.0 | ITU-T G.9903 | 2013-05-07 | 15 | 11.1002/1000/12049 | +| 3.0 | ITU-T G.9903 | 2014-02-22 | 15 | 11.1002/1000/12088 | +| 3.1 | ITU-T G.9903 (2014) Amd. 1 | 2015-08-13 | 15 | 11.1002/1000/12539 | +| 4.0 | ITU-T G.9903 | 2017-08-13 | 15 | 11.1002/1000/13333 | + +## Keywords + +Narrowband power line communications, G3-PLC, OFDM, PHY, physical layer, MAC medium access control, routing, LOADng + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +# FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2017 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +# Table of Contents + +| | | Page | +|------|------------------------------------------------------------------|------| +| 1 | Scope ..... | 1 | +| 2 | References..... | 1 | +| 3 | Conventions and definitions ..... | 2 | +| 3.1 | Conventions..... | 2 | +| 3.2 | Terms defined elsewhere..... | 2 | +| 3.3 | Terms defined in this Recommendation..... | 2 | +| 4 | Abbreviations and acronyms ..... | 3 | +| 5 | Introduction to OFDM and the power line channel..... | 5 | +| 6 | General description..... | 6 | +| 6.1 | Overall infrastructure..... | 6 | +| 6.2 | Coexistence with other PLC networks ..... | 7 | +| 7 | Physical layer specification ..... | 8 | +| 7.1 | Introduction ..... | 8 | +| 7.2 | System parameters..... | 9 | +| 7.3 | Data rate, Reed-Solomon block size and maximum PSDU length ..... | 9 | +| 7.4 | Frame structure..... | 15 | +| 7.5 | Preamble..... | 16 | +| 7.6 | Frame control header..... | 18 | +| 7.7 | Payload of PHY frame..... | 22 | +| 7.8 | Scrambler..... | 22 | +| 7.9 | FEC coding..... | 23 | +| 7.10 | Interleaver..... | 25 | +| 7.11 | Mapping for DBPSK/DQPSK/D8PSK..... | 30 | +| 7.12 | Frequency domain pre-emphasis ..... | 32 | +| 7.13 | OFDM generation (IFFT and CP addition) ..... | 32 | +| 7.14 | Windowing ..... | 32 | +| 7.15 | Tone masking and tone mapping..... | 33 | +| 7.16 | Coherent modulation scheme ..... | 34 | +| 7.17 | PHY primitives..... | 40 | +| 8 | Transmitter specifications..... | 50 | +| 8.1 | Output level measurement..... | 50 | +| 8.2 | Transmit spectrum mask..... | 50 | +| 8.3 | Transmitter attenuation..... | 50 | +| 8.4 | Spurious transmission..... | 50 | +| 8.5 | System clock frequency tolerance ..... | 50 | +| 8.6 | Transmitter spectral flatness..... | 52 | +| 8.7 | Crossing MV/LV transformer ..... | 52 | + +| | Page | +|----------------------------------------------------------------------------------------------------------------|------| +| 8.8 MV coupler (informative) ..... | 52 | +| 8.9 AC phase detection..... | 54 | +| 9 Data link layer specifications..... | 56 | +| 9.1 Introduction ..... | 56 | +| 9.2 Conventions..... | 56 | +| 9.3 MAC sublayer specification..... | 56 | +| 9.4 IPv6 adaptation sublayer specifications ..... | 104 | +| 9.5 Functional description ..... | 165 | +| 10 Security ..... | 166 | +| 10.1 Access control and authentication ..... | 166 | +| 10.2 Confidentiality and integrity..... | 168 | +| 10.3 Anti-replay and DoS prevention..... | 168 | +| 10.4 Authentication and key distribution protocol – Selections from [IETF
RFC 3748] ..... | 169 | +| 10.5 EAP method..... | 170 | +| Annex A – Protocol implementation conformance statement ..... | 175 | +| A.1 Overview ..... | 175 | +| A.2 PICS proforma tables ..... | 175 | +| Annex B – Routing cost..... | 178 | +| B.1 Composite metric method..... | 178 | +| Annex C – Device starting sequence of messages..... | 180 | +| Annex D – The lightweight on-demand Ad hoc distance-vector routing protocol – next
generation (LOADng)..... | 181 | +| D.1 Introduction ..... | 181 | +| D.2 Terminology and notation ..... | 181 | +| D.3 Applicability statement..... | 182 | +| D.4 Protocol overview and functioning ..... | 182 | +| D.5 Protocol parameters ..... | 185 | +| D.6 Protocol message content ..... | 186 | +| D.7 Information base..... | 188 | +| D.8 LOADng router sequence numbers ..... | 190 | +| D.9 Route maintenance ..... | 191 | +| D.10 Unidirectional link handling..... | 191 | +| D.11 Common rules for RREQ and RREP messages ..... | 192 | +| D.12 Route requests (RREQs)..... | 195 | +| D.13 Route replies (RREPs)..... | 196 | +| D.14 Route errors (RERRs)..... | 199 | +| D.15 Route reply acknowledgments (RREP_ACKs)..... | 201 | +| D.16 Metrics..... | 202 | + +| | Page | +|--------------------------------------------------------------------|-------------| +| D.17 Security considerations..... | 202 | +| Annex E – Commissioning in 6LoWPAN ..... | 205 | +| E.1 Introduction ..... | 205 | +| E.2 Terminology ..... | 205 | +| E.3 Bootstrapping ..... | 207 | +| E.4 IANA consideration..... | 214 | +| E.5 Security considerations..... | 214 | +| Annex F – Regional requirements for Japan..... | 215 | +| F.1 Overview ..... | 215 | +| F.2 Physical layer specifications for ARIB bandplan..... | 215 | +| F.3 Data link layer specifications ..... | 216 | +| Annex G – Regional requirements for the USA ..... | 217 | +| Appendix I – Examples on encoding and decoding..... | 218 | +| I.1 Example for data encoding..... | 218 | +| I.2 Example for data decoding..... | 218 | +| Appendix II – Test vectors for cryptographic building blocks ..... | 219 | +| II.1 Introduction ..... | 219 | +| Bibliography..... | 221 | + + + +## Recommendation ITU-T G.9903 + +# Narrowband orthogonal frequency division multiplexing power line communication transceivers for G3-PLC networks + +# 1 Scope + +Recommendation ITU-T G.9903 contains the physical layer (PHY) and data link layer (DLL) specification for the G3-PLC narrowband orthogonal frequency division multiplexing (OFDM) power line communication transceivers, for communications via alternating current and direct current electric power lines over frequencies below 500 kHz. This Recommendation supports indoor and outdoor communications over low-voltage lines, medium-voltage lines, through transformer low-voltage to medium-voltage and through transformer medium-voltage to low-voltage power lines in both urban and long distance rural communications. This Recommendation addresses grid to utility meter applications, advanced metering infrastructure (AMI), and other 'Smart Grid' applications such as the charging of electric vehicles, home automation, and home area networking (HAN) communications scenarios. + +This Recommendation supports coexistence with other narrowband PLC technologies via frequency division and via the preamble-based coexistence mechanism specified in clause 10 of [IEEE 1901.2]. + +This Recommendation does not contain the control parameters that determine spectral content, power spectral density (PSD) mask requirements and the set of tools and procedures to support the reduction and measurement of the transmit PSD; all of which are detailed in Recommendation [ITU-T G.9901]. + +# 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +- [ITU-T G.9901] Recommendation ITU-T G.9901 (2014), *Narrowband orthogonal frequency division multiplexing power line communication transceivers – Power spectral density specification*. +- [ITU-T G.9905] Recommendation ITU-T G.9905 (2013), *Centralized metric-based source routing*. +- [ARIB STD-T84] ARIB STD-T84, *Power Line Communication Equipment (10kHz – 450kHz)*. +- [CISPR16-1-2] International Electrotechnical Commission, CISPR 16-1-2:2014, *Specification for radio disturbance and immunity measuring apparatus and methods – Part 1-2: Radio disturbance and immunity measuring apparatus – Coupling devices for conducted disturbance measurements*. +- [IEEE 802-2001] IEEE Std 802-2001 (R2007), *IEEE Standard for Local and Metropolitan Area Networks. Overview and Architecture*. +- [IEEE 802.2] IEEE 802.2:1998, *Information technology – Telecommunications and information exchange between systems – Local and metropolitan area networks – Specific requirements – Part 2: Logical Link Control*. + +- [IEEE 802.15.4] IEEE 802.15.4:2006, *IEEE Standard for Information technology – Telecommunications and information exchange between systems – Local and metropolitan area networks – Specific requirements – Part 15.4: Wireless Medium Access (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (WPANs)*. +- [IEEE 1901.2] IEEE 1901.2 (2013), *IEEE Standard for Low-Frequency (less than 500 kHz) Narrowband Power Line Communications for Smart Grid Applications*. +- [IETF RFC 2119] IETF RFC 2119 (1997), *Key words for use in RFCs to Indicate Requirement Levels*. +- [IETF RFC 2284] IETF RFC 2284 (1998), *PPP Extensible Authentication Protocol (EAP)*. +- [IETF RFC 2865] IETF RFC 2865 (2000), *Remote Authentication Dial In User Service (RADIUS)*. +- [IETF RFC 3748] IETF RFC 3748 (2004), *Extensible Authentication Protocol (EAP)*. +- [IETF RFC 4291] IETF RFC 4291 (2006), *IP Version 6 Addressing Architecture*. +- [IETF RFC 4764] IETF RFC 4764 (2007), *The EAP-PSK Protocol: A Pre-Shared Key Extensible Authentication Protocol (EAP) Method*. +- [IETF RFC 4861] IETF RFC 4861 (2007), *Neighbor Discovery for IP version 6 (IPv6)*. +- [IETF RFC 4862] IETF RFC 4862 (2007), *Ipv6 Stateless Address Autoconfiguration*. +- [IETF RFC 4944] IETF RFC 4944 (2007), *Transmission of IPv6 Packets over IEEE 802.15.4 Networks*. +- [IETF RFC 5444] IETF RFC 5444 (2009), *Generalized Mobile Ad Hoc Network (MANET) Packet/Message Format*. +- [IETF RFC 6282] IETF RFC 6282 (2011), *Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks*. +- [IETF RFC 6775] IETF RFC 6775 (2012), *Neighbor Discovery Optimization for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)*. +- [TTC JJ-300.11] TTC standard JJ-300.11 (2014): *Homenetwork Communication Interface for ECHONET Lite (ITU-T G.9903 Narrow band OFDM PLC), version 2.0*. + +# 3 Conventions and definitions + +## 3.1 Conventions + +Binary numbers are indicated by the prefix '0b' followed by the binary digits. + +Hexadecimal numbers are indicated by the prefix '0x' followed by the hexadecimal digits. + +## 3.2 Terms defined elsewhere + +None. + +## 3.3 Terms defined in this Recommendation + +This Recommendation defines the following terms: + +**3.3.1 active tone:** A tone that carries data according to the tone map field. Masked tones and pilot tones are not active tones. + +**3.3.2 inactive tone:** A tone that carries dummy data according to the tone map field. Masked tones and pilot tones are not inactive tones. + +- 3.3.3 masked tone:** A tone with a null amplitude according to the tone mask parameter. Thus, it contributes neither to the OFDM signal's power spectrum density nor to the LQI calculation. +- 3.3.4 modulation scheme:** Two modulation schemes are defined: differential and coherent. +- 3.3.5 modulation type:** The following modulation types are defined: robust modes, BPSK, DBPSK, QPSK, DQPSK, 8-PSK, D8PSK, and 16-QAM. +- 3.3.6 pilot tone:** A tone used in coherent modulation schemes that carries a specific pattern in order to help the receiver with clock recovery and channel estimation. +- 3.3.7 tone map:** A bitmap containing a list of the sub-bands (groups of tones) that are either active (bit set to 1) or inactive (bit set to zero). A bit in the bitmap represents a group of consecutive tones and the number of tones per group depends on the bandplan. + +# 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|---------|----------------------------------------------------| +| 6LoWPAN | IPv6 over Low power Wireless Personal Area Network | +| 8-PSK | 8 Phase Shift Keying | +| 16-QAM | 16 Quadrature Amplitude Modulation | +| AAA | Authentication, Authorization and Accounting | +| ACK | Acknowledge | +| ADP | Adaptation | +| AFE | Analogue Front End | +| AGC | Automatic Gain Control | +| AMM | Automated Meter Management | +| AMN | Artificial Mains Network | +| ARQ | Automatic Repeat Request | +| BPSK | Binary Phase Shift Keying | +| CIFS | Contention Inter-Frame Space | +| CP | Cyclic Prefix | +| CRC | Cyclic Redundancy Check | +| D8PSK | Differential 8 Phase Shift Keying | +| DBPSK | Differential Binary Phase Shift Keying | +| DCI | Destination Context Identifier | +| DQPSK | Differential Quadrature Phase Shift Keying | +| DSI | Device Specific Information | +| EAP | Extensible Authentication Protocol | +| ED | End Device | +| EIFS | Extended Inter-frame Space | +| FCH | Frame Control Header | +| FEC | Forward Error Correction | + +| | | +|------|-----------------------------------------------| +| FFT | Fast Fourier Transform | +| FL | Frame Length | +| GF | Galois Field | +| GI | Guard Interval | +| GMK | Group Master Key | +| GTS | Guaranteed Time Slot (see [IEEE 802.15.4]) | +| HPCW | High Priority Contention Window | +| IB | Information Base | +| ICI | Inter-Carrier Interference | +| IFFT | Inverse Fast Fourier Transform | +| IFS | Inter-frame Spacing | +| IS | Information System | +| LBA | LoWPAN Bootstrapping Agent | +| LBD | LoWPAN Bootstrapping Device | +| LBP | LoWPAN Bootstrapping Protocol | +| LBS | LoWPAN Bootstrapping Server | +| LFSR | Linear Feedback Shift Register | +| LQ | Link Quality | +| LSB | Least Significant Bit | +| LSF | Last Segment Flag | +| MAC | Media Access Control | +| MIB | Management Information Base | +| MPDU | MAC Protocol Data Unit | +| MSB | Most Significant Bit | +| MSE | Mean Square Error | +| NACK | Negative Acknowledgement | +| NIB | Neighbour Information Base | +| NPCW | Normal Priority Contention Window | +| NSDU | Network Service Data Unit | +| OFDM | Orthogonal Frequency Division Multiplexing | +| PAN | Personal Area Network | +| PAR | Peak to Average Ratio | +| PCS | Physical Carrier Sense | +| PDC | Phase Detection Counter | +| PHY | Physical layer | +| PIB | PAN Information Base | +| PICS | Protocol Implementation Conformance Statement | + +| | | +|--------|--------------------------------------------| +| PLC | Power Line Communication | +| PN | Pseudo Noise | +| POS | Personal Operating Space | +| PPDU | PHY Protocol Data Unit | +| PPM | Parts Per Million | +| PSDU | PHY Service Data Unit | +| PSI | PAN Specific Information | +| PSK | Pre-Shared Key | +| QPSK | Quadrature Phase Shift Keying | +| RA | Router Advertisement | +| RADIUS | Remote Authentication Dial in User Service | +| RERR | Route Error | +| RES | Reserved (bit fields) | +| RIFS | Response Inter-frame Space | +| rms | Root Mean Square | +| RREP | Route Reply | +| RREQ | Route Request | +| RS | Reed-Solomon | +| RX | Receiver | +| SC | Segment Count | +| SCI | Source Context Identifier | +| S-FSK | Spread Frequency Shift Keying | +| SN | Sequence Number | +| SNR | Signal to Noise Ratio | +| SSCS | Service-Specific Convergence Sublayer | +| TMI | Tone Map Index | +| TMR | Tone Map Request | +| TX | Transmitter | +| TX | Transmit | +| VCS | Virtual Carrier Sense | + +Furthermore, the abbreviations given in the following clauses also apply: + +- clause 4 of [IEEE 802.15.4]. +- clause 1.2 of [IETF RFC 4944]. + +# 5 Introduction to OFDM and the power line channel + +Power line communication has been used for many decades, but a variety of new services and applications require greater reliability and higher data rates. However, the power line channel is very hostile. Channel characteristics and parameters vary with frequency, location, time and the + +type of equipment connected to it. The lower frequency regions from 10 kHz to 200 kHz are especially susceptible to interference. Besides background noise, the power line channel is subject to impulsive noise and narrowband interference and group delays of up to several hundred microseconds. + +OFDM is a modulation technique that efficiently utilizes the assigned bandwidth, allowing the use of advanced channel coding techniques. This combination enables a very robust communication in the presence of narrowband interference, impulsive noise and frequency selective attenuation. OFDM-based ITU-T G.9903 specifications address the following main objectives: + +- 1) provide robust communication in extremely harsh power line channels; +- 2) provide a minimum of 20 kbit/s effective data rate in the normal mode of operation; +- 3) provide the ability of notching selected frequencies, allowing the cohabitation with S-FSK narrow-band communication; +- 4) provide a dynamic tone adoption capability to varying power line channel to ensure a robust communication. + +# 6 General description + +## 6.1 Overall infrastructure + +The following diagram illustrates an example of an automated meter management (AMM) system. + +The system provides a reliable two-way communication using an OFDM-based PLC link between the meters installed at the customer's premises and the concentrator, communicating in a master and slave configuration. + +![Figure 6-1 – Network architecture diagram showing the flow of data from meters through a PLC link, concentrator, and WAN to an AMM central system, which then connects to various information systems. Below the diagram, icons represent the physical locations: End user (house), Low voltage network (map), MV/LV substation (transformer), Communication network (satellite), and Monitoring centre (person at computer).](16c1175b5f05a4b55e6d396fc51b15b3_img.jpg) + +The diagram illustrates the network architecture for an Automated Meter Management (AMM) system. It is divided into two horizontal layers. The top layer shows the logical flow of data: **Meters** (three blue rectangles) are connected via a **PLC link** to a **Concentrator** (a pink circle). The Concentrator is connected to a **WAN** (represented by a cloud icon). The WAN connects to an **AMM central system** (a large blue rectangle). The AMM central system is connected to five **Information systems** (pink rectangles): **Metering and administration IS**, **Grid IS**, **Accounting and finance IS**, **Rollout IS**, and **Operation IS**. The **Metering and administration IS** is further connected to **Utilities IS** (a green rectangle). A **Distribution automation equipment** (a green rectangle) is also connected to the Concentrator. The bottom layer shows the physical locations corresponding to the logical components: **End user** (house icon), **Low voltage network** (map icon), **MV/LV substation** (transformer icon), **Communication network** (satellite icon), and **Monitoring centre** (person at computer icon). The text G.9903(12)-Amd.1(13)\_F6-1 is located in the bottom right corner. + +Figure 6-1 – Network architecture diagram showing the flow of data from meters through a PLC link, concentrator, and WAN to an AMM central system, which then connects to various information systems. Below the diagram, icons represent the physical locations: End user (house), Low voltage network (map), MV/LV substation (transformer), Communication network (satellite), and Monitoring centre (person at computer). + +**Figure 6-1 – Network architecture** + +The AMM architecture consists of the five following main components: + +- The meter which needs to integrate the capability of measuring power consumption, simple load control and customer remote information. + +- The hub which acts as an intermediary between the AMM information system (IS) and the meters. Complementary equipment supplied by the electrical network that can be connected downstream of the hub. +- The PLC (LAN) technology which allows the use of a low-voltage electrical network to exchange data and commands between meters and hubs. +- A remote connection (WAN) allows connection between the hubs and the AMM central IS. +- The central system, which not only handles its own functional services but also supplies metering services to the existing or forthcoming enterprise services (deployment IS, network IS, management-finance IS, customer-supplier IS-Intervention management IS, etc.). The customer-supplier IS is the interface between the suppliers and AMM for handling their requirements. + +## 6.2 Coexistence with other PLC networks + +Two mechanisms are defined to allow coexistence between ITU-T G.9903 devices and other narrowband PLC technologies operating in the same frequency band: + +- frequency division coexistence; +- preamble-based coexistence. + +### 6.2.1 Frequency division coexistence mechanism + +A first method consists in assigning non-overlapping bandplans to devices complying with this Recommendation within communication range. A second method is to exploit the tone masking feature (see clause 7.15 and description of macToneMask attribute in Table 9-15) to avoid any overlapping frequencies. Frequency division coexistence provides a means to ensure coexistence between devices complying with this Recommendation and both single (e.g., existing narrowband Frequency Shift Keying/Phase Shift Keying systems) and multiple carrier PLC systems. + +### 6.2.2 Preamble-based coexistence mechanism (optional) + +Devices complying with this Recommendation may support the preamble-based coexistence mechanism specified in clauses 10.2.2 and 10.3 to 10.5 of [IEEE 1901.2] to fairly share the medium with other types of narrowband PLC technologies supporting the same preamble-based coexistence mechanism. Support for this coexistence mechanism is optional in this Recommendation, with the exception given in Annex G. + +If devices complying with this Recommendation support the preamble-based coexistence mechanism, then Tables 10-2 and 10-3 of [IEEE 1901.2] shall be revised as specified below. + +The IDs (identifiers) listed in Table 10-2 of [IEEE 1901.2] shall be replaced by the identifiers listed in Table 6-1. + +**Table 6-1 – Attributes for the preamble-based coexistence mechanism** + +| Attribute | Identifier | +|----------------------------|------------| +| Beta | 0x0117 | +| aMacMaxCoexistenceBackoffs | 0x0118 | +| macAlpha | 0x0119 | +| K | 0x011A | +| macNdcTime | 0x011B | + +NOTE – The other attributes listed in Table 10-2 of [IEEE 1901.2] (aCEIFS, macLongPreambleDuration, macDCEIFS, macMinChannelIdleTime) do not require an identifier as their values depend exclusively on the values of other attributes which have their own identifier. + +The IDs (identifiers) and default values listed in Table 10-3 of [IEEE 1901.2] shall be replaced by the ones listed in Table 6-2. + +**Table 6-2 – Coexistence control PIB attributes** + +| Attribute | Identifier | Default value | +|---------------------------------|-------------------|----------------------| +| macCoexPreambleDetectionEnabled | 0x011C | FALSE | +| macCoexPreambleEnabled | 0x011D | FALSE | + +# **7 Physical layer specification** + +This clause specifies the physical layer block using the orthogonal frequency division multiplexing (OFDM) system in the CENELEC and FCC bandplans. + +## **7.1 Introduction** + +The power line channel is very hostile. Channel characteristics and parameters vary with frequency, location, time and the type of equipment connected to it. The lower frequency regions from 10 kHz to 200 kHz are especially susceptible to interference. Furthermore, the power line is a very frequency selective channel. Besides background noise, it is subject to impulsive noise often occurring at 50/60 Hz and narrowband interference and group delays of up to several hundred microseconds. + +OFDM can efficiently utilize limited bandwidth channels allowing the use of advanced channel coding techniques. This combination facilitates a very robust communication over a power line channel. + +Figure 7-1 shows the block diagram of an OFDM transmitter. The available bandwidth is divided into a number of sub-channels, which can be viewed as many independent Phase Shift Keying modulated subcarriers with different non-interfering (orthogonal) subcarrier frequencies. Convolutional and Reed-Solomon coding provide redundancy bits allowing the receiver to recover lost bits caused by background and impulsive noise. A time-frequency interleaving scheme is used to decrease the correlation of received noise at the input of the decoder, providing diversity. + +The OFDM signal is generated by performing inverse fast Fourier transform (IFFT) on the complex-valued signal points produced by differentially encoded phase modulation that are allocated to individual subcarriers. An OFDM symbol is built by appending a cyclic prefix to the beginning of each block generated by IFFT. The length of a cyclic prefix is chosen so that the channel group delay does not cause excessive interference between successive OFDM symbols. Windowing reduces the out-of-band leakage of the transmit signals. + +Channel estimation is used for link adaptation. Based on the quality of the received signal, the receiver (if requested by the transmitter) shall feed back the suggested modulation scheme to be used by the transmitting station in subsequent packets transmitted to the same receiver. Moreover, the system differentiates the subcarriers with insufficient SNR and does not transmit data on them. + +![Block diagram of an OFDM transceiver. The transmitter path starts with FCH and Data inputs to a Scrambler. The output goes to a Reed-Solomon encoder, then a Convolutional encoder. The output of the Convolutional encoder is split into three parallel paths: Bit, Robust (RC4), and S-Robust (RC6), which are then interleaved. The interleaved data is fed into an OFDM modulator block containing Mapping (DBPSK, DQPSK, D8PSK), Pre-emphasis, IFFT, Add CP, and Windowing. The output of the Windowing block is connected to an AFE, which is connected to a Power Line. A feedback loop from the AFE output goes back to the Mapping block. The diagram is labeled G.9903(12)-Amd.1(13)_F7-1.](8fbdfc3d17fb1dae7b2d8f5a287fa9fc_img.jpg) + +``` + +graph LR + FCH --> Scrambler + Data --> Scrambler + Scrambler --> RS[Reed-Solomon encoder] + RS --> Conv[Convolutional encoder] + Conv --> Interleaver + subgraph Interleaver + Bit + Robust[Robust RC4] + SRobust[S-Robust RC6] + end + Interleaver --> Modulator + subgraph Modulator[OFDM modulator] + Mapping[Mapping DBPSK, DQPSK, D8PSK] --> Pre[Pre-emphasis] + Pre --> IFFT + IFFT --> CP[Add CP] + CP --> Windowing + end + Windowing --> AFE + AFE --> PL[Power Line] + AFE -.-> Mapping + +``` + +Block diagram of an OFDM transceiver. The transmitter path starts with FCH and Data inputs to a Scrambler. The output goes to a Reed-Solomon encoder, then a Convolutional encoder. The output of the Convolutional encoder is split into three parallel paths: Bit, Robust (RC4), and S-Robust (RC6), which are then interleaved. The interleaved data is fed into an OFDM modulator block containing Mapping (DBPSK, DQPSK, D8PSK), Pre-emphasis, IFFT, Add CP, and Windowing. The output of the Windowing block is connected to an AFE, which is connected to a Power Line. A feedback loop from the AFE output goes back to the Mapping block. The diagram is labeled G.9903(12)-Amd.1(13)\_F7-1. + +**Figure 7-1 – Block diagram of an OFDM transceiver** + +## 7.2 System parameters + +The differential modulations (DBPSK, DQPSK, and D8PSK) for each subcarrier make the receiver design significantly simpler compared to coherent modulations (BPSK, QPSK, 8-PSK and 16-QAM) since no tracking circuitry is required at the receiver for detecting the phase of each subcarrier. Instead, the phases of subcarriers in the adjacent symbol are taken as reference for detecting the phases of the subcarriers in the current symbol. However, coherent modulation, which offers greater robustness, is an option available to ITU-T G.9903 devices (see clause 7.16). + +As specified in Annex B of [ITU-T G.9901], the maximum number of subcarriers that can be used is selected to be 128, resulting in an IFFT size of 256. This yields a frequency spacing between the OFDM subcarriers equal to 1.5625 kHz ( $F_s/N$ ) for CENELEC bandplans and 4.6875 kHz ( $F_s/N$ ) for the FCC bandplan, where $F_s$ is the sampling frequency and $N$ is the IFFT size. Note that imperfection such as sampling clock frequency variation can cause inter-carrier interference (ICI). In practice, the ICI caused by a typical sampling frequency variation of about 2% of the frequency spacing is negligible. In other words, considering ±25 ppm sampling frequency in transmitter and receiver clocks, the drift of the subcarriers is approximately equal to 8 Hz that is approximately 0.5% of the selected frequency spacing. Considering these selections, the number of usable subcarriers is 36 for the CENELEC-A bandplan, 16 for the CENELEC-B bandplan and 72 for the FCC bandplan. + +The system works in two different modes namely normal and robust modes. + +In normal mode, the FEC is composed of a Reed-Solomon encoder and a convolutional encoder. The system also supports Reed-Solomon code with a parity of 8 and 16 bytes. + +In robust mode, the FEC is composed of Reed-Solomon and convolutional encoders followed by a repetition code. The repetition code, repeats each bit four times making the system more robust to channel impairments. + +A super robust mode is used for the FCH only (see clause 7.9.3.2). + +## 7.3 Data rate, Reed-Solomon block size and maximum PSDU length + +### 7.3.1 Data rate calculation and RS block size + +The data rate is calculated based on the number of symbols per PHY frame ( $N_s$ ), number of subcarrier per symbol ( $N_{CAR}$ ) and the number of parity bits added by FEC blocks. + +An example of how to calculate the data rate is given below using the following CENELEC-A bandplan parameters: + +| | | | +|---|---------------------------------|----------------------------------| +| – | Number of FFT points | $N = 256$ | +| – | Number of subcarriers | $N_{\text{CAR}} = 36$ | +| – | Number of overlapped samples | $N_{\text{O}} = 8$ | +| – | Number of cyclic prefix samples | $N_{\text{CP}} = 30$ | +| – | Number of FCH symbols | $N_{\text{FCH}} = 13$ | +| – | Sampling frequency | $F_{\text{s}} = 0.4 \text{ MHz}$ | +| – | Number of symbols in preamble | $N_{\text{PRE}} = 9.5$ | + +Consider the system in the CENELEC-A band working in the robust mode. The total number of bits carried by the whole PHY frame is equal to: + +$$\text{Total\_No\_Bits} = N_{\text{s}} \times N_{\text{CAR}} = 40 \times 36 = 1\,440 \text{ bits}$$ + +The number of bits required at the input of the robust encoder is given by: + +$$\text{No\_Bits\_Robust} = 1440 \times \text{RobustRate} = 1440 \times 1/4 = 360 \text{ bits}$$ + +Considering the fact that the convolutional encoder has a rate equal to 1/2 ( $\text{CCRate} = 1/2$ ) and also consider adding $\text{CCZeroTail} = 6$ bits of zeros to terminate the states of the encoder to all zero states then the maximum number of symbols at the output of the Reed-Solomon encoder ( $\text{MAXRS}_{\text{bytes}}$ ) shall be equal to: + +$$\text{MAXRS}_{\text{Bytes}} = \text{floor} \left( \frac{\text{NoBitsRobust} \times \text{CCRate} - \text{CCZeroTail}}{8} \right) = \text{floor} \left( \frac{360 \times 0.5 - 6}{8} \right) = 21$$ + +Removing 8 bytes associated with the parity bits (in robust mode) we obtain: + +$$\text{DataLength} = (21 - \text{ParityLength}) \times 8 = 104 \text{ bits}$$ + +These 104 bits are carried within the duration of a PHY frame. The duration of a PHY frame is calculated by the following formula: + +$$T_{\text{Frame}} = \frac{(N_{\text{s}} + N_{\text{FCH}}) \times (N_{\text{CP}} + N - N_{\text{O}}) + (N_{\text{PRE}} \times N)}{F_{\text{s}}}$$ + +Where $N_{\text{PRE}}$ , $N$ , $N_{\text{O}}$ and $N_{\text{CP}}$ are the number of symbols in the preamble, FFT length, the number of samples overlapped at each side of one symbol and the number of samples in the cyclic prefix, respectively. $N_{\text{FCH}}$ is the number of symbols in the FCH. The $F_{\text{s}}$ is the sampling frequency. + +Substituting the above numbers in the equation, $T_{\text{Frame}}$ (PHY frame duration) for a 40-symbol frame is obtained as follows: + +$$T_{\text{Frame}} = \frac{(40 + 13) \times (256 + 22) + (9.5 \times 256)}{400000} = 0.043 \text{ s}$$ + +Therefore the data rate is calculated as: + +$$\text{Data rate} = 104/0.042 \sim 2.4 \text{ kbit/s}$$ + +#### 7.3.1.1 CENELEC-A bandplan + +Mandatory values for the OFDM control parameters for the CENELEC-A bandplan are given in Table B.1 of [ITU-T G.9901]. The frequency band used for the CENELEC-A bandplan is defined in Table B.2 of [ITU-T G.9901]. + +The number of symbols in each PHY (physical layer) frame is selected based on two parameters, the required data rate and the acceptable robustness. The number of symbols, Reed-Solomon block sizes and data rate associated with 36 tones is tabulated in Tables 7-1 and 7-2. + +Table 7-3 shows the rate including the data transmitted in the FCH. To calculate the data rate, it is assumed that the packets are continuously transmitted with no inter-frame time gap. + +**Table 7-1 – RS block size for various modulations** + +| CENELEC-A
Number of
symbols | Reed-Solomon
blocks (bytes)
D8PSK
(Out/In)
(Note 1) | Reed-Solomon
blocks (bytes)
DQPSK
(Out/In)
(Note 1) | Reed-Solomon
blocks (bytes)
DBPSK
(Out/In)
(Note 1) | Reed-Solomon
blocks (bytes)
Robust
(Out/In)
(Note 2) | +|--------------------------------------------|----------------------------------------------------------------------------|----------------------------------------------------------------------------|----------------------------------------------------------------------------|-----------------------------------------------------------------------------| +| 12 | (80/64) | (53/37) | (26/10) | N/A | +| 20 | (134/118) | (89/73) | (44/28) | N/A | +| 32 | (215/199) | (143/127) | (71/55) | N/A | +| 40 | N/A | (179/163) | (89/73) | (21/13) | +| 52 | N/A | (233/217) | (116/100) | (28/20) | +| 56 | N/A | (251/235) | (125/109) | (30/22) | +| 112 | N/A | N/A | (251/235) | (62/54) | +| 252 | N/A | N/A | N/A | (141/133) | + +NOTE 1 – Reed-Solomon with 16 bytes parity. +NOTE 2 – Reed-Solomon with 8 bytes parity. + +**Table 7-2 – Data rate for various modulations (excluding FCH)** + +| CENELEC-A | Data rate per modulation type, bit/s | | | | +|------------------------------|---------------------------------------------|--------------------------------|--------------------------------|--------------------------------| +| Number of
symbols | D8PSK, P16
(Note 1) | DQPSK, P16
(Note 1) | DBPSK, P16
(Note 1) | Robust, P8
(Note 2) | +| 12 | 21 829 | 12 619 | 3 410 | N/A | +| 20 | 32 534 | 20 127 | 7 720 | N/A | +| 32 | 42 619 | 27 198 | 11 778 | N/A | +| 40 | N/A | 30 385 | 13 608 | 2 423 | +| 52 | N/A | 33 869 | 15 608 | 3 121 | +| 56 | N/A | 34 792 | 16 137 | 3 257 | +| 112 | N/A | N/A | 20 224 | 4 647 | +| 252 | N/A | N/A | N/A | 5 592 | + +NOTE 1 – Reed-Solomon with a 16 byte parity. +NOTE 2 – Reed-Solomon with an 8 byte parity. +NOTE – N/A means not applicable and the reason for this is that the corresponding number of symbols specified results in an RS encoder block length that exceeds the maximum allowable limit of 255. + +**Table 7-3 – Data rate for various modulations (including FCH)** + +| CENELEC-A
Number of symbols | Data rate per modulation type, bit/s | | | | +|--------------------------------|--------------------------------------|------------------------|------------------------|------------------------| +| | D8PSK, P16
(Note 1) | DQPSK, P16
(Note 1) | DBPSK, P16
(Note 1) | Robust, P8
(Note 2) | +| 12 | 23 235 | 14 026 | 4 817 | N/A | +| 20 | 33 672 | 21 264 | 8 857 | N/A | +| 32 | 43 501 | 28 081 | 12 662 | N/A | +| 40 | N/A | 31 154 | 14 377 | 3 192 | +| 52 | N/A | 34 513 | 16 252 | 3 765 | +| 56 | N/A | 35 402 | 16 748 | 3 867 | +| 112 | N/A | N/A | 20 579 | 5 002 | +| 252 | N/A | N/A | N/A | 5 765 | + +NOTE 1 – Reed-Solomon with a 16 byte parity. +NOTE 2 – Reed-Solomon with an 8 byte parity. +NOTE – N/A means not applicable and the reason for this is that the corresponding number of symbols specified results in an RS encoder block length that exceeds the maximum allowable limit of 255. + +#### 7.3.1.2 CENELEC-B bandplan + +Mandatory values for the OFDM control parameters for the CENELEC-B bandplan are given in Table B.1 of [ITU-T G.9901]. + +The frequency band used for the CENELEC-B bandplan is defined in Table B.3 of [ITU-T G.9901]. The number of symbols, Reed-Solomon block sizes, and data rate associated with 16 tones is tabulated in Tables 7-4 and 7-5. + +Table 7-6 shows the rate including the data transmitted in the FCH. To calculate the data rate, it is assumed that the packets are continuously transmitted with no inter-frame time gap. + +**Table 7-4 – RS block size for various modulations** + +| CENELEC B
Number of symbols | Reed-Solomon blocks (bytes) | Reed-Solomon blocks (bytes) | Reed-Solomon blocks (bytes) | Reed-Solomon blocks (bytes) | +|--------------------------------|-------------------------------|-------------------------------|-------------------------------|--------------------------------| +| | D8PSK
(Out/In)
(Note 1) | DQPSK
(Out/In)
(Note 1) | DBPSK
(Out/In)
(Note 1) | Robust
(Out/In)
(Note 2) | +| 12 | 35/19 | 23/7 | N/A | N/A | +| 20 | 59/43 | 39/23 | 19/3 | N/A | +| 32 | 95/79 | 63/47 | 31/15 | N/A | +| 40 | 119/103 | 79/63 | 39/23 | 9/1 | +| 52 | 155/139 | 103/87 | 51/35 | 12/4 | +| 56 | 167/151 | 111/95 | 55/39 | 13/5 | +| 112 | N/A | 223/207 | 111/95 | 27/19 | +| 252 | N/A | N/A | 251/235 | 62/54 | + +NOTE 1 – Reed-Solomon with a 16 byte parity. +NOTE 2 – Reed-Solomon with an 8 byte parity. + +**Table 7-5 – Data rate for various modulations (excluding FCH)** + +| CENELEC B | Data rate per modulation type, bps | | | | +|-----------|------------------------------------|------------------------|------------------------|------------------------| +| | D8PSK, P16
(Note 1) | DQPSK, P16
(Note 1) | DBPSK, P16
(Note 1) | Robust, P8
(Note 2) | +| 12 | 4309 | 1587 | N/A | N/A | +| 20 | 8425 | 4506 | 587 | N/A | +| 32 | 12853 | 7646 | 2440 | N/A | +| 40 | 15055 | 9208 | 3361 | 146 | +| 52 | 17631 | 11035 | 4439 | 507 | +| 56 | 18344 | 11541 | 4738 | 607 | +| 112 | N/A | 15806 | 7253 | 1450 | +| 252 | N/A | N/A | 9303 | 2137 | + +NOTE 1 – Reed-Solomon with a 16 byte parity. +NOTE 2 – Reed-Solomon with an 8 byte parity. +NOTE – N/A means not applicable and the reason for this is that the corresponding number of symbols specified results in an RS encoder block length that exceeds the maximum allowable limit of 255. + +**Table 7-6 – Data rate for various modulations (including FCH)** + +| CENELEC B | Data rate per modulation type, bps | | | | +|-----------|------------------------------------|------------------------|------------------------|------------------------| +| | D8PSK, P16
(Note 1) | DQPSK, P16
(Note 1) | DBPSK, P16
(Note 1) | Robust, P8
(Note 2) | +| 12 | 5245 | 2523 | N/A | N/A | +| 20 | 9233 | 5314 | 1396 | N/A | +| 32 | 13524 | 8318 | 3111 | N/A | +| 40 | 15658 | 9811 | 3964 | 749 | +| 52 | 18154 | 11558 | 4962 | 1030 | +| 56 | 18845 | 12042 | 5239 | 1108 | +| 112 | N/A | 16121 | 7568 | 1765 | +| 252 | N/A | N/A | 9467 | 2301 | + +NOTE 1 – Reed-Solomon with a 16 byte parity. +NOTE 2 – Reed-Solomon with an 8 byte parity. +NOTE – N/A means not applicable and the reason for this is that the corresponding number of symbols specified results in an RS encoder block length that exceeds the maximum allowable limit of 255. + +#### 7.3.1.3 FCC bandplan + +Mandatory values for the OFDM control parameters for the FCC bandplan are given in Table B.4 of [ITU-T G.9901]. The frequency bands used for the FCC bandplan are defined in Table B.5 of [ITU-T G.9901]. + +As specified in Table B.5 of [ITU-T G.9901], the subcarrier spacing is 4.6875 kHz and the number of usable subcarriers is 72. DBPSK, DQPSK and D8PSK modulation schemes are supported, resulting in an up to 300 kbit/s data rate in the normal mode of operation. + +The number of symbols in each PHY frame is selected based on two parameters, the required data rate and the acceptable robustness. The number of symbols, Reed-Solomon block sizes and data rate associated with 72 tones are tabulated for several values as examples in Tables 7-7 and 7-8. + +**Table 7-7 – RS block size for various modulations** + +| FCC
Number of
symbols | Reed-Solomon
blocks (bytes) | Reed-Solomon
blocks (bytes) | Reed-Solomon
blocks (bytes) | Reed-Solomon
blocks (bytes) | +|-----------------------------|--------------------------------|--------------------------------|--------------------------------|--------------------------------| +| | D8PSK
(Out/In)
(Note 1) | DQPSK
(Out/In)
(Note 1) | DBPSK
(Out/In)
(Note 1) | Robust
(Out/In)
(Note 2) | +| 12 | (161/145) | (107/91) | (53/37) | (12/4) | +| 20 | N/A | (179/163) | (89/73) | (21/13) | +| 28 | N/A | (251/235) | (125/109) | (30/22) | + +NOTE 1 – Reed-Solomon with a 16 byte parity. +NOTE 2 – Reed-Solomon with an 8 byte parity. + +**Table 7-8 – Data rate for various modulations (excluding FCH)** + +| FCC
Number of
symbols | Data rate
(bit/s) | Data rate
(bit/s) | Data rate
(bit/s) | Data rate
(bit/s) | +|-----------------------------|----------------------|----------------------|----------------------|----------------------| +| | D8PSK
(Note 1) | DQPSK
(Note 1) | DBPSK
(Note 1) | Robust
(Note 2) | +| 12 | 152,899 | 95,957 | 39,015 | 4,217 | +| 20 | N/A | 138,135 | 61,864 | 11,016 | +| 28 | N/A | 166,469 | 77,213 | 15,584 | + +NOTE 1 – Reed-Solomon with a 16 byte parity. +NOTE 2 – Reed-Solomon with an 8 byte parity. + +### 7.3.2 Maximum PSDU length calculation + +The maximum PSDU length in bytes for an ITU-T G.9903 PHY packet (Max\_PSDUBytes) is a function of the PHY configuration comprising of the number of available subcarriers per symbol (NCAR), modulation type (MOD) and other dependent parameters. Given a PHY configuration, Max\_PSDUBytes can be calculated using the following set of equations: + +$$N_S = FL_{Band} \times \min \left[ FL_{max}, \text{ceil} \left( \frac{(MaxRSBlockSize \times 8 + CC_{ZeroTail}) \times Rep\_Code}{FL_{Band} \times N_{car} \times mod\_size \times CC_{Rate}} \right) \right]$$ + +where: + +- MaxRSBlockSize = 255 bytes, +- $N_S$ is the number of symbols in the PHY packet, +- $CC_{Rate} = 0.5$ , +- $CC_{ZeroTail} = 6$ , +- $FL_{Band} = 4$ for CENELEC bandplans and $FL_{Band} = 1$ for FCC bandplan, +- $FL_{max}$ is the maximum possible frame length ( $FL_{max} = 63$ for CENELEC bandplans, $FL_{max} = 511$ for FCC bandplan), +- Rep\_Code denotes the repetition coding (Rep\_Code = 4 for Robust mode; Rep\_Code = 1 for all other modes), + +- $mod_{size}$ is the number of bits per constellation symbol, i.e.: + - 1 for Robust, DBPSK or BPSK + - 2 for DQPSK or QPSK + - 3 for D8PSK or 8-PSK + - 4 for 16-QAM + +Adjust the number of symbols in the PHY packet if Reed-Solomon block size per calculated NS is more than MaxRSBlockSize, i.e., + +$$if \left\lfloor \left( \left( (N_S \times N_{car} \times mod_{size}) - CC_{ZeroTail} \times \frac{Rep\_Code}{CC_{Rate}} \right) \times \frac{CC_{Rate}}{8 \times Rep\_Code} \right) \right\rfloor > MaxRSBlockSize$$ + +then { NS = NS – 4; } + +Max\_PSDUBytes + +$$= \max \left[ 0, \text{floor} \left( \left( (N_S * N_{car} \times mod_{size}) - CC_{ZeroTail} \times \frac{Rep\_Code}{CC_{Rate}} \right) \times \frac{CC_{Rate}}{8 \times Rep\_Code} \right) - ParityLength \right]$$ + +The PHY interleaver bit padding is calculated using the following equation: + +$$RSBlockSize = Max\_PSDU_{Bytes} + ParityLength$$ + +$$Interleaver\_padding = \frac{N_S \times N_{car} \times Bits\_per\_subCarrier}{Rep\_Code} - \frac{(RSBlockSize \times 8 + CC_{ZeroTail})}{CC_{Rate}}$$ + +## 7.4 Frame structure + +The PHY supports two types of frames. A typical data frame for the OFDM PHY is shown in Figure 7-2. Each frame starts with a preamble which is used for synchronization and detection in addition to AGC adaptation. SYNCP simply refers to symbols that are multiplied by +1 in the sign function above, and SYNCN refers to symbols multiplied by –1. The preamble consists of eight SYNCP symbols followed by one and a half SYNCN symbols with no cyclic prefix between adjacent symbols. The preamble is followed by 13 data symbols allocated to the frame control header (FCH). The FCH has the important control information required to demodulate the data frame. Data symbols are transmitted next. The first FCH symbol uses the phase from the last preamble SYNCP symbol and the first data symbol uses the phase from the last FCH symbol. In the figures, "GI" stands for guard interval, which is the interval containing the cyclic prefix. + +![Figure 7-2 – Typical data frame structure. The diagram shows a sequence of symbols: 8x SYNCP, 1.5x SYNCM, followed by a series of FCH symbols (GI, FCH1, GI, FCH2, GI, FCH3, ..., GI, FCH13, GI) and then DATA (D1, ...). The first part is labeled 'PREAMBLE'. The FCH symbols are grouped under a bracket labeled 'FCH'. The DATA part is labeled 'DATA'. Arrows labeled 'Overlap' point to the boundaries between the GI and FCH symbols. A reference code 'G.9903(12)-Amd.1(13)_F7-2' is at the bottom right.](c5452f95f3b28f1bfe29e84fbc2e1267_img.jpg) + +Figure 7-2 – Typical data frame structure. The diagram shows a sequence of symbols: 8x SYNCP, 1.5x SYNCM, followed by a series of FCH symbols (GI, FCH1, GI, FCH2, GI, FCH3, ..., GI, FCH13, GI) and then DATA (D1, ...). The first part is labeled 'PREAMBLE'. The FCH symbols are grouped under a bracket labeled 'FCH'. The DATA part is labeled 'DATA'. Arrows labeled 'Overlap' point to the boundaries between the GI and FCH symbols. A reference code 'G.9903(12)-Amd.1(13)\_F7-2' is at the bottom right. + +**Figure 7-2 – Typical data frame structure** + +The PHY also supports an ACK/NACK frame which only consists of the preamble and the FCH. The frame structure of the ACK frame is shown in Figure 7-3. The bit fields in the FCH, explained in clause 7.6, will perform the ACK/NACK signalling. + +![Figure 7-3 – ACK/NACK frame structure. The diagram shows a sequence of symbols: 8x SYNCP, 1.5x SYNCM, followed by a series of FCH symbols (GI, FCH1, GI, FCH2, GI, FCH3, ..., GI, FCH13). The first part is labeled 'PREAMBLE'. The FCH symbols are grouped under a bracket labeled 'FCH'. Arrows labeled 'Overlap' point to the boundaries between the GI and FCH symbols. A reference code 'G.9903(12)-Amd.1(13)_F7-3' is at the bottom right.](ae53f90bb87d6d09e2d6b5278d7c338f_img.jpg) + +Figure 7-3 – ACK/NACK frame structure. The diagram shows a sequence of symbols: 8x SYNCP, 1.5x SYNCM, followed by a series of FCH symbols (GI, FCH1, GI, FCH2, GI, FCH3, ..., GI, FCH13). The first part is labeled 'PREAMBLE'. The FCH symbols are grouped under a bracket labeled 'FCH'. Arrows labeled 'Overlap' point to the boundaries between the GI and FCH symbols. A reference code 'G.9903(12)-Amd.1(13)\_F7-3' is at the bottom right. + +**Figure 7-3 – ACK/NACK frame structure** + +## 7.5 Preamble + +The preamble is composed of 8 identical SYNCP symbols and 1½ identical SYNCM symbols. Each of the SYNCP and SYNCM symbols is 256 samples and is pre-stored in the transmitter and transmitted right before the data symbols. The SYNCP symbols are used for AGC adaptation, symbol synchronization, channel estimation and initial phase reference estimation. The SYNCM symbols are identical to the SYNCP symbols except that all the subcarriers are $\pi$ phase shifted. At the receiver, the phase distance between symbol SYNCP and symbol SYNCM waveforms is used for frame synchronization. A SYNCP symbol is generated by creating the desired number of equally spaced subcarriers with the phase of each subcarrier given by $\phi_c$ . One way to generate this signal is to start in the frequency domain and create complex subcarriers with the initial phases $\phi_c$ , as shown in Tables 7-9, 7-10 and 7-11. Figure 7-15 shows how the subcarriers are mapped to the IFFT input. + +All preamble symbols (SYNCP and SYNCM) shall have the same gain factor compared to data symbols. The gain is defined to be 3 dB. + +**Table 7-9 – Preamble phase vector for CENELEC-A bandplan** + +| c | $\phi_c$ | c | $\phi_c$ | c | $\phi_c$ | +|----|-------------|----|-------------|----|-------------| +| 23 | $2(\pi/8)$ | 35 | $1(\pi/8)$ | 47 | $13(\pi/8)$ | +| 24 | $1(\pi/8)$ | 36 | $11(\pi/8)$ | 48 | $2(\pi/8)$ | +| 25 | $0(\pi/8)$ | 37 | $5(\pi/8)$ | 49 | $6(\pi/8)$ | +| 26 | $15(\pi/8)$ | 38 | $14(\pi/8)$ | 50 | $10(\pi/8)$ | +| 27 | $14(\pi/8)$ | 39 | $7(\pi/8)$ | 51 | $13(\pi/8)$ | + +**Table 7-9 – Preamble phase vector for CENELEC-A bandplan** + +| c | \phi_c | c | \phi_c | c | \phi_c | +|----------|----------------------------|----------|----------------------------|----------|----------------------------| +| 28 | $12(\pi/8)$ | 40 | $15(\pi/8)$ | 52 | 0 | +| 29 | $10(\pi/8)$ | 41 | $7(\pi/8)$ | 53 | $2(\pi/8)$ | +| 30 | $7(\pi/8)$ | 42 | $15(\pi/8)$ | 54 | $3(\pi/8)$ | +| 31 | $3(\pi/8)$ | 43 | $6(\pi/8)$ | 55 | $5(\pi/8)$ | +| 32 | $15(\pi/8)$ | 44 | $13(\pi/8)$ | 56 | $6(\pi/8)$ | +| 33 | $11(\pi/8)$ | 45 | $2(\pi/8)$ | 57 | $7(\pi/8)$ | +| 34 | $6(\pi/8)$ | 46 | $8(\pi/8)$ | 58 | $7(\pi/8)$ | + +**Table 7-10 – Preamble phase vector for CENELEC B bandplan** + +| C | \phi_c | c | \phi_c | c | \phi_c | +|----------|----------------------------|----------|----------------------------|----------|----------------------------| +| 63 | $2(\pi/8)$ | 69 | $15(\pi/8)$ | 75 | $5(\pi/8)$ | +| 64 | $1(\pi/8)$ | 70 | $8(\pi/8)$ | 76 | $7(\pi/8)$ | +| 65 | $15(\pi/8)$ | 71 | 0 | 77 | $9(\pi/8)$ | +| 66 | $13(\pi/8)$ | 72 | $7(\pi/8)$ | 78 | $10(\pi/8)$ | +| 67 | $10(\pi/8)$ | 73 | $13(\pi/8)$ | | | +| 68 | $5(\pi/8)$ | 74 | $2(\pi/8)$ | | | + +**Table 7-11 – Preamble phase vector for FCC bandplan** + +| C | \phi_c | C | \phi_c | C | \phi_c | c | \phi_c | +|----------|----------------------------|----------|----------------------------|----------|----------------------------|----------|----------------------------| +| | | | | 52 | $10(\pi/8)$ | 77 | $8(\pi/8)$ | +| | | | | 53 | $5(\pi/8)$ | 78 | $14(\pi/8)$ | +| | | | | 54 | 0 | 79 | $3(\pi/8)$ | +| | | | | 55 | $12(\pi/8)$ | 80 | $9(\pi/8)$ | +| | | | | 56 | $6(\pi/8)$ | 81 | $15(\pi/8)$ | +| | | | | 57 | $1(\pi/8)$ | 82 | $3(\pi/8)$ | +| | | 33 | $2(\pi/8)$ | 58 | $12(\pi/8)$ | 83 | $8(\pi/8)$ | +| | | 34 | $(\pi/8)$ | 59 | $6(\pi/8)$ | 84 | $13(\pi/8)$ | +| | | 35 | $(\pi/8)$ | 60 | 0 | 85 | $\pi/8$ | +| | | 36 | 0 | 61 | $10(\pi/8)$ | 86 | $5(\pi/8)$ | +| | | 37 | 0 | 62 | $3(\pi/8)$ | 87 | $9(\pi/8)$ | +| | | 38 | $15(\pi/8)$ | 63 | $13(\pi/8)$ | 88 | $13(\pi/8)$ | +| | | 39 | $14(\pi/8)$ | 64 | $6(\pi/8)$ | 89 | $\pi/8$ | +| | | 40 | $12(\pi/8)$ | 65 | $15(\pi/8)$ | 90 | $4(\pi/8)$ | +| | | 41 | $11(\pi/8)$ | 66 | $7(\pi/8)$ | 91 | $7(\pi/8)$ | + +**Table 7-11 – Preamble phase vector for FCC bandplan** + +| C | $\phi_c$ | C | $\phi_c$ | C | $\phi_c$ | c | $\phi_c$ | +|---|----------|----|-------------|----|-------------|-----|-------------| +| | | 42 | $9(\pi/8)$ | 67 | 0 | 92 | $10(\pi/8)$ | +| | | 43 | $7(\pi/8)$ | 68 | $8(\pi/8)$ | 93 | $13(\pi/8)$ | +| | | 44 | $4(\pi/8)$ | 69 | 0 | 94 | $15(\pi/8)$ | +| | | 45 | $\pi/8$ | 70 | $8(\pi/8)$ | 95 | $\pi/8$ | +| | | 46 | $15(\pi/8)$ | 71 | $15(\pi/8)$ | 96 | $3(\pi/8)$ | +| | | 47 | $12(\pi/8)$ | 72 | $6(\pi/8)$ | 97 | $4(\pi/8)$ | +| | | 48 | $9(\pi/8)$ | 73 | $14(\pi/8)$ | 98 | $5(\pi/8)$ | +| | | 49 | $5(\pi/8)$ | 74 | $4(\pi/8)$ | 99 | $7(\pi/8)$ | +| | | 50 | $(\pi/8)$ | 75 | $11(\pi/8)$ | 100 | $7(\pi/8)$ | +| | | 51 | $14(\pi/8)$ | 76 | $2(\pi/8)$ | 101 | $8(\pi/8)$ | +| | | | | | | 102 | $9(\pi/8)$ | +| | | | | | | 103 | $10(\pi/8)$ | +| | | | | | | 104 | $10(\pi/8)$ | + +## 7.6 Frame control header + +The FCH is a data structure transmitted at the beginning of each PHY data frame and contains information regarding the current frame. It has information about the type of frame, the tone map index of the frame, the length of the frame, etc. The FCH data is protected with CRC5 for CENELEC bandplans and CRC8 for FCC bandplan. Clauses 7.6.1 and 7.6.2 define the structure of the FCH and the calculation of the associated CRC. The FCH shall use the default tone map (all unmasked subcarriers). + +### 7.6.1 CENELEC bandplans + +The thirteen data symbols immediately after the preamble are used for the frame control header (FCH). They are transmitted in super robust mode (see clause 7.9.3.2) regardless of the modulation type and scheme of the payload. Its structure is given in Table 7-12 for the data frame and Table 7-14 for the ACK/NACK frame. + +#### 7.6.1.1 FCH for a data frame + +Bandplans are divided into sub-bands (groups of tones) to selectively adapt to the quality of the media (see clause 7.15). For the CENELEC bandplans, each sub-band contains 6 tones. Each bit of the tone map field is associated with one sub-band (a group of 6 tones), indicating if it carries data. The 6-bit tone map field covers all the CENELEC bandplans. Each bit set to one indicates that the associated group of tones carries data in the payload of the PHY frame. + +The tone map splitting for CENELEC bandplans is given in Table 7-13. + +**Table 7-12 – FCH bit fields for data frames for CENELEC bandplans** + +| Field | Byte | Bit number | Bits | Description | +|---------------------------|------|------------|------|----------------------------------------------------------------------------------------------------------------------------------------| +| PDC | 0 | 7-0 | 8 | Phase detection counter (see clause 8.10) | +| MOD | 1 | 7-6 | 2 | Modulation type:
0: Robust Mode (see clause 7.9.3)
1: DBPSK or BPSK
2: DQPSK or QPSK
3: D8PSK or 8-PSK | +| FL | 1 | 5-0 | 6 | PHY frame length in PHY symbols FL gives the number of symbols in the frame according to the formula $FL = \text{Number of symbols}/4$ | +| Reserved by ITU-T | 2 | 7-6 | 2 | Shall be set to zero | +| TM[5:0] | 2 | 5-0 | 6 | TM[5:0] – Tone map
In CENELEC-B bandplan, TM[5:3] are reserved by ITU-T and shall be set to zero | +| Payload modulation scheme | 3 | 7 | 1 | 0: Differential
1: Coherent
Note – The coherent modulation scheme specified in clause 7.16 is optional | +| DT | 3 | 6-4 | 3 | Delimiter type:
0: Acknowledgment is not requested
1: Acknowledgment is requested
2-7: Reserved by ITU-T | +| FCCS | 3 | 3-0 | 4 | Frame control check sequence (CRC5)
(see clause 7.6.1.3) | +| | 4 | 7 | 1 | | +| ConvZeros | 4 | 6-1 | 6 | 6 zeros for convolutional encoder | + +**Table 7-13 – Tone map field mapping for CENELEC bandplans** + +| Tone map field | CENELEC-A bandplan | CENELEC-B bandplan | +|----------------|-----------------------|--------------------------| +| TM[0] | 35.9375 to 43.75 kHz | 98.4375 to 106.25 kHz | +| TM[1] | 45.3125 to 53.125 kHz | 107.8125 to 115.625 kHz | +| TM[2] | 54.6875 to 62.5 kHz | 117.1875 to 121.875 kHz | +| TM[3] | 64.0625 to 71.875 kHz | Unused in CENELEC-B band | +| TM[4] | 73.4375 to 81.25 kHz | Unused in CENELEC-B band | +| TM[5] | 82.8125 to 90.625 kHz | Unused in CENELEC-B band | + +#### 7.6.1.2 FCH for ACK/NACK frame + +Table 7-14 shows the structure of a positive acknowledgment (ACK) or a negative acknowledgment (NACK). A node shall send an ACK or a NACK after receiving a data frame with an FCH requiring an answer (with the delimiter type field set to 1). + +**Table 7-14 – FCH bit fields for ACK/NACK frames for CENELEC bandplans** + +| Field | Byte | Bit number | Bits | Description | +|-------------------|------|------------|------|------------------------------------------------------------------------------------------------------------------------------------------------| +| FCS-1 | 0 | 7-0 | 8 | MAC FCS[7:0] | +| SSCA | 1 | 7 | 1 | Subsequent segment collision avoidance (see clause 9.3.2):
0: No further segment is expected
1: Further segments are expected | +| Reserved by ITU-T | 1 | 6-0 | 7 | Shall be set to zero | +| FCS-2 | 2 | 7-0 | 8 | MAC FCS[15:8] | +| Reserved by ITU-T | 3 | 7 | 1 | Shall be set to zero | +| DT | 3 | 6-4 | 3 | Delimiter type:
0-1: Reserved by ITU-T
2: Positive acknowledgement (ACK)
3: Negative acknowledgement (NACK)
4-7: Reserved by ITU-T | +| FCCS | 3 | 3-0 | 4 | Frame control check sequence (CRC5) (see clause 7.6.1.3) | +| | 4 | 7 | 1 | | +| ConvZeros | 4 | 6-1 | 6 | 6 zeros for convolutional encoder | + +#### 7.6.1.3 CRC5 + +A 5-bit cyclic redundancy check (CRC) is used for error detection in the FCH. The CRC5 is computed using an initial value of 0b11111. The CRC5 is calculated using the following standard generator polynomial of degree 5: + +$$G(x) = x^5 + x^2 + 1$$ + +Data bits are shifted to the CRC5 register starting with the most significant bit of the first byte of the FCH. The CRC5 is the remainder of the division of the FCH polynomial by the generator polynomial. The one's complement of the remainder is used as the FCCS for the FCH, where the FCCS field is packed as follows: bit 3 to bit 0 of Byte 3 are packed with FCCS bit 3 to bit 0, respectively, and bit 7 of Byte 4 is packed with FCCS bit 4 (MSB). + +### 7.6.2 FCC bandplan + +The twelve data symbols immediately after the preamble constitute the frame control header (FCH). They are transmitted in super robust mode (see clause 7.9.3.2) using BPSK with coherent modulation regardless of the modulation type and scheme of the payload. However, no pilot tone shall be inserted in the frame control header. If the payload modulation scheme is differential, the S1 and S2 symbols shall not be included after the FCH. Its structure is given in Table 7-15 for the data frame and Table 7-16 for the ACK/NACK frame. + +#### 7.6.2.1 FCH for a data frame + +The bandplan is divided into sub-bands (groups of tones) to selectively adapt to the quality of the media (see clause 7.15). For the FCC bandplan, each sub-band contains 3 tones. Each bit of the tone map field is associated with one sub-band, indicating if it carries data. The tone map field is a 24 bit field which covers the FCC bandplan. Each bit set to one indicates that the associated group of tones carries data in the payload of the PHY frame. + +**Table 7-15 – FCH bit fields for data frames for the FCC bandplan** + +| Field | Byte | Bit Number | Bits | Description | +|---------------------------|------|------------|------|------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| PDC | 0 | 7-0 | 8 | Phase detection counter (see clause 8.10) | +| MOD | 1 | 7-5 | 3 | Modulation type
0: Robust mode (differential or coherent)
1: DBPSK or BPSK
2: DQPSK or QPSK
3: D8PSK or 8-PSK
4: 16-QAM
5-7: Reserved by ITU-T | +| Payload modulation scheme | 1 | 4 | 1 | Payload modulation scheme:
0: Differential
1: Coherent
NOTE – The coherent modulation scheme, specified in clause 7.16, is optional. | +| DT | 1 | 3-1 | 3 | Delimiter type:
0: Start of frame with no response expected
1: Start of frame with response expected
2-7: Reserved by ITU-T | +| FL | 1 | 0 | 1 | PHY frame length in PHY symbols. FL represents the number of symbols in the frame | +| | 2 | 7-0 | 8 | | +| TM[7:0] | 3 | 7-0 | 8 | TM[7:0]: Tone map | +| TM[15:8] | 4 | 7-0 | 8 | TM[15:8]: Tone map | +| TM[23:16] | 5 | 7-0 | 8 | TM[23:16]: Tone map | +| Reserved by ITU-T | 6 | 7-5 | 3 | Shall be set to zero | +| Two RS Blocks | 6 | 4 | 1 | 0: Transmitter is transmitting two RS blocks.
1: Transmitter is transmitting one RS block. | +| Reserved by ITU-T | 6 | 3-0 | 4 | Shall be set to zero | +| Reserved by ITU-T | 7 | 7-6 | 2 | Shall be set to zero | +| FCCS | 7 | 5-0 | 6 | Frame control check sequence (CRC8) | +| | 8 | 7-6 | 2 | | +| ConvZeros | 8 | 5-0 | 6 | Zeros for convolutional encoder | + +#### 7.6.2.2 FCH for ACK/NACK frame + +Table 7-16 shows the structure of a positive acknowledgment (ACK) or a negative acknowledgment (NACK) that a node shall send after receiving a data frame with an FCH requiring an answer (with the delimiter type field set to 1). + +**Table 7-16 – FCH bit fields for ACK/NACK frames for FCC bandplan** + +| Field | Byte | Bit Number | Bits | Description | +|-------------------|------|------------|------|-------------------------------------------------------------------------------------------------------------------------------------------------| +| FCS-1 | 0 | 7-0 | 8 | MAC FCS[7:0] | +| SSCA | 1 | 7 | 1 | Subsequent segment collision avoidance (see clause 9.3.2):
0: No further segment is expected
1: Further segments are expected | +| Reserved by ITU-T | 1 | 6 – 4 | 3 | Shall be set to zero | +| DT | 1 | 3 - 1 | 3 | Delimiter type:
0-1 : Reserved by ITU-T
2: Positive acknowledgement (ACK)
3: Negative acknowledgement (NACK)
4-7: Reserved by ITU-T | +| Reserved by ITU-T | 1 | 0 | 1 | Shall be set to zero | +| Reserved by ITU-T | 2 | 7-0 | 8 | Shall be set to zero | +| FCS-2 | 3 | 7-0 | 8 | MAC FCS[15:8] | +| Reserved by ITU-T | 4 | 7-0 | 8 | Shall be set to zero | +| Reserved by ITU-T | 5 | 7-0 | 8 | Shall be set to zero | +| Reserved by ITU-T | 6 | 7-0 | 8 | Shall be set to zero | +| Reserved by ITU-T | 7 | 7-6 | 2 | Shall be set to zero | +| FCCS | 7 | 5-0 | 6 | Frame control check sequence (CRC8) (see clause 7.6.2.3) | +| | 8 | 7-6 | 2 | | +| ConvZeros | 8 | 5-0 | 6 | Zeros for convolutional encoder | + +#### 7.6.2.3 CRC8 + +An 8-bit cyclic redundancy check (CRC) is used for error detection in the FCH. The CRC8 is computed as a function of the 58-bit sequence using an initial value of 0xFF. The CRC8 is calculated using the following eighth degree generator polynomial: + +$$G(x) = x^8 + x^2 + x + 1$$ + +Data bits are shifted to the CRC8 register starting with the most significant bit of the first byte of the FCH. The CRC8 is the remainder of the division of the FCH polynomial by the generator polynomial. The one's complement of the remainder is used as the FCCS for the FCH, where the FCCS field is packed as follows: bit 5 to bit 0 of Byte 7 are packed with FCCS bit 7 to bit 2, respectively, and bit 7 to bit 6 of Byte 8 are packed with FCCS bit 1 to bit 0 (LSB). + +## 7.7 Payload of PHY frame + +The data to transport in a physical frame (PSDU) is provided by the upper layer as a byte stream and is read most significant bit first into the scrambler. The upper layer shall be responsible for padding the data to accommodate the requirement of the PHY layer (see clause I.1). + +## 7.8 Scrambler + +The data scrambler block helps give the data a random distribution. The data stream is 'XOR-ed' with a repeating PN sequence using the following generator polynomial: + +$$S(x) = x^7 \oplus x^4 \oplus 1$$ + +This is illustrated in Figure 7-4. The bits in the scrambler are initialized to all-ones at the start of processing the FCH and at the start of processing the PHY payload. + +![Figure 7-4 – Data scrambler diagram. The diagram shows a feedback loop with two shift registers. The first register contains bits X^7, X^6, X^5. The second register contains bits X^4, X^3, X^2, X^1. The output of the second register is summed with 'Data in' at an adder to produce 'Scrambled data out'. The output of the first register is summed with the output of the second register at another adder, and the result is fed back to the input of the first register. The diagram is labeled G.9903(12)-Amd.1(13)_F7-4.](5d3455c6c2a37cb3aff761fedeb8644e_img.jpg) + +Figure 7-4 – Data scrambler diagram. The diagram shows a feedback loop with two shift registers. The first register contains bits X^7, X^6, X^5. The second register contains bits X^4, X^3, X^2, X^1. The output of the second register is summed with 'Data in' at an adder to produce 'Scrambled data out'. The output of the first register is summed with the output of the second register at another adder, and the result is fed back to the input of the first register. The diagram is labeled G.9903(12)-Amd.1(13)\_F7-4. + +Figure 7-4 – Data scrambler + +## 7.9 FEC coding + +The FEC encoder is composed of a Reed-Solomon encoder followed by a convolutional encoder. In robust mode, an encoder, namely, repetition code by 4, is used after the convolutional encoder in order to repeat the bits at the output of convolutional encoder four times. In super robust mode, an encoder, namely, repetition code by 6, is used after the convolutional encoder in order to repeat the bits at the output of the convolutional encoder six times. + +### 7.9.1 Reed-Solomon encoder + +For the data portion of a frame, data from the scrambler is encoded by shortened systematic codes using Galois field $GF(2^8)$ . Only one RS block is used by a frame. Depending on the mode used the following parameters are applied: + +- Normal mode: RS( $N = 255$ , $K = 239$ , $T = 8$ ) + - Robust mode: RS( $N = 255$ , $K = 247$ , $T = 4$ ) +- The RS symbol word length (i.e., the size of the data words used in the Reed-Solomon block) is fixed at 8 bits. The value of $T$ (number of correctable symbol errors) can be either 4 or 8 for different configurations. For the robust mode, the code with $T=4$ is used. The number of parity words in an RS-block is $2T$ bytes. + +$$\text{Code generator polynomial } g(x) = \prod_{i=1}^{2T} (x - \alpha^i)$$ + +$$\text{Field generator polynomial: } p(x) = x^8 + x^4 + x^3 + x^2 + 1 \text{ (435 octal)}$$ + +The representation of $\alpha^0$ is "00000001", where the left most bit of this RS symbol is the MSB and is the first in time from the scrambler and is the first in time out of the RS encoder. + +The arithmetic is performed in the Galois field $GF(2^8)$ , where $\alpha^1$ is a primitive element that satisfies the primitive binary polynomial $x^8 + x^4 + x^3 + x^2 + 1$ . A data byte $(d^7, d^6, \dots, d^1, d^0)$ is identified with the Galois field element $d^7\alpha^7 + d^6\alpha^6 + \dots + d^1\alpha + d^0$ . + +The first bit in time from the data scrambler becomes the most significant bit of the symbol at the input of the RS encoder. Each RS encoder input block is formed by one or more fill symbols ("00000000") followed by the message symbols. Output of the RS encoder (with fill symbols discarded) proceeds in time from the first message symbol to the last message symbol followed by parity symbols, with each symbol shifted out most significant bit first. + +ITU-TG.9903 devices have the option to split a packet of any size into two RS blocks. The "Two RS Blocks" bit in its FCH shall be set to specify whether one or two RS blocks are being transmitted. + +### 7.9.2 Convolutional encoder + +The bit stream at the output of the Reed-Solomon block is encoded with a standard rate = 1/2, K=7 convolutional encoder. The tap connections are defined as $x = 0b1111001$ and $y = 0b1011011$ , as shown in Figure 7-5. + +![Diagram of a convolutional encoder with rate 1/2 and constraint length K=7. The input data 'I' enters a series of six delay elements (squares). The output of the encoder is split into two paths: 'X output (G1 = 171_8)' and 'Y output (G2 = 133_8)'. Each output path is the result of an XOR operation (represented by a circle with a cross) between the input data and a combination of the outputs of the delay elements. The text 'Rate - 1/2, constraint length K = 7' is shown below the diagram. A reference code 'G.9903(12)-Amd.1(13)_F7-5' is in the bottom right corner.](14252bcd35912bd656e98b16b2ee51c0_img.jpg) + +Diagram of a convolutional encoder with rate 1/2 and constraint length K=7. The input data 'I' enters a series of six delay elements (squares). The output of the encoder is split into two paths: 'X output (G1 = 171\_8)' and 'Y output (G2 = 133\_8)'. Each output path is the result of an XOR operation (represented by a circle with a cross) between the input data and a combination of the outputs of the delay elements. The text 'Rate - 1/2, constraint length K = 7' is shown below the diagram. A reference code 'G.9903(12)-Amd.1(13)\_F7-5' is in the bottom right corner. + +Figure 7-5 – Convolutional encoder + +When the last bit of data to the convolutional encoder has been received, the convolutional encoder inserts six tail bits which are required to return the convolutional encoder to the "zero state". This improves the error probability of the convolutional decoder, which relies on future bits when decoding. The tail bits are defined as six zeros. + +For CENELEC bandplans, zero bit padding is used to fit the encoded bits into a number of OFDM symbols that is a multiple of 4. The location of the bit padding shall be at the end of the convolutional encoder output and, in case of the robust mode, the bit padding is done before the repetition block. + +#### 7.9.2.1 Encoding 2 Reed-Solomon blocks + +If the transmitter decides to divide the PSDU it shall be divided into two equal-size RS blocks, neither of which shall exceed the maximum size of 255 octets (including the parity octets). The bit padding is done for each RS block separately. + +The PHY shall split the PSDU into two RS blocks after the scrambler, and then it shall pass each block to the RS encoder separately. The resulting two consecutive RS blocks shall then be passed to the convolutional encoder and each block shall be encoded separately. The output of the convolutional encoder has two equal-size segments and each segment shall be independently repetition encoded (if needed), zero bit padded (if needed), and interleaved. In other words, each RS block in the two RS blocks case shall be processed in the same way as in the single RS block case. All interleaver output is then treated as a whole. There shall be no re-initialization of the PN sequence for mapping or pilot tone computation between the two RS blocks. + +### 7.9.3 Robust and super robust modes + +Robust and super robust modes provide extensive time and frequency diversity to improve the ability of the system to operate under adverse conditions. + +#### 7.9.3.1 Repetition coding by 4 + +In robust mode, every bit at the output of the convolutional encoder is repeated four times and then passed as input to the interleaver as described in clause 7.10. This encoder (RC4) is only activated in robust mode. The underlying modulation type may be either DBPSK or BPSK according to the modulation scheme used for the payload. + +#### 7.9.3.2 Repetition coding by 6 + +In the super robust mode, every bit at the output of the convolutional encoder is repeated six times and then passed as input to the interleaver as described in clause 7.10. Only the FCH uses the super robust mode but without Reed-Solomon encoding. The underlying modulation type shall always be DBPSK. + +## 7.10 Interleaver + +The interleaver is designed as such so that it can provide protection against two different sources of error: + +- A burst error that corrupts a few consecutive OFDM symbols. +- A frequency deep fade that corrupts a few adjacent frequencies for a large number of OFDM symbols. + +To fight both problems at the same time, interleaving is done in two steps. In the first step, each column is circularly shifted a different number of times. Therefore, a corrupted OFDM symbol is spread over different symbols. In the second step, each row is circularly shifted a different number of times, which prevents a deep frequency fade from disrupting the whole column. + +The elementary interleaver is used for CENELEC and FCC bandplans when macCENELECLegacyMode or macFCCLegacyMode is set to 0. Otherwise, the full block interleaver is processed for all bandplans. + +### 7.10.1 Elementary interleaver + +We define $m$ as the number of used data carriers in each OFDM symbol, $n$ as the number of OFDM symbols used by the frame and $total\_number\_of\_bits$ as the total number of coded bits without zero padding bits in the frame. + +$$n = \text{ceil} \left( \frac{Total\_number\_of\_bits}{FL_{Band} * m * mod_{size}} \right) * FL_{Band}$$ + +with: + +- $mod_{size}=1, 2, 3, 4$ is the modulation size, i.e., the number of bits per constellation symbol and +- $FL_{Band} = 4$ for CENELEC bandplans and $FL_{Band} = 1$ for FCC bandplan. + +From $m$ and $n$ the circular shift parameters $m_i, m_j, n_i$ and $n_j$ are derived. + +To get a proper parameter set, $m_i, m_j, n_i$ and $n_j$ should be the smallest figures to comply with these conditions: + +- $\text{GCD}(m_i, m) = \text{GCD}(m_j, m) = 1$ +- $m_i < m_j < m$ +- $\text{GCD}(n_i, n) = \text{GCD}(n_j, n) = 1$ +- $n_j < n_i < n$ + +These parameters form an elementary permutation matrix (dimensions are $m$ columns and $n$ rows) taking input bits from their original position to the interleaved position following the formula below: + +$$\begin{aligned} J_{(i,j)} &= (j \times n_j + i \times n_i) \% n \\ I_{(i,j)} &= (i \times m_i + j \times m_j) \% m \end{aligned}$$ + +where: + +- $(i,j)$ are the original bit position ( $i = 0, 1, \dots, m-1$ and $j = 0, 1, \dots, n-1$ ) +- $(I,J)$ are their corresponding interleaved position. + +When macCENELECLegacyMode or macFCCLegacyMode is different from 0, and if the initial value $I_{(1,0)}$ is zero, the circular shift parameters $n_j$ and $n_i$ shall be swapped before performing interleaving. $I_{(1,0)}$ is computed as: + +$$I_{(1,0)} = ( 1 \times m_i + J_{(1,0)} \times m_j ) \% m \text{ and } J_{(1,0)} = ( 0 \times n_j + 1 \times n_i ) \% n.$$ + +In this case, the interleaved position follows the formula below: + +$$J_{(i,j)} = ( j \times n_i + i \times n_j ) \% n$$ + +$$I_{(i,j)} = ( i \times m_i + J_{(i,j)} \times m_j ) \% m$$ + +where: + +$(i,j)$ are related to the original bit position ( $i = 0, 1, \dots, m-1$ and $j = 0, 1, \dots, n-1$ ) + +$(I,J)$ are related to the corresponding interleaved position. + +For DBPSK or BPSK modulation, the permutation matrix corresponds to the elementary permutation matrix while other modulations use multiple times the elementary permutation matrix. Thus, the dimensions of the permutation matrix for DQPSK, QPSK, D8PSK and 8-PSK modulations are $m$ columns and $n \times \text{mod\_size}$ rows. + +The data to be interleaved are stored in the input buffer and shows which dimensions are $m$ columns and $n \times \text{mod\_size}$ rows. + +The data bits are put in the input buffer row by row, as shown in Figure 7-6. Zero padding will be used to match permutation matrix dimensions. + +![Figure 7-6: Bit order input into the input buffer. A diagram showing a grid of cells representing the input buffer. The horizontal axis is labeled 'Subcarrier Number' and 'i = 0...m-1'. The vertical axis is labeled 'j = 0...n x mod_size - 1'. The grid has columns labeled 0, 1, ..., m-1 and rows labeled m, m+1, ..., 2m-1. The bottom row is labeled (n x mod_size - 1) x m. The bottom right cell is labeled n x mod_size x m - 1. A small label G.9903(12)-Amd.1(13)_F7-6 is at the bottom right.](b54ce9bffd341cd643e196d5f4538829_img.jpg) + +Subcarrier Number + $i = 0 \dots m-1$ + +| | | | | +|--------------------------------------------|-------|-----|------------------------------------------| +| 0 | 1 | ... | $m-1$ | +| $m$ | $m+1$ | ... | $2m-1$ | +| | | | | +| | | | | +| $(n \times \text{mod\_size} - 1) \times m$ | | | $n \times \text{mod\_size} \times m - 1$ | + +G.9903(12)-Amd.1(13)\_F7-6 + +Figure 7-6: Bit order input into the input buffer. A diagram showing a grid of cells representing the input buffer. The horizontal axis is labeled 'Subcarrier Number' and 'i = 0...m-1'. The vertical axis is labeled 'j = 0...n x mod\_size - 1'. The grid has columns labeled 0, 1, ..., m-1 and rows labeled m, m+1, ..., 2m-1. The bottom row is labeled (n x mod\_size - 1) x m. The bottom right cell is labeled n x mod\_size x m - 1. A small label G.9903(12)-Amd.1(13)\_F7-6 is at the bottom right. + +**Figure 7-6 – Bit order input into the input buffer** + +Once interleaved each bit is stored in an output buffer as shown in Figure 7-7. + +![Figure 7-7: Permutation matrix used with different modulations. The diagram shows three rows of processing. The first row is for DBPSK modulation, showing a 2x4 input buffer, an elementary permutation matrix, and a 2x4 output buffer. The second row is for DQPSK modulation, showing a 4x4 input buffer, a 2x4 permutation matrix (composed of two elementary permutation matrices), and a 4x4 output buffer. The third row is for D8PSK modulation, showing a 6x4 input buffer, a 3x4 permutation matrix (composed of three elementary permutation matrices), and a 6x4 output buffer. Each row has arrows indicating the flow from input buffer to modulation block to output buffer.](f9c64800d9bace9b4315646d1057be3c_img.jpg) + +G.9903(12)-Amd.1(13)\_F7-7 + +Figure 7-7: Permutation matrix used with different modulations. The diagram shows three rows of processing. The first row is for DBPSK modulation, showing a 2x4 input buffer, an elementary permutation matrix, and a 2x4 output buffer. The second row is for DQPSK modulation, showing a 4x4 input buffer, a 2x4 permutation matrix (composed of two elementary permutation matrices), and a 4x4 output buffer. The third row is for D8PSK modulation, showing a 6x4 input buffer, a 3x4 permutation matrix (composed of three elementary permutation matrices), and a 6x4 output buffer. Each row has arrows indicating the flow from input buffer to modulation block to output buffer. + +**Figure 7-7 – Permutation matrix used with different modulations** + +After interleaving, the mapping functions used for modulation read the output buffer row by row. Each sequence of *modsize* bit(s) is (are) computed to form a symbol. + +An example is given here for information purposes. + +A simple search is done to find a good set of parameters based on $m$ and $n$ . + +For a given value of $n$ , $n_j$ shall be the first co-prime larger than 2 and $n_i$ shall be the second co-prime larger than 2. When macCENELEClegacyMode or macFCClegacyMode is different from 0 and if the initial value $I_{(1,0)}$ is zero, the circular shift parameters $n_i$ and $n_j$ shall be swapped. Similarly, for a given value of $m$ , $m_i$ shall be the first co-prime larger than 2 and $m_j$ shall be the second co-prime larger than 2. If it is not possible to find (a) required co-prime number(s) in normal or swapping case, a default value of 1 shall be used. In this special case, the condition $n_j$ less than $n_i$ or $m_i$ less than $m_j$ does not apply. + +Figure 7-8 displays the spreading behaviour of the interleaver for $n = 8$ , $m = 10$ , $n_i = 5$ , $n_j = 3$ , $m_i = 3$ and $m_j = 7$ . + +![Figure 7-8: Example of spreading behaviour. Two 8x10 grids are shown. The left grid has a vertical column of 8 cells shaded, labeled 'Position (i, j)'. The right grid has 8 cells shaded at various positions, labeled 'Position (I, J)'. Between the grids are the equations J = (3j + 5i) mod 8 and I = (3i + 7j) mod 10. A small label G.9903(12)-Amd.1(13)_F7-8 is at the bottom right.](e451401f8fa77b466f401d5fce15b26c_img.jpg) + +Figure 7-8: Example of spreading behaviour. Two 8x10 grids are shown. The left grid has a vertical column of 8 cells shaded, labeled 'Position (i, j)'. The right grid has 8 cells shaded at various positions, labeled 'Position (I, J)'. Between the grids are the equations J = (3j + 5i) mod 8 and I = (3i + 7j) mod 10. A small label G.9903(12)-Amd.1(13)\_F7-8 is at the bottom right. + +**Figure 7-8 – Example of spreading behaviour** + +The calculation of $n_i$ , $n_j$ , $m_i$ and $m_j$ are explained as below: + +- $n = 8$ (co-prime numbers for 8 except 1 and 2 are: 3, 5, 7). The first number is 3, so $n_j = 3$ ; and the next co-prime with 8 is 5, so $n_i = 5$ ; that is the first co-prime number other than 1 and 2 of $n$ shall be $n_j$ , and the second co-prime of $n$ other than 1 and 2 shall be $n_i$ ; +- $m = 10$ (co-prime numbers for 10 except 1 and 2 are: 3, 7, 9). The first number we meet in the set is 3, so $m_i = 3$ ; and the next is 7, so $m_j = 7$ ; that is the first co-prime of $m$ other than 1 and 2 shall be $m_i$ , and the next co-prime shall be $m_j$ . + +Here, we use DBPSK and DQPSK as examples. Suppose we have 3 active tones ( $m = 3$ ) and 2 symbols ( $n = 2$ ). + +With DBPSK modulation: + +If the input bit stream is "123456", the input bit stream will be loaded into the matrix as Figure 7-9(a). The vertical dimension of the matrix is $n \times \text{mod\_size}$ (i.e., $2 \times 1 = 2$ ). After that, interleaving is done with interleaving block size $n \times m$ (i.e., $2 \times 3$ ). After all the bits have been processed, the bits 1'2'3'...6' are mapped to the modulator as shown in Figure 7-9(c). + +![Figure 7-9: Example of interleaving with DBPSK. Three 2x3 grids are shown, labeled a), b), and c). Grid a) contains bits 1, 2, 3, 4, 5, 6. Grid b) contains bits 1', 2', 3', 4', 5', 6'. Grid c) contains bits 1', 2', 3', 4', 5', 6'. Arrows labeled 'Interleaving' and 'Modulation' connect the grids. Text labels indicate vertical dimensions: 'Vertical dimension = n x Mod.Size = 2 x 1 = 2' for a) and b), and 'Vertical dimension = n symbols = 2' for c). A small label G.9903(12)-Amd.1(13)_F7-9 is at the bottom right.](315bdbeafb39026e19b77c26b19d9d1f_img.jpg) + +Figure 7-9: Example of interleaving with DBPSK. Three 2x3 grids are shown, labeled a), b), and c). Grid a) contains bits 1, 2, 3, 4, 5, 6. Grid b) contains bits 1', 2', 3', 4', 5', 6'. Grid c) contains bits 1', 2', 3', 4', 5', 6'. Arrows labeled 'Interleaving' and 'Modulation' connect the grids. Text labels indicate vertical dimensions: 'Vertical dimension = n x Mod.Size = 2 x 1 = 2' for a) and b), and 'Vertical dimension = n symbols = 2' for c). A small label G.9903(12)-Amd.1(13)\_F7-9 is at the bottom right. + +**Figure 7-9 – Example of interleaving with DBPSK** + +With DQPSK modulation: + +If the input bit stream is "1 2 3 4 5 6 ... 12", the input bit stream will be loaded into the matrix as Figure 7-10(a). The vertical dimension of the matrix is $n \times \text{mod\_size}$ (i.e., $2 \times 2 = 4$ ). After that, interleaving is done with interleaving block size $n \times m$ (i.e., $2 \times 3$ ). After all the bits have been processed, the bits 1' 2' 3'...11' 12' are mapped to the modulator as shown in Figure 7-10(c). + +![Figure 7-10: Example of interleaving with DQPSK. The diagram shows three stages: (a) Input bits arranged in a 4x3 grid (rows 1-12). (b) Interleaved bits arranged in a 4x3 grid (rows 1'-12'). (c) Modulated symbols arranged in a 2x3 grid (rows 2'1', 4'3', 6'5', 8'7', 10'9', 12'11'). Arrows indicate the flow from (a) to (b) via 'Interleaving' and from (b) to (c) via 'Modulation'. A note indicates that interleaving is done twice in (b).](f57c7b37d7a05a99618104f390089f03_img.jpg) + +: One bit + +G.9903(12)-Amd.1(13)\_F7-10 + +Figure 7-10: Example of interleaving with DQPSK. The diagram shows three stages: (a) Input bits arranged in a 4x3 grid (rows 1-12). (b) Interleaved bits arranged in a 4x3 grid (rows 1'-12'). (c) Modulated symbols arranged in a 2x3 grid (rows 2'1', 4'3', 6'5', 8'7', 10'9', 12'11'). Arrows indicate the flow from (a) to (b) via 'Interleaving' and from (b) to (c) via 'Modulation'. A note indicates that interleaving is done twice in (b). + +**Figure 7-10 – Example of interleaving with DQPSK** + +Interleaving itself can be done using the following piece of code: + +``` +for ( i = 0; i < size; i += ILV_SIZE ) //See note below +``` + +``` +for ( j = 0; j < ILV_SIZE; j++ ) +``` + +``` +y[ i + ILV_TBL[j] ] = (i+j) < size ? x[i+j]: 0; +``` + +where the interleaving table ILV\_TBL and the interleaving size ILV\_SIZE are defined as follows: + +``` +ILV_SIZE = m * n +``` + +``` +for ( j = 0; j < n; j++ ) +``` + +``` +{ +``` + +``` + for ( i = 0; i < m; i++ ) +``` + +``` +{ +``` + +``` + J = ( j * nj + i * ni ) % n; +``` + +``` + I = ( i * mi + J * mj ) % m; +``` + +``` + ILV_TBL[ i + j * m ] = I + J * m; +``` + +``` +} +``` + +``` +} +``` + +NOTE – For the above DBPSK example, $ILV\_SIZE = m \times n = 3 \times 2 = 6$ , $size = 3 \times 2 = 6$ , so the loop runs once. For the above DQPSK example, $ILV\_SIZE = m \times n = 3 \times 2 = 6$ , $size = 3 \times 4 = 12$ , so the loop runs twice. + +### 7.10.2 Full block interleaver + +In the full block interleaver, the value of n is computed as: + +$$n = \text{ceil} \left( \frac{\text{Total\_number\_of\_bits}}{m \times \text{mod\_size}} \right) \times \text{mod\_size}$$ + +The derivation and computation of co-prime numbers are as described in the elementary interleaver clause. + +Suppose the input bit stream to the interleaver is "ABCDEFGHIJKL...", and it is put into the interleaver block as shown in Figure 7-11. Then, after interleaving, the bit stream becomes "A'B'C'D'E'F'G'H'I'J'K'L'...". + +Finally, the interleaved bit stream is mapped to the modulator as shown below for the DQPSK case, where two consecutive bits are put into the same DQPSK symbol. The same exact procedure is applied to D8PSK as shown in Figure 7-12. + +![Figure 7-11: Interleaving process for QPSK/DQPSK case. The diagram shows three stages: Interleaver input, Interleaver output, and the mapping to an OFDM symbol. The input is an 8x6 grid of bits (A-L) mapped to 6 subcarriers. The output is an interleaved 8x6 grid. The final mapping shows 4 OFDM symbols, each containing 6 subcarriers, with one QPSK symbol highlighted.](e64c7b989e5bdb2708cd7aefd18b06e1_img.jpg) + +Interleaver input + +Subcarrier number + $m = 6$ + +| | | | | | | +|---|---|---|---|---|---| +| A | B | C | D | E | F | +| G | H | I | J | K | L | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | + +$n = 8$ + +one bit + +Interleaver output + +Subcarrier number + $m = 6$ + +| | | | | | | +|----|----|----|----|----|----| +| A' | B' | C' | D' | E' | F' | +| G' | H' | I' | J' | K' | L' | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | + +$n = 8$ + +one bit + +To modulator + +Subcarrier number + $m = 6$ + +OFDM symbol number $= 4$ + +| | | | | | | +|--------|--------|--------|--------|--------|--------| +| A', B' | C', D' | E', F' | G', H' | I', J' | K', L' | +| | | | | | | +| | | | | | | +| | | | | | | + +    One QPSK symbol + +G.9903(14)\_F7-11 + +Figure 7-11: Interleaving process for QPSK/DQPSK case. The diagram shows three stages: Interleaver input, Interleaver output, and the mapping to an OFDM symbol. The input is an 8x6 grid of bits (A-L) mapped to 6 subcarriers. The output is an interleaved 8x6 grid. The final mapping shows 4 OFDM symbols, each containing 6 subcarriers, with one QPSK symbol highlighted. + +**Figure 7-11 – Interleaving process for QPSK/DQPSK case** + +![Figure 7-12: Interleaving process for 8-PSK/D8PSK case. The diagram shows three stages: Interleaver input, Interleaver output, and the mapping to an OFDM symbol. The input is a 9x6 grid of bits (A-L) mapped to 6 subcarriers. The output is an interleaved 9x6 grid. The final mapping shows 3 OFDM symbols, each containing 6 subcarriers, with one 8PSK symbol highlighted.](02bb4edc0dbdf4f0749ffd3e0ea2805c_img.jpg) + +Interleaver input + +Subcarrier number + $m = 6$ + +| | | | | | | +|---|---|---|---|---|---| +| A | B | C | D | E | F | +| G | H | I | J | K | L | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | + +$n = 9$ + +one bit + +Interleaver output + +Subcarrier number + $m = 6$ + +| | | | | | | +|----|----|----|----|----|----| +| A' | B' | C' | D' | E' | F' | +| G' | H' | I' | J' | K' | L' | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | +| | | | | | | + +$n = 9$ + +one bit + +To modulator + +Subcarrier number + $m = 6$ + +OFDM symbol number $= 3$ + +| | | | | | | +|----------|----------|----------|----------|--|--| +| A',B',C' | D',E',F' | G',H',I' | J',K',L' | | | +| | | | | | | +| | | | | | | +| | | | | | | + +    One 8PSK symbol + +G.9903(14)\_F7-12 + +Figure 7-12: Interleaving process for 8-PSK/D8PSK case. The diagram shows three stages: Interleaver input, Interleaver output, and the mapping to an OFDM symbol. The input is a 9x6 grid of bits (A-L) mapped to 6 subcarriers. The output is an interleaved 9x6 grid. The final mapping shows 3 OFDM symbols, each containing 6 subcarriers, with one 8PSK symbol highlighted. + +**Figure 7-12 – Interleaving process for 8-PSK/D8PSK case** + +In the case where some subcarriers are masked i.e., some tones are notched, or serve as pilots – interleaving is done in the same way as shown above, except that the $m$ and $n$ values shall be adjusted based on how many tones are actually used (i.e., active). For example, in Figure 7-11, where certain tones are masked or serve as pilots, in the above example, $m$ (where $m$ is the number of active carriers in an OFDM symbol) is less than 6 and $n$ is larger than 8. + +## 7.11 Mapping for DBPSK/DQPSK/D8PSK + +Each subcarrier is modulated with differential binary or differential quadrature phase shift keying (DBPSK or DQPSK or D8PSK). Forward error correction (FEC) is applied to both the frame control information (super robust encoding) and the data (concatenated Reed-Solomon and convolutional encoding) in the communication packet. + +The mapping block is also responsible for assuring that the transmitted signal conforms to the given tone map and tone mask. The tone map and mask are discussed in clause 7.15. + +Data bits are mapped for differential modulation (DBPSK, DQPSK, D8PSK). Instead of using the phase reference vector $\phi$ , each phase vector uses the same subcarrier, previous symbol, as its phase reference. The first FCH symbol uses the phase from the last preamble SYNCp symbol and the first data symbol uses the phase from the last FCH symbol. The data encoding for DBPSK, DQPSK and D8PSK is defined in Tables 7-17, 7-18 and 7-19, where $\Psi_k$ is the phase of the $k$ -th subcarrier from the previous symbol. In DBPSK a phase shift of 0 degrees represents a binary "0" and a phase shift of 180 degrees represent a binary "1". In DQPSK a pair of 2 bits is mapped to 4 different output phases. The phase shifts of 0, 90, 180 and 270 degrees represent binary "00", "01", "11" and "10", respectively. In D8PSK a triplet of 3 bits is mapped to one of 8 different output phases. The phase + +shifts of 0, 45, 90, 135, 180, 225, 270 and 315 degrees represent binary 000, 001, 011, 010, 110, 111, 101 and 100 respectively. + +**Table 7-17 – DBPSK encoding table of k-th subcarrier** + +| Input bit | Output phase | +|-----------|----------------| +| 0 | $\Psi_k$ | +| 1 | $\Psi_k + \pi$ | + +**Table 7-18 – DQPSK encoding table of k-th subcarrier** + +| Input bit pattern (X, Y), Y is from first interleaver matrix | Output phase | +|--------------------------------------------------------------|-------------------| +| 00 | $\Psi_k$ | +| 01 | $\Psi_k + \pi/2$ | +| 11 | $\Psi_k + \pi$ | +| 10 | $\Psi_k + 3\pi/2$ | + +**Table 7-19 – D8PSK encoding table of k-th subcarrier** + +| Input bit pattern (X, Y, Z), Z is from first interleaver matrix | Output phase | +|-----------------------------------------------------------------|-------------------| +| 000 | $\Psi_k$ | +| 001 | $\Psi_k + \pi/4$ | +| 011 | $\Psi_k + \pi/2$ | +| 010 | $\Psi_k + 3\pi/4$ | +| 110 | $\Psi_k + \pi$ | +| 111 | $\Psi_k + 5\pi/4$ | +| 101 | $\Psi_k + 3\pi/2$ | +| 100 | $\Psi_k + 7\pi/4$ | + +Alternatively, the phase differences used to compute "output phases" in Tables 7-17, 7-18 and 7-19 can be represented in a constellation diagram (with reference phase assumed equal to 0 degrees), as shown in Figure 7-13. + +![Figure 7-13 – Constellation encoding. Three diagrams showing the mapping of bits to phases on a circle. DBPSK shows (1) at -1 and (0) at +1. DQPSK shows (11) at -1, (00) at +1, (01) at +1j, and (10) at -1j. D8PSK shows (110) at -1, (000) at +1, (010) at -0.707+0.707j, (001) at 0.707+0.707j, (111) at -0.707-0.707j, (100) at 0.707-0.707j, (101) at -1j, and (011) at +1j. The vertical axis is labeled Q with +1 and -1 markers.](e76da0473640f804b16197e57460061f_img.jpg) + +Figure 7-13 – Constellation encoding. Three diagrams showing the mapping of bits to phases on a circle. DBPSK shows (1) at -1 and (0) at +1. DQPSK shows (11) at -1, (00) at +1, (01) at +1j, and (10) at -1j. D8PSK shows (110) at -1, (000) at +1, (010) at -0.707+0.707j, (001) at 0.707+0.707j, (111) at -0.707-0.707j, (100) at 0.707-0.707j, (101) at -1j, and (011) at +1j. The vertical axis is labeled Q with +1 and -1 markers. + +G.9903(14)\_F7-13 + +**Figure 7-13 – Constellation encoding** + +## 7.12 Frequency domain pre-emphasis + +Frequency domain pre-emphasis provides a mechanism to frequency shape the transmit signal. This mechanism may be used for spectral shaping of the transmitted signal, compensation for frequency-dependent attenuation introduced to the signal as it goes through the power line or transmission of signal over a noisy channel. + +The frequency shaping of the signal may be computed from the TXRES and TXCOEF parameters that are part of the neighbour table appropriate for the band of operation. Pre-emphasis has to be applied to all OFDM symbols (including preamble, FCH and data symbols). + +![Block diagram of the pre-emphasis filter](329c96049bb432e9c2cbda4e224a0c9c_img.jpg) + +The diagram shows a 'Complex constellation' input entering a circular block with an 'X' symbol. Below this block, an arrow points to it from the text '4-bit filter coefficients (real)'. The output of the 'X' block enters a rectangular block labeled 'Right shift by 3 bits'. The output of this block is labeled 'Complex output'. In the bottom right corner of the diagram, the text 'G.9903(14)\_F7-14' is present. + +Block diagram of the pre-emphasis filter + +**Figure 7-14 – Block diagram of the pre-emphasis filter** + +## 7.13 OFDM generation (IFFT and CP addition) + +The OFDM signal can be generated using IFFT. The IFFT block takes the 256-point IFFT of the input vector and generates the main 256 time-domain OFDM words pre-pended by 30 samples of cyclic prefix. In other words, we take the last 30 samples at the output of the IFFT and place them in front of symbol. The useful output is the real part of the IFFT coefficients. The input/output configuration is as depicted in Figure 7-15. + +![IFFT input/output and CP addition diagram](26e334e61dd059cff029338a2a604d8d_img.jpg) + +The diagram illustrates the OFDM generation process. On the left, 'Modulated subcarriers' are shown as a vertical stack of points labeled $C_0$ , $C_{46}$ , $C_{115}$ , and $C_{511}$ , with '0' at the top and bottom. These are input into an 'IFFT' block. The output of the IFFT block goes into a 'Take real part' block. The output of this block goes into a 'CP extension' block. This block is divided into two sections: the top section is labeled 'CP extension' and the bottom section is a solid blue rectangle. A dashed curved arrow points from the bottom section back to the top section, with the text 'Repeat 30 samples at the end of symbol'. In the bottom right corner of the diagram, the text 'G.9903(14)\_F7-15' is present. + +IFFT input/output and CP addition diagram + +**Figure 7-15 – IFFT input/output and CP addition** + +## 7.14 Windowing + +In order to reduce the out-of-band emission and to reduce the spectral side lobe, the shaping is applied to all the FCH and payload symbols. Then the tails and heads of successive symbols are overlapped and added together. This process is described below. Each side of a symbol is first shaped as shown in Figure 7-16 (a raised cosine function is used in this example). + +![Figure 7-16: Windowing using a raised cosine for the shaping function. The diagram shows a symbol (n-1) divided into three parts: 8 samples (Head), the main symbol body, and 8 samples (Tail). A raised cosine function is applied to the head and tail samples, as indicated by the curves and arrows. The window function is shown as a flat line across the main symbol body. The diagram is labeled G.9903(14)_F7-16.](9a5927586a691c4908aa2cf98bd47ebb_img.jpg) + +Figure 7-16: Windowing using a raised cosine for the shaping function. The diagram shows a symbol (n-1) divided into three parts: 8 samples (Head), the main symbol body, and 8 samples (Tail). A raised cosine function is applied to the head and tail samples, as indicated by the curves and arrows. The window function is shown as a flat line across the main symbol body. The diagram is labeled G.9903(14)\_F7-16. + +**Figure 7-16 – Windowing using a raised cosine for the shaping function** + +The windowing function should have the sum of the overlapped head and tail samples equal to one. The window function has a value equal to one at all the remaining samples of the symbol. The 8 tail and 8 head shaped samples of the symbol from each side of the symbol are overlapped with the tail and head samples of adjacent symbols as shown in Figure 7-17. + +![Figure 7-17: Overlap/add. This diagram illustrates the overlap-add process for constructing the n-th symbol. It shows three symbols: (n-1)-th, n-th, and (n+1)-th. The (n-1)-th symbol has Head, (n-1)-th symbol, and Tail parts. The n-th symbol has Head, n-th symbol, and Tail parts. The (n+1)-th symbol has Head, (n+1)-th symbol, and Tail parts. Arrows and plus signs show the overlap of the Tail of (n-1)-th with the Head of n-th, and the Tail of n-th with the Head of (n+1)-th. The final symbol is shown as the n-th symbol with its head and tail parts added to the (n+1)-th symbol's head and tail parts. The diagram is labeled G.9903(14)_F7-17.](c99bf3a0530a3e58f5f2d2790ba7441b_img.jpg) + +Figure 7-17: Overlap/add. This diagram illustrates the overlap-add process for constructing the n-th symbol. It shows three symbols: (n-1)-th, n-th, and (n+1)-th. The (n-1)-th symbol has Head, (n-1)-th symbol, and Tail parts. The n-th symbol has Head, n-th symbol, and Tail parts. The (n+1)-th symbol has Head, (n+1)-th symbol, and Tail parts. Arrows and plus signs show the overlap of the Tail of (n-1)-th with the Head of n-th, and the Tail of n-th with the Head of (n+1)-th. The final symbol is shown as the n-th symbol with its head and tail parts added to the (n+1)-th symbol's head and tail parts. The diagram is labeled G.9903(14)\_F7-17. + +**Figure 7-17 – Overlap/add** + +In other words, to construct the $n$ -th symbol, first its 8 head samples are overlapped with the 8 tail samples of the $(n-1)$ -th symbol and its 8 tail samples are overlapped with the 8 head samples of the $(n+1)$ -th symbol. Finally, the corresponding overlapped parts are added together. Note that the head of the first symbol is overlapped with the tail of the preamble. And the tail of the last symbol is sent out with no overlapping applied. + +## 7.15 Tone masking and tone mapping + +The tone mask is a static PAN-wide parameter defined by `macToneMask` – see Table 9-15. Each bit set to one in the tone mask indicates that the associated tone will be used for the communication (less the significant bit representing the lowest frequency of the CENELEC or FCC bandplans). Thus, masked subcarriers are not assigned phase symbols and their amplitude is zero. The tone mask is applied to the preamble, FCH and payload. + +The tone map is an adaptive parameter that, based on channel estimation, contains a list of subcarriers that are to be used for communication between two ITU-T G.9903 devices. For example, the tone map contains information on which subcarriers shall not carry information, for example those subcarriers that suffer deep fades or very low SNR. The tone map shall apply only to the payload. In the case where the robust mode is used, all subcarriers are used to carry information (the tone map is all ones). + +ITU-T G.9903 devices shall estimate the SNR of the received signal subcarriers and adaptively select the usable tones, optimum modulation and code rate to ensure reliable communication over the power line channel. It shall also specify which power level the remote transmitter shall use and + +which gain values it should apply for various sections of the spectrum. The per-tone quality measurement enables the system to adaptively avoid transmitting data on subcarriers with poor quality. Using a tone map indexing system, where the index is passed from receiver to transmitter and vice versa, allows the receiver to adaptively select which group of subcarriers will be used for data transmission and which ones will be used to send dummy data that the receiver shall ignore. + +The goal of the adaptive tone mapping is to allow the ITU-T G.9903 receiver to achieve the greatest possible throughput given the channel conditions existing between them. In order to accomplish this goal, the receiver shall inform the remote transmitter which tones it should use to send data bits on and which tones it should use to send dummy data bits that the receiver shall ignore. The receiver shall also inform the remote transmitter how much amplification or attenuation it should apply to each of the tones. + +The source station's MAC layer may request a destination station to estimate a channel condition by setting the TMR bit of the MAC header as described in Table 9-5. + +The destination station has to estimate this particular communication link between two points and choose optimal PHY parameters. This information will be sent back to the originator as a tone map response. + +The parameters of the tone map response message are shown in Table 9-9. + +The number of tones after tone masking and tone mapping shall always be 6 or more. + +### 7.15.1 PN modulating unused subcarriers + +For inactive tones (subcarriers that carry no information), the mapping function shall use binary values taken from a pseudo noise (PN) sequence. The number of required bit outputs of the PN sequence depends on the modulation types. For example, DBPSK, DQPSK and D8PSK require 1, 2 and 3 bit outputs from the PN sequence, respectively. + +The PN sequence shall be generated using the same generator polynomial introduced in clause 7.5. Based on Figure 7-18, the bits in the PN sequence generator shall all be initialized to ones at the start of the FCH and sequenced to the next value according to tone modulation and for every inactive, pilot, or masked carrier. + +For every $m$ consecutive bits output by the LFSR for a single constellation symbol of size $2^m$ , the first bit shall be mapped to the LSB and the last bit shall be mapped to the MSB of the constellation symbol, respectively. + +![Diagram of a PN sequence generator using a linear feedback shift register (LFSR). The diagram shows two shift register blocks. The left block contains stages X^7, X^6, and X^5. The right block contains stages X^4, X^3, X^2, and X^1. The output of the right block (X^1) is fed back through an XOR gate (marked with a '+') and then back into the input of the left block (X^7). The output of the right block is also the final output of the generator. A label 'G.9903(14)_F7-18' is present below the diagram.](63a2519518616620ef0e53d98b923c05_img.jpg) + +Diagram of a PN sequence generator using a linear feedback shift register (LFSR). The diagram shows two shift register blocks. The left block contains stages X^7, X^6, and X^5. The right block contains stages X^4, X^3, X^2, and X^1. The output of the right block (X^1) is fed back through an XOR gate (marked with a '+') and then back into the input of the left block (X^7). The output of the right block is also the final output of the generator. A label 'G.9903(14)\_F7-18' is present below the diagram. + +**Figure 7-18 – PN sequence generator using linear feedback shift register (LFSR)** + +## 7.16 Coherent modulation scheme + +For CENELEC bands, ITU-T G.9903 devices operate using a differential modulation scheme for FCH and payload. However, the device may support a coherent modulation scheme for the payload. If requested by the tone map response received from a neighbour node, a coherent modulation scheme shall be used with this neighbour (if supported). Otherwise, the differential modulation scheme shall be used. + +For an FCC band, the FCH is coded using super robust mode with BPSK modulation. + +This clause describes the operation of ITU-T G.9903 devices when operating in the optional coherent scheme. This clause only describes the portions of the standard that are different from the + +main differential scheme. Portions of the coherent transmitter that are not described here shall operate exactly as described in the differential scheme. + +### **7.16.1 Frame structure – Coherent modulation scheme** + +In a similar way to differential mode, the coherent mode shall support two types of frames: data frames and ACK/NACK frames. The frame structure of data frames shall be identical to the one used in differential mode except for two changes: + +- a) The data portion of the PHY frame shall be preceded by an S1 symbol followed by an S2 symbol, where both symbols shall be inserted between the last FCH symbol and the first data symbol. The S2 symbol shall have the same phase reference vector used in differential mode for a SYNCP symbol. The only difference from a SYNCP symbol is that the S2 symbol consists of a SYNCP symbol plus a cyclic prefix of 30 samples and an overlap of 8 samples, resulting in 278 samples when an IFFT size of 256 is used. Hence, the duration of the S2 symbol shall be the same as for that of an FCH symbol or a data symbol. The S1 symbol shall be an inverted S2 symbol (i.e., $-S2$ ), hence it will also consist of 278 samples. +- b) Pilot tones shall be inserted in the data symbols as described in clause 7.16.10 on pilot tones. + +The frame structure of the ACK/NACK frames for coherent mode shall be identical to the one used in differential mode. + +### **7.16.2 Preamble – Coherent modulation scheme** + +The preamble for the coherent scheme is composed of 8 or (8+4=12) identical SYNCP symbols followed by a SYNCM symbol that is followed by a half SYNCM symbol. The SYNCP and SYNCM symbols for the coherent scheme are identical to the ones generated in the differential scheme. The initial phases used for both schemes are shown in Table 7-11. + +All coherent mode preamble symbols (SYNCP, SYNCM and the additional symbols between the last FCH symbol and the first data symbol) shall have the same gain factor compared to data symbols and their gain is defined to be 3 dB, the same as in the differential mode – see clause 7.5. + +### **7.16.3 Frame control header – Coherent modulation scheme** + +The thirteen (CENELEC bandplans) or twelve (FCC bandplan) symbols following immediately after the preamble constitute the frame control header (FCH). The FCH has the same structure in both differential and coherent modulation schemes. The "Payload Modulation Scheme" bit in the FCH for data frames shall be used to indicate whether the payload is modulated coherently or not. + +### **7.16.4 CRC – Coherent modulation scheme** + +The CRC used in coherent mode shall be identical to the one used in differential mode. + +### **7.16.5 Data scrambler – Coherent modulation scheme** + +The data scrambler used in coherent mode shall be identical to the one used in differential mode. + +### **7.16.6 FEC coding – Coherent modulation scheme** + +The FEC encoder for coherent mode shall be identical to the one used for differential mode. + +### **7.16.7 Payload padding – Coherent modulation scheme** + +The payload padding for coherent mode shall be identical to the one used for differential mode. + +### **7.16.8 Interleaver – Coherent modulation scheme** + +The interleaver for coherent mode shall be identical to the interleaver in differential mode where the pilot tones shall not be considered part of the active tones and hence shall be completely ignored by + +the interleaver. This means that the number of subcarriers 'm' shall not include in it the pilot tones (nor the masked tones as is the case for differential mode). + +### 7.16.9 Coherent mapping for BPSK, QPSK, 8-PSK, 16-QAM and robust modes – Coherent modulation scheme + +The mapping block is responsible for assuring that the transmitted signal conforms to the given tone map and tone mask. The tone map and tone mask are discussed in clause 7.15. The tone mask is a predefined (static) system-wide parameter defining the start, stop and notch frequencies. The tone map is an adaptive parameter that, based on channel estimation, contains a list of carriers that are to be used for a particular communication between two modems. + +Data bits are mapped for coherent modulation (BPSK, QPSK, 8-PSK, 16-QAM or robust) as follows: For a given symbol, instead of using the same carrier, the previous symbol as its phase reference, it uses the preamble phase of the same carrier as its reference. This predefined phase reference is identical to the one that is specified for differential modulation as shown in Table 7-11. Both the FCH symbols and data symbols use the same phase reference vector. + +#### 7.16.9.1 Mapping for BPSK and robust mode – Coherent modulation scheme + +In BPSK (and robust) modulation a phase shift of $0^\circ$ represents a binary "0" and a phase shift of $180^\circ$ represents a binary "1" as illustrated in Table 7-20. + +**Table 7-20 – BPSK and robust encoding table of k-th subcarrier** + +| Input bit | Output phase | +|-----------|----------------| +| 0 | $\Psi_k$ | +| 1 | $\Psi_k + \pi$ | + +The constellation shall be identical to the one used for differential mode. + +#### 7.16.9.2 Mapping for QPSK modulation – Coherent modulation scheme + +In QPSK a pair of 2 bits is mapped to 4 different output phases. The phase shifts of $0^\circ$ , $90^\circ$ , $180^\circ$ and $270^\circ$ represent binary "00", "01", "11" and "10" respectively, as illustrated in Table 7-21. + +**Table 7-21 – QPSK encoding table of k-th subcarrier** + +| Input bit pattern (X, Y),
Y leaves interleaver first | Output phase | +|---------------------------------------------------------|-------------------| +| 00 | $\Psi_k$ | +| 01 | $\Psi_k + \pi/2$ | +| 11 | $\Psi_k + \pi$ | +| 10 | $\Psi_k + 3\pi/2$ | + +The constellation shall be identical to the one used for differential mode. + +#### 7.16.9.3 Mapping for 8-PSK modulation – Coherent modulation scheme + +In 8-PSK a triplet of 3 bits is mapped to one of 8 different output phases. The phase shifts of $0^\circ$ , $45^\circ$ , $90^\circ$ , $135^\circ$ , $180^\circ$ , $225^\circ$ , $270^\circ$ and $315^\circ$ represent binary 000, 001, 011, 010, 110, 111, 101 and 100 respectively, as illustrated in Table 7-22. + +**Table 7-22 – 8-PSK encoding table of k-th subcarrier** + +| Input bit pattern (X, Y, Z),
Z leaves interleaver first | Output phase | +|------------------------------------------------------------|-------------------| +| 000 | $\Psi_k$ | +| 001 | $\Psi_k + \pi/4$ | +| 011 | $\Psi_k + \pi/2$ | +| 010 | $\Psi_k + 3\pi/4$ | +| 110 | $\Psi_k + \pi$ | +| 111 | $\Psi_k + 5\pi/4$ | +| 101 | $\Psi_k + 3\pi/2$ | +| 100 | $\Psi_k + 7\pi/4$ | + +The constellation shall be identical to the one used for differential mode. + +#### **7.16.9.4 Mapping for 16-QAM modulation (applies only to FCC bandplan) – Coherent modulation scheme** + +The 16-QAM modulation is optional. + +In 16-QAM modulation, 4 bits are mapped to one of sixteen different constellation points. The mapping is shown in Figure 7-19 and Table 7-23. + +![Figure 7-19 – 16-QAM constellation diagram. The diagram shows four points in the first quadrant of the I-Q plane. The horizontal axis is labeled 'I' and has tick marks at +1 and +3. The vertical axis is labeled 'Q' and has tick marks at +1 and +3. The points are: (1, 1) labeled '1111', (3, 1) labeled '1101', (1, 3) labeled '0111', and (3, 3) labeled '0101'. A small label 'G.9903(14)_F7-19' is at the bottom right.](933151db66eefe2e64a0a4da5d37e05e_img.jpg) + +Figure 7-19 – 16-QAM constellation diagram. The diagram shows four points in the first quadrant of the I-Q plane. The horizontal axis is labeled 'I' and has tick marks at +1 and +3. The vertical axis is labeled 'Q' and has tick marks at +1 and +3. The points are: (1, 1) labeled '1111', (3, 1) labeled '1101', (1, 3) labeled '0111', and (3, 3) labeled '0101'. A small label 'G.9903(14)\_F7-19' is at the bottom right. + +**Figure 7-19 – 16-QAM constellation diagram** + +The complete constellation description is given in Table 7-23. + +**Table 7-23 – Mapping for 16-QAM** + +| Bits [d 1 d 0 ] | I | Bit [d 3 d 2 ] | Q | +|---------------------------------------|----|--------------------------------------|----| +| 00 | -3 | 00 | -3 | +| 10 | -1 | 10 | -1 | +| 11 | 1 | 11 | 1 | +| 01 | 3 | 01 | 3 | + +The resulting outputs values "d" are formed by multiplying the resulting (I+jQ) value by a normalization factor equal to $1/\sqrt{(10)}$ : + +$$d = (I + jQ) \times \frac{1}{\sqrt{(10)}}$$ + +The purpose of the normalization factor is to achieve the same average power for all mappings. + +### 7.16.10 Pilot tones – Coherent modulation scheme + +Pilot tones can be used in coherent mode to help with clock recovery and channel estimation, particularly in harsh environments where strong noise and frequent channel variations occur. Pilot tones shall only be inserted in data symbols and shall not be inserted in FCH symbols. + +For pilot tone assignment, the pilot indices shall be sequentially enumerated over only the active subcarrier set: + +$$P(i,j) = (\text{OFFSET} + (\text{FreqSpacing} \times i) + 2 \times j) \% M_{\text{ACTIVE}} \quad (7-1)$$ + +Where: + +- $P(i,j)$ is the relative position of pilot $i$ in symbol $j$ within the set of active subcarriers. The set of active subcarriers is enumerated as $0, 1, 2, \dots, M_{\text{ACTIVE}}-1$ +- $M$ is the number of subcarriers per symbol in a given band ( $M=36$ for CENELEC A; $M=16$ for CENELEC B; $M=72$ for FCC) +- $M_{\text{ACTIVE}}$ is the number of subcarriers in the bandplan that are not masked nor inactive ( $M_{\text{ACTIVE}} \leq M$ ) +- $\text{FreqSpacing}$ = Frequency spacing between pilots within the same symbol expressed in multiples of the subcarrier spacing (12 for CENELEC A; 8 for CENELEC B; 12 for FCC band) +- $i$ = pilot index = $0, 1, 2, \dots, \text{ceil}(M_{\text{ACTIVE}} / \text{FreqSpacing})-1$ +- $j$ = symbol number = $0, 1, 2, 3, \dots, N-1$ +- $N$ = total number of data symbols per frame. +- $\text{OFFSET}$ (6 for CENELEC A and CENELEC B; 36 for FCC). + +The absolute pilot tone index with respect to FFT numbering is given by: + +$$P_{\text{abs}}(i,j) = \text{STARTINDEX} + Q_{\text{ACTIVE}}(P(i,j)) \quad (7-2)$$ + +Where: + +- $Q = [0, 1, 2, \dots, M-1]$ is a vector of the relative indices of the subcarriers of a given band. $\text{Length}(Q) = M$ +- $Q_{\text{ACTIVE}}$ is a vector of the relative indices of the active subcarriers of the given band. $Q_{\text{ACTIVE}}$ is derived from $Q$ by excluding inactive and masked subcarriers. $\text{Length}(Q_{\text{ACTIVE}}) = M_{\text{ACTIVE}}$ +- $\text{STARTINDEX}$ is the absolute index with respect to FFT numbering of the first subcarrier in the bandplan (23 for CENELEC A; 63 for CENELEC B; 33 for FCC). + +The pilot tones shall consist of sine waves at the specified tone frequencies modulated in QPSK using the constellation specified in clause 7.16.9.2. The bits that get mapped to the constellation points shall be generated following the PN sequence generation procedure described in clause 7.15.1. + +The pilot tones' indexes shall be ordered first in ascending order, and then each pilot tone shall be modulated with the output of the PN sequence generator. + +For every two consecutive output bits for pilot tones from the PN sequence generator, the first bit shall be mapped to the LSB of the QPSK symbol and the second bit shall be mapped to the MSB of the QPSK symbol. + +![Block diagram of an LFSR used to generate data bits. It consists of two shift registers, one with 4 stages (X^4 to X^1) and another with 3 stages (X^7 to X^5). The output of the 4-stage register is XORed with the output of the 3-stage register. This XOR result is fed back to the input of the 4-stage register and also XORed with 'Data in' to produce 'Scrambled data out'. The diagram is labeled G.9903(14)_F7-20.](c1df61cc3717e878a48e530218403403_img.jpg) + +Block diagram of an LFSR used to generate data bits. It consists of two shift registers, one with 4 stages (X^4 to X^1) and another with 3 stages (X^7 to X^5). The output of the 4-stage register is XORed with the output of the 3-stage register. This XOR result is fed back to the input of the 4-stage register and also XORed with 'Data in' to produce 'Scrambled data out'. The diagram is labeled G.9903(14)\_F7-20. + +**Figure 7-20 – LFSR used to generate the data bits that are used to modulate the pilot tones** + +#### 7.16.10.1 Example of pilot tone assignment + +Below is an example of the application of Equations (7-1) and (7-2). + +With the CENELEC A bandplan we have the following initial parameters: + +$M = 36;$ + +$FreqSpacing = 12;$ + +$OFFSET = 6;$ + +$STARTINDEX = 23;$ + +If neither masked nor inactive (ToneMap equal to 0x3F) subcarriers are present, the derived parameters are: + +$M_{ACTIVE} = M = 36;$ + +$i = [0:2] = [0 \ 1 \ 2]$ + +$Q = [0:M] = [0:35] = [0 \ 1 \ 2 \ 3 \ 4 \ \dots \ 34 \ 35];$ + +$Q_{ACTIVE} = Q = [0:35];$ + +$Length(Q_{ACTIVE}) = M_{ACTIVE} = 36$ + +Given $N = 10$ OFDM symbols, pilot tones are allocated as follows: + +$j = [0:9] = [0 \ 1 \ 2 \ 3 \ 4 \ \dots \ 8 \ 9]$ + +$P(i,j) =$ + +| | | | | | | | | | | +|----|----|----|----|----|----|----|----|----|----| +| 6 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 22 | 24 | +| 18 | 20 | 22 | 24 | 26 | 28 | 30 | 32 | 34 | 0 | +| 30 | 32 | 34 | 0 | 2 | 4 | 6 | 8 | 10 | 12 | + +$P_{abs}(i,j) =$ + +| | | | | | | | | | | +|----|----|----|----|----|----|----|----|----|----| +| 29 | 31 | 33 | 35 | 37 | 39 | 41 | 43 | 45 | 47 | +| 41 | 43 | 45 | 47 | 49 | 51 | 53 | 55 | 57 | 23 | +| 53 | 55 | 57 | 23 | 25 | 27 | 29 | 31 | 33 | 35 | + +### 7.16.11 Frequency domain pre-emphasis – Coherent modulation scheme + +For further study. + +### 7.16.12 OFDM generation (IFFT and CP addition) – Coherent modulation scheme + +OFDM generation for coherent mode shall be identical to the procedure used for differential mode. + +### 7.16.13 Windowing – Coherent modulation scheme + +Windowing for coherent mode shall follow the identical procedure used for differential mode and shall apply to S1 and S2 symbols accordingly. + +### 7.16.14 Adaptive tone mapping and transmit power control – Coherent modulation scheme + +Adaptive tone mapping and transmit power control shall follow the identical procedure used for differential mode. However, transmit power scaling per sub band shall not be allowed for coherent modulation. In particular, pilot tones shall not have any special treatment when it comes to transmit power control and shall follow the same mechanism applied to data tones. + +## 7.17 PHY primitives + +### 7.17.1 Data primitive + +The receipt of the PD-DATA.request primitive by the PHY entity will cause the transmission of the supplied PSDU to be attempted. The PHY will first construct a PHY protocol data unit (PPDU) containing the supplied PSDU, and then transmit the PPDU. If the PD-DATA.request primitive is received by the PHY while the receiver is not enabled, or the transmitter is busy transmitting, the PHY shall first construct a PPDU containing the supplied PSDU, and then transmit the PPDU. When the PHY entity has completed the transmission successfully, it shall issue the PD-DATA.confirm primitive with a status of SUCCESS. If a PD-DATA.request primitive is received while the receiver is enabled (TXOFF\_RXON state), the PHY entity shall discard the PSDU and issue the PD-DATA.confirm primitive with a BUSY\_RX status. If a PD-DATA.request primitive is received while the transmitter is already busy transmitting (BUSY\_TX state), the PHY entity shall discard the PSDU and issue the PD-DATA.confirm primitive with a BUSY\_TX status. If the processing or transmission of PHY is not possible due to invalid parameters or for any other reason, the PHY entity shall discard the PSDU and issue the PD-DATA.confirm primitive with a FAILED status. + +The receipt of the PD-ACK.request primitive by the PHY entity will cause the transmission of the ACK/NACK frame to be attempted. The PHY will first construct an ACK/NACK frame and then transmit it. When the PHY entity has completed the transmission successfully, it shall issue the PD-ACK.confirm primitive with a SUCCESS status. If a PD-ACK.request primitive is received while the receiver is enabled (TXOFF\_RXON state), the PHY entity shall discard the constructed ACK/NACK frame and issue the PD-ACK.confirm primitive with a BUSY\_RX status. If a PD-ACK.request primitive is received while the transmitter is already busy transmitting (BUSY\_TX state), the PHY entity shall discard the constructed ACK/NACK frame and issue the PD-ACK.confirm primitive with a BUSY\_TX status. If the processing or transmission of PHY is not possible due to invalid parameters or for any other reason, the PHY entity shall discard the constructed ACK/NACK frame and issue the PD-ACK.confirm primitive with a FAILED status. + +![Sequence diagram showing the flow of PD-DATA and PD-ACK primitives between MAC and PHY entities.](36fd537a1e39baa2471ecfaaf869751a_img.jpg) + +``` +sequenceDiagram + participant MAC + participant PHY + Note right of PHY: G.9903(14)_F7-21 + MAC->>PHY: PD-DATA.request +PD-ACK.request + PHY-->>MAC: PD-DATA.confirm +PD-ACK.confirm + PHY-->>MAC: PD-DATA.indication +PD-ACK.indication +``` + +The diagram illustrates the interaction between a MAC entity and a PHY entity. The MAC entity sends request primitives (PD-DATA.request and PD-ACK.request) to the PHY entity. The PHY entity responds with confirm primitives (PD-DATA.confirm and PD-ACK.confirm) back to the MAC entity. Additionally, the PHY entity sends indication primitives (PD-DATA.indication and PD-ACK.indication) to the MAC entity. The diagram is labeled G.9903(14)\_F7-21. + +Sequence diagram showing the flow of PD-DATA and PD-ACK primitives between MAC and PHY entities. + +Figure 7-21 – Data or ACK primitive flow + +#### 7.17.1.1 PD-DATA.request + +The PD-DATA.request primitive is generated by a local MAC sublayer entity and issued to its PHY entity to request the transmission of an MPDU. The semantics of the PD-DATA.request primitive is as follows: + +``` +PD-DATA.request ( + psduLength + psdu +) +``` + +Table 7-24 specifies the parameters for the PD-DATA.request primitive. + +**Table 7-24 – The parameters for the PD-DATA.request primitive** + +| Name | Type | Valid range | Description | +|------------|---------------|----------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------| +| psduLength | Integer | 0x00-0xEF for CENELEC bandplans
0x00-0x1EE for FCC bandplan | The number of bytes contained in the PSDU to be transmitted by the PHY entity. The effective maximum PSDU length can be derived as described in clause 7.3.2. | +| Psdu | Integer Array | Any | The set of bytes forming the PSDU request to be transmitted by the PHY entity. | + +The PHY should start the transmission no later than $0.1 \times aSlotTime$ after the PD-DATA.request is issued by the MAC. The aSlotTime is defined in Table 9-14. + +#### 7.17.1.2 PD-DATA.confirm + +The PD-DATA.confirm primitive confirms the end of the transmission of an MPDU (i.e., PSDU) from a local PHY entity to a peer PHY entity. The semantics of the PD-DATA.confirm primitive is as follows: + +``` +PD-DATA.confirm ( + status +) +``` + +Table 7-25 specifies the parameters for the PD-DATA.confirm primitive. + +**Table 7-25 – The parameters for the PD-DATA.confirm primitive** + +| Name | Type | Valid range | Description | +|--------|-------------|-----------------------------------------|------------------------------------------------| +| Status | Enumeration | SUCCESS,
BUSY_RX,
BUSY_TX, FAILED | The result of the request to transmit a packet | + +#### 7.17.1.3 PD-DATA.indication + +The PD-DATA.indication primitive indicates the transfer of an MPDU (i.e., PSDU) from the PHY to the local MAC sublayer entity. The semantics of the PD-DATA.indication primitive is as follows: + +``` +PD-DATA.indication ( + psduLength, + psdu, +``` + +ppduLinkQuality + CarrierSNR, + PhaseDifferential, + PayloadModulationType, + PayloadModulationScheme + ToneMap, + DT + +) + +Table 7-26 specifies the parameters for the PD-DATA.indication primitive. + +**Table 7-26 – The parameters for the PD-DATA.indication primitive** + +| Name | Type | Valid range | Description | +|------------------------|---------|----------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| psduLength | Integer | 0x00-0xEF for CENELEC bandplans
0x00-0x1EE for FCC bandplan | The number of bytes contained in the PSDU received by the PHY entity | +| PsdU | Integer | – | The set of bytes forming the PSDU received by the PHY entity | +| ppduLinkQuality | Integer | 0x00-0xFF | Link quality (forward LQI) value measured during reception of the PPDU | +| CarrierSNR | Array | 0x00-0x3F | The PHY provides the SNR value per each carrier of the last received frame (see clause 7.17.2.4). | +| PhaseDifferential | Integer | 0x00-0x05 | The PHY computes and provides the phase difference in multiples of 60 degrees to the MAC layer of the last received frame.
0: local node and neighbour node are in phase
1: local node leads neighbour node by 60 degrees
2: local node leads neighbour node by 120 degrees
3: neighbour node and local node are in phase opposition
4: neighbour node leads local node by 120 degrees
5: neighbour node leads local node by 60 degrees | +| PayloadModulation Type | Integer | 0x00-0x04 | The modulation type used in the last received frame.
0: Robust mode
1: DBPSK or BPSK
2: DQPSK or QPSK
3: D8PSK or 8-PSK
4: 16-QAM | + +**Table 7-26 – The parameters for the PD-DATA.indication primitive** + +| Name | Type | Valid range | Description | +|--------------------------|---------|-------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| | | | NOTE – The 16-QAM modulation is optional and may be used in an FCC bandplan only when the coherent modulation scheme applies. | +| PayloadModulation Scheme | Integer | 0x00-0x01 | The payload modulation scheme used in the last received frame.
0: Differential
1: Coherent | +| ToneMap | Array | 0x00-0x01 | Tone map parameter used in the last received frame.
The value of 0 indicates to the remote transmitter that dummy data should be transmitted on the corresponding subcarrier while a value of 1 indicates that valid data should be transmitted on the corresponding subcarrier. | +| DT | Integer | 0x00-0x07 | Delimiter type used in the last received frame.
0: Acknowledgment is not requested
1: Acknowledgment is requested
2-7: Reserved by ITU-T | + +The forward LQI shall be measured for each received packet and is a characterization of the quality of the underlying power line channel. + +The LQI is an integer ranging from 0x00 to 0xFF and LQI values in-between shall be uniformly distributed between these two limits. The LQI value is derived from the average SNR (where averaging is done over all active tones and pilot tones, if present, in the bandplan and over all OFDM symbols in the received packet) where the SNR-to-LQI mapping is: + +- SNR $\leq -10$ dB maps to LQI 0x00 +- SNR $\geq 53.75$ dB maps to LQI 0xFF +- $-10 < \text{SNR} < 53.75$ dB is linearly interpolated between 0x00 and 0xFF (the nominal step size is 0.25 dB). + +Active tones are defined as tones which carry data (pilot tones and dummy bit tones are not included). + +The forward LQI value is computed in the PHY and passed to the MAC with the PD-DATA.indication primitive through the ppduLinkQuality parameter – see Table 7-26. The LQI shall be measured and reported and it may be used to determine the transmission parameters, such as modulation modes. + +#### 7.17.1.4 PD-ACK.request + +The PD-ACK.request primitive requests to send an ACK frame to the PHY from the local MAC sublayer entity. The semantics of the PD-ACK.request primitive is as follows: + +PD-ACK.request ( +    FCH +) + +Table 7-27 specifies the parameter for the PD-ACK.request primitive. + +**Table 7-27 – The parameters for the PD-ACK.request primitive** + +| Name | Type | Valid range | Description | +|------|-----------|----------------|--------------------------------------------------------------------------------------------------------------------| +| FCH | Structure | Clause 7.6 PHY | The MAC layer provides all frame control header parameters described in clause 7.6 to construct FCH frame for ACK. | + +#### 7.17.1.5 PD-ACK.confirm + +The PD-ACK.confirm confirms the end of the transmission of an ACK packet. The semantics of the PD-ACK.confirm primitive is as follows: + +``` +PD-ACK.confirm ( + Status +) +``` + +Table 7-28 specifies the parameter for the PD-ACK.confirm primitive. + +**Table 7-28 – The parameters for the PD-ACK.confirm primitive** + +| Name | Type | Valid range | Description | +|--------|-------------|----------------------------------------|-----------------------------------| +| Status | Enumeration | SUCCESS
BUSY_RX,
BUSY_TX, FAILED | Confirm transmission of ACK frame | + +#### 7.17.1.6 PD-ACK.indication + +The PD-ACK.indication primitive indicates reception of the ACK frame from the PHY to the local MAC sublayer entity. The semantics of the PD-ACK.indication primitive is as follows: + +``` +PD-ACK.indication ( + FCH +) +``` + +Table 7-29 specifies the parameter for the PD-ACK.indication primitive. + +**Table 7-29 – The parameters for the PD-ACK.indication primitive** + +| Name | Type | Valid range | Description | +|------|-----------|----------------|----------------------------------------------------------------------------------------------------| +| FCH | Structure | Clause 7.6 PHY | The MAC layer receives all frame control header parameters described in clause 7.6 from PHY layer. | + +### 7.17.2 Management primitives + +There are two types of management primitives: Get and Set. They are used to initiate commands or retrieve data from the PHY. The PLME\_SET.request and PLME\_SET.confirm primitives allow configuration of the PHY. The PLME\_GET.request and PLME\_GET.confirm primitives allow the retrieval of specific parameters from the PHY. + +![Diagram showing the management primitive flow between MAC and PHY layers. The MAC layer sends PLME_SET.request and PLME_GET.request to the PHY layer. The PHY layer responds with PLME_SET.confirm and PLME_GET.confirm. The diagram is labeled G.9903(14)_F7-22.](4162c218fc7881cd90fc9574e07d2327_img.jpg) + +``` + +graph LR + MAC[MAC] --> PHY[PHY]: PLME_SET.request + PHY --> MAC: PLME_SET.confirm + MAC --> PHY: PLME_GET.request + PHY --> MAC: PLME_GET.confirm + +``` + +G.9903(14)\_F7-22 + +Diagram showing the management primitive flow between MAC and PHY layers. The MAC layer sends PLME\_SET.request and PLME\_GET.request to the PHY layer. The PHY layer responds with PLME\_SET.confirm and PLME\_GET.confirm. The diagram is labeled G.9903(14)\_F7-22. + +**Figure 7-22 – Management primitive flow** + +#### **7.17.2.1 PLME\_SET.request** + +The semantics of the PLME\_SET.request primitive is as follows: + +``` + +PLME_SET.request ( + TXPower + PayloadModulationType + PayloadModulationScheme + ToneMap + PreEmphasis + ToneMask + DT +) + +``` + +Table 7-30 specifies the parameters for the PLME\_SET.request primitive. + +**Table 7-30 – The parameters for the PLME\_SET.request primitive** + +| Name | Type | Valid range | Description | +|--------------------------|---------|-------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| TXPower | Integer | 0x00-0x20 | The MAC layer uses this primitive to notify the PHY about the gain/power setting PHY has to use to transmit the next packet. | +| PayloadModulation Type | Integer | 0x0-0x4 | This sets the transmitter modulation for the next frame:
0: Robust mode
1: DBPSK or BPSK
2: DQPSK or QPSK
3: D8PSK or 8-PSK
4: 16-QAM
Note – The 16-QAM modulation is optional and may be used only in an FCC bandplan when a coherent modulation scheme applies. | +| PayloadModulation Scheme | Integer | 0x0-0x1 | Defines whether the differential or optional coherent modulation scheme shall be used for the payload. | + +**Table 7-30 – The parameters for the PLME\_SET.request primitive** + +| Name | Type | Valid range | Description | +|-------------|---------|-------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| | | | 0: Differential
1: Coherent | +| ToneMap | Array | 0x0-0x1 | Tone map parameter
The value of 0 indicates to the remote transmitter that dummy data should be transmitted on the corresponding subcarrier while a value of 1 indicates that valid data should be transmitted on the corresponding subcarrier. | +| PreEmphasis | Array | 0x00-0x1F | Specify transmit gain for each sub-band represented by tone map. | +| ToneMask | Array | 0x0-0x1 | Tone mask parameter.
The value of 0 indicates tone is notched, 1 indicates that tone is enabled. | +| DT | Integer | 0x00-0x07 | Delimiter type as specified in Table 7-12. | + +#### 7.17.2.2 PLME\_SET.confirm + +The PHY stores new parameters and returns a new stored value back to the MAC layer. The semantics of the PLME\_SET.confirm primitive is as follows: + +PLME\_SET.confirm ( +    TXPower +    PayloadModulationType +    PayloadModulationScheme +    ToneMap +    PreEmphasis +    ToneMask +    DT +) + +Table 7-31 specifies the parameters for the PLME\_SET.confirm primitive. + +**Table 7-31 – The parameters for the PLME\_SET.confirm primitive** + +| Name | Type | Valid range | Description | +|------------------------|---------|-------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| TXPower | Integer | 0x00-0x20 | Returns new stored value back to MAC | +| PayloadModulation Type | Integer | 0x0-0x04 | Returns new stored value back to MAC:
0: Robust mode
1: DBPSK or BPSK
2: DQPSK or QPSK
3: D8PSK or 8-PSK
4: 16-QAM
Note – The 16-QAM modulation is optional and may be used in FCC bandplan only when coherent modulation scheme applies. | + +**Table 7-31 – The parameters for the PLME\_SET.confirm primitive** + +| Name | Type | Valid range | Description | +|--------------------------|---------|-------------|-------------------------------------------------------------------------------------------------------------------------------------------| +| PayloadModulation Scheme | Integer | 0x0-0x1 | Defines whether the differential or optional coherent modulation schemes shall be used for the payload.
0: Differential
1: Coherent | +| ToneMap | Array | 0x0-0x1 | Returns new stored value back to MAC | +| PreEmphasis | Array | 0x00-0x1F | Returns new stored value back to MAC | +| ToneMask | Array | 0x0-0x1 | Returns new stored value back to MAC | +| DT | Integer | 0x00-0x07 | Delimiter type as specified in Table 7-12 | + +#### 7.17.2.3 PLME\_GET.request + +The PLME\_GET.request primitive requests the PHY to get the parameters described in Table 7-32. The semantics of the PLME\_GET.request primitive is as follows: + +PLME\_GET.request ( +) + +#### 7.17.2.4 PLME\_GET.confirm + +The semantics of the PLME\_GET.confirm primitive is as follows: + +PLME\_GET.confirm ( +    CarrierSNR, +    PhaseDifferential, +    PayloadModulationType, +    PayloadModulationScheme +    ToneMap, +    DT +) + +Table 7-32 specifies the parameters for the PLME\_GET.confirm primitive. + +**Table 7-32 – The parameters for the PLME\_GET.confirm primitive** + +| Name | Type | Valid range | Description | +|--------------------------|---------|-------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| CarrierSNR | Array | 0x00-0x3F | The PHY provides the SNR value per each carrier of the last received frame. | +| PhaseDifferential | Integer | 0x00-0x05 | The PHY computes and provides the phase difference in multiples of 60 degrees to the MAC layer of the last received frame.
0: local node and neighbour node are in phase
1: local node leads neighbour node by 60 degrees
2: local node leads neighbour node by 120 degrees
3: neighbour node and local node are in phase opposition
4: neighbour node leads local node by 120 degrees
5: neighbour node leads local node by 60 degrees | +| PayloadModulation Type | Integer | 0x00-0x04 | The modulation type used in the last received frame.
0 : Robust mode
1 : DBPSK or BPSK
2 : DQPSK or QPSK
3 : D8PSK or 8-PSK
4 : 16-QAM
NOTE – The 16-QAM modulation is optional and may be used in an FCC bandplan only when the coherent modulation scheme applies. | +| PayloadModulation Scheme | Integer | 0x00-0x01 | The payload modulation scheme used in the last received frame.
0 : Differential
1 : Coherent | +| ToneMap | Array | 0x00-0x01 | Tone map parameter used in the last received frame.
The value of 0 indicates to the remote transmitter that dummy data should be transmitted on the corresponding subcarrier while a value of 1 indicates that valid data should be transmitted on the corresponding subcarrier. | +| DT | Integer | 0x00-0x07 | Delimiter type used in the last received frame.
0: Acknowledgment is not requested
1: Acknowledgment is requested
2-7: Reserved by ITU-T | + +CarrierSNR is an array of integers ranging from 0x00 to 0x3F, where values in-between shall be uniformly distributed between these two limits. The CarrierSNR values are normalized to the range from –10 dB or lower (0x00) to 53 dB or higher (0x3F), where the value of –9 dB is represented as 0x01 and the value of 52 dB is represented as 0x3E. + +#### 7.17.2.5 PLME\_SET\_TRX\_STATE.request + +The PLME\_SET\_TRX\_STATE.request primitive requests the PHY to change the state. The semantics of the PLME\_SET\_TRX\_STATE.request primitive is as follows: + +PLME\_SET\_TRX\_STATE.request ( +    State +) + +Table 7-33 specifies the parameters for the PLME\_SET\_TRX\_STATE.request primitive. + +**Table 7-33 – The parameters for the PLME\_SET\_TRX\_STATE.request primitive** + +| Name | Type | Valid range | Description | +|-------|-------------|--------------------------|----------------------------------------------------------------------------------------------------------------------| +| State | Enumeration | TXON_RXOFF
TXOFF_RXON | Turns off the RX PHY when transmitting packet. Turns off the transmitter and enable RX when PHY is not transmitting. | + +#### 7.17.2.6 PLME\_SET\_TRX\_STATE.confirm + +The PLME\_SET\_TRX\_STATE.confirm primitive confirms the changing PHY state. The semantics of the PLME\_SET\_TRX\_STATE.confirm primitive is as follows: + +PLME\_SET\_TRX\_STATE.confirm ( +    Status +) + +Table 7-34 specifies the parameters for PLME\_SET\_TRX\_STATE.confirm primitive. + +**Table 7-34 – The parameters for the PLME\_SET\_TRX\_STATE.confirm primitive** + +| Name | Type | Valid range | Description | +|--------|-------------|-------------------------------|--------------------------------------------------------------------------| +| Status | Enumeration | SUCCESS
BUSY_TX
BUSY_RX | Confirm RX and TX are set or provide error message if TX or RX are busy. | + +#### 7.17.2.7 PLME\_CS.request + +The PLME\_CS.request primitive requests the PHY to get media status using carrier sense. The semantics of the PLME\_CS.request primitive is as follows: + +PLME\_CS.request ( +) + +#### 7.17.2.8 PLME\_CS.confirm + +The PLME\_CS.confirm primitive reports media status. The semantics of the PLME\_CS.confirm primitive is as follows: + +PLME\_CS.confirm ( +    Status +) + +Table 7-35 specifies the parameters for the PLME\_CS.confirm primitive. + +**Table 7-35 – The parameters for the PLME\_CS.confirm primitive** + +| Name | Type | Valid range | Description | +|--------|-------------|--------------|-------------------------| +| Status | Enumeration | IDLE
BUSY | Power line media status | + +A physical carrier sense (PCS) shall be provided by the PHY upon detection of aSlotTime preamble symbols. The PCS shall go back to idle if synchronisation has not been achieved. The status of the media is tracked by the virtual carrier sense (VCS), see clause 9.3.1 for more details. + +# 8 Transmitter specifications + +## 8.1 Output level measurement + +See the main body of [ITU-T G.9901]. + +## 8.2 Transmit spectrum mask + +See clause B.3 of [ITU-T G.9901]. + +## 8.3 Transmitter attenuation + +ITU-T G.9903 nodes shall operate with an output level determined by the value of attribute macTransmitAtten (see Table 9-15). A node shall apply to its maximum output level the attenuation level stored in attribute macTransmitAtten, allowing a reduction of its maximum output level of up to 25 dB. This attenuation is calibrated when measuring the output level using the standard Termination Networks TN1 or TN2 as specified in clause 6 of [ITU-T G.9901]. When macTransmitAtten is greater than 0, no transmitter gain shall be applied to the transmitted signal (TX GAIN shall still be stored in the neighbour table but it shall be ignored). + +## 8.4 Spurious transmission + +See clause B.3.1 of [ITU-T G.9901]. + +## 8.5 System clock frequency tolerance + +The system clock tolerance shall be $\pm 25$ ppm maximum. The transmit frequency and symbol timing shall be derived from the same system clock oscillator. + +## 8.6 Transmitter constellation + +### 8.6.1 Transmitter constellation error + +The relative constellation rms error, averaged over all subcarriers in a symbol, and averaged over several OFDM symbols, shall not exceed $-15$ dB from the ideal signal rms level. + +### 8.6.2 Transmit modulation accuracy test + +The transmit modulation accuracy test shall be performed by instrumentation capable of converting the transmitted signal into a stream of samples at 400 K samples per second or more, with sufficient accuracy in terms of amplitude, DC offsets and phase noise. The sampled signal shall be processed in a manner similar to an actual receiver, according to the following steps, or an equivalent procedure: + +- 1) Pass a sequence of 37 bytes all-ones, representing a 12-symbol QPSK frame, through an ideal floating-point transmitter and save the complex input to the IFFT block for each of the 12 data symbols as $A_{i,c}e^{j\Phi_{i,c}}$ , where $A_{i,c}e^{j\Phi_{i,c}}$ is the reference constellation point corresponding to the $i$ -th OFDM symbol carried over the $c$ -th subcarrier. Index ' $i$ ' shall have + +values between 0 and 11 while index 'c' shall be between 0 and M-1 (M is the number of subcarriers in a given bandplan). The ideal transmitter should include all the transmitter blocks specified in this Recommendation, including scrambler, forward error correction, interleaver and mapper. + +- 2) Next, use the transmitter under test to generate the same frame using the bits specified in step 1. +- 3) Connect the test equipment that will simulate the receiver directly to the transmitter to detect the start of frame. +- 4) Save all time samples of the 12 OFDM symbols of the frame. +- 5) Offline, apply a floating point FFT on each OFDM symbol and store the complex values as $B_{i,c}e^{j\Theta_{i,c}}$ where 'i' is the OFDM symbol number and 'c' is the carrier number corresponding to that symbol. $B_{i,c}e^{j\Theta_{i,c}}$ represents the actually transmitted constellation point and, ideally, $A_{i,c}e^{j\Phi_{i,c}} = B_{i,c}e^{j\Theta_{i,c}}$ . +- 6) Compute the mean square error (MSE) between the ideal constellation points and the actually transmitted ones obtained at the end of step 5 for each symbol as the sum of the squared Euclidean distance between the two points over all the subcarriers in the symbol. The MSE of the *i*-th symbol is defined as: + +$$MSE_i = \frac{1}{M} \sum_{c=0}^{M-1} \left| A_{i,c}e^{j\Phi_{i,c}} - B_{i,c}e^{j\Theta_{i,c}} \right|^2$$ + +where M is the number of subcarriers per symbol in a given band (M=36 for CENELEC A; M=24 for CENELEC B; M= 72 for FCC). + +- 7) Next, compute the total MSE as the sum of the MSEs of the each OFDM symbols: + +$$Total\_MSE = \sum_{i=0}^{11} MSE_i$$ + +- 8) Compute the average energy of the reference constellation points carried by the *i*-th OFDM symbol: + +$$Avg\_En^{(ref)} = \frac{1}{M} \sum_{c=0}^{M-1} |A_{i,c}|^2$$ + +and the total average energy for all transmitted OFDM symbols as: + +$$Tot\_En^{(ref)} = \sum_{i=0}^{11} Avg\_En_i^{(ref)}$$ + +The normalized total MSE in dB should satisfy the following equation: + +$$10\log_{10}\left(\frac{Total\_MSE}{Tot\_En^{(ref)}}\right) < -15\text{dB}$$ + +### 8.6.3 Error vector magnitude limits + +For the EVM calculation, the calculation given in clause 8.6.2 can be re-used here. For the preamble EVM calculation, the total average energy is calculated over six symbols starting from the third symbol: + +a) +$$\text{Tot\_En}^{(ref)} = \sum_{i=2}^7 \text{Avg\_En}_i^{(ref)}$$ + +b) +$$\text{Total\_MSE} = \sum_{i=2}^7 \text{MSE}_i$$ + +The values of EVM calculated for both data and preamble symbols shall not exceed the values given in Table 8-1. + +**Table 8-1 – Maximum allowed EVM values** + +| Modulation | EVM, dB (Note) | +|--------------|----------------| +| 1, 2, 3 bits | -15 | +| 4 bits | -19 | + +NOTE – These EVM requirements shall be met for all carriers which have equal transmit power levels; however, for 3 and 4 bit modulations, the transmit power levels under which these requirements are met may be lower than those for 1 and 2 bit modulation. + +## 8.7 Transmitter spectral flatness + +The output signal voltage, when measured using a peak detector with a 200 Hz bandwidth and loaded on an artificial mains network (AMN), shall not exceed 5dB between the highest and the lowest peaks measured at the frequency of the subcarriers. + +When measuring the transmitter spectral flatness, no transmitter gain shall be applied to the transmitted signal (TXGAIN and TXCOEF shall be set to zero) and the AMN shall comply with clauses 4.3 and 4.4 of [CISPR16-1-2], as specified in clauses 6 and 7.1 of [ITU-T G.9901]. + +## 8.8 Crossing MV/LV transformer + +ITU-T G.9903 devices operate over both low-voltage and medium-voltage power lines. When operating over a medium-voltage power line an ITU-T G.9903 device can communicate with ITU-T G.9903 devices operating over low-voltage power lines. This means that the receiver on the LV side can detect the transmitted signal after it has been severely attenuated as a result of going through an MV/LV transformer. As the signal goes through the transformer, it is expected to experience overall severe attenuation in its power level as well as frequency-dependent attenuation. Both the transmitter and receiver have mechanisms to compensate for this attenuation. The transmitter can adjust its overall signal level as well as shape its power spectrum, while the receiver has an automatic gain control in order to achieve enough gain to compensate for the overall attenuation. + +An ITU-T G.9903 node, in addition to being able to operate in normal mode, can operate as a repeater. When configured in "repeater" mode, the ITU-T G.9903 node can decode received frames and then retransmit them at a higher signal level in order to partially compensate for the attenuation introduced by the transformer. The repeater, when needed, can be placed on the LV side of the MV/LV transformer. + +## 8.9 MV coupler (informative) + +ITU-T G.9903 devices interface with the MV power line through a PLC coupling device, which is basically a high-pass filter whose purpose is to permit the PLC signal to pass, but to reject the power system frequency and protect the communications equipment from the power system voltage and transient voltages caused by switching operations. + +The basic circuit diagram is shown in the figure below. A complete coupling comprises a line trap to prevent the PLC signal from being short-circuited by the substation, and a coupling filter formed by the coupling capacitor and the coupling device. + +For ITU-T G.9903 devices, resolving impedance mismatching is very important in the sense of transferring maximum power to the signal input terminal of the MV power distribution lines. It is recommended that any transformer being used should be verified by measuring transmission and reflection characteristics through a vector network analyser. + +The proposed coupling interface, shown in Figure 8-1, should interface between the PLC device and the MV medium (with 24 kV and impedance of 75 $\Omega$ to 175 $\Omega$ ). + +![Figure 8-1 – Proposed coupling circuit diagram. The diagram shows a 'Medium voltage powerline' at the top connected to a 'Cut out switch' and a 'Capacitor'. These are enclosed in a dashed box. Below the capacitor is a 'high pass filter'. The output of the high pass filter is connected to an 'MV/LV coupler', which is a transformer. The secondary of the transformer is connected to an 'OFDM PLC modem'. The modem contains three blocks: 'Line driver', 'AFE', and 'Baseband', connected in series. Ground symbols are shown at the bottom of the powerline and the MV/LV coupler. A reference code 'G.9903(12)-Amd.1(13)_F8-1' is at the bottom right.](65e8c0628536d6d4245e9ab46ba070c3_img.jpg) + +Figure 8-1 – Proposed coupling circuit diagram. The diagram shows a 'Medium voltage powerline' at the top connected to a 'Cut out switch' and a 'Capacitor'. These are enclosed in a dashed box. Below the capacitor is a 'high pass filter'. The output of the high pass filter is connected to an 'MV/LV coupler', which is a transformer. The secondary of the transformer is connected to an 'OFDM PLC modem'. The modem contains three blocks: 'Line driver', 'AFE', and 'Baseband', connected in series. Ground symbols are shown at the bottom of the powerline and the MV/LV coupler. A reference code 'G.9903(12)-Amd.1(13)\_F8-1' is at the bottom right. + +**Figure 8-1 – Proposed coupling circuit** + +**Table 8-2 – Coupler technical characteristics (informative)** + +| Parameter | Measurement conditions | Value | +|----------------------------------------------|--------------------------------------------------------------------------------------|-----------------------------------------| +| Medium-voltage circuit parameters | | | +| Primary test voltage $U_N$ | Voltage between the device input and grounding output | $24/\sqrt{3}$ kV rms | +| Test short-term alternating voltage $U_{TH}$ | Voltage between the device input and grounding output during one minute | 50 kV rms | +| Maximum short-term working voltage $U_{MAX}$ | Medium voltage during nine hours | 26 kV rms
9 hours | +| Test lightning impulse voltage $U_L$ | Impulse with duration of 1,2/50 us between the device input and the grounding output | 125 kV | +| Partial discharge level | | $\leq 20$ pC | +| Ambient temperature during operation | | $-40^\circ\text{C} - +65^\circ\text{C}$ | +| Coupling capacitor capacity $C_c$ | $-40^\circ\text{C} < T_a < +70^\circ\text{C}$ | 1.5 nF – 13 nF | +| Fuse operate time max | at $I \geq 30$ A
at $I \geq 45$ A | $t \leq 100$ ms
$t \leq 10$ ms | +| Low-voltage circuit parameters | | | + +**Table 8-2 – Coupler technical characteristics (informative)** + +| Parameter | Measurement conditions | Value | +|---------------------------------------------------------------------------------------------------------------------|----------------------------------------------|------------------------------------| +| Nominal line side impedance $R_{LINE}$ | | $75 \Omega \leq R \leq 170 \Omega$ | +| Nominal equipment side impedance $R_{LOAD}$ | | $75 \Omega$ | +| Maximum operating attenuation in receive and transmit direction at $R_{LOAD} = 75 \Omega$ , $R_{LINE} = 170 \Omega$ | $35 \text{ kHz} \leq f \leq 170 \text{ kHz}$ | 3 dB | + +## 8.10 AC phase detection + +It is necessary to know which phase each meter is placed on in an AMM application. This information is mainly useful at the system level in order to check for unexpected losses on the distribution line and shall be stored in the neighbour table. In addition, this information provides an indication of the presence of incorrect neutral and phase installations, which may result in hazardous installations or wrong energy consumption measurements. + +Three phases on the mains are sinusoidal waveforms with a phase shift of $120^\circ$ from each other where each full cycle is equal to 20 ms at 50 Hz and 16.66 ms at 60 Hz. A zero-crossing detector delivers an output pulse at the transition through zero volts of the rising edge of the 50 Hz (or 60 Hz) sinusoidal waveform. The transmitter generates a time stamp based on an internal counter at the instant a packet is transmitted using the phase detection counter (PDC) field of the FCH (see Tables 7-12 and 7-15). The receiver provides its own time stamp of the instant the packet is received and computes the delay and phase difference between the transmitter and the receiver. To support this computation: + +- 1) All devices including the meter and PAN coordinator shall have an internal timer that is synchronized with the zero-crossing detector. +- 2) All devices shall have a zero-crossing detector that delivers an output pulse signal on a sinusoidal power line rising edge. This characteristic of the zero-crossing detector is shown in Figure 8-2. +- 3) It is recommended that the zero-crossing detector output pulse signal shall reach 90% of its final value with a time deviation of no more than $\pm 5 \%$ of the power line time cycle from the actual zero crossing in the absence of noise. +- 4) The reference packet location to be used for the calculation of the phase detection in both transmit and receive shall be the first sample of the PHY FCH. +- 5) The 8-bit PDC shall count from 0 to 255 in one period of the mains. For example, the counter's ticks represent a time resolution of (20/256) ms for a 50 Hz mains and (16.66/256) ms for a 60 Hz mains. + +![Diagram of a zero-crossing detector. A sinusoidal waveform labeled 'mains' enters a block labeled 'Zero-crossing detector'. The output of the block is a pulse signal. The diagram shows the pulse width and the full cycle of the mains waveform. The text 'G.9903(14)_F8-2' is visible in the bottom right corner of the diagram area.](cfc2672ccfdf7b47212ef2b8d72c0ff3_img.jpg) + +Diagram of a zero-crossing detector. A sinusoidal waveform labeled 'mains' enters a block labeled 'Zero-crossing detector'. The output of the block is a pulse signal. The diagram shows the pulse width and the full cycle of the mains waveform. The text 'G.9903(14)\_F8-2' is visible in the bottom right corner of the diagram area. + +**Figure 8-2 – Zero-crossing detector** + +Determining the phase difference (PhaseDifferential) between the transmitter and the receiver is triggered upon creation of a neighbour table entry. On the basis of the phase detection counter (PDC) provided in the FCH, the result of the computation is stored in the neighbour table (see Tables 9-20 and 9-21). The procedure to determine the phase difference between the transmitter and receiver is as follows: + +- 1) An 8-bit counter (Tx\_PDC) in the transmitter represents the time between the last zero crossing prior to transmission of the packet FCH and the time stamp of the first FCH sample transmitted on the mains. This requires a transmitter to account for its implementation-specific packet processing delay. Tx\_PDC provides a time stamp which is placed in the FCH part of frame upon transmission of the payload: + +$$\text{Tx\_PDC} = \text{PDC} + (\text{transmission\_delay} \times \text{PDC\_Frequency})$$ + +where PDC is the raw count read from the transmitter's PDC before assembling the FCH, transmission\_delay is the transmitter's packet processing delay and PDC\_Frequency is the frequency of the PDC (12.8 kHz for 50 Hz and 15.36 kHz for 60 Hz mains). + +- 2) On the receiving node, once a packet is detected, the receiver implements an 8-bit counter (Rx\_PDC) to account for the time difference between the last zero crossing and the time stamp of the first sample of the first FCH symbol as received from the mains. This calculation requires the receiver to account for the time difference between the start of the received packet's preamble and the instant the packet is detected by the receiver: + +$$\text{Rx\_PDC} = \text{PDC} - (\text{detection\_delay} \times \text{PDC\_Frequency})$$ + +where PDC is the raw count read from the receiver's PDC when a packet is detected, detection\_delay is the time difference between the receiver's packet detection and the time the first sample of the FCH for the current packet is received from the mains and PDC\_Frequency is as defined above. + +- 3) Upon determining the RX\_PDC value, the receiver shall compute the delay between the transmit and receive nodes, which is the difference between Tx\_PDC and Rx\_PDC values. + +- a) Compute the phase detection count differential between Tx and Rx: + +$$\text{CounterDifferential} = (\text{Rx\_PDC} - \text{Tx\_PDC})$$ + +- b) If the reference zero crossing of the transmitter and the receiver are not the same, CounterDifferential can assume negative values. In this case, the following correction shall be applied: + +$$\text{If } (\text{CounterDifferential} < 0) \text{ CounterDifferential} = \text{CounterDifferential} + 256$$ + +- c) The phase differential expressed in multiples of 60 degrees is then computed as: + +$$\text{PhaseDifferential} = \text{round}(\text{CounterDifferential} / 60\_Degrees\_PDC) \% 6$$ + +Where: + +- 60\_Degrees\_PDC is the value of 60 degrees expressed in multiples of 256/360 increments, i.e., $60\_Degrees\_PDC = 60 * (256/360) = 42.66$ . +- "%" is the modulo operator. + +PhaseDifferential can assume six integer values between 0 and 5. If PhaseDifferential is an even number (0, 2, 4), then no phase/neutral inversion is detected. If PhaseDifferential is an odd number (1, 3, 5) then a phase/neutral inversion is detected. + +The PhaseDifferential value is passed to the MAC via the PLME\_GET.confirm primitive. + +NOTE – When a local node is determining the phase of a neighbour node, the transmitter (TX) corresponds to the neighbour node and the receiver (RX) corresponds to the local node. + +# 9 Data link layer specifications + +## 9.1 Introduction + +The ITU-T G.9903 data link layer specification comprises two sublayers: + +- the MAC sublayer based on [IEEE 802.15.4]; and +- the adaptation sublayer based on [IETF RFC 4944]. + +The present Recommendation specifies the necessary selections from and extensions to these standards. + +## 9.2 Conventions + +In this clause, the status of each requirement from the reference documents is given using the following convention: + +- I = "Informative". The statements of the reference document are provided for information only. +- N = "Normative": The statements of the reference document shall apply without modifications or remarks. +- S = "Selection": The statements of the reference document shall apply with the selections specified. +- E = "Extension": The statements of the reference document shall apply with the extensions (modifications and remarks noted under the part title) specified. +- N/R = "Not Relevant": The statements of the reference document do not apply. An explanation may be given under the part title. + +## 9.3 MAC sublayer specification + +### 9.3.1 Channel access + +#### 9.3.1.1 Overview + +The channel access is accomplished by using the carrier sense multiple access with collision avoidance (CSMA/CA) mechanism with a random back-off time. The random back-off mechanism spreads the time over which stations attempt to transmit, thereby reducing the probability of collision. Each time a device wishes to transmit data frames it shall wait for a contention period according to the packet's priority and then start the random period as described in clause 9.3.1.3. If the channel is found to be idle following the random back-off, the device shall transmit its data. If the channel is found to be busy following the random back-off, the device shall wait for the next contention period according to the packet's priority and then start another random period before trying to access the channel again. + +A carrier sense is a fundamental part of the distributed access procedure. The physical carrier sense (PCS) is provided by the PHY as described in clause 9.3.1.3. In the latter case, the PCS shall stay high long enough to be detected and the virtual carrier sense (VCS) to be asserted by the MAC. A virtual carrier sense mechanism tracks the expected duration of channel occupancy. Virtual carrier sense is set by the length of the received packet or upon collision including the time to wait for the next transmission window as specified in clauses 9.3.1.2 and 9.3.1.4. In these cases, the virtual carrier sense tracks the expected duration of the BUSY state of the medium. The medium shall also be considered busy when the station is transmitting. The VCS is also set upon collision, FCH decoding error or when the station powers up with respect to the EIFS. + +A collision occurs in each of the following circumstances: + +- The transmitting station receives something other than an ACK or NACK response when a response is expected. + +- The transmitting station shall infer a collision from the absence of any response to a transmission when a response is expected. Note that the absence of a response could also be the result of a bad channel. Since there is no way to distinguish between the two causes a collision is inferred. + +#### 9.3.1.2 Inter-frame (IFS) spacing + +The time intervals between frames on the medium constitute the inter-frame space and are necessary due to propagation and processing times. As shown in Figure 9-1, three inter-frame space values are defined. Contention inter-frame space (CIFS) occurs after the end of the previous transmission. The second defined interval is the response inter-frame space (RIFS). + +RIFS is the time between the end of a transmission and the start of its associated response. If no response is expected, the CIFS is in effect. + +An extended inter-frame space (EIFS) is defined for conditions when the station does not have complete knowledge of the state of the medium. This can occur when the station initially attaches to the network, when errors in the received frames make them impossible to decode unambiguously. If a packet is received and correctly decoded before the expiration of the EIFS, then the EIFS is cancelled. The EIFS is significantly longer than the other inter-frame spaces, providing protection from collision for an ongoing frame transmission or segment burst when any of these conditions occur. The EIFS is calculated as follows: + +$$aEIFS = aSymbolTime \times (N_{FCH} + aMaxFrameSize + aCIFS + aRIFS) + aAckTime$$ + +where $N_{FCH}$ is the number of symbols in the frame control header (FCH). + +![Figure 9-1 – IFS. The diagram illustrates three scenarios for inter-frame spacing. The top section, 'Interframe space if no response expected', shows a box for 'End of last transmission' followed by a double-headed arrow labeled 'CIFS' and then a box for 'Contention state'. The middle section, 'Interframe space if response expected', shows a box for 'End of last transmission', followed by a double-headed arrow labeled 'RIFS', a box for 'Ack', followed by a double-headed arrow labeled 'CIFS', and finally a box for 'Contention state'. The bottom section, 'Extended interframe space (EIFS) period', shows a box for 'EIFS due to frame errors or collision', followed by a box for 'Backoff', and finally a box for 'Frame transmission'. A small text 'G.9903(12)-Amd.1(13)_F9-1' is at the bottom right of the diagram.](dd6c544ab685b25dd17f59456efcfbfc_img.jpg) + +Figure 9-1 – IFS. The diagram illustrates three scenarios for inter-frame spacing. The top section, 'Interframe space if no response expected', shows a box for 'End of last transmission' followed by a double-headed arrow labeled 'CIFS' and then a box for 'Contention state'. The middle section, 'Interframe space if response expected', shows a box for 'End of last transmission', followed by a double-headed arrow labeled 'RIFS', a box for 'Ack', followed by a double-headed arrow labeled 'CIFS', and finally a box for 'Contention state'. The bottom section, 'Extended interframe space (EIFS) period', shows a box for 'EIFS due to frame errors or collision', followed by a box for 'Backoff', and finally a box for 'Frame transmission'. A small text 'G.9903(12)-Amd.1(13)\_F9-1' is at the bottom right of the diagram. + +G.9903(12)-Amd.1(13)\_F9-1 + +Figure 9-1 – IFS + +#### 9.3.1.3 CSMA-CA + +The present specification supports only an unslotted version of the CSMA-CA algorithm for non-beacon PAN described in [IEEE 802.15.4]. + +Channel access is accomplished by using the carrier sense multiple access with collision avoidance (CSMA/CA) mechanism with a random back-off time. The channel occupancy is sensed using physical carrier sense (PCS) which is provided by the PHY upon detection of the preamble and virtual carrier sense (VCS), which is a logical version of carrier sense and shall be asserted by the MAC. When there is traffic on the channel which is detected by the PCS, the VCS is asserted by the MAC. The VCS allows the MAC to factor in the expected duration of channel occupancy. VCS is + +set to BUSY for the duration of the detected packet or upon a collision. The medium is also considered BUSY when the station itself is transmitting. + +The random back-off mechanism spreads the time over which stations attempt to transmit, thereby reducing the probability of collision, using an additive decrease multiplicative increase (ADMI) back-off mechanism. + +The CSMA/CA algorithm shall be used before the transmission of data frames, MAC command frames and beacon frames during the active scan. + +If the macBroadcastMaxCWEnabled attribute is set to TRUE, then the MAC sublayer shall use the maximum CSMA contention window corresponding to macMaxBE for every broadcast data frame (excluding command and beacon frames) transmitted with normal priority to reduce network congestion. + +The algorithm is implemented using units of time called back-off periods, where one back-off period shall be equal to aUnitBackoffPeriod symbols, which is equal to aSlotTime. + +Each device shall maintain four variables for each transmission attempt: NB, NBF, minCWCount, and CW. + +NB is the number of times the CSMA-CA algorithm was required to back off while attempting the current transmission; this value shall be initialized to 0 before each new transmission attempt. + +NBF is a count of back-off attempts. It is used to control channel access fairness. + +minCWCount is the number of times the contention window reaches its minimum value $2^{\text{macMinBE}}$ . + +CW is the contention window for each device. On device startup, the CW is initialized to $2^{\text{macMinBE}}$ . The device shall then update the CW based on channel access success or failure as follows. + +For every channel access failure, the CW value doubles. The maximum value of CW is bounded by $2^{\text{macMaxBE}}$ . + +Upon a successful transmission, the CW value is adjusted using the formula: + +$$\text{CW}[\text{next}] = \max(\text{CW}[\text{prev}] - \text{macA} \times 2^{\text{macMinBE}}, 2^{\text{macMinBE}})$$ + +The default (recommended) value of macA is set as 8. + +Note that if macMinBE is set to 0, collision avoidance is disabled during the first iteration of this algorithm. + +Figures 9-2 and 9-3 illustrate the steps of the CSMA/CA algorithm for normal and high priority packets, respectively. The MAC sublayer shall first initialize NB and NBF to zero step (1), and then proceed directly to step (2). + +The MAC sublayer shall wait for the correct contention window according to the packet's priority as shown in Figures 9-2 and 9-3. The MAC may also transmit the higher priority packet in the NPCW according to the normal priority back-off mechanism. When the VCS state is IDLE, meaning no IFS window is currently counted, the MAC sublayer shall invoke the CSMA process. If the channel is IDLE, then the packet is transmitted. + +The MAC sublayer shall check if $\text{CW} = 2^{\text{macMinBE}}$ . If it is verified, it shall increment the minCWCount and reset NBF to zero, otherwise it shall reset minCWCount to zero. It shall then verify whether the $\text{minCWCount} > \text{macMinCWAttempts}$ . If yes, it shall reset CW to $2^{\text{macMaxBE}}$ . It shall then go to step (4). + +The MAC sublayer shall delay for a random number of complete back-off periods in the range 0 to CW-1 [step (4)]: $\text{Backoff Time} = \text{Random}(\text{CW}) \times \text{aSlotTime}$ and then request that the PHY performs a PCS (physical carrier sense) [step (5)]. + +If the channel is BUSY [step (6, No)] and if the NBF is less than macCSMAFairnessLimit, then the MAC sublayer shall increment NB and NBF and double the CW ensuring that CW does not exceed $2^{\text{macMaxBE}}$ . If the NBF is greater than or equal to macCSMAFairnessLimit and it is a multiple of macK (fairness rate adaptation factor), then the CW is linearly decreased as in the case of a successful transmission. In all other cases, the CW value remains unchanged. + +Note that for high priority packets, the CW shall not exceed the macHighPriorityWindowSize. + +If the value of NB is less than or equal to macMaxCSMABackoffs, the CSMA/CA algorithm shall return to step (2). + +If the value of NB is greater than macMaxCSMABackoffs, the CSMA/CA algorithm shall terminate with a channel access failure status and the frame is dropped. + +If the channel is IDLE [step (6, Yes)], the MAC sublayer shall begin transmission of the frame at the start of the slot boundary. + +![](15de63f0b5df62e6ab9164f2a72e2e33_img.jpg) + +``` + +graph TD + Start([CSMA/CA]) --> Init[NB = 0, NBF = 0 (1)] + Init --> Wait[Wait for NPCW start (2)] + Wait --> IfCW{If CW = 2macMinBE} + IfCW --|No|--> ResetCount[minCWcount = 0] + IfCW --|Yes|--> IncCount[minCWcount++, NBF = 0] + ResetCount --> IfMinCW{If minCWcount > macMinCWAttempts} + IncCount --> IfMinCW + IfMinCW --|Yes (3)|--> SetCW[CW = 2macMaxBE] + IfMinCW --|No (4)|--> Delay[Delay for random(CW) unit backoff periods] + SetCW --> Delay + Delay --> PCS[Perform PCS (5)] + PCS --> Idle{Channel idle? (6)} + Idle --|No|--> IncNB[NB++, NBF++] + Idle --|Yes|--> SuccessCW[CW = max(CW - macA × 2macMinBE, 2macMinBE)] + SuccessCW --> Success([SUCCESS]) + IncNB --> IfFair{NBF >= macCSMAFairnessLimit} + IfFair --|No|--> UpdateCW[CW = min(2 × CW, 2macMinBE)] + IfFair --|Yes|--> IfMod{mod(NBF, macK) == 0} + IfMod --|No|--> CheckNB + IfMod --|Yes|--> FairCW[CW = max(CW - macA × 2macMinBE, 2macMinBE)] + UpdateCW --> CheckNB{NB > macMaxCSMABackoffs? (7)} + FairCW --> CheckNB + CheckNB --|No|--> Wait + CheckNB --|Yes|--> Failure([FAILURE]) + +``` + +Figure 9-2 – CSMA/CA algorithm for a normal priority contention window (NPCW) + +60 Rec. ITU-T G.9903 (08/2017) + +![](af6c3f383ddc0c142cdd7e186cc78199_img.jpg) + +``` + +graph TD + Start([CSMA/CA]) --> Init["NB = 0 (1)"] + Init --> Wait["Wait for HPCW start"] + Wait --> Delay["Delay for +random(macHighPriorityWindowSize) +* aSlotTime (2)"] + Delay --> PCS["Perform PCS (3)"] + PCS --> Idle{Channel idle?} + Idle -- No --> NBinc["NB++ (4)"] + NBinc --> MaxNB{NB > +macMaxCSMABackoffs?} + MaxNB -- No --> Wait + MaxNB -- Yes --> Failure([FAILURE]) + Idle -- Yes --> Success([SUCCESS]) + style Success fill:none + style Failure fill:none + style Start fill:none + +``` + +G.9903(12)-Amd.1(13)\_F9-3 + +**Figure 9-3 – CSMA/CA algorithm for a high priority contention window (HPCW)** + +#### **9.3.1.4 Priority** + +Prioritized access to the channel can be beneficial for real time application or control application when an urgent message shall be delivered as soon as possible. Only two levels of priority (high and normal) will be used to minimize complexity. Priority resolution is implemented by using two contention time windows during the contention state as shown in Figure 9-4. + +![Timeline diagram showing priority contention windows (HPCW and NPCW) following an Ack frame.](331afcb1534110b4c4f6ddf553a0f7e0_img.jpg) + +The diagram illustrates the timing of contention windows. It starts with a block labeled 'End of last transmission', followed by a 'RIFS' (Recovery Interframe Space) interval indicated by dashed vertical lines. This is followed by an 'Ack' frame block. After the Ack frame, a 'CIFS' (Collision Interframe Space) interval occurs. The 'Contention state' begins after CIFS and is divided into two contiguous windows: 'High priority' and 'Normal priority'. A 'CFS' (Contention Free Slot) marker is at the start of the High priority window. The entire contention state is bounded by dashed vertical lines and a double-headed arrow below. + +G.9903(12)-Amd.1(13)\_F9-4 + +Timeline diagram showing priority contention windows (HPCW and NPCW) following an Ack frame. + +**Figure 9-4 – Priority contention windows** + +The first slot of contention window is called the contention free slot (CFS). The contention free slot shall be used for transmission of subsequent segments of a MAC frame without the back-off procedure to prevent possible interruption from other nodes and to simplify the MAC frame reassembly procedure on a receiver. In this case, only the first segment is sent using either a normal or high priority contention window and the rest are sent using the contention free slot. + +The high and normal priority stations will compete for channels during the high priority contention window (HPCW) and normal priority contention window (NPCW) correspondingly. Since HPCW is located before NPCW, high priority stations will get access to the channel before the station with normal priority. The duration of HPCW and NPCW are calculated as follow: + +$$\text{HPCW time} = \text{macHighPriorityWindowSize} \times \text{aSlotTime};$$ + +$$\text{NPCW time} = (2^{\text{maxBE}} \times \text{aSlotTime});$$ + +$$\text{CFS time} = \text{aSlotTime};$$ + +Each station that does not have a packet to transmit may optionally wait for a random period in the normal priority contention window, according to the algorithm described in clause 9.3.1.3. If the MAC sublayer receives a packet for transmission during the back-off count, it may transmit the packet at the end of the count when the packet's priority is higher or equal to the current priority contention window. If there is no packet to transmit, the station may perform a PCS. If the channel is IDLE, the station may assume the IDLE state. If the channel is BUSY, the station may assume the BUSY state and may wait for the end of packet event to start the RIFS as described in clause 9.3.1.2. + +#### 9.3.1.5 ARQ + +The automatic repeat request (ARQ) is implemented based on acknowledged and unacknowledged retransmission. The MAC sublayer uses a response type as part of its ARQ mechanism. ACK is a traditional positive acknowledgement that when received allows the transmitter to assume successful delivery of the frame. The negative acknowledgement (NACK) is used to inform a packet originator that the receiver received the packet but it was corrupted. The usage of ACK and NACK responses is described in clause 9.3.2. + +If the originator does not receive an acknowledgement after a waiting period of `macAckWaitDuration` microseconds, it assumes that the transmission was unsuccessful and retries the frame transmission in the correct contention period as specified in clause 9.3.2.5. If an acknowledgement is still not received after several retries, the originator can choose either to terminate the transaction or to try again. When the acknowledgement is not requested, the originator assumes the transmission was successful. Also if acknowledgement is not requested the originator can retransmit the same packets few times to increase probability of data delivery. The receiver shall be able distinguish and discard redundant copies using the sequence number and segment count. The retransmitted packet will have the same sequence number and segment count as the original. The retransmission of a packet or segment shall trigger the generation of new `PD-DATA.request` primitive(s). + +A device shall not transmit a new command or a data frame during retransmission of the current frame. + +The acknowledgement cannot be requested for broadcast transmission. On the transmit side the ARQ shall configure the number of retransmissions (cf. `macMaxFrameRetries` from clause 7.4.2 of [IEEE 802.15.4]) as shown in Figure 9-5. + +On the receive side the ARQ generates acknowledgement for the PLC packet with the correct FCS (CRC16) if the packet corresponds to this address and may generate the NACK only when the FCS fails, but the packet corresponds to its address as shown in Figure 9-6. + +The received packet FCS (16 bits) will be sent back to the packet originator as a part of an acknowledgement (frame control header). + +All nodes will detect ACK during response time but only one station expecting ACK will accept it as acknowledgement and use 16 bit of the FCS from ACK for identification. + +![Flowchart of the Transmit ARQ protocol. The process starts with 'TX ARQ', followed by 'Transmit packet with response expected according to CSMA/CA'. It then enters a loop: 'Receive ACK?' (Yes leads to 'SUCCESS', No leads to 'Receive NACK?'). 'Receive NACK?' (Yes leads to 'Wait EIFS', No leads to 'Response time expired?'). 'Response time expired?' (No loops back to 'Transmit packet...', Yes leads to 'Wait EIFS'). 'Wait EIFS' leads to 'Number of retries expired?' (No loops back to 'Transmit packet...', Yes leads to 'Discard packet'). 'Discard packet' leads to 'FAILURE'.](c3254408eadbf152632a8faf16310722_img.jpg) + +``` +graph TD; TX[TX ARQ] --> TP[Transmit packet with response expected according to CSMA/CA]; TP --> RA{Receive ACK?}; RA -- Yes --> S([SUCCESS]); RA -- No --> RN{Receive NACK?}; RN -- Yes --> WE[Wait EIFS]; RN -- No --> RE{Response time expired?}; RE -- No --> TP; RE -- Yes --> WE; WE --> NR{Number of retries expired?}; NR -- No --> TP; NR -- Yes --> DP[Discard packet]; DP --> F([FAILURE]); +``` + +G.9903(12)-Amd.1(13)\_F9-5 + +Flowchart of the Transmit ARQ protocol. The process starts with 'TX ARQ', followed by 'Transmit packet with response expected according to CSMA/CA'. It then enters a loop: 'Receive ACK?' (Yes leads to 'SUCCESS', No leads to 'Receive NACK?'). 'Receive NACK?' (Yes leads to 'Wait EIFS', No leads to 'Response time expired?'). 'Response time expired?' (No loops back to 'Transmit packet...', Yes leads to 'Wait EIFS'). 'Wait EIFS' leads to 'Number of retries expired?' (No loops back to 'Transmit packet...', Yes leads to 'Discard packet'). 'Discard packet' leads to 'FAILURE'. + +**Figure 9-5 – Transmit ARQ** + +![Flowchart for Receive ARQ process. It starts with 'RX ARQ' (oval), followed by 'Receive packet with response expected' (rectangle). A decision diamond 'Valid FCS?' follows. If 'Yes', it goes to 'Send ACK' (rectangle) and then 'SUCCESS' (oval). If 'No', it goes to another decision diamond 'Valid to send NACK?'. If 'Yes', it goes to 'Send NACK' (rectangle), then 'Discard packet' (rectangle), and finally 'FAILURE' (oval). If 'No', it goes directly to 'Discard packet' (rectangle) and then 'FAILURE' (oval). A small note 'G.9903(12)-Amd.1(13)_F9-6' is at the bottom right.](a4de02b04a1a8f6cb8121ac2e11bf95a_img.jpg) + +``` + +graph TD + RX_ARQ([RX ARQ]) --> RP[Receive packet with response expected] + RP --> VFCS{Valid FCS?} + VFCS -- Yes --> SA[Send ACK] + SA --> SUCCESS([SUCCESS]) + VFCS -- No --> VSN{Valid to send NACK?} + VSN -- Yes --> SN[Send NACK] + SN --> DP[Discard packet] + VSN -- No --> DP + DP --> FAILURE([FAILURE]) + +``` + +G.9903(12)-Amd.1(13)\_F9-6 + +Flowchart for Receive ARQ process. It starts with 'RX ARQ' (oval), followed by 'Receive packet with response expected' (rectangle). A decision diamond 'Valid FCS?' follows. If 'Yes', it goes to 'Send ACK' (rectangle) and then 'SUCCESS' (oval). If 'No', it goes to another decision diamond 'Valid to send NACK?'. If 'Yes', it goes to 'Send NACK' (rectangle), then 'Discard packet' (rectangle), and finally 'FAILURE' (oval). If 'No', it goes directly to 'Discard packet' (rectangle) and then 'FAILURE' (oval). A small note 'G.9903(12)-Amd.1(13)\_F9-6' is at the bottom right. + +**Figure 9-6 – Receive ARQ** + +#### 9.3.1.6 Segmentation and reassembly overview + +The ITU-T G.9903 PHY layer supports different types of modulation and tone maps. The number of data bytes of the PHY payload can change dynamically based on channel conditions. This requires implementing MAC payload fragmentation on the MAC sublayer. If the size of the MAC payload plus the MAC header is too large to fit within one PSDU, it must be partitioned into smaller segments that can each fit within a PSDU. This process of partitioning the MAC frame into PSDUs is called segmentation and the reverse process is called reassembly. The segmentation may require the addition of padding bytes to the last segment to fit the last PHY frame. The acknowledgement and retransmission occurs independently for the resulting MAC segment. All forms of addressing (unicast and broadcast) are subject to the segmentation. + +The segment control field definitions are shown in Table 9-5. + +When segmentation occurs, each resulting segment shall be created as follows: + +- The MAC header (MHR) and FCS (MFR) are presented in each segment. +- All segments have the same value in the sequence number field, using the value assigned for the MAC frame. Only the segment count is incremented for following segments. +- Segment count (SC) shall be set to 0 for the first segment and incremented for each following segment. +- If data encryption is required it must be done before packet segmentation. On the receiver side data decryption is done after packet reassembly. The Security Enabled field is set to 1 for all segments of a ciphered frame. The Auxiliary Security Header is only present in the first segment of a ciphered frame. +- All segments except the last one shall set the contention control (CC) bit to inform the receiver that the next PHY frame will be sent in the contention free slot. The last segment clears the contention control bit to allow the normal contention access to the channel. + +- For a frame that requires setting the TMR bit, the TMR bit shall be set in the last segment only. +- Last segment flag (LSF) shall be set to 1 to indicate the last segment of the MAC frame. +- Segment length (SL) specifies the length of the MAC payload in bytes for the current segment excluding the MAC header, byte padding and FCS. When security is activated, the MAC payload is constituted of the ciphered payload and the MIC-32. + +The segment control fields (see Table 9-5) SL, SC and LSF are used to keep track of segments of the fragmented MAC packet and assembling the whole packet on the receiver side. + +### 9.3.2 MAC acknowledgement + +The present specification does not use the MAC acknowledgement frame specified in [IEEE 802.15.4] but specifies positive and negative acknowledgements using the frame control header (see clause 7.6). + +The frame control header (FCH) contains information used by all stations in the network for channel access, as well as PHY receiver information used by the destination. For this reason, the frame control header has specific physical layer encoding and modulation as defined in clause 7.6. + +Only the frame control header will be used as positive (ACK) or negative (NACK) acknowledgement. + +The packet originator may request an acknowledgement by setting the delimiter type field of the frame control header (see clause 7.6). + +#### 9.3.2.1 ACK Generation + +If the MAC frame is received without error as determined by the FCS, the receiver shall send an ACK to the originator only if an acknowledgement is requested and the destination address and PAN ID of the frame match the receiver's device address and PAN ID. + +#### 9.3.2.2 NACK Generation + +If the MAC frame is received with errors as determined by the FCS, the receiver may send a NACK to the originator only if an acknowledgement is requested and the destination address and PAN ID of the frame match the receiver's device address and PAN ID. The NACK frame shall have its SSCA bit set to prevent other nodes from transmitting during retransmission. + +#### 9.3.2.3 NACK Generation avoidance + +If the receiver can determine that the error is caused by collision, it may avoid sending a NACK (no response) to invoke a collision state on the transmitting station. The transmitting station shall infer a collision from the absence of any response to a transmission when a response is expected. + +#### 9.3.2.4 ACK and NACK validity + +The transmitter shall extract the FCS field from the received ACK/NACK and compare it with the FCS of the transmitted packet to determine the validity of the response. If it matches, the ACK/NACK response is accepted otherwise it will be ignored and treated as a collision. + +The FCS field contains a 16-bit CRC calculated over the MHR and MAC payload parts of the frame using an MSBit endianess convention as described in [IEEE 802.15.4] clause 7.2.1.9. + +As an example, consider the following frame: + +| MHR | Payload | FCS | +|----------------------------------------------------------|----------------------------------------------------|------| +| 09 00 0F 61 C8 6A 1D 78 0C 01 88 77 66 55 44
33 22 11 | 11 22 33 44 55 66 77 88 99 AA BB CC DD
EE FF 00 | xxxx | + +The computed CRC-16 on this frame is 0xD131 and it is stored into the frame in a Little Endian format as follows: + +| MHR | Payload | FCS | +|----------------------------------------------------------|----------------------------------------------------|-------| +| 09 00 0F 61 C8 6A 1D 78 0C 01 88 77 66 55 44
33 22 11 | 11 22 33 44 55 66 77 88 99 AA BB CC DD
EE FF 00 | 31 D1 | + +These 16 bits of the FCS are stored in the ACK and NACK frame as follows: + +TM[7:0] = FCS[15:8] = 0xD1 + +PDC[7:0] = FCS[7:0] = 0x31 + +#### 9.3.2.5 Segment Retransmission + +If a valid NACK is received, the transmitting station shall attempt the retransmission of a segment or frame (in the case of no segmentation) after a CIFS interval. + +In case of retransmission, only the corrupted segment shall be retransmitted as long as macMaxFrameRetries has not been exceeded. + +If neither ACK nor NACK is received while an acknowledgement was requested, the transmitting station shall attempt a segment retransmission after an EIFS interval using CSMA/CA, starting from the first segment. In this case, the retransmitted frame may be sent with different PHY transmission parameters (i.e., more reliable modulation, tone map, modulation scheme or power). The algorithm to select the new transmission parameters is left to the implementation but the last retransmission shall be done in the default robust mode. In the case of successful transmission, the parameters of the neighbour table entry (except TMValidTime) shall be updated accordingly. + +#### 9.3.2.6 Subsequent segment collision avoidance + +The CFS (contention free slot) is used to prevent other nodes from transmitting during the transmission of multiple segments. However, this still does not protect from collisions due to the possible presence of hidden nodes. Indeed, losses due to collisions occur when a node which is not in the sensing region of the transmitter but is in the sensing region of the receiver (hidden node) transmits a frame while the segmented frames are transmitted. + +To solve this case, upon receipt of a segment, the destination node shall send an ACK or a NACK frame with its SSCA field set to 1 if subsequent segments are expected. The SSCA flag is set in ACK/NACK if the incoming frame has the LSF (last segment field) in the segment control header (SCH) set to 0. Hence, the ACK or NACK frames are indicating nodes located in the transmitter's sensing region that subsequent segments will follow. With this mechanism, when no more segments are expected, the SSCA field is set back to 0. + +![Diagram illustrating subsequent segment collision avoidance. It shows a sequence of three segments (Segment #1, Segment #2, Segment #3) transmitted over time. Between Segment #1 and Segment #2, an ACK frame is sent with the SSCA bit set. Between Segment #2 and Segment #3, another ACK frame is sent with the SSCA bit set. After Segment #3, a final ACK frame is sent with the SSCA bit unset. The diagram also shows RIFS (Recovery Interframe Space) and CIFS (Collision Interframe Space) intervals. A 'Vulnerable period' is indicated by a double-headed arrow spanning from the start of Segment #1 to the start of Segment #3.](1274805226c5a1f8b875aea0296b9f0f_img.jpg) + +The diagram shows a sequence of frames: Segment #1, followed by RIFS, then an ACK frame with 'SSCA bit set', followed by CIFS, then Segment #2, followed by RIFS, then another ACK frame with 'SSCA bit set', followed by CIFS, then Segment #3, followed by RIFS, and finally an ACK frame with 'SSCA bit unset'. A double-headed arrow labeled 'Vulnerable period' spans from the start of Segment #1 to the start of Segment #3. The text 'G.9903(14)\_F9-7' is in the bottom right corner. + +Diagram illustrating subsequent segment collision avoidance. It shows a sequence of three segments (Segment #1, Segment #2, Segment #3) transmitted over time. Between Segment #1 and Segment #2, an ACK frame is sent with the SSCA bit set. Between Segment #2 and Segment #3, another ACK frame is sent with the SSCA bit set. After Segment #3, a final ACK frame is sent with the SSCA bit unset. The diagram also shows RIFS (Recovery Interframe Space) and CIFS (Collision Interframe Space) intervals. A 'Vulnerable period' is indicated by a double-headed arrow spanning from the start of Segment #1 to the start of Segment #3. + +**Figure 9-7 – Subsequent segment collision avoidance** + +Figure 9-7 shows the collision avoidance mechanism where the ACK frame for every segment except the last segment carries an indication that the receiver is expecting a subsequent segment. This causes the hidden nodes to back off for EIFS and prevents collision. Hence, the vulnerable period is reduced to the transmission of the first segment. + +### 9.3.3 MAC sublayer service specification + +#### 9.3.3.1 Selections + +The MAC services and primitives are as given in clauses 7.1.1 to 7.1.17 of [IEEE 802.15.4] together with the following statements and modifications shown in Table 9-1. + +References to clauses in the "Clause" column refer to the referenced document, while references to clauses/annexes in the "Title and remarks" column refer to this Recommendation unless specifically indicated otherwise. The interpretation of the statement column is given in clause 9-2. + +**Table 9-1 – Selections from clause 7.1 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.1 | MAC sublayer service specification | N | +| 7.1.1 | MAC data service
– MCPS-PURGE primitives are not used in this specification. | S | +| 7.1.1.1 | MCPS-DATA.request | N | +| 7.1.1.1.1 | Semantics of the service primitive
Extensions are described in clause 9.3.11.1
– | E | +| 7.1.1.1.2 | Appropriate usage | N | +| 7.1.1.1.3 | Effect on receipt
– GTS transmission is not used
– Only unslotted CSMA-CA for non-beacon-enabled PAN is used
– Indirect transmission is not supported | S | +| 7.1.1.2 | MCPS-DATA.confirm | N | +| 7.1.1.2.1 | Semantics of the service primitive
– Modification: Time stamp is optional and defined as the absolute time in milliseconds at which the frame was created and eventually after the encryption (32 bit value). | E | +| 7.1.1.2.2 | When generated | N | +| 7.1.1.2.3 | Appropriate usage | N | +| 7.1.1.3 | MCPS-DATA.indication | N | +| 7.1.1.3.1 | Semantics of the service primitive
Extensions are described in clause 9.3.11.2 | E | +| 7.1.1.3.2 | When generated | N | +| 7.1.1.3.3 | Appropriate usage | N | +| 7.1.1.4 | MCPS-PURGE.request | N/R | +| 7.1.1.5 | MCPS-PURGE.confirm | N/R | +| 7.1.1.6 | Data service message sequence chart | N | +| 7.1.2 | MAC management service | N | +| 7.1.3 | Association primitives | N/R | +| 7.1.3.1 | MLME-ASSOCIATE.request
– MLME-ASSOCIATE.request is not used in this specification.
Association is performed by the 6LoWPAN bootstrap protocol described in clause 9.4.4. | N/R | + +**Table 9-1 – Selections from clause 7.1 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.1.3.2 | MLME-ASSOCIATE.indication
– MLME-ASSOCIATE.indication is not used in this specification.
Association is performed by the 6LoWPAN bootstrap protocol described in clause 9.4.4. | N/R | +| 7.1.3.3 | MLME-ASSOCIATE.response
– MLME-ASSOCIATE.response is not used in this specification.
Association is performed by the 6LoWPAN bootstrap protocol described in clause 9.4.4. | N/R | +| 7.1.3.4 | MLME-ASSOCIATE.confirm
– MLME-ASSOCIATE.confirm is not used in this specification.
Association is performed by the 6LoWPAN bootstrap protocol described in clause 9.4.4 | N/R | +| 7.1.3.5 | Association message sequence chart
– The association message sequence chart described in Figure 31 shall be ignored for this specification, as association is performed using the bootstrap mechanism described in clause 9.4.4. | N/R | +| 7.1.4 | Disassociation primitive | N/R | +| 7.1.4.1 | MLME-DISASSOCIATE.request
– MLME-DISASSOCIATE.request is not used in this specification.
Disassociation is performed by the 6LoWPAN bootstrap protocol described in clause 9.4.4. | N/R | +| 7.1.4.2 | MLME-DISASSOCIATE.indication
– MLME-DISASSOCIATE.indication is not used in this specification.
Disassociation is performed by the 6LoWPAN bootstrap protocol described in clause 9.4.4. | N/R | +| 7.1.4.3 | MLME-DISASSOCIATE.confirm
– MLME-DISASSOCIATE.confirm is not used in this specification.
Disassociation is performed by the 6LoWPAN bootstrap protocol described in clause 9.4.4. | N/R | +| 7.1.4.4 | Disassociation message sequence chart
– The disassociation message sequence chart described in Figure 31 shall be ignored for this specification, as disassociation is performed using the bootstrap mechanism described in clause 9.4.4. | N/R | +| 7.1.5 | Beacon notification primitive | N | +| 7.1.5.1 | MLME-BEACON-NOTIFY.indication
– Only non-beacon-enabled PANs are used
– This primitive is generated upon receipt of a beacon during an active scan. | S | +| 7.1.5.1.1 | Semantics of the service primitive
MLME-BEACON-NOTIFY.indication (
PANDescriptor
)
PANDescriptor is described in Table 9-57. | S | + +**Table 9-1 – Selections from clause 7.1 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.1.5.1.2 | When generated
– This primitive is generated upon receipt of a beacon during an active scan. | S | +| 7.1.5.1.3 | Appropriate usage | N | +| 7.1.6 | Primitives for reading PIB attributes | N | +| 7.1.6.1 | MLME-GET.request | N | +| 7.1.6.1.1 | Semantics of the service primitive | N | +| 7.1.6.1.2 | Appropriate usage | N | +| 7.1.6.1.3 | Effect on receipt | N | +| 7.1.6.2 | MLME-GET.confirm | N | +| 7.1.6.2.1 | Semantics of the service primitive | N | +| 7.1.6.2.2 | When generated | N | +| 7.1.6.2.3 | Appropriate usage | N | +| 7.1.7 | GTS management primitives
– GTS are not used in this Recommendation. | N/R | +| 7.1.8 | Primitives for orphan notification
– Beacon synchronization is not used in this Recommendation. | N/R | +| 7.1.9 | Primitives for resetting the MAC sublayer | N | +| 7.1.9.1 | MLME-RESET.request | N | +| 7.1.9.1.1 | Semantics of the service primitive | N | +| 7.1.9.1.2 | Appropriate usage | N | +| 7.1.9.1.3 | Effect on receipt | N | +| 7.1.9.2 | MLME-RESET.confirm | N | +| 7.1.9.2.1 | Semantics of the service primitive | N | +| 7.1.9.2.2 | When generated | N | +| 7.1.9.2.3 | Appropriate usage | N | +| 7.1.10 | Primitives for specifying the receiver enable time
– The primitives for specifying the receiver enable time are not used in the present application of the norm. The receiver is always enabled. | N/R | +| 7.1.11 | Primitives for channel scanning | N | +| 7.1.9.1 | MLME-SCAN.request | N | +| 7.1.11.1.1 | Semantics of the service primitive
– The only supported values for the ScanType parameter is 0x01 for active scan.
– The ScanChannels parameter is not used and all of its 27 bits shall be set to 0.
– The ChannelPage parameter is not used and shall be set to 0.
– The SecurityLevel shall be 0. Thus the KeyIdMode, KeyIndex and KeySource parameters can be ignored and set to 0. | S | + +**Table 9-1 – Selections from clause 7.1 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.1.11.1.2 | Appropriate usage
– Only active scan is supported
– ED scans, passive scans and orphan scans are not used. All devices shall be capable of performing active scans. | S | +| 7.1.11.1.3 | Effect on receipt
– Only active scan is supported.
– ED scan, passive scan and orphan scan are not supported.
– There is no physical channel notion during the scans, as the underlying PHY layer does not support multiple channels. | S | +| 7.1.11.2 | MLME-SCAN.confirm
During active scan, MLME-BEACON-NOTIFY.indication is generated in response to MLME-SCAN.request as soon as a beacon is received. | N | +| 7.1.11.2.1 | Semantics of the service primitive | S | +| 7.1.11.2.2 | When generated | S | +| 7.1.11.2.3 | Appropriate usage | N | +| 7.1.11.3 | Channel scan message sequence chart
– Figure 79 shall be ignored (ED scan not supported)
– Figure 82 shall be ignored (passive scan not supported)
– Figure 86 shall be ignored (orphan scan not supported)
– Active scan message sequence chart is specified in clause 9.4.4.2.2 and replaces Figure 83 of the reference document. | S | +| 7.1.12 | Communication status primitive | N | +| 7.1.12.1 | MLME-COMM-STATUS.indication
– This primitive is also used to inform the upper layers in case of an ALTERNATE_PANID_DETECTION. | E | +| 7.1.12.1.1 | Semantics of the service primitive
– Valid values for the status parameters are:
SUCCESS, CHANNEL_ACCESS_FAILURE, NO_ACK,
COUNTER_ERROR, FRAME_TOO_LONG,
IMPROPER_KEY_TYPE, IMPROPER_SECURITY_LEVEL,
SECURITY_ERROR, UNAVAILABLE_KEY,
UNSUPPORTED_LEGACY, UNSUPPORTED_SECURITY or
INVALID_PARAMETER, ALTERNATE_PANID_DETECTION | E | +| 7.1.12.1.2 | When generated
– This primitive is not used to notify the upper layer about association, disassociation, indirect transmission and transactions management.
– The alternate PAN ID detection is performed by scanning all incoming PAN IDs of frames received by the device. The MAC layer generates the MLME-COMM-STATUS.indication primitive with status ALTERNATE_PANID_DETECTION on receiving a frame with a source or destination PAN ID that is different from the configured macPanId and 0xFFFF. | E | +| 7.1.12.1.3 | Appropriate usage
– Upon receipt of the MLME-COMM-STATUS.indication primitive with a status equal to ALTERNATE_PANID_DETECTION, the next higher layer is notified of an existing alternate PAN. | E | + +**Table 9-1 – Selections from clause 7.1 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.1.13 | Primitives for writing PIB attributes | N | +| 7.1.13.1 | MLME-SET.request | N | +| 7.1.13.1.1 | Semantics of the service primitive | N | +| 7.1.13.1.2 | Appropriate usage | N | +| 7.1.13.1.3 | Effect on receipt | N | +| 7.1.13.2 | MLME-SET.confirm | N | +| 7.1.13.2.1 | Semantics of the service primitive | N | +| 7.1.13.2.2 | When generated | N | +| 7.1.13.2.3 | Appropriate usage | N | +| 7.1.14 | Primitives for updating the superframe configuration
– This primitive is only used on the PAN coordinator in case of network formation (see clause 9.5.1). | S | +| 7.1.14.1 | MLME-START.request
– This primitive is only used to initiate a new PAN. | S | +| 7.1.14.1.1 | Semantics of the service primitive
– Primitive parameters shall be set as described in clause 9.5.1. | S | +| 7.1.14.1.2 | Appropriate usage | N | +| 7.1.14.1.3 | Effect on receipt
– Primitive parameters shall be set as described in clause 9.5.1. | S | +| 7.1.14.2 | MLME-START.confirm | N | +| 7.1.14.2.1 | Semantics of the service primitive | N | +| 7.1.14.2.2 | When generated | N | +| 7.1.14.2.3 | Appropriate usage | N | +| 7.1.14.3 | Message sequence chart for updating the superframe configuration
– Figure 38 shall be ignored. | N/R | +| 7.1.15 | Primitives for synchronizing with a coordinator | N/R | +| 7.1.15.1 | MLME-SYNC.request | N/R | +| 7.1.15.2 | MLME-SYNC-LOSS.indication | N/R | +| 7.1.15.2.1 | Semantics of the service primitive | N/R | +| 7.1.15.2.2 | When generated | N/R | +| 7.1.15.2.3 | Appropriate usage | N/R | +| 7.1.15.3 | Message sequence chart for synchronizing with a coordinator
– Synchronization with beacons is not used in this Recommendation. | N/R | +| 7.1.16 | Primitives for requesting data from a coordinator
– Indirect transmission and transactions are not supported by the present specification. | N/R | +| 7.1.17 | MAC enumeration description | N | + +NOTE – Time stamp shall refer to a free running counter in milliseconds. The counter is initialized to zero at node start-up. + +#### 9.3.3.2 Extensions + +As shown in Table 9-2, the quality of service (QOS) parameter defines the level of priority assigned to the MSDU to be transmitted. Clause 9.3.1 defines the priority mechanism of ITU-T G.9903 devices. + +**Table 9-2 – QualityOfService parameter description** + +| Name | Type | Valid range | Description | +|------------------|---------|-------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| QualityOfService | Integer | 0x00-0x01 | The QOS (quality of service) parameter of the MSDU to be transmitted by the MAC sublayer entity. This value can take one of the following values:
0 = Normal priority
1 = High priority | + +### 9.3.4 MAC frame formats + +#### 9.3.4.1 Selections + +The MAC frame formats as described in clause 7.2 of [IEEE 802.15.4] apply, with the selections specified in Table 9-3. + +**Table 9-3 – Selections from clause 7.2 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.2 | MAC frame formats | N | +| 7.2.1 | General MAC frame format
– Segment control fields are added to the MHR (see clause 9.3.4.2)
– Detailed descriptions of the segment control fields are shown in Table 9-5. | E | +| 7.2.1.1 | Frame control field
NOTE – The Ack request field must be set with a value consistent with the PHY layer DT field. | N | +| 7.2.1.1.1 | Frame type subfield
– The present specification does not use an acknowledgement frame type value.
– The detailed ACK implementation is described in Annex E. An acknowledgement can be sent by invoking the PD-ACK.request primitive. | S | +| 7.2.1.1.2 | Security enabled subfield | N | +| 7.2.1.1.3 | Frame pending subfield
– Indirect transmission is not supported, so this bit shall be set to 0. | S | +| 7.2.1.1.4 | Acknowledgement request subfield
– The present specification translates the acknowledgement request subfield to the proper delimiter type of frame control header.
– The detailed ACK implementation is described in Annex E. An acknowledgement can be sent by invoking the PD-ACK.request primitive. | S | +| 7.2.1.1.5 | PAN ID compression subfield | N | +| 7.2.1.1.6 | Destination addressing mode subfield | N | +| 7.2.1.1.7 | Frame version subfield | S | + +**Table 9-3 – Selections from clause 7.2 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| | – These 2 bits are reserved for future use. In this version of the specification they shall be set to 0. | | +| 7.2.1.1.8 | Source addressing mode subfield | N | +| 7.2.1.2 | Sequence number field | N | +| 7.2.1.3 | Destination PAN identifier field | N | +| 7.2.1.4 | Destination address field | N | +| 7.2.1.5 | Source PAN identifier field | N | +| 7.2.1.6 | Source address field | N | +| 7.2.1.7 | Auxiliary security header field
– Possible lengths for the auxiliary security header are 0 and 6 bytes (see clause 10). | S | +| 7.2.1.8 | Frame payload field | N | +| 7.2.1.9 | FCS field | N | +| 7.2.2 | Format of individual frame types | N | +| 7.2.2.1 | Beacon frame format | N | +| 7.2.2.1.1 | Beacon frame MHR fields | N | +| 7.2.2.1.2 | Superframe specification field
– Beacons are not transmitted at regular time intervals (beaconless network). Therefore the beacon order parameter of the superframe specification field is not used and shall be set to 0.
– The receiver is active all the time when not transmitting. Therefore the superframe order parameter of the superframe specification field is not used and shall be set to 0.
– No superframe structure is used for communication, so the final CAP slot parameter of the superframe specification field is not used and shall be set to 0.
– Devices will not be operating on batteries, so the battery life extension subfield of the superframe specification field is not used and shall be set to 0.
– Within the framework of the present Recommendation, the association is performed by the 6LoWPAN bootstrap protocol in the upper layer, so the association permit parameter of the superframe specification field is meaningless here, and shall be set to 1. If another profile is used, this field shall be set as described in clause 7.2.2.1.2 of [IEEE 802.15.4]. | S | +| 7.2.2.1.3 | GTS specification field
– The GTS descriptor count shall be set to 0 (GTS are not supported).
– The PAN coordinator never accepts a GTS request, therefore the GTS permit parameter of the GTS specification field shall be set to 0. | S | +| 7.2.2.1.4 | GTS direction field
– The GTS feature is not used and the GTS direction field shall not be present in the frame. | N/R | +| 7.2.2.1.5 | GTS list field
– The GTS feature is not used and considering the values of the GTS specification field described in clause 7.2.2.1.3 of [IEEE 802.15.4], | N/R | + +**Table 9-3 – Selections from clause 7.2 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| | this list shall be empty. | | +| 7.2.2.1.6 | Pending address specification field
– Indirect transmission is not supported in this specification.
Consequently, the 'number of short addresses pending' is always 0 and the 'number of extended addresses pending' is also 0. | S | +| 7.2.2.1.7 | Address list field
– Indirect transmission is not used and this field shall not be present in beacons. | N/R | +| 7.2.2.1.8 | Beacon payload field
– The beacon payload field is two bytes long and contains the route cost to the coordinator (RC_COORD) encoded in big-endian. The route cost shall be based on the route cost calculation, as specified in clause 9.4.3. RC_COORD may be approximated by saving the lowest route cost extracted from the routing packets that originated from the PAN coordinator (for LOADng routing packets, see clause 9.4.3.2.7). If a device has failed to communicate with the PAN coordinator it shall set RC_COORD to its maximum value of 0xFFFF. A device shall initialize RC_COORD to 0x7FFF on association or if it is at adpMaxHops hops from the PAN coordinator. The PAN coordinator shall set its RC_COORD to 0x0000. | S, E | +| 7.2.2.2 | Data frame format | N | +| 7.2.2.2.1 | Data frame MHR fields | N | +| 7.2.2.2.2 | Data payload field | N | +| 7.2.2.3 | Acknowledgement frame format
– The acknowledgement frame format described in clause 7.2.2.3 of [IEEE 802.15.4] is not relevant.
– The detailed ACK implementation is described in Annex E. An acknowledgement can be sent by invoking the PD-ACK.request primitive. | S | +| 7.2.2.4 | MAC command frame format | N | +| 7.2.2.4.1 | MAC command frame MHR fields | N | +| 7.2.2.4.2 | Command frame identifier field | N | +| 7.2.2.4.3 | Command payload field | N | +| 7.2.3 | Frame compatibility
– The use of the frame version subfield is reserved | N/R | + +#### 9.3.4.2 Extensions + +Tables 9-4 and 9-5 define the segment control field added in the MAC header (MHR) specified in [IEEE 802.15.4], clause 7.2. + +**Table 9-4 – General MAC frame format** + +| | | | | | | | | | | +|---------------------------|---------------|-----------------|-----------------|---------------------|------------|----------------|---------------------------|-----------------|----------| +| Size (in Bytes): 3 | 2 | 1 | 0/2 | 0/2/8 | 0/2 | 0/2/8 | 0/6 | Variable | 2 | +| Segment control | Frame control | Sequence number | Destination PAN | Destination address | Source PAN | Source address | Auxiliary security header | Frame payload | FCS | +| MHR | | | | | | | | MAC payload | MFR | + +**Table 9-5 – Segment control fields** + +| Field | Byte | Bit number | Bits | Description | +|---------|------|------------|------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| RES | 0 | 7-4 | 4 | Reserved by ITU-T | +| TMR | 0 | 3 | 1 | Tone map request
1: Tone map is requested
0: Tone map is not requested | +| CC | 0 | 2 | 1 | Contention control:
0: next frame shall be transmitted using contention access
1: next segment shall be transmitted using the contention free slot (CFS) – see clause 9.3.1.4 | +| CAP | 0 | 1 | 1 | Channel access priority:
0: Normal
1: High | +| LSF | 0 | 0 | 1 | Last segment flag
0: Not last segment
1: Last segment | +| SC | 1 | 7-2 | 6 | Segment count | +| SL[9-8] | 1 | 1-0 | 2 | Segment length of MAC frame | +| SL[7-0] | 2 | 7-0 | 8 | Segment length of MAC frame | + +NOTE – The fields are depicted in the order in which they are transmitted by the PHY, from left to right, where the leftmost byte is transmitted first in time. Bits within each field are numbered from 0 (rightmost and least significant) to k – 1 (leftmost and most significant), where the length of the field is k bits. + +### 9.3.5 MAC command frames + +#### 9.3.5.1 Selections + +The MAC frame formats described in clause 7.3 of [IEEE 802.15.4] apply, with the selections specified in Table 9-6. + +**Table 9-6 – Selections from clause 7.3 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.3 | MAC command frames
– All devices are Full Function Devices
– The supported command list is defined in clause 9.3.5.2.1 | S, E | +| 7.3.1 | Association request command
– Within the framework of the present Recommendation, association is performed by the 6LoWPAN Bootstrap protocol described in | N/R | + +**Table 9-6 – Selections from clause 7.3 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| | clause 9.4.4.2.2, so clause 7.3.1 of [IEEE 802.15.4] is not relevant | | +| 7.3.2 | Association response command
– Within the framework of the present Recommendation, association is performed by the 6LoWPAN Bootstrap protocol described in clause 9.4.4.2.2, so clause 7.3.2 of [IEEE 802.15.4] is not relevant. | N/R | +| 7.3.3 | Disassociation Notification command
– Within the framework of the present Recommendation, association is performed by the 6LoWPAN Bootstrap protocol described in clause 9.4.4.2.2, so clause 7.3.2 of [IEEE 802.15.4] is not relevant. | N/R | +| 7.3.4 | Data Request command | N/R | +| 7.3.5 | PAN ID conflict notification command
– PAN ID conflict notification is not used in this specification | N/R | +| 7.3.6 | Orphan notification command
– Orphan notification is not used in this Recommendation | N/R | +| 7.3.7 | Beacon request command
– This command shall be implemented in every device | S | +| 7.3.8 | Coordinator realignment command
– The coordinator realignment command is not used in this Recommendation | N/R | +| 7.3.9 | GTS request command
– GTS are not used in this Recommendation. | N/R | + +#### 9.3.5.2 Extensions + +##### 9.3.5.2.1 MAC command frames supported + +The present Recommendation supports the MAC command frames described in Table 9-7. + +**Table 9-7 – MAC command frames** + +| Command frame identifier | Command name | Clause | +|--------------------------|-------------------|-------------------------------------| +| 0x00-0x06 | Reserved by ITU-T | – | +| 0x07 | Beacon request | See clause 7.3.7 of [IEEE 802.15.4] | +| 0x08-0x09 | Reserved by ITU-T | – | +| 0x0A | Tone map response | See clause 9.3.5.2.2 | +| 0x0B-0xFF | Reserved by ITU-T | – | + +##### 9.3.5.2.2 Tone map response + +The MAC sublayer generates a tone map response command if the tone map request (TMR) bit of a received packet segment control field is set. It means that a packet originator requested tone map information from destination device. The destination device has to estimate this particular communication link between two points and choose optimal PHY parameters. The tone map response contains the number of used tones and allocation (tone map), modulation mode and TX power control parameters. The tone map response command frame shall be formatted as illustrated in Table 9-8. + +The channel estimation response command frame shall be formatted as illustrated in Table 9-8: + +**Table 9-8 – Tone map response format** + +| | | | | +|-------------------------------------------------------------------------|------------------------------------------|----------------------------------------------------------------|------------| +| Size (in Bytes):
(see clause 7.2.2.4 of
[IEEE 802.15.4]) | 1 | 7 (for CENELEC
bandplans)
12 (for FCC bandplan) | 2 | +| MHR fields | Command frame identifier (see Table 9-7) | Tone map response payload (see Tables 9-9 and 9-10) | MFR Fields | + +The tone map response message parameters are shown in Table 9-9 for the case of CENELEC bandplans and in Table 9-10 for the case of FCC bandplan. + +**Table 9-9 – Tone map response message description for CENELEC bandplans** + +| Field | Byte | Bit number | Bits | Description | +|---------------------------|-------------|-------------------|-------------|-----------------------------------------------------------------------------------------------------| +| TXRES | 0 | 7 | 1 | Tx Gain resolution corresponding to one gain step.
0: 6 dB
1: 3 dB | +| TXGAIN | 0 | 6-3 | 4 | Desired transmitter gain specifying how many gain steps are requested. | +| MOD | 0 | 2-1 | 2 | Modulation type:
0 – Robust mode
1 – DBPSK or BPSK
2 – DQPSK or QPSK
3 – D8PSK or 8-PSK | +| Payload modulation scheme | 0 | 0 | 1 | 0: Differential
1: Coherent
The coherent scheme specified in clause 7.16 is optional. | +| Reserved by ITU-T | 1 | 7-6 | 2 | Shall be set to zero | +| TM[5:0] | 1 | 5-0 | 6 | Tone map [5:0]
In CENELEC-B bandplan, TM[5:3] are reserved by ITU-T and shall be set to zero | +| LQI | 2 | 7-0 | 8 | Link quality indicator | +| TXCOEF[3:0] | 3 | 7-4 | 4 | Specifies the number of gain steps requested for the tones represented by TM[0] (optional) | +| TXCOEF[7:4] | 3 | 3-0 | 4 | Specifies the number of gain steps requested for the tones represented by TM[1] (optional) | +| TXCOEF[11:8] | 4 | 7-4 | 4 | Specifies the number of gain steps requested for the tones represented by TM[2] (optional) | +| TXCOEF[15:12] | 4 | 3-0 | 4 | Specifies the number of gain steps requested for the tones represented by TM[3] (optional) | +| TXCOEF[19:16] | 5 | 7-4 | 4 | Specifies the number of gain steps requested for the tones represented by TM[4] (optional) | +| TXCOEF[23:20] | 5 | 3-0 | 4 | Specifies the number of gain steps requested for the tones represented by TM[5] (optional) | +| Reserved by ITU-T | 6 | 7-0 | 8 | Shall be set to zero | + +**Table 9-10 – Tone map response message description for FCC bandplan** + +| Field | Byte | Bit number | Bits | Definition | +|---------------------------|------|------------|------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| TXRES | 0 | 7 | 1 | Tx Gain resolution corresponding to one gain step
0: 6 dB
1: 3 dB | +| TXGAIN | 0 | 6-3 | 4 | Desired transmitter gain specifying how many gain steps are requested | +| MOD | 0 | 2-0 | 3 | Modulation type:
0 – Robust mode
1 – DBPSK or BPSK
2 – DQPSK or QPSK
3 – D8PSK or 8-PSK
4 – 16-QAM
5-7: Reserved by ITU-T
NOTE – The 16-QAM modulation is optional and may be used only when the coherent modulation scheme applies. | +| TM[0:7] | 1 | 7-0 | 8 | Tone map [0:7] | +| TM[8:15] | 2 | 7-0 | 8 | Tone map [8:15] | +| TM[16:23] | 3 | 7-0 | 8 | Tone map [16:23] | +| LQI | 4 | 7-0 | 8 | Link quality indicator | +| TXCOEF[1:0] | 5 | 7-6 | 2 | Specifies the number of gain steps requested for the tones represented by TM[0] (optional) | +| TXCOEF[3:2] | 5 | 5-4 | 2 | Specifies the number of gain steps requested for the tones represented by TM[1] (optional) | +| TXCOEF[5:4] | 5 | 3-2 | 2 | Specifies the number of gain steps requested for the tones represented by TM[2] (optional) | +| TXCOEF[7:6] | 5 | 1-0 | 2 | Specifies the number of gain steps requested for the tones represented by TM[3] (optional) | +| .... | ... | ... | ... | ... | +| TXCOEF[47:46] | 10 | 1-0 | 2 | Specifies the number of gain steps requested for the tones represented by TM[23] (optional) | +| Payload modulation scheme | 11 | 7 | 1 | 0: Differential
1: Coherent
The coherent scheme specified in clause 7.16 is optional. | +| Reserved by ITU-T | 11 | 6-0 | 7 | Shall be set to zero at the transmitter and ignored by the receiver | + +Where: + +- MOD: a parameter that specifies the desired modulation type. The receiver computes the SNR of the *tone map request* message that it receives from the transmitter and it decides which of the DBPSK, BPSK, DQPSK, QPSK, D8PSK, 8-PSK, 16-QAM modulations or robust mode it wants the transmitter to use when sending the next data frame. Tables 9-11 and 9-12 lists the allowed bit values and the modulation types they correspond to. + +**Table 9-11 – MOD field for CENELEC bandplans** + +| MOD value | Interpretation | | +|-----------|--------------------------------|----------------------------| +| | Differential modulation scheme | Coherent modulation scheme | +| 00 | Robust mode | Robust mode | +| 01 | DBPSK modulation | BPSK modulation | +| 10 | DQPSK modulation | QPSK modulation | +| 11 | D8PSK modulation | 8-PSK modulation | + +**Table 9-12 – MOD field for FCC bandplan** + +| MOD value | Interpretation | | +|-----------|--------------------------------|----------------------------| +| | Differential modulation scheme | Coherent modulation scheme | +| 000 | Robust mode | Robust mode | +| 001 | DBPSK modulation | BPSK modulation | +| 010 | DQPSK modulation | QPSK modulation | +| 011 | D8PSK modulation | 8-PSK modulation | +| 100 | Reserved by ITU-T | 16-QAM modulation | +| 101-111 | Reserved by ITU-T | Reserved by ITU-T | + +- TXRES: a parameter that specifies the transmit gain resolution corresponding to one gain step. +- TXGAIN: a parameter that specifies to the transmitter the total amount of gain that it shall apply to its transmitted signal. The value in this parameter shall specify the total number of gain steps needed. One gain step value is given by TXRES. The receiver computes the received signal level and compares it to a VTARGET (pre-defined desired receive level). The difference in dB between the two values is mapped to a 4-bit value that specifies the amount of gain increase or decrease that the transmitter shall apply to the next frame to be transmitted. A "0" in the most significant bit indicates a positive gain value, hence an increase in the transmitter gain and a "1" indicates a negative gain value, hence a decrease in the transmitter gains (e.g., 0b0101 represents an increase of 5 steps while 0b1101 represents a decrease of 5 steps). A value of TXGAIN = 0 informs the transmitter to use the same gain value it used for the previous frame (default value). +- TM: a parameter that specifies the tone map. The receiver estimates the per-tone quality of the channel and maps each sub-band (6 tones per sub-band for CENELEC bandplans, 3 tones for the FCC bandplan) to a one-bit value where a value of 0 indicates to the remote transmitter that dummy data shall be transmitted on the corresponding subcarrier while a value of "1" indicates that valid data shall be transmitted on the corresponding subcarrier. +- TXCOEF (optional): a parameter that specifies transmitter gain for each group of tones represented by one valid bit of the tone map. The receiver measures the frequency-dependent attenuation of the channel and may request the transmitter to compensate for this attenuation by increasing the transmit power on sections of the spectrum that are experiencing attenuation in order to equalize the received signal. Each group of tones is mapped to a 4-bit value for CENELEC-A or a 2-bit value for FCC where a "0" in the most significant bit indicates a positive gain value, hence an increase in the transmitter gain scaled by TXRES is requested for that section and a "1" indicates a negative gain value, hence a decrease in the transmitter gain scaled by TXRES is requested for that section (e.g., 0b0101 represents an increase of 5 steps while 0b1101 represents a decrease of 5 steps). + +Implementing this feature is optional and it is intended for frequency selective channels. If this feature is not implemented, the value zero shall be used. + +- The LQI value is computed in the PHY and passed to the MAC with the PD-DATA.indication primitive through the ppduLinkQuality parameter – see Table 7-26. +- Payload modulation scheme: a parameter that specifies the modulation scheme used for the PHY payload. A value of 0 indicates to the remote transmitter that a differential scheme shall be used, while a value of "1" indicates that a coherent scheme shall be used. If the receiver does not implement the optional coherent scheme, this field is ignored and differential modulation will be used by the remote device. + +On receipt of a tone map response command frame, the MAC sublayer updates the neighbour table with the corresponding tone map and communication parameters for that device. If no entry already exists in the table for that device a new entry may be added, based on implementation-dependent limitations. The neighbour table is defined in Table 9-21. + +The following procedure shall be used to perform the adaptive tone mapping function: + +- a) When a station is ready to transmit data it will first check if the neighbour table already has a record related to the destination device address. If the record does not exist or is expired (TMRValidTime counter is "0"), the MAC sublayer sets the TMR bit of an outgoing packet segment control field and requests new tone map information. In this case the MAC data shall be sent in robust mode (note that the TMR bit shall not be set for MAC frames other than data frames and tone map responses and that the use of the TMR bit in the tone map response frame is optional): +- b) If a neighbour table record exists (TMRValidTime is greater than "0"), the MAC sublayer does not need to send a tone map request message. In this case, the MAC sublayer uses information from the neighbour table to properly configure the physical TX in transmitting mode and construct the frame control header (FCH) of the outgoing frame. +- c) When the destination station receives a data frame it shall check the tone map request bit in the segment control field. If the bit is set, the destination station shall measure the per-carrier quality of the channel, construct and send a tone map response message back to the originator station. The destination station shall not send a tone map response message if the tone map request bit is not set. The tone map response message shall always be transmitted using the default robust mode. The destination device uses parameters from the frame control header to decode the MAC data fields. +- d) The destination station shall attempt to send a tone map response message as soon as possible after receiving a tone map request message from the source station. +- e) If the source station receives a tone map response message, it will update a neighbour table record related to the destination address with a new tone map, modulation and TX gain parameters. If the record does not exist, the MAC sublayer will create a new one. The TMRValidTime shall be set to macTMRTTL (defined in clause 9.3.6.2.2). After receiving a tone map response message, a device shall begin to use the updated neighbour table information for all transmissions to the associated destination until the TMRValidTime field reaches the value "0". +- f) If the source station does not receive a tone map response message after transmitting a tone map request message to a certain destination, it shall set the tone map request bit in the segment control of the next MAC data frame that it wants to transmit to the same destination. In other words, the MAC sublayer will continue to transmit a tone map request message to the same destination. +- g) The MAC sublayer shall not send a tone map request message to the destination device if no data has been sent to this device. + +The tone map request/response message sequence chart is shown in clause 9.3.9.2.4. + +### 9.3.6 MAC constants and PIB attributes + +#### 9.3.6.1 Selections + +The MAC frame formats described in clause 7.4 of [IEEE 802.15.4] apply, with the selections specified in Table 9-13. + +**Table 9-13 – Selections from clause 7.4 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.4 | MAC constants and PIB attributes | N | +| 7.4.1 | MAC constants
  • – The aExtendedAddress parameter shall be equal to the EUI-48 address of the device mapped to an EUI-64 address.
  • – The aMaxMACPayloadSize parameter is fixed to 400 bytes by the present Recommendation.
  • – The aUnitBackoffPeriod parameter shall be set to aSlotTime.
  • – IEEE 802.15.4 MAC constants not listed here are not used by this Recommendation.
  • – Additional MAC sublayer constants are defined in clause 9.3.6.2.1.
| S, E | +| 7.4.2 | MAC PIB attributes
The IEEE 802.15.4 MAC PIB attributes used by this Recommendation are listed in Table 9-18. IEEE 802.15.4 MAC PIB attributes not listed in Table 9-18 are not used by this Recommendation.
Additional MIB attributes are defined in clause 9.3.6.2.2 | S,E | + +#### 9.3.6.2 Extensions + +##### 9.3.6.2.1 Additional MAC sublayer constants + +Table 9-14 defines the list of MAC sublayer constants added by the present Recommendation. + +**Table 9-14 – Additional MAC sublayer constants to clause 7.4.1 of [IEEE 802.15.4]** + +| Constant | Description | Value | +|------------------|---------------------------------------------------------------------------------------------------|-----------------------------------------------------------------| +| aPreamSymbolTime | Defines the duration of one preamble symbol on the physical layer (in microseconds). | 640 for CENELEC bandplans
213 for the FCC bandplan | +| aSymbolTime | Defines the duration of one data symbol on the physical layer (in microseconds). | 695 for CENELEC bandplans
232 for the FCC bandplan | +| aSlotTime | The duration of the contention slot time (in data symbols). | 2 | +| aCIFS | Defines the contention inter-frame space (number of data symbols). It is defined in clause 9.3.1. | 8 for CENELEC
10 for FCC | +| aRIFS | Defines the response inter-frame space (number of data symbols). It is defined in clause 9.3.1. | 8 for CENELEC
10 for FCC | +| aEIFS | Defines the duration of the extended inter-frame space. It is defined in clause 9.3.1. | $aSymbolTime \times (aMaxFrameSize + aRIFS + aCIFS) + aAckTime$ | +| aMinFrameSize | Defines the minimum MAC frame size in data | 4 for CENELEC bandplans | + +**Table 9-14 – Additional MAC sublayer constants to clause 7.4.1 of [IEEE 802.15.4]** + +| Constant | Description | Value | +|---------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------| +| | symbols. | 1 for the FCC bandplan | +| aMaxFrameSize | Defines the maximum MAC frame size in data symbols. | 252 for CENELEC bandplans
511 for the FCC bandplan | +| aAckTime | Defines the duration of acknowledgement:
$N_{PRE}$ – number of preamble symbols is defined in clause 7.3.1.
$N_{FCH}$ – number of FCH symbols is defined in clause 7.3.1. | $N_{PRE} \times aPremSymbolTime + N_{FCH} \times aSymbolTime$ | + +##### 9.3.6.2.2 Additional MAC sublayer attributes + +Table 9-15 defines the list of additional MAC sublayer attributes for this Recommendation. + +**Table 9-15 – Additional attributes to clause 7.4.2 of [IEEE 802.15.4]** + +| Attribute | Identifier | Type | Range | Description | Default value | +|---------------------------|------------|------------------|-----------------|-------------------------------------------------------------------------------------------------------|---------------| +| macHighPriorityWindowSize | 0x0100 | Unsigned integer | 1-7 | The high priority contention window size in number of slots.
Default value is $7 \times aSlotTime$ | 7 | +| macTxDataPacketCount | 0x0101 | Unsigned integer | 0-4 294 967 295 | Statistic counter of successfully transmitted unicast MSDUs | 0 | +| macRxDataPacketCount | 0x0102 | Unsigned integer | 0-4 294 967 295 | Statistic counter of successfully received unicast MSDUs | 0 | +| macTxCmdPacketCount | 0x0103 | Unsigned integer | 0-4 294 967 295 | Statistic counter of successfully transmitted command packets | 0 | +| macRxCmdPacketCount | 0x0104 | Unsigned integer | 0-4 294 967 295 | Statistic counter of successfully received command packets | 0 | +| macCSMAFailCount | 0x0105 | Unsigned integer | 0-4 294 967 295 | Counts the number of times the CSMA back-offs reach macMaxCSMABackoffs | 0 | +| macCSMANoACKCount | 0x0106 | Unsigned integer | 0-4 294 967 295 | Counts the number of times an ACK is not received while transmitting a | 0 | + +**Table 9-15 – Additional attributes to clause 7.4.2 of [IEEE 802.15.4]** + +| Attribute | Identifier | Type | Range | Description | Default value | +|------------------------|------------|---------------------|------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------|---------------| +| | | | | unicast data frame
(The loss of ACK
is attributed to
collisions) | | +| macRxDatBroadcastCount | 0x0107 | Unsigned
integer | 0-4 294
967 295 | Statistic counter of
successfully
received broadcast
frames | 0 | +| macTxDatBroadcastCount | 0x0108 | Unsigned
integer | 0-4 294
967 295 | Statistic counter of
the number of
broadcast frames
sent | 0 | +| macBadCRCCount | 0x0109 | Unsigned
integer | 0-4 294
967 295 | Statistic counter of
the number of
frames received
with bad CRC | 0 | +| macNeighbourTable | 0x010A | Set | – | The neighbour
table defined in
clause 9.3.7.2 | Empty | +| Reserved by ITU-T | 0x010B | | | | | +| macCSMAFairnessLimit | 0x010C | Unsigned
integer | (2 ×
(macMax
BE -
macMinB
E)) -255 | Channel access
fairness limit.
Specifies how
many failed back-
off attempts, back-
off exponent is set
to minBE | 25 | +| macTMRTTL | 0x010D | Unsigned
integer | 0-255 | Maximum time to
live for an entry in
the neighbour table
in minutes | 10 | +| macPOSTableEntryTTL | 0x010E | Unsigned
integer | 0-255 | Maximum time to
live for an entry in
the POS table in
minutes | 255 | +| macRCCoord | 0x010F | Unsigned
integer | 0-65535 | Route cost to
coordinator to be
used in the beacon
payload as
RC_COORD | 65535 | + +**Table 9-15 – Additional attributes to clause 7.4.2 of [IEEE 802.15.4]** + +| Attribute | Identifier | Type | Range | Description | Default value | +|----------------------------------------|-------------------|---------------------|-------------------------------------|----------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------| +| macToneMask | 0x0110 | 72 bits | 0x0-
0xFFFFF
FFFFFF
FFFFFF | Defines the tone mask to use during symbol formation. | 0x00000
0000FF
FFFFFF
F for
CENEL
EC-A
bandpla
n;
0xFFFF
FFFFFF
FFFFFF
FF for
the FCC
bandpla
n | +| macBeaconRandomizationWind
owLength | 0x0111 | Unsigned
integer | 1-254 | Duration time in seconds for beacon randomization. | 12 | +| macA | 0x0112 | Unsigned
Integer | 3-20 | This parameter controls the adaptive CW linear decrease | 8 | +| macK | 0x0113 | Unsigned
Integer | 1-
macCSM
AFairness
Limit | Rate adaptation factor for channel access fairness limit | 5 | +| macMinCWAttempts | 0x0114 | Unsigned
Integer | 0-0xFF | Number of consecutive attempts while using minimum CW | 10 | +| macCENELECLegacyMode | 0x0115 | Unsigned
integer | 0-255 | This read only attribute indicates the capability of the node. See Table 9-16. | 1 | +| macFCCLegacyMode | 0x0116 | Unsigned
integer | 0-255 | This read only attribute indicates the capability of the device. See Table 9-17. | 1 | +| macBroadcastMaxCWEnabled | 0x011E | Bool | FALSE
TRUE | If enabled, MAC uses maximum contention window as specified in clause 9.3.1.3 | FALSE | +| macTransmitAtten | 0x011F | Unsigned
integer | 0-25 | Attenuation of the output level in dB | 0 | + +**Table 9-15 – Additional attributes to clause 7.4.2 of [IEEE 802.15.4]** + +| Attribute | Identifier | Type | Range | Description | Default value | +|-------------|------------|------|-------|-------------------------------------------|---------------| +| macPOSTable | 0x0120 | Set | – | The POS table defined in clause 9.3.7.2.1 | Empty | + +Table 9-16 shows macCENELECLegacyMode values and descriptions. + +**Table 9-16 – macCENELECLegacyMode values and description** + +| macCENELEC LegacyMode value | Description | +|-----------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------| +| 0 | The following configuration is used:
– Elementary interleaving
– Interleaver parameters $n_i$ and $n_j$ are not swapped when $I(i,j) = 0$ | +| 1 | The following configuration is used:
– Full block interleaving
– Interleaver parameters $n_i$ and $n_j$ are swapped when $I(i,j) = 0$ | +| 2-255 | Reserved by ITU-T | + +Table 9-17 shows macFCCLegacyMode values and descriptions. + +**Table 9-17 – macFCCLegacyMode values and description** + +| macFCCLegacyMode value | Description | +|------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| 0 | The following configuration is used:
– Differential FCH modulation
– Elementary interleaving
– Interleaver parameters $n_i$ and $n_j$ are not swapped when $I(i,j) = 0$
– Single RS block | +| 1 | The following configuration is used:
– Coherent FCH modulation
– Full block interleaving
– Interleaver parameters $n_i$ and $n_j$ are swapped when $I(i,j) = 0$
– Two RS blocks | +| 2-255 | Reserved by ITU-T | + +##### 9.3.6.2.3 MAC sublayer attributes and their associated ID + +Table 9-18 indicates existing [IEEE 802.15.4] MAC sublayer attributes used by the present Recommendation. + +**Table 9-18 – MAC sublayer attributes and their associated ID** + +| Attribute | Identifier | Type | Range | Description | Default value | +|-----------------------|------------|---------|---------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------| +| macAckWaitDuration | 0x0040 | Integer | 0x0-0xFFFF | Duration of acknowledgement in microseconds | aSymbolTime × (
aRIFS +
aCIFS) +
aAckTime | +| macBSN | 0x0049 | Integer | 0x0-0xFF | Beacon frame sequence number | random | +| macDSN | 0x004C | Integer | 0x0-0xFF | Data or command frame sequence number | random | +| macMaxBE | 0x0047 | Integer | 0-20 | Maximum value of back-off exponent. It should always be greater or equal than macMinBE | 8 | +| macMaxCSMABackoffs | 0x004E | Integer | 0-0xFF | Maximum number of back-off attempts | 50 | +| macMaxFrameRetries | 0x0059 | Integer | 0-10 | Maximum number of retransmission | 5 | +| macMinBE | 0x004F | Integer | 0-20 | Minimum value of back-off exponent | 3 | +| macPanId | 0x0050 | Integer | 0x0-0xFFFF | PAN ID | 0xFFFF | +| macSecurityEnabled | 0x005D | Boolean | TRUE – FALSE | Security enabled | TRUE | +| macShortAddress | 0x0053 | Integer | 0x0-0xFFFF | Device short address | 0xFFFF | +| macPromiscuousMode | 0x0051 | Boolean | – | Promiscuous mode enabled | FALSE | +| macTimeStampSupported | 0x005C | Boolean | – | MAC frame time stamp support enable | TRUE | +| macKeyTable | 0x0071 | Set | – | This attribute holds GMK keys required for MAC layer ciphering. The attribute can hold two 16-byte keys. The row index corresponds to the key identifier value. For security reason, the key entries cannot be read, only written or deleted. | Empty | +| macFrameCounter | 0x0077 | Integer | 0x00000000–
0xFFFFFFFF | The outgoing frame counter for this device | 0x00000000 | + +### 9.3.7 MAC functional description + +#### 9.3.7.1 Selections + +The MAC functional description described in clause 7.5 of [IEEE 802.15.4] applies, with the selections specified in Table 9-19. + +**Table 9-19 – Selections from clause 7.5 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.5 | MAC functional description
– beacon-enabled PAN and GTS are not supported
– GTS contention free access is not supported. | S | +| 7.5.1 | Channel access
– See clause 9.3.1 for the channel access functional description. | E | +| 7.5.1.1 | Superframe structure | N/R | +| 7.5.1.2 | Incoming and outgoing frame structure | N/R | +| 7.5.1.3 | Inter-frame (IFS) spacing
– See clause 9.3.1 for the inter-frame spacing description. | E | +| 7.5.1.4 | CSMA-CA algorithm
– See clause 9.3.1 for a description of the CSMA-CA algorithm (including priority, ARQ, segmentation and reassembly overview). | E | +| 7.5.2 | Starting and maintaining PANs | N | +| 7.5.2.1 | Scanning through channels
– Passive scanning is not supported
– Orphan scanning is not supported
– ED scanning is not supported
– Active scanning is the only supported scanning mode
– As there is no channel page or channel list notion at the physical level, a scan request is agnostic to a physical channel. | S | +| 7.5.2.1.1 | ED channel scan
– ED channel scan is not supported by the present Recommendation | N/R | +| 7.5.2.1.2 | Active channel scan
– Active channel scan is only used by an un-associated device prior to starting association and by the PAN coordinator prior to starting a new network.
– As there is no channel page or channel list notion at the physical level, a scan request does not care about a particular channel. | S | +| 7.5.2.1.3 | Passive channel scan
– Passive channel scan is not supported by the present Recommendation. | N/R | +| 7.5.2.1.4 | Orphan channel scan
– Orphan channel scan is not supported by the present Recommendation. | N/R | +| 7.5.2.2 | PAN identifier conflict resolution
PAN conflict handling is not used in this specification. | N/R | +| 7.5.2.3 | Starting and realigning a PAN | N | +| 7.5.2.3.1 | Starting a PAN | N | +| 7.5.2.3.2 | Realigning a PAN
– PAN realignment is not supported by the present specification. | N/R | + +**Table 9-19 – Selections from clause 7.5 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.5.2.3.3 | Realignment in a PAN
– PAN realignment is not supported by the present specification. | N/R | +| 7.5.2.3.4 | Updating superframe configuration and channel PIB attributes
– The macBeaconOrder parameter shall be set to 15 to have a beaconless PAN.
– The phyCurrentPage and phyCurrentChannel parameters are not used and shall be set to 0. | S | +| 7.5.2.4 | Beacon generation
– Only non-beacon-enabled PAN are used
– Beacon shall be transmitted using the robust mode
– Beacon transmission shall be randomized between 0 and macBeaconRandomizationWindowLength seconds
– When the node is waiting for its beacon transmission it shall ignore any additional incoming beacon request frame | S, E | +| 7.5.2.5 | Device discovery
– Device discovery is done using the active scanning procedure described in clause 9.4.4.2.2.2, to force a coordinator to send a beacon. | E | +| 7.5.3 | Association and disassociation | N | +| 7.5.3.1 | Association
– Association is fully described in clause 9.4.4. | N/R | +| 7.5.3.2 | Disassociation
– Disassociation is fully described in clause 9.4.4. | N/R | +| 7.5.4 | Synchronization | N/R | +| 7.5.4.1 | Synchronization with beacons
– Beacon synchronization is not used in this Recommendation. | N/R | +| 7.5.4.2 | Synchronization without beacons | N/R | +| 7.5.4.3 | Orphaned device realignment
Network connection status shall be supervised by the upper layers. | N/R | +| 7.5.5 | Transaction handling
– Transactions are not supported in the present Recommendation. | N/R | +| 7.5.6 | Transmission, reception and acknowledgement | N | +| 7.5.6.1 | Transmission | N | +| 7.5.6.2 | Reception and rejection | N | +| 7.5.6.3 | Extracting pending data from a coordinator | N/R | +| 7.5.6.4 | Use of acknowledgements and retransmissions | N | +| 7.5.6.4.1 | No acknowledgement | E | +| 7.5.6.4.2 | Acknowledgement
– The present Recommendation defines an acknowledgement differently.
The detailed ACK implementation is described in clause 9.3.2. | E | +| 7.5.6.4.3 | Retransmissions | N | +| 7.5.6.5 | Promiscuous mode | N | +| 7.5.6.6 | Transmission scenario | N | + +**Table 9-19 – Selections from clause 7.5 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.5.7 | GTS allocation and management
– GTS are not used in this Recommendation | N/R | +| 7.5.8 | Frame security | N | +| 7.5.8.1 | Security-related MAC PIB attributes
– Key table contains two 16-byte keys. They represent GMK as described in clause 10.5.2. The adpActiveKeyIndex parameter selects the key used to cipher outgoing frames.
– Device table is used
– Security level table is not used
– Automatic request attributes are not used
– Default key source is not used. | S | +| 7.5.8.1.1 | Key table
– Key table contains two 16-byte keys. | S | +| 7.5.8.1.2 | Device table
The table is only used to provide the anti-replay mechanism on incoming frames (key selection and blacklist are not used). | S | +| 7.5.8.1.3 | Minimum security level table | N/R | +| 7.5.8.1.4 | Frame counter
The frame counter shall be restored after a power cycle or when MLME-RESET.request is invoked. The stored value needs to be greater than the last used frame count.
Management of reset and recovery of the frame-counter is beyond the scope of this recommendation and shall be handled at higher layers. | E | +| 7.5.8.1.5 | Automatic request attributes | N/R | +| 7.5.8.1.6 | Default key source | N/R | +| 7.5.8.1.7 | PAN coordinator address | N/R | +| 7.5.8.2 | Functional description | N | +| 7.5.8.2.1 | Outgoing frame security procedure | N | +| 7.5.8.2.2 | Outgoing frame key retrieval procedure | N/R | +| 7.5.8.2.3 | Incoming frame security procedure
– The KeyIndex parameter selects the actual key from Key table. | S | +| 7.5.8.2.4 | Incoming frame security material retrieval procedure | N/R | +| 7.5.8.2.5 | KeyDescriptor lookup table | N/R | +| 7.5.8.2.6 | Blacklist checking procedure | N/R | +| 7.5.8.2.7 | DeviceDescriptor lookup procedure | N/R | +| 7.5.8.2.8 | Incoming security level checking procedure | N/R | +| 7.5.8.2.9 | Incoming key usage policy checking procedure | N/R | + +#### 9.3.7.2 Extensions + +##### 9.3.7.2.1 POS table + +Each time a message is received (filtered according to clause 7.5.6.2 of [IEEE 802.15.4]), an entry in the POS table (see Table 9-20) is created or updated (if the entry is already present). In the case where the table is full, the entry corresponding to the shortest valid time is removed. + +**Table 9-20 – POS table for CENELEC and FCC bandplans** + +| Field name | Size | Description | +|---------------|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Short address | 16 bits | The MAC short address of the neighbour which this entry refers to. | +| LQI | 8 bits | Link quality indicator of the last received packet from this neighbour. | +| POSValidTime | 8 bits | Remaining time in minutes until when this entry is considered valid. Every time an entry is created, it is set to macPOSTableEntryTTL. When it reaches zero, this entry is no longer valid in the table and may be removed. | + +##### 9.3.7.2.2 Neighbour Table + +Every device shall maintain a "neighbour table" which contains information about all the devices with which a unicast message has been exchanged. Each time a tone map response command is received the table is updated. In case the table is full, the entry corresponding to the shortest valid time is removed. This table shall be accessible by the adaptation, MAC sublayers and physical layer. Each entry of this table contains the fields listed in Table 9-21. + +**Table 9-21 – Neighbour table for CENELEC bandplans** + +| Field name | Size | Description | +|---------------------------|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Short address | 16 bits | The MAC short address of the neighbour which this entry refers to. | +| Payload modulation scheme | 1 bit | Payload modulation scheme to be used when transmitting to this neighbour.
0: Differential
1: Coherent
The coherent scheme (see clause 7.16) is optional. | +| ToneMap | 6 bits | The tone map to be used when transmitting to this neighbour. | +| ModulationType | 2 bits | Modulation type to be used when transmitting to this neighbour.
0: Robust mode
1: DBPSK or BPSK
2: DQPSK or QPSK
3: D8PSK or 8-PSK | +| TXGAIN | 4 bits | Transmitter gain to be used when transmitting to this neighbour. | +| TXRES | 1 bit | Transmitter gain corresponding to one gain step.
0: 6 dB
1: 3 dB | +| TXCOEF[3:0] | 4 bits | Number of gain steps requested for the tones represented by TM[0] (optional) | +| TXCOEF[7:4] | 4 bits | Number of gain steps requested for the tones represented by TM[1] (optional) | +| TXCOEF[11:8] | 4 bits | Number of gain steps requested for the tones represented by TM[2] | + +**Table 9-21 – Neighbour table for CENELEC bandplans** + +| Field name | Size | Description | +|-------------------|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| | | (optional) | +| TXCOEF[15:12] | 4 bits | Number of gain steps requested for the tones represented by TM[3] (optional) | +| TXCOEF[19:16] | 4 bits | Number of gain steps requested for the tones represented by TM[4] (optional) | +| TXCOEF[23:20] | 4 bits | Number of gain steps requested for the tones represented by TM[5] (optional) | +| Reverse LQI | 8 bits | Link quality indicator of the link to the neighbour | +| PhaseDifferential | 3 bits | Phase difference in multiples of 60 degrees between the mains phase of the local node and the neighbour node (see clause 7.17.2.4 and clause 8.10) | +| TMRValidTime | 8 bits | Remaining time in minutes until when the parameters are considered valid.
  • – When an entry is created, this value shall be set to the default value.
  • – When it reaches 0, a tone map request may be issued if data is sent to this device. Upon successful receipt of a tone map response, this value is set to macTMRTTL (see Table 9-15).
  • – When a MAC failure occurs (when macMaxFrameRetries attempts have failed), this value shall be set to 0.
| + +**Table 9-22 – Neighbour table for FCC bandplan** + +| Field name | Size | Description | +|---------------------------|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Short address | 16 bits | The MAC short address of the node which this entry refers to. | +| Payload modulation scheme | 1 bit | Payload modulation scheme to be used when transmitting to this neighbour
0: Differential
1: Coherent
The coherent scheme specified in clause 7.16 is optional. | +| ToneMap | 24 bits | Tone Map to be used when transmitting to this neighbour. | +| ModulationType | 3 bits | Modulation type to be used when transmitting to this neighbour.
0: Robust mode
1: DBPSK or BPSK
2: DQPSK or QPSK
3: D8PSK or 8-PSK
4: 16-QAM
5-7: Reserved by ITU-T
Note – The 16-QAM modulation is optional and may be used only when the coherent modulation scheme applies. | +| TXGAIN | 4 bits | Tx Gain to be used when transmitting to this neighbour. | +| TXRES | 1 bit | Transmitter gain corresponding to one gain step. 0: 6 dB
1: 3 dB | + +**Table 9-22 – Neighbour table for FCC bandplan** + +| Field name | Size | Description | +|---------------|--------|-------------------------------------------------------------------------------| +| TXCOEF[1:0] | 2 bits | Number of gain steps requested for the tones represented by TM[0] (optional) | +| TXCOEF[3:2] | 2 bits | Number of gain steps requested for the tones represented by TM[1] (optional) | +| TXCOEF[5:4] | 2 bits | Number of gain steps requested for the tones represented by TM[2] (optional) | +| TXCOEF[7:6] | 2 bits | Number of gain steps requested for the tones represented by TM[3] (optional) | +| TXCOEF[9:8] | 2 bits | Number of gain steps requested for the tones represented by TM[4] (optional) | +| TXCOEF[11:10] | 2 bits | Number of gain steps requested for the tones represented by TM[5] (optional) | +| TXCOEF[13:12] | 2 bits | Number of gain steps requested for the tones represented by TM[6] (optional) | +| TXCOEF[15:14] | 2 bits | Number of gain steps requested for the tones represented by TM[7] (optional) | +| TXCOEF[17:16] | 2 bits | Number of gain steps requested for the tones represented by TM[8] (optional) | +| TXCOEF[19:18] | 2 bits | Number of gain steps requested for the tones represented by TM[9] (optional) | +| TXCOEF[21:20] | 2 bits | Number of gain steps requested for the tones represented by TM[10] (optional) | +| TXCOEF[23:22] | 2 bits | Number of gain steps requested for the tones represented by TM[11] (optional) | +| TXCOEF[25:24] | 2 bits | Number of gain steps requested for the tones represented by TM[12] (optional) | +| TXCOEF[27:26] | 2 bits | Number of gain steps requested for the tones represented by TM[13] (optional) | +| TXCOEF[29:28] | 2 bits | Number of gain steps requested for the tones represented by TM[14] (optional) | +| TXCOEF[31:30] | 2 bits | Number of gain steps requested for the tones represented by TM[15] (optional) | +| TXCOEF[33:32] | 2 bits | Number of gain steps requested for the tones represented by TM[16] (optional) | +| TXCOEF[35:34] | 2 bits | Number of gain steps requested for the tones represented by TM[17] (optional) | +| TXCOEF[37:36] | 2 bits | Number of gain steps requested for the tones represented by TM[18] (optional) | +| TXCOEF[39:38] | 2 bits | Number of gain steps requested for the tones represented by TM[19] (optional) | +| TXCOEF[41:40] | 2 bits | Number of gain steps requested for the tones represented by TM[20] (optional) | +| TXCOEF[43:42] | 2 bits | Number of gain steps requested for the tones represented by TM[21] (optional) | + +**Table 9-22 – Neighbour table for FCC bandplan** + +| Field name | Size | Description | +|-------------------|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| TXCOEF[45:44] | 2 bits | Number of gain steps requested for the tones represented by TM[22] (optional) | +| TXCOEF[47:46] | 2 bits | Number of gain steps requested for the tones represented by TM[23] (optional) | +| Reverse LQI | 8 bits | Link quality indicator of the link to the neighbour | +| PhaseDifferential | 3 bits | Phase difference in multiples of 60 degrees between the AC mains phase of the local node and the neighbour node (see clause 7.17.2.4 and clause 8.10) | +| TMRValidTime | 8 bits | Remaining time in minutes until when the parameters are considered valid.
  • – When an entry is created, this value shall be set to the default value.
  • – When it reaches 0, a tone map request may be issued if data is sent to this device. Upon successful receipt of a tone map response, this value is set to macTMRTTL (see Table 9-15).
  • – When a MAC failure occurs (when macMaxFrameRetries attempts have failed), this value shall be set to 0.
| + +The neighbour table is available in the information base under the attribute *macNeighbourTable* (see clause 9.3.6.2.2). + +### 9.3.8 MAC security suite specifications + +The security suite specifications described in clause 7.6 of [IEEE 802.15.4] apply, with the selections specified in Table 9-23. + +**Table 9-23 – Selections from clause 7.6 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.6 | Security suite specification | N | +| 7.6.1 | PIB security material
  • – Key table contains two 16-byte keys. They represent GMK, as described in clause 10.5.2. The adpActiveKeyIndex parameter selects the key used to cipher outgoing frames.
  • – Automatic request attributes are not used
  • – Default key source is not used
  • – Device table is used, the DeviceDescriptor only contains ShortAddress and FrameCounter fields, the other fields are not used.
  • – Security level table is not used (incoming frame filtering is managed at 6loWPAN layer and described in clause 9.4.2.3.2)
| S | +| 7.6.2 | Auxiliary security header | N | +| 7.6.2.1 | Integer and octet representation | N | +| 7.6.2.2 | Security control field | N | +| 7.6.2.2.1 | Security level subfield
  • – Two values are allowed by the present Recommendation:
    0x00 = "none",
    0x05 = "ENC-MIC-32"
| S | + +**Table 9-23 – Selections from clause 7.6 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|-----------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.6.2.2.2 | Key identifier mode subfield
– One key identifier mode is allowed by the present Recommendation:
0x01 = "Key determined from the 1-octet Key Index subfield"
The number of keys is limited to 2 (KeyIndex value is 0x0-0x1) | S | +| 7.6.2.3 | Frame counter field | N | +| 7.6.2.4 | Key identifier field | N | +| 7.6.2.4.1 | Key source subfield | N/R | +| 7.6.2.4.2 | Key index subfield
– Key index value is 0x0-0x1 | N | +| 7.6.3 | Security operations | N | +| 7.6.3.1 | Integer and octet representation | N | +| 7.6.3.2 | CCM* Nonce
Nonce is formatted as follows, with the first field defining the most significant byte and the last the least significant byte:
– PAN ID (2 bytes)
– Source Short Address (2 bytes)
– PAN ID (2 bytes)
– Source Short Address (2 bytes)
– Frame Counter (4 bytes)
– Security Level (1 bytes)
NOTE 1 – The encrypted frame shall contain the source short address and PAN ID in the MAC header.
NOTE 2 – Fields bigger than a single byte are used in the order from the byte containing the highest numbered bits to the byte containing the lowest numbered bits (Big Endian). | S, E | +| 7.6.3.3 | CCM* prerequisites | N | +| 7.6.3.3.1 | Authentication field length | N | +| 7.6.3.4 | CCM* transformation data representation | N | +| 7.6.3.4.1 | Key and nonce data inputs | N | +| 7.6.3.4.2 | a data and m data
– Two values are allowed by the present Recommendation:
0x00 = "none",
0x05 = "ENC-MIC-32". | S | +| 7.6.3.4.3 | c data output
– Two values are allowed by the present Recommendation:
0x00 = "none",
0x05 = "ENC-MIC-32". | S | +| 7.6.3.5 | CCM* inverse transformation data representation | N | +| 7.6.3.5.1 | Key and nonce data inputs | N | +| 7.6.3.5.2 | c data and a data | N | +| 7.6.3.5.3 | m data output | N | + +### 9.3.9 Message sequence chart illustrating MAC – PHY + +#### 9.3.9.1 Selections + +The message sequence chart illustrating MAC – PHY interaction described in clause 7.7 of [IEEE 802.15.4] applies, with the selections specified in Table 9-24. + +**Table 9-24 – Selections from clause 7.7 of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|--------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 7.7 | Message sequence chart illustrating MAC-PHY interaction
– Figure 78: replaced by clause 9.3.9.2.1
– Figure 79: N/R
– Figure 80: N/R
– Figure 81: N/R
– Figure 82: N/R
– Figure 83: replaced by clause 9.3.9.2.2
– Figures 84 and 85: replaced by clause 9.3.9.2.3
– Figure 86: N/R
– Additional figure about channel estimation in clause 9.3.9.2.4 | S, E | + +#### 9.3.9.2 Extensions + +##### 9.3.9.2.1 PAN start message sequence chart for PAN coordinators + +![Sequence chart for PAN start message sequence for PAN coordinators. Lifelines: Upper layers, Adaptation sublayer, MAC sublayer, PHY layer. The sequence includes ADPM-RESET, ADPM-SET, ADPM-DISCOVERY, and ADPM-NETWORK-Start operations.](235e996e83e7d5198cf9d909f5713cdd_img.jpg) + +``` +sequenceDiagram + participant UL as Upper layers + participant AS as Adaptation sublayer + participant MS as MAC sublayer + participant PL as PHY layer + + Note right of MS: Active scan + + UL->>AS: ADPM-RESET.request + AS->>MS: MLME-RESET.request + MS-->>AS: MLME-RESET.confirm + AS-->>UL: ADPM-RESET.confirm + + UL->>AS: ADPM-SET.request (DeviceType = Server) + AS-->>UL: ADPM-SET.confirm (Status = SUCCESS) + + UL->>AS: ADPM-DISCOVERY.request + AS->>MS: MLME-SCAN.request + MS-->>AS: MLME-SCAN.confirm + AS-->>UL: ADPM-DISCOVERY.confirm + + UL->>AS: ADPM-NETWORK-Start.request + AS->>MS: MLME-SET.request (Short Address) + MS-->>AS: MLME-SET.confirm + AS->>MS: MLME-Start.request + Note left of AS: Initialize internal variables + MS->>PL: PLME_SET_TRX_STATE.request (RxonTxoff) + PL-->>MS: PLME_SET_TRX_STATE.confirm (SUCCESS) + AS-->>UL: ADPM-NETWORK-Start.confirm +``` + +Sequence chart for PAN start message sequence for PAN coordinators. Lifelines: Upper layers, Adaptation sublayer, MAC sublayer, PHY layer. The sequence includes ADPM-RESET, ADPM-SET, ADPM-DISCOVERY, and ADPM-NETWORK-Start operations. + +G.9903(14)\_F9-8 + +Figure 9-8 – PAN start message sequence chart + +##### 9.3.9.2.2 Active scan message sequence chart + +![Active scan message sequence chart showing interactions between Adaptation sublayer, MAC sublayer, PHY layer, and Distant PHY layer.](bbf92fa724597efff9a7b4625ec54041_img.jpg) + +``` + +sequenceDiagram + participant Adaptation sublayer + participant MAC sublayer + participant PHY layer + participant Distant PHY layer + + Note left of MAC sublayer: Backoff period (depends on priority) + Note right of PHY layer: Perform CS + Note left of MAC sublayer: Scan duration + + Adaptation sublayer->>MAC sublayer: MLME-SCAN.request (active) + activate MAC sublayer + MAC sublayer->>PHY layer: PLME_SET_TRX_STATE.request (TXOFF_RXON) + PHY layer-->>MAC sublayer: PLME_SET_TRX_STATE.confirm (SUCCESS) + Note left of MAC sublayer: Backoff period (depends on priority) + MAC sublayer->>PHY layer: PLME_CS.request + PHY layer-->>MAC sublayer: PLME_CS.confirm(IDLE) + Note right of PHY layer: Perform CS + MAC sublayer->>PHY layer: PLME_SET_TRX_STATE.request (TXON_RXOFF) + PHY layer-->>MAC sublayer: PLME_SET_TRX_STATE.confirm (SUCCESS) + MAC sublayer->>PHY layer: PLME_SET.request + PHY layer-->>MAC sublayer: PLME_SET.confirm(IDLE) + MAC sublayer->>PHY layer: PD_DATA.request + PHY layer->>Distant PHY layer: Beacon request + PHY layer-->>MAC sublayer: PD_DATA.confirm + MAC sublayer->>PHY layer: PLME_SET_TRX_STATE.request (TXOFF_RXON) + PHY layer-->>MAC sublayer: PLME_SET_TRX_STATE.confirm (SUCCESS) + Note left of MAC sublayer: Scan duration + PHY layer->>Distant PHY layer: Beacon + PHY layer-->>MAC sublayer: PD_DATA.indication + Note left of MAC sublayer: MLME-BEACON-NOTIFY.indication + MAC sublayer-->>Adaptation sublayer: MLME-SCAN.confirm (SUCCESS) + deactivate MAC sublayer + +``` + +The sequence chart illustrates the message exchange for an active scan. It begins with the Adaptation sublayer sending an **MLME-SCAN.request (active)** to the MAC sublayer. The MAC sublayer then initiates a series of PHY layer requests: **PLME\_SET\_TRX\_STATE.request (TXOFF\_RXON)**, **PLME\_CS.request**, **PLME\_SET\_TRX\_STATE.request (TXON\_RXOFF)**, **PLME\_SET.request**, and **PD\_DATA.request**. The PHY layer responds with confirmations: **PLME\_SET\_TRX\_STATE.confirm (SUCCESS)**, **PLME\_CS.confirm(IDLE)**, **PLME\_SET.confirm(IDLE)**, and **PD\_DATA.confirm**. The **PD\_DATA.request** triggers a **Beacon request** to a Distant PHY layer. After another **PLME\_SET\_TRX\_STATE.request (TXOFF\_RXON)** and **PLME\_SET\_TRX\_STATE.confirm (SUCCESS)**, the MAC sublayer enters a scan duration. A **Beacon** is received from the Distant PHY layer via **PD\_DATA.indication**, which also triggers an **MLME-BEACON-NOTIFY.indication** to the Adaptation sublayer. Finally, the MAC sublayer sends an **MLME-SCAN.confirm (SUCCESS)** back to the Adaptation sublayer. Internal MAC sublayer events include a **Backoff period (depends on priority)** and a **Scan duration**. The PHY layer also performs a **CS** (Clear Sense) check. + +Active scan message sequence chart showing interactions between Adaptation sublayer, MAC sublayer, PHY layer, and Distant PHY layer. + +G.9903(14)\_F9-9 + +Figure 9-9 – Active scan message sequence chart + +##### 9.3.9.2.3 Data transmission message sequence chart + +![Sequence diagram showing data transmission between Adaptation sublayer, MAC sublayer, and PHY layer entities.](74fd2e41231630ea45706acca03e46f7_img.jpg) + +``` + +sequenceDiagram + participant Adaptation sublayer (Left) + participant MAC sublayer (Left) + participant PHY layer (Left) + participant PHY layer (Right) + participant MAC sublayer (Right) + participant Adaptation sublayer (Right) + + Note left of MAC sublayer (Left): Backoff period (depends on priority) + Note right of PHY layer (Left): Perform CS + Note left of MAC sublayer (Left): macAckWaitDuration + + Adaptation sublayer (Left)->>MAC sublayer (Left): MCPS-DATA.request + MAC sublayer (Left)->>PHY layer (Left): PLME_SET_TRX_STATE.request (TXOFF_RXON) + PHY layer (Left)-->>MAC sublayer (Left): PLME_SET_TRX_STATE.confirm (SUCCESS) + Note left of MAC sublayer (Left): Backoff period (depends on priority) + MAC sublayer (Left)->>PHY layer (Left): PLME_CS.request + PHY layer (Left)-->>MAC sublayer (Left): PLME_CS.confirm (IDLE) + Note right of PHY layer (Left): Perform CS + MAC sublayer (Left)->>PHY layer (Left): PLME_SET_TRX_STATE.request (TXON_RXOFF) + PHY layer (Left)-->>MAC sublayer (Left): PLME_SET_TRX_STATE.confirm (SUCCESS) + MAC sublayer (Left)->>PHY layer (Left): PLME_SET.request + PHY layer (Left)-->>MAC sublayer (Left): PLME_SET.confirm + MAC sublayer (Left)->>PHY layer (Left): PD_DATA.request + PHY layer (Left)->>PHY layer (Right): PHY frame + PHY layer (Right)->>MAC sublayer (Right): PD_DATA.indication + MAC sublayer (Right)->>Adaptation sublayer (Right): MCPS-DATA.indication + MAC sublayer (Left)->>PHY layer (Left): PLME_SET_TRX_STATE.request (TXOFF_RXON) + PHY layer (Left)-->>MAC sublayer (Left): PLME_SET_TRX_STATE.confirm (SUCCESS) + Note left of MAC sublayer (Left): macAckWaitDuration + PHY layer (Right)->>MAC sublayer (Right): PD_ACK.request (ACK) + MAC sublayer (Right)->>PHY layer (Right): PD_ACK.confirm + PHY layer (Right)->>PHY layer (Left): ACK + PHY layer (Left)->>MAC sublayer (Left): PD_Ack.indication (ACK) + MAC sublayer (Left)->>Adaptation sublayer (Left): MCPS-DATA.confirm + MAC sublayer (Right)->>PHY layer (Right): PLME_SET_TRX_STATE.request (TXOFF_RXON) + PHY layer (Right)-->>MAC sublayer (Right): PLME_SET_TRX_STATE.confirm (SUCCESS) + +``` + +The sequence diagram illustrates the message exchange for data transmission. It begins with the Adaptation sublayer sending an MCPS-DATA.request to the MAC sublayer. The MAC sublayer then initiates a series of PLME requests to the PHY layer: PLME\_SET\_TRX\_STATE.request (TXOFF\_RXON), PLME\_CS.request, PLME\_SET\_TRX\_STATE.request (TXON\_RXOFF), PLME\_SET.request, and PD\_DATA.request. The PHY layer responds with confirmations and performs actions like 'Perform CS' and 'Backoff period (depends on priority)'. The PD\_DATA.request results in a 'PHY frame' being sent to the remote PHY layer. The remote PHY layer sends a PD\_DATA.indication to its MAC sublayer, which in turn sends an MCPS-DATA.indication to the remote Adaptation sublayer. The MAC sublayer on the left then sends another PLME\_SET\_TRX\_STATE.request (TXOFF\_RXON). After a 'macAckWaitDuration', the remote PHY layer sends a PD\_ACK.request (ACK) to its MAC sublayer, which responds with PD\_ACK.confirm. This ACK is then forwarded by the left PHY layer as PD\_Ack.indication (ACK) to its MAC sublayer, which finally sends an MCPS-DATA.confirm to the left Adaptation sublayer. The sequence concludes with the remote MAC sublayer sending a PLME\_SET\_TRX\_STATE.request (TXOFF\_RXON) to its PHY layer, which responds with a SUCCESS confirmation. + +Sequence diagram showing data transmission between Adaptation sublayer, MAC sublayer, and PHY layer entities. + +G.9903(14)\_F9-10 + +Figure 9-10 – Data transmission message sequence chart + +##### 9.3.9.2.4 Channel estimation message sequence chart + +![Sequence diagram for channel estimation (tone map request) message sequence chart. Lifelines: Adaptation sublayer, MAC sublayer, PHY layer, PHY layer, MAC sublayer, Adaptation sublayer. The sequence shows the interaction between these layers to perform a tone map request and response.](48b17e34bf39cb8a801a634c791250c0_img.jpg) + +``` + +sequenceDiagram + participant Adaptation sublayer + participant MAC sublayer + participant PHY layer + participant PHY layer + participant MAC sublayer + participant Adaptation sublayer + + Note left of MAC sublayer: Backoff period (depends on priority) + Note right of PHY layer: Perform CS + Note right of MAC sublayer: macAckWaitDuration + Note right of MAC sublayer: macAckWaitDuration + + Adaptation sublayer->>MAC sublayer: MCPS-DATA.request + MAC sublayer->>PHY layer: PLME_SET_TRX_STATE.request (TXOFF_RXON) + PHY layer-->>MAC sublayer: PLME_SET_TRX_STATE.confirm (SUCCESS) + Note left of MAC sublayer: Backoff period (depends on priority) + MAC sublayer->>PHY layer: PLME_CS.request + PHY layer-->>MAC sublayer: PLME_CS.confirm (IDLE) + Note right of PHY layer: Perform CS + MAC sublayer->>PHY layer: PLME_SET_TRX_STATE.request (TXON_RXOFF) + PHY layer-->>MAC sublayer: PLME_SET_TRX_STATE.confirm (SUCCESS) + MAC sublayer->>PHY layer: PLME_SET.request + PHY layer-->>MAC sublayer: PLME_SET.confirm + MAC sublayer->>PHY layer: PD_DATA.request (ToneMap request, TMR = 1) + PHY layer-->>PHY layer: PHY frame + PHY layer->>MAC sublayer: PD_DATA.confirm + PHY layer->>MAC sublayer: PD_DATA.indication (ToneMap request, TMR = 1) + MAC sublayer-->>Adaptation sublayer: MCPS-DATA.indication + MAC sublayer->>PHY layer: PLME_SET_TRX_STATE.request (TXOFF_RXON) + PHY layer-->>MAC sublayer: PLME_SET_TRX_STATE.confirm (SUCCESS) + Note left of MAC sublayer: macAckWaitDuration + MAC sublayer->>PHY layer: PD_ACK.request (ACK) + PHY layer-->>MAC sublayer: ACK + MAC sublayer-->>PHY layer: PD_Ack.indication (ACK) + PHY layer->>PHY layer: PHY frame + PHY layer-->>MAC sublayer: PD_DATA.confirm + PHY layer->>MAC sublayer: PD_DATA.indication (ToneMap response) + MAC sublayer-->>PHY layer: PD_Ack.indication (ACK) + MAC sublayer->>PHY layer: PLME_SET_TRX_STATE.request (TXON_RXOFF) + PHY layer-->>MAC sublayer: PLME_SET_TRX_STATE.confirm (SUCCESS) + MAC sublayer->>PHY layer: PD_ACK.request (ACK) + PHY layer-->>MAC sublayer: ACK + MAC sublayer-->>PHY layer: PD_ACK.confirm + PHY layer->>MAC sublayer: PD_ACK.indication (ACK) + Note right of MAC sublayer: macAckWaitDuration + MAC sublayer-->>Adaptation sublayer: MCPS-DATA.confirm + +``` + +Sequence diagram for channel estimation (tone map request) message sequence chart. Lifelines: Adaptation sublayer, MAC sublayer, PHY layer, PHY layer, MAC sublayer, Adaptation sublayer. The sequence shows the interaction between these layers to perform a tone map request and response. + +G.9903(14)\_F9-11 + +Figure 9-11 – Channel estimation (tone map request) message sequence chart + +### 9.3.10 MAC annexes + +The MAC annexes of [IEEE 802.15.4] apply, with the selections specified in Table 9-25. + +**Table 9-25 – Selections from the MAC annexes of [IEEE 802.15.4]** + +| Clause | Title and remarks/modifications | Statement | +|---------|--------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| Annex A | Service-specific convergence sublayer (SSCS)
– The convergence sublayer in [IEEE 802.2] is not used in this Recommendation. | N/R | +| Annex B | CCM* mode of operation | N | +| Annex C | Test vectors for cryptographic building blocks | N | +| Annex D | Protocol implementation conformance statement (PICS)
– The protocol implementation conformance tables are given in Annex A. | E | +| Annex E | Coexistence with other IEEE standards and proposed standards
– This annex relates to wireless PHY standards and is not relevant for PLC technology. | N/R | +| Annex F | [IEEE 802.15.4] regulatory requirements
– This annex relates to wireless PHY standards and is not relevant for PLC technology. | N/R | + +### 9.3.11 Modified MAC sublayer data primitives + +#### 9.3.11.1 MCPS-DATA.request + +The semantics of the MCPS-DATA.request primitive is as follows: + +``` +MCPS-DATA.request ( +SrcAddrMode, +DstAddrMode, +DstPANId, +DstAddr, +msduLength, +msdu, +msduHandle, +TxOptions, +SecurityLevel, +KeyIdMode, +KeySource, +KeyIndex, +QualityOfService +) +``` + +Table 9-26 specifies the parameters for the MCPS-DATA.request primitive. + +**Table 9-26 – MCPS-DATA.request parameters** + +| Name | Type | Valid range | Description | +|-------------------|----------------|-------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| SrcAddrMode | Integer | 0x00-0x03 |

The source addressing mode for this primitive and subsequent MPDUs.

This value can take one of the following values:

0x00 = no address (addressing fields omitted, see clause 7.2.1.1.8 of [IEEE 802.15.4])

0x01 = Reserved by ITU-T

0x02 = 16-bit short address

0x03 = 64-bit extended address.

| +| DstAddrMode | Integer | 0x00-0x03 |

The destination addressing mode for this primitive and subsequent MPDUs

This value can take one of the following values:

0x00 = no address (addressing fields omitted, see clause 7.2.1.1.6 of [IEEE 802.15.4])

0x01 = Reserved by ITU-T

0x02 = 16-bit short address

0x03 = 64-bit extended address.

| +| DstPANId | Integer | 0x0000-0xFFFF |

The 16-bit PAN identifier of the entity to which the MSDU is being transferred.

Note – PAN identifier value is logically ANDed with 0xFCFF.

| +| DstAddr | Device address | As specified by the DstAddrMode parameter |

The individual device address of the entity to which the MSDU is being transferred.

| +| msduLength | Integer | $\leq$ aMaxMACPayload Size |

The number of octets contained in the MSDU to be transmitted by the MAC sublayer entity.

| +| Msdu | Set of octets | – |

The set of octets forming the MSDU to be transmitted by the MAC sublayer entity

| +| msduHandle | Integer | 0x00-0xFF |

The handle associated with the MSDU to be transmitted by the MAC sublayer entity.

| +| TxOptions | Bitmap | 3-bit field |

The 3 bits (b0, b1, b2) indicate the transmission options for this MSDU.

For b0:

0: unacknowledged transmission.

1: acknowledged transmission

Bits b1 and b2 are reserved by ITU-T and shall be set to zero.

| +| QualityOf Service | Integer | 0x00-0x01 |

The QOS (quality of service) parameter of the MSDU to be transmitted by the MAC sublayer entity

This value can take one of the following values:

0 = normal priority

1 = high priority

| +| SecurityLevel | Integer | 0x00 and 0x05 |

The security level to be used as described in

| + +**Table 9-26 – MCPS-DATA.request parameters** + +| Name | Type | Valid range | Description | +|-----------|-----------------|-------------|-------------------------------------------------------------------------------------------------------------------------------------------| +| | | | clause 9.3.8. | +| KeyIdMode | Integer | 0x01 | The mode used to identify the key to be used (see clause 9.3.8). This parameter is ignored if the SecurityLevel parameter is set to 0x00. | +| KeySource | Set of 0 octets | – | Not used | +| KeyIndex | Integer | 0x00-0x01 | The index of the key to be used (see clause 9.3.8). | + +#### 9.3.11.2 MCPS-DATA.indication + +The semantics of the MCPS-DATA.indication primitive is as follows: + +MCPS-DATA.indication ( + +SrcAddrMode, + +SrcPANId, + +SrcAddr, + +DstAddrMode, + +DstPANId, + +DstAddr, + +msduLength, + +msdu, + +msduLinkQuality, + +DSN, + +Timestamp, + +SecurityLevel, + +KeyIdMode, + +KeySource, + +KeyIndex, + +QualityOfService + +) + +Table 9-27 specifies the parameters for the MCPS-DATA.indication primitive. + +**Table 9-27 – MCPS-DATA.indication parameters** + +| Name | Type | Valid range | Description | +|-------------|---------|-------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| SrcAddrMode | Integer | 0x00-0x03 | The source addressing mode for this primitive and subsequent MPDUs. This value can take one of the following values:
0x00 = no address (addressing fields omitted, see clause 7.2.1.1.8 of [IEEE 802.15.4])
0x01 = Reserved by ITU-T | + +**Table 9-27 – MCPS-DATA.indication parameters** + +| Name | Type | Valid range | Description | +|------------------|-----------------|-------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| | | | 0x02 = 16-bit short address
0x03 = 64-bit extended address. | +| SrcPANId | Integer | 0x0000-0xFFFF | The 16-bit PAN identifier of the device from which the frame was received.
NOTE – PAN identifier value is logically ANDed with 0xFCFF. | +| SrcAddr | Device address | As specified by the SrcAddrMode parameter | The address of the device which sent the message. | +| DstAddrMode | Integer | 0x00-0x03 | The destination addressing mode for this primitive and subsequent MPDUs. This value can take one of the following values:
0x00 = no address (addressing fields omitted, see clause 7.2.1.1.6 of [IEEE 802.15.4])
0x01 = Reserved by ITU-T
0x02 = 16-bit short address
0x03 = 64-bit extended address. | +| DstPANId | Integer | 0x0000-0xFFFF | The 16-bit PAN identifier of the entity to which the MSDU is being transferred.
NOTE – PAN identifier value is logically ANDed with 0xFCFF. | +| DstAddr | Device address | As specified by the DstAddrMode parameter | The individual device address of the entity to which the MSDU is being transferred. | +| msduLength | Integer | ≤aMaxMACPayload Size | The number of octets contained in the MSDU to be indicated to the upper layer. | +| msdu | Set of octets | – | The set of octets forming the MSDU received by the MAC sublayer entity. | +| msduLink Quality | Integer | 0x00-0xFF | The (forward) LQI value measured during reception of the message. | +| DSN | Integer | 0x00-0xFF | The DSN of the received frame | +| Timestamp | Integer | 0x00000000-0xFFFFFFFF | The absolute time in milliseconds at which the frame was received and constructed, decrypted (assuming encryption was valid) (32 bit value) (optional). | +| SecurityLevel | Integer | 0x00 and 0x05 | The security level to be used as described in clause 9.3.8. | +| KeyIdMode | Integer | 0x01 | The mode used to identify the key used (see Table 96 in clause 7.6.2.2.2 of [IEEE 802.15.4]). This parameter is ignored if the SecurityLevel parameter is set to 0x00. | +| KeySource | Set of 0 octets | As specified by the KeyIdMode parameter | Not used | +| KeyIndex | Integer | 0x00-0x01 | The index of the key to be used (see clause 9.3.8). | + +**Table 9-27 – MCPS-DATA.indication parameters** + +| Name | Type | Valid range | Description | +|-------------------|---------|-------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| QualityOf Service | Integer | 0x00-0x02 | The QOS (quality of service) parameter of the MSDU received by the MAC sublayer entity.
This value can take one of the following values:
0 = normal priority
1 = high priority | + +## 9.4 IPv6 adaptation sublayer specifications + +### 9.4.1 Information base attributes + +#### 9.4.1.1 General + +Table 9-28 lists the information base (IB) attributes of the adaptation sublayer. + +**Table 9-28 – Adaptation sublayer IB attributes** + +| Attribute | Identifier | Type | Read only | Range | Description | Default | +|------------------------------|------------|------------------|-----------|----------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------| +| adpSecurityLevel | 0x00 | Unsigned Integer | No | See Table 9-22, clause 7.6.2.2.1 | The minimum security level to be used for incoming and outgoing adaptation frames, as described in clause 9.4.2.3.2. | 5 (ENC-MIC-32) | +| adpPrefixTable | 0x01 | Set | No | – | Contains the list of prefixes defined on this PAN.
Note that it is assumed that the link local IPv6 address exists independently and is not affected by the prefixes defined in the prefix table. | Empty | +| adpBroadcastLogTableEntryTTL | 0x02 | Unsigned integer | No | 0-65535 | Maximum time to live of an adpBroadcastLogTable entry (in minutes). | 2 | +| adpMetricType | 0x03 | Unsigned Integer | Yes | 0-0x0F | Metric type to be used for routing purposes | 0x0F | +| adpLowLQIValue | 0x04 | Unsigned Integer | No | 0-255 | The low LQI value defines the LQI value, used in metric computation, | 0 | + +**Table 9-28 – Adaptation sublayer IB attributes** + +| Attribute | Identifier | Type | Read only | Range | Description | Default | +|-----------------------------|-------------------|------------------|------------------|---------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------| +| | | | | | below which a link to a neighbour is considered as an unreliable link. This value shall be lower than adpHighLQIValue | | +| adpHighLQIValue | 0x05 | Unsigned Integer | No | 0-255 | The high LQI value defines the LQI value, used in metric computation, above which a link to a neighbour is considered as a reliable link. This value is greater than adpLowLQIValue. | 255 | +| adpRREPWait | 0x06 | Unsigned Integer | No | 0-255 | An RREP shall be generated after a delay of adpRREPWait seconds after either the arrival of the first RREQ or the transmission of the latest RREP. adpRREPWait shall be strictly less than adpNetTraversalTime | 4 | +| adpContextInformation Table | 0x07 | Set | No | – | Contains the context information associated to each CID extension field. | Empty | +| adpCoordShortAddress | 0x08 | Integer | No | 0x0000-0x7FFF | Defines the short address of the coordinator | 0x0000 | +| adpRLCEnabled | 0x09 | Boolean | No | FALSE
TRUE | Enables the sending of RLCREQ frame by the device | FALSE | +| adpAddRevLinkCost | 0x0A | Unsigned integer | No | 0x00-0xFF | It represents an additional cost to take into account a possible asymmetry in the link (See Annex B) | 0 | + +**Table 9-28 – Adaptation sublayer IB attributes** + +| Attribute | Identifier | Type | Read only | Range | Description | Default | +|--------------------------|------------|------------------|-----------|---------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|---------| +| adpBroadcastLogTable | 0x0B | Set | Yes | – | Contains the broadcast log table, see Table 9-32. | Empty | +| adpRoutingTable | 0x0C | Set | Yes | – | Contains the routing table, see Table 9-31. | Empty | +| adpUnicastRREQGenEnabled | 0x0D | Boolean | No | FALSE
TRUE | If TRUE, the RREQ shall be generated with its "unicast RREQ" flag set to '1'.
If FALSE, the RREQ shall be generated with its "unicast RREQ" flag set to '0'. | TRUE | +| adpGroupTable | 0x0E | Set | No | – | Contains the group addresses to which the device belongs. | Empty | +| adpMaxHops | 0x0F | Unsigned integer | No | 0-0x0E | Defines the maximum number of hops to be used by the routing algorithm. | 8 | +| adpDeviceType | 0x10 | Unsigned integer | No | 0-2 | Defines the type of device connected to the modem:
0: PAN device
1: PAN coordinator
2: Not defined | 2 | +| adpNetTraversalTime | 0x11 | Unsigned integer | No | 0-255 | Maximum time that a packet is expected to take to reach any node from any node in seconds. | 20 | +| adpRoutingTableEntryTTL | 0x12 | Unsigned integer | No | 0-65535 | Maximum time-to-live of a routing table entry (in minutes). | 360 | +| adpKr | 0x13 | Unsigned integer | No | 0-31 | A weight factor for robust mode to calculate link cost (Note 1). | 0 | +| adpKm | 0x14 | Unsigned integer | No | 0-31 | A weight factor for modulation to calculate link cost (Note 1). | 0 | + +**Table 9-28 – Adaptation sublayer IB attributes** + +| Attribute | Identifier | Type | Read only | Range | Description | Default | +|----------------------------|------------|------------------|-----------|---------|----------------------------------------------------------------------------------------------------------------------------------------------------|---------| +| adpKc | 0x15 | Unsigned integer | No | 0-31 | A weight factor for number of active tones to calculate link cost (Note) | 0 | +| adpKq | 0x16 | Unsigned integer | No | 0-50 | A weight factor for LQI to calculate route cost 1) | 10 | +| adpKh | 0x17 | Unsigned integer | No | 0-31 | A weight factor for hop to calculate link cost (1) | 4 | +| adpRREQRetries | 0x18 | Unsigned integer | No | 0-255 | The number of RREQ retransmission in case of RREP reception time out. | 0 | +| adpRREQWait | 0x19 | Unsigned integer | No | 0-255 | Time in seconds to wait between two consecutive RREQ or RLCREQ generations. | 30 | +| adpWeakLQIValue | 0x1A | Unsigned Integer | No | 0-255 | The weak link value defines the LQI value below which a link to a neighbour is considered as a weak link. A value of 52 represents an SNR of 3 dB. | 52 | +| adpKrt | 0x1B | Unsigned Integer | No | 0-31 | A weight factor for the number of active routes in the routing table to calculate link cost (Note 1). | 0 | +| adpSoftVersion | 0x1C | Set | Yes | – | The software version | – | +| adpSnifferMode | 0x1D | Unsigned Integer | No | 0-1 | Sniffer mode activation/deactivation | 0 | +| adpBlacklistTable | 0x1E | Set | Yes | – | Contains the list of the blacklisted neighbours | Empty | +| adpBlacklistTableEntry TTL | 0x1F | Unsigned Integer | No | 0-65535 | Maximum time-to-live of a blacklisted neighbour entry (in minutes). | 10 | + +**Table 9-28 – Adaptation sublayer IB attributes** + +| Attribute | Identifier | Type | Read only | Range | Description | Default | +|-----------------------------|------------|------------------|-----------|------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------| +| adpMaxJoinWaitTime | 0x20 | Unsigned Integer | No | 0-1023 | Network join timeout in seconds for LBD | 20 | +| adpPathDiscoveryTime | 0x21 | Unsigned integer | No | 0-255 | Timeout for path discovery in seconds | 40 | +| adpActiveKeyIndex | 0x22 | Unsigned Integer | Yes | 0-1 | Index of the active GMK to be used for data transmission (Note 2). | 0 | +| adpDestinationAddressSet | 0x23 | Set | No | – | Contains the list of the addresses of the device for which this LOADng router is providing connectivity | Empty | +| adpDefaultCoordRouteEnabled | 0x24 | Boolean | No | FALSE TRUE | If TRUE, the adaptation layer adds a default route to the coordinator after successful completion of the bootstrapping procedure. If FALSE no default route will be created. | FALSE | +| adpDisableDefaultRouting | 0xF0 | Boolean | No | FALSE TRUE | If TRUE, the default routing (LOADng) is disabled. If FALSE, the default routing (LOADng) is enabled. See clause 9.4.3. | FALSE | + +NOTE 1 – Link cost calculation is provided in Annex B. +NOTE 2 – Write access to this attribute can be used if the ADP internal re-keying procedure is not applied. + +An example of an IPv6 prefix table entry compliant with [IETF RFC 4861] is given in Table 9-29. The IPv6 prefix table is available in the information base under the attribute adpPrefixTable (see Table 9-28). + +**Table 9-29 – Example of prefix table entry (informative)** + +| Field | Length | Description | +|--------------------|----------|-----------------------------------------------------------------------------------------------------| +| Prefix length | 8 bits | Number of leading bits in the prefix that are valid. The value ranges from 0 to 128. | +| L | 1 bit | 1-bit on-link flag | +| A | 1 bit | 1-bit autonomous address-configuration flag | +| Valid lifetime | 32 bits | Length of time in seconds during which the prefix is valid for the purpose of on-link determination | +| Preferred lifetime | 32 bits | Length of time in seconds during which addresses generated from the prefix remain preferred | +| Prefix | Variable | IPv6 address or a prefix of an IPv6 address | + +The adpContextInformationTable is a data set of 16 entries. An example of the structure of each entry compliant with [IETF RFC 6775] is given in Table 9-30. + +**Table 9-30 – Context information table entry (informative)** + +| Field | Length | Description | +|----------------|----------|-------------------------------------------------------------------------------------------------------------------------------------------------| +| CID | 4 bits | Corresponds to the 4-bit context information used for source and destination addresses (SCI, DCI). | +| Context length | 8 bits | Indicates the length of the carried context (up to 128-bit contexts may be carried). | +| Context | variable | Corresponds to the carried context used for compression/decompression purposes. | +| C | 1 bit | Indicates if the context is valid for use in compression. | +| Valid Lifetime | 16 bits | Remaining time in minutes during which the context information table is considered valid. It is updated upon receipt of the advertised context. | + +#### 9.4.1.2 Routing, broadcast and blacklisted neighbour table description + +Table 9-31 describes the routing table entry. Its entries are updated by the routing set defined as per clause 9.4.3.1 (see clause D.7.1 in Table 9-37). The routing table is available in the information base under the attribute *adpRoutingTable* (see Table 9-28). + +**Table 9-31 – Routing table entry** + +| Field | Terminology used in Annex D for routing set | Length | Description | +|---------------------|---------------------------------------------|---------|-----------------------------------------------------------------------------| +| Destination Address | R_dest_addr | 16 bits | Address of the destination. | +| Next Hop Address | R_next_addr | 16 bits | Address of the next hop on the route towards the destination. | +| Route Cost | R_metric | 16 bits | Cumulative link cost along the route towards the destination (see Annex B). | +| Hop count | R_hop_count | 4 bits | Number of hops of the selected route to the destination. | +| Weak Link Count | R_weak_link_count | 4 bits | Number of weak links to destination. It ranges from 0 to adpMaxHops. | + +**Table 9-31 – Routing table entry** + +| Field | Terminology used in Annex D for routing set | Length | Description | +|------------|---------------------------------------------|---------|-------------------------------------------------------------------------------------------| +| Valid Time | | 16 bits | Remaining time in minutes until when this entry in the routing table is considered valid. | + +Table 9-32 describes the broadcast log table entry. The broadcast log table is available in the information base under the attribute *adpBroadcastLogTable* (see Table 9-28). + +**Table 9-32 – Broadcast log table entry** + +| Field | Length | Description | +|-----------------|---------|--------------------------------------------------------------------------------------------------| +| Source Address | 16 bits | The 16-bit source address of a broadcast packet. This is the address of the broadcast initiator. | +| Sequence Number | 8 bits | The sequence number contained in the BC0 header. | +| Valid Time | 16 bits | Remaining time in minutes until when this entry in the broadcast log table is considered valid. | + +Table 9-33 describes the blacklisted neighbour table entry. Its entries are updated by the blacklisted neighbour set defined as per clause 9.4.3.1 (see clause D.7.3 in Table 9-37). The blacklisted neighbour table is available in the information base under the attribute *adpBlacklistTable* (see Table 9-28). + +**Table 9-33 – Blacklisted neighbour table entry** + +| Field | Terminology used in Annex D | Length | Description | +|-------------------------------|-----------------------------|---------|---------------------------------------------------------------------------------------------------------| +| Blacklisted Neighbour Address | B_neighbour_address | 16 bits | The 16-bit address of the blacklisted neighbour. | +| Valid Time | | 16 bits | Remaining time in minutes until when this entry in the blacklisted neighbour table is considered valid. | + +### 9.4.2 Data frame format, datagram transmission and addressing + +#### 9.4.2.1 Selections from [IETF RFC 4944] + +The data frame format, the theory of operation for datagram transmission using the IEEE 802.15.4 MAC sublayer and the addressing scheme are specified in [IETF RFC 4944] using the selections listed in Table 9-34. + +**Table 9-34 – Selections from [IETF RFC 4944]** + +| Clause | Title and remarks/modifications | Statement | +|--------|--------------------------------------------------------------------|-----------| +| 1 | Introduction | N | +| 1.1 | Requirements notation | N | +| 1.2 | Terms used | N | +| 2 | [IEEE 802.15.4] mode for IP
– Data frames shall be acknowledged | S | + +**Table 9-34 – Selections from [IETF RFC 4944]** + +| Clause | Title and remarks/modifications | Statement | +|--------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| | – Only non-beacon-enabled networks are used. | | +| 3 | Addressing modes | N | +| 4 | Maximum transmission unit | N | +| 5 | LoWPAN adaptation layer and frame format
– Extension: additional command frame header: see clause 9.4.2.3.1.
– When more than one LoWPAN header is used in the same packet, they shall appear in the following order:
Mesh addressing header
Broadcast header
Fragmentation header
Command frame header (see clause 9.4.2.3.1). | E | +| 5.1 | Dispatch type and header
ESC pattern '01 111111' shall be updated with '01 000000' as defined in [IETF RFC 6282]. | N | +| 5.2 | Mesh addressing type and header
– The value of the HopsLeft field shall not exceed adpMaxHops (see clause 9.4.2.1)
NOTE – When the node is the originator and next hop is the final destination address, the mesh header shall be omitted in the frame. | S | +| 5.3 | Fragmentation type and header | N | +| 6 | Stateless address auto-configuration
– The 64-bit interface identifier (see [IETF RFC 4291]) shall be derived from a "pseudo 48-bit address" formed with the PAN identifier and the short address as follows: 0xYYYY:00FF:FE00:XXXX where 0xYYYY is the PAN identifier and XXXX is the short address.
– Additional care shall be taken when choosing a PAN identifier, so as not to interfere with I/G and U/L bits of the interface identifier. If the PAN identifiers are chosen randomly, then they shall be logically ANDed with 0xFCFF. | S | +| 7 | IPv6 link local address | N | +| 8 | Unicast address mapping | N | +| 9 | Multicast address mapping | N | +| 10 | Header compression | N/R | +| 10.1 | Encoding of IPv6 header fields | N/R | +| 10.2 | Encoding of UDP header fields | N/R | +| 10.3 | Non-compressed fields | N/R | +| 10.3.1 | Non-compressed IPv6 fields | N/R | +| 10.3.2 | Non-compressed and partially compressed UDP fields | N/R | +| 11 | Frame delivery in a link-layer mesh | S | +| 11.1 | LoWPAN broadcast | N | +| 12 | IANA considerations | N | +| 13 | Security considerations | N | +| 14 | Acknowledgements | N/R | + +**Table 9-34 – Selections from [IETF RFC 4944]** + +| Clause | Title and remarks/modifications | Statement | +|------------|-----------------------------------------------|-----------| +| 15 | References | N/R | +| 15.1 | Normative references | N | +| 15.2 | Informative references | I | +| Appendix A | Alternatives for delivery of frames in a mesh | N/R | + +#### 9.4.2.2 Selections from [IETF RFC 6282] + +[IETF RFC 6282] specifies a header compression format that updates the one defined in clause 10 of [IETF RFC 4944]. The selections of [IETF RFC 6282] listed in Table 9-35 apply. + +**Table 9-35 – Selections from [IETF RFC 6282]** + +| Clause | Title and remarks/modifications | Statement | +|--------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 1 | Introduction | N | +| 1.1 | Requirements language | N | +| 2 | Specific updates to [IETF RFC 4944] | N | +| 3 | IPv6 header compression | N | +| 3.1 | LOWPAN_IPHC Encoding Format | N | +| 3.1.1 | Base format | N | +| 3.1.2 | Context identifier extension | N | +| 3.2 | IPv6 header encoding | N | +| 3.2.1 | Traffic class and flow label compression | N | +| 3.2.2 | Deriving IIDs from the encapsulating header
– 64 bit interface identifiers are created as described in clause 6 of [IETF RFC 4944]. | S | +| 3.2.3 | Stateless multicast address compression | N | +| 3.2.4 | Stateful multicast address compression | N | +| 4 | IPv6 next header compression | N | +| 4.1 | LOWPAN_NHC format | N | +| 4.2 | IPv6 extension header compression
– If applicable, the fragment Header's "Reserved" field shall be processed as a regular IPv6 extension header "Length" field.
– Trailing padding options (Pad1 or PadN) may be elided for any type of IPv6 header.
– Headers following an IPv6 fragment header shall not be compressed. | S | +| 4.3 | UDP header compression | N | +| 4.3.1 | Compressing UDP ports | N | +| 4.3.2 | Compressing UDP Checksum | N | +| 4.3.3 | UDP LOWPAN_NHC format | N | +| 5 | IANA considerations | N | +| 6 | Security considerations | N | + +**Table 9-35 – Selections from [IETF RFC 6282]** + +| Clause | Title and remarks/modifications | Statement | +|--------|---------------------------------|-----------| +| 7 | Acknowledgements | N/R | +| 8 | References | N/R | +| 8.1 | Normative references | N | +| 8.2 | Informative references | I | + +#### 9.4.2.3 Extensions + +##### 9.4.2.3.1 Command frame header + +In addition to the LoWPAN header specified in [IETF RFC 4944], this Recommendation defines a new one: command frame header. This is used for the mesh routing procedure defined in clause 9.4.3. + +As shown in Figure 9-12, the ADP sublayer command frames are identified using the ESC header type (see clause 5.1 of [IETF RFC 4944]), followed by an 8-bit dispatch field indicating the type of ADP command. This header shall be in the last position if more than one header is present in the 6LowPAN frame. + +![Diagram of Command frame header format showing ESC header type (01 000000b), Command Id, and Command Payload fields across 24 bits.](a3d6b1f562612dbd5a5d7c4ce91999d1_img.jpg) + +The diagram illustrates the bit layout of the Command frame header. It consists of three main fields: + + +- ESC header type:** Occupies bits 0 through 7. The value is specified as 01 000000b. +- Command Id:** Occupies bits 8 through 15. This field is 8 bits wide. +- Command Payload:** Occupies bits 16 through 23. This field is also 8 bits wide. + + The bits are numbered 0 to 23, with a '1' above bit 8 and a '2' above bit 16 to indicate byte boundaries. + +Diagram of Command frame header format showing ESC header type (01 000000b), Command Id, and Command Payload fields across 24 bits. + +**Figure 9-12 – Command frame header format** + +The ADP sublayer command frames are specified in Table 9-36. + +**Table 9-36 – Command frame header identifier** + +| Command | Command Id | Comments | Specified in... | +|---------------------------------------|------------|--------------------------------------------------------------------------------------------------------------------------------------|-----------------| +| LOADng message | 0x01 | Used for LOADng routing protocol (default-routing) | Clause 9.4.3 | +| LoWPAN bootstrapping protocol message | 0x02 | Used for LoWPAN Bootstrap procedure | Clause 9.4.4 | +| Reserved by ITU-T | 0x03-0x0F | Reserved by ITU-T | | +| CMSR protocol messages | 0x10-0x1F | Used when the default-routing LOADng is disabled and CMSR (non-default routing) as specified in [ITU-T G.9905] is used in its place. | [ITU-T G.9905] | + +##### 9.4.2.3.2 Security processing for adaptation layer frames + +As the bootstrapping protocol is implemented in the adaptation layer and is required to use frames without any additional security at the MAC layer, the management of the security level for incoming and outgoing frames is implemented by the adaptation layer. + +For incoming frames: + +- If the frame contains the LBP protocol, it is processed as described in clause 9.4.4. + +- Otherwise, if MCPS-Data.indication SecurityLevel < adpSecurityLevel, the frame is dropped. + +For outgoing frames: + +- If the frame contains the LBP protocol, it is sent as described in clause 9.4.4. +- Otherwise, MCPS-Data.request SecurityLevel is set to adpSecurityLevel. + +### 9.4.3 Mesh routing + +In this clause, the protocol messages employ the following notation: + +MsgType.field + +where: + +- MsgType is the type of a message (e.g., RREQ) +- field is the field in the message (e.g., originator). + +#### 9.4.3.1 Selections from Annex D + +LOADng is the ITU-T G.9903 default routing mechanism and shall be supported by ITU-T G.9903 devices. In this Recommendation, the LOADng protocol specified in Annex D is exclusively used in the context of layer-2 routing and the term "routing domain" used in Annex D shall be interpreted as "layer-2 routing domain." + +The LOADng protocol specified in Annex H may however be disabled. This allows ITU-T G.9903 devices to support either point-to-point single hop communication or a non-default routing protocol. + +The mesh routing as described in Annex D applies, with the selections specified in Table 9-37. + +**Table 9-37 – Selections from Annex D** + +| Clause | Title and remarks/modifications | Statement | +|--------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| D.1 | Introduction | N | +| D.2 | Terminology and notation | N | +| D.2.1 | Message and message field notation | N | +| D.2.2 | Variable notation | N | +| D.2.3 | Other notation | N | +| D.2.4 | Terminology
– Route metric is the same as route cost
– Link metric is the same as link cost. | S | +| D.3 | Applicability statement
– Only 16-bit addressing is supported. | S | +| D.4 | Protocol overview and functioning | N | +| D.4.1 | Overview | N | +| D.4.2 | LOADng routers and LOADng interfaces
– The RREP_ACK message is not supported. | S | +| D.4.3 | Information base overview
– The routing set is an internal data set of the LOADng routing protocol. It is used to update the routing table which is stored within the adaptation layer MIB under the adpRoutingTable attribute.
– The local interface set is stored within the MAC layer MIB under the macShortAddress attribute.
– The Blacklisted neighbour set is stored within the adaptation layer MIB | S | + +**Table 9-37 – Selections from Annex D** + +| Clause | Title and remarks/modifications | Statement | +|--------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| |

under the adpBlacklistTable attribute.

  • – The destination address set is stored within the adaptation layer MIB under the adpDestinationAddressSet attribute.
  • – The pending acknowledgement set is not supported.
| | +| D.4.4 |

Signalling overview

  • – The RREP_ACK message is not supported. Validation that a link is bidirectional is performed using the RREP message ACK frame.
| S, E | +| D.5 | Protocol parameters | N | +| D.5.1 | Protocol and port numbers | N/R | +| D.5.2 |

Router parameters

  • – NET_TRAVERSAL_TIME is stored within the adaptation layer MIB under the adpNetTraversalTime attribute.
  • – RREQ_RETRIES is stored within the adaptation layer MIB under the adpRREQRetries attribute.
  • – RREQ_MIN_INTERVAL is related to the adpRREQWait attribute which is stored within the adaptation layer MIB.
  • – R_HOLD_TIME is related to the adpRoutingTableEntryTTL attribute stored within the adaptation layer MIB. R_HOLD_TIME = adpRoutingTableEntryTTL.
  • – MAX_DIST is linked to the adpKr, adpKm, adpKc, adpKq, adpKh attributes which are stored in the adaptation layer MIB and the route cost calculation described in Annex B.
  • – B_HOLD_TIME is stored within the adaptation layer MIB under the adpBlacklistTableEntryTTL attribute.
  • – MAX_HOP_LIMIT is stored within the adaptation layer MIB under the adpMaxHops attribute.
  • – The following parameter is added:
    WEAK_LINK_THRESHOLD is stored within the adaptation layer MIB under the adpWeakLQIValue attribute.
| S, E | +| D.5.3 |

Interface parameters

  • – RREQ_MAX_JITTER is not supported.
  • – RREQ_ACK_REQUIRED is not supported.
  • – USE_BIDIRECTIONAL_LINK_ONLY is always set to TRUE.
  • – RREQ_ACK_TIMEOUT is not supported.
  • – RREP_ACK_REQUIRED is not supported.
| S | +| D.5.4 | Constants | N | +| D.6 | Protocol message content | N | +| D.6.1 |

Route request (RREQ) message

  • – RREQ.addr-length = 1 (exclusively 6LoWPAN 16-bit short addresses are used).
  • – The following field is added:
    RREQ.weak-link-count is an unsigned integer and specifies the total number of weak link hops which the packet has traversed from RREQ.originator.
    RREQ.weak-link-count is mutable.
  • – Message format is described in clause 9.4.3.2.7.2.
| S, E | + +**Table 9-37 – Selections from Annex D** + +| Clause | Title and remarks/modifications | Statement | +|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| D.6.2 | Route reply (RREP) message
  • – RREP.addr-length = 1 (exclusively 6LoWPAN 16-bit short addresses are used)
  • – RREP.ackrequired flag is always cleared ('0').
  • – The following field is added:
    RREP.weak-link-count is an unsigned integer and specifies the total number of weak link hops which the packet has traversed from RREP.originator
    RREP.weak-link-count is mutable
  • – Message format is described in clause 9.4.3.2.7.2.
| S, E | +| D.6.3 | Route reply acknowledgement (RREP_ACK) message | N/R | +| D.6.4 | Route error (RERR) message
  • – RERR.addr-length = 1 (exclusively 6LoWPAN 16-bit short addresses are used)
  • – Error code definition is given in Table 9-38
  • – Message format is described in clause 9.4.3.2.7.3.
| S, E | +| D.7 | Information base | N | +| D.7.1 | Routing set
  • – Routing tuples include the following additional field:
    R_weak_link_count is the number of weak link hops of the selected route to the destination with address R_dest_addr. (See Table 9-31).
| E | +| D.7.2 | Local interface set | N | +| D.7.3 | Blacklisted neighbour set
Modification: The blacklisted neighbour table available in the adaptation layer MIB under the adpBlacklistTable attribute stores:
Blacklisted Neighbour Address
Valid Time: associated remaining time in seconds until when this entry in the blacklisted neighbour table is considered valid. B_valid_time is not used. | E | +| D.7.4 | Destination address set | N | +| D.7.5 | Pending acknowledgement set | N/R | +| D.8 | LOADng router sequence numbers
When the same short address is always allocated to a PAN device, it is recommended to restore the LOADng router sequence number after a power cycle. | N | +| D.9 | Route maintenance | N | +| D.10 | Unidirectional link handling
  • – MAC acknowledgment signalling is used to handle unidirectional links. Practically, MCPS-DATA.confirm status triggers blacklisting for the following possible values: TRANSACTION_EXPIRED, NO_ACK
| N | +| D.10.1 | Blacklist usage | N | +| D.11 | Common rules for RREQ and RREP messages
  • – Add the following variable:
    weak-link-count is a variable, representing the weak-link-count, as included in the received RREQ or RREP message.
| E | + +**Table 9-37 – Selections from Annex D** + +| Clause | Title and remarks/modifications | Statement | +|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| D.11.1 | Identifying invalid RREQ or RREP messages | N | +| D.11.2 | RREQ and RREP message processing
  • – link-metric is calculated as specified in clause 9.4.3.2.6
  • – The following extensions are added to this clause:
For step 4. add:
* if LQI < WEAK LINK THRESHOLD, then increment weak-link-count
For step 7. add:
* R_weak_link_count:= MAX_HOP_COUNT
Step 8.1. is modified as follows:
+ R_seq_num = MSG.seq-num; AND
+ R_metric_type = used-metric-type; AND
+ R_weak_link_count > weak-link-count
OR
+ R_seq_num = MSG.seq-num; AND
+ R_metric_type = used-metric-type; AND
+ R_weak_link_count = weak-link-count; AND
+ R_metric > route-metric
OR
+ R_seq_num = MSG.seq-num; AND
+ R_metric_type = used-metric-type; AND
+ R_weak_link_count = weak-link-count; AND
+ R_metric = route-metric; AND
+ R_hop_count > MSG.hop-count
OR
+ R_seq_num = MSG.seq-num; AND
+ R_metric_type is not equal to used-metric-type; AND
+ R_metric_type = HOP_COUNT
OR
+ R_seq_num < MSG.seq-num
For step 8.1.1 the Routing Tuple is also updated as follows:
– R_weak_link_count: = weak-link-count
– R_bidirectional := TRUE, if the message being processed is an RREP, otherwise FALSE
For step 8.1.3 the Routing Tuple is also updated as follows:
– R_weak_link_count: = 1, if link-metric > WEAK_LINK_THRESHOLD, otherwise 0 | S, E | +| D.12 | Route requests (RREQs) | N | +| D.12.1 | RREQ generation
  • – RREQ.metric-type shall be set to adpMetricType
  • – RREQ.weak-link-count = 0
  • – If adpUnicastRREQGenEnabled is TRUE the "unicast RREQ" flag shall be set to '1'. Otherwise, the "unicast RREQ" flag shall be set to '0'. Note that the "unicast RREQ" flag is set when an RREQ message is generated and shall not be changed when an RREQ message is forwarded.
| E | + +**Table 9-37 – Selections from Annex D** + +| Clause | Title and remarks/modifications | Statement | +|--------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| D.12.2 | RREQ processing | N | +| D.12.3 | RREQ forwarding
  • – A step 5. is added:
    RREQ.weak-link-count: = weak-link-count
  • – Flag field of the RREQ received is propagated to the Flag field of the RREQ to be forwarded.
| E | +| D.12.4 | RREQ transmission
  • – RREQ messages are transmitted as described below:
    • 1) If the "unicast RREQ" flag is set to '0', the RREQ is broadcasted.
    • 2) If the "unicast RREQ" flag is set to '1' and no valid entry is found in the routing set such as R_dest_addr = RREQ.destination, the RREQ shall be broadcasted.
    • 3) If the "unicast RREQ" flag is set to '1' and a valid entry is found in the routing set with R_dest_addr = RREQ.destination, the RREQ shall be sent in unicast along this route. If the transmission of the unicast RREQ failed (No ACK received as described in clause 9.3.2), the RREQ shall be broadcasted.
| N | +| D.13 | Route replies (RREPs) | N | +| D.13.1 | RREP generation
  • – RREP.weak-link-count: = 0
  • – An RREP in response to a (set of) received RREQ messages (with identical RREQ.originator and RREQ.seq-num) shall be generated after a delay of adpRREPWait seconds after either the arrival of the first RREQ or the transmission of the latest RREP. A value of 0 means that an RREP may be generated immediately as a response to each RREQ processed.
| E | +| D.13.2 | RREP processing | N | +| D.13.3 | RREP forwarding
  • – An additional step is added between step 4 and step 5:
    RREQ.weak-link-count: = weak-link-count
  • – Flag field of the RREP received is propagated to the Flag field of the RREP to be forwarded.
| E | +| D.13.4 | RREP transmission
  • – RREP messages always use acknowledged transmission.
  • – If a RREP transmission is successful, the routing tuple is updated with R_bidirectional := TRUE, if the message being processed is an RREP, otherwise FALSE.
  • – If a RREP transmission fails, P_next_hop address shall be blacklisted by creating a blacklisted neighbour tuple according to clause D.7.3.
| E | +| D.14 | Route errors (RERRs) | N | +| D.14.1 | Identifying invalid RERR messages | N | +| D.14.2 | RERR generation
  • – An RERR is only generated after the local repair mechanism specified in clause 9.4.3.2.5 fails
| E | +| D.14.3 | RERR processing | N | + +**Table 9-37 – Selections from Annex D** + +| Clause | Title and remarks/modifications | Statement | +|--------|-----------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| D.14.4 | RERR forwarding | N | +| D.14.5 | RERR transmission | N | +| D.15 | Route reply acknowledgements (RREP_ACKs) | N/R | +| D.15.1 | Identifying invalid RREP_ACK messages | N/R | +| D.15.2 | RREP_ACK generation | N/R | +| D.15.3 | RREP_ACK processing | N/R | +| D.15.4 | RREP_ACK forwarding | N/R | +| D.15.5 | RREP_ACK transmission | N/R | +| D.16 | Metrics
The following metric types are defined:
– COMPOSITE_METRIC = 0x0F (see Annex B)
– HOP_COUNT = 0x00 (considering only the number of hops) | E | +| D.16.1 | Specifying new metrics | N | +| D.17 | Security considerations | I | +| D.17.1 | Confidentiality | I | +| D.17.2 | Integrity | I | +| D.17.3 | Channel jamming and state explosion | I | +| D.17.4 | Interaction with external routing domains | I | + +#### 9.4.3.2 Extensions to Annex D + +##### 9.4.3.2.1 Unicast packet routing + +The routing of the unicast packet is performed using the following algorithm on receipt of an MCPS-DATA.indication from the MAC layer (see also Figure 9-13 for the corresponding flow-chart): + +IF (MAC destination address = address of device) + +IF (No mesh header present in 6LoWPAN headers) + +Generate an ADPD-DATA.indication primitive to indicate the arrival of a frame to the upper layer, with the following characteristics (see clause 9.4.6.1.4): + +(1) + +- DstAddrMode = 0x02 +- DstAddr = MAC destination address +- SrcAddr = MAC source address +- NsduLength = length of the payload +- Nsdu = the payload +- LinkQualityIndicator = msduLinkQuality (see clause 9.3.11.2) +- SecurityEnabled = (SecurityLevel != 0) + +ELSE + +IF (6LoWPAN destination address = 6LoWPAN address of device) or an address stored in the destination address set + +Generate an ADPD-DATA.indication primitive to indicate the arrival of a frame to the upper layer, with the following characteristics (see clause 9.4.6.1.4): + +- DstAddrMode = 0x02 +- DstAddr = 6LoWPAN destination address +- (2) – SrcAddr = The originator address in the 6LoWPAN mesh header +- NsduLength = length of the payload +- Nsdu = the payload +- LinkQualityIndicator = msduLinkQuality (see clause 9.3.11.2) +- SecurityEnabled = ( $SecurityLevel \neq 0$ ) + +ELSE + +$HopsLft = HopsLft - 1$ , as specified in clause 5.2 of [IETF RFC 4944] + +IF ( $HopsLft > 0$ ) + +IF (6LoWPAN destination address is in the routing table) + +(3) Forward the packet to the next hop found in the routing table, by invoking an MCPS-DATA.request primitive. + +ELSE + +- (4) – Perform a route repair as described in clause 9.4.3.2.5. +- Queue the packet for a sending retry + +ELSE + +IF (6LoWPAN destination address is in the routing table) + +- (5) – Delete the routing table entry for the 6LoWPAN destination address, +- Issue a RERR to the originator address in the 6LoWPAN mesh header, +- Drop the frame. + +ELSE + +- (6) – Issue a RERR to the originator address in the 6LoWPAN mesh header, +- Drop the frame. + +ELSE + +IF (MAC destination address = 0xFFFF) + +This is a broadcast frame: execute algorithm described in clause 9.4.3.2.2. + +ELSE + +Drop the frame + +![Flowchart of Unicast packet routing processing. The process starts with 'Reception of a frame'. It checks if the MAC destination address equals the device's address. If YES, it checks if no mesh header is present in the 6LoWPAN header. If YES, it goes to (1). If NO, it checks if the 6LoWPAN destination address matches the device's address or an address in the destination address set. If YES, it goes to (2). If NO, it decrements HopsLft. If HopsLft > 0, it checks if the 6LoWPAN destination is in the routing table. If YES, it goes to (3). If NO, it goes to (4). If HopsLft is not greater than 0, it checks if the 6LoWPAN destination is in the routing table. If YES, it goes to (5). If NO, it goes to (6). If the MAC destination address is not the device's address, it checks if it is 0xFFFF. If YES, it executes broadcast frame processing. If NO, it drops the frame.](f2b561f8d2d2b8402379552179d9fbef_img.jpg) + +``` + +graph TD + Start([Reception of a frame]) --> D1{If MAC destination address = address of the device} + D1 -- YES --> D2{If no mesh header present in 6LoWPAN header} + D2 -- YES --> (1) + D2 -- NO --> D3{If 6LoWPAN destination address = 6LoWPAN address of device or an address stored in the destination address set} + D3 -- YES --> (2) + D3 -- NO --> H[HopsLft=HopsLft-1] + H --> D4{HopsLft > 0} + D4 -- YES --> D5{If 6LoWPAN destination is in the routing table} + D5 -- YES --> (3) + D5 -- NO --> (4) + D4 -- NO --> D6{If 6LoWPAN destination is in the routing table} + D6 -- YES --> (5) + D6 -- NO --> (6) + D1 -- NO --> D7{If MAC destination address = 0xFFFF} + D7 -- YES --> B([Execute broadcast frame processing]) + D7 -- NO --> Drop([Drop the frame]) + +``` + +G.9903(17)\_F9-13 + +Flowchart of Unicast packet routing processing. The process starts with 'Reception of a frame'. It checks if the MAC destination address equals the device's address. If YES, it checks if no mesh header is present in the 6LoWPAN header. If YES, it goes to (1). If NO, it checks if the 6LoWPAN destination address matches the device's address or an address in the destination address set. If YES, it goes to (2). If NO, it decrements HopsLft. If HopsLft > 0, it checks if the 6LoWPAN destination is in the routing table. If YES, it goes to (3). If NO, it goes to (4). If HopsLft is not greater than 0, it checks if the 6LoWPAN destination is in the routing table. If YES, it goes to (5). If NO, it goes to (6). If the MAC destination address is not the device's address, it checks if it is 0xFFFF. If YES, it executes broadcast frame processing. If NO, it drops the frame. + +**Figure 9-13 – Unicast packet routing processing** + +##### 9.4.3.2.2 Multicast/broadcast + +###### 9.4.3.2.2.1 Packet routing + +The packet routing mechanism is based on clause 11.1 of [IETF RFC 4944]. This clause details more precisely the routing of broadcast and multicast packets. + +As described in clause 11.1 of [IETF RFC 4944], each broadcast packet has a BC0 header containing a sequence number. Each time a node sends a broadcast packet, it shall increment this sequence number. + +Each node shall have a broadcast log table. This table is used for routing broadcast packets and each entry contains the parameters described in Table 9-32. + +Each time a device receives a broadcast address with a HopsLft field of a mesh header (see clause 5.2 of [IETF RFC 4944]) strictly greater than 0, it shall check if an entry already exists in the broadcast log table having the same SrcAddr and SeqNumber. If an entry exists, the received frame is silently discarded. Otherwise, a new entry is added in the table and the TimeToLive field is initialized with the value adpBroadcastLogTableEntryTTL (see Table 9-28). When this value reaches 0, the entry is removed from the broadcast log table. + +When a device receives a broadcast frame, so that it has to create an entry in the broadcast log table, it shall decrement its HopsLft field. If HopsLft is not zero, it triggers the transmission of the received broadcast frame. + +This can be summarized by the following algorithm, executed upon receipt of a frame whose destination address is 0xFFFF (see also Figure 9-14 for the corresponding flow-chart): + +IF (final destination address = broadcast address) or (final destination address is found in adpGroupTable) + +IF ((SrcAddr, SeqNumber) exists in broadcast log table) or (SrcAddr = macShortAddr obtained from the MAC PIB) + +Discard frame + +ELSE + +- Create one entry (SrcAddr, SeqNumber, adpBroadcastLogTableEntryTTL) in the broadcast log table, with the corresponding frame characteristics. +- Generate an ADPD-DATA.indication primitive to the upper layer with the following characteristics: + - DstAddrMode = 0x02 + - DstAddr = destination address in the 6LoWPAN mesh header (multicast or broadcast address) + - SrcAddr = the originator address in the 6LoWPAN mesh header + - NsduLength = the length of the data + - Nsdu = the data + - LinkQualityIndicator = msduLinkQuality (see clause 9.3.11.2) + - SecurityEnabled = (SecurityLevel != 0) +- $HopsLft = HopsLft - 1$ +- If ( $HopsLft > 0$ ), trigger the frame transmission. + +![Flowchart of broadcast frame routing processing. The process starts with an oval 'Destination Address = 0xFFFF'. An arrow leads to a diamond 'If (final destination address = broadcast address) or (final destination address is found in adpGroupTable)'. A 'YES' arrow leads to another diamond 'If (SrcAddr, SeqNumber) exists in broadcast table or ScrAddr=macShortAddr'. From this second diamond, a 'YES' arrow leads to a box 'Discard frame', and a 'NO' arrow leads down to a box '(1)'.](536768a30136cd5c2d57f46c25d1d804_img.jpg) + +``` + +graph TD + Start([Destination Address = 0xFFFF]) --> D1{If (final destination address = broadcast address) or (final destination address is found in adpGroupTable)} + D1 -- YES --> D2{If (SrcAddr, SeqNumber) exists in broadcast table or ScrAddr=macShortAddr} + D2 -- YES --> Discard[Discard frame] + D2 -- NO --> Box1["(1)"] + +``` + +Flowchart of broadcast frame routing processing. The process starts with an oval 'Destination Address = 0xFFFF'. An arrow leads to a diamond 'If (final destination address = broadcast address) or (final destination address is found in adpGroupTable)'. A 'YES' arrow leads to another diamond 'If (SrcAddr, SeqNumber) exists in broadcast table or ScrAddr=macShortAddr'. From this second diamond, a 'YES' arrow leads to a box 'Discard frame', and a 'NO' arrow leads down to a box '(1)'. + +G.9903(17)\_F9-14 + +**Figure 9-14 – Broadcast frame routing processing** + +NOTE – In case of a multicast address, the broadcast address 0xFFFF is used at the MAC level as mentioned in clause 3 of [IETF RFC 4944]. Multicast frames are routed using the same algorithm as broadcast frames. + +The broadcast log table is available in the information base with the attribute adpBroadcastLogTable (see Tables 9-28 and 9-32). + +###### **9.4.3.2.2.2 Groups** + +Each device can belong to one or more groups of devices. The IB attribute adpGroupTable (see Table 9-28) stores a list of 16-bit group addresses. + +When the device receives a MAC broadcast message and if the final destination address in the 6LoWPAN mesh header is equal to one of the 16-bit group addresses in adpGroupTable, then an ADPD-DATA.indication primitive is generated to the upper layer (as described in clause 9.4.3.2.2.1). + +Groups can be added or removed from the adpGroupTable using the ADPM-SET.request primitive. The size of this table is implementation specific and shall have at least one entry. The way groups are managed by upper layers is beyond the scope of this document. + +##### **9.4.3.2.3 Route discovery** + +###### **9.4.3.2.3.1 Manual route discovery** + +A manual route discovery can be triggered by the upper layer, for maintenance or performance purposes. This is done through the invocation of the ADPM-ROUTE-DISCOVERY.request primitive. The adaptation sublayer then generates an RREQ frame and executes the algorithms as described in clause 9.4.3.1. + +After the algorithm is completed, the adaptation sublayer generates an ADPM-ROUTE-DISCOVERY.confirm primitive with the corresponding status code and eventually modifies its routing table. + +Only one route discovery procedure can be processed at the same time. Any other ADPM-ROUTE-DISCOVERY.request will be ignored. + +All devices shall support the LOADng protocol and modify their routing tables accordingly. + +###### **9.4.3.2.3.2 Automatic route discovery** + +If an ADPD.DATA.request primitive is invoked with its DiscoverRoute parameter set to TRUE, and if no entry is available in the routing table for the device designated by DstAddr, then the adaptation layer generates an RREQ and executes the algorithms described in clause 9.4.3.1 in order to find a route to the destination. If the route discovery succeeds, then the data frame is sent to the destination according to the newly discovered route. If the route discovery fails, then the adaptation layer shall generate an ADPD-DATA.confirm primitive with the status code ROUTE\_ERROR. + +If an ADPD.DATA.request primitive is invoked with its DiscoverRoute parameter set to FALSE, and if no entry is available in the routing table for the device designated by DstAddr, then the adaptation layer shall generate an ADPD-DATA.confirm primitive with the status code ROUTE\_ERROR. + +Route repairing procedures are described in clause 9.4.3.2.5. + +###### **9.4.3.2.3.3 Route Request generation frequency limit** + +A node shall wait adpRREQWait seconds between two successive RREQ generations to limit the number of broadcast packets in the network. The definition of the adpRREQWait attribute is given in clause 9.4.1.1. + +##### **9.4.3.2.4 Path discovery** + +###### **9.4.3.2.4.1 Operation** + +A path discovery can be triggered by the upper layers, for maintenance or performance purposes. This is done through the invocation of the ADPM-PATH-DISCOVERY.request primitive. + +The adaptation sublayer then generates a path request frame (PREQ) and executes the algorithms described in the following sub-clauses. + +After the algorithm is completed (upon receipt of the path reply frame (PREP) with an expected originator corresponding to the path discovery destination (DstAddr) or after adpPathDiscoveryTime elapsed after PREQ transmission), the adaptation sublayer generates an ADPM-PATH-DISCOVERY.confirm primitive to the upper layer. + +A path reply frame received adpPathDiscoveryTime seconds after its PREQ frame has been transmitted shall be ignored. + +DstAddr (destination field in the PREQ frame and expected originator field in the PREP frame) is used as the identifier of the path discovery, so that only one path discovery procedure can be processed for the same destination at the same time. A second call to path discovery for the same destination when the first one is still in progress shall result in a ALREADY\_IN\_PROGRESS status. A PREQ frame is sent along the forward path while carrying an updated hop-by-hop link Cost information associated with the metric type field is given by ADPM-PATH-DISCOVERY.request. Similarly, a PREP frame is sent along the reverse path while carrying updated hop-by-hop link cost information. Note that the metric type field (PathMetricType) given by ADPM-PATH-DISCOVERY.request shares the same identifiers and computation procedures with the adpMetricType attribute. However, they may be different (i.e., path discovery can collect a metric different from the one used for routing). + +During a path discovery, link repair, route error and routing table updates shall not be allowed. + +###### **Generating a path request (PREQ)** + +The node that generates the PREQ message (see clause 9.4.3.2.7.4) shall: + +Set the destination address of the node towards where the PREQ message will be propagated, as directed by the upper layers. + +Set its own address as the originator address. + +Set the metric type (as directed by the upper layers) designating the link cost to report in path discovery messages. + +Then, the actions described in transmitting a PREQ shall apply. + +###### **Processing a path request (PREQ)** + +On receiving a path request (PREQ), the i-th node on the forward path shall (see clause 9.4.3.2.7.4): + +Append its 16-bit address to the Hop-i forward path field. + +Append the link cost designated by the PathMetricType and updated with the incoming frame to the Hop-i forward path link cost field. If the metric is not supported by the node, then the "Metric Not Supported" (MNS) field is set to 1 and its link cost field is set to 0. + +If the PREQ destination address is the address of the node that received the PREQ message or an address stored in its destination address set, then the PREQ is not forwarded and the PREP generation applies. + +Otherwise, the actions described in transmitting a PREQ shall apply. + +###### **Transmitting a path request (PREQ)** + +If the PREQ destination address is found in the routing table, then the PREQ message is forwarded to the next hop towards destination (see clause 9.4.3.2.1). Yet, route repair procedure is not used. + +If the PREQ destination address is not found in the routing table or if the PREQ transmission fails, then PREP generation applies. + +###### Generating a path reply (PREP) + +The node that generates the PREP message (see clause 9.4.3.2.7.5) shall: + +Set the PREQ originator address as the destination address. + +Set the PREQ destination address as the expected originator address. + +Set the originator to its own address or the PREQ destination when it is in the destination address set. + +Append the PathMetricType, the MNS and the reserved bits, the forward path addresses and their associated link cost as conveyed by the PREQ message. + +Then, the actions described in transmitting a PREP shall apply. + +###### Processing a path reply (PREP) + +On receiving a path reply (PREP), the j-th node on the reverse path shall (see clause 9.4.3.2.7.5): + +Append its 16-bit address to Hop-j reverse path field. + +Append the link cost designated by the PathMetricType and updated with the incoming frame to Hop-j forward path link cost field. If the metric is not supported by the node, then the "Metric Not Supported" (MNS) field is set to 1 and its link cost field is set to 0. + +If the PREP destination address is the address of the node receiving the PREP, then an ADPM-PATH-DISCOVERY.confirm (see clause 9.4.6.2.21) is sent to the upper layer with the PathAddress field containing a table of addresses of the nodes constituting the path (or part of the path) and their associated forward and reverse link costs. + +Otherwise, the actions described in transmitting a PREQ shall apply. + +###### Transmitting a path reply (PREP) + +If the PREP destination address is found in the routing table, then the node just forwards the PREP message to the next hop towards destination (see clause 9.4.3.2.1). Yet, route repair procedure is not used. + +If the PREP destination address is not found in the routing table or if the PREP transmission fails, then the node discards the PREP. + +##### 9.4.3.2.5 Route repair and route error + +A route repair is performed in two cases: + +- when an intermediate node receives a packet for a destination address which is not present in the routing table, +- when a transmission is assumed unsuccessful (MCPS-DATA.confirm status equals to TRANSACTION\_EXPIRED or NO\_ACK). + +The data packet pending is buffered during the route repair procedure. + +For a route repair, the node follows the route discovery procedure (see clause 9.4.3) with the following characteristics: + +- RREQ is generated with the originator address set to its own address and the destination address set to the data packet's final destination address +- Hop Limit field is set to + - adpMaxHops, in case the route repair is triggered by the originator of the data frame following an unsuccessful transmission; + - (HopLeft – 1), in case the route repair is triggered by an intermediate node with HopLeft value taken from the data frame that triggers the route repair procedure + +- Route repair flag in the RREQ message is set to '1' +- RREP messages generated in response to these RREQ messages, have their repair flag set to '1' + +If the route discovery is successful, the node updates its routing table and shall transmit the buffered data packet to the destination through the new route. + +If the packet transmission fails again due to a link break, then the route repair is considered failed and shall not be performed again. + +If the route repair procedure fails at an intermediate node, then this node sends an RERR to the originator and the buffered data packet is discarded. + +The RERR message carries an error code that indicates the reason of the repair failure. The error codes are defined in Table 9-38. RERR generation shall comply with clause 9.4.3.2.3.3. + +**Table 9-38 – Routing error codes** + +| Code | Description | +|------------|---------------------------------------------| +| 0 | No available route | +| 1 to 251 | ITU-T reserved | +| 252 to 255 | Unassigned: reserved for experimental usage | + +##### 9.4.3.2.6 Link cost computation + +Both forward and reverse link costs may be used for route cost computation as defined in Annex B. While the forward link cost can be computed from the received RREQ, the reverse link cost can be obtained by the following methods: + +- 1) Using the neighbour table: + +If the previous hop information is in the neighbour table and is still valid, it can be used to compute reverse link cost. + +- 2) Using RLCREQ (reverse link cost request) and RLCREP (reverse link cost reply): + +If adpRLCEnabled is set to TRUE, a unicast RLCREQ may be sent to the previous hop to request the reverse link cost. Upon receipt of the RLCREQ, the previous hop shall compute the reverse link cost and reply with RLCREP such as RLCREP.link-cost = reverse link cost. + +A LOADng router shall wait at least adpRREQWait seconds between two consecutive RLCREQ messages. + +##### 9.4.3.2.7 Routing packet and message formats + +The packet and message formats which are described in this clause shall be used for the implementation of LOADng (see Annex D). + +###### 9.4.3.2.7.1 General packet format + +Generation, forwarding and processing of the packet shall follow the LOADng protocol. Some of the routing packets are expected to have their content changed for each hop. Accordingly 6loWPAN mesh header and broadcast header shall not be used: + +- when RREQ messages are broadcasted, RREQ messages are sent to the MAC layer broadcast address without a 6loWPAN broadcast header. +- All routing messages are sent without 6loWPAN mesh header. + +The general format for all packets, generated, forwarded and processed according to Annex D, is given in Figure 9-15 and Table 9-39. + +![Figure 9-15 – General routing message format diagram showing a 32-bit word structure. The first byte (bits 0-7) is labeled 'Type'. The remaining 31 bits (bits 8-31) are labeled 'Message'.](e47d450f315d0b633906c03cc91f90ef_img.jpg) + +Figure 9-15 – General routing message format diagram showing a 32-bit word structure. The first byte (bits 0-7) is labeled 'Type'. The remaining 31 bits (bits 8-31) are labeled 'Message'. + +**Figure 9-15 – General routing message format** + +**Table 9-39 – Packet field descriptions** + +| Field | Length | Description | +|---------|----------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Type | 8 bits | Specifies the type of the message
0 for RREQ messages
1 for RREP messages
2 for RERR messages
252 for PREQ messages
253 for PREP messages
254 for RLCREQ messages
255 for RLCREP messages | +| Message | Variable | The field is described in clause 9.4.3.2.7.2 for RREQ and RREP messages, in clause 9.4.3.2.7.3 for RERR messages, in clause 9.4.3.2.7.4 for PREQ messages, in clause 9.4.3.2.7.5 for PREP messages, in clause 9.4.3.2.7.6 for RLCREQ messages and in clause 9.4.3.2.7.7 for RLCREP. | + +###### **9.4.3.2.7.2 Route request (RREQ) and route reply (RREP) message format** + +The RREQ and RREP messages are identified with the type field equal to 0 and 1 respectively. The RREQ and RREP formats are given in Figure 9-16 and Table 9-40, and are generated, forwarded and processed according to Annex D. + +![Figure 9-16 – RREQ and RREP message format diagram showing a 32-bit word structure. The first 16 bits (bytes 0-1) are 'Destination'. The next 16 bits (bytes 2-3) are split into 'Sequence-Number' (bits 0-15), 'Flags' (bits 16-23), 'Metric type' (bits 24-31), and 'Route-cost' (bits 32-47). The next 16 bits (bytes 4-5) are split into 'Hop limit' (bits 0-7), 'Hop Count' (bits 8-15), 'Weak link' (bits 16-23), and 'Reserved' (bits 24-31).](ca9fd3bd2fe73a46244dd1d017ffa3b5_img.jpg) + +Figure 9-16 – RREQ and RREP message format diagram showing a 32-bit word structure. The first 16 bits (bytes 0-1) are 'Destination'. The next 16 bits (bytes 2-3) are split into 'Sequence-Number' (bits 0-15), 'Flags' (bits 16-23), 'Metric type' (bits 24-31), and 'Route-cost' (bits 32-47). The next 16 bits (bytes 4-5) are split into 'Hop limit' (bits 0-7), 'Hop Count' (bits 8-15), 'Weak link' (bits 16-23), and 'Reserved' (bits 24-31). + +**Figure 9-16 – RREQ and RREP message format** + +**Table 9-40 – Route request (RREQ) and route reply (RREP) message field descriptions** + +| Field | Length | Description | +|-------------|---------|-------------------------------------| +| Destination | 16 bits | Destination address of RREQ or RREP | +| Originator | 16 bits | Originator address of RREQ or RREP | + +**Table 9-40 – Route request (RREQ) and route reply (RREP) message field descriptions** + +| Field | Length | Description | +|-------------------|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Sequence-Number | 16 bits | Refers to RREQ.seq-num or RREP.seq-num (see Annex D). | +| Flags | 4 bits | Specifies the interpretation of the remainder message:
For RREQ messages:
bit 0 (route repair): when set ('1'), the RREQ message is triggered for a route repair procedure as described in clause 9.4.3.2.5.
bit 1 (unicast RREQ): when set ('1'), the RREQ message is sent in unicast along an already installed route towards RREQ.destination if such a valid route exists in the routing set. Otherwise, it is broadcasted.
bits 2 to 3 (reserved by ITU-T): shall be set to zero.
For RREP messages:
bit 0 (route repair): when set ('1'), the RREP message is triggered for a route repair procedure as described in clause 9.4.3.2.5.
bits 1 to 3 (reserved by ITU-T): shall be set to zero.
Endianess:
bit 0 is the most significant bit (MSB) of the field, and bit 3 is the least significant bit (LSB). | +| Metric Type | 4 bits | Metric type used for routing and shall be set to adpMetricType (see Table 9-28). | +| Route Cost | 16 bits | Cumulative link cost along the route towards the destination. Refers to RREQ.route-metric or RREP.route-metric. | +| Hop Limit | 4 bits | Maximum number of hops of the route. Refers to RREQ.hop-limit or RREP.hop-limit. | +| Hop Count | 4 bits | Number of hops of the route. Refers to RREQ.hop-count or RREP.hop-count. | +| Weak Link Count | 4 bits | Total number of weak links which the message has traversed from RREQ.originator or RREP.originator. | +| Reserved by ITU-T | 4 bits | Shall be set to zero. | + +###### **9.4.3.2.7.3 Route error (RERR) message format** + +The RERR message is identified with the type field equal to 2. The RERR format is given in Figure 9-17 and Table 9-41, and is generated, forwarded and processed according to Annex D. + +![Diagram of RERR message format showing fields: Destination, Originator, Error Code, Unreachable-Address, Hop limit, and Reserved, with bit positions 0-15 indicated above.](8942c590307508b28df9c207bad75740_img.jpg) + +The diagram illustrates the RERR message format. It is a 16-bit structure divided into several fields. Above the diagram, the numbers 0, 1, 2, and 3 are placed at the top, corresponding to the first four nibbles (4 bits) of the message. Below these, the numbers 0 through 1 are repeated for each of the four nibbles, indicating the bit positions (0-15) from left to right. The message is structured as follows: + +- Destination:** Bits 0-7 (first nibble 0, second nibble 1). +- Originator:** Bits 8-15 (third nibble 2, fourth nibble 3). +- Error Code:** Bits 0-3 (first nibble 0). +- Unreachable-Address:** Bits 4-11 (second nibble 1, third nibble 2). +- Hop limit:** Bits 12-13 (third nibble 2). +- Reserved:** Bits 14-15 (fourth nibble 3). + +Diagram of RERR message format showing fields: Destination, Originator, Error Code, Unreachable-Address, Hop limit, and Reserved, with bit positions 0-15 indicated above. + +**Figure 9-17 – RERR message format** + +**Table 9-41 – Route error (RERR) message field descriptions** + +| Field | Length | Definition | +|---------------------|---------|-------------------------------------------------| +| Destination | 16 bits | Destination address of RERR packet | +| Originator | 16 bits | Originator address of RERR packet | +| ErrorCode | 8 bits | Error code definition is given in Table 9-38 | +| Unreachable-Address | 16 bits | Refers to RERR.unreachableAddress (see Annex D) | +| Hop Limit | 4 bits | Refers to RERR.hop-limit (see Annex D). | +| Reserved by ITU-T | 4 bits | Shall be set to zero. | + +###### **9.4.3.2.7.4 Path request (PREQ) message format** + +The PREQ message is identified with the type field equal to 252. It is generated, forwarded and processed according to clause 9.4.3.2.4. The PREQ message format is shown in Figure 9-18 and its field definitions are given in Table 9-42. + +![Diagram of PREQ message format showing bit positions 0 to 3 and field layout including Destination, Originator, PathMetricType, Reserved, Hop-1 Forward Path Address, Hop-1 Forward Path MNS, Hop-1 Forward Path Link Cost, and Hop-N Forward Path Address.](90321ffa3cade82e4a57d6250d046c88_img.jpg) + +The diagram illustrates the PREQ message format across four 32-bit words (0, 1, 2, 3). Each word is 32 bits long, with bit positions 0 through 31 indicated at the top. The layout is as follows: + +- Word 0:** Bits 0-15 are Destination; bits 16-31 are Originator. +- Word 1:** Bits 0-3 are PathMetricType; bits 4-31 are Reserved. +- Word 2:** Bits 0-15 are Hop-1 Forward Path Address; bits 16-17 are Hop-1 Forward Path MNS (M, N, S); bits 18-23 are Reserved; bits 24-31 are Hop-1 Forward Path Link Cost. +- Word 3:** Bits 0-15 are Hop-N Forward Path Address; bits 16-17 are Hop-N Forward Path MNS (M, N, S); bits 18-23 are Reserved; bits 24-31 are Hop-N Forward Path Link Cost. + +Diagram of PREQ message format showing bit positions 0 to 3 and field layout including Destination, Originator, PathMetricType, Reserved, Hop-1 Forward Path Address, Hop-1 Forward Path MNS, Hop-1 Forward Path Link Cost, and Hop-N Forward Path Address. + +**Figure 9-18 – PREQ message format** + +**Table 9-42 – Path request (PREQ) message field descriptions** + +| Field | Length | Description | +|------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Destination | 16 bits | Destination address of the PREQ packet | +| Originator | 16 bits | Originator address of the PREQ packet | +| PathMetricType | 4 bits | Metric type to be used for reporting the link cost | +| Reserved by ITU-T | 28 bits | Shall be set to 0 | +| Hop-1 Forward Path Address | 16 bits | 16-bit address of the first node on the forward path | +| Hop-1 Forward Path MNS | 1 bit | Metric not supported field by the first node on the forward path
0 : The metric is supported by the node
1 : The metric is not supported by the node | +| Reserved by ITU-T | 7 bits | Shall be set to 0 | +| Hop-1 Forward Path Link Cost | 8 bits | Link cost of the first node on the forward path | + +**Table 9-42 – Path request (PREQ) message field descriptions** + +| Field | Length | Description | +|------------------------------|---------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Hop-N Forward Path Address | 16 bits | 16-bit address of the last node on the forward path | +| Hop-N Forward Path MNS | 1 bit | Metric not supported field by the last node on the forward path
0 : The metric is supported by the node
1 : The metric is not supported by the node | +| Reserved by ITU-T | 7 bits | Shall be set to 0 | +| Hop-N Forward Path Link Cost | 8 bits | Link cost of the last node on the forward path | + +###### **9.4.3.2.7.5 Path reply (PREP) message format** + +The PREP message is identified with the type field equal to 253. It is generated, forwarded and processed according to clause 9.4.3.2.4. The PREP message format is shown in Figure 9-19 and its field definitions are given in Table 9-43. The greyed-out cells in Figure 9-19 and Table 9-43 contain the forward path fields taken from the PREQ message which remain unchanged in the PREP message. + +![Figure 9-19 – PREP message format diagram showing a 32-bit word structure with Destination, Expected Originator, and Originator sections, including fields like PathMetricType, Reserved, Hop-1 Forward Path Address, Hop-N Forward Path Address, Hop-1 Reverse Path Address, and Hop-N Reverse Path Address with associated MNS and Link Cost fields.](a612e74e004b3bc8e33ead4a5e857ed9_img.jpg) + +The diagram illustrates the PREP message format across four 32-bit words (0, 1, 2, 3). Each word is divided into 32 bits (0-31). + +- Word 0:** Bits 0-15 are Destination; bits 16-31 are Expected Originator. +- Word 1:** Bits 0-15 are PathMetricType (1 bit) and Reserved (15 bits); bits 16-31 are Originator. +- Word 2:** Bits 0-15 are Hop-1 Forward Path Address; bits 16-17 are MNS; bits 18-31 are Reserved. +- Word 3:** Bits 0-15 are Hop-N Forward Path Address; bits 16-17 are MNS; bits 18-31 are Reserved. +- Word 4:** Bits 0-15 are Hop-1 Reverse Path Address; bits 16-17 are MNS; bits 18-31 are Reserved. +- Word 5:** Bits 0-15 are Hop-N Reverse Path Address; bits 16-17 are MNS; bits 18-31 are Reserved. +- Word 6:** Bits 0-15 are Hop-1 Reverse Path Address; bits 16-17 are MNS; bits 18-31 are Reserved. +- Word 7:** Bits 0-15 are Hop-1 Reverse Path Address; bits 16-17 are MNS; bits 18-31 are Reserved. + +Greyed-out cells in the original figure correspond to the forward path fields in Words 2, 3, and 4. + +Figure 9-19 – PREP message format diagram showing a 32-bit word structure with Destination, Expected Originator, and Originator sections, including fields like PathMetricType, Reserved, Hop-1 Forward Path Address, Hop-N Forward Path Address, Hop-1 Reverse Path Address, and Hop-N Reverse Path Address with associated MNS and Link Cost fields. + +**Figure 9-19 – PREP message format** + +**Table 9-43 – Path reply (PREP) message field description** + +| Field | Length | Description | +|------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Destination | 16 bits | Destination address of the PREP packet | +| Expected Originator | 16 bits | Destination address of the PREQ packet (and expected originator of the PREP packet). | +| PathMetricType | 4 bits | Metric type to be used for reporting the link cost | +| Reserved by ITU-T | 12bits | Shall be set to 0 | +| Originator | 16 bits | Originator address of the PREP packet. | +| Hop-1 Forward Path Address | 16 bits | 16-bit address of the first node on the forward path | +| Hop-1 Forward Path MNS | 1 bit | Metric not supported by the first node on the forward path
0 : The metric is supported by the node
1 : The metric is not supported by the node | +| Reserved by ITU-T | 7 bits | Shall be set to 0 | +| Hop-1 Forward Path Link Cost | 8 bits | Link cost of the first node on the forward path | +| ... | ... | ... | +| Hop-1 Reverse Path Address | 16 bits | 16-bit address of the first node on the reverse path | +| Hop-1 Reverse Path MNS | 1 bit | Metric not supported field by the first node on the reverse path
0 : The metric is supported by the node
1 : The metric is not supported by the node | +| Reserved by ITU-T | 7 bits | Shall be set to 0 | +| Hop-1 Reverse Path Link Cost | 8 bits | Link cost of the first node on the reverse path | +| ... | ... | ... | +| Hop-M Reverse Path Address | 16 bits | 16-bit address of the last node on the reverse path | +| Hop-M Reverse Path MNS | 1 bit | Metric not supported by the last node on the reverse path
0 : The metric is supported by the node
1 : The metric is not supported by the node | +| Reserved by ITU-T | 7 bits | Shall be set to 0 | +| Hop-M Reverse Path Link Cost | 8 bits | Link cost of the last node on the reverse path | + +NOTE – The greyed-out cells contain the forward path fields taken from the PREQ message which remain unchanged in the PREP message. + +###### 9.4.3.2.7.6 RLCREQ message format + +The RLCREQ message is identified with the type field equal to 254. It is generated and processed according to clause 9.4.3.2.6. The RLCREQ message format is shown in Figure 9-20 and its field definitions are given in Table 9-44. + +![](e492fe1061d82aa76cbf7114f57eb90c_img.jpg) + +0 1 2 3 + +0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|-------------|--|--|--|--|--|--|--|----------|--|--|--|--|--|--|--|------------|--|--|--|--|--|--|--|--|--|--|--|--|--|--|--| +| Destination | | | | | | | | | | | | | | | | Originator | | | | | | | | | | | | | | | | +| Metric type | | | | | | | | Reserved | | | | | | | | | | | | | | | | | | | | | | | | + +**Figure 9-20 – RLCREQ message format** + +**Table 9-44 – RLCREQ message field descriptions** + +| Field | Length | Description | +|-------------------|---------|----------------------------------------------------------------------------------| +| Destination | 16 bits | Destination address of the RLCREQ packet | +| Originator | 16 bits | Originator address of the RLCREQ packet | +| Metric-type | 4 bits | Metric type used for routing and shall be set to adpMetricType (see Table 9-28). | +| Reserved by ITU-T | 4 bits | Shall be set to 0. | + +###### 9.4.3.2.7.7 RLCREP message format + +The RLCREP message is identified with the type field equal to 255. It is generated and processed according to clause 9.4.3.2.6. The RLCREP message format is shown in Figure 9-21 and its field definitions are given in Table 9-45. + +![](4d45c2b40c053dd2b36d2c1f9271728e_img.jpg) + +0 1 2 3 + +0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +|-------------|--|--|--|--|--|--|--|----------|--|--|--|--|--|--|--|------------|--|--|--|--|--|--|--|--|--|--|--|--|--|--|--| +| Destination | | | | | | | | | | | | | | | | Originator | | | | | | | | | | | | | | | | +| Metric type | | | | | | | | Reserved | | | | | | | | Link Cost | | | | | | | | | | | | | | | | + +**Figure 9-21 – RLCREP message format** + +**Table 9-45 – RLCREP message field descriptions** + +| Field | Length | Description | +|-------------------|---------|----------------------------------------------------------------------------------| +| Destination | 16 bits | Destination address of the RLCREP packet | +| Originator | 16 bits | Originator address of the RLCREP packet | +| Metric type | 4 bits | Metric type used for routing and shall be set to adpMetricType (see Table 9-28). | +| Reserved by ITU-T | 4 bits | Shall be set to 0. | +| Link cost | 8 bits | Link cost from the destination to the originator of the RLCREP packet. | + +### 9.4.4 Commissioning of new devices + +#### 9.4.4.1 Selections from Annex E + +The commissioning of new devices on an existing network described in Annex E applies, with the selections specified in Table 9-46. + +**Table 9-46 – Selections from Annex E** + +| Clause | Title and remarks/modifications | Statement | +|-----------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| E.1 | Introduction | N | +| E.2 | Terminology | N | +| E.2.1 | Requirements notation | N | +| E.3 | Bootstrapping
– Obtaining a 16-bit short address and security credentials are mandatory parts of the commissioning process. | S | +| E.3.1 | Resetting the device | N | +| E.3.2 | Scanning through channels
– For getting the information of other devices within POS, the device shall perform an active scan. | S | +| E.3.3 | LoWPAN bootstrapping mechanism
– 'LBA discovery phase' is described in clause 9.4.4.2.2. | E | +| E.3.3.1 | LoWPAN bootstrapping protocol message format | N | +| E.3.3.1.1 | LBP message
– Some enhancements and clarifications to the LBP message format are given in clause 9.4.4.2.1. | E | +| E.3.3.2 | LoWPAN bootstrapping information base
The "Short_Addr" attribute is sent during bootstrapping and stored in the macShortAddress attribute in MAC PIB
The following parameters are not sent, but set locally
– PAN_ID corresponds to the macPanId attribute in MAC PIB
– Address_of_LBS corresponds to the adpCoordShortAddress attribute in ADP IB
The other parameters listed are not supported.
Additional parameters are defined in clause 9.4.4.2.1.3. | S, E | +| E.3.3.3 | LBA discovering phase
– Some enhancements and clarifications to 6LoWPAN bootstrapping procedure are given in clause 9.4.4.2.2.
– The LBD shall perform an active scan instead of broadcasting an LBA solicitation message. | E | +| E.3.3.4 | LoWPAN bootstrapping protocol (LBP) | S | +| E.3.3.5 | LBP in secured 6LoWPAN
LBP messages exchanged between the LBD and LBA (the LBS takes the LBA role if no relaying is needed) are sent with the following content:
– MAC layer:
– The LBD uses its EUI-64 address
– The LBA uses its 16-bit short address. The choice of the LBA is controlled by ADPM-NETWORK-JOIN.request LBAAddress parameter
– Destination and source PAN ID = The PAN ID passed as an | S | + +**Table 9-46 – Selections from Annex E** + +| Clause | Title and remarks/modifications | Statement | +|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| | argument to the ADPM-NETWORK-JOIN.request primitive
  • – Quality of service = normal priority
  • – SecurityLevel = no security
  • – The adaptation layer only contains the LBP message, no other header is allowed.
LBP messages exchanged between the LBA and LBS are relayed by using the routing algorithm as described in clause 9.4.4 with the DiscoverRoute parameter set to TRUE and the SecurityLevel set to a adpSecurityLevel. | | +| E.3.3.6 | Role of entities in LBP
  • – If an LBD does not find any LBA during the LBA discovery phase, it shall still perform LBA discoveries as long as it is not commissioned. Note that LBA discovery is done using active scans rather than broadcasting LBA solicitation messages.
  • – Only secured networks are used.
  • – Blacklisting by the LBA is not supported.
| S | +| E.3.4 | Assigning the short address
Short addresses are assigned in a centralized fashion by the LBS. | S | +| E.3.5 | Obtaining IPv6 address
Obtaining a non-link-local IPv6 address is out of the scope of this Recommendation. | N/R | +| E.3.6 | Configuration parameters
  • – The values of the configuration parameters shall be:
    CHANNEL_LIST = 0xFFFF800 (not used)
    SCAN_DURATION = ADPM-DISCOVERY.request duration parameter value (see clause 9.4.6.2.2)
    SUPERFRAME_ORDER = 15
    BEACON_ORDER = 15
    START_RETRY_TIME = 0 (not used)
    JOIN_RETRY_TIME = 0 (not used)
    ASSOCIATION_RETRY_TIME = 0 (not used)
| M | +| E.4 | IANA consideration | N/R | +| E.5 | Security considerations | N | + +#### 9.4.4.2 Extensions to Annex E + +##### 9.4.4.2.1 LoWPAN bootstrapping protocol (LBP) message format + +###### 9.4.4.2.1.1 General + +The LBP message format and the details of its related fields are described in Figure 9-22 and Table 9-47, respectively. + +![Figure 9-22 – LBP message format diagram showing a 16-bit header and variable-length data. The header is split into two 8-bit bytes. The first byte contains 'T' (bit 0) and 'Code' (bits 1-3). The second byte contains 'Transaction-id' (bits 0-5). Below the header is 'A_LBD' (8 bytes) and 'Bootstrapping data' (variable length).](845e014e3b8677eb735d0e21f21206be_img.jpg) + +G.9903(14)\_F9-22 + +Figure 9-22 – LBP message format diagram showing a 16-bit header and variable-length data. The header is split into two 8-bit bytes. The first byte contains 'T' (bit 0) and 'Code' (bits 1-3). The second byte contains 'Transaction-id' (bits 0-5). Below the header is 'A\_LBD' (8 bytes) and 'Bootstrapping data' (variable length). + +**Figure 9-22 – LBP message format** + +**Table 9-47 – LBP message format** + +| Field | Length | Description | +|--------------------|----------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| T | 1 bit | Identifies the type of message
0: Message from LBD
1: Message to LBD | +| Code | 3 bits | Identifies the message code defined in Table 9-48. | +| Transaction-id | 12 bits | Reserved by ITU-T, set to 0 by the sender and ignored by the receiver. | +| A_LBD | 8 bytes | Indicates the EUI-64 address of the bootstrapping device (LBD). | +| Bootstrapping Data | Variable | Contains additional information elements. Two types are defined:
Embedded EAP messages (see clause 9.4.4.2.1.2),
Configuration parameters (see clause 9.4.4.2.1.3). | + +**Table 9-48 – T and code fields in LBP message** + +| T | Code | LBD message | Description | +|-----|-------|-------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| 0 | 0b001 | JOINING | The LBD requests joining a PAN and provides the necessary authentication material | +| 1 | 0b001 | ACCEPTED | Authentication succeeded with the delivery of device specific information (DSI) to the LBD | +| 1 | 0b010 | CHALLENGE | Authentication in progress. PAN specific information (PSI) may be delivered to the LBD. | +| 1 | 0b011 | DECLINE | Authentication failed | +| 0/1 | 0b100 | KICK | KICK frame is used by a PAN coordinator to force a device to lose its MAC address, or by any device to inform the coordinator that it left the PAN.
On receipt of this frame, a device shall set its short address to the default value of 0xFFFF, disconnect itself from the network and perform a reset of the MAC and adaptation layers.
See clause 9.4.4.2.2.7 for details of the kicking procedure. | + +###### 9.4.4.2.1.2 Embedded EAP messages + +LBP messages embed extended authentication messages (EAP) as defined in [IETF RFC 3748]. Figure 9-23 describes a minor modification to fit the generic LBP information element format and Table 9-49, its related fields. + +![Diagram of Embedded EAP message format (generic). It shows a header with Code (6 bits), two 1-bit flags (0 and 0), and Identifier (8 bits). Below the header are Length (2 bytes) and Data (variable) fields. Bit positions 0-5 are shown for the first byte, and 0-5 for the second byte.](5ee80a63ec53c60d7306b5a44984afcf_img.jpg) + +G.9903(14)\_F9-23 + +Diagram of Embedded EAP message format (generic). It shows a header with Code (6 bits), two 1-bit flags (0 and 0), and Identifier (8 bits). Below the header are Length (2 bytes) and Data (variable) fields. Bit positions 0-5 are shown for the first byte, and 0-5 for the second byte. + +**Figure 9-23 – Embedded EAP message format (generic)** + +**Table 9-49 – Fields in embedded EAP message** + +| Field | Length | Description | +|------------|----------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Code | 6 bits | Identifies the type of EAP packet (6-bit). EAP codes are assigned as follows:
0b000001: Request (sent to the peer = LBD)
0b000010: Response (sent by the peer)
0b000011: Success (sent to the peer)
0b000100: Failure (sent to the peer)
The code field is slightly different from a regular EAP code field as specified in [IETF RFC 3748]. The conversion appears straightforward in both directions. The proper conversion shall apply when the EAP message is propagated over another protocol (i.e., RADIUS) and in case of integrity protection covering the EAP header. | +| Identifier | 8 bits | Aids in matching responses with requests | +| Length | 2 bytes | Indicates the length, in bytes, of the EAP packet including the code, identifier, length and data fields. A message with the length field set to a value larger than the number of received bytes shall be silently discarded. | +| Data | variable | The format of the data field is determined by the code field.
NOTE – Refer to [IETF RFC 3748] for more details on:
Specific format for request / response messages and the introduction of the type field (Identity, Nak, etc.)
Specific format for success / failure messages with an empty data field. | + +###### **9.4.4.2.1.3 Configuration parameters** + +The configuration parameter format and the detail of its related fields are described in Figure 9-24 and Table 9-50, respectively. Note that a single configuration message can consist of multiple concatenated configuration parameters. + +![Diagram of Configuration parameter format. It shows a header with Attr-ID (6 bits), M (1 bit), and Len (1 bit). Below the header is the Value field. Bit positions 0-5 are shown for the first byte, and 0-5 for the second byte.](78151e5dd542eada99ead8203dfce76b_img.jpg) + +Diagram of Configuration parameter format. It shows a header with Attr-ID (6 bits), M (1 bit), and Len (1 bit). Below the header is the Value field. Bit positions 0-5 are shown for the first byte, and 0-5 for the second byte. + +**Figure 9-24 – Configuration parameter format** + +**Table 9-50 – Fields in embedded EAP message** + +| Field | Length | Description | +|---------|---------------------------------|--------------------------------------------------------------------------------------------------------------------| +| Attr-ID | 6 bits | Represents the ID of the attribute in the LoWPAN information base (LIB) | +| M | 1 bit | Identifies the type of the attribute:
0: Device specific information (DSI)
1: PAN specific information (PSI) | +| Len | 8 bits | Indicates the length, in bytes, of the Value field | +| Value | variable (defined by Len field) | Contains the value of the attribute. Its format is defined by Attr-ID. | + +The following additional parameters are defined in Table 9-51. + +**Table 9-51 – Parameters for embedded EAP message** + +| Attribute | Attr_ID | Type | Attribute description | +|------------------|---------|------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| GMK | 9 | P | Provide a GMK key. Upon receipt, the key is installed in the provided key identifier slot.
Constituted of the following fields:
id (1 byte): the key identifier of the GMK
gmk (16 bytes): the value of the current GMK | +| GMK-activation | 10 | P | Indicate the GMK to use for outgoing messages
Constituted of the following field:
id (1 byte): the key identifier of the active GMK | +| GMK-removal | 11 | P | Indicates a GMK to delete
Constituted of the following field:
id (1 byte): the key identifier of the GMK to delete | +| Parameter-result | 12 | D | Indicate the result of the reception of parameters:
Constituted of the following fields:
result (1 byte): can take the following values:
– 0x00: Success
– 0x01: Missing required parameter
– 0x02: Invalid parameter value
– 0x03: Unknown parameter ID
Attr-ID+type (1 byte): indicates the parameter related to the result. Encoded as defined in Figure 9-24 first byte. If result = Success, Attr-ID = 0x00 and is ignored. | + +##### 9.4.4.2.2 6LoWPAN bootstrapping procedures + +###### 9.4.4.2.2.1 Overview + +This clause proposes some enhancements and clarifications to the 6LoWPAN bootstrapping procedure. This procedure is executed when the ADPM-NETWORK-JOIN.request primitive is invoked by the upper layer. + +Figure 9-25 provides an overview of the messages exchanged between devices during the bootstrapping procedure. + +![Sequence chart showing bootstrapping protocol messages between Other device, LBD, LBA, and LBS. The sequence starts with BeaconReq and Beacon messages, followed by a series of Joining, Challenge, and Accepted messages between LBD, LBA, and LBS.](c93353297f7ed04bc9173ac1f224d406_img.jpg) + +``` + +sequenceDiagram + participant Other device + participant LBD + participant LBA + participant LBS + + LBD->>Other device: BeaconReq + LBD->>LBA: BeaconReq + Other device->>LBD: Beacon(Pan2,LbaAddr2) + LBA->>LBD: Beacon(Pan1, LbaAddr1) + Other device->>LBD: Beacon(Pan3,LbaAddr3) + Other device->>LBD: Beacon(Pan4,LbaAddr4) + + LBD->>LBA: Joining () + LBA->>LBS: Joining () + LBS->>LBA: Challenge(EAPReq(mes1)) + LBA->>LBD: Challenge(EAPReq(mes1)) + + LBD->>LBA: Joining(EAPRes(mes2)) + LBA->>LBS: Joining(EAPRes(mes2)) + LBS->>LBA: Challenge(EAPReq(mes3)) + LBA->>LBD: Challenge(EAPReq(mes3)) + + LBD->>LBA: Joining(EAPRes(mes4)) + LBA->>LBS: Joining(EAPRes(mes4)) + LBS->>LBA: Accepted(EAPSuccess) + LBA->>LBD: Accepted(EAPSuccess) + +``` + +G.9903(14)\_F9-25 + +Sequence chart showing bootstrapping protocol messages between Other device, LBD, LBA, and LBS. The sequence starts with BeaconReq and Beacon messages, followed by a series of Joining, Challenge, and Accepted messages between LBD, LBA, and LBS. + +**Figure 9-25 – Bootstrapping protocol messages sequence chart** + +Figure 9-26 summarizes the forwarded messages involved during a nominal association procedure on a PAN between different protocol layers of the devices, when a single LBP protocol message needs to be exchanged between the LBD and the LBS. + +![Sequence chart showing bootstrapping protocol messages for forwarding. The diagram is divided into three main sections: LBD (Left), LBA (Middle), and LBS (Right). Each section contains lifelines for 'Upper layer', 'Adaptation sublayer', and 'MAC sublayer'. The sequence starts with ADPM-DISCOVERY.request from LBD Upper layer to LBD Adaptation sublayer, which calls MLME-SCAN.request (active) on the MAC sublayer. The MAC sublayer sends a Beacon request command to the LBA MAC sublayer, which responds with a Beacon. The LBD MAC sublayer receives MLME-BEACON-NOTIFY.indication and MLME-SCAN.confirm, then sends ADPM-DISCOVERY.confirm to the Upper layer. The LBD Upper layer 'Chooses an LBA' and sends ADPM-NETWORK-JOIN.request to the Adaptation sublayer. The Adaptation sublayer sends MCPS-DATA.request to the MAC sublayer, which sends MAC Data to the LBA MAC sublayer. The LBA MAC sublayer sends MCPS-DATA.indication to the Adaptation sublayer, which sends MCPS-DATA.request to the LBS MAC sublayer. The LBS MAC sublayer sends MAC Data to the LBS Adaptation sublayer, which sends ADPM-LBP.indication to the LBS Upper layer. The LBS Upper layer sends ADPM-LBP.request (to LBA) to the Adaptation sublayer, which sends MCPS-DATA.request to the MAC sublayer. The MAC sublayer sends MAC Data to the LBA MAC sublayer, which sends MCPS-DATA.indication to the Adaptation sublayer, which sends MCPS-DATA.request to the LBD MAC sublayer. The LBD MAC sublayer sends MAC Data to the LBD Adaptation sublayer, which sends MCPS-DATA.indication to the Upper layer. The Upper layer 'Processes LBP message' and sends ADPM-NETWORK-JOIN.confirm to the Adaptation sublayer. A dashed box labeled 'Other LBP messages flow' is shown at the bottom. Two message boxes are shown: 'LBP message 1' (MAC-Dst = LBA 16-bit address, MAC-Src = LBD 64-bit address, LBD 64-bit address in payload) and 'LBP message 2' (MAC-Dst = next hop to LBA, MAC-Src = LBS 16-bit address, ADP-Dst = LBA 16-bit address, ADP-Src = LBS 16-bit address, LBD 64-bit address in payload). The diagram is labeled G.9903(14)_F9-26.](8181865f1fd5e629dbe12ed89d22dc83_img.jpg) + +Sequence chart showing bootstrapping protocol messages for forwarding. The diagram is divided into three main sections: LBD (Left), LBA (Middle), and LBS (Right). Each section contains lifelines for 'Upper layer', 'Adaptation sublayer', and 'MAC sublayer'. The sequence starts with ADPM-DISCOVERY.request from LBD Upper layer to LBD Adaptation sublayer, which calls MLME-SCAN.request (active) on the MAC sublayer. The MAC sublayer sends a Beacon request command to the LBA MAC sublayer, which responds with a Beacon. The LBD MAC sublayer receives MLME-BEACON-NOTIFY.indication and MLME-SCAN.confirm, then sends ADPM-DISCOVERY.confirm to the Upper layer. The LBD Upper layer 'Chooses an LBA' and sends ADPM-NETWORK-JOIN.request to the Adaptation sublayer. The Adaptation sublayer sends MCPS-DATA.request to the MAC sublayer, which sends MAC Data to the LBA MAC sublayer. The LBA MAC sublayer sends MCPS-DATA.indication to the Adaptation sublayer, which sends MCPS-DATA.request to the LBS MAC sublayer. The LBS MAC sublayer sends MAC Data to the LBS Adaptation sublayer, which sends ADPM-LBP.indication to the LBS Upper layer. The LBS Upper layer sends ADPM-LBP.request (to LBA) to the Adaptation sublayer, which sends MCPS-DATA.request to the MAC sublayer. The MAC sublayer sends MAC Data to the LBA MAC sublayer, which sends MCPS-DATA.indication to the Adaptation sublayer, which sends MCPS-DATA.request to the LBD MAC sublayer. The LBD MAC sublayer sends MAC Data to the LBD Adaptation sublayer, which sends MCPS-DATA.indication to the Upper layer. The Upper layer 'Processes LBP message' and sends ADPM-NETWORK-JOIN.confirm to the Adaptation sublayer. A dashed box labeled 'Other LBP messages flow' is shown at the bottom. Two message boxes are shown: 'LBP message 1' (MAC-Dst = LBA 16-bit address, MAC-Src = LBD 64-bit address, LBD 64-bit address in payload) and 'LBP message 2' (MAC-Dst = next hop to LBA, MAC-Src = LBS 16-bit address, ADP-Dst = LBA 16-bit address, ADP-Src = LBS 16-bit address, LBD 64-bit address in payload). The diagram is labeled G.9903(14)\_F9-26. + +**Figure 9-26 – Bootstrapping protocol messages forwarding sequence chart** + +###### 9.4.4.2.2.2 Discovering phase + +At the beginning of the bootstrapping procedure, an end device (also known as LoWPAN bootstrapping device or LBD) shall launch an "active channel scan" (see Table 9-19). + +The higher layer can start an active scan by invoking the ADPM-DISCOVERY.request primitive, and by specifying the duration of the scan. It is recommended that the Duration parameter is greater than macBeaconRandomizationWindowLength. The adaptation layer then invokes the MLME-SCAN.request primitive of the MAC layer with the following parameters: + +- ScanType = 0x01 +- ScanChannels = all bits to 0 (not used) +- ScanDuration = ADPM-DISCOVERY.request duration parameter value +- ChannelPage = 0 (not used) +- SecurityLevel = 0 +- KeyIdMode = Ignored +- KeySource = Ignored +- KeyIndex = Ignored. + +The LBD sends a 1-hop broadcast Beacon.request frame and any full feature device in the neighbourhood shall reply by sending a beacon frame with its PAN identifier, short address and capabilities, as defined in Table 9-19. + +Upon receiving each beacon frame, the MAC layer in the LBD issues an MLME-BEACON-NOTIFY.indication primitive with the PANDescriptor parameters corresponding to the beacon. At the end of scan duration, the adaptation layer generates an ADPM-DISCOVERY.confirm primitive which contains the PANDescriptorList. + +The choice of the LBA to be used for joining the network is implementation-specific but can be based on the following criteria: + +- minimum value of route cost to coordinator +- maximum value of beacon link quality +- short address, according to a round robin algorithm. + +After finishing the scan procedure, the device can join the network following the procedure described in clause 9.4.4.2.2.6. + +###### 9.4.4.2.2.3 Access control phase + +Once the discovery phase is finished, the LBD send an LBP JOINING frame to the LBA. This frame includes a field that carries the EUI-64 address of the joining LBD. + +This frame, as any other frame during the initial part of the bootstrapping process, is transmitted between the LBD and the LBA without any additional security at the MAC layer. + +When received by the LBA, this frame is relayed by the LBA to the LBS. It is assumed that the LBA is fully bootstrapped with the full capability to directly transmit any message to the LBS in a secure way. + +The LBP protocol has been designed to fit two different authentication architectures: + +- the authentication function is directly supported by the LBS and in this case all the authentication material (access lists, credentials, etc.) shall be loaded in the LBS; or +- the authentication function is supported by a remote (and usually centralized) AAA server, and in this case, the LBS is only in charge of forwarding the EAP messages to the AAA server over a standard AAA protocol (i.e., RADIUS [IETF RFC 2865]). + +The following procedure description is only based on the first architecture but extension to the second one appears straightforward. + +So, when received by the LBS, the EUI-64 address may be compared with an access control list (white list or black list) with the following possibilities: + +- this address does not fit the access control list and the LBS send back an LBP DECLINE message, embedding an EAP failure message; or +- this address fit the access control list (or the access control is not implemented) and the LBS sends back an LBP CHALLENGE message, embedding an EAP request message. This latter message also carries the first authentication message. +- In this version of this Recommendation, the EAP identity phase is skipped as proposed by [IETF RFC 3748] to directly move to the authentication phase by sending the first message of the selected EAP method. +- The EAP identity phase could be reintroduced later when the need for roaming features arise. + +In both cases, these messages are relayed by the LBA to the LBD. + +###### 9.4.4.2.2.4 Authentication and key distribution phase + +The authentication phase is wholly dependent on the EAP method in place. The EAP protocol is very flexible and supports various EAP methods. Each method is characterized by its credentials (shared secret, certificate, SIM cards, etc.) and by its signature and encryption algorithms. + +Refer to clause 10.5 for further details on the proposed EAP method used in this Recommendation. + +Note that if addition of other EAP methods is possible, care must be taken to validate the security of the chosen method before integration. EAP methods that have been deprecated must not be provided (e.g., EAP-MD5). + +Methods are ordinary based on two round-trip exchanges: + +- the first one for mutual authentication and initial exchange of ciphering material; +- the second one for mutual control of session keys derivation. + +At the end, the EAP method used should provide the LBD with: + +- Group session keys for a global PAN security. These keys are shared by all the authenticated nodes in the PAN. Every MAC data frame with the SecurityEnabled field set to 1, except those involved in the initial phases of the bootstrapping procedure, is securely transmitted with encryption and decryption at every hop. These group keys shall be refreshed periodically or when a node is detached from the PAN. Group key updates are handled by higher layers. +- Optionally, configuration parameters are provided by the LBS. + +Other keys may be derived for additional security services provided at the application level. + +As the short address is used during the encryption process (see Table 9-23, clause 7.6.3.2), it is recommended that its attribution respects the following rule: a short address shall be assigned to only one node (no address re-use) for a given Group session key. When the Group session key is changed, unused addresses can be re-assigned to different nodes. + +###### 9.4.4.2.2.5 Authorization and initial configuration phase + +Upon completion of the authentication and key distribution process, the LBS shall send back an LBP DECLINE message if the authentication has failed. This message is relayed by the LBA to the LBD to inform the LBD that the LBS did not accept the join request of LBD. + +If the LBS accepts the join request of the LBD, it sends back an LBP ACCEPTED message, embedding an EAP success message within it. This message is relayed by the LBA to the LBD. At this stage, the LBD owns a 16-bit short address and a session key allowing the secure transmission of the messages within the PAN. + +Upon receipt of the LBP message, the LBD may set up an optimized route to the LBS with the help of the LOADng protocol (see clause 9.4.3). If the ADP IB attribute adpDefaultCoordRouteEnabled is set to TRUE, the path used by the device during association phase shall be stored in the routing set as an initial route between LBD and LBS without invoking the LOADng protocol. For that purpose the adaptation layer shall create or update an initial default entry to the routing set as follows: + +- R\_dest\_addr = adpCoordShortAddress +- R\_next\_addr = LBA address +- R\_metric = 0x7FFF +- R\_metric\_type = adpMetricType +- R\_hop\_count = adpMaxHops +- R\_weak\_link\_count = adpMaxHops + +- R\_seq\_num = -1 +- R\_bidirectional = TRUE +- R\_local\_iface\_addr = macShortAddress +- R\_valid\_time = adpRoutingTableEntryTTL + +If adpDefaultCoordRouteEnabled is set to TRUE and once the join procedure has been successfully completed, it is recommended to issue an ADPM-ROUTE-DISCOVERY towards the PAN coordinator with the adpUnicastRREQGenEnabled ADP IB attribute set to TRUE to refresh the initial routing table entry and to announce the route to the PAN coordinator. + +###### 9.4.4.2.2.6 Joining a PAN for any node except coordinator + +The network joining procedure is performed by a device which is not a PAN coordinator and does not have a short address (default short address of a device upon reset is 0xffff which means no short address). During this procedure, the device is authenticated, associated with the network and receives GMK and a short address assigned by the coordinator. After a successful discovery phase as described in clause 9.4.4.2.2.2, this procedure may be triggered by invocation of the ADPM-NETWORK.JOIN.request primitive with PAN ID and LBAAddress of one of the discovered devices as listed in PANDescriptor of ADPM-DISCOVERY.confirm. The selection criteria for PAN ID and LBAAddress is implementation specific. + +If the join is successful, the upper layer is informed by a successful ADPM-NETWORK.JOIN.confirm which includes the assigned short address and PAN ID of the network. In case of failure, this procedure may be repeated after repeating the discovery phase. + +If the join procedure is not complete within *adpMaxJoinWaitTime*, a fail confirmation shall be sent to the upper layer. + +The upper layer in the LBS receives the join request of a device as well as subsequent authentication messages as ADPM-LBP.indication primitives with embedded LBP messages. It also sends the authentication messages as well as acceptance and short address embedded in LBP messages to the LBD by invoking ADPM-LBP.request. The processing of received LBP messages and the construction of LBP messages to be sent to the LBD is performed in the upper layer of the LBS. This includes the processing and construction of EAP messages as described in clause 10.5. + +In the LBD, all the LBP messages are processed internally and the upper layer is not aware of the message exchanges during the authentication procedure. Upon completion or timeout, the upper layer of the LBD receives an ADPM-NETWORK.JOIN.confirm with success or failure status. + +###### 9.4.4.2.2.7 Leaving a PAN – Removal of a device by the PAN coordinator + +The PAN coordinator may instruct a device to remove itself from the network invoking the ADPM-LBP.request primitive, using a KICK frame. This frame is a standard LBP message frame with its T field set to 1 and its code field set to 0b100. The bootstrapping data in that message shall be empty. + +When a device receives this message, it shall check if the A\_LBD field of the LBP message is its own address. If not, the message is silently discarded. Otherwise, the device shall perform the following steps: + +- acknowledge the frame if necessary +- set its 16-bit short address to 0xFFFF; +- generate an ADPM-NETWORK-LEAVE.indication +- invoke an MLME-RESET.request primitive with the SetDefaultPIB parameter set to TRUE +- invoke its ADPM-RESET.request primitive to reset itself. + +Figure 9-27 describes the messages exchanged during the removal of a device from the PAN by the coordinator. + +![Figure 9-27: Message sequence chart during the removal of a device by the coordinator. The diagram shows two lifelines: 'Device' and 'PAN coordinator'. The 'Device' lifeline has 'Upper layer' and 'Adaptation sublayer' components. The 'PAN coordinator' lifeline also has 'Adaptation sublayer' and 'Upper layer' components. The sequence of messages is: 1. The PAN coordinator's Upper layer sends an ADPM-LBP.request (Kick(device)) to its Adaptation sublayer. 2. The PAN coordinator's Adaptation sublayer sends an LBP Kick message to the Device's Adaptation sublayer. 3. The Device's Adaptation sublayer sends an ADPM-NETWORK-LEAVE.indication to its Upper layer. 4. The PAN coordinator's Adaptation sublayer sends an ADPM-LBP.confirm to its Upper layer. The diagram is labeled G.9903(14)_F9-27.](0757c1ca2d4a19ca824d92246e610fc7_img.jpg) + +Figure 9-27: Message sequence chart during the removal of a device by the coordinator. The diagram shows two lifelines: 'Device' and 'PAN coordinator'. The 'Device' lifeline has 'Upper layer' and 'Adaptation sublayer' components. The 'PAN coordinator' lifeline also has 'Adaptation sublayer' and 'Upper layer' components. The sequence of messages is: 1. The PAN coordinator's Upper layer sends an ADPM-LBP.request (Kick(device)) to its Adaptation sublayer. 2. The PAN coordinator's Adaptation sublayer sends an LBP Kick message to the Device's Adaptation sublayer. 3. The Device's Adaptation sublayer sends an ADPM-NETWORK-LEAVE.indication to its Upper layer. 4. The PAN coordinator's Adaptation sublayer sends an ADPM-LBP.confirm to its Upper layer. The diagram is labeled G.9903(14)\_F9-27. + +**Figure 9-27 – Message sequence chart during the removal of a device by the coordinator** + +Upon completion of this procedure, the device shall restart the joining network procedure described in clause 9.4.4.2.2. + +###### 9.4.4.2.2.8 Leaving a PAN – Removal of a device by itself + +A device may also call the ADPM-NETWORK-LEAVE.request primitive to remove itself from the network and notify the PAN coordinator about this removal. + +If the ADPM-NETWORK-LEAVE.request primitive is invoked by a device which is the PAN coordinator, then the adaptation sublayer shall issue an ADPM-NETWORK-LEAVE.confirm primitive with the status INVALID\_REQUEST. + +If the ADPM-NETWORK-LEAVE.request primitive is invoked by a device which is not the PAN coordinator, then the adaptation sublayer shall: + +- Send a KICK frame to the PAN coordinator using a standard LBP message with KICK frame as described in Table 9-49 with T field set to 0 and its Code field set to 0b100. The bootstrapping data in that message should be empty. +- Set its 16-bit short address to 0xFFFF. +- Invoke an MLME-RESET.request primitive with the SetDefaultPIB parameter set to TRUE. +- Reset itself. + +Figure 9-28 describes the messages exchanged during the removal of a device initiated by the device itself. + +![Figure 9-28: Message sequence chart during the removal of a device by itself. The diagram shows two lifelines: 'Device' and 'PAN coordinator'. The 'Device' lifeline has 'Upper layer' and 'Adaptation sublayer' components. The 'PAN coordinator' lifeline also has 'Adaptation sublayer' and 'Upper layer' components. The sequence of messages is: 1. The Device's Upper layer sends an ADPM-NETWORK-LEAVE.request (NULL) to its Adaptation sublayer. 2. The Device's Adaptation sublayer sends an LBP Kick message to the PAN coordinator's Adaptation sublayer. 3. The Device's Adaptation sublayer sends an ADPM-NETWORK-LEAVE.confirm to its Upper layer. 4. The PAN coordinator's Adaptation sublayer sends an ADPM-LBP.indication (Kick(device)) to its Upper layer. The diagram is labeled G.9903(14)_F9-28.](b6098e84ba6261a5152f5a4fa790c579_img.jpg) + +Figure 9-28: Message sequence chart during the removal of a device by itself. The diagram shows two lifelines: 'Device' and 'PAN coordinator'. The 'Device' lifeline has 'Upper layer' and 'Adaptation sublayer' components. The 'PAN coordinator' lifeline also has 'Adaptation sublayer' and 'Upper layer' components. The sequence of messages is: 1. The Device's Upper layer sends an ADPM-NETWORK-LEAVE.request (NULL) to its Adaptation sublayer. 2. The Device's Adaptation sublayer sends an LBP Kick message to the PAN coordinator's Adaptation sublayer. 3. The Device's Adaptation sublayer sends an ADPM-NETWORK-LEAVE.confirm to its Upper layer. 4. The PAN coordinator's Adaptation sublayer sends an ADPM-LBP.indication (Kick(device)) to its Upper layer. The diagram is labeled G.9903(14)\_F9-28. + +**Figure 9-28 – Message sequence chart during the removal of a device by itself** + +On the PAN coordinator side, an ADPM-LBP.indication containing the KICK message is generated to inform the upper layers. This message contains the 64-bit address of the device which had removed itself from the PAN. + +### 9.4.5 Sniffer mode (optional mode) + +This mode is used to support monitoring of the transmitted packets on the power line. Once activated, the modem will process all packets regardless of their destination address. The sniffer modem shall generate an ADPD-DATA.indication for any received packet. The modem activated in sniffer mode shall not forward packets. If a sniffer modem receives a fragment, it shall add an IPv6 fragment header to the packet so the upper layer can detect it. The fragment offset field and the identification field shall be set to the offset of the LOWPAN header and the Datagram\_Tag respectively. + +### 9.4.6 Adaptation sublayer service primitives + +#### 9.4.6.1 ADP data primitives + +##### 9.4.6.1.1 Overview + +The ADPD is used to transport the NSDU to other devices on the network and supports the following primitives: + +- ADPD-DATA.request +- ADPD-DATA.confirm +- ADPD-DATA.indication. + +##### 9.4.6.1.2 ADPD-DATA.request + +###### 9.4.6.1.2.1 Semantics of the service primitive + +This primitive requests the transfer of the NSDU to another device or multiple devices. The semantics of this primitive are as follows: + +``` +ADPD-DATA.request ( + NsduLength, + Nsdu, + NsduHandle, + DiscoverRoute, + QualityOfService, + ) +``` + +**Table 9-52 – Parameters of the ADPD-DATA.request primitive** + +| Name | Type | Valid range | Description | +|---------------|---------------|---------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| NsduLength | Integer | 0-1 280 | The size of the NSDU, in bytes | +| Nsdu | Set of octets | – | The NSDU to send | +| NsduHandle | Integer | 0x00-0xFF | The handle of the NSDU to transmit. This parameter is used to identify in the ADPD-DATA.confirm primitive which request it is concerned with. It can be randomly chosen by the application layer. | +| DiscoverRoute | Boolean | TRUE or FALSE | If TRUE, a route discovery procedure will be performed prior to sending the frame if a route to the | + +**Table 9-52 – Parameters of the ADPD-DATA.request primitive** + +| Name | Type | Valid range | Description | +|------------------|---------|-------------|------------------------------------------------------------------------------------------------------------------------------------| +| | | | destination is not available in the routing table.
If FALSE, no route discovery is performed. | +| QualityOfService | Integer | 0x00-0x01 | The requested quality of service (QoS) of the frame to send. Allowed values are:
0x00 = normal priority
0x01 = high priority | + +###### 9.4.6.1.2.2 When generated + +This primitive is generated by the upper layer to request the sending of a given NSDU. + +###### 9.4.6.1.2.3 Effect on receipt + +If this primitive is received when the device has not joined a network, the adaptation sublayer will issue an ADPD-DATA.confirm primitive with the status INVALID\_REQUEST. Otherwise, the ADPD constructs a 6LoWPAN frame with the following characteristics depending on the transmission mode. + +- In the case of a unicast frame: + - If the destination is not a neighbour of the device, the mesh addressing header is present as described in clause 5.2 of [IETF RFC 4944], where: + - V shall be set to 1, to specify that the originator address is a 16-bit network address; + - F shall be set to 1, to specify that the originator address is a 16-bit network address; + - HopsLft = MaxHops; + - Originator address = The 16-bit network address of the sending device, available in the NIB; + - Final destination address = 16-bit destination address of the device designated by the IPv6 address "DstAddr". + - The broadcast header is not present. + - If necessary, the fragmentation header shall be present to transport NSDUs which do not fit in an entire IEEE 802.15.4 frame. In this case, clause 5.3 of [IETF RFC 4944] applies. +- In the case of a multicast frame: + - The mesh addressing header is present as described in clause 5.2 of [IETF RFC 4944], where + - V shall be set to 1, to specify that the originator address is a 16-bit network address; + - F shall be set to 1, to specify that the originator address is a 16-bit network address; + - HopsLft = MaxHops; + - Originator address = The 16-bit network address of the sending device, available in the NIB; + - Final destination address = multicast group address; + - The broadcast header is present with the following values: + +- Sequence number = previous sequence number + 1 +- If necessary, the fragmentation header shall be present to transport NSDUs which do not fit in an entire IEEE 802.15.4 frame. In this case, clause 5.3 of [IETF RFC 4944] applies. + +Once the frame is constructed, it is routed according to the procedures described in clause 9.4.3.2.1 if the destination address is a unicast address. If the frame is to be transmitted, the MCPS-Data.request primitive is invoked, with the following parameters in the case of a unicast sending: + +- SrcAddrMode = 0x02, for 16-bit address +- DstAddrMode = 0x02, for 16-bit address +- SrcPANId = DstPANId = the value of macPANId obtained from the MAC PIB +- SrcAddr = the value of macShortAddr obtained from the MAC PIB +- DstAddr = the 16-bit address of the next hop determined by the routing procedure +- msduLength = the length of the frame, or fragment in the case of fragmentation, in bytes +- msdu = the frame itself +- msduHandle = NsduHandle +- TxOptions: + - b0 = 1 +- SecurityLevel = dpSecurityLevel +- KeyIdMode, KeySource: Ignored +- KeyIndex: Ignored if SecurityLevel=0; otherwise it depends on the security policy. + +In the case of a broadcast (or multicast) frame, the MCPS-Data.request primitive is invoked with the following parameters: + +- SrcAddrMode = 0x02, for 16-bit address +- DstAddrMode = 0x02, for 16-bit address +- SrcPANId = DstPANId = the value of macPANId obtained from the MAC PIB +- SrcAddr = the value of macShortAddr obtained from the MAC PIB +- DstAddr = 0xFFFF +- msduLength = the length of the frame, or fragment in the case of fragmentation, in bytes +- msdu = the frame itself +- msduHandle = NsduHandle +- TxOptions: + - b0 = 1 +- SecurityLevel = dpSecurityLevel +- KeyIdMode, KeySource: Ignored +- KeyIndex: Ignored if SecurityLevel=0; otherwise it depends on the security policy. + +If adpDisableDefaultRouting is set to TRUE and no non-default routing mechanism is separately specified, point-to-point single hop communication between ITU-T G.9903 devices can be established in the following way: the mesh addressing header is not included in unicast frames and the DstAddr field in MCPS-Data.request is set to the 16-bit destination address of the device designated by the IPv6 destination address without consulting the routing table or the neighbour table. + +If security processing fails for that frame it shall be discarded and an ADPD-DATA.confirm primitive shall be generated with the status code returned by the security processing suite. + +If the DiscoverRoute parameter is set to TRUE then, the route discovery procedure shall be initiated prior to sending the frame in case the final destination address is not available in the routing table. For a complete description of this procedure, see clause 9.4.3. + +##### 9.4.6.1.3 ADPD-DATA.confirm + +###### 9.4.6.1.3.1 Semantics of the service primitive + +This primitive reports the result of a previous ADPD-DATA.request primitive. + +The semantics of this primitive are as follows: + +``` +ADPD-DATA.confirm ( + Status, + NsduHandle +) +``` + +**Table 9-53 – Parameters of the ADPD-DATA.confirm primitive** + +| Name | Type | Valid range | Description | +|------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------| +| Status | Enum | SUCCESS,
INVALID_IPV6_FRAME,
INVALID_REQUEST,
NO_KEY,
BAD_CCM_OUTPUT,
ROUTE_ERROR,
BT_TABLE_FULL,
FRAME_NOT_BUFFER
ED or any status values
returned from security
suite or the
MCPS-DATA.confirm
primitive | The status code of a previous ADPD-DATA.request identified by its NsduHandle. | +| NsduHandle | Integer | 0x00-0xFF | The handle of the NSDU confirmed by this primitive. | + +###### 9.4.6.1.3.2 When generated + +This primitive is generated in response to an ADPD-DATA.request primitive. The status parameter indicates if the request succeeded or the reason for failure. + +###### 9.4.6.1.3.3 Effect on receipt + +On receipt of this primitive, the upper layer is notified of the status of a previous ADPD-DATA.request primitive. + +##### 9.4.6.1.4 ADPD-DATA.indication + +###### 9.4.6.1.4.1 Semantics of the service primitive + +This primitive is used to transfer received data from the adaptation sublayer to the upper layer. The semantics of this primitive are as follows: + +``` +ADPD-DATA.indication ( + NsduLength, +``` + +NsdU, + LinkQualityIndicator, + ) + +**Table 9-54 – Parameters of the ADPD-DATA.indication primitive** + +| Name | Type | Valid range | Description | +|----------------------|---------------|-------------|----------------------------------------------------------------| +| NsdULength | Integer | 0-1280 | The size of the NSDU, in bytes | +| NsdU | Set of octets | – | The received NSDU | +| LinkQualityIndicator | Integer | 0x00-0xFF | The value of the link quality during the receipt of the frame. | + +###### 9.4.6.1.4.2 When generated + +This primitive is generated by the adaptation sublayer when a valid data frame whose final destination is the current station that has been received. + +###### 9.4.6.1.4.3 Effect on receipt + +On generation of this primitive the upper layer is notified of the arrival of a data frame. + +#### 9.4.6.2 ADP management service + +##### 9.4.6.2.1 Overview + +The ADPM allows the transport of command frames used for network maintenance. The list of primitives supported by the ADPM is: + +- ADPM-DISCOVERY.request +- ADPM-DISCOVERY.confirm +- ADPM-NETWORK-START.request +- ADPM-NETWORK-START.confirm +- ADPM-NETWORK-JOIN.request +- ADPM-NETWORK-JOIN.confirm +- ADPM-NETWORK-JOIN.indication +- ADPM-NETWORK-LEAVE.request +- ADPM-NETWORK-LEAVE.indication +- ADPM-NETWORK-LEAVE.confirm +- ADPM-RESET.request +- ADPM-RESET.confirm +- ADPM-GET.request +- ADPM-GET.confirm +- ADPM-SET.request +- ADPM-SET.confirm +- ADPM-NETWORK-STATUS.indication +- ADPM-ROUTE-DISCOVERY.request +- ADPM-ROUTE-DISCOVERY.confirm +- ADPM-PATH-DISCOVERY.request +- ADPM-PATH-DISCOVERY.confirm + +- ADPM-LBP.request +- ADPM-LBP.confirm +- ADPM-LBP.indication +- ADPM-Buffer.indication. + +##### 9.4.6.2.2 ADPM-DISCOVERY.request + +###### 9.4.6.2.2.1 Semantics of the service primitive + +This primitive allows the upper layer to request the ADPM to scan for networks operating in its POS. + +The semantics of this primitive are as follows: + +``` +ADPM-DISCOVERY.request ( + Duration, +) +``` + +**Table 9-55 – Parameters of the ADPM-DISCOVERY.request primitive** + +| Name | Type | Valid range | Description | +|----------|---------|-------------|---------------------------------------------------| +| Duration | Integer | 0x00-0xFF | The number of seconds the active scan shall last. | + +###### 9.4.6.2.2.2 When generated + +This primitive is generated by the next upper layer to get informed of the current networks operating in the POS of the device. + +###### 9.4.6.2.2.3 Effect on receipt + +On receipt of this primitive, the ADP layer will initiate an active scan by invoking the MLME-SCAN.request, as described in clause 9.4.4.2.2.2. + +##### 9.4.6.2.3 ADPM-DISCOVERY.confirm + +###### 9.4.6.2.3.1 Semantics of the service primitive + +This primitive is generated by the ADP layer upon completion of a previous ADPM-DISCOVERY.request. + +The semantics of this primitive are as follows: + +``` +ADPM-DISCOVERY.confirm ( + Status, + PANCount, + PANDescriptor +) +``` + +**Table 9-56 – Parameters of the ADPM-DISCOVERY.confirm primitive** + +| Name | Type | Valid range | Description | +|--------|------|----------------------------|---------------------------------------------------------------------------------------| +| Status | Enum | FAILED, SUCCESS, NO_BEACON | SUCCESS if at least one MLME-BEACON-NOTIFY.indication is received.
NO_BEACON if no | + +**Table 9-56 – Parameters of the ADPM-DISCOVERY.confirm primitive** + +| Name | Type | Valid range | Description | +|---------------|-------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------| +| | | | MLME-BEACON-NOTIFY.indication is received.
In all other cases, FAILED. | +| PANCount | Integer | 0x00-0xFF | The number of entries in the PANDescriptor | +| PANDescriptor | List of PAN descriptors | This list contains the PAN descriptors as described in Table 9-57. Filtering and sorting the PAN descriptor is outside the scope of this Recommendation. | The PAN ID and LBA operating in the POS of the device. | + +**Table 9-57 – PAN descriptor structure specification** + +| Name | Type | Valid range | Description | +|-------------|---------|---------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------| +| PAN ID | Integer | 0x0000-0xFFFF
PAN identifier must be logically ANDed with 0xFCFF | The 16-bit PAN identifier. | +| LinkQuality | Integer | 0x00-0xFF | The 8-bit link quality of the LBA. It is used by the associating device to select the LBA and PAN. | +| LBAAddress | Integer | 0x0000-0xFFFF | The 16 bit short address of a device in this PAN to be used as the LBA by the associating device. | +| RC_COORD | Integer | 0x0000-0xFFFF | The estimated route cost from the LBA to the coordinator. It is used by the associating device to select the LBA and PAN. | + +###### 9.4.6.2.3.2 When generated + +This primitive is generated by the ADP layer for the upper layer on completion of an ADPM-DISCOVERY.request primitive. + +###### 9.4.6.2.3.3 Effect on receipt + +On receipt of this primitive, the upper layer is notified of the completion of the network scan and obtains a list of found LBAs. + +##### 9.4.6.2.4 ADPM-NETWORK-START.request + +###### 9.4.6.2.4.1 Semantics of the service primitive + +This primitive allows the upper layer to request the starting of a new network. It shall only be invoked by a device designated as the PAN coordinator during the factory process. + +The semantics of this primitive are as follows: + +ADPM-NETWORK-START.request ( + + + +###### 9.4.6.2.5.3 Effect on receipt + +On receipt of this primitive, the next higher layer is notified about the status of its previous ADPM-NETWORK-START.request. + +##### 9.4.6.2.6 ADPM-NETWORK-JOIN.request + +###### 9.4.6.2.6.1 Semantics of the service primitive + +This primitive allows the next upper layer to join an existing network. + +The semantics of this primitive are as follows: + +ADPM-NETWORK-JOIN.request ( +                                        PANId, +                                        LBAAddress +) + +**Table 9-60 – Parameters of the ADPM-NETWORK-JOIN.request primitive** + +| Name | Type | Valid range | Description | +|------------|----------------|---------------|--------------------------------------------------------------------------------------------------| +| PANId | Integer | 0x0000-0xFFFF | The 16-bit PAN identifier of the network to join. | +| LBAAddress | 16-bit address | 0x0000-0xFFFF | The 16-bit short address of the device acting as a LoWPAN bootstrap agent as defined in Annex E. | + +###### 9.4.6.2.6.2 When generated + +The upper layer invokes this primitive when it wishes to join an existing PAN using the MAC association procedure. + +###### 9.4.6.2.6.3 Effect on receipt + +On receipt of this primitive by a device which has already joined, the adaptation sublayer generates an ADPM-NETWORK-JOIN.confirm with the status INVALID\_REQUEST. + +On receipt of this primitive by a device which has not already joined, the adaptation sublayer initiates the MAC association procedure ("bootstrap") described in clause 9.4.4.2.2. + +On completion, an MLME-SET.request is invoked to set the 16-bit short address of the device which was obtained during the "bootstrapping" phase. Then, an ADPM-NETWORK-JOIN.confirm primitive is generated with a status of SUCCESS. + +##### 9.4.6.2.7 ADPM-NETWORK-JOIN.confirm + +###### 9.4.6.2.7.1 Semantics of the service primitive + +This primitive is generated by the ADP layer to indicate the completion status of a previous ADPM-NETWORK-JOIN.request. + +The semantics of this primitive are as follows: + +ADPM-NETWORK-JOIN.confirm ( +                                        Status, +                                        NetworkAddress, +                                        PANId +) + +**Table 9-61 – Parameters of the ADPM-NETWORK-JOIN.confirm primitive** + +| Name | Type | Valid range | Description | +|----------------|---------|-----------------------------------------------|--------------------------------------------------------------------------------------------------------------------------| +| Status | Status | SUCCESS,
INVALID_REQUEST,
NOT_PERMITTED | The result of the attempt to join the network. | +| NetworkAddress | Integer | 0x0001-0x7FFF, 0xFFFF | The 16-bit network address that was allocated to the device. If the allocation fails, this address is equal to 0xFFFF. | +| PANId | Integer | 0x0000-0xFFFF | The 16-bit address of the PAN of which the device is now a member.
NOTE – PANId value is logically ANDed with 0xFCFF. | + +###### 9.4.6.2.7.2 When generated + +This primitive is generated in response to an ADPM-NETWORK-JOIN.request primitive and allows the upper layer to obtain information on the status of its request. + +The status NOT\_PERMITTED is given if the device was unable to authenticate itself to the PAN coordinator. + +###### 9.4.6.2.7.3 Effect on receipt + +On receipt of this primitive, the upper layer is informed on the status of its request. + +##### 9.4.6.2.8 ADPM-NETWORK-LEAVE.request + +This primitive allows a non-coordinator device to remove itself from the network as described in clause 9.4.4.2.2.8. The removal of a device by the coordinator is performed using an ADPM-LBP.request according to the procedure described in clause 9.4.4.2.2.7. + +###### 9.4.6.2.8.1 Semantics of the service primitive + +The semantics of this primitive are as follows: + +ADPM-NETWORK-LEAVE.request ( ) + +###### 9.4.6.2.8.2 When generated + +The next higher layer of a non-coordinator device generates this primitive to request to leave the network. + +###### 9.4.6.2.8.3 Effect on receipt + +On receipt of this primitive by a device which is not associated with any network or by a device which is a PAN coordinator, the adaptation sublayer shall issue an ADPM-NETWORK-LEAVE.confirm primitive with the status INVALID\_REQUEST. + +On receipt of this primitive by a device which is associated with a network, the device removes itself from the network using the procedure described in clause 9.4.4.2.2.8. If that procedure is successful, then the device issues an ADPM-NETWORK-LEAVE.confirm primitive with the status SUCCESS. + +##### 9.4.6.2.9 ADPM-NETWORK-LEAVE.indication + +###### 9.4.6.2.9.1 Semantics of the service primitive + +This primitive is generated by the ADP layer of a non-coordinator device to inform the upper layer that it has been unregistered from the network by the coordinator. The semantics of this primitive are as follows: + +ADPM-NETWORK-LEAVE.indication ( +) + +###### 9.4.6.2.9.2 When generated + +This primitive is generated by the adaptation sublayer of a device when it has been removed from the network by the PAN coordinator or by the adaptation sublayer of the PAN coordinator when a device has decided to leave the network. + +###### 9.4.6.2.9.3 Effect on receipt + +On receipt of this primitive, the upper layer of the device is notified that it is no more a part of the PAN. + +##### 9.4.6.2.10 ADPM-NETWORK-LEAVE.confirm + +###### 9.4.6.2.10.1 Semantics of the service primitive + +This primitive allows the upper layer to be informed of the status of its previous ADPM-NETWORK-LEAVE.request. + +The semantics of this primitive are as follows: + +ADPM-NETWORK-LEAVE.confirm ( +Status, +) + +**Table 9-62 – Parameters of the ADPM-NETWORK-LEAVE.confirm primitive** + +| Name | Type | Valid range | Description | +|--------|------|----------------------------------------------------------------------------------------------------|----------------------------| +| Status | Enum | SUCCESS, INVALID_REQUEST, UNKNOWN_DEVICE or any status returned by the MCPS-DATA.confirm primitive | The status of the request. | + +###### 9.4.6.2.10.2 When generated + +This primitive is generated on completion of a device removal. If it is successful, the SUCCESS code is given. Otherwise, an error status is given as explained in clause 9.4.4.2.2.8. + +###### 9.4.6.2.10.3 Effect on receipt + +On receipt, the upper layer is notified of the result of its request. + +##### 9.4.6.2.11 ADPM-RESET.request + +###### 9.4.6.2.11.1 Semantics of the service primitive + +This primitive allows the upper layer to request that the ADP layer performs a reset. + +The semantics of this primitive are as follows: + +ADPM-RESET.request ( + +) + +This primitive has no parameter. + +###### 9.4.6.2.11.2 When generated + +This primitive allows a reset of the adaptation sublayer and allows the resetting of the MIB attributes. + +###### 9.4.6.2.11.3 Effect on receipt + +On receipt of this primitive the following steps are performed: + +- the adaptation sublayer issues an MLME-RESET.request primitive with the SetDefaultPIB parameter set to TRUE and waits for the MLME-RESET.confirm primitive; +- the adaptation sublayer clears all of its internal variables and flushes its routing and neighbour tables; +- the adaptation sublayer issues an ADPM-RESET.confirm primitive with the status SUCCESS, or DISABLE\_TRX\_FAILURE if the MAC reset operation failed. + +##### 9.4.6.2.12 ADPM-RESET.confirm + +###### 9.4.6.2.12.1 Semantics of the service primitive + +This primitive allows the upper layer to be notified of the completion of an ADPM-RESET.request primitive. + +The semantics of this primitive are as follows: + +``` +ADPM-RESET.confirm ( + Status +) +``` + +Table 9-63 – Parameters of the ADPM-RESET.confirm primitive + +| Name | Type | Valid range | Description | +|--------|------|----------------------------------------------------------------|----------------------------| +| Status | Enum | Any status value returned from the MLMERESET.confirm primitive | The status of the request. | + +###### 9.4.6.2.12.2 When generated + +This primitive is generated by the ADP layer when a previous ADPM-RESET.request primitive has completed. + +###### 9.4.6.2.12.3 Effect on receipt + +The upper layer is notified of the completion of the command. + +##### 9.4.6.2.13 ADPM-GET.request + +###### 9.4.6.2.13.1 Semantics of the service primitive + +This primitive allows the upper layer to get the value of an attribute from the information base. + +The semantics of this primitive are as follows: + +``` +ADPM-GET.request ( + AttributeId, + AttributeIndex +) +``` + +**Table 9-64 – Parameters of the ADPM-GET.request primitive** + +| Name | Type | Valid Range | Description | +|----------------|---------|----------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------| +| AttributeId | Integer | See clause 9.4.1 | The identifier of the IB attribute to read. | +| AttributeIndex | Integer | Depends on attribute, see clause 9.4.1 | The index within the table of the specified IB attribute to read. This parameter is valid only for IB attributes that are tables. | + +###### **9.4.6.2.13.2 When generated** + +This primitive is generated by the upper layer to read the value of an attribute from the IB. + +###### **9.4.6.2.13.3 Effect on receipt** + +On receipt of this primitive, the adaptation sublayer attempts to retrieve the selected attribute in the information base. If the attribute is not found, the adaptation layer generates an ADPM-GET.confirm primitive with the status UNSUPPORTED\_ATTRIBUTE. If the attribute is found (and is a table), but the AttributeIndex is out of range, the adaptation layer generates an ADPM-GET.confirm primitive with the status INVALID\_INDEX. + +Otherwise, the adaptation sublayer generates an ADPM-GET.confirm primitive with the status SUCCESS and the value read from the IB in the AttributeValue parameter. + +##### **9.4.6.2.14 ADPM-GET.confirm** + +###### **9.4.6.2.14.1 Semantics of the service primitive** + +This primitive allows the upper layer to be informed of the status of a previously issued ADPM-GET.request primitive. + +The semantics of this primitive are as follows: + +``` +ADPM-GET.confirm ( + Status, + AttributeId, + AttributeIndex, + AttributeValue +) +``` + +**Table 9-65 – Parameters of the ADPM-GET.confirm primitive** + +| Name | Type | Valid range | Description | +|----------------|---------|-------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------| +| Status | Enum | SUCCESS, UNSUPPORTED_ATTRIBUTE or INVALID_INDEX | The status of the reading. | +| AttributeId | Integer | See clause 9.4.1 | The identifier of the IB attribute read. | +| AttributeIndex | Integer | Depends on attribute, see clause 9.4.1 | The index within the table of the specified IB attribute read. This parameter is valid only for IB attributes that are tables. | +| AttributeValue | Various | Attribute specific | The value of the attribute read from the IB. | + +###### 9.4.6.2.14.2 When generated + +This primitive is generated by the adaptation sublayer in response to an ADPM-GET.request primitive. + +###### 9.4.6.2.14.3 Effect on receipt + +On receipt of this primitive the upper layer is informed on the status of its request and eventually gets the desired value. + +##### 9.4.6.2.15 ADPM-SET.request + +###### 9.4.6.2.15.1 Semantics of the service primitive + +This primitive allows the upper layer to set the value of an attribute in the information base. + +The semantics of this primitive are as follows: + +``` +ADPM-SET.request( + AttributeId, + AttributeIndex, + AttributeValue +) +``` + +**Table 9-66 – Parameters of the ADPM-SET.request primitive** + +| Name | Type | Valid range | Description | +|----------------|---------|----------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------| +| AttributeId | Integer | See clause 9.4.1 | The identifier of the IB attribute to write | +| AttributeIndex | Integer | Depends on attribute, see clause 9.4.1 | The index within the table of the specified IB attribute to be written. This parameter is valid only for IB attributes that are tables | +| AttributeValue | Various | Depends on attribute | The value to write | + +###### 9.4.6.2.15.2 When generated + +This primitive is generated by the upper layer to write the value of an attribute in the IB. + +###### 9.4.6.2.15.3 Effect on receipt + +On receipt of this primitive the adaptation sublayer attempts to write the selected attribute in the information base. If the attribute is not found, the adaptation layer generates an ADPM-SET.confirm primitive with the status UNSUPPORTED\_ATTRIBUTE. If the attribute is found (and is a table), but the AttributeIndex is out of range, the adaptation layer generates an ADPM-SET.confirm primitive with the status INVALID\_INDEX. If the attribute is found but is read only, the adaptation layer generates an ADPM-SET.confirm primitive with the status READ\_ONLY. If the attribute is found, and it is not read only but the AttributeValue is out of range, the adaptation layer generates an ADPM-SET.confirm primitive with the status INVALID\_PARAMETER. Otherwise, the adaptation layer generates an ADPM-SET.confirm primitive with the status SUCCESS. + +##### 9.4.6.2.16 ADPM-SET.confirm + +###### 9.4.6.2.16.1 Semantics of the service primitive + +This primitive allows the upper layer to be informed about a previous ADPM-SET.request primitive. + +The semantics of this primitive are as follows: + +``` +ADPM-SET.confirm ( + Status, + AttributeId, + AttributeIndex +) +``` + +**Table 9-67 – Parameters of the ADPM-SET.confirm primitive** + +| Name | Type | Valid range | Description | +|----------------|---------|-------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------| +| Status | Enum | SUCCESS, UNSUPPORTED_ATTRIBUTE, READ_ONLY, INVALID_PARAMETER or INVALID_INDEX | The status of the writing. | +| AttributeId | Integer | See clause 9.4.1 | The identifier of the IB attribute written. | +| AttributeIndex | Integer | Depends on attribute, see clause 9.4.1 | The index within the table of the specified IB attribute written. This parameter is valid only for IB attributes that are tables. | + +###### 9.4.6.2.16.2 When generated + +This primitive is generated by the adaptation layer in response to an ADPM-SET.request primitive. + +###### 9.4.6.2.16.3 Effect on receipt + +On receipt of this primitive, the upper layer is informed on the status of its request. + +##### 9.4.6.2.17 ADPM-NETWORK-STATUS.indication + +###### 9.4.6.2.17.1 Semantics of the service primitive + +This primitive allows the next higher layer of a PAN coordinator or a PAN device to be notified when a particular event occurs on the PAN. + +The semantics of this primitive are as follows: + +``` +ADPM-NETWORK-STATUS.indication ( + PAN ID, + SrcAddrMode, + SrcAddr, + DstAddrMode, + DstAddr, + status, + SecurityLevel, + KeyIdMode, + KeySource, + KeyIndex +) +``` + +The parameters are identical to the ones used by MLME-COMM-STATUS.indication, described in Table 9-1 and references therein. + +###### 9.4.6.2.17.2 When generated + +This primitive is generated if the underlying MAC layer generates an MLME-COMM-STATUS.indication. + +###### 9.4.6.2.17.3 Effect on receipt + +On receipt, the upper layer of a PAN coordinator or PAN device is informed that an alternate PAN ID was detected or that a MAC event occurred. + +##### 9.4.6.2.18 ADPM-ROUTE-DISCOVERY.request + +###### 9.4.6.2.18.1 Semantics of the service primitive + +This primitive allows the upper layer to initiate a route discovery. + +The semantics of this primitive are as follows: + +ADPM-ROUTE-DISCOVERY.request ( +                                            DstAddr, +                                            MaxHops +) + +**Table 9-68 – Parameters of the ADPM-ROUTE-DISCOVERY.request primitive** + +| Name | Type | Valid range | Description | +|---------|---------------|-------------|--------------------------------------------------------------------------------------| +| DstAddr | Short address | 0x00-0x7FFF | The short unicast destination address of the route discovery. | +| MaxHops | Integer | 0x01-0x0E | This parameter indicates the maximum number of hops allowed for the route discovery. | + +###### 9.4.6.2.18.2 When generated + +This primitive is generated by the upper layer of a device to obtain a route to another device. + +###### 9.4.6.2.18.3 Effect on receipt + +An ADPM-ROUTE-DISCOVERY.confirm with the status INVALID\_REQUEST is generated if the DstAddr is not a unicast IPv6 address, or if the MaxHops value is out of range. + +On receipt of this primitive the device will initiate a route discovery procedure as described in clause 9.4.3.2.3. + +##### 9.4.6.2.19 ADPM-ROUTE-DISCOVERY.confirm + +###### 9.4.6.2.19.1 Semantics of the service primitive + +This primitive allows the upper layer to be informed of the completion of a route discovery. + +The semantics of this primitive are as follows: + +ADPM-ROUTE-DISCOVERY.confirm ( +                                            Status +) + +**Table 9-69 – Parameters of the ADPM-ROUTE-DISCOVERY.confirm primitive** + +| Name | Type | Valid range | Description | +|--------|--------|---------------------------------------|------------------------------------| +| Status | Status | SUCCESS, INVALID_REQUEST, ROUTE_ERROR | The status of the route discovery. | + +###### **9.4.6.2.19.2 When generated** + +This primitive is generated by the adaptation layer on completion of a route discovery, as described in clause 9.4.3.2.3 and Annex D. + +###### **9.4.6.2.19.3 Effect on receipt** + +On receipt of this primitive the upper layer is informed on the completion of the route discovery. If the status value is SUCCESS, the routing table has been correctly updated with a brand new route to the desired destination and the device may begin sending frames to that destination. + +##### **9.4.6.2.20 ADPM-PATH-DISCOVERY.request** + +###### **9.4.6.2.20.1 Semantics of the service primitive** + +This primitive allows the upper layer to initiate a path discovery. + +The semantics of this primitive are as follows: + +``` +ADPM-PATH-DISCOVERY.request ( + DstAddr + PathMetricType +) +``` + +**Table 9-70 – Parameters of the ADPM-PATH-DISCOVERY.request primitive** + +| Name | Type | Valid range | Description | +|----------------|---------------|-------------|--------------------------------------------------------------| +| DstAddr | Short address | 0-0x7FFF | The short unicast destination address of the path discovery. | +| PathMetricType | Integer | 0-0x0F | The metric type to be used for the path discovery. | + +###### **9.4.6.2.20.2 When generated** + +This primitive is generated by the upper layer of a device to obtain the path to another device. + +###### **9.4.6.2.20.3 Effect on receipt** + +An ADPM-PATH-DISCOVERY.confirm with the status ROUTE\_ERROR is generated if the DstAddr is not in the routing table or if transmission of a PREQ message has failed. + +An ADPM-PATH-DISCOVERY.confirm with the status ALREADY\_IN\_PROGRESS shall be generated if a path discovery with the same DstAddr is being processed. + +On receipt of this primitive the device will initiate a path discovery procedure as described in clause 9.4.3.2.4. + +##### **9.4.6.2.21 ADPM-PATH-DISCOVERY.confirm** + +###### **9.4.6.2.21.1 Semantics of the service primitive** + +This primitive allows the upper layer to be informed of the completion of a path discovery. + +The semantics of this primitive are as follows: + +``` +ADPM-PATH-DISCOVERY.confirm ( + DstAddr, + Status + PathTable +) +``` + +**Table 9-71 – Parameters of the ADPM-PATH-DISCOVERY.confirm primitive** + +| Name | Type | Valid range | Description | +|-----------|----------------|---------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| DstAddr | Device address | 0-0x7FFF | The short unicast destination address of the path discovery. | +| Status | Status | SUCCESS, INCOMPLETE PATH, TIMEOUT, ALREADY_IN_PROGRESS, ROUTE_ERROR | The status of the path discovery:
If the desired destination has been reached, Status is set to SUCCESS.
If the path discovery has only a part of the path to its desired final destination, Status is set to INCOMPLETE PATH.
If adpPathDiscoveryTime seconds after PREQ transmission, no PREP has been received, Status is set to TIMEOUT.
If a path discovery with the same DstAddr is being processed, Status is set to ALREADY_IN_PROGRESS.
If DstAddr is not in the routing table of the path discovery initiator or the transmission of a PREQ message has failed, Status is set to ROUTE_ERROR. | +| PathTable | Set | – | Table constituted of all the information contained in the received PREP message, starting from PathMetricType. | + +###### 9.4.6.2.21.2 When generated + +This primitive is generated by the adaptation layer on completion of a path discovery as described in clause 9.4.3.2.4. + +###### 9.4.6.2.21.3 Effect on receipt + +On receipt of this primitive the upper layer is informed on the completion of the path discovery. + +##### 9.4.6.2.22 ADPM-LBP.request + +###### 9.4.6.2.22.1 Semantics of the service primitive + +This primitive allows the upper layer of the client to send the LBP message to the server modem. + +The semantics of this primitive are as follows: + +``` +ADPM-LBP.request ( + DstAddrType, + DstAddr, + NsduLength, + Nsdu, +) +``` + +NsduHandle, + MaxHops, + DiscoveryRoute, + QualityOfService, + SecurityEnabled + ) + +**Table 9-72 – Parameters of the ADPM-LBP.request primitive** + +| Name | Type | Valid range | Description | +|------------------|---------------|-------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| DstAddrType | Integer | 0x02-0x03 | The type of destination address contained in the DstAddr parameter. The allowed values are:
0x02 = 2 Byte address (LBA or LBD address)
0x03 = 8 Byte address (LBD address). | +| DstAddr | Set of octets | – | 16-bit address of LBA or LBD or 64 bit address (extended address of LBD) | +| NsduLength | Integer | 0-1 280 | The size of the NSDU, in bytes | +| Nsdu | Set of octets | – | The NSDU to send | +| NsduHandle | Integer | 0x00-0xFF | The handle of the NSDU to transmit. This parameter is used to identify in the ADPM-LBP.confirm primitive which request it is concerned with. It can be randomly chosen by the application layer. | +| MaxHops | Integer | 0x01-0x0E | The number of times the frame will be repeated by network routers. | +| DiscoveryRoute | Boolean | TRUE-FALSE | If TRUE, a route discovery procedure will be performed prior to sending the frame if a route to the destination is not available in the routing table.
If FALSE, no route discovery is performed. | +| QualityOfService | Integer | 0x00-0x01 | The requested quality of service (QoS) of the frame to send. Allowed values are:
0x00 = standard priority
0x01 = high priority | +| SecurityEnabled | Boolean | TRUE-FALSE | If TRUE, this parameter enables the MAC layer security for sending the frame. | + +###### 9.4.6.2.22.2 When generated + +This primitive is generated by the LBS to perform the authentication, re-keying and leave procedure. + +###### 9.4.6.2.22.3 Effect on receipt + +On receipt of this primitive the modem sends the coming frame to the destination. + +##### 9.4.6.2.23 ADPM-LBP.confirm + +###### 9.4.6.2.23.1 Semantics of the service primitive + +This primitive reports the result of a previous ADPM-LBP.request primitive. + +The semantics of this primitive are as follows: + +``` +ADPM-LBP.confirm ( + Status, + NsduHandle, +) +``` + +**Table 9-73 – Parameters of the ADPM-LBP.confirm primitive** + +| Name | Type | Valid range | Description | +|------------|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------| +| Status | Enum | SUCCESS,
INVALID_REQUEST,
NO_KEY,
BAD_CCM_OUTPUT,
ROUTE_ERROR,
BT_TABLE_FULL,
FRAME_NOT_BUFFERED or any status values returned from the security suite or the MCPS-DATA.confirm primitive | The status code of a previous ADPM-LBP.request identified by its NsduHandle. | +| NsduHandle | Integer | 0x00-0xFF | The handle of the NSDU confirmed by this primitive. | + +###### 9.4.6.2.23.2 When generated + +This primitive is generated in response to an ADPM-LBP.request primitive, the status parameter indicates if the request succeeded or the reason for failure. + +###### 9.4.6.2.23.3 Effect on receipt + +On receipt of this primitive the upper layer is notified of the status of a previous ADPM-LBP.request primitive. + +##### 9.4.6.2.24 ADPM-LBP.indication + +###### 9.4.6.2.24.1 Semantics of the service primitive + +This primitive is used to transfer a received LBP frame from the ADP layer to the upper layer. + +The semantics of this primitive are as follows: + +``` +ADPM-LBP.indication ( + SrcAddr, + NsduLength, + Nsdu, + LinkQualityIndicator, + SecurityEnabled +) +``` + +**Table 9-74 – Parameters of the ADPM-LBP.indication primitive** + +| Name | Type | Valid range | Description | +|----------------------|---------------|---------------|-------------------------------------------------------------------------------------------------------------------------------| +| SrcAddr | Integer | 0x0000-0xFFFF | 16-bit address of the LBA. When directly communicating with the LBD (using extended addressing), this field is set to 0xFFFF. | +| NsduLength | Integer | 0-1 280 | The size of the NSDU, in bytes | +| Nsdu | Set of octets | – | The NSDU to send | +| LinkQualityIndicator | Integer | 0x00-0xFF | The value of the link quality during reception of the frame. | +| SecurityEnabled | Boolean | TRUE-FALSE | TRUE if the frame was received with a security level greater or equal to adpSecurityLevel, FALSE otherwise. | + +###### **9.4.6.2.24.2 When generated** + +This primitive is generated by the ADP layer of the client modem when a valid LBP frame whose final destination is the current station has been received. + +###### **9.4.6.2.24.3 Effect on receipt** + +On generation of this primitive the upper layer is notified of the arrival of an LBP frame. + +##### **9.4.6.2.25 ADPM-BUFFER.indication** + +###### **9.4.6.2.25.1 Semantics of the service primitive** + +This primitive allows the next higher layer to be notified when the modem has reached its capability limit to perform the next frame. + +The semantics of this primitive are as follows: + +``` +ADPM-BUFFER.indication ( + BufferReady +) +``` + +**Table 9-75 – Parameters of the ADPM-BUFFER.indication primitive** + +| Name | Type | Valid range | Description | +|-------------|---------|-------------|---------------------------------------------------------------------------------------------------------| +| BufferReady | Boolean | TRUE-FALSE | TRUE: modem is ready to receipt more data frame.
FALSE: modem is not ready, stop sending data frame. | + +###### **9.4.6.2.25.2 When generated** + +This primitive is generated with a status of FALSE when the adaptation layer of a modem has buffered a data request packet and no more additional buffer space is left. If afterward, the modem has enough buffer space available again to process a data request packet, this primitive is generated with a status of TRUE and sent to the next higher layer. + +###### **9.4.6.2.25.3 Effect on receipt** + +On receipt, the upper layer shall stop the data flow if BufferReady is equal to FALSE and open it if BufferReady is TRUE. + +#### **9.4.6.3 Behaviour to MAC indications** + +##### **9.4.6.3.1 Overview** + +This clause describes the behaviour of the adaptation layer in response to an unsolicited indication from the MAC layer. + +##### **9.4.6.3.2 MCPS-DATA.indication** + +On receipt of this indication, the adaptation layer shall execute the routing algorithm as described in clause 9.4.3. + +##### **9.4.6.3.3 MLME-ASSOCIATE.indication** + +Nothing shall be done upon receipt of this primitive by the adaptation layer. + +##### **9.4.6.3.4 MLME-DISASSOCIATE.indication** + +Nothing shall be done upon receipt of this primitive by the adaptation layer. + +##### **9.4.6.3.5 MLME-BEACON-NOTIFY.indication** + +When an MLME-BEACON-NOTIFY.indication is received, and if an ADPM-DISCOVERY.request is currently operating, the adaptation layer shall add the PANId to the PANDescriptorList which will be forwarded to the upper layer in the ADPM-DISCOVERY.confirm primitive. + +##### **9.4.6.3.6 MLME-GTS.indication** + +Nothing shall be done upon receipt of this primitive by the adaptation layer. + +##### **9.4.6.3.7 MLME-ORPHAN.indication** + +Nothing shall be done upon receipt of this primitive by the adaptation layer. + +##### **9.4.6.3.8 MLME-COMM-STATUS.indication** + +On receipt of this primitive, the adaptation layer shall generate an ADPM-NETWORK-STATUS.indication primitive, with the parameters identical to the MLME-COMM-STATUS.indication parameters. + +## **9.5 Functional description** + +### **9.5.1 Network formation** + +The network formation can only be performed by the PAN coordinator. Any device other than the PAN coordinator shall not attempt to perform a network formation. + +Prior to the network formation, the PAN coordinator shall perform an active scan as described in clause 9.4.4.2.2.2. If the PANDescriptorList given by the ADPM-DISCOVERY.confirm primitive is empty, then the PAN coordinator can start a new network. If the PANDescriptorList is not empty, the PAN coordinator may inform the rest of the system that a PAN is already operating in the POS of the device and may start a new network afterwards. The procedures and decisions associated with this behaviour are implementation specific. + +After the network discovery, the PAN coordinator shall set its PAN ID to the predefined value stored in it. This value can be obtained remotely from a configuration server or locally computed. The way this PAN ID is chosen and set in the coordinator is implementation specific. + +NOTE – The PAN identifier shall be logically ANDed with 0xFCFF, as described in clause 6 of [IETF RFC 4944]; see also Table 9-34. + +Once the PAN identifier has been determined, the adaptation sublayer shall invoke the MLME-START.request with the following parameters: + +- PANId = the PAN identifier computed; +- LogicalChannel = 0 (not used); +- ChannelPage = 0 (not used); +- StartTime = 0 (not used); +- BeaconOrder = 15 (beaconless network); +- SuperframeOrder = 15 (not used); +- PANCoordinator = TRUE; +- BatteryLifeExtension = FALSE (not used); +- CoordRealignment = FALSE; +- CoordRealignSecurityLevel, CoordRealignKeyIdMode, CoordRealignKeySource and CoordRealignKeyIndex: not used, shall be set to 0; +- BeaconSecurityLevel = 0; +- BeaconKeyIdMode, BeaconKeySource, BeaconKeyIndex: not used, shall be set to 0. + +The MAC sublayer then generates an MLME-START.confirm primitive with the corresponding status code, which is forwarded to the upper layers through the generation of an ADPM-NETWORK-START.confirm. + +# 10 Security + +## 10.1 Access control and authentication + +An end device (ED) may not access the network without a preliminary identification (with comparison to white or black lists) and authentication. Identification and authentication are based on two parameters that personalize every ED: + +- an EUI-48 MAC address as defined in [IEEE 802-2001]. This address may be easily converted into an EUI-64 as requested by [IEEE 802.15.4] and related documents. +- A 128-bit shared secret (also known as pre-shared key or PSK) used as a credential during the authentication process. It is shared by the ED itself (also known as peer) and an authentication server. The mutual authentication is based on proof that the other party knows the PSK. It is of the highest importance that the PSK remains secret. + +The identification and authentication processes are activated when an ED restarts and may also be launched at any time according to the security policy in place. The related material is carried by the 6LoWPAN bootstrapping protocol (LBP) (see clause 9.4.4) that embeds the extensible authentication protocol (EAP) (see clause 9.4.4.2.1.2). + +As shown in Figure 10-1, the LBP and EAP have been designed to be relayed by intermediates nodes. Then during the bootstrapping phase, if an ED (also known as LBD) that has not yet acquired a routable 16-bit address is at a 1-hop distance from the PAN coordinator (also known as LBS) they can communicate directly. Otherwise, they shall use an intermediate node (also known as LBA) located at a 1-hop distance of the LBD. + +Moreover, two different authentication architectures shall be considered: + +- The authentication server function is directly supported by the LBS and in this case all the authentication material (access lists, credentials, etc.) shall be loaded in the LBS. +- The authentication server function is supported by a remote (and usually centralized) AAA server and in this case, the LBS is only in charge of forwarding the EAP messages to the AAA server over a standard AAA protocol (i.e., RADIUS [IETF RFC 2865]). + +![Four diagrams (a-d) illustrating LBP and EAP relaying capabilities. Diagram a shows single hop-local authentication between LBD EAP peer and LBS EAP server. Diagram b shows multi hop-local authentication involving an LBA relay. Diagram c shows single hop-remote authentication involving a WAN and an EAP server. Diagram d shows multi hop-remote authentication involving an LBA relay, a WAN, and an EAP server. A legend at the bottom indicates Clear (orange line), Ciphred (black line), and Relay (orange line with a square marker).](88c92858439684b2103e88cb143fb98e_img.jpg) + +**a) Single hop-local authentication** + +LBD EAP peer (1 hop) ↔ LBS EAP server + +Messages: EAP, LBP, MAC + +**b) Multi hop-local authentication** + +LBD EAP peer (1 hop) ↔ LBA (n hops) ↔ LBS EAP server + +Messages: EAP, LBP, MAC + +**c) Single hop-remote authentication** + +LBD EAP peer (1 hop) ↔ LBS (WAN) ↔ EAP server + +Messages: EAP, LBP, MAC, RADIUS, IPv4 + +**d) Multi hop-remote authentication** + +LBD EAP peer (1 hop) ↔ LBA (n hops) ↔ LBS (WAN) ↔ EAP server + +Messages: EAP, LBP, MAC, RADIUS, IPv4 + +Legend: — Clear — Ciphred — Relay + +G.9903(12)-Amd.1(13)\_F10-1 + +Four diagrams (a-d) illustrating LBP and EAP relaying capabilities. Diagram a shows single hop-local authentication between LBD EAP peer and LBS EAP server. Diagram b shows multi hop-local authentication involving an LBA relay. Diagram c shows single hop-remote authentication involving a WAN and an EAP server. Diagram d shows multi hop-remote authentication involving an LBA relay, a WAN, and an EAP server. A legend at the bottom indicates Clear (orange line), Ciphred (black line), and Relay (orange line with a square marker). + +**Figure 10-1 – LBP and EAP relaying capabilities** + +The authentication process is wholly dependent on the EAP method in place. The EAP protocol is very flexible and supports various EAP methods (EAP-MD5, EAP-AKA, EAP-TLS, etc.). Each method is characterized by its credentials (shared secret, certificate, SIM cards, etc.) and by its signature and encryption algorithms. + +The method adopted for this Recommendation is EAP-PSK (see clause 10.5), the main design goals of which are: + +- Simplicity: it is entirely based on a single credential (a 128-bit pre-shared key) and a single cryptographic algorithm (AES-128). +- Security: it appears very conservative in its design following well-known and improved cryptographic schemes. + +- Extensibility: in this Recommendation, it is easily extended to support group key distribution (see clause 10.5.2). + +## 10.2 Confidentiality and integrity + +As shown by Figure 10-2, confidentiality and integrity services are ensured at different levels: + +- At the MAC level: as defined in [IEEE 802.15.4], a CCM\* type of ciphering is delivered to every frame transmitted between nodes in the network. It is a universal low layer confidentiality and integrity service (with anti-replay capabilities). The MAC frames are encrypted and decrypted at every hop. The only exceptions are some well-controlled frames in the early stages of the bootstrapping process. To fairly support this service, all the nodes in the network receive the same group master key (GMK). This GMK is individually and securely distributed to every node by using the EAP-PSK secure channel. + +![Diagram illustrating confidentiality and security services in a network. A central red node is connected to five yellow nodes, which are in turn connected to five grey nodes. Solid black lines represent MAC CCM* connections between adjacent nodes. Dashed blue lines with arrows represent the EAP-PSK PCHANNEL, showing secure communication paths from the central red node to all other nodes (yellow and grey) and between adjacent yellow nodes.](983d280cd52a5a13a1b422e9bf040467_img.jpg) + +Legend: + +- MAC CCM\* +- > EAP-PSK PCHANNEL + +G.9903(12)-Amd.1(13)\_F10-2 + +Diagram illustrating confidentiality and security services in a network. A central red node is connected to five yellow nodes, which are in turn connected to five grey nodes. Solid black lines represent MAC CCM\* connections between adjacent nodes. Dashed blue lines with arrows represent the EAP-PSK PCHANNEL, showing secure communication paths from the central red node to all other nodes (yellow and grey) and between adjacent yellow nodes. + +**Figure 10-2 – Confidentiality and security** + +- At the EAP-PSK level: as defined in [IETF RFC 4764], the EAP-PSK provides confidentiality and integrity (and replay protection) services, also known as protected Channel (PCHANNEL) to the messages exchanged over the EAP between the EAP server and any peer. + +## 10.3 Anti-replay and DoS prevention + +It is always difficult to prevent DoS attacks, especially those targeting the physical level, but by nature their impact is limited to a small area. + +The CCM\* ciphering mode is generalized at the MAC layer. It prevents unauthenticated devices accessing the network and having malicious actions on routing, provisioning and any other low layer processes. The only exception is the well-controlled bootstrapping process. + +Moreover, an anti-replay mechanism is specified at the MAC sublayer. + +## 10.4 Authentication and key distribution protocol – Selections from [IETF RFC 3748] + +Authentication and key distribution are supported by the extensible authentication protocol (EAP) as given in [IETF RFC 3748] together with the selections listed in Table 10-1. + +**Table 10-1 – Selections from [IETF RFC 3748]** + +| Clause | Title and remarks/modifications | Statement | +|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 1 | Introduction | N | +| 2 | Extensible authentication protocol (EAP)
– Initial identity request (allows roaming and EAP method negotiation) is for further study and shall be bypassed. | S | +| 2.1 | Support for sequences | N | +| 2.2 | EAP multiplexing model
– Only one EAP method is defined (cf. 9.4.4). | S | +| 2.3 | Pass-through behaviour
– Over the LBP, the code field is slightly different from a regular EAP code field as specified in [IETF RFC 3748]. The conversion appears straightforward in both directions. The proper conversion shall apply when the EAP message is propagated over another protocol (i.e., RADIUS) and in case of integrity protection covering the EAP header. | S | +| 2.4 | Peer-to-peer operation | N | +| 3 | Lower layer behaviour | N | +| 3.1 | Lower layer requirements
– LBP and underlying protocols provide:
– Reliable transport
– Error detection (CRC)
– No lower layer security when bootstrapping
– MTU size greater than 1 020 octets (by fragmentation)
– No duplication
– Ordering guaranties | S | +| 3.2 | EAP usage within PPP | N/R | +| 3.3 | EAP usage within IEEE 802 | N/R | +| 3.4 | Lower layer indications | N | +| 4 | EAP packet format
– Over the LBP, the code field is slightly different from a regular EAP code field. | S | +| 4.1 | Request and response
– Over the LBP, the code field is slightly different from a regular EAP code field. | S | +| 4.2 | Success and failure
– Over the LBP, the code field is slightly different from a regular EAP code field. | S | +| 4.3 | Retransmission behaviour | N | +| 5 | Initial EAP request/response types
– For the type field, the only available values are 3 ("Nak" – in response only) and the value assigned to the EAP method (see clause 10.5). Other values are left for further study. | S | + +**Table 10-1 – Selections from [IETF RFC 3748]** + +| Clause | Title and remarks/modifications | Statement | +|------------|---------------------------------|-----------| +| 5.1 | Identity | N/R | +| 5.2 | Notification | N/R | +| 5.3 | "Nak" | N | +| 5.4 | MD5-Challenge | N/R | +| 5.5 | One-time password (OTP) | N/R | +| 5.6 | Generic token card (GTC) | N/R | +| 5.7 | Expanded types | N/R | +| 5.8 | Experimental | N/R | +| 6 | IANA considerations | N | +| 7 | Security considerations | N | +| 8 | Acknowledgements | I | +| 9 | References | N | +| Appendix A | Changes from [IETF RFC 2284] | I | + +## 10.5 EAP method + +The EAP protocol is very flexible and supports various EAP methods (EAP-MD5, EAP-AKA, EAP-TLS, etc.). Each method is characterized by its credentials (shared secret, certificate, SIM cards, etc.) and by its signature and encryption algorithms. + +For this Recommendation, the recommended method is the pre-shared key EAP method (EAP-PSK) as given in [IETF RFC 4764] together with the selections listed in Table 10-2. + +**Table 10-2 – Selections from [IETF RFC 4764]** + +| Clause | Title and remarks/modifications | Statement | +|------------|------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------| +| 1 | Introduction | N | +| 2 | Protocol overview | N | +| 3 | Cryptographic design of EAP-PSK | N | +| 4 | EAP-PSK message flows
– EAP-PSK extension capabilities are used for group key distribution in full compliance with [IETF RFC 4764]. See clause 10.5.2. | N | +| 5 | EAP-PSK message format
– EAP-PSK extension capabilities are used for group key distribution in full compliance with [IETF RFC 4764]. See clause 10.5.2. | N | +| 6 | Rules of operation for EAP-PSK protected channel | N | +| 7 | IANA considerations | N | +| 8 | Security considerations | N | +| 9 | Security claims | I | +| 10 | Acknowledgements | I | +| 11 | References | N | +| Appendix A | Generation of the PSK from a password – discouraged. | N/R | + +### 10.5.1 Overview of the EAP-PSK + +According to the EAP specification the EAP-PSK supports the following key hierarchy: + +| | | +|------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Pre-shared key (PSK) | PSK is the long-term 128-bit credential shared by the EAP server and the peer. | +| Authentication key (AK) | A 128-bit key derived from the PSK that the EAP peer and server use to mutually authenticate. | +| Key-derivation key (KDK) | A 128-bit key derived from the PSK that the EAP peer and server use to derive session keys (such as TEK, MSK and EMSK). | +| Transient EAP Key (TEK) | A session key that is used to establish a protected channel between the EAP peer and server during the EAP authentication. EAP-PSK uses a 128-bit TEK in conjunction with AES-128 in the EAX mode of operation as a cipher suite. | +| Master session key (MSK) | A session key derived between the EAP peer and server. The EAP-PSK generates a 512-bit MSK that may be used to provide security at the application level. | +| Extended master session key (EMSK) | A session key derived between the EAP peer and server. The EAP-PSK generates a 512-bit EMSK. It is not used in this Recommendation and shall not be generated. | + +![Figure 10-3 – EAP-PSK key hierarchy overview. This diagram illustrates the key derivation process for EAP-PSK between an EAP peer and an EAP server. Both start with a 128-bit PSK (Shared secret). The EAP peer derives a 128-bit KDK (Key derivation) and a 128-bit AK (Authentication) using AES-128 in modified counter mode. The EAP server does the same. The peer then generates a 128-bit RAND-P and an ID-P (EUI-64). The server generates a 128-bit RAND-S and an ID-S (EUI-64). They exchange messages (mess1 to mess4) for authentication. The peer then derives a 128-bit TEK (Transient), a 512-bit EMSK (Future use), and a 512-bit MSK (Key derivation). The server derives a 512-bit MSK (Key derivation), a 512-bit EMSK (Future use), and a 128-bit TEK (Transient). The peer uses the 128-bit TEK to encrypt a plain text payload using AES-128 EAX. The server uses the 128-bit TEK to decrypt the payload, verifying the 16-byte tag. The EAP-PSK protected channel is shown as a central oval containing a 32-bit nonce, a 22-byte header, and a plain text payload.](3f1b6583b85a3ffee7d3341f131a657c_img.jpg) + +Figure 10-3 – EAP-PSK key hierarchy overview. This diagram illustrates the key derivation process for EAP-PSK between an EAP peer and an EAP server. Both start with a 128-bit PSK (Shared secret). The EAP peer derives a 128-bit KDK (Key derivation) and a 128-bit AK (Authentication) using AES-128 in modified counter mode. The EAP server does the same. The peer then generates a 128-bit RAND-P and an ID-P (EUI-64). The server generates a 128-bit RAND-S and an ID-S (EUI-64). They exchange messages (mess1 to mess4) for authentication. The peer then derives a 128-bit TEK (Transient), a 512-bit EMSK (Future use), and a 512-bit MSK (Key derivation). The server derives a 512-bit MSK (Key derivation), a 512-bit EMSK (Future use), and a 128-bit TEK (Transient). The peer uses the 128-bit TEK to encrypt a plain text payload using AES-128 EAX. The server uses the 128-bit TEK to decrypt the payload, verifying the 16-byte tag. The EAP-PSK protected channel is shown as a central oval containing a 32-bit nonce, a 22-byte header, and a plain text payload. + +G.9903(12)-Amd.1(13)\_F10-3 + +**Figure 10-3 – EAP-PSK key hierarchy overview** + +### 10.5.2 Group key distribution + +The 128-bit group master key (GMK) is generated by the EAP server. Then it is securely and individually delivered to the EAP peers via the EAP-PSK protected channel (PCHANNEL), carried as a regular extension to EAP-PSK in message 3, as defined in clause 10.5.3. + +GMK is assumed to be random. GMK generation is considered as purely implementation dependent. + +GMK is distributed to the peer in two circumstances: + +- during the bootstrapping process; +- during the re-keying process. The GMK lifetime is rather long (several tens of years for meter collecting usage) due to the 4 byte counter included in the nonce. Nevertheless it is good policy to re-key the network. + +The re-keying procedure is handled at higher layers and is outside the scope of this Recommendation. + +It is recommended to change the GMK on a regular basis. The following criteria can be used (whichever comes first): + +- every 90 days +- when the PAN coordinator has sent 1000000 frames secured using the current GMK. + +### 10.5.3 Configuration extension format + +The configuration extension is defined to be transported in EAP-PSK PCHANNEL, in compliance with the generic extension field (EXT) (see [IETF RFC 4764] clause 5.3). The configuration extension format and fields are described in Table 10-3. + +**Table 10-3 – Configuration extension fields** + +| Field | Length | Description | +|--------------------------------------------------------------------------------------------|----------|----------------------------------------------------------------------------------------| +| EXT_Type | 1 byte | Indicates the type of the extension
0x02: configuration parameters | +| Parameters | variable | One or more configuration parameter, as defined in clause 9.4.4.2.1.3 and Figure 9-24. | +| NOTE – The EXT_Type value of 0x01 is reserved and should not be used in future extensions. | | | + +### 10.5.4 Peer side procedure + +Once a peer receives a configuration field embedded in a message 3, it shall apply the received parameters as defined in clause 9.4.4.2.1.3. + +In the case of bootstrapping, the following parameters are mandatory: Short-Addr, GMK and GMK-activation. + +If one or more parameter were invalid or missing, the peer sends a message 4 with R = DONE\_FAILURE and an embedded configuration field with at least one Parameter-result indicating the error. + +If all the parameters were correct, the peer sends a message 4 with R = DONE\_SUCCESS and an embedded configuration field with one Parameter-result indicating result = Success. + +In the case of bootstrapping, the peer keeps sending the frames in clear text up to the reception of an LBP ACCEPTED message. Then it starts sending ciphered frames using the active-GMK. + +In the case of re-keying, the peer keeps sending messages according to the previously assigned policy until the receipt of an LBP ACCEPTED message embedding a GMK-activation parameter. Then, it acknowledges the message with an LBP JOINING message embedding a Parameter-result and starts sending frames using the new GMK. + +After switching to the new GMK, a peer may keep receiving some messages encrypted with the previous GMK during a transient period. The previous GMK may be deleted after receipt of an LBP message including a GMK-remove parameter. + +### 10.5.5 Server side procedure + +The bootstrapping procedure is defined in clause 9.4.4.2.2. + +In the case of re-keying, the EAP server generates a new GMK. The new GMK-ID shall be chosen to be different from the key identifier associated with the previous GMK. + +Then it executes an EAP-PSK authentication exchange (starting with message EAP-PSK #1 to Accepted1(EAPSuccess) with every formerly associated peer, in order to transmit the new GMK. These messages are exchanged directly between the LBS and the peers (an LBA relay is not used) and ciphered following the PAN security configuration. + +If the EAP server does not receive the EAP responses from a peer, it may retry the EAP-PSK exchange described above. The PAN coordinator may remove the peer device using the procedure described in clause 9.4.4.2.2.7 if the EAP server has failed to complete the EAP-PSK exchange. + +Once the EAP server has completed the GMK transmission to all peers, it may send an LBP ACCEPTED message with a GMK-activation parameter to each peer to invoke switching to the new GMK (those messages are acknowledged by the peer). On reception of the GMK-activation parameter, the peer shall empty its DeviceTable (in order to allow re-use of previously allocated short addresses). + +Figure 10-4 describes the messages exchanged during a GMK re-keying procedure. + +![Sequence diagram of GMK re-keying message exchange between LBD, LBA, LBS, and LBS upper layer.](b1123ddbaa09fda65dcdf91d8caaa0f2_img.jpg) + +``` + +sequenceDiagram + participant LBD + participant LBA + participant LBS + participant LBS_upper_layer as LBS upper layer + + Note right of LBS_upper_layer: ADPM-LBP.Request (EAPReq(mes1)) + LBS_upper_layer->>LBS: ADPM-LBP.Request (EAPReq(mes1)) + LBS->>LBA: Challenge(EAPReq(mes1)) + LBA->>LBD: Challenge(EAPReq(mes1)) + LBD->>LBA: Joining(EAPRes(mes2)) + LBA->>LBS: Joining(EAPRes(mes2)) + LBS->>LBS_upper_layer: ADPM-LBP.Indication + Note right of LBS_upper_layer: ADPM-LBP.Request (EAPReq(mes3)) + LBS_upper_layer->>LBS: ADPM-LBP.Request (EAPReq(mes3)) + LBS->>LBA: Challenge(EAPReq(mes3)) + LBA->>LBD: Challenge(EAPReq(mes3)) + LBD->>LBA: Joining(EAPRes(mes4)) + LBA->>LBS: Joining(EAPRes(mes4)) + LBS->>LBS_upper_layer: ADPM-LBP.Indication + Note right of LBS_upper_layer: ADPM-LBP.Request (EAPSuccess) + LBS_upper_layer->>LBS: ADPM-LBP.Request (EAPSuccess) + LBS->>LBA: Accepted(EAPSuccess) + LBA->>LBD: Accepted(EAPSuccess) + LBS->>LBS_upper_layer: ADPM-LBP.Confirm + Note right of LBS_upper_layer: Repeat for all devices in PAN... + Note left of LBS_upper_layer: ADPM-LBP.Request (GMK-activation) + LBS_upper_layer->>LBS: ADPM-LBP.Request (GMK-activation) + LBS->>LBA: Accepted(GMK-activation) + LBA->>LBD: Accepted(GMK-activation) + LBS->>LBS_upper_layer: ADPM-LBP.Confirm + LBD->>LBA: Joining(Parameter-result) + LBA->>LBS: Joining(Parameter-result) + LBS->>LBS_upper_layer: ADPM-LBP.Indication + Note right of LBS_upper_layer: Repeat for all devices in PAN... + +``` + +The sequence diagram illustrates the message exchange for GMK re-keying. It begins with the LBS upper layer sending an ADPM-LBP.Request (EAPReq(mes1)) to the LBS. The LBS then sends a Challenge(EAPReq(mes1)) to the LBA, which in turn sends it to the LBD. The LBD responds with Joining(EAPRes(mes2)) to the LBA, which is passed to the LBS, which then sends an ADPM-LBP.Indication to the upper layer. This is followed by a second challenge-response cycle: ADPM-LBP.Request (EAPReq(mes3)) from the upper layer to LBS, Challenge(EAPReq(mes3)) from LBS to LBA to LBD, and Joining(EAPRes(mes4)) from LBD to LBA to LBS, leading to another ADPM-LBP.Indication. The EAP success phase follows with ADPM-LBP.Request (EAPSuccess) from the upper layer to LBS, Accepted(EAPSuccess) from LBS to LBA to LBD, and ADPM-LBP.Confirm from LBS to the upper layer. A loop 'Repeat for all devices in PAN...' follows. The GMK activation phase then occurs with ADPM-LBP.Request (GMK-activation) from the upper layer to LBS, Accepted(GMK-activation) from LBS to LBA to LBD, ADPM-LBP.Confirm from LBS to the upper layer, Joining(Parameter-result) from LBD to LBA to LBS, and ADPM-LBP.Indication from LBS to the upper layer. A final loop 'Repeat for all devices in PAN...' is indicated. + +Sequence diagram of GMK re-keying message exchange between LBD, LBA, LBS, and LBS upper layer. + +Figure 10-4 – GMK re-keying message sequence chart + +# Annex A + +## Protocol implementation conformance statement + +(This annex forms an integral part of this Recommendation.) + +## A.1 Overview + +Compliance with the clauses of [IEEE 802.15.4] shall be consistent with the extensions and selections defined in this annex. + +The first part of this annex entirely takes as reference the protocol implementation conformance statement of [IEEE 802.15.4], Annex D. + +The second part of this annex gives similar tables to ensure that all items related to the physical layer of ITU-T G.9903 have been taken into account. + +## A.2 PICS proforma tables + +### A.2.1 Functional device types (from clause D.7.1 of [IEEE 802.15.4]) + +Table A.1 – PICS – Functional device types (from clause D.7.1 of [IEEE 802.15.4]) + +| Item number | Support | | | Comments | +|-------------|---------|-----|----|----------| +| | N/A | Yes | No | | +| FD1 | | X | | | +| FD2 | | | X | | +| FD3 | | X | | | +| FD4 | | X | | | +| FD5 | | X | | | + +### A.2.2 PHY functions (from clause D.7.2.1 of [IEEE 802.15.4]) + +Table A.2 – PICS – PHY functions (from clause D.7.2.1 of [IEEE 802.15.4]) + +| Item number | Support | | | Comments | +|-------------|---------|-----|----|----------------------------| +| | N/A | Yes | No | | +| PLF1 | | X | | | +| PLF2 | | X | | | +| PLF3 | X | | | Radio specific requirement | +| PLF4 | X | | | Radio specific requirement | +| PLF5 | X | | | Radio specific requirement | +| PLF6 | | X | | | +| PLF7 | X | | | Radio specific requirement | +| PLF8 | | X | | | +| PLF8.1 | X | | | Radio specific requirement | +| PLF8.2 | | X | | | +| PLF8.3 | X | | | Radio specific requirement | + +### A.2.3 PHY packet (from clause D.7.2.2 of [IEEE 802.15.4]) + +**Table A.3 – PICS – PHY packet (from clause D.7.2.2 of [IEEE 802.15.4])** + +| Item number | Support | | | Comments | +|-------------|---------|-----|----|----------| +| | N/A | Yes | No | | +| PLP1 | | X | | | + +### A.2.4 Radio frequency (from clause D.7.2.3 of [IEEE 802.15.4]) + +**Table A.4 – PICS – Radio frequency (from clause D.7.2.3 of [IEEE 802.15.4])** + +| Item number | Support | | | Comments | +|-------------|---------|-----|----|----------------------------| +| | N/A | Yes | No | | +| RF1 | X | | | Radio specific requirement | +| RF1.1 | X | | | Radio specific requirement | +| RF1.2 | X | | | Radio specific requirement | +| RF1.3 | X | | | Radio specific requirement | +| RF1.4 | X | | | Radio specific requirement | +| RF2 | X | | | Radio specific requirement | + +### A.2.5 MAC sublayer functions (from clause D.7.3.1 of [IEEE 802.15.4]) + +**Table A.5 – PICS – MAC sublayer functions (from clause D.7.3.1 of [IEEE 802.15.4])** + +| Item number | Support | | | Comments | +|-------------|---------|-----|----|----------------------------------------| +| | N/A | Yes | No | | +| MLF1 | | X | | | +| MLF1.1 | | | X | Indirect transmission is not supported | +| MLF2 | | X | | | +| MLF2.1 | | X | | | +| MLF2.2 | | X | | | +| MLF2.3 | | X | | | +| MLF3 | | X | | | +| MLF3.1 | | X | | | +| MLF3.2 | | X | | | +| MLF4 | | X | | | +| MLF5 | | | X | | +| MLF5.1 | | | X | | +| MLF5.2 | | | X | | +| MLF6 | | X | | | +| MLF7 | | X | | | +| MLF8 | | | X | Performed by 6LoWPAN | +| MLF9 | | X | | | +| MLF9.1 | | X | | | + +**Table A.5 – PICS – MAC sublayer functions (from clause D.7.3.1 of [IEEE 802.15.4])** + +| Item number | Support | | | Comments | +|-------------|---------|-----|----|-----------------------------------------------| +| | N/A | Yes | No | | +| MLF9.2 | | X | | | +| MLF9.2.1 | | X | | | +| MLF9.2.2 | | X | | | +| MLF10.1 | X | | | Radio specific requirement | +| MLF10.2 | | X | | | +| MLF10.3 | | | X | Not necessary for non-beacon-enabled networks | +| MLF10.4 | | | X | | +| MLF11 | | | X | | +| MLF12 | | | X | | +| MLF13 | | | X | | + +**A.2.6 MAC frames (from clause D.7.3.2 of [IEEE 802.15.4])** + +**Table A.6 – PICS – MAC frames (from clause D.7.3.2 of [IEEE 802.15.4])** + +| Item number | Support | | | | | | Comments | | +|-------------|-------------|-----|----|----------|-----|----|---------------------------------------------------|--| +| | Transmitter | | | Receiver | | | | | +| | N/A | Yes | No | N/A | Yes | No | | | +| MF1 | | X | | | X | | | | +| MF2 | | X | | | X | | | | +| MF3 | | X | | | X | | Acknowledgement frames are described in clause 9. | | +| MF4 | | X | | | X | | | | +| MF4.1 | | | X | | | X | Association performed by 6LoWPAN | | +| MF4.2 | | | X | | | X | Association performed by 6LoWPAN | | +| MF4.3 | | | X | | | X | Association performed by 6LoWPAN | | +| MF4.4 | | | X | | | X | No transaction support | | +| MF4.5 | | | X | | | X | Performed by 6LoWPAN | | +| MF4.6 | | | X | | | X | | | +| MF4.7 | | X | | | X | | | | +| MF4.8 | | | X | | | X | | | +| MF4.9 | | | X | | | X | | | + +## Annex B + +### Routing cost + +(This annex forms an integral part of this Recommendation.) + +This annex describes the link cost and route cost computation to be used for routing. + +In this Annex, the conventional rounding rule of "rounding half towards zero" shall be used when values are rounded. + +A route cost is defined as the sum of all the link costs on the route. As described in Annex D, a route cost is a 16-bit unsigned integer, lower cost values meaning better routes. + +The route cost of route P, $RC_P$ , where P refers to the N-hop route going from node 0 to node N-1 through nodes 1 ... N-1 is computed as: + +$$RC_P = \sum_{i=0}^{N-1} C_{i,i+1}$$ + +where $C_{i,i+1}$ is the link cost between devices i and (i+1). + +Different link cost computation methods can be implemented, each identified by their respective *adpMetricType* value. This annex defines the link computation cost specified below. + +#### B.1 Composite metric method + +The composite metric method is associated with the *adpMetricType* value of 0x0F and defines the link cost as follows: + +$$LinkCost = \max(C_{i \rightarrow j}, C_{j \rightarrow i}) + AdpKrt * \frac{NumberOfActiveRoutes}{MaximumNumberOfActiveRoutes} + adpKh$$ + +where $C_{i \rightarrow j}$ and $C_{j \rightarrow i}$ are the directional link costs (forward and reverse direction, respectively) between i to j. The directional link cost is computed as follow: + +$$\begin{aligned} DirectionalLinkCost = & adpKr * MOD_{Kr} + adpKm * MOD_{Km} \\ & + adpKc * \frac{(MaximumNumberOfTones - NumberOfActiveTones)}{MaximumNumberOfTones} \\ & + adpKq * MAX \left( 0, MIN \left( 1, \frac{adpHighLQIValue - LQI}{adpHighLQIValue - adpLowLQIValue} \right) \right) \end{aligned}$$ + +where: + +$MOD_{Kr} = 1$ for robust mode, 0 for other modulations + +$MOD_{Km} = 3$ for DBPSK or BPSK modulation (including robust mode), 2 for DQPSK or QPSK modulation, 1 for D8PSK or 8-PSK modulation and 0 for 16-QAM modulation + +and *adpKr*, *adpKm*, *adpKc*, *adpKq*, *adpKh* and *adpKrt* as defined in Table 9-28. + +For the forward direction ( $C_{i \rightarrow j}$ ), modulation, tone map and LQI information is based on quality measurement of the received routing messages. When a unicast frame is received, the frame's modulation and tone map configuration may be used instead. + +For the reverse direction ( $C_{j \rightarrow i}$ ), the directional link cost may be obtained as follows (see the flowchart in Figure B.1): + +- Modulation, tone map and LQI information for computing the directional link cost shall be taken from the neighbour table, if the parameters of the neighbour table entry of the destination node are valid. + +- If modulation, tone map and LQI information are not available and if adpRLCEnabled is set to TRUE, then the RLC mechanism defined in clause 9.4.3.2.6 shall be used. If the procedure is successful, the resulting RLCREP message will then provide the reverse directional link cost value. In case of failure, the next method shall be used. +- Else, the forward link cost is used to estimate the reverse link cost, using the formula: + - $C_{j \rightarrow i} = C_{i \rightarrow j} + \text{adpAddRevLinkCost}$ + - adpAddRevLinkCost represents an additional cost to take into account a possible asymmetry in the link. This attribute is defined in Table 9-28. + +![Flowchart explaining the directional link cost computation. The process starts with a decision: 'If modulation, tone map and LQI are available in the neighbour table'. If YES, it goes to 'Generate the directional link cost with these parameters.'. If NO, it goes to 'If adpEnableRLC is TRUE'. If YES, it goes to 'If RLC procedure is successful'. If YES, it goes to 'Generate the directional link cost with these parameters.'. If NO, it goes to 'Generate the directional link cost using forward Link Cost and adpAddRevLinkCost'. If NO from the 'If adpEnableRLC is TRUE' decision, it also goes to 'Generate the directional link cost using forward Link Cost and adpAddRevLinkCost'.](76355e5a3237d2474f3ae61bbeba2eb5_img.jpg) + +``` + +graph TD + A{If modulation, tone map and LQI are available in the neighbour table} -- YES --> B([Generate the directional link cost with these parameters.]) + A -- NO --> C{If adpEnableRLC is TRUE} + C -- YES --> D{If RLC procedure is successful} + C -- NO --> E([Generate the directional link cost using forward Link Cost and adpAddRevLinkCost]) + D -- YES --> F([Generate the directional link cost with these parameters.]) + D -- NO --> E + +``` + +Flowchart explaining the directional link cost computation. The process starts with a decision: 'If modulation, tone map and LQI are available in the neighbour table'. If YES, it goes to 'Generate the directional link cost with these parameters.'. If NO, it goes to 'If adpEnableRLC is TRUE'. If YES, it goes to 'If RLC procedure is successful'. If YES, it goes to 'Generate the directional link cost with these parameters.'. If NO, it goes to 'Generate the directional link cost using forward Link Cost and adpAddRevLinkCost'. If NO from the 'If adpEnableRLC is TRUE' decision, it also goes to 'Generate the directional link cost using forward Link Cost and adpAddRevLinkCost'. + +G.9903(14)\_FB.1 + +**Figure B.1 – Flowchart explaining the directional link cost computation** + +## Annex C + +### Device starting sequence of messages + +(This annex forms an integral part of this Recommendation.) + +Each device shall start with an adpDeviceType attribute of Not\_Defined (see Table 9-28) and then the following procedure is performed: + +- a) Reset the equipment by sending the ADPM-RESET.request. +- b) Set the type of the device to PAN device or PAN coordinator mode and optionally set the PIB parameters to configure it. +- c) If the equipment is a PAN device it shall perform the following steps: + - discovery procedure by invoking the ADPM-DISCOVERY.request; + - if there is a PAN device or a PAN coordinator in its POS, it shall then invoke the ADPM-NETWORK-JOIN.request to perform the bootstrapping procedure. +- d) Otherwise (if the equipment is a PAN coordinator) it shall perform the following steps: + - discovery procedure by invoking the ADPM-DISCOVERY.request; + - if there is no PAN device in the PAN coordinator's POS, it shall invoke the ADPM-NETWORK-START to start a network; otherwise, it should inform the rest of the system that a PAN is already operating in its POS, and may start a new network afterwards as described in clause 9.5.1. The procedures and decisions associated with this behaviour are implementation specific. + +Equipment cannot send or receive data packets unless they have joined the network. + +## Annex D + +### The lightweight on-demand Ad hoc distance-vector routing protocol – next generation (LOADng) + +(This annex forms an integral part of this Recommendation.) + +#### D.1 Introduction + +The lightweight on-demand ad-hoc distance-vector routing protocol –next generation (LOADng) is a reactive routing protocol. As a reactive protocol, the basic operations of LOADng include the generation of route requests (RREQs) by a LOADng router (originator) for when discovering a route to a destination, forwarding of such RREQs until they reach the destination LOADng router, generation of route replies (RREPs) upon receipt of an RREQ by the indicated destination, and unicast hop-by-hop forwarding of these RREPs towards the originator. If a route is detected to be broken, e.g., if forwarding of a data packet to the recorded next hop on the route towards the intended destination is detected to fail, a Route Error (RERR) message is returned to the originator of that data packet to inform the originator about the route breakage. + +#### D.2 Terminology and notation + +##### D.2.1 Message and message field notation + +LOADng routers generate and process messages, each of which has a number of distinct fields. For describing the protocol operation, specifically the generation and processing of such messages, the following notation is employed: + +MsgType.field + +where: + +MsgType: is the type of message (e.g., RREQ or RREP) + +field: is the field in the message (e.g., originator). + +The different messages, their fields and their meaning are described in clause D.6. + +The motivation for separating the high-level messages and their content from the low-level encoding and frame format for transmission is to allow discussions of the protocol logic to be separated from the message encoding and frame format, and to support different frame formats. + +##### D.2.2 Variable notation + +Variables are introduced into the specification solely as a way of clarifying the description. The following notation is used: + +MsgType.field – If "field" is a field in the message MsgType, then MsgType.field is also used to represent the value of that field. + +bar – A variable (not prepended by MsgType), usually obtained through calculations based on the value(s) of element(s). + +##### D.2.3 Other notation + +This document uses the following additional notational conventions: + +a:= b An assignment operator, whereby the left side (a) is assigned the value of the right side (b). + +c = d A comparison operator, returning TRUE if the value of the left side (c) is equal to the value of the right side (d). + +#### D.2.4 Terminology + +This document uses the following terminology: + +| | | +|--------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| jLOADng router – | A router that implements this routing protocol. A LOADng router is equipped with at least one, and possibly more, LOADng interfaces. | +| LOADng interface – | A LOADng router's attachment to a communications medium, over which it receives and generates control messages, according to this Recommendation. A LOADng interface is assigned one or more addresses. | +| Link – | A link between two LOADng interfaces exists if either of them can receive control messages, according to this Recommendation, from the other. | +| Message – | The fundamental entity carrying protocol information, in the form of address objects and TLVs. | +| Link metric – | The cost (weight) of a link between a pair of LOADng interfaces. | +| Route metric – | The sum of the link metrics for the links that an RREQ or RREP has crossed. | + +#### D.3 Applicability statement + +LOADng is a reactive protocol, i.e., routes are discovered only when a data packet is sent by a router (e.g., on behalf of an attached host), and when the router has no route for this destination. In this case, the router floods route requests (RREQ) throughout the network for discovering the destination. Reactive protocols require state only for the routes currently in use, contrary to proactive protocols, which periodically send control traffic and store routes to all destinations in the network. Flooding RREQs may lead to frame collisions and therefore data loss. Moreover, each transmission on a network interface consumes energy, reducing the life-time of battery-driven routers. Consequently, in order to reduce the amount of control traffic, LOADng (and in general reactive protocols) are most suitable under the following constraints: + +- Few concurrent traffic flows in the network (i.e., traffic only flows between a few sources and destinations). +- State requirements on the router are very stringent, i.e., it is beneficial to store only few routes on a router. + +Specifically, the applicability of LOADng is determined by its characteristics, which for this protocol are: + +- is a reactive routing protocol; +- is designed to work in networks with dynamic topology in which the links may be lossy due to collisions, channel instability or movement of routers; +- supports the use of optimized flooding for RREQs; +- enables any LOADng router to discover bidirectional routes to destinations in the routing domain, i.e., to any other LOADng router, as well as hosts or networks attached to that LOADng router, in the same routing domain; +- supports addresses of any length, from 16 octets to a single octet; +- supports per-destination route maintenance; if a destination becomes unreachable, rediscovery of that single (bidirectional) route is performed, without the need for global topology recalculation. + +#### D.4 Protocol overview and functioning + +The objective of this protocol is for each LOADng router to independently: + +- Discover a bi-directional route to any destination in the network. + +- Establish a route only when there is data traffic to be sent along that route. +- Maintain a route only for as long as there is data traffic being sent along that route. +- Generate control traffic based on network events only: when a new route is required, or when an active route is detected broken. Specifically, this protocol does not require periodic signalling. + +#### D.4.1 Overview + +These objectives are achieved, for each LOADng router, by performing the following tasks: + +- When having a data packet to deliver to a destination, for which no tuple in the routing set exists and where the data packet source is local to that LOADng router (i.e., is an address in the local interface set or destination address set of that LOADng router), generate a Route Request (RREQ) encoding the destination address, and transmit this RREQ over all of its LOADng interfaces. +- Upon receiving an RREQ, insert or refresh a tuple in the Routing Set, recording a route towards the originator address from the RREQ, as well as to the neighbour LOADng router from which the RREQ was received. This will install the Reverse Route (towards the originator address from the RREQ). +- Upon receiving an RREQ, inspect the indicated destination address: + - If that address is an address in the destination address set or in the local interface set of the LOADng router, generate a Route Reply (RREP), which is unicast in a hop-by-hop fashion along the installed reverse route. + - If that address is not an address in the destination address set or in the local interface set of the LOADng router, consider the RREQ as a candidate for forwarding. +- When an RREQ is considered a candidate for forwarding, retransmit it according to the flooding operation, specified for the network. +- Upon receiving an RREP, insert or refresh a tuple in the routing set, recording a route towards the originator address from the RREP, as well as to the neighbour LOADng router, from which that RREP was received. This will install the forward route (towards the originator address from the RREP). The originator address is either an address from the local interface set of the LOADng router, or an address from its destination address set (i.e., an address of a host attached to that LOADng router). +- Upon receiving an RREP, forward it, as unicast, to the recorded next hop along the corresponding reverse route until the RREP reaches the LOADng router that has the destination address from the RREP in its local interface set or destination address set. +- When forwarding an RREQ or RREP, update the route metric, as contained in that RREQ or RREP message. + +A LOADng router generating an RREQ specifies which metric type it desires. Routers receiving an RREQ will process it and update route metric information in the RREQ according to that metric, if they can. All LOADng routers, however, will update information in the RREQ so as to be able to support a "hop-count" default metric. If a LOADng router is not able to understand the metric type, specified in an RREQ, it will update the route metric value to its maximum value, so as to ensure that this is indicated to the further recipients of the RREQ. Once the route metric value is set to its maximum value, no LOADng router along the path towards the destination may change the value. + +#### D.4.2 LOADng routers and LOADng interfaces + +A LOADng router has a set of at least one, and possibly more, LOADng interfaces. Each LOADng interface: + +- is configured with one or more addresses; + +- has a number of interface parameters. + +In addition to a set of LOADng interfaces as described above, each LOADng router: + +- has a number of router parameters; +- has an information base; +- generates and processes RREQ, RREP, RREP\_ACK and RERR messages, according to this Recommendation. + +#### D.4.3 Information base overview + +Necessary protocol state is recorded by way of five information sets: the "Routing Set", the "Local Interface Set", the "Blacklisted Neighbour Set", the "Destination Address Set", and the "Pending Acknowledgment Set". + +The routing set contains tuples, each representing the next-hop on, and the metric of, a route towards a destination address. Additionally, the routing set records the sequence number of the last message received from the destination. This information is extracted from the message (RREQ or RREP) that generated the tuple so as to enable routing. The routing table is to be updated using this routing set. (A LOADng router may choose to use any or all destination addresses in the routing set to update the routing table, this selection is outside the scope of this Recommendation.) + +The local interface set contains tuples, each representing a local LOADng interface of the LOADng router. Each tuple contains a list of one or more addresses of that LOADng interface. + +The blacklisted neighbour set contains tuples representing neighbour LOADng interface addresses of a LOADng router with which unidirectional connectivity has been recently detected. + +The destination address set contains tuples representing addresses, for which the LOADng router is responsible, i.e., addresses of this LOADng router, or of hosts and networks directly attached to this LOADng router and which use it to connect to the routing domain. These addresses may in particular belong to devices which do not implement LOADng, and thus cannot process LOADng messages. A LOADng router provides connectivity to these addresses by generating RREPs in response to RREQs directed towards them. + +The pending acknowledgment set contains tuples, representing transmitted RREPs for which an RREP\_ACK is expected, but where this RREP\_ACK has not yet been received. + +The routing set, the blacklisted neighbour set and the pending acknowledgment set are updated by this protocol. The local interface set and the destination address set are used, but not updated by this protocol. + +#### D.4.4 Signalling overview + +This protocol generates and processes the following routing messages: + +**Route request (RREQ)** – Generated by a LOADng router when it has a data packet to deliver to a given destination, where the data packet source is local to that LOADng router (i.e., is an address in the local interface set or destination address set of that LOADng router), but where it does not have an available tuple in its routing set indicating a route to that destination. An RREQ contains: + +- the (destination) address to which a forward route is to be discovered by way of soliciting the LOADng router with that destination address in its local interface set or in its destination address set to generate an RREP; +- the (originator) address for which a reverse route is to be installed by RREQ forwarding and processing, i.e., the source address of the data packet which triggered the RREQ generation; +- the sequence number of the LOADng router, generating the RREQ. + +An RREQ is flooded through the network, according to the flooding operation specified for the network. + +**Route reply (RREP)** – Generated as a response to an RREQ by the LOADng router which has the address (destination) from the RREQ in its local interface set or in its destination address set. An RREP is sent in unicast towards the originator of that RREQ. An RREP contains: + +- the (originator) address to which a forward route is to be installed when forwarding the RREP; +- the (destination) address towards which the RREP is to be sent. More precisely, the destination address determines the unicast route which the RREP follows; +- the sequence number of the LOADng router, generating the RREP. + +**Route reply acknowledgment (RREP\_ACK)** – Generated by a LOADng router as a response to an RREP, in order to signal to the neighbour that transmitted the RREP that the RREP was successfully received. Receipt of an RREP\_ACK indicates that the link between these two neighbouring LOADng routers is bidirectional. An RREP\_ACK is unicast to the neighbour from which the RREP has arrived, and is not forwarded. RREP\_ACKs are generated only in response to an RREP which, by way of a flag, has explicitly indicated that an RREP\_ACK is desired. + +**Route error (RERR)** – Generated by a LOADng router when a link on an active route to a destination is detected as broken by way of inability to forward a data packet towards that destination. An RERR is unicast to the source of the undeliverable data packet. + +## D.5 Protocol parameters + +The following parameters and constants are used in this specification. + +### D.5.1 Protocol and port numbers + +None. + +### D.5.2 Router parameters + +NET\_TRAVERSAL\_TIME is the maximum time that a packet is expected to take when traversing from one end of the network to the other. + +RREQ\_RETRIES is the maximum number of subsequent RREQs that a particular LOADng router may generate in order to discover a route to a destination, before declaring this destination unreachable. + +RREQ\_MIN\_INTERVAL is the minimal interval (in milliseconds) of RREQs that a particular LOADng router is allowed to send. + +R\_HOLD\_TIME is the minimum time a routing tuple SHOULD be kept in the routing set after it was last refreshed. + +MAX\_DIST is the value representing the maximum possible metric (R\_metric field). + +B\_HOLD\_TIME is the time during which the link between the neighbour LOADng router and this LOADng router shall be considered as non-bidirectional, and that therefore RREQs received from that neighbour LOADng router shall be ignored during that time (B\_HOLD\_TIME). + +B\_HOLD\_TIME should be greater than $2 \times \text{NET\_TRAVERSAL\_TIME} \times \text{RREQ\_RETRIES}$ , to ensure that subsequent RREQs will reach the destination via a route, excluding the link to the blacklisted neighbour. + +MAX\_HOP\_LIMIT is the maximum limit of the number of hops that LOADng routing messages are allowed to traverse. + +### **D.5.3 Interface parameters** + +Different LOADng interfaces (on the same or on different LOADng routers) may employ different interface parameter values and may change their interface parameter values dynamically. A particular case is where all LOADng interfaces on all LOADng routers within a given LOADng routing domain employ the same set of interface parameter values. + +RREQ\_MAX\_JITTER is the default value of MAXJITTER used in [b-IETF RFC 5148] for RREQ messages forwarded by this LOADng router on this interface. + +RREP\_ACK\_REQUIRED is a Boolean flag, which indicates (if set) that the LOADng router is configured to expect that each RREP it sends be confirmed by an RREP\_ACK, or (if cleared) that no RREP\_ACK is expected for this interface. + +USE\_BIDIRECTIONAL\_LINK\_ONLY is a Boolean flag, which indicates if the LOADng router only uses verified bidirectional links for data packet forwarding on this interface. It is set by default. If cleared, the LOADng router can use links which have not been verified to be bidirectional on this interface. + +RREP\_ACK\_TIMEOUT is the minimum amount of time after transmission of an RREP, that a LOADng router SHOULD wait for an RREP\_ACK from a neighbour LOADng router, before considering the link to this neighbour to be unidirectional. + +### **D.5.4 Constants** + +MAX\_HOP\_COUNT is the maximum number of hops as representable by the encoding that is used. It shall not be used to limit the scope of a message; the router parameter MAX\_HOP\_LIMIT can be used to limit the scope of a LOADng routing message. + +## **D.6 Protocol message content** + +The protocol messages, generated and processed by LOADng, are described in this clause using the notational conventions described in clause D.2. Unless stated otherwise, the message fields described below are set by the LOADng router that generates the message, and shall not be changed by intermediate LOADng routers. + +### **D.6.1 Route request (RREQ) messages** + +A route request (RREQ) message has the following fields: + +RREQ.addr-length is an unsigned integer field, encoding the length of the originator and destination addresses as follows: RREQ.addr-length := the length of an address in octets – 1 + +RREQ.seq-num is an unsigned integer field, containing the sequence number (see clause D.8) of the LOADng router, generating the RREQ message. + +RREQ.metric-type is an unsigned integer field and specifies the type of metric requested by this RREQ. + +RREQ.route-metric is a unsigned integer field, of length defined by RREQ.metric-type, which specifies the route metric of the route (the sum of the link metrics of the links), through which this RREQ has travelled. + +RREQ.hop-count is an unsigned integer field and specifies the total number of hops which the message has traversed from the RREQ.originator. + +RREQ.hop-limit is an unsigned integer field and specifies the number of hops that the message is allowed to traverse. + +RREQ.originator is an identifier of RREQ.addr-length + 1 octets, specifying the address of the LOADng interface over which this RREQ was generated, and to which a route (the "reverse route") is supplied by this RREQ. In case the message is generated by a LOADng router on behalf of an + +attached host, RREQ.originator corresponds to an address of that host, otherwise it corresponds to an address of the sending LOADng interface of the LOADng router. + +RREQ.destination is an identifier of RREQ.addr-length + 1 octets, specifying the address to which the RREQ should be sent, i.e., the destination address for which a route is sought. + +The following fields of an RREQ message are immutable, i.e., they shall not be changed during the processing or forwarding of the message: RREQ.addr-length, RREQ.seq-num, RREQ.originator, and RREQ.destination. + +The following fields of an RREQ message are mutable, i.e., they will be changed by intermediate routers during processing or forwarding, as specified in clause D.12.2 and clause D.12.3: REQ.metric-type, RREQ.route-metric, RREQ.hop-limit and RREQ.hop-count. + +Any additional field that is added to the message by an extension to this protocol, e.g., by way of TLVs, shall be considered immutable, unless the extension specifically defines the field as mutable. + +## **D.6.2 Route reply (RREP) messages** + +A route reply (RREP) message has the following fields: + +RREP.addr-length is an unsigned integer field, encoding the length of the originator and destination addresses as follows: RREP.addr-length := the length of an address in octets – 1 + +RREP.seq-num is an unsigned integer field, containing the sequence number (see clause D.8) of the LOADng router, generating the RREP message. + +RREP.metric-type is an unsigned integer field and specifies the type of metric, requested by this RREP. + +RREP.route-metric is an unsigned integer field, of length defined by RREP.metric-type, which specifies the route metric of the route (the sum of the link metrics of the links) through which this RREP has travelled. + +RREP.ackrequired is a Boolean flag which, when set ('1'), at least one RREP\_ACK shall be generated by the recipient of an RREP if the RREP is successfully processed. When cleared ('0'), an RREP\_ACK shall not be generated in response to processing of the RREP. + +RREP.hop-count is an unsigned integer field and specifies the total number of hops which the message has traversed from RREP.originator to RREP.destination. + +RREP.hop-limit is an unsigned integer field and specifies the number of hops that the message is allowed to traverse. + +RREP.originator is an identifier of RREP.addr-length + 1 octets, specifying the address for which this RREP was generated, and to which a route (the "forward route") is supplied by this RREP. In case the message is generated on a LOADng router on behalf of an attached host, RREP.originator corresponds to an address of that host, otherwise it corresponds to an address of the LOADng interface of the LOADng router, over which the RREP was generated. + +RREP.destination is an identifier of RREP.addr-length + 1 octets, specifying the address to which the RREP should be sent (i.e., this address is equivalent to RREQ.originator of the RREQ that triggered the RREP.) + +The following fields of an RREP message are immutable, i.e., they shall not be changed during the processing or forwarding of the message: RREP.addr-length, RREP.seq-num, RREP.originator and RREP.destination. + +The following fields of an RREP message are mutable, i.e., they will be changed by intermediate routers during processing or forwarding, as specified in clause D.13.2 and clause D.13.3: RREP.metric-type, RREP.route-metric, RREP.ackrequired, RREP.hop-limit and RREP.hop-count. + +Any additional field that is added to the message by an extension to this protocol, e.g., by way of TLVs, shall not be considered immutable, unless the extension specifically defines the field as mutable. + +#### **D.6.3 Route reply acknowledgement (RREP\_ACK) messages** + +A route reply acknowledgement (RREP\_ACK) message has the following fields: + +RREP\_ACK.addr-length is an unsigned integer field, encoding the length of the destination and originator addresses as follows: RREP\_ACK.addr-length := the length of an address in octets – 1 + +RREP\_ACK.seq-num is an unsigned integer field and contains the value of RREP.seq-num from the RREP for which this RREP\_ACK is sent. + +RREP\_ACK.destination is an identifier of RREP\_ACK.addr-length + 1 octets and contains the value of the RREP.originator field from the RREP for which this RREP\_ACK is sent. + +RREP\_ACK messages are sent only across a single link and are never forwarded. + +#### **D.6.4 Route error (RERR) messages** + +A route error (RERR) message has the following fields: + +RERR.addr-length is an unsigned integer field, encoding the length of RERR.destination and RERR.unreachableAddress, as follows: RERR.addr-length := the length of an address in octets – 1 + +RERR.errorcode is an unsigned integer field and specifies the reason for the error message being generated. + +RERR.unreachableAddress is an identifier of RERR.addr-length + 1 octets, specifying an address, which has become unreachable, and for which an error is reported by way of this RERR message. + +RERR.originator is an identifier of RERR.addr-length + 1 octets, specifying the address of the LOADng interface over which this RERR was generated by a LOADng router. + +RERR.destination is an identifier of RERR.addr-length + 1 octets, specifying the destination address of this RERR message. RERR.destination is in general, the source address of a data packet, for which delivery to RERR.unreachableAddress has failed, and the unicast destination of the RERR message is the LOADng router which has RERR.destination listed in a local interface tuple or in a destination address tuple. + +RERR.hop-limit is an unsigned integer field and specifies the number of hops that the message is allowed to traverse. + +The following fields of an RERR message are immutable, i.e., they shall not be changed during processing or forwarding of the message: RERR.addr-length, RERR.errorcode, RERR.unreachableAddress, RERR.originator and RERR.destination. + +The following fields of an RERR message are mutable, i.e., they will be changed by intermediate routers during processing or forwarding, as specified in clause D.14.3 and clause D.14.4: RERR.hop-limit. + +Any additional field that is added to the message by an extension to this protocol, e.g., by way of TLVs, shall be considered immutable, unless the extension specifically defines the field as mutable. + +### **D.7 Information base** + +Each LOADng router maintains an information base, containing the information sets necessary for protocol operation, as described in the following clauses. The organization of information into these information sets is non-normative, given so as to facilitate the description of message generation, forwarding and processing rules in this Recommendation. An implementation may choose any representation or structure for when maintaining this information. + +### D.7.1 Routing set + +The routing set records the next hop on the route to each known destination, when such a route is known. It consists of routing tuples: + +(R\_dest\_addr, R\_next\_addr, R\_metric, R\_metric\_type, R\_hop\_count, R\_seq\_num, R\_bidirectional, R\_local\_iface\_addr, R\_valid\_time) + +where: + +R\_dest\_addr is the address of the destination, either an address of a LOADng interface of a destination LOADng router, or an address of an interface reachable via the destination LOADng router, but which is outside the routing domain. + +R\_next\_addr is the address of the "next hop" on the selected route to the destination. + +R\_metric is the metric associated with the selected route to the destination with address R\_dest\_addr. + +R\_metric\_type specifies the metric type for this routing tuple – in other words, how R\_metric is defined and calculated. + +R\_hop\_count is the hop count of the selected route to the destination with address R\_dest\_addr. + +R\_seq\_num is the value of the RREQ.seq-num or RREP.seq-num field of the RREQ or RREP which installed or last updated this tuple. For the routing tuples installed by previous hop information of RREQ or RREP, R\_seq\_num shall be set to –1. + +R\_bidirectional is a Boolean flag, which specifies if the routing tuple is verified as representing a bidirectional route. Data traffic SHOULD only be routed through a routing tuple with R\_bidirectional flag equals TRUE, unless the LOADng router is configured as accepting routes without bidirectionality verification explicitly by setting USE\_BIDIRECTIONAL\_LINK\_ONLY to FALSE of the interface with R\_local\_iface\_address. + +R\_local\_iface\_addr is an address of the local LOADng interface, through which the destination can be reached. + +R\_valid\_time specifies the time until when the information recorded in this routing tuple is considered valid. + +### D.7.2 Local interface set + +A LOADng router's local interface set records its local LOADng interfaces. It consists of local interface tuples, one per LOADng interface: + +(I\_local\_iface\_addr\_list) + +where: + +I\_local\_iface\_addr\_list is an unordered list of the network addresses of this LOADng interface. + +The implementation shall initialize the local interface set with at least one tuple containing at least one address of a LOADng interface. The local interface set shall be updated if there is a change of the LOADng interfaces of a LOADng router (i.e., a LOADng interface is added, removed or changes addresses). + +### D.7.3 Blacklisted neighbour set + +The blacklisted neighbour set records the neighbour LOADng interface addresses of a LOADng router, with which connectivity has been detected to be unidirectional. Specifically, the blacklisted neighbour set records neighbours from which an RREQ has been received (i.e., through which a forward route would be possible) but to which it has been determined that it is not possible to + +communicate (i.e., forwarding route replies via this neighbour fails, rendering installing the forward route impossible). It consists of blacklisted neighbour tuples: + +(B\_neighbour\_address, B\_valid\_time) + +where: + +B\_neighbour\_address is the address of the blacklisted neighbour LOADng interface. + +B\_valid\_time – specifies the time until when the information recorded in this tuple is considered valid. + +#### D.7.4 Destination address set + +The destination address set records addresses, for which a LOADng router will generate RREPs in response to received RREQs, in addition to its own LOADng interface addresses (as listed in the local interface set). The destination address set thus represents those destinations (i.e., hosts), for which this LOADng router is providing connectivity. It consists of destination address tuples: + +(D\_address) + +where: + +D\_address is the address of a destination node attached to this LOADng router and for which this LOADng router provides connectivity. + +The destination address set is used for generating signalling, but is not itself updated by signalling specified in this document. Updates to the destination address set are due to changes of the environment of a LOADng router – hosts or external networks being connected to or disconnected from a LOADng router. The destination address set may be administratively provisioned, or provisioned by external protocols. + +#### D.7.5 Pending acknowledgment set + +The pending acknowledgment set contains information about RREPs which have been transmitted with the RREP.ackrequired flag set, and for which an RREP\_ACK has not yet been received. It consists of pending acknowledgment tuples: + +(P\_next\_hop, P\_originator, P\_seq\_num, P\_ack\_received, P\_ack\_timeout) + +where: + +P\_next\_hop is the address of the neighbour LOADng interface to which the RREP was sent. + +P\_originator is the address of the originator of the RREP. + +P\_seq\_num is the RREP.seq-num field of the sent RREP. + +P\_ack\_received is a Boolean flag, which specifies the tuple has been acknowledged by a corresponding RREP\_ACK message. The default value is FALSE. + +P\_ack\_timeout is the time after which the tuple shall be expired. + +#### D.8 LOADng router sequence numbers + +Each LOADng router maintains a single sequence number, which shall be included in each RREQ or RREP message it generates. Each LOADng router shall make sure that no two messages (both RREQ and RREP) are generated with the same sequence number, and shall generate sequence numbers so that these are monotonically increasing. This sequence number is used as information for when comparing routes to the LOADng router having generated the message. + +However, with a limited number of bits for representing sequence numbers, wrap-around (that the sequence number is incremented from the maximum possible value to zero) can occur. To prevent this from interfering with the operation of the protocol, the following shall be observed. The + +term MAXVALUE designates in the following the largest possible value for a sequence number. The sequence number S1 is said to be "greater than" (denoted '>') the sequence number S2 if: + +$$S2 < S1 \text{ AND } S1 - S2 \leq \text{MAXVALUE}/2 \text{ OR}$$ + +$$S1 < S2 \text{ AND } S2 - S1 > \text{MAXVALUE}/2$$ + +## D.9 Route maintenance + +Tuples in the routing set are maintained by way of five different mechanisms: + +- RREQ/RREP exchange, specified in clause D.12 and clause D.13 +- data traffic delivery success +- data traffic delivery failure +- external signals indicating that a tuple in the routing set needs updating +- information expiration. + +Routing tuples in the routing set contain a validity time, which specifies the time until when the information recorded in this tuple is considered valid. After this time, the information in such tuples is to be considered as invalid, for the processing specified in this Recommendation. + +Routing tuples for actively used routes (i.e., routes via which traffic is currently transiting) SHOULD NOT be removed, unless there is evidence that they no longer provide connectivity – i.e., unless a link on that route has broken. + +To this end, one or more of the following mechanisms (non-exhaustive list) may be used: + +- If a lower layer mechanism provides signals, such as when delivery to a presumed neighbour LOADng router fails, this signal may be used to indicate that a link has broken, trigger early expiration of a routing tuple from the routing set, and to initiate route error signalling (see clause D.14). Conversely, absence of such a signal when attempting delivery may be interpreted as validation that the corresponding routing tuple(s) are valid, and their R\_valid\_time refreshed correspondingly. Note that when using such a mechanism, care should be taken to prevent an intermittent error (e.g., an incidental wireless collision) triggering corrective action and signalling. This depends on the nature of the signals, provided by the lower layer, but can include the use of a hysteresis function or other statistical mechanisms. +- Conversely, for each successful delivery of a packet to a neighbour or destination, if signalled by a lower layer or a transport mechanism, or each positive confirmation of the presence of a neighbour by way of an external neighbour discovery protocol, may be interpreted as validation that the corresponding routing tuple(s) are valid, and their R\_valid\_time refreshed correspondingly. Note that when refreshing a routing tuple corresponding to a destination of a data packet, the routing tuple corresponding to the next hop towards that destination SHOULD also be refreshed. + +Furthermore, a LOADng router may experience that a route currently used for forwarding data packets is no longer operational, and shall act to either rectify this situation locally (clause D.13) or signal this situation to the source of the data packets for which delivery was unsuccessful (clause D.14). + +If a LOADng router fails to deliver a data packet to a next-hop, it shall generate an RERR message, as specified in clause D.14. + +## D.10 Unidirectional link handling + +Each LOADng router shall monitor the bidirectionality of the links to its neighbours and set the R\_bidirectional flag of related routing tuples when processing route replies (RREP). To this end, one or more of the following mechanisms may be used (non-exhaustive list): + +- If a lower layer mechanism provides signals, such as when delivery to a presumed neighbour LOADng router fails, this signal may be used to detect that a link to this neighbour is broken or is unidirectional; the LOADng router shall then blacklist the neighbour (see clause D.10.1). +- RREP\_ACK message exchange, as described in clause D.15. +- Upper layer mechanisms, such as transport-layer acknowledgments, may be used to detect unidirectional or broken links. + +When a LOADng router detects, via one of these mechanisms, that a link to a neighbour LOADng router is unidirectional or broken, the LOADng router shall blacklist this neighbour (see clause D.10.1). Conversely, if a LOADng router detects via one of these mechanisms that a previously blacklisted LOADng router has a bidirectional link to this LOADng router, it may remove it from the blacklist before the B\_valid\_time of the corresponding tuple. + +#### D.10.1 Blacklist usage + +The Blacklist is maintained according to clause D.7.3. When an interface of neighbour LOADng router is detected to have a unidirectional link to the LOADng router, it is blacklisted, i.e., a tuple (B\_neighbour\_address, B\_valid\_time) is created thus: + +- B\_neighbour\_address := the address of the blacklisted neighbour LOADng router interface +- B\_valid\_time := current\_time + B\_HOLD\_TIME. + +When a neighbour LOADng router interface is blacklisted, i.e., when there is a corresponding (B\_neighbour\_address, B\_valid\_time) tuple in the blacklisted neighbour set, it is temporarily not considered as a neighbour, and thus: + +- Every RREQ received from this neighbour LOADng router interface shall be discarded. + +#### D.11 Common rules for RREQ and RREP messages + +RREQ and RREP messages, both, supply routes between their recipients and the originator of the RREQ or RREP message. The two message types therefore share common processing rules and differ only in the following: + +- RREQ messages are multicast or broadcast, intended to be received by all LOADng routers in the network, whereas RREP messages are all unicast, intended to be received only by LOADng routers on a specific route towards a specific destination. +- Receipt of an RREQ message by a LOADng router, which has the RREQ.destination address in its local interface set or destination address set shall trigger the procedures for generation of an RREP message. +- Receipt of an RREP message with RREP.ackrequired set shall trigger the generation of an RREP\_ACK message. + +For the purpose of the processing description in this clause, the following additional notation is used: + +received-route-metric is a variable, representing the route metric, as included in the received RREQ or RREP message, see clause D.16. + +used-metric-type is a variable, representing the type of metric used for calculating received-route-metric, see clause D.16. + +previous-hop is the address of the LOADng router, from which the RREQ or RREP message was received. + +> is the comparison operator for sequence numbers, as specified in clause D.8. + +MSG is shorthand for either an RREQ or RREP message, used for when accessing message fields in the description of the common RREQ and RREP message processing in the following clauses. + +hop-count is a variable, representing the hop-count, as included in the received RREQ or RREP message. + +hop-limit is a variable, representing the hop-limit, as included in the received RREQ or RREP message. + +link-metric is a variable, representing the link metric between this LOADng router and the LOADng router from which the RREQ or RREP message was received, as calculated by the receiving LOADng router, see clause D.16. + +route-metric is a variable, representing the route metric, as included in the received RREQ or RREP message, plus the link-metric for the link, over which the RREQ or RREP was received, i.e., the total route cost from the originator to this LOADng router. + +#### **D.11.1 Identifying invalid RREQ or RREP messages** + +A received RREQ or RREP message is invalid, and shall be discarded without further processing, if any of the following conditions are true: + +- The address length specified by this message (i.e., MSG.addr-length + 1) differs from the length of the address(es) of this LOADng router. +- The address contained in MSG.originator presents in the Local Interface Set or Destination Address Set. +- There is a tuple in the routing set where: + - R\_dest\_addr = MSG.originator + - R\_seq\_num > MSG.seq-num +- For RREQ messages only, an RREQ shall be considered invalid if the previous-hop is blacklisted (i.e., its address is in a tuple in the blacklisted neighbour set, see clause D.10.1). + +A LOADng router may recognize additional reasons for identifying that an RREQ or RREP message is invalid for processing, e.g., to allow a security protocol to perform the verification of integrity check values and to prevent the processing of an unverifiable RREQ or RREP message by this protocol. + +#### **D.11.2 RREQ and RREP message processing** + +A received and valid RREQ or RREP message is processed as follows: + +- 1) Included TLVs are processed/updated according to their specification. +- 2) Set the variable hop-count to MSG.hop-count + 1. +- 3) Set the variable hop-limit to MSG.hop-limit – 1. +- 4) If MSG.metric-type is known to this LOADng router, and if MSG.metric-type is not HOP\_COUNT, then: + - Set the variable used-metric-type to the value of MSG.metric-type. + - Determine the link metric over the link over which the message was received, according to used-metric-type, and set the variable link-metric to the calculated value. + - Compute the route metric to MSG.originator according to used-metric-type by adding link-metric to the received-route-metric advertised by the received message, and set the variable route-metric to the calculated value. +- 5) Otherwise: + - Set the variable used-metric-type to HOP\_COUNT. + +- Set the variable route-metric to MAX\_DIST, see clause D.16. + - Set the variable link-metric to MAX\_DIST. +- 6) Find the routing tuple (henceforth, matching routing tuple) where R\_dest\_addr = MSG.originator +- 7) If no matching routing tuple is found, then create a new matching routing tuple (the "reverse route" for RREQ messages or "forward route" for RREP messages) with: +- R\_dest\_addr := MSG.originator + - R\_next\_addr := previous-hop + - R\_metric\_type := used-metric-type + - R\_metric := MAX\_DIST + - R\_hop\_count := hop-count + - R\_seq\_num := –1 + - R\_valid\_time := current time + R\_HOLD\_TIME + - R\_bidirectional := FALSE + - R\_local\_iface\_addr := the address of the LOADng interface through which the message was received. +- 8) The matching routing tuple, existing or new, is compared to the received RREQ or RREP message: +- If: +- R\_seq\_num = MSG.seq-num; AND + - R\_metric\_type = used-metric-type; AND + - R\_metric > route-metric +- OR +- R\_seq\_num = MSG.seq-num; AND + - R\_metric\_type = used-metric-type; AND + - R\_metric = route-metric; AND + - R\_hop\_count > hop-count +- OR +- R\_seq\_num = MSG.seq-num; AND + - R\_metric\_type does not equal to used-metric-type; AND + - R\_metric\_type = HOP\_COUNT +- OR +- R\_seq\_num < MSG.seq-num +- Then: +- The message is used for updating the routing set. The tuple that has R\_dest\_addr equal to MSG.originator is updated as follows: + - R\_next\_addr := previous-hop + - R\_metric\_type = used-metric-type + - R\_metric := route-metric + - R\_hop\_count := hop-count + - R\_seq\_num := MSG.seq-num + +- $R\_valid\_time := \text{current time} + R\_HOLD\_TIME$ +- $R\_bidirectional := \text{TRUE}$ , if the message being processed is an RREP. +- If previous-hop is not equal to MSG.originator, and if there is no matching routing tuple in the routing set with $R\_dest\_addr = \text{previous-hop}$ , create a new matching routing tuple with: + - $R\_dest\_addr := \text{previous-hop}$ + - $R\_next\_addr := \text{previous-hop}$ +- The routing tuple with $R\_dest\_addr = \text{previous-hop}$ , existing or new, is updated as follows: + - $R\_metric\_type := \text{used-metric-type}$ + - $R\_metric := \text{link-metric}$ + - $R\_hop\_count := 1$ + - $R\_seq\_num := -1$ + - $R\_valid\_time := \text{current time} + R\_HOLD\_TIME$ + - $R\_bidirectional := \text{TRUE}$ , if the processed message is an RREP, otherwise $\text{FALSE}$ . + - $R\_local\_iface\_addr := \text{the address of the LOADng interface through which the message was received}$ . + +Else: + +- If the message is an RREQ, it is not processed further and is not considered for forwarding. +- If it is an RREP and if RREP.ackrequired is set, an RREP\_ACK message shall be sent to the previous-hop, according to clause D.15.2. The RREP is not considered for forwarding. + +## D.12 Route requests (RREQs) + +Route requests (RREQs) are generated by a LOADng router when it has data packets to deliver to a destination, where the data packet source is local to that LOADng router (i.e., is an address in the local interface set or destination address set of that LOADng router), but for which the LOADng router has no matching tuple in the routing set. Furthermore, if there is a matching tuple in the routing set with the $R\_bidirectional$ set to $\text{FALSE}$ , and the parameter $\text{USE\_BIDIRECTIONAL\_LINK\_ONLY}$ of the interface with $R\_local\_iface\_address$ equals $\text{TRUE}$ , an RREQ shall be generated. + +After originating an RREQ, a LOADng router waits for a corresponding RREP. If no such RREP is received within $2 * \text{NET\_TRAVERSAL\_TIME}$ milliseconds, the LOADng router may issue a new RREQ for the sought destination (with an incremented $\text{seq\_num}$ ) up to a maximum of $\text{RREQ\_RETRIES}$ times. Two consequent RREQs generated on an interface of a LOADng router SHOULD be separated at least $\text{RREQ\_MIN\_INTERVAL}$ . + +### D.12.1 RREQ generation + +An RREQ message is generated according to clause D.6 with the following content: + +- $\text{RREQ.addr-length}$ set to the length of the address, as specified in clause D.6; +- $\text{RREQ.metric-type}$ set to the desired metric type; +- $\text{RREQ.route-metric} := 0$ . +- $\text{RREQ.seq-num}$ set to the next unused sequence number, maintained by this LOADng router; +- $\text{RREQ.hop-count} := 0$ ; +- $\text{RREQ.hop-limit} := \text{MAX\_HOP\_LIMIT}$ ; +- $\text{RREQ.destination} := \text{the address to which a route is sought}$ ; + +- RREQ.originator := one address of the LOADng interface of the LOADng router that generates the RREQ. If the LOADng router is generating an RREQ on behalf of a host connected to this LOADng router, the source address of the data packet, generated by that host, is used. + +### D.12.2 RREQ processing + +The variables hop-count and hop-limit have been updated in clause D.11.2 (when processing the message) and are used in this clause. On receiving an RREQ message, a LOADng router shall process the message according to this clause: + +- 1) If the message is invalid for processing, as defined in clause D.11.1, the message shall be discarded without further processing. The message is not considered for forwarding. +- 2) Otherwise, the message is processed according to clause D.11.2. +- 3) If RREQ.destination is listed in I\_local\_iface\_addr\_list of any local interface tuple, or corresponds to D\_address of any destination address tuple of this LOADng router, the RREP generation process in clause D.13.1 SHALL be applied. The RREQ is not considered for forwarding. +- 4) Otherwise, if hop-count is less than MAX\_HOP\_COUNT and hop-limit is greater than 0, the message is considered for forwarding according to clause D.12.3. + +### D.12.3 RREQ forwarding + +The variables used-metric type, hop-count, hop-limit and route-metric have been updated in clause D.11.2 (when processing the message) and are used in this clause to update the content of the message to be forwarded. An RREQ considered for forwarding SHALL be updated as follows, prior to it being transmitted: + +- 1) RREQ.metric-type := used-metric-type (as set in clause D.11.2) +- 2) RREQ.route-metric := route-metric (as set in clause D.11.2) +- 3) RREQ.hop-count := hop-count (as set in clause D.11.2) +- 4) RREQ.hop-limit := hop-limit (as set in clause D.11.2) + +An RREQ SHALL be forwarded according to the flooding operation, specified for the network. This may be by way of classic flooding, a reduced relay set mechanism such as [b-IETF RFC 6621], or any other information diffusion mechanism such as [b-IETF RFC 6206]. Care shall be taken that NET\_TRAVERSAL\_TIME is chosen so as to accommodate the maximum time that it may take for an RREQ to traverse the network, accounting for in-router delays incurring due to or imposed by such algorithms. + +### D.12.4 RREQ transmission + +RREQs, whether initially generated or forwarded, are sent to all neighbour LOADng routers through all interfaces in the local interface set. + +When an RREQ is transmitted, all receiving LOADng routers will process the RREQ message and as a consequence consider the RREQ message for forwarding at the same, or at almost the same, time. If using data link and physical layers that are subject to packet loss due to collisions, such RREQ messages SHOULD be jittered as described in [b-IETF RFC 5148], using RREQ\_MAX\_JITTER, in order to avoid such losses. + +## D.13 Route replies (RREPs) + +Route replies (RREPs) are generated by a LOADng router in response to an RREQ (henceforth denoted "corresponding RREQ"), and are sent by the LOADng router which has, in either its destination address set or in its local interface set, the address from RREQ.destination. RREPs are sent hop by hop in unicast towards the originator of the RREQ, in response to which the RREP was + +generated, along the reverse route installed by that RREQ. A LOADng router, upon forwarding an RREP, installs the forward route towards the RREP.destination. + +Thus, with the forwarding of RREQs installing the reverse route and the forwarding of RREPs installing the forward route, bidirectional routes are provided between the RREQ.originator and RREQ.destination. + +### D.13.1 RREP generation + +At least one RREP SHALL be generated in response to a (set of) received RREQ messages with identical (RREQ.originator, RREQ.seq-num). An RREP may be generated immediately as a response to each RREQ processed, in order to provide the shortest possible route establishment delays, or may be generated after a certain delay after the arrival of the first RREQ, in order to use the "best" received RREQ (e.g., received over the lowest-cost route) but at the expense of longer route establishment delays. A LOADng router may generate further RREPs for subsequent RREQs received with the same (RREQ.originator, RREQ.seq-num) pairs, if these indicate a better route, at the expense of additional control traffic being generated. In all cases however, the content of an RREP is as follows: + +- RREP.addr-length set to the length of the address, as specified in clause D.6; +- RREP.seq-num set to the next unused sequence number, maintained by this LOADng router; +- RREP.metric-type set to the same value as the RREQ.metric-type in the corresponding RREQ if the metric type is known to the router. Otherwise, RREP.metric-type is set to HOP\_COUNT; +- RREP.route-metric := 0; +- RREP.hop-count := 0; +- RREP.hop-limit := MAX\_HOP\_LIMIT; +- RREP.destination := the address to which this RREP message is to be sent; this corresponds to the RREQ.originator from the RREQ message, in response to which this RREP message is generated; +- RREP.originator := the address of the LOADng router, generating the RREP. If the LOADng router is generating an RREP on behalf of the hosts connected to it, or on behalf of one of the addresses contained in the LOADng routers destination address set, the host address is used. + +The RREP that is generated is transmitted according to clause D.13.4. + +### D.13.2 RREP processing + +The variables hop-count and hop-limit have been updated in clause D.11.2 (when processing the message) and are used in this clause. On receiving an RREP message, a LOADng router shall process the message according to this clause: + +- 1) If the message is invalid for processing, as defined in clause D.11.1, the message shall be discarded without further processing. The message is not considered for forwarding. +- 2) Otherwise, the message is processed according to clause D.11.2. +- 3) If RREP.ackrequired is set, an RREP\_ACK message shall be sent to the previous-hop, according to clause D.15.2. +- 4) If hop-count is equal to MAX\_HOP\_COUNT or hop-limit is equal to 0, the message is not considered for forwarding. +- 5) Otherwise, if RREP.destination is not listed in I\_local\_iface\_addr\_list of any local interface tuple and does not correspond to D\_address of any destination address tuple of this + +LOADng router, the RREP message is considered for forwarding according to clause D.13.3. + +### D.13.3 RREP forwarding + +The variables used-metric type, hop-count, hop-limit and route-metric have been updated in clause D.11.2 (when processing the message) and are used in this clause to update the content of the message to be forwarded. An RREP message considered for forwarding, shall be updated as follows, prior to it being transmitted: + +- 1) RREP.metric-type := used-metric-type (as set in clause D.11.2) +- 2) RREP.route-metric := route-metric (as set in clause D.11.2) +- 3) RREP.hop-count := hop-count (as set in clause D.11.2) +- 4) RREP.hop-limit := hop-limit (as set in clause D.11.2) +- 5) The RREP is transmitted, according to clause D.13.4. + +The RREP message is then unicast to the next hop towards RREP.destination. + +### D.13.4 RREP transmission + +An RREP is ultimately destined for the LOADng router which has the address listed in the RREP.destination field in either its local interface set or in its destination address set. The RREP is forwarded in unicast towards that LOADng router. The RREP shall, however, be transmitted so as to allow it to be processed in each intermediate LOADng router to: + +- install proper forward routes; AND +- permit that RREP.hop-count be updated to reflect the route. + +RREP transmission is accomplished by the following procedure: + +- 1) Find the routing tuple (henceforth, the "Matching Routing Tuple") in the routing set, where: + - R\_dest\_addr = RREP.destination +- 2) Find the local interface tuple (henceforth, "Matching Interface Tuple"), where: + - I\_local\_iface\_addr\_list contains R\_local\_iface\_addr from the matching routing tuple. +- 3) If RREP\_ACK\_REQUIRED is set for the LOADng interface, identified by the matching interface tuple: + - Create a new pending acknowledgment tuple with: + - P\_next\_hop := R\_next\_addr from the matching routing tuple + - P\_originator := RREP.originator + - P\_seq\_num := RREP.seq-num + - P\_ack\_received := FALSE + - P\_ack\_timeout := current\_time + RREP\_ACK\_TIMEOUT + - Set RREP.ackrequired to true. +- 4) Otherwise: + - Set RREP.ackrequired to false. +- 5) The RREP is transmitted over the LOADng interface, identified by the matching interface tuple to the neighbour LOADng router, identified by R\_next\_addr from the matching routing tuple. + +When a pending acknowledgement tuple expires, if P\_ack\_received = FALSE, the P\_next\_hop address shall be blacklisted by creating a blacklisted neighbour tuple according to clause D.7.3 + +## D.14 Route errors (RERRs) + +If a LOADng router fails to deliver a data packet to a next hop or a destination, and if neither the source nor destination address of that data packet belongs to the destination address set of that LOADng router, it shall generate a Route Error (RERR). This RERR shall be sent along the reverse route towards the source of the data packet for which delivery was unsuccessful (to the last LOADng router along the reverse route, if the data packet was originated by a host behind that LOADng router). + +The following definition is used in this clause: + +- "EXPIRED" indicates that a timer is set to a value clearly preceding the current time (e.g., current time – 1). + +### D.14.1 Identifying invalid RERR messages + +A received RERR is invalid, and shall be discarded without further processing, if any of the following conditions are true: + +- The address length specified by this message (i.e., RERR.addr-length + 1) differs from the length of the address(es) of this LOADng router. +- The address contained in RERR.originator is an address of this LOADng router. + +A LOADng router may recognize additional reasons, external to this specification, for identifying that an RERR message is invalid for processing, e.g., to allow a security protocol to perform the verification of signatures and prevent the processing of an unverifiable RERR message by this protocol. + +### D.14.2 RERR generation + +A packet with an RERR message is generated by the LOADng router, detecting the link breakage, with the following content: + +- RERR.error-code := the error code corresponding to the event causing the RERR to be generated +- RERR.addr-length := the length of the address, as specified in clause D.6 +- RERR.unreachableAddress := the destination address from the unsuccessfully delivered data packet +- RERR.originator := one address of the LOADng interface of the LOADng router that generates the RERR +- RERR.destination := the source address from the unsuccessfully delivered data packet, towards which the RERR is to be sent +- RERR.hop-limit := MAX\_HOP\_LIMIT + +### D.14.3 RERR processing + +For the purpose of the processing description below, the following additional notation is used: + +previous-hop is the address of the LOADng router from which the RERR was received. + +hop-limit is a variable, representing the hop-limit, as included in the received RERR message. + +Upon receiving an RERR, a LOADng router shall perform the following steps: + +- 1) If the RERR is invalid for processing, as defined in clause D.14.1, the RERR shall be discarded without further processing. The message is not considered for forwarding. +- 2) Included TLVs are processed/updated according to their specification. +- 3) Set the variable hop-limit to RERR.hop-limit – 1. +- 4) Find the routing tuple (henceforth "Matching Routing Tuple") in the routing set where: + +- R\_dest\_addr = RERR.unreachableAddress + - R\_next\_addr = previous-hop +- 5) If no matching routing tuple is found, the RERR is not processed further but is considered for forwarding, as specified in clause D.14.4. + - 6) Otherwise, if one matching routing tuple is found: + - 1) If RERR.errorcode corresponds to "No available route", this matching routing tuple is updated as follows: + - R\_valid\_time := EXPIRED + +Extensions to this Recommendation may define additional error codes and may insert processing rules here for RERRs with that error code. + - 2) If hop-limit is greater than 0, the RERR message is considered for forwarding, as specified in clause D.14.4. + +#### D.14.4 RERR forwarding + +An RERR is, ultimately, destined for the LOADng router which has, in either its destination address set or in its local interface set, the address from RERR.originator. + +An RERR, considered for forwarding is therefore processed as follows: + +- 1) RERR.hop-limit := hop-limit (as set in clause D.14.3) +- 2) Find the destination address tuple (henceforth, matching destination address tuple) in the destination address set where: + - D\_address = RERR.destination +- 3) If one or more matching destination address tuples are found, the RERR message is discarded and not retransmitted, as it has reached the final destination. +- 4) Otherwise, find the local interface tuple (henceforth, matching local interface tuple) in the local interface set where: + - I\_local\_iface\_addr\_list contains RERR.destination. +- 5) If a matching local interface tuple is found, the RERR message is discarded and not retransmitted, as it has reached the final destination. +- 6) Otherwise, if no matching destination address tuples or local interface tuples are found, the RERR message is transmitted according to clause D.14.5. + +#### D.14.5 RERR transmission + +An RERR is ultimately destined for the LOADng router which has the address listed in the RERR.destination field in either its local interface set or in its destination address set. The RERR is forwarded in unicast towards that LOADng router. The RERR shall however, be transmitted so as to allow it to be processed in each intermediate LOADng router to: + +- Allow intermediate LOADng routers to update their routing sets, i.e., remove tuples for this destination. + +RERR transmission is accomplished by the following procedure: + +- 1) Find the routing tuple (henceforth, the "Matching Routing Tuple") in the routing set, where: + - R\_dest\_addr = RERR.destination +- 2) Find the local interface tuple (henceforth, "Matching Interface Tuple"), where: + - I\_local\_iface\_addr\_list contains R\_local\_iface\_addr from the matching routing tuple. + +- 3) The RERR is transmitted over the LOADng interface, identified by the matching interface tuple to the neighbour LOADng router, identified by R\_next\_addr from the matching routing tuple. + +## **D.15 Route reply acknowledgments (RREP\_ACKs)** + +A LOADng router shall signal in a transmitted RREP that it is expecting an RREP\_ACK, by setting RREP.ackrequired flag in the RREP. When doing so, the LOADng router shall also add a tuple (P\_next\_hop, P\_originator, P\_seq\_num, P\_ack\_timeout) to the pending acknowledgment set, and set P\_ack\_timeout to current\_time + RREP\_ACK\_TIMEOUT, as described in clause D.13.4. + +The following definition is used in this clause: + +"EXPIRED" indicates that a timer is set to a value clearly preceding the current time (e.g., current\_time - 1). + +### **D.15.1 Identifying invalid RREP\_ACK messages** + +A received RREP\_ACK is invalid, and shall be discarded without further processing, if any of the following conditions are true: + +- The address length specified by this message (i.e., RREP\_ACK.addr-length + 1) differs from the length of the address(es) of this LOADng router. + +A LOADng router may recognize additional reasons, external to this Recommendation, for identifying that an RREP\_ACK message is invalid for processing, e.g., to allow a security protocol to perform the verification of signatures and prevent the processing of an unverifiable RREP\_ACK message by this protocol. + +### **D.15.2 RREP\_ACK generation** + +Upon receipt of an RREP message with the RREP.ackrequired flag set, a LOADng router shall generate at least one RREP\_ACK and send this RREP\_ACK in unicast to the neighbour which originated the RREP. + +An RREP\_ACK message is generated by a LOADng router with the following content: + +- RREP\_ACK.addr-length := the length of the address, as specified in clause D.6; +- RREP\_ACK.seq-num := the value of the RREP.seq-num field of the received RREP; +- RREP\_ACK.destination := RREP.originator of the received RREP. + +### **D.15.3 RREP\_ACK processing** + +On receiving an RREP\_ACK from a LOADng neighbour LOADng router, a LOADng router shall do the following: + +- 1) If the RREP\_ACK is invalid for processing, as defined in clause D.15.1, the RREP\_ACK shall be discarded without further processing. +- 2) Find the routing tuple (henceforth, matching routing tuple) where: + - R\_dest\_addr = previous-hop; + +The matching routing tuple is updated as follows: + +- R\_bidirectional := TRUE +- 3) If a pending acknowledgement tuple (henceforth, matching pending acknowledgement tuple) exists, where: + - P\_next\_hop is the address of the LOADng router from which the RREP\_ACK was received. + - P\_originator = RREP\_ACK.destination + +- $P\_seq\_num = RREP\_ACK.seq-num$ + +then the RREP has been acknowledged. The matching pending acknowledgement tuple is updated as follows: + +- $P\_ack\_received := TRUE$ +- $P\_ack\_timeout := EXPIRED$ + +#### **D.15.4 RREP\_ACK forwarding** + +An RREP\_ACK is intended only for a specific direct neighbour and shall not be forwarded. + +#### **D.15.5 RREP\_ACK transmission** + +An RREP\_ACK is transmitted in unicast to the neighbour LOADng router from which the RREP was received. + +### **D.16 Metrics** + +This Recommendation enables the use of different metrics for when calculating route metrics. + +Metrics as defined in LOADng are additive, and the routes that are to be created are those with the minimum sum of the metrics along that route. + +#### **D.16.1 Specifying new metrics** + +When defining a metric, the following considerations SHOULD be taken into consideration: + +- The definition of the $R\_metric$ field, as well as the value of $MAX\_DIST$ . + +### **D.17 Security considerations** + +Currently, this protocol does not specify any special security measures. As a reactive routing protocol, this protocol is a potential target for various attacks. Various possible vulnerabilities are discussed in this clause. + +By way of (i) enabling inclusion of TLVs and (ii) permitting that LOADng recognizes external reasons for rejecting RREQ, RREP, RREP\_ACK and RERR messages, the development of security measures, appropriate for a given deployment, is however supported. This architecture is a result of the observation that with respect to security in LOADng routed networks, "one size rarely fits all". This, as LOADng deployment domains have varying security requirements ranging from "unbreakable" to "virtually none", depending on, e.g., physical access to the network, or on security available on other layers. The virtue of this approach is that LOADng routing protocol specifications (and implementations) can remain "generic", with extensions providing proper deployment-domain specific security mechanisms. + +#### **D.17.1 Confidentiality** + +This protocol floods route requests (RREQs) to all the LOADng routers in the network, when there is traffic to deliver to a given destination. Hence, if used in an unprotected network (such as an unprotected wireless network): + +- Part of the network topology is revealed to anyone who listens, specifically (i) the identity (and existence) of the source LOADng router; (ii) the identity of the destination; and (iii) the fact that a path exists between the source LOADng router and the LOADng router from which the RREQ was received. +- The network traffic patterns are revealed to anyone who listens to the LOADng control traffic, specifically which pairs of devices communicate. If, for example, a majority of traffic originates from or terminates in a specific LOADng router, this may indicate that this LOADng router has a central role in the network. + +This protocol also unicasts route replies (RREPs) from the destination of an RREQ to the originator of that same RREQ. Hence, if used in an unprotected network (such as an unprotected wireless network): + +- Part of the network topology is revealed to anyone who is near or on the unicast path of the RREP (such as within radio range of LOADng routers on the unicast path in an unprotected wireless network), specifically that a path from the originator (of the RREP) to the destination (of the RREP) exists. + +Finally, this protocol unicasts route errors (RERRs) when an intermediate LOADng router detects that the path from a source to a destination is no longer available. Hence, if used in an unprotected network (such as an unprotected wireless network): + +- A disruption of the network topology is revealed to anyone who is near or on the unicast path of the RERR (such as within radio range of LOADng routers on the unicast path in an unprotected wireless network), specifically that a path from the originator (of the RERR) to the destination (of the RERR) has been disrupted. + +This protocol signalling behaviour enables, for example, an attacker to identify central devices in the network (by monitoring RREQs) so as to target an attack, and (by way of monitoring RERRs) to measure the success of an attack. + +### **D.17.2 Integrity** + +A LOADng router injects topological information into the network by way of transmitting RREQ and RREP messages, and removes installed topological information by way of transmitting RERR messages. If some LOADng routers for some reason, malice or malfunction, inject invalid control traffic, network integrity may be compromised. Therefore, message authentication is recommended. Different such situations may occur, for instance: + +- 1) A LOADng router generates RREQ messages, pretending to be another LOADng router. +- 2) A LOADng router generates RREP messages, pretending to be another LOADng router. +- 3) A LOADng router generates RERR messages, pretending to be another LOADng router. +- 4) A LOADng router generates RERR messages, indicating that a link on a path to a destination is broken. +- 5) A LOADng router forwards altered control messages. +- 6) A LOADng router does not forward control messages. +- 7) A LOADng router forwards RREPs and RREQs, but does not forward unicast data traffic. +- 8) A LOADng router "replays" previously recorded control messages from another LOADng router. + +Authentication of the originator LOADng router for control messages (for situations 1, 2 and 3) and on individual links announced in the control message (for situation 2 and 4) may be used as a countermeasure. However, to prevent routers from repeating old (and correctly authenticated) information (situation 8), temporal information is required, requiring a router to positively identify such a delayed message. + +In general, integrity check values and other required security information may be transmitted as a separate message type, or signatures and security information may be transmitted within the control messages, using the TLV mechanism. Either option permits that "secured" and "unsecured" routers can coexist in the same network, if desired. + +### **D.17.3 Channel jamming and state explosion** + +A reactive protocol, LOADng control messages are generated in response to network events. For RREQs, such an event is that a data packet is present in a router which does not have a route to the destination of the data packet, or that the router receives an RERR message, invalidating a route. + +For RREPs, such an event is the receipt of an RREQ corresponding to a destination owned by the LOADng router. + +A router that forwards an RREQ records the reverse route state. A router that forwards an RREP records the forward route state. If some routers for some reason, malice or malfunction, generates excessive RREQ, RREP or RERRs, otherwise correctly functioning LOADng routers may fall victim to either "indirect jamming" (being "tricked" into generating excessive control traffic) or an explosion in the state necessary for maintaining protocol state (potentially, exhausting the available memory resources). + +Different such situations may occur, for instance: + +- 1) A router, within a short time, generates RREQs to an excessive amount of destinations in the network (possibly all destinations, possibly even destinations not present in the network), causing intermediate routers to allocate the state for the forward routes. +- 2) A router generates excessively frequent RREQs to the same (existing) destination, causing the corresponding LOADng router to generate excessive RREPs. +- 3) A router generates RERRs for a destination to the source LOADng router for traffic to that destination, causing that LOADng router to flood renewed RREQs. + +For situation 1, the state required for recording forward and/or reverse routes may exceed the memory available in the intermediate LOADng routers – to the detriment of being able to record the state for other routes. This is, in particular, if a LOADng router generates RREQs for destinations "not present in the network". + +A router which, within a short time, generates RREPs to an excessive amount of destinations in the network (possibly all destinations, possibly even destinations not present in the network), will not have the same network-wide effect: an intermediate router receiving an RREP for a destination for which no reverse route exists will neither attempt forwarding the RREP nor allocate the state for the forward route. + +For situations 1, 2, and 3, a possible countermeasure is to rate-limit the number of control messages that a LOADng router forwards on behalf of another LOADng router. Such a rate limit should take into consideration the expected normal traffic for a given LOADng deployment. Authentication may furthermore be used so as to prohibit a LOADng router from forwarding control traffic from any non-authenticated router (with the assumption being that an authenticated router is not expected to exhibit such rogue behaviour). + +#### **D.17.4 Interaction with external routing domains** + +Some applications may require sending messages from nodes in a domain to nodes in a different domain that may be governed by other routing mechanisms and other addressing schemes. In this case, a LOADng router device may act as a proxy between the different domains and forward application layer messages between them. A LOADng proxy router is considered as the final destination for the LOADng protocol and will respond to RREQ messages and can reach hosts in its destination address set that are inside the external domain using the routing protocol governing that domain. Care shall be taken to not allow potentially insecure and untrustworthy information to be injected into the external domain, and vice versa. + +## Annex E + +### Commissioning in 6LoWPAN + +(This annex forms an integral part of this Recommendation.) + +#### Abstract + +The commissioning process defines the startup procedure executed by any 6LoWPAN device. This document defines the startup procedure that should be followed by a 6LoWPAN device in any open or secured network. + +#### E.1 Introduction + +6LoWPAN is a low-power wireless personal area network (LoWPAN) which is comprised of the IEEE 802.15.4-2006 standard IEEE 802.15.4 devices. One of the design goals for 6LoWPAN architecture is to ensure minimum human intervention during the provisioning of a sensor device in a PAN. However, a 6LoWPAN device requires a set of pre-deployed information, called a LoWPAN information base (LIB), to find the right PAN, to successfully join with the PAN, and to establish communication within the PAN. A device needs a specific procedure, named a bootstrapping protocol for 6LoWPAN device, to collect information from the LoWPAN bootstrapping server (LBS) and to start communication in a PAN. This procedure needs to be well defined for the interoperability of devices from different vendors. This procedure involves extracting LIB, security credentials, becoming part of an existing network, obtaining a 16-bit short address, and IP settings. + +#### E.2 Terminology + +**Active Scan:** An active scan is used by a device to locate all coordinators transmitting beacon frames within its personal operating space, which is provided by [IEEE 802.15.4]. It requests other devices to transmit the beacon frame. + +**association:** An [IEEE 802.15.4] device can be assigned a dynamic 16 bit short address during an association operation with a neighbour device (or router) which is also called the parent device. After getting the short address, a device can communicate with its parent or child by using only the assigned short address. + +**coordinator:** A full-function device (FFD) which is the principal controller of a 6LoWPAN. It is also called a PAN coordinator. It MAY initiate the synchronization of the entire 6LoWPAN by transmitting beacons. + +**ED Scan:** An ED scan allows a device to obtain a measure of the peak energy in each requested channel, which is provided by [IEEE 802.15.4]. + +**full-function device (FFD):** A device implementing the complete protocol set of [IEEE 802.15.4]. It is capable of operating as a router (multi-hop packet forwarding) for its associated neighbours. + +**neighbour table:** A table which has the information of neighbour devices in a personal operating space. + +**LoWPAN bootstrapping information base (LIB):** A set of pre-deployed information that is necessary for a particular 6LoWPAN device to find the desired PAN and to successfully join the PAN. This information is categorized into two groups; PAN specific information (PSI), which is the same for every device in a PAN (for example, PAN ID), and device specific information (DSI), which is specific for each particular node (for example short address). + +**PSI:** PAN specific information inside the LIB, a portion of information, called PSI, is the same for every device in the target PAN. For example, PAN\_ID, PAN\_Type, etc. + +**DSI:** Device specific information inside the LIB, other than PSI, there is some information that may vary from device to device. For example, Role\_of\_Device, Short\_Addr, etc. + +**LoWPAN bootstrapping device (LBD):** LBD is a device that is to be deployed in the target network. LBD is assumed to have no prior information about the 6LoWPAN within which it is going to join. The only information it has is the EUI-64 address and a "Join key" (in the case of a secured PAN). + +**LoWPAN bootstrapping server (LBS):** An entity that contains the LIB of each device to be bootstrapped. It indexes this information with the EUI-64 address of each 6LoWPAN device. LBS has two modules in it: network management and account module (NAM) and the authentication module (AM). NAM keeps track of the LIB of each device indexed by the EUI-64 address, whereas AM participates in the authentication process on behalf of the LBD using the LBD's 'Authentication credentials'. Based on the 'LBP Message', the LBS verifies the LBD with the help of the authentication server (in the case of a secured PAN) and sends an ACCEPT message with the necessary information; otherwise it sends a DECLINE message. In the case of a secured PAN, the LBS initiates the authentication mechanism issuing an authentication request into the appropriate format that is acceptable by a particular authentication server. Any challenge or reply message from the authentication server is encapsulated in the 'LIB message' by the LBS and is sent back to the LBD through the LBA. + +**LoWPAN bootstrapping agent (LBA):** An FFD that has already joined the PAN and thus, it is already a member of the PAN. It is also a neighbour of a new LBD, and thus it helps the bootstrapping LBD by receiving LBP messages from the LBD and forwarding it to the LBS. + +**open 6LoWPAN:** An open 6LoWPAN is a PAN where any device is welcomed. + +**close 6LoWPAN:** A close 6LoWPAN is a PAN where only a pre-defined set of devices are allowed to join based on their EUI-64 address. This account is managed by the LBS. If the close 6LoWPAN is secured, it is called a secured 6LoWPAN. + +**secured 6LoWPAN:** A secured 6LoWPAN is a close 6LoWPAN that also maintains a secured message exchange in the PAN. + +**PAN ID:** The 16 bit 6LoWPAN identifier which is administratively assigned to a 6LoWPAN and is unique within the PAN. + +**passive scan:** A passive scan, like an active scan, is used by an FFD to locate all coordinators transmitting beacon frames within its personal operating space, which is provided by [IEEE 802.15.4]. The difference is that the passive scan is a receive-only operation and does not request the beacon frame. + +**personal operating space (POS):** The area within the reception range of the wireless transmission of an [IEEE 802.15.4] packet. + +**reduced function device (RFD):** An [IEEE 802.15.4] device of 6LoWPAN which does not have the functionality of the router. That is, it cannot forward IPv6 packets to the next hop device. It can only be the end device of 6LoWPAN. + +**Short Address:** A 16 bit address dynamically assigned to a device from the PAN. + +### E.2.1 Requirements notation + +The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this annex are to be interpreted as described in [IETF RFC 2119]. + +### E.3 Bootstrapping + +Bootstrapping is defined as collecting the LIB from the LBS, obtaining security credentials (optional), associating with the right PAN, obtaining a 16-bit short address (optional) and constructing an IPv6 address using an IPv6 prefix. Specifically, this includes the process of starting the network, associating with other nodes, obtaining the unique IPv6 address and constructing security credentials for 6LoWPAN. + +#### E.3.1 Resetting the device + +After the device is started, it first performs a MAC layer reset. + +#### E.3.2 Scanning through channels + +During this phase, functions supported by 802.15.4 are used for scanning channels. For getting the information of other devices within the POS, the device should perform a scan. The device can use either an active scan or a passive scan. During the scanning procedure, the device receives beacon frames from other devices. + +#### E.3.3 LoWPAN bootstrapping mechanism + +This protocol defines a mechanism to extract the LIB from a currently unknown LBS and it also defines a message format for an LIB message exchange. In this protocol, the LBD exchanges an LBP message with the LBS through its one hop neighbour LBA. So, at the beginning of the LBP, it needs to find an LBA using the 'LBA discovery phase' that is described in clause E.3.3.3. + +##### E.3.3.1 LoWPAN bootstrapping protocol message format + +In this clause we define a message format which is necessary for the LBP. + +###### E.3.3.1.1 LBP message + +![Diagram of the Bootstrapping message format showing fields for Transaction-id, A_LBD, and Bootstrapping Data with bit numbering.](56ec21575673a0ed999fb9c6a44e474f_img.jpg) + +The diagram illustrates the structure of an LBP message. At the top, bit positions are indicated from 0 to 15. The first byte (bits 0-7) is split into two nibbles: 'T' (bits 0-3) and 'Code' (bits 4-7). The next byte (bits 8-15) is the 'Transaction-id'. Below this header is a large section for 'A\_LBD', followed by 'Bootstrapping Data' at the bottom. A dashed line at the very bottom indicates the end of the message structure. + +| | | | | | | | | | | | | | | | | +|----------------------|------|-----------------|--|--|--|--|--|--|--|--|--|--|--|--|--| +| 0 | | 1 | | | | | | | | | | | | | | +| Bits 0 1 2 3 4 5 6 7 | | 8 9 0 1 2 3 4 5 | | | | | | | | | | | | | | +| T | Code | Transaction-id | | | | | | | | | | | | | | +| A_LBD | | | | | | | | | | | | | | | | +| Bootstrapping Data | | | | | | | | | | | | | | | | + +Diagram of the Bootstrapping message format showing fields for Transaction-id, A\_LBD, and Bootstrapping Data with bit numbering. + +Figure E.1 – Bootstrapping message format + +**Table E.1 – Fields in bootstrapping message** + +| Field name | Size | Description | +|--------------------|----------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| T | 1 bit | Type of message
It defines message type.
0 : Message from LBD
1 : Message to LBD | +| Code | 3 bits | 0b000 : Reserved
0b001 : ACCEPTED indicates authentication of the LBD has been accepted.
0b010 : CHALLENGE indicates that the authentication process has not been finished. The authentication server has sent a challenge that has to be replied to by the LBD.
0b011 : DECLINE. In the case of an unsecured 6LoWPAN, the LBS may send this code to indicate that the LBD's EUI-64 address is not allowed to join the PAN. In the case of a secured 6LoWPAN, the LBS may send this code to indicate that the LBD's EUI-64 address is not allowed to join the PAN or the authentication of the LBD has failed.
0b100-0b111 : Reserved | +| Seq | 12 bits | Sequence number
Seq identifies the number of messages transmitted by the LBD. Corresponding incoming message from the LBS should also have the same Seq. | +| A_LBD | 8 bytes | Address of bootstrapping device (LBD)
64-bit EUI-64 address of the LBD. | +| Bootstrapping Data | Variable | The format of bootstrapping data is given below. | + +![](3eb2c6bfde13eae0df07b28c24d52e5d_img.jpg) + +Bits + +| | | | | | | | | | | | | | | | | +|---------------------|--|--|--|--|--|--|--|---|---|---------------|--|--|--|-------|--| +| 0 1 2 3 4 5 6 7 8 9 | | | | | | | | | | 1 0 1 2 3 4 5 | | | | | | +| Type | | | | | | | | M | L | Len | | | | Value | | + +**Figure E.2 – Bootstrapping data format** + +**Table E.2 – Fields in bootstrapping data** + +| Field name | Size | Description | +|------------|----------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Type | 6 bits | ID of the attribute in the LIB if 'L' bit is set. Otherwise, this field defines a particular authentication type.
A list of authentication mechanisms and their corresponding 'Type' is for further study. | +| M | 1 bit | Type of the attribute
This field defines the type of attribute in the LIB
0 : Device specific information (DSI)
1 : PAN specific information (PSI) | +| Len | 1 byte | Length of the value in octets | +| Value | Variable | Data of the type | + +### E.3.3.2 LoWPAN bootstrapping information base + +One of the important goals of the LBP is to receive a set of information from the LBS by a joining LBD. This information comprises of PSI and DSI. The following table shows the attribute name, attribute ID (attr\_ID), purpose of the attribute and its type. + +**Table E.3 – Attributes in LoWPAN bootstrapping information base** + +| Attribute name | Attr_ID | Type | Attribute description | +|-----------------------------------|---------|------|--------------------------------------------------------------------------------------------------------------| +| PAN_ID | 1 | P | This is the network identification for the default network. | +| PAN_type | 2 | P | Secured/closed/open | +| Address_of_LBS | 3 | P | Address of the LBS. 0x0000 in case of no LBS. For example in open 6LoWPAN. | +| Join_Time | 4 | P | It specifies the time when this node should start trying to join the target PAN. | +| Role_of_Device | 5 | D | Agent/No_Agent | +| Short_Addr | 7 | D | 16-bit address for a new device which is unique inside the PAN. | +| Short_Addr_Distribution_Mechanism | 8 | P | 0: Short address is provided by the LBS
1: Short address is assigned by the device itself | +| Other_Device_Specific_Info | 15 | D | Using this attribute, a device and LBS can exchange any type of data or security key required by the device. | + +### E.3.3.3 LBA discovering phase + +The LBD has to send an LBP message to the LBS server under the support of an LBA. To find the LBA, it broadcasts an LBA solicitation message within its one hop neighbours and waits for an LBA advertisement. Any device capable of being an LBS/LBA replies to the broadcast specifying its capability as an LBS/LBA. If there is any LBS in its neighbour, the LBD selects that LBS, otherwise it selects one of the LBAs. + +### E.3.3.4 LoWPAN bootstrapping protocol (LBP) + +The LBD sends an LBP message to the LBA, as it does not know the address or path to the LBS of the target PAN. The LBA forwards the LBP message to the LBS on behalf of the LBD. The LBS replies with one or multiple LBP messages destined to the LBA as the LBD is still not part of the network. If the network is a secured 6LoWPAN and the LBD is an authentic node, we assume that the LBD has the necessary pre-deployed keys and the knowledge of the authentication mechanism necessary to authenticate in a target PAN. In this case, the LBD sends the necessary information in the 'bootstrapping data' field so that the LBS can initiate the authentication process using that 'authentication credentials'. The LBS converts the LBP message into an appropriate authentication request for the particular authentication server and sends it. A reply/challenge from the authentication server, for example an EAP authenticator or AAA server, is encapsulated in the LBP message's 'bootstrapping data' field and is sent back to the LBD through the LBA. The LBA also keeps track of successful authentication, failed authentication and an incomplete conversation of the authentication process, and maintains a 'black list' of malicious devices to avoid repeated attacks. Detecting a malicious device based on these 3 pieces of information and marking that node as 'Blacklisted' belongs to the scope of security policy and out of the scope of this Recommendation. + +The following figure shows a simple example of a bootstrapping mechanism. + +![Sequence diagram showing the Simple LBP message sequence between LBD, LBA, and LBS. The sequence starts with LBD sending an LBA solicitation (1hop broadcast) to LBA. LBA responds with an LBA advertisement (unicast to LBD). LBD then sends an LBP message (JR) to LBA. LBA forwards the LBP Message (JR) to LBS. LBS responds with an LBP Message (Jrep) to LBA. Finally, LBA sends an LBP Message (JRep only) to LBD. A note at the bottom right indicates G.9903(12)-Amd.1(13)_FE.3. A legend below the diagram states JR = Join Request, JRep = Join Reply.](bbdb91b475e5915fd7e690eea9e6220b_img.jpg) + +``` + +sequenceDiagram + participant LBD + participant LBA + participant LBS + Note right of LBS: G.9903(12)-Amd.1(13)_FE.3 + LBD->>LBA: LBA solicitation (1hop broadcast) + LBA-->>LBD: LBA advertisement (unicast to LBD) + LBD->>LBA: LBP message (JR) + LBA->>LBS: LBP Message (JR) + LBS-->>LBA: LBP Message (Jrep) + LBA-->>LBD: LBP Message (JRep only) + +``` + +JR = Join Request, JRep = Join Reply + +Sequence diagram showing the Simple LBP message sequence between LBD, LBA, and LBS. The sequence starts with LBD sending an LBA solicitation (1hop broadcast) to LBA. LBA responds with an LBA advertisement (unicast to LBD). LBD then sends an LBP message (JR) to LBA. LBA forwards the LBP Message (JR) to LBS. LBS responds with an LBP Message (Jrep) to LBA. Finally, LBA sends an LBP Message (JRep only) to LBD. A note at the bottom right indicates G.9903(12)-Amd.1(13)\_FE.3. A legend below the diagram states JR = Join Request, JRep = Join Reply. + +**Figure E.3 – Simple LBP message sequence chart** + +### E.3.3.5 LBP in secured 6LoWPAN + +In a secured 6LoWPAN, the LBD must exchange authentication credentials using its join key. Apart from requesting network resources, in the case of a secured network, this process may need to exchange several encrypted messages between the LBD and authentication server. The LBA and LBS serve as a 'secured tunnel' for the authentication message exchange process. Both the LBA and LBS keep account of the last LIB request/reply processed by themselves. + +Example: LBP with EAP + +The following figure shows how the LBP works with another authentication protocol like EAP. At first the LBD broadcasts an LIB request (1 hop) to the LBA. The LBA already has a secured route to the LBP so it just unicasts the LIB request to the LBS. The LBS sends an EAP packet prepared with the LBD's authentication credentials and sends it to the authenticator. It is also possible that an LBS entity and authenticator entity resides on a single system. As discussed earlier, the LBS serves as a translator between an LBP and EAP message exchange in this authentication process and finally when AM indicates the success of authentication, it sends all network resources along with the ACCEPTED code. In the case of failure in the authentication process, a DECLINE code is sent to the LBD. + +![Sequence diagram showing LBP message exchange between LBD, LBA, LBS, EAP, and EAP authentication server. The diagram is divided into three phases: One hop (LBD to LBA), Multi-hop LBP (LBA to LBS), and EAP (LBS to EAP server).](f803be090d37a5189dbc87c1c87b6c63_img.jpg) + +The sequence diagram illustrates the interaction for LBP message exchange with EAP authentication. It features five lifelines: LBD (LoWPAN bootstrapping device), LBA (LoWPAN bootstrapping agent), LBS (LoWPAN border router), EAP (Extensible Authentication Protocol), and an EAP authentication server. The LBS contains an 'Authenticator module' with 'AM' (Authenticator Module) and 'NAM' (Network Access Module). The sequence is divided into three horizontal segments: 'One hop' (between LBD and LBA), 'Multi-hop LBP' (between LBA and LBS), and 'EAP' (between LBS and the EAP authentication server). The message flow is as follows: + + +- One hop:** LBD sends an 'LBA solicitation (1hop broadcast)' to LBA. LBA responds with 'LBA advertisement' and 'LBP message (JR)'. LBD replies with 'LBP message (challenge from EAP)' and 'LBP message (reply for EAP)'. +- Multi-hop LBP:** LBA forwards an 'LBP message (on behalf of LBD)' to LBS. LBS responds with 'LBP message (challenge of EAP)'. LBA then forwards 'LBP message (reply for EAP)' to LBD. +- EAP:** LBS sends an 'EAP reply' to the EAP authentication server, which responds with 'Next challenge'. + + Vertical ellipses indicate repeated or ongoing exchanges. The diagram is labeled 'G.9903(12)-Amd.1(13)\_FE.4'. + +Sequence diagram showing LBP message exchange between LBD, LBA, LBS, EAP, and EAP authentication server. The diagram is divided into three phases: One hop (LBD to LBA), Multi-hop LBP (LBA to LBS), and EAP (LBS to EAP server). + +**Figure E.4 – LBP message sequence chart with EAP authentication** + +### E.3.3.6 Role of entities in LBP + +Role of LoWPAN bootstrapping device (LBD): + +- It selects the LBA using the LBA discovery phase. +- If it does not find an LBA, it gives up after waiting for a certain amount of time. +- If it receives an LBP message with the code "CHALLENGE", it must send another LBP message containing the appropriate value against the challenge/query in the bootstrapping data field. +- It **MUST** increment seq for every new LBP message. For retransmission seq should remain same. + +Role of LoWPAN bootstrapping agent (LBA): + +When the LBA receives an LBP message from the LBD. + +- 1) If the LBD is already on the black list, discard. +- 2) If the LBD is new, and 6LoWPAN is an open network: + - a) Send 'LBP message' with ACCEPTED along with all PSI from its own LIB. + - b) If there is an LBS in the PAN, forward the 'LBP message' to the LBS for DSI. +- 3) If the LBD is old, and 6LoWPAN is an open network: + - a) If it matches with the last seq no. send the last reply; + - b) otherwise discard. +- 4) If the LBD is new, and 6LoWPAN is a secured network: + - a) forward the LBP message to LBS. +- 5) If the LBD is old, and 6LoWPAN is a secured network: + - a) If it matches with the last seq no. send the previously saved last LBP message 'for LBD'. + - b) If the LBP has completed, discard. + +- c) If the LBP is 'CHALLENGE' and new seq is next to the last one, forward the message to the LBS. + +When the LBA receives an LBP message from the LBS (for LBD): + +- If it is ACCEPTED and a 16-bit short address is the responsibility of the LBA, it calculates and appends the 16-bit short address with the LIB reply. +- Otherwise, if it is ACCEPTED, DECLINED or CHALLENGE, forward it to the corresponding LBD. +- If it is not ACCEPTED or DECLINED, delete the previously saved LBP message and save this LBP message. +- If it is DECLINED based on the security policy, mark it as 'Blacklisted'. +- If there is no activity in some of the flow (LBD-LBS pair), mark the LBD and based on the security policy include it in 'Black list'. + +Role of LoWPAN bootstrapping server (LBS): + +In the case of an open 6LoWPAN: + +- If the LBD is 'valid' that means its EUI-64 is in an accepted list or not in the rejection list, it sends an ACCEPTED code and the necessary DSI and 16-bit short address (if the address should be assigned centrally). + +In the case of a secured 6LoWPAN: + +- The AM of the LBS determines the authentication server for a particular EUI address and sends authentication mechanism initiation with the authentication credentials to that authentication server. +- When it gets a reply from the authentication server, if it is success, it prepares a success reply; if it is failure, it prepares a failure reply; if it is challenge/query, it prepares a processing reply for the LBD and sends it to the LBA. +- When the AM module receives 'success' from the authentication server, it informs 'success' to the NAM and sends the success response to NAM. NAM then sends the DSI along with the response in an LBP message. + +### E.3.4 Assigning the short address + +During the LBP procedure, the LBD may set a short address either by itself or after receiving the address from the PAN. The short address must be unique in a PAN and may be given by a centralized or distributed way. + +One of the approaches to distribute the short address among the LBDs is in a centralized fashion where a centralized entity (e.g., LBS) assigns a 16-bit short address for an LBD. Allocation of the short address MAY be based on First-Available-Address-First or a randomly chosen one or using any other algorithm. + +The distributed approach is another way to assign a 16-bit short address to LBDs. In this approach, the LBA assigns a short address to the joining device, LBD. A hierarchical addressing scheme could be used by the LBA for this purpose. The following figure describes the address calculation scheme. This scheme requires one parameter MC, the maximum number of addresses a LBA can assign. If the present LBD is the first of the children, then it gets the short address by the following formula: + +$$FC = MC \times AP + 1$$ + +where FC is the LBD address, and AP is the address of the LBA. + +If LBD is not the first child of this LBA, it receives the address which is next to the last address assigned by that LBA. + +For example, if LBA (1) assigned address 6 to its last LBD, it assigns address 7 to its next LBD. + +![Diagram of the assignment scheme of the short address. A Coordinator (0) is at the top, connected to four routers (1, 2, 3, 4). Router 1 is connected to nodes 5, 6, 7, 8. Router 4 is connected to nodes 17, 18, 19, 20. Node 17 is connected to nodes ..., 69, 70, 71, 72, ... . An arrow points to router 4 with the label 'Routers'. The text 'G.9903(12)-Amd.1(13)_FE.5' is at the bottom.](33d39ec22f2b13308b36d07d0af593e1_img.jpg) + +MC = 4 + +G.9903(12)-Amd.1(13)\_FE.5 + +Diagram of the assignment scheme of the short address. A Coordinator (0) is at the top, connected to four routers (1, 2, 3, 4). Router 1 is connected to nodes 5, 6, 7, 8. Router 4 is connected to nodes 17, 18, 19, 20. Node 17 is connected to nodes ..., 69, 70, 71, 72, ... . An arrow points to router 4 with the label 'Routers'. The text 'G.9903(12)-Amd.1(13)\_FE.5' is at the bottom. + +**Figure E.5 –The assignment scheme of the short address** + +### E.3.5 Obtaining IPv6 address + +The IPv6 interface identifier of a device can be obtained as described in clause 6 of [IETF RFC 4944]. After having a unique IPv6 interface identifier, the device begins to obtain an IPv6 address prefix. The IPv6 address prefix for a particular 6LoWPAN is stored by the IPv6 router in the 6LoWPAN. ICMPv6 is used to share these parameters. Routers in 6LoWPAN are supposed to broadcast router advertisement (RA) messages periodically. The RA message must contain the prefix option which can be used in the 6LoWPAN. Devices which wish to obtain an IPv6 address prefix may wait for an RA message until RA\_WAIT\_TIME elapsed. After that, if no RA message is received, they may broadcast a router solicitation message for requesting the RA message. + +The router solicitation and RA messages can have additional option fields as described in [IETF RFC 4861]. Source/Target link-layer address option field should contain the EUI-64 address or the combined address with PAN ID and 16-bit short address of the source or target device as below. + +![](181cffb84431bf3ff6130a6334dbc2ed_img.jpg) + +| | | | | | | | | | | | | | | | | | +|----------------|---|---|---|---|---|---|---|---|------------|---|---|---|---|---|---|---| +| 0 | | | | | | | | | 1 | | | | | | | | +| Bits | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 | 1 | 2 | 3 | 4 | 5 | +| Code | | | | | | | | | Identifier | | | | | | | | +| EUI-64 Address | | | | | | | | | | | | | | | | | +| Reserved | | | | | | | | | | | | | | | | | + +**Figure E.6 – Source link-layer address option field** + +![Diagram of Target link-layer address option field structure. It shows a 16-bit field divided into two bytes. The first byte (bits 0-7) is 'Type'. The second byte (bits 8-15) is 'Length'. Below these are four multi-byte fields: PAN ID, Short Address, and Reserved.](978794771205b002dd72295a59de7919_img.jpg) + +| | | | | | | | | | | | | | | | | +|--------------------------------------|--|--|--|--|--|--|--|--------|--|--|--|--|--|--|--| +| 0 | | | | | | | | 1 | | | | | | | | +| Bits 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 | | | | | | | | | | | | | | | | +| Type | | | | | | | | Length | | | | | | | | +| PAN ID | | | | | | | | | | | | | | | | +| Short Address | | | | | | | | | | | | | | | | +| Reserved | | | | | | | | | | | | | | | | + +Diagram of Target link-layer address option field structure. It shows a 16-bit field divided into two bytes. The first byte (bits 0-7) is 'Type'. The second byte (bits 8-15) is 'Length'. Below these are four multi-byte fields: PAN ID, Short Address, and Reserved. + +**Figure E.7 – Target link-layer address option field** + +Multiple IPv6 routers could form a single or multiple 6lowpan(s). If there are multiple routers in a 6LoWPAN, the device should consider which one is to be selected as a default router. One possible way of selection is to compare the hop counts travelled of the RA message of each router. The detailed algorithm for the selection is for further study. + +### E.3.6 Configuration parameters + +This section gives default values for some important parameters associated with the 6LoWPAN commissioning protocol. A particular node may wish to change certain parameters. + +**Table E.4 – Parameters used in the commissioning protocol** + +| Parameter name | Value | +|------------------------|------------| +| CHANNEL_LIST | 0xFFFFF800 | +| SCAN_DURATION | 3 | +| SUPERFRAME_ORDER | 15 | +| BEACON_ORDER | 15 | +| START_RETRY_TIME | 1 000 ms | +| JOIN_RETRY_TIME | 4 000 ms | +| ASSOCIATION_RETRY_TIME | 4 000 ms | + +## E.4 IANA consideration + +For further study. + +## E.5 Security considerations + +[IEEE 802.15.4] devices are required to support AES link-layer security. The MAC layer also provides all keying material necessary to provide the security services. It is not defined however, when security shall be used especially when combining with bootstrapping. After the device starts and joins the network, security services such as key management and device authentication should be done automatically. Detailed algorithms for security on bootstrapping, is for further study. + +## Annex F + +### Regional requirements for Japan + +(This annex forms an integral part of this Recommendation.) + +#### F.1 Overview + +This annex describes the domestic practices, standards and the way to apply the ITU-T G.9903 system under these conditions in Japan. The additional specifications described in this annex are defined for the purpose of complying with [ARIB STD-T84], which is based on Japanese Radio Regulatory Laws. + +ITU-T G.9903 devices for use within the Japanese environment shall comply with ITU-T G.9903 specifications for the FCC bandplan defined in this Recommendation. The additional specifications described in this annex shall take precedence over the ITU-T G.9903 specifications for the FCC bandplan. + +#### F.2 Physical layer specifications for ARIB bandplan + +##### F.2.1 System fundamental parameters for ARIB bandplan + +The frequency bands used for the ARIB bandplan are defined in clause 2.1 of [TTC JJ-300.11]. + +The frame control header uses 72 bits, resulting in 16 FCH symbols in case of no notching. + +Modulations D8PSK and 16-QAM shall not be supported. + +The preamble phase vector sequence shall be defined as Table F.1, optimized for 54 subcarriers. + +**Table F.1 – Preamble phase vector for the ARIB bandplan** + +| c | $\phi_c$ | c | $\phi_c$ | c | $\phi_c$ | +|----|-------------|----|-------------|----|-------------| +| 33 | $2(\pi/8)$ | 51 | $1(\pi/8)$ | 69 | $15(\pi/8)$ | +| 34 | $(\pi/8)$ | 52 | $12(\pi/8)$ | 70 | $3(\pi/8)$ | +| 35 | $(\pi/8)$ | 53 | $6(\pi/8)$ | 71 | $8(\pi/8)$ | +| 36 | 0 | 54 | $15(\pi/8)$ | 72 | $13(\pi/8)$ | +| 37 | $15(\pi/8)$ | 55 | $9(\pi/8)$ | 73 | $1(\pi/8)$ | +| 38 | $14(\pi/8)$ | 56 | $2(\pi/8)$ | 74 | $4(\pi/8)$ | +| 39 | $13(\pi/8)$ | 57 | $11(\pi/8)$ | 75 | $8(\pi/8)$ | +| 40 | $11(\pi/8)$ | 58 | $4(\pi/8)$ | 76 | $11(\pi/8)$ | +| 41 | $9(\pi/8)$ | 59 | $12(\pi/8)$ | 77 | $14(\pi/8)$ | +| 42 | $6(\pi/8)$ | 60 | $4(\pi/8)$ | 78 | $1(\pi/8)$ | +| 43 | $3(\pi/8)$ | 61 | $12(\pi/8)$ | 79 | $3(\pi/8)$ | +| 44 | 0 | 62 | $3(\pi/8)$ | 80 | $4(\pi/8)$ | +| 45 | $12(\pi/8)$ | 63 | $10(\pi/8)$ | 81 | $6(\pi/8)$ | +| 46 | $9(\pi/8)$ | 64 | $1(\pi/8)$ | 82 | $7(\pi/8)$ | +| 47 | $4(\pi/8)$ | 65 | $7(\pi/8)$ | 83 | $8(\pi/8)$ | + +**Table F.1 – Preamble phase vector for the ARIB bandplan** + +| c | $\phi_c$ | c | $\phi_c$ | c | $\phi_c$ | +|----------|-------------|----------|-------------|----------|-------------| +| 48 | $0(\pi/8)$ | 66 | $14(\pi/8)$ | 84 | $9(\pi/8)$ | +| 49 | $12(\pi/8)$ | 67 | $3(\pi/8)$ | 85 | $10(\pi/8)$ | +| 50 | $6(\pi/8)$ | 68 | $9(\pi/8)$ | 86 | $10(\pi/8)$ | + +### **F.3 Data link layer specifications** + +#### **F.3.1 TM (tone map)** + +The receiver estimates the per-tone quality of the channel and maps each sub-band (3 tones per sub-band). Since there are only 54 active carrier in the ARIB band, the tone map should occupy the first 18 bits (Tone map [0:17]), while the remaining 6 bits of the tone map should be set to a value of "0". + +#### **F.3.2 CIFS** + +In order to comply with the carrier sense regulation of [ARIB STD-T84], the duration of CIFS shall be 108 symbols (25 ms). In the retransmission, the CIFS parameter shall be same as for the ITU-T G.9903 specifications for the FCC bandplan. The range of macMaxFrameRetries (maximum number of retransmissions) shall be 0-7. + +#### **F.3.3 LBP joining procedure** + +The ID\_S and ID\_P fields may be set to 64 bit EUI or a variable size user ID which could be up to 36 ASCII characters (36 bytes). + +## **Annex G** + +### **Regional requirements for the USA** + +(This annex forms an integral part of this Recommendation.) + +This annex describes the domestic practices, standards and the application method for the preamble-based coexistence mechanism in clause 6.2.2 in the USA. + +For devices complying with this Recommendation operating in the USA, the default value of attribute macCoexPreambleDetectionEnabled shall be set to TRUE (see Table 6-2). + +If the coexistence preamble is detected, then at least one narrowband PLC technology using a native preamble different from the one specified in this Recommendation is present and operating over the same frequency band. In this case, attribute macCoexPreambleEnabled (see Table 6-2) shall also be set to TRUE. + +# Appendix I + +## Examples on encoding and decoding + +(This appendix does not form an integral part of this Recommendation.) + +### I.1 Example for data encoding + +Suppose we have a 40-byte MAC frame to send in DQPSK mode (2 bits per symbol) with 25 carriers available (due to notching and/or tone-mapping). + +The size of the data at the interleaver input is equal to $\text{inter\_input\_size} = (((40 \times 8) + (16 \times 8)) + 6) \times 2 = 908$ bits (Reed-Solomon adds 16 bytes, the convolutional encoder adds 6 bits and multiplies the size by 2). + +Using CENELEC bandplans ( $\text{FL}_{\text{Band}} = 4$ ) as an example, the minimal interleaver buffer size: + +- We have 25 carriers, so $m = 25$ . +- We have $n = \text{FL} \times \text{FL}_{\text{Band}} \times \text{bits\_per\_symbol}$ , so + - $\text{FL} = \text{ceiling}(\text{inter\_input\_size} / (m \times \text{FL}_{\text{Band}} \times \text{bits\_per\_symbols}))$ + - $= \text{ceiling}( 908 / (25 \times 4 \times 2) ) = \text{ceiling}( 4,54 ) = 5$ and $n = 40$ . + +As $m=25$ and $n=40$ , the matrix can "store" 1000 bits and the data is 908 bits long, so 92 bits of padding must be added. Those 92 bits of padding are split between byte padding and bit padding, the byte padding being maximized (with the constraint that the input is in bytes). So the upper layer shall add $\text{floor}( 92 / 2 / 8 ) = 5$ bytes of padding before the data enters the scrambler, and the 12 remaining bits of bit padding shall be added by the PHY layer at the interleaver input. + +### I.2 Example for data decoding + +When decoding a frame, we need to compute the amount of bit padding to process the frame. The FCH contains the following information (decoding the example in above clause): + +- $\text{FL} = 5$ +- DQPSK modulation (2 bits per symbol) +- 25 carriers used (tone-map + notching information) + +Using CENELEC bandplans ( $\text{FL}_{\text{Band}} = 4$ ) as an example, the interleaver buffer can hold $25 \times (4 \times \text{FL} \times 2) = 1\,000$ bits. + +In these 1 000 bits: + +- $16 \times 8 \times 2$ bits were added by Reed-Solomon. +- 12 bits were added by the convolutional encoder. +- The remaining 732 bits are a mix of data and padding: + - The data part is equal to $\text{floor}(732/2/8)$ bytes = 45 bytes. + - The bit padding is equal to $732 - (\text{data\_size} \times 8 \times 2)$ bits = 12 bits. + +In the 45 bytes of data, 5 bytes of byte padding are removed by the MAC layer using the "Segment length" header information. + +## Appendix II + +### Test vectors for cryptographic building blocks + +(This appendix does not form an integral part of this Recommendation.) + +This appendix provides sample test vectors, with the aim of providing implementers with a reference example to clarify the security mechanism. All the following test vectors are represented in hexadecimal form. + +#### II.1 Introduction + +These examples illustrate the creation of MAC secured frames, through the ciphering of a MAC data frame. The common settings for the test vectors are the following: + +- Sender short MAC address = 0x002A +- Sender PAN ID = 0x781D +- Sender macDSN parameter is set to 0x29. +- Sender neighbour table has one entry for MAC address 0x010C with: + - TMRValidTimeset to macTMRTTL (so no ToneMap is requested). + - Modulation = DBPSK mode. + - ToneMap = all sub-carriers used, TXGAIN = 0, TXCOEF = 0 for each carrier group +- Sender macFrameCounter set to 2 685 554 979 (0xA0125123). +- Sender macKeyTable contains one GMK: KeyIndex = 0x00, Key = 0xAB10341145111BC3C12DE8FF11142204 +- Receiver short MAC address = 0x010C +- Receiver PAN ID = 0x781D +- The transmission is acknowledged. +- The QoS is set to normal priority. + +##### II.1.1 Short frame ciphering + +In this case, the MSDU unencrypted payload is composed of 45 bytes equal to 0x75. This results in an encrypted frame that lasts for one segment only. + +Inputs for the encryption and authentication transformations are: + +- Nonce: 0x781D002A781D002AA012512305 +- a data: 0x6988291D780C012A000D235112A000 +- MSDU: 75757575...75 ( $0x75*45$ ) + +Outputs after the transformations are: + +- MIC-32: 0xB87AB7B7 +- Encrypted frame: + +0100316988291D780C012A000D235112A000721D8CF9AF919FB134363150CA78ACFBE73CE + 52064C728B2E0388157D0F1A3C19CD14FDD0D465CF50D923B2A7FB87AB7B7000000000847 + 4 + +##### II.1.2 Long frame ciphering + +In this case, the MSDU unencrypted payload is composed of 300 bytes equal to 0xA2. This results in an encrypted frame that lasts for two segments. + +Inputs for the encryption and authentication transformations are: + +- Nonce: 0x781D002A781D002AA012512305 +- a data: 0x6988291D780C012A000D235112A000 +- MSDU: A2A2A2...A2 (0xA2\*300) + +Outputs after the transformations are: + +- MIC-32: 0xDD28E342 +- Encrypted frames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ibliography + +- [b-EUI 64] EUI-64™ (in force), *Guidelines for 64-bit Global Identifier, IEEE.* +- [b-IEEE 754-2008] IEEE 754-2008, *IEEE Standard for Floating-Point Arithmetic.* +- [b-IETF RFC 3513] IETF RFC 3513 (2003), *Internet Protocol Version 6 (IPv6) Addressing Architecture.* +- [b-IETF RFC 3561] IETF RFC 3561 (2003), *Ad hoc On-Demand Distance Vector (AODV) Routing.* +- [b-IETF RFC 5148] IETF RFC 5148 (2008), *Jitter Considerations in Mobile Ad Hoc Networks (MANETs).* +- [b-IETF RFC 6130] IETF RFC 6130 (2011), *Mobile Ad Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP).* +- [b-IETF RFC 6206] IETF RFC 6206 (2011), *The Trickle Algorithm.* +- [b-IETF RFC 6621] IETF RFC 6621 (2012), *Simplified Multicast Forwarding.* + + + + + +## SERIES OF ITU-T RECOMMENDATIONS + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file diff --git 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+**Protocol for identifying home network topology** + +Recommendation ITU-T G.9973 + +ITU-T + +![ITU logo](1d7527f4316cfe2d342b08d1653d1592_img.jpg) + +The logo of the International Telecommunication Union (ITU) features a stylized globe with a red lightning bolt striking through it. The letters "ITU" are prominently displayed in blue and white within the globe. + +ITU logo + +International +Telecommunication +Union + +# ITU-T G-SERIES RECOMMENDATIONS **TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS** + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------|----------------------| +| INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS | G.100–G.199 | +| GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS | G.200–G.299 | +| INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES | G.300–G.399 | +| GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES | G.400–G.449 | +| COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY | G.450–G.499 | +| TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS | G.600–G.699 | +| DIGITAL TERMINAL EQUIPMENTS | G.700–G.799 | +| DIGITAL NETWORKS | G.800–G.899 | +| DIGITAL SECTIONS AND DIGITAL LINE SYSTEM | G.900–G.999 | +| MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE – GENERIC AND USER-RELATED ASPECTS | G.1000–G.1999 | +| TRANSMISSION MEDIA CHARACTERISTICS | G.6000–G.6999 | +| DATA OVER TRANSPORT – GENERIC ASPECTS | G.7000–G.7999 | +| PACKET OVER TRANSPORT ASPECTS | G.8000–G.8999 | +| ACCESS NETWORKS | G.9000–G.9999 | +| Metallic access networks | G.9700–G.9799 | +| Optical line systems for local and access networks | G.9800–G.9899 | +| In premises networks | G.9900–G.9999 | + +*For further details, please refer to the list of ITU-T Recommendations.* + +## Recommendation ITU-T G.9973 + +# Protocol for identifying home network topology + +## Summary + +Based on Recommendation ITU-T G.9971, Recommendation ITU-T G.9973 specifies the configuration management protocol. This protocol is used to manage devices in the Internet protocol (IP) home network for the purpose of showing users the layer 2 home network topology. Recommendation ITU-T G.9973 also enables fault management utilizing device information that the local agent (LA) of the device manages. They are described in TTC JJ-300.00. + +## History + +| Edition | Recommendation | Approval | Study Group | Unique ID* | +|---------|----------------|------------|-------------|---------------------------------------------------------------------------| +| 1.0 | ITU-T G.9973 | 2011-10-29 | 15 | 11.1002/1000/11405 | +| 2.0 | ITU-T G.9973 | 2017-08-13 | 15 | 11.1002/1000/13340 | + +## Keywords + +Access gateway, Ethernet, fault, home network, IP, LLDP, management, non-Ethernet data link, protocol, topology, UDA, UpnP. + +--- + +\* To access the Recommendation, type the URL in the address field of your web browser, followed by the Recommendation's unique ID. For example, . + +## FOREWORD + +The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. + +The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. + +In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. + +## NOTE + +In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words "shall" or some other obligatory language such as "must" and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. + +## INTELLECTUAL PROPERTY RIGHTS + +ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. + +As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at . + +© ITU 2017 + +All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. + +## Table of Contents + +| | Page | +|-------------------------------------------------------------------------------------------|------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Definitions ..... | 2 | +| 3.1 Terms defined elsewhere ..... | 2 | +| 3.2 Terms defined in this Recommendation..... | 2 | +| 4 Abbreviations and acronyms ..... | 2 | +| 5 Conventions ..... | 3 | +| 6 The applied area of the protocol for identifying home network topology..... | 3 | +| 7 Functional requirements of the protocol for identifying the home network topology ..... | 3 | +| 8 The protocol for identifying home network topology ..... | 4 | +| 8.1 Management information ..... | 5 | +| 8.2 Interaction between the local manager and the local L3 agent ..... | 5 | +| 8.3 Interaction between the local manager and the local L2 agent ..... | 6 | +| 9 Connectivity check between the local manager and the local agents..... | 6 | +| 9.1 Connectivity check between the local manager and the local L3 agent..... | 7 | +| 9.2 Connectivity check between the local manager and the local L2 agent..... | 7 | +| Annex A – Detailed fields and values of TLVs ..... | 8 | +| Bibliography..... | 9 | + + + +# Protocol for identifying home network topology + +## 1 Scope + +Various kinds of Internet protocol (IP) terminal devices, such as personal computers (PCs), digital televisions (TVs), gaming devices, and portable music devices, have recently been, and continue to be, connected to the IP home network. Furthermore, their number is increasing. The kinds of transmission media (power line communication (PLC), wireless, unshielded twisted pair (UTP), etc.) used to connect each IP terminal are also becoming more varied. Under such circumstances, most users are unable to troubleshoot the IP home network by themselves, without the availability of appropriate network services. It is desired to introduce a simple and easy IP home network management that can localize the fault in each device and network and help recover from trouble. + +[ITU-T G.9971] describes three kinds of management requirements for the IP home network: configuration management; fault management; and performance management. Based on [ITU-T G.9971], this Recommendation specifies the configuration management protocol that is described in [TTC JJ-300.00]. This protocol is used to manage devices in the IP home network for the purpose of showing the layer 2 (L2) home network topology to users within the home network only (behind the access gateway (AGW)). On the other hand, [b-BBF TR-069], covering the customer premises equipment (CPE) wide area network (WAN) management protocol, is the candidate for the remote home network management protocol from outside the AGW. Although it may be necessary in the future to study the interaction between this management protocol and the CPE WAN management protocol, it lies outside the scope of this Recommendation. + +This Recommendation also enables fault management utilizing device information that the local agent (LA) of the device manages. + +This Recommendation identifies devices on a single link as shown in Figure 8-1. Note that "a single link" means the one data link layer, which constitutes one IP domain between the AGW and the IP terminal. As the deployment of new link-layer technologies such as [b-IEEE 802.15.4] will enable and require the use of multiple links in the home network, this Recommendation covers multiple links composed of IP devices and may be extended to cover multiple links composed of IP and non-IP devices in the future. + +Home network security is important. A device using this Recommendation to collect information about the home network will be required to take certain steps to ensure that the information is not accessible through the WAN interface of the AGW. + +## 2 References + +The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. + +[ITU-T G.9971] Recommendation ITU-T G.9971 (2010), *Requirements of transport functions in IP home networks*. + +[IEEE 802.1AB] IEEE 802.1AB-2016, *IEEE standard for local and metropolitan area networks – Station and media access control connectivity discovery*. + +- [IEEE 802.1D] IEEE 802.1D-2004, *IEEE Standard for local and metropolitan area networks: media access control (MAC) bridges*. +- [IETF RFC 1701] Internet Engineering Task Force Request For Comments 1701 (1994), *Generic routing encapsulation (GRE)*. +- [ISO/IEC 29341-1] ISO/IEC 29341-1:2011, *Information technology – UPnP Device Architecture – Part 1: UPnP Device Architecture Version 1.0*. +- [TTC JJ-300.00] TTC JJ-300.00 (2017), *Home-network topology identifying protocol (HTIP)*. + +## 3 Definitions + +### 3.1 Terms defined elsewhere + +None. + +### 3.2 Terms defined in this Recommendation + +None. + +## 4 Abbreviations and acronyms + +This Recommendation uses the following abbreviations and acronyms: + +| | | +|--------|------------------------------------| +| AGW | Access Gateway | +| CPE | Customer Premises Equipment | +| DDD | Device Description Document | +| DVD | Digital Versatile Disk | +| GRE | Generic Routing Encapsulation | +| ICMP | Internet Control Message Protocol | +| ID | Identifier | +| IP | Internet Protocol | +| L2 | Layer 2 | +| L3 | Layer 3 | +| LA | Local Agent | +| LLDP | Link Layer Discovery Protocol | +| LLDPDU | LLDP Data Unit | +| LM | Local Manager | +| MAC | Media Access Control | +| OUI | Organizationally Unique Identifier | +| PC | Personal Computer | +| PLC | Power Line Communication | +| TLV | Type, Length, Value | +| TTL | Time To Live | +| TV | Television | +| UDA | UPnP Device Architecture | + +| | | +|------|-------------------------| +| UTP | Unshielded Twisted Pair | +| UPnP | Universal Plug and Play | +| WAN | Wide Area Network | + +## 5 Conventions + +In this Recommendation: + +The keyword "**must**" implies that it is strictly required to claim conformance. + +The keyword "**should**" implies that it is recommended for performance improvement, etc. although it is not absolutely required to claim conformance. + +The keyword "**may**" implies that it is not required to claim conformance. + +## 6 The applied area of the protocol for identifying home network topology + +Figure 6-1 shows the home network area in which the protocol specified by this Recommendation is applied. Both the access network and the IP/non-IP home network behind the IP terminal lie outside the scope of this Recommendation. Moreover, the IP home network that is directly connected from the access network without the AGW also lies outside the scope. + +The target home network is composed of the IP terminal, the network equipment and the AGW, where one or more IP terminals can be connected to the IP home network and zero or more pieces of network equipment can reside within the IP home network. The network equipment is a hardware device that has two or more ports and a function to transfer frames and packets received at one port to the other by using a media access control (MAC) forwarding table (e.g., Ethernet bridge). The AGW has two kinds of function: the home network side and the access network side, while it contains L2 or layer 3 (L3) functions. This Recommendation only covers configuration management on the home network side functions of the AGW. Moreover, even if the AGW contains an L3 function, such as an IP routing function, this Recommendation only covers the functions necessary for identifying L2 home network topology. + +![Diagram illustrating the applied area of the protocol for identifying home network topology. The diagram shows a sequence of components: Access network (dashed box), AGW (solid box), Network equipment (solid box), IP terminal (solid box), and IP/non-IP home network (dashed box). The AGW, Network equipment, and IP terminal are grouped together within a shaded area labeled 'The applied area of the protocol'. The AGW is connected to the Access network on its left and the Network equipment on its right. The Network equipment is connected to the IP terminal on its right. The IP terminal is connected to the IP/non-IP home network on its right. The label 'G.9973(17)_F6-1' is present in the bottom right corner of the diagram.](b28af4985cdef1e519e3aaf26561dcb3_img.jpg) + +Diagram illustrating the applied area of the protocol for identifying home network topology. The diagram shows a sequence of components: Access network (dashed box), AGW (solid box), Network equipment (solid box), IP terminal (solid box), and IP/non-IP home network (dashed box). The AGW, Network equipment, and IP terminal are grouped together within a shaded area labeled 'The applied area of the protocol'. The AGW is connected to the Access network on its left and the Network equipment on its right. The Network equipment is connected to the IP terminal on its right. The IP terminal is connected to the IP/non-IP home network on its right. The label 'G.9973(17)\_F6-1' is present in the bottom right corner of the diagram. + +Figure 6-1 – The applied area of the protocol + +## 7 Functional requirements of the protocol for identifying the home network topology + +The protocol is mainly used for identifying the home network topology. It is also used for checking the connectivity between the local manager (LM) and the LA, the specifications of which are given in clause 11.1 of [ITU-T G.9971]. This Recommendation specifies the protocol that meets some of the requirements listed in clause 11.3 of [ITU-T G.9971]. The functional requirements, as well as their relationship with those in [ITU-T G.9971], are given below. Figure 8-1 is also helpful for understanding these requirements. + +R1 (based on R11-C1 and R11-C2 in [ITU-T G.9971]): The local L3 agent must be able to acquire the IP and MAC addresses of the device where the local L3 agent resides. The local L3 agent must also be able to transmit the IP and MAC addresses to the LM in the manner described in clause 8.2. + +R2 (based on R11-C3 in [ITU-T G.9971]): The local L2 agent must be able to acquire the MAC forwarding table retained by the device where the local L2 agent resides. The local L2 agent must also be able to transmit the MAC forwarding table to the LM in the manner described in clause 8.3. + +R3 (based on R11-C4 in [ITU-T G.9971]): The local L3 agent must be able to acquire and transmit its device information to the LM in the manner described in clause 8.2. + +R4 (based on R11-C5 in [ITU-T G.9971]): The local L2 agent must be able to acquire and transmit its device information to the LM in the manner described in clause 8.3. + +R5 (based on R11-L2 in [ITU-T G.9971]): The local L3 agent should be able to respond to a connectivity check command from the LM in the manner described in clause 9.1. + +R6 (based on R11-L2 in [ITU-T G.9971]): The local L2 agent should be able to send packets periodically to the LM for checking connectivity in the manner described in clause 9.2. + +R7: The local L2 agent must be able to acquire the MAC address of the device where the local L2 agent resides. The local L2 agent must also be able to transmit the MAC address to the LM in the manner described in clause 8.3. + +R8: The local L2 agent must be able to acquire the IP address of the device where the local L2 agent resides. (Required when the local L2 agent supports the function to transmit a link layer discovery protocol data unit (LLDPDU) encapsulated in an IP packet in the manner described in clause 8.3) + +## 8 The protocol for identifying home network topology + +This clause describes the interaction between the LM and the local L3 agent, as well as the LM and the local L2 agent. + +Management information to identify the IP home network topology falls into two areas: device information and MAC forwarding table information. One example of device information is the device category, such as the network equipment or PC. Device information resides in the local L3 agent or the local L2 agent, while the MAC forwarding table information resides in the local L2 agent of the network equipment or the AGW. + +Management information can be retrieved by the LM, which can reside in any device in the IP home network, according to the last paragraph of clause 11.1 of [ITU-T G.9971]. Figure 8-1 shows a typical case where the LM resides in the AGW. The AGW has both the local L2 and L3 agents. The network equipment has the local L2 agent, and there are two types of the IP terminal which has the local L2 agent and the local L3 agent, respectively. The local L3 agent of the IP terminal sends device information by using the UPnP device architecture (UDA), while the local L2 agent of the network equipment sends both device information and MAC forwarding table information by using the link layer discovery protocol (LLDP). Note that the local L2 and L3 agents of the AGW locally send device information to the LM. The LM can identify the IP home network topology by analysing the collection of this management information. By utilizing this IP home network topology information, some applications can perform fault localization in response to the failure of network services. + +![Diagram illustrating the protocol for identifying home network topology. It shows three main components: AGW (Access Gateway), Network equipment, and IP terminals. The AGW contains a Local manager (red oval), a Local L2 agent (blue oval), and a Local L3 agent (blue oval). The Network equipment contains a Local L2 agent (blue oval). There are two IP terminals: the top one contains a Local L3 agent (blue oval), and the bottom one contains a Local L2 agent (blue oval). Arrows indicate two types of transmissions: 'Transmission of device information from local L3 agent (clause 8.2)' from the top IP terminal to the AGW, and 'Transmission of device and MAC forwarding table information from local L2 agent (clause 8.3)' from the Network equipment to the AGW. A dashed vertical line separates the Network equipment from the IP terminals. The diagram is labeled G.9973(17)_F8-1.](cfef993dcc8fb513de79eb1f93cf26ae_img.jpg) + +Diagram illustrating the protocol for identifying home network topology. It shows three main components: AGW (Access Gateway), Network equipment, and IP terminals. The AGW contains a Local manager (red oval), a Local L2 agent (blue oval), and a Local L3 agent (blue oval). The Network equipment contains a Local L2 agent (blue oval). There are two IP terminals: the top one contains a Local L3 agent (blue oval), and the bottom one contains a Local L2 agent (blue oval). Arrows indicate two types of transmissions: 'Transmission of device information from local L3 agent (clause 8.2)' from the top IP terminal to the AGW, and 'Transmission of device and MAC forwarding table information from local L2 agent (clause 8.3)' from the Network equipment to the AGW. A dashed vertical line separates the Network equipment from the IP terminals. The diagram is labeled G.9973(17)\_F8-1. + +**Figure 8-1 – The protocol for identifying home network topology** + +## 8.1 Management information + +Each LA of the device, such as the IP terminal, the network equipment or AGW, manages device information representing the device. It consists of at least the following four kinds of management information. Fault management information may be added to the device information as described in clause 6.1 of [TTC JJ-300.00]. The string length of the management information is described in clause 6.1 of [TTC JJ-300.00]. + +- a) Device category: represents the category of each device, such as TV or digital versatile disk (DVD) recorder. +- b) Manufacturer code: represents the company that produced the device. It is a company identifier (ID) [organizationally unique identifier (OUI) code] registered by IEEE. +- c) Model name: represents the device's brand or series name assigned by the manufacturer. +- d) Model number: represents the device's model number assigned by the manufacturer. + +MAC forwarding table information is specified for the network equipment. It represents the pair of the network equipment port and one or more MAC addresses of devices, such as the IP terminal or the network equipment or the AGW, connected to this port. + +## 8.2 Interaction between the local manager and the local L3 agent + +The local L3 agent must send device information to the LM by utilizing the universal plug and play (UPnP-) controlled device function described in [ISO/IEC 29341-1] (UDA). Note that it uses the "basic device information" part of the device description document (DDD) message per the local L3 agent. The detailed methods and timing for the LM to retrieve device information from the local L3 agent must comply with clause 2 "Description" in the UDA, while that for IPv6 must comply with Annex A in the UDA. Each element of the basic device information, such as device category, manufacturer code, model name and model number, must comply with [TTC JJ-300.00]. Moreover, detailed specifications of each element, such as the name space and the character length, must follow clause 6.2 of [TTC JJ-300.00]. + +When the local L3 agent transmits the device information to the LM, the IP and MAC addresses are set in the packet header. Therefore, the IP and MAC addresses can be transmitted to the LM. + +The LM may transmit setting information by utilizing the UPnP-controlled device function to the local L3 agent. The local L3 agent that receives the setting information then responds with the updated result by reflecting the setting information. + +## 8.3 Interaction between the local manager and the local L2 agent + +The local L2 agent must send device information and MAC forwarding table information to the LM by utilizing LLDP. Both types of information are broadcast from all ports via the LLDP agent specified in [IEEE 802.1AB]. According to [IEEE 802.1AB], the local L2 agent hands both types of information to the LLDP agent, which broadcasts it from all managed ports after attaching the device MAC address. The detailed mechanism must comply with clause 6.3 of [TTC JJ-300.00]. Instead of broadcasting both types of information, the unicast transmission may be used by the local L2 agent. + +The local L2 agent must manage the device information, MAC forwarding table information of the device on which it resides and the chassis ID identifying the local L2 agent. Moreover, the local L2 agent may manage the list of its LLDP agents' MAC addresses. The detailed mechanism to specify the chassis ID lies outside the scope of this Recommendation. + +The local L2 agent sends this management information periodically or when it is updated. The detailed specifications for timing or methods must comply with [IEEE 802.1AB]. + +The LM may transmit setting information by utilizing the LLDP message to the local L2 agent. The local L2 agent that receives the setting information then reflects the setting information. + +Figure 8-2 shows the LLDPDU frame format used by the local L2 agent. The LLDPDU header consists of the destination MAC address, the source MAC address and the LLDP Ethernet type. The source MAC address must be one of the MAC addresses managed by the LLDP agent, while the Ethernet type for LLDP must be 88-CC. According to [TTC JJ-300.00], the destination MAC address must be set to FF-FF-FF-FF-FF-FF for broadcast. The destination MAC address may be set for the unicast transmission. Each network equipment that receives the LLDPDU must handle it according to [IEEE 802.1D]. + +![Figure 8-2 – LLDPDU format diagram showing the structure of an LLDPDU frame. The frame is divided into an Ethernet header (Destination MAC address, Source MAC address, Ethernet type = 88-CC (LLDP)) and the LLDPDU payload. The LLDPDU payload contains a series of Type, Length, Value (TLV) elements: TLV1, TLV2, ..., Device category TLV, Manufacturer code TLV, Model name TLV, Model number TLV, MAC forwarding table TLV1, MAC forwarding table TLV2, ..., TLVn, and End of LLDPDU TLV.](08441fa90c5fd11994626f662ac13f19_img.jpg) + +| | | | | | | | | | | | | | | | +|-------------------------|--------------------|------------------------------|--------|------|-----|---------------------|-----------------------|----------------|------------------|---------------------------|---------------------------|-----|------|-------------------| +| Destination MAC address | Source MAC address | Ethernet type = 88-CC (LLDP) | TLV1 | TLV2 | ... | Device category TLV | Manufacturer code TLV | Model name TLV | Model number TLV | MAC forwarding table TLV1 | MAC forwarding table TLV2 | ... | TLVn | End of LLDPDU TLV | +| Ethernet header | | | LLDPDU | | | | | | | | | | | | + +G.9973(11)\_F8-2 + +Figure 8-2 – LLDPDU format diagram showing the structure of an LLDPDU frame. The frame is divided into an Ethernet header (Destination MAC address, Source MAC address, Ethernet type = 88-CC (LLDP)) and the LLDPDU payload. The LLDPDU payload contains a series of Type, Length, Value (TLV) elements: TLV1, TLV2, ..., Device category TLV, Manufacturer code TLV, Model name TLV, Model number TLV, MAC forwarding table TLV1, MAC forwarding table TLV2, ..., TLVn, and End of LLDPDU TLV. + +**Figure 8-2 – LLDPDU format** + +The four instances of type, length, value (TLVs) (TLV type=0-3) that [IEEE 802.1AB] specifies as mandatory must be contained in the LLDPDU: TLV type=0 represents "End Of LLDPDU TLV"; TLV type=1 represents "Chassis ID TLV"; TLV type=2 represents "Port ID TLV"; TLV type=3 represents "TTL TLV" (where TTL is time to live). Note that the detailed specifications must comply with clause 6.3.1 of [TTC JJ-300.00]. + +Device information and MAC forwarding table information must be sent in TLV format with extended TLV fields. Detailed fields and values are provided in Annex A. + +The local L2 agent may send the management information with the LLDPDU by using an encapsulation protocol over the IP in the data link layer that does not support the Ethernet frame. For this case, the device in which the local L2 agent resides must support generic routing encapsulation (GRE; see [IETF RFC 1701]) as an encapsulation protocol. Any other encapsulation protocols may also be supported. The detailed settings for GRE must comply with clause 6.3 of [TTC JJ-300.00]. + +## 9 Connectivity check between the local manager and the local agents + +The connectivity checks between the LM and the LAs are executed in L3 and L2. The former is described in clause 9.1, while the latter is described in clause 9.2. + +### **9.1 Connectivity check between the local manager and the local L3 agent** + +Two connectivity checks are possible in response to a fault. One is that the LM re-tries to retrieve device information from the local L3 agent (the number of re-tries lies outside the scope of this Recommendation). The other is that the LM sends an Internet control message protocol (ICMP) echo request message to the local L3 agent and receives an ICMP echo reply message. The former can be realized by referring to clause 8.2. The detailed specifications of the latter must comply with clause 7.1 of [TTC JJ-300.00]. + +### **9.2 Connectivity check between the local manager and the local L2 agent** + +The LM can keep the chassis ID as well as TTL by interacting with the local L2 agent as described in clause 8.3. Therefore, the LM can perform the connectivity check by checking whether or not the next LLDPDU comes after the previous one within the TTL period. The detailed specifications must comply with clause 7.2 of [TTC JJ-300.00]. + +## Annex A + +### Detailed fields and values of TLVs + +(This annex forms an integral part of this Recommendation.) + +This annex is extracted from [TTC JJ-300.00]. + +As shown in Figure A.1, the extension of type, length and value (TLV) fields is accomplished by setting TLV type = 127 in TLV header in accordance with [IEEE 802.1AB]. Moreover, the TLV information string must contain TTC OUI = E0-27-1A as well as TTC subtype, which is specified in Table 6-3 of [TTC JJ-300.00]. The TLV data represent device information in the case of TTC subtype = 1, while the TLV data represent MAC forwarding table information in the case of TTC subtype = 2. + +![](a26e142d3df5bef41a84a9dd099d7825_img.jpg) + +| | | | | | +|----------------------------|-------------------------------------------|----------------------------------|--------------------------|------------------------| +| TLV type = 127
(7 bits) | TLV information string length
(9 bits) | TTC OUI = E0-27-1A
(3 octets) | TTC subtype
(1 octet) | Data
(0-257 octets) | +| TLV header | | TLV information string | | | + +G.9973(11)\_FA.1 + +**Figure A.1 – TLV format for device and MAC forwarding table information** + +In accordance with clause 6.3.2 of [TTC JJ-300.00], Figure A.2 shows the data part of device information, which consists of device information ID, string length and device information data. Device information IDs represent the device category, manufacturer code, model name and model number. It may include the additional device information ID for fault management that is described in clause 8.1. Device information data represent the value of device information for each device. The detailed specifications of device information IDs and device information data must comply with clause 6.3.2 of [TTC JJ-300.00]. + +![](f6e8acf9f931452d01688d311b5c0364_img.jpg) + +| | | | +|------------------------------------|-------------------------------------------------------|-------------------------------------------| +| Device information ID
(1 octet) | String length of device information data
(1 octet) | Device information data
(0-255 octets) | +|------------------------------------|-------------------------------------------------------|-------------------------------------------| + +G.9973(1')\_FA.2 + +**Figure A.2 – Data format in TLV for device information** + +In accordance with clause 6.3.3 of [TTC JJ-300.00], Figure A.3 shows the data part of MAC forwarding table information, which consists of the kind of interface, port number, the number of MAC addresses connected to the port, and MAC addresses, including each string length. Their detailed specifications must comply with clause 6.3.3 of [TTC JJ-300.00]. + +![](704082cc3e11776bda29595c76411362_img.jpg) + +| | | | | | | | | +|-------------------------------------------------|-----------------------------------|-------------------------------------------|-----------------------------|-----------------------------------------------------------------|---------------------------|-----|---------------------------| +| String length of kind of interface
(1 octet) | Kind of interface
(0-4 octets) | String length of port number
(1 octet) | Port number
(0-4 octets) | The number of MAC addresses connecting to the port
(1 octet) | MAC address
(6 octets) | ... | MAC address
(6 octets) | +|-------------------------------------------------|-----------------------------------|-------------------------------------------|-----------------------------|-----------------------------------------------------------------|---------------------------|-----|---------------------------| + +G.9973(11)\_FA.3 + +**Figure A.3 – Data format in TLV for MAC forwarding table information** + +## Bibliography + +- [b-BBF TR-069] Broadband Forum Technical Report TR-069 Issue 1 Amendment 5 (2013), *CPE WAN management protocol v.1.4.* +- [b-IEEE 802.15.4] IEEE 802.15.4 (2015), *IEEE standard for low-rate wireless networks.* + + + + + + + +## **SERIES OF ITU-T RECOMMENDATIONS** + +| | | +|-----------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------| +| Series A | Organization of the work of ITU-T | +| Series D | Tariff and accounting principles and international telecommunication/ICT economic and policy issues | +| Series E | Overall network operation, telephone service, service operation and human factors | +| Series F | Non-telephone telecommunication services | +| Series G | Transmission systems and media, digital systems and networks | +| Series H | Audiovisual and multimedia systems | +| Series I | Integrated services digital network | +| Series J | Cable networks and transmission of television, sound programme and other multimedia signals | +| Series K | Protection against interference | +| Series L | Environment and ICTs, climate change, e-waste, energy efficiency; construction, installation and protection of cables and other elements of outside plant | +| Series M | Telecommunication management, including TMN and network maintenance | +| Series N | Maintenance: international sound programme and television transmission circuits | +| Series O | Specifications of measuring equipment | +| Series P | Telephone transmission quality, telephone installations, local line networks | +| Series Q | Switching and signalling, and associated measurements and tests | +| Series R | Telegraph transmission | +| Series S | Telegraph services terminal equipment | +| Series T | Terminals for telematic services | +| Series U | Telegraph switching | +| Series V | Data communication over the telephone network | +| Series X | Data networks, open system communications and security | +| Series Y | Global information infrastructure, Internet protocol aspects, next-generation networks, Internet of Things and smart cities | +| Series Z | Languages and general software aspects for telecommunication systems | \ No newline at end of file