.
+
+
+
+## Reference software for ITU-T H.264 advanced video coding
+
+# 1 Scope
+
+This Recommendation provides accompanying reference software for Rec. ITU-T H.264 | ISO/IEC 14496-10 as an electronic attachment. The software is an integral part of this Recommendation.
+
+The use of this reference software is not required for making an implementation of an encoder or decoder in conformance to Rec. ITU-T H.264 | ISO/IEC 14496-10. Requirements established in Rec. ITU-T H.264 | ISO/IEC 14496-10 take precedence over the behaviour of the reference software.
+
+# 2 References
+
+## 2.1 Normative references
+
+The following Recommendations and International Standards contain provisions which, through reference in this text, constitute provisions of this Recommendation | International Standard. At the time of publication, the editions indicated were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this Recommendation | International Standard are encouraged to investigate the possibility of applying the most recent edition of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently valid International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently valid ITU-T Recommendations.
+
+### 2.1.1 ITU-T Recommendations
+
+- None.
+
+### 2.1.2 Identical Recommendations | International Standards
+
+- None.
+
+### 2.1.3 Paired Recommendations | International Standards equivalent in technical content
+
+- Recommendation ITU-T H.264 (2007), *Advanced video coding for generic audiovisual services*.
+ISO/IEC 14496-10:2008, *Information technology – Coding of audio-visual objects – Part 10: Advanced video coding*.
+
+## 2.2 Additional references
+
+- None.
+
+# 3 Definitions
+
+For the purposes of this Recommendation, the terms, definitions, abbreviations and symbols specified in Rec. ITU-T H.264 | ISO/IEC 14496-10 (particularly in clause 3) apply. Definitions 3.1, 3.2, and 3.3 below replace the corresponding definitions in Rec. ITU-T H.264 | ISO/IEC 14496-10. Definitions 3.4 and 3.5 are additional definitions.
+
+**3.1 bitstream:** A sequence of bits that may conform to Rec. ITU-T H.264 | ISO/IEC 14496-10. A bitstream that conforms to Rec. ITU-T H.264 | ISO/IEC 14496-10 will contain one or more IDR slices, and may contain additional I, P, B, SI, SP, EI, EP or EB slices.
+
+**3.2 decoder:** An embodiment of a process that operates on a bitstream and may conform to the decoding process requirements specified for conformance to Rec. ITU-T H.264 | ISO/IEC 14496-10. The scope of decoder, as considered herein, does not include a display process, which is outside the scope of this Recommendation.
+
+**3.3 encoder:** An embodiment of a process, not specified in this Recommendation, that produces a bitstream.
+
+**3.4 reference software decoder:** The decoding software accompanying this Recommendation.
+
+**3.5 reference software encoder:** The encoding software accompanying this Recommendation.
+
+# 4 Abbreviations
+
+For the purposes of this Recommendation, relevant abbreviations are specified in clause 4 of Rec. ITU-T H.264 | ISO/IEC 14496-10.
+
+# 5 Conventions
+
+For the purposes of this Recommendation, relevant conventions are specified in clause 5 of Rec. ITU-T H.264 | ISO/IEC 14496-10.
+
+# 6 Reference software for Rec. ITU-T H.264 | ISO/IEC 14496-10
+
+The reference software for Rec. ITU-T H.264 | ISO/IEC 14496-10 is found in the electronic attachment to this Recommendation.
+
+The attached software package contains six separate parts:
+
+- JM software: Support for the Baseline, Constrained Baseline, Main, Extended, High, High 10, High 4:2:2, High 4:4:4 Predictive, High 10 Intra, High 4:2:2 Intra, High 4:4:4 Intra, and CAVLC 4:4:4 Intra profiles.
+- JSVM software: Support for the Scalable Baseline, Scalable High, and Scalable High Intra profiles.
+- JMVC software: Support for the Multiview High and Stereo High profiles.
+- MFC software: Support for the MFC High profile.
+- MVCD and 3D-AVC software: Support for the Multiview Depth High and Enhanced Multiview Depth High profiles.
+- MFCD software: Support for the MFC Depth High Profile
+
+
+
+## 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
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+
+
+
+
+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
+
+**H.310**
+
+(09/98)
+
+SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS
+Infrastructure of audiovisual services – Systems and
+terminal equipment for audiovisual services
+
+---
+
+**Broadband audiovisual communication systems
+and terminals**
+
+ITU-T Recommendation H.310
+
+(Previously CCITT Recommendation)
+
+---
+
+# ITU-T H-SERIES RECOMMENDATIONS **AUDIOVISUAL AND MULTIMEDIA SYSTEMS**
+
+| | |
+|------------------------------------------------------------------------------------------------------------|--------------------|
+| Characteristics of transmission channels used for other than telephone purposes | H.10–H.19 |
+| Use of telephone-type circuits for voice-frequency telegraphy | H.20–H.29 |
+| Telephone circuits or cables used for various types of telegraph transmission or simultaneous transmission | H.30–H.39 |
+| Telephone-type circuits used for facsimile telegraphy | H.40–H.49 |
+| Characteristics of data signals | H.50–H.99 |
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100–H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | |
+| General | H.200–H.219 |
+| Transmission multiplexing and synchronization | H.220–H.229 |
+| Systems aspects | H.230–H.239 |
+| Communication procedures | H.240–H.259 |
+| Coding of moving video | H.260–H.279 |
+| Related systems aspects | H.280–H.299 |
+| Systems and terminal equipment for audiovisual services | H.300–H.399 |
+| Supplementary services for multimedia | H.450–H.499 |
+
+*For further details, please refer to ITU-T List of Recommendations.*
+
+# **ITU-T RECOMMENDATION H.310**
+
+# **BROADBAND AUDIOVISUAL COMMUNICATION SYSTEMS AND TERMINALS**
+
+## **Summary**
+
+This Recommendation covers the technical requirements for the systems and terminals of broadband audiovisual communication services defined in H.200/AV.100-series Recommendations. Both H.310 unidirectional and bidirectional broadband audiovisual terminals are defined. The classification of H.310 terminals into different terminal types is based on a set of audiovisual, network adaptation, and signalling capabilities. With these capabilities, H.310 terminals support a wide range of conversational and distributive applications and services. This revision enhances the interworking between different type of H.310 terminals.
+
+###### **Source**
+
+ITU-T Recommendation H.310 was revised by ITU-T Study Group 16 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 25th of September 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 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 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 1998
+
+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 ..... | 3 |
+| 3 Definitions ..... | 5 |
+| 4 Abbreviations ..... | 6 |
+| 5 Conventions ..... | 8 |
+| 6 System description ..... | 8 |
+| 6.1 System configuration ..... | 8 |
+| 6.2 Terminal types ..... | 10 |
+| 6.2.1 Unidirectional terminal types (ROT and SOT) ..... | 10 |
+| 6.2.2 Bidirectional terminal types (RAST) ..... | 11 |
+| 6.3 Terminal capabilities ..... | 12 |
+| 6.3.1 Video capabilities ..... | 12 |
+| 6.3.2 Audio capabilities ..... | 14 |
+| 6.3.3 Data capabilities ..... | 15 |
+| 6.3.4 Network Adaptation Capabilities (NAC) ..... | 15 |
+| 6.3.5 Signalling capabilities ..... | 18 |
+| 6.4 The use of the H.245 control channel ..... | 22 |
+| 6.4.1 Master slave determination ..... | 23 |
+| 6.4.2 Capabilities exchange ..... | 24 |
+| 6.4.3 Logical channel signalling ..... | 25 |
+| 6.4.4 Mode request ..... | 27 |
+| 6.4.5 Round trip delay ..... | 27 |
+| 6.4.6 Maintenance loop ..... | 28 |
+| 6.4.7 Specific commands and indications ..... | 29 |
+| 7 H.310 call phases ..... | 29 |
+| 7.1 Native H.310 communication call procedures ..... | 29 |
+| 7.1.1 Phase A (call setup) ..... | 32 |
+| 7.1.2 Phase B (audiovisual communication) ..... | 33 |
+| 7.1.3 Phase C (call release) ..... | 33 |
+| 7.2 H.320/H.321 interoperation call procedures ..... | 34 |
+| 8 Multipoint communication ..... | 34 |
+| 8.1 Native H.310 communication modes ..... | 34 |
+| 8.2 H.320/H.321 interoperation modes ..... | 34 |
+| 8.3 Other aspects ..... | 34 |
+
+| | Page | |
+|--------------------------------------------------------------------------------------|--------------------------------------------------------------------------------|----|
+| 9 | Equipment requirements..... | 34 |
+| 10 | Error resilience ..... | 35 |
+| 10.1 | Video layer ..... | 35 |
+| 10.2 | Multimedia multiplex layer..... | 35 |
+| 11 | Maintenance loop ..... | 35 |
+| 12 | Intercommunications ..... | 36 |
+| 12.1 | Intercommunication between different terminal types..... | 37 |
+| 12.2 | Intercommunication with N-ISDN terminals ..... | 38 |
+| 12.3 | Intercommunication with telephony..... | 38 |
+| 12.4 | Intercommunication with audiovisual terminals connected to other networks..... | 38 |
+| Annex A – Protocol stack for control channel ..... | | 38 |
+| A.1 | General ..... | 38 |
+| A.2 | X.214 ..... | 39 |
+| A.3 | X.224 ..... | 39 |
+| A.4 | LAPF (Q.922)..... | 39 |
+| A.5 | FR-SSCS (I.365.1) and H.222.1 ..... | 40 |
+| A.5.1 | FR-SSCS (I.365.1) ..... | 40 |
+| A.5.2 | H.222.0 and H.222.1 ..... | 40 |
+| Annex B – Use of DSS 2 signalling by H.310 terminals..... | | 41 |
+| B.1 | DSS 2 signalling information elements..... | 41 |
+| B.2 | ATM signalling required for the H.310 control VC..... | 44 |
+| B.3 | ATM Signalling Required for RAST-1 A/V VC ..... | 45 |
+| B.4 | ATM Signalling Required for H.310 SOT/ROT-1 ..... | 47 |
+| B.5 | ATM Signalling Required for RAST-5 A/V VC ..... | 48 |
+| B.6 | ATM Signalling Required for H.310 SOT-5..... | 50 |
+| B.7 | ATM Signalling Required for H.310 ROT-5 ..... | 52 |
+| Annex C – Procedures for intercommunication between RAST-1 and RAST-5 terminals .... | | 53 |
+| C.1 | Introduction ..... | 53 |
+| C.2 | Two RAST-5 terminals on CPN ..... | 54 |
+| C.3 | RAST-5 Terminal on CPN with RAST-1 Terminal on Public B-ISDN ..... | 55 |
+| C.3.1 | RAST-5 Terminal on CPN calls RAST-1 Terminal on B-ISDN..... | 55 |
+| C.3.2 | RAST-1 Terminal on B-ISDN calls RAST-5 Terminal on CPN..... | 56 |
+| C.4 | RAST-5 Terminal on CPN with RAST-1 Terminal on CPN..... | 57 |
+
+| | Page |
+|----------------------------------------|-------------|
+| Appendix I – Bit and byte order ..... | 58 |
+| Appendix II – H.310 CorrelationID..... | 58 |
+
+
+
+# **BROADBAND AUDIOVISUAL COMMUNICATION SYSTEMS AND TERMINALS**
+
+*(revised in 1998)*
+
+# **1 Scope**
+
+This Recommendation covers the technical requirements for the systems and terminals of broadband audiovisual communication services defined in H.200/AV.100-series Recommendations.
+
+This Recommendation defines both *unidirectional* and *bidirectional* broadband audiovisual terminals. The classification of H.310 terminals into different terminal types is based on audiovisual and ATM adaptation layer capabilities which are defined in 6.2. There are two classes of unidirectional terminals: Receive-Only Terminal (ROT) and Send-Only Terminal (SOT) classes.
+
+In this Recommendation, bidirectional terminal types are referred to as Receive-and-Send Terminal (RAST) types. The definition of H.310 RAST terminals is based on the following interoperability principles:
+
+- 1) Interworking between H.310 RAST terminal types and other N-ISDN/B-ISDN (H.320/H.321) audiovisual terminals is mandatory.
+- 2) Interworking among the *different* H.310 RAST terminal types is also mandatory.
+
+Three types of RAST terminals are defined: RAST-1, RAST-5, and RAST-1&5.
+
+RAST-1 and RAST-1&5 terminals may be connected to public networks and customer premise networks (private networks), while RAST-5 terminals may only be connected to customer premise networks (private networks).
+
+For interworking with H.320/H.321 terminals, all three RAST terminal types support common H.320 audiovisual modes. For interworking between RAST-5 terminals and RAST-1 and H.320/H.321 terminals, a gateway, that is not inside the public network but in the customer premises, between a B-ISDN and a customer-premises ATM network is needed to provide interoperability functions.
+
+The video and audio coding and other technical aspects that are applicable to more than one distinct service are covered in H.200/AV.200-series Recommendations.
+
+Figure 1 shows a generic broadband audiovisual communication system. It consists of terminal equipment, network, Multipoint Control Unit (MCU) and the constituent elements of the terminal equipment. The corresponding Recommendations are also identified.
+
+
+
+Figure 1/H.310 – Broadband audiovisual communication system and terminal configuration. The diagram shows the internal architecture of an H.310 terminal and its connection to a network. On the left, inputs for Audio (G-Series, H.200/AV.255), Video (H.261/H.262), and Other data (End-to-end signalling via H.242/H.230 and H.245 Protocol Stack, and User-to-network signalling via Q.2931) are shown. These connect to internal processing blocks: 'Generic Packetized Multimedia Multiplex/Synchronization H.222.0', 'Packet-based Multimedia Multiplex/Synchronization in ATM Environments H.222.1', and 'Circuit-based Multimedia Multiplex/Synchronization H.221'. The terminal is connected to a 'Broadband ISDN network' (represented by an oval) via an 'MCU' (represented by a rectangle). The connection interface is labeled with 'A A L', 'A T M', and 'P H Y' on the terminal side, and 'I.363.1/5', 'I.361', and 'I.432' on the network side. A 'SAAL Q.2100' block is also shown at the interface. The entire terminal configuration is enclosed in a box labeled 'Scope of H.310'.
+
+**Figure 1/H.310 – Broadband audiovisual communication system and terminal configuration**
+
+All H.310 terminals are required to support H.245 as their communication control protocol so that they can support their intended services and interoperate among each other. Accordingly, H.310 terminals shall use the H.222.1 acknowledged procedures for the subchannel signalling.
+
+It is important to note that the generic H.310 terminal shown in Figure 1 can represent any of the unidirectional or bidirectional terminal types defined in this Recommendation.
+
+The definition of H.310 terminal types is intended for the support of the following applications:
+
+- Conversational services (e.g. videoconferencing and videotelephony services).
+- Retrieval services.
+- Messaging services.
+- Distribution services with individual presentation by the recipient (e.g. video-on-demand services).
+- Distribution services without individual presentation by the recipient (e.g. broadcast TV services).
+- Video transmission.
+- Surveillance.
+
+## 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] CCITT Recommendation G.711 (1988), *Pulse Code Modulation (PCM) of voice frequencies.*
+- [2] CCITT Recommendation G.722 (1988), *7 kHz audio-coding within 64 kbit/s.*
+- [3] ITU-T Recommendation G.723.1 (1996), *Speech codecs: Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s.*
+- [4] CCITT Recommendation G.728 (1992), *Coding of speech at 16 kbit/s using low-delay code excited linear prediction.*
+- [5] ITU-T Recommendation G.729 (1996), *Coding of speech at 8 kbit/s using Conjugate Structure Algebraic-Code-Excited Linear-Prediction (CS-ACELP).*
+- [6] Annex A to G.729 (1996), *Reduced complexity 8 kbit/s CS-ACELP speech codec.*
+- [7] CCITT Recommendation H.100 (1988), *Visual telephone systems.*
+- [8] ITU-T Recommendation H.221 (1997), *Frame structure for a 64 to 1920 kbit/s channel in audiovisual teleservices.*
+- [9] ITU-T Recommendation H.222.0 (1995) | ISO/IEC 13818-1:1996, *Information technology – Generic coding of moving pictures and associated audio information: Systems.*
+- [10] ITU-T Recommendation H.222.1 (1996), *Multimedia multiplex and synchronization for audiovisual communication in ATM environments.*
+- [11] ITU-T Recommendation H.224 (1994), *A real time control protocol for simplex applications using the H.221 LSD/HSD/MLP channels.*
+- [12] ITU-T Recommendation H.230 (1997), *Frame-synchronous control and indication signals for audiovisual systems.*
+- [13] ITU-T Recommendation H.233 (1995), *Confidentiality system for audiovisual services.*
+- [14] ITU-T Recommendation H.234 (1994), *Encryption key management and authentication system for audiovisual services.*
+- [15] ITU-T Recommendation H.242 (1997), *System for establishing communication between audiovisual terminals using digital channels up to 2 Mbit/s.*
+- [16] ITU-T Recommendation H.245 (1998), *Control protocol for multimedia communication.*
+- [17] ITU-T Recommendation H.261 (1993), *Video codec for audiovisual services at $p \times 64$ kbit/s.*
+- [18] ITU-T Recommendation H.262 (1995) | ISO/IEC 13818-2:1995, *Information technology – Generic coding of moving pictures and associated audio information: Video.*
+- [19] ITU-T Recommendation H.263 (1998), *Video coding for low bit rate communication.*
+- [20] ITU-T Recommendation H.281 (1994), *A far end camera control protocol for videoconferences using H.224.*
+
+- [21] ITU-T Recommendation H.320 (1997), *Narrow-band visual telephone systems and terminal equipment.*
+- [22] ITU-T Recommendation H.321 (1998), *Adaptation of H.320 visual telephone terminals to B-ISDN environments.*
+- [23] ITU-T Recommendation I.311 (1996), *B-ISDN general network aspects.*
+- [24] ITU-T Recommendation I.361 (1995), *B-ISDN ATM layer specification.*
+- [25] ITU-T Recommendation I.363.1 (1996), *B-ISDN ATM adaptation layer specification: Type 1 AAL.*
+- [26] ITU-T Recommendation I.363.5 (1996), *B-ISDN ATM adaptation layer specification: Type 5 AAL.*
+- [27] CCITT Recommendation Q.922 (1992), *ISDN data link layer specification for frame mode bearer services.*
+- [28] ITU-T Recommendation Q.2010 (1995), *Broadband integrated services digital network overview – Signalling capability set 1, release 1.*
+- [29] ITU-T Recommendation Q.2110 (1994), *B-ISDN ATM adaptation layer – Service Specific Connection Oriented Protocol (SSCOP).*
+- [30] ITU-T Recommendation Q.2130 (1994), *B-ISDN signalling ATM adaptation layer – Service specific coordination function for support of signalling at the user-network interface (SSCF at UNI).*
+- [31] ITU-T Recommendation Q.2931 (1995), *Digital subscriber Signalling System No. 2 – User-Network Interface (UNI) layer 3 specification for basic call/connection control.*
+- [32] ITU-T Recommendation Q.2941.1 (1997), *Digital subscriber Signalling System No. 2: Generic identifiers transport.*
+- [33] ITU-T Recommendation Q.2961.1 (1995), *Digital subscriber Signalling System No. 2 (DSS 2) – Additional traffic parameters: Additional signalling capabilities to support traffic parameters for the tagging option and the sustainable cell rate parameter set.*
+- [34] ITU-T Recommendation Q.2961.2 (1997), *Digital subscriber Signalling System No. 2 – Additional traffic parameters: Support of ATM transfer capability in the broadband bearer capability information element.*
+- [35] ITU-T Recommendation Q.2971 (1995), *Digital subscriber Signalling System No. 2 – User-network interface layer 3 specification for point-to-multipoint call/connection control.*
+- [36] ITU-T Recommendation T.84 (1996) | ISO/IEC 10918-3:1996, *Information technology – Digital compression and coding of continuous-tone still images: Extensions.*
+- [37] ITU-T Recommendation T.120 (1996), *Data protocols for multimedia conferencing.*
+- [38] ITU-T Recommendation T.123 (1996), *Network specific data protocol stacks for multimedia conferencing.*
+- [39] ITU-T Recommendation T.434 (1996), *Binary file transfer format for the telematic services.*
+- [40] ITU-T Recommendation X.214 (1995) | ISO/IEC 8072:1996, *Information technology – Open Systems Interconnection – Transport service definition.*
+- [41] ITU-T Recommendation X.224 (1995) | ISO/IEC 8073:1997, *Information technology – Open Systems Interconnection – Protocol for providing the connection-mode transport service.*
+
+- [42] ITU-T Recommendation X.680 (1997) | ISO/IEC 8824-1:1998, *Information technology – Abstract Syntax Notation One (ASN.1): Specification of basic notation.*
+- [43] ITU-T Recommendation X.691 (1997) | ISO/IEC 8825-2:1998, *Information technology – ASN.1 encoding rules – Specification of Packed Encoding Rules (PER).*
+- [44] ISO/IEC 11172-3:1993, *Information technology – Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s – Part 3: Audio.*
+- [45] ISO/IEC 13818-3:1995, *Information technology – Generic coding of moving pictures and associated audio information – Part 3: Audio.*
+- [46] ISO/IEC 13818-6:1998, *Information technology – Generic coding of moving pictures and associated audio information – Part 6: Extensions for DSM-CC.*
+
+## 3 Definitions
+
+This Recommendation defines the following terms.
+
+- 3.1 **audiovisual information:** Information including audio and/or video information.
+- 3.2 **bidirectional logical channel:** A bidirectional logical channel consists of a pair of associated transmission paths between two terminals, one in each direction of transmission.
+- 3.3 **bidirectional terminal:** A terminal which can send and receive audiovisual information.
+- 3.4 **capability:** A terminal has a particular capability if it is able to encode and transmit or receive and decode that particular signal.
+- 3.5 **channel:** A channel is a unidirectional link between two end points.
+- 3.6 **command:** A command is a message that requires action but no explicit response.
+- 3.7 **control and indication:** End-to-end signalling between terminals, consisting of control, which requires action but no explicit response in the receiver, and indication which contains information but does not require action or response in the receiver.
+- 3.8 **customer premises network:** An ATM network administered by the user.
+- 3.9 **elementary stream:** Elementary stream is a generic term for a coded video, coded audio or other coded bit stream.
+- 3.10 **entry:** The word entry is used to refer to elements in sets or tables, such as capability sets.
+- 3.11 **gateway:** A function that converts transmission formats and/or protocols between different network environments.
+- 3.12 **in-band:** In-band messages are those that are transported within the channel or logical channel to which they refer.
+- 3.13 **indication:** An indication is a message that contains information but does not require action or response.
+- 3.14 **logical channel:** A logical channel is a unidirectional path or bidirectional path for the transmission of information.
+- 3.15 **logical channel number:** A logical channel number is a number that identifies a single logical channel.
+- 3.16 **logical channel signalling:** Logical channel signalling is a set of procedures that are used to open and close logical channels.
+
+- 3.17 master terminal:** A master terminal is the terminal that is determined as being the master terminal by the master-slave determination procedure used by this Recommendation.
+- 3.18 medium type:** A medium type is a single form of information that is presented to a user or the data representing that information: video, audio and text are example medium types.
+- 3.19 mode:** A mode is a set of elementary streams that a terminal is transmitting, intends to transmit, or would like to receive.
+- 3.20 multimedia communication:** Multimedia communication refers to the transmission and/or reception of signals of two or more medium types simultaneously.
+- 3.21 multipoint:** Multipoint refers to the simultaneous interconnection of three or more terminals to allow communication among several sites through the use of multipoint control units (bridges) that centrally direct the flow of information.
+- 3.22 non-standard:** Not conforming to a national or international standard referenced in this Recommendation.
+- 3.23 out-of-band:** Out-of-band messages are those that are not transported within the user-to-user information channel.
+- 3.24 public network:** An ATM network administered by the network provider for public access.
+- 3.25 request:** A request is a message that results in action by the remote terminal and requires an immediate response from it.
+- 3.26 response:** A response is a message that is the response to a request.
+- 3.27 session:** A session is a period of communication between two terminals which may be conversational or non-conversational (for example retrieval from a database).
+- 3.28 slave terminal:** A slave terminal is the terminal that is determined as being the slave terminal by the master-slave determination procedure used by this Recommendation.
+- 3.29 subchannel:** A channel in Recommendation H.222.1 formed from packets having a unique multiplex identifier field value. A subchannel carries one H.222.1 elementary stream. A subchannel is unidirectional. There may be many subchannels within one ATM virtual channel.
+- 3.30 support:** The ability to operate in a given mode; however, a requirement to support a mode does not mean that the mode shall actually be used at all times: unless prohibited, other modes may be used by mutual negotiation.
+- 3.31 terminal:** A terminal is any endpoint and may be a user's terminal or some other communication system such as an MCU or an information server.
+- 3.32 unidirectional logical channel:** A unidirectional logical channel is a path for the transmission of a single elementary stream from one terminal to another.
+- 3.33 unidirectional terminal:** A terminal which can only send or receive audiovisual information.
+
+## 4 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+| | |
+|-------|------------------------------|
+| AAL | ATM Adaptation Layer |
+| ASN.1 | Abstract Syntax Notation One |
+| ATM | Asynchronous Transfer Mode |
+| B-BC | Broadband Bearer Capability |
+
+| | |
+|----------|-------------------------------------------------------------------------------------------|
+| B-HLI | Broadband High-Layer Information |
+| B-ISDN | Broadband ISDN |
+| B-LCSE | Bidirectional Logical Channel Signalling Entity |
+| C&I | Control and Indication |
+| CBR | Constant Bit Rate |
+| CESE | Capability Exchange Signalling Entity |
+| CIF | Common Intermediate Format (of a video picture: refer to Recommendations H.261 and H.263) |
+| CLCSE | Close Logical Channel Signalling Entity |
+| CPCS | Common Part Convergence Sublayer (of ATM Adaptation Layer 5) |
+| CPCS-UU | CPCS User-to-User |
+| CPI | Common Part Indicator |
+| CRC | Cyclic Redundancy Check |
+| CS | Convergence Sublayer |
+| DSM-CC | Digital Storage Media – Command and Control |
+| DSS 2 | Digital Subscriber Signalling System No. 2 |
+| FEC | Forward Error Correction |
+| FR-SSCS | Frame Relay Service Specific Convergence Sublayer |
+| GOB | Group Of Blocks (of a video picture: refer to Recommendations H.261 and H.263) |
+| IE | Information Element |
+| ISDN | Integrated Services Digital Network |
+| LCSE | Logical Channel Signalling Entity |
+| MCU | Multipoint Control Unit |
+| MLSE | Maintenance Loop Signalling Entity |
+| MSDSE | Master Slave Determination Signalling Entity |
+| MRSE | Mode Request Signalling Entity |
+| NAC | Network Adaptation Capabilities |
+| N-BC | Narrow-band Bearer Capability |
+| N-ISDN | Narrow-band ISDN |
+| PDU | Protocol Data Unit |
+| PES | Packetized Elementary Stream |
+| PID | Packet Identifier (refer to ITU-T Rec. H.222.0 ISO/IEC 13818-1) |
+| PS | Program Stream |
+| PTS | Presentation Time Stamp |
+| QCIF | Quarter CIF |
+| QoS | Quality of Service |
+| RAST | Receive-and-Send Terminal |
+| RAST-1 | Receive-and-Send Terminal with an AAL 1 interface |
+| RAST-1&5 | Receive-and-Send Terminal with AAL 1 and AAL 5 interfaces |
+| RAST-5 | Receive-and-Send Terminal with an AAL 5 interface |
+| ROT | Receive-Only Terminal |
+| ROT-1 | Receive-Only Terminal with an AAL 1 interface |
+
+| | |
+|---------|-------------------------------------------------------|
+| ROT-1&5 | Receive-Only Terminal with AAL 1 and AAL 5 interfaces |
+| ROT-5 | Receive-Only Terminal with an AAL 5 interface |
+| RTDSE | Round Trip Delay Signalling Entity |
+| SAP | Service Access Point |
+| SAR | Segmentation And Reassembly |
+| SDT | Structured Data Transfer |
+| SDU | Service Data Unit |
+| SOT | Send-Only Terminal |
+| SOT-1 | Send-Only Terminal with an AAL 1 interface |
+| SOT-1&5 | Send-Only Terminal with AAL 1 and AAL 5 interfaces |
+| SOT-5 | Send-Only Terminal with an AAL 5 interface |
+| SQCIF | Sub QCIF |
+| SRTS | Synchronous Residual Time Stamp |
+| SSCOP | Service Specific Connection-Oriented Protocol |
+| SSCS | Service Specific Convergence Sublayer |
+| TS | Transport Stream |
+| UNI | User Network Interface |
+| VBR | Variable Bit Rate |
+| VC | ATM Virtual Channel |
+| VFS | Video Frame Synchronous |
+| VOD | Video On Demand |
+
+## 5 Conventions
+
+The word "shall" is used in this Recommendation to specify a mandatory requirement.
+
+The word "should" is used in this Recommendation to specify a suggested, but not required, course of action.
+
+The word "may" is used in this Recommendation to specify an optional course of action, without expressing a preference.
+
+The term "11172 audio" is used in this Recommendation to represent ISO/IEC 11172-3.
+
+The term "13818 audio" is used in this Recommendation to represent ISO/IEC 13818-3.
+
+# 6 System description
+
+## 6.1 System configuration
+
+The interaction among the H.310 terminal capabilities is based on the protocol reference model shown in Figure 2, which illustrates the protocol stacks for the audiovisual, data, call management (DSS 2 and H.245), and other control and indication signals that can be supported by the different terminal types of this Recommendation.
+
+
+
+The diagram illustrates the H.310 protocol reference model. At the top, several functional blocks are shown: Call Management, Audio (G.711, G.722, G.728, 11172, 13818), Video (H.261, H.262), Private Data, Synchronous Signalling (Note 2), and T.120 (Note 1). Below these, various protocol stacks are depicted. On the left, Call Management connects to H.245 and H.242/H.230. H.245 connects to X.224 Class 0, which connects to LAPF (Q.922). LAPF connects to FR-SSCS (I.365.1), which connects to CPCS 5 (I.363.5), which connects to SAR 5 (I.363.5). Call Control DSS 2 (Note 7) connects to SSCS.UNI (Q.2130), which connects to SSCOP (Q.2110), which connects to CPCS 5 (I.363.5), which connects to SAR 5 (I.363.5). In the center, Audio and Video connect to H.221 (Note 6). H.221 connects to a large box containing Note 4 (CS 1 (I.363.1) and SAR 1 (I.363.1)) and Note 5 (CPCS 5 (I.363.5) and SAR 5 (I.363.5)). Private Data connects to H.222.1, which contains H.222.0 and Network adaptation. Synchronous Signalling (Note 2) connects to H.222.1. T.120 (Note 1) connects to X.224 Classe 0, which connects to LAPF (Q.922), which connects to FR-SSCS (I.365.1), which connects to CPCS 5 (I.363.5), which connects to SAR 5 (I.363.5). All stacks converge to a common base: ATM (I.361).
+
+Figure 2/H.310 – H.310 protocol reference model diagram showing various protocol stacks for Call Management, Audio, Video, Private Data, Synchronous Signalling, and T.120 over an ATM (I.361) base. The diagram includes multiple protocol layers such as H.245, X.224 Class 0, LAPF (Q.922), FR-SSCS (I.365.1), CPCS 5 (I.363.5), and SAR 5 (I.363.5). It also features seven numbered notes explaining specific protocol details and configurations.
+
+T1604890-98
+
+NOTE 1 – T.120 may be carried within the H.222.1 multiplex or in a separate ATM virtual channel, as specified in Recommendation T.123.
+
+NOTE 2 – Video frame synchronous signals are described in 6.3.5.3.
+
+NOTE 3 – H.222.1/H.222.0 functions include multiplexing, timebase recovery, media synchronization, jitter removal, buffer management, security and access control, in-band signalling, and trick modes. Recommendation H.222.1 specifies elements and procedures from the generic H.222.0, for their use in ATM environments, and also specifies code points and procedures for ITU-T defined elementary streams.
+
+NOTE 4 – AAL type 1 CS functions include transmission clock recovery, jitter removal, bit error correction, cell loss correction, and data structure preservation.
+
+NOTE 5 – AAL type 5 (CPCS) functions include bit error detection, cell loss detection, and data structure preservation.
+
+NOTE 6 – H.221 is required in the H.310 RAST-1, RAST-5 and RAST-1&5 terminals for interworking with H.320/H.321 terminals.
+
+NOTE 7 – B-ISDN signalling is referred to as Digital Subscriber Signalling System No. 2 (DSS 2). DSS 2 is composed of the suite of protocols shown in Table 1. The protocol stack for the Q.2931 signalling messages is specified in Recommendation Q.2010.
+
+**Figure 2/H.310 – H.310 protocol reference model**
+
+**Table 1/H.310 – Summary of DSS 2 protocols**
+
+| Recommendation | Title |
+|----------------|------------------------------------------------------------------------------------------------------|
+| Q.2931 | User network interface layer 3 specification for basic call/connection control |
+| Q.2941.1 | DSS 2 user generated identifiers |
+| Q.2961 | Support of additional traffic parameters |
+| Q.2961.2 | ATM transfer capability coding in the broadband bearer capability information element |
+| Q.2962 | Negotiation of traffic and QoS parameters (during call/connection establishment) |
+| Q.2963 | Renegotiation/modification of traffic and QoS parameters (for already established calls/connections) |
+| Q.2964 | B-ISDN look-ahead |
+| Q.2971 | Point-multipoint call/connection control |
+| Q.298x | Multiconnection calls |
+
+## **6.2 Terminal types**
+
+This Recommendation defines both unidirectional and bidirectional broadband audiovisual terminals. The classification of H.310 terminals into different terminal types is based on audiovisual and AAL capabilities as summarized in Table 2.
+
+**Table 2/H.310 – Definition of H.310 terminal types**
+
+| | | | AAL | | |
+|-----------------------|----------------|------|--------|--------|----------|
+| | | | AAL 1 | AAL 5 | AAL 1& 5 |
+| Audiovisual transport | Unidirectional | ROT | ROT-1 | ROT-5 | ROT-1&5 |
+| | | SOT | SOT-1 | SOT-5 | SOT-1&5 |
+| | Bidirectional | RAST | RAST-1 | RAST-5 | RAST-1&5 |
+
+### **6.2.1 Unidirectional terminal types (ROT and SOT)**
+
+Two classes of unidirectional terminals are defined: Send-Only Terminal (SOT) and Receive-Only Terminal (ROT).
+
+Three types of H.310 unidirectional terminals are defined, based on their supported AALs, for each of the two classes. The H.310 defined unidirectional terminal types are:
+
+- H.310 ROT-1 and SOT-1 which support AAL 1;
+- H.310 ROT-5 and SOT-5 which support AAL 5;
+- H.310 ROT-1&5 and SOT-1&5 is a composite terminal supporting both AAL 1 and AAL 5.
+
+Each of these terminal types shall support the H.310 native communication mode. The native communication mode consists of H.222.1, with ISO/IEC 11172-3 Layer 2, H.262 and H.245 as the audio, video and control protocols.
+
+Each of these terminals may be connected to public B-ISDN and customer premise networks (private networks).
+
+NOTE – Some pairs of unidirectional terminal will not interwork with each other. This may be due to incompatible class, such as ROT-1 connecting with ROT-1&5, or due to incompatible type, such as ROT-1 connecting to SOT-5.
+
+### 6.2.2 Bidirectional terminal types (RAST)
+
+Three types of H.310 bidirectional receive and send terminals (RAST) are defined based on their communication modes and supported AALs. The H.310 defined terminal types are:
+
+- H.310 RAST-1 which supports AAL 1;
+- H.310 RAST-5 which supports AAL 5;
+- H.310 RAST-1&5 is a composite terminal supporting both AAL 1 and AAL 5.
+
+Each of these terminal types shall support an H.310 native communication mode as well as an H.320/H.321 interoperation mode. Figure 3 depicts the protocol stacks for these two modes for each of the terminal types.
+
+
+
+Figure 3/H.310 – Protocol stacks for native H.310 and H.320/H.321 interoperation communication modes. The diagram shows three protocol stacks for RAST-1, RAST-5, and RAST-1&5. Each stack is a 3x3 grid of protocol layers. The top row contains H.245, H.262/G.711, and H.242/H.261/G.711. The middle row contains X.224 LAPF FR-SSCS, H.222.0/H.222.1, and H.221. The bottom row contains AAL 5, AAL 1, and AAL 1. The left column represents Native H.310 Communication Mode, and the right column represents H.320/H.321 Interoperation Mode. For RAST-1, the layers are H.245, H.262/G.711, H.242/H.261/G.711 in the top row; X.224 LAPF FR-SSCS, H.222.0/H.222.1, H.221 in the middle row; and AAL 5, AAL 1, AAL 1 in the bottom row. For RAST-5, the layers are H.245, H.262/G.711, H.242/H.261/G.711 in the top row; X.224 LAPF FR-SSCS, H.222.0/H.222.1, H.221/NALa) in the middle row; and AAL 5, AAL 5, AAL 5 in the bottom row. For RAST-1&5, the layers are H.245, H.262/G.711, H.262/G.711 in the top row; X.224 LAPF FR-SSCS, H.222.0/H.222.1, H.222.0/H.222.1 in the middle row; and AAL 5, AAL 1, AAL 5 in the bottom row. The H.320/H.321 Interoperation Mode for RAST-1&5 includes H.242/H.261/G.711, H.221, and AAL 1 in the top, middle, and bottom rows respectively.
+
+T1604900-98
+
+a) NAL Network Adaptation Layer (see Annex B/H.321).
+
+**Figure 3/H.310 – Protocol stacks for native H.310 and H.320/H.321 interoperation communication modes**
+
+NOTE – Figure 3 corresponds to the "separate VC" case in Annex A.
+
+The H.310 RAST-1 terminal supports AAL 1. Its native H.310 communication mode consists of H.222.1, with G.711, H.262, and H.245 as the audio, video, and control protocols. Its H.320/H.321 interoperation mode supports the full H.321/Annex A protocol stack.
+
+The H.310 RAST-5 terminal supports AAL 5. Its native H.310 communication mode consists of H.222.1 with G.711, H.262, and H.245 as the audio, video and control protocols. Its H.320/H.321 interoperation mode supports the full H.321/Annex B protocol stack.
+
+The H.310 RAST-1&5 is a composite of the RAST-1 and RAST-5 terminal types and supports all four modes described above.
+
+The RAST-1 and RAST-1&5 terminals connect to public B-ISDN and customer premise networks (private networks) and can interwork with H.320 via an I.580 interworking unit and directly with H.321/Annex A terminals. The RAST-5 terminal connects to customer premise networks (private networks), can directly interwork with H.321/Annex B terminals and requires a gateway to interwork with H.320, H.321/Annex A and H.310 RAST-1 terminals. See clause 12 for interworking scenarios.
+
+## 6.3 Terminal capabilities
+
+The definition and classification of H.310 terminal types and their communication modes are based on the following capabilities:
+
+- Audiovisual and Data;
+- Network Adaptation;
+- signalling (both user-to-user and user-to-network).
+
+A *communication mode* is defined as a combination of certain parameters of the above capabilities. Based on the different capabilities of H.310 terminals, two classes of communication modes are specified:
+
+- H.320/H.321 interoperation modes;
+- native H.310 communication modes.
+
+Unidirectional H.310 terminals need only support native H.310 communication modes of operation, that is, unidirectional terminals may optionally support the H.320/H.321 interoperation modes.
+
+At the start of the call, H.310 terminals shall identify the remote terminal type (H.320/H.321, H.310 bidirectional, etc.) via exchange of Q.2931 information elements, and shall use either H.245 or H.242 to perform capability exchange and other procedures.
+
+This Recommendation mandates the support of particular functionalities by the different terminal types. However, this does not imply that a particular communication mode shall be used by that terminal type during a given communication session. For example, RAST terminals shall support H.261 video capabilities for interworking with H.320/H.321 terminals, but the use of H.261 in the native mode, that is, when H.222.1 is used, is optional.
+
+The following subclauses describe mandatory and optional capabilities. Optional capabilities are included as guidelines for implementations and are in no way intended to be exhaustive lists of what may be implemented.
+
+### 6.3.1 Video capabilities
+
+All H.310 terminals shall support Recommendation H.262 at the Main Profile at Main Level (MP@ML) conformance point. Other H.262 profiles and levels may be optionally supported.
+
+H.310 terminals shall adhere to the hierarchical relationship, as defined in clause 8/H.262, among the different H.262 profiles and levels. Therefore, it should be noted that H.262 Simple Profile at Main Level (SP@ML) and Main Profile at Low Level (MP@LL) shall be supported by all H.310 terminals.
+
+When compliance with a H.262 conformance point, that is a given profile at a given level, is supported, H.310 terminals shall adhere to the video parameter constraints specified in clause 8/H.262 for that conformance point. However, terminals may indicate a capability for the functionality of a given profile with reduced level parameters using H.245, and such a communication mode may be established using the relevant procedures of H.245 when both terminals have the necessary capability.
+
+The mandatory and optional video and audio capabilities are summarized in Table 3.
+
+**Table 3/H.310 – Audiovisual capabilities of H.310 terminals**
+
+| Terminal type | | Audiovisual capabilities | | | |
+|--------------------------------------------------------|--|--------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| | | Video | | Audio | |
+| | | Mandatory | Optional | Mandatory | Optional |
+| ROT-1
SOT-1
ROT-5
SOT-5
ROT-1&5
SOT-1&5 | | H.262 MP@ML | H.262 MP@H14L
H.262 MP@HL
H.262 SNR@LL
H.262 SNR@ML
H.262 Spatial@H14L
H.262 HP@ML
H.262 HP@H14L
H.262 HP@HL | 11172-3 Layer 2 | 11172-3 Layer 3 |
+| RAST-1
RAST-5
RAST-1&5 | | H.262 MP@ML | H.261 QCIF
H.261 CIF
H.262 MP@H14L
H.262 MP@HL
H.262 SNR@LL
H.262 SNR@ML
H.262 Spatial@H14L
H.262 HP@ML
H.262 HP@H14L
H.262 HP@HL
H.263 SQCIF
H.263 QCIF
H.263 CIF
H.263 4CIF
H.263 16CIF | G.711 | 11172-3 Layer 1
11172-3 Layer 2
11172-3 Layer 3
13818-3 Layer 1
13818-3 Layer 2
13818-3 Layer 3
G.711
G.722
G.728
G.723.1
G.729
Annex A/G.729 |
+| RAST-1
RAST-5
RAST-1&5 | | Native mode | | | 11172-3 Layer 1
11172-3 Layer 2
11172-3 Layer 3
13818-3 Layer 1
13818-3 Layer 2
13818-3 Layer 3
G.722
G.728
G.723.1
G.729
Annex A/G.729 |
+
+**Table 3/H.310 – Audiovisual capabilities of H.310 terminals (concluded)**
+
+| Terminal type | | Audiovisual capabilities | | | |
+|------------------------------|-----------------|--------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| | | Video | | Audio | |
+| | | Mandatory | Optional | Mandatory | Optional |
+| RAST-1
RAST-5
RAST-1&5 | H.320/1
mode | H.261 QCIF
H.261 CIF | H.262 MP@ML
H.262 MP@H14L
H.262 MP@HL
H.262 SNR@LL
H.262 SNR@ML
H.262 Spatial@H14L
H.262 HP@ML
H.262 HP@H14L
H.262 HP@HL
H.263 SQCIF
H.263 QCIF
H.263 CIF
H.263 4CIF
H.263 16CIF | G.711 | 11172-3 Layer 1
11172-3 Layer 2
11172-3 Layer 3
13818-3 Layer 1
13818-3 Layer 2
13818-3 Layer 3
G.722
G.728
G.723.1
G.729
Annex A/G.729 |
+
+#### 6.3.1.1 Unidirectional video capabilities
+
+Unidirectional H.310 terminals are not required to support any of the H.261 or H.263 video coding modes.
+
+#### 6.3.1.2 Bidirectional video capabilities
+
+All H.310 bidirectional terminals shall support Recommendation H.261 with both the Common Intermediate Format (CIF) and Quarter CIF (QCIF) picture resolutions. This enables the interworking between H.310 and a wide range of existing and future H.320/H.321 terminals.
+
+Bidirectional terminals have the option of supporting Recommendation H.263 with any of the picture formats and any of the optional modes.
+
+### 6.3.2 Audio capabilities
+
+The mandatory and optional video and audio capabilities are summarized in Table 3.
+
+#### 6.3.2.1 Unidirectional audio capabilities
+
+Unidirectional H.310 terminals shall support ISO/IEC 11172-3 audio Layer 2.
+
+The support of ISO/IEC 11172-3 Layer 3, ISO/IEC 13818-3, and ITU-T G-series audio Recommendations is optional.
+
+#### 6.3.2.2 Bidirectional audio capabilities
+
+All bidirectional H.310 terminals shall support Recommendation G.711 (both A-law and $\mu$ -law). This enables existing and future H.320/H.321 terminals to interwork with H.310 terminals.
+
+Bidirectional terminals may optionally support one or more of the following audio Recommendations: G.722 at 64 kbit/s, G.722 at 56 kbit/s, G.722 at 48 kbit/s, G.723.1 at either 5.3 or 6.3 kbit/s, G.728 (16 kbit/s), G.729 (8 kbit/s), and Annex A/G.729 (8 kbit/s).
+
+The support of ISO/IEC 11172-3 and ISO/IEC 13818-3 audio standards is optional.
+
+### 6.3.3 Data capabilities
+
+The support of data protocols is optional in H.310 terminals. Data protocols may be multiplexed with other audiovisual information by using either the H.222.1 or ATM layer multiplexing functions.
+
+T.120 is the default basis of data interoperability between an H.310 terminal and other H.310, H.320, H.321, H.322, H.323 or H.324 terminals. When any optional data application is implemented using one or more of the ITU-T Recommendations which can be negotiated via H.245, the equivalent T.120 applications shall be one of those provided (if such applications have been recommended by the ITU-T). A terminal that provides far-end camera control using H.281 and H.224 is not required to also support a T.120 far-end camera control protocol. Another exception is transparent user data.
+
+### 6.3.4 Network Adaptation Capabilities (NAC)
+
+The network adaptation capabilities of H.310 terminals include the multimedia multiplex and synchronization mechanism, ATM adaptation layer, transfer rate, and ATM VC capabilities.
+
+The mandatory and optional network adaptation capabilities are summarized in Table 4.
+
+**Table 4/H.310 – Network adaptation capabilities of H.310 terminals**
+
+| Terminal type | | Network adaptation capabilities | | | | | | | |
+|--------------------|-----------------|---------------------------------|------------|--------------------------|----------|--------------------|----------|------------------------|-------------------------------------------------------|
+| | | Multimedia multiplex | | AAL for audiovisual data | | Number of ATM VC's | | Transfer rate (kbit/s) | |
+| | | Mandatory | Optional | Mandatory | Optional | Mandatory | Optional | Mandatory | Optional |
+| ROT-1
SOT-1 | | H.222.1
TS | H.222.1 PS | AAL 1 | AAL 5 | 2 | > 2 | 6144
9216 | n*64 |
+| ROT-5
SOT-5 | | H.222.1
TS | H.222.1 PS | AAL 5 | AAL 1 | 2 | > 2 | 6144
9216 | n*64 |
+| ROT-1&5
SOT-1&5 | | H.222.1
TS | H.222.1 PS | AAL 1
AAL 5 | – | 2 | > 2 | 6144
9216 | n*64 |
+| RAST-1 | Native mode | H.222.1
TS | H.222.1 PS | AAL 1 | AAL 5 | 2 | > 2 | 6144
9216 | n*64 |
+| | H.320/1
mode | H.221 | – | AAL 1 | – | 2 | > 2 | B
2B
H0 | n × B
n × H0
H 11
H 12 |
+| RAST-5 | Native mode | H.222.1
TS | H.222.1 PS | AAL 5 | AAL 1 | 2 | > 2 | 6144
9216 | n*64 |
+| | H.320/1
mode | H.221 | – | AAL 5 | – | 2 | > 2 | B
2B
H0 | n × B
n × H0
H 11
H 12 |
+| RAST-1&5 | Native mode | H.222.1
TS | H.222.1 PS | AAL 1
AAL 5 | – | 2 | > 2 | 6144
9216 | n*64 |
+| | H.320/1
mode | H.221 | – | AAL 1
AAL 5 | – | 2 | > 2 | B
2B
H0 | n × B
n × H0
H 11
H 12 |
+
+#### **6.3.4.1 Multimedia multiplex and synchronization**
+
+Multiplexing of audio, video, data, and control signals in H.310 terminals is accomplished using the multimedia multiplex protocols and procedures defined in Recommendations H.221 and H.222.1. Recommendation H.222.1 specifies both H.222.0 and H.222.1 specific functions (e.g. error protection, jitter removal, ITU-T defined stream\_id and descriptors, etc.).
+
+H.310 terminals may support multiple instances of H.222.0/H.222.1. In this case ATM layer multiplexing is also used, since there is one instance of H.222.0/H.222.1 per ATM VC.
+
+All H.310 terminals shall support Recommendations H.222.0/H.222.1 for the multiplexing and synchronization of video, audio, data, and control signals. The support of H.222.1 Transport Stream multiplexing is mandatory for all H.310 terminals. The support of H.222.1 Program Stream multiplexing is optional for H.310 terminals.
+
+All bidirectional H.310 terminals shall support Recommendation H.221 for interworking with H.320 and H.321 terminals.
+
+NOTE – Unidirectional H.310 terminals are not required to support the H.221 multiplexing capability.
+
+#### **6.3.4.2 ATM adaptation layer**
+
+The different types of signals supported by H.310 terminals require different ATM adaptation layer functions. The H.310 AAL capabilities for the multimedia multiplexed, in-band signalling, and out-of-band signalling data signals are specified.
+
+AAL Segmentation And Reassembly (SAR) and Convergence Sublayer (CS) functions are supported by H.310 terminals. Both AAL types 1 and 5 are used for the transfer of the multiplexed constant bit rate signals over ATM networks.
+
+NOTE 1 – The definition of AAL functions and capabilities for the adaptation of variable bit rate audiovisual signals is under study.
+
+Data protocols may either be multiplexed with other audiovisual elementary streams using the H.222.1 multiplex layer or be multiplexed at the ATM layer.
+
+H.245 messages may either be multiplexed with other audiovisual elementary streams using the H.222.1 multiplex layer or be multiplexed at the ATM layer. The protocol stacks for these two means of multiplexing are specified in Annex A, and are referred to as "single VC" and "separate VC" respectively.
+
+H.310 terminals support the Q.2931 protocol stack for performing out-of-band call management and signalling functions. In addition to the Q.2130 (SSCS.UNI) and Q.2110 (SSCOP) layers, the AAL 5 CPCS and SAR sublayers represent an integrated part of the Q.2931 protocol stack.
+
+##### **The use of AAL type 1**
+
+RAST-1 and RAST-1&5 terminals shall support the adaptation of H.221 multiplexed audiovisual data using the AAL 1 SAR and CS functions which are defined in Recommendation I.363.1 and supported in H.321 Annex A terminals. This will enable the interworking between H.310 and H.321/Annex A terminals.
+
+RAST-1 and RAST-1&5 terminals shall support the adaptation of H.222.1 multiplexed bit streams into ATM using AAL type 1. The mode of AAL 1 with no FEC and no interleaving shall be supported, and the mode with (128, 124) Reed-Solomon Forward Error Correction (FEC) code without interleaving may optionally be supported1.
+
+ROT-1, ROT-1&5, SOT-1, and SOT-1&5 terminals shall support the adaptation of H.222.1 multiplexed bit streams into ATM using AAL type 1. The mode of AAL 1 with no FEC and no interleaving shall be supported, and the mode with (128, 124) Reed-Solomon Forward Error Correction (FEC) code with interleaving may optionally be supported1.
+
+Neither the Structure Data Transfer (SDT) mode nor the Synchronous Residual Time Stamp (SRTS) of AAL type 1 is supported by H.310 terminals for the transfer of H.222.1 multiplexed data.
+
+NOTE 2 – H.310 terminals that operate in the H.320/H.321 Annex A communication mode shall support the AAL type 1 SDT functions when doing so.
+
+All bidirectional H.310 terminals shall be capable of interworking. For RAST-5 terminals, and RAST-1&5 terminals when working with AAL 5, a gateway in the customer premises network shall be used to provide the AAL 1 adaptation function.
+
+##### **The use of AAL type 5**
+
+RAST-5 and RAST-1&5 terminals shall support the adaptation of H.221 multiplexed audiovisual data into ATM using the AAL 5 SAR and CPCS functions which are defined in Recommendation I.363.5. This will enable the interworking between H.310 and H.321 terminals.
+
+ROT-5, ROT-1&5, SOT-5, SOT-1&5, RAST-5, and RAST-1&5 terminals shall support the adaptation of H.222.1 multiplexed bit streams into ATM using AAL type 5.
+
+The rules and protocols used for the mapping of H.222.1 Program Stream and Transport Stream packets into the AAL 5 Protocol Data Unit (PDU) is specified in Recommendation H.222.1. Only SAR and common part CS (CPCS) functions are supported as defined in Recommendation I.363.5. Therefore, Service Specific Convergence Sublayer (SSCS) functions are neither defined nor supported by H.310 AAL 5 unidirectional terminals.
+
+When detecting an errored cell (using the CRC function of the AAL 5 CPCS sublayer), the AAL 5 PDU may be passed to the user (i.e. H.222.1) according to the corrupted-data delivery option specified in Recommendation I.363.5.
+
+The usage of the AAL 5 CPCS User-To-User (CPCS-UU) indication field is not specified in this Recommendation. Moreover, in H.310 SOT terminals, the Common Part Indicator (CPI) field shall always be set to zero (i.e. only the 64-bit alignment function is used).
+
+#### **6.3.4.3 ATM virtual connections**
+
+All H.310 terminals shall support at least two ATM VCs. In the native H.310 communication mode, there shall be one VC for the transfer of H.245 messages and at least one VC for H.222.1 multiplexed audiovisual and data signals. In the H.320/H.321 interoperation mode, two VCs shall be supported for the transfer of two B-channel signals.
+
+Additional VCs may optionally be used for transfer of audiovisual and/or data signals, such as T.120 data, or for other purposes.
+
+---
+
+1 These specifications are in alignment with Recommendation J.82 "Transport of MPEG-2 constant bit rate television signals in B-ISDN". Note that Recommendation J.82 specifies the mandatory use of (128, 124) Reed-Solomon Forward Error Correction Code with interleaving.
+
+#### 6.3.4.4 Transfer rate
+
+H.310 terminals are capable of supporting a wide range of possible transfer rates. The transfer rate capabilities of H.310 terminals are defined at the AAL-SAP.
+
+Bidirectional H.310 terminals shall support the B, 2B, and H0 narrow-band ISDN transfer rates of H.320/H.321 terminals. Other H.320/H.321 rates (e.g. H11 and H12) are optional. This will enable the interworking of H.310 terminals with a wide range of H.320/H.321 terminals.
+
+All H.310 terminals shall support constant bit rate transfer rates for native H.310 communication mode. The mandatory transfer rates are P = 6.144 Mbit/s (for MP@ML medium quality services) and Q = 9.216 Mbit/s (for MP@ML high quality services) where P/Q is 2/3. Other optional rates of $n \times 64$ kbit/s (n is an integer from 1 to 65 535) can be negotiated through H.245 capability messages and related procedures.
+
+NOTE – Until an appropriate network environment is available everywhere, it would be desirable that all terminals support a rate of $90 \times 64$ kbit/s, compatible with a VC-2 (Virtual Container 2).
+
+The specification of VBR transfer rates is under study.
+
+### 6.3.5 Signalling capabilities
+
+The mandatory and optional signalling capabilities are summarized in Table 5.
+
+**Table 5/H.310 – Signalling capabilities of H.310 terminals**
+
+| Terminal type | | Signalling capabilities | | | |
+|--------------------------------------------------------|--------------|-------------------------|-----------|----------------------------|-----------|
+| | | User-to-user signalling | | User-to-network signalling | |
+| | | Mandatory (Rec.) | Optional | Mandatory (Rec.) | Optional |
+| ROT-1
SOT-1
ROT-5
SOT-5
ROT-1&5
SOT-1&5 | | H.245 | DSM-CC UU | Q.2931 | DSM-CC UN |
+| RAST-1 | Native mode | H.245 | DSM-CC UU | Q.2931 | DSM-CC UN |
+| | H.320/1 mode | H.242/H.230 | – | Q.2931 | – |
+| RAST-5 | Native mode | H.245 | DSM-CC UU | Q.2931 | DSM-CC UN |
+| | H.320/1 mode | H.242/H.230 | – | Q.2931 | – |
+| RAST-1&5 | Native mode | H.245 | DSM-CC UU | Q.2931 | DSM-CC UN |
+| | H.320/1 mode | H.242/H.230 | – | Q.2931 | – |
+
+#### 6.3.5.1 User-to-network signalling
+
+All H.310 terminals shall support Recommendation Q.2931 for user-to-network signalling.
+
+#### 6.3.5.2 User-to-user signalling
+
+All H.310 terminals shall support H.245 messages and procedures for user-to-user signalling. The exact set of H.245 messages and procedures that are mandated in H.310 terminals, and their usage, are specified in 6.4. H.245 signalling is only supported in the native H.310 communication mode.
+
+All bidirectional H.310 terminals shall support Recommendations H.242 and H.230 for interworking with H.320 and H.321 terminals.
+
+#### 6.3.5.3 Video Frame Synchronous (VFS) Control and Indication (C&I) signalling
+
+VFS C&I signalling is accomplished using the syntax given in Table 6. All H.310 terminals shall support this syntax and shall react to all the signals classified as controls in the appropriate way specified below. Terminals are not required to react to any of the signals classified as indications, but may optionally do so. The set of indications which invoke an action is implementation dependent. The reaction, if any, to each indication signal is also implementation dependent.
+
+**Table 6/H.310 – Syntax for H.310 video frame synchronous control and indication signals**
+
+| | |
+|----------------------------------------------------------------|-------------------------------------------------------|
+| H310-TERMINAL-MANAGEMENT DEFINITIONS AUTOMATIC TAGS ::= | |
+| BEGIN | |
+| -- Export all symbols | |
+| VideoFrameSynchronousCandIPDU | ::= SEQUENCE |
+| { | |
+| elementaryStream | CHOICE |
+| { | |
+| ts-PID | INTEGER (1..8191), |
+| ps-StreamID | SEQUENCE |
+| { | |
+| streamID | INTEGER (0..255), |
+| streamIDExtension | INTEGER (0..255) OPTIONAL |
+| }, | |
+| ... | |
+| }, | |
+| resourceID | INTEGER (0..65535) OPTIONAL, |
+| videoFrameSynchronousCandI | CHOICE |
+| { | |
+| videoFrameSynchronousControl | VideoFrameSynchronousControl, |
+| videoFrameSynchronousIndication | VideoFrameSynchronousIndication, |
+| ... | |
+| }, | |
+| ... | |
+| } | |
+| VideoFrameSynchronousControl | ::= CHOICE |
+| { | |
+| nonStandard | NonStandardParameter, |
+| videoFreezePictureReleaseControl | NULL, -- not used for Recommendation H.261 |
+| | or H.263 |
+| ... | |
+| } | |
+
+| | |
+|----------------------------------------|-----------------------------------------------------------------------|
+| VideoFrameSynchronousIndication | ::= CHOICE |
+| { | |
+| nonStandard | NonStandardParameter, |
+| closedCaption | OCTET STRING, |
+| splitScreenIndication | NULL, -- not used for Recommendation H.261
or H.263 |
+| documentCameraIndication | NULL, -- not used for Recommendation H.261
or H.263 |
+| ... | |
+| } | |
+| NonStandardParameter | ::= SEQUENCE |
+| { | |
+| nonStandardIdentifier | NonStandardIdentifier, |
+| data | OCTET STRING |
+| } | |
+| NonStandardIdentifier | ::= CHOICE |
+| { | |
+| object | OBJECT IDENTIFIER, |
+| h221NonStandard | SEQUENCE |
+| { | |
+| t35CountryCode | INTEGER (0..255), |
+| t35Extension | INTEGER (0..255), |
+| manufacturerCode | INTEGER (0..65535) |
+| } | |
+| } | |
+| END | |
+
+The following video frame synchronous control and indication signals shall be supported by all H.310 terminals:
+
+- video freeze picture release control;
+- split-screen indication;
+- document camera indication;
+- closed caption.
+
+##### Syntax
+
+The syntax for Video Frame Synchronous (VFS) Control and Indication (C&I) is specified using the notation defined in ASN.1 [38] and is shown in Table 6. Messages shall be encoded for transmission by applying the packed encoding rules specified in [39] using the basic aligned variant. The first bit in each octet which is transmitted is the most significant bit of the octet as is specified in Recommendation X.691.
+
+This information is packed in PES packets, and Presentation Time Stamp (PTS) shall be used for timing the event. Multiple **VideoFrameSynchronousCandIPDUs** can exist in a single PES packet.
+
+The PES packets including VFS C&I information shall be transmitted in the video synchronous subchannel of the ITU-T H.222.1 type C elementary stream as specified in Recommendation H.222.1. If the VFS C&I information is delivered in a Transport Stream (TS), the **stuffing\_byte** field of the TS adaptation\_field() defined in Recommendation H.222.0 shall be used for alignment with the TS packets.
+
+##### Semantics
+
+The elementary stream to which the VFS control or indication is applied, the target elementary stream, shall be specified using **ts-PID** if it is included in a Transport Stream. This field shall have the identical value with the **PID** field of the target elementary stream, which is specified in Table 2-3/H.222.0.
+
+A target elementary stream included in a Program Stream shall be specified using **streamID**. If the target elementary stream is a Recommendation H.222.1 type A-E stream, **streamIDExtension** shall be used additionally. These fields shall have identical values with the **stream\_id** and **stream\_ID\_extension** fields of the target elementary stream, which are specified in Tables 2-34/H.222.0 and 2/H.222.1.
+
+**resourceID** shall be present only in the case when a VFS C&I is applied to an elementary stream included in a different Transport Stream or Program Stream.
+
+##### Procedures
+
+For the VFS C&I signals that can be signified at the video stream level, such as "video freeze picture release control", "split-screen indication", and "document camera indication" which are provided in Recommendations H.261 and H.263, the video synchronous subchannel shall not be used for transmission. The following are the procedures of H.310 VFS C&I signals:
+
+###### a) *Freeze picture release control*
+
+This control is signified by **videoFreezePictureReleaseControl** or the "video freeze picture release control" signal embedded in the video elementary stream (i.e. Recommendation H.261 or H.263). When a decoder receives **videoFreezePicture** specified in Recommendation H.245, it shall complete updating of the current video frame but subsequently display the frozen picture. The picture shall be frozen until **videoFreezePictureReleaseControl** is received or a timeout period of at least six seconds has expired (this specification is the same as in Recommendation H.230). If a terminal or a Multipoint Control Unit (MCU) wishes to continue the freezing of the picture at the remote end more than six seconds, it should send **videoFreezePicture/H.245** repeatedly with an appropriate period.
+
+NOTE – When H.262 streams are switched by an MCU, the switched stream shall start with an H.262 sequence\_header().
+
+###### b) *Closed caption*
+
+This information is transmitted using the **closedCaption** field in the **OCTET STRING** format. The detailed usage of this indication is defined in the specification of each individual application.
+
+###### c) *Split-screen indication*
+
+This indication is signified by **splitScreenIndication** or the "split-screen indication" signal embedded in the video elementary stream (i.e. Recommendation H.261 or H.263). The indication can be transmitted when the transmitted picture is in the split-screen state defined in Recommendation H.100. An example of the response to this indication at the receiving terminal is presenting each segment of the picture on a separate monitor.
+
+###### d) *Document camera indication*
+
+This indication is signified by **documentCameraIndication** or the "document camera indication" signal embedded in the video elementary stream (i.e. Recommendation H.261 or H.263). The indication can be transmitted when the transmitted frame includes still picture information, for example documents. An example of the response to this indication at the receiving terminal is holding and presenting the still picture on a separate monitor.
+
+## 6.4 The use of the H.245 control channel
+
+All H.310 terminals shall support H.245 messages and procedures in the native H.310 communication mode. The exact set of H.245 messages and procedures that are mandated in H.310 terminals, and their usage, are specified in this subclause.
+
+The H.245 control channel carries end-to-end control messages governing operation of the H.310 system, including capabilities exchange, opening and closing of logical channels, mode preference requests, round trip delay, maintenance loop and master slave determination.
+
+There shall be exactly one control channel in each direction within H.310 systems, which shall use the messages and procedures of Recommendation H.245. The H.245 control channel shall be set up at the beginning of communication, before the transmission of audiovisual information.
+
+Recommendation H.245 specifies a number of independent protocol entities which support terminal-to-terminal signalling. A protocol entity is specified by its syntax (messages), semantics, and a set of procedures which specify the exchange of messages and the interaction with the user. H.310 terminals shall support the syntax, semantics and procedures of the following protocol entities, as specified in the following subclauses:
+
+- Master slave determination.
+- Capabilities exchange.
+- Logical channel signalling.
+- Bidirectional logical channel signalling.
+- Close logical channel signalling.
+- Mode request.
+- Round trip delay determination.
+- Maintenance loop signalling.
+- Specific commands and indications.
+
+Figure 4 shows the interaction between the H.245 protocol entities and H.310.
+
+
+
+The diagram illustrates the configuration of H.245 entities within an H.310 terminal. It is structured as follows:
+
+- A large outer rectangle represents the **Rec. H.310** layer.
+- Inside this rectangle, at the top, is a box labeled **Rec. H.310**.
+- Below this box, a horizontal line separates it from the **Rec. H.245** layer.
+- The **Rec. H.245** layer contains a row of nine boxes, each representing a specific protocol entity. From left to right, they are: **Master slave determination**, **Capability exchange**, **Logical channel signalling**, **Bidirectional logical channel signalling**, **Close logical channel signalling**, **Mode request**, **Round trip delay determination**, **Maintenance loop procedure**, and **Specific commands and indications**.
+- Below these nine boxes, within the same outer rectangle, is a box labeled **Rec. H.245**.
+- Vertical double-headed arrows connect the top **Rec. H.310** box to each of the nine protocol entity boxes, and each of these boxes to the bottom **Rec. H.245** box, indicating bidirectional interaction.
+
+Diagram showing the configuration of H.245 entities in an H.310 terminal. It illustrates the interaction between the Rec. H.310 layer and the Rec. H.245 layer, which contains nine specific protocol entities.
+
+T1604910-98
+
+**Figure 4/H.310 – Configuration of H.245 entities in H.310 terminal**
+
+All H.245 messages are conveyed by the underlying protocol stack, as specified in Annex A, which provides a reliable end-to-end transmission of H.245 messages using acknowledgement of correct receipt within each layer protocol.
+
+H.310 terminals shall be capable of identifying all H.245 **MultimediaSystemControlPDU** messages, and shall respond to all messages needed to realize required H.310 functions. H.310 terminals shall send the **FunctionNotSupported** message in response to unrecognizable request, response, command or the H.245 message which is not supported by the H.310 terminal.
+
+Non-standard capabilities and control messages may be issued using the **NonStandardParameter** structure defined in Recommendation H.245. Note that while the meaning of non-standard messages is defined by individual organizations, equipment built by any manufacturer may signal any non-standard message, if the meaning is known.
+
+All timers defined in Recommendation H.245 should have periods of at least the maximum data delivery time allowed by the layer carrying H.245, including any retransmissions.
+
+The following subclauses outline the sequence of primitives exchanged between H.310 and the H.245 entities. Restrictions, which are applied to the direction from the H.310 entity to the H.245 entities, to the sequence of primitives defined in Recommendation H.245 are stated in the following subclauses.
+
+### 6.4.1 Master slave determination
+
+Master slave determination shall follow the procedures of Recommendation H.245, which provides the mechanism on an even basis to determine which is the master terminal and which is the slave terminal. The master terminal will be permitted to manage the resource limited to only one avoiding the simultaneous initiation of similar events by two or more terminals. The master terminal has precedence where conflict of requests occurs.
+
+There shall be exactly one MSDSE in one H.310 terminal. The H.310 terminal can start the master slave determination procedure by issuing **DETERMINE.request** primitive to its MSDSE without parameter.
+
+When the **DETERMINE.confirm** primitive is received from the MSDSE after **DETERMINE.request** was issued, the master slave determination has been successfully completed and confirmed by the peer terminal. The result of determination is indicated in the **TYPE** parameter of the **DETERMINE.confirm** primitive. If the **REJECT.indication** primitive is received instead, the determination procedure has failed. The H.310 terminal may reissue **DETERMINE.request** for retrying the master slave determination. When **DETERMINE.indication** is received, the peer terminal has also invoked the master slave determination procedure and H.310 shall follow the incoming side protocol described below. **DETERMINE.request** shall not be issued until **DETERMINE.confirm** or **REJECT.indication** primitive is received, after **DETERMINE.request** has been issued.
+
+When the peer terminal invoked the master slave determination procedure, H.310 will receive **DETERMINE.indication** from the MSDSE. The **TYPE** parameter in **DETERMINE.indication** indicates the preliminary result of master slave determination. However, it is necessary to confirm the result between the local and remote terminals. Therefore, H.310 shall wait for the **DETERMINE.confirm** primitive. When the **ERROR.indication** primitive is received, mismatch of state between local MSDSE and remote MSDSE may have occurred. It should be noted that **REJECT.indication** will follow **ERROR.indication** in some error situations. In these cases, the previously received result indicated by the **TYPE** parameter in the **DETERMINE.indication** primitive shall be discarded and ignored. **DETERMINE.request** shall not be issued until **DETERMINE.confirm** or **REJECT.indication** primitive is received, after **DETERMINE.indication** has been received.
+
+At the start of the communication, the H.310 terminal shall not have a preference that it is a master or a slave. H.245 procedures in which the master and slave distinction is necessary (see Table 7), shall not be initiated until the master/slave status has been determined.
+
+Only one random number shall be chosen by the terminal for one call, except in the case of identical random numbers, as described in Recommendation H.245. It should be noted that identical means identical modulo $2^{23}$ .
+
+Terminals may reinvoke the master slave determination if necessary, according to the procedures described above. The value of counter N100 is 3 for H.310 terminal.
+
+**Table 7/H.310 – Necessity of the master slave determination procedure**
+
+| H.245 procedure | Master/slave result is required? |
+|------------------------------------------|-----------------------------------------|
+| Master slave determination | Irrelevant |
+| Capabilities exchange | No |
+| Logical channel signalling | Yes |
+| Bidirectional logical channel signalling | Yes |
+| Close logical channel signalling | No |
+| Mode request | Yes |
+| Round trip delay determination | No |
+| Maintenance loop signalling | Yes |
+| Specific commands and indications | No |
+
+### **6.4.2 Capabilities exchange**
+
+Capabilities exchange shall follow the procedures of Recommendation H.245, which provides for separate receive and transmit capabilities.
+
+Receive capabilities describe the terminals ability to receive and process incoming information streams. Transmitters shall limit the content of their transmitted information to that which the receiver has indicated it is capable of receiving. The absence of a receive capability indicates that the terminal cannot receive (is a transmitter only).
+
+Transmit capabilities describe the terminals ability to transmit information streams. Transmit capabilities serve to offer receivers a choice of possible modes of operation, so that the receiver may request the mode which it prefers to receive.
+
+There shall be exactly one outgoing CESE and one incoming CESE in one H.310 terminal. H.310 terminal can start the capability exchange procedure by issuing TRANSFER.request primitive to its outgoing CESE with proper parameters. The value of PROTOID parameter shall be "1" for terminals conforming to this Recommendation. MUXCAP and CAPDESCRIPTORS parameters with at least one capability set is mandatory for the H.310 terminal. Though the use of CAPTABLE parameter is optional, CAPTABLE parameter is required at the start of the communication, because the remote terminal does not have any knowledge about capability table entries which are referred to by the CAPDESCRIPTORS parameter. When H.310 terminal reinvokes the capability exchange procedure after the successful completion of a capability exchange, CAPTABLE can be omitted provided that CAPTABLEEntries are not changed from those that have already been transmitted.
+
+When the TRANSFER.response primitive is received from the outgoing CESE after TRANSFER.request has been issued, the capability message has been successfully transmitted to the peer terminal. If the REJECT.indication primitive is received instead, the previously sent capability message has not been accepted by the peer terminal (SOURCE=USER), or the timer has expired before receiving the response from the peer terminal (SOURCE=PROTOCOL). The H.310 terminal may reissue the TRANSFER.request primitive for retrying the capability message transmission in these cases. TRANSFER.request shall not be issued until TRANSFER.confirm or REJECT.indication primitive has been received, after TRANSFER.request has been issued.
+
+H.310 shall respond to the TRANSFER.indication primitive received from the incoming CESE, by issuing the TRANSFER.response primitive if the capabilities can be accepted successfully, or by issuing the REJECT.request primitive if the capabilities are not acceptable. The H.310 terminal may receive REJECT.indication, before responding to TRANSFER.indication. In this case, H.310 shall discard and ignore the contents of the previously received TRANSFER.indication and shall not respond to that indication until a new TRANSFER.indication is received.
+
+At the start of the communication, the H.310 terminal shall recognize that its own transmit capability declared to the remote terminal and the receive capability of remote terminal are null. Therefore, audiovisual communication cannot be started before the capability exchange procedure is carried out. The H.310 terminal can update its knowledge about its own declared and remote capabilities, only after the capability exchange procedure has been successfully completed.
+
+Terminals may reinvoke the capability exchange procedure at any time, according to the procedures described above.
+
+### 6.4.3 Logical channel signalling
+
+Each logical channel carries information from a transmitter to a receiver, and is identified by a logical channel number unique for each direction of transmission.
+
+Logical channels are opened and closed using the **OpenLogicalChannel** and **CloseLogicalChannel** messages and procedures of Recommendation H.245.
+
+When a logical channel is opened, the **OpenLogicalChannel** message fully describes the content of the logical channel, including media type, algorithm in use and any options, and all other information needed for the receiver to interpret the contents of the logical channel. Logical channels may be closed when no longer needed.
+
+Certain media types, including data protocols such as T.120, inherently require a bidirectional channel for their operation. In such cases a bidirectional logical channel, which is capable of information transmission in both directions, may be opened using the bidirectional channel opening procedures of Recommendation H.245.
+
+NOTE 1 – A pair of unidirectional logical channels, each of which is opened by the open logical channel procedure, can be applied to a bidirectional operation of those media providing the transmission in each direction. However, the use of bidirectional logical channel is strongly recommended for bidirectional media in this Recommendation.
+
+Bidirectional logical channels in H.310 may have asymmetrical characteristics, such that the medium type in each direction of transmission might be different.
+
+H.310 supports multiple logical channels. There shall be one outgoing LCSE and one incoming LCSE for each logical channel. There shall also be one outgoing CLCSE and one incoming CLCSE managing the same logical channel as an incoming LCSE and an outgoing LCSE, respectively. H.310 terminal can start the open logical channel procedure by issuing the ESTABLISH.request primitive to its outgoing LCSE of the required logical channel with proper parameters.
+
+FORWARD\_PARAM parameter describes the content of the logical channel, which will be transferred by the **OpenLogicalChannel** message to the peer terminal.
+
+When the ESTABLISH.response primitive is received from the outgoing LCSE after ESTABLISH.request was issued, the logical channel is successfully opened and H.310 terminal can start audiovisual information transmission through this logical channel. If the REJECT.indication primitive is received instead, either the open logical channel request has not been accepted by the peer terminal (SOURCE=USER), or the timer has expired before receiving a response from the peer terminal (SOURCE=LCSE). The H.310 terminal may reissue the ESTABLISH.request for retrying the open logical channel request in these cases.
+
+H.310 may close a logical channel which has been successfully opened by issuing the RELEASE.request primitive at the outgoing LCSE. The RELEASE.confirm primitive is passed to H.310 when the logical channel has been successfully closed. If the ERROR.indication primitive precedes the RELEASE.confirm primitive, then the local timer has expired before a response was received from the peer terminal.
+
+Before the ESTABLISH.confirm or the RELEASE.indication primitive is received in response to an earlier ESTABLISH.request, H.310 may close the logical channel using the RELEASE.indication primitive at the outgoing LCSE.
+
+Before the RELEASE.confirm primitive is received in response to a previously sent RELEASE.request primitive, H.310 may establish the logical channel using the ESTABLISH.request primitive at the outgoing LCSE.
+
+When the ERROR.indication primitive is received from the outgoing LCSE, a timer expiry or a mismatch of state has occurred and the logical channel has been closed. The ERROR.indication primitive is followed by either the RELEASE.indication or the RELEASE.confirm primitive.
+
+The H.310 terminal shall respond to the ESTABLISH.indication primitive received from the incoming LCSE, by issuing ESTABLISH.response if the opening of the logical channel can be accepted, or by RELEASE.request if the logical channel cannot be opened.
+
+H.310 may receive RELEASE.indication, before responding to ESTABLISH.indication. It is no longer necessary to respond to the previous ESTABLISH.request primitive and the logical channel shall be kept closed. Whenever RELEASE.indication is received, H.310 shall regard that the logical channel is now closed and unavailable. If RELEASE.indication is followed by ESTABLISH.indication, the logical channel immediately becomes unavailable and H.310 shall decide whether new logical channel with parameters conveyed by ESTABLISH.indication is acceptable.
+
+Incoming side of the H.310 terminal can request to close a logical channel using the close logical channel procedure by issuing the CLOSE.request primitive to outgoing LCSE. The logical channel is kept opened unless CLOSE.confirm is received. If REJECT.indication is received, H.310 may reinvoke the close logical channel procedure.
+
+NOTE 2 – Receipt of CLOSE.confirm indicates that the remote H.310 terminal will close the logical channel. The channel is not closed until it does so.
+
+If H.310 receives audiovisual information through a logical channel that is not open, the receiving H.310 terminal should request the closing of that logical channel by invoking close logical channel procedure to recover from the mismatch of state of local and remote LCSEs.
+
+When contention occurs between the open logical channel procedure and the close logical channel procedure for the same channel, the close logical channel always has a higher priority than the open logical channel. Therefore, if H.310 wants to re-open the logical channel, the open logical channel
+
+procedure can be invoked only after the close logical channel procedure has been successfully completed.
+
+The open bidirectional logical channel procedure is very similar to the procedure for unidirectional logical channel. The only difference is that the incoming side H.310 shall wait for ESTABLISH.confirm from the incoming B-LCSE, after H.310 responds to ESTABLISH.indication by ESTABLISH.response. Though a unidirectional channel can become active by issuing ESTABLISH.response, bidirectional channel cannot become active until ESTABLISH.confirm is received.
+
+### 6.4.4 Mode request
+
+The H.310 terminal is able to request a remote terminal to change its transmit mode of operation by using the mode request procedure of Recommendation H.245.
+
+The terminal shall select the requesting mode of operation from the valid transmission capabilities of the peer terminal previously received by successfully completed capability exchange procedure(s). If the peer terminal is receive only, and does not have any transmission capabilities, the mode request procedure shall not be invoked.
+
+There shall be exactly one outgoing MRSE and incoming MRSE in one H.310 terminal. The H.310 terminal can start the mode request procedure by issuing the TRANSFER.request primitive to its outgoing MRSE with proper parameters. MODE-ELEMENT parameter describes the requesting mode of operation for a remote terminal.
+
+When the TRANSFER.response primitive is received from the outgoing MRSE after TRANSFER.request was issued, the requested mode has been accepted by the peer terminal. The contents of logical channels in the receiving direction will soon be changed by the remote terminal according to the requested communication mode. If the REJECT.indication primitive is received instead, the requested mode has not been accepted by the peer terminal (SOURCE=USER), or the timer has expired before receiving a response from the peer terminal (SOURCE=PROTOCOL). The H.310 terminal may reissue TRANSFER.request for retrying the mode request procedure with the same parameters in the latter case, or with different parameters in the former case.
+
+NOTE – It is recommended for the H.310 terminal that TRANSFER.request should not be issued until TRANSFER.confirm or REJECT.indication primitive has been received, after TRANSFER.request has been issued.
+
+H.310 shall respond to TRANSFER.indication received from the incoming MRSE, by issuing the TRANSFER.response primitive if the requested mode can be accepted, or by REJECT.request if the requested mode is not acceptable. The H.310 terminal may receive REJECT.indication, before responding to TRANSFER.indication. In this case, H.310 shall discard and ignore the previously received TRANSFER.indication and shall not respond to that indication until a new TRANSFER.indication is received.
+
+Terminals may invoke the mode request procedure at any time, according to the procedures described above.
+
+### 6.4.5 Round trip delay
+
+The round trip delay procedure of H.245 enables the H.310 terminal to measure the round trip delay of H.245 message transmission between a local terminal and a remote terminal. This delay includes all the processing delay of underlying protocol layers for H.245 message transmission and H.245 message processing time of H.245 entities as well as delay in physical transmission line. This round trip delay procedure can be used to determine if the peer H.245 entity is still alive (i.e. as a keep alive function).
+
+There shall be exactly one RTDSE in one H.310 terminal. H.310 terminal can start the round trip delay procedure by issuing TRANSFER.request primitive to its RTDSE.
+
+When the TRANSFER.confirm primitive is received from the RTDSE after TRANSFER.request was issued, H.310 can estimate the value of the measured round trip delay using DELAY parameter in TRANSFER.confirm primitive.
+
+NOTE – The round trip delay procedure in Recommendation H.245 specifies that the DELAY parameter indicates the value of the timer T105 which cannot be directly interpreted as delay itself. Therefore, the actual delay value is: time out value of T105 – DELAY parameter.
+
+If EXPIRY.indication primitive is received instead, the peer H.245 entity has not responded before the local timer has expired. In this case, the remote H.245 entity may not be alive and H.245 procedures may not be usable. The local H.310 terminal may take appropriate actions, such as release the call or indicate to the human user, in this error situation.
+
+It is not necessary for H.310 to respond to any incoming messages concerning the round trip delay procedure, because the **RoundTripDelayResponse** message is automatically issued within RTDSE in response to the **RoundTripDelayRequest** message.
+
+Terminals may invoke the round trip delay procedure at any time, according to the procedures described above.
+
+### 6.4.6 Maintenance loop
+
+The maintenance loop procedure of Recommendation H.245 provides a maintenance loop function for the H.310 terminal.
+
+There shall be exactly one outgoing MLSE and incoming MLSE for each logical channel, and one of each for the system loop, in one H.310 terminal. The H.310 terminal can start the maintenance loop procedure by issuing LOOP.request primitive to an outgoing MLSE with proper parameters. LOOP\_TYPE parameter indicates the type of loop operation to the remote terminal.
+
+When the LOOP.confirm primitive is received from the outgoing MLSE after LOOP.request was issued, maintenance loop operation has been established by the peer terminal. Data received from logical channels will be that transmitted by the local terminal and then looped back. If the RELEASE.indication primitive is received instead, the maintenance loop is not accepted by the peer terminal. If ERROR.indication(B) primitive is received, the timer has expired before receiving a response from the peer terminal. LOOP.request shall not be issued until LOOP.confirm or RELEASE.indication primitive is received, after LOOP.request has been issued.
+
+When the ERROR.indication primitive is received, mismatch of state between local MLSE and remote MLSE may have occurred. In these error cases, RELEASE.indication will follow ERROR.indication, the maintenance loop procedure has failed and the state of local outgoing MLSE shall be kept not looped.
+
+The H.310 terminal shall respond to LOOP.indication received from the incoming MLSE, by LOOP.response if the requested maintenance loop operation can be accepted, or by RELEASE.request if the maintenance loop is not acceptable.
+
+Whenever the H.310 terminal receives RELEASE.indication, H.310 shall regard that the loop operation is released and the state of incoming MLSE immediately becomes not looped.
+
+The H.310 terminal which invoked the maintenance loop procedure shall be responsible for releasing the looped operation, when the maintenance loop becomes unnecessary. Terminals may invoke the maintenance loop procedure at any time, according to the procedures described above.
+
+### **6.4.7 Specific commands and indications**
+
+H.310 shall support the following H.245 commands and indications:
+
+SendTerminalCapabilitySet
+
+EncryptionCommand
+
+FlowControlCommand
+
+EndSessionCommand
+
+MiscellaneousCommand
+
+FunctionNotSupported
+
+MiscellaneousIndication
+
+JitterIndication
+
+NewATMVCIndication
+
+NewATMVCCCommand
+
+UserInputIndication
+
+# **7 H.310 call phases**
+
+The call and signalling procedures (between two H.310 terminals or between an H.310 terminal and an H.320/H.321 terminal) described in this clause are based on the following principles:
+
+- 1) An H.310 terminal (initiating or receiving a call) is able to identify the remote terminal type (H.320/H.321, H.310 RAST, etc.) via Q.2931 signalling at the beginning of the call (i.e. prior to audiovisual communications).
+- 2) When two H.310 terminals are communicating, a default H.245 (logical) channel is established over the initial ATM VC at the beginning of the call.
+- 3) When two H.310 terminals communicate, each terminal indicates its capabilities (specified in 6.3) to the remote terminal using the capabilities exchange messages and procedures described in Recommendation H.245.
+- 4) When an H.310 terminal communicates with an H.320/H.321 terminal, the two terminals use the H.242 and H.230 messages and procedures for capability exchanges and other in-band signalling needs as done in H.320/H.321 terminals.
+- 5) For the different types of native H.310 communication modes, in-band signalling during the call is based on H.245 messages and procedures.
+
+Depending on the type of the two communicating terminals, an H.310 terminal shall employ one of the following two call procedures: native H.310 communication call procedures or H.320/H.321 interoperation call procedures.
+
+## **7.1 Native H.310 communication call procedures**
+
+The native H.310 communication call procedures shall be supported by all unidirectional and bidirectional H.310 terminals.
+
+The H.310 correlationID is composed of a session identification field and the 2 octet H.245 "resourceID" as indicated in Table 8. The H.245 resourceID in the H222LogicalChannelParameters is used to indicate which ATM Virtual Channel the logical channel is associated with. The session identification field is currently undefined and is reserved for future use.
+
+**Table 8/H.310 – Definition of H.310 CorrelationID**
+
+| H.310 CorrelationID | |
+|-----------------------|------------------|
+| Session ID (Reserved) | H.245 resourceID |
+
+In allocating H.245 resourceIDs, the side that sets up the initial H.245 VC chooses values starting from the lowest possible value and the other side (the called side), chooses values starting from the highest in the range.
+
+The Generic Identifier Transport (GIT) Information Element shall be used for the transmission of the H.310 correlationID in the Q.2931 SETUP message. The GIT information element is specified in Recommendation Q.2941.1.
+
+Since the resourceID is the only valid element in the correlation ID at this time, only the resourceID is sent in the Q.2931 SETUP. This is pictorially shown in Figure 5. When coding the GIT, the identifier related standard/application is coded as this Recommendation, the identifier type as Resource, and the identifier length as two octets.
+
+
+
+The diagram illustrates the structure of the H.310 Correlation ID. At the top, a bracket labeled "H.310 Correlation ID" spans over a table with two columns: "Session ID" and "H.245 Resource ID". Below the "Session ID" column, a downward arrow points to the text "Reserved (Not used)". Below the "H.245 Resource ID" column, a downward arrow points to the text "Placed in Q.2931 GIT Identifier Type = Resource". To the right of the second arrow, the text "T1604920-98" is present.
+
+Diagram of H.310 Correlation ID structure showing Session ID and H.245 Resource ID fields with their respective uses.
+
+**Figure 5/H.310 – Use of H.310 CorrelationID**
+
+Optionally, the H.310 correlationID may also be sent in the user-to-user information IE.
+
+The native H.310 communication call procedures are divided into the following call phases as shown in Figure 6.
+
+
+
+```
+
+graph TD
+ subgraph PhaseA [Phase A (Call Setup)]
+ A1["A1:
+Initial VC Setup
+Q.2931"]
+ A2["A2:
+Capability Exchange
+Master Slave Determination
+H.245"]
+ A3["A3:
+Additional VC Setup
+Q.2931"]
+ A4["A4:
+Logical Channels Setup
+H.245"]
+ A1 --> A2
+ A2 --> A3
+ A3 --> A4
+ end
+ subgraph PhaseB [Phase B (Audiovisual communication)]
+ BST["Audiovisual Signal Transfer"]
+ subgraph Loop [ ]
+ L["- Mode Request and Switching
+- C&I Signalling
+- Maintenance Loop
+- Round Trip Delay
+H.245
+- Capability Exchange
+H.245
+- Additional VC Setup
+Q.2931
+- Logical Channels Setup/Release
+H.245"]
+ end
+ BST --> Loop
+ Loop --> BST
+ end
+ subgraph PhaseC [Phase C (Call Release)]
+ C1["C1:
+Logical Channels Release
+H.245"]
+ C2["C2:
+Virtual Channel Release
+Q.2931"]
+ C1 --> C2
+ end
+ PhaseA --> PhaseB
+ PhaseB --> PhaseC
+ style Loop fill:none,stroke:none
+
+```
+
+The diagram illustrates the call phases for native H.310 communication, organized into three main vertical sections:
+
+- Phase A (Call Setup):** This section contains four sequential steps:
+ - A1: Initial VC Setup (Q.2931)
+ - A2: Capability Exchange, Master Slave Determination (H.245)
+ - A3: Additional VC Setup (Q.2931)
+ - A4: Logical Channels Setup (H.245)
+- Phase B (Audiovisual communication):** This section begins with "Audiovisual Signal Transfer". Below this is a loop containing several operations:
+ - Mode Request and Switching
+ - C&I Signalling
+ - Maintenance Loop
+ - Round Trip Delay (H.245)
+ - Capability Exchange (H.245)
+ - Additional VC Setup (Q.2931)
+ - Logical Channels Setup/Release (H.245)
+- Phase C (Call Release):** This section contains two sequential steps:
+ - C1: Logical Channels Release (H.245)
+ - C2: Virtual Channel Release (Q.2931)
+
+Arrows indicate the flow from Phase A to Phase B, and from Phase B to Phase C. Within Phase B, an arrow points from the "Audiovisual Signal Transfer" box into the loop, and another arrow points from the loop back to the same box.
+
+Flowchart of H.310 call phases: Phase A (Call Setup), Phase B (Audiovisual communication), and Phase C (Call Release).
+
+T1604930-98
+
+**Figure 6/H.310 – H.310 call phases for native H.310 communication**
+
+### 7.1.1 Phase A (call setup)
+
+Phase A is a call-setup procedure phase which is divided into the following subphases.
+
+NOTE 1 – The call procedures defined here are based on establishing two or more VCs: one for H.245 messages, and the others for the transfer of audiovisual and other data. A single-VC call procedure is under study.
+
+#### Phase A1 (initial VC setup)
+
+In this phase, the initial ATM Virtual Channel (VC) using a Q.2931 SETUP message is established. The exact parameters and DSS 2 Information Elements (IEs) used for this phase are described in Annex B.
+
+One of the key features of this phase is that it enables an H.310 terminal (initiating or receiving a call) to either identify the type of remote H.310 terminal or infer that the remote terminal is not an H.310 terminal type. This is done by using the Broadband Bearer Capability (B-BC), Narrow-band Bearer Capability (N-BC) and other information elements of the Q.2931 SETUP message. An H.310 terminal shall set these information elements to the appropriate parameters which indicate the H.310 terminal type. If an H.310 terminal does not receive the N-BC information element from the remote terminal, then the H.310 terminal can assume that it is not communicating with an H.320/H.321 terminal.
+
+The initial VC shall have a bit rate of 64 kbit/s at the AAL-SAP, for the transfer of H.245 messages using the separate VC stack described in Annex A.
+
+NOTE 2 – Interaction between the arrival of the initial call and the human user is under study in the light of audio communication start up and charging aspects.
+
+#### Phase A2 (capability exchange and master slave determination)
+
+In this phase, it is assumed that each H.310 terminal has already identified that the remote terminal is an H.310 terminal type. Therefore, at this stage the two terminals shall exchange their capability information using the capability exchange signalling protocol defined in Recommendation H.245 as described in 6.4.2 over the initial VC that has been established in Phase A1. At the same time as this, the two terminals shall determine which is master and which is slave using the master slave determination signalling protocol defined in Recommendation H.245 as specified in 6.4.1. Based on the capabilities of the two terminals, an appropriate common mode of communication shall be determined.
+
+H.310 terminals shall be capable of operating in both master and slave modes, and shall set **terminalType** to 128 and set **statusDeterminationNumber** to a random number in the range 0 to $2^{24}-1$ . Only one random number shall be chosen by the terminal for each call, except in the case of identical random numbers, as described in Recommendation H.245.
+
+#### Phase A3 (additional VC setup)
+
+This paragraph applies to the case where MCU is not used in the session. In this phase, and based on the communication mode determined above, the calling terminal, that is, the one that initiated the first VC SETUP message, shall firstly indicate the characteristics of the additional VC(s) to the remote end using the H.245 **NewATMVCIndication** message, and then shall set up the additional VC(s) with the appropriate parameters, such as bit rate and AAL type, for the transfer of the audiovisual and other data between the two H.310 terminals.
+
+NOTE 3 – This allows the remote end to receive the H.245 **NewATMVCIndication** message before responding to the VC-setup message.
+
+This paragraph applies to the case where MCU is used in the session. If the terminal is talking to an MCU, that is, it has received the H.245 **multipointModeCommand** message, the terminal shall wait
+
+for the H.245 **NewATMVCIndication** message or the H.245 **NewATMVCCCommand** message. In the former case, the additional VC(s) with the appropriate parameters, such as bit rate and AAL type, for the transfer of the audiovisual and other data shall be initiated by the MCU. In the latter case, the additional VC(s) with the appropriate parameters shall be initiated by the terminal.
+
+#### **Phase A4 (logical channels setup)**
+
+The choice of communication mode can be made by either the master or the slave. An H.310 terminal shall open the desired video, audio, data, and/or control logical channels using the logical channel signalling protocol and bidirectional logical channel signalling protocol defined in Recommendation H.245 as described in 6.4.3.
+
+### **7.1.2 Phase B (audiovisual communication)**
+
+In addition to the transfer of audiovisual and other data during Phase B of the call, one or more of the following procedures may also take place.
+
+#### **Mode request and switching**
+
+H.310 terminals can request a new mode of audiovisual communication over the different logical channels (established over a given VC) using the mode request signalling protocol defined in Recommendation H.245 as described in 6.4.4, and can switch to a new mode using the logical channel signalling protocol and bidirectional logical channel signalling protocol, and aided by the close logical channel signalling protocol, defined in Recommendation H.245 as described in 6.4.3.
+
+#### **Control & Indication (C&I) signalling**
+
+H.310 terminals can use H.230-like C&I signals provided by Recommendation H.245, in addition to the video frame synchronous C&I signals defined in 6.3.5.3. Specific H.230-like C&I signals which the H.310 terminal shall support is given in 6.4.7.
+
+#### **Maintenance loops and round trip delay signalling**
+
+H.310 terminals can perform loops for maintenance purposes using the maintenance loop signalling protocol defined in Recommendation H.245 as described in 6.4.6. Further information is provided on maintenance loops in clause 11.
+
+H.310 terminals can use the round trip delay signalling protocol defined in Recommendation H.245 as described in 6.4.5 to determine the round trip delay between the two terminals and also to determine if the far-end H.245 entity is "still alive".
+
+During Phase B, depending on the capabilities of the terminals involved and the requests of users, the following procedures may also be invoked:
+
+- capability exchange;
+- additional VC setup;
+- logical channels setup.
+
+These procedures are identical to those for Phases A2, A3 and A4, respectively.
+
+### **7.1.3 Phase C (call release)**
+
+Phase C is a call release procedure phase which is divided into the following subphases.
+
+#### **Phase C1 (logical channels release)**
+
+In this phase, all logical channels are closed and **EndSessionCommand** is transmitted, using the procedures described in Recommendation H.245.
+
+#### Phase C2 (virtual channels release)
+
+In this phase, all ATM VCs are released using the procedures described in Recommendation Q.2931.
+
+## 7.2 H.320/H.321 interoperation call procedures
+
+The H.320/H.321 interoperation call procedures shall be supported by all bidirectional H.310 RAST type terminals.
+
+Interoperation between an H.310 RAST terminal and an H.320/H.321 terminal shall be through the use of circuit transport service which requires inclusion of both broadband and narrow-band information elements (B-BC, ATM Traffic Descriptor, AAL parameters, etc.; N-BC, N-LLC, N-HLC).
+
+After determining that the remote terminal is an H.320/H.321 terminal type based on the Q.2931 SETUP message, an H.310 RAST terminal shall follow the call procedures described in Recommendations H.320 and H.321.
+
+NOTE – See clause 7/H.321 for interactions between an H.310 RAST-5 terminal or a RAST-1&5 terminal when working with AAL 5, the gateway and an H.320 or H.321/Annex A terminal.
+
+# 8 Multipoint communication
+
+H.310 terminals may be used in multipoint configuration through MCUs which may be accommodated in B-ISDN, N-ISDN or other networks.
+
+## 8.1 Native H.310 communication modes
+
+When an H.310 terminal is involved in the multipoint communication, MCUs may force terminals into a particular common mode of transmission by sending to the terminal a receive capability set listing only the desired mode of transmission or by sending the **RequestMode** message. The H.310 terminal shall obey the **multipointModeCommand** message of Recommendation H.245. It shall also obey **videoFreezePicture** and **videoFastUpdatePicture** messages of Recommendation H.245 and **videoFreezePictureRelease** message of this Recommendation for the video display control.
+
+Since each link in a multipoint configuration may be operating at different bit rates, MCUs may choose to send H.245 **FlowControlCommand** messages to limit the transmitted bit rates to those which can be sent to receivers.
+
+## 8.2 H.320/H.321 interoperation modes
+
+The requirements that apply to H.320 terminals also apply to H.310 terminals. See 4.5/H.320.
+
+NOTE – The clock synchronization of terminals connected to different types of networks and communicating through MCU(s) is for further study.
+
+## 8.3 Other aspects
+
+Cascaded MCU operation, encryption and other aspects of multipoint communication are under study.
+
+# 9 Equipment requirements
+
+Audio level setting for G.711, G.722, G.728 is as specified in Recommendation H.320. Audio level setting for other audio coding including ISO/IEC 11172 audio, ISO/IEC 13818 audio is under study. Other aspects of equipment requirements are also under study.
+
+# 10 Error resilience
+
+## 10.1 Video layer
+
+Several methods of error resilience at the video layer are provided as information in D.13/H.262.
+
+## 10.2 Multimedia multiplex layer
+
+An optional method of error resilience is defined in Recommendation H.222.1 which employs the use of two ATM virtual connections and the modified and restricted use of data partitioning specified in Recommendation H.262.
+
+# 11 Maintenance loop
+
+Some loopback functions are defined in Recommendation H.245 to allow verification of some functional aspects of the terminal, correct operation of the system and satisfactory quality of the service to the remote party. H.310 RAST terminals shall support the following loop back, as shown in Figure 6:
+
+- a) Normal mode: no loop. Indicated in a) of Figure 7.
+- b) System loop at the multiplex-AAL interface (toward the AAL interface). Upon receiving the **systemLoop** request as defined in Recommendation H.245, loopback toward the AAL side shall be made, as indicated in b) of Figure 7. The bit rate should not be changed in response to this request. Support for this loopback is mandatory for all terminals, but users may optionally disable response to it.
+- c) Logical channel loopback in H.222.1 multiplex (toward the multiplex interface). Upon receiving the **logicalChannelLoop** request, each information stream for the specified logical channel should be looped back on the corresponding reverse logical channel, as indicated in c) of Figure 7. This loopback is optional, and should be used only on logical channels opened using the bidirectional channel procedures of Recommendation H.245.
+- d) Media loop at analogue I/O interface (optional): Upon receiving the **mediaLoop** request as defined in Recommendation H.245, loopback of the content of the selected logical channel should be activated as close as possible to the analogue interface of the video/audio codec towards the video/audio codec, so that decoded and re-coded media content is looped, as indicated in d) of Figure 7. This loopback is optional, and should be used only on logical channels opened using the bidirectional channel procedures of Recommendation H.245.
+
+The system loopback (**systemLoop**) request may also be used during actual conversations, for example to measure the network delay.
+
+The message loopback off (**MaintenanceLoopOffCommand**) requires that all loopbacks currently in effect be turned off.
+
+
+
+The figure illustrates four maintenance loop scenarios in an H.310 terminal architecture. Each scenario shows a flow from a camera/monitor through a Codec, a Multiplex, and an AAL.
+
+- a) Normal:** The standard flow where data from the camera is encoded by the Codec, multiplexed, and sent to the AAL. Return data from the AAL is decoded by the Codec and displayed on the monitor.
+- b) System loopback:** The flow is looped back at the AAL interface. Data from the Multiplex is sent to the AAL and immediately looped back to the Multiplex.
+- c) Logical Channel loopback:** The flow is looped back at the Multiplex. Data from the Codec is multiplexed and immediately looped back to the Codec. A note indicates that this applies to "One logical channel only" and "Other logical channels" continue to function normally.
+- d) Media loopback:** The flow is looped back at the Codec interface. Data from the camera is encoded and immediately looped back to the camera/monitor.
+
+T1604940-98
+
+Four diagrams (a, b, c, d) illustrating maintenance loops in an H.310 terminal architecture. Each diagram shows a flow from a camera/monitor through a Codec, a Multiplex, and an AAL. (a) Normal: Standard forward and backward flow. (b) System loopback: Loopback at the AAL interface. (c) Logical Channel loopback: Loopback at the Multiplex for one logical channel. (d) Media loopback: Loopback at the Codec interface. A label 'T1604940-98' is present at the bottom right of diagram (d).
+
+**Figure 7/H.310 – Maintenance loops**
+
+# 12 Intercommunications
+
+Interworking between bidirectional (RAST) H.310 terminals and H.320/H.321 is mandatory. In addition, interworking among the different types of bidirectional H.310 terminals is also mandatory. Figure 8 illustrates the interworking scenarios for H.310 terminals.
+
+
+
+Diagram illustrating the interworking of H.310 terminals. A central 'Customer Premises ATM network (ATM LAN)' is connected to two gateways, G1 and G2. G1 is connected to a 'B-ISDN' node, which in turn connects to H.310 RAST-1, H.310 RAST-1&5, H.321/Annex A, and H.321/Annexes A and B terminals. G2 is connected to an 'N-ISDN' node, which connects to an 'I.580 Gateway (AAL 1)' and an 'H.320' terminal. The ATM LAN also connects directly to H.310 RAST-5, H.310 RAST-1, H.310 RAST-1&5, H.321/Annex B, H.321/Annex A, and H.321/Annexes A and B terminals. A label 'T1604950-98' is present in the bottom right of the diagram area.
+
+G1 = AAL 1/AAL 5 Gateway
+
+G2 = H.321 Annex B/H.320 Gateway
+
+**Figure 8/H.310 – Interworking of H.310 terminals**
+
+## 12.1 Intercommunication between different terminal types
+
+Since the support of AAL type 1 (for the transfer of H.222.1 and H.221 audiovisual signals over B-ISDN) is mandatory for H.310 RAST-1 and RAST-1&5 terminals, these terminals can interwork with each other and with H.321 without a gateway function.
+
+Similarly, since the support of AAL type 5 (for the transfer of H.222.1 and H.221 audiovisual signals over B-ISDN) is mandatory for H.310 RAST-5 and RAST-1&5 terminals, these terminals can interwork with each other and with H.321/Annex B without a gateway function.
+
+RAST-5 terminals and RAST-1&5 terminals working in the AAL 5 mode shall interwork with RAST-1 terminals and RAST-1&5 terminals working in the AAL 1 mode and with H.321 with a gateway that is located in the customer premises ATM network. This gateway is needed to provide interworking functions between:
+
+- a) RAST-5 and RAST-1;
+- b) RAST-5 and RAST-1&5 working in AAL 1 mode; and
+- c) RAST-5 or RAST-1&5 working in AAL 5 mode and H.321 terminals.
+
+Communication procedures for the above cases a) and b) are given in Annex C, while those for case c) are given in clause 7/H.321.
+
+Similarly, a gateway between an N-ISDN and a customer premises ATM network is needed to provide interworking functions between RAST-5 terminals and RAST-1&5 terminals working in the AAL 5 mode and H.320 terminals.
+
+It is important to note that H.310 RAST-1 terminals and H.310 RAST-1&5 terminals can be deployed on (or interface with) both B-ISDN and customer premises ATM networks. However, H.310 RAST-5 terminals can only interface with customer premises networks.
+
+## 12.2 Intercommunication with N-ISDN terminals
+
+For interworking with H.320/H.321 terminals, all RAST terminal types shall support the following modes:
+
+- a) H.261 CIF/QCIF.
+- b) G.711.
+
+Additionally, for interworking with H.320/H.321 terminals, all RAST terminal types shall support the following modes.
+
+- c) H.221/H.242-H.230.
+- d) 1B, 2B and H0 transfer modes.
+- e) Two ATM VCs (for supporting the 2B communication mode with H.320).
+
+NOTE – For the clock synchronization of terminals connected to different types of networks, refer to Annex C/H.321.
+
+## 12.3 Intercommunication with telephony
+
+For further study.
+
+## 12.4 Intercommunication with audiovisual terminals connected to other networks
+
+For further study.
+
+# ANNEX A
+
+## Protocol stack for control channel
+
+This annex defines two protocol stacks for the control channel.
+
+## A.1 General
+
+Figure A.1 shows two protocol stacks for the control channel. Two modes of operation are envisaged. Figure A.1 a) shows the protocol stack when the messages are transported in a separate ATM VC to that used for multimedia data. Figure A.1 b) shows the protocol stack when the messages are transported in the same ATM VC as that used for multimedia data.
+
+The X.224 SDU shall contain a whole number of octets, not to exceed 2048 octets, representing one or more H.245 **MultimediaSystemControlPDU** messages.
+
+
+
+T1604960-98
+
+Protocol stack diagram for control channel showing two configurations: a) Separate VC and b) Single VC. Both stacks start with Rec. H.245 at the top. Stack (a) includes X.224 class 0, LAPF (Rec. Q.922), FR-SSCS (Rec. I.365.1), AAL 5, and ATM. Stack (b) includes X.224 class 0, LAPF (Rec. Q.922), Rec. H.222.0/Rec. H.222.1, CS 1/5, AAL 1/5, and ATM. The label 'Rec. X.214' is placed between the two stacks.
+
+**Figure A.1/H.310 – Protocol stack for control channel**
+
+## A.2 X.214
+
+A connection-mode service shall be used for the transport of MultimediaSystemControl messages as defined in Recommendation X.214.
+
+A single Transport Connection (TC) shall be used for the transport of MultimediaSystemControl messages.
+
+The encoded representation of individual MultimediaSystemControl messages shall be transported in single Transport Service Data Units (TSDUs). The bits produced by the ASN.1 encoding process shall be put into TSDU octets, with the first bit generated going into the Most Significant Bit (MSB) of the octet, and progressing down to the Least Significant Bit (LSB).
+
+## A.3 X.224
+
+X.214 service shall be provided by X.224 class 0.
+
+## A.4 LAPF (Q.922)
+
+Q.922 shall be used to provide a network connection of type A defined in 5.4.3/X.224, that is, a connection with acceptable residual error rate and acceptable rate of signalled errors. This shall be done by use of information (I) frames.
+
+Frame types UI and XID shall not be transmitted. The address field format shall be two octets (10-bit DLCIs). The default values of Q.922 system parameters, k, N200, N201, T.200, T.203, are used for H.310. Values of k, N201 and T.200 can be negotiated in Q.922 data link connection setup. The values of N200 and T.203 need not be negotiated between terminals and may be set locally on each side.
+
+## **A.5 FR-SSCS (I.365.1) and H.222.1**
+
+Both FR-SSCS (see Recommendation I.365.1) and H.222.1 provide octet transmission with structure. The transparency procedure specified in 2.6/Q.922 shall not be used, that is, no zero bits shall be inserted after any sequence of five consecutive 1 bits. No flags shall be present.
+
+### **A.5.1 FR-SSCS (I.365.1)**
+
+FR-SSCS (see Recommendation I.365.1) emulates the Frame Relaying Bearer Service (FRBS) on top of the Common Part Convergence Sublayer (CPCS) of AAL type 5, providing the core service at the DL-CORE-SAP as defined in clause 2/I.365.1. FR-SSCS is used as the DL-CORE sublayer combined with DL-CONTROL sublayer described in clause 4/Q.922. The structure of FR-SSCS-PDUs is exactly the same as the Q.922 frame without flags, zero bit insertion, and FCS.
+
+### **A.5.2 H.222.0 and H.222.1**
+
+Q.922 octets shall be transported in PES packets defined in Recommendation H.222.0 so that the first octet of a PES packet is the first octet of the address field and the last octet of the PES packet is the last octet of the FCS field, as defined in 2.2/Q.922.
+
+# ANNEX B
+
+## Use of DSS 2 signalling by H.310 terminals
+
+## B.1 DSS 2 signalling information elements
+
+The following information elements are required in the SETUP message to establish the following types of connections for H.310 terminals.
+
+**Table B.1/H.310 – DSS 2 signalling information elements**
+
+| Information element | H.310 Control VC | H.310 RAST A/V VC | H.310 ROT/SOT A/V VC |
+|----------------------------------|---------------------------------------------------------|-------------------|----------------------|
+| Protocol discriminator | M | M | M |
+| Call Reference | M | M | M |
+| Message type | M | M | M |
+| Message length | M | M | M |
+| AAL Parameters | M | M | M |
+| ATM Traffic descriptor | M | M | M |
+| Broadband bearer capability | M | M | M |
+| Broadband repeat indicator | CM | O | O |
+| Broadband low layer information | M | M | M |
+| Generic Identifier Transport | M | M | M |
+| Broadband High layer information | O | O | O |
+| Notification Indicator | O | O | O |
+| Called party number | M | M | M |
+| Called party subaddress | C | C | C |
+| Calling party number | M | M | M |
+| Calling party subaddress | C | C | C |
+| Connection identifier | O | O | O |
+| Extended QoS parameters | O | O | O |
+| End-to-end transit delay | O | O | O |
+| QoS parameter | M | M | M |
+| Broadband sending complete | C | C | C |
+| Transit network selection | O | O | O |
+| Endpoint reference | NA | NA | NA |
+| NA | Not Applicable | | |
+| O | Optional | | |
+| CM | Conditionally Mandatory | | |
+| M | Required | | |
+| C | Conditional (if appropriate for the network being used) | | |
+
+The next subclauses summarize the use of the information elements that are unique to H.310 RAST/ROT/SOT. The elements that are not specifically described here are coded in accordance with the requirements of DSS 2 specification.
+
+**Table B.2/H.310 – DSS 2 signalling information elements specific to H.310 RAST-1 and ROT/SOT-1**
+
+| Information element | H.310 Control VC | H.310 RAST-1 A/V VC | H.310 ROT/SOT-1 A/V VC |
+|---------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------|
+| AAL Parameters | AAL Type = AAL 5
Forward CPCS SDU size
Backward CPCS SDU size
SSCS Type = Frame Relay | AAL Type = AAL 1
Subtype = Video signal transport
CBR rate = $n \times 64$
Multiplier = As negotiated by H.245
Source Clock Frequency Recovery = As negotiated by H.245
Error Correction = As negotiated by H.245
SDT Block Size = Impl. specific | |
+| ATM Traffic descriptor | Forward PCR and Backward PCR = 167 cells per second which corresponds to 64 kbit/s
Sustainable Cell Rate = Impl. specific
Maximum burst size = Impl. specific | Forward PCR = Implementation specific
Backward PCR = Implementation specific
(Note 1) | |
+| Broadband bearer capability | Bearer Class = BCOB-X
Broadband Transfer Capability = BTC10
User Plane Connection = PtP | Bearer Class = BCOB-A
Broadband Transfer Capability = CBR
Timing Requirements = end-to-end timing required
User Plane Connection = PtP | |
+| Broadband repeat indicator | Set when more than one B-LLI element is present | | |
+| Broadband low layer information | User Layer 3 = H.310
Terminal type = ROT/SOT/RAST
Terminal capability = AAL 1
Forward Multiplexing = NO
Backward Multiplexing = NO | User Layer 3 = H.310
Terminal type = RAST
Terminal capability = AAL 1
Forward Multiplexing = TS
Backward Multiplexing = TS | User Layer 3 = H.310
Terminal type = ROT/SOT
Terminal capability = AAL 1
Forward Multiplexing = TS
Backward Multiplexing = Null
(Note 1) |
+| Generic Identifier Transport | | H.310 Correlation ID | |
+
+NOTE 1 – Forward and Backward are set according to which terminal sends the original SETUP message.
+NOTE 2 – **Terminal type** and **Terminal capability** in the B-LLI for the additional channels are encoded, but not used at the receiving end. This is applied to the following tables in this annex.
+
+**Table B.3/H.310 – DSS 2 signalling information elements specific to H.310 RAST-5 and ROT/SOT-5**
+
+| Information element | H.310 Control VC | H.310 RAST-5 A/V VC | H.310 ROT/SOT-5 A/V VC |
+|---------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------|
+| AAL Parameters | AAL Type = AAL 5
Forward CPCS SDU size
Backward CPCS SDU size
SSCS Type = Frame Relay | AAL Type = AAL 5
Forward CPCS SDU size
Backward CPCS SDU size
SSCS Type = Null | |
+| ATM Traffic descriptor | Forward PCR and Backward PCR = 167 cells per second which corresponds to 64 kbit/s
Sustainable Cell Rate = Impl. specific
Maximum burst size = Impl. specific | Forward PCR = Implementation specific
Backward PCR = Implementation specific
(Note 1) | |
+| Broadband bearer capability | Bearer Class = BCOB-X
Broadband Transfer Capability = BTC10
User Plane Connection = PtP | Bearer Class = BCOB-X
Broadband Transfer Capability = CBR
User Plane Connection = PtP | |
+| Broadband repeat indicator | Set when more than one B-LLI element is present | | |
+| Broadband low layer information | User Layer 3 = H.310
Terminal type = ROT/SOT/RAST
Terminal capability = AAL 5
Forward Multiplexing = NO
Backward Multiplexing = NO | User Layer 3 = H.310
Terminal type = RAST
Terminal capability = AAL 5
Forward Multiplexing = TS
Backward Multiplexing = TS | User Layer 3 = H.310
Terminal type = ROT/SOT
Terminal capability = AAL 5
Forward Multiplexing = TS
Backward Multiplexing = Null
(Note 1) |
+| Generic Identifier Transport | | H.310 Correlation ID | |
+
+NOTE 1 – Forward and Backward are set according to which terminal sends the original SETUP message.
+NOTE 2 – **Terminal capability** for RAST-5 terminal shall be set taking both terminal and gateway into account, if the terminal is supported by a gateway.
+
+## B.2 ATM signalling required for the H.310 control VC
+
+The following tables define the ATM signalling information elements for the H.310 control channel. The AAL, Traffic Descriptor and Broadband Bearer Capabilities IEs are defined similarly for other applications.
+
+The control VC Protocol stack can be assumed based on Terminal identification exchanged in B-LLI. The Quality of Service (QoS) parameters shall be coded in accordance with the requirements of the network and are not specifically defined here.
+
+**Table B.4/H.310 – AAL parameters IE**
+
+| IE parameter | Value | Notes |
+|--------------------------------------|------------|--------------------------------------------------------------------|
+| AAL type | AAL 5 | |
+| Forward Maximum AAL 5 CPCS SDU size | | Value sufficient for transporting H.245 messages up to 2048 octets |
+| Backward Maximum AAL 5 CPCS-SDU size | | Value sufficient for transporting H.245 messages up to 2048 octets |
+| SSCS Type | '00000100' | Frame Relay SSCS |
+
+**Table B.5/H.310 – ATM Traffic Descriptor IE**
+
+| IE parameter | Value | Notes |
+|-------------------------|-----------------------------------------------|---------------------------------------------------------------------|
+| Forward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the control connection |
+| Backward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the control connection |
+
+**Table B.6/H.310 – Broadband Bearer Capabilities IE**
+
+| IE parameter | Value | Notes |
+|-------------------------------------|-----------------|---------------------------------------------------------------|
+| Bearer Class | BCOB-X | |
+| Broadband Transfer Capability | BTC10 = '01010' | VBR with End-to-End Timing not required
(Non-realtime VBR) |
+| User Plane Connection configuration | Point-to-Point | |
+
+**Table B.7/H.310 – Broadband Low Layer IE**
+
+| IE parameter | Value | Notes |
+|-----------------------------------------|-----------------------------------------------------------------|------------------------------------------------------------------------------|
+| User Information Layer 3 Protocol Field | '01100' | Rec. H.310 |
+| Terminal Type | '0001' = H.310 ROT
'0010' = H.310 SOT
'0011' = H.310 RAST | Specify the appropriate terminal type for the expected mode of operation |
+| Terminal capability | '001' = AAL 1 only
'010' = AAL 5 only
'010' = AAL 1 & 5 | Specify the appropriate terminal capability regarding the supported AAL type |
+| Forward Multiplexing Capability | '000' | No multiplex |
+| Backward Multiplexing Capability | '000' | No multiplex |
+
+## **B.3 ATM Signalling Required for RAST-1 A/V VC**
+
+The following tables define the signalling elements required to establish a bidirectional (RAST) audiovisual virtual circuit from a terminal. The QoS parameters shall be coded in accordance with the requirements of the network.
+
+**Table B.8/H.310 – AAL parameters IE**
+
+| IE parameter | Value | Notes |
+|---------------------------------|------------------------|------------------------|
+| AAL type | AAL 1 | |
+| Subtype | Video signal transport | |
+| CBR rate | $N \times 64$ kbit/s | |
+| Multiplier | m | As negotiated by H.245 |
+| Source Clock Frequency Recovery | | As negotiated by H.245 |
+| Error Correction Method | | As negotiated by H.245 |
+
+The Peak Cell Rate for the video service component is calculated using the MPEG-2 encoded rate plus AAL 1 overhead and specified as shown in Table B.9. The ATM Traffic Descriptor includes only the user plane information rate for the service components in that one VC.
+
+The video service component PCR may be specified using Cell Loss Priority, $CLP = 0 + 1$ and $CLP = 0$ or $CLP = 0 + 1$ .
+
+**Table B.9/H.310 – ATM Traffic Descriptor IE**
+
+| IE parameter | Value | Notes |
+|-------------------------|-----------------------------------------------|--------------------------------------------------------------------------|
+| Forward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the video service component |
+| Backward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the video service component |
+
+**Table B.10/H.310 – Broadband Bearer Capabilities IE**
+
+| IE parameter | Value | Notes |
+|-------------------------------------|----------------------------|--------------|
+| Bearer Class | BCOB-A | |
+| Broadband Transfer Capability | Constant Bit Rate | |
+| Timing Requirements | End-to-end timing required | |
+| Susceptibility to clipping | Susceptible to clipping | |
+| User Plane Connection configuration | Point-to-Point | |
+
+**Table B.11/H.310 – Broadband Low Layer IE**
+
+| IE parameter | Value | Notes |
+|------------------------------------------------------------------------------------------|---------------------|---------------------------|
+| User Information Layer 3 Protocol Field | '01100' | Rec. H.310 |
+| Terminal Type | '0011' = H.310 RAST | Receive and Send Terminal |
+| Terminal capability | '001' = AAL 1 only | |
+| Forward Multiplexing Capability (Note) | '001' | Transport Stream |
+| Backward Multiplexing Capability (Note) | '001' | Transport Stream |
+| NOTE – Program Stream is also an option for Forward and Reverse Multiplexing Capability. | | |
+
+The Generic Identifier Transport Information Element is a generic parameter that indicates the correspondence of the VC to a certain previously established request carried outside ATM signalling. Table B.12 identifies the parameters of the Generic Identifier Transport IE for use in an H.310 environment.
+
+**Table B.12/H.310 – Generic Identifier Transport IE**
+
+| IE parameter | Value | Notes |
+|-----------------------------|------------------------------------|----------------------|
+| Identifier Related Standard | '00000010' | Rec. H.310 |
+| Resource | Identifier for the virtual circuit | H.310 Correlation ID |
+
+## B.4 ATM Signalling Required for H.310 SOT/ROT-1
+
+The following tables define the signalling elements required to establish an audiovisual virtual circuit for a ROT or SOT terminal.
+
+The QoS parameters shall be coded in accordance with the requirements of the network.
+
+**Table B.13/H.310 – AAL parameters IE**
+
+| IE parameter | Value | Notes |
+|---------------------------------|------------------------|------------------------|
+| AAL type | AAL 1 | |
+| Subtype | Video signal transport | |
+| CBR rate | $N \times 64$ kbit/s | |
+| Multiplier | m | As negotiated by H.245 |
+| Source Clock Frequency Recovery | | As negotiated by H.245 |
+| Error Correction Method | | As negotiated by H.245 |
+
+The Peak Cell Rate for the video service component is calculated using the MPEG-2 encoded rate plus AAL 1 overhead and specified as shown in Table B.14. The ATM Traffic Descriptor includes only the user plane information rate for the service components in that one VC.
+
+The video service component PCR may be specified using Cell Loss Priority, $CLP = 0 + 1$ and $CLP = 0$ or $CLP = 0 + 1$ .
+
+The Forward and Backward Peak Cell Rates are set according to which terminal sends the original SETUP message.
+
+**Table B.14/H.310 – ATM Traffic Descriptor IE**
+
+| IE parameter | Value | Notes |
+|-------------------------|-----------------------------------------------|--------------------------------------------------------------------------|
+| Forward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the video service component |
+| Backward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the video service component |
+
+**Table B.15/H.310 – Broadband Bearer Capabilities IE**
+
+| IE parameter | Value | Notes |
+|-------------------------------------|----------------------------|-------|
+| Bearer Class | BCOB-A | |
+| Broadband Transfer Capability | Constant Bit Rate | |
+| Timing Requirements | End-to-end timing required | |
+| Susceptibility to clipping | Susceptible to clipping | |
+| User Plane Connection configuration | Point-to-Point | |
+
+The Forward and Backward Multiplexing Capability parameters are set according to which terminal sends the original SETUP message.
+
+**Table B.16/H.310 – Broadband Low Layer IE**
+
+| IE parameter | Value | Notes |
+|------------------------------------------------------------------------------------------|--------------------------------------------------------------------------|------------|
+| User Information Layer 3 Protocol Field | '01100' | Rec. H.310 |
+| Terminal Type | '0010' = H.310 ROT
'0001' = H.310 SOT | |
+| Terminal capability | '001' = AAL 1 only | |
+| Forward Multiplexing Capability (Note) | If ROT then '000' = No multiplex
If SOT then '001' = Transport Stream | |
+| Backward Multiplexing Capability (Note) | If ROT then '001' = Transport Stream
If SOT then '000' = No multiplex | |
+| NOTE – Program Stream is also an option for Forward and Reverse Multiplexing Capability. | | |
+
+The Generic Identifier Transport Information Element is a generic parameter that indicates the correspondence of the VC to a certain previously established request carried outside ATM signalling. Table B.17 identifies the parameters of the Generic Identifier Transport IE for use in an H.310 environment.
+
+**Table B.17/H.310 – Generic Identifier Transport IE**
+
+| IE parameter | Value | Notes |
+|-----------------------------|------------------------------------|----------------------|
+| Identifier Related Standard | '00000010' | Rec. H.310 |
+| Resource | Identifier for the virtual circuit | H.310 Correlation ID |
+
+## B.5 ATM Signalling Required for RAST-5 A/V VC
+
+The following tables define the signalling elements required to establish a bidirectional (RAST) audiovisual virtual circuit from a terminal. The QoS parameters shall be coded in accordance with the requirements of the network.
+
+**Table B.18/H.310 – AAL parameters IE**
+
+| IE parameter | Value | Notes |
+|--------------------------------------|-------------|----------------------------------------------------------------------------------------------------|
+| AAL type | AAL 5 | |
+| Forward Maximum AAL 5 CPCS SDU size | N*188 bytes | Default value for the video service component in this specification is 376 bytes. N is an integer. |
+| Backward Maximum AAL 5 CPCS-SDU size | N*188 bytes | Default value for the video service component in this specification is 376 bytes. N is an integer. |
+| SSCS Type | Null | |
+
+The Peak Cell Rate for the video service component is calculated using the MPEG-2 encoded rate plus AAL 5 overhead and specified as shown in Table B.19. The ATM Traffic Descriptor includes only the user plane information rate for the service components in that one VC.
+
+The video service component PCR may be specified using Cell Loss Priority, CLP = 0 + 1 and CLP = 0 or CLP = 0 + 1.
+
+**Table B.19/H.310 – ATM Traffic Descriptor IE**
+
+| IE parameter | Value | Notes |
+|-------------------------|-----------------------------------------------|---------------------------------------------------------------------------|
+| Forward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the video service component. |
+| Backward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the video service component. |
+
+**Table B.20/H.310 – Broadband Bearer Capabilities IE**
+
+| IE parameter | Value | Notes |
+|-------------------------------------|-------------------|-------|
+| Bearer Class | BCOB-X | |
+| Broadband Transfer Capability | Constant Bit Rate | |
+| User Plane Connection configuration | Point-to-Point | |
+
+**Table B.21/H.310 – Broadband Low Layer IE**
+
+| IE parameter | Value | Notes |
+|------------------------------------------------------------------------------------------|---------------------|---------------------------|
+| User Information Layer 3 Protocol Field | '01100' | Rec. H.310 |
+| Terminal Type | '0011' = H.310 RAST | Receive and Send Terminal |
+| Terminal capability | '010' = AAL 5 only | |
+| Forward Multiplexing Capability (Note) | '001' | Transport Stream |
+| Backward Multiplexing Capability (Note) | '001' | Transport Stream |
+| NOTE – Program Stream is also an option for Forward and Reverse Multiplexing Capability. | | |
+
+The Generic Identifier Transport Information Element is a generic parameter that indicates the correspondence of the VC to a certain previously established request carried outside ATM signalling. Table B.22 identifies the parameters of the Generic Identifier Transport IE for use in an H.310 environment.
+
+**Table B.22/H.310 – Generic Identifier Transport IE**
+
+| IE parameter | Value | Notes |
+|-----------------------------|------------------------------------|----------------------|
+| Identifier Related Standard | '00000010' | Rec. H.310 |
+| Resource | Identifier for the virtual circuit | H.310 Correlation ID |
+
+## B.6 ATM Signalling Required for H.310 SOT-5
+
+For an H.310 SOT terminal, the Forward and Backwards Maximum AAL 5 CPCS SDU sizes are set according to which terminal sends the original SETUP message. Table B.23 shows the settings if the SOT terminal sends the SETUP message.
+
+**Table B.23/H.310 – AAL type IE**
+
+| IE parameter | Value | Notes |
+|--------------------------------------|---------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------|
+| AAL type | AAL 5 | |
+| Forward Maximum AAL 5 CPCS SDU size | N*188 bytes | Default value for the video service component in this specification is 376 bytes. N is an integer. |
+| Backward Maximum AAL 5 CPCS-SDU size | 0 bytes if the video service component is unidirectional, otherwise implementation specific | |
+| SSCS Type | '00000000' | Null |
+
+The Peak Cell Rate for the video service component is calculated using the MPEG-2 encoded rate plus the AAL 5 overhead. The ATM Traffic Descriptor includes only the user plane information rate for the service components in that one VC.
+
+The video service component PCR may be specified using Cell Lost Priority CLP = 0 + 1 and CLP = 0 or CLP = 0 + 1.
+
+The Forward and Backward Peak Cell Rates are set according to which terminal sends the original SETUP message. The following tables show the settings if the SOT terminal sends the SETUP message.
+
+**Table B.24/H.310 – ATM Traffic Descriptor**
+
+| IE parameter | Value | Notes |
+|-------------------------|-------------------------------------------------------------------------------------------|--------------------------------------------------------------------------|
+| Forward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the video service component |
+| Backward Peak Cell Rate | 0 cells/s if video service component is unidirectional, otherwise implementation specific | |
+
+**Table B.25/H.310 – Broadband Bearer Capabilities IE**
+
+| IE parameter | Value | Notes |
+|-------------------------------------|-------------------|-------|
+| Bearer Class | BCOB-X | |
+| Broadband Transfer Capability | Constant Bit Rate | |
+| User Plane Connection configuration | Point-to-Point | |
+
+**Table B.26/H.310 – Broadband Low Layer IE**
+
+| IE parameter | Value | Notes |
+|------------------------------------------------------------------------------|--------------------|--------------------|
+| User Information Layer 3 Protocol Field | '01100' | Rec. H.310 |
+| Terminal Type | '0010' = H.310 SOT | Send Only Terminal |
+| Terminal capability | '010' = AAL 5 only | |
+| Forward Multiplexing Capability (Note) | '001' | Transport Stream |
+| Backward Multiplexing Capability (Note) | '000' | No multiplex |
+| NOTE – Program Stream is also an option for Forward Multiplexing Capability. | | |
+
+The QoS parameters shall be coded in accordance with the requirements of the network.
+
+The Generic Identifier Transport Information Element is a generic parameter that indicates the correspondence of the VC to a certain previously established request carried outside ATM signalling. Table B.27 identifies the parameters of the Generic Identifier Transport IE for use in an H.310 environment.
+
+**Table B.27/H.310 – Generic Identifier Transport IE**
+
+| IE parameter | Value | Notes |
+|-----------------------------|------------------------------------|----------------------|
+| Identifier Related Standard | '00000010' | Rec. H.310 |
+| Resource | Identifier for the virtual circuit | H.310 Correlation ID |
+
+## **B.7 ATM Signalling Required for H.310 ROT-5**
+
+The Forward and Backward Maximum AAL 5 CPCS SDU sizes are set according to which terminal sends the original SETUP message. The following table shows the settings if the ROT terminal sends the SETUP message.
+
+**Table B.28/H.310 – AAL parameters IE**
+
+| IE parameter | Value | Notes |
+|--------------------------------------|----------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------|
+| AAL type | AAL 5 | |
+| Forward Maximum AAL 5 CPCS SDU size | 0 bytes if video service component is unidirectional otherwise implementation specific | |
+| Backward Maximum AAL 5 CPCS-SDU size | N*188 bytes | Default value for the video service component in this specification is 376 bytes. N is an integer. |
+| SSCS Type | Null | |
+
+The Peak Cell Rate for the video service component is calculated using the MPEG-2 encoded rate plus the AAL 5 overhead. The ATM Traffic Descriptor includes only the user plane information rate for the service components in that one VC.
+
+The video service component Peak Cell Rate may be specified using CLP = 0 + 1 and CLP = 0 or CLP = 0 + 1.
+
+The Forward and Backward Peak Cell Rates are set according to which terminal sends the original SETUP message. The following tables show the settings if the ROT terminal sends the SETUP message.
+
+**Table B.29/H.310 – ATM Traffic Descriptor IE**
+
+| IE parameter | Value | Notes |
+|-------------------------|-------------------------------------------------------------------------------------------|--------------------------------------------------------------------------|
+| Forward Peak Cell Rate | 0 cells/s if video service component is unidirectional, otherwise implementation specific | |
+| Backward Peak Cell Rate | Implementation and program selection specific | Set to the Peak Cell Rate value required for the video service component |
+
+**Table B.30/H.310 – Broadband Bearer Capabilities IE**
+
+| IE parameter | Value | Notes |
+|-------------------------------------|-------------------|-------|
+| Bearer Class | BCOB-X | |
+| Broadband Transfer Capability | Constant Bit Rate | |
+| User Plane Connection configuration | Point-to-Point | |
+
+**Table B.31/H.310 – Broadband Low Layer IE**
+
+| IE parameter | Value | Notes |
+|------------------------------------------------------------------------------|--------------------|-----------------------|
+| User Information Layer 3 Protocol Field | '01100' | Rec. H.310 |
+| Terminal Type | '0001' = H.310 ROT | Receive Only Terminal |
+| Terminal capability | '010' = AAL 5 only | |
+| Forward Multiplexing Capability (Note) | '000' | No multiplex |
+| Backward Multiplexing Capability (Note) | '001' | Transport Stream |
+| NOTE – Program Stream is also an option for Reverse Multiplexing Capability. | | |
+
+These QoS parameters shall be coded in accordance with the requirements of the network.
+
+The Generic Identifier Transport Information Element is a generic parameter that indicates the correspondence of the VC to a certain previously established request carried outside ATM signalling. Table B.32 identifies the parameters of the Generic Identifier Transport IE for use in an H.310 environment.
+
+**Table B.32/H.310 – Generic Transport Identifier IE**
+
+| IE parameter | Value | Notes |
+|-----------------------------|------------------------------------|----------------------|
+| Identifier Related Standard | '00000010' | Rec. H.310 |
+| Resource | Identifier for the virtual circuit | H.310 Correlation ID |
+
+# ANNEX C
+
+## Procedures for intercommunication between RAST-1 and RAST-5 terminals
+
+## C.1 Introduction
+
+The procedures are defined to meet the following requirements:
+
+- Two terminals are connected directly as far as possible without use of the conversion gateway. If necessary, a minimum number of gateways are used for protocol conversion.
+- To achieve this, H.245 message exchange is used to take advantage of the fact that H.245 is common to all H.310 terminals including its transport method.
+
+- The extended communication procedures should be a superset of the one stipulated for simple direct communications.
+
+For the description of this annex, CPN stands for customer premises ATM network while B-ISDN is the public network. Audiovisual connection is meant to cover audio, video and data.
+
+It is important to note that the terminal connected to a CPN has the knowledge of its associated gateway capability, thus it shall indicate its terminal type in B-LLI according to the combined capability of its own and that of the associated gateway. A RAST-5 terminal, for example, shall indicate "AAL 1 and AAL 5" in B-LLI if it is supported by the AAL 1/AAL 5 conversion gateway. The mechanism for a terminal to obtain the associated gateway capability is not part of this specification; it may be manual, it may be automatic.
+
+## C.2 Two RAST-5 terminals on CPN
+
+This is the case where two terminals both on CPN are connected through B-ISDN as shown in Figure C.1.
+
+
+
+The diagram shows three main network components represented by ovals: a CPN on the left, a B-ISDN network in the center, and another CPN on the right.
+ - On the left CPN, there is a box labeled 'H.310 RAST-5 Terminal A' and a box labeled 'GW' (Gateway). An arrow points from Terminal A to the GW, and another arrow points from the GW into the B-ISDN network.
+ - On the right CPN, there is a box labeled 'H.310 RAST-5 Terminal B' and a box labeled 'GW'. An arrow points from Terminal B to the GW, and another arrow points from the GW into the B-ISDN network.
+ - In the center B-ISDN oval, two horizontal double-headed arrows span across it. The top arrow is labeled 'Initial VC for H.245' and the bottom arrow is labeled 'Additional VC for Audio, Video and Data'. These arrows connect the GW on the left to the GW on the right.
+ - Below the B-ISDN oval, there is a box labeled 'H.310 RAST-1 Terminal C' with an arrow pointing up into the B-ISDN network.
+
+Diagram illustrating communication between two RAST-5 terminals (Terminal A and Terminal B) connected via a B-ISDN network. Both terminals are connected to their respective CPN (Customer Premises Network) via a Gateway (GW). The B-ISDN network is shown as a central oval. Two communication paths are indicated: 'Initial VC for H.245' and 'Additional VC for Audio, Video and Data'. Terminal C (H.310 RAST-1) is also shown connected to the B-ISDN network.
+
+T1604970-98
+
+**Figure C.1/H.310 – Communication between two RAST-5 terminals**
+
+Communication is established as follows:
+
+- 1) Terminal A calls Terminal B and sets up the H.245 control session by indicating its type as AAL 1 and AAL 5 in B-LLI because it is supported by the AAL 1/AAL 5 conversion gateway.
+- 2) H.245 is used to exchange terminal capabilities, including terminal type and the gateway address(es) and facilities. Both terminals indicate that they have their local gateways.
+- 3) According to the H.245 capability exchange, Terminal A infers that both terminals are of the same type (RAST-5), thus no gateway is required.
+- 4) According to the communication mode determination, the calling Terminal A indicates parameters of the additional VC to the called Terminal B by sending NewATMVCIndication message.
+
+- 5) Terminal A sets up the audiovisual connection directly to Terminal B with parameters set in the **NewATMVCIndication** message.
+
+**Table C.1/H.310 – GIT – Terminal A to Terminal B**
+
+| IE parameter | Code | Semantics |
+|-----------------------------|------------------------|----------------------------------------------|
+| Identifier related standard | 00000010 | Rec. H.310 |
+| Identifier type | 00000010 | Resource |
+| Value (2 octets) | e.g. 00000000 00000000 | H.245 resourceID (the lowest possible value) |
+
+## C.3 RAST-5 Terminal on CPN with RAST-1 Terminal on Public B-ISDN
+
+This is the case where a RAST-5 terminal on CPN communicates with a RAST-1 terminal on public B-ISDN as shown in Figure C.2. There are two subcases depending on which side calls.
+
+
+
+The diagram illustrates the network architecture for communication between a RAST-5 terminal on a CPN and a RAST-1 terminal on a B-ISDN. On the left, 'H.310 RAST-5 Terminal A' is connected to a 'CPN' circle, which is further connected to a 'GW' (Gateway) box. On the right, 'H.310 RAST-5 Terminal B' is connected to another 'CPN' circle, which is connected to its own 'GW' box. In the center is a large circle labeled 'B-ISDN'. 'H.310 RAST-1 Terminal C' is connected to the 'B-ISDN' circle. An arrow labeled 'Initial VC for H.245' originates from Terminal A and points to Terminal C. Another arrow labeled 'Additional VC for Audio, Video and Data' originates from Terminal A, passes through the first 'GW', enters the 'B-ISDN' circle, and points to Terminal C. A small text label 'T1604980-98' is located in the bottom right corner of the diagram area.
+
+Diagram showing communication between RAST-5 Terminal A on CPN and RAST-1 Terminal C on B-ISDN via a Gateway (GW). Terminal A sends an 'Initial VC for H.245' to Terminal C. Terminal A also sends an 'Additional VC for Audio, Video and Data' to Terminal C via the GW. Terminal B is shown on the right side of the diagram, connected to a CPN and a GW, but not involved in the communication with Terminal C.
+
+**Figure C.2/H.310 – Communication between RAST-5 on CPN and RAST-1 on B-ISDN**
+
+### C.3.1 RAST-5 Terminal on CPN calls RAST-1 Terminal on B-ISDN
+
+- 1) Terminal A calls Terminal C and sets up the H.245 control session.
+- 2) The call is accepted by Terminal C because the remote terminal type indicates AAL 1 and AAL 5 in B-LLI.
+- 3) H.245 is used to exchange terminal capabilities, including terminal type and the gateway address(es) and facilities. Terminal A will indicate that it has a local gateway. Terminal C will not indicate that it has a gateway. Audiovisual communication modes are determined by Terminal A based on its own capabilities and those of the gateway and Terminal C.
+- 4) The calling Terminal A indicates parameters of the additional VC to the called Terminal C by sending **NewATMVCIndication** message.
+
+- 5) Terminal A sets up a concatenated audiovisual connection through the gateway with parameters set in the **NewATMVCIndication** message.
+- 6) The gateway sets up a connection to Terminal C using the next connection ATM address and H.310 Correlation\_ID passed to it in the SETUP message from Terminal A.
+
+Generic Identifier Transport IE shall be coded as in Tables C.2 and C.3.
+
+**Table C.2/H.310 – GIT – Terminal A to GW**
+
+| IE parameter | Code | Semantics |
+|-----------------------------|------------------------|----------------------------------------------|
+| Identifier related standard | 00000010 | Rec. H.310 |
+| Identifier type | 00000010 | Resource |
+| Value (2 octets) | e.g. 00000000 00000000 | H.245 resourceID (the lowest possible value) |
+| Identifier type | 00000011 | End Station (to be defined by SG 11) |
+| Value (up to 20 octets) | (to be specified) | ATM address of Terminal C |
+
+**Table C.3/H.310 – GIT – GW to Terminal C**
+
+| IE parameter | Code | Semantics |
+|-----------------------------|------------------------|----------------------------------------------|
+| Identifier related standard | 00000010 | Rec. H.310 |
+| Identifier type | 00000010 | Resource |
+| Value (2 octets) | e.g. 00000000 00000000 | H.245 resourceID (the lowest possible value) |
+
+### **C.3.2 RAST-1 Terminal on B-ISDN calls RAST-5 Terminal on CPN**
+
+- 1) Terminal C calls Terminal A and sets up the H.245 control session.
+- 2) The call is accepted by Terminal A based on the knowledge of its associated gateway even though the remote terminal type indicates AAL 1 in B-LLI.
+- 3) H.245 is used to exchange terminal capabilities, including terminal type and the gateway address(es) and facilities. Terminal A will indicate that it has a local gateway. Terminal C will not indicate that it has a gateway.
+- 4) Audiovisual communication modes are determined by Terminal C based on its own capabilities and those of the gateway and Terminal A.
+- 5) The calling Terminal C indicates parameters of the additional VC to the called Terminal A by sending **NewATMVCIndication** message.
+- 6) Terminal C sets up a concatenated audiovisual connection through the gateway identified by Terminal A with parameters set in the **NewATMVCIndication** message.
+- 7) The gateway sets up a connection to Terminal A using the next connection ATM Address and H.310 Correlation\_ID passed to it in the SETUP message from Terminal C.
+
+Generic Identifier Transport IE shall be coded as in Tables C.4 and C.5.
+
+**Table C.4/H.310 – GIT – Terminal C to GW**
+
+| IE parameter | Code | Semantics |
+|-----------------------------|------------------------|----------------------------------------------|
+| Identifier related standard | 00000010 | Rec. H.310 |
+| Identifier type | 00000010 | Resource |
+| Value (2 octets) | e.g. 00000000 00000000 | H.245 resourceID (the lowest possible value) |
+| Identifier type | 00000011 | End Station (to be defined by SG 11) |
+| Value (up to 20 octets) | (to be specified) | ATM address of Terminal A |
+
+**Table C.5/H.310 – GIT – GW to Terminal A**
+
+| IE parameter | Code | Semantics |
+|-----------------------------|------------------------|----------------------------------------------|
+| Identifier related standard | 00000010 | Rec. H.310 |
+| Identifier type | 00000010 | Resource |
+| Value (2 octets) | e.g. 00000000 00000000 | H.245 resourceID (the lowest possible value) |
+
+## C.4 RAST-5 Terminal on CPN with RAST-1 Terminal on CPN
+
+This is the case where a RAST-5 terminal on CPN communicates with a RAST-1 terminal on CPN through public B-ISDN as shown in Figure C.3. The procedures are identical to those defined in C.3 because RAST-1 terminals have no associated gateways.
+
+
+
+The diagram illustrates a network topology for H.310 communication. On the left, an 'H.310 RAST-5 Terminal A' is connected to a 'CPN' (Packet Switched Network). This CPN is connected to a 'GW' (Gateway). The 'GW' is connected to a central 'B-ISDN' (Integrated Services Digital Network). The 'B-ISDN' is connected to another 'CPN', which is in turn connected to another 'GW'. This second 'GW' is connected to an 'H.310 RAST-1 Terminal D'. A direct horizontal line labeled 'Initial VC for H.245' connects Terminal A and Terminal D. A line labeled 'Additional VC for Audio, Video and Data' originates from Terminal A, goes to the first 'GW', then through the 'B-ISDN' to the second 'GW', and finally to Terminal D. Below the 'B-ISDN', there is a box labeled 'H.310 RAST-1 Terminal C' which is not connected to any network elements in this diagram.
+
+Diagram showing communication between RAST-5 Terminal A and RAST-1 Terminal D via CPN and B-ISDN. Terminal A connects to a CPN, which connects to a Gateway (GW). The GW connects to a B-ISDN. The B-ISDN connects to another CPN, which connects to another Gateway (GW). The second GW connects to Terminal D. A direct line labeled 'Initial VC for H.245' connects Terminal A to Terminal D. A line labeled 'Additional VC for Audio, Video and Data' connects Terminal A to the first GW, then through the B-ISDN to the second GW, and finally to Terminal D. Terminal C is shown below the B-ISDN.
+
+T1604990-98
+
+**Figure C.3/H.310 – Communication between RAST-5 on CPN and RAST-1 on CPN**
+
+# APPENDIX I
+
+## Bit and byte order
+
+This appendix is supplied as a summary of bit and octet order in this Recommendation, including the elements specified in Recommendations H.261, H.262, H.263, G.711, G.722, G.723.1, G.728, G.729, ISO/IEC 11172 audio, ISO/IEC 13818 audio, Recommendations H.245, H.222.0 and H.222.1. In case of any discrepancy, the normative text of the various Recommendations shall take precedence over this appendix. H.261, H.262, H.263, G.711, G.722, G.723.1, G.728, G.729, ISO/IEC 11172 audio, ISO/IEC 13818 audio, H.245, H.222.0 and H.222.1 each produce a sequence of bits. Within this sequence of bits there are fields of various lengths, in some cases aligned with octet boundaries. In the case of H.261, H.262, H.263, G.711, G.722, G.723.1, G.728, G.729, ISO/IEC 11172 audio, ISO/IEC 13818 audio, H.245, H.222.0 and H.222.1 these fields are ordered Most Significant Bit (MSB) first. Figure I.1 illustrates this, with "M" indicating the MSB of each field and "L" indicating the Least Significant Bit (LSB) of each field.
+
+
+
+| | | | | | | | | | |
+|-------|---|---|---|---|---|---|---|---|------|
+| First | M | L | M | L | M | L | M | L | Last |
+|-------|---|---|---|---|---|---|---|---|------|
+
+Diagram illustrating bit and byte order. It shows a sequence of bits starting with 'First' and ending with 'Last'. The sequence is divided into four octets. Each octet contains two bits: the first bit is labeled 'M' (Most Significant Bit) and the second bit is labeled 'L' (Least Significant Bit). The sequence of bits is: M L M L M L M L.
+
+T1521660-96
+
+**Figure I.1/H.310 – Output from H.261, H.262, G.711, G.722, G.723.1, G.728, G.729, ISO/IEC 11172 audio, ISO/IEC 13818 audio, H.245, H.222.0, H.222.1**
+
+# APPENDIX II
+
+## H.310 CorrelationID
+
+This appendix is for clarifying the use of the H.310 CorrelationID and its relationship to the H.245 resourceID.
+
+When multiple VCs are involved in an H.310 communication, H.245 needs to be able to indicate a particular logical channel in a particular VC. Conventions are necessary for the:
+
+- association of the multiple VCs originated at a particular terminal;
+- identification of each VC.
+
+Since H.310 currently assumes that a single session exists between any two instances of H.310, the association of the multiple VCs can be uniquely identified by the Calling party number/Called party number and Calling party subaddress/Called party subaddress in the Q.2931 SETUP message. The identification of each VC is accomplished by using the H.245 resourceID (2 bytes). This is depicted in Figure II.1.
+
+
+
+Diagram of a single session case showing two terminals, A and C, connected to a central terminal B. Terminal A has three horizontal lines (channels) labeled A, B, and C. Terminal C also has three horizontal lines labeled A, B, and C. These lines connect to terminal B. Above the lines from A and C, the text 'Correlation ID' is present, with sub-labels A, B, and C. A double-headed arrow between the lines from A and C is labeled 'Differentiated by calling/called party number pairs'. The diagram is labeled T1605000-98 at the bottom right.
+
+**Figure II.1/H.310 – Identification of VCs in single session case**
+
+To prepare for the eventual possibility that multiple H.310 sessions will exist between two terminals, as shown in Figure II.2, the correlationID has been defined as follows:
+
+correlationID = session ID ; Identification of a session
+ + resource ID (2 bytes) ; Identification of a logical channel
+
+
+
+Diagram of a multi-session case showing two terminals, A and B. Terminal A has two groups of three horizontal lines. The top group is labeled 'Session 1' and the bottom group is labeled 'Session 2'. Each group has lines labeled A, B, and C. Above each group, the text 'Correlation ID' is present, with sub-labels A, B, and C. The lines connect to terminal B. The diagram is labeled T1605010-98 at the bottom right.
+
+**Figure II.2/H.310 – Identification of VCs in multi-session case**
+
+However, the current H.310 specification does not assume the multi-session case so the resourceID is the only valid element in the correlation ID for the moment.
+
+
+
+# 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 |
+| Series Z | Programming languages |
\ No newline at end of file
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+
+
+**ITU-T**
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+**H.324**
+
+(04/2009)
+
+SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS
+
+Infrastructure of audiovisual services – Systems and
+terminal equipment for audiovisual services
+
+---
+
+**Terminal for low bit-rate multimedia
+communication**
+
+Recommendation ITU-T H.324
+
+# ITU-T H-SERIES RECOMMENDATIONS **AUDIOVISUAL AND MULTIMEDIA SYSTEMS**
+
+| | |
+|-------------------------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100–H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | |
+| General | H.200–H.219 |
+| Transmission multiplexing and synchronization | H.220–H.229 |
+| Systems aspects | H.230–H.239 |
+| Communication procedures | H.240–H.259 |
+| Coding of moving video | H.260–H.279 |
+| Related systems aspects | H.280–H.299 |
+| Systems and terminal equipment for audiovisual services | H.300–H.349 |
+| Directory services architecture for audiovisual and multimedia services | H.350–H.359 |
+| Quality of service architecture for audiovisual and multimedia services | H.360–H.369 |
+| Supplementary services for multimedia | H.450–H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | |
+| Overview of Mobility and Collaboration, definitions, protocols and procedures | H.500–H.509 |
+| Mobility for H-Series multimedia systems and services | H.510–H.519 |
+| Mobile multimedia collaboration applications and services | H.520–H.529 |
+| Security for mobile multimedia systems and services | H.530–H.539 |
+| Security for mobile multimedia collaboration applications and services | H.540–H.549 |
+| Mobility interworking procedures | H.550–H.559 |
+| Mobile multimedia collaboration inter-working procedures | H.560–H.569 |
+| BROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES | |
+| Broadband multimedia services over VDSL | H.610–H.619 |
+| Advanced multimedia services and applications | H.620–H.629 |
+| IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV | |
+| General aspects | H.700–H.719 |
+| IPTV terminal devices | H.720–H.729 |
+| IPTV middleware | H.730–H.739 |
+| IPTV application event handling | H.740–H.749 |
+| IPTV metadata | H.750–H.759 |
+| IPTV multimedia application frameworks | H.760–H.769 |
+| IPTV service discovery up to consumption | H.770–H.779 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## Recommendation ITU-T H.324
+
+## Terminal for low bit-rate multimedia communication
+
+## Summary
+
+Recommendation ITU-T H.324 describes terminals for low bit-rate multimedia communication, utilizing ITU-T V.34 modems operating over the general switched telephone network (GSTN), I.400-series user-network interface for integrated services digital network (ISDN) or an appropriate wireless interface for mobile networks. ITU-T H.324 terminals may carry real-time voice, data and video, or any combination, including videotelephony.
+
+ITU-T H.324 terminals may be integrated into personal computers or implemented in stand-alone devices such as videotelephones. Support for each media type (voice, data, video) is optional, but if supported, the ability to use a specified common mode of operation is required, so that all terminals supporting that media type can interwork. This Recommendation allows more than one channel of each type to be in use. Other Recommendations in this series include Recommendation ITU-T H.223 (multiplex), Recommendation ITU-T H.245 (control), Recommendation ITU-T H.263 (video codec) and Recommendation ITU-T G.723.1 (audio codec).
+
+This Recommendation makes use of the logical channel signalling procedures of Recommendation ITU-T H.245, in which the content of each logical channel is described when the channel is opened. Procedures are provided for expression of receiver and transmitter capabilities, so transmissions are limited to what receivers can decode, and so that receivers may request a particular desired mode from transmitters. Since the procedures of this Recommendation are also planned for use by Recommendation ITU-T H.310 for ATM networks, and Recommendation ITU-T H.323 for non-guaranteed bandwidth LANs, interworking with these systems should be straightforward.
+
+ITU-T H.324 terminals may be used in multipoint configurations through multipoint control units (MCUs), and may interwork with ITU-T H.320 terminals on the ISDN, as well as with terminals on wireless networks.
+
+Annex A defines the data protocol stack for use with the ITU-T H.324 control channel.
+
+Annex B defines high-level data link control (HDLC) frame structure transparency for asynchronous transmission.
+
+Annex C defines the use of ITU-T H.324 terminals in error-prone transmission environments ("also referred to elsewhere as ITU-T H.324/M").
+
+Annex D defines the use of ITU-T H.324 terminals on ISDN circuits ("also referred to elsewhere as ITU-T H.324/I").
+
+Annex E defines timer T401 initialization for operation over geostationary-satellite channels.
+
+Annex F supports multilink operation on the GSTN and ISDN.
+
+Annex G defines the use of ISO/IEC 14496-1 ("MPEG-4 systems") generic capabilities in ITU-T H.324 terminals.
+
+Annex H supports multilink operation on error-prone mobile networks.
+
+Annex I defines the use of HTTP in ITU-T H.324 terminals, enabling non-conversational services with a user interface through web-like menus.
+
+Annex J summarizes the OIDs defined in this Recommendation and defines ITU-T H.324 generic capabilities which are used in ITU-T H.245 signalling-based systems.
+
+Annex K defines the media-oriented negotiation acceleration (MONA) procedure, which allows media channels to be established in a fast and flexible manner.
+
+Annex L defines procedures to establish and carry text conversation sessions in the ITU-T H.324 multimedia environment.
+
+Annex M defines the nature of ITU-T H.245 messages used by ITU-T H.324 endpoints.
+
+This revised version of this Recommendation introduces a number of enhancements and clarifications to the previous version, primarily the introductions of Annex K (MONA), Annex L (text conversation) and Annex M (ITU-T H.245 messages).
+
+## Source
+
+Recommendation ITU-T H.324 was approved on 29 April 2009 by ITU-T Study Group 16 (2009-2012) under Recommendation ITU-T A.8 procedures.
+
+# 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 2010
+
+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 | Block diagram and functional elements ..... | 1 |
+| 1.2 | System elements outside the scope of this Recommendation ..... | 2 |
+| 1.3 | Functional elements covered by this Recommendation ..... | 2 |
+| 2 | References..... | 3 |
+| 2.1 | Normative references..... | 3 |
+| 2.2 | Informative references..... | 5 |
+| 3 | Definitions ..... | 6 |
+| 4 | Abbreviations and acronyms ..... | 7 |
+| 5 | Conventions ..... | 8 |
+| 6 | Functional requirements ..... | 8 |
+| 6.1 | Required elements ..... | 8 |
+| 6.2 | Information streams..... | 9 |
+| 6.3 | Modem..... | 9 |
+| 6.4 | Multiplex ..... | 9 |
+| 6.5 | Control channel ..... | 11 |
+| 6.6 | Video channels ..... | 14 |
+| 6.7 | Audio channels ..... | 17 |
+| 6.8 | Data channels..... | 18 |
+| 7 | Terminal procedures ..... | 23 |
+| 7.1 | Phase A – Call set-up of voiceband channel ..... | 23 |
+| 7.2 | Phase B – Initial analogue telephony communication ..... | 24 |
+| 7.3 | Phase C – Establishment of digital communication, modem training..... | 24 |
+| 7.4 | Phase D – Initialization ..... | 25 |
+| 7.5 | Phase E – Communication..... | 25 |
+| 7.6 | Phase F – End of session ..... | 26 |
+| 7.7 | Phase G – Supplementary services and call clearing ..... | 26 |
+| 8 | Interoperation with other terminals ..... | 27 |
+| 8.1 | Speech only terminals..... | 27 |
+| 8.2 | ITU-T H.320 multimedia telephone terminals over the ISDN..... | 27 |
+| 8.3 | Multimedia telephone terminals over mobile radio..... | 27 |
+| 9 | Optional enhancements..... | 27 |
+| 9.1 | Data facilities..... | 27 |
+| 9.2 | Encryption ..... | 28 |
+| 9.3 | Multilink..... | 30 |
+
+| | Page | |
+|---------|---------------------------------------------------------------------------------------|----|
+| 10 | Multipoint considerations ..... | 30 |
+| 10.1 | Establishment of common mode ..... | 30 |
+| 10.2 | Multipoint rate matching ..... | 30 |
+| 10.3 | Multipoint lip synchronization ..... | 30 |
+| 10.4 | Multipoint encryption ..... | 31 |
+| 10.5 | Cascaded MCU operation..... | 31 |
+| 11 | Maintenance..... | 31 |
+| 11.1 | Loopbacks for maintenance purposes ..... | 31 |
+| Annex A | – Protocol stack for control channel..... | 33 |
+| A.1 | General ..... | 33 |
+| A.2 | SRP mode ..... | 34 |
+| A.3 | LAPM/ITU-T V.42 mode..... | 36 |
+| A.4 | WNSRP control frame signalling on the control channel ..... | 36 |
+| Annex B | – HDLC frame structure transparency for asynchronous transmission..... | 40 |
+| Annex C | – Multimedia telephone terminals over error-prone channels..... | 41 |
+| C.1 | Abstract..... | 41 |
+| C.2 | General ..... | 41 |
+| C.3 | Changes to procedures..... | 42 |
+| C.4 | Interworking ..... | 42 |
+| C.5 | Terminal procedures..... | 42 |
+| C.6 | Initialization of multiplex level at the start of a session..... | 42 |
+| C.7 | Dynamic change of level or option during session ..... | 44 |
+| C.8 | Control channel definition for mobile terminals ..... | 45 |
+| Annex D | – Operation on ISDN circuits (H.324/I) ..... | 49 |
+| D.1 | Scope ..... | 49 |
+| D.2 | References ..... | 49 |
+| D.3 | Definitions ..... | 49 |
+| D.4 | Functional requirements ..... | 49 |
+| D.5 | Terminal procedures..... | 51 |
+| Annex E | – Timer T401 initialization for operation over geostationary-satellite channels ..... | 54 |
+| E.1 | Introduction ..... | 54 |
+| E.2 | Determination of timer value..... | 54 |
+| E.3 | Timer tuning procedure ..... | 55 |
+| Annex F | – Multilink operation..... | 56 |
+| F.1 | Scope ..... | 56 |
+| F.2 | References ..... | 56 |
+| F.3 | Functional requirements ..... | 56 |
+| F.4 | Overview ..... | 56 |
+| F.5 | Procedures ..... | 56 |
+
+| | Page |
+|----------------------------------------------------------------------------------------|------|
+| F.6 Maximum transmit skew ..... | 62 |
+| F.7 Sequence diagram for establishment of multilink operation..... | 62 |
+| Annex G – Usage of ISO/IEC 14496-1 generic capabilities in ITU-T H.324 terminals ..... | 64 |
+| G.1 Scope ..... | 64 |
+| G.2 References ..... | 64 |
+| G.3 General ..... | 64 |
+| G.4 Choice of error protection for ISO/IEC 14496 data streams..... | 64 |
+| G.5 Framing of ISO/IEC 14496-1 data streams ..... | 64 |
+| Annex H – Mobile multilink operation..... | 65 |
+| H.1 Scope ..... | 65 |
+| H.2 Definitions and format conventions ..... | 65 |
+| H.3 Functional requirements ..... | 65 |
+| H.4 Overview ..... | 65 |
+| H.5 Mobile multilink layer specification ..... | 66 |
+| H.6 Procedures ..... | 69 |
+| H.7 Header modes ..... | 72 |
+| Annex I – Usage of HTTP generic capability in ITU-T H.324 terminals ..... | 73 |
+| I.1 General ..... | 73 |
+| I.2 Logical channel for HTTP ..... | 74 |
+| I.3 HTTP generic capability..... | 74 |
+| I.4 References ..... | 74 |
+| Annex J – ASN.1 OIDs defined in this Recommendation..... | 75 |
+| J.1 Summary of OIDs defined in this Recommendation ..... | 75 |
+| J.2 Session reset capability identifier..... | 75 |
+| Annex K – Media oriented negotiation acceleration procedure ..... | 76 |
+| K.1 Abstract..... | 76 |
+| K.2 General ..... | 76 |
+| K.3 References ..... | 76 |
+| K.4 Definitions and format conventions ..... | 76 |
+| K.5 Terminal procedures..... | 77 |
+| K.6 MONA signalling ..... | 77 |
+| K.7 Channel establishment method negotiation..... | 80 |
+| K.8 Channel establishment via the signalling preconfigured channel (SPC)..... | 88 |
+| K.9 Preconfigured channel establishment ..... | 92 |
+| K.10 Accelerated ITU-T H.245 procedures ..... | 97 |
+| Annex L – Text conversation in ITU-T H.324 ..... | 101 |
+| L.1 Introduction ..... | 101 |
+| L.2 Scope ..... | 101 |
+| L.3 Definitions ..... | 101 |
+
+| | Page |
+|-------------------------------------------------------------------|-------------|
+| L.4 Procedures for ITU-T T.140 text conversation ..... | 101 |
+| L.5 Framing and buffering of ITU-T T.140 data ..... | 103 |
+| L.6 Presentation considerations ..... | 103 |
+| Annex M – ITU-T H.245 messages used by ITU-T H.324 endpoints..... | 106 |
+| Appendix I – Bit and octet order..... | 110 |
+| Appendix II – ITU-T V.8 bis codepoints..... | 111 |
+
+# Recommendation ITU-T H.324
+
+## Terminal for low bit-rate multimedia communication
+
+# 1 Scope
+
+This Recommendation covers the technical requirements for very low bit-rate multimedia telephone terminals operating over the general switched telephone network (GSTN).
+
+ITU-T H.324 terminals provide real-time video audio or data, or any combination, between two multimedia telephone terminals over a GSTN voice band network connection. Communication may be either 1-way or 2-way. Multipoint communication using a separate multipoint control unit (MCU) among more than two ITU-T H.324 terminals is possible. MCUs and other non-terminal devices are not bound by the requirements in this Recommendation, but they should comply where practical.
+
+The multimedia telephone terminals defined in this Recommendation can be integrated into personal computers (PCs) or workstations, or be stand-alone units.
+
+Interworking with visual telephone systems on the integrated services digital network (ISDN) (known as the ITU-T H.320-series of Recommendations) and on mobile radio networks are also covered.
+
+## 1.1 Block diagram and functional elements
+
+A generic ITU-T H.324 multimedia videophone system is shown in Figure 1. It consists of terminal equipment, GSTN modem, GSTN network, multipoint control unit (MCU) and other system operation entities. ITU-T H.324 implementations are not required to have each functional element.
+
+
+
+The diagram illustrates the functional elements of an ITU-T H.324 multimedia system. On the left, four external components are shown: 'Video I/O equipment', 'Audio I/O equipment', 'User data applications ITU-T T.120, etc.', and 'System control'. These are connected to a central dashed box labeled 'Scope of ITU-T H.324'. Inside this box, the components connect to internal functional blocks: 'Video codec ITU-T H.263/ITU-T H.261' (receiving input from Video I/O), 'Audio codec ITU-T G.723.1' (receiving input from Audio I/O and connected to a 'Receive path delay' block), 'Data protocols ITU-T V.14, LAPM, etc.' (receiving input from User data applications), and 'Control protocol ITU-T H.245' (receiving input from System control and connected to 'SRP/LAPM procedures'). All four internal blocks feed into a 'Multiplex/demultiplex ITU-T H.223' block. This block connects to a 'Modem ITU-T V.34/ITU-T V.8' block, which in turn connects to an external 'GSTN network' (represented by a circle). Below the Modem block is a 'Modem control ITU-T V.250' block, which also connects to the GSTN network. The GSTN network is further connected to an external 'MCU' (Multipoint Control Unit) block. A small label 'H.324(09)\_F01' is located in the bottom right corner of the diagram area.
+
+Block diagram for ITU-T H.324 multimedia system
+
+Figure 1 – Block diagram for ITU-T H.324 multimedia system
+
+## 1.2 System elements outside the scope of this Recommendation
+
+The following system elements are covered by other Recommendations or are not subject to standardization, and are therefore not defined in this Recommendation:
+
+- Video I/O equipment including cameras and monitors, their control and selection, video processing to improve compression or provide split-screen functions.
+- Audio I/O equipment including microphone and loudspeaker, telephone instrument or equivalent, attached audio devices providing voice activation sensing, multiple microphone mixers, acoustic echo cancellation.
+- Data application equipment such as computers, non-standardized data application protocols, telematic visual aids such as electronic whiteboards, etc.
+- GSTN network interface supporting appropriate signalling, ringing functions and voltage levels, in accordance with national standards.
+- Human user system control, user interface and operation.
+
+## 1.3 Functional elements covered by this Recommendation
+
+The scope of this Recommendation is indicated by the elements within the dashed line of Figure 1, which include:
+
+- The video codec (ITU-T H.263 or ITU-T H.261) carries out redundancy reduction coding and decoding for video streams.
+- The audio codec (ITU-T G.723.1) encodes the audio signal from the microphone for transmission, and decodes the audio code which is output to the speaker. Optional delay in the receiving audio path compensates for the video delay, so as to maintain audio and video synchronization.
+- The data protocols support data applications such as electronic whiteboards, still image transfer, file exchange, database access, audiographics conferencing, remote device control, network protocols, etc. Standardized data applications include ITU-T T.120 for real-time audiographics conferencing, ITU-T T.84 simple point-point still image file transfer, ITU-T T.434 simple point-point file transfer, ITU-T H.224/ITU-T H.281 far-end camera control, ISO/IEC TR 9577 network protocols including point-to-point protocol (PPP) and Internet Protocol (IP), and transport of user data using buffered ITU-T V.14 or LAPM/ITU-T V.42. Other applications and protocols may also be used via ITU-T H.245 negotiation.
+- The control protocol (ITU-T H.245) provides end-to-end signalling for proper operation of the ITU-T H.324 terminal, and signals all other end-to-end system functions including reversion to analogue speech-only telephony mode. It provides for capability exchange, signalling of commands and indications, and messages to open and fully describe the content of logical channels.
+- The multiplex protocol (ITU-T H.223) multiplexes transmitted video, audio, data and control streams into a single bitstream, and demultiplexes a received bitstream into various multimedia streams. In addition, it performs logical framing, sequence numbering, error detection and error correction by means of retransmission, as appropriate to each media type.
+- The modem (ITU-T V.34) converts the ITU-T H.223 synchronous multiplexed bitstream into an analogue signal that can be transmitted over the GSTN, and converts the received analogue signal into a synchronous bitstream that is sent to the multiplex/demultiplex protocol unit. [ITU-T V.250] (Former Recommendation ITU-T 25 *ter*) is used to provide control/sensing of the modem/network interface, when the modem with network signalling and ITU-T V.8/ITU-T V.8 *bis* functional elements is a separate physical item.
+
+# 2 References
+
+## 2.1 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; 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.711] Recommendation ITU-T G.711 (1988), *Pulse code modulation (PCM) of voice frequencies*.
+- [ITU-T G.723.1] Recommendation ITU-T G.723.1 (1996), *Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s*.
+- [ITU-T G.725] Recommendation ITU-T G.725 (1988), *System aspects for the use of the 7 kHz audio codec within 64 kbit/s*.
+- [ITU-T H.221] Recommendation ITU-T H.221 (2004), *Frame structure for a 64 to 1920 kbit/s channel in audiovisual teleservices*.
+- [ITU-T H.223] Recommendation ITU-T H.223 (2001), *Multiplexing protocol for low bit rate multimedia communication*.
+- [ITU-T H.224] Recommendation ITU-T H.224 (2005), *A real time control protocol for simplex applications using the H.221 LSD/HSD/MLP channels*.
+- [ITU-T H.226] Recommendation ITU-T H.226 (1998), *Channel aggregation protocol for multilink operation on circuit-switched networks*.
+- [ITU-T H.233] Recommendation ITU-T H.233 (2002), *Confidentiality system for audiovisual services*.
+- [ITU-T H.234] Recommendation ITU-T H.234 (2002), *Encryption key management and authentication system for audiovisual services*.
+- [ITU-T H.239] Recommendation ITU-T H.239 (2005), *Role management and additional media channels for H.300-series terminals*.
+- [ITU-T H.241] Recommendation ITU-T H.241 (2005), *Extended video procedures and control signals for H.300-series terminals*.
+- [ITU-T H.245] Recommendation ITU-T H.245 (2005), *Control protocol for multimedia communication*.
+- [ITU-T H.261] Recommendation ITU-T H.261 (1993), *Video codec for audiovisual services at $p \times 64$ kbit/s*.
+- [ITU-T H.263] Recommendation ITU-T H.263 (2005), *Video coding for low bit rate communication*.
+- [ITU-T H.264] Recommendation ITU-T H.264 (2005), *Advanced video coding for generic audiovisual services*.
+- [ITU-T H.281] Recommendation ITU-T H.281 (1994), *A far end camera control protocol for videoconferences using H.224*.
+- [ITU-T H.320] Recommendation ITU-T H.320 (2004), *Narrow-band visual telephone systems and terminal equipment*.
+
+- [ITU-T T.30] Recommendation ITU-T T.30 (2005), *Procedures for document facsimile transmission in the general switched telephone network.*
+- [ITU-T T.84] Recommendation ITU-T T.84 (1996) | ISO/IEC 10918-3:1997, *Information technology – Digital compression and coding of continuous-tone still images: Extensions.*
+- [ITU-T T.120] Recommendation ITU-T T.120 (1996), *Data protocols for multimedia conferencing.*
+- [ITU-T T.134] Recommendation ITU-T T.134 (1998), *Text chat application entity.*
+- [ITU-T T.140] Recommendation ITU-T T.140 (1998), *Protocol for multimedia application text conversation.*
+- [ITU-T T.434] Recommendation ITU-T T.434 (1999), *Binary file transfer format for the telematic services.*
+- [ITU-T V.8] Recommendation ITU-T V.8 (2000), *Procedures for starting sessions of data transmission over the public switched telephone network.*
+- [ITU-T V.8 bis] Recommendation ITU-T V.8 bis (2000), *Procedures for the identification and selection of common modes of operation between data circuit-terminating equipments (DCEs) and between data terminal equipments (DTEs) over the public switched telephone network and on leased point-to-point telephone-type circuits.*
+- [ITU-T V.14] Recommendation ITU-T V.14 (1993), *Transmission of start-stop characters over synchronous bearer channels.*
+- [ITU-T V.34] Recommendation ITU-T V.34 (1998), *A modem operating at data signalling rates of up to 33 600 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits.*
+- [ITU-T V.42] Recommendation ITU-T V.42 (2002), *Error-correcting procedures for DCEs using asynchronous-to-synchronous conversion.*
+- [ITU-T V.42 bis] Recommendation ITU-T V.42 bis (1990), *Data compression procedures for data circuit-terminating equipment (DCE) using error correction procedures.*
+- [ITU-T V.140] Recommendation ITU-T V.140 (2005), *Procedures for establishing communication between two multiprotocol audiovisual terminals using digital channels at a multiple of 64 or 56 kbit/s.*
+- [ITU-T V.250] Recommendation ITU-T V.250 (2003)1, *Serial asynchronous automatic dialling and control.*
+- [ITU-T X.691] Recommendation ITU-T X.691 (2002) | ISO/IEC 8825-2:2002, *Information technology – ASN.1 encoding rules – Specification of Packed Encoding Rules (PER).*
+- [ISO/IEC 13239] ISO/IEC 13239:2002, *Information technology – Telecommunications and information exchange between systems – High-level data link control (HDLC) procedures.*
+- [ISO/IEC 14496-1] ISO/IEC 14496-1:2001, *Information technology – Coding of audio-visual objects – Part 1: Systems.*
+
+1 Former Recommendation ITU-T V.25 ter (1997), renumbered as Recommendation ITU-T V.250 in 1998.
+
+- [ISO/IEC 14496-2] ISO/IEC 14496-2:2004, *Information technology – Coding of audio-visual objects – Part 2: Visual*.
+- [ISO/IEC 14496-3] ISO/IEC 14496-3:2001, *Information technology – Coding of audio-visual objects – Part 3: Audio*.
+- [ISO/IEC TR 9577] ISO/IEC TR 9577:1999, *Information technology – Protocol identification in the network layer*.
+- [ETSI TS 126 071] ETSI TS 126 071 V6.0.0 (2004-12), *Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); AMR speech Codec; General description (3GPP TS 26.071 version 6.0.0 Release 6)*.
+- [ETSI TS 126 171] ETSI TS 126 171 V6.0.0 (2004-12), *Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); AMR speech Codec, wideband; General description (3GPP TS 26.171 version 6.0.0 Release 6)*.
+- [IETF RFC 2616] IETF RFC 2616 (1999), *Hypertext Transfer Protocol – HTTP/1.1*.
+
+## 2.2 Informative references
+
+- [ITU-T E.164] Recommendation ITU-T E.164 (2005), *The international public telecommunication numbering plan*.
+- [ITU-T F.703] Recommendation ITU-T F.703 (2000), *Multimedia conversational services*.
+- [ITU-T G.114] Recommendation ITU-T G.114 (2003), *One-way transmission time*.
+- [ITU-T G.703] Recommendation ITU-T G.703 (2001), *Physical/electrical characteristics of hierarchical digital interfaces*.
+- [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.722] Recommendation ITU-T G.722 (1988), *7 kHz audio-coding within 64 kbit/s*.
+- [ITU-T G.722.1] Recommendation ITU-T G.722.1 (2005), *Low-complexity coding at 24 and 32 kbit/s for hands-free operation in systems with low frame loss*.
+- [ITU-T G.728] Recommendation ITU-T G.728 (1992), *Coding of speech at 16 kbit/s using low-delay code excited linear prediction*.
+- [ITU-T H.230] Recommendation ITU-T H.230 (2004), *Frame-synchronous control and indication signals for audiovisual systems*.
+- [ITU-T H.262] Recommendation ITU-T H.262 (2000) | ISO/IEC 13818-2:2000, *Information technology – Generic coding of moving pictures and associated audio information: Video*.
+- [ITU-T H.310] Recommendation ITU-T H.310 (1998), *Broadband audiovisual communication systems and terminals*.
+- [ITU-T H.323] Recommendation ITU-T H.323 (2006), *Packet-based multimedia communications systems*.
+- [ITU-T Q.931] Recommendation ITU-T Q.931 (1998), *ISDN user-network interface layer 3 specification for basic call control*.
+- [ITU-T T.35] Recommendation ITU-T T.35 (2000), *Procedure for the allocation of ITU-T defined codes for non-standard facilities*.
+
+- [ITU-T T.39] Recommendation ITU-T T.39 (1997), *Application profiles for simultaneous voice and facsimile terminals.*
+- [ITU-T T.51] Recommendation ITU-T T.51 (1992), *Latin based coded character sets for telematic services.*
+- [ITU-T T.123] Recommendation ITU-T T.123 (2007), *Network-specific data protocol stacks for multimedia conferencing.*
+- [ITU-T T.126] Recommendation ITU-T T.126 (2007), *Multipoint still image and annotation protocol.*
+- [ITU-T T.127] Recommendation ITU-T T.127 (2007), *Multipoint binary file transfer protocol.*
+- [ITU-T V.24] Recommendation ITU-T V.24 (2000), *List of definitions for interchange circuits between data terminal equipment (DTE) and data circuit-terminating equipment (DCE).*
+- [ITU-T X.21] Recommendation ITU-T X.21 (1992), *Interface between Data Terminal Equipment and Data Circuit-terminating Equipment for synchronous operation on public data networks.*
+- [ITU-T X.680] Recommendation ITU-T X.680 (2002) | ISO/IEC 8824-1:2002, *Information technology – Abstract Syntax Notation One (ASN.1): Specification of basic notation.*
+- [IETF RFC 1490] IETF RFC 1490 (1993), *Multiprotocol Interconnect over Frame Relay.*
+- [IETF RFC 1661] IETF RFC 1661 (1994), *The Point-to-Point Protocol (PPP).*
+
+# 3 Definitions
+
+For the purposes of this Recommendation, the definitions given in clause 3 of both [ITU-T H.223] and [ITU-T H.245] apply, along with the following:
+
+- 3.1 adaptation layer service data unit (AL-SDU):** The logical unit of information exchanged between the ITU-T H.223 multiplex and the audio codec, video codec or data protocol above.
+- 3.2 channel:** A unidirectional link between two endpoints.
+- 3.3 codec:** Coder/decoder, used to convert audio or video signals to/from digital format.
+- 3.4 connection:** A bidirectional link between two endpoints.
+- 3.5 control channel:** Dedicated logical channel number 0 carrying system control protocol per [ITU-T H.245].
+- 3.6 data:** Information streams other than control, audio and video, carried in a logical data channel (see [ITU-T H.223]).
+- 3.7 in-band signalling:** Control signals sent within a specific logical channel other than the control channel, carrying information applicable only to that logical channel.
+- 3.8 interworking adapter:** A device connected to terminals or MCUs working according to two or more Recommendations, which translates the content of one or more logical channels to allow interoperation between otherwise incompatible equipment.
+- 3.9 lip synchronization:** Operation to provide the feeling that speaking motion of the displayed person is synchronized with the voice sounds.
+- 3.10 logical channel:** One of several logically distinct channels carried over a single bitstream.
+- 3.11 media:** One or more of audio, video or data.
+
+- 3.12 multilink:** The use of more than one physical connection to obtain a larger aggregate bit rate.
+- 3.13 multipoint:** The simultaneous interconnection of three or more terminals to allow communication among several sites through the use of multipoint control units (bridges) which centrally direct the flow of information.
+- 3.14 MUX-PDU:** The logical unit of information exchanged between the ITU-T H.223 multiplex layer and the underlying physical layer. It is a packet framed by HDLC flags and using HDLC zero-bit insertion for transparency.
+- 3.15 non-segmentable:** The ITU-T H.223 mode of operation in which AL-SDUs must be sent as consecutive octets in a single MUX-PDU. See [ITU-T H.223].
+- 3.16 segmentable:** The ITU-T H.223 mode of operation in which AL-SDUs may be sent in separate multiplex slots carried on one or more MUX-PDUs (see [ITU-T H.223]).
+- 3.17 support:** The ability to operate in a given mode; however, a requirement to "support" a mode does not mean that the mode must actually be used at all times. Unless prohibited, other modes may be used by mutual negotiation.
+- 3.18 videophone:** A terminal capable of sending and receiving audio and video information simultaneously.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|--------|--------------------------------------------------------|
+| AL-SDU | Adaptation Layer Service Data Unit (see [ITU-T H.223]) |
+| ASN.1 | Abstract Syntax Notation One |
+| BC | Bearer Capability |
+| BCH | Bose-Chaudhuri-Hocquenghem |
+| CIF | Common Intermediate Format |
+| CCSRL | Control Channel Segmentation and Reassembly Layer |
+| CPF | Compatible Protocol Field |
+| CRC | Cyclic Redundancy Check |
+| DCE | Data Circuit-Terminating Equipment |
+| DTE | Data Terminal Equipment |
+| DTMF | Dual Tone Multi-Frequency |
+| EIV | Encryption Initialization Vector |
+| GSTN | General Switched Telephone Network |
+| HLC | High Level Capability |
+| HDLC | High-Level Data Link Control (per [ISO/IEC 13239]) |
+| IP | Internet Protocol |
+| ISDN | Integrated Services Digital Network |
+| LAPM | Link Access Procedures for Modems (per [ITU-T V.42]) |
+| LC | Logical Channel |
+| LCN | Logical Channel Number (per [ITU-T H.223]) |
+
+| | |
+|-------|-----------------------------------------------------------|
+| LS | Last Segment |
+| MCU | Multipoint Control Unit |
+| MONA | Media Oriented Negotiation Acceleration |
+| MUX | Multiplexer |
+| NLPID | Network Layer Protocol Identifier (per [ISO/IEC TR 9577]) |
+| NSRP | Numbered Simple retransmission protocol Response Frames |
+| OID | Object Identifier |
+| PDU | Protocol Data Unit |
+| PER | Packed Encoding Rules |
+| PPP | Point-to-Point Protocol |
+| QCIF | Quarter Common Intermediate Format |
+| SDU | Service Data Unit |
+| SE | Session Exchange (per [ITU-T H.233]) |
+| SQCIF | Sub Quarter Common Intermediate Format |
+| SRP | Simple Retransmission Protocol (see Annex A) |
+| WNSRP | Windowed NSRP |
+
+# 5 Conventions
+
+The word "shall" is used in this Recommendation to specify a mandatory requirement.
+
+The word "should" is used in this Recommendation to specify a suggested, but not required, course of action.
+
+The word "may" is used in this Recommendation to specify an optional course of action, without expressing a preference.
+
+References in this Recommendation to specific ITU-T H.245 ASN.1 message structures are presented in **this typeface**.
+
+ITU-T H.324/I Systems or endpoints conforming to Annex D.
+
+ITU-T H.324/M Systems or endpoints conforming to Annex C.
+
+# 6 Functional requirements
+
+## 6.1 Required elements
+
+ITU-T H.324 implementations are not required to have each functional element, except for the ITU-T V.34 modem, ITU-T H.223 multiplex and ITU-T H.245 system control protocol, all of which shall be supported by all ITU-T H.324 terminals.
+
+ITU-T H.324 terminals offering audio communication shall support the ITU-T G.723.1 audio codec. ITU-T H.324 terminals offering video communication shall support the ITU-T H.263 and ITU-T H.261 video codecs. ITU-T H.324 terminals offering real-time audiographic conferencing should support the ITU-T T.120 protocol suite. In addition, other video and audio codecs, and other data protocols, may optionally be used via negotiation over the ITU-T H.245 control channel.
+
+If a modem external to the ITU-T H.324 terminal is used, terminal/modem control shall conform to [ITU-T V.250].
+
+The presence of optional facilities is signalled via the ITU-T H.245 control channel. If both ends support an optional facility, and choose to make use of it, the opening of a path to carry such information streams is negotiated according to the procedures of [ITU-T H.245].
+
+NOTE – This Recommendation does not specify a particular implementation. Any implementation that provides the required functionality, and that conforms to the bitstream format ultimately described by this Recommendation, is considered compliant.
+
+## 6.2 Information streams
+
+Multimedia information streams are classified into video, audio, data and control as follows:
+
+- Video streams are continuous traffic carrying moving colour pictures. When used, the bit rate available for video streams may vary according to the needs of the audio and data channels.
+- Audio streams are real-time, but may optionally be delayed in the receiver processing path to maintain synchronization with the video streams. In order to reduce the average bit rate of audio streams, voice activation may be provided.
+- Data streams may represent still pictures, facsimile, documents, computer files, computer application data, undefined user data and other data streams.
+- Control streams pass control commands and indications between remote counterparts. Terminal-to-modem control conforms to [ITU-T V.250] for terminals using external modems connected by a separate physical interface. Terminal-to-terminal control is according to [ITU-T H.245].
+
+## 6.3 Modem
+
+Modems used for ITU-T H.324 terminals shall operate in full duplex, synchronous mode and conform to [ITU-T V.34] and [ITU-T V.8]. Support of [ITU-T V.8 *bis*] is optional. The output of the ITU-T H.223 multiplex shall be applied directly to the [ITU-T V.34] synchronous data pump. When an external, non-integrated ITU-T V.34 modem is used, control between the modem and the terminal shall be via [ITU-T V.250]. In such cases, the physical interface is implementation-specific. The use of the optional ITU-T V.34 auxiliary channel is reserved for further study.
+
+## 6.4 Multiplex
+
+Logical channels of video, audio, data or control information may be transmitted, after the channels have been established according to the procedures of [ITU-T H.245]. Logical channels are unidirectional, and are independent in each direction of transmission. Any number of logical channels of each media type may be transmitted, except for the ITU-T H.245 control channel of which there shall be one. The multiplex method used to transmit these logical channels shall conform to [ITU-T H.223]. The optional exclusive-OR procedure of clause 6.4.2 of [ITU-T H.223] shall not be used by [ITU-T H.324] terminals.
+
+The ITU-T H.223 multiplex consists of a multiplex layer, which mixes the various logical channels into a single bitstream, and an adaptation layer, which handles error control and sequence numbering, as appropriate to each information stream. The multiplex layer transfers logical channel information in packets called MUX-PDUs, delimited by HDLC flags and using HDLC zero-bit insertion for transparency. Each MUX-PDU contains a one-octet header followed by a variable number of information field octets. The header octet includes a multiplex code, which specifies, by reference to a multiplex table, the mapping of the information field octets to various logical channels. Each MUX-PDU may contain a different multiplex code, and therefore a different mix of logical channels.
+
+ITU-T H.324 terminals shall signal their ITU-T H.223 capabilities via the ITU-T H.245 **H223Capability** message.
+
+### 6.4.1 Logical channel numbers
+
+Each logical channel is identified by a logical channel number (LCN), in the range 0 to 65535, which serves only to associate logical channels with the corresponding entries in the ITU-T H.223 multiplex table. Logical channel numbers are selected arbitrarily by the transmitter, except that logical channel 0 shall be permanently assigned to the ITU-T H.245 control channel.
+
+### 6.4.2 Multiplex table entries
+
+Multiplex table entries are independent in each direction of transmission, and are sent from transmitters to receivers using the ITU-T H.245 **MultiplexEntrySend** request message. Multiplex table entry 0 shall not be sent, but shall be permanently assigned to logical channel 0, used for the control channel. Multiplex table entry 0 shall therefore be used for initial capability exchanges and transmission of initial multiplex table entries.
+
+### 6.4.3 Flow control
+
+ITU-T H.324 terminals shall respond to the ITU-T H.245 **FlowControlCommand** message, which commands a limit to the overall bit rate of one or more logical channels, or the entire multiplex.
+
+When one or more logical channels are limited by the **FlowControlCommand**, other less restricted logical channels may increase their transmission rate. The limit applies to the content of the logical channel at the input to the multiplex layer, before flags or zero-bit insertion is applied.
+
+When the entire ITU-T H.223 multiplex is limited by the **FlowControlCommand**, or when the terminal has no information to send, the terminal shall send HDLC flags in place of logical channel information. The limit applies to the entire multiplex output, including opening flags, header octets and inserted zero bits, but not including idle flags.
+
+### 6.4.4 Error control
+
+The multiplex layer of [ITU-T H.223] does not perform error control, except for a CRC on the header octet. Error control for each logical channel is handled separately by the adaptation layers of [ITU-T H.223], which may use a variety of error control techniques, including but not limited to, error detection and retransmission.
+
+### 6.4.5 Adaptation layers
+
+[ITU-T H.223] defines three adaptation layers, AL1, AL2 and AL3. AL1 is intended primarily for variable-rate framed information, including unframed octets treated as a single frame of indefinite length. AL2 is intended primarily for digital audio, and includes an 8-bit CRC and optional sequence numbers. AL3 is intended primarily for digital video and includes provision for retransmission.
+
+The logical unit of information exchanged between the ITU-T H.223 multiplex and the audio codec, video codec, data protocol or control protocol above is called an AL-SDU.
+
+Logical channels carried by the ITU-T H.223 multiplex may be of either "segmentable" or "non-segmentable" type, as defined in [ITU-T H.223], and signalled by [ITU-T H.245] when each channel is opened. AL-SDUs of segmentable logical channels may be segmented by the ITU-T H.223 multiplex. AL-SDUs of non-segmentable logical channels are not segmented by the ITU-T H.223 multiplex. Generally, segmentable channels should be used for variable bit-rate information streams such as control, video and data, while non-segmentable channels should be used for constant bit-rate streams such as audio.
+
+Receivers shall signal their capability to process various adaptation layers and channel types according to [ITU-T H.245]. Transmitters shall signal which adaptation layers, options and channel type are used for each logical channel when opening the channel, according to [ITU-T H.245].
+
+## 6.5 Control channel
+
+The control channel carries end-to-end control messages governing operation of the ITU-T H.324 system, including capabilities exchange, opening and closing of logical channels, mode preference requests, multiplex table entry transmission, flow control messages and general commands and indications.
+
+There shall be exactly one control channel in each direction within ITU-T H.324, which shall use the messages and procedures of [ITU-T H.245]. The control channel shall be carried on logical channel 0. The control channel shall be considered to be permanently open from the establishment of digital communication until the termination of digital communication; the normal procedures for opening and closing logical channels shall not apply to the control channel.
+
+General commands and indications shall be chosen from the message set contained in [ITU-T H.245]. In addition, other command and indication signals may be sent which have been specifically defined to be transferred in-band within video, audio or data streams (see the appropriate Recommendation to determine if such signals have been defined).
+
+ITU-T H.245 messages fall into four categories: request, response, command and indication. Request messages require a specific action by the receiver, including an immediate response. Response messages respond to a corresponding request. Command messages require a specific action, but do not require a response. Indication messages are informative only, and do not require any action or response. ITU-T H.324 terminals shall respond to all supported ITU-T H.245 commands and requests as specified in [ITU-T H.245], and shall transmit accurate indications reflecting the state of the terminal.
+
+NOTE 1 – All control channel messages are sent over a link layer protocol which acknowledges correct receipt. This acknowledgement is distinct from the response messages, which convey content beyond that of correct receipt of the message.
+
+ITU-T H.324 terminals shall be capable of parsing all ITU-T H.245 **MultimediaSystemControlMessage** messages, and shall send and receive all messages needed to implement required ITU-T H.324 functions and those optional functions which are supported by the terminal. All messages and procedures of [ITU-T H.245] related to required ITU-T H.324 functions are required, except for those explicitly described as optional, or which are related to defined optional capabilities the terminal does not support. ITU-T H.324 terminals shall send the **FunctionNotSupported** message in response to unrecognized request, response or command messages.
+
+A control channel indication, **UserInputIndication**, is available for transport of user input alphanumeric characters from a keypad or keyboard, equivalent to the DTMF signals used in analogue telephony. This may be used to manually operate remote equipment such as voice mail or video mail systems, menu-driven information services, etc. ITU-T H.324 terminals shall support the transmission of user input characters 0-9, '\*' and '#'. Transmission of other characters is optional.
+
+NOTE 2 – If the encryption procedures of this Recommendation are in use, the control channel will not be encrypted. Users are therefore cautioned regarding the carriage of user data in the control channel, the use of non-standard messages and the confidentiality risk from traffic analysis of the control channel.
+
+### 6.5.1 Capabilities exchange
+
+Capabilities exchange shall follow the procedures of [ITU-T H.245], which provides for separate receive and transmit capabilities, as well as a system by which the terminal may describe its ability to operate in various combinations of modes simultaneously.
+
+Receive capabilities describe the terminal's ability to receive and process incoming information streams. Transmitters shall limit the content of their transmitted information to that which the receiver has indicated it is capable of receiving. The absence of a receive capability indicates that the terminal cannot receive (is a transmitter only).
+
+Transmit capabilities describe the terminal's ability to transmit information streams. Transmit capabilities serve to offer receivers a choice of possible modes of operation, so that the receiver may request the mode which it prefers to receive. The absence of a transmit capability indicates that the terminal is not offering a choice of preferred modes to the receiver (but it may still transmit anything within the capability of the receiver).
+
+The transmitting terminal assigns each individual mode the terminal is capable of operating in a number in a **capabilityTable**. For example, ITU-T G.723.1 audio, ITU-T G.728 audio and ITU-T H.263 CIF video would each be assigned separate numbers.
+
+These capability numbers are grouped into **AlternativeCapabilitySet** structures. Each **AlternativeCapabilitySet** indicates that the terminal is capable of operating in exactly one mode listed in the set. For example, an **AlternativeCapabilitySet** listing {G.711, G.723.1, G.728} means that the terminal can operate in any one of those audio modes, but not more than one.
+
+These **AlternativeCapabilitySet** structures are grouped into **simultaneousCapabilities** structures. Each **simultaneousCapabilities** structure indicates a set of modes the terminal is capable of using simultaneously. For example, a **simultaneousCapabilities** structure containing the two **AlternativeCapabilitySet** structures {H.261, H.263} and {G.711, G.723.1, G.728} means that the terminal can operate either of the video codecs simultaneously with any one of the audio codecs. The **simultaneousCapabilities** set { {H.261}, {H.261, H.263}, {G.711, G.723.1, G.728} } means the terminal can operate two video channels and one audio channel simultaneously: one video channel per [ITU-T H.261], another video channel per either [ITU-T H.261] or [ITU-T H.263], and one audio channel per either [ITU-T G.711], [ITU-T G.723.1] or [ITU-T G.728].
+
+NOTE – The actual capabilities stored in the **capabilityTable** are often more complex than presented here. For example, each ITU-T H.263 capability indicates details including the ability to support various picture formats at given minimum picture intervals, and ability to use optional coding modes. For a complete description, see [ITU-T H.245].
+
+The terminal's total capabilities are described by a set of **CapabilityDescriptor** structures, each of which is a single **simultaneousCapabilities** structure and a **capabilityDescriptorNumber**. By sending more than one **CapabilityDescriptor**, the terminal may signal dependencies between operating modes by describing different sets of modes which it can simultaneously use. For example, a terminal issuing two **CapabilityDescriptor** structures, one { {H.261, H.263}, {G.711, G.723.1, G.728} } as in the previous example, and the other { {H.262}, {G.711} }, means the terminal can also operate the ITU-T H.262 video codec, but only with the low-complexity ITU-T G.711 audio codec.
+
+Terminals may dynamically add capabilities during a communication session by issuing additional **CapabilityDescriptor** structures, or remove capabilities by sending revised **CapabilityDescriptor** structures. All ITU-T H.324 terminals shall transmit at least one **CapabilityDescriptor** structure.
+
+Non-standard capabilities and control messages may be issued using the **NonStandardParameter** structure defined in [ITU-T H.245]. Note that while the meaning of non-standard messages is defined by individual organizations, equipment built by any manufacturer may signal any non-standard message, if the meaning is known.
+
+Terminals may reissue capability sets at any time, according to the procedures of [ITU-T H.245].
+
+### 6.5.2 Logical channel signalling
+
+Each logical channel carries information from a transmitter to a receiver, and is identified by a logical channel number unique for each direction of transmission.
+
+Logical channels are opened and closed using the **OpenLogicalChannel** and **CloseLogicalChannel** messages and procedures of [ITU-T H.245]. When a logical channel is opened, the **OpenLogicalChannel** message fully describes the content of the logical channel, including media type, algorithm in use, ITU-T H.223 adaptation layer and any options, and all other information needed for the receiver to interpret the content of the logical channel. Logical channels may be closed when no longer needed. Open logical channels may be inactive, if the information source has nothing to send.
+
+Logical channels in this Recommendation are unidirectional, so asymmetrical operation, in which the number and type of information streams is different in each direction of transmission, is allowed. However, if a receiver is capable only of certain symmetrical modes of operation, it may send a receive capability set that reflects its limitations. Terminals may also be capable of using a particular mode in only one direction of transmission.
+
+Certain media types, including data protocols such as ITU-T T.120 and LAPM, and video carried over AL3, inherently require a bidirectional channel for their operation. In such cases, a pair of unidirectional logical channels, one in each direction, may be opened and associated together to form a bidirectional channel using the bidirectional channel opening procedures of [ITU-T H.245]. Such pairs of associated channels need not share the same logical channel number, since logical channel numbers are independent in each direction of transmission.
+
+#### 6.5.2.1 Channel muting
+
+Logical channels may be temporarily inactive. Such temporary inactivation (muting) should be indicated to the far-end terminal using the ITU-T H.245 miscellaneous indication **logicalChannelInactive**.
+
+The ITU-T H.245 miscellaneous indication **logicalChannelActive** should be used to indicate when a normal signal has resumed on the logical channel. These indications are intended to be used to inform the human user that the far end has muted or unmuted the channel.
+
+Before sending the **logicalChannelInactive** message, the transmitter should ensure that no data is sent on the logical channel.
+
+However, regardless of whether or not **logicalChannelInactive** or **logicalChannelActive** messages are received, receivers shall decode the contents of the logical channel normally.
+
+### 6.5.3 Mode preferences
+
+Receivers may request transmitters to send a particular mode using the ITU-T H.245 **RequestMode** message, which describes the desired mode. Except when in receipt of **multipointModeCommand**, transmitters may deny such requests, but should comply if possible.
+
+### 6.5.4 Interface to multiplex
+
+The control channel shall be segmentable and use logical channel 0. All ITU-T H.324 terminals shall support transmission of ITU-T H.245 control messages over the framed AL1 layer of ITU-T H.223 according to the procedures in Annex A, which ensure reliable delivery by retransmission of errored frames.
+
+Annex A defines a simple retransmission protocol (SRP) as a data link layer for ITU-T H.245. All ITU-T H.324 terminals shall support the SRP defined in Annex A. Terminals may optionally use LAPM/ITU-T V.42 as a data link layer instead of the SRP, if this mode is negotiated per the procedure in Annex A. In the LAPM/ITU-T V.42 mode, several control messages may be streamed using the procedures of LAPM, avoiding a wait for acknowledgement of each frame before the next message may be sent.
+
+More than one ITU-T H.245 control message may be sent in each SRP or LAPM frame.
+
+### 6.5.5 Timer and counter values and protocol errors
+
+All timers defined in [ITU-T H.245] shall have periods of at least the maximum data delivery time allowed by the data link layer carrying ITU-T H.245, including any retransmissions. For SRP, a period of at least $T401 \times (N400 + 1)$ [that is, acknowledgement timer $\times$ (retransmit counter + 1)].
+
+The ITU-T H.245 retry counter N100 should be at least 3.
+
+If an ITU-T H.245 protocol error occurs, the terminal may optionally retry the ITU-T H.245 procedure or may take other appropriate action, such as disconnection or reversion to analogue telephony, depending on predetermined configuration.
+
+### 6.5.6 Resolution of logical channel conflicts
+
+In the event of a conflict when requests to open logical channels are initiated at the same time, ITU-T H.324 terminals should follow the optional recommended procedure in clause C.4.1.3 of [ITU-T H.245] or clause C.5.1.3 of [ITU-T H.245], as appropriate.
+
+The master which experiences such a conflict shall reject the channel with a **masterSlaveConflict** reason. The slave which receives the **OpenLogicalChannelReject** message with the **masterSlaveConflict** reason should retry to open a logical channel with the media type most preferred by the master terminal, unless the master terminal has already opened a logical channel which suits the purpose intended by the slave terminal.
+
+## 6.6 Video channels
+
+All ITU-T H.324 terminals offering video communication shall support both the ITU-T H.263 and ITU-T H.261 video codecs, except that ITU-T H.320 interworking adapters (which are not terminals) do not have to support ITU-T H.263 (see clause 8.2). The ITU-T H.261 and ITU-T H.263 codecs shall be used without BCH error correction and without error correction framing. There are five standardized image formats: 16CIF, 4CIF, CIF, QCIF and SQCIF. Video may be supported in either one direction (transmit or receive) or both directions.
+
+CIF and QCIF are defined in [ITU-T H.261]. For the ITU-T H.263 algorithm, SQCIF, 4CIF and 16CIF are defined in [ITU-T H.263]. For the ITU-T H.261 algorithm, SQCIF is any active picture size less than QCIF, filled out by a black border, and coded in the QCIF format. For all these formats, the pixel aspect ratio is the same as that of the CIF format.
+
+NOTE 1 – The resulting *picture* aspect ratio for ITU-T H.263 SQCIF is different from the other formats.
+
+Table 1 shows which picture formats are required, and which are optional for ITU-T H.324 terminals which support video.
+
+**Table 1 – Picture formats for video terminals**
+
+| Picture format | Luminance pixels | Encoder | | Decoder | |
+|----------------|-----------------------------------|-------------------|--------------------------|-------------------|-------------------|
+| | | ITU-T H.261 | ITU-T H.263 | ITU-T H.261 | ITU-T H.263 |
+| SQCIF | 128 × 96 for ITU-T H.263 (Note 1) | Optional (Note 1) | Required (Notes 2 and 3) | Optional (Note 1) | Required (Note 2) |
+| QCIF | 176 × 144 | Required | Required (Notes 2 and 3) | Required | Required (Note 2) |
+| CIF | 352 × 288 | Optional | Optional | Optional | Optional |
+| 4CIF | 704 × 576 | Not defined | Optional | Not defined | Optional |
+| 16CIF | 1408 × 1152 | Not defined | Optional | Not defined | Optional |
+
+NOTE 1 – ITU-T H.261 SQCIF is any active size less than QCIF, filled out by a black border, coded in QCIF format.
+NOTE 2 – Optional for ITU-T H.320 interworking adapters.
+NOTE 3 – Mandatory to encode one of the picture formats QCIF and SQCIF; optional to encode both formats.
+
+All video decoders shall signal the maximum bit rate which can be decoded in the ITU-T H.245 **maxBitRate** parameter.
+
+Which picture formats, minimum number of skipped pictures and algorithm options can be accepted by the receiver is determined during the capability exchange using [ITU-T H.245]. After that, the transmitter is free to open any video LC which is in line with the receiver's capability. Receivers which indicate capability for a particular algorithm option shall also be capable of accepting video bitstreams which do not make use of that option as specified in [ITU-T H.245].
+
+When each video logical channel is opened, all supported operating modes for that channel are signalled to the receiver via [ITU-T H.245]. The picture header within the video bitstream indicates which mode is actually used for each picture, within the capabilities stated in the **OpenLogicalChannel** message. Receivers may signal, via [ITU-T H.245], a preference for a certain mode.
+
+NOTE 2 – In previous versions of this Recommendation, this paragraph was incorrect and inconsistent with [ITU-T H.245]. The semantics of [ITU-T H.245] shall be followed.
+
+Other video codecs, and other picture formats, may also be used via ITU-T H.245 negotiation. [ITU-T H.264] may optionally be used as a video codec, the signalling and procedures for the use of [ITU-T H.264] in ITU-T H.320 systems are defined in [ITU-T H.241]. [ITU-T H.264] represents an evolution of the existing video coding standards ([ITU-T H.261], [ITU-T H.262], and [ITU-T H.263]) and it was developed in response to the growing need for higher compression of moving pictures for various applications. More than one video channel may be transmitted, as negotiated via the ITU-T H.245 control channel.
+
+NOTE 3 – The method of continuous presence multipoint operation, in which a single picture is divided into multiple sub-pictures, should not be used by ITU-T H.324 terminals. Instead, multiple logical channels of video should be used.
+
+### 6.6.1 Interface to multiplex
+
+All ITU-T H.324 terminals offering video communication shall support the required video codecs in segmentable logical channels using ITU-T H.223 adaptation layer AL3, and using a control field of at least one octet. Support of retransmission is required in encoders, with a minimum AL3 **sendBufferSize** of 1024 octets.
+
+The size of each AL-SDU, and their alignment with the video bitstream, is determined by video encoders, within the limit of the maximum AL3 SDU size the receiver indicates it is capable of. Video pictures may span more than one AL-SDU. ITU-T H.261 AL-SDUs are not required to align with logical structures in the video bitstream. ITU-T H.263 encoders shall align picture start codes with the start of an AL-SDU.
+
+NOTE – ITU-T H.263 pictures are a whole number of octets in length, since encoders add fill zero bits at the end of each picture as needed to fill out the final octet.
+
+If video communication is supported only in one direction (transmit or receive), the ITU-T H.223 adaptation layer AL3 protocol for the reverse direction shall also be supported, even if no video information will be sent on the reverse channel. Since the AL3 protocol requires a reverse channel for operation, logical channels using AL3 shall be opened using the ITU-T H.245 procedures for opening associated logical channels in each direction of transmission (bidirectional channels).
+
+While ITU-T H.223 AL3 allows for the retransmission of video information with detected errors, the receiving terminal may decide not to request a retransmission, based on factors including, but not limited to, the measured network delay, the error rate, whether the terminal is part of a multipoint conference, whether there is interworking with an ITU-T H.320 terminal, and the effectiveness of its error concealment techniques.
+
+When a video codec receives an AL-DRTX indication from ITU-T H.223 AL3, indicating that the local AL3 layer was unable to satisfy a retransmission request, it should encode the next video picture in the INTRA coding mode.
+
+Other video codecs, adaptation layers and options may be used via ITU-T H.245 negotiation.
+
+#### **6.6.1.1 ITU-T H.263 reference picture selection mode support**
+
+Annex N of [ITU-T H.263], reference picture selection mode, may optionally be supported. In this mode, video backchannel messages may be mixed with the video data in the opposite direction according to [ITU-T H.263], or video backchannel messages may be carried on an additional separate logical channel.
+
+In the case where Annex N of ITU-T H.263 video backchannel messages are carried on a separate LC, the procedure to set up the LC for the video backward channel is different depending on whether the video communication is unidirectional or bidirectional.
+
+In the case of bidirectional video communication, the LCs for original video data shall first be opened as bidirectional LCs which shall support ITU-T H.223 AL3. The LCs for the video backchannel messages shall next be opened by the terminal which originated the video LCs. The backchannel LCs shall be opened as bidirectional LCs with the LC dependency parameters indicating dependency on the corresponding video LC flowing in the same direction. The backchannel LCs shall support ITU-T H.223 AL2. Until the backchannel LCs are established, the terminal shall not send any video data which requests backchannel messages.
+
+In the case of unidirectional video communication, a single bidirectional LC shall be opened, which shall support ITU-T H.223 AL3. Variable length stuffing (BSTUF), defined in [ITU-T H.263], shall be used to make all the backward channel messages whole numbers of octets in length.
+
+### **6.6.2 Multiple channels of video**
+
+More than one channel of video may be transmitted, as negotiated, via [ITU-T H.245].
+
+The procedures of [ITU-T H.239] may be used with ITU-T H.324 systems. These procedures should be used when more than one channel of video is in use, in order to indicate the role of each channel in a conference, for example, "live" video of conference participants or video of "presentation" materials.
+
+## 6.7 Audio channels
+
+All ITU-T H.324 terminals offering audio communication shall support both the high and low rates of the ITU-T G.723.1 audio codec. ITU-T G.723.1 receivers shall be capable of accepting silence frames. The choice of high rate low rate or silence is made by the transmitter, and is signalled to the receiver in-band in the audio channel, as part of the syntax of each audio frame. Transmitters may switch ITU-T G.723.1 rates on a frame-by-frame basis, based on bit rate, audio quality or other preferences. Receivers may signal, via [ITU-T H.245], a preference for a particular audio rate or mode. Audio may be supported in either one direction (transmit or receive) or both directions.
+
+Alternative audio codecs may also be used, via ITU-T H.245 negotiation. Coders may omit sending audio signals during silent periods after sending a single frame of silence, or may send silence background fill frames if such techniques are specified by the audio codec Recommendation in use.
+
+More than one audio channel may be transmitted, as negotiated via the ITU-T H.245 control channel.
+
+NOTE – Each audio channel is independent. Grouping of audio channels into stereo pairs or other synchronized groups is for further study.
+
+### 6.7.1 Delay compensation
+
+The ITU-T H.263 and ITU-T H.261 video codecs require some processing delay, while the ITU-T G.723.1 audio codec involves much less delay. Lip synchronization is not mandatory, but if it is to be maintained, additional delay must be added in the audio path to compensate.
+
+An ITU-T H.324 terminal shall not add delay for this purpose in its transmitting audio path. Instead, since video and audio coder delays may vary according to implementation, ITU-T H.324 terminals shall signal, via **H223SkewIndication** messages in the ITU-T H.245 control channel, the average skew by which their transmitted video signal trails the audio signal.
+
+Intermediate processing points such as MCUs or interworking adapters may alter the video/audio skew (see clause 10.3), and shall transmit appropriately modified video/audio skew indications, reflecting their transmitted streams. Video signals shall not precede audio signals; if necessary, video path delay shall be added to prevent this.
+
+Receiving terminals may optionally use this information to add appropriate delay in the audio path to achieve lip synchronization.
+
+### 6.7.2 Maximum delay jitter
+
+Audio AL-SDUs shall be transmitted periodically at an interval determined by the audio codec Recommendation in use (audio frame interval). The transmission of each audio AL-SDU at the ITU-T H.223 multiplex shall commence no later than 10 milliseconds after a whole multiple of the audio frame interval, measured from transmission of the first audio frame (audio delay jitter). Transmitters capable of further limiting their audio delay jitter may so signal using the ITU-T H.245 **maximumDelayJitter** parameter of the **H223Capability** message, so that receivers may optionally reduce their jitter delay buffers.
+
+### 6.7.3 Interface to multiplex
+
+All ITU-T H.324 terminals offering audio communication shall support the ITU-T G.723.1 codec using ITU-T H.223 adaptation layer AL2. The use of the sequence number option of AL2 is optional, but is not recommended for ITU-T G.723.1, since sequence numbers are generally not useful when the maximum delay jitter is less than the audio frame interval.
+
+For all frame-oriented audio codecs, AL-SDUs shall be transmitted in non-segmentable logical channels. Receivers shall signal the maximum number of audio frames they are capable of accepting in a single audio AL-SDU. Transmitters may send any whole number of audio frames in
+
+each AL-SDU, up to the maximum stated by the receiver. Transmitters shall not split audio frames across AL-SDUs, and shall send whole numbers of octets in each audio AL-SDU.
+
+NOTE 1 – Sample-based codecs, such as ITU-T G.711, shall be considered to be frame-oriented, with a frame size of one sample.
+
+For audio algorithms such as ITU-T G.723.1 which use more than one size of audio frame, audio frame boundaries within each AL-SDU shall be signalled in-band to the audio channel. For audio algorithms which use a fixed frame size, audio frame boundaries shall be implied by the ratio of AL-SDU size to audio frame size.
+
+Other adaptation layers and options may be used via ITU-T H.245 negotiation.
+
+NOTE 2 – Transmitters using alternative audio codecs should also support AL2, unless another adaptation layer has been specified for use with a particular codec.
+
+### 6.7.4 Use of [ITU-T G.722.1] for wideband audio
+
+[ITU-T G.722.1] may be used for wideband audio applications. ITU-T G.722.1 frames shall be sent using AL2. Audio frame boundaries within each AL-SDU shall be implied by the ratio of AL-SDU size to ITU-T G.722.1 frame size at the currently selected ITU-T G.722.1 bit rate.
+
+## 6.8 Data channels
+
+All data channels are optional. Standardized options for data applications include:
+
+- ITU-T T.120-series for point-to-point and multipoint audiographic teleconferencing including database access, still image transfer and annotation, application sharing, real-time file transfer, etc.;
+- ITU-T T.84 (SPIFF) point-to-point still image transfer cutting across application borders;
+- ITU-T T.434 point-to-point telematic file transfer cutting across application borders;
+- ITU-T H.224 for real-time control of simplex applications, including ITU-T H.281 far-end camera control;
+- network link layer, per [ISO/IEC TR 9577] (supports IP and PPP network layers, among others);
+- unspecified user data from external data ports;
+- ITU-T T.30 facsimile transfer;
+- ITU-T T.140 text conversation protocol.
+
+These data applications may reside in an external computer or other dedicated device attached to the ITU-T H.324 terminal through an ITU-T V.24 or equivalent interface (implementation-dependent), or may be integrated into the ITU-T H.324 terminal itself. Each data application makes use of an underlying data protocol for link layer transport. For each data application supported by the ITU-T H.324 terminal, this Recommendation requires support for a particular underlying data protocol to ensure interworking of data applications.
+
+NOTE – The ITU-T H.245 control channel is not considered a data channel.
+
+Standardized link layer data protocols used by data applications include:
+
+- buffered ITU-T V.14 mode for transfer of asynchronous characters, without error control;
+- LAPM/ITU-T V.42 for error-corrected transfer of asynchronous characters. Additionally, depending on application, ITU-T V.42 *bis* data compression may be used;
+- HDLC frame tunnelling for transfer of HDLC frames;
+- transparent data mode for direct access by unframed or self-framed protocols.
+
+All ITU-T H.324 terminals offering real-time audiographic conferencing should support the ITU-T T.120 protocol suite.
+
+All data protocols shall operate within ITU-T H.223 logical channels. All protocol procedures referring to link establishment or link termination (including set-up and disconnection of physical channels) shall be interpreted as referring to opening and closing of logical channels, and shall not affect the ITU-T H.324 physical link. For all protocol procedures which distinguish between an originator and an answerer, the ITU-T H.324 master terminal, determined according to the **MasterSlaveDetermination** procedure of [ITU-T H.245], shall be the originator, and the slave terminal shall be the answerer.
+
+More than one data channel, or more than one protocol, may be used at the same time (each in a separate logical channel), as negotiated via the ITU-T H.245 control channel. Other data protocols and applications may be used via ITU-T H.245 negotiation.
+
+### 6.8.1 Data protocols
+
+This clause describes these data protocols as if they are resident in the ITU-T H.324 terminal, connected through an ITU-T V.24 interface to an external computer or other dedicated device running the data application, as shown in Figure 2. The ITU-T V.24 interface may be replaced by a logical equivalent. ITU-T H.324 terminals with integrated data applications need not implement procedures related to the ITU-T V.24 interface which have no net effect on the transmitted bitstream.
+
+
+
+Figure 2: Data application – Data protocol interface. The diagram shows a flow from left to right: an 'External computer or other dedicated device' connected to a 'Data application' box. This box is connected via an 'ITU-T V.24' interface to an 'ITU-T H.324 terminal' box. Inside the terminal, the flow goes through a 'Data protocol' block and then a 'ITU-T H.223 multiplex' block. From the multiplex, the flow goes via another 'ITU-T V.24' interface to a 'Modem' box. Finally, the Modem is connected to a 'GSTN network' represented by a circle. A label 'H.324(09)\_F02' is present near the Modem to GSTN connection.
+
+**Figure 2 – Data application – Data protocol interface**
+
+ITU-T H.324 terminals offering any data protocol described here shall support that protocol using segmentable logical channels and ITU-T H.223 adaptation layer AL1, in the framed or unframed mode as specified below. Other ALs may be used if receivers indicate the capability to do so via ITU-T H.245 negotiation.
+
+#### 6.8.1.1 Buffered ITU-T V.14
+
+In the buffered ITU-T V.14 mode, asynchronous characters and BREAK signals arriving at the ITU-T V.24 interface shall be converted to a synchronous bitstream using the procedures of [ITU-T V.14]. Operation at the ITU-T V.24 interface shall use buffering and flow-control across the DTE-DCE interface as described in clause 7.9 of [ITU-T V.42] and clause 1.3 of [ITU-T V.14].
+
+The resulting bitstream shall be placed into the octets of an unframed AL1 AL-SDU, preserving the original bit ordering (least significant bit first). The unframed AL-SDU should be transferred to the underlying AL in a streaming mode without waiting for the end of the AL-SDU (which will never occur).
+
+If receipt of characters at the ITU-T V.24 interface pauses, the terminal may omit transmission of octets containing only stop bits (because the line is idle), after transmitting the octet containing the final character, plus at least two stop bits.
+
+The receiver shall perform the reverse operation.
+
+#### 6.8.1.2 LAPM/ITU-T V.42
+
+In the LAPM/ITU-T V.42 mode, asynchronous characters and BREAK signals arriving at the ITU-T V.24 interface shall be transferred to the far end using the procedures of [ITU-T V.42] in the LAPM mode. The alternative procedure of Annex A of [ITU-T V.42] is not required.
+
+The procedures of [ITU-T V.42] shall be followed, except that:
+
+- The flag sequence and transparency procedures of clause 8.1.1.2 of [ITU-T V.42] shall not be performed, as the ITU-T H.223 multiplex provides equivalent functions. Instead, the entire content of each frame between the opening and closing flags shall be placed in a single framed AL1 AL-SDU, without application of the zero-bit insertion transparency procedure.
+- The detection phase of [ITU-T V.42] shall be bypassed, proceeding directly to the protocol establishment phase.
+- Aborts shall be sent using the procedure of [ITU-T H.223], instead of the procedure in [ITU-T V.42].
+- Only frames shall be sent; interframe time filling flags shall not be sent.
+
+The receiver shall perform the reverse operations.
+
+If ITU-T V.42 *bis* data compression is to be used, it shall be negotiated in-band to the LAPM/ITU-T V.42 channel according to the procedures of [ITU-T V.42 *bis*].
+
+Since the LAPM/ITU-T V.42 protocol requires a reverse channel for operation, LAPM/ITU-T V.42 logical channels shall be opened using the ITU-T H.245 procedures for opening associated logical channels in each direction of transmission (bidirectional channels).
+
+ITU-T H.324 terminals declaring capability for LAPM/ITU-T V.42 in only one direction of transmission shall support the ITU-T V.42/LAPM protocol for the reverse direction, even if no payload data will be sent on the reverse channel.
+
+#### 6.8.1.3 HDLC frame tunnelling
+
+In the HDLC frame tunnelling mode, HDLC frames arrive at the ITU-T V.24 interface from the data application.
+
+If the ITU-T V.24 interface is operating synchronously, inserted zero bits shall be removed and the entire content of each frame between the opening and closing flags shall be placed in a single framed AL1 AL-SDU, for transmission through the ITU-T H.223 multiplex. Aborts shall be sent using the procedure of [ITU-T H.223]. Only frames shall be sent; flags (including interframe time filling flags) shall not be sent.
+
+If the ITU-T V.24 interface is operating asynchronously, HDLC frames arrive at the ITU-T V.24 interface encoded as a sequence of asynchronous characters using octet-stuffing according to clause 4.5.2 of [ISO/IEC 13239] instead of the usual zero-bit insertion transparency procedure of HDLC. This recognized alternative to the zero-bit insertion procedure makes the implementation of HDLC protocols over asynchronous serial links possible. Typical personal computer serial ports do not support synchronous operation, making this operation mode important. In particular, the PSTN basic mode profile of [ITU-T T.123] specifies this mode of operation.
+
+If operating asynchronously, the terminal shall receive HDLC frames at the ITU-T V.24 interface according to the procedure given in Annex B. After execution of the receiver procedure given there, the entire content of each frame between the opening and closing flags shall be placed in a single framed AL1 AL-SDU, without application of the zero-bit insertion or octet-stuffing transparency procedures, for transmission through the ITU-T H.223 multiplex. Aborts shall be sent using the procedure of [ITU-T H.223]. Only frames shall be sent; flags (including interframe time filling flags) shall not be sent.
+
+The receiver shall perform the reverse operation. The choice of asynchronous or synchronous ITU-T V.24 interface is a local matter and does not need to be signalled to the far end.
+
+NOTE – Since the HDLC octet-stuffing transparency procedure serves only to transport HDLC frames across an asynchronous interface, integrated terminals containing the HDLC protocol (ITU-T T.120, ITU-T H.224 or other) may omit the octet stuffing/unstuffing procedure, directly placing each HDLC frame in an AL-SDU, since the stuffing and unstuffing procedures cancel each other out inside the terminal. However, such integrated terminals shall still signal the HDLC frame tunnelling data protocol, for proper interworking with far-end terminals.
+
+#### **6.8.1.4 Transparent data**
+
+In the transparent data mode, octets arriving at the ITU-T V.24 interface shall be placed directly into the octets of an unframed AL-SDU, preserving the original bit ordering (least significant bit first). No framing or transparency procedure shall be applied. The unframed AL-SDU should be transferred to the underlying AL in a streaming mode without waiting for the end of the AL-SDU (which will never occur).
+
+The receiver shall perform the reverse operation.
+
+NOTE – The transparent data protocol may be considered equivalent to a variable-rate synchronous data channel, as it simply transports octets without any additional framing or protocol.
+
+### **6.8.2 Data applications**
+
+Data applications make use of an underlying data protocol, as described in the previous clause. This clause describes these data applications as if they are resident in an external computer running the application, connected through an ITU-T V.24 interface to the ITU-T H.324 terminal. The ITU-T V.24 interface may be replaced by a logical equivalent. Data applications integrated with the ITU-T H.324 terminal may choose to omit procedures related to the ITU-T V.24 interface which have no net effect on the transmitted bitstream.
+
+#### **6.8.2.1 ITU-T T.120 multimedia teleconferencing applications**
+
+The ITU-T T.120-series of Recommendations is for point-to-point and multipoint audiographic teleconferencing including database access, still image transfer and annotation, application sharing, real-time file transfer, etc.
+
+All ITU-T H.324 terminals offering real-time audiographic conferencing should support the ITU-T T.120 protocol suite.
+
+ITU-T H.324 terminals supporting ITU-T T.120 shall use the PSTN basic mode profile protocol stack specified in [ITU-T T.123], except that when arriving at the ITU-T V.24 interface from the ITU-T T.120 protocol implementation, the HDLC frame tunnelling data protocol described above shall be used. ITU-T H.324 terminals shall declare the ITU-T T.120 capability and mode if, and only if, they are compliant with this paragraph.
+
+Since ITU-T T.120 requires a reverse channel for operation, ITU-T T.120 logical channels shall be opened using the ITU-T H.245 procedures for opening associated logical channels in each direction of transmission (bidirectional channels).
+
+NOTE – ITU-T T.120 data can also be transported as unspecified user data, but this mode is discouraged, since ITU-T H.324 terminals will not be able to automatically negotiate use of ITU-T T.120 in this mode.
+
+#### **6.8.2.2 ITU-T T.84 (SPIFF) point-to-point still image transfer cutting across application borders**
+
+This application supports the point-to-point transfer of ITU-T T.84 (SPIFF – still picture interchange file format) still images (JPEG, JBIG or facsimile group 3/4 coded) through application borders (e.g., a digital photocamera connected through an ITU-T V.24 interface to the sending
+
+ITU-T H.324 terminal, and a digital photoprinter connected through another ITU-T V.24 interface to the receiving ITU-T H.324 terminal).
+
+The file exchange format to be used for ITU and ISO/IEC applications crosscutting application borders is defined in [ITU-T T.84].
+
+[ITU-T H.245] should be used for the determination of still image profiles supported by the end-applications and the selection of an appropriate profile.
+
+The data protocol used shall be LAPM/ITU-T V.42 as described in clause 6.8.1.2.
+
+NOTE – The ITU-T T.120 protocol series [ITU-T T.126] also performs still image transfer, among many other functions, within the framework of audiographic teleconferencing, and is preferred for such applications. [ITU-T T.84] is concerned with passing still images over one or more application borders using the ITU-T | ISO/IEC standardized common file-interchange format. The ITU-T T.84 (SPIFF) file exchange format is backwards compatible with JFIF, the predecessor "*de facto* standard" JPEG file format, widely used in PC applications and on the Internet. [ITU-T T.126] is also compatible with this file format.
+
+#### **6.8.2.3 ITU-T T.434 point-to-point telematic file transfer cutting across application borders**
+
+This application supports the point-to-point transfer of ITU-T T.434 defined telematic files through application borders (e.g., an intelligent memory card connected to the sending ITU-T H.324 terminal, and a computerized database connected through an ITU-T V.24 interface to the receiving ITU-T H.324 terminal).
+
+The data protocol used shall be LAPM/ITU-T V.42 as described in clause 6.8.1.2.
+
+NOTE – The ITU-T T.120 protocol series ([ITU-T T.127], which also uses [ITU-T T.434]) also performs file transfer, among many other functions, within the framework of audiographic teleconferencing, and is preferred for such applications. The ITU-T T.434 application is concerned with point-to-point passing of telematic files over one or more application borders without implementing the entire protocol set of the ITU-T T.120 series, which is indeed needed for file sharing among many users in a collaborative working environment.
+
+#### **6.8.2.4 ITU-T H.224 real-time control protocol for ITU-T H.281 far-end camera control**
+
+[ITU-T H.224] is for real-time simplex device control. The only currently standardized application is [ITU-T H.281] for far-end camera control.
+
+ITU-T H.324 terminals supporting ITU-T H.224 shall use the HDLC frame tunnelling protocol to transport HDLC frames. There shall be no more than one ITU-T H.224 channel in use, and references in [ITU-T H.224] to the LSD channel of [ITU-T H.221] shall be interpreted as referring to the ITU-T H.224 logical channel. The maximum transmission time requirements of [ITU-T H.224] shall be met, with the ITU-T H.224 logical channel considered as operating at 4800 bit/s, regardless of the actual bit rate of the channel.
+
+#### **6.8.2.5 Network link layer**
+
+The network link layer data application supports ISO network layer protocols defined by [ISO/IEC TR 9577], which include Internet Protocol (IP) and IETF point-to-point protocol (PPP), among others. The particular network layer protocol to be used shall be identified in ITU-T H.245 data application capability and data mode messages using the network layer protocol identifier (NLPID) as defined in [ISO/IEC TR 9577].
+
+For the NLPID application, the link layer which is defined for use with asynchronous GSTN modems shall be used. If this link layer uses HDLC framing, the HDLC frame tunnelling protocol shall be supported by the ITU-T H.324 terminal. Otherwise, the transparent data protocol shall be supported by the ITU-T H.324 terminal.
+
+NOTE – Use of the NLPID is extensively described in [IETF RFC 1490].
+
+#### 6.8.2.6 External data ports and unspecified user data
+
+All ITU-T H.324 terminals offering external data ports for transport of unspecified user data shall support both the buffered ITU-T V.14 data protocol mode and the HDLC frame tunnelling mode. Means shall be provided to configure the ITU-T H.324 terminal for ITU-T T.120 protocol on external data ports. If so configured, the HDLC frame tunnelling protocol and ITU-T T.120 capability and mode shall be used by the terminal.
+
+Other data protocols may optionally be used by ITU-T H.245 negotiation.
+
+#### 6.8.2.7 ITU-T T.30 facsimile
+
+This application supports document facsimile transmission according to Annex C of [ITU-T T.30], and is signalled by the **t30fax** data application codepoint in [ITU-T H.245]. The facsimile data channel shall be carried within an ITU-T H.223 logical channel using the AL1 adaptation layer in the segmentable mode. The data channel carrying the ITU-T T.30 protocol shall be opened using the bidirectional logical channel procedures of [ITU-T H.245].
+
+Error correction is inherent in the use of Annex C of [ITU-T T.30] for facsimile communication. Therefore, the HDLC frame tunnelling data protocol shall be used for ITU-T T.30 operation.
+
+NOTE – This ITU-T T.30 operation mode is the same as that used by [ITU-T T.39], and will interwork with ITU-T T.39 terminals in the MSVF mode. However, full conformance with [ITU-T T.39] involves additional requirements beyond those of this Recommendation.
+
+#### 6.8.2.8 ITU-T T.140 text conversation protocol
+
+This application supports text conversation according to [ITU-T T.140], and is signalled and implemented as described in Annex L.
+
+NOTE – In previous versions of this Recommendation, the **t140** data application codepoint in ITU-T H.245 was specified to signal the support of ITU-T T.140 using the AL1 transparent data protocol. This codepoint is no longer to be used for new implementations; instead, the method described in Annex L is to be used. It is believed that no implementations of this mode using the **t140** data application codepoint for signalling have been deployed.
+
+# 7 Terminal procedures
+
+The provision of the communication is made in the following steps:
+
+- Phase A: Call set-up of voiceband channel.
+- Phase B: Initial analogue telephony communication.
+- Phase C: Establishment of digital communication, modem training.
+- Phase D: Initialization.
+- Phase E: Communication.
+- Phase F: End of session.
+- Phase G: Supplementary services and call clearing.
+
+## 7.1 Phase A – Call set-up of voiceband channel
+
+The calling terminal shall request the connection according to procedures for analogue telephony, according to national standards.
+
+When a call is initiated by a terminal which is external to the modem (a separate physical item connected by an interface), the procedures of [ITU-T V.250] shall be used. Upon successful completion of call set-up, the ITU-T H.324 terminal shall proceed to phase B.
+
+## 7.2 Phase B – Initial analogue telephony communication
+
+### 7.2.1 ITU-T V.8 procedure
+
+When the procedures of [ITU-T V.8] are in use, phase B shall be bypassed, proceeding directly to phase C.
+
+### 7.2.2 ITU-T V.8 *bis* procedure
+
+When the procedures of [ITU-T V.8 *bis*] are in use, an optional phase B begins when the called party has answered. Phase B is normal analogue telephony voice mode. In this mode users have the opportunity to speak before proceeding to multimedia telephony.
+
+If the terminal is conditioned to go directly into digital communication mode, phase B shall be bypassed, proceeding directly to phase C. If the terminal is conditioned for initial analogue telephony voice mode, the terminal shall proceed to phase C when:
+
+- the user manually causes the terminal to initiate an ITU-T V.8 *bis* transaction; or
+- the terminal detects an initiation signal from the distant terminal.
+
+## 7.3 Phase C – Establishment of digital communication, modem training
+
+### 7.3.1 ITU-T V.8 procedure
+
+The terminal shall follow the call start-up procedure described in [ITU-T V.8]. The calling terminal should not transmit ITU-T V.8 calling tones CT or CNG, and should transmit calling tone CI. The answer terminal shall support ITU-T V.8 CM/JM exchanges, and shall transmit answer tone without waiting for call signals. ITU-T H.324 terminals should signal the "H.324" ITU-T V.8 call function (value 0x21), and shall not signal an ITU-T V.8 protocol category.
+
+If the ITU-T V.8 start-up procedure detects an ITU-T V.34 modem, the start-up procedure for that modem shall be followed. Upon completion of the modem start-up procedure and establishment of digital communication, the terminal shall proceed to phase D – Initialization.
+
+If the ITU-T V.8 procedure fails to detect an ITU-T V.34 modem, or the handshake and the establishment of the digital connection is not successful after a suitable period the calling terminal may, depending on predetermined configuration, go to telephony mode, disconnect the line, or go to another operating mode more suitable for the detected modem. Such other modes are outside the scope of this Recommendation.
+
+NOTE – The terminal shall wait for a suitable call set-up period, in addition to processing, signal detection and maximum round-trip delays, before deciding on further action.
+
+### 7.3.2 ITU-T V.8 *bis* procedure
+
+The terminal shall follow the call start-up procedure described in [ITU-T V.8 *bis*]. If the ITU-T V.8 *bis* procedure detects that the distant terminal is not capable of ITU-T V.8 *bis*, but is capable of ITU-T V.8, the phase C procedure for ITU-T V.8 (above) shall be followed. If the ITU-T V.8 *bis* procedure detects a distant ITU-T H.324 terminal supporting the capabilities desired for this call, the ITU-T V.34 start-up procedure shall be followed.
+
+Upon completion of the ITU-T V.8 *bis* procedures and establishment of digital communication, the terminal shall proceed to phase D – Initialization.
+
+NOTE – Some successful ITU-T V.8 *bis* transactions result in a return to telephony mode (phase B).
+
+If the ITU-T V.8 *bis* procedure fails, results in a return to analogue telephony, or the handshake and the establishment of the digital connection is not successful after the period specified in [ITU-T V.8 *bis*], the calling terminal may, depending on predetermined configuration, go to telephony mode, disconnect the line, or go to another operating mode more suitable for the detected modem. Such other modes are outside the scope of this Recommendation.
+
+## 7.4 Phase D – Initialization
+
+After digital communication has been established, a minimum of 16 HDLC flags shall be transmitted in order to ensure synchronization. Following this, system-to-system communication shall be initiated using the ITU-T H.245 control channel. Since no multiplex table entries have yet been sent to the receiver, initial control messages shall be sent using multiplex table entry 0.
+
+Terminal system capabilities are exchanged by transmission of the ITU-T H.245 **TerminalCapabilitySet** message. This capability PDU shall be the first message sent. The ITU-T H.245 **MasterSlaveDetermination** message shall also be sent at this time, in which the terminals exchange random numbers, according to the procedure in [ITU-T H.245], to determine the master and slave terminals. ITU-T H.324 terminals shall be capable of operating in both master and slave modes, and shall set **terminalType** to 128 and set **statusDeterminationNumber** to a random number in the range 0 to $2^{24} - 1$ . Only one random number shall be chosen by the terminal for each call, except in the case of identical random numbers, as described in [ITU-T H.245].
+
+If the initial capability exchange or master/slave determination procedures fail, these should be retried at least two additional times before the terminal abandons the connection attempt and proceeds to phase G.
+
+NOTE – For **terminalType**, the range from 0 to 127 is reserved for possible use by MCUs or other non-terminal devices which may need to be slave at all times, and the range 129 to 255 is reserved for possible use by MCUs or other non-terminal devices which may need to be master at all times.
+
+After these procedures are complete, and the far end's capabilities have been received, the procedures of [ITU-T H.245] may then be used to open logical channels for various information streams. Multiplex table entries may be sent before or after logical channels are opened, but information shall not be transmitted over a logical channel until the channel is open, and an appropriate ITU-T H.223 multiplex table entry has been defined.
+
+### 7.4.1 Exchange of video by mutual agreement
+
+The indication **videoIndicateReadyToActivate**, "video indicate ready-to-activate", is defined in [ITU-T H.245]. Its use is optional, but when used, the procedure shall be as follows:
+
+Terminal X has been set so that video is not transmitted unless, and until, the remote terminal has also indicated readiness to transmit video. Terminal X shall send the indication **videoIndicateReadyToActivate** when the initial capability exchange has been completed, but shall not transmit a video signal until it has received either **videoIndicateReadyToActivate** or incoming video.
+
+A terminal which has not been set in this optional way is not obliged to wait until receipt of **videoIndicateReadyToActivate** or video before initiating its video transmission.
+
+## 7.5 Phase E – Communication
+
+During a session, the procedures for changing logical channel attributes, capability, receive mode, etc., shall be carried out as defined in [ITU-T H.245].
+
+### 7.5.1 Rate changes and retrains
+
+During phase E communication, the modem may retrain or alter its rate of data transmission, with or without momentary disruption of data transmission and loss of data. Upon any such momentary disruption of data transfer, the terminal shall not restart phase D, but shall remain in phase E and execute the normal ITU-T H.324 error recovery procedures according to [ITU-T H.223].
+
+### 7.5.2 Involuntary disconnection
+
+Should the terminal detect involuntary, unrecoverable loss of modem communication, or of the underlying GSTN connection, the terminal shall immediately proceed to phase G, analogue telephony mode or line disconnection, bypassing phase F.
+
+## 7.6 Phase F – End of session
+
+Either terminal may initiate the end of the session. The initiating terminal shall use the following procedure:
+
+- 1) For each logical channel carrying video, it shall stop sending video at the end of a complete picture and then close the logical channel.
+- 2) It shall close all outgoing logical channels carrying data and audio.
+- 3) It shall transmit the ITU-T H.245 message **EndSessionCommand**, and then discontinue all ITU-T H.245 message transmissions. This message shall contain an indication to the far end regarding the mode the terminal will enter after the end of the session (disconnect line, analogue telephony, or other mode).
+- 4) On subsequent receipt of **EndSessionCommand** from the remote end, it shall proceed to phase G, except that if the initiating terminal indicated an intention to disconnect the line after the end of session, the terminal shall not wait for receipt of **EndSessionCommand** from the remote end, but shall proceed directly to phase G.
+
+A terminal receiving **EndSessionCommand** without first having transmitted it, shall:
+
+- a) if the initiating terminal's **EndSessionCommand** message indicated "disconnect line", optionally follow 3) above, then proceed to phase G;
+- b) otherwise, follow 3) above, then proceed to phase G. If possible, the responding terminal should proceed to the new mode indicated in the initiating terminal's **EndSessionCommand** message.
+
+## 7.7 Phase G – Supplementary services and call clearing
+
+If the terminal arrived at phase G by involuntary disconnection, it shall disconnect or revert to analogue telephony, depending on predetermined configuration.
+
+A terminal wishing to terminate a call shall first initiate the end of session procedure described in phase F.
+
+In phase G, the terminal should proceed as it indicated in the **EndSessionCommand** message. If it indicated a change to another digital communication mode, it shall begin the new mode at the equivalent of phase D. Otherwise, it shall initiate the clearance procedures defined in [ITU-T V.34], except that it shall not physically disconnect the GSTN connection if it indicated an intention to revert to analogue telephony mode.
+
+These procedures ensure that:
+
+- the distant terminal does not erroneously invoke a fault procedure;
+- the human user gets the right indications via tones and announcements from the network exchange;
+- relevant messages can be displayed for the human user by the terminal.
+
+### 7.7.1 Reset of ITU-T H.324 session
+
+In phase G, if both the terminal and the far end have the **sessionResetCapability**, defined in Annex J, in **Capability.genericControlCapability**, and the mode indicated in the **EndSessionCommand** message is **gstnOptions.v34H324**, the terminal shall reset the ITU-T H.324 session by moving immediately to phase D without changing communication mode and without disconnecting the
+
+physical connection. Before sending synchronization flags as indicated in phase D, the receiver of the **EndSessionCommand** message with **gstnOptions.v34H324** shall answer with the same message and then transmit one's complemented synchronization flags to distinguish the new session from the old one. The amount of one's complemented synchronization flags transmitted shall be at least 10 consecutive flags. The maximum number of one's complemented synchronization flags transmitted shall be equivalent to the number of synchronization flags possible to be sent in a period of 500 ms. If the initiator of the session reset procedure received one's complemented synchronization flags without receiving the **EndSessionCommand** message first, it shall start transmitting one's complemented synchronization flags of its own and proceed with the procedure.
+
+# 8 Interoperation with other terminals
+
+## 8.1 Speech only terminals
+
+ITU-T H.324 videophones shall support interoperation with analogue speech-only telephones.
+
+## 8.2 ITU-T H.320 multimedia telephone terminals over the ISDN
+
+Interoperation with multimedia telephone terminals over the ISDN [ITU-T H.320] can be provided by:
+
+- using on the ISDN an interworking adapter; or
+- using dual-mode (ISDN and GSTN) terminals on the ISDN.
+
+An ITU-T H.324/ITU-T H.320 interworking adapter is located at the interface between ISDN and GSTN signals. It transcodes the ITU-T H.223 and ITU-T H.221 multiplexes, and the content of control, audio and data logical channels between the ITU-T H.324 and ITU-T H.320 protocols.
+
+In order to ease communication between ITU-T H.324 and ITU-T H.320 terminals via interworking adapters, ITU-T H.324 terminals which support video shall support the ITU-T H.261 video codec in the QCIF picture format so that the additional delay of video transcoding can be avoided. When this mode is in use, interworking adapters shall insert and remove ITU-T H.261 and ITU-T H.263 BCH error correction and error correction framing as appropriate for each terminal type. ITU-T H.324 terminals shall respond to the ITU-T H.245 **FlowControlCommand**, so that transmitted ITU-T H.324 video streams can be matched to the ITU-T H.320 video bit rate in use by the ITU-T H.221 multiplex.
+
+Dual-mode (ITU-T H.320 and ITU-T H.324) terminals on the ISDN shall send ITU-T H.324 GSTN signals by the use of a "virtual modem", which generates and receives an ITU-T V.34 analogue signal encoded as an ITU-T G.711 audio bitstream over the ISDN.
+
+## 8.3 Multimedia telephone terminals over mobile radio
+
+It is expected that multimedia telephone terminals will also be used on mobile radio networks. Rate matching between wireless terminals and GSTN terminals can be achieved by the use of the ITU-T H.245 **FlowControlCommand**. Wireless operation is for further study.
+
+# 9 Optional enhancements
+
+## 9.1 Data facilities
+
+A terminal may have physical I/O ports for external telematic and other equipment, or there may be data applications within the terminal itself. Data transmission may be activated and deactivated by local action.
+
+When a logical channel is opened to carry data originating at a port, the **portNumber** parameter of the ITU-T H.245 **OpenLogicalChannel** message should contain the number of the relevant port, so
+
+that data on the logical channel may be routed to a corresponding port at the far end, if so desired by the far-end user. For example, in the case where a terminal has general purpose physical I/O ports intended for connection to telematic or other equipment, such ports might be labelled "1", "2", "3", etc., up to the number of actual ports.
+
+## 9.2 Encryption
+
+Encryption may optionally be used by ITU-T H.324 terminals. Encryption, including selection of algorithm and key exchange, shall conform to the procedures of [ITU-T H.233] and this Recommendation with the following modifications to the procedures defined in [ITU-T H.233]. The ability to support encryption shall be signalled by the presence of the **h233EncryptionTransmitCapability** and **h233EncryptionReceiveCapability** parameters of the **Capability** message of ITU-T H.245.
+
+In [ITU-T H.233], specific reference is made to [ITU-T H.221] in describing how encryption takes place. In applying ITU-T H.233 to ITU-T H.324 terminals, references to [ITU-T H.221], FAS and BAS channels therein shall be ignored and appropriate substitute Recommendations be taken from this subclause. Messages referred to as carried in the ITU-T H.221 ECS channel shall be re-interpreted as being carried within the **encryptionSE** parameter of the ITU-T H.245 **EncryptionCommand** or encryption initialization vector (EIV) logical channel, as specified below.
+
+### 9.2.1 EncryptionSE messages
+
+ITU-T H.233 session exchange (SE) messages shall be carried in the **encryptionSE** parameter of the ITU-T H.245 **EncryptionCommand** message. Since the ITU-T H.245 control channel is carried on a reliable data link layer using retransmission of errored frames, the error protection bits described in [ITU-T H.233] shall not be applied to SE messages.
+
+The ITU-T H.233 header for SE messages shall have the value binary 00000000, indicating an SE message in a single block, not followed by related blocks.
+
+The ITU-T H.233 media identifier value shall be binary 00000000, which shall indicate encryption of all logical channels except for the EIV and ITU-T H.245 control channels. The use of other values is for further study.
+
+NOTE – Non-standard encryption algorithms may be referenced in SE messages after associating a non-standard algorithm with an ITU-T H.233 algorithm identifier value using the **encryptionAlgorithmID** parameter of the **EncryptionCommand** message.
+
+### 9.2.2 Encryption initialization vector (EIV) channel
+
+The encryption initialization vector (EIV) logical channel is used for the transmission of ITU-T H.233 initialization vector (IV) messages.
+
+To ensure accurate synchronization of the IV messages with the ITU-T H.223 multiplex bitstream, the EIV channel is an independent logical channel which shall be non-segmentable, and shall use adaptation layer AL2 of the ITU-T H.223 multiplex. The entire IV message, exactly as defined in [ITU-T H.233], including error protection bits, shall be placed in a single AL-SDU. The sequence number option of AL2 shall not be used.
+
+Messages carried within the EIV channel shall retain the error protection mechanism of [ITU-T H.233].
+
+### 9.2.3 Encryption procedure
+
+The encrypter shall produce a pseudo-random bitstream (cipher stream) corresponding to all bits output by the ITU-T H.223 multiplex prior to insertion of flags and application of the HDLC zero-bit insertion procedure.
+
+When encryption is activated according to [ITU-T H.233], the ITU-T H.223 bitstream shall, prior to flag insertion and application of the HDLC zero-bit insertion procedure, be exclusive-ORed with the pseudo-random bitstream generated by the encrypter. However, the exclusive-OR procedure shall not be applied to the ITU-T H.223 header octet nor to the octets belonging to the ITU-T H.245 control channel or EIV channel, which shall all be passed transparently to the HDLC zero-bit insertion and flag insertion stage.
+
+For each transmitted ITU-T H.223 header octet or octet belonging to the EIV or control channels, eight bits shall be discarded from the pseudo-random bitstream generated by the encrypter. Nothing is discarded from the pseudo-random bitstream for transmitted flags or for bits added by the HDLC zero-bit insertion process.
+
+The receiver shall apply the reverse procedure.
+
+### 9.2.4 Encryption initialization vectors
+
+Once an encrypted session is in progress, the transmitter should periodically send new IV messages in order to limit the duration of repeated pseudo-random bitstream in the event of a collision with a previously used state of the pseudo-random bitstream generator. The frequency of these messages is left to the discretion of the implementer.
+
+As shown in Figure 3, new initialization vectors (IVs) take effect at the start of the next ITU-T H.223 MUX-PDU following the MUX-PDU containing an IV message. The old IV continues in effect through the entirety of the MUX-PDU containing the IV message, at the end of which any remaining pseudo-random bits generated using the old IV are discarded. In order for the receiver to have time to process the new IV before needing to use it, the transmitter shall wait a minimum time after sending the last octet of the IV message, as specified by the receiver's **h233IVResponseTime** capability, before starting transmission of the next MUX-PDU. If necessary, the transmitter shall send idle flags to meet the receiver's **h233IVResponseTime** requirement.
+
+NOTE – Definition, by the implementer, of an appropriate ITU-T H.223 multiplex table entry allows octets from other logical channels to follow an IV message within the same MUX-PDU so that no transmission bandwidth is squandered in meeting the receiver's IV processing delay requirement.
+
+
+
+Figure 3: Encryption IV synchronization diagram. The diagram shows a sequence of data units: Flag (F), Header octet (H), Logical channel octets (represented by a dashed line), and an Initialization Vector (IV). This is followed by another Flag (F), then a sequence of Flags (F, F, F), a Header octet (H), more Logical channel octets (dashed line), and a final Flag (F). Two arrows labeled 'MUX-PDU' point to the first and second header octets. A horizontal double-headed arrow labeled 'h233IVResponseTime' spans from the end of the IV message to the start of the second MUX-PDU. A vertical arrow labeled 'New IV takes effect here' points to the start of the second MUX-PDU. A legend at the bottom left defines 'F' as Flag, 'H' as Header octet, and '...' as Logical channel octets. The diagram is labeled 'H.324(09)\_F03' in the bottom right.
+
+**Figure 3 – Encryption IV synchronization**
+
+### 9.2.5 Error recovery
+
+In the event of line errors that cause flag emulation, flag erasure or erroneous HDLC zero-bit removal, it is possible that a newly received flag, signifying the end of the previous MUX-PDU, will not align with the octet boundaries of the preceding data. In order to maximize the resilience of the encryption system against synchronization loss under these circumstances, the decryptor should, for each new flag received, re-align its pseudo-random bitstream generator to the nearest octet boundary. This allows recovery from up to at least three zero-bit removal errors between valid flags, although it does not provide any protection against flag emulation or erasure.
+
+In the event that the receiver suspects that it has lost encryption synchronization, it shall send an **encryptionIVrequest** command, except that it should not re-send such commands at intervals less than the maximum expected round-trip response time.
+
+Upon receipt of an **encryptionIVrequest** command, the transmitter shall, at its earliest opportunity, send a new IV message, except that it should ignore **encryptionIVrequest** commands received within the minimum expected round-trip response time since sending the last IV message.
+
+## 9.3 Multilink
+
+[ITU-T H.226] describes a protocol for aggregation of data over multiple independent channels.
+
+Annex F defines the operation of ITU-T H.324 over multiple independent physical connections, aggregated together according to [ITU-T H.226] to provide a higher total bit rate. These connections may be GSTN circuits, or ISDN circuits as defined in Annex D. The use of both GSTN and ISDN connections in the same call is supported.
+
+Annex H defines the operation of H.324/M over up to eight independent physical connections, aggregated together according to the mobile multilink layer defined in that annex to provide a higher total bit rate. These connections are error-prone mobile channels, as defined in Annex C, all having the same transmission rate.
+
+# 10 Multipoint considerations
+
+ITU-T H.324 terminals may be used in multipoint configurations via interconnection through MCUs, as indicated in Figure 4 (note that cascaded MCU operation is for further study).
+
+
+
+The diagram illustrates a multipoint configuration. At the top center is a circle labeled 'MCU'. Below it, two more circles labeled 'MCU' are positioned. The left 'MCU' is connected to the top 'MCU' and to two ovals labeled 'Terminal'. The right 'MCU' is connected to the top 'MCU' and to two ovals labeled 'Terminal'. A small label 'H.324(09)\_F04' is located near the bottom right 'Terminal'.
+
+Figure 4 – Multipoint configuration diagram showing three MCUs and five Terminals.
+
+Figure 4 – Multipoint configuration
+
+## 10.1 Establishment of common mode
+
+MCUs may force terminals into a particular common mode of transmission by sending to the terminal a receive capability set listing only the desired mode of transmission. ITU-T H.324 terminals shall obey the **MultipointModeCommand** message of [ITU-T H.245].
+
+## 10.2 Multipoint rate matching
+
+Since the modems on each link in a multipoint configuration may be operating at different bit rates, MCUs may choose to send ITU-T H.245 **FlowControlCommand** messages to limit the transmitted bit rates to those which can be sent to receivers.
+
+## 10.3 Multipoint lip synchronization
+
+In a multipoint configuration, each terminal may be transmitting a different **H223SkewIndication** message for associated video and audio channels. To enable lip synchronization at receiving
+
+terminals, MCUs shall transmit accurate **H223SkewIndication** messages. MCUs may accomplish this by adding delay to equalize the audio/video skew for all transmitting terminals, or, when switching between broadcasting terminals, may transmit a new **H223SkewIndication** message reflecting the audio/video skew of the current broadcaster.
+
+## 10.4 Multipoint encryption
+
+In a multipoint configuration, the MCU is considered to be a trusted entity. Each port of the MCU encrypts/decrypts the ITU-T H.223 bitstream from the ITU-T H.324 terminal or MCU attached to that port as though it were an ITU-T H.324 terminal in accordance with clause 9.2.
+
+## 10.5 Cascaded MCU operation
+
+Multipoint operation in a cascaded MCU configuration is for further study.
+
+# 11 Maintenance
+
+## 11.1 Loopbacks for maintenance purposes
+
+Some loopback functions are defined in [ITU-T H.245] to allow verification of some functional aspects of the terminal, to ensure correct operation of the system and satisfactory quality of the service to the remote party. The message loopback off (**MaintenanceLoopOffCommand**) requires that all loopbacks currently in effect be turned off.
+
+### 11.1.1 Normal mode
+
+Normal (no loopback) operation mode is illustrated in Figure 5a.
+
+### 11.1.2 System loopback
+
+Operation in system loopback mode is for further study.
+
+### 11.1.3 Media loopback
+
+Media loopback operates at the analogue I/O interface (toward modem). Upon receiving the **mediaLoop** request as defined in [ITU-T H.245], loopback of the content of the selected logical channel shall be activated as close as possible to the analogue interface of the video/audio codec towards the video/audio codec, so that decoded and re-coded media content is looped, as indicated in Figure 5c. While in this mode, the terminal shall respond normally to received data, including ITU-T H.245 messages. Media loopback provides a subjective test of ITU-T H.324 operation through the far-end codec for human user evaluation. It should be used only on video and audio channels.
+
+This loopback is optional, and should be used only on logical channels opened using the bidirectional channel procedures of [ITU-T H.245].
+
+### 11.1.4 Logical channel loopback
+
+Logical channel loopback operates in the ITU-T H.223 multiplex (toward modem). Upon receiving the **logicalChannelLoop** request, each received ITU-T H.223 MUX-SDU for the specified logical channel shall be looped back to the transmitter on the corresponding reverse logical channel, as indicated in Figure 5d. While in this mode, the terminal shall respond normally to received data, including ITU-T H.245 messages.
+
+This loopback is optional, and should be used only on logical channels opened using the bidirectional channel procedures of [ITU-T H.245].
+
+
+
+Diagram a) Normal: Shows a standard system architecture. On the left, a camera and a monitor are connected to a 'Codec' block. The 'Codec' is connected to a 'Multiplex' block, which is in turn connected to a 'Modem' block. Arrows indicate the flow of data from left to right through the components.
+
+a) Normal
+
+
+
+Diagram b) System loopback: Shows the same architecture as (a), but with a loopback connection. An arrow branches off from the output of the 'Multiplex' block and loops back into its input, bypassing the 'Modem' block.
+
+b) System loopback
+
+
+
+Diagram c) Media loopback: Shows the same architecture as (a), but with a loopback connection. An arrow branches off from the output of the 'Codec' block and loops back into its input, bypassing both the 'Multiplex' and 'Modem' blocks.
+
+c) Media loopback
+
+
+
+Diagram d) Logical channel loopback: Shows the same architecture as (a). Inside the 'Multiplex' block, there are two dashed arrows pointing from the output back to the input. A legend indicates that one dashed arrow represents 'One logical channel only' and the other represents 'Other logical channels'.
+
+d) Logical channel loopback
+
+H.324(09)\_F05
+
+**Figure 5 – Loopback**
+
+# Annex A
+
+## Protocol stack for control channel
+
+(This annex forms an integral part of this Recommendation)
+
+This annex defines the data protocol stack for use with the ITU-T H.324 control channel.
+
+## A.1 General
+
+Figure A.1 shows the control channel protocol stack for use with this Recommendation.
+
+
+
+ITU-T H.245
+
+---
+
+SRP or LAPM/ITU-T V.42
+
+---
+
+ITU-T H.223 – Framed AL1
+ITU-T H.223 – MUX
+
+---
+
+Physical layer (ITU-T V.34 modem)
+
+---
+
+H.324(09)\_FA.1
+
+Figure A.1: Protocol stack for ITU-T H.324 control channel. The diagram shows four stacked layers: ITU-T H.245 at the top, followed by SRP or LAPM/ITU-T V.42, then ITU-T H.223 – Framed AL1 and ITU-T H.223 – MUX, and finally the Physical layer (ITU-T V.34 modem) at the bottom. Horizontal lines separate the layers. Below the stack is the label H.324(09)\_FA.1.
+
+**Figure A.1 – Protocol stack for ITU-T H.324 control channel**
+
+The control protocol of [ITU-T H.245] requires a reliable link layer for proper operation.
+
+Two means of transporting **MultimediaSystemControlMessage** messages are defined: simple retransmission protocol (SRP) frames and LAPM/ITU-T V.42 I frames. In the SRP mode, each SRP command frame must be acknowledged with an SRP response frame before the next command can be transmitted. In the LAPM/ITU-T V.42 mode, multiple frames may be sent in a streaming mode, before an acknowledgement is received for the first frame. All ITU-T H.324 terminals shall support the SRP mode, and shall use SRP as the ITU-T H.245 link layer upon initial communication. The LAPM/ITU-T V.42 mode is optional, and is preferred for use by complex terminals.
+
+In both cases, bits produced by the ITU-T X.691 encoding process shall be put into the octets of an information field, with the first bit generated going into the most significant bit (MSB) of the first octet, and progressing down to the least significant bit (LSB) of the last octet. One or more complete ITU-T H.245 **MultimediaSystemControlMessage** messages may be sent in each information field, to be transported in a single SRP or LAPM frame.
+
+When possible, multiple ITU-T H.245 messages should be sent in each single frame in order to reduce the number of round-trip message exchanges and frame header overhead.
+
+NOTE 1 – The specified ITU-T X.691 encoding process produces **MultimediaSystemControlMessage** messages which are each a multiple of 8 bits in length (see clause 10.1.3 of [ITU-T X.691]), so all messages begin on an octet boundary.
+
+ITU-T H.324 terminals capable of using LAPM/ITU-T V.42 as the control channel link layer shall so indicate by setting the **transportWithI-frames** parameter of the **H223Capability** structure true. Such terminals, upon receiving the corresponding indication from the far-end terminal, shall henceforth, and without further notification of intent, proceed to establish an error-corrected
+
+connection according to the procedures given in clause 6.8.1.2 and subsequently transmit control channel messages only using LAPM/ITU-T V.42 for the duration of the connection. The terminal shall, however, transmit a SRP response message in reply to any SRP command message received.
+
+The transition to LAPM/ITU-T V.42 mode shall take place regardless of the state of any ITU-T H.245 transactions in progress; any pending transactions shall proceed using LAPM/ITU-T V.42 for transfer of additional messages.
+
+NOTE 2 – Since the ITU-T H.245 control channel is not considered a data channel, ability to operate the control channel over LAPM/ITU-T V.42 is signalled only in the **transportWithI-frames** parameter of **H223Capability**, and is not signalled as a data protocol.
+
+## A.2 SRP mode
+
+All terminals shall support the transfer of **MultimediaSystemControlMessage** messages using SRP mode. Each SRP frame shall be placed in a single framed AL1 AL-SDU.
+
+NOTE – The procedures of the SRP mode are based on those of XID frame transfer in [ITU-T V.42].
+
+### A.2.1 SRP command frames
+
+SRP command frames, as shown in Figure A.2, shall be used to send ITU-T H.245 control messages. All fields shall be formatted as specified in [ITU-T H.223] (note that these formats are consistent with [ITU-T V.42]).
+
+
+
+| | | | |
+|---------------------|---------------------------------|---------------------------------------------------|-------------------|
+| Header
(1 octet) | Sequence
number
(1 octet) | Information field
(one or more ASN.1 messages) | FCS
(2 octets) |
+|---------------------|---------------------------------|---------------------------------------------------|-------------------|
+
+H.324(09)\_FA.2
+
+**Figure A.2 – Format of SRP command frames for MultimediaSystemControlMessage messages**
+
+The SRP command frame header octet shall have the value binary 11111001 (decimal 249). This may be considered equivalent to an HDLC address octet with the DLCI value 62, C/R bit set to 0, and EA bit set to 1.
+
+The sequence number shall be set arbitrarily by a terminal for the first SRP command frame sent and shall be incremented modulo 256 for each new SRP command frame sent. Retransmissions of the same SRP frame, sent according to the procedures below, shall not increment the sequence number, but shall use the same sequence number as the original transmission, so that receivers can distinguish between separate valid messages and retransmissions of a single message (possibly sent in error if the original SRP response frame was lost).
+
+The information field shall contain a whole number of octets, not to exceed 2048 octets, representing one or more ITU-T H.245 **MultimediaSystemControlMessage** messages. The procedure specified by [ITU-T X.691] shall be used to fill any spare bits in the last octet.
+
+The FCS field shall contain a 16-bit CRC, applied to the entire frame content, as described in clause 8.1.1.6.1 of [ITU-T V.42].
+
+### A.2.2 SRP response frames
+
+SRP response frames shall be used to acknowledge correct receipt of SRP command frames from the far end. Each SRP response frame shall consist of a header octet and FCS field only, and shall not contain any other fields.
+
+The SRP response frame header octet shall have the value binary 11111011 (decimal 251). This may be considered equivalent to an HDLC address octet with the DLCI value 62, C/R bit set to 1, and EA bit set to 1.
+
+The FCS field shall contain a 16-bit CRC, applied to the entire frame content, as described in clause 8.1.1.6.1 of [ITU-T V.42].
+
+### **A.2.3 SRP procedure at transmitter**
+
+The SRP procedure makes use of an acknowledgement timer T401 and retransmission counter N400.
+
+The period of T401 is a local matter; the two terminals may operate with different periods of T401. Appendix IV of [ITU-T V.42] shows the various factors that influence T401.
+
+The maximum value of N400 is a local matter; the two terminals may operate with different maximum values of N400. While no default maximum is specified for N400, it should be at least 5.
+
+When the terminal transmits a new SRP command frame, timer T401 shall then be started and the retransmission counter, N400, reset. No additional SRP command frames shall be sent until a response SRP frame with correct header and FCS is received, or timer T401 expires.
+
+If a valid SRP response frame is received, a new SRP command frame, with an incremented sequence number, may be transmitted.
+
+If timer T401 expires before receipt of a valid SRP response frame, the terminal shall:
+
+- retransmit the SRP command (with the same sequence number) as above;
+- restart timer T401; and
+- increment the retransmission counter (N400).
+
+After retransmission of the SRP command N400 times and failure to receive a valid SRP response, the terminal shall consider modem communication to be lost, and take appropriate action.
+
+### **A.2.4 SRP procedure at receiver**
+
+On receipt of an SRP command frame with correct header and FCS, the receiving terminal shall acknowledge by transmitting an SRP response frame within 500 milliseconds.
+
+If the received SRP command frame has the same sequence number as the previously received command frame, it shall not be passed to the ITU-T H.245 layer, since it is a retransmission of an already-processed command.
+
+Receipt of all other frames shall be ignored, except that if the terminal has signalled ability to operate in LAPM/ITU-T V.42 mode, the receiver shall check the DLCI value of the received frame header. If the DLCI value matches that specified for use in the LAPM/ITU-T V.42 mode, the terminal shall respond according to the procedures of LAPM/ITU-T V.42, as described below.
+
+### **A.2.5 Numbered SRP response frames (NSRP)**
+
+The standard SRP response frame does not include a sequence number, which can result in transmitter uncertainty as to which SRP command frame is being acknowledged. Therefore, this optional numbered SRP response frame (NSRP) procedure is strongly preferred. Use of the NSRP allows smaller values of T401 and more reliable control channel operation.
+
+Each NSRP response frame, as shown in Figure A.3, shall consist of a header octet, sequence number and FCS field.
+
+
+
+| | | |
+|---------------------|---------------------------------|-------------------|
+| Header
(1 octet) | Sequence
number
(1 octet) | FCS
(2 octets) |
+|---------------------|---------------------------------|-------------------|
+
+H.324(09)\_FA.3
+
+**Figure A.3 – Format of NSRP response frame**
+
+The NSRP response frame header octet shall have the value binary 11110111 (decimal 247). This may be considered equivalent to an HDLC address octet with the DLCI value 61, C/R bit set to 1, and EA bit set to 1. The FCS field shall contain a 16-bit CRC, applied to the entire frame content, as described in clause 8.1.1.6.1 of [ITU-T V.42].
+
+Terminals supporting NSRP shall signal this capability via [ITU-T H.245].
+
+Terminals which support the NSRP mode shall transmit SRP response frames until receipt of the NSRP capability in [ITU-T H.245]. After that time, only NSRP response frames shall be sent to acknowledge received SRP command frames.
+
+Terminals shall accept received SRP response frames until receipt of the first NSRP response frame. After that time, only NSRP response frames shall be accepted.
+
+All other SRP procedures are as described in previous clauses.
+
+## A.3 LAPM/ITU-T V.42 mode
+
+Terminals may optionally support the transfer of **MultimediaSystemControlMessage** messages using LAPM/ITU-T V.42.
+
+SRP frames shall be used to transfer **MultimediaSystemControlMessage** messages before LAPM/ITU-T V.42 transmission is initiated but shall not be used for this purpose after LAPM/ITU-T V.42 transmission has been used.
+
+In the LAPM/ITU-T V.42 mode, the information field, as defined for the SRP mode above, shall be placed into a single LAPM/ITU-T V.42 I-frame and transferred using procedures of LAPM/ITU-T V.42, as described in clause 6.8.1.2, except that the procedures for opening logical channels shall not be used, as the control channel is considered already open at the start of digital communication.
+
+The address field shall be one octet with the 6-bit DLCI field set to binary 111111 (decimal 63).
+
+ITU-T V.42 *bis* data compression should not be used.
+
+Default values for all ITU-T V.42 parameters shall be as specified in [ITU-T V.42], except for N401, maximum number of octets in an information field, which shall have a default value of 2048 octets, in order to accommodate large capability sets.
+
+## A.4 WNSRP control frame signalling on the control channel
+
+Windowed NSRP (WNSRP) control frames shall be assigned to the control channel with LCN 0 using multiplex table entry 15.
+
+For backward compatibility reasons, SRP/NSRP command and response frames, depending on the involved multiplexer level, are the only control frames sent using multiplex table entry 0 before receiving any indication from the remote terminal regarding its capabilities.
+
+A receiver terminal that does not support multiplex table entry 15 from the beginning of the call shall ignore it as stated in clause 6.4.1.1 of [ITU-T H.223]. Furthermore, a receiver terminal receiving a control frame using multiplex table entry 15 with a header it does not recognize shall ignore that frame.
+
+### A.4.1 WNSRP command frames
+
+The WNSRP command frame format is the same as that of an SRP command frame except that the WNSRP command frame header octet shall be 11110001 (decimal 241).
+
+
+
+| | | | |
+|---------------------|---------------------------------|---------------------------------------------------|-------------------|
+| Header
(1 octet) | Sequence
number
(1 octet) | Information field
(one or more ASN.1 messages) | FCS
(2 octets) |
+|---------------------|---------------------------------|---------------------------------------------------|-------------------|
+
+H.324(09)\_FA.4
+
+**Figure A.4 – Format of WNSRP command frames for
+MultimediaSystemControlMessage messages**
+
+The standard SRP command frame does not allow the use of the sequence number for a window of SRP commands, which causes each SRP command frame to be acknowledged using a full round-trip. During call set-up, the number of control messages passed between the terminals can reach more than 5, which accounts for too many round-trips for call set-up. Use of the WNSRP allows reduction of the sequential round-trips needed by parallelizing them.
+
+Terminals supporting WNSRP shall support the following additional capabilities:
+
+- Terminals do not signal this capability via [ITU-T H.245].
+- For WNSRP mode detection, terminals shall transmit WNSRP command frames using multiplex table entry 15 until the receipt of the first incoming WNSRP response or command frame. After switching to WNSRP mode, all WNSRP control frames shall be sent using multiplex table entry 0.
+- Terminals shall transmit both SRP command frames and WNSRP command frames until the receipt of the first incoming WNSRP response or command frame, in which case they shall stop sending SRP command frames and switch to the WNSRP mode only.
+- Received SRP command frames shall always be acknowledged using SRP/NSRP response frames.
+- Terminals shall have an additional mode counter N402. The maximum value of this mode counter is a local matter; the two terminals may operate with different mode counters. The minimal value of this mode counter N402 shall be 1. On receipt of an SRP or NSRP response, frame N402 shall be incremented.
+- Terminals that do not receive WNSRP response or command frames, but receive N402 number of SRP or NSRP response frames, shall stop sending WNSRP command frames and use SRP or NSRP only.
+- The sequence number used for the first SRP and WNSRP command frames shall be zero and shall be incremented by modulo 256 for each new SRP and WNSRP command frame sent. This allows sending of multiple WNSRP command frames from the beginning of the call.
+- Terminals that switched to WNSRP mode cannot revert back to using SRP or NSRP.
+
+### A.4.2 WNSRP response frames
+
+The WNSRP response frame format is the same as that of an NSRP response frame except that the WNSRP response frame header octet shall be 11110011 (decimal 243).
+
+WNSRP response frames shall be used to acknowledge correct receipt of WNSRP command frames from the far end.
+
+
+
+| | | |
+|---------------------|---------------------------------|-------------------|
+| Header
(1 octet) | Sequence
number
(1 octet) | FCS
(2 octets) |
+|---------------------|---------------------------------|-------------------|
+
+H.324(09)\_FA.5
+
+**Figure A.5 – Format of WNSRP response frame**
+
+After switching to WNSRP mode, the terminal shall stop transmitting SRP command frames and start transmitting one or more WNSRP command frames without waiting for the response of the previous transmitted frame. Each transmitted WNSRP command frame shall make use of an acknowledgement timer T401 and a retransmission counter N400.
+
+### A.4.3 WNSRP procedure at the transmitter
+
+The WNSRP procedure makes use of the same acknowledgement timer T401 and the retransmission counter N400 that are used for the SRP procedure in clause A.2.3.
+
+The period of T401 is a local matter; the two terminals may operate with different periods of T401. Appendix IV of [ITU-T V.42] shows the various factors that influence T401.
+
+The maximum value of N400 is a local matter; the two terminals may operate with different maximum values of N400. While no default maximum is specified for N400, it should be at least 5.
+
+Each WNSRP command frame shall be associated with its own acknowledgement timer T401 and a retransmission counter N400.
+
+When the terminal transmits a new WNSRP command frame, timer T401 shall then be started for that specific command frame and the retransmission counter, N400, reset.
+
+A new WNSRP command frame can be sent by incrementing the sequence number, without the need to wait for a WNSRP response frame on pending WNSRP command frames.
+
+The transmitter shall store each WNSRP command frame until it receives the WNSRP response frame that acknowledges its receipt.
+
+If a valid WNSRP response frame is received for a WNSRP command frame, the associated timer T401 shall be stopped.
+
+If timer T401 expires before receipt of a valid WNSRP response frame for a given WNSRP command frame, the terminal shall:
+
+- retransmit the WNSRP command (with the same sequence number) as above;
+- restart timer T401; and
+- increment the retransmission counter (N400).
+
+On receipt of a WNSRP response frame, the terminal shall:
+
+- retransmit any WNSRP command that was created before the acknowledged WNSRP command frame;
+- restart timer T401 for the retransmitted WNSRP commands; and
+- increment the retransmission counter (N400) for the retransmitted WNSRP commands.
+
+NOTE – This retransmission reduces the timeout on WNSRP command frames that the transmitter knows it will not get acknowledgements for.
+
+After retransmission of the WNSRP command N400 times and failure to receive a valid WNSRP response, the terminal shall consider modem communication to be lost, and take appropriate action.
+
+### **A.4.4 WNSRP procedure at the receiver**
+
+On receipt of a WNSRP command frame with correct header and FCS, the receiving terminal shall acknowledge by transmitting a WNSRP response frame.
+
+If the received WNSRP command frame has the same sequence number as the previously received command frame, it shall not be passed to the ITU-T H.245 layer, since it is a retransmission of an already-processed command.
+
+If the received WNSRP command frame has a sequence number that is higher than the expected sequence number, the receiver shall store the WNSRP command frame until the receipt of the expected sequence number frame(s) and only then forward the stored WNSRP command frame to the ITU-T H.245 layer. If the receiver cannot store the WNSRP command frame (because its window is too small or because of low memory) it shall ignore the WNSRP command frame and shall not send an acknowledgement for the ignored WNSRP command frame.
+
+On receipt of the first SRP command frame with a sequence number other than zero, the terminal shall consider the call as a call without WNSRP and revert to using SRP or NSRP.
+
+# Annex B
+
+## HDLC frame structure transparency for asynchronous transmission
+
+(This annex forms an integral part of this Recommendation)
+
+When operating in the HDLC frame tunnelling mode, the ITU-T H.324 terminal shall implement at the asynchronous ITU-T V.24 interface the following procedures taken from clause 4.5.2 of [ISO/IEC 13239].
+
+The control escape octet is a transparency identifier that identifies an octet occurring within a frame to which the following transparency procedure is applied. The encoding of the escape octet is given in Figure B.1.
+
+
+
+| | | | | | | | |
+|---|---|---|---|---|---|---|---|
+| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
+| 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 |
+
+Complemented bit —————↑
+H.324(09)\_FB.1 ↑ First bit transmitted
+
+Diagram of the control escape octet for HDLC frame tunnelling procedure. It shows an 8-bit octet: 01111101. Bit 8 is 0, bits 7-4 are 1, bit 3 is 1, bit 2 is 0, and bit 1 is 1. An arrow labeled 'Complemented bit' points to bit 6 (the second '1'). An arrow labeled 'First bit transmitted' points to bit 1 (the last '1'). The text 'H.324(09)\_FB.1' is below the diagram.
+
+**Figure B.1 – Control escape octet for HDLC frame tunnelling procedure**
+
+The transmitter shall examine the frame content between the opening and closing flag sequences (01111110) including the address control and FCS fields and, following completion of the FCS calculation, shall:
+
+- upon the occurrence of the flag or a control escape octet, complement the 6th bit of the octet; and
+- insert a control escape octet immediately preceding the octet resulting from the above prior to transmission.
+
+The receiver shall examine the frame content between the two flag octets and shall, upon receipt of a control escape octet and prior to FCS calculation:
+
+- discard the control escape octet; and
+- restore the immediately following octet by complementing its 6th bit.
+
+Other octet values may optionally be included in the transparency procedure by the transmitter.
+
+# Annex C
+
+# Multimedia telephone terminals over error-prone channels
+
+(This annex does not form an integral part of this Recommendation)
+
+## C.1 Abstract
+
+This annex describes specific issues to allow the use of ITU-T H.324 terminals in error-prone transmission environments. These issues include specific options for ITU-T H.324 terminals, e.g.:
+
+- the mandatory use of NSRP;
+- the use of robust versions of the terminal multiplexer (several different levels of robustness are provided);
+- procedure for level set-up;
+- procedure for dynamic change between levels during a session.
+
+## C.2 General
+
+This annex describes multimedia terminals that use a robust multiplexing procedure to improve operation over error-prone channels. In this annex, terminals supporting robust multiplexing will be referred to as "mobile terminals". Except as noted below, all features of ITU-T H.324 terminals apply to these terminals. Four different multiplexer levels are described, offering progressively increased robustness at the cost of progressively increased overhead and complexity.
+
+- ITU-T H.223 level 0: This term is used to describe [ITU-T H.223].
+- ITU-T H.223 level 1: Described in Annex A of [ITU-T H.223]. The HDLC flag in ITU-T H.223 used to delimit MUX-PDUs in Level 0 is replaced with a longer flag that leads to improved MUX-PDU synchronization. HDLC bit stuffing is not used. The control channel segmentation and reassembly layer (CCSRL) is introduced for the transmission of the control channel. The transmitter side shall take necessary precautions to prevent possible flag emulation for the control channel. Flag emulation can be prevented, e.g., by detecting N 16-bit flags in each MUX-SDU for the channel and by breaking the SDU into N+1 segments. This may also apply to data channels.
+- ITU-T H.223 level 2: Described in Annex B of [ITU-T H.223]. Includes the features of Annex A of [ITU-T H.223]. In addition, the header describing the MUX-PDU contents includes error protection.
+- ITU-T H.223 level 3: Described in Annex C of [ITU-T H.223]. Includes the features of Annex B of [ITU-T H.223]. In addition, error protection and other features are provided to increase the protection of the AL-PDUs. Described in Annex D of [ITU-T H.223] as an optional definition of Annex C of [ITU-T H.223].
+
+In addition to the hierarchy offered by the level structure, some of the multiplex levels contain options.
+
+If the terminal is connected to an octet-oriented network interface, the transmitter shall align the first transmitted bit to the network octet timing. Note that the MUX-PDU of ITU-T H.223 level 1 and higher levels have an octet-aligned structure. Therefore, the receiver may use the octet timing information from the network interface to detect the start of a MUX-PDU to reduce the mis-synchronisation.
+
+Mobile terminals shall support the NSRP and the SRP mode of Annex A. If both terminals start the session in level 0 initially, the SRP mode shall be used. Otherwise, both terminals shall start with NSRP mode.
+
+If both terminals in a session support level 3 of [ITU-T H.223], then adaptation layers AL1M, AL2M, and AL3M as defined in level 3 of [ITU-T H.223] may also be used in Annexes A and B of [ITU-T H.223] (levels 1 and 2). However, bidirectional channels shall use either the ITU-T H.223 adaptation layers or the Annex C of [ITU-T H.223] adaptation layers for level 3 of [ITU-T H.223], but not a mixture of the two.
+
+It is possible that the level may differ in the two directions of a session.
+
+## **C.3 Changes to procedures**
+
+The procedures to be used when making and using a mobile terminal based on a robust multiplexing protocol are exactly the same as those for this Recommendation with the following exceptions:
+
+- Mobile terminals may be implemented with any appropriate wireless interface in place of the ITU-T V.34 modem. The specification of this interface is not within the scope of this annex. All references to the "ITU-T V.34 modem" in this Recommendation shall for wireless terminals be replaced with "wireless interface".
+- If ITU-T V.34 is not used, ITU-T V.8 shall not be used.
+- All ITU-T H.324 terminals should support Annex C of [ITU-T G.723.1].
+
+## **C.4 Interworking**
+
+Since all mobile terminals support ITU-T H.223 level 0, no interworking function is needed when communicating with an ITU-T H.324 terminal that does not support any of the robust multiplexing annexes (Annexes A, B, C and D of [ITU-T H.223]).
+
+## **C.5 Terminal procedures**
+
+The steps for provision of communication are as listed in clause 7, with the following modifications:
+
+- Depending on the access procedures to be used for wireless telephony, phase A and phase B may be bypassed.
+- Phase C: The terminal shall establish digital communications using local standards.
+- Phase D: The value of timer T401 shall be defined using the procedures in Annex E. The transmission of 16 consecutive HDLC flags is replaced with the level set-up procedure defined in clause C.6.
+- Phase G: If the terminal arrived at phase G by involuntary disconnection, it shall disconnect or revert to the set-up procedures in phases A and C, depending on predetermined configuration.
+
+## **C.6 Initialization of multiplex level at the start of a session**
+
+All mobile terminals based on this Recommendation support level 0. However, if two terminals want to establish connection in an error-prone environment, it is more likely that this will succeed in the higher levels.
+
+This set-up procedure describes a method for achieving the highest level supported by both terminals. It is used after the physical line has been established and before any capability exchange (phase D) for both terminals take place. This procedure is not used in ITU-T H.223 level 0; however, it shall be used in all terminals which support level 1 or higher, unless outband signalling for this purpose is available. The use of out-of-band signalling is for further study.
+
+### C.6.1 Definition of stuffing sequences
+
+The level set-up procedure shall use the stuffing methods described in the appropriate Recommendations as listed in Table C.1. The stuffing sequences are also used when the entire ITU-T H.223 multiplex is limited by the **FlowControlCommand**.
+
+**Table C.1 – Definition of stuffing sequences according to Recommendations**
+
+| Level | Stuffing sequence | Comments |
+|-------|------------------------------------------------------------------------------|-------------------------------------|
+| 0 | Consecutive HDLC flags | See clause 6.3.1 of [ITU-T H.223] |
+| 1 | Consecutive PN flags | See clause A.2.1.1 of [ITU-T H.223] |
+| 2 | Consecutive combination of PN flag + header field (MC = 0000, MPL = 0000000) | See clause B.3.2.3 of [ITU-T H.223] |
+| 3 | Consecutive combination of PN flag + header field (MC = 1111, MPL = 0000000) | See clause C.3.1 of [ITU-T H.223] |
+
+### C.6.2 Definition of level set-up procedure
+
+Each terminal shall start transmitting the stuffing sequence of its highest supported level. The terminal shall also search for the stuffing sequences at its receiving entity until it recognizes that the other terminal also supports either:
+
+- a) the same level; or
+- b) a lower level.
+
+If the other terminal supports the same level, the procedure described in phase D of the call set-up procedure in this Recommendation shall be used.
+
+If the terminal detects a stuffing sequence of a level that is lower than its own highest supported level, it shall immediately change the stuffing sequence of its transmitting entity according to the detected lower level. This ensures that all sessions will be initialized with both terminals operating at the same level. Then the terminals shall continue with the procedure described in phase D of the call set-up procedure in this Recommendation.
+
+Each terminal shall start searching for the stuffing sequence of level 0 first. It should be noted that ITU-T H.223-compliant terminals will send a sequence of at least 16 consecutive HDLC flags.
+
+For improving reliability, the receiving entity may only detect a stuffing sequence if it was sent $n$ times, e.g., $n = 5$ . However, this is only valid for the level set-up procedure.
+
+The stuffing mode shall be determined entirely by the multiplex level, and has no dependence on the adaptation layer used.
+
+If both terminals start with level 3, the stuffing mode of Annex C of [ITU-T H.223] shall be used, even if one channel is opened in AL1, AL2 or AL3.
+
+### C.6.3 Definition of the parameters for the control channel
+
+After both terminals are running in the same level, the highest supported level is known for both terminals. For achieving a very error-robust control channel (logical channel 0), the control channel shall be defined according to the highest level (see Table C.2).
+
+The CCSRL defined in this annex shall be used by all mobile levels to transport the control channel.
+
+**Table C.2 – Definition of the parameters of the control channel according to the level**
+
+| Level | Definition of the parameters | Comments |
+|-------|-----------------------------------------------------------------------------------------------------------------------------------------------------|----------|
+| 0 | The same as in clause 6.5.4 | |
+| 1 | The same as in clause 6.5.4, except that NSRP or LAPM/ITU-T V.42 as defined in Annex A shall be used, and CCSRL defined in this annex shall be used | |
+| 2 | The same as level 1 | |
+| 3 | The same as level 1 | |
+
+This configuration shall not be changed during the entire session even if the levels for the other channels are changed to lower levels.
+
+### C.6.4 Definition of other parameters
+
+The minimum size of the send buffer, $B_s$ , for AL1M and AL3M shall be set to 4096 octets.
+
+## C.7 Dynamic change of level or option during session
+
+The procedure described below for changing multiplex options during a session assumes that a capabilities exchange has taken place between a receiver (terminal A) and a transmitter (terminal B), and that an ITU-T H.245 command for a level change will be sent by the receiver terminal to the transmitter terminal. A terminal, which has the capability to change ITU-T H.223 multiplex levels or options during a session, shall set **modeChangeCapability** in **mobileOperationTransmitCapability** to true. Levels and options supported by the terminal are indicated using the codepoint in **mobileOperationTransmitCapability**.
+
+A terminal, which has the above capability and has received the ITU-T H.245 message with **modeChangeCapability** of true, may start the ITU-T H.223 mode change procedure, illustrated in Figure C.1. Only levels supported by both terminals may be commanded. Note that the "replacementFor" procedure described in [ITU-T H.245] may be used when changing from a mobile adaptation layer (ALXM) to a regular ITU-T H.223 adaptation layer (ALX) or vice versa.
+
+The recommended procedure for changing levels and level option between mobile terminals is the following:
+
+- 1) The receiver side of terminal A sends the ITU-T H.245 command **H223MultiplexReconfiguration.h223ModeChange** to the corresponding transmitter side in terminal B indicating that a level change has to be made.
+- 2) Soon after detecting this command, the transmitter side of terminal B shall:
+ - stop transmitting MUX-PDUs with payload;
+ - begin transmitting successive ones complemented synchronization flags of the current level. The number of ones complemented synchronization flags transmitted shall be at least 10. The maximum number of ones complemented synchronization flags transmitted should be equivalent to the number of synchronization flags possible to be sent in a period of 500 ms;
+ - begin transmitting valid MUX-PDUs of the new level.
+- 3) The receiver side of terminal A uses the transition between the last ones complemented synchronization flag of the series in step 2 and the first regular (non-complemented) synchronization flag of the new level to synchronize to the multiplex of the new level.
+
+If terminal A does not receive the successive complemented synchronization flags within the value specified by T401 plus a margin, terminal A should restart this procedure.
+
+If terminal B receives a command to change to a level option in which it already is, terminal B shall take no action.
+
+While servicing an option change command, terminal B shall not initiate an option change procedure for the other direction.
+
+
+
+The diagram shows the interaction between Terminal A (receiver side) and Terminal B (transmitter side) during a level or option change procedure. Both terminals start at Level j. Terminal A initiates the change by sending an 'ITU-T H.245 change' and 'ITU-T H.223 multiplex option command' to Terminal B. Terminal B responds with 'Current level' and 'Is Complement sync flags B → A'. Terminal A then sends a series of messages labeled (1), (2), ..., (m). Finally, Terminal B sends 'Normal sync flags of the new level B → A' to Terminal A, and Terminal A changes to level k. A timer T401 is shown on the receiver side. The diagram is labeled H.324(09)\_FC.1.
+
+Sequence diagram illustrating the level or option change procedure between Terminal A (receiver side) and Terminal B (transmitter side).
+
+**Figure C.1 – Level or option change procedure**
+
+Note that after changing from level 0 to some higher levels, MUX-PDU octet alignment shall be preserved. Therefore, the transmitter shall add as many "0" bits after the level change sequence as necessary to octet align the first synchronization flag of the new level. In the transmitter, the reference for the octet alignment is the first bit of the first transmitted synchronization flag. In the receiver, the reference for the octet alignment is the first bit of the first detected synchronization flag in the initial level set-up procedure.
+
+## C.8 Control channel definition for mobile terminals
+
+Annex A defines the protocol stack for control channels for use with generic ITU-T H.324 terminals. For mobile applications, however, a reliable link layer may not be available under certain high bit error rate channels. These high bit error rates make the successful transmission of large ITU-T H.245 messages unlikely, in particular the capability exchange message. This problem is circumvented by defining a segmentation layer between the ITU-T H.245 and NSRP or LAPM/ITU-T V.42 layers (see Annex A), as illustrated in Figure C.2. This modified protocol stack shall be used for the control channel in terminals defined by this annex.
+
+
+
+H.324(09)\_FC.2
+
+Protocol stack diagram for ITU-T H.324 control channel. The stack consists of five layers: ITU-T H.245 at the top, followed by Control channel segmentation and reassembly layer (CCSRL), NSRP or LAPM/ITU-T V.42, ITU-T H.223 – Framed AL1 and ITU-T H.223 – MUX, and Physical layer at the bottom. Horizontal lines separate the layers. A label H.324(09)\_FC.2 is at the bottom right.
+
+**Figure C.2 – Protocol stack for ITU-T H.324 control channel**
+
+### C.8.1 Control channel segmentation and reassembly layer (CCSRL)
+
+#### C.8.1.1 Framework of CCSRL
+
+CCSRL is designed for segmenting **MultimediaSystemControlMessage** messages (CCSRL-SDUs) into one or more segments (CCSRL-PDUs). The CCSRL user shall always be [ITU-T H.245].
+
+#### C.8.1.2 Primitives exchanged between CCSRL and the CCSRL user
+
+The information exchanged between CCSRL and the CCSRL user includes the following primitives:
+
+- CCSRL-DATA.request (CCSRL-SDU).
+- CCSRL-DATA.indication (CCSRL-SDU).
+
+##### C.8.1.2.1 Description of primitives
+
+- CCSRL-DATA.request: This primitive is issued by the CCSRL user to CCSRL to request the transfer of an CCSRL-SDU to a corresponding CCSRL user.
+- CCSRL-DATA.indication: This primitive is issued to an CCSRL user by CCSRL to indicate the arrival of an CCSRL-SDU.
+
+##### C.8.1.2.2 Description of parameters
+
+- CCSRL-SDU: This parameter specifies the information exchanged between CCSRL and the CCSRL user. The length of the CCSRL-SDU may be variable. Each transmitted CCSRL-SDU shall contain an integral number of octets. The maximum size of CCSRL-SDUs that a CCSRL receiver can accept shall be 256 octets.
+
+NOTE – The maximum size of CCSRL-SDUs is 256 octets, even though the maximum ITU-T H.245 **MultimediaSystemControlMessage** message length is 2048 octets according to clause A.2.1. This effectively limits the maximum **MultimediaSystemControlMessage** message length to 256 octets for "H.324/M" systems. This limitation is required for interworking with deployed "H.324/M" endpoints. Sending more than 256 octets in a single CCSRL-SDU is for further study.
+
+- CCSRL-PDU: This parameter specifies the information exchanged between the CCSRL and the lower layer. The length of the CCSRL-PDU is variable.
+
+#### C.8.1.3 Functions of CCSRL
+
+CCSRL provides the function of segmenting an CCSRL-SDU containing one or more ASN.1 messages (encoded as defined in [ITU-T X.691]) into one or more CCSRL-SDU segments.
+
+#### C.8.1.4 Format and coding of CCSRL
+
+The format of the CCSRL-PDU is illustrated in Figure C.3.
+
+
+
+The diagram illustrates the structure of a CCSRL-PDU. It consists of two main parts: a header and a payload. The header is a single octet, divided into 8 bits (numbered 8 to 1 from left to right), labeled as the 'Last segment (LS) field (1 octet)'. The payload is one or more octets, labeled as 'CCSRL-PDU payload (1 or more octets)'. A vertical double-headed arrow on the left indicates the entire structure is the 'CCSRL-PDU'. On the right, the word 'Octet' is followed by a vertical list of numbers: 1, 2, ..., indicating the sequence of octets. Below the diagram, the text 'H.324(09)\_FC.3' is present.
+
+Diagram of CCSRL-PDU format showing a header field and a payload field.
+
+Figure C.3 – CCSRL-PDU format
+
+##### C.8.1.4.1 Last segment (LS) field
+
+The 8-bit LS field indicates the last segment of an CCSRL-SDU. It shall be set to "1111 1111" on the CCSRL-PDU containing the last segment of an CCSRL-SDU. It shall be set to "0000 0000" otherwise. All other combinations for an LS field are invalid.
+
+##### C.8.1.4.2 CCSRL-PDU payload field
+
+The payload field of an CCSRL-PDU shall contain an CCSRL-SDU segment of at least one octet. The first octet of the CCSRL-PDU payload field shall be the first octet of the CCSRL-SDU segment.
+
+#### C.8.1.5 Procedures for encoding
+
+Information received from the CCSRL user in an CCSRL-SDU by means of an CCSRL-DATA.request primitive shall be passed to the layer below using the following procedure:
+
+- i) break the CCSRL-SDU into an appropriate number of segments;
+- ii) for each CCSRL-SDU segment:
+ - a) set LS to "1111 1111" if this is the last segment of an CCSRL-SDU. Otherwise, set LS to "0000 0000";
+ - b) pass the generated CCSRL-PDU to the underlying layer.
+
+#### C.8.1.6 Procedures for error control
+
+An invalid CCSRL-PDU is one which:
+
+- does not contain an integral number of octets; or
+- is longer than the maximum CCSRL-PDU size; or
+- is equal to 0 octet; or
+- contains an invalid LS field.
+
+CCSRL-PDUs which are invalid shall be discarded.
+
+#### C.8.1.7 Interface to [ITU-T H.245]
+
+Interface to [ITU-T H.245] is defined by primitives defined in clause C.8.1.2.
+
+#### C.8.1.8 Interface to NSRP or LAPM/ITU-T V.42
+
+Interface to NSRP or LAPM/ITU-T V.42 are defined in clauses C.8.2 and C.8.3, respectively, as delivery of CCSRL-PDUs.
+
+### C.8.2 NSRP mode
+
+The general description of the NSRP protocol given in clause A.2 shall be followed with the following exceptions: the terminal shall transmit frames generated by the segmentation layer defined above whereby complete ITU-T H.245 **MultimediaSystemControlMessage** messages of clause A.2 are replaced by CCSRL frames. This is a generalization of the NSRP protocol concept, where an ITU-T H.245 message no longer needs to be transmitted within a single NSRP frame, but can be transmitted in segments.
+
+### C.8.3 LAPM/ITU-T V.42 mode
+
+The description of the LAPM/ITU-T V.42 for ITU-T H.324 terminals provided in clause A.3 is also applicable, with the exception that counter N401, maximum number of octets in an information field, may be set to a value smaller than 2048, but not shorter than the size of the frames generated by the CCSRL. Moreover, ITU-T H.245 **MultimediaSystemControlMessage** messages are not necessarily transmitted within one single LAPM/ITU-T V.42 frame but may be segmented and transmitted within CCSRL frames.
+
+# Annex D
+
+# Operation on ISDN circuits (H.324/I)
+
+(This annex forms an integral part of this Recommendation)
+
+## D.1 Scope
+
+This annex defines an operation mode for this Recommendation on ISDN circuits at bit rates ranging from 56 kbit/s to 1920 kbit/s. This channel capacity may be provided as a single B/H0/H11/H12-channel or multiple B/H0-channels, according to the multilink procedures. Operation on restricted networks (at 56 kbit/s for each channel) is also covered.
+
+The mode of operation defined by this annex is referred to as " H.324/I".
+
+ITU-T H.324/I terminals provide backwards compatibility with the installed base of ITU-T H.320 terminals, and forward compatibility with ITU-T H.324 Annex C terminals (mobile), while providing direct interoperation with:
+
+- ITU-T H.324 terminals on the GSTN (using GSTN modems);
+- ITU-T H.324 terminals operating on ISDN through user substitution of ITU-T I.400-series ISDN interfaces for ITU-T V.34 modems; and
+- voice telephones (both GSTN and ISDN).
+
+H.324/I offers users and implementers many technical improvements incorporated in the second-generation standards [ITU-T H.310], [ITU-T H.323] and this Recommendation, and corrects limitations and problems discovered with [ITU-T H.320].
+
+## D.2 References
+
+See clause 2.
+
+## D.3 Definitions
+
+This annex defines the following term:
+
+**D.3.1 restricted channel:** A channel carried on a network whose B-channels are effectively restricted to 56 kbit/s, or whose channels at H0 or higher are restricted by ones-density considerations. This can be because the network inherently operates at 56 kbit/s, or because it provides a 64 kbit/s local interface, of 7 out of each 8 bits are delivered to the far end.
+
+## D.4 Functional requirements
+
+Except as noted below, all features and requirements of this Recommendation apply to H.324/I terminals.
+
+Additionally, H.324/I terminals shall comply with the following clauses.
+
+Procedures and requirements in this annex relating to ITU-T G.711 audio (voice telephony, ITU-T V.8, ITU-T V.8 *bis* modems) do not apply to H.324/I terminals connected to networks which do not provide octet or septet timing alignment, since transmission and reception of ITU-T G.711 audio telephony is impossible without such alignment.
+
+NOTE – Octet/septet timing is needed to use ITU-T G.711 audio with ordinary telephones which do not support ITU-T V.140 (for modem or speech). ITU-T V.24 type interfaces and some restricted (56 kbit/s) digital networks do not provide octet timing, so only H.324/I and ITU-T H.320 modes can be supported.
+
+### D.4.1 Modem interface
+
+H.324/I terminals shall use an ITU-T I.400-series ISDN user-network interface in place of the ITU-T V.34 modem. All references to the "ITU-T V.34 modem" in this Recommendation shall, for
+
+H.324/I, be replaced with "ITU-T I.400-series ISDN user-network interface" (see Note). The output of the ITU-T H.223 multiplex shall be applied directly to each bit of the digital channel, in the order defined by [ITU-T H.223].
+
+Within each octet or septet of the channel, any bit position determined by the ITU-T V.140 phase 2 procedure to be unusable shall be skipped and filled with 1s. Each octet or septet of digital channels using octet/septet timing shall be filled in the order starting with bit 1 (most significant bit of ITU-T G.711 audio) and progressing toward bit 8 (least significant bit of ITU-T G.711 audio).
+
+[ITU-T V.8] or [ITU-T V.8 *bis*] shall be used only when operating with far-end terminals determined to be on the GSTN by the procedures below.
+
+NOTE – For leased line networks, the network interface is defined in [ITU-T G.703] for bit rates in the range of 64 kbit/s to 2048 kbit/s. An alternative interface is defined in [ITU-T X.21]. For $n \times H_0$ channels, timeslot allocation is given in clause 5 of [ITU-T G.704] for the ITU-T G.703 interface. It is stressed that interworking towards ISDN requires synchronous operation of the leased line network.
+
+### **D.4.2 ITU-T H.320 ISDN interoperation**
+
+In order to provide continued compatibility for existing users of ITU-T H.320 systems on ISDN, H.324/I terminals shall support operation in conformance with [ITU-T H.320]. If video transmission or reception is supported in the ITU-T H.324 mode of the H.324/I terminal, video transmission or reception shall also be supported in the ITU-T H.320 mode.
+
+### **D.4.3 ITU-T H.324 GSTN interoperation**
+
+H.324/I terminals shall support interoperation with ITU-T H.324 terminals on GSTN (using ITU-T V.34 modems) according to this Recommendation.
+
+H.324/I terminals shall send ITU-T H.324 GSTN signals by the use of a "virtual modem", which generates and receives an ITU-T V.34 analogue signal encoded as an ITU-T G.711 audio bitstream over the ISDN (note that the functional equivalent to a "virtual modem" can also be provided by attaching an ordinary ITU-T V.34 modem to the analogue output of an ITU-T I.400-series ISDN terminal adapter).
+
+### **D.4.4 Voice telephone interoperation**
+
+H.324/I terminals shall support interoperation with voice telephones using ITU-T G.711 speech coding as a speech or 3.1 kHz audio bearer service call. Other modes such as ITU-T G.722 audio may optionally be supported as well.
+
+Interconnection between the ISDN and GSTN networks for speech or 3.1 kHz audio bearer service is provided in the network, and does not affect terminals.
+
+### **D.4.5 NSRP support for ITU-T H.245 control channel**
+
+H.324/I terminals shall support the NSRP mode for the ITU-T H.245 control channel, as defined in Annex A. This is in addition to support for the standard SRP mode which is required by Annex A. The LAPM/ITU-T V.42 protocol stack may optionally be supported as well.
+
+### **D.4.6 ITU-T V.140 support**
+
+ITU-T H.324/I terminals shall support [ITU-T V.140].
+
+Upon initial connection of each digital channel (on the lowest numbered time-slot of a multi-channel connection such as an $H_0$ channel), H.324/I terminals shall use the procedures of [ITU-T V.140] to determine network end-to-end connectivity and to automatically negotiate a selected mode for the call among the H.324/I, ITU-T H.320, ITU-T H.324 and voice telephone modes (or any other modes which the terminal supports).
+
+In this case, the H.324/I terminal should signal the "*Recommendations H.221 and H.242*" BC and LLC information elements as described in [ITU-T Q.931], and shall not signal the "*Recommendations H.223 and H.245*" BC and LLC information elements.
+
+#### **D.4.6.1 Exceptional bypass of [ITU-T V.140]**
+
+The ITU-T V.140 procedures may be bypassed for a particular connection when all of the following conditions apply:
+
+- 1) it is known from ISDN D-channel signalling that the far-end terminal is capable of supporting H.324/I; and
+- 2) it is known that all channels of both terminals are connected to 64 kbit/s octet-aligned network interfaces; and
+- 3) it is known (perhaps from analysis of the national telephone number of the far-end terminal) that the interconnecting network transfers all bits end-to-end between the two terminals, without possibility of bit misalignment or loss.
+
+In this case, the H.324/I terminal shall signal the "*Recommendations H.223 and H.245*" BC and LLC information elements in [ITU-T Q.931]. If phase D of the ITU-T H.324 call set-up procedure is not complete within 5 seconds of the establishment of the digital channel, the H.324/I terminal shall automatically disconnect the digital channel and automatically re-establish it using the normal ITU-T V.140 procedures.
+
+This ITU-T V.140 bypass procedure can be used only for single-channel H.324/I calls.
+
+### **D.4.7 terminalOnHold**
+
+The terminal shall revert to voice telephony mode when it receives an ITU-T H.245 **EndSessionCommand** message which signals **terminalOnHold** in **isdnOptions**. ITU-T G.711 speech coding shall be used. The encoder can choose the ITU-T G.711 law for the outgoing audio. The decoder shall determine the proper ITU-T G.711 law of the incoming audio, for example by using the procedures of Appendix I of [ITU-T G.725]. ITU-T G.711 law is allowed to be different in each direction. The terminal shall periodically send an ITU-T V.140 signature as long as it is on hold.
+
+## **D.5 Terminal procedures**
+
+The steps for provision of communication are as listed in clause 7 but with the following modifications.
+
+### **D.5.1 Phase A – Call set-up of digital channel**
+
+In phase A, the calling terminal shall request the connection according to procedures for the digital network in use (ITU-T I.400-series ISDN D-channel signalling, etc.).
+
+If the call is rejected by the network due to mismatch of ISDN bearer capability (BC) or high level capability (HLC) values, the terminal shall follow the procedures of [ITU-T V.140] to retry the call with different values.
+
+Upon successful completion of call set-up, the terminal shall initiate ITU-T V.140 procedures, as described below.
+
+#### **D.5.1.1 Transmitted signals**
+
+While executing the ITU-T V.140 phase 1 procedure, the H.324/I terminal shall transmit in bits 1-6 of each octet and in the ITU-T V.140 compatible protocol field (CPF), signals conforming to:
+
+- ITU-T H.320 (send H.221 FAS and BAS signalling in CPF); and
+- if ITU-T V.8 *bis* is supported, ITU-T V.8 *bis* (send initial ITU-T V.8 *bis* messages in bits 1-6 of ITU-T G.711 audio); or
+
+- if ITU-T V.8 *bis* is not supported, ITU-T V.8 (send initial ITU-T V.8 messages in bits 1-6 of ITU-T G.711 audio).
+
+These signals are sent in order that far-end terminals of these types (which do not support H.324/I or ITU-T V.140) will initiate their negotiation.
+
+Additionally, if the far-end terminal is known from ISDN D-channel signalling to be compatible with H.324/I, bits 1-6 of each octet should be set to 1 while executing this procedure. Otherwise, H.324/I terminals should send ITU-T G.711 coded speech on bits 1-6 of each octet while executing this procedure, so that voice telephony is established immediately upon connection of the circuit, if the far-end terminal supports voice telephony.
+
+#### D.5.1.2 Received signals
+
+While executing the ITU-T V.140 phase 1 procedure, the H.324/I terminal shall search the received data for signals conforming to:
+
+- ITU-T V.140 signature;
+- HDLC flags followed by an ITU-T H.223 MUX\_PDU on the digital channel or, if Annex C is supported, all possible stuffing sequences defined in Table C.1;
+- ITU-T H.320 (search for ITU-T H.221 FAS and BAS signalling);
+- If ITU-T V.8 *bis* is supported, ITU-T V.8 *bis* (search for initial ITU-T V.8 *bis* messages in ITU-T G.711 audio);
+- ITU-T V.8 (search for initial ITU-T V.8 messages in ITU-T G.711 audio).
+
+Additionally, bits 1-6 of each octet may be decoded as audio according to [ITU-T G.711] and delivered to the user while executing this procedure, so that voice telephony is established immediately upon connection of the circuit, if the far-end terminal supports voice telephony.
+
+#### D.5.1.3 Procedure
+
+Based on the received signal, the H.324/I terminal shall follow the algorithm below:
+
+- if ITU-T V.140 signature is detected, the H.324/I terminal shall proceed with ITU-T V.140 and upon completion of those procedures, proceed to the mode negotiated. Otherwise;
+- if ITU-T H.324 signalling is detected on the digital channel, the terminal shall proceed to phase D. Otherwise;
+- if ITU-T V.8 *bis* or ITU-T V.8 signalling is detected, the H.324/I terminal shall proceed with ITU-T V.8 *bis* or ITU-T V.8 and upon completion of those procedures, proceed to the mode negotiated. Otherwise;
+- if signals corresponding to any other operation mode supported by the terminal (such as ITU-T H.320 or other ISDN or PSTN protocols) are detected, the terminal may enter an operation mode appropriate to the detected signal. Otherwise;
+- if none of the above signals are detected after a time sufficient to detect these signals if they were present, the terminal shall enter voice telephone mode.
+
+The mode entered as a result of this negotiation should begin at the equivalent of phase B. For ITU-T H.324 GSTN mode, the terminal shall begin at phase B of this Recommendation according to clause 7.2. For ITU-T H.320 mode, the terminal shall begin at phase B1 of [ITU-T H.320]. For H.324/I mode, the terminal shall proceed to phase B, below.
+
+### D.5.2 Phase B – Initial telephony communication
+
+An optional phase B is voice telephony mode. In this mode, users have the opportunity to speak before proceeding to multimedia telephony.
+
+If the terminal is conditioned to go directly into multimedia communication mode, phase B shall be bypassed, proceeding directly to phase D. If the terminal is conditioned for initial telephony voice mode, the terminal shall proceed to phase D when:
+
+- the user manually causes the terminal to initiate an ITU-T V.140 phase 3 transaction; or
+- the terminal detects an ITU-T V.140 phase 3 initiation signal from the distant terminal.
+
+### **D.5.3 Phase C – Establishment of digital communication**
+
+There is no phase C, as the digital connection is already established. Terminals shall proceed directly to phase D.
+
+### **D.5.4 Phases D through G**
+
+All remaining phases (D through G) shall proceed as specified in the main body of this Recommendation, or as defined in clause C.5 if Annex C is supported.
+
+# Annex E
+
+# Timer T401 initialization for operation over geostationary-satellite channels
+
+(This annex forms an integral part of this Recommendation)
+
+## E.1 Introduction
+
+Two key aspects in transmission of multimedia communications through geostationary-satellite channels are the bit error rate and the transmission delay. The raw bit error rate can be as high as $10^{-2}$ , or even worse in fading conditions. However, channel encoding is used to give a typical channel BER of $10^{-5}$ or better. One-way transmission delay depends heavily on the connection used, as illustrated in Table E.1 for a typical mobile satellite system. These delay values are much larger than for typical cable GSTN lines (examples are given in Table A.1 of [ITU-T G.114]).
+
+**Table E.1 – Example of end-to-end delay values for communications via mobile geostationary-satellite channels**
+
+| | Double-hop worst case [ms] | Single-hop typical case [ms] |
+|-----------------------------------------------|----------------------------|------------------------------|
+| Mobile geostationary-satellite channel | | |
+| Free space transmission delay | 260 (Note) | 260 |
+| Coding/processing delay | 170 | 170 |
+| GSTN | | |
+| Second GSTN satellite hop | 260 | – |
+| Rest of GSTN | 100 | 100 |
+| Total | 790 | 530 |
+| NOTE – As per Table A.1 of [ITU-T G.114]. | | |
+
+## E.2 Determination of timer value
+
+Hence, careful determination of a suitable value for timer T401 is necessary for proper operation of an ITU-T H.324 terminal over geostationary-satellite channels. The use of one of the two following procedures is required:
+
+### a) *Generic T401 value definition*
+
+The use of an initial large value for timer T401, to ensure an appropriate throughput when geostationary communication satellite channels are used. For ITU-T H.324 mobile terminals, the minimum initial value for timer T401 shall be in the range of 1600-2100 ms. This value should also be used for fixed ITU-T H.324 terminals to support communication over geostationary-satellite channels. Tuning of the value of the timer T401 should be performed after the connection is established (see tuning procedure below), and the optimized value of the T401 timer may be larger or smaller than the initial value.
+
+### b) *T401 value definition with ITU-T V.42 and NSRP protocols*
+
+Timer T401 shall be initialized with an arbitrarily small value. The timer tuning procedure shall be used during phase D of the communication to define an optimized value for timer T401 (see tuning procedure below). This approach will work with the numbered SRP (NSRP) protocol and the ITU-T V.42 protocol, but it will not work when the SRP protocol is used while the actual round-trip delay is larger than the initial small value of T401.
+
+Procedure a) is more generic and more robust because it is applicable to existing as well as future ITU-T H.324 terminals. However, procedure a) may require larger buffers and, in some cases, may result in a longer start-up time. In ITU-T H.324 connections where ITU-T V.42 or NSRP are supported, the use of procedure b) could be advantageous.
+
+## **E.3 Timer tuning procedure**
+
+In either of the two procedures defined above, it is recommended that the value initially defined for timer T401 be tuned to a value close to but greater than the actual round-trip delay for a given connection. This should be performed to minimize the size of the buffers in the ITU-T H.324 terminal, speed up error recovery and increase overall throughput.
+
+The ITU-T H.245 round-trip delay estimation procedure may be used to tune the value of the timer T401. However, an implementer may explore other alternatives, such as:
+
+- observing the system response time to receive the acknowledgement for the first SRP message sent;
+- exploring modem training results available in some implementations of V-series modems.
+
+It should be noted that the total buffer size allocated for data retransmission in the error control protocol must be compatible with the T401 value obtained from the tuning procedure. This is important, especially for procedure b) in clause E.2, to avoid buffer overrun.
+
+# Annex F
+
+# Multilink operation
+
+(This annex forms an integral part of this Recommendation)
+
+## F.1 Scope
+
+This annex defines the operation of ITU-T H.324 over multiple independent physical connections, aggregated together according to [ITU-T H.226] to provide a higher total bit rate. These connections may be GSTN circuits, or ISDN circuits as defined in Annex D. The use of both GSTN and ISDN connections in the same call is supported.
+
+## F.2 References
+
+See clause 2.
+
+## F.3 Functional requirements
+
+For use on GSTN connections, terminals compliant with this annex shall comply with ITU-T H.324 and support ITU-T V.8 *bis* operation.
+
+For use on ISDN connections, terminals compliant with this annex shall comply with Annex D.
+
+## F.4 Overview
+
+In summary, the establishment of an ITU-T H.324 multilink call involves the following steps:
+
+- 1) Initial channel physical connection is established.
+- 2) ITU-T V.8 *bis* or ITU-T V.140 is executed, selecting *ITU-T H.324-Multilink* as the mode for the call.
+- 3) ITU-T H.324 operation begins on the initial channel, using ITU-T H.226.
+- 4) ITU-T H.245 is used to exchange information about available additional channels, including a 32-bit **callAssociationNumber** which will be used to identify the call.
+- 5) An additional channel physical connection is established.
+- 6) ITU-T V.8 *bis* or ITU-T V.140 is executed on the new channel, selecting *Multilink-Additional-Connection* as the mode; the initiator supplies the previously received **callAssociationNumber** to identify that the new channel is associated with the existing call.
+- 7) The new channel is added to the ITU-T H.226 channel set as part of the ITU-T H.324 multilink call.
+
+Figure F.2 illustrates these steps. Steps 5, 6 and 7 may proceed in parallel for any number of additional channels.
+
+## F.5 Procedures
+
+### F.5.1 Establishing multilink ITU-T H.324 operation
+
+#### F.5.1.1 Establishment of initial physical connection
+
+The initial physical connection shall be established according to the procedures of ITU-T H.324 (for GSTN circuits) or Annex D (for ISDN circuits), call set-up phases A and B.
+
+#### F.5.1.2 Execution of ITU-T V.8 *bis* or ITU-T V.140 procedure on initial connection
+
+Multilink operation shall be initiated via the capabilities exchange and mode selection procedures of [ITU-T V.8 *bis*] (according to phase C of the ITU-T H.324 call set-up procedure) in the case of a
+
+GSTN initial physical connection, or [ITU-T V.140] (according to Annex D) in the case of an ISDN initial physical connection.
+
+Using the procedures of ITU-T V.8 *bis* or ITU-T V.140, as appropriate, if the *H.324-Multilink* capability is present at both terminals of a connection, the terminal performing the mode selection may choose *H.324-Multilink* as the selected mode of communication.
+
+If *H.324-Multilink* is chosen as the selected mode, the procedures defined in this annex for ITU-T H.324 multilink operation shall be used for all subsequent communications until the end of the communication session or until the procedures of ITU-T V.8 *bis* or ITU-T V.140, as appropriate, are re-established to negotiate into a different mode.
+
+NOTE – Since ITU-T V.8 *bis* is an integral part of establishing multilink operation for ITU-T H.324, ITU-T V.8 *bis* is required for this mode over GSTN, unlike basic ITU-T H.324 which allows the use of ITU-T V.8 instead.
+
+#### F.5.1.3 Initiation of H.226 and ITU-T H.324 operation
+
+If *ITU-T H.324-Multilink* is the selected mode of communication, once the procedures of ITU-T V.8 *bis* or ITU-T V.140 have been completed, all subsequent communication shall apply the procedures of ITU-T H.226 to all data transmitted over the connection. Specifically, the ITU-T H.324 bitstream that would otherwise be transmitted in ordinary ITU-T H.324 (or Annex D) operation is instead used as the input to the ITU-T H.226 input queue as defined by the transmitter model in [ITU-T H.226]. Similarly, received information shall pass through the ITU-T H.226 receiver and the data stream produced by the output queue defined in the ITU-T H.226 receiver model shall be used as input to the ordinary ITU-T H.324 (or Annex D) receiver. The model of ITU-T H.324 multilink operation is shown in Figure F.1. Prior to associating any additional physical connections, ITU-T H.226 shall initially operate using a channel set size of one.
+
+ITU-T H.324 call set-up shall complete according to phases D and E of the ITU-T H.324 call set-up procedure, using the procedures of [ITU-T H.226] to transport the ITU-T H.223 bitstream.
+
+It is possible that, upon establishment of the initial connection, the terminals may not yet know if any additional connections will later be established. If no additional connections are established, ITU-T H.324 multilink operation shall continue to be used, as defined for a channel set size of one, throughout the ITU-T H.324 communication session.
+
+
+
+The diagram illustrates the data flow in ITU-T H.324 multilink operation. At the top, a box labeled 'ITU-T H.324' contains a smaller box labeled 'ITU-T H.223'. Below this, a large box labeled 'ITU-T H.226' contains two sub-boxes: 'Input queue' on the left and 'Output queue' on the right. A downward arrow points from the 'ITU-T H.223' box to the 'Input queue'. An upward arrow points from the 'Output queue' to the 'ITU-T H.223' box. At the bottom, three vertical double-headed arrows represent 'Physical connections', with ellipses between them. The label 'H.324(09)\_FF.1' is in the bottom right corner.
+
+Diagram of ITU-T H.324 multilink operation model showing data flow between ITU-T H.324 and ITU-T H.226 components over physical connections.
+
+Figure F.1 – Model of ITU-T H.324 multilink operation
+
+### F.5.2 Adding physical connections
+
+The procedures for adding associated physical connections require one of the two terminals to be designated as the initiator and the other as the responder. If the initial physical connection is over GSTN, the terminal considered the *calling station* as defined in [ITU-T V.8 bis] shall be considered the initiator, and the *answering station* as defined in [ITU-T V.8 bis] shall be considered the responder. If the initial physical connection is over ISDN, the initiator and responder shall correspond to the *initiator* and *responder* as determined in phase 3 of [ITU-T V.140].
+
+The procedures for establishing and associating additional connections may be used on multiple connections at the same time.
+
+#### F.5.2.1 Exchanging call information
+
+At any time after ITU-T H.324 multilink operation is established, the initiator may begin the procedures to establish additional connections.
+
+To request the information needed to establish and associate additional connections, the initiator shall send the ITU-T H.245 **MultilinkRequest.callInformation** message to the responder. In this message, the initiator shall indicate the maximum number of additional connections that it is capable of establishing in the **maxNumberOfAdditionalConnections** parameter.
+
+On receipt of a **MultilinkRequest.callInformation** message, the responder shall send the ITU-T H.245 **MultilinkResponse.callInformation** message to the initiator. In this message, the responder shall include the **DialingInformation** parameter, with contents as described below, as well as a **callAssociationNumber**. The **callAssociationNumber** shall contain a 32-bit random number (uniformly distributed). Any subsequent **callInformation** exchanges within the same ITU-T H.324 session shall re-use the identical **callAssociationNumber**.
+
+The **DialingInformation** parameter should be used to provide explicit dialling information to allow the initiator to establish the additional connections. If this information is not available, it shall indicate the maximum number of additional connections available with no indication of how to dial those connections.
+
+##### F.5.2.1.1 Differential automatic dialling information
+
+If the responder chooses to provide dialling information for the additional connections, it may do so using the **differential** choice of the **DialingInformation** parameter. In this case, the responder shall provide a list of **DialingInformationNumber** parameters, one for each potential additional connection. The length of this list indicates implicitly the maximum number of additional connections available. For each potential additional connection, **DialingInformationNumber** includes up to three subparameters that indicate the dialling information for this connection differentially relative to the corresponding information for the already established initial connection.
+
+The **networkAddress** parameter shall include the least significant (right-most) portion of the telephone number for this connection, up to and including the most significant digit that is different from the number for the initially established connection, and shall include no digits that are more significant than this. If the number for the additional connection is identical to that of the initial connection, the **networkAddress** parameter shall consist of a zero-length string (since there are no differing digits in the telephone number).
+
+NOTE – The differential digit method is used instead of the full ITU-T E.164 digit string because the first few digits of the number to be dialled can vary based on the geographic location of the two terminals; for example, whether or not they are located in the same city.
+
+If there is a subaddress used for dialling, and the subaddress of a given connection is different from that of the initial connection, the responder shall include the subaddress, in full, in the optional **subAddress** parameter.
+
+The responder shall indicate the network types supported for the connection (GSTN, ISDN or both) using the **networkType** parameter.
+
+##### F.5.2.1.2 Automatic dialling information not available
+
+If the responder chooses not to provide any dialling information (or if the dialling information is provided using an out-of-band mechanism), it shall indicate this using the **infoNotAvailable** setting of the **DialingInformation** parameter. In this case, the responder shall indicate the maximum number of additional connections that are available.
+
+NOTE – It is suggested that, whenever possible, the responder should indicate the explicit dialling information to allow the initiator to automatically establish additional connections. This avoids the need for the user at the calling terminal to provide these numbers explicitly.
+
+#### F.5.2.2 Establishing additional physical connections
+
+The initiator of the initial physical connection may, at any time, establish additional physical connections to be used for multilink operation. It shall not establish additional connections that exceed the maximum number of additional connections indicated by the responder during the exchange of call information.
+
+If the initiator chooses to establish additional connections, it shall do so using the following procedure.
+
+In the case that the responder provided dialling information in a **DialingInformation.differential** parameter, the initiator shall form the network address (telephone number) to be dialled by taking the network address used to dial the initially established connection, and replacing the least significant N digits with the contents of the **networkAddress** parameter. If this parameter has zero length, the network address used to dial the initial connection shall be used in full without modification.
+
+For example, if the initial connection was established by dialling "0019786234349", and the **networkAddress** parameter contains "51", the number to be dialled for the additional connection is "0019786234351".
+
+If the **subAddress** parameter is present, the contents of this parameter shall fully replace any subaddress used to establish the initial connection. Use of the **networkType** parameter by the initiator is a local matter, beyond the scope of this Recommendation.
+
+In the case that the responder did not provide any dialling information (indicated by **infoNotAvailable**), the initiator may either choose not to add additional connections, or may attempt to determine the network address of the additional connections through other means (e.g., requesting from the local user or through an out-of-band communication mechanism). Any such means is beyond the scope of this Recommendation.
+
+##### F.5.2.2.1 Responder request to add additional connections
+
+At any time after exchange of call information according to clause F.5.2.1, the responder may request that the initiator add physical connections. This shall be done using the **MultilinkRequest.addConnection** message in [ITU-T H.245]. The responder shall indicate the connections desired to be added using the **DialingInformation** structure as described above. On receiving this message, the initiator shall respond with an **MultilinkResponse.addConnection** message indicating that it either intends to add the connections as requested, or that it does not intend to do so, along with the appropriate reason code.
+
+NOTE – It is possible that the responder could be the terminal that establishes additional physical connections instead of the initiator. The procedures and exchange of information needed to facilitate this are for further study.
+
+#### F.5.2.3 Associating additional physical connections
+
+Upon establishment of a GSTN circuit, the procedures of [ITU-T V.8 *bis*] shall be executed, leading to establishment of a ITU-T V-series modem data connection.
+
+Upon establishment of an ISDN circuit, the procedures of [ITU-T V.140] shall be executed.
+
+##### F.5.2.3.1 ITU-T V.8 *bis* or ITU-T V.140 capability exchange
+
+When an additional physical connection is established, the capability list in ITU-T V.8 *bis* or ITU-T V.140 shall include the *Multilink-Additional-Connection* capability.
+
+If a terminal is only capable of establishing this connection such that it is associated with an already established session, it shall only indicate the *Multilink-Additional-Connection* capability and no others (it shall not indicate H.324 or H.324-*Multilink* capability).
+
+If a terminal is capable of allowing this connection to either be associated with an already established connection, or to be an independent connection, then other capabilities in addition to *Multilink-Additional-Connection* may be listed as well. The additional capabilities indicate *only* the capabilities for independent connections, therefore, the H.324 or H.324-*Multilink* capability may or may not be included depending on whether the terminal can support a separate ITU-T H.324 or ITU-T H.324-*multilink* session in addition to the existing ITU-T H.324-*multilink* session.
+
+NOTE – The *Multilink-Additional-Connection* capability indicates the ability for the connection to be associated with an existing ITU-T H.226 session. The H.324 or H.324-*Multilink* capabilities indicate the ability for the connection to become a new ITU-T H.324 or ITU-T H.324-*multilink* session.
+
+##### F.5.2.3.2 ITU-T V.8 *bis* or ITU-T V.140 mode selection
+
+To associate a connection with an existing ITU-T H.324-*multilink* session, the terminal that issues the ITU-T V.8 *bis* or ITU-T V.140 mode selection command shall indicate *Multilink-Additional-Connection* as the selected mode, and shall set the call association parameter to the value of the **callAssociationNumber** previously specified in the **MultilinkResponse.callInformation** message.
+
+On reception of a *Multilink-Additional-Connection* mode selection command, the receiving terminal shall determine which existing ITU-T H.324-*multilink* session to associate the new connection with by comparing the call association number in the mode selection command with the **callAssociationNumber** corresponding to any existing sessions. If the terminal has no existing sessions with the corresponding **callAssociationNumber**, it shall reject the connection.
+
+NOTE – Since V.8 *bis* is an integral part of establishing multilink operation for ITU-T H.324, ITU-T V.8 *bis* is required for this mode over GSTN, unlike basic ITU-T H.324 which allows the use of ITU-T V.8 instead.
+
+### F.5.3 Removing physical connections
+
+#### F.5.3.1 Removing last remaining connection
+
+Phases F and G of the ITU-T H.324 call set-up procedures shall be followed to remove the last remaining physical connection at the end of an ITU-T H.324 session. Note that the last remaining connection need not be the same as the initially established connection.
+
+#### F.5.3.2 Removing additional connections
+
+At any time, a terminal may remove additional physical connections. Note that the initially established connection may be removed just like any other connection. Removal of the last remaining connection (which may or may not be the same as the initially established connection) is described above.
+
+If a connection is removed intentionally, the terminal initiating the removal shall remove this channel from the ITU-T H.226 channel set prior to removal of the physical connection (allowing sufficient time for local data buffers for that channel to empty). Also prior to removal of the physical connection, it shall send the **MultilinkRequest.removeConnection** message in ITU-T H.245
+
+to the remote site. In this message it shall indicate which channel is to be removed. It shall wait until it either receives the **MultilinkResponse.removeConnection** message from the remote site indicating that the corresponding channel has stopped being used, or a locally specified time-out, and then it should remove the physical connection.
+
+On receipt of a **MultilinkRequest.removeConnection** message, a terminal shall remove the indicated channel from its transmitted ITU-T H.226 channel set (assuming that the indicated channel is bidirectional, and is in use by this terminal). In any case, it shall send the **MultilinkResponse.removeConnection** message in response to the remote site, indicating that this channel is no longer (or was never) in use.
+
+Identification of the channel to be removed is done with respect to the channel numbering received via ITU-T H.226 from the terminal to which the **MultilinkRequest.removeConnection** is being sent. The **connectionIdentifier** parameter in each message shall identify a channel by indicating a combination of **channelTag** and **sequenceNumber** corresponding to a recently received ITU-T H.226 header on the channel to be removed. If a channel tag was not specified at all in the header, a value of zero shall be used for the **channelTag** parameter. In the **MultilinkResponse.removeConnection**, the **connectionIdentifier** shall be identical to the value in the corresponding **MultilinkRequest.removeConnection** message.
+
+NOTE – Since the value of the channel tag is meaningful only with respect to a particular header set, the sequence number must be used in combination with the channel tag to uniquely specify the channel to be removed. The receiver of a **MultilinkRequest.removeConnection** must have the ability to determine, from these two values, which channel the requester intends to be removed. To do this, it must have the ability to remember the correspondence between physical connections and channel tags for header sets that have already been sent. Maintaining the same value of channel tag for a given physical channel is a straightforward means of determining this correspondence without explicitly saving these values for all header sets.
+
+If a connection is removed accidentally, each terminal should, as soon as possible, begin transmission of a new ITU-T H.226 data set which no longer includes this connection in the channel set.
+
+### F.5.4 Negotiating the maximum header interval
+
+For use with this annex, the value of the ITU-T H.226 maximum header interval shall not be greater than 2 seconds, unless negotiated to another value as described below.
+
+A terminal may send the **MultilinkRequest.maximumHeaderInterval** message in [ITU-T H.245]. In this message, it may either indicate that it wishes to know the actual interval being used by the remote transmitter without altering it, or it may request a particular value to be used instead.
+
+A terminal receiving a **MultilinkRequest.maximumHeaderInterval** message shall respond by sending a **MultilinkResponse.maximumHeaderInterval** message. If the corresponding request indicated a request for information about the current minimum rate, the terminal shall provide the value that its transmitter is currently using as the maximum header interval in the response. If the corresponding request specified a particular minimum rate to use, the terminal should attempt to comply with this request by modifying the maximum header interval used by its transmitter. Whether or not it makes a change to the maximum header interval, the response shall indicate the new value that is in use (which may be different from the requested value).
+
+NOTE – A receiver may use its knowledge of the maximum header interval used by the remote transmitter to help ensure that data over a physical channel are continuing to be received successfully. By knowing the maximum interval between headers, long periods of time with no headers may indicate a malfunctioning channel. The ability to request a maximum header interval also allows a terminal to bound the error propagation of data that it is receiving.
+
+### F.5.5 Using the optional data CRC
+
+In [ITU-T H.226], a transmitter may include an optional CRC on the data. This CRC may be used by a receiver to determine the quality of a given channel. A terminal may indicate its desire that the remote terminal send this CRC in all subsequent data sets by sending the ITU-T H.245 **MultilinkIndication.crcDesired** message. The receiving terminal may optionally comply, there is no explicit acknowledgment or response required.
+
+### F.5.6 Using the excessive error indication
+
+A terminal may indicate to the remote terminal that excessive errors are being received on a particular connection. The means for the terminal to determine the error rate or the criterion for determining what is excessive is defined locally at that terminal. It could, for example, result from receiving an excessive number of ITU-T H.226 headers that contain errors, from the failure to receive ITU-T H.226 headers at the minimum specified rate, or from an excessive rate of errors detected using the optional data CRC. In any case, the indication should be given with the expectation that the remote terminal will take some corrective action. This indication is made by sending the **MultilinkIndication.excessiveError** message in ITU-T H.245 indicating which connection is causing problems. The connection is indicated using the **connectionIdentifier** parameter in the same manner as defined above for the **MultilinkRequest.removeConnection** message.
+
+On receipt of this message, a terminal may choose to take corrective action. The particular corrective action that it should take is not specified. Examples include removing the connection from use or lowering the rate of the connection in the hope of reducing the error rate.
+
+## F.6 Maximum transmit skew
+
+In using ITU-T H.226 for ITU-T H.324 multilink operation, as defined in this annex, the value of the maximum transmit skew shall equal 50 milliseconds.
+
+## F.7 Sequence diagram for establishment of multilink operation
+
+Figure F.2 shows the sequence of events in establishing multilink operation. In the figure, solid lines represent exchanges over the initial connection, dotted lines represent exchanges over additional connection(s), and heavy solid lines represent exchanges over all connections.
+
+
+
+```
+
+sequenceDiagram
+ participant Initiator
+ participant Responder
+ Note right of Initiator: Establish initial connection
+ Initiator->>Responder: Initial ITU-T V.140 or ITU-T V.8 bis exchange (ITU-T H.324-Multilink as mode choice)
+ Note left of Responder: ...
+ Responder->>Initiator: Begin ITU-T H.226 operation on initial connection
+ Responder->>Initiator: Begin ITU-T H.324 operation on initial connection
+ Note left of Responder: ...
+ Initiator->>Responder: MultilinkRequest.callInformation
+ Responder->>Initiator: MultilinkResponse.callInformation (with dialingInformation and callAssociationNumber)
+ Note right of Initiator: Establish additional connection(s)
+ Initiator-->>Responder: Additional connection ITU-T V.140 or ITU-T V.8 bis exchange (Multilink-Additional-Connection as mode choice)
+ Note left of Responder: ...
+ Responder->>Initiator: callAssociationNumber
+ Responder->>Initiator: Expand ITU-T H.226 operation to any established connections
+ Note right of Responder: H.324(09)_FF.2
+
+```
+
+The sequence diagram illustrates the interaction between an Initiator and a Responder to establish a multilink operation. The process begins with the Initiator sending a message to 'Establish initial connection'. This is followed by an 'Initial ITU-T V.140 or ITU-T V.8 bis exchange (ITU-T H.324-Multilink as mode choice)' from the Initiator to the Responder. A vertical ellipsis indicates further messages. The Responder then sends 'Begin ITU-T H.226 operation on initial connection' and 'Begin ITU-T H.324 operation on initial connection' to the Initiator. Another vertical ellipsis follows. The Initiator sends a 'MultilinkRequest.callInformation' message, and the Responder responds with 'MultilinkResponse.callInformation (with dialingInformation and callAssociationNumber)'. Next, the Initiator sends 'Establish additional connection(s)', followed by an 'Additional connection ITU-T V.140 or ITU-T V.8 bis exchange (Multilink-Additional-Connection as mode choice)' message. A third vertical ellipsis is shown. The Responder sends 'callAssociationNumber' and 'Expand ITU-T H.226 operation to any established connections' to the Initiator. The diagram concludes with the text 'H.324(09)\_FF.2' in the bottom right corner.
+
+Sequence diagram for establishing multilink operation between an Initiator and a Responder.
+
+**Figure F.2 – Sequence diagram for establishing multilink operation**
+
+# Annex G
+
+# Usage of ISO/IEC 14496-1 generic capabilities in ITU-T H.324 terminals
+
+## G.1 Scope
+
+This annex defines the usage of [ISO/IEC 14496-1] ("MPEG-4 systems") generic capabilities in ITU-T H.324 terminals and the framing and error protection of the corresponding data streams.
+
+## G.2 References
+
+See clause 2.
+
+## G.3 General
+
+The codepoint for [ISO/IEC 14496-1] presented herein shall only be used for applications that want to make use of the object descriptor and scene description capability of [ISO/IEC 14496-1]. In this case, any type of ISO/IEC 14496 data stream to be used shall be indicated by means of the ISO/IEC 14496-1 generic capability during capability exchange as defined in [ITU-T H.245].
+
+Applications that only want to use ISO/IEC 14496-2 ("MPEG-4 visual") and/or ISO/IEC 14496-3 ("MPEG-4 audio") data streams, shall use the ISO/IEC 14496-2 generic capability and/or the ISO/IEC 14496-3 generic capability, respectively, as defined in [ITU-T H.245] for a fast set-up.
+
+NOTE – ITU-T H.324 terminals using these ISO/IEC 14496 codepoints shall support the mandatory audio and video codecs as applicable.
+
+## G.4 Choice of error protection for ISO/IEC 14496 data streams
+
+The error protection of the ISO/IEC 14496 data streams can be arbitrarily negotiated, requested and chosen by use of the "transport" field in the generic capability for [ISO/IEC 14496-1]. By usage of this field, an appropriate **DataProtocolCapability** shall be indicated.
+
+## G.5 Framing of ISO/IEC 14496-1 data streams
+
+Each individual SL packet (as defined in [ISO/IEC 14496-1]) to be transmitted shall be mapped on exactly one ITU-T H.223 AL-SDU as defined in [ITU-T H.223].
+
+# Annex H
+
+# Mobile multilink operation
+
+(This annex forms an integral part of this Recommendation)
+
+## H.1 Scope
+
+This annex defines the operation of ITU-T H.324 over up to eight independent physical connections, aggregated together according to the mobile multilink layer defined in this annex to provide a higher total bit rate. These connections are error-prone mobile channels as defined in Annex C, all having the same transmission rate.
+
+The difference between Annexes H and F is that Annex H is primarily intended to be used on error-prone connections by not using HDLC framing and with less flexibility in terms of the number, the bit rate and the delay differences of the channels involved in the aggregation than Annex F, in order to work on mobile connections. Annex H is not intended to be a replacement of Annex F on connections with very low bit error rates.
+
+## H.2 Definitions and format conventions
+
+### H.2.1 Definition of terms
+
+This annex defines the following terms:
+
+**H.2.1.1 header:** A collection of parameters whose beginning is marked by one flag.
+
+**H.2.1.2 sample:** The smallest unit of data which is always kept contiguous when distributing data among multiple channels. The size of the sample is an integer number of octets.
+
+### H.2.2 Format conventions
+
+See clause 3.2 of [ITU-T H.223].
+
+## H.3 Functional requirements
+
+For use on mobile connections, terminals compliant with this annex shall comply with Annex C. The multilink operation is limited to channels having the same characteristics. In particular, the channels to be aggregated shall have the same bit rate. Since the channels as defined in Annex C do not utilise ITU-T V.8 *bis* or ITU-T V.140, in-band signalling is defined in this annex for the purpose of setting up the mobile multilink, as well as the addition and the removal of additional connections.
+
+## H.4 Overview
+
+In summary, the establishment of a mobile multilink call involves the following steps:
+
+- 1) Initial channel physical connection is established.
+- 2) The mobile multilink is set up using the in-band joint multilink and multiplex set-up procedure.
+- 3) ITU-T H.324 operation begins on the initial connection.
+- 4) ITU-T H.245 is used to exchange information about available additional channels, including a 32-bit **callAssociationNumber**, which will be used to identify the call.
+- 5) An additional physical connection is established.
+- 6) In-band control frames are exchanged between the initiator and the responder to set up an additional connection to be associated with the mobile multilink. The initiator supplies the
+
+previously received **callAssociationNumber** to identify that the new connection is associated with the existing call.
+
+- 7) The new connection is added to the mobile multilink layer as part of the ITU-T H.324 mobile multilink call.
+
+## H.5 Mobile multilink layer specification
+
+### H.5.1 Overview
+
+The mobile multilink is a layer between an ITU-T H.223 multiplex and up to eight physical channels (Figure H.1). Its function is to aggregate the physical channels in order to provide a higher total bit rate for an Annex C. The transmission rate of each of the physical channels involved shall have the same value.
+
+
+
+The diagram illustrates the mobile multilink layer structure. At the top is a box labeled "ITU-T H.223 level 0, 1, 2 or 3 multiplex". Below it is a box labeled "Mobile multilink layer". Between these two boxes are two vertical arrows: a downward arrow on the left and an upward arrow on the right. Below the "Mobile multilink layer" box are three pairs of vertical double-headed arrows, representing connections to "Physical channels". The text "H.324(09)\_FH.1" is located to the right of the bottom right double-headed arrow.
+
+Diagram of the mobile multilink layer structure showing the ITU-T H.223 multiplex, the mobile multilink layer, and physical channels.
+
+**Figure H.1 – Overview of the mobile multilink layer**
+
+The input to the mobile multilink layer shall be a bitstream from an ITU-T H.223 level 0, 1, 2 or 3 multiplex as defined in [ITU-T H.223] and in Annexes A, B, C and D of [ITU-T H.223]. The output from the multilink layer shall be distributed onto the physical channels.
+
+In order to recover the multiplexed stream at the receiving side from one or more physical channels, a synchronization mechanism is needed. This is achieved by a framing format where header information is inserted at regular intervals into the physical channels.
+
+### H.5.2 Mobile multilink framing
+
+Data to be sent over the physical channels shall be segmented into frames. A frame shall start with a 16-bit flag, followed by a 2- or 5-octet header after which the payload follows as shown in Figure H.2. The number of octets in the payload is signalled in the header.
+
+
+
+The diagram shows the framing format as a vertical stack of three boxes. The top box is labeled "Flag (2 octets)". The middle box is labeled "Header (2 or 5 octets)". The bottom box is labeled "Payload (0 to SS\*SPF octets)".
+
+Diagram of the mobile multilink layer framing format showing the flag, header, and payload.
+
+NOTE – The SS and SPF parameters are defined in clause H.5.2.2.
+
+**Figure H.2 – Mobile multilink layer framing format**
+
+#### H.5.2.1 Flag
+
+A mobile multilink frame shall begin with the 16-bit flag shown in Figure H.3 or its one's complement flag if the full header is used or the compressed header is used, respectively. If synchronization is lost on the receiving side, a search for this flag should be performed to reacquire synchronization. Since this sequence of bits is not unique in the bitstream but can be emulated by data in the payload part of the framing format, a multilink receiver should also check that a valid header can be decoded before synchronization is accepted.
+
+| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | Octet |
+|---|---|---|---|---|---|---|---|-------|
+| 1 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 1 |
+| 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 2 |
+
+**Figure H.3 – 16-bit flag pattern for the mobile multilink**
+
+NOTE – The flags defined in Annex A of [ITU-T H.223] are at a Hamming distance of 8 from this flag.
+
+#### H.5.2.2 Header
+
+Two types of headers are defined: the full header and the compressed header. The full header contains all information for initial operation, whereas the compressed header contains minimum information, which can be used after information frame synchronization has been acquired. The distinction between these headers is made by the polarity of the flag field. The full header is preceded by a flag field as shown in Figure H.3 and the compressed header is preceded by the one's complemented flag.
+
+##### H.5.2.2.1 Full header configuration
+
+The full header is shown in Figure H.4.
+
+| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | Octet |
+|------------------|---|----|---|---|----|---|---|-------|
+| FT | L | SN | | | CT | | | 1 |
+| SS | | | | | | | | 2 |
+| SPF | | | | | | | | 3 |
+| 16-bit CRC field | | | | | | | | 4 |
+| | | | | | | | | 5 |
+
+**Figure H.4 – Full header format**
+
+Two types of frames are defined, control frames and information frames, as indicated by the FT (frame type) bit. FT shall be set to "1" for control frames used for in-band signalling to add connections. FT shall be set to "0" for information frames carrying ITU-T H.223 multiplexed data in the payload part.
+
+The 3-bit sequence number (SN) field shall be incremented by one modulo 8 for each new information frame and shall have the same value for all channels in use.
+
+The 3-bit channel tag (CT) field is a unique identifier for a channel in multilink session.
+
+The L bit shall be set to "1" for the channel that is the highest numbered channel. For all other channels, the L bit shall be set to "0".
+
+The 8-bit sample size (SS) field indicates the size of a sample in octets (see clause H.5.4). The value 0 of SS is reserved for future use.
+
+The 8-bit samples per frame (SPF) field indicates the length in samples of the payload (see clause H.5.4).
+
+The product of SS and SPF gives the size of the payload in octets.
+
+The last two octets of the header hold a 16-bit CRC field (see clause 7.4.3.2.3 of [ITU-T H.223]) as protection for the 3 octets following the flag.
+
+##### H.5.2.2.2 Compressed header configuration
+
+The compressed header is shown in Figure H.5.
+
+
+
+| | | | | | | | | |
+|-----------------|---|----|---|---|----|---|---|-------|
+| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | Octet |
+| X | L | SN | | | CT | | | 1 |
+| 8-bit CRC field | | | | | | | | 2 |
+
+**Figure H.5 – Compressed header format**
+
+The CT, SN and L fields are identical to those described in clause H.5.2.2.1.
+
+The X bit is set to "0". The value "1" is reserved for future use.
+
+The 8-bit CRC field (see clause 7.3.3.2.3 of [ITU-T H.223]) is used as protection for the octet following the one's complemented flag.
+
+#### H.5.2.3 Control frames
+
+To support in-band signalling for the handling of initial and additional connections to the multilink layer, control frames are used.
+
+Control frames use the full header format with the FT bit set to "1". There are three types of control frames defined as shown in Figure H.6.
+
+| Control frame | MUX Level | Control Field | | | | | | Payload |
+|--------------------|-----------|---------------|----|----|----|----|-----|--------------------------------------------------|
+| | | L | FT | CT | SN | SS | SPF | |
+| Initial | 0 | 0 | 1 | 0 | 0 | 1 | 0 | – |
+| | 1 | 0 | 1 | 0 | 1 | 1 | 0 | – |
+| | 2 | 0 | 1 | 0 | 2 | 1 | 0 | – |
+| | 3 | 0 | 1 | 0 | 3 | 1 | 0 | – |
+| Request additional | – | 1 | 1 | 0 | 0 | 1 | 6 | 6-octet payload as described in clause H.6.2.3.1 |
+| Accept additional | – | 1 | 1 | 0 | 0 | 1 | 0 | – |
+
+**Figure H.6 – Header and payload for control frames**
+
+*initial* control frames are used for setting up a multilink session between two terminals, including multiplex level set-up. The SN field is set to the level of the multiplex, i.e., 0, 1, 2 or 3.
+
+*request additional* control frames are used for requesting to add a physical connection to an already existing multilink session.
+
+*accept additional* control frames are used for accepting the request to add a physical connection to an already existing multilink session.
+
+The use of these control frames is described in clause H.6.
+
+### H.5.3 Stuffing frames
+
+In the event that the mobile multilink layer has no information to send on a channel, such as when a channel is no longer part of the multilink session but has not been disconnected yet, a flag shown in Figure H.3, followed by 5 zero octets shall be sent as the stuffing sequence.
+
+For connections that are part of a multilink session, it is the responsibility of the ITU-T H.223 multiplex to supply the multilink with the correct amount of data, taking into account the overhead for the multilink framing.
+
+### H.5.4 Information frames
+
+Information frames use either the full header format with the FT bit set to "0" or the compressed header. For all channels in use the same type of header (full header or compressed header) shall be used.
+
+Information frames are generated for each block of ITU-T H.223 bitstream. The size of a block is (number of channels \* SS \* SPF) octets. A block is divided into samples of SS octets. Then samples are put onto the payload part of information frames. The first sample shall be placed on the frame with the lowest CT value, the next sample on the next lowest numbered frame, and so on. After a sample has been placed on the highest numbered frame, the process shall be repeated using the lowest numbered frame until all samples in the block have been sent.
+
+NOTE 1 – On channels having a burst characteristic, it may be advantageous to choose a value for a sample larger than one octet. For instance, a value that is related to the mean burst length may be a good choice.
+
+NOTE 2 – All the information frames for this block have the same values of SS and SPF.
+
+The L bit shall be set to "1" for the highest numbered channel and to "0" for the remaining channels.
+
+The SN field shall be incremented by one modulo 8 for each block of ITU-T H.223 bitstream.
+
+The CT value indicates the channel onto which the information frame is transmitted.
+
+NOTE 3 – In the case that a header cannot be interpreted due to a CRC error, a receiver may assume that the header contained a CT value identical to a previously correct received header.
+
+## H.6 Procedures
+
+### H.6.1 Establishing mobile multilink operation
+
+#### H.6.1.1 Establishment of initial connection
+
+The procedure described in clauses C.5 and C.6 shall be applied except for clause C.6.2, which is replaced by clause H.6.1.2.
+
+#### H.6.1.2 Joint multilink and multiplex set-up over the initial connection
+
+After the establishment of the initial physical connection, a terminal that intends to use the mobile multilink shall start transmitting control frames for *initial connection* (Figure H.6). This sequence of control frames jointly sets up both the mobile multilink layer and the ITU-T H.223 multiplex level. The terminal shall set the SN field of the header to its highest supported multiplex level, which shall be 0, 1, 2 or 3.
+
+If the terminal detects an Annex C stuffing sequence in place of mobile multilink control frames, it shall immediately start the Annex C set-up procedure according to clause C.6.2.
+
+If the terminal detects control frames for *initial connection* with a multiplex level lower than its own transmitted level, it shall immediately change its value in the SN field according to the detected lower level.
+
+When the terminal detects control frames with a multiplex level that is identical to its own transmitted level, multilink and multiplex set-up has been completed. The ITU-T H.223 multiplex shall then start its operation using the multiplex level indicated in the SN field.
+
+#### H.6.1.3 Initiation of mobile multilink operation
+
+If the mobile multilink is set up, all subsequent communication shall apply the mobile multilink mode to all data transmitted over the connection. Specifically, the ITU-T H.324 bitstream that would otherwise be transmitted in Annex C operation is instead used as the input to the mobile multilink. Similarly, received information shall pass through the mobile multilink receiver and the data output stream produced shall be used as input to the ordinary Annex C receiver.
+
+It is possible that, upon establishment of the initial connection, the terminals may not yet know if any additional connections will later be established. If no additional connections are established, ITU-T H.324 mobile multilink operation shall continue to be used, on the initial connection, throughout the ITU-T H.324 communication session.
+
+The initial connection shall be assigned a CT value of "0" initially until another connection is added to the session.
+
+The ITU-T H.245 **TerminalCapabilitySet** message shall include the **mobileMultilinkFrameCapability** in **H223Capability**.
+
+### **H.6.2 Adding physical connections**
+
+The procedures for adding associated physical connections require one of the two terminals to be designated as the initiator and the other as the responder. The terminal that originates the first physical connection shall be the initiator, and the terminal that answers the first physical connection shall be the responder.
+
+The procedures for establishing and associating additional connections may be performed on multiple connections at the same time.
+
+When one or more channels are added to a multilink session, the transmitting entity of the multilink shall assign a channel tag from 0 to (N-1) to each of the channels before the next information frames are transmitted, where N is the number of connections in use.
+
+#### **H.6.2.1 Exchanging call information**
+
+See clause F.5.2.1 with multilink replaced with mobile multilink.
+
+##### **H.6.2.1.1 Differential automatic dialling information**
+
+See clause F.5.2.1.1.
+
+The responder may use the **networkType** of **mobile**.
+
+##### **H.6.2.1.2 Automatic dialling information not available**
+
+See clause F.5.2.1.2.
+
+#### **H.6.2.2 Establishing additional physical connections**
+
+See clause F.5.2.2 with multilink replaced with mobile multilink.
+
+##### **H.6.2.2.1 Responder request to add additional connections**
+
+See clause F.5.2.2.1.
+
+#### **H.6.2.3 Associating additional physical connections**
+
+Upon establishment of an additional physical connection, the exchange of control frames between the initiator and the responder will determine if the connection can be associated with an existing mobile multilink session or if the connection is an independent connection by using the following procedure.
+
+##### **H.6.2.3.1 Procedure for initiator**
+
+The initiator shall immediately start to send control frames for *request additional*. The payload for *request additional* control frames shall contain the **callAssociationNumber** that was determined in clause H.6.2.1 and a 16-bit CRC field, see Figure H.7.
+
+
+
+| | |
+|---------------------------------------------------|-------|
+| callAssociationNumber field | Octet |
+| | 1 |
+| | 2 |
+| | 3 |
+| CRC field (see clause 7.4.3.2.3 of [ITU-T H.223]) | 4 |
+| | 5 |
+| | 6 |
+
+**Figure H.7 – Payload for *request additional* control frames**
+
+If it detects control frames for *accept additional*, it shall add this connection to the existing session that has the same **callAssociationNumber**. If it cannot detect a control frame for *accept additional* until the appropriate timer expires, it shall disconnect this additional connection.
+
+##### H.6.2.3.2 Procedure for responder
+
+##### H.6.2.3.2.1 Responder capable of an independent session
+
+If the responder allows another independent session of either mobile multilink or Annex C, it shall immediately start to send control frames for *initial connection* with its highest supported multiplex level.
+
+If it detects a control frame for *request additional* that has the same **callAssociationNumber** as that of an existing session, it shall immediately start to send multiple control frames for *accept additional*, and shall add this connection to the session. The number of control frames sent should be sufficient for the receiver to detect taking into account the mobile channel condition.
+
+If it detects a control frame for *initial connection*, it shall start a new session according to the procedure in clause H.6.1. If it detects a stuffing sequence for Annex C, it shall start the Annex C set-up procedure according to clause C.6.
+
+##### H.6.2.3.2.2 Responder not capable of an independent session
+
+If the responder is not capable of another independent session, it shall immediately start to send control frames for *accept additional*.
+
+If it detects control frames for *request additional* that has the same **callAssociationNumber** as that of an existing session, it shall add this connection to the session. If it detects control frames for *initial connection* or stuffing sequence for Annex C, it shall disconnect this additional connection.
+
+### H.6.3 Removing physical connections
+
+#### H.6.3.1 Removing last remaining connection
+
+Phases F and G in clause C.5 shall be followed to remove the last remaining physical connection at the end of an ITU-T H.324 session.
+
+#### H.6.3.2 Removing additional connections
+
+See clause F.5.3.2 with references to ITU-T H.226, ITU-T H.226 channel set, ITU-T H.226 header and ITU-T H.226 data set replaced by the mobile multilink, mobile multilink connections, mobile multilink header and mobile multilink frames, respectively, except for the procedure when a connection is removed accidentally. If a connection is removed accidentally, each terminal shall assign a channel tag to each of the remaining channels before the next information frames are transmitted.
+
+When one or more channels are removed from a multilink session, the transmitting entity of the multilink shall assign a channel tag from 0 to (N-1) to each of the channels, where N is the number of connections in use.
+
+## H.7 Header modes
+
+Mobile multilink operation has two modes for information frame transmission: full header mode and compressed header mode. This clause defines these modes and the mode transition procedures.
+
+### H.7.1 Full header mode
+
+In full header mode, the full header defined in Figure H.4 is used for information frames on all channels. In this mode, the transmitter may change the value of SS and SPF in the information frame header, but the transmitter shall send the **MobileMultilinkReconfigurationIndication** message to the receiver before changing the values.
+
+Mobile multilink starts with this mode, and the initial value of SS shall be set to "1", and that of SPF shall be set to "255".
+
+### H.7.2 Compressed header mode
+
+In compressed header mode, the compressed header defined in Figure H.5 is used for information frames on all channels. In this mode, the transmitter shall use the same SS and SPF values with those used for the last information frames in full header mode.
+
+### H.7.3 Mode transition (from full header to compressed header)
+
+When the receiver has synchronized the frame timing of the information frames in full header mode, the receiver shall send the **MobileMultilinkReconfigurationCommand** with the detected SS and SPF values and the status of **synchronized**. On the receipt of this command, the transmitter shall assess the SS and SPF values in the command message. If these values are the same as the values in use, then the transmitter shall change the mode from full header mode to compressed header mode. Otherwise, the transmitter shall continue the operation in full header mode.
+
+### H.7.4 Transition from compressed header mode to full header mode
+
+If the receiver finds that better SS and SPF values for the current channel conditions (e.g., bit error rate or burst error characteristics), the receiver may request to change these values by sending **MobileMultilinkReconfigurationCommand** with the detected SS and SPF values and the status of **reconfiguration**. On the receipt of this command, the transmitter shall move to the full header mode. The receiver should use the values for SS and SPF in the command message, but the actual value used for the information frames is up to the transmitter.
+
+# Annex I
+
+## Usage of HTTP generic capability in ITU-T H.324 terminals
+
+(This annex forms an integral part of this Recommendation)
+
+## I.1 General
+
+This annex defines the usage of hypertext transfer protocol (HTTP) [IETF RFC 2616] capability in ITU-T H.324 terminals. HTTP is an application-level protocol for distributed, collaborative, hypermedia information systems, and its technical specifications are provided in [IETF RFC 2616]. The capability presented in this annex is used for applications that want to make use of HTTP capabilities in ITU-T H.324 terminals.
+
+The purpose of using an HTTP channel associated with an ITU-T H.324 call is to permit the HTTP client (e.g., web browser) to remotely operate a far-end ITU-T H.324 endpoint (in which the HTTP server is implemented). This is especially useful in cases where the far-end ITU-T H.324 endpoint is an automatic device.
+
+For example, by selecting items on a web page, the human user could cause the far-end system to switch input video or audio sources, or control far-end audio pickup. In another example, the human user could choose via a web page to view one of a set of stored audiovisual streams, which might contain entertainment or educational material.
+
+Figure AnI.1 illustrates such an example. In this example, an ITU-T H.324 Annex I terminal (on the left) receives audiovisual content from a content server where ITU-T H.324 Annex I is implemented. The logical channel for HTTP transactions, which is used to select the audiovisual content to be sent, is opened using ITU-T H.245 logical channel signalling. Separate logical channels for delivery of audio and video data may be opened using ITU-T H.245 logical channel signalling, if necessary.
+
+
+
+The diagram illustrates the internal architecture and data flow of an ITU-T H.324 Annex I terminal and a content server connected via a circuit-switched connection.
+
+- Annex I/ITU-T H.324 terminal (Left):**
+ - Contains an **HTTP client** connected to an **Underlying protocol** block (LCN i).
+ - Contains an **Audio decoder** connected to an **Audio** block (LCN j).
+ - Contains a **Video decoder** connected to a **Video** block (LCN k).
+ - Both the **Underlying protocol** and the **Audio/Video** blocks are connected to an **ITU-T H.223 MUX**.
+ - The **ITU-T H.223 MUX** is connected to the **Circuit-switched connection**.
+- Content server with Annex I/ITU-T H.324 (Right):**
+ - Contains a **Server HTTP** connected to an **Underlying protocol** block (LCN i).
+ - Contains an **Audio content** source connected to an **Audio** block (LCN j).
+ - Contains a **Video content** source connected to a **Video** block (LCN k).
+ - Both the **Underlying protocol** and the **Audio/Video** blocks are connected to an **ITU-T H.223 MUX**.
+ - The **ITU-T H.223 MUX** is connected to the **Circuit-switched connection**.
+- Signalling and Data Flow:**
+ - An orange arrow labeled **Logical channel signalling For HTTP/audio/video** points from the terminal's **ITU-T H.245** block (LCN 0) to the server's **ITU-T H.245** block (LCN 0).
+ - A blue double-headed arrow labeled **Exchange information about audio/video content** connects the terminal's **Underlying protocol** (LCN i) and the server's **Server HTTP** (LCN i).
+ - A black arrow labeled **Audio content** points from the server's **Audio** block (LCN j) to the terminal's **Audio decoder**.
+ - A black arrow labeled **Video content** points from the server's **Video** block (LCN k) to the terminal's **Video decoder**.
+
+Diagram of an application using ITU-T H.324 Annex I. It shows an Annex I/ITU-T H.324 terminal on the left and a Content server with Annex I/ITU-T H.324 on the right, connected by a circuit-switched connection. The terminal contains an HTTP client, audio and video decoders, and an ITU-T H.223 MUX. The server contains an HTTP server, audio and video content sources, and an ITU-T H.223 MUX. Logical channels (LCN 0, i, j, k) are shown for signalling, HTTP, audio, and video respectively.
+
+Figure AnI.1 – An application using ITU-T H.324 Annex I
+
+## I.2 Logical channel for HTTP
+
+The terminals which intend to use the HTTP capability shall open bidirectional logical channels for HTTP messages encapsulated by the underlying protocol specified in Table I.3.
+
+The error protection for these logical channels may be arbitrarily negotiated, requested and chosen by use of the "transport" field in the generic capability.
+
+## I.3 HTTP generic capability
+
+Table I.1 defines the capability identifier for HTTP generic capability. Tables I.2 and I.3 define the associated capability parameters.
+
+**Table I.1 – Capability identifier for HTTP capability**
+
+| Capability name | HTTP |
+|-----------------------------|-----------------------------------------------------------------|
+| Capability class | Data application |
+| Capability identifier type | Standard |
+| Capability identifier value | itu-t (0) recommendation (0) h(8) 324 generic-capabilities(1) 0 |
+| maxBitRate | This field shall be included. |
+| nonCollapsingRaw | This field shall not be included. |
+| Transport | This field shall be included. |
+
+**Table I.2 – Mode for HTTP capability**
+
+| Parameter name | mode |
+|----------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter description | This is a nonCollapsing GenericParameter.
mode indicates the operating mode of the terminal:
1) Server
2) Client
3) Server and Client (this mode may be used in capability exchange, but shall not be set in logical channel signalling) |
+| Parameter identifier value | 0 |
+| Parameter status | Mandatory |
+| Parameter type | unsignedMin |
+| Supersedes | – |
+
+**Table I.3 – Underlying protocol for HTTP capability**
+
+| Parameter name | underlyingProtocol |
+|----------------------------|--------------------------------------------------------------------------------------------------------------------------------|
+| Parameter description | This is a nonCollapsing GenericParameter.
underlyingProtocol indicates the protocol under HTTP:
0) None
1) TCP/IP/PPP |
+| Parameter identifier value | 1 |
+| Parameter status | Mandatory |
+| Parameter type | unsignedMin |
+| Supersedes | – |
+
+## I.4 References
+
+See clause 2.
+
+# Annex J
+
+## ASN.1 OIDs defined in this Recommendation
+
+(This annex forms an integral part of this Recommendation)
+
+This annex summarizes the OIDs defined in this Recommendation and defines ITU-T H.324 generic capabilities which are used in ITU-T H.245 signalling-based systems.
+
+## J.1 Summary of OIDs defined in this Recommendation
+
+**Table J.1 – Summary of OIDs defined in this Recommendation**
+
+| OID | Clause reference |
+|-----------------------------------------------------------------------------------------------|------------------|
+| { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) sessionResetCapability(1) } | 7.7.1 |
+| { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) mona(2) } | K.10.1 |
+| { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) mona(2) mos(1) } | K.8.3 |
+| { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) mona(2) mosack(2) } | K.8.3 |
+| { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) textConversationCapability(3) } | L.4.1 |
+
+## J.2 Session reset capability identifier
+
+**Table J.2 – Capability identifier for session reset**
+
+| Capability name | sessionResetCapability |
+|-----------------------------|-------------------------------------------------------------------------------------------|
+| Capability identifier type | Standard |
+| Capability identifier value | { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) sessionResetCapability(1) } |
+| maxBitRate | This parameter is not used. |
+| Collapsing | This field shall not be used and shall be ignored by receivers. |
+| nonCollapsing | This field shall not be used and shall be ignored by receivers. |
+| nonCollapsingRaw | This field shall not be used and shall be ignored by receivers. |
+| Transport | This field shall not be used and shall be ignored by receivers. |
+
+# Annex K
+
+# Media oriented negotiation acceleration procedure
+
+(This annex forms an integral part of this Recommendation)
+
+## K.1 Abstract
+
+This annex specifies an optional enhancement to the ITU-T H.324 call set-up procedure, to be used only in conjunction with Annex C, which allows media channels to be established in a fast and flexible manner.
+
+## K.2 General
+
+When the optional media oriented negotiation acceleration procedure is in use, there is an initial transmission of messages called MONA preference messages that are used to transmit preferences relevant to initial set-up of the media channels. The details of media channel set-up fall to one of several established signalling methods, depending on the channel set-up capabilities and preferences of the terminals as exchanged in the preference messages. Terminals may utilize a fast channel set-up which does not wait for capability exchange, but which requires fallback in the case where the initial channel transmission attempts do not succeed. Terminals may also utilize a flexible accelerated channel set-up method that depends on an initial exchange of preferences and the execution of a common inference algorithm on both sides. All terminals are capable of a reasonably fast fallback mechanism implemented as a minor change to the existing ITU-T H.245 procedures.
+
+## K.3 References
+
+See clause 2.
+
+## K.4 Definitions and format conventions
+
+### K.4.1 Definitions
+
+This annex defines the following terms:
+
+**K.4.1.1 inferred common mode (ICM):** The unique non-conflicting media mode determined by both terminals based on media preferences of local and peer MOS profile requests (always the same for both terminals). ICM is applicable to MOS only.
+
+**K.4.1.2 normal multiplexer level operation (NMLO):** The normal operation of the ITU-T H.223 multiplexer on the bearer channel. This is phase E of ITU-T H.324.
+
+### K.4.2 Abbreviations
+
+This annex uses the following abbreviations:
+
+| | |
+|-----|---------------------------------------|
+| ACP | Accelerated ITU-T H.245 Procedures |
+| FEA | Frame Emulation Avoidance (procedure) |
+| FI | Frame Information |
+| MOS | Media Oriented Set-up |
+| MPC | Media Preconfigured Channel |
+| MTE | Multiplexer Table Entry |
+| OLC | Open Logical Channel |
+| PL | Payload Length |
+| PSR | Payload Segmentation and Reassembly |
+
+| | |
+|-----|---------------------------------------------|
+| RTD | Round Trip Delay |
+| SPC | Signalling Preconfigured Channel |
+| SPP | Signalling Preconfigured channel Preference |
+| SSN | Segment Sequence Number |
+
+### K.4.3 Format conventions
+
+The numbering, field mapping and bit transmission conventions used are consistent with those used in clause 3.2 of [ITU-T H.223].
+
+## K.5 Terminal procedures
+
+The steps for provision of communication are as listed in clause C.5 with the following modifications:
+
+Phase D: MONA phase, as specified in this annex, is inserted during the level set-up procedure.
+
+## K.6 MONA signalling
+
+The initial exchange of preferences between MONA-capable terminals is performed using preference messages, short messages that include signalling to accelerate the establishment of multimedia sessions. These messages shall include the information of the supported methods for initial media channel creation.
+
+### K.6.1 Framing
+
+The MONA preference message frames are octet aligned and have the structure shown in Table K.1.
+
+**Table K.1 – Structure of a MONA preference message frame**
+
+| |
+|------------------------------------------------|
+| Frame Information (FI) (1 octet) |
+| Reserved (Always 0x00) (1 octet) |
+| Payload Length (PL) (1 octet) |
+| Payload
(0 or more octets up to 150 octets) |
+| CRC (2 octets) |
+
+The **Frame Information (FI)** bit allocation is shown in Table K.2. Bit 8 is reserved and shall be set to 1. Bit 7 represents the **Last Segment (LS)** flag, and the three following bits represent the **Segment Sequence Number (SSN)**. The three least significant bits are reserved and shall be set to 0.
+
+**Table K.2 – Bit structure of the MONA Frame Information (FI) field**
+
+| | | | | | | | |
+|---|----|------|------|------|---|---|---|
+| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
+| 1 | LS | SSN3 | SSN2 | SSN1 | 0 | 0 | 0 |
+
+The **Payload Length (PL)** field indicates the payload size in octets before the application of the frame emulation avoidance (FEA) procedure.
+
+The **Payload** consists of the preference message capability description, as defined below.
+
+The **cyclic redundancy check (CRC)** field is 16 bits and is determined by applying the CRC described in clause 8.1.1.6.1 of [ITU-T V.42] to the entire frame, excluding the MONA synchronization flags and the CRC field, and before FEA.
+
+On detecting a CRC error or undefined frame information or undefined reserved bits, the corresponding MONA preference message frame shall be discarded, except in cases where MONA framing is used to encapsulate MPC media data. In such cases, the terminal may have a media decoder capable of error correction and/or concealment, and so the corrupted media may be salvaged as appropriate.
+
+The MONA synchronization flag is defined in Table K.3.
+
+**Table K.3 – Structure of the MONA synchronization flag**
+
+| | |
+|------|-----------------|
+| 0xA3 | 1 0 1 0 0 0 1 1 |
+| 0x35 | 0 0 1 1 0 1 0 1 |
+
+One MONA synchronization flag shall be inserted immediately before and after each preference message frame. Only one MONA synchronization flag shall exist between two consecutive preference message frames.
+
+Segmentation and reassembly of preference message frames is done using a modified version of the control channel segmentation and reassembly layer (CCSRL) procedure defined in clause C.8.1. The following modifications are made:
+
+- The LS flag shall be used in place of CCSRL LS. LS shall be set to 1 on the PDU containing the last segment of an SDU. It shall be set to 0 otherwise.
+- The SSN shall be set to 0 for the first segment and monotonically incremented for each segment, the maximum value of SSN shall be 6. The value 7 is reserved.
+
+A flag emulation avoidance (FEA) procedure shall be performed against synchronization flags for all multiplexer levels of ITU-T H.324 before transmitting a MONA preference message frame onto the bearer. Frame information, payload length, payload and CRC are included in the FEA procedure. All octets with values 0xA3, 0x35, 0xE1, 0x4D, 0x1E, 0xB2, 0x19, 0xB1, 0x7E and 0xC5 shall have an octet with value 0xC5 inserted immediately preceding them.
+
+### K.6.2 Payload
+
+The preference message payload contains the information of the initial accelerated call set-up method capabilities. These capabilities indicate which methods may be used for establishment of media channels. The payload is defined in Tables K.4 and K.5. For transmission, this payload is considered to consist of 16-bit words which are sent in little-endian order.
+
+**Table K.4 – Bit fields defining preference message capabilities**
+
+| 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
+|---------|-----|--------|----|----------|----|----|--------|--------|---------|---|---|---|---|---|---|
+| VER | SPC | MPC-RX | | | | | | | | | | | | | |
+| ACK | SPP | MPC-TX | | | | | | | | | | | | | |
+| MONA-ML | | | | Reserved | | | SPC-DA | SPC-DC | EXT-LEN | | | | | | |
+
+**Table K.5 – Preference message capability definition**
+
+| Capability name | Description |
+|---------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Version (VER) | MONA version number (2 bits). It shall be set to 0 for the current version. The value 3 is reserved. |
+| Signalling preconfigured channel (SPC) support | Set to 1 if the MONA terminal supports negotiation of logical channels using the signalling preconfigured channel, set to 0 otherwise. |
+| Media preconfigured channel receive bits (MPC-RX) | (13 bits) Describes which media preconfigured channel configurations the MONA terminal is capable of receiving.
The bit numbers, (from 1 to 13) as shown in Table K.4, correspond exactly to the MUX code values in the media preconfigured channel configuration (See Table K.15). |
+| Acknowledgement state (ACK) | The MONA terminal shall set ACK in its outgoing preference messages as follows:
00 – MONA terminal has not successfully received any incoming preference messages
01 – MONA terminal acknowledges receiving at least one incoming preference message containing an ACK value of 00
10 – MONA terminal acknowledges receiving at least one incoming preference message containing an ACK value of 01
11 – Reserved |
+| Signalling preconfigured channel preference (SPP) | Set to 1 if the MONA terminal prefers negotiation of logical channels using the signalling preconfigured channel, set to 0 otherwise. |
+| Media preconfigured channel transmit bits (MPC-TX) | (13 bits) Describes which media preconfigured channel configurations the MONA terminal is capable of sending.
The bit numbers (from 1 to 13) as shown in Table K.4 correspond exactly to the MUX code values in the media preconfigured channel configuration (See Table K.15). |
+| MONA multiplex level (MONA-ML) | (5 bits) Represents the multiplexer level preference of the terminal.
First 3 MSBs indicate initial multiplexer level. Fourth bit indicates using ITU-T H.223 Annex A double flag mode. Fifth bit indicates using ITU-T H.223 Annex B optional header mode.
Operating multiplexer level shall be determined as defined in clause C.6.2 but without transmission, recognizing the MONA-ML in the transmitted and received preference message as the starting points. |
+| Reserved | Reserved bits shall be set to zero. Non-zero values received shall be ignored. |
+| Signalling preconfigured channel delay attempt (SPC-DA) | (1 bit) SPC delay attempt. When set (to 1), it is an indication that a device wants the peer device to not time out for SPC upon not receiving SPC MOS Ack.
SPC-DA shall not be set if SPC-DC is set. |
+| Signalling preconfigured channel delay capable (SPC-DC) | (1 bit) SPC delay capable. When set (to 1), it is an indication that a device is capable of delaying time out for SPC upon not receiving SPC MOS Ack.
SPC-DC shall not be set if SPC-DA is set. |
+| Extension length (EXT-EN) | (7 bits) Length of additional capability information, in octets. |
+
+Terminals shall support at least one preconfigured channel receive capability.
+
+NOTE – This requirement may be met by setting SPC to 1, or by setting at least one non-zero bit within MPC-RX.
+
+The SPC field indicates whether the terminal supports channel negotiation using the procedures defined in clause K.8. The SPP field indicates whether the terminal prefers channel negotiation using the procedures defined in clause K.8. Interpretation of these fields is given in clause K.7.
+
+Media oriented negotiation acceleration multiplex level (MONA-ML) is used to signal the multiplex level used in the case where the media channels are negotiated using the accelerated procedures of this annex (see clauses K.8, K.9 and K.10).
+
+The ACK bits are used by the terminal to signal the acknowledgement state of the peer's preference message.
+
+The SPC-DC and SPC-DA fields are used to signal SPC MOS request delay capability or request. Interpretation of these fields is given in clause K.8.1.1.
+
+Future protocol versions may add extra fields to the end of the capability information defined in Table K.4. The length of such extra information in octets is provided in the EXT-LEN field. For compatibility with such future versions, a terminal that receives a preference message with VER set to an unknown version should discard the extra information.
+
+Preference message frames may be used to encapsulate media per the definition in clause K.9.3 and encapsulate signalling per the definition of clause K.9.4.
+
+## **K.7 Channel establishment method negotiation**
+
+### **K.7.1 MONA algorithm**
+
+A MONA-capable terminal begins the session establishment procedure by transmitting at least ten repetitions of the preference message which contains information about its channel establishment capabilities and preferences. All outgoing preference messages sent from a terminal during a particular session shall contain identical information in the preference message capability payload, with the exception of the acknowledgement state (ACK).
+
+The ACK bits are used by the terminal to signal an acknowledgement of the peer's preference message. These bits are set to 00 in the initial transmission. After receiving at least one incoming preference message, the ACK bits in subsequent outgoing preference messages shall be set to 01 to acknowledge the reception of the incoming preference message. After receiving at least one incoming preference message with the ACK set to 01, the ACK bits in subsequent outgoing preference messages shall be set to 10. Upon receiving an incoming preference message with ACK containing value 10, or receiving the first non-empty ITU-T H.223 MUX-PDU, the terminal shall stop sending outgoing preference messages. In the case of an active SPC/MOS negotiation, a terminal shall continue sending preference messages encapsulating the SPC/MOS messages until completion of the procedures of clause K.8.
+
+After sending the initial preference message repetitions, but before receiving incoming preference messages from the remote end, the MONA-capable terminal may make outgoing transmissions with any combination of the following:
+
+- It may send media data on one or more media preconfigured channels (per definition in clause K.9.3).
+- It may send session signalling data on the signalling preconfigured channel (per the definition in clause K.9.4).
+- It may send multiplexer level set-up flags (per the definition in clause K.7.1.1).
+
+The MONA-capable terminal shall not transmit media on any preconfigured channels not indicated in the MPC-TX bits of the outgoing preference messages sent by the terminal. The terminal shall continue to send at least one preference message between each pair of outgoing preconfigured channel PDUs until the stopping criterion (defined previously) is reached.
+
+Upon the successful receipt of an incoming preference message, the MONA-capable terminal shall examine the received MPC-RX bits to determine which outgoing media preconfigured channels were not successfully established. The transmission of any such unsuccessful channels shall be immediately dropped.
+
+At this point, the channel negotiation behaviour of the terminal is determined as follows:
+
+- If both terminals have indicated support for the procedures of clause K.8 (SPC) and at least one of the two terminals indicates preference for those procedures (SPP), then all outgoing media preconfigured channels shall be dropped, and channel negotiation shall proceed using the procedures of clause K.8.
+
+NOTE 1 – In this case, the media preconfigured channels are never considered to be successfully established.
+
+- If both terminals have indicated support for the procedures of clause K.8 (SPC) and a comparison of the MPC sending and receiving capabilities (expressed as the MPC-RX and MPC-TX bits exchanged between both sides) indicates that no successful preconfigured channels can be established in the current session, then channel negotiation shall proceed using the procedures of clause K.8.
+
+NOTE 2 – Such determination may be made by logical AND-ing of the local MPC-RX bits with the remote MPC-TX bits, and likewise AND-ing of the remote MPC-RX bits with the local MPC-TX bits.
+
+- In all other cases, the terminal shall establish the missing outgoing media channels for each media type using one of the following procedures:
+
+- If examination of the received MPC-RX bits indicates that a media preconfigured channel can be successfully established for the given media type, the terminal may begin transmitting media on the appropriate preconfigured channel.
+
+NOTE 3 – Successful channel establishment is guaranteed in this case. If this is used for fallback following a failed transmission attempt, then it is equivalent to the MPC-Fallback procedure defined in clause K.9.3.
+
+- The terminal may establish the outgoing channel using the procedures of clause K.10 (ACP).
+
+- If the procedures of clause K.8 (SPC) are used to establish media channels, the following apply:
+
+- SPC negotiation procedures exchange media oriented set-up (MOS) request messages in order to establish media channels.
+- The SPC channel negotiation will make use of any MOS request messages previously exchanged using the signalling preconfigured channel. The initial exchange of MOS request messages is independent of the exchange of preference messages.
+- If one or both sides have not sent initial signalling preconfigured channel transmissions, they shall begin to do so as soon as the decision to use SPC has been made through the exchange of preference messages. A terminal may delay transmission of SPC/MOS requests in accordance with the use of SPC-DC and SPC-DA as described in Table K.5 and clause K.8.1.1.
+
+NOTE 4 – Terminals supporting SPC will achieve better session set-up if they transmit SPC/MOS at an earlier time than the SPP determination.
+
+- Upon receiving the first incoming ITU-T H.245 message from a remote MONA terminal, a MONA terminal shall immediately initiate outgoing ITU-T H.245 TerminalCapabilitySet (TCS) and MasterSlaveDetermination (MSD) procedures, if such procedures have not yet been started.
+
+NOTE 5 – Prior to sending any ITU-T H.245 messages during a session, ITU-T H.245 TerminalCapabilitySet (TCS) and MasterSlaveDetermination (MSD) requests are required to be sent according to clause 7.4. The use of ITU-T H.245 signalling, including ACP, requires initiating both the TerminalCapabilitySet (TCS) and MasterSlaveDetermination (MSD) procedures.
+
+#### K.7.1.1 Multiplexer flag interleaving
+
+A terminal should insert stuffing flags of its multiplexer level, as described in clause C.6.1, between adjacent preference messages and/or preconfigured channel PDUs. No more than 20 stuffing flags shall be inserted. Interleaving should be halted upon reception of a preference message.
+
+The initial level used for such interleaved flags shall match the multiplexer level preference signalled in the MONA-ML field.
+
+Figure K.1 illustrates some acceptable patterns of MONA sync flags, MONA preference message frames and multiplexer level stuffing flags.
+
+
+
+| | | | | | | |
+|----------------|--------------------------|----------------|--------------------------------------|----------------|--------------------------|----------------|
+| MONA sync flag | Preference message frame | MONA sync flag | | | | |
+| MONA sync flag | Preference message frame | MONA sync flag | Preference message frame | MONA sync flag | | |
+| MONA sync flag | Preference message frame | MONA sync flag | MUX level flags
(no more than 20) | MONA sync flag | Preference message frame | MONA sync flag |
+
+Figure K.1: Illustration showing several acceptable patterns of MONA sync flags, MONA preference message frames and multiplexer level stuffing flags. The diagram consists of three horizontal rows of colored boxes. The first row shows a sequence of MONA sync flag (green), Preference message frame (yellow), and MONA sync flag (green). The second row shows a sequence of MONA sync flag (green), Preference message frame (yellow), MONA sync flag (green), Preference message frame (yellow), and MONA sync flag (green). The third row shows a sequence of MONA sync flag (green), Preference message frame (yellow), MONA sync flag (green), MUX level flags (no more than 20) (blue), MONA sync flag (green), Preference message frame (yellow), and MONA sync flag (green).
+
+H.324(09)\_FK.1
+
+**Figure K.1 – Illustration showing several acceptable patterns of MONA sync flags, MONA preference message frames and multiplexer level stuffing flags**
+
+#### K.7.1.2 Legacy interworking
+
+When communicating with a legacy terminal, a MONA terminal will encounter standard multiplexer level flags. In order to have negligible impact on set-up time with the legacy terminal, a MONA terminal should try to detect the standard multiplexer level set-up as soon as possible and revert to legacy behaviour, cease all MONA transmissions and follow normal start-up procedures as defined in Annex C. Either of the following conditions shall initiate fallback to legacy behaviour:
+
+- More than 20 valid consecutive multiplexer level stuffing flags are detected, as described in clause C.6.
+- A normal start-up procedure is detected with a normal ITU-T H.245 TerminalCapabilitySet message as the first non-empty ITU-T H.223 MUX-PDU at an initial multiplexer level agreed by detecting standard multiplexer level set-up.
+
+### K.7.2 Terminal requirements and illustrative behaviour
+
+#### K.7.2.1 Minimum terminal requirements
+
+It is possible for a MONA terminal to implement all aspects of the channel negotiation methods defined in clauses K.8, K.9 and K.10. However, a complete implementation is not required. The minimum set of channel negotiation method elements which shall be supported by all compliant MONA terminals are as follows:
+
+- 1) MONA terminals shall support the MONA signalling defined in clause K.6 and the MONA algorithm defined in clause K.7.1.
+- 2) MONA terminals shall be capable of opening incoming and outgoing channels using the accelerated ITU-T H.245 procedures (ACP) defined in clause K.10.
+- 3) MONA terminals shall support at least one preconfigured channel receive capability. This may be met in one of two ways:
+ - a) the terminal may set SPC to 1, to indicate the capability of negotiating channels via the SPC procedures (clause K.8); or
+ - b) the terminal may set one or more MPC-RX bits to 1, to indicate the capability to receive media using the MPC procedures (clause K.9).
+
+Hence, MONA terminal implementations could be classified into three classes:
+
+- **Class I: SPC+MPC+ACP** – The terminal supports all three procedures.
+- **Class II: MPC+ACP** – The terminal supports the MPC and ACP procedures.
+- **Class III: SPC+ACP** – The terminal supports the SPC and ACP procedures.
+
+#### K.7.2.2 Typical decision logic (informative)
+
+The following figures show how typical MONA terminal classes would establish a single outgoing audio and a single outgoing video channel. A key to the symbols used in these diagrams is provided in Figure K.2.
+
+
+
+```
+graph TD; A[/Start condition/] --> B((Action)); B --> C[Event]; C --> D{Decision?}; D -- Y --> E[ ]; D -- N --> F[⊠ End]; style E fill:none,stroke:none;
+```
+
+Flowchart illustrating typical decision logic for MONA terminal classes. The flow starts with a 'Start condition' (parallelogram), followed by an 'Action' (circle), then an 'Event' (horizontal line), a 'Decision?' (diamond) with 'Y' (Yes) and 'N' (No) paths, and finally an 'End' (square with X). The diagram is labeled H.324(09)\_FK.2.
+
+Figure K.2 – Key to the symbols used in Figures K.3 through K.6
+
+##### **K.7.2.2.1 Capability class I: SPC + MPC + ACP**
+
+Figure K.3 shows the logic which a class I MONA terminal would follow in order to establish the outgoing audio and video channels to a remote MONA terminal. Depending on the specific capabilities and preferences expressed by the terminals, it is possible that all channels would be established using a single method (SPC, ACP or MPC), or that a combination of MPC and ACP techniques could be applied on a per-channel basis.
+
+
+
+```
+
+graph TD
+ Start[/MONA-to-MONA:
+Terminal supports
+SPC + MPC + ACP/] --> Step1((Transmit MONA preference messages
+(initial repetitions)))
+ Step1 --> Step2((Transmit MOS requests on SPC
+and/or outgoing media on MPC(s)
+and/or standard level set-up flags))
+ Step2 --> Step3((MONA preference message(s)
+received from remote end))
+ Step3 --> Step4((Drop unsuccessful
+outgoing MPCs, if any))
+ Step4 --> Decision1{Does
+remote terminal
+support SPC
+(test SPC bit)?}
+ Decision1 -- N --> Decision4{Are all desired
+outgoing channels
+established?}
+ Decision1 -- Y --> Decision2{Does
+either terminal
+prefer SPC
+(test SPP bits)?}
+ Decision2 -- Y --> Step5((Drop all outgoing MPC
+transmissions))
+ Decision2 -- N --> Decision3{Are any
+MPCs possible
+(test MPC-RX,
+MPC-TX)?}
+ Decision3 -- Y --> Step6((Drop any outgoing SPC
+transmission))
+ Decision3 -- N --> Step7((Establish all channels
+using SPC procedures))
+ Step5 --> Step7
+ Step6 --> Decision4
+ Step7 --> Decision4
+ Decision4 -- Y --> End[All outgoing channels
+established successfully]
+ Decision4 -- N --> Decision5{Prefer
+ACP or MPC
+to open missing
+channel?}
+ Decision5 -- ACP --> Step8((Establish missing
+channel using ACP))
+ Decision5 -- MPC --> Decision6{Does a
+compatible MPC
+exist for the
+channel?}
+ Decision6 -- N --> Step8
+ Decision6 -- Y --> Step9((Transmit media
+for missing
+channel using
+compatible MPC))
+ Step8 --> Step10[Execute procedures within
+dotted line independently per
+missing outgoing channel]
+ Step9 --> Step10
+ Step10 --> Decision4
+
+```
+
+H.324(09)\_FK.3
+
+Flowchart illustrating the logic typically used by a class I MONA terminal to establish outgoing audio and video channels to a remote MONA terminal. The process starts with a terminal supporting SPC + MPC + ACP, followed by transmitting preference messages and MOS requests. It then checks for remote SPC support and preferences, leading to either dropping transmissions or establishing channels via SPC or ACP/MPC procedures.
+
+**Figure K.3 – Logic typically used by a class I MONA terminal to establish outgoing audio and video channels to a remote MONA terminal**
+
+##### K.7.2.2.2 Capability class II: MPC + ACP
+
+Figure K.4 shows the logic which a class II MONA terminal would follow in order to establish the outgoing audio and video channels to a remote MONA terminal. In this case, it is possible that all channels are established using either MPC or ACP, or that the two methods may be applied on a per-channel basis.
+
+
+
+```
+
+graph TD
+ Start[/MONA-to-MONA:
+Terminal supports
+MPC + ACP/] --> T1(( ))
+ T1 --> T1_desc[Transmit MONA preference messages
+(initial repetitions)]
+ T1_desc --> T2(( ))
+ T2 --> T2_desc[Transmit outgoing media
+on 1 or more MPCs and/or
+standard level set-up flags]
+ T2_desc --> T3(( ))
+ T3 --> T3_desc[MONA preference message(s)
+received from remote end]
+ T3_desc --> T4(( ))
+ T4 --> T4_desc[Drop unsuccessful
+outgoing MPCs, if any]
+ T4_desc --> D1{Are all desired
+outgoing channels
+established?}
+ D1 -- Y --> End[All outgoing channels
+established successfully
+H.324(09)_FK.4]
+ D1 -- N --> D2{Prefer
+ACP or MPC
+to open missing
+channel?}
+ subgraph Loop [Execute procedures within
+dotted line independently per
+missing outgoing channel]
+ D2 -- ACP --> T5(( ))
+ D2 -- MPC --> D3{Does a
+compatible MPC
+exist for the
+channel?}
+ D3 -- N --> T5
+ D3 -- Y --> T6(( ))
+ T6 --> T6_desc[Transmit media for
+missing channel using
+compatible MPC]
+ T5 --> T5_desc[Establish missing
+channel using ACP]
+ end
+ T6_desc --> End
+ T5_desc --> End
+
+```
+
+Flowchart showing the logic for establishing outgoing channels for a class II MONA terminal. The process starts with terminal support for MPC + ACP, followed by preference message transmission, media transmission, and handling of received preference messages. A loop for missing channels uses either MPC or ACP based on preference and compatibility.
+
+**Figure K.4 – Logic typically used by a class II MONA terminal to establish outgoing audio and video channels to a remote MONA terminal**
+
+##### K.7.2.2.3 Capability class III: SPC + ACP
+
+Figure K.5 shows the logic which a class III MONA terminal would follow in order to establish the outgoing audio and video channels to a remote MONA terminal. For this case, either SPC or ACP will be selected depending on the contents of the sent and received MONA preference frames. The selected method will then be used to establish all audio and video channels in the current session.
+
+
+
+```
+graph TD; A[/MONA-to-MONA:
+Terminal supports
+SPC + ACP/] --> B((Transmit
+MONA preference messages
+(initial repetitions))); B --> C((Transmit MOS requests
+on SPC and/or standard
+level set-up flags)); C --> D[MONA preference message(s)
+received from remote end]; D --> E{Does
+remote terminal
+support SPC
+(test SPC bit)?}; E -- Y --> F{Does
+either terminal
+prefer SPC
+(test SPP bits)?}; E -- N --> G((Establish all channels
+using ACP)); F -- Y --> H((Establish all channels
+using SPC procedures)); F -- N --> G; G --> I[All outgoing channels
+established successfully]; H --> I; H -- H.324(09)_FK.5 --> I;
+```
+
+The flowchart illustrates the logic for establishing outgoing audio and video channels for a class III MONA terminal. It begins with a terminal that supports both SPC and ACP. The process involves transmitting MONA preference messages and MOS requests. Upon receiving a MONA preference message from the remote end, the terminal checks if the remote terminal supports SPC (by testing the SPC bit). If not, it establishes all channels using ACP. If the remote terminal does support SPC, the terminal then checks if either terminal prefers SPC (by testing SPP bits). If SPC is preferred, it establishes all channels using SPC procedures. Otherwise, it falls back to using ACP. Both methods lead to all outgoing channels being established successfully. The diagram is labeled H.324(09)\_FK.5.
+
+Flowchart showing the logic for establishing outgoing audio and video channels for a class III MONA terminal.
+
+Figure K.5 – Logic typically used by a class III MONA terminal to establish outgoing audio and video channels to a remote MONA terminal
+
+##### K.7.2.2.4 MONA-to-legacy case
+
+Figure K.6 shows the logic by which a MONA terminal would detect that the remote terminal is not MONA-capable, and so revert to legacy ITU-T H.245 session negotiation (signalling) in order to establish the audio and video channels. This logic is applicable to any of the MONA capability classes.
+
+
+
+```
+graph TD; A[/MONA-to-legacy/] --> B(( )); B --> C[Transmit MONA preference messages
+(initial repetitions)]; C --> D(( )); D --> E[Transmit MOS requests on SPC
+and/or outgoing media on MPC(s) and/or
+standard level set-up flags]; E --> F[Detect incoming
+>20 legacy stuffing flags or
+normal ITU-T H.245 TerminalCapabilitySet]; F --> G(( )); G --> H[Drop outgoing MONA transmissions
+and revert to legacy behavior]; H --> I[Session established via
+regular ITU-T H.245 negotiation]; I --- J[H.324(09)_FK.6];
+```
+
+The flowchart illustrates the logic for the MONA-to-legacy case. It begins with a parallelogram labeled 'MONA-to-legacy'. The process then enters a loop: first, a circle followed by the text 'Transmit MONA preference messages (initial repetitions)'; second, another circle followed by 'Transmit MOS requests on SPC and/or outgoing media on MPC(s) and/or standard level set-up flags'; third, a circle followed by 'Detect incoming >20 legacy stuffing flags or normal ITU-T H.245 TerminalCapabilitySet'. If the detection condition is met, the flow proceeds to a circle followed by 'Drop outgoing MONA transmissions and revert to legacy behavior', which then leads to a crossed square symbol followed by 'Session established via regular ITU-T H.245 negotiation'. A small label 'H.324(09)\_FK.6' is at the bottom right.
+
+Flowchart for the MONA-to-legacy case logic flow.
+
+Figure K.6 – Logic flow for the MONA-to-legacy case
+
+## K.8 Channel establishment via the signalling preconfigured channel (SPC)
+
+### K.8.1 MOS profile exchange
+
+#### K.8.1.1 Procedure
+
+If a terminal supports the SPC, it shall send its MOS request (**mos**) using the SPC (see Table K.6) as defined in clause K.7.1. The MOS request transmissions should be repeated until a MOS **requestAck** (see Table K.14) is detected, or one of the conditions in clause K.8.2 is fulfilled. For the latter case, the procedure in clause K.8.2 shall be followed.
+
+When a MOS request is detected and decoded successfully from the MOS SPC, the terminal accepts it by beginning the transmission and processing of media data as determined by the ICM at NMLO using the agreed mobile level. MOS **requestAck** shall be sent on receiving every MOS request.
+
+Delayed transmission of MOS requests is only allowed when both the SPC-DA is set in the local PM and the SPC-DC is set in the remote PM received.
+
+If MOS is completed successfully, ITU-T H.245 message exchange is skipped and opened logical channels operate immediately. The procedure is shown in Figure K.7.
+
+NOTE 1 – The channels established through the MOS procedure operate immediately on their determined multiplexer entries and require no special framing.
+
+
+
+```
+
+sequenceDiagram
+ participant Terminal A with MOS support
+ participant Terminal B with MOS support
+ Note right of Terminal B: H.324(09)_FK.7
+ Terminal A->>Terminal B: mos request
+ Terminal B-->>Terminal A: MOS requestAck
+ Terminal B->>Terminal A: mos request
+ Terminal A-->>Terminal B: MOS requestAck
+ Note over Media: Media
+
+```
+
+Sequence diagram of MOS call flow between Terminal A and Terminal B. Terminal A sends a 'mos request' to Terminal B. Terminal B responds with a 'MOS requestAck'. Terminal A then sends another 'mos request' to Terminal B, which responds with another 'MOS requestAck'. The messages are shown crossing over a 'Media' block at the bottom. The diagram is labeled H.324(09)\_FK.7.
+
+**Figure K.7 – MOS call flow**
+
+NOTE 2 – A device that has delayed transmission of its MOS request could send extra media decoder refresh points in the early part of its media session to help ensure early session quality in case its first MOS request is delayed in processing or corrupted.
+
+For the master slave determination, when the **terminalType** (Table K.7) fields differ, the terminal which has higher **terminalType** value shall be the master. When the **terminalType** fields in the MOS request of the two terminals are identical, and the two terminals have different values of **caller** (Table K.11) field, the caller shall be the master; if the **caller** fields are identical, the **terminalType** and **statusDeterminationNumber** (Table K.12) fields in the MOS request of the two terminals are used according to the master slave determination procedure in clause C.2 of [ITU-T H.245] and in an inferred manner without additional ITU-T H.245 signalling.
+
+NOTE 3 – The master slave relationship determined through MOS/SPC is used for at least the MOS/SPC procedures but would be overridden by a later ITU-T H.245 MasterSlaveDetermination (MSD) procedure.
+
+Unexpected MOS-SDUs shall be discarded.
+
+#### K.8.1.2 Logical channels
+
+A terminal indicates its requested logical channels by listing ITU-T H.245 **OpenLogicalChannel** (OLC) requests according to an order of preference in **mediaProfile** (Table K.8). The requests shall be processed in the same order.
+
+Logical channel numbers (LCNs) are assigned by the message originator. OLC requests with the same LCN indicate alternative media capabilities for the logical channel. For bidirectional logical channels, the reverse LCN shall be the same as the forward LCN. If a reverse LCN is already assigned, the next available LCN shall be assigned. The highest LCN shall be 13, and any OLC requests that lead to LCN exceeding 13 shall be ignored.
+
+If ICM contains an ITU-T H.223 adaptation layer type not supported by a terminal, the terminal shall fallback as described in clause K.8.2.
+
+#### K.8.1.3 Multiplex table entries
+
+The logical channel number shall be mapped to ITU-T H.223 multiplex entry index. For example, if logical channel 1 is opened, multiplex entry index 1 will be associated to this logical channel as "{LCN1, RC UCF}". For a reverse logical channel, the logical channel number shall be mapped to multiplex entry index at the ITU-T H.223 demultiplexer.
+
+Explicit multiplex table entries may be set using **additionalInfo** (Table K.10) parameter.
+
+Alternate multiplex entries may be signalled similarly as assigning LCNs for alternative media capabilities in clause K.8.1.2.
+
+NOTE 1 – Outgoing LCNs specified in explicit multiplex table entries for transmission are not expected to be changed.
+
+NOTE 2 – For example or alternative logical channels of {AMR, G.723.1} with LCN 3 and {H.263, H.261} with LCN 2, additional multiplex entries may be set as follows:
+
+- Index 5: (empty); Index 5: {LC 3, RC 22}, {LC 2, RC UCF}
+- Index 7: {LC 3, RC 32}, {LC 2, RC UCF}; Index 7: {LC 3, RC 25}, {LC 2, RC UCF}
+- Index 8: {LC 3, RC 7}, {LC 2, RC UCF}
+
+This represents, when AMR is selected, multiplex entries are: Index 7: {LC 3, RC 32}, {LC 2, RC UCF}; Index 8: {LC 3, RC 7}, {LC 2, RC UCF}; when ITU-T G.723.1 is selected, multiplex entries are: Index 5: {LC 3, RC 22}, {LC 2, RC UCF}; Index 7: {LC 3, RC 25}, {LC 2, RC UCF}.
+
+### K.8.2 Fallback procedure
+
+A fallback procedure shall be used by a MOS terminal to switch to the next phase of normal operation mode as described in clause K.7.
+
+MONA fallback is specified in clause K.7.2, the following additional conditions shall also initiate a fallback from MOS:
+
+- A normal ITU-T H.245 **TerminalCapabilitySet** message with empty **genericControlCapability** containing MOS OID after completion of the MOS procedure.
+- A terminal does not detect a valid MOS request, or does not accept the ICM, within a multiple of the network round trip delay (RTD) period. Typically, three RTDs are adopted.
+
+An exception to the timeout-initiated fallback as above is that timeout fallback shall not occur if the SPC-DC capability was set in transmitted PMs and the SPC-DA indication was set in received PMs (as in this situation, the remote terminal may delay its SPC MOS request). In this case, the device shall not fallback from MOS before a MOS request is received.
+
+### K.8.3 MOS messages
+
+Table K.6 defines the capability identifier for the **mos** capability and Tables K.7 to K.12 define the associated parameters. Tables K.13 and K.14 define the MOS Ack capability identifier and parameter, respectively.
+
+**Table K.6 – MOS capability identifier**
+
+| | |
+|-----------------------------|--------------------------------------------------------------------------------|
+| Capability name | mos |
+| Capability class | Control capability |
+| Capability identifier type | Standard |
+| Capability identifier value | { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) mona(2) mos(1) } |
+
+**Table K.7 – MOS parameter – terminalType**
+
+| | |
+|----------------------------|----------------------------------------|
+| Parameter name | terminalType |
+| Parameter description | Terminal type as defined in clause 7.4 |
+| Parameter identifier value | 2 |
+| Parameter status | Mandatory |
+| Parameter type | unsignedMax |
+| Supersedes | – |
+
+**Table K.8 – MOS parameter – mediaProfile**
+
+| | |
+|----------------------------|----------------------------------------------------------------------------------------------------------------|
+| Parameter name | mediaProfile |
+| Parameter description | One or more ITU-T H.245 OpenLogicalChannel structures specifying media channels in order of preference. |
+| Parameter identifier value | 4 |
+| Parameter status | Optional |
+| Parameter type | octetString |
+| Supersedes | – |
+
+**Table K.9 – MOS parameter – mediaSymmetric**
+
+| | |
+|----------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name | mediaSymmetric |
+| Parameter description | When set, all media capabilities are symmetric as per [ITU-T H.245]. When this parameter is absent, all media capabilities are non-symmetric as per [ITU-T H.245]. |
+| Parameter identifier value | 5 |
+| Parameter status | Optional |
+| Parameter type | logical |
+| Supersedes | – |
+
+**Table K.10 – MOS parameter – additionalInfo**
+
+| | |
+|----------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name | additionalInfo |
+| Parameter description | One or more ITU-T H.245 MultimediaSystemControlMessage such as UserInputIndication, MultiplexEntrySend and TerminalCapabilitySet. OpenLogicalChannel should not be included. No ITU-T H.245 response shall be generated for request messages interpreted as commands. Only messages with settings within the mandatory limit of the Recommendation shall be sent as receivers, receivers shall ignore messages outside these limits. Response messages are meaningless. Values specified in this parameter take precedence to inferred values. An exception is to MultiplexEntrySend such that inferred multiplex entry index takes precedence.
If a TerminalCapabilitySet is supplied, OPTIONAL fields such as multiplexCapability, capabilityTable and capabilityDescriptors are optional. Capabilities already inferred from mediaProfile parameter should not be included. Additional capabilities such as receiveUserInputCapability may be appended to capabilityTable.
|
+| Parameter identifier value | 6 |
+| Parameter status | Optional |
+| Parameter type | octetString |
+| Supersedes | – |
+
+**Table K.11 – MOS parameter – caller**
+
+| | |
+|----------------------------|-----------------------------------------------------------------------------------------|
+| Parameter name | caller |
+| Parameter description | Indication that the terminal is a caller. When not specified, the terminal is a callee. |
+| Parameter identifier value | 7 |
+| Parameter status | Mandatory |
+| Parameter type | logical |
+| Supersedes | – |
+
+**Table K.12 – MOS parameter – statusDeterminationNumber**
+
+| | |
+|----------------------------|--------------------------------------------------------------|
+| Parameter name | statusDeterminationNumber |
+| Parameter description | A random number as defined in clause B.1.1 of [ITU-T H.245]. |
+| Parameter identifier value | 8 |
+| Parameter status | Mandatory |
+| Parameter type | unsigned32Max |
+| Supersedes | – |
+
+**Table K.13 – MOS Ack capability identifier**
+
+| | |
+|-----------------------------|-----------------------------------------------------------------------------------|
+| Capability name | mos Ack |
+| Capability class | Control capability |
+| Capability identifier type | Standard |
+| Capability identifier value | { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) mona(2) mosack(2) } |
+
+**Table K.14 – MOS Ack parameter – requestAck**
+
+| | |
+|----------------------------|---------------------------------------------------------------------------------------------------|
+| Parameter name | requestAck |
+| Parameter description | Acknowledge receipt of MOS message. One Ack message shall be sent for every MOS message received. |
+| Parameter identifier value | 10 |
+| Parameter status | Mandatory |
+| Parameter type | logical |
+| Supersedes | – |
+
+## K.9 Preconfigured channel establishment
+
+This clause specifies a procedure by which media channels may be established before capabilities and intents are exchanged. Specifically, a MONA terminal is allowed to send media before receiving any capability or other information from the opposite terminal. This allows for fastest possible set-up of channels, but limits the set-up options to a small set of fixed channel configurations.
+
+### K.9.1 General
+
+When the procedures of the current clause are in use, several of the ITU-T H.223 multiplex table entries are defined to reference default configurations for the multiplex table, codec configuration and other related parameters. Such default operation points may be used to quickly establish
+
+channels for data flow, called preconfigured channels. Preconfigured channels may be used to carry media data, or they may be used to exchange signalling data in order to negotiate regular logical channels. Once a preconfigured channel is established, it may be used for the duration of the session. media preconfigured channels may be replaced through ITU-T H.245-based negotiation of a regular logical channel of the same media type. If the procedures of clause K.7.1 determine that SPC-based negotiation will not be used to establish channels in the current session, then any current transmission of SPC data shall be dropped.
+
+NOTE – MPC does not include a mechanism to signal symmetric codec requirements. If a terminal has such requirements, it could use MPC limited to a single codec of a given media type for both transmit and receive. Alternately, it could use the SPC or ACP negotiation methods which do support symmetric codec negotiation.
+
+### K.9.2 Channel configurations
+
+The following combinations shown in Table K.15 of codec, LCN and multiplex table configuration shall be used within the MPC establishment procedure in order to establish preconfigured channels.
+
+**Table K.15 – Channel configurations**
+
+| Codec | MUX code | LCN | Multiplex table entry |
+|----------------------------------------|----------|-----|-----------------------|
+| Reserved (ITU-T H.245) | 0 | – | – |
+| ETSI TS 126 071 (AMR) | 1 | 1 | {1 ucf} |
+| ETSI TS 126 171 (AMR-WB) | 2 | 2 | {2 ucf} |
+| ITU-T H.264 | 3 | 3 | {3 ucf} |
+| ISO/IEC 14496-2 (MPEG-4 part 2) | 4 | 4 | {4 ucf} |
+| ITU-T H.263 | 5 | 5 | {5 ucf} |
+| Reserved | 6..11 | | |
+| Unspecified, left for operator use | 12..13 | | |
+| Signalling preconfigured channel (SPC) | 14 | 14 | {14 ucf} |
+| Reserved (WNSRP) | 15 | – | – |
+
+Each of the media codec options is associated with fixed configuration information. The configuration information consists of the whole state pertaining to a logical channel, as if that channel would have been opened using the normal open logical channel procedure of [ITU-T H.245].
+
+#### K.9.2.1 AMR speech (mux code 1)
+
+##### **Codec configuration:**
+
+maxBitRate = 12.2 kbit/s
+
+maxAl-sdu-Frames = 1
+
+##### **ITU-T H.223 configuration:**
+
+AL2 with sequence numbers
+
+maxAl-sdu-Frames = 1
+
+#### K.9.2.2 AMR-WB speech (mux code 2)
+
+##### **Codec configuration:**
+
+maxbitRate = 23.85 kbit/s
+
+maxAl-sduFrames = 1
+
+octetAlign = TRUE
+modeSet = all modes available
+modeChangePeriod = anytime
+modeChangeNeighbour = FALSE
+crc = FALSE
+
+##### **ITU-T H.223 configuration:**
+
+AL2 with sequence numbers
+(non-segmentable)
+
+#### **K.9.2.3 ITU-T H.264 visual (mux code 3)**
+
+##### **Codec configuration:**
+
+Sequence and picture parameter sets shall be inferred to be set as if the following, base64 encoded bitstream were received at the decoder:
+
+Base64: AAAAASdCoAqVoLE6AeEQjUAAAABKM4Gag==
+
+Hex: 00 00 00 01 27 42 a0 0a 95 a0 b1 3a 01 e1 10 8d 40 00 00 00 01 28 ce 06 6a
+
+##### **ITU-T H.223 configuration:**
+
+AL2 with sequence numbers
+(segmentable)
+
+NOTE – The above base64 coded bitstream corresponds to a single sequence parameter set with ID 0, and a single picture parameter set with ID 0. The properties are set to a widely accepted operation point of ITU-T H.264, which can be summarized as baseline profile, level 1.0, QCIF picture format, 8-bit frame\_num, one reference picture and constrained intra prediction on.
+
+#### **K.9.2.4 MPEG-4 visual (mux code 4)**
+
+##### **Codec configuration:**
+
+QCIF only
+
+maxBitRate = 64 kbit/s
+
+profileAndLevel = 8
+
+object = 1
+
+decoderConfigurationInformation:
+
+Base64: AAABsAgAAAG1CQAAAQAAAAEgAIRdTCgsIJCijw==
+
+Hex: 00 00 01 b0 08 00 00 01 b5 09 00 00 01 00 00 00 01 20 00 84 5d 4c 28 2c 20 90 a2 8f
+
+##### **ITU-T H.223 configuration:**
+
+AL2 with sequence numbers
+(segmentable)
+
+#### **K.9.2.5 ITU-T H.263 (mux code 5)**
+
+##### **Codec configuration:**
+
+QCIF only, with qcifMPI = 2
+
+maxBitRate = 64 kbit/s
+
+unrestrictedVector = FALSE
+arithmeticCoding = FALSE
+advancedPrediction = FALSE
+pbFrames = FALSE
+
+##### **ITU-T H.223 configuration:**
+
+AL2 with sequence numbers
+(segmentable)
+
+NOTE 1 – The ITU-T H.263 codec configuration is consistent with profile 0, level 10 defined in Annex X of [ITU-T H.263].
+
+NOTE 2 – A MONA terminal which opens an ITU-T H.263 channel using MPC procedures may or may not be capable of adjusting the videoTemporalSpatialTradeOff value used by its encoder. If a MONA terminal has this capability and wishes to allow adjustment of the value, it is required by clause B.14.2 of [ITU-T H.245] to send ITU-T H.245 MiscellaneousIndication messages including videoTemporalSpatialTradeOff values to the remote terminal. The remote terminal could use the presence or absence of such indications to infer whether the capability is supported.
+
+NOTE 3 – Other H263VideoCapability parameters not listed here are considered to be 'off' or not present.
+
+### **K.9.3 Sending procedure – Media preconfigured channels**
+
+MONA terminals may use preconfigured channels to establish the initial outgoing audio and visual connections to the remote terminal. The timing for the initiation of outgoing media preconfigured channel transmissions is restricted by the following rules (see also clause K.7.1):
+
+- Media preconfigured channel transmission may not start until the initial outgoing preference message repetition requirement has been met.
+- Media preconfigured channel transmission may not begin after the decision has been made to negotiate media channels using the procedures of clause K.8 (SPC).
+- Preconfigured channel transmission for a particular media type shall not begin after an outgoing channel of the same media type has been already established (whether via a different media preconfigured channel or by any other means). Equivalently, a preconfigured channel may only be used for the initial establishment of a channel for a given media type.
+- Transmission shall be limited to a single preconfigured channel per media type at any given time.
+
+Media preconfigured channels shall be formatted according to the following rules:
+
+- Until the receipt of at least one incoming preference message, outgoing preconfigured channel media PDUs shall be encapsulated within MONA preference messages.
+ - The framing for preference messages is defined in clause K.6.1.
+ - The payload for preference messages consists of the preference message capability payload defined in clause K.6.2, immediately followed by:
+ - One octet where the MUX code is carried in the least significant four bits. The MUX code is taken from the appropriate media preconfigured channel configuration defined in clause K.9.2.
+ - Media data in the form of a complete AL-PDU, including additional fields added at the adaptation layer.
+ - If the payload formed as above is larger than 150 octets, the payload will be subject to the usual segmentation and reassembly procedure for MONA framing (see clause K.6.1).
+
+NOTE 1 – As a consequence of the segmentation, the AL-PDU boundaries will be naturally marked by the last segment (LS) bit of the MONA frame information (FI) field.
+
+NOTE 2 – The PSR and FEA procedures normally used for preference messages are applied as well to preference messages which encapsulate media payloads.
+
+NOTE 3 – In order to meet audio jitter requirements, a MONA terminal may find it necessary to insert MONA-encapsulated audio frames between fragmented segments of MONA-encapsulated video or SPC signalling data. In this case, the receiver may use the fact that MPC audio configurations are nonsegmentable in order to correctly parse and recover the audio data. MONA-encapsulated data types which are segmentable (e.g., video and SPC signalling data) cannot be interleaved with one another, as the receiver may not be able to determine the payload types for the interleaved fragments.
+
+- After the receipt of at least one incoming preference message, outgoing preconfigured channel media PDUs are sent as standard ITU-T H.223 MUX PDUs, using the appropriate MUX code and configuration described in clause K.9.2. The MUX Level is agreed via the MONA-ML negotiation defined in Table K.5.
+
+NOTE 4 – Upon receiving a remote terminal's preference message and recognizing that one or more codecs (for a given media type) may be transmitted to establish a channel, the selection of which codec to employ is a local matter and no preference rules exist for making the determination.
+
+The initial MPC transmission results in the successful establishment of preconfigured channels only if the remote terminal supports receipt of the specific configurations transmitted. The remote terminal signals this in its outgoing MPC-RX field. The sending terminal discovers whether the initial outgoing preconfigured channels were established upon receipt of the first incoming preference message from the remote terminal. Upon learning the remote terminal's capabilities, the sending terminal shall drop all current unsuccessful transmissions. Each unsuccessful transmission may be replaced via a new preconfigured channel transmission that the remote terminal is known to support. This procedure is known as "MPC-Fallback". Alternately, the accelerated ITU-T H.245 procedures described in clause K.10 may be used to establish a successful channel. More details on the selection of negotiation procedures are given in clause K.7.
+
+Once established, a media preconfigured channel shall be treated as though it were negotiated using ITU-T H.245 logical channel procedures. ITU-T H.245 messages which reference the channel shall do so using the appropriate LCN defined in clause K.9.2.
+
+Any terminal which begins MPC transmission before the receipt of the first incoming preference message may need to switch its outgoing codec, since such a switch may be necessary in the event that the initial transmission does not lead to successful channel establishment.
+
+For media codecs that employ cross-AL SDU prediction (e.g., video codecs employing inter-picture prediction), it is recommended to send decoder refresh points (e.g., intra frames) frequently during the session set-up.
+
+Terminals implementing the procedures of this clause should be capable of responding to the ITU-T H.245 videoFastUpdatePicture command.
+
+### **K.9.4 Sending procedure – Signalling preconfigured channel**
+
+MOS messages as defined in clause K.8.3 are transmitted over the signalling preconfigured channel. MOS messages shall be ITU-T H.245 genericRequest messages (using GenericMessage) and shall be encoded as ITU-T H.245 MultimediaSystemControlMessage according to packed encoding rules (PER) as defined in [ITU-T X.691]. PDUs carrying MOS messaging within the signalling preconfigured channel shall be encapsulated using the MONA preference message frame structure as defined in clause K.6.1, and following PSR procedure and FEA according to clause K.8.2.
+
+Signalling preconfigured channels shall be formatted according to the following rules:
+
+- The framing for preference messages is defined in clause K.6.1.
+- The payload for preference messages consists of the preference message capability payload defined in clause K.6.2, immediately followed by:
+ - One octet where the MUX code is carried in the least significant four bits. The MUX code is the signalling preconfigured channel configuration defined in clause K.9.2.
+ - Encoded MOS message for the PDU.
+
+NOTE 1 – The PSR and FEA procedures normally used for preference messages are applied as well to preference messages which encapsulate signalling payloads.
+
+NOTE 2 – The signalling encapsulation does not change on the receipt of any incoming preference message.
+
+NOTE 3 – MOS messages are not used after completion of MOS signalling and are always formatted as specified in this clause. No further specification of adaptation layer is made.
+
+### K.9.5 Receiving procedure
+
+Terminals which support media preconfigured channel establishment shall search for incoming preconfigured channel PDUs for which receive capability was indicated in the MPC-RX field of the outgoing preference messages. When acceptable incoming preconfigured channels are detected, the terminal shall begin to decode the received audio and/or video data. Incoming preconfigured channel data for unknown or unsupported codec configurations shall be ignored by the receiver.
+
+A terminal which is capable of media preconfigured channel data shall be prepared to accept new incoming audio and/or video preconfigured channels at any time until one of the following conditions are met:
+
+- The terminal determines (per the decision algorithm in clause K.7.1) that the remote terminal will not use the procedures of this clause to establish a preconfigured channel of the given media type.
+- An incoming channel of the given media type is successfully established, whether via a media preconfigured channel or by any other means.
+
+## K.10 Accelerated ITU-T H.245 procedures
+
+### K.10.1 Accelerated ITU-T H.245 signalling
+
+Terminals shall signal MONA parameters by specifying the **mona** capability identifier, OID { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) mona(2) }, in the **genericInformation.messageIdentifier** field of the **TerminalCapabilitySet** message. This message may be sent after at least one incoming MONA preference message has been received. The MUX level is agreed via the MONA-ML negotiation defined in Table K.5.
+
+Master/slave status shall be determined once the terminal has received the **MasterSlaveDetermination** message or the **MasterSlaveDeterminationAck** message from the remote terminal. When such status is determined, the terminal shall select the most preferred channels and shall send the corresponding **OpenLogicalChannel** messages. The terminal should start sending media without waiting to receive acknowledgement messages for its outgoing **TerminalCapabilitySet**, **MasterSlaveDetermination** or **OpenLogicalChannel** messages. Accelerated ITU-T H.245 procedures are shown in Figure K.8.
+
+### K.10.2 The MONA capability definition
+
+Table K.16 defines the capability identifier for the **mona** capability. Tables K.17, K.18 and K.19 define the associated parameters.
+
+**Table K.16 – MONA capability identifier**
+
+| | |
+|-----------------------------|-------------------------------------------------------------------------|
+| Capability name | mona |
+| Capability class | Control capability |
+| Capability identifier type | Standard |
+| Capability identifier value | { itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) mona(2) } |
+
+**Table K.17 – MONA parameter – mediaBuffering**
+
+| | |
+|----------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name | mediaBuffering |
+| Parameter description | A terminal indicating this parameter's value as 1 is able to buffer incoming media which arrives before the relevant OLC message is received from the remote terminal, allowing faster call set-up. In this case, the receiving terminal is responsible for managing the buffer and limiting the delay introduced by the buffering. The size of the buffer is left to the implementation. |
+| Parameter identifier value | 3 |
+| Parameter status | Shall be present once for capability exchange |
+| Parameter type | unsignedMin, with the value 0 or 1 |
+| Supersedes | – |
+
+**Table K.18 – MONA parameter – audioEntry**
+
+| | |
+|----------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name | audioEntry |
+| Parameter description | This parameter indicates which multiplex entry shall be reserved in the call for an audio channel established using the accelerated ITU-T H.245 procedures. - • The value shall differ from that of videoEntry.
- • The value shall differ from the multiplex codes corresponding to outgoing media preconfigured channels (MPCs) which are currently established or which are candidates for later establishment.
|
+| Parameter identifier value | 4 |
+| Parameter status | May be present only once for capability exchange |
+| Parameter type | unsignedMin, with the value 1 to 15 |
+| Supersedes | – |
+
+**Table K.19 – MONA parameter – videoEntry**
+
+| | |
+|----------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name | videoEntry |
+| Parameter description | This parameter indicates which multiplex entry shall be reserved in the call for a video channel established using the accelerated ITU-T H.245 procedures.
- • The value shall differ from that of audioEntry.
- • The value shall differ from the multiplex codes corresponding to outgoing media preconfigured channels (MPCs) which are currently established or which are candidates for later establishment.
|
+| Parameter identifier value | 5 |
+| Parameter status | May be present only once for capability exchange |
+| Parameter type | unsignedMin, with the value 1 to 15 |
+| Supersedes | – |
+
+### K.10.3 Opening accelerated channels
+
+The procedures of this clause may be used to establish outgoing channels once the remote terminal's **TerminalCapabilitySet** is known. The procedures below are only required for opening channels when no existing channels of the same media types have previously been established successfully, as described in clause K.7.
+
+Channels opened using these procedures shall always be unidirectional channels.
+
+The terminal may start sending media on an accelerated video channel and on an accelerated audio channel simultaneously with sending the **OpenLogicalChannel** messages. The entry used for the transmission of the media shall be the one specified by the **videoEntry** or **audioEntry** parameter in the **mona** capability found in the outgoing **TerminalCapabilitySet**. The receiver terminal shall infer the media type of the incoming media from the received **OpenLogicalChannel** messages. The receiver terminal shall ignore or buffer incoming media MUX-SDUs on the accelerated video and on the accelerated audio channel until the corresponding **OpenLogicalChannel** message is received.
+
+If no outgoing video or audio channels are currently opened, and the relevant entry in the multiplexing table is not defined or is defined for a closed logical channel, then a terminal may send an **OpenLogicalChannel** message and simultaneously start sending the corresponding media.
+
+The multiplex table may be later reconfigured by sending a **MultiplexEntrySend** message for channels opened using these procedures.
+
+For media codecs that employ cross-AL-SDU prediction (e.g., video codecs employing interpicture prediction), it is recommended to send decoder refresh points (e.g., intraframes) frequently during the session set-up.
+
+
+
+Sequence diagram for accelerated ITU-T H.245 procedures for both audio and video channels. The diagram shows a Master and a Slave exchanging messages. The Master sends TCS+MSD to the Slave. The Slave responds with TCS Ack+MSD Ack+. The Master then sends OLC (audio)+OLC (video) to the Slave. The Slave responds with OLC Ack (audio)+OLC Ack (video). The Master then sends MES to the Slave. The Slave responds with MES Ack. The Master then sends OLC Ack (audio)+OLC Ack (video) to the Slave. The Slave responds with Playback buffered media. The Master then sends Playback buffered media to the Slave. The Slave responds with Prepare to ignore or buffer media. The Master then sends Start sending media on audio and video channels to the Slave. The Slave responds with Start sending media on audio and video channels. The Master then sends Playback buffered media to the Slave. The Slave responds with Playback buffered media. The diagram is labeled H.324(09)\_FK.8.
+
+Figure K.8 – Accelerated ITU-T H.245 procedures for both audio and video channels
+
+### K.10.4 Handling OpenLogicalChannelReject
+
+The terminal receiving an **OpenLogicalChannel** using the accelerated ITU-T H.245 procedures may reject the proposed channel and ignore any media received for this channel. In this case, the terminal shall not buffer any incoming media for this media type until a new **OpenLogicalChannel** is received for it. Channel rejection procedures are shown in Figure K.9.
+
+The terminal which has received the **OpenLogicalChannelReject** message should reopen a channel with a different media type using the regular **OpenLogicalChannel** procedure.
+
+
+
+Sequence diagram for channel rejection during accelerated ITU-T H.245 procedures. The diagram shows a Master and a Slave exchanging messages. The Master sends TCS+MSD to the Slave. The Slave responds with TCS Ack+MSD Ack+. The Master then sends OLC (audio)+OLC (video) to the Slave. The Slave responds with OLC Ack (audio)+OLC Reject (video). The Master then sends OLC (video) to the Slave. The Slave responds with MES. The Master then sends MES Ack to the Slave. The Slave then sends OLC Ack (video) to the Master. The Master then sends MES to the Slave. The Slave responds with MES Ack. The Master then sends Playback buffered media to the Slave. The Slave responds with Prepare to ignore or buffer media. The Master then sends Start sending media on audio and video channels to the Slave. The Slave responds with Start sending media on audio and video channels. The Master then sends Playback buffered media to the Slave. The Slave responds with Playback buffered media on the audio channel and clean up buffered media on the video channel. The Master then sends Playback buffered media to the Slave. The Slave responds with Playback buffered media on the video channel. The diagram is labeled H.324(09)\_FK.9.
+
+Figure K.9 – Channel rejection during accelerated ITU-T H.245 procedures
+
+# Annex L
+
+## Text conversation in ITU-T H.324
+
+(This annex forms an integral part of this Recommendation)
+
+## L.1 Introduction
+
+Standardized, character-oriented text conversation facilities are needed in all networks. When building text conversation facilities on multimedia protocols, an opportunity is created to use any combination of text, video and voice in a conversation. The initiative to standardize this combination comes from the needs of persons with communication-related disabilities. The availability of the three media in a conversation offers communication opportunities over any one of the media alone. Anyone may find valuable a commonly available, standardized text conversation addition to multimedia conversation services, enhancing videotelephony to "total conversation" as defined in [ITU-T F.703].
+
+Since ITU-T H.324 is a framework where components can be included when required, single function text terminals as well as text and voice terminals can be useful subsets of the full total conversation terminal. These subsets correspond to text telephones available for the PSTN.
+
+[ITU-T T.140] specifies a text conversation protocol. It is a common presentation level suitable for straightforward real-time text conversation in multimedia services and in text telephony. It is based on the ISO/IEC 10646-1 character code so as to be suitable for any language. It is introduced throughout the ITU-T H-series multimedia protocols.
+
+This annex describes how text conversation facilities are added to the ITU-T H.324 multimedia environment.
+
+## L.2 Scope
+
+The scope of this annex is to specify ITU-T H.324 procedures to establish and carry text conversation sessions in the ITU-T H.324 multimedia environment.
+
+## L.3 Definitions
+
+This annex defines the following terms:
+
+**L.3.1 total conversation:** Conversational services offering real-time communication in video, text and voice [ITU-T F.703].
+
+**L.3.2 T140PDU:** protocol data unit from [ITU-T T.140], i.e., a collection of data submitted in ITU-T T.140 format for transmission.
+
+## L.4 Procedures for ITU-T T.140 text conversation
+
+### L.4.1 Capability signalling
+
+A terminal which is capable of text conversation according to [ITU-T T.140] shall signal this in its capability set by including `UserInputCapability.genericUserInputCapability`, using the capability identifier given in Table L.1 below.
+
+**Table L.1 – Capability identifier for ITU-T H.324 text conversation**
+
+| | |
+|-----------------------------|----------------------------------------------------------------------------------------------|
+| Capability name | ITU-T H.324 text conversation capability identifier |
+| Capability identifier type | standard |
+| Capability identifier value | {itu-t(0) recommendation(0) h(8) 324 generic-capabilities(1) textConversationCapability(3) } |
+| maxBitRate | This field shall not be included. |
+| Collapsing | This field shall not be included. |
+| nonCollapsing | This field shall not be included. |
+| nonCollapsingRaw | This field shall not be included. |
+| Transport | This field shall not be included. |
+
+### **L.4.2 ITU-T T.140 operation**
+
+The ITU-T T.140 output octets shall be included in one or more ITU-T H.245 UserInputIndication messages in the genericInformation structure. The GenericInformation message shall contain in the CapabilityIdentifier.standard structure the OID given for the ITU-T H.324 text conversation capability identifier in Table L.1, and an ITU-T T.140 message parameter according to Table L.2.
+
+**Table L.2 – ITU-T T.140 message parameter**
+
+| | |
+|----------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name | ITU-T T.140 message |
+| Parameter description | The value of this parameter shall contain a sequence of two GenericParameter structures, terminal label (see Table L.3), followed by ITU-T T.140 octets (see Table L.4). |
+| Parameter identifier value | 1 |
+| Parameter status | Optional |
+| Parameter type | genericParameter |
+| Supersedes | None |
+
+The ITU-T T.140 message parameter given in Table L.2 shall be itself composed of a sequence of two GenericParameter structures, the terminal label parameter shown in Table L.3, followed by the ITU-T T.140 octets parameter shown in Table L.4.
+
+**Table L.3 – Terminal label parameter**
+
+| | |
+|----------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name | Terminal label |
+| Parameter description | The value of this parameter shall contain an unsignedMin parameter representing the values of the ITU-T H.245 McuNumber and TerminalNumber structures which identify the terminal from which the ITU-T T.140 octets originated.
The value of the parameter shall be constructed as follows:
Value = McuNumber * 256 + TerminalNumber |
+| Parameter identifier value | 2 |
+| Parameter status | Optional |
+| Parameter type | unsignedMin |
+| Supersedes | None |
+
+The terminal label parameter serves to identify which terminal sent the ITU-T T.140 octets. This information may be useful, for example, to label the source of the ITU-T T.140 text.
+
+**Table L.4 – ITU-T T.140 octets parameter**
+
+| | |
+|----------------------------|---------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name | ITU-T T.140 octets |
+| Parameter description | The value of this parameter shall contain octets according to [ITU-T T.140].
This parameter shall not exceed 128 octets in length. |
+| Parameter identifier value | 3 |
+| Parameter status | Optional |
+| Parameter type | octetString |
+| Supersedes | None |
+
+The destination node and originating node concepts of ITU-T T.140 are mapped to the two ITU-T H.324 endpoints.
+
+The ITU-T T.140 user identity is an alias for an ITU-T H.324 endpoint. When the source is an MCU, the terminal label should be used as the transmitting ITU-T T.140 user identity. Data from one source only shall be provided in one ITU-T T.140 message.
+
+ITU-T T.140 operations should use the WNSRP procedures (see clause A.4).
+
+## L.5 Framing and buffering of ITU-T T.140 data
+
+Transmission of ITU-T T.140 data shall be done according to the following specifications.
+
+### L.5.1 Common considerations
+
+ITU-T T.140 data at the source terminal should be collected in a buffer before transmission in the channel. On low bit-rate channels, such buffering is recommended in order to reduce overhead. Buffering of data in intervals of not more than 0.3 seconds is recommended.
+
+On reception, the data content of the data channel is retrieved and used as ITU-T T.140 data.
+
+## L.6 Presentation considerations
+
+### L.6.1 One-to-one sessions
+
+The one-to-one case represents a direct conversation in text between two parties, where the text entered at one endpoint is displayed shortly after at the other endpoint. Character by character display is desirable. Typical examples are situations like the traditional text telephony in PSTN and multimedia conversation applications with video, text and audio used for person-to-person calls as shown in Figure L.1.
+
+| Anne | Eve |
+|--------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------|
+| Hi, this is Anne.
Have you heard that I will come to Paris in November? | Oh, hello Anne, I am glad you are calling!
No, that was new to me. What brings you here? |
+
+**Figure L.1 – Possible display of a one-to-one text call**
+
+### L.6.2 Multipoint considerations
+
+Without further specification, two alternative options exist for ITU-T H.324 endpoints with ITU-T T.140 text conversation to participate in multipoint text conversations:
+
+- 1) An MCU coordinates the ITU-T T.140 data stream to the ITU-T H.324 endpoint to contain data from a number of remote endpoints.
+- 2) Instead of the procedures described in this annex, the T.134 application member of ITU-T T.120 data conferencing is used as the channel for ITU-T T.140 data. Multipoint sessions are coordinated through the ITU-T T.120 concepts.
+
+#### L.6.2.1 Informative examples for multipoint text conversation
+
+In order to clarify the use of text conversation, and especially the different multipoint cases, the following examples of possible set-ups and applications are given without being normative.
+
+In these cases, the value of the terminal label parameter (see Table L.3) is associated with information provided in the ITU-T H.245 TerminalID structure to label the source of messages and to coordinate the positioning of the text in the area belonging to the source. This coordination is maintained during build-up of entries and possible erasures, as shown in the examples below.
+
+##### L.6.2.1.1 Many-to-many
+
+All users have write permission, forming an unmanaged conference.
+
+The display can be arranged as specified in ITU-T T.140 with one window for each participant as shown in Figure L.2.
+
+| Anne | Eve |
+|-------------------------------------------------------------------------|----------------------------------------------------------|
+| Hi, this is Anne. Have you heard that I will come to Paris in November? | Oh, hello guys! How are you Steve? |
+| Steve | Bill |
+| Hi there! This is Steve, I'm fine. | Hello Anne! I am happy that you are on the big Internet! |
+
+**Figure L.2 – Possible display of an unmanaged four-to-four text session**
+
+The display of a many-to-many conference can also be ordered in one window with labels for each participant's entries (Internet relay chat style). Entries that are not yet completed may be displayed in a separate real-time entry area and moved when completed to the history area by a new line or any other decided entry delimiter as shown in Figure L.3.
+
+| |
+|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Steve> Hi there!
Anne> Have you heard that I will come to Paris in November?
Bill> Hello Anne! I am happy that you are on the big Internet!
Eve> Oh, hello guys! How are you Steve? |
+| Steve> I'm fi |
+
+**Figure L.3 – Possible display of an unmanaged four-to-four text session IRC style with one entry in creation (Steve is typing an unfinished sentence)**
+
+##### **L.6.2.1.2 One-to-many with managed right to type**
+
+One writer at a time is given the right to transmit text to many readers. The right to type can be passed to other writers, in a managed meeting.
+
+A typical application is in distance education when the teacher normally has the right to type, but can hand it over to a participant.
+
+##### **L.6.2.1.3 One-to-many with fixed right to type**
+
+One writer types text in the session from one fixed endpoint, the other endpoints display the text in a receiving window. The right to type cannot be transferred.
+
+A typical application is found in subtitled speeches as shown in Figure L.4.
+
+| |
+|--------------------------------------------------------------------------------|
+| We are proud to announce today a new superior system for intergalactic travel. |
+|--------------------------------------------------------------------------------|
+
+**Figure L.4 – Example of one-to-many text session**
+
+# Annex M
+
+## ITU-T H.245 messages used by ITU-T H.324 endpoints
+
+(This annex forms an integral part of this Recommendation)
+
+The following rules apply to the use of ITU-T H.245 messages by ITU-T H.324 endpoints:
+
+- An endpoint shall not malfunction or otherwise be adversely affected by receiving ITU-T H.245 messages that it does not recognize. An endpoint receiving an unrecognizable request, response or command shall return "function not supported" (this is not required for indications).
+- FunctionNotSupported and FunctionNotUnderstood are intended as responses to messages that are not understood (because they are non-standard or from a later version of the standard), see clause B.14.1 of [ITU-T H.245], rather than as responses to messages and/or procedures that have not been implemented.
+- The following abbreviations are used in Tables M.1 to M.10:
+M Mandatory
+O Optional
+F Forbidden to transmit
+- A message marked as mandatory for the receiving endpoint indicates that the endpoint shall accept the message and take the appropriate action. A message marked as mandatory for the transmitting endpoint indicates that the endpoint shall generate the message under the appropriate circumstances.
+
+An implemented optional request message at a terminal's transmitting endpoint causes the corresponding response message at the terminal's receiving endpoint to be mandatory.
+
+**Table M.1 – Master slave determination messages**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|---------------------------|---------------------------|------------------------------|
+| Determination | M | M |
+| Determination acknowledge | M | M |
+| Determination reject | M | M |
+| Determination release | M | M |
+
+**Table M.2 – Terminal capability messages**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|----------------------------|---------------------------|------------------------------|
+| Capability set | M | M |
+| Capability set acknowledge | M | M |
+| Capability set reject | M | M |
+| Capability set release | M | M |
+
+**Table M.3 – Logical channel signalling messages**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|-----------------------------------|----------------------------------|-------------------------------------|
+| Open logical channel | M | M |
+| Open logical channel acknowledge | M | M |
+| Open logical channel reject | M | M |
+| Open logical channel confirm | M | M |
+| Close logical channel | M | M |
+| Close logical channel acknowledge | M | M |
+| Request channel close | M | O |
+| Request channel close acknowledge | O | O |
+| Request channel close reject | O | M |
+| Request channel close release | O | M |
+
+**Table M.4 – Multiplex table signalling messages**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|----------------------------------|----------------------------------|-------------------------------------|
+| Multiplex entry send | M | M |
+| Multiplex entry send acknowledge | M | M |
+| Multiplex entry send reject | M | M |
+| Multiplex entry send release | M | M |
+
+**Table M.5 – Request multiplex table signalling messages**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|-------------------------------------|----------------------------------|-------------------------------------|
+| Request multiplex entry | M | O |
+| Request multiplex entry acknowledge | O | O |
+| Request multiplex entry reject | O | M |
+| Request multiplex entry release | O | M |
+
+**Table M.6 – Request mode messages**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|--------------------------|----------------------------------|-------------------------------------|
+| Request mode | M | O |
+| Request mode acknowledge | O | O |
+| Request mode reject | O | M |
+| Request mode release | O | M |
+
+**Table M.7 – Round trip delay messages**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|---------------------------|----------------------------------|-------------------------------------|
+| Round trip delay request | M | O |
+| Round trip delay response | O | M |
+
+**Table M.8 – Maintenance loop messages**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|------------------------------|----------------------------------|-------------------------------------|
+| Maintenance loop request | M | O |
+| Maintenance loop acknowledge | O | O |
+| Maintenance loop reject | O | M |
+| Maintenance loop command off | O | O |
+
+**Table M.9 – Commands**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|---------------------------------------|----------------------------------|-------------------------------------|
+| Send terminal capability set | M | O |
+| Encryption | O | O |
+| Flow control | M | O |
+| End session | M | M |
+| Miscellaneous commands | | |
+| Equalize delay | O | O |
+| Zero delay | O | O |
+| Multipoint mode command | O | O |
+| Cancel multipoint mode command | O | O |
+| Video freeze picture | O | O |
+| Video fast update picture | M | O |
+| Video fast update GOB | M | O |
+| Video fast update MB | M | O |
+| Video temporal spatial trade off | O | O |
+| Video send sync every GOB | O | O |
+| Video send sync every GOB cancel | O | O |
+| Max ITU-T H.223 MUXPDU size | O | O |
+| ITU-T H.223 multiplex reconfiguration | O | O |
+| Mobile multilink reconfiguration | O | O |
+
+**Table M.10 – Indications**
+
+| Message | Receiving endpoint status | Transmitting endpoint status |
+|---------------------------------------------|----------------------------------|-------------------------------------|
+| Function not understood | M | M |
+| Function not supported | M | M |
+| Miscellaneous indication | | |
+| Logical channel active | O | O |
+| Logical channel inactive | O | O |
+| Video indicate ready to activate | O | O |
+| Video temporal spatial trade off | O | O |
+| Video not decoded MBs | O | O |
+| Vendor indications | O | O |
+| Jitter indication | O | O |
+| ITU-T H.223 skew indication | M | O |
+| H2250maximumskewindication | F | F |
+| New ATM virtual channel indication | F | F |
+| User input | M (for 0-9, * and #) | M (for 0-9, * and #) |
+| Flow control indication | O | O |
+| Mobile multilink reconfiguration indication | O | O |
+
+Non-standard commands, requests, etc., are allowed.
+
+# Appendix I
+
+## Bit and octet order
+
+(This appendix does not form an integral part of this Recommendation)
+
+This appendix is supplied as a summary of bit and octet order in this Recommendation, including [ITU-T H.223], [ITU-T H.261], [ITU-T H.263], [ITU-T H.245] and [ITU-T G.723.1]. In case of any discrepancy, the normative text of the various Recommendations shall take precedence over this appendix.
+
+[ITU-T H.261], [ITU-T H.263], [ITU-T G.723.1] and [ITU-T H.245] each produce a sequence of bits which are delivered as octets to the ITU-T H.223 multiplex. Within this sequence of bits there are fields of various lengths, in some cases aligned with octet boundaries. In the case of [ITU-T H.261], [ITU-T H.263], [ITU-T G.723.1] and [ITU-T H.245], these fields are ordered most significant bit (MSB) first. Figure ApI.1 illustrates this, with "M" indicating the MSB of each field and "L" indicating the least significant bit (LSB) of each field.
+
+
+
+| | | | | | | | | | | | |
+|------------------|---|---|---|---|---|---|---|---|---|---|------|
+| First | M | L | M | L | M | L | M | L | M | L | Last |
+| H.324(09)_FApI.1 | | | | | | | | | | | |
+
+**Figure ApI.1 – Output from [ITU-T H.261]/[ITU-T H.263]/[ITU-T G.723.1]/[ITU-T H.245]**
+
+Upon delivery to the ITU-T H.223 multiplex, this bit sequence is split into octets, each with a defined MSB/LSB position, as shown in Figure ApI.2.
+
+
+
+| | | | | | | | | | | | |
+|------------------|---------|---|-------------|---|-------------|---|-------------|---|-------------|---|-------------|
+| | M | L | M | L | M | L | M | L | M | L | |
+| First | M | L | M | L | M | L | M | L | M | L | Last |
+| | Octet n | | Octet n + 1 | | Octet n + 2 | | Octet n + 3 | | Octet n + 4 | | Octet n + 5 |
+| H.324(09)_FApI.2 | | | | | | | | | | | |
+
+**Figure ApI.2 – Output split into octets**
+
+The ITU-T H.223 multiplex then transmits each of these octets in the order LSB first (the reverse of the original order), applying the transparency procedure (inserting a '0' after each sequence of five '1's) as it does so.
+
+For example, a sequence of six octets, with hexadecimal values 0x92, 0xF1, 0x39, 0x35, 0x31, 0x30 would be transmitted as shown in Figure ApI.3.
+
+
+
+| | | | | | | | | | | | |
+|--------------------|-----------------------------------------------------------------------------------|---|-------------|---|-------------|---|-------------|---|-------------|---|-------------|
+| | M | L | M | L | M | L | M | L | M | L | |
+| | Octet n | | Octet n + 1 | | Octet n + 2 | | Octet n + 3 | | Octet n + 4 | | Octet n + 5 |
+| First | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | Last |
+| | 0x92 | | 0xF1 | | 0x39 | | 0x35 | | 0x31 | | 0x30 |
+| is transmitted as: | | | | | | | | | | | |
+| First | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 1 | Last |
+| | 1 0 0 0 1 1 1 1 1 0 0 1 1 1 0 0 1 0 1 0 1 1 0 0 1 0 0 0 1 1 1 0 0 0 0 0 1 1 1 0 0 | | | | | | | | | | |
+| | ↑ 0 bit will be inserted here | | | | | | | | | | |
+| H.324(09)_FApI.3 | | | | | | | | | | | |
+
+**Figure ApI.3 – Example sequence**
+
+# Appendix II
+
+## ITU-T V.8 *bis* codepoints
+
+(This appendix does not form an integral part of this Recommendation)
+
+ITU-T V.8 *bis* capability exchange may be used during call set-up to help terminals quickly decide, in the most common cases, if operation in ITU-T H.324 mode is desired. ITU-T V.8 *bis* capabilities indicate only the most basic and commonly used modes, and are not a substitute for ITU-T H.245 procedures. If an ITU-T H.324 operation mode not signalled by ITU-T V.8 *bis* is desired, the terminal must complete call establishment and perform an ITU-T H.245 capabilities exchange to determine if the far-end terminal supports the desired mode.
+
+Within the ITU-T V.8 *bis* communications capabilities (CC) field for this Recommendation, the CC field is formatted into one or more subfields. Each subfield ends with the octet in which bit [n] is set to 1. Following the first subfield, the remaining subfields, if present, shall appear in the same order in which the bits indicating their presence are transmitted.
+
+NOTE 1 – Implementers should refer directly to [ITU-T V.8 *bis*] for the actual bit assignments.
+
+In the first subfield, the following bits are allocated:
+
+| Name | Meaning |
+|-------------|----------------------------------------------------------------------------------------------------------------|
+| Video | Shall be set only if bidirectional video is supported per clause 6.6. |
+| Audio | Shall be set only if bidirectional audio is supported per clause 6.7. |
+| Encryption | Shall be set only if encryption is supported per clause 9.2. |
+| Data | Indicates that a data subfield is present. Shall be set only if one or more bits in the data subfield are set. |
+
+NOTE 2 – Possible future allocations include profiles (new subfield).
+
+In the Data subfield, the following bits are allocated:
+
+| Name | Meaning |
+|-------------|--------------------------------------------------------------------------------------------------------------------------------------|
+| T.120 | Shall be set only if ITU-T T.120 conferencing is supported per clause 6.8.2.1. |
+| T.84 | Shall be set only if ITU-T T.84 still image transfer is supported per clause 6.8.2.2. |
+| T.434 | Shall be set only if ITU-T T.434 file transfer is supported per clause 6.8.2.3. |
+| V.42 | Shall be set only if ITU-T V.42 user data is supported per clauses 6.8.1.2 and 6.8.2.6. |
+| V.14 | Shall be set only if ITU-T V.14 user data is supported per clauses 6.8.1.1 and 6.8.2.6. |
+| PPP | Shall be set only if IETF point-to-point protocol is supported via the network layer protocol identifier (NLPID) per clause 6.8.2.5. |
+| T.140 | Shall be set only if ITU-T T.140 text conversation protocol for multimedia application is supported per clause 6.8.2.8. |
+
+NOTE 3 – Other modes beside those indicated in [ITU-T V.8 *bis*], such as unidirectional modes, may be supported by terminals as signalled via ITU-T H.245 capabilities exchange.
+
+
+
+
+
+# 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
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+
+
+# Recommendation**ITU-T H.430.3 (V2) (09/2023)**
+
+SERIES H: Audiovisual and multimedia systems
+
+Infrastructure of audiovisual services – Telepresence,
+immersive environments, virtual and extended reality
+
+---
+
+## **Service scenario for immersive live experience (ILE)**
+
+
+
+The logo of the International Telecommunication Union (ITU), featuring the letters 'ITU' in blue inside a circle with a globe-like grid pattern.
+
+ITU logo
+
+## ITU-T H-SERIES RECOMMENDATIONS
+
+## **Audiovisual and multimedia systems**
+
+| | |
+|---------------------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100-H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | H.200-H.499 |
+| General | H.200-H.219 |
+| Transmission multiplexing and synchronization | H.220-H.229 |
+| Systems aspects | H.230-H.239 |
+| Communication procedures | H.240-H.259 |
+| Coding of moving video | H.260-H.279 |
+| Related systems aspects | H.280-H.299 |
+| Systems and terminal equipment for audiovisual services | H.300-H.349 |
+| Directory services architecture for audiovisual and multimedia services | H.350-H.359 |
+| Quality of service architecture for audiovisual and multimedia services | H.360-H.369 |
+| Telepresence, immersive environments, virtual and extended reality | H.420-H.439 |
+| Supplementary services for multimedia | H.450-H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | H.500-H.549 |
+| VEHICULAR GATEWAYS AND INTELLIGENT TRANSPORTATION SYSTEMS (ITS) | H.550-H.599 |
+| BROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES | H.600-H.699 |
+| IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV | H.700-H.799 |
+| E-HEALTH MULTIMEDIA SYSTEMS, SERVICES AND APPLICATIONS | H.800-H.899 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# Recommendation ITU-T H.430.3 (V2)
+
+## Service scenario for immersive live experience (ILE)
+
+## Summary
+
+Recommendation ITU-T H.430.3 identifies service scenarios by analysing several use cases of immersive live experience (ILE) services, in order to classify them and to establish a reference model for ILE. The 2023 edition of Recommendation ITU-T H.430.3 appends service scenarios and use cases of interactive immersive services as part of ILE. This Recommendation also summarizes several use cases and identifies candidate technologies for implementing ILE, including related standards gap analysis.
+
+## History \*
+
+| Edition | Recommendation | Approval | Study Group | Unique ID |
+|---------|--------------------|------------|-------------|--------------------|
+| 1.0 | ITU-T H.430.3 | 2018-08-29 | 16 | 11.1002/1000/13668 |
+| 2.0 | ITU-T H.430.3 (V2) | 2023-09-13 | 16 | 11.1002/1000/15652 |
+
+## Keywords
+
+Immersive live experience (ILE), service scenario, standards gap analysis, use cases.
+
+---
+
+\* 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 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 elsewhere ..... | 1 |
+| 3.2 Terms defined in this Recommendation..... | 2 |
+| 4 Abbreviations and acronyms ..... | 2 |
+| 5 Conventions ..... | 2 |
+| 6 High-level service category ..... | 2 |
+| 7 Categorized service scenarios..... | 3 |
+| 7.1 Live sports scenario ..... | 3 |
+| 7.2 Entertainment scenarios..... | 5 |
+| 7.3 Telepresence scenarios ..... | 7 |
+| 7.4 Remote operation scenarios..... | 9 |
+| 7.5 Emergency scenarios ..... | 10 |
+| 7.6 Remote assistance scenarios..... | 11 |
+| Appendix I – Use cases for immersive live experience services ..... | 12 |
+| I.1 Introduction ..... | 12 |
+| I.2 Use cases of ILE services ..... | 12 |
+| I.3 Configuration of ILE ..... | 21 |
+| I.4 Candidate technologies used for ILE ..... | 22 |
+| I.5 Standards gap analysis of ILE related technologies ..... | 23 |
+| Bibliography..... | 26 |
+
+## Introduction
+
+In recent times, many major sporting and music events have not only been broadcast, but also delivered to remote sites for public or live viewing with the aim of sharing the emotional experience with spectators there as if they themselves were also in the event venue. At the same time, ultra-high definition (UHD) broadcasting known as 4K (resolution of approximately 4 000 pixels) and 8K (resolution of approximately 8 000 pixels) broadcasting is becoming increasingly popular. It is therefore expected that many people all over the world wish to share in the excitement of viewing sporting or musical events on UHD TV or public viewing sites in the near future. However, realistic experience with flat displays has limitations.
+
+In order to provide highly realistic sensations to audiences at remote sites, immersive live experience (ILE) needs to be implemented to reconstruct event sites virtually with presentation of real-sized objects and sound direction by transmitting environmental information together with audio and video streams. For example, using ILE musicians could harmonize with player images that are transmitted from several locations. By using ILE, real objects, in this case musicians at the remote sites, can collaborate with three dimensional images of remote musicians that are projected on to the screen. ILE enables virtual concerts with highly realistic sensations.
+
+In order to share the enthusiasm of event venues with large audiences even if they are remote from the event venue, implementing ILE services based on standardized designs is desirable. ILE can allow audiences anywhere in the world cheer their favourite sporting teams or musical artists at remote sites even if they are not themselves present in the event venue and they may feel a sense of togetherness and even become passionate just as though they were actually present in the event venue.
+
+This Recommendation specifies several service scenarios for ILE to identify key requirements and architectural frameworks to implement its services and provides several use cases around the world. The 2023 edition of this Recommendation appends service scenarios and use cases of interactive immersive services as part of ILE. This Recommendation also provides candidate technologies for implementing ILE and standardization gap analysis of ILE-related technologies.
+
+# Recommendation ITU-T H.430.3 (V2)
+
+## Service scenario for immersive live experience (ILE)
+
+# 1 Scope
+
+This Recommendation analyses several use cases for immersive live experience (ILE), specifies service scenarios, and identifies key requirements and architectural considerations.
+
+This Recommendation includes:
+
+- service scenarios;
+- use cases of ILE services;
+- candidate technologies for implementing ILE;
+- standards gap analysis of ILE related technologies.
+
+# 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 immersive live experience (ILE)** [b-ITU-T H.430.1]: A shared viewing experience that stimulates emotions within audiences at both the event site and the remote sites, as if the audience at the remote sites had wandered into substantial event venue and had actually watched the events taking place in front of them. This impression is due to high-realistic sensations provided by a combination of multimedia technologies such as sensorial information acquisition, media processing, media transport, media synchronization and media presentation.
+
+**3.1.2 haptics** [b-ISO 9241-910]: Sensory and/or motor activity based in the skin, muscles, joints, and tendons.
+
+NOTE – Haptics consists of two parts: touch and kinaesthesia.
+
+**3.1.3 touch** [b-ISO 9241-910]: Sense based on receptors in the skin.
+
+**3.1.4 cutaneous** [b-ISO 9241-910]: Belonging to the skin.
+
+**3.1.5 tactile** [b-ISO 9241-910]: Appertaining to touch.
+
+**3.1.6 kinaesthesia** [b-ISO 9241-910]: Sense and motor activity based in the muscles, joints and tendons.
+
+**3.1.7 kinaesthetic** [b-ISO 9241-910]: Appertaining to kinaesthesia.
+
+**3.1.8 vibrotactile** [b-ISO 9241-910]: Vibration-based stimulation of the skin.
+
+## 3.2 Terms defined in this Recommendation
+
+None.
+
+# 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|-------|-------------------------------|
+| 3D | three Dimensional |
+| 4D | four Dimensional |
+| 6DoF | six Degrees of Freedom |
+| AR | Augmented Reality |
+| CI | Composition Information |
+| codec | coder-decoder |
+| DJ | Disc Jockey |
+| EMG | Electromyograph |
+| HMD | Head-Mounted Device |
+| IIS | Interactive Immersive Service |
+| ILE | Immersive Live Experience |
+| IPTV | Internet Protocol Television |
+| MMT | MPEG media transport |
+| mux | multiplexer |
+| OMAF | Omnidirectional Media Format |
+| QoS | Quality of Service |
+| UHD | Ultra-High Definition |
+| VR | Virtual Reality |
+
+# 5 Conventions
+
+Service scenarios in this Recommendation are described using the following template, in relation to other Recommendations, use cases, requirements, etc.
+
+| Title-X: high-level service scenario title | Sub-title: Specific title of service scenario related to the high-level service scenario |
+|---------------------------------------------------|-------------------------------------------------------------------------------------------------|
+| Description | General description for service scenario of ILE |
+| Service scenario | General explanation of how a service works |
+| Stakeholder (actor)/domains | Roles of related stakeholders and domains |
+| Main requirements | Service and technical requirements |
+| Source (references) | Use cases in Appendix I or reference document, websites |
+
+# 6 High-level service category
+
+This clause briefly describes the high-level service categories shown in Figure 1. ILE services or use cases can be classified into several categories of scenario, such as live sports, entertainment and telepresence.
+
+
+
+**Immersive live experience use cases**
+
+**Live sports scenario**
+Sports continue to sustain popularity among other contents and present a great opportunity to harness technologies available to further enhance the experience for spectators
+
+**Entertainment scenario**
+Music concerts or theatrical plays require live experience on stage where actors perform to appeal to their audiences and there are ways to reproduce the similar or better experience without actors on stage
+
+**Telepresence scenario**
+Figure, either a person or an object, could be transported in real time to remote places as a whole for informative purposes
+
+**Remote operation scenario**
+Remote surgery and collaborative operation could be realized by interactive immersive video, audio and haptic information with remote persons
+
+⋮
+
+Categorization for use cases of Immersive Live Experience is not limited to above scenarios and more classification should be further studied
+
+H.430.3(23)\_F01
+
+A diagram showing 'Immersive live experience use cases' branching into four categories: Live sports scenario, Entertainment scenario, Telepresence scenario, and Remote operation scenario. A note below states that categorization is not limited to these and more classification should be studied. The code H.430.3(23)\_F01 is in the bottom right.
+
+**Figure 1 – High-level service categories of ILE services**
+
+Major categories for use cases of ILE include, but are not limited to, the following.
+
+- Live sports scenario: Sport continues to maintain popularity among other content and presents a great opportunity to harness technologies available to further enhance the experience for spectators.
+- Entertainment scenario: Concerts or stage plays require live experience where actors perform to their audiences; there are ways to reproduce a similar or better experience without live actors.
+- Telepresence scenario: An image of a figure, either a person or an object, can be transported in real time to remote places as a whole for informative purposes.
+- Remote operation scenario: Remote surgery and collaborative operation can be effectively realized by interactive immersive video, audio and haptic information with remote persons.
+
+# **7 Categorized service scenarios**
+
+## **7.1 Live sports scenario**
+
+The following tables describe live sports scenarios.
+
+| Live sports | Live broadcast service of first-person synchronous view |
+|-------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service is provided by transmission by high-definition media of a first person viewpoint of an athlete in real time via a camera installed in sports equipment. |
+
+| Live sports | Live broadcast service of first-person synchronous view |
+|-----------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Service scenario | A synchronous camera is installed on the front of a fast-moving vehicle, such as a racing car or bobsleigh, whose perspective is fixed to face straight ahead along the racecourse. In other words, the camera provides a first person synchronous view as if audience members were riding in the athlete's vehicle.
The camera is equipped with network capability of sufficiently high bandwidth to seamlessly upload its live feed in ultra-high definition (UHD) to a backend system that is then broadcast to user devices.
The view is provided via either a big screen or mobile device screen. The additional information related to the race, such as speed, acceleration, current ranking and remaining distance to the finish line, can enhance the excitement of ongoing competition.
The purpose of the service is to simulate the game-like experience of becoming an athlete on the track in real time.
|
+| Stakeholders (actors) | Institutes managing facilities at sports venues, participating athletes, producers with broadcasting rights, network providers. |
+| Main requirements | Extremely stringent delay, ultra-high-definition coder-decoder (codec), reliable and broadband uplink. |
+| Source (references) | KT use case, see clause I.2.7. |
+
+| Live sports | Live 360° virtual reality service of single point view |
+|-----------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service provides an immersive experience of attending a live event at a sports venue by constructing a 360° panoramic view in real time via multiple camera feeds from the site. |
+| Service scenario | A camera capable of filming live panoramic views or several high-definition cameras is or are installed at the venue such as a gymnasium, an ice rink (for figure skating events) and stadia (for ball games, athletic sports and opening or closing ceremonies).
The live feeds from cameras at multiple angles are transmitted via a high-bandwidth uplink to a backend system for distribution with minimum latency.
In order to view several media, including broadcasting, in an appropriate form, a user might need to wear a special device like virtual reality (VR) goggles or a head-mounted device (HMD) that constantly process and piece together multiple images to project the real world. For this purpose, it can be used in pseudo-three dimensional (pseudo-3D) displays without special wearable devices such as VR goggles or an HMD.
The purpose of the service is to enable viewers to observe every event live around the venue so that they feel as if they are present at the remote location.
|
+| Stakeholders (actors) | Institutes managing facilities at sports venues, participating athletes, producers with broadcasting rights, network providers, VR manufacturers. |
+| Main requirements | Extremely stringent delay, UHD codec, reliable and broadband connection, massive connectivity, VR media processing (e.g., image stitching). |
+| Source (references) | NTT use case (Kirari!), see clauses I.2.1, I.2.8, I.2.9 and I.3.
KT use case, see clause I.2.7.
|
+
+| Live sports | Live broadcast service of selected multi objective view |
+|-----------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The broadcasting service provides a user-selected view of live game action in high definition from among other preinstalled cameras at the venue with the aid of position information of athletes on a 3D map. |
+| Service scenario | A number of cameras is installed at strategic locations along the racecourse where live action of athletes can be best captured simultaneously.
With the aid of a 3D map interface, viewers can select any point of interest on the map at any given time for better angles of an action. Every competing athlete is tracked in real time and their corresponding locations continuously indicated on the map.
The service provides a perspective of the racecourse from all angles to better track favourite athletes in action. |
+| Stakeholders (actors) | Institutes managing facilities at sports venues, participating athletes, producers with broadcasting rights, network providers, outdoor positioning information providers. |
+| Main requirements | Extremely stringent delay, UHD codec, reliable and broadband uplink, massive connectivity, location-based services (e.g., 3D map, precise positioning). |
+| Source (references) | KT use case [b-Sohn], see also clause I.2.7. |
+
+| Live sports | Becoming-player sports viewing |
+|-----------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service provides a becoming-player experience by using haptic sense in addition to video and audio during a sports match. A combination of visual-auditory-haptic senses aims to reproduce becoming-player sensations for real players at the event site. |
+| Service scenario | At the viewing site, people are in front of a monitor and move as if they are players in the stadium at the event site. Sound from the event site is transmitted to vibration platforms on which people stand, equipped with vibration devices. While watching the game on the monitor, each person moves their devices as if they are one of the players at the event site.
As a result, people feel as if they are standing in the stadium at the event site due to the vibrations of their feet, and at the same time, they feel as if vibrations are occurring in their bodies in response to their movements. They are able to feel the physical movements of players and reproduce them through their own bodies.
The purpose of the service is to provide audiences with becoming-player sports viewing by interactive ILE with haptic information, which can be further enhanced by addition of special effects, such as lighting, temperature and humidity. |
+| Stakeholders (actors) | Interested people: producers with broadcasting rights, promoters of a sports event, video, audio and haptic equipment providers, data analytics providers, network providers. |
+| Main requirements | High-definition codec, high definition audio, haptic sensing, haptic transmission, haptic reproduction, video/audio/haptic multiplexer (mux), converter, reliable and broadband connectivity. |
+| Source (references) | NTT West use case, see clause I.2.16. |
+
+## 7.2 Entertainment scenarios
+
+The following tables describe entertainment scenarios.
+
+| Entertainment | On-stage holographic performance show service |
+|----------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service provides holographic media of concerts that are live-streamed or pre-recorded for audiences at special theatres with capability of reconstructing the live environment. |
+
+| Entertainment | On-stage holographic performance show service |
+|-----------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Service scenario | A live concert performance is captured or pre-recorded by several UHD cameras at multiple angles and using high-quality microphone systems. Then, high-quality UHD video and audio is processed separately at the initial stage. Processed media streams, including video, audio and other sensory data, should be transmitted synchronously from the event to remote sites.
A theatre similar to one set up for the original concert hall is reconstructed at a remote site for highly realistic effects where the processed media stream is regenerated to simulate the live event. Audiences at such a remote site can experience almost the same visual and sound quality as the original on holographic or pseudo-3D projection.
The purpose of the service is to evoke the sense of a concert-like environment that is on a par with a real concert but without actual performers on stage.
|
+| Stakeholders (actors) | Concert performers, concert producers, network providers, hologram equipment providers. |
+| Main requirements | UHD codec, hologram conversion, on stage hologram or pseudo-3D projection, video/audio mux. |
+| Source (references) | NTT use case (Kirari!), see clauses I.2.1, I.2.8, I.2.9 and I.3.
KT use case, see clause I.2.7. |
+
+| Entertainment | Live interactive service |
+|-----------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service provides virtual scenes in collaboration with real people and transmitted images in real time. The images are extracted from real people in different places and transmitted by real-time high-definition media. The transmitted images and sounds are reconstructed and interact with real people at a remote site. The service, which might be considered as a variation of live interactive service, also provides virtual scenes in collaboration with real people and transmitted images in real time. Haptic information is interactively communicated within remote places and event sites.
|
+| Service scenario | Live video images of artists at event venues are extracted in real time and transmitted in various media formats synchronously over high-speed networks with low latency. In viewing sites, transmitted images and sounds are dynamically projected and mapped on to multiple transparent screens that are spatially set up. As an optional feature, the vibration of artists or audiences can be captured at each site and transmitted to other sites including studios without audience, in order to share amount of excitement and to play music synchronously even in noisy situations.
A real person, such as a disc jockey (DJ) or master of ceremonies, at the remote site can collaborate and interact with artists in event venues by transmitted images.
The purpose of this service is to provide the audience at a remote site with a new immersive experience as if they are watching the live stage of a DJ interacting with artists in the event venue who are teleported to remote sites beyond time and space. By adding haptic communication, this service may provide new entertainment feature which realize location free concerts, and the audience in event venues and remote sites with a new immersive experience as if they are watching one complete live stage in the event venue.
|
+| Stakeholders (actors) | Institutes managing facilities at event venue, participating artists, producers with broadcasting rights, network providers. |
+| Main requirements | Extremely stringent delay, UHD codec, reliable and broadband uplink and downlink, haptic communication. |
+| Source (references) | NTT use case, see clauses I.2.8, I.2.9, I.2.10 and I.2.11. |
+
+| Entertainment | Multi-angle viewing service |
+|-----------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service projects virtual pseudo-3D images on to a special arena, which can be viewed from any angle, and reconstructs sound direction. The images are captured by several cameras at the event site and transmitted with audio and spatial information synchronously to remote sites, at which the images and sound are reconstructed in a special arena. The users can simultaneously watch the images from their standpoints. |
+| Service scenario | The images of artists or sport players at an event site are extracted by using several cameras and their sounds captured by using several microphones. In addition, 3D-sensing and object-tracking information is captured to fix spatial locations. These video and audio streams are synchronously transmitted to the viewing site with spatial information via high-speed networks.
At the viewing site, these images and sounds are reconstructed in a special arena, which has multiple screens and an array of loudspeakers.
The audiences at viewing sites can see images from any angle outside the special arena and synchronously hear sounds. In order to realize image or auditory localization, pseudo-3D image displaying and wave field synthesis might be used in a special arena.
The purpose of this service is to provide experience of real events that are reconstructed images and sounds in a special arena in real time. By using this service, several audiences can watch the event at viewing sites such as sport bars.
|
+| Stakeholders (actors) | Institutes managing facilities at event venue, participating artists, producers with broadcasting rights, network providers. |
+| Main requirements | Extremely stringent delay, UHD codec, reliable and broadband uplink and downlink, pseudo-3D display, wave field synthesis. |
+| Source (references) | NTT use case, see clauses I.2.8, I.2.9, I.2.10 and I.2.11. |
+
+## 7.3 Telepresence scenarios
+
+The following tables describe telepresence scenarios.
+
+| Telepresence | Live ultra-high-definition presence video view service |
+|-----------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service provides a real-time holographic presentation of a person of interest in UHD with augmented information or special effects around the figure for audiences at viewing sites. |
+| Service scenario | A single person of interest such as someone being interviewed or highlighted is captured in real time by a special holographic camera.
Once high-definition video and digital audio are encoded, they are synchronously transmitted via an ultra-high-speed network to a viewing site where the holographic video and audio are decoded and reproduced in real time.
Various special effects like animation or information in many formats can be projected on to an original object or person for amusement or marketing. For a better feeling of reality, projection of the person or object at their actual size is preferred.
The purpose of the service is to provide ILE of telepresence of a person or object at their actual size that can be further enhanced by addition of special effects.
|
+| Stakeholders (actors) | Interested people: producers with broadcasting rights, hologram equipment providers, data analytics providers, network providers. |
+| Main requirements | High-definition codec, hologram conversion, hologram projection, high-definition audio, video/audio mux, converter, reliable and broadband connectivity. |
+
+| Telepresence | Live ultra-high-definition presence video view service |
+|---------------------|------------------------------------------------------------------------------------------------------------------------------|
+| Source (references) | KT use case [b-KT PC], see also clause I.2.7.
NTT use case [b-NTT JKF], see also clauses I.2.8, I.2.9, I.2.10 and I.2.11. |
+
+| Telepresence | Immersive live meeting |
+|-----------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | This service provides teleconferencing where participants from remote sites are represented as highly realistic images to each other in order to induce an immersive experience of being present in the same meeting room. |
+| Service scenario | Each participant image is captured by cameras, then high-resolution video and audio are transmitted over extremely low latency and high bandwidth networks. A highly realistic image of each participant is distributed to all others in real time.
Users can view the scene at the reconstruction end and feel themselves to be in a fully immersive meeting environment, where they can interact with actual figures of people.
The purpose of this service is to provide a portrait capture and display service for video conferences, board games, etc. |
+| Stakeholders (actors) | Business discussants, image capture equipment providers, network providers, game producers. |
+| Main requirements | Image capture equipment, UHD codec, reliable and broadband uplink and downlink, virtual or holographic display device. |
+| Source (references) | OKI use case, see clause I.2.4. |
+
+| Telepresence | Interactive presence service with haptic sense |
+|-----------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service provides haptic sense in addition to video and audio of a person during face-to-face conversation. A combination of visual-auditory-haptic senses aims to reproduce the atmosphere of a real conversation, by using a communication system with other people who share a similar desk at a remote site. |
+| Service scenario | A user is seated in front of a communication system, whose display shows the upper body of another user at a remote site. The area between the display and user is a shared space for haptic interaction. The area shows the hands of another user and vibrators are attached behind the screen to reproduce vibrotactile information at the remote site.
Vibrotactile information from the remote user is captured by sensing devices and transmitted from the remote to the other site. Haptic information is reproduced by the vibration devices synchronously with visual and auditory information from the remote user.
The purpose of the service is to provide interactive ILE of telepresence of a person or object at actual size with haptic information, which can be further enhanced by addition of special effects, such as lighting, temperature and humidity. |
+| Stakeholders (actors) | Interested people: producers with broadcasting rights, hologram equipment providers, data analytics providers, network providers. |
+| Main requirements | High-definition codec, hologram conversion, hologram projection, high-definition audio, haptic sensing, haptic transmission, haptic reproduction, video/audio/haptic mux, converter, reliable and broadband connectivity. |
+| Source (references) | NTT use case [b-NTT ICC]. |
+
+## 7.4 Remote operation scenarios
+
+The following tables describe remote operation scenarios.
+
+| Remote operation | Interactive live object control |
+|-----------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | This service provides interactive control of actual objects from remote sites in real time so that users can experience additional senses of touch and control, providing an increased degree of reality as a result. |
+| Service scenario | Certain spatial dimensions are set up at a real-world location, which users can physically pilot from remote sites. The boundaries of the space are marked by sensors installed on the corners. Selected physical object(s) is (are) placed inside the setting delimited by the boundaries. Such objects are scanned and digitally encoded in advance or in real time to create an exact replica for display and control of the virtual object. With this or these physical object(s), a user can navigate and manipulate the virtual objects with a high degree of ease and comfort.
This virtual object is coordinated in a central location, distributed over a network of high bandwidth and low latency and fed into an HMD or 3D display in real time for multiple users at different places where they interact with each other in similar settings to the first as if they are all in the same venue. Especially with such items under control, users interact with virtual objects in a far more immersive and live manner.
The purpose of the service is to provide users with a great degree of manoeuvrability via a virtual world combined with physical object(s), further enhancing immersive and live aspects of user interaction experience.
|
+| Stakeholders (actors) | VR producers, government and travel agencies for scenery rights, sports associations, HMD and sensor equipment providers, network providers. |
+| Main requirements | VR production, object encoding and coordination, UHD codec, reliable and broadband downlink, extremely stringent delay, HMD and VR sensors. |
+| Source (references) | Tektonspace use case [b-Tektonspace]. |
+
+| Remote operation | Remote object operation |
+|-----------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service provides interactive remote control capabilities. Users can perform operations on remote objects via their virtual images. |
+| Service scenario | A high-resolution image of remote object(s), with the help of capture equipment, is generated by a combination of XR, holographic 3D image, surrounding audio, haptic information and other multimedia technologies. The image is transmitted to remote users over extremely low latency and high bandwidth networks in real time. Users can perform a series of operations on remote object(s) by interacting with this image. Information about operations on the image is captured and converted into control signals, transmitted to remote auxiliary facilities through extremely low latency and reliable networks. The facilities perform operations on remote object(s) in accordance with the control signals received. Feedback information about remote object(s) is reflected in the image in real time.
The purpose of this service is to provide interactive remote capabilities for industrial control, remote maintenance, remote surgery, prototype design and test, etc.
|
+| Stakeholders (actors) | Manufacturers, medical institutions, image equipment providers, sensor equipment providers, auxiliary equipment providers, network providers. |
+| Main requirements | Image capture equipment, sensor equipment, UHD codec, reliable and broadband uplink and downlink, ultra-low latency, extremely stringent delay, multiple stream synchronization, hologram conversion and projection, holographic display device. |
+
+| Remote operation | Remote object operation |
+|-------------------------|---------------------------------------------|
+| Source (references) | Remote surgery use case, see clause I.2.12. |
+
+| Remote operation | Real-time multi-user collaboration |
+|-------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | This service provides multi-user manipulation on 3D or holographic images of real objects or digital models, which can be simultaneously viewed from any angle or position and changed by users. |
+| Service scenario | The images of real object(s) captured by high-definition cameras or laser scanners and virtual object(s) generated by computer as an option are transmitted to multiple users after media processing (e.g., media selection, rendering). Multiple users can synchronously view the virtual object(s) on display devices from different angles, and manipulate the virtual object(s) via peripheral equipment(s) (e.g., camera, data glove). During the collaboration, remote users can see a virtual scene of the event site and all real-time changes in the virtual object(s), and communicate and collaborate with each user at the event and other remote sites as if they work in the same place.
The purpose of this service is to provide users with synchronous interaction on real and virtual object(s) by immersive communication with each other user for remote teaching, remote training, remote collaborative design, etc.
|
+| Stakeholders (actors) | Capture equipment providers, network providers, display equipment providers, peripheral equipment providers, owners of the physical object, simulated data providers, collaborative participants. |
+| Main requirements | Capture device, UHD codec, reliable and broadband uplink and downlink, hologram or 3D display, real-time media processing. |
+| Source (references) | Multi-user collaborative design use case, see clause I.2.13. |
+
+## 7.5 Emergency scenarios
+
+The following tables describe emergency scenarios.
+
+| Emergency | Live streaming service in inaccessible areas |
+|-----------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | The service provides real time reconstruction of scenes in inaccessible areas that cannot be reached by humans immediately, such as post-disaster environments, polar regions or inaccessible mountains. |
+| Service scenario | This scenario provides an immersive experience for inaccessible areas. By using robots and unmanned aerial vehicles carrying microphones, holographic cameras, environmental sensors in position or by using pre-installed sensors, UHD video and audio are captured and processed.
In close proximity to these areas, in a location that people can reach, high-bandwidth and low-latency wireless network coverage is needed to transmit high-quality holographic data.
These scenes are reconstructed in real time at the viewing site (possibly the disaster relief command centre or the polar experience museum). In addition to holographic video and high-quality audio projection abilities, viewing sites also require testing by manufacturers under extreme conditions, such as a challenging temperature and humidity simulator for human tolerance.
|
+| Stakeholders (actors) | Government, travel producers, hologram equipment providers, network providers. |
+| Main requirements | Capture device, environment analysis and position assign system, UHD codec, reliable and broadband uplink, hologram projection. |
+| Source (references) | NA. |
+
+## 7.6 Remote assistance scenarios
+
+The following tables describe remote assistance scenarios.
+
+| Remote assistance | Remote assistance |
+|--------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Description | This service provides remote assistance to users by professionals. Users can experience highly realistic guidance by using this service. |
+| Service scenario | This service contains one guiding site as a remote site and guided sites as event sites. An original image is captured from one guided site and transmitted to another to project the virtual image. Professionals can demonstrate on the image for guidance. The demonstration (voice, action, signs, etc.) is captured and transmitted to guided sites. Then representatives at guided sites demonstrate on the real object. Users at guided sites can do the same operation on a real object according to the guidance presented. Changes in real object and demonstration are synchronously reflected in the images at both sites. |
+| Stakeholders (actors) | Government, rescue centres, education or technical support centres, hologram equipment providers, augmented reality (AR) equipment providers, network providers. |
+| Main requirements | Capture device, reliable and broadband uplink, AR or holographic display device. |
+| Source (references) | Emergency treatment guidance use case, see clause I.2.14.
Remote maintenance guidance use case, see clause I.2.15. |
+
+# Appendix I
+
+## Use cases for immersive live experience services
+
+(This appendix does not form an integral part of this Recommendation.)
+
+This appendix provides several use cases for ILE services and identifies candidate technologies for implementing ILE. In addition, this appendix summarizes standards gap analysis related to ILE technologies.
+
+### I.1 Introduction
+
+ILE is a completely new service, so it is important to create common understanding through identifying use cases for it. In addition, this appendix identifies standardization gaps within and outside ITU-T, since several key technologies may already be standardized in ITU-T or in other standards development organizations.
+
+This appendix includes:
+
+- use cases of ILE services;
+- configuration of ILE;
+- candidate technologies for implementing ILE;
+- standards gap analysis of ILE-related technologies.
+
+### I.2 Use cases of ILE services
+
+#### I.2.1 Use case – Kirari! (NTT)
+
+Nowadays, big events such as worldwide sports events like the soccer World Cup are not only broadcast on live television but can also be watched on public or live viewing sites for sharing emotions with audiences. Watching styles are becoming more diversified. It is expected that sharing emotions with audiences will be increased by highly realistic television and public viewing sites using 4K and 8K technologies.
+
+In order to provide UHD content and highly realistic sensations for audiences in remote sites, NTT has been working on research and development of immersive telepresence technology called "Kirari!", which consists of real time and synchronous media transmission, UHD media codecs, spatial and environmental information transmission, etc. As shown in Figure I.1, Kirari! enables audiences who can be anywhere in the world to feel highly realistic sensations as if they were present in a major event venue. At the event site, multiple cameras and sensors capture information about objects and the environment, and the information is sent to remote sites with some media transformation in real time. At the remote sites, virtual images reconstruct the atmosphere of the event site using time-synchronized media such as 3D projection, surrounding audio and lighting. Audiences at remote sites can share emotions with spectators at the event site and watch their favourite stars with their own eyes.
+
+
+
+Figure I.1 – Concept of Kirari! A composite image showing a world map with three circular insets of people, connected by blue curved arrows. Below the map, a group of people is shown clapping. Overlaid text reads: 'Audiences can have the emotions and get stars in their eyes by Immersive Live Experience'. A small code 'H.430.3(18)\_FI.1' is in the bottom right corner.
+
+**Figure I.1 – Concept of Kirari!**
+
+#### **I.2.2 Use case – High-quality video for VR streaming (Fraunhofer HHI)**
+
+One of the critical elements to produce ILE effectively is to capture the 360° surrounding environment of a source venue. Several camera systems can be used to deliver such VR video content such as direct stitching by using mirrors, depth-aware stitching and depth-enabled light-field rendering.
+
+Multi-view reconstruction enables a 3D image of a real person or object to be projected on to a computer-generated background and provides an immersive experience of being present in the virtual surroundings.
+
+Another sophisticated video streaming technology can be employed, in which many tile-based images are encoded using high efficiency video coding and then stitched together to render a cubic virtual environment.
+
+#### **I.2.3 Use case – 3D interactive experience (B<>Com)**
+
+With advanced technologies using six degrees of freedom (6DoF) VR reconstruction of the surrounding environment, sparse camera arrays, and a light field of representation and compression and point cloud, a 3D interactive service delivers a virtual environment in which a single or multiple users can interact with each other or computer-generated 3D objects in an ultra-realistic way. This service provides users with the ultimate natural feeling of virtual presence.
+
+#### **I.2.4 Use case – Ultra-realistic telework and 4K/8K broadcast (OKI)**
+
+High-resolution displays along with high definition sound systems transform separate working places into one integrated immersive office in which people can collaborate as if they were right next to each other.
+
+The general public is able to watch big sporting events such as the Olympic or Paralympic Games, which are broadcast in extremely high definition of 4K or 8K. This service provides viewers with much crisper and more accurate images of sports events and produces an ILE even in a 2D setting.
+
+#### **I.2.5 Use case – High-quality cloud-based 360° rendering and streaming (Fraunhofer FOCUS)**
+
+Cloud-based 360° video playout enables high-quality 360° experience on low capability devices such as hybrid TVs and mobile devices. By moving a simple remote control, video adjusts the angle of a scene accordingly in real time, providing some degree of immersive experience. The video is produced and rendered on a backend system from signals received by remote control of movement.
+
+#### **I.2.6 Use case – Multi-channel 4K and 8K broadcast service (NHK)**
+
+Live video of 8K quality is broadcast over satellite with multiple videos of high quality up to 4K supplemented over broadband in order to provide a high degree of excitement about live action.
+
+#### I.2.7 Use case – Immersive live experience over 5G technologies (KT)
+
+5G technologies of high bandwidth and low latency provide robust infrastructure on which ILE is featured for a batch of 5G services.
+
+A high-speed bobsleigh equipped with a high resolution camera provides a first person synchronous view in real time over 5G radio technologies augmented with various physical status information points about the athlete such as heart rate to give an immersive feel of what the athlete sees and feels.
+
+The 360° VR/TimeSlice service lets audiences with HMDs absorb a sense of immersive presence with access to all angle views around the venues and through mobile devices, also a 360° peripheral view of any athlete selected by the viewer allowing a close up monitoring of events such as ice hockey tournaments or figure skating.
+
+Hologram Live teleports a real size image of a person or object from remote sites and creates a virtual environment in which an interview can be conducted live. This multi-site service utilizes hologram technologies to carefully integrate two live images from different venues into one place to coordinate or choreograph multi-party activities as if everyone were present at the same spot.
+
+#### I.2.8 Use case – Interaction with images (NTT)
+
+On 2017-03-13, a music live showcase was presented as a remote interactive performance between Tokyo and Austin, Texas.
+
+Featuring a Japanese electronic music producer and DJ in Austin, and Japanese artists in Tokyo, NTT showed a live performance experience, *Cyber teleportation Tokyo at SXSW* [b-NTT Krause], in which the audience experienced an immersive synchronized performance of a DJ in Austin and the artists "teleported" from Tokyo.
+
+The live video images of the artists in Tokyo were extracted in real time and transported in various media formats synchronously over the network, then dynamically projected on to multiple double-sided transparent screens that were spatially set up in the Austin live space (see Figure I.2) by utilizing NTT's Kirari! technology. The latency is about 400 ms, so the interaction was sufficient.
+
+The network infrastructure used for this showcase was established using NTT's network testbed GEMnet2, in cooperation with Internet2 (a consortium of US universities providing an advanced networking environment), the Lonestar Education and Research Network and the University of Texas System, and Greater Austin Area Telecommunication Network.
+
+These technologies provided the audience in Austin with a new immersive experience as if they were seeing the interplay live on stage of the DJ with the artists in Tokyo who were teleported to Austin.
+
+
+
+Figure I.2: Four panels showing the stage setup for the Cyber teleportation Tokyo at SXSW. The top-left panel shows a wide view of the stage with multiple transparent screens displaying colorful graphics. The top-right panel shows a crowd of people with their hands raised, looking at the screens. The bottom-left panel shows a close-up of the transparent screens displaying data-like visualizations. The bottom-right panel shows a person on stage, possibly a DJ, interacting with the screens. A small text label 'H.430.3(18)\_FI.2' is visible in the bottom right corner of the image area.
+
+**Figure I.2 – Computer-generated images of the stage at *Cyber teleportation Tokyo at SXSW***
+
+#### I.2.9 Use case – Multi-angle viewing styles (NTT)
+
+Several cameras at an event site and transmitting images all over the world, enables the atmosphere of the event site to be captured and reconstructed at viewing sites. NTT has developed a new viewing
+
+style for audiences who watch a reconstructed event together at a remote site, namely *Kirari! for Arena*, which reconstructs the atmosphere of the event site allowing viewing from several angles by audiences at viewing sites, by capturing object images with their location information. Figure I.3 shows an image constructed by "*Kirari! for Arena*" of a judo event.
+
+
+
+A 3D reconstructed image of a judo match. Two judokas, one in a white gi and the other in a blue gi, are engaged in a match on a red mat. The background is dark, with some blurred figures of spectators visible in the shadows.
+
+H.430.3(18)\_FI.3
+
+**Figure I.3 – Image constructed by *Kirari! for Arena* of judo**
+
+3D-sensing and object-tracking technologies are key functionalities for realizing *Kirari! for Arena*. In order to reconstruct the atmosphere of an event site at viewing sites, capture of 3D position information of objects and object tracking are required. The combination of object recognition using deep learning, object tracking using particulate filters and depth sensors using lasers enables rough tracking of object location. The location information enables reproduction of natural motion in depth in addition to horizontal direction at viewing sites.
+
+Another key functionality is pseudo-3D image localization, which reconstructs the atmosphere of an event site at viewing sites and displays natural motion of objects even in the depth direction. This also enables many audiences to observe a displayed object from any angle. Pseudo-3D image localization can reconstruct event venues with moving objects at viewing sites, so that dynamic display achieves spatial position relations as if players were moving around fields in front of audiences.
+
+By using a simple display device, as shown in Figure I.4, audiences can watch objects displayed as pseudo-3D images without recognition of the display devices. Displayed at viewing sites on the horizontal floor plane is a projected pseudo-3D image reflected by an angled half mirror, which transmits some incident light and reflects the rest. In this case, it is difficult to move images in the depth direction since the pseudo-3D images are fixed at the same location. In order to display moving objects in the depth direction, utilization of visual effects is required for audience perception.
+
+
+
+A photograph of a physical display setup. A large, dark, angular structure made of four half-mirrors is positioned on a stage. In the center, a small, brightly lit area on the floor displays a projected image of a judo match, appearing as a pseudo-3D effect to the audience.
+
+H.430.3(18)\_FI.4
+
+**Figure I.4 – Simple display device using four half mirrors**
+
+#### I.2.10 Use case – Remote ensemble concert using haptic communication (NTT)
+
+Remote or virtual concerts, which are realized by using telecommunication network, are challenges addressed recently. At some remote concerts, musicians are located in several different places, like Tokyo and Paris, and they play instruments or sing songs synchronously. This type of remote concerts is called "remote ensemble concert".
+
+Remote ensemble concerts need communication networks with very low latency, because players who are in different places have to play synchronously. Most music players recognize the baton of conductor, sound of drumstick and some vibrations when they start playing, so haptic communication may be needed for remote ensemble concerts.
+
+As an example, Figure I.5 shows an image of a remote ensemble concert.
+
+
+
+The diagram illustrates a remote ensemble concert setup. At the center is a light blue cloud labeled "Network". Four pink ovals, each representing a location, are connected to this central network. The locations are: "Concert hall A with audiences" (top left), "Concert hall B with audiences" (top right), "Studio without audiences" (bottom left), and "Live viewing site with audiences" (bottom right). Each location contains an "ILE display" and "Real musicians". In Concert hall A and B, the ILE display shows a virtual stage with multiple video feeds of musicians. In the Studio, the ILE display shows a single video feed of a musician playing a saxophone. In the Live viewing site, the ILE display shows a virtual stage with multiple video feeds of musicians. The audiences are represented by silhouettes of people in the concert halls and live viewing site.
+
+H.430.3(23)\_FI.5
+
+Diagram of a remote ensemble concert setup showing four locations connected via a central network cloud.
+
+**Figure I.5 – Images of a remote ensemble concert**
+
+This example is a live concert event involving four locations. Real musicians play instruments in three places, and audiences are located at three places. In concert hall A, an ILE display is installed to show real musicians at remote places, allowing audiences to see them as well as local real musicians. At a live viewing site, there are ILE systems that reconstruct a virtual event venue with combination of other places, and audiences can enjoy virtual concert. All musicians have to play synchronously, so timing recognition is critical when they start playing music. In concert halls A and B, musicians may need vibration signals as cues because of the noisy situation. Vibration signals might be sent from hall A to hall B and studio allowing synchronous playing of music. In addition, real musicians in the studio, where there is no audience, may feel the atmosphere in halls A and B and live viewing site by video, sound and some vibration information.
+
+The benefits of haptic communication such as vibration transmission in a remote ensemble concert are considered at the start of a music performance, especially to adjust timing, as follows:
+
+- vibration might not be affected by a noisy environment;
+- for instrumental playing, vibration might not hinder music performance;
+- vibration can be used even in dark concert hall such as rock concert with lighting effects or stage effects, and stage monitor display might hinder stage effects;
+
+— players can pick up cue from the conductor cue by vibration, thus players can see audiences in the concert halls and in the remote sites through display.
+
+When a rhythm is constant, haptic signals might be generated by a beat manager such as a conductor, sequencer or metronome. For a remote ensemble concert, a haptic signal might be generated by information from a remote site. An electromyograph (EMG) signal is obtained on starting to play musical instruments because humans move muscle to make sound. For example, an EMG signal is generated when a drummer raises a drumstick, since this involves arm movement. Thus, an EMG signal can be detected before the stick hits the drum. If information from the EMG is transmitted earlier than that of sound, other players like guitarists at another site can feel the vibration triggered by the EMG information before the drum is heard from the remote site.
+
+In this example, it might be needed to implement interactive haptic communication, in addition to 3D videos, audios, lighting, and stage effects, within these four sites for a successful remote ensemble concert.
+
+#### I.2.11 Use case – Public booth for vibrotactile communication (NTT)
+
+A public booth for vibrotactile communication has been introduced as an interactive immersive service (IIS) using vibrotactile communication. This service utilizes an interactive audio-visual-haptic media that allows users to feel vibrations of other people at remote site who share feelings at the same desk. The system configuration is shown in Figure I.6.
+
+
+
+Figure I.6: Configuration of the public booth for vibrotactile communication. The diagram shows two identical booths connected by a central 'Communication system' consisting of two 'Terminal' units and a 'Network'. Each booth contains a 'Camera', 'Screens', 'Projectors', a 'Sensor', and a 'Vibrator'. A hand is shown interacting with the 'Vibrator' and 'Sensor' in each booth. Orange arrows labeled 'Vibration' show the flow of data from the sensor in one booth, through the network, to the vibrator in the other booth. The diagram is labeled H.430.3(23)\_FI.6.
+
+**Figure I.6 – Configuration of the public booth for vibrotactile communication**
+
+Figure I.6 shows a pair of booths that connects via a communication system (terminals and network). Each booth has a camera, one round screen, a projector, a vibration sensor and a vibrator. Behind the round screen, a vibrator is attached to provide vibrotactile sense to the user and a vibration sensor to capture vibration generated by the user. In order to avoid vibration howling, a sound equalizer and a howling compressor might be needed. The sound equalizer removes high-frequency vibration signals, where humans cannot feel vibration, and signals of specific frequency bands that cause strong howling by resonant frequency of booth and screen. A compressor controls howling in real time.
+
+NTT Labs demonstrated the public booth for vibrotactile communication in exhibition spaces in Tokyo in 2019. Figure I.7 is an image of the demonstration.
+
+
+
+A photograph showing a person from behind, seated at a desk and interacting with a large, curved projection surface. The surface displays a virtual environment where a hand is visible, and there are various objects like cups and a basket on the desk. The person's hands are on the surface, and they appear to be interacting with the virtual content.
+
+A person interacting with a large, curved screen displaying a virtual environment, demonstrating vibrotactile communication.
+
+H.430.3(23)\_FI.7
+
+**Figure I.7 – Demonstration of the public booth for vibrotactile communication**
+
+This demonstration used high-definition video and audio communication system and the Internet. Vibrotactile information was carried by one of two audio channels, which were used for stereo sound transmission, and was fully synchronized with video images. The video signals were carried by a video codec such as one compliant with [b-ITU-T H.264], and the audio and vibrotactile signals were carried by audio codec such as MPEG-4 AAC-LD. The audio and vibrotactile signals can also be carried by MPEG-4 ALS.
+
+This demonstration provided several experiences using vibrotactile information between two users. When seated in front of a booth, user A can see the upper half of the body including the hands of user B, who is seated in front of another booth at a remote site, at actual size on the round screen. In the appropriate areas, both users can see each other's hands and feel vibrations. For example, if user A hits the desk with the hand, user B can hear the sound and feel the vibration simultaneously. This kind of interactive experience makes users feel as if they are seated at the same desk.
+
+In this demonstration, users can also feel vibrations of rolling balls, drawing pictures, and touching and scuffing the screen from the other side.
+
+#### **I.2.12 Use case – Remote surgery**
+
+Based on extremely stringent delay and reliable connectivity, remote surgery is one critical application of telemedicine. As shown in Figure I.8, it involves the patient and auxiliary facility in the local site, and the doctor and holographic stereogram of the patient in a remote site.
+
+
+
+Two side-by-side photographs. The left photograph (a) shows a robotic arm with multiple joints performing a surgical procedure on a patient lying on a table. The right photograph (b) shows two surgeons in blue surgical gowns and masks standing in an operating room. They are looking at a large screen that displays a holographic stereogram of a patient's torso, showing internal structures.
+
+Two side-by-side images illustrating remote surgery. Image (a) shows a robotic arm performing surgery on a patient. Image (b) shows two surgeons in an operating room, with a holographic stereogram of a patient visible on a screen.
+
+H.430.3(23)\_FI.8
+
+**a) b)**
+**Figure I.8 – Remote surgery: a) local site; b) remote site**
+
+First, the holographic stereogram of the patient in the local site is generated by holographic technology and captured with the help of cameras and sensors; the result is displayed at the remote site. The remote doctor can view the real-time status (such as pulse count, blood pressure measurements and blood vessel status on the surface of the skin) of the local patient.
+
+Second, the remote doctor performs a series of operations on the holographic stereogram. Haptic information about operations (such as touch and kinaesthesia) is captured by cameras and sensors, converted into control signals and transmitted to local auxiliary facilities (such as mechanical arms) through networks.
+
+Finally, local auxiliary facilities perform represented operations on the local patient and the feedback interactive information is reflected on the remote holographic stereogram in real time. The remote doctor can judge the result and continue to the next.
+
+#### 1.2.13 Use case – Multi-user collaborative design
+
+With advanced 3D display technologies, a design prototype or physical model is represented by a high-resolution 3D image at actual size at different sites, and can be watched or modified by users. Highly realistic image(s) of the user(s) at the event site is or are transferred to the remote site and presented at life size and in real time, and *vice versa*. Figure I.9 is an image of an example of multi-user collaboration for vehicle design. Colleagues who work in the office (event site) can communicate and collaborate with a colleague who works from home (remote site) to interact with the virtual vehicle model.
+
+
+
+The diagram illustrates a multi-user collaborative design environment for a vehicle. At the top, a central 'Network' hub connects two main locations: 'Remote site' (Home A) and 'Event site' (Office B).
+- **Remote site:** Contains 'Colleague A' and icons for a head-mounted display and a haptic glove. An arrow points from this site to a 'Virtual office B' containing 'Colleague A', 'Virtual B' (a person icon), a 3D car model, and 'Virtual C' (a person icon).
+- **Event site:** Contains 'Colleague B' and 'Colleague C', along with icons for a head-mounted display, a haptic glove, and a gear. An arrow points from this site to a 'Design model and virtual colleague at office B', which shows 'Virtual A' (a person icon), 'Colleague B', a 3D car model, and 'Colleague C'.
+- **Vehicle parts:** A speech bubble from 'Colleague B' contains icons for various vehicle components like a steering wheel, engine, and gears.
+- **Labels:** 'Home A', 'Colleague A', 'Remote site', 'Office B', 'Colleague B', 'Colleague C', 'Event site', 'Virtual office B with colleagues and virtual design model', 'Design model and virtual colleague at office B', 'Network', and 'Vehicle parts'.
+- **Reference:** H.430.3(23)\_F1.9
+
+Diagram illustrating multi-user collaboration for vehicle design across remote and event sites connected via a network.
+
+**Figure I.9 –Multi-user collaboration**
+
+In the collaborative design process, each user's ideas and operations on the virtual object are tracked and captured via cameras, wearable devices or other accessories, and delivered to other users working at different sites in real-time. Users at the event site can design the virtual object with natural experience, e.g., by moving it, modifying components or attributes, labelling instructions and testing new configurations. The users at the event and remote sites can watch the same virtual object from an arbitrary viewing angle, discuss the design plan and design the virtual object simultaneously. This service provides 3D visualization of the design process, immersive interaction with virtual objects and immersive communication for users in real-time.
+
+#### **I.2.14 Use case – Emergency treatment guidance**
+
+Many injured people die in emergency situations (drowning, heart disease, stroke, etc.) due to lack of appropriate treatment in the first minutes after the event. Guidance is in high demand due to the deficiency of emergency treatment knowledge.
+
+Remote rescue centre professionals can guide on-site people to treat emergencies appropriately in a timely fashion. The operation on the replica of the patient performed by surgeons is captured and presented to people on site, who can then perform the same treatment on a real patient. In addition, if a natural disaster such as an earthquake occurs, trapped people can be guided to treat themselves.
+
+#### **I.2.15 Use case – Remote maintenance guidance**
+
+If faults occur, a customer calls a technical support centre for assistance and is guided by a specialist for maintenance.
+
+An image of the real device is captured at the customer site and transmitted to the support centre. The specialist demonstrates maintenance on the virtual image using voice, action, signs, etc. The demonstration is captured and transmitted to the customer site and represented as if demonstrating on the real device. The customer conducts the same operation on the real device, and any changes of device are synchronously reflected in virtual image. The device is then fixed with the guidance of the specialist.
+
+#### **I.2.16 Use case – Becoming-player sports viewing (NTT West use case)**
+
+In sports viewing, audiences cheer with enthusiasm because they have empathy with players, and player performance can improve through the enthusiastic cheering. "Becoming-player sports viewing" is a new experience, in which audience emotions at viewing sites can be evoked using haptic information from the event site.
+
+One use case is the fencing project that was demonstrated in Numazu-city in Shizuoka, Japan in 2021. In the stadium (event site) for a fencing match at the Roppongi Hills Arena in Tokyo, Japan, six microphones were installed at the side of the piste (on which the match must occur), mainly to capture the sound of a fencer's foot stepping on the piste and the sound of swords colliding with each other. The captured sounds were mixed into two channel audio, and transmitted to Numazu by telecommunication network. This use case involves a sabre match (one of three disciplines in fencing), in which the weapon is used to slash rather than stab, unlike the other two. Thus, the sabres make big sounds and intense vibrations.
+
+Figure I.10 is an image of this use case. At the viewing site in Numazu, two children with experience of sabre stood facing each other in front of the monitor, as if they were in the stadium in Tokyo. The video image captured by the camera in Tokyo was displayed on the monitor at Numazu. The sound from Tokyo was transmitted to the speakers, including output from the vibration platform that the two children stood on and the sword-type vibration device held in their hands. The sound signal from the left channel mix of output from the platform and the device on the left side of the viewing site was sent to one speaker, and the sound signal from the right channel mix was sent to another for the right side. The children were instructed to move their hands while synchronizing to each of the players they were becoming. The video images and sounds from Numazu were sent to the monitor and speakers in Tokyo.
+
+
+
+Figure I.10 – Becoming-player sports viewing. The diagram is split into two panels. The left panel, 'Roppongi hills arena', shows a fencing match on a screen. Below the screen are three pairs of microphones (L-1, R-1; L-2, R-2; L-3, R-3) connected to a 'MIXER'. The mixer outputs 'L-Mix' and 'R-Mix' to a 'TRANSMISSION SYSTEM'. The transmission system connects to a 'CAM' and 'MONITOR' setup, which in turn connects to 'L-SP' (left speaker) and 'R-SP' (right speaker). The right panel, 'F3 BASE (Numazu)', shows two children standing on platforms, holding handles. They are connected to a 'TRANSMISSION SYSTEM' via 'L-MIC' and 'R-MIC'. The transmission system connects to a 'CAM' and 'MONITOR' setup, which shows the fencing match. The children are also connected to 'L-SP' and 'R-SP' speakers. The diagram illustrates a system for immersive sports viewing where users can feel the movements of the players.
+
+Figure I.10 – Becoming-player sports viewing
+
+As a result, children felt as if they were standing in the stadium in Tokyo due to the vibrations of their feet, and at the same time, they felt as if vibrations were occurring in their hands in response to their movements. They were able to feel the physical movements of the players, such as footwork and swordplay, and reproduce them through their own bodies.
+
+After the demonstration, the children's impressions were, "I was happy to win", and, "I was disappointed to lose", so the children talked about winning and losing as if they had become players themselves.
+
+### I.3 Configuration of ILE
+
+If transmitting a soccer game to gymnasiums for example, there is a big difference in the sizes of venues as well as the sound and lighting equipment. Figure I.11 shows a configuration of Kirari! as an example of an ILE service, in order to reconstruct the atmosphere of a soccer stadium in a remote site. The following approaches can achieve highly realistic sensations as if audiences in a gymnasium had entered a soccer stadium.
+
+- 1) Objects such as soccer players are measured in $(x, y, z)$ coordinates and are extracted images in real time at the stadium. In order to reconstruct the extracted objects in the gymnasium, information about the object is transmitted in real time.
+- 2) Video, audio and lighting information, except for objects previously described, is also transmitted to gymnasiums after transforming information based on the data of the hall environment such as the width and height of screens, the number of projectors, the types of audio equipment and characteristics of the lighting equipment. This transforming function calculates parameters from the gymnasium environmental data to reconstruct the atmosphere of the stadium at remote sites. For example, the following are the actual parameters: i) $(x, y, z)$ coordinates of objects; ii) range of captured environmental and spatial information except for objects; iii) region of sound space.
+- 3) At remote sites, environmental information is reconstructed by projection mapping technology. Then another projector shows objects in 3D and numerous speakers reconstruct the audio space and auditory lateralization.
+
+
+
+The diagram illustrates the configuration of Kirari! for a soccer match. On the left, an 'Event venue' shows a soccer match. Arrows point to a central box labeled 'Media synchronization for high-realistic sense'. This box contains three sections: (i) 'Extraction objects' with a soccer player and the function $f(x, y, z)$ ; (ii) 'Environmental and spatial info' with a soccer goal; and (iii) 'Sound space info' with multiple speaker icons. Arrows from this box point to 'Viewing sites', represented by a grid of screens. Above the viewing sites is a callout box with technical specifications: 'Size: 10 m × 5 m × 5 m', 'Projector: 4K × 4', 'Speaker: 5.1 ch', 'light: 5', and '....'. The text 'H.430.3(23)\_FI.11' is at the bottom right.
+
+Figure I.11: Configuration of Kirari! showing the flow from Event venue to Media synchronization for high-realistic sense to Viewing sites.
+
+**Figure I.11 – Configuration of Kirari!**
+
+As shown in Figure I.12, audiences in remote sites can feel ultra-highly realistic sensations by pseudo-3D projection and auditory lateralization of Kirari! Audiences experience emotions as though they are watching actual events, exceeding those provided by 2D displays. Kirari! provides new experiences for audiences.
+
+
+
+The diagram shows a 'Viewing site' (represented by a grid of screens) projecting a 3D image of a soccer match. An audience is shown watching the projection. Below the audience, a callout box contains the text 'Reconstruct images fitting sizes or environments of viewing sites'. The text 'H.430.3(23)\_FI.12' is at the bottom right.
+
+Figure I.12: Reconstruction atmosphere of event venue at viewing site showing a 3D projection of a soccer match with an audience.
+
+**Figure I.12 – Reconstruction atmosphere of event venue at viewing site**
+
+### I.4 Candidate technologies used for ILE
+
+Candidate technologies used in ILE that aim to realize pseudo 3D presentations in real time are described in this clause and include highly realistic media synchronization, real-time object image extraction, highly realistic auditory lateralization and extra-wide video stitching technologies.
+
+#### (1) Highly realistic media synchronization
+
+The MPEG media transport (MMT) technology has features that synchronize video and audio streams by using absolute time management. However, it is necessary to synchronize several elements such as lighting and spatial information to reconstruct a virtual field of the event venue at remote sites. A signalling descriptor of MMT is required to model spatial information such as size of objects, positional relations and direction of sounds.
+
+By using this technology, it is possible to handle asset information related to physical spatial position information such as the size of screen, resolution of displays and spatial position. Using the transmitted spatial size of images and auditory lateralization information together with multiple audio and video streams constituting the event venue, a virtual field of the event
+
+venue can be reconstructed highly realistically at the viewing site, depending on its specifications.
+
+For IISs, interactive media require multiple concurrent streams to be delivered. Coordination and synchronization of multiple concurrent streams is a key technology to control their establishment, synchronization and reconstruction according to specific scenarios and service policies.
+
+#### (2) Real-time object image extraction
+
+Real-time object image extraction is a key technology to realize live experience, and extracted objects are displayed as pseudo-3D images at the viewing site. This may be achieved by a combination of contour detection technology using sensor information such as distance and temperature, and image-processing technology, which identifies boundaries of target objects at high speed and in high resolution. Real-time image extraction can clip purely the target object to be presented as a pseudo-3D image at the viewing site.
+
+#### (3) Highly realistic auditory lateralization
+
+Highly realistic auditory lateralization aims to reconstruct a virtual acoustic field over a wide viewing area. This enables sound direction from actual-sized objects projected on to wide screens to be reproduced, thus audiences can feel voice and sound as if they come from the projected objects.
+
+#### (4) Extra-wide video stitching
+
+Video-stitching technology pieces together processed video images of multiple high-definition cameras, adjusts the images and enables highly realistic field images to be reconstructed in real time for major sports venues, and track and field events such as athletics.
+
+#### (5) Intelligent distribution technology of massive multimedia data
+
+Intelligent distribution technology of massive multimedia data aims to select appropriate media processing servers in accordance with the requirements of codec, compression and rendering.
+
+#### (6) Network status awareness and quality of service scheduling
+
+Network status awareness and quality of service (QoS) scheduling aim to guarantee the quality of experience of IISs. Network status awareness is the capability to collect QoS and network resource information. QoS scheduling is the capability to update policies based on the collected information.
+
+### **I.5 Standards gap analysis of ILE related technologies**
+
+#### **I.5.1 ITU-T work**
+
+There exist several Recommendations related to Internet protocol television (IPTV) services. For example, IPTV architecture [b-ITU-T Y.1910], establishes the reference model and function blocks. However, there are no specifications about immersive services in those IPTV-related Recommendations.
+
+#### **I.5.2 ISO/IEC JTC1 SC29 (MPEG) work**
+
+ISO/IEC JTC1 SC29, MPEG, has been working with ITU-T SG16 on video codecs for many years. MPEG has developed media transport technologies called MMT. Media coding technology called visual volumetric video-based coding (V3C) has been developed by MPEG as well.
+
+##### **ISO/IEC 23008-1**
+
+[b-ISO/IEC 23008-1], which was developed in MPEG, gives an MMT overview, and extends existing media transport technologies such as MPEG2-TS [b-ITU-T H.222.0] and specifies multi-source content delivery. This enables synchronous media transmission between video and sound, but
+
+transporting special environment information is not considered in [b-ISO/IEC 23008-1]. In other words, MMT cannot resolve synchronous media transportation.
+
+##### **ISO/IEC 23008-11**
+
+MPEG has also developed [b-ISO/IEC 23008-11], which is a composition information (CI) specification of terminal devices. Display of a real-sized object needs to be considered as CI; however, [b-ISO/IEC 23008-11] does not cover spatial environments such as bezel size of display devices and spatial position information. Therefore, CI is inefficient for displaying actual-sized objects.
+
+##### **MPEG-I Project**
+
+From the systems perspective, the MPEG-I project has laid out a basic foundation of coding, signalling, encapsulation and delivery formats for both mono and stereoscopic 360° video and audio in omnidirectional media format (OMAF) in its initial phase. However, a rich set of features in immersive media including 6DoF, point clouds, light fields that could enhance new use cases is set to be further explored in the next phase.
+
+##### **ISO/IEC 23090-2**
+
+[b-ISO/IEC 23090-2], which was developed in MPEG, specifies the OMAF for coding, storage, delivery and rendering of omnidirectional media, including video, images, audio and timed text. An omnidirectional image or video can contain graphics elements generated by computer graphics but encoded as image or video. Multiple viewpoints, each corresponding to an omnidirectional camera, are supported. [b-ISO/IEC 23090-2] also specifies storage and delivery of overlay images or video intended for rendering over an omnidirectional background image or video.
+
+##### **ISO/IEC 23090-5**
+
+[b-ISO/IEC 23090-5], which was developed in MPEG, specifies the syntax, semantics and decoding for visual volumetric media using video-based coding methods. [b-ISO/IEC 23090-5] also specifies processes that can be needed for reconstruction of visual volumetric media, which can also include additional processes such as post-decoding, pre-reconstruction, post-reconstruction and adaptation. This enables the coding and processing for holographic images.
+
+#### **I.5.3 ISO work**
+
+##### **ISO 9241-910**
+
+[b-ISO 9241-910] provides a framework for understanding and communicating various aspects of tactile or haptic interaction. [b-ISO 9241-910] defines terms, describes structures and models, and gives explanations related to the other parts of the ISO 9241-9XX subseries. [b-ISO 9241-910] also provides guidance on how various forms of interaction can be applied to a variety of user tasks. [b-ISO 9241-910] applies to all types of interactive systems making use of tactile/haptic devices and interactions. [b-ISO 9241-910] does not address purely kinaesthetic interactions such as gestures.
+
+#### **I.5.4 Institute of Electrical and Electronics Engineers work**
+
+In March 2016, the Institute of Electrical and Electronics Engineers (IEEE) Standards Association approved the creation of the IEEE P1918.1 standards working group. The core activities of the working group can be classified into three distinct areas: 1) definitions and use-cases; 2) haptic codecs; and 3) reference architectural framework.
+
+Ongoing IEEE activity on haptic codecs for the tactile internet [b-IEEE P1918.1.1] is attempting to standardize the first kinaesthetic codec. [b-IEEE P1918.1.1] focuses on standardization of a corresponding tactile codec. [b-IEEE P1918.1] and [b-IEEE P1918.1.1] draft standards were planned for completion in 2019. However, there is no codec standard published at the time of publication.
+
+#### **I.5.5 Work in broadcasting area**
+
+In the broadcasting standardization area, standardization of media transport technologies has been started.
+
+##### **Association of Radio Industries and Business**
+
+[b-ARIB STD-B60] is a media transport standard based on MMT and [b-ISO/IEC 23008-1]. [b-ARIB STD-B60] aims to enhance terrestrial broadcasting services. However, as shown in clause I.6.2, [b-ARIB STD-B60] does not specify synchronous media transportation.
+
+##### **ITU-R**
+
+ITU-R has started considering new media transport technologies based on ARIB B-60. This work is not yet finalized.
+
+#### **I.5.6 Work in cinema area**
+
+Today, four dimensional (4D) cinemas that provide highly realistic sensation for users have been developed and deployed all over the world. 4D means that the user can sense several feelings such as vibration of seats, lighting and smell in addition to 3D video and surround sound. 4D cinemas can only be provided at specific theatres that are equipped with special devices, with special programmes that are designed for 4D. Moreover, a 4D cinema does not have live content transmission capability.
+
+On the other hand, there exist several 4D cinema technologies such as 4DX and MX4D, but there are no standards so far.
+
+Therefore, ILE services cannot be covered by this area.
+
+#### **I.5.7 Standardization gaps**
+
+Standardization of terminal devices decreases the cost of highly realistic IPTV services and standardization of the transmission issue provides interoperability between providers of services and content.
+
+As previously mentioned, standardization of all key features of ILE services has not progressed, so it is necessary to start standardization work in ITU-T.
+
+## Bibliography
+
+- [b-ITU-T H.222.0] Recommendation ITU-T H.222.0 (2023), *Information technology – Generic coding of moving pictures and associated audio information: Systems: Various corrections and updates.*
+- [b-ITU-T H.264] Recommendation ITU-T H.264 (2021), *Advanced video coding for generic audiovisual service.*
+- [b-ITU-T H.430.1] Recommendation ITU-T H.430.1 (2018), *Requirements for immersive live experience (ILE) services.*
+- [b-ITU-T Y.1910] Recommendation ITU-T Y.1910 (2008), *IPTV functional architecture.*
+- [b-ISO 9241-910] ISO 9241-910:2011, *Ergonomics of human-system interaction – Part 910: Framework for tactile and haptic interaction.*
+- [b-ISO/IEC 23008-1] International Standard ISO/IEC 23008-1:2023, *Information technology – High efficiency coding and media delivery in heterogeneous environments – Part 1: MPEG media transport (MMT).*
+- [b-ISO/IEC 23008-11] International Standard ISO/IEC 23008-11:2015, *Information technology – High efficiency coding and media delivery in heterogeneous environments – Part 11: MPEG media transport composition information.*
+- [b-ISO/IEC 23090-2] International Standard ISO/IEC 23090-2:2023, *Information technology – Coded representation of immersive media – Part 2: Omnidirectional media format.*
+- [b-ISO/IEC 23090-5] International Standard ISO/IEC 23090-5:2023, *Information technology – Coded representation of immersive media – Part 5: Visual volumetric video-based coding (V3C) and video-based point cloud compression (V-PCC).*
+- [b-IEEE P1918.1] IEEE P1918.1, *IEEE Draft Standard for tactile Internet: Application scenarios, definitions and terminology, architecture, functions, and technical assumptions.*
+- [b-IEEE P1918.1.1] IEEE P1918.1.1, *IEEE Draft Standard for haptic codecs for the tactile Internet.*
+- [b-ARIB STD-B60] Association of Radio Industries and Businesses Standard ARIB STD-B60 version 1.14 (2019), *MMT-based media transport scheme in digital broadcasting systems.* Available [viewed 2023-11-20] at: [https://www.arib.or.jp/english/html/overview/doc/6-STD-B60\\_v1\\_14-E1.pdf](https://www.arib.or.jp/english/html/overview/doc/6-STD-B60_v1_14-E1.pdf)
+- [b-KT PC] Chosunbiz (2016). *Kt기자간담회.. 5G 홀로그램라이브* [KT press conference. 5G hologram live]. San Bruno, CA: Youtube. Available [viewed 2023-11-20] at:
+- [b-NTT JKF] SHOCHIKUch (2016). *『KABUKI LION 獅子王』遠隔舞台挨拶in Las Vegas.* [Japan Kabuki Festival in Las Vegas 2016]. San Bruno, CA: Youtube. Available [viewed 2023-11-20] at: .
+- [b-NTT Krause] Krause, J. (2017). *Cyber teleportation Tokyo at SXSW.* Austin, TX: SXSW. Available [viewed 2023-11-21] at:
+
+- [b-NTT ICC] Intercommunication Center (2023). *Public booth for vibrotactile communication*. Tokyo: Intercommunication Center. Available [viewed 2023-11-20] at:
+- [b-Sohn] Sohn Ji-young (2018). Hard to follow cross-country skiing? 5G is here to help. *The Korea Herald*. Seoul: Herald Corporation. Available [viewed 2023-11-20] at:
+- [b-Tektonspace] Tektonspace (2017). *VR walk through*. San Bruno, CA: Youtube. Available [viewed 2023-11-20] at:
+
+
+
+
+
+## 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
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+
+
+
+
+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
+
+**H.460.10**
+
+(03/2004)
+
+SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS
+Infrastructure of audiovisual services – Supplementary
+services for multimedia
+
+---
+
+**Call party category within H.323 systems**
+
+ITU-T Recommendation H.460.10
+
+---
+
+# ITU-T H-SERIES RECOMMENDATIONS **AUDIOVISUAL AND MULTIMEDIA SYSTEMS**
+
+| | |
+|-------------------------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100–H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | |
+| General | H.200–H.219 |
+| Transmission multiplexing and synchronization | H.220–H.229 |
+| Systems aspects | H.230–H.239 |
+| Communication procedures | H.240–H.259 |
+| Coding of moving video | H.260–H.279 |
+| Related systems aspects | H.280–H.299 |
+| Systems and terminal equipment for audiovisual services | H.300–H.349 |
+| Directory services architecture for audiovisual and multimedia services | H.350–H.359 |
+| Quality of service architecture for audiovisual and multimedia services | H.360–H.369 |
+| Supplementary services for multimedia | H.450–H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | |
+| Overview of Mobility and Collaboration, definitions, protocols and procedures | H.500–H.509 |
+| Mobility for H-Series multimedia systems and services | H.510–H.519 |
+| Mobile multimedia collaboration applications and services | H.520–H.529 |
+| Security for mobile multimedia systems and services | H.530–H.539 |
+| Security for mobile multimedia collaboration applications and services | H.540–H.549 |
+| Mobility interworking procedures | H.550–H.559 |
+| Mobile multimedia collaboration inter-working procedures | H.560–H.569 |
+| BROADBAND AND TRIPLE-PLAY MULTIMEDIA SERVICES | |
+| Broadband multimedia services over VDSL | H.610–H.619 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# **ITU-T Recommendation H.460.10**
+
+## **Call party category within H.323 systems**
+
+## **Summary**
+
+This Recommendation specifies a mechanism that allows calling H.323 endpoints to signal calling party category information in the forward direction, and allows called H.323 endpoints to signal called party category information in the backward direction.
+
+###### **Source**
+
+ITU-T Recommendation H.460.10 was approved on 15 March 2004 by ITU-T Study Group 16 (2001-2004) 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 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 References..... | 1 |
+| 3 Call party category..... | 2 |
+| 4 Call party category info parameter ..... | 2 |
+| 4.1 Call party category info ASN.1 definition ..... | 3 |
+| 4.2 Description of ASN.1 types and fields ..... | 3 |
+
+
+
+## Call party category within H.323 systems
+
+# 1 Scope
+
+A calling party's category (CPC) parameter is defined by ISUP that describes the nature of the calling party, e.g., operator language, test call, payphone, etc. In addition, a called party category indicator is included in the ISUP backward call indicators parameter. ISUP variants used in some regional networks (in North America) define an originating line information (OLI) parameter to carry this information instead of the CPC parameter. R2 signalling uses the Group II forward signals to carry similar information. ITU-T Rec. H.450.12 defines a partyCategory field that identifies the category of either the calling party or the called party involved in the call.
+
+This information would be very useful for making routing and accounting decisions within the H.323 network. A mechanism is, therefore, required to support the signalling of the calling party category in H.323 networks.
+
+A calling endpoint should be able to signal calling party category information in the forward direction. The calling party category parameter may be included in Setup, ARQ and LRQ messages. H.323 devices, gateways, gatekeepers and border elements may apply routing and accounting policies based on the value of the calling party category.
+
+A called endpoint should be able to signal called party category information in the backward direction. The called party category parameter may be included in progress, alerting or connect messages. H.323 devices, gateways, gatekeepers and border elements may apply routing and accounting policies based on the value of the called party category.
+
+This Recommendation specifies a mechanism that allows calling H.323 endpoints to signal calling party category information in the forward direction and allows called H.323 endpoints to signal called party category information in the backward direction.
+
+## 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 H.225.0 (2003), *Call signalling protocols and media stream packetization for packet-based multimedia communication systems*.
+- ITU-T Recommendation H.323 (2003), *Packet-based multimedia communications systems*.
+- ITU-T Recommendation Q.763 (1999), *Signalling System No. 7 – ISDN user part formats and codes plus Amendment 2 (2002), Support for the International Emergency Preference Scheme*.
+- ITU-T Recommendation H.460.4 (2002), *Call priority designation for H.323 calls*.
+- ANSI T1.113-20001, *Signalling System No. 7 (SS7) – Integrated Services Digital Network (ISDN) User Part*.
+
+---
+
+1 T1 standards are maintained since November 2003 by ATIS.
+
+# 3 Call party category
+
+The call party category parameter is used to transport calling party category information in messages sent by the calling H.323 endpoint in the forward direction, and to transport called party category information in messages sent by the called H.323 endpoint in the backward direction. If the calling party category has the value of the International Emergency Preference Scheme (IEPS), then the use of H.460.4 procedures is not precluded.
+
+A H.323 endpoint or gatekeeper may include the call party category parameter in H.225.0 RAS and call signalling (Q.931) messages using the generic extensibility framework.
+
+When sending the call party category parameter in the call signalling messages, it shall be coded in the genericData parameter in the H.225.0 H323-UU-PDU in the user-user information element.
+
+When sending the call party category parameter in the RAS messages, it shall be coded in the genericData parameter in the request parameter of the H.225.0 RAS Message.
+
+The GenericData parameter indicates the callPartyCategory feature and contains a callPartyCategory parameter.
+
+Table 1 defines the call party category feature.
+
+**Table 1/H.460.10 – Call party category feature**
+
+| | |
+|---------------------------|--------------------------------------------------------------------------------------------------------------------------------------|
+| Feature name: | Call party category |
+| Feature Description: | This feature allows a H.323 endpoint to include calling party category or called party category information in a signalling message. |
+| Feature identifier type: | Standard |
+| Feature identifier value: | 10 |
+
+## 4 Call party category info parameter
+
+Table 2 defines the call party category info parameter.
+
+**Table 2/H.460.10 – Call party category info parameter**
+
+| | |
+|-----------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter name: | Call party category info |
+| Parameter description: | The call party category information parameter is the data sent in H.225.0 RAS and call signalling messages. The content is a raw field consisting of the ASN.1 PER encoded CallPartyCategoryInfo as specified in the ASN.1 in 4.1. |
+| Parameter identifier type: | Standard |
+| Parameter identifier value: | 1 |
+| Parameter type: | Raw |
+| Parameter cardinality: | Once and only once |
+
+### 4.1 Call party category info ASN.1 definition
+
+The call party category info definition used within the GenericData is shown below.
+
+```
+CALL-PARTY-CATEGORY DEFINITIONS AUTOMATIC TAGS ::=
+BEGIN
+
+CallPartyCategoryInfo ::= SEQUENCE
+{
+ callPartyCategory CallPartyCategory OPTIONAL,
+ originatingLineInfo OriginatingLineInfo OPTIONAL,
+ ...
+}
+
+CallPartyCategory ::= INTEGER (0..255)
+
+OriginatingLineInfo ::= INTEGER (0..255)
+
+END
+```
+
+### 4.2 Description of ASN.1 types and fields
+
+**CallPartyCategoryInfo** – The H.323 endpoint may include this field to signal the calling or called party category or originating line information parameters in call signalling or RAS messages.
+
+**CallPartyCategory** – The H.323 endpoint may include this field to signal the calling or called party category information in call signalling or RAS messages. The contents are values that are defined in ITU-T Rec. Q.763 (1999) and its Amendment 2 (2002).
+
+**OriginatingLineInfo** – The calling H.323 endpoint may include this field to signal the originating line information parameter in call signalling or RAS messages. The contents are values that are defined in ANSI T1.113.3-2000, Annex C.
+
+
+
+
+
+# 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
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+
+
+**ITU-T**
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+**H.460.16**
+
+(01/2005)
+
+SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS
+
+Infrastructure of audiovisual services – Supplementary
+services for multimedia
+
+---
+
+**Multiple-message release sequence capability
+within H.323 systems**
+
+ITU-T Recommendation H.460.16
+
+# ITU-T H-SERIES RECOMMENDATIONS **AUDIOVISUAL AND MULTIMEDIA SYSTEMS**
+
+| | |
+|-------------------------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100–H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | |
+| General | H.200–H.219 |
+| Transmission multiplexing and synchronization | H.220–H.229 |
+| Systems aspects | H.230–H.239 |
+| Communication procedures | H.240–H.259 |
+| Coding of moving video | H.260–H.279 |
+| Related systems aspects | H.280–H.299 |
+| Systems and terminal equipment for audiovisual services | H.300–H.349 |
+| Directory services architecture for audiovisual and multimedia services | H.350–H.359 |
+| Quality of service architecture for audiovisual and multimedia services | H.360–H.369 |
+| Supplementary services for multimedia | H.450–H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | |
+| Overview of Mobility and Collaboration, definitions, protocols and procedures | H.500–H.509 |
+| Mobility for H-Series multimedia systems and services | H.510–H.519 |
+| Mobile multimedia collaboration applications and services | H.520–H.529 |
+| Security for mobile multimedia systems and services | H.530–H.539 |
+| Security for mobile multimedia collaboration applications and services | H.540–H.549 |
+| Mobility interworking procedures | H.550–H.559 |
+| Mobile multimedia collaboration inter-working procedures | H.560–H.569 |
+| BROADBAND AND TRIPLE-PLAY MULTIMEDIA SERVICES | |
+| Broadband multimedia services over VDSL | H.610–H.619 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## **ITU-T Recommendation H.460.16**
+
+# **Multiple-message release sequence capability within H.323 systems**
+
+## **Summary**
+
+This Recommendation specifies a mechanism that allows H.323 endpoints to negotiate and use a multiple-message release sequence.
+
+###### **Source**
+
+ITU-T Recommendation H.460.16 was approved on 8 January 2005 by ITU-T Study Group 16 (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 2005
+
+All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU.
+
+## CONTENTS
+
+| | | |
+|-----|-------------------------------------------------------------------------|---|
+| 1 | Scope ..... | 1 |
+| 2 | References..... | 1 |
+| 3 | Introduction ..... | 1 |
+| 4 | Feature description..... | 2 |
+| 4.1 | H.501 signalling ..... | 2 |
+| 4.2 | RAS signalling..... | 2 |
+| 4.3 | Call signalling – negotiation..... | 2 |
+| 4.4 | Call signalling – release..... | 4 |
+| 4.5 | Call signalling timers..... | 4 |
+| 5 | Generic data usage..... | 5 |
+| 5.1 | Multiple-message release sequence feature..... | 5 |
+| 5.2 | Multiple-message release sequence parameters ..... | 5 |
+| 6 | Message flows ..... | 6 |
+| 6.1 | Three-message sequence ..... | 6 |
+| 6.2 | Time-outs..... | 7 |
+| 6.3 | Two-message sequence ..... | 7 |
+| 6.4 | Simultaneous initiation of two-message MMRS procedure..... | 8 |
+| 6.5 | Simultaneous initiation of two- and three-message MMRS procedures ..... | 8 |
+| 6.6 | Simultaneous initiation of MMRS and H.225.0 procedures ..... | 9 |
+
+
+
+# Multiple-message release sequence capability within H.323 systems
+
+# 1 Scope
+
+This Recommendation specifies a mechanism, using the generic extensibility framework defined in ITU-T Rec. H.460.1, which allows endpoints to use a multiple-message release sequence rather than the single release complete message procedure defined in ITU-T Rec. H.225.0. It includes the capability for one endpoint to inform the other that it supports and will use the alternate multiple-message release sequence.
+
+# 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 H.225.0 (2003), *Call signalling protocols and media stream packetization for packet-based multimedia communication systems*.
+- ITU-T Recommendation H.323 (2003), *Packet-based multimedia communications systems*.
+- ITU-T Recommendation Q.931 (1998), *ISDN user-network interface layer 3 specification for basic call control*.
+
+# 3 Introduction
+
+The call control signalling defined in ITU-T Rec. H.225.0 is based on Q.931 signalling. ITU-T Rec. Q.931 defined a multiple-message sequence to be used between the user and the network to control release of a connection. This used the disconnect message from the user as a request to release a connection, and then the release and release complete messages to actually release the connection. This allowed additional information to be passed in both directions during the disconnect process and allowed the initiator of the disconnect to supervise the operation and to retransmit the request in case of failure.
+
+ITU-T Rec. H.225.0 does not use the disconnect and release messages and, therefore, depends on a single message without acknowledgement by the application. While this suffices for many cases, some applications require the functionality of a multiple-message sequence for release of a connection. Further, an occasional loss of the release complete message could cause significant problems.
+
+This Recommendation, using the generic extensibility framework, provides the capability with H.225.0 of performing the multiple-message release sequence of a connection in a way that is analogous to Q.931. The H.225.0 facility message is used for the additional messages of the sequence, with the addition of the GEF parameter defined herein to distinguish its place and function in the sequence.
+
+The multiple-message release sequence may be used to provide additional capabilities such as:
+
+- 1) supervision of acknowledgement of release and repetition in case of failure;
+- 2) inclusion of supplemental information in both directions during the release procedure;
+
+- 3) provision of in-band tones and announcements;
+- 4) full coordination of release of resources;
+- 5) called user release control.
+
+# 4 Feature description
+
+## 4.1 H.501 signalling
+
+When a Gatekeeper uses the H.501 access request procedures to request that another gatekeeper perform address resolution, it may indicate the requirement for support of the MMRS feature by inclusion of the MMRS parameters. The responding gatekeeper shall use this information in the selection of a location, which matches the address and complies with any MMRS support requirement.
+
+## 4.2 RAS signalling
+
+### 4.2.1 Registration
+
+Support for the MMRS feature shall be indicated by the endpoint in an RRQ when the endpoint initially attempts to register. This shall indicate that MMRS will be supported by the endpoint if requested and it may indicate if support for MMRS is required for all calls to and from this endpoint. A gatekeeper may reject a registration due to the lack of support for MMRS by inclusion of **neededFeatureNotSupported** in the **rejectReason** in the RRJ, for example, if the gatekeeper knows that all calls in the network must use the MMRS procedures. The **desiredFeatures** field shall not be used to carry the MMRS parameter in an RRQ.
+
+### 4.2.2 Location request
+
+When an endpoint sends an LRQ to the gatekeeper for address resolution, it may indicate the requirement or desire for MMRS support by inclusion of the MMRS indication in either the **neededFeatures** or the **desiredFeatures** field. The gatekeeper shall use this information for the selection of a location, which matches the address and complies with any MMRS support requirement.
+
+### 4.2.3 Admission request
+
+Support for the MMRS feature for an individual call is negotiated between an endpoint and gatekeeper at call set-up time as part of the admission request procedure. For this purpose, an endpoint that supports this feature shall include the feature descriptor defined in 5.1 in **supportedFeatures** and may include the **neededFeatures** in the ARQ message in order to indicate whether the endpoint requires support for MMRS for the calls for which admission is being requested. If support for the feature is not indicated, a gatekeeper may reject an ARQ due to the lack of support for MMRS by the endpoint by inclusion of **neededFeatureNotSupported** in the **rejectReason** in the ARJ, for example, if the network or destination endpoint requires the use of MMRS.
+
+The MMRS parameter shall not be including in the **desiredFeatures** field in RAS admission request signalling, since support either is or is not required. Further, the "MMRS Sse Required" parameter shall not be used, since support always implies that it can be used if required by call signalling.
+
+## 4.3 Call signalling – negotiation
+
+The required or optional use of the MMRS procedure shall be negotiated by the two ends exchanging call-signalling messages using the Setup message and the first positive response to that
+
+setup. Positive responses are the setup acknowledge, alerting, call proceeding, progress, and connect messages.
+
+### 4.3.1 Setup
+
+If the calling endpoint supports the MMRS feature, but does not require the called endpoint to support it, it shall include the MMRS feature identifier in the **supportedFeatures** field in the setup to indicate its support for the feature. If the calling endpoint requires that the called party supports the MMRS feature as a condition for setting up the call, it shall include the MMRS feature identifier in the **neededFeatures** field. The MMRS feature identifier shall not be included in the **desiredFeatures** field since support either is or is not required.
+
+In addition, the setup may also include the "MMRS Use Required" parameter to indicate that the feature must be used by the responder if the responder initiates release of this call.
+
+In summary, the following combinations of supported, needed, and use required are possible in the setup message:
+
+| Case | Supported
(by sender) | (Support)
needed
(by responder) | Use
required |
+|------|--------------------------|---------------------------------------|-----------------|
+| 1 | Yes | No | No |
+| 2 | Yes | Yes | No |
+| 3 | Yes | Yes | Yes |
+
+### 4.3.2 Response
+
+Depending on the contents of the setup messages, the response shall be as follows:
+
+- If the setup indicated that support for MMRS by the responder is not required, the first positive response to setup may contain the **supportFeatures** field indicating that the responder supports the feature. In addition, the response message may include the "MMRS Use Required" parameter to indicate that the feature must be used by the other endpoint if the other endpoint initiates release of this call.
+
+Otherwise, the absence of the MMRS feature indication in the **supportedFeatures** field indicates that the responder does not support MMRS. The originator and responder shall continue to set up the call as normal.
+
+- If the setup indicated that support for MMRS is needed (required) but that use of the feature is not required for this call, the first positive response to setup may contain the **supportFeatures** field indicating that the responder supports the feature. In addition, the response message may include the "MMRS Use Required" parameter to indicate that the responder requires that the feature be used by the other endpoint if the other endpoint initiates release of this call.
+
+Otherwise, the absence of the MMRS feature indication in the **supportedFeatures** field indicates that the responder does not support MMRS. The responder shall continue to set up the call as normal, however the originator may decide to release the call setup.
+
+- If the setup indicated that MMRS must be used for this call, the first positive response to setup may contain the MMRS feature indication in the **supportedFeatures** to indicate that the responder supports the feature and will use it to release calls. Otherwise, the absence of the MMRS feature indication in the **supportedFeatures** field indicates that the responder does not support MMRS or cannot use it for this call, in which case the originator may release the call setup.
+
+## 4.4 Call signalling – release
+
+### 4.4.1 Facility message encoding
+
+The function of the Q.931 disconnect and release messages are provided by the H.225.0 facility message. The corresponding fields of the facility message shall be used to carry the information normally in the disconnect and release messages. Those additional fields, which are not defined in H.225.0 as being included in the facility message but are required in the release sequence shall be encoded in the "MMRS Additional IEs" parameter.
+
+### 4.4.2 Facility message procedures
+
+The "MMRS Procedure" parameter shall be used in facility messages between endpoints and gatekeepers and between endpoints to indicate the procedure to be used to release the connection.
+
+Either end may initiate the release procedure, independent of which one originally established the call. The "originator" in the following description refers to the end, which initiates the release.
+
+When sending the first facility message of the MMRS, the originator shall include the "MMRS procedure" parameter to indicate one of the following:
+
+- 1) "treat as Q.931 Disconnect message", that is, it is a request for the other end to begin a release procedure which may include delays or time-outs before the actual release occurs. The originator shall set T305 or T306.
+- 2) "treat as Q.931 Release message", that is, it must be responded to immediately with the release complete message, and if not, the originator will repeat the message. The originator shall set T308.
+
+It should be noted that, as in ITU-T Rec. Q.931, the use of the first "treat as Q.931 Disconnect message" is optional and the procedure functions properly if the first message sent is the "treat as Q.931 Release message". When the MMRS parameters exchanged indicates that MMRS must be used for this call, the "treat as Q.931 Disconnect message" is optional and its use depends on other factors such as the need to provide in-band tones and announcements.
+
+The action taken by the responder shall be as follows:
+
+Upon receipt of a facility message indicated as "treat as Q.931 Disconnect message", the responder may apply timeouts, or other feature specific procedures, before sending the response. Upon completion of such specific procedures, the responder shall send a facility message indicated as "treat like Q.931 Release message" and shall set T308.
+
+Upon receipt of a facility message indicated as "treat as Q.931 Release message", the responder shall immediately return a release complete message.
+
+Upon receipt of a release complete message, the responder shall clear all resources and not return any message, that is, it shall operate as defined in ITU-T Rec. H.225.0.
+
+Further procedures for timeouts, message repetition, and treatment of glare shall be as defined in ITU-T Rec. Q.931. In addition, upon time-out of T308 the second time, the endpoint shall send a release complete message.
+
+## 4.5 Call signalling timers
+
+In addition to the timers defined in ITU-T Rec. H.225.0, the following additional timers are used with the MMRS feature (see Tables 9-1/Q.931 and 9-2/Q.931):
+
+- 1) T305 defines how long the sender of a facility message marked as "treat as Q.931 Disconnect message" should wait for a response facility message before taking other action. It is set when facility marked as "treat as Q.931 Disconnect message" without progress indicator No. 8 is sent. Its default value is 30 seconds.
+
+- 2) T306 defines how long the sender of a facility message marked as "treat as Q.931 Disconnect message" should wait for a response facility message before taking other action. It is set when facility marked as "treat as Q.931 Disconnect message" with progress indicator No. 8 is sent. Its default value is 30 seconds (see 7.2.2.23/H.225.0 and 4.5.23/Q.931).
+- 3) T308 defines how long the sender of a facility message marked as "treat as Q.931 Release message" should wait for a response release complete message before taking other action, either resending the facility message or entering failure procedures. Its default value is 4 seconds.
+
+# 5 Generic data usage
+
+When sending the MMRS parameter in H.501 access request and service request messages, it shall be coded in the **common.genericData** field of the message.
+
+When sending the MMRS parameter in H.225.0 RAS messages, the parameter shall be coded in the **genericData** field in the request parameter of the H.225.0 **RasMessage**.
+
+When sending the MMRS parameter in the H.225.0 call signalling messages, it shall be coded in the **genericData** field in the H.225.0 H323-UU-PDU in the user-user information element.
+
+The **genericData** parameter indicates the MMRS feature and contains the MMRS parameters.
+
+## 5.1 Multiple-message release sequence feature
+
+Table 1 defines the multiple-message release sequence feature.
+
+**Table 1/H.460.16 – Multiple-message release sequence feature**
+
+| Feature name | Multiple-message release sequence |
+|--------------------------|------------------------------------------------------------------------------------------------------------------------------------------------|
+| Feature Description | This feature allows one end to inform the other that it intends to use the multiple-message release sequence procedure or that it is using it. |
+| Feature identifier type | Standard |
+| Feature identifier value | 16 |
+
+## 5.2 Multiple-message release sequence parameters
+
+Tables 2 to 4 define the multiple-message release sequence parameters.
+
+**Table 2/H.460.16 – Multiple-message release sequence use parameter**
+
+| Parameter name | MMRS use required |
+|----------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter description | This parameter is sent in H.225.0 call signalling setup/response messages to indicate that the MMRS procedures must be used for this call. |
+| Parameter identifier type | Standard |
+| Parameter identifier value | 1 |
+| Parameter type | No content |
+| Parameter cardinality | Zero or one |
+
+**Table 3/H.460.16 – Multiple-message release sequence procedure parameter**
+
+| Parameter name | MMRS procedure |
+|----------------------------|----------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter description | This parameter is sent in the H.225.0 facility message to indicate how this message should be interpreted in supporting the MMRS procedures. |
+| Parameter identifier type | Standard |
+| Parameter identifier value | 2 |
+| Parameter type | number8 |
+| Parameter valid values | 1 = treat as Q.931 disconnect message
2 = treat as Q.931 release message |
+| Parameter cardinality | Zero or one. |
+
+**Table 4/H.460.16 – Multiple-message release sequence additional IEs parameter**
+
+| Parameter name | MMRS additional IEs |
+|----------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Parameter description | This parameter is sent in the H.225.0 call signalling facility message to pass additional information elements not defined in facility which are contained in the Q.931 disconnect and release messages. |
+| Parameter identifier type | Standard |
+| Parameter identifier value | 3 |
+| Parameter type | raw |
+| Parameter cardinality | Zero or one |
+
+NOTE – The MMRS additional IEs parameter is used to pass the cause, progress, and signal information elements defined in the Q.931 disconnect and release messages. The binary representation of the required IEs shall be contained in the raw parameter (similar to the procedure defined in ITU-T Rec. H.460.5).
+
+# 6 Message flows
+
+This clause provides message flows for the use of the MMRS procedure. In each case, the originating endpoint in the figure is the one, which initiates the release, not the one, which sets up the call.
+
+## 6.1 Three-message sequence
+
+When the signalling during call setup has determined that both endpoints support the MMRS procedure, the message flow for call release using three messages is as shown in Figure 1.
+
+
+
+```
+
+sequenceDiagram
+ participant Originating endpoint
+ participant Responding endpoint
+ Note left of Originating endpoint: T305
+ Originating endpoint->>Responding endpoint: Facility – treat as Q.931 disconnect
+ Note right of Responding endpoint: T308
+ Responding endpoint->>Originating endpoint: Facility – treat as Q.931 release
+ Originating endpoint->>Responding endpoint: Release complete
+ Note right of Responding endpoint: H.460.16_F01
+
+```
+
+Sequence diagram showing the three-message release sequence between an Originating endpoint and a Responding endpoint. The sequence starts with the Originating endpoint sending a 'Facility – treat as Q.931 disconnect' message to the Responding endpoint. The Responding endpoint then sends a 'Facility – treat as Q.931 release' message back to the Originating endpoint. Finally, the Originating endpoint sends a 'Release complete' message to the Responding endpoint. The diagram includes labels for the endpoints, the messages, and the protocol standards T305 and T308. The figure is labeled H.460.16\_F01.
+
+**Figure 1/H.460.16 – Message flow for three-message sequence**
+
+## 6.2 Time-outs
+
+If a time-out occurs while waiting for the response facility or release complete message, the appropriate message is repeated or a new message is sent. Figure 2 shows the case of the three-message procedure when all messages from the responding endpoint are lost, causing multiple time-outs at the originating endpoint. (Since T308 is generally much less than T305, several timeouts may also occur at the responding endpoint in this example.)
+
+
+
+This sequence diagram illustrates a three-message procedure for call release between an originating endpoint and a responding endpoint. The originating endpoint sends a 'Facility – treat as Q.931 disconnect' message. The responding endpoint receives it and sends a 'Facility – treat as Q.931 release' message, which is lost. The originating endpoint times out (T305) and retransmits the 'Facility – treat as Q.931 disconnect' message. The responding endpoint receives this and sends another 'Facility – treat as Q.931 release' message, which is also lost. The originating endpoint times out (T308) and retransmits the 'Facility – treat as Q.931 disconnect' message. The responding endpoint receives this and sends a 'Release complete' message, which is lost. The originating endpoint times out (T308) and sends a 'Release complete' message. The responding endpoint receives this and completes the release. The diagram is labeled H.460.16\_F02.
+
+Sequence diagram illustrating time-outs in a three-message procedure between an originating and a responding endpoint.
+
+Figure 2/H.460.16 – Time-outs
+
+## 6.3 Two-message sequence
+
+When the signalling during call setup has determined that both endpoints support the MMRS procedure, the message flow for call release using two messages is as shown in Figure 3. In this case, the originating endpoint does not use the optional "treat as Q.931 Disconnect" message.
+
+
+
+This sequence diagram illustrates a two-message sequence for call release between an originating endpoint and a responding endpoint. The originating endpoint sends a 'Facility – treat as Q.931 release' message. The responding endpoint receives it and sends a 'Release complete' message. The originating endpoint receives this and completes the release. The diagram is labeled H.460.16\_F03.
+
+Sequence diagram illustrating the message flow for a two-message sequence between an originating and a responding endpoint.
+
+Figure 3/H.460.16 – Message flow for two-message sequence
+
+## 6.4 Simultaneous initiation of two-message MMRS procedure
+
+When the signalling during call setup has determined that both endpoints support the MMRS procedure, if both endpoints initiate call release at the same instant, the messages will cross. The resulting message flow is shown in Figure 4.
+
+
+
+```
+
+sequenceDiagram
+ participant L as Originating endpoint
+ participant R as Originating endpoint
+ Note over L: T308
+ Note over R: T308
+ L->>R: Facility – treat as Q.931 release
+ R->>L: Facility – treat as Q.931 release
+ L->>R: Release complete
+ R->>L: Release complete
+
+```
+
+Sequence diagram illustrating the message flow for simultaneous initiation of two-message MMRS procedure. Two vertical lines represent the 'Originating endpoint' on both sides. The sequence of messages is as follows:
+
+- Both endpoints simultaneously send a 'Facility – treat as Q.931 release' message to each other. These messages cross.
+- Both endpoints simultaneously receive a 'Release complete' message from the other endpoint. These messages also cross.
+
+Timing diagrams T308 are shown on both sides, indicating the sequence of events. The diagram is labeled H.460.16\_F04.
+
+Sequence diagram for simultaneous initiation of two-message MMRS procedure.
+
+**Figure 4/H.460.16 – Message flow for simultaneous initiation of two-message MMRS procedure**
+
+## 6.5 Simultaneous initiation of two- and three-message MMRS procedures
+
+When the signalling during call setup has determined that both endpoints support the MMRS procedure, if both endpoints initiate call release at the same instant, the messages will cross. If one initiates the two-message sequence and the other the three-message sequence, the resulting message flow is shown in Figure 5.
+
+
+
+```
+
+sequenceDiagram
+ participant L as Originating endpoint
+ participant R as Originating endpoint
+ Note over L: T305
+ Note over R: T308
+ L->>R: Facility – treat as Q.931 disconnect
+ R->>L: Facility – treat as Q.931 release
+ R->>L: Release complete
+ L->>R: (Message ignored)
+
+```
+
+Sequence diagram illustrating the message flow for simultaneous initiation of two- and three-message MMRS procedures. Two vertical lines represent the 'Originating endpoint' on both sides. The sequence of messages is as follows:
+
+- The left endpoint sends a 'Facility – treat as Q.931 disconnect' message. The right endpoint sends a 'Facility – treat as Q.931 release' message. These messages cross.
+- The left endpoint receives a 'Release complete' message from the right endpoint.
+- The right endpoint receives a message from the left endpoint, but it is ignored, as indicated by a 'Message ignored' box. This message is likely a 'Facility' message that the right endpoint does not expect at this stage of its three-message sequence.
+
+Timing diagrams T305 and T308 are shown on the left and right sides respectively, indicating the sequence of events. The diagram is labeled H.460.16\_F05.
+
+Sequence diagram for simultaneous initiation of two- and three-message MMRS procedures.
+
+**Figure 5/H.460.16 – Message flow for simultaneous initiation of two- and three-message MMRS procedure**
+
+## 6.6 Simultaneous initiation of MMRS and H.225.0 procedures
+
+When the signalling during call setup has determined that both endpoints support but do not require that the MMRS procedure be used, if both endpoints initiate call release using different procedures at the same instant, the different messages will cross. The resulting message flow is shown in Figure 6. In this case, the endpoint, which initiated the three-message sequence, will receive the normal H.225.0 release complete message in response and treat it as the proper response. The endpoint, which initiated the H.225.0 single message sequence, will receive the facility, which it will ignore.
+
+
+
+The diagram illustrates the message exchange between two endpoints, Originating endpoint A and Originating endpoint B, during simultaneous call release initiation. The sequence of messages is as follows:
+
+- Originating endpoint A sends a **Facility – treat as Q.931 disconnect** message to Originating endpoint B.
+- Originating endpoint B sends a **Release complete** message to Originating endpoint A.
+- Originating endpoint A receives the **Release complete** message and treats it as a proper response, indicated by a callout box labeled **Treated as proper response**.
+- Originating endpoint B receives the **Facility – treat as Q.931 disconnect** message and ignores it, indicated by a callout box labeled **Message ignored**.
+
+The diagram also includes a **T305** label near the start of the message exchange on the left side. The diagram is labeled **H.460.16\_F06** in the bottom right corner.
+
+Sequence diagram showing message flow between Originating endpoint A and Originating endpoint B for simultaneous initiation of MMRS and H.225.0 procedures.
+
+Figure 6/H.460.16 – Message flow for simultaneous initiation of both procedures
+
+
+
+
+
+## **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 | 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
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@@ -0,0 +1,267 @@
+
+
+**ITU-T**
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+**H.460.17**
+
+(09/2005)
+
+SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS
+
+Infrastructure of audiovisual services – Supplementary
+services for multimedia
+
+---
+
+**Using H.225.0 call signalling connection as
+transport for H.323 RAS messages**
+
+ITU-T Recommendation H.460.17
+
+# ITU-T H-SERIES RECOMMENDATIONS **AUDIOVISUAL AND MULTIMEDIA SYSTEMS**
+
+| | |
+|-------------------------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100–H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | |
+| General | H.200–H.219 |
+| Transmission multiplexing and synchronization | H.220–H.229 |
+| Systems aspects | H.230–H.239 |
+| Communication procedures | H.240–H.259 |
+| Coding of moving video | H.260–H.279 |
+| Related systems aspects | H.280–H.299 |
+| Systems and terminal equipment for audiovisual services | H.300–H.349 |
+| Directory services architecture for audiovisual and multimedia services | H.350–H.359 |
+| Quality of service architecture for audiovisual and multimedia services | H.360–H.369 |
+| Supplementary services for multimedia | H.450–H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | |
+| Overview of Mobility and Collaboration, definitions, protocols and procedures | H.500–H.509 |
+| Mobility for H-Series multimedia systems and services | H.510–H.519 |
+| Mobile multimedia collaboration applications and services | H.520–H.529 |
+| Security for mobile multimedia systems and services | H.530–H.539 |
+| Security for mobile multimedia collaboration applications and services | H.540–H.549 |
+| Mobility interworking procedures | H.550–H.559 |
+| Mobile multimedia collaboration inter-working procedures | H.560–H.569 |
+| BROADBAND AND TRIPLE-PLAY MULTIMEDIA SERVICES | |
+| Broadband multimedia services over VDSL | H.610–H.619 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## **ITU-T Recommendation H.460.17**
+
+# **Using H.225.0 call signalling connection as transport for H.323 RAS messages**
+
+## **Summary**
+
+The current version of ITU-T Rec. H.323 requires two completely independent transports: one for RAS and another for H.225.0 call signalling. For several reasons, one of them is FW/NAT traversal; it would be advantageous to be able to use the same transport for both protocols.
+
+This Recommendation defines the mechanism of encapsulating RAS messages inside H.225.0 messages and the method for discovering the ability of a peer H.323 entity to support features defined in this Recommendation.
+
+###### **Source**
+
+ITU-T Recommendation H.460.17 was approved on 13 September 2005 by ITU-T Study Group 16 (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 2005
+
+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 Abbreviations..... | 2 |
+| 5 Feature Description..... | 2 |
+| 6 Discovering remote entity's support of RAS over H.225.0 ..... | 2 |
+| 7 Transport of RAS over H.225.0..... | 2 |
+| 7.1 Usage of H.225.0..... | 2 |
+| 7.2 Generic data usage..... | 3 |
+| 7.3 RAS over H.225.0 feature definition..... | 3 |
+| 7.4 RAS over H.225.0 parameters..... | 4 |
+| 8 Security considerations..... | 4 |
+
+
+
+# Using H.225.0 call signalling connection as transport for H.323 RAS messages
+
+## 1 Scope
+
+This Recommendation defines the mechanism of encapsulating RAS messages inside H.225.0 messages and the method for discovering the ability of a peer H.323 entity to support features defined 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.
+
+- [1] ITU-T Recommendation H.323 (2003), *Packet-based multimedia communications systems*.
+- [2] ITU-T Recommendation H.225.0 (2003), *Call signalling protocols and media stream packetization for packet-based multimedia communication systems*.
+- [3] ITU-T Recommendation H.460.1 (2002), *Guidelines for the Use of the Generic Extensible Framework*.
+- [4] ITU-T Recommendation H.235.0 (2005), *H.323 security: Framework for security in H-series (H.323 and other H.245-based) multimedia systems*.
+- [5] ITU-T Recommendation H.235.1 (2005), *H.323 security: Baseline security profile*.
+- [6] ITU-T Recommendation H.235.2 (2005), *H.323 security: Signature security profile*.
+- [7] ITU-T Recommendation H.235.3 (2005), *H.323 security: Hybrid security profile*.
+- [8] ITU-T Recommendation H.235.4 (2005), *H.323 security: Direct and selective routed call security*.
+- [9] ITU-T Recommendation H.235.5 (2005), *H.323 security: Framework for secure authentication in RAS using weak shared secrets*.
+- [10] ITU-T Recommendation H.235.6 (2005), *H.323 security: Voice encryption profile with native H.235/H.245 key management*.
+- [11] ITU-T Recommendation H.235.7 (2005), *H.323 security: Usage of the MIKEY key management protocol for the Secure Real Time Transport Protocol (SRTP) within H.235*.
+- [12] IETF RFC 2246 (1999), *The TLS Protocol Version 1.0*.
+
+## 3 Terms and Definitions
+
+This Recommendation defines the following term:
+
+**3.1 RAS over H.225.0:** The mechanism allowing transport of RAS messages inside the H.225.0 call signalling connection.
+
+## 4 Abbreviations
+
+This Recommendation uses the following abbreviations:
+
+| | |
+|------|--------------------------------------|
+| EP | Endpoint |
+| GK | Gatekeeper |
+| RAS | Registration, Admission and Status |
+| RCF | Registration Confirm |
+| RRQ | Registration Request |
+| SCTP | Stream Control Transmission Protocol |
+| TCP | Transport Control Protocol |
+| TLS | Transport Level Security |
+| TSAP | Transport Service Access Point |
+
+## 5 Feature Description
+
+This Recommendation defines two mechanisms:
+
+- Discovery of the remote entity's support of RAS over H.225.0
+- Transport of RAS messages over the H.225.0 call signalling connection.
+
+## 6 Discovering remote entity's support of RAS over H.225.0
+
+RAS messages are sent between EP and GK or between two GKs. In both cases the first RAS message between two particular H.323 entities is sent in the GK direction. The support of RAS over H.225.0 by a particular GK may be either known *a priori* (provisioned) or may require discovery. H.460 feature negotiation mechanisms cannot be used in this case because the discovery should be performed before the first message between the H.323 entities is sent.
+
+Annex O/H.323 GK discovery mechanism should be used for discovery of support of RAS over H.225.0. The service for the discovery shall be either h323rs or h323ls. The H.225.0 transport will be discovered based on the following rules:
+
+In the case of H.225.0 signalling over TCP, the transport shall be tcp.
+
+In the case of H.225.0 signalling over Annex E/H.323, the transport shall be h323mux.
+
+In the case of H.225.0 signalling over SCTP, the transport shall be sctp.
+
+If the IP address of the GK is known *a priori* and the port is unknown, the well-known H.225.0 call signalling port 1720 shall be used for RAS over H.225.0 procedure.
+
+## 7 Transport of RAS over H.225.0
+
+## 7.1 Usage of H.225.0
+
+The entity which supports RAS over H.225.0 shall also support persistent H.225.0 transport connections as described in 7.3/H.323. An endpoint shall indicate such support by setting maintainConnection in RRQ to TRUE.
+
+If both the entity sending the RAS message, and the entity receiving it support RAS over H.225.0, then they should use it for RAS messages transport.
+
+In order to keep the transport connection open, the two entities should use lightweight RRQ, as described in 7.2.2.1/H.323. In the case of NAT traversal, the timeToLive value should be shorter
+
+than the NAT binding timeout. The entities may use the IRR mechanism to support the same functionality. Alternatively, for the cases when transport is TCP, an entity which established the TCP connection may periodically send empty TPKT packets (packets containing bytes 03 00 00 04 only). A keep-alive interval in the range of 5 to 30 seconds should be used except in cases where it is known (for example, from the specifics of the network) that a longer interval will not result in the closure of pinholes.
+
+To send a RAS message between two H.323 entities supporting RAS over the H.225.0 feature, a persistent H.225.0 transport connection shall be used between the entities. If such a connection is already established it may be re-used, or a new connection may be established. If no persistent connection is currently established, then it shall be established. Generally, the entity sending the first RAS message establishes the connection to the entity receiving the RAS message. The H.225.0 signalling TSAP of the entity receiving the RAS message is used as the transport connection destination. The same transport connection should be used for RAS over H.225.0 signalling and regular H.225.0 signalling.
+
+If desired, more than one H.225.0 transport connection between the same two entities may be used for RAS messages transfer. No association is mandated between RAS messages and transport connections in such a case.
+
+To signal that the same GK's H.225.0 transport signalling TSAP shall be used for all RAS and H.225.0 communication, the callSignalAddress and rasAddress fields of the RRQ and RCF shall contain a SEQUENCE OF containing zero elements.
+
+The H.225.0 FACILITY message shall be used to transfer RAS messages. The CRV field of the message shall have a value of 0 (including the flag bit). Such a message shall contain User-user Information Element with the h323-message-body field of H323-UU-PDU set to empty. The genericData field of the H323-UU-PDU shall contain RAS messages as described in 7.2 and 7.4.
+
+An H.323 entity, which supports RAS over H.225.0, shall also support tunnelling of H.245 channel over H.225.0.
+
+## 7.2 Generic data usage
+
+RAS messages to be sent over H.225.0 call signalling shall be encapsulated in the genericData field of the H323-UU-PDU in the User-user Information Element of the H.225.0 FACILITY message. Each such genericData field has the id field specifying RAS over H.225.0 (as defined in Table 1) and one or more RAS message parameters (as defined in Table 2) containing binary encoding of one RAS message each.
+
+## 7.3 RAS over H.225.0 feature definition
+
+Table 1 defines the RAS over the H.225.0 feature.
+
+**Table 1/H.460.17 – RAS over H.225.0 feature**
+
+| | |
+|---------------------------|----------------------------------------------------------------------------------------|
+| Feature name: | RAS over H.225.0 |
+| Feature Description: | This feature allows transport of RAS messages over H.225.0 call signalling connection. |
+| Feature identifier type: | Standard |
+| Feature identifier value: | 17 |
+
+## 7.4 RAS over H.225.0 parameters
+
+Table 2 defines the RAS over H.225.0 parameters.
+
+**Table 2/H.460.17 – RAS message parameter**
+
+| | |
+|-----------------------------|----------------------------------------------------------------|
+| Parameter name: | RAS message |
+| Parameter description: | This parameter contains basic-aligned PER-encoded RAS message. |
+| Parameter identifier type: | Standard |
+| Parameter identifier value: | 1 |
+| Parameter type: | raw |
+| Parameter cardinality: | One or more |
+
+## 8 Security considerations
+
+The transport of RAS messages provided by RAS over H.225.0 mechanism does not provide a means of security. It relies on the security mechanisms provided by underlying transport and security mechanisms defined for RAS messages.
+
+TLS may be used for the RAS over a TCP or SCTP channel. The procedure for supporting TLS is out of the scope of this Recommendation and needs to be addressed by H.235.
+
+
+
+## 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 | 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
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+
+
+
+
+The logo of the International Telecommunication Union (ITU) features a globe with a lightning bolt superimposed on it, and the letters 'ITU' written across the center.
+
+ITU logo
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+**H.460.5**
+
+(11/2002)
+
+SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS
+Supplementary services for multimedia
+
+---
+
+**H.225.0 transport of multiple Q.931 information
+elements of the same type**
+
+ITU-T Recommendation H.460.5
+
+---
+
+# ITU-T H-SERIES RECOMMENDATIONS **AUDIOVISUAL AND MULTIMEDIA SYSTEMS**
+
+| | |
+|-------------------------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100–H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | |
+| General | H.200–H.219 |
+| Transmission multiplexing and synchronization | H.220–H.229 |
+| Systems aspects | H.230–H.239 |
+| Communication procedures | H.240–H.259 |
+| Coding of moving video | H.260–H.279 |
+| Related systems aspects | H.280–H.299 |
+| SYSTEMS AND TERMINAL EQUIPMENT FOR AUDIOVISUAL SERVICES | H.300–H.399 |
+| SUPPLEMENTARY SERVICES FOR MULTIMEDIA | H.450–H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | |
+| Overview of Mobility and Collaboration, definitions, protocols and procedures | H.500–H.509 |
+| Mobility for H-Series multimedia systems and services | H.510–H.519 |
+| Mobile multimedia collaboration applications and services | H.520–H.529 |
+| Security for mobile multimedia systems and services | H.530–H.539 |
+| Security for mobile multimedia collaboration applications and services | H.540–H.549 |
+| Mobility interworking procedures | H.550–H.559 |
+| Mobile multimedia collaboration inter-working procedures | H.560–H.569 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## **ITU-T Recommendation H.460.5**
+
+### **H.225.0 transport of multiple Q.931 information elements of the same type**
+
+## **Summary**
+
+This Recommendation specifies the method of transferring duplicate Q.931 information elements in the H.225.0 messages. Such a method is required to overcome limitations imposed by ITU-T Rec. H.225.0. ITU-T Rec. H.225.0 allows for the inclusion of only a single Q.931 information element of a particular type in the single H.225.0 message.
+
+###### **Source**
+
+ITU-T Recommendation H.460.5 was prepared by ITU-T Study Group 16 (2001-2004) and approved under the WTSA Resolution 1 procedure on 29 November 2002.
+
+## 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 | Terms and definitions ..... | 1 |
+| 4 | The conversion procedure..... | 1 |
+| 5 | Generic Data Parameter specification ..... | 1 |
+
+
+
+## ITU-T Recommendation H.460.5
+
+### H.225.0 transport of multiple Q.931 information elements of the same type
+
+## 1 Scope
+
+ITU-T Rec. H.225.0 forbids including multiple Q.931 information elements (IEs) of the same type in the same message.
+
+This Recommendation specifies the method of transferring duplicate Q.931 IEs in H.225.0.
+
+## 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 H.225.0 (2000), *Call signalling protocols and media stream packetization for packet-based multimedia communications systems*.
+- ITU-T Recommendation H.323 (2000), *Packet-based multimedia communications systems*.
+- ITU-T Recommendation Q.931 (1998), *ISDN user-network interface layer 3 specification for basic call control*.
+
+## 3 Terms and definitions
+
+For the purposes of this Recommendation the definitions given in clause 3 of ITU-T Recs H.323, H.225.0 and H.245 apply.
+
+## 4 The conversion procedure
+
+To transfer a Q.931 message containing multiple IEs of the same type over the H.225.0 protocol, the conversion specified in this clause shall be performed.
+
+The conversion applies to all IEs except for the IEs that have the first appearance of the particular IE identifier. The binary representations (that includes IE identifier, length and content) of all such IEs shall be assembled into a single octet string. The resulting octet string shall be used as the value of the GEF parameter, as defined in clause 5, "Generic Data Parameter specification". In accordance with ITU-T Rec. H.225.0, IEs shall not be duplicated in the Q.931 part of the H.225.0 message.
+
+## 5 Generic Data Parameter specification
+
+This clause defines the DuplicateIEs feature and parameter
+
+| | |
+|---------------------------|---------------------------------|
+| Feature name: | DuplicateIEs |
+| Feature Description: | The duplicate Q.931 IE support. |
+| Feature identifier type: | Standard |
+| Feature identifier value: | 5 |
+
+| | |
+|-----------------------------|--------------------------------------------------------------------|
+| Parameter name: | IEsString |
+| Parameter description: | The binary representation of the 2 to last IEs of particular type. |
+| Parameter identifier type: | Standard |
+| Parameter identifier value: | 1 |
+| Parameter type: | raw |
+| Parameter cardinality: | 1 |
+
+
+
+## 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
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@@ -0,0 +1,840 @@
+
+
+
+
+ITU logo: A globe with a lightning bolt and the letters ITU.
+
+INTERNATIONAL TELECOMMUNICATION UNION
+
+**ITU-T**
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+**H.530**
+
+(03/2002)
+
+SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS
+
+Mobility and Collaboration procedures – Security for
+mobile multimedia systems and services
+
+---
+
+**Symmetric security procedures for H.323
+mobility in H.510**
+
+ITU-T Recommendation H.530
+
+---
+
+# ITU-T H-SERIES RECOMMENDATIONS **AUDIOVISUAL AND MULTIMEDIA SYSTEMS**
+
+| | |
+|-------------------------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100–H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | |
+| General | H.200–H.219 |
+| Transmission multiplexing and synchronization | H.220–H.229 |
+| Systems aspects | H.230–H.239 |
+| Communication procedures | H.240–H.259 |
+| Coding of moving video | H.260–H.279 |
+| Related systems aspects | H.280–H.299 |
+| SYSTEMS AND TERMINAL EQUIPMENT FOR AUDIOVISUAL SERVICES | H.300–H.399 |
+| SUPPLEMENTARY SERVICES FOR MULTIMEDIA | H.450–H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | |
+| Overview of Mobility and Collaboration, definitions, protocols and procedures | H.500–H.509 |
+| Mobility for H-Series multimedia systems and services | H.510–H.519 |
+| Mobile multimedia collaboration applications and services | H.520–H.529 |
+| Security for mobile multimedia systems and services | H.530–H.539 |
+| Security for mobile multimedia collaboration applications and services | H.540–H.549 |
+| Mobility interworking procedures | H.550–H.559 |
+| Mobile multimedia collaboration inter-working procedures | H.560–H.569 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+## **ITU-T Recommendation H.530**
+
+# **Symmetric security procedures for H.323 mobility in H.510**
+
+## **Summary**
+
+The purpose of this Recommendation is to describe security procedures for an H.323 multimedia mobility environment. This Recommendation provides the details about the security procedures for H.510.
+
+## **Source**
+
+ITU-T Recommendation H.530 was prepared by ITU-T Study Group 16 (2001-2004) and approved under the WTSA Resolution 1 procedure on 29 March 2002.
+
+## **Keywords**
+
+Annex D/H.235, authentication, encryption, integrity, key management, mobility, multimedia security, security profile.
+
+## 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 2002
+
+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 | Introduction ..... | 1 |
+| 3 | Specification conventions ..... | 1 |
+| 4 | Terms and definitions ..... | 3 |
+| 5 | Abbreviations and symbols..... | 4 |
+| 6 | References..... | 5 |
+| 6.1 | Normative references..... | 5 |
+| 6.2 | Non-normative references ..... | 5 |
+| 7 | Security requirements and constraints for mobility ..... | 6 |
+| 8 | Hop-by-hop security with symmetric cryptographic techniques..... | 7 |
+| 8.1 | Assumptions ..... | 8 |
+| 8.2 | Secure location updating procedures..... | 8 |
+| 8.2.1 | MT to V-GK ..... | 11 |
+| 8.2.2 | V-GK to MRP ..... | 14 |
+| 8.2.3 | MRP to V-BE ..... | 15 |
+| 8.2.4 | V-BE to H-BE ..... | 16 |
+| 8.2.5 | H-BE to MRP ..... | 17 |
+| 8.2.6 | MRP to AuF ..... | 17 |
+| 8.3 | Terminal authentication..... | 19 |
+| 8.4 | Unregistration ..... | 21 |
+| 8.5 | Application of the symmetric security protocol in the home domain ..... | 21 |
+| 8.6 | List of Object Identifiers ..... | 22 |
+| 9 | End-to-end security..... | 22 |
+
+
+
+# Symmetric security procedures for H.323 mobility in H.510
+
+# 1 Scope
+
+The purpose of this Recommendation is to provide recommendations for security procedures in H.323 mobility environments such as under the scope of ITU-T Rec. H.510. This Recommendation provides the details about the security procedures for ITU-T Rec. H.510.
+
+# 2 Introduction
+
+So far, the signalling capabilities of ITU-T Rec. H.235 in its versions 1 and 2 [4] are designed to handle security in mostly static H.323 [5] environments. Those environments and multimedia systems can achieve some limited mobility within gatekeeper zones; ITU-T Rec. H.323 [5] in general and ITU-T Rec. H.235 [4] specifically provide only very little support for secure roaming of mobile users and terminals across different domains with many involved entities in a mobility, distributed environment for example.
+
+The H.323 mobility scenarios depicted in ITU-T Rec. H.510 [6] regarding terminal mobility pose a new situation with their flexible and dynamic character also from a security point of view. Roaming H.323 users and mobile terminals have to be authenticated by a foreign, visited domain. Likewise, the mobile user would like to obtain evidence about the true identity of the visited domain. In addition to that, it may be also useful to obtain evidence about the identity of the terminals complementing user authentication. Thus, these requirements demand for mutual authentication of the user and the visited domain and optionally also of the identity of the terminal.
+
+As the mobile user is usually known only to the home domain where the user is subscribed and assigned a password, the visited domain initially does not know the mobile user. As such, the visited domain does not share any established security relationship with the mobile user and the mobile terminal. In order to let the visited domain achieve the authentication and authorization assurance for the mobile user and for the mobile terminal, the visited domain would relay certain security tasks such as authorization checks or key management to the home domain through intermediate network and service entities. This requires securing the communication and key management between the visited domain and the home domain too.
+
+While, in principle, mobility H.323 environments are more open than closed H.323 networks, there is of course also need to appropriately secure the key management tasks. It is also true that communication within and across the mobility domains deserves protection against malicious tampering.
+
+In summary, this Recommendation describes a generic security concept for mobility among domains for multimedia applications and multimedia services. The technical details describe the deployment for H.323 and for H.510 in particular, but are considered potentially open to other environments.
+
+## 3 Specification conventions
+
+In this Recommendation the following conventions are used:
+
+- "shall" indicates a mandatory requirement.
+- "should" indicates a suggested but optional course of action.
+- "may" indicates an optional course of action rather than a recommendation that something take place.
+
+References to clauses, subclauses, annexes and appendices refer to those items within this Recommendation unless another Recommendation is explicitly listed. For example, "1.4" refers to clause 1.4 of this Recommendation; "6.4/H.245" refers to clause 6.4 in Recommendation H.245.
+
+This Recommendation shows several mobility functional entities such as border elements. For a general description of those functional elements and their interaction, please refer to ITU-T Rec. H.510 [6]. As this Recommendation only describes user/terminal mobility security, interaction with other mobility related functional entities such as mobility routing proxies like VLF, HLF is just briefly mentioned; such functional entities are considered not an integral part of this Recommendation. Specifically, the security architecture does not depend on the presence or absence of such functional elements nor does the security architecture require separating any such function. For simplicity, this Recommendation rather assumes these functions co-located in compound network elements, but for completeness those network entities are shown as decomposed functional entities. Of course, the security concepts could be extended in a straightforward manner to cover those elements when present as well by functionally decomposing and separating them.
+
+All those optional network entities appear as dashed boxes in the diagrams. Regarding the home domain, an authentication entity (AuF) functioning as a back-end security service may be separate or may be co-located with the home border element or other appropriate H.323 entities [5], e.g. the home gatekeeper (H-GK). Which of those instantiations actually apply is left as a local implementation matter.
+
+In this Recommendation, the **authentication function (AuF)** is understood as the security functional entity in the home domain that maintains security relationship with the subscribed mobile users and the subscribed mobile terminals if necessary. Among further tasks not described in this Recommendation, the AuF shall accomplish at least the following tasks:
+
+- Evaluate incoming **AuthenticationRequest** messages from a visited domain, check the authenticity and integrity of such messages, and particularly, the AuF shall authenticate the mobile user and optionally also the mobile terminal (MT) if provided and desired.
+- Upon successful authentication of the mobile user/terminal, the AuF shall decide upon granting authorization. Exactly how the AuF would achieve this decision is outside the scope of this Recommendation, but some policy database or certain access rules might be appropriate.
+- Further on, the AuF shall support and assist the visited domain in the key management task; specifically, the AuF shall authenticate a received Diffie-Hellman half-key and $GK_{ID}$ from the visited domain using the corresponding user shared secret.
+- Finally, the AuF shall respond back to the visited domain about the security authorization decision taken, with the authenticated value Diffie-Hellman half-key and $GK_{ID}$ included.
+
+The AuF could be thought of as a security module – potentially physically separate from other functional entities – with specific security functionality such as protected key storage, cryptographic algorithm and mechanism support, secured administration and maintenance access, reliability, etc. However, this Recommendation does not assume presence of any such feature in the AuF. Rather, the AuF may also well be co-located with other H.323 functional entities [5] in the home domain such as in the border element, in the gatekeeper, in a mobility routing proxy (MRP) or in any other appropriate entity. The concept of the AuF leaves it open on whether it would be best implemented in hardware, in software, or in a combination of both.
+
+This Recommendation introduces a **mobility routing proxy (MRP)** as an optional functional entity. The MRP acts as an intermediate functional entity, terminating the security association of a hop-by-hop link. The MRP shall forward the security tokens by re-computing anew the hop-by-hop message authentication codes in the **CryptoToken**. The MRP may encompass the functionality of a mobility management functional entity (e.g. of a HLF or of a VLF or of any other mobility
+
+back-end service entity). The MRP may appear in the visited domain or in the home domain, or in any other domain traversed.
+
+In case a shown MRP does not occur in the actual communication, the hop-by-hop links entering and leaving the MRP shall be considered to belong to the same security association and re-computation of the **CryptoToken** shall be omitted.
+
+This Recommendation uses the term **password** when a user-entered password string is meant. The password in this Recommendation is understood to be the assigned security key, which the mobile user shares with his or her home domain. This user password and derived user shared secret shall be applied for the purpose of user authentication.
+
+Different to that, a **shared secret** is the security key that is part of the security parameters for the cryptographic algorithms; it can be derived from a password (see H.235 procedure 10.3.5 [4]) or it can be assigned per configuration or by other means.
+
+Likewise, the mobile terminal may have been assigned a separate security shared secret by the home domain for the purpose of terminal authentication.
+
+The assignment and distribution of passwords and shared secrets among the functional entities is outside the scope of this Recommendation.
+
+This Recommendation uses the term **service relationship** to reference an established security association between two functional entities, such as between a visited border element (V-BE) and a home border element (H-BE). Among other parameters of such a service relationship, it is essential that at least a shared key $ZZ_n$ be present, by which traffic between both functional entities is secured (e.g. IPSEC or Annex D/H.235 [4]).
+
+The **AuthenticationRejection** message used in this Recommendation indicates a failed security check by the AuF. The **AuthenticationRejection** message shall hold the same **Clear-** and **CryptoTokens** as the related **AuthenticationConfirmation** message.
+
+The object identifiers are referenced through a symbolic reference in the text (e.g. "G1"). Clause 8.6 lists the actual numeric values for the symbolic object identifiers.
+
+# 4 Terms and definitions
+
+For the purposes of this Recommendation the definitions given in clause 3 of ITU-T Recs H.323 [5], H.225.0 [1], H.225.0 Annex G [2], H.235 [4], H.501 [3], H.510 [6] and X.800 [7] apply along with those in this clause.
+
+**4.1 authentication function (AuF):** The AuF is the security functional entity in the home domain that maintains security relationship with the subscribed mobile users and the subscribed mobile terminals.
+
+**4.2 credential:** In this Recommendation, a credential [such as $\text{HMAC}_{ZZ}(\text{GK}_{\text{ID}})$ or $\text{HMAC}_{ZZ}(\text{W})$ ] is understood as some piece of data to which the AuF cryptographically has applied its shared secret $ZZ$ that it shares with the mobile user. The credential is transferred to prove authorization and timeliness in the authorization check.
+
+**4.3 home border element (H-BE):** This is a border element (BE) placed within the home domain.
+
+**4.4 mobility routing proxy (MRP):** The MRP is an optional functional entity that acts as an intermediate functional entity, terminating the security association of a hop-by-hop link.
+
+**4.5 password:** Referring to a user-entered password string.
+
+**4.6 service relationship:** References an established security association between two functional entities, assuming that at least a shared key is present.
+
+**4.7 shared secret:** Refers to the security key for the cryptographic algorithms; it may be derived from a password.
+
+**4.8 visited border element (V-BE):** This is a border element (BE) placed within the visited domain.
+
+## 5 Abbreviations and symbols
+
+This Recommendation uses the following abbreviations and symbols:
+
+| | |
+|-------------------|----------------------------------------------------------------------------------------------------------------------------------|
+| AuF | Authentication Function, see ITU-T Rec. H.510 [6] |
+| BE | Border Element, see ITU-T Rec. H.225.0 Annex G [2] |
+| CH n | Challenge number $n$ |
+| DH | Diffie-Hellman |
+| EP ID | MT endpoint identifier, see ITU-T Rec. H.225.0 [1] |
+| GK | Gatekeeper, see ITU-T Rec. H.510 [6] |
+| GK ID | Visited Gatekeeper identifier, see ITU-T Rec. H.225.0 [1] |
+| GRJ | Gatekeeper Reject |
+| GRQ | Gatekeeper Request |
+| H-BE | Home BE |
+| H-GK | Home GK |
+| HLF | Home Location Function |
+| HMAC-SHA1-96 | Hashed Message Authentication Code with Secure Hash Algorithm 1 |
+| HMAC Z | Key Hashed message authentication code/response with shared secret $Z$ , if $Z$ is not shown then the next-hop secret is applied |
+| IPSEC | Internet Protocol Security |
+| K | Dynamic session/link key |
+| MRP | Mobility Routing Proxy |
+| MT | Mobile Terminal, see ITU-T Rec. H.510 [6] |
+| NTP | Network Time Protocol |
+| OID | Object Identifier |
+| PKI | Public-key infrastructure |
+| PW | Mobile User Password |
+| R 1 | Random number |
+| RIP | Request in Progress |
+| RRJ | Registration Reject |
+| RRQ | Registration Request |
+| SNTP | Simple Network Time Protocol |
+| T n | Timestamp number $n$ |
+| V-BE | Visited BE |
+
+| | |
+|-----------------|---------------------------------------------------------------------------------------|
+| V-GK | Visited GK |
+| VLF | Visitor Location Function |
+| W | Compound value with arithmetic combination of Diffie-Hellman half-keys |
+| WT | Mobility ClearToken |
+| XT | CryptoToken for MT authentication |
+| ZZ | Shared secret/password of the mobile user, which is shared with the corresponding AuF |
+| ZZMT | Shared secret of the mobile terminal MT, which is shared with the corresponding AuF |
+| ZZ n | Shared-secret number $n$ |
+| ⊕ | Bitwise XOR |
+
+# 6 References
+
+## 6.1 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; 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 H.225.0 Version 4 (2000), *Call signalling protocols and media stream packetization for packet-based multimedia communications systems*.
+- [2] ITU-T Recommendation H.225.0 Annex G (Draft), *Communication between administrative domains*.
+- [3] ITU-T Recommendation H.501 (2002), *Protocol for mobility management and intra/inter-domain communication in multimedia systems*.
+- [4] ITU-T Recommendation H.235 Version 2 (2000), *Security and encryption for H-series (H.323 and other H.245-based) multimedia terminals*.
+- [5] ITU-T Recommendation H.323 Version 4 (2000), *Packet-based multimedia communication systems*.
+- [6] ITU-T Recommendation H.510 (2002), *Mobility for H.323 multimedia systems*.
+- [7] ITU-T Recommendation X.800 (1991), *Security architecture for Open Systems Interconnection for CCITT applications*.
+
+## 6.2 Non-normative references
+
+- [8] IETF RFC 1305 (1992), *Network Time Protocol (Version 3) Specification, Implementation and Analysis, Internet Engineering Task Force*.
+- [9] IETF RFC 2030 (1996), *Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI; Internet Engineering Task Force*.
+
+# 7 Security requirements and constraints for mobility
+
+Multimedia mobility management and application to H.323 mobility environments face the following security requirements and constraints:
+
+- This Recommendation shall support and facilitate better security interworking of H.323-secured systems when deployed in a mobility environment with distributed components and separately managed domains.
+- The mobile user shall be authenticated when roaming across domains. The mobile user authentication shall serve as a base for granting user access and service permission. The authentication shall be accomplished through the home AuF when initially attaching to a foreign visited domain. For any further interaction with the visited domain, the mobile user authentication shall be accomplished through the visited domain without necessarily querying the home AuF each time.
+- The mobile terminal should be authenticated when roaming across domains. The mobile terminal authentication may be used to detect and trace black-list/white-list MTs. The MT authentication should be accomplished in conjunction with the mobile user authentication, instead of a separate and additional procedure.
+- A scenario should be supported where the MTs are maintained in a different AuF (possibly in a different domain) than the mobile users. In such a scenario, the visited domain shall query the user's home domain with a single authentication request rather than separate authentication requests. The user's home AuF may then further delegate queries for the MT authentication, but such communication is not part of this Recommendation.
+- Based upon the trust relationship between visited domain and home domain, the visited domain shall authenticate towards the mobile user, e.g. in that the MT is able to authenticate the visited gatekeeper. Likewise, the visited domain should authenticate towards the home AuF.
+
+NOTE – As visited domain and home domain usually do not share an established security relationship, one cannot expect to achieve strong authentication between those two domains in a strict sense. However, some trust assurance could be achieved by relying on the hop-by-hop secured links between the visited domain and the home domain.
+
+- The mobility management protocols within and across domains shall be secured against masquerade, loss of integrity and if possible against loss of confidentiality.
+- Denial-of-service attacks should be minimized as far as possible.
+- User profile and user service profile information, as well as any security keys shall be transmitted securely across and within domains. The latter demands secure key management in a mobility environment. This includes the requirement that such sensitive information shall not be made available to any intermediate entities and domains unless required. This means that the MT user password shall not be made available to any functional entity except MT and AuF. This also means that the MT shared secret shall not be made available to any functional entity except MT and AuF. Further, this means that the negotiated dynamic session key for securing communication between the MT and the visited domain shall not be made available to other intermediate network entities.
+- The dynamic session key shall be authentic and cryptographically bound to the accomplished authentication. This includes the requirement for the session key to be fresh.
+- The overall security architecture shall take the trust relationships among domains into account. On one hand, this requires taking the security relationship among entities and domains into account. On the other hand, cheating entities (such as potentially a masqueraded visited gatekeeper (V-GK) but also any other entity) shall be detected and the likelihood of cheating be minimized.
+
+- The security techniques to be applied shall take existing H.235 [4] and other security techniques into account with enhancement only if necessary.
+- The security architecture deployed shall be simple and shall not require assuming additional security infrastructure measures such as smart cards and complex management protocols.
+
+# 8 Hop-by-hop security with symmetric cryptographic techniques
+
+As symmetric security techniques are deployed according to Annex D/H.235 [4] in non-mobility, quasi-static H.323 environments, this Recommendation shows the security architecture with security procedures in a mobility H.323 environment, which deploys the same security techniques as well. Basically, this Recommendation describes a security architecture that is based upon a security infrastructure only using symmetrically shared secrets. The shared secrets are defined on a hop-by-hop or pair-wise base between the communicating entities.
+
+This is a simple security model and does not require using a specific public-key security infrastructure for example. The hop-by-hop security architecture is designed to deploy well-engineered Annex D/H.235 [4] security symmetric techniques to a large extend. It is believed that symmetric crypto techniques provide rather high performance and thus, such techniques are generally applicable in the mobility environment as well.
+
+Figure 1 depicts the security architecture for an H.323 mobility environment according to H.510 [6], which is based upon H.501 [3]. The figure shows the principal architectural relationship of the functional entities. Furthermore, the figure shows the security relationship of keys among the entities. The figures also shows the case when the MT is attached to home gatekeeper in the home domain.
+
+
+
+The diagram illustrates the security architecture for a mobility H.323 environment, showing functional entities and shared secrets across two domains: Visited domain and Home domain.
+
+**Visited domain:** Contains functional entities MT (Mobile Terminal), V-GK (Visited Gatekeeper), MRP (Mobility Registration Protocol), and V-BE (Visited Border Element). The MT is connected to the V-GK. The V-GK, MRP, and V-BE are grouped within a dashed box.
+
+**Home domain:** Contains functional entities H-BE (Home Border Element), MRP (Mobility Registration Protocol), AuF (Authentication Function), MRP (Mobility Registration Protocol), H-GK (Home Gatekeeper), and MT (Mobile Terminal). The H-BE, MRP, AuF, MRP, and H-GK are grouped within a dashed box. The MT is connected to the H-GK.
+
+**Shared secrets and keys:**
+
+- Dynamic link key K (between MT and V-GK, and between H-GK and MT)
+- Shared secret ZZ4 (between V-GK and MRP)
+- Shared secret ZZ5 (between MRP and V-BE)
+- Shared secret ZZ2 (between V-BE and H-BE)
+- Shared secret ZZ6 (between H-BE and MRP)
+- Shared secret ZZ3 (between MRP and AuF)
+- Shared secret ZZ7 (between AuF and MRP)
+- Shared secret ZZ8 (between MRP and H-GK)
+
+**Groupings:**
+
+- User password/Shared secret ZZ (grouping ZZ4, ZZ5, ZZ2, ZZ6, ZZ3)
+- MT shared secret ZZMT (grouping ZZ7, ZZ8)
+
+T1610770-02
+
+Diagram of security architecture for mobility H.323 environment showing functional entities and shared secrets in Visited and Home domains.
+
+**Figure 1/H.530 – Security architecture for mobility H.323 environment**
+
+It is assumed that the MT and the AuF in the home domain share an administered password ZZ that is assigned during the user's subscription process. Further on, the V-GK and the next functional element one hop away (e.g. a MRP) share a shared secret ZZ4, and the MRP shares a shared secret ZZ5 with V-BE. As an example, if a MRP does not occur in a particular environment, then a shared secret shall be assumed between the V-GK and the V-BE accordingly and the security protection of relayed messages shall be applied accordingly.
+
+It is assumed that the H-BE and a MRP share a shared secret ZZ6 and the MRP shares a shared secret ZZ3 with the AuF. Among the domains, there is a shared secret ZZ2 assumed between V-BE and H-BE or there should be IPSEC or other appropriate network security protection as a generic security means. The shared secrets ZZ2-ZZ6 may be applied for security protection of the H.501 [3] mobility management protocol or may serve as shared secret for underlying IPSEC. While the user
+
+password and the shared secrets *ZZ2-ZZ6* and *ZZMT* are statically administered, the link key *K* is dynamically assigned as part of the signalling and authentication procedure. The dynamic link key *K* is shared between the MT and the V-GK.
+
+As described in 8.5, the AuF and the MRP share a shared secret *ZZ7* and the MRP and the H-GK share a shared secret *ZZ8*.
+
+NOTE 1 – This security architecture depends on trusted intermediate nodes. This means that any intermediate nodes such as V-BE and H-BE and potentially also MRP, AuF and GK may read and intercept signalling information in transit that is not actually targeted for them. This should not be a real issue as long as there is full trust assumed within a domain and, further, a tight, mutual trust relationship between visited domain and home domain with no other intermediate domains involved in the H.323 communication [5] in-between these two domains.
+
+NOTE 2 – Generally, using shared secrets limits scalability; thus, only a small number of domains and BE nodes may use this principle in controlled environments. For example, it is anticipated that the security architecture described in this Recommendation scales up to a number of approximately 500 network domains such as proved feasible in the GSM networks. It is assumed that the security architecture herein would not scale well beyond significantly more network domains than those say 500. Thus, support for a large-scale secure mobility environment is left for further study.
+
+## 8.1 Assumptions
+
+The H.530 security protocol deployed in this Recommendation, when used in conjunction with H.501 [3], assumes synchronized time on each leg in case of Annex D/H.235 [4] techniques applied at the application layer (i.e. V-GK-to-MRP, MRP-to-V-BE, V-BE-to-H-BE, H-BE-to-MRP and MRP-to-AuF). In case of network or transport security techniques applied on those links, synchronized time among the listed entities is not required. The security architecture further assumes synchronized time clocks between the MT and the AuF in the home domain. This could be achieved through NTP (IETF RFC 1305, [8]) or SNTP (IETF RFC 2030, [9]) time and clock synchronization protocols for example.
+
+NOTE – No time synchronization is assumed between the MT and any visited GK. For mutual authentication of the MT and the visited GK, challenge-response security techniques are deployed. No time synchronization is required for IPSEC security protection of H.501 [3].
+
+The H.225.0 RAS [1] protocol shall be applied for signalling communication between MT and V-GK, while the H.501 [3] mobility management protocol shall be applied between any other functional entities shown. H.501 [3] shall use H.235 [4] signalling facilities for message security protection and secured mobility management and may in addition use IPSEC for enhanced security.
+
+## 8.2 Secure location updating procedures
+
+While the MT and the visited GK usually never had any contact before and thus cannot deploy common subscription information, the visited GK when receiving an initial message from the MT is not able at first to immediately authenticate the MT, and vice versa. For this reason, the V-GK relays the task of MT user authentication and authorization to the AuF in the domain where the MT user is subscribed. The AuF shall perform the user/MT authentication and decide upon the authorization. The AuF responds with the result of the security verification and delivers security information such as credentials towards the visited GK and towards the MT for the session.
+
+Since the authentication and authorization query to the AuF usually only occurs when the MT and the user initially attach to the visited domain, there is no immediate need to execute this procedure at any later point in time during the same call/session, unless explicitly deemed adequate by the V-GK security policy. Thus, the V-GK is able to operate autonomously from the AuF once having received the authorization credentials. This makes the V-GK behave as a local operating security server in the visited domain.
+
+This Recommendation supports two procedures for secure location updating.
+
+Both procedures occur during initial authentication: It is common to both procedures that authentication is identical using **AuthenticationRequest** and **AuthenticationConfirmation** beyond the visited GK. The only difference between the two is that either the **GRQ** or the **RRQ** message is applied.
+
+- Authentication during the V-GK discovery phase: This procedure is applicable when the MT has already an endpoint ID and knows a priori the visited gatekeeper identifier. In this case, it is possible to secure the **GRQ** message according to Annex D; see Figure 2.
+- Authentication during the MT and user registration: This procedure applies when the MT does not know the visited gatekeeper identifier and does not yet have an endpoint ID assigned. Thus, MT and GK first complete the discovery procedure (insecure) and thereby exchange their IDs. After that, the MT and user authenticate when sending initial **RRQ**; see Figure 3.
+
+
+
+The diagram illustrates the following sequence of events:
+
+- The H.323 MT computes DH: $g^x \bmod p$ and sends message 1) GRQ( $EP_{ID}$ , $GK_{ID}$ , 0, $CH_1$ , $T_1$ , $g^x$ , HMAC $_{ZZ}$ (GRQ)) to the V-GK.
+- The V-GK computes DH: $g^y \bmod p$ and $W := g^x \oplus g^y$ . It sends message 3) to the MRP.
+- The MRP sends message 4) to the V-BE.
+- The V-BE sends message 5) to the H-BE.
+- The H-BE sends message 6) to the MRP.
+- The MRP sends message 7) to the AuF.
+- The AuF sends message 8) back to the MRP.
+- The MRP sends message 9) back to the H-BE.
+- The H-BE sends message 10) back to the V-BE.
+- The V-BE sends message 11) back to the MRP.
+- The MRP sends message 12) back to the V-GK.
+- The V-GK sends message 13) GCF( $GK_{ID}$ , $EP_{ID}$ , $CH_1$ , $CH_2$ , $(T_{13})$ , $g^y$ , HMAC $_{ZZ}$ (W), HMAC $_{ZZ}$ ( $GK_{ID}$ ), HMAC $_K$ (GCF)) to the MT. The MT computes $K := g^{xy} \bmod p$ and $W := g^x \oplus g^y$ .
+- The MT sends message 14) RRQ( $EP_{ID}$ , $GK_{ID}$ , $CH_2$ , $CH_3$ , $(T_{14})$ , HMAC $_K$ (RRQ)) to the V-GK.
+- The V-GK sends message 15) RCF( $GK_{ID}$ , $EP_{ID}$ , $CH_3$ , $CH_4$ , $(T_{15})$ , HMAC $_K$ (RCF)) back to the MT.
+
+A shaded region labeled "AuthenticationRequest" and "AuthenticationConfirmation" encompasses steps 3 through 12. A label T1610780-02 is present in the bottom right of the diagram area.
+
+Sequence diagram of H.530 authentication and key management during GK discovery phase. The diagram shows interactions between H.323 MT, V-GK, MRP, V-BE, H-BE, and AuF. The MT sends a GRQ message to the V-GK. The V-GK computes DH and sends an AuthenticationRequest to the MRP. The MRP forwards it through V-BE and H-BE to the AuF. The AuF sends an AuthenticationConfirmation back through the chain. The V-GK then sends a GCF message to the MT. The MT computes K and W, and sends an RRQ message to the V-GK. The V-GK sends an RCF message back to the MT.
+
+Figure 2/H.530 – Authentication and key management during GK discovery phase
+
+
+
+The diagram illustrates the authentication and key management process during the registration phase of H.530. It involves the following sequence of interactions:
+
+- H.323 MT** sends **GRQ( $EP_{ID}$ )** to **V-GK**.
+- V-GK** responds with **GCF( $GK_{ID}$ )**.
+- H.323 MT** computes $DH: g^x \bmod p$ and sends **1) RRQ( $EP_{ID}$ , $GK_{ID}$ , 0, $CH_1$ , $T_1$ , $g^x$ , $HMAC_{ZZ}(RRQ)$ )** to **V-GK**.
+- V-GK** computes $DH: g^y \bmod p$ and $W := g^x \oplus g^y$ .
+- V-GK** sends **2) RIP(...)** to **H.323 MT**.
+- V-GK** sends **AuthenticationRequest( $RRQ(\dots)$ , $GK_{ID}$ , $W$ , $HMAC$ )** to **MRP**.
+- MRP** relays it to **V-BE** (3), **H-BE** (4), **MRP** (5), and **AuF** (6).
+- AuF** sends responses back through the chain: **MRP** (7), **H-BE** (8), **V-BE** (9), **MRP** (10), and **V-GK** (11).
+- V-GK** computes $K := g^{xy} \bmod p$ and sends **AuthenticationConfirmation( $HMAC_{ZZ}(W)$ , $HMAC_{ZZ}(GK_{ID})$ , $HMAC$ )** to **H.323 MT** (12).
+- H.323 MT** receives **13) RCF( $GK_{ID}$ , $EP_{ID}$ , $CH_1$ , $CH_2$ , $(T_{13})$ , $g^y$ , $HMAC_{ZZ}(W)$ , $HMAC_{ZZ}(GK_{ID})$ , $HMAC_K(RCF)$ )** from **V-GK**.
+- H.323 MT** computes $K := g^{xy} \bmod p$ and $W := g^x \oplus g^y$ .
+- H.323 MT** sends **14) ARQ( $EP_{ID}$ , $GK_{ID}$ , $CH_2$ , $CH_3$ , $(T_{14})$ , $HMAC_K(ARQ)$ )** to **V-GK**.
+- V-GK** sends **15) ACF( $GK_{ID}$ , $EP_{ID}$ , $CH_3$ , $CH_4$ , $(T_{15})$ , $HMAC_K(ACF)$ )** to **H.323 MT**.
+
+T1610790-02
+
+Sequence diagram for H.530 authentication and key management during registration phase. Lifelines: H.323 MT, V-GK, MRP, V-BE, H-BE, MRP, AuF. The process involves GRQ, GCF, RRQ, RIP, RCF, ARQ, and ACF messages with associated cryptographic computations like DH, HMAC, and XOR.
+
+**Figure 3/H.530 – Authentication and key management during registration phase**
+
+Secure location updating occurs either:
+
+- when a user and an MT contact a visited domain for the first time without any prior information available in the visited domain; or
+- when there already is some temporary information available about the MT and the user in the visited domain.
+
+The former case requires full execution of the authentication procedures whereby the visited domain gathers sufficient information from the home domain in order to serve the MT. This procedure includes reporting results of the authentication, authorization check, and credentials by the home domain. This procedure may further carry service profile information towards the visited gatekeeper. It is to be noted that such procedure usually involves network communication and interaction with potentially several entities, and therefore might take some time to complete.
+
+The latter case would not make it necessary for the V-GK to contact the home domain, although this is not precluded. The visited gatekeeper would reuse locally stored information without contacting the home domain. This could happen in case of a lost and re-established connection, or of a local change of the network point of attachment. Whenever the MT possesses a valid link key, the MT shall attempt to use it first before falling back to deploying an initial location update.
+
+Primarily, the user authenticates explicitly by applying the password, which the user obtained at subscription time. However, for mobile terminal authentication, it may optionally also be possible that the MT authenticates additionally towards the AuF (see the procedure described in 8.3).
+
+Basically, the secure location updating procedure proceeds as follows: The initial RAS message that the visited GK receives is encapsulated in an **AuthenticationRequest** and relayed through one or several functional entities to the AuF in the home domain. This is done because the visited GK is not able to authenticate the MT and the user. The AuF verifies the relayed information, authenticates the MT/user and then decides upon the MT/user's authorization using some criterion. Alternatively, the AuF may remember the MT/user and shall deliver result of the authentication and authorization check by credentials towards the V-GK and MT using **AuthenticationConfirmation/AuthenticationRejection**.
+
+The visited domain authenticates towards the MT/user when delivering the dynamic link key, in response to the challenge of the MT. The MT/user authenticates with any subsequent RAS message towards the V-GK using challenge and response techniques. Likewise, the MT is able to authenticate the V-GK.
+
+Due to the principle of hop-by-hop security, it is necessary for any intermediate nodes or proxies to verify the applied H.235 [4] security on each leg and re-compute the **CryptoToken** with the message digest anew, as long as network or transport security means are not available. If network or transport security means are available, then re-computation of the message digest in the **CryptoToken** may be omitted.
+
+As the execution of the authentication procedures and network communication between V-GK and AuF may take some time, it may be necessary for the V-GK to send a **RIP** message to the MT indicating that the request is in progress.
+
+The diagrams in Figures 4 through 10 depict the message flow and emphasize H.235 [4] security. The depicted message flow is given for the scenario where the authentication occurs during the registration phase. A similar description applies to the procedures when secure location updating occurs during V-GK discovery; in this case, the encapsulated **RRQ** is to be substituted with **GRQ**. The signalling elements for the optional MT authentication are defined in 8.3 and for simplicity they are not shown in most of the figures. For reasons of space and clarity, the message flow is separated into several phases – each in a separate figure – that all belong together. A logical end-to-end message flow results when reading the numbered messages in sequence.
+
+### 8.2.1 MT to V-GK
+
+Figure 4 shows the initial registration phase between the MT and the visited GK. Each RAS message conveys a new challenge and the previous challenge value. Except for the first message, the HMAC message integrity check value serves as the computed response to the previous challenge; that HMAC shall be computed according to Annex D/H.235 [4] using the dynamic link key *K* as shared secret. The computation of the HMAC shall follow Procedure I of D.6.3.2/H.235 [4]; without using the **timeStamp** field. If the MT or the visited GK include timestamps anyway (such as $T_{13}$ , $T_{14}$ and $T_{15}$ ), then these timestamps should not be checked because synchronized time cannot be assumed between MT and V-GK.
+
+
+
+```
+
+sequenceDiagram
+ participant MT
+ participant V-GK
+ Note left of MT: compute DH: $g^x \bmod p$
+ MT->>V-GK: 1) RRQ(..., EPID, GKID, 0, CH1, T1, $g^x$ , HMAC-SHA1(ZZ, RRQ()))
+ Note right of V-GK: Compute DH: $g^y \bmod p$
+ $W := g^x \oplus g^y$
+ V-GK-->>MT: 2) RIP(...)
+ Note right of V-GK: 3) ...
+ Note right of V-GK: Compute link key $= g^{xy} \bmod p$
+ V-GK-->>MT: 12) ...
+ Note right of V-GK: 13) RCF(..., GKID, EPID, CH1, CH2, (T13), $g^y$ ,
+WT(HMACZZ(W), HMACZZ(GKID)), HMAC-SHA1(K, RCF()))
+ Note left of MT: Compute link key $K = g^{xy} \bmod p$
+ $W := g^x \oplus g^y$
+ MT->>V-GK: 14) ARQ(..., EPID, GKID, CH2, CH3, (T14), HMAC-SHA1(K, ARQ()))
+ V-GK->>MT: 15) ACF(..., GKID, EPID, CH4, CH5, (T15), HMAC-SHA1(K, ACF()))
+ Note right of V-GK: T1610800-02
+
+```
+
+Sequence diagram showing the initial registration phase and further RAS messages between MT and V-GK. The diagram includes message exchanges 1) through 15) and cryptographic computations for Diffie-Hellman key exchange.
+
+**Figure 4/H.530 – Initial registration phase and further RAS messages
+between MT and V-GK**
+
+For the initial registration, the MT shall generate a fresh challenge CH1 and include it in the **challenge** field in the **ClearToken** of the **RRQ**, see message 1). The **password** field in the **ClearToken** shall convey the previous challenge value. For the initial **RRQ/GRQ**, the previous challenge shall be set to all zeros.
+
+Further, the MT shall generate a fresh Diffie-Hellman half-key $g^x \bmod p$ with random $x$ kept secret and include the half-key in the **halfkey** field of the **dhkey** field within the **ClearToken** of the message. The applied prime number shall be included in **modsize** while the Diffie-Hellman generator shall be included in **generator** of that **ClearToken**. For the Diffie-Hellman (DH) system parameters, the available parameters as given in Table D.4/H.235 [4] shall be taken, where Generator is 2 and the 1024-bit mod-P prime referred to by "Z" are recommended.
+
+The V-GK receives the challenged **RRQ** and encapsulates it in **applicationMessage** within an **AuthenticationRequest**, see message 3) and sends it to the next hop (e.g. MRP).
+
+The V-GK shall generate a fresh Diffie-Hellman half-key $g^y \bmod p$ with random $y$ kept secret. For the Diffie-Hellman system parameters, the available parameters as given in Table D.4/H.235 [4] shall be taken; where Generator is 2 and the 1024-bit mod-P prime referred to by "Z" are recommended.
+
+Taking the received Diffie-Hellman half-key $g^x \bmod p$ and its own Diffie-Hellman half-key $g^y \bmod p$ , the V-GK shall compute a compound value $W$ by bitwise XORing both values.
+
+This compound value $W$ shall be included in the **halfkey** field of the **dhkey** field within a separate mobility **ClearToken** of the **AuthenticationRequest** message. The **generalID** of that **ClearToken** shall convey the $GK_{ID}$ . The **tokenOID** of that mobility **ClearToken** shall be set to "G2". Any other parameters in that mobility **ClearToken** shall be unused. The AuF will authenticate this **ClearToken** information and compute the corresponding credentials. The mobility **ClearToken** is shown as **WT()**.
+
+The **AuthenticationRequest** message shall convey integrity protection according to Annex D/H.235 [4], unless the link between the V-GK and the next hop (e.g. MRP) is secured by IPSEC.
+
+NOTE 1 – As the mobility **ClearToken** is integral part of the **AuthenticationRequest** message, full message integrity protection already covers the integrity of any conveyed **Clear** and/or **CryptoTokens**. Thus, no separate protection of the mobility **ClearToken** is necessary.
+
+The V-GK may submit an unsecured **RIP** message to the MT to indicate message processing in progress, see message 2). Due to the fact that the MT and visited GK do not share a common secret yet, the V-GK is not able to authenticate and integrity protect this immediate **RIP** message.
+
+NOTE 2 – The MT should not trust unprotected **RIP** messages as they might not be authentic, they might be replayed or stem from denial-of-service attacks. The MT should be prepared to treat replayed **RIP** messages and cope with potential message flooding. It is up to the security policy of the MT how to treat such unprotected **RIP** messages.
+
+Until the **RCF** is submitted as message 13), the V-GK has time to compute the dynamic link $K$ using the Diffie-Hellman half-key of the MT and its own secret $y$ . For HMAC-SHA1-96 message integrity protection of the H.225.0 RAS [1] messages, the 96 leftmost bits shall be taken from the resulting Diffie-Hellman shared secret as represented in network byte order.
+
+The V-GK receives an **AuthenticationConfirmation/AuthenticationRejection** with the result of the authentication and authorization check by the AuF and conveyed credentials; see message 12).
+
+The V-GK may supervise reception of **AuthenticationConfirmation/AuthenticationRejection** messages using a timer. The timer duration should be chosen long enough by taking the network transit and the AuF processing into account. If the timer expires and the corresponding reply from the AuF has not arrived, the V-GK shall send an unprotected **RCF**.
+
+The V-GK shall generate a new challenge $CH_2$ and build **RCF**. The **RCF** shall convey the previous challenge $CH_1$ within **password**, a new challenge $CH_2$ within **challenge** within the **ClearToken** inside the **CryptoToken** of **RCF**. That **ClearToken** shall also convey the computed Diffie-Hellman half-key of the V-GK in the **halfkey** field of the **dhkey** field within the **ClearToken** of that message. The applied prime number shall be included in **modsize** while the DH-generator shall be included in **generator** of that **ClearToken**.
+
+Further, the V-GK shall forward the credentials from the AuF to the MT. The credentials encompass the mobility **ClearToken** shown as **WT()**. This mobility **ClearToken** conveys on one hand the authenticated compound value $W$ in the **halfkey** field of the **dhkey** field and on the other hand the authenticated V-GK ID. The **tokenOID** shall be set to "G2" and any other parameters in that mobility **ClearToken** shall be unused.
+
+The V-GK computes the HMAC upon the entire **RCF** message using the link key $K$ . Thus, the HMAC serves as a response to the previous challenge according to Annex D/H.235 procedure I [4], see message 13).
+
+In addition to the authorization check performed by the AuF, the visited GK may decide by its own criteria on whether to allow or disallow the MT. Thus, the visited GK may reject a **GRQ/RRQ** even if the AuF confirmed authentication and authorization. In such a case, the visited GK shall respond with a **GRJ/RRJ** indicating the **reason** according to B.2.2/H.235 [4].
+
+The MT receives the protected **RCF** with challenges, Diffie-Hellman half-key and credentials such as the authenticated compound value $W$ and authenticated $GK_{ID}$ ; see message 13). The MT extracts these parameters from the mobility **ClearToken**. The MT shall compute the dynamic link key $K$ in an analogue fashion as the V-GK did and as described above. The MT shall verify the HMAC as response of the entire **RCF** message using the link key $K$ . The MT shall compute the compound value $W$ by bitwise XORing the received $g^y \bmod p$ and its own $g^x \bmod p$ . The MT shall verify the correctness of the authenticated compound value $W$ in the **halfkey** field in the mobility **ClearToken** by applying the shared secret $ZZ$ . The MT shall verify the correctness of the authenticated $GK_{ID}$ in the **generator** field in the mobility **ClearToken** by applying the shared secret $ZZ$ . If the authenticity of either value cannot be proved, the link key $K$ or the V-GK cannot be assumed to be authentic either. This may indicate fraudulent network entities or failed authentication in general. In this case, the MT shall ignore the **RCF** and restart again with a fresh **RRQ**.
+
+In case the V-GK receives an **AuthenticationRejection** and indicated **reason**, then the V-GK shall send an **RRJ** to the MT, see message 13). The security **reason** indicates a security error, as the AuF probably was not able to identify the MT/user. The V-GK shall then forward this error in **RRJ reason**.
+
+As MT and V-GK do not share synchronized clocks, any optional timestamps conveyed within a RAS message shall be ignored.
+
+NOTE 3 – Since the V-GK cannot authenticate an initial unprotected **GRQ/RRQ** message, they might be replayed or stem from denial-of-service attacks. Visited gatekeepers receiving an unexpectedly high number of protected or unprotected RAS messages may assume a denial-of-service attack and immediately refuse further message processing.
+
+### 8.2.2 V-GK to MRP
+
+The communication between the V-GK and the next hop functional element (e.g. MRP) serves the following purposes:
+
+- relaying authentication and authorization of the MT and user towards the AuF;
+- relaying authorization confirmation from the AuF towards the MT.
+
+Figure 5 shows the protocol message flow. The **AuthenticationRequest** message 2) entirely carries the **RRQ/GRQ** RAS message as received from the MT. Further, the **AuthenticationRequest** message carries a mobility **ClearToken** conveying compound value $W$ and the $GK_{ID}$ . The mobility **ClearToken** is shown as **WT()**. If authentication of the MT is performed, the V-GK includes a separate **CryptoToken** for that purpose; see 8.3.
+
+
+
+1) ...
+
+Compute DH: $g^y \bmod p$
+
+$W := g^x \oplus g^y$
+
+3) AuthenticationRequest (RRQ(..., EPID, GKID, 0, CH1, T1, HMAC1), T3,
+WT(GKID, W),
+HMAC-SHA1(ZZ4, T3, Authentication Request (...)))
+
+4) ...
+
+11) ...
+
+12) AuthenticationConfirmation (... , T12,
+WT(GKID, EPID, HMACZZ(GKID), HMACZZ(W)),
+HMAC-SHA1(ZZ4, T12, AuthenticationConfirmation (...)))
+
+Compute link key $K = g^{xy} \bmod p$
+
+13) ...
+
+14) ...
+
+T1610810-02
+
+Sequence diagram showing the transmission of authentication information between V-GK and MRP. The diagram includes steps 1) through 14). Step 1) is an incoming request to V-GK. V-GK computes DH: g^y mod p and W := g^x ⊕ g^y. Step 3) is an AuthenticationRequest message from V-GK to MRP. Step 4) is a response from MRP. Step 11) is another response from MRP. Step 12) is an AuthenticationConfirmation message from MRP to V-GK. V-GK then computes the link key K = g^xy mod p. Steps 13) and 14) are outgoing messages from V-GK. The diagram is labeled T1610810-02.
+
+**Figure 5/H.530 – Transmission of authentication information between V-GK and MRP**
+
+In case the link between V-GK and MRP is not protected by network security (e.g. IPSEC), **AuthenticationRequest** shall be secured according to Annex D/H.235 [4] with a new timestamp T3 and HMAC computed with key ZZ4. Otherwise, **AuthenticationRequest** message may not need security protection by Annex D/H.235 [4].
+
+**AuthenticationConfirmation** or **AuthenticationRejection** in message 12) carry the authenticated values from the AuF as credentials in a separate mobility **ClearToken** shown as **WT()**. If the link between V-GK and MRP is not protected by network security (e.g. IPSEC), **AuthenticationConfirmation** shall be secured according to Annex D/H.235 [4] with a new timestamp T12 and HMAC with key ZZ4. Otherwise, **AuthenticationConfirmation/AuthenticationRejection** may not need security protection by Annex D/H.235 [4].
+
+The conveyed GKID and EPID within that mobility **ClearToken** allow the V-GK to associate the received **AuthenticationConfirmation/AuthenticationRejection** message with the corresponding **AuthenticationRequest** message.
+
+In case the V-GK does not have a service relationship with the MRP (e.g. missing key ZZ4), then the V-GK shall not send an **AuthenticationRequest** but rather respond with **AuthenticationRejection** and reason set to **noServiceRelationship**.
+
+### 8.2.3 MRP to V-BE
+
+A MRP (if present and the conveyed hop count is not exceeded and if a service relationship is present with the V-BE) shall forward the received **AuthenticationRequest** message to the V-BE; see message 4) in Figure 6. The forwarded message shall be secured according to Annex D/H.235 [4] with a new timestamp T4 and HMAC computed with key ZZ5. Otherwise, **AuthenticationRequest** message may not need security protection by Annex D/H.235 [4].
+
+
+
+```
+
+sequenceDiagram
+ participant MRP
+ participant V-BE
+ Note left of MRP: 3)
+ MRP->>V-BE: 4) AuthenticationRequest (RRQ(...), T4, WT(GKID, W), HMAC-SHA1(ZZ5, T4, Authentication Request (...)))
+ Note right of V-BE: 5)
+ Note right of V-BE: 10)
+ V-BE->>MRP: 11) AuthenticationConfirmation (..., T11, WT(GKID, EPID, HMACZZ(GKID), HMACZZ(W)), HMAC-SHA1(ZZ5, T11, AuthenticationConfirmation (...)))
+ Note left of MRP: 12)
+
+```
+
+T1610820-02
+
+Sequence diagram showing authentication information transmission between MRP and V-BE. The diagram includes messages 4, 11, and 12. Message 4 is an AuthenticationRequest from MRP to V-BE. Message 11 is an AuthenticationConfirmation from V-BE to MRP. Message 12 is a response from MRP. External messages 3, 5, 10, and 12 are also shown.
+
+**Figure 6/H.530 – Transmission of authentication information between MRP and V-BE**
+
+A V-BE shall forward an **AuthenticationConfirmation** or an **AuthenticationRejection** to the MRP.
+
+**AuthenticationConfirmation** or **AuthenticationRejection** in message 11) carry the authenticated values as credentials from the AuF. If the link between V-BE and MRP is not protected by network security (e.g. IPSEC), **AuthenticationConfirmation/AuthenticationRejection** shall be secured according to Annex D/H.235 [4] with a new timestamp $T_{11}$ and HMAC with key ZZ5. Otherwise, **AuthenticationConfirmation/AuthenticationRejection** may not need security protection by Annex D/H.235 [4].
+
+If the hop count is exceeded, then the MRP shall not send an **AuthenticationRequest** message, but it shall rather reply with the **AuthenticationRejection** with reason set to **hopCountExceeded**; (see message 12).
+
+In case the MRP does not have a service relationship with the V-BE (e.g. missing key ZZ5), then the V-GK shall not send an **AuthenticationRequest**, but it shall rather respond with **AuthenticationRejection** and reason set to **noServiceRelationship**; see message 12).
+
+### 8.2.4 V-BE to H-BE
+
+Figure 7 depicts the message flow between two BEs of two adjacent domains at the time of initial registration. Security may be realized either using IPSEC according to ITU-T Rec. H.501 [3] or by using the shared secret ZZ2 that is shared between V-BE and H-BE. In the latter case, the H.501 [3] message shall be secured according to Annex D/H.235 [4].
+
+
+
+```
+
+sequenceDiagram
+ participant V-BE
+ participant H-BE
+ Note left of V-BE: 4)
+ V-BE->>H-BE: 5) AuthenticationRequest (RRQ(...), T5, WT(GKID, W), HMAC-SHA1(ZZ2, T5, AuthenticationRequest (...)))
+ Note right of H-BE: 6)
+ Note right of H-BE: 9)
+ H-BE->>V-BE: 10) AuthenticationConfirmation (..., T10, WT(GKID, EPID, HMACZZ(GKID), HMACZZ(W)), HMAC-SHA1(ZZ2, T10, AuthenticationConfirmation (...)))
+ Note left of V-BE: 11)
+
+```
+
+T1610830-02
+
+Sequence diagram showing authentication information transmission between V-BE and H-BE. The diagram includes messages 5, 10, and 11. Message 5 is an AuthenticationRequest from V-BE to H-BE. Message 10 is an AuthenticationConfirmation from H-BE to V-BE. Message 11 is a response from V-BE. External messages 4, 6, 9, and 11 are also shown.
+
+**Figure 7/H.530 – Transmission of authentication information between BEs**
+
+If the conveyed hop count is not exceeded and a service relationship is present with the H-BE, the H.501 [3] **AuthenticationRequest** message carries the entire **RRQ** including the related Clear- and CryptoTokens; see message 5). This is done to let the AuF validate the **RRQ** message and authenticate the user/MT. An H.501 [3] message is secured such that the entire message is integrity-protected similarly as described by Annex D/H.235, where the computed hash is stored in the **CryptoToken** of the **MessageCommonInfo**. BEs shall insert new timestamps ( $T_5$ , $T_{10}$ ) for each H.501 [3] message.
+
+The **AuthenticationConfirmation/AuthenticationRejection** carry the authenticated values as credentials from the AuF in a mobility **ClearToken** shown as **WT()**.
+
+In case the MT user is not authorized to use the mobile H.323 service, the AuF should send **AuthenticationRejection** with **reason** set to security. For any other security failure, the AuF shall set **reason** to an error as appropriate to B.2.2/H.235 [4].
+
+If the hop count is exceeded, then the V-BE shall not send an **AuthenticationRequest** message, but rather reply with the **AuthenticationRejection** with reason set to **hopCountExceeded**; see message 11).
+
+In case the V-BE does not have a service relationship with the H-BE (e.g. missing key ZZ2), then the V-BE shall not send an **AuthenticationRequest**, but rather respond with **AuthenticationRejection** and **reason** set to **noServiceRelationship**; see message 11).
+
+### 8.2.5 H-BE to MRP
+
+In case a MRP is present, the message flow proceeds according to Figure 8.
+
+
+
+```
+
+sequenceDiagram
+ participant H-BE
+ participant MRP
+ Note left of H-BE: 5) ...
+ H-BE->>MRP: 6) AuthenticationRequest (RRQ(...), T6,
+WT(GKID, W),
+HMAC-SHA1(ZZ6, T6, AuthenticationRequest (...)))
+ Note right of MRP: 7) ...
+ MRP-->>H-BE: 8) ...
+ MRP->>H-BE: 9) AuthenticationConfirmation (..., T9,
+WT(GKID, EPID, HMACZZ(GKID), HMACZZ(W)),
+HMAC-SHA1(ZZ6, T9, AuthenticationConfirmation (...)))
+ Note left of H-BE: 10) ...
+
+```
+
+T1610840-02
+
+Sequence diagram showing the transmission of authentication information between H-BE and MRP. Message 6 is an AuthenticationRequest from H-BE to MRP containing RRQ, timestamp T6, and WT credentials. Message 9 is an AuthenticationConfirmation from MRP to H-BE containing timestamp T9 and various HMAC-protected credentials.
+
+**Figure 8/H.530 – Transmission of authentication information between H-BE and MRP**
+
+### 8.2.6 MRP to AuF
+
+Figure 9 shows the message flow between the MRP (if present, if the hop count is not exceeded and if a service relationship is present) and the AuF. If no MRP is present, then the previous network entity shall be substituted instead. Similar to the figures before, the shared secret ZZ3 secures the transmitted messages.
+
+
+
+```
+
+sequenceDiagram
+ participant MRP
+ participant AuF
+ Note left of MRP: 6) ...
+ MRP->>AuF: 7) AuthenticationRequest (RRQ(0, CH1, T1, HMAC1), T7, WT(GK_{ID}, W), HMAC-SHA1(ZZ3, T7, AuthenticationRequest (...)))
+ AuF-->>MRP: 8) AuthenticationConfirmation (..., T_8, WT(GK_{ID}, EP_{ID}, HMAC_{ZZ}(GK_{ID}), HMAC_{ZZ}(W)), HMAC-SHA1(ZZ3, T_8, AuthenticationConfirmation (...)))
+ Note left of MRP: 9) ...
+ Note right of AuF: T1610850-02
+
+```
+
+Sequence diagram showing the transmission of authentication information between MRP and AuF. The diagram includes three messages: 6) ... (incoming to MRP), 7) AuthenticationRequest (RRQ(0, CH1, T1, HMAC1), T7, WT(GKID, W), HMAC-SHA1(ZZ3, T7, AuthenticationRequest (...))) (MRP to AuF), and 8) AuthenticationConfirmation (... T8, WT(GKID, EPID, HMACZZ(GKID), HMACZZ(W)), HMAC-SHA1(ZZ3, T8, AuthenticationConfirmation (...))) (AuF to MRP). Message 9) ... is an outgoing response from MRP. A reference T1610850-02 is shown at the bottom right.
+
+**Figure 9/H.530 – Transmission of authentication information between MRP and AuF**
+
+Upon reception of the **AuthenticationRequest**, the AuF may successively trust the other functional entities in the chain to have preserved the integrity of the conveyed **RRQ**; see message 7). The AuF shall verify the **AuthenticationRequest** and then verify the encapsulated **RRQ** as described by Annex D/H.235 procedure I [4]. The conveyed timestamp $T_1$ indicates freshness of the **RRQ** and shall be checked.
+
+If the MT/user is known to the AuF and authorized, the AuF shall respond with **AuthenticationConfirmation**; see message 8). Further, if MT authentication is desired, the AuF shall verify the corresponding conveyed **CryptoToken**. Otherwise, when the MT/user cannot be authenticated or is unknown to the AuF, a protected **AuthenticationRejection** shall be submitted with a **reason** set to an appropriate error as defined in B.2.2/H.235 [4].
+
+When the AuF is not able to apply the shared secret **ZZ**, the computation of the authenticated values for the credentials as described below shall be omitted, and no such result shall be included in the **AuthenticationRejection** message. In that case, a mobility **ClearToken** is not present in the **AuthenticationRejection** message.
+
+Otherwise, the AuF shall also compute the credentials of the authenticated compound value $W$ using HMAC-SHA1-96 key hash function and **ZZ** as the shared key. The authenticated compound value $W$ shall be included in a separate mobility **ClearToken**, where the result is stored in the **halfkey** field of the **dhkey** field within that mobility **ClearToken**. Further, the AuF shall compute an authenticated $GK_{ID}$ as another credential using HMAC-SHA1-96 key hash function and **ZZ** as the shared key. The result shall be included within **generator** in that **ClearToken**. The **generalID** shall convey the $GK_{ID}$ , while the **sendersID** shall convey the $EP_{ID}$ in that **ClearToken**. This shall allow the V-GK to associate an **AuthenticationConfirmation/AuthenticationRejection** with the corresponding **AuthenticationRequest** message. The **tokenOID** of that **ClearToken** shall be set to "G2" and any other parameters in that mobility **ClearToken** shall be unused. The mobility **ClearToken** is shown as **WT()**.
+
+A new timestamp $T_8$ shall be used and the response message shall be secured by according to Annex D/H.235 procedure I [4] using the shared secret **ZZ3**; see message 8).
+
+If the hop count is exceeded, then the MRP shall not send an **AuthenticationRequest** message, but rather reply with the **AuthenticationRejection** with reason set to **hopCountExceeded**; see message 9).
+
+If the MRP does not have a service relationship with the AuF (e.g. missing key **ZZ3**), then the MRP shall not send an **AuthenticationRequest**, but rather respond with **AuthenticationRejection** and **reason** set to **noServiceRelationship**; see message 9).
+
+NOTE – The AuF is not able to fully authenticate the V-GK in a strict sense. This is because the V-GK is not able to cryptographically prove its identity. However, the AuF certifies by the credential whatever V-GK identity is submitted. Thus, the MT/user is assured that the V-GK with which the MT/user is talking is always the same one as has been certified during the authentication procedure.
+
+## 8.3 Terminal authentication
+
+Authentication of the mobile terminal (MT) is an additional, optional feature, which is supported in addition to authentication of the mobile user. MT authentication shall be used, when mobile user authentication alone is not considered sufficient and when the MT has a corresponding shared secret *ZZMT*. It is assumed that the mobile terminal owns an assigned shared secret *ZZMT*, which it shares with the AuF. Assignment and distribution of this shared secret is outside the scope of this Recommendation.
+
+Actually, two scenarios for MT authentication are supported:
+
+- The AuF to which the mobile user is subscribed is identical to the AuF that maintains the subscribed MTs. In this case, the AuF is able to authenticate and decide upon authorization both for the user and the MT.
+- The AuF to which the mobile user is subscribed is different from the AuF where the MT is subscribed. In this case, the **AuthenticationRequest** shall first be sent to the user's AuF. It is the responsibility of that user AuF to locate and contact the appropriate MT AuF that is responsible for the MT. Such an MT AuF may be located in a different domain. Any such communication and necessary security protection beyond the AuF or among AuFs are outside the scope of this Recommendation.
+
+Authentication of the mobile terminal is accomplished in conjunction with user authentication. For terminal authentication, a separate **CryptoToken** XT() is used. This **CryptoToken** is carried within the security fields of the user authentication messages of either **GRQ** or **RRQ**, depending on whether user and terminal authentication occurs during the discovery phase of the visited GK or during the registration phase; see 8.2.
+
+The mobile terminal authenticates itself towards the AuF by proving knowledge or possession of the shared secret *ZZMT*. This allows the AuF to verify correctness the provided **CryptoToken** and to acknowledge this property as part of the authorization response (**AuthenticationConfirmation/AuthenticationRejection**) back to the visited domain. Then, the visited domain can decide upon the authorization of the MT.
+
+The keyed HMAC-SHA1-96 algorithm is used as the cryptographic authentication function. The procedure deployed basically follows the procedure I of Annex D/H.235 [4] with the exception that the integrity check is computed just over the specific mobile terminal **CryptoToken**, instead of over the entire message as actually described by Annex D/H.235 procedure I [4].
+
+The specific **CryptoH323Token** for mobile terminal authentication shall contain the following fields:
+
+- **NestedCryptoToken** containing a **CryptoToken**, which itself contains the **cryptoHashedToken** containing the following fields:
+ - **TokenOID** set to:
+ - "G1" indicating the authentication/integrity computation includes only the contents of this **CryptoToken**.
+- **HashedVals** containing the **ClearToken** field used with the following fields:
+ - **TokenOID** set to:
+ - "T" indicating that **ClearToken** is being used for authentication/integrity (see D.11/H.235 [4]).
+
+- **timestamp** containing the time stamp.
+- **random** containing a monotonically increasing sequence number. This number allows to make unique two messages with the same timestamp (within the clock resolution).
+- **generalID** containing the identifier of the recipient (only in case of unicast messages). In this scenario, this is the identifier of the home domain.
+- **sendersID** contains the identifier of the sender. In this scenario, this is the endpoint identifier of the MT.
+- **Token** containing **HASHED** with the fields:
+ - **algorithmOID** set to "U" indicating HMAC-SHA1-96; (see D.11/H.235 [4]).
+ - **params** set to NULL.
+ - **hash** containing the authenticator computed using HMAC-SHA1-96. The authenticator shall be computed over the entire **CryptoH323Token**.
+
+The receiving AuF shall verify the found **CryptoToken**, which is conveying MT authentication. In case the verification check fails, the AuF shall consider the MT not as authorized. In this case, the AuF shall respond with **AuthenticationRejection** and reason set to **security**. For any other security failure, the AuF shall set **reason** to an error according to B.2.2/H.235 [4].
+
+Figure 10 shows the message flow for mobile terminal authentication during the registration phase of the mobile terminal. The specific **CryptoToken** for MT authentication is shown as XT().
+
+
+
+```
+
+sequenceDiagram
+ participant MT
+ participant V-GK
+ Note left of MT: 1) RRQ(..., EP_ID, GK_ID, 0, CH_1, T_1, g^x, XT(T_1, R_1, EP_ID, AuF-ID, ..., HMAC-SHA1(ZZMT, XT()), HMAC-SHA1(ZZ, RRQ()))
+ MT->>V-GK: 1) RRQ(...)
+ Note right of V-GK: 2) RIP(...)
+ V-GK-->>MT: 2) RIP(...)
+ Note right of V-GK: 3) ...
+ V-GK->>External: 3) ...
+ Note left of External: 12) ...
+ External-->>V-GK: 12) ...
+ Note right of V-GK: 13) RCF(..., GK_ID, EP_ID, CH_1, CH_2, (T_13), g^y, WT(HMAC_ZZ(W), HMAC_ZZ(GK_ID)), HMAC-SHA1(K, RCF()))
+ V-GK-->>MT: 13) RCF(...)
+ Note left of MT: 14) ARQ(..., EP_ID, GK_ID, CH_2, CH_3, (T_14), HMAC-SHA1(K, ARQ()))
+ MT->>V-GK: 14) ARQ(...)
+ Note right of V-GK: 15) ACF(..., GK_ID, EP_ID, CH_4, CH_5, (T_15), HMAC-SHA1(K, ACF()))
+ V-GK-->>MT: 15) ACF(...)
+
+```
+
+T1610860-02
+
+Sequence diagram showing MT authentication between MT and V-GK. The diagram includes five main message exchanges: 1) RRQ from MT to V-GK with CryptoToken XT(); 2) RIP from V-GK to MT; 3) ... from V-GK to an external entity; 12) ... from the external entity to V-GK; 13) RCF from V-GK to MT; 14) ARQ from MT to V-GK; 15) ACF from V-GK to MT. Each message contains specific parameters and cryptographic tokens.
+
+**Figure 10/H.530 – MT authentication**
+
+The authentication procedure of the MT shall be done explicitly only during **GRQ** or **RRQ**. In any later RAS messages exchanged between the MT and the V-GK, MT authentication is done implicitly through the ongoing user authentication and message integrity. No particular means for further MT authentication are necessary.
+
+## 8.4 Unregistration
+
+A MT or V-GK upon reception of UCF shall release the link key $K$ .
+
+## 8.5 Application of the symmetric security protocol in the home domain
+
+While the security mobility protocol described in this Recommendation would usually be deployed for MTs attached to foreign visited domains, this clause describes the case how this security mobility protocol may also be deployed for MTs attached to the home domain. This allows deployment of the mobility security protocol to be independent of where the MT actually attaches. It includes the case also for non-mobility environments, which nevertheless supports H.530.
+
+Figure 11 shows the scenario where an MT is attached to the home GK in the home domain and the authentication and authorization occurs during the registration phase. A similar scenario not shown is also possible, where the authentication and authorization occur during the gatekeeper discovery phase.
+
+
+
+The sequence diagram illustrates the authentication and authorization process in the home domain. The entities involved are AuF (Authentication Function), MRP (Mobility Registration Proxy, optional), H-GK (Home Gatekeeper), and H.323 MT (Mobile Terminal). The process begins with the MT sending a GRQ (EPID) to the H-GK, which responds with GCF (GKID). The MT then computes a Diffie-Hellman (DH) value $g^x \bmod p$ and sends an RRQ (EPID, GKID, 0, CH1, $T_1$ , $g^x$ , HMACZZ(RRQ)) to the H-GK. The H-GK computes its own DH value $g^y \bmod p$ and calculates $W := g^x \oplus g^y$ . It then sends a RIP(...) message to the MT. The H-GK also sends an AuthenticationRequest (RRQ(...), GKID, $W$ , HMAC) to the AuF. The AuF responds with an AuthenticationConfirmation (HMACZZ( $W$ ), HMACZZ(GKID), HMAC) to the H-GK. The H-GK then sends an RCF (GKID, EPID, CH1, CH2, ( $T_{13}$ ), $g^y$ , HMACZZ( $W$ ), HMACZZ(GKID), HMAC $\bar{K}$ (RCF)) to the MT. The MT computes $K := g^{xy} \bmod p$ and $W := g^x \oplus g^y$ , then sends an ARQ (EPID, GKID, CH2, CH3, ( $T_{14}$ ), HMAC $K$ (ARQ)) to the H-GK. Finally, the H-GK sends an ACF (GKID, EPID, CH3, CH4, ( $T_{15}$ ), HMAC $K$ (ACF)) to the MT. The diagram also shows internal message flows between the AuF and H-GK (labeled 7, 8, 3, 12) and a reference code T1610870-02.
+
+Sequence diagram of MT authentication in the home domain during registration phase. Entities: AuF, MRP (dashed), H-GK, H.323 MT. The diagram shows the flow of messages for registration, including GRQ, GCF, RRQ, RIP, RCF, ARQ, and ACF messages with associated cryptographic computations like DH key exchange and HMAC verification.
+
+Figure 11/H.530 – MT authentication in the home domain during registration phase
+
+In any case, the H-GK shall behave exactly as a V-GK in the visited domain as shown in Figure 11 and following the security procedures respectively as described above. The shared secret ZZ4 shall be substituted by ZZ8, and ZZ3 by ZZ7, respectively.
+
+The MRP shown is an optional entity. When the MRP is not present, AuF and H-GK have a direct security relationship established. As a special case, AuF and H-GK may even be co-located, thus making communication between both entities a local issue.
+
+## 8.6 List of Object Identifiers
+
+Table 1 lists all the OIDs referenced in this Recommendation.
+
+**Table 1/H.530 – Object Identifiers used by H.530**
+
+| Object Identifier reference | Object Identifier value(s) | Description |
+|-----------------------------|-----------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| "G1" | {itu-t (0) Recommendation (0) h (8) 235 version (0) 2 10} | Used to indicate a mobility CryptoToken for authentication of the MT |
+| "G2" | {itu-t (0) Recommendation (0) h (8) 235 version (0) 2 11} | Used to indicate a mobility ClearToken that holds $GK_{ID}$ and compound value $W$ within AuthenticationRequest or the corresponding AuF-authenticated values within AuthenticationConfirmation/AuthenticationRejection or GCF/GRJ, RCF/RCF |
+
+## 9 End-to-end security
+
+An end-to-end security architecture in an H.323 mobility environment that is relying on a public-key infrastructure (PKI) concepts is subject of further study.
+
+
+
+## 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
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+
+
+# Recommendation **ITU-T H.553 (12/2025)**
+
+SERIES H: Audiovisual and multimedia systems
+
+Vehicular gateways and intelligent transportation systems (ITS) – Architecture for vehicular gateways
+
+---
+
+## **Functional requirements and architecture of a vehicular multimedia system for heterogeneous access network selection**
+
+
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features the letters "ITU" in a bold, blue, sans-serif font, superimposed on a stylized globe icon with intersecting lines.
+
+ITU logo
+
+## ITU-T H-SERIES RECOMMENDATIONS
+
+### **Audiovisual and multimedia systems**
+
+| | |
+|-----------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100-H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | H.200-H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | H.500-H.549 |
+| VEHICULAR GATEWAYS AND INTELLIGENT TRANSPORTATION SYSTEMS (ITS) | H.550-H.599 |
+| Architecture for vehicular gateways | H.550-H.559 |
+| Vehicular gateway interfaces | H.560-H.569 |
+| BROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES | H.600-H.699 |
+| IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV | H.700-H.799 |
+| E-HEALTH MULTIMEDIA SYSTEMS, SERVICES AND APPLICATIONS | H.800-H.899 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# Recommendation ITU-T H.553
+
+# Functional requirements and architecture of a vehicular multimedia system for heterogeneous access network selection
+
+## Summary
+
+Recommendation ITU-T H.553 specifies the functional requirements and architecture of a vehicular multimedia system for heterogeneous access network selection when connected vehicles support external communication networks, such as wireless wide area networks (WWAN) and wireless short-range communication networks.
+
+## History\*
+
+| Edition | Recommendation | Approval | Study Group | Unique ID |
+|---------|----------------|------------|-------------|--------------------|
+| 1.0 | ITU-T H.553 | 2025-12-14 | 21 | 11.1002/1000/16601 |
+
+## Keywords
+
+Connected vehicles, heterogeneous access network selection, VGP.
+
+---
+
+\* 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 ..... | 1 |
+| 3.1 Terms defined elsewhere ..... | 1 |
+| 3.2 Terms defined in this Recommendation..... | 2 |
+| 4 Abbreviations and acronyms ..... | 2 |
+| 5 Conventions ..... | 2 |
+| 6 Introduction..... | 2 |
+| 7 Functional architecture ..... | 3 |
+| 8 Functional requirements of heterogeneous access network management (HANM) .... | 4 |
+| 8.1 Requirements of network analysis..... | 4 |
+| 8.2 Requirements of decision-making..... | 5 |
+| 8.3 Requirements of data fusion and deduplication ..... | 5 |
+| 9 Functional requirements of access network management (ANM) ..... | 5 |
+| 9.1 Requirements of access network monitor..... | 5 |
+| 9.2 Requirements of access network selection ..... | 6 |
+| 10 Functional requirements of network handover management (NHM)..... | 6 |
+| 10.1 Requirements of MIB ..... | 6 |
+| 10.2 Requirements of network switch ..... | 6 |
+| 11 Interfaces of heterogeneous access network selection..... | 7 |
+| Bibliography..... | 8 |
+
+
+
+# Recommendation ITU-T H.553
+
+## Functional requirements and architecture of a vehicular multimedia system for heterogeneous access network selection
+
+## 1 Scope
+
+This Recommendation specifies the functional requirements and architecture of a vehicular multimedia system for heterogeneous access network selection. This Recommendation defines the following:
+
+- Functional architecture including heterogeneous access network selection;
+- Functional requirements of heterogeneous access network management;
+- Functional requirements of access network management;
+- Functional requirements of network handover management;
+- Interfaces of heterogeneous access network selection.
+
+## 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 H.550](#)] Recommendation ITU-T H.550 (2017), *Architecture and functional entities of vehicle gateway platforms*.
+
+# 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 functional entity** [b-ITU-T Y.2012]: An entity that comprises an indivisible set of specific functions. Functional entities are logical concepts, while groupings of functional entities are used to describe practical, physical implementations.
+
+**3.1.2 intelligent transport systems (ITS)** [b-ITU-R handbook]: ITS can be defined as systems utilizing the combination of computers, communications, positioning and automation technologies to improve the safety, management and efficiency of terrestrial transport systems.
+
+**3.1.3 vehicle gateway (VG)** [b-ITU-T F.749.1]: A VG is a device in a vehicle that enables communications between a device in the vehicle and another device which may be physically located either inside the vehicle or outside the vehicle (e.g., roadside station, cloud-based server, etc.). A VG provides standardized interfaces and protocols, communications across heterogeneous networks, optimized network selection based on application needs and network Quality of Service (QoS), arbitration and integration of network communications, security and switching network connections to maintain service continuity.
+
+**3.1.4 vehicle gateway platform (VGP)** [b-ITU-T F.749.1]: A VGP is the collection of ICT hardware and software in a vehicle operating as an open platform to provide an integrated runtime environment for delivering the communications services of a VG. A VGP may also provide higher
+
+layer communications services such as interaction with the driver through the driver-vehicle access services and so on. Subsystems dedicated solely to vehicle operation are not considered part of the VGP. Supported applications/services include ITS and infotainment.
+
+### 3.2 Terms defined in this Recommendation
+
+None.
+
+## 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|-------|-----------------------------------------------|
+| ANM | Access Network Management |
+| CIEN | Communication Interface for External Networks |
+| C-V2X | Cellular Vehicle-to-everything |
+| HANM | Heterogeneous Access Network Management |
+| MIB | Management Information Base |
+| NHM | Network Handover Management |
+| QoS | Quality of Service |
+| RSU | Roadside Unit |
+| VG | Vehicle Gateway |
+| VGP | Vehicle Gateway Platform |
+| WWAN | Wireless Wide Area Network |
+
+## 5 Conventions
+
+In this Recommendation:
+
+- The keywords "required to" indicate a requirement which must be strictly followed and from which no deviation is permitted if conformance to this document is to be claimed.
+- The keywords "is recommended" indicate a requirement which is recommended but which is not absolutely required. Thus, this requirement need not be present to claim conformance.
+
+# 6 Introduction
+
+With the rapid development of industry, connected vehicles can support ubiquitous connectivity to external communication networks. Meanwhile, the connected vehicles utilize peripheral equipment such as radars and cameras to collect data. Based on the vehicles' local processing and the cooperation with other vehicles, road infrastructure and cloud server, multiple application scenarios of vehicle systems have been implemented.
+
+To provide consistency and continuous service in a wider range of communication to users, the vehicle system supports both wireless wide area networks (WWANs) and wireless short-range communication networks for one same application. These two network types differ in their physical layer protocols, transmission rates, and quality of service (QoS) capabilities. Therefore, the vehicle system incorporates a unified functionality of network selection to manage the collaboration of different communication networks and process data from multiple communication networks to ensure reliable support for a specific application. For example, in the heterogeneous access network environment, the vehicle system can use both WWAN and a wireless short-range communication network to support a traffic lights application, so the vehicle system can receive traffic light
+
+information both from the cloud server through WWAN and from a roadside unit (RSU) through a wireless short-range communication network, as illustrated in Figure 1.
+
+
+
+The diagram illustrates a multi-communication setup. At the top, three blue cylinders represent 'Cloud-based servers'. Below them, a cellular tower icon represents 'WWAN'. At the bottom right, a dashed box labeled 'Vehicle' contains a blue rectangle labeled 'VGP' and a black car icon. At the bottom left, a dashed box labeled 'Infrastructure' contains a traffic light icon and a small building icon representing an RSU. A blue arrow points from the VGP up through the WWAN tower to the cloud servers. Another blue arrow points from the VGP to the RSU in the infrastructure box, labeled 'Wireless short-range communication'. A small label 'H.553(25)' is in the bottom right corner.
+
+Figure 1: Overview of a multi-communication technology connection. The diagram shows a vehicle containing a VGP (Vehicle Gateway Platform) connected to cloud-based servers via a WWAN (Wide Area Network) and to an infrastructure unit (containing a traffic light and RSU) via wireless short-range communication.
+
+**Figure 1 – Overview of a multi-communication technology connection**
+
+A heterogeneous access network is a network system composed of multiple wireless access technologies with distinct types and characteristics. These technologies exhibit significant differences in physical layer protocols, coverage range, transmission rates, QoS, and management mechanisms. Through collaborative integration, they achieve complementary advantages to provide users with seamless and high-efficiency communication services.
+
+Heterogeneous access network selection is the technical process of dynamically selecting the optimal access network for a vehicle's vehicle gateway platform (VGP), which supports multiple types of access network (e.g., IMT-2020 [b-ITU-R M.2150-2], cellular vehicle-to-everything (C-V2X), Wireless LAN, etc.) to meet user service requirements (such as bandwidth, latency, cost, etc.).
+
+Thus, it is important to define the functional requirements of network selection for heterogeneous access networks. The vehicle system has a unified requirement of network selection to manage the service, which can avoid inconsistent service issues from different communication networks due to delay or other problems. The vehicle system supports the functionality of different network quality analysis, and can process the receiving information, including data fusion and deduplication.
+
+## 7 Functional architecture
+
+Figure 2 presents the functional architecture and interfaces of a vehicular multimedia system for heterogeneous access network selection based on [ITU-T H.550]. The related new functionalities in the various subsystems of a VGP for heterogeneous access network selection include:
+
+- Heterogeneous access network management (HANM): It supports network selection and data processing in the session management functional entity, including network analysis, decision-making, data fusion and deduplication.
+- Access network management (ANM): It supports monitoring communication network status and selection of access network connections in the networking and transport functional entity. It includes access network monitor and access network selection.
+
+- Network handover management (NHM): It supports the storage of configuration and current status information, and the handover of access network connections. It includes the management information base (MIB) and network switch in the wired and wireless access management functional entity.
+
+
+
+The diagram illustrates the functional architecture and interfaces of heterogeneous access network selection. It is organized into three main layers: External application, Vehicle gateway platform (VGP), and Vehicle gateway (VG).
+
+- External application** and **SAM** are at the top, connected to the VGP via double-headed arrows.
+- Vehicle gateway platform (VGP)** contains three main functional blocks:
+ - Services**: Includes 'Software and application data management service', 'Driver-vehicle access (DVA) service', and 'Other services'.
+ - Service functionalities**: Includes 'Session management' (with 'Heterogeneous access network management' containing 'Network analysis', 'Decision-making', and 'Data fusion and deduplication') and 'In-vehicle resource access management'.
+ - Management**: Includes 'Device management', 'Security management', and 'Wired and wireless access management' (containing 'Network handover management', 'MIB', and 'Network switch').
+- Vehicle gateway (VG)** is at the bottom, containing:
+ - Networking and transport**: Includes 'Access network management' (with 'Access network monitor' and 'Access network selection').
+ - Communication interfaces**: Categorized into 'nomadic devices' (USB, Wireless LAN, Short range wireless), 'external networks' (Cellular, Wireless LAN, Short-to-medium range wireless), and 'in-vehicle networks' (Short-to-medium range wireless).
+
+**Interfaces:**
+
+- Chn** (dashed red double-headed arrow) connects 'Data fusion and deduplication' in Session management to 'Access network selection' in Access network management.
+- Cha** (dashed red double-headed arrow) connects 'Access network monitor' in Access network management to 'Network analysis' in Heterogeneous access network management.
+- Can** (dashed red double-headed arrow) connects 'Access network selection' in Access network management to 'Network handover management' in Wired and wireless access management.
+- Cac** (dashed red double-headed arrow) connects 'Access network monitor' in Access network management to 'Network switch' in Wired and wireless access management.
+
+**Legend:**
+
+- New function
+- ← - - - → New interface
+
+H.553(25)
+
+Functional architecture and interfaces of heterogeneous access network selection diagram
+
+**Figure 2 – Functional architecture and interfaces of heterogeneous access network selection**
+
+# 8 Functional requirements of heterogeneous access network management (HANM)
+
+HANM in the session management functional entity supports network selection and data processing, including network analysis, decision making, data fusion and deduplication.
+
+### 8.1 Requirements of network analysis
+
+The requirements for network analysis of the HANM function are as follows:
+
+NA-001 – Network analysis is required to analyse the availability of access networks and evaluate the available network capability (including maximum bandwidth, minimum latency and highest reliability).
+
+NA-002 – Network analysis is required to track the dynamic changes in external network state and evaluate the resource usage of the network.
+
+NA-003 – Network analysis is required to identify network misbehaviour, potential security threats and prevent unauthorized access.
+
+NA-004 – Network analysis is required to receive the information of network configuration (e.g., software and hardware parameters), network status (e.g., connection, disconnection) and QoS (including real-time bandwidth, throughput and packet loss rate) reported by the networking and transport layer.
+
+NA-005 – Network analysis is required to provide access to the MIB containing configuration and status information.
+
+### **8.2 Requirements of decision-making**
+
+The requirements for decision-making of the HANM are as follows:
+
+DM-001 – Decision-making is required to support access network selection based on service types, traffic characteristics and access network characteristics, and to deliver user data over the selected access network.
+
+DM-002 – Decision-making is required to support the mechanism or strategy to establish, manage and disconnect networks based on the results of network analysis.
+
+DM-003 – Decision-making is required to support the network handover triggering mechanism and resource conflict control mechanism to ensure service continuity.
+
+DM-004 – Decision-making is recommended to support the seamless handover mechanism between different access networks, minimize the interruption time and maintain ongoing communications during handover.
+
+DM-005 – Decision-making is recommended to support simultaneous data transmission via different access networks (e.g., dual connectivity).
+
+### **8.3 Requirements of data fusion and deduplication**
+
+The requirements for data fusion and deduplication of the HANM function are as follows:
+
+DFD-001 – Data fusion and deduplication are required to have the capability to receive multi-source data and identify the source of data delivery.
+
+DFD-002 – Data fusion and deduplication are required to have the capability of duplicate data detection and deduplication.
+
+DFD-003 – Data fusion and deduplication are required to support multi-source data processing, including pre-processing (e.g., filtering aged or inaccurate data), and fusion of data from different access networks according to the quality and source.
+
+DFD-004 – Data fusion and deduplication are required to have the capability to transmit the processed data to the corresponding services.
+
+# **9 Functional requirements of access network management (ANM)**
+
+ANM in the function entity of networking and transport supports to monitor communications network status and select access network connections, including access network monitor and access network selection.
+
+### **9.1 Requirements of access network monitor**
+
+The requirements for access network monitor of the ANM function are as follows:
+
+ANM-001 – The access network monitor is required to receive information regarding network configuration, network status and QoS reported by external communication networks.
+
+ANM-002 – The access network monitor is required to provide access to the MIB containing the configuration and status information.
+
+ANM-003 – The access network monitor is required to track the dynamic changes in external network state and evaluate the resource usage of the network.
+
+ANM-004 – The access network monitor is required to identify network misbehaviour, potential security threats and prevent unauthorized access.
+
+### **9.2 Requirements of access network selection**
+
+The requirements for access network selection of the ANM function are as follows:
+
+ANS-001 – The access network selection is required to analyse the availability of different access networks, and evaluate the available network capability (including bandwidth, latency and reliability).
+
+ANS-002 – The access network selection is required to select the access network to deliver application data as indicated by the function of heterogeneous access network management.
+
+ANS-003 – The access network selection is recommended to select the access network based on service types, traffic characteristics and access network characteristics, and deliver application data over the selected access network.
+
+ANS-004 – The access network selection is recommended to select the seamless handover mechanism among different access networks to minimize the interruption time and maintain ongoing communications during handover.
+
+ANS-005 – The access network selection is recommended to select two or more different access networks to simultaneously deliver application data (e.g., dual connectivity).
+
+## **10 Functional requirements of network handover management (NHM)**
+
+NHM in the wired and wireless management functional entity supports the storage of configuration and status information and the handover of access network connections, including management of the MIB and the network switch.
+
+### **10.1 Requirements of MIB**
+
+The requirements for MIB of NHM are as follows:
+
+MIB-001 – MIB is required to support real-time fault detection of different access networks and to report any detected faults.
+
+MIB-002 – MIB is required to store and modify the configuration information of the handover strategy, including thresholds of network performance metrics, preferred access network.
+
+MIB-003 – MIB is required to store the configuration and status information of different access network, including signal strength and data rate.
+
+MIB-004 – MIB is required to report the configuration and status information of different access networks.
+
+## **10.2 Requirements of network switch**
+
+The requirements for the network switch of NHM are as follows:
+
+NS-001 – The network switch is recommended to analyse the availability of different access networks, and evaluate the available network capability (including bandwidth, latency and reliability).
+
+NS-002 – The network switch is recommended to select the access network based on the handover strategy stored in MIB.
+
+NS-003 – The network switch is recommended to support the network handover triggering mechanism and resource conflict control mechanism to ensure service continuity.
+
+# **11 Interfaces of heterogeneous access network selection**
+
+The interfaces of heterogeneous access network selection are defined in Figure 2 based on [ITU-T H.550]. All independent functional blocks for heterogeneous access network selection are interconnected through the control reference points which include the following:
+
+- Cha reference point: control reference point between HANM and ANM.
+- Cac reference point: control reference point between ANM and communication interface for external networks (CIEN).
+- Chn reference point: control reference point between HANM and NHM.
+- Can reference point: control reference point between ANM and NHM.
+
+The requirements for the control reference points are as follows:
+
+CRP-001 – Cha reference point is required to send control messages, including the information of network configuration (ANM to HANM), network status (ANM to HANM) and QoS (ANM to HANM).
+
+CRP-002 – Cac reference point is required to send control messages, including the information of the network configuration (CIEN to ANM), network status (CIEN to ANM) and QoS (CIEN to ANM) of different access networks.
+
+CRP-003 – Chn reference point is required to send control messages, including the configuration and status of the networks (NHM to HANM), the mechanisms or strategies to establish, manage and disconnect networks (NHM to HANM).
+
+CRP-004 – Can reference point is required to send control messages, including the configuration and status of the networks (NHM to ANM), the mechanisms or strategies to establish, manage and disconnect networks (NHM to ANM).
+
+## Bibliography
+
+- [b-ITU-T F.749.1] Recommendation ITU-T F.749.1 (2015), *Functional requirements for vehicle gateways*.
+- [b-ITU-T Y.2012] Recommendation ITU-T Y.2012 (2010), *Functional requirements and architecture of next generation networks*.
+- [b-ITU-R M.2150-2] Recommendation ITU-R M.2150-2 (2023), *Detailed specifications of the terrestrial radio interfaces of International Mobile Telecommunications-2020 (IMT-2020)*.
+- [b-ITU-R handbook] ITU-R Handbook (2006), *Land Mobile (including wireless access), Volume 4: Intelligent Transport Systems*, 109 p.
+
+
+
+
+## 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
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+
+
+# Recommendation**ITU-T H.626.6 (02/2024)**
+
+SERIES H: Audiovisual and multimedia systems
+
+Broadband, triple-play and advanced multimedia services –
+Advanced multimedia services and applications
+
+---
+
+## **Architecture for big data application in video surveillance systems**
+
+
+
+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 H-SERIES RECOMMENDATIONS
+
+### **Audiovisual and multimedia systems**
+
+| | |
+|-----------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100-H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | H.200-H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | H.500-H.549 |
+| VEHICULAR GATEWAYS AND INTELLIGENT TRANSPORTATION SYSTEMS (ITS) | H.550-H.599 |
+| BROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES | H.600-H.699 |
+| Broadband multimedia services over VDSL | H.610-H.619 |
+| Advanced multimedia services and applications | H.620-H.629 |
+| Content delivery and ubiquitous sensor network applications | H.640-H.649 |
+| IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV | H.700-H.799 |
+| E-HEALTH MULTIMEDIA SYSTEMS, SERVICES AND APPLICATIONS | H.800-H.899 |
+
+*For further details, please refer to the list of ITU-T Recommendations.*
+
+# Recommendation ITU-T H.626.6
+
+## Architecture for big data application in video surveillance systems
+
+## Summary
+
+Recommendation ITU-T H.626.6 defines an architecture for big data application in video surveillance systems, including the functional architecture and reference points. As the amount of video data is growing in video surveillance systems, a suitable architecture is needed to support the requirements for big data application in video surveillance systems to deal with the structured and unstructured data, and to enhance the efficiency of huge data retrieval and data mining across time and space range. This Recommendation is based on Recommendation ITU-T F.743.7, *Requirements for big data-enhanced visual surveillance services*.
+
+## History \*
+
+| Edition | Recommendation | Approval | Study Group | Unique ID |
+|---------|----------------|------------|-------------|--------------------|
+| 1.0 | ITU-T H.626.6 | 2024-02-13 | 16 | 11.1002/1000/15848 |
+
+## Keywords
+
+Architecture, big data, video surveillance system.
+
+---
+
+\* 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..... | 2 |
+| 4 Abbreviations and acronyms ..... | 2 |
+| 5 Conventions ..... | 3 |
+| 6 Functional architecture for big data application in VSS(s) ..... | 3 |
+| 6.1 Functional architecture in VSBD ..... | 4 |
+| 6.2 Functional entities ..... | 4 |
+| 7 Reference points ..... | 6 |
+| 7.1 Reference point Va/Va'..... | 6 |
+| 7.2 Reference point Vd/Vd' ..... | 6 |
+| 7.3 Reference point Da/Da'..... | 7 |
+| 7.4 Reference point Cb ..... | 7 |
+| 7.5 Reference point Ca ..... | 7 |
+| Bibliography..... | 8 |
+
+
+
+# Recommendation ITU-T H.626.6
+
+## Architecture for big data application in video surveillance systems
+
+# 1 Scope
+
+This Recommendation specifies the functional architecture and reference points for big data application in video surveillance systems (VSS).
+
+The scope of this Recommendation includes:
+
+- Functional architecture for big data application in video surveillance systems;
+- Reference points for big data application in video surveillance 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 F.743] Recommendation ITU-T F.743 (V2) (2019), *Requirements and service description for video surveillance*.
+- [ITU-T F.743.1] Recommendation ITU-T F.743.1 (2015), *Requirements for intelligent visual surveillance*.
+- [ITU-T F.743.7] Recommendation ITU-T F.743.7 (2019), *Requirements for big data-enhanced visual surveillance services*.
+- [ITU-T H.626] Recommendation ITU-T H.626 (V2) (2019), *Architectural requirements for video surveillance system*.
+- [ITU-T H.626.5] Recommendation ITU-T H.626.5 (V2) (2022), *Architecture for intelligent video surveillance systems*.
+- [ITU-T L.1390] Recommendation ITU-T L.1390 (2022), *Energy saving technologies and best practices for 5G radio access network (RAN) equipment*.
+
+# 3 Definitions
+
+### 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 application** [b-ITU-T Y.101]: A structured set of capabilities, which provide value-added functionality supported by one or more services.
+
+**3.1.2 big data** [ITU-T L.1390]: A term that describes the large volume of data – both structured and unstructured – that inundates a business on a day-to-day basis. Big data can be analysed for insights that lead to better decisions and strategic business moves.
+
+**3.1.3 central control server** [b-ITU-T H.626.3]: A device located at the central part of the visual surveillance system. It is used for centralized system management, service operation management and access control.
+
+NOTE – The centre control server (CCS) consists of a centre management unit and a service-control unit.
+
+**3.1.4 customer unit** [ITU-T H.626]: A device located at the customer part of a video surveillance system and used to present multimedia information (such as audio, video, image, alarm signal, etc.) to the end user.
+
+**3.1.5 functional architecture** [b-ITU-T Y.2012]: A set of functional entities and the reference points between them used to describe the structure of an NGN. These functional entities are separated by reference points, and thus, they define the distribution of functions.
+
+**3.1.6 functional entity** [b-ITU-T Y.2012]: An entity that comprises an indivisible set of specific functions. Functional entities are logical concepts, while groupings of functional entities are used to describe practical, and physical implementations.
+
+**3.1.7 interface** [b-ITU-T Y.101]: A shared boundary between two functional units.
+
+NOTE – An interface is defined by various characteristics pertaining to the functions, physical interconnections, signal exchanges, and other characteristics as appropriate.
+
+**3.1.8 media** [b-ITU-T Y.101]: Plural of medium.
+
+**3.1.9 media server** [ITU-T H.626]: A device located at the centre part of a video surveillance system. It is used to forward real-time media stream as well as store, retrieve and replay historical media stream. The media server (MS) receives the media stream from the premises unit or other media server and forwards the media stream to another customer unit or media server. It consists of a media distribution unit and a media storage unit.
+
+**3.1.10 premises unit** [ITU-T H.626]: A device located at the remote part of a video surveillance system and used to capture multimedia information (such as audio, video, image, alarm signal, etc.) from a surveilled object.
+
+**3.1.11 reference point** [b-ITU-T Y.2012]: A conceptual point at the conjunction of two non-overlapping functional entities that can be used to identify the type of information passing between these functional entities.
+
+**3.1.12 service** [b-ITU-T Y.101]: A structured set of capabilities intended to support applications.
+
+**3.1.13 video surveillance system (VSS)** [ITU-T F.743]: A telecommunication system focusing on video (but including audio) application technology, which is used to remotely capture multimedia (such as audio, video, image, alarm signals, etc.) and present them to the end user in a friendly manner, based on a managed broadband network with quality, security and reliability ensured.
+
+## 3.2 Terms defined in this Recommendation
+
+None.
+
+## 4 Abbreviations and acronyms
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|-------|------------------------------------------|
+| AEF | Analysis Evaluation Function |
+| AMF | Analysis Management Function |
+| APP | Application |
+| ASCF | Analysis Service Control Function |
+| BDAU | Big Data Application Unit |
+| CCS | Centre Control Server |
+| CFBDA | Console Function of Big Data Application |
+
+| | |
+|------|----------------------------------------------------|
+| CSF | Computing Service Function |
+| CU | Customer Unit |
+| CMU | Centre Management Unit |
+| DMAF | Data Mining and Analysis Function |
+| DSS | Data Storage and Service |
+| DSU | Data Storage Unit |
+| ISU | Information Storage Unit |
+| IVS | Intelligent Visual Surveillance |
+| MDU | Media Distribution Unit |
+| MS | Media Server |
+| MSU | Media Storage Unit |
+| PU | Premises Unit |
+| VAEU | Visual Analysis Engine Unit |
+| VSAF | Video Streaming Access Function |
+| VSBD | Big Data application in Video Surveillance systems |
+| VSS | Video Surveillance System |
+
+## 5 Conventions
+
+Functional entities: In the context of VSBD architecture, "functional entities" are defined as a collection of functionalities. It is represented by the following symbol:
+
+
+
+A rectangular box with a black border containing the text 'Functional entities'.
+
+Function modules: In the context of VSBD architecture, "function modules" are defined as groups of functionalities that has not been further subdivided at the level of detail described in this Recommendation. It is represented by the following symbol:
+
+
+
+A rectangular box with a blue border containing the text 'Function modules'.
+
+NOTE – In the future, other groups or other Recommendations may possibly further subdivide these function modules.
+
+# 6 Functional architecture for big data application in VSS(s)
+
+This clause describes the functional architecture for big data application in video surveillance systems (VSBD) and functional entities.
+
+Big data is defined in [ITU-T L.1390], and big data application are also analysed for insights that lead to better decisions and strategic business moves from the amount of data. The scenarios of VSBD are defined in [ITU-T F.743.7], they are:
+
+- Intelligent video retrieval. For example, VSBD can use characteristic information such as licence plate, vehicle type, colour, brand type or body feature of the target vehicle as input, to retrieve similar objects in multiple videos with the trajectories displayed to users.
+
+- Intelligent event detection. For example, VSBD can detect a fire disaster by analysing the related real-time videos as well as sensing data from smoke detectors and temperature sensors in areas of concern to the users.
+- Status prediction. For example, according to the data collected by cameras, VSBD can analyse the rules and forecast future traffic flow in order to achieve efficient traffic control.
+
+### 6.1 Functional architecture in VSBD
+
+The system's functional architecture is illustrated in Figure 6-1.
+
+
+
+The diagram illustrates the functional architecture of a Video Surveillance and Broadcasting (VSBD) system within a 'VS system' boundary. Inside the boundary, the 'CCS' (Centre Control System) contains 'CMU' (Centre Management Unit) and 'SCU' (Service Control Unit). The 'VSBD' (Video Surveillance and Broadcasting Device) contains 'BDAU' (Big Data Application Unit), 'DSU' (Data Storage Unit), and 'VAEU' (Visual Analysis Engine Unit). The 'DSU' contains 'MSU' (Media Storage Unit) and 'ISU' (Image Storage Unit). The 'MS' (Media System) contains 'MDU' (Media Distribution Unit). Outside the boundary are 'PU' (Premises Unit) and 'CU' (Customer Unit). Arrows represent different types of data flow: Media (black), Control (red), and Video and image information (green). Control signals include 'Ps', 'Cm', 'Cs', 'Cb', 'Mp', 'Mp'', 'Pc', 'Mc', 'Mc'', 'Ca', 'Da', 'Da'', 'Vd', 'Vd'', 'Va', 'Va''.
+
+Figure 6-1 – Functional architecture diagram showing the internal components of a VS system and its interaction with external units. The VS system contains CCS (CMU, SCU), VSBD (BDAU, DSU with MSU and ISU, VAEU), and MS (MDU). External units include PU and CU. Arrows indicate Media (black), Control (red), and Video and image information (green) flows between these components.
+
+Figure 6-1 – Functional architecture
+
+The VSBD is an end-to-end system without a customer unit focusing on a large amount of video (but including audio) data, which is to collect, store, process, analyse, apply, and display the video data. It consists of a big data application unit (BDAU), data storage unit (DSU) and visual analysis engine unit (VAEU).
+
+The VSBD is different from the intelligent visual surveillance (IVS) system and the application (APP) defined in [ITU-T F.743.1] and the data storage and service (DSS) defined in [ITU-T H.626.5].
+
+The centre management unit (CMU), service-control unit (SCU), media distribution unit (MDU), media storage unit (MSU), premises unit (PU) and customer unit (CU) are defined in [ITU-T H.626]. And the rest in Figure 6-1 is described in clause 6.2 and the reference points in clause 7.
+
+## 6.2 Functional entities
+
+This clause defines the functional entities for VSBD.
+
+#### 6.2.1 Big data application unit
+
+The BDAU is the functional entity of application aspects. It consists of a video streaming access function (VSAF), console function of big data application (CFBDA) and a data mining and analysis function (DMAF).
+
+The main tasks of BDAU are application selection, application operation, application presentation, application access such as video streaming access function, portal service presentation, data mining and analysis service selection.
+
+Figure 6-2 shows the function modules of the BDAU.
+
+
+
+A block diagram showing three functional modules. On the left is a box labeled "Console function of big data application". A red arrow points from this box to a central box labeled "Video streaming access function". Above the central box is another box labeled "Data mining and analysis function", connected by a green upward-pointing arrow. Below the central box is the text "H.626.6(24)".
+
+Figure 6-2 – Function modules of BDAU
+
+Figure 6-2 – Function modules of BDAU
+
+##### 6.2.1.1 Video streaming access function
+
+VSAF is a functional module for access and re-transmission.
+
+The main tasks of VSAF are to access data storage and re-transmit analysis data. For example, VSAF can be used to get the original video data according to monitoring time. VSAF can also be used to decode the original video data to get the required video data and send the video frames to the video analysis engine for analysis.
+
+#### 6.2.1.2 Console function of big data application
+
+CFBDA is the portal of VSBD.
+
+The main task of the CFBDA is to interact with the CU. The CFBDA provides the interface to operate and control the VSBD. Through the CFBDA, the authorized end user can, e.g., manage alarm task, video enrichment task, data retrieval and analysis task, subject research-prediction task, etc.
+
+#### 6.2.1.3 Data mining and analysis function
+
+DMAF is the display carrier for the results of big data analysis.
+
+The main tasks of DMAF are to play and display the result and information of data mining and analysis such as video enrichment, real-time deploy-control and alarming, data retrieval and analysis and status prediction.
+
+#### 6.2.2 Visual analysis engine unit
+
+VAEU is the functional entity for visual analysis aspects. It consists of an analysis service control function (ASCF), analysis management function (AMF), computing service function (CSF) and analysis evaluation function (AEF).
+
+The main tasks of VAEU are to analyse the video data and output the analysis results.
+
+Figure 6-3 shows the function modules of the VAEU.
+
+
+
+A block diagram showing four functional modules. On the left is a box labeled "Analysis service control function". Two red arrows point from this box to two boxes in the center: "Analysis management function" (top) and "Analysis evaluation function" (bottom). These two central boxes are connected by a green double-headed vertical arrow. To the right is a box labeled "Computer service function". Green arrows point from the "Analysis management function" and the "Analysis evaluation function" to the "Computer service function". A long red arrow originates from the bottom of the "Analysis service control function" box and points to the bottom of the "Computer service function" box. Below the "Computer service function" box is the text "H.626.6(24)".
+
+Figure 6-3 – Function modules of VAEU
+
+Figure 6-3 – Function modules of VAEU
+
+##### **6.2.2.1 Analysis service control function**
+
+ASCF is the functional module for service-control aspects.
+
+The main tasks of the ASCF are service description, service registration, service access, service selection, service scheduling, service monitoring, service tracking and service management.
+
+##### **6.2.2.2 Analysis management function**
+
+AMF is the functional module for video or image process aspects.
+
+The main tasks of the AMF are to identify specific objects automatically and output the analysis results to the BDAU, recognize information including triggered events and acquired data, load or unload one or more intelligent analysis algorithms on the CSF according to the different requirements and evaluation from the AEF, send capability lists, statuses and analysis results to the AEF.
+
+##### **6.2.2.3 Computing service function**
+
+CSF is the functional module for computing aspects.
+
+The main task of the CSF is to provide calculation ability to the AMF and AEF according to the different requirements.
+
+#### **6.2.2.4 Analysis evaluation function**
+
+AEF is the functional module for evaluating aspects to improve the accuracy of the visual analysis.
+
+The main tasks of the AEF are to evaluate the quality and performance of capabilities and send the report to the AMF. According to the different requirements, the AEF evaluates analysis results by checking the statuses of capability lists and choosing the one which has the best performance capability.
+
+#### **6.2.3 Data storage function**
+
+DSF is the functional entity for data storage aspects. It consists of MSU and an information storage unit (ISU). MSU is defined in [ITU-T H.626]. ISU is the function module to store, index, download and provide serving of video and image information from the VAEU.
+
+The main tasks of the DSF are to store data, index data, download data and provide data serving.
+
+## **7 Reference points**
+
+This clause defines reference points. The reference points Cm, Cs, Ps, Ds, Ds', Mp, Mp', Mc, Mc' and Pc are defined in [ITU-T H.626].
+
+## **7.1 Reference point Va/Va'**
+
+Reference points Va and Va' are between the BDAU and the VAEU.
+
+Va is used to report the results of the intelligent analysis task from the VAEU to the BDAU.
+
+Va' is used to send the user request of a big data analysis task (such as search target by image, search target by attribute, etc.) from the BDAU to the VAEU, report the status of the big data analysis task from the VAEU to the BDAU, and control the big data analysis task from the VAEU to the BDAU.
+
+## **7.2 Reference point Vd/Vd'**
+
+Reference points Vd and Vd' are between the VAEU and the DSU.
+
+Vd is used to transmit the authorized video and image data from the DSU to the VAEU when the data stored in the DSU is required to be accessed by the BDAU's users and transmit video and image information from the VAEU to the DSU when the analysed information is required to be collected to the DSU.
+
+Vd' is used to send data access request from the VEAU to the DSU, and support data operations like information query, etc., based on the request from the VEAU to the DSU.
+
+## **7.3 Reference point Da/Da'**
+
+Reference points Da and Da' are between the DSU and the BDAU.
+
+Da is used to transmit the authorized video and image information from the DSU to the BDAU when the data stored in the DSS is required to be accessed by the BDAU's users and transmit video and image information from the BDAU to the DSU when the information captured by the BDAU is required to be collected to the DSU.
+
+Da' is used to send video and image information access request from the BDAU to the DSU such as information query or subscription and so on.
+
+## **7.4 Reference point Cb**
+
+Reference point Cb lies between the centre control server (CCS) and the BDAU. It is used to send the user authentication request from the BDAU to the CMU and return the authentication result.
+
+## **7.5 Reference point Ca**
+
+Reference point Ca lies between the CU and the BDAU. It is used by the CU to select, search, play, download and install applications.
+
+## Bibliography
+
+- [b-ITU-T H.626.3] Recommendation ITU-T H.626.3 (2018), *Architecture for visual surveillance system interworking*.
+- [b-ITU-T Y.101] Recommendation ITU-T Y.101 (2000), *Global Information Infrastructure terminology: Terms and definitions*.
+- [b-ITU-T Y.2012] Recommendation ITU-T Y.2012 (2010), *Functional requirements and architecture of next generation 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
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+
+
+International Telecommunication Union
+
+**ITU-T**
+
+TELECOMMUNICATION
+STANDARDIZATION SECTOR
+OF ITU
+
+**H.627**
+
+(08/2020)
+
+SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS
+
+Broadband, triple-play and advanced multimedia services –
+Advanced multimedia services and applications
+
+# --- **Signalling and protocols for a video surveillance system**
+
+Recommendation ITU-T H.627
+
+**ITU-T**
+
+
+
+The logo of the International Telecommunication Union (ITU) is located in the bottom right corner. It features a stylized globe with a red lightning bolt striking across it. To the right of the globe, the text "ITU" is written in a bold, blue font, and below it, "International Telecommunication Union" is written in a smaller, blue font.
+
+ITU logo: A globe with a red lightning bolt and the text 'ITU International Telecommunication Union'.
+
+## ITU-T H-SERIES RECOMMENDATIONS **AUDIOVISUAL AND MULTIMEDIA SYSTEMS**
+
+| | |
+|---------------------------------------------------------------------------------------------|--------------------|
+| CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS | H.100–H.199 |
+| INFRASTRUCTURE OF AUDIOVISUAL SERVICES | |
+| General | H.200–H.219 |
+| Transmission multiplexing and synchronization | H.220–H.229 |
+| Systems aspects | H.230–H.239 |
+| Communication procedures | H.240–H.259 |
+| Coding of moving video | H.260–H.279 |
+| Related systems aspects | H.280–H.299 |
+| Systems and terminal equipment for audiovisual services | H.300–H.349 |
+| Directory services architecture for audiovisual and multimedia services | H.350–H.359 |
+| Quality of service architecture for audiovisual and multimedia services | H.360–H.369 |
+| Telepresence, immersive environments, virtual and extended reality | H.420–H.439 |
+| Supplementary services for multimedia | H.450–H.499 |
+| MOBILITY AND COLLABORATION PROCEDURES | |
+| Overview of Mobility and Collaboration, definitions, protocols and procedures | H.500–H.509 |
+| Mobility for H-Series multimedia systems and services | H.510–H.519 |
+| Mobile multimedia collaboration applications and services | H.520–H.529 |
+| Security for mobile multimedia systems and services | H.530–H.539 |
+| Security for mobile multimedia collaboration applications and services | H.540–H.549 |
+| VEHICULAR GATEWAYS AND INTELLIGENT TRANSPORTATION SYSTEMS (ITS) | |
+| Architecture for vehicular gateways | H.550–H.559 |
+| Vehicular gateway interfaces | H.560–H.569 |
+| BROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES | |
+| Broadband multimedia services over VDSL | H.610–H.619 |
+| Advanced multimedia services and applications | H.620–H.629 |
+| Ubiquitous sensor network applications and Internet of Things | H.640–H.649 |
+| IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV | |
+| General aspects | H.700–H.719 |
+| IPTV terminal devices | H.720–H.729 |
+| IPTV middleware | H.730–H.739 |
+| IPTV application event handling | H.740–H.749 |
+| IPTV metadata | H.750–H.759 |
+| IPTV multimedia application frameworks | H.760–H.769 |
+| IPTV service discovery up to consumption | H.770–H.779 |
+| Digital Signage | H.780–H.789 |
+| E-HEALTH MULTIMEDIA SYSTEMS, SERVICES AND APPLICATIONS | |
+| Personal health systems | H.810–H.819 |
+| Interoperability compliance testing of personal health systems (HRN, PAN, LAN, TAN and WAN) | H.820–H.859 |
+| Multimedia e-health data exchange services | H.860–H.869 |
+| Safe listening | H.870–H.879 |
+
+For further details, please refer to the list of ITU-T Recommendations.
+
+# Recommendation ITU-T H.627
+
+# Signalling and protocols for a video surveillance system
+
+## Summary
+
+Recommendation ITU-T H.627V2 specifies detailed signalling flows and relevant protocols of a video surveillance system, based on the requirements specified in Recommendation ITU-T F.743V2 and the functional architecture specified in Recommendation ITU-T H.626V2.
+
+This edition updates the title, adds overall requirements, as well as revising the signalling flows and relevant protocols.
+
+## History
+
+| Edition | Recommendation | Approval | Study Group | Unique ID* |
+|---------|----------------|------------|-------------|---------------------------------------------------------------------------|
+| 1.0 | ITU-T H.627 | 2012-06-29 | 16 | 11.1002/1000/11676 |
+| 2.0 | ITU-T H.627 | 2020-08-13 | 16 | 11.1002/1000/14342 |
+
+## Keywords
+
+Protocols, signalling, video surveillance system.
+
+---
+
+\* 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 2020
+
+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 Introduction to functional architecture of VSS..... | 4 |
+| 7 Overall requirements of signalling and media stream ..... | 5 |
+| 7.1 Introduction of related protocols ..... | 5 |
+| 7.2 SIP header requirements..... | 5 |
+| 7.3 Extended media command set ..... | 6 |
+| 7.4 Media stream keepalive mechanism..... | 9 |
+| 7.5 Transmission of multiple response messages..... | 9 |
+| 7.6 RTP-based video or audio data packaging ..... | 10 |
+| 7.7 SDP definitions..... | 12 |
+| 7.8 TCP-based media transmission ..... | 16 |
+| 8 Signalling flows and relevant protocols ..... | 17 |
+| 8.1 Registration and de-registration ..... | 17 |
+| 8.2 Real-time media stream..... | 20 |
+| 8.3 Device configuration and control ..... | 35 |
+| 8.4 Alarm event notification and distribution..... | 44 |
+| 8.5 Device information query..... | 47 |
+| 8.6 Status information reporting..... | 74 |
+| 8.7 Historical media file retrieval..... | 76 |
+| 8.8 Historical media file playback..... | 78 |
+| 8.9 Historical media file download ..... | 98 |
+| 8.10 Time calibration..... | 116 |
+| 8.11 Subscription and notification..... | 118 |
+| 8.12 Audio broadcast and audio intercom..... | 125 |
+| 8.13 Instant image snapshot ..... | 130 |
+| Annex A – Extended control command set ..... | 134 |
+| A.1 Overall requirements ..... | 134 |
+| A.2 Command definitions ..... | 134 |
+| A.3 PU control commands ..... | 162 |
+
+
+
+# Recommendation ITU-T H.627
+
+# Signalling and protocols for a video surveillance system
+
+# 1 Scope
+
+This Recommendation specifies in detail signalling and relevant protocols of a video surveillance system (VSS) based on the functional architecture specified in [ITU-T H.626V2].
+
+# 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.711] Recommendation ITU-T G.711 (1988), *Pulse code modulation (PCM) of voice frequencies.*
+- [ITU-T G.723.1] Recommendation ITU-T G.723.1 (2006), *Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s.*
+- [ITU-T G.729] Recommendation ITU-T G.729 (2012), *Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear prediction (CS-ACELP).*
+- [ITU-T H.222.0] ISO/IEC 13818-1:2019|ITU-T H.222.0 (2018), *Information technology – Generic coding of moving pictures and associated audio information – Systems.*
+- [ITU-T H.264V13] Recommendation ITU-T H.264 (2019), *Advanced video coding for generic audiovisual services.*
+- [ITU-T H.265] Recommendation ITU-T H.265 (2019), *High-efficiency video coding.*
+- [ITU-T H.626V2] Recommendation ITU-T H.626 (2019), *Architectural requirements for a video surveillance system.*
+- [IETF RFC 2250] IETF RFC 2250 (1998), *RTP payload format for MPEG1/MPEG2 video.*
+- [IETF RFC 3261] IETF RFC 3261 (2002), *SIP: Session initiation protocol.*
+- [IETF RFC 3428] IETF RFC 3428 (2002), *Session initiation protocol (SIP) extension for instant messaging.*
+- [IETF RFC 3550] IETF RFC 3550 (2003), *RTP: A transport protocol for real-time applications.*
+- [IETF RFC 3551] IETF RFC 3551 (2003), *RTP profile for audio and video conferences with minimal control.*
+- [IETF RFC 3725] IETF RFC 3725 (2004), *Best current practices for third party call control (3pcc) in the session initiation protocol (SIP).*
+- [IETF RFC 4566] IETF RFC 4566 (2006), *SDP: Session description protocol.*
+- [IETF RFC 4571] IETF RFC 4571 (2006), *Framing real-time transport protocol (RTP) and RTP control protocol (RTCP) packets over connection-oriented transport.*
+
+- [IETF RFC 5905] IETF RFC 5905 (2010), *Network time protocol version 4: Protocol and algorithms specification*.
+- [IETF RFC 6086] IETF RFC 6086 (2011), *Session initiation protocol (SIP) INFO method and package framework*.
+- [IETF RFC 6184] IETF RFC 6184 (2011), *RTP payload format for H.264 video*.
+- [IETF RFC 6665] IETF RFC 6665 (2012), *SIP – Specific event notification*.
+- [IETF RFC 7798] IETF RFC 7798 (2016), *RTP payload format for high efficiency video coding (HEVC)*.
+- [IETF RFC 7826] IETF RFC 7826 (2016), *Real-time streaming protocol version 2.0*.
+
+# 3 Definitions
+
+## 3.1 Terms defined elsewhere
+
+This Recommendation uses the following terms defined elsewhere:
+
+**3.1.1 central control server (CCS)** [b-ITU-T H.626.3]: A device located at the central part of the visual surveillance system. It is used for centralized system management, service operation management and access control.
+
+NOTE – The centre control server consists of centre management unit and service control unit.
+
+**3.1.2 centre management unit** [ITU-T H.626V2]: A device located at the main part of a video surveillance system. It is used for centralized system management, service operation management, etc. The main functions include management, authorization, accounting, charging, location and presence.
+
+**3.1.3 customer unit** [ITU-T H.626V2]: A device located at the customer part of a video surveillance system and used to present multimedia information (such as audio, video, image, alarm signal, etc.) to the end-user.
+
+**3.1.4 interface** [b-ITU-T Y.101]: A shared boundary between two functional units.
+
+NOTE – An interface is defined by various characteristics pertaining to the functions, physical interconnections, signal exchanges and other characteristics as appropriate.
+
+**3.1.5 media distribution unit** [ITU-T H.626V2]: A device located at the centre part of a video surveillance system. It is used to transport media from the premises unit (PU) to the customer unit (CU). The main functions include media receiving, media processing, media routing, media transmission, media forwarding, media replication, etc.
+
+**3.1.6 media server** [ITU-T H.626V2]: A device located at the centre part of a video surveillance system. It is used to forward real-time media stream as well as store, retrieve and replay historical media stream. The media server receives the media stream from premises unit or other media server and forwards the media stream to other customer unit or media server. It consists of media distribution unit and media storage unit.
+
+**3.1.7 media storage unit** [ITU-T H.626V2]: A device located at the centre part of a video surveillance system. It is used to retrieve, store media and provide a streaming media serving capability. The main functions include media storage, media serving, media indexing media downloading, etc.
+
+**3.1.8 premises unit** [ITU-T H.626V2]: A device located at the remote part of a video surveillance system and used to capture multimedia information (such as audio, video, image, alarm signal, etc.) from a surveilled object.
+
+**3.1.9 service control unit** [ITU-T H.626V2]: A device located at the main part of a video surveillance system. It is used to access service control and signal call control between the PU and
+
+the CU. The main functions include access registration, access authentication, identification, authorization, call control, location, presence, and target media serving function selection.
+
+**3.1.10 video surveillance system** [ITU-T H.626V2]: A telecommunication service focusing on video (including audio and image) application technology, which is used to remotely capture multimedia (such as audio, video, image, alarm signal, etc.) and present them to the end user in a user-friendly manner, based on a managed broadband network with ensured quality, security and reliability.
+
+## **3.2 Terms defined in this Recommendation**
+
+None.
+
+# **4 Abbreviations and acronyms**
+
+This Recommendation uses the following abbreviations and acronyms:
+
+| | |
+|-------|------------------------------------|
+| AAC | Advanced Audio Coding |
+| ACK | Acknowledgement |
+| B2BUA | Back to Back User Agent |
+| CBR | Constant Bitrate |
+| CCS | Central Control Server |
+| CIF | Common Intermediate Format |
+| CMU | Centre Management Unit |
+| CPG | Control Protocol Gateway |
+| CRLF | Carriage Return and Line Feed |
+| CU | Customer Unit |
+| ECCS | Extended Control Command Set |
+| EMCS | Extended Media Command Set |
+| FI | Focus Iris |
+| ID | Identifier |
+| IP | Internet Protocol |
+| IPC | IP Camera |
+| MDU | Media Distribution Unit |
+| MS | Media Server |
+| MSU | Media Storage Unit |
+| NPT | Normal Play Time |
+| NTP | Network Time Protocol |
+| OSD | On-Screen Display |
+| PCM | Pulse Code Modulation |
+| PES | Packetized Elementary Stream |
+| PESA | Packetized Elementary Stream Audio |
+| PESV | Packetized Elementary Stream Video |
+
+| | |
+|-------|----------------------------------------------------|
+| PS | Program Stream |
+| PSM | Program Stream Map |
+| PTZ | Pan/Tilt/Zoom |
+| PU | Premises Unit |
+| QCIF | Quarter Common Intermediate Format |
+| RTCP | Real-time Transport Control Protocol |
+| RTP | Real-time Transport Protocol |
+| RTSP | Real-time Streaming Protocol |
+| SCU | Service Control Unit |
+| SDP | Session Description Protocol |
+| SIP | Session Initiation Protocol |
+| SMPTE | Society of Motion Picture and Television Engineers |
+| SN | Serial Number |
+| SRG | Signal Routing Gateway |
+| SSRC | Synchronization Source |
+| TCP | Transmission Control Protocol |
+| UA | User Agent |
+| UDP | User Datagram Protocol |
+| URI | Uniform Resource Identifier |
+| UTC | Coordinated Universal Time |
+| VBR | Variable Bitrate |
+| VSS | Video Surveillance System |
+| XML | extensible Markup Language |
+
+# 5 Conventions
+
+None.
+
+# 6 Introduction to functional architecture of VSS
+
+The functional architecture of a VSS is illustrated in Figure 6-1. Regarding the detailed entities and function, see clause 6.2 of [ITU-T H.626V2].
+
+
+
+Functional architecture of VSS diagram showing components: CCS (CMU, SCU), MS (MDU, MSU), PU, and CU. It illustrates media and control signal flows between these units. Media flows are shown with black arrows, and control flows with red arrows. Labels include Ps, Cs, Cm, Ds, Ds', Mp, Mp', Mc, Mc', and Pc. A legend at the bottom indicates black arrows for Media and red arrows for Control. The diagram is labeled H.627(20)\_F6-1.
+
+CMU: centre management unit, MDU: media distribution unit; MSU: media storage unit; SCU: service control unit
+
+**Figure 6-1 – Functional architecture of VSS**
+
+# 7 Overall requirements of signalling and media stream
+
+## 7.1 Introduction of related protocols
+
+The structure of communication protocols is illustrated in Figure 7-1. Regarding the detailed protocols and data formats, see clause 7.1 of [ITU-T H.626V2].
+
+
+
+| Session channel | | | Media stream channel | |
+|-----------------|------|------|-----------------------------|---------------------------------------------------|
+| SDP | ECCS | EMCS | ITU-T H.264/
ITU-T H.265 | ITU-T G.711/
ITU-T G.723.1/
ITU-T G.729/AAC |
+| SIP | | | RTP/RTCP | |
+| TCP/UDP | | | TCP/UDP | |
+| IP | | | | |
+
+H.627(20)\_F7-1
+
+**Figure 7-1 – Structure of communication protocols**
+
+## 7.2 SIP header requirements
+
+With reference to [IETF RFC 3261], the session initiation protocol (SIP) uniform resource identifier (URI) formats in From and To headers of SIP messages within the VSS are specified as follows:
+
+```
+sip[s]:username@domain;uri-parameters
+```
+
+in which it shall be ensured that the username is unique in the same VSS, and the identifier (ID) uniform codes specified in [ITU-T H.626V2] should be adopted; the domain should adopt the first 14 digits in the ID uniform codes, or adopt the IP: port format, while the port should adopt 5060; URI parameters can be used to carry the extended parameters.
+
+The SIP URI values of other headers in SIP messages should comply with the signal communication provisions of [IETF RFC 3261].
+
+The Subject header field of the INVITE message sent by the CCS is used to identify the different media links. The VSS has the capability of media distribution: for the video with the same sender ID, only one request shall be initiated to the target VSS or device and the video resources are sent to different receivers.
+
+The format of the subject field is as follows:
+
+Subject: Media stream sender ID: Sender's media stream serial number, media stream receiver ID: Receiver's media stream serial number.
+
+The various fields are described as follows:
+
+Media stream sender ID: The media stream sender ID code complies with the specification in [ITU-T H.626V2].
+
+Sender's media stream serial number (SN): The sender's media stream SN is a character string that consists of no more than 20 digits. When the requested media is the real-time media stream, the value of the first digit is 0, and the value is unique for each media link; when the requested media is the historical media stream, the value of the first digit is 1, and the value is unique for each media link.
+
+Media stream receiver ID: The media stream receiver ID code complies with the specification in [ITU-T H.626V2].
+
+Receiver's media stream SN: The identification SN of the media stream receiver is a non-repeating character string at the same moment. When the receiver is a client, it can be taken as the ID of the display window.
+
+## 7.3 Extended media command set
+
+### 7.3.1 Command names and descriptions
+
+The historical media file playback control commands are implemented through the request message from the client to the server and the response message from the server to the client. The request and response adopt part of the request and response message formats in the real-time streaming protocol (RTSP) [IETF RFC 7826].
+
+A message includes a start line, one or more message headers, a blank line (namely the line without content before carriage return and line feed (CRLF)) representing the end of the header and a message body (optional). An example is as follows:
+
+```
+message =start-line
+message header
+CRLF
+[message body]
+```
+
+The messages include requests and responses. Each pair of request-response messages shall include the same CSeq header field, with the specific description shown as follows.
+
+#### a) Request
+
+The start line format of the request message is Method SP RTSP-Version CRLF, where Method: request command; SP: blank character; RTSP-Version: protocol version number; CR: carriage return; LF: line feed. Request commands include: PLAY, PAUSE, TEARDOWN;
+
+#### b) Response
+
+The start line format of the response message is:
+
+```
+Status-Line = RTSP-Version SP Status-Code SP Reason-Phrase CRLF.
+```
+
+where RTSP-Version: protocol version number; Status-Code: 3-bit status code, used for representing the host status when responding to the request; Reason-Phrase: textual interpretation corresponding to the status code.
+
+### 7.3.2 Command definitions
+
+#### CD-1: Media playing command
+
+The client sends the PLAY request message, and requests the server to send the media stream. Range headers shall be supported, which provides the time range for playing in the Range header so as to play the media in the specified time period; see clause 12.40 of [IETF RFC 7826]. The time range shall support normal play time (NPT) and Society of Motion Picture and Television Engineers (SMPTE) relative timestamp ranges. The RTP-Info header information is given in the response message from the server; see clause 18.45 of [IETF RFC 7826]. The RTP-Info should be returned in the 200 OK of the SIP INFO, and the seq and rtptime parameters should be carried in the RTP-Info field.
+
+The value of the Range header is "npt=now-", without carrying the Scale header, representing that it resumes playing at the original speed from the paused position.
+
+Example:
+
+```
+PLAY RTSP/2.0
+CSeq:2
+Range:npt=now-
+```
+
+Example of the video playback PLAY command returns RTP-Info (take random drag and drop as an example):
+
+Request info:
+
+```
+INFO SIP:media stream sender code@ media stream sender domain name or IP
+address port SIP/2.0
+From: ;tag=e3719a0b
+To: ;tag=949c43d7
+Call-ID: wlss-f7c53b46-eea27828118c3b50449185980f4bfd0@172.20.16.4
+Via: SIP/2.0/UDP media stream receiver domain name or IP address
+Content-Length: the byte length of message
+CSeq: 2 INFO
+Content-Type: Application/EMCS
+Max-Forwards: 70
+
+PLAY RTSP/2.0
+CSeq: 4
+Range: npt=100-
+```
+
+Response example:
+
+```
+SIP/2.0 200 OK
+Via: SIP/2.0/UDP media stream receiver domain name or IP address
+From: ;tag=e3719a0b
+To: