1、 International Telecommunication Union ITU-T H.225.0TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2009) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Transmission multiplexing and synchronization Call signalling protocols and media stream packetization for
2、packet-based multimedia communication systems Recommendation ITU-T H.225.0 ITU-T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS H.100H.199 INFRASTRUCTURE OF AUDIOVISUAL SERVICES General H.200H.219 Transmission multiplexing and synchronization
3、H.220H.229Systems aspects H.230H.239 Communication procedures H.240H.259 Coding of moving video H.260H.279 Related systems aspects H.280H.299 Systems and terminal equipment for audiovisual services H.300H.349 Directory services architecture for audiovisual and multimedia services H.350H.359 Quality
4、of service architecture for audiovisual and multimedia services H.360H.369 Supplementary services for multimedia H.450H.499 MOBILITY AND COLLABORATION PROCEDURES Overview of Mobility and Collaboration, definitions, protocols and procedures H.500H.509 Mobility for H-Series multimedia systems and serv
5、ices H.510H.519 Mobile multimedia collaboration applications and services H.520H.529 Security for mobile multimedia systems and services H.530H.539 Security for mobile multimedia collaboration applications and services H.540H.549 Mobility interworking procedures H.550H.559 Mobile multimedia collabor
6、ation inter-working procedures H.560H.569 BROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES Broadband multimedia services over VIDAL H.610H.619 Advanced multimedia services and applications H.620H.629 PIT MULTIMEDIA SERVICES AND APPLICATIONS FOR PIT General aspects H.700H.719 PIT terminal devi
7、ces H.720H.729 PIT middleware H.730H.739 PIT application event handling H.740H.749 IPTV metadata H.750H.759 IPTV multimedia application frameworks H.760H.769 IPTV service discovery up to consumption H.770H.779 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T H.225.0
8、 (12/2009) i Recommendation ITU-T H.225.0 Call signalling protocols and media stream packetization for packet-based multimedia communication systems Summary This Recommendation covers the technical requirements for narrow-band visual telephone services defined in H.200 and F.720-series Recommendatio
9、ns, in those situations where the transmission path includes one or more packet-based networks, each of which is configured and managed to provide a non-guaranteed Quality of Service (QoS) which is not equivalent to that of N-ISDN, such that additional protection or recovery mechanisms beyond those
10、mandated by ITU-T Rec. H.320 need be provided in the terminals. It is noted that ITU-T Rec. H.322 addresses the use of some other LANs which are able to provide the underlying performance not assumed by the ITU-T Recs H.323 and H.225.0. This Recommendation describes how audio, video, data, and contr
11、ol information on a packet-based network can be managed to provide conversational services in H.323 equipment. Products claiming compliance with Version 7 of H.225.0 (this version) shall comply with all of the mandatory requirements of this Recommendation. Version 7 products can be identified by H.2
12、25.0 messages containing a protocolIdentifier value of itu-t (0) recommendation (0) h (8) 2250 version (0) 7. This revision incorporates the following changes: 1) Correction of defects identified in the H.323-Series Implementors Guide which include: a) Editing corrections. b) Clarification to the le
13、ngth of information element, where “*“ denotes an undefined maximum length. b) Clarification to User-user information element in Setup acknowledge, Status and Status inquiry messages. c) Addition of destinationInfo field to H.225.0 ReleaseComplete and Notify messages. 2) Incorporation of multi-langu
14、age caller and called party identification. 3) Clarifications to the processing of H.225.0 Call Signalling messages errors in clause 7.1. History Edition Recommendation Approval Study Group 1.0 ITU-T H.225.0 1996-11-11 16 2.0 ITU-T H.225.0 1998-02-06 16 2.1 ITU-T H.225.0 Annex I 1998-09-25 16 2.2 IT
15、U-T H.225.0 Annex G 1999-05-27 16 3.0 ITU-T H.225.0 1999-09-30 16 4.0 ITU-T H.225.0 2000-11-17 16 4.1 ITU-T H.225.0 (2000) Amend. 1 2002-11-29 16 5.0 ITU-T H.225.0 2003-07-14 16 6.0 ITU-T H.225.0 2006-05-29 16 6.1 ITU-T H.225.0 (2006) Amend. 1 2007-01-13 16 7.0 ITU-T H.225.0 v7 2009-12-14 16 ii Rec.
16、 ITU-T H.225.0 (12/2009) 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-
17、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 stud
18、y 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-Ts purview, the necessary standards are prepared on a c
19、ollaborative 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 c
20、ertain 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 requi
21、rements. 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 Righ
22、t. 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
23、 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 http:/www.itu.int/ITU-T/ipr/. ITU 2010 All rights res
24、erved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T H.225.0 (12/2009) iii CONTENTS Page 1 Scope 1 2 References. 3 3 Definitions 5 4 Abbreviations 5 4.1 General abbreviations . 5 4.2 RAS message abbreviations . 6 5 Con
25、ventions 7 6 Packetization and synchronization mechanism 8 6.1 General approach 8 6.2 Use of RTP/RTCP 11 7 H.225.0 message definitions . 14 7.1 Use of Q.931 messages . 14 7.2 Common Q.931 information elements . 17 7.3 Q.931 based H.225.0 call signalling message details . 27 7.4 Q.932-based H.225.0 c
26、all signalling message details 41 7.5 H.225.0 call signalling timer values . 46 7.6 H.225.0 common message elements 47 7.7 Required support of RAS messages . 60 7.8 Terminal and gateway discovery messages 61 7.9 Terminal and gateway registration messages . 63 7.10 Terminal/gatekeeper unregistration
27、messages 69 7.11 Terminal to gatekeeper admission messages 71 7.12 Terminal to gatekeeper requests for changes in bandwidth . 76 7.13 Location request messages . 78 7.14 Disengage messages . 82 7.15 Status request messages 84 7.16 Non-standard message 88 7.17 Message not understood . 88 7.18 Gateway
28、 resource availability messages 89 7.19 RAS timers and Request in Progress (RIP) 90 7.20 Service control messages 92 7.21 AdmissionConfirmSequence 93 7.22 Error Code Mapping . 93 8 Mechanisms for maintaining QoS 95 8.1 General approach and assumptions 95 8.2 Use of RTCP in measuring QoS . 95 8.3 Aud
29、io/Video jitter procedures 96 iv Rec. ITU-T H.225.0 (12/2009) Page 8.4 Audio/Video skew procedures . 96 8.5 Procedures for maintaining QoS 96 8.6 Echo control 97 Annex A RTP/RTCP . 98 Annex B RTP profile 99 Annex C RTP payload format for H.261 video streams . 99 Annex D RTP payload format for H.261A
30、 video streams 100 D.1 Introduction 100 D.2 H.261A RTP packetization . 100 Annex E Video packetization . 102 E.1 H.263 102 Annex F Audio and multiplexed packetization . 103 F.1 G.723.1 . 103 F.2 G.728 104 F.3 G.729 104 F.4 Silence suppression 107 F.5 GSM codecs 108 F.6 G.722.1 . 109 F.7 TIA/EIA-136
31、ACELP . 110 F.8 TIA/EIA-136 US1 111 F.9 IS-127 EVRC 113 F.10 H.223 MUX-PDU packetization 115 Annex G Communication between and within administrative domains . 116 G.1 Scope 116 G.2 Definitions 117 G.3 Abbreviations . 118 G.4 Normative references 118 G.5 System models 118 G.6 Operation 121 G.7 Signal
32、ling examples 127 G.8 Annex G profiles 136 Annex H H.225.0 message syntax (ASN.1) . 141 Annex I H.263+ video packetization 178 Appendix I RTP/RTCP algorithms . 178 Appendix II RTP profile . 179 Appendix III H.261 packetization . 179 Rec. ITU-T H.225.0 (12/2009) v Page Appendix IV H.225.0 operation o
33、n different packet-based network protocol stacks . 180 IV.1 TCP/IP/UDP . 180 IV.2 SPX/IPX . 183 IV.3 SCTP . 184 Appendix V ASN.1 usage in this Recommendation . 185 V.1 Tagging . 185 V.2 Types 185 V.3 Constraints and ranges 185 V.4 Extensibility 185 Appendix VI H.225.0 identifiers of tunnelled signal
34、ling protocols 185 Rec. ITU-T H.225.0 (12/2009) 1 Recommendation ITU-T H.225.0 Call signalling protocols and media stream packetization for packet-based multimedia communication systems 1 Scope This Recommendation describes the means by which audio, video, data, and control are associated, coded, an
35、d packetized for transport between H.323 equipment on a packet-based network. This includes the use of an H.323 gateway, which in turn may be connected to H.320, H.324, or H.310/H.321 terminals on N-ISDN, GSTN, or B-ISDN respectively. The equipment descriptions and procedures are described in ITU-T
36、Rec. H.323 while this Recommendation covers protocols and message formats. Communication via an H.323 gateway to an H.322 gateway for guaranteed Quality of Service (QoS) LANs and thus to H.322 endpoints is also possible. This Recommendation is intended to operate over a variety of different packet-b
37、ased networks, including IEEE 802.3, Token Ring, etc. Thus, this Recommendation is defined as being above the Transport layer such as TCP/IP/UDP, SPX/IPX, etc. Specific profiles for particular transport protocol suites are included in Appendix IV. Thus, the scope of H.225.0 communication is between
38、H.323 entities on the same packet-based network, using the same transport protocol. This packet-based network may be a single segment or ring, or it logically could be an enterprise data network comprising multiple packet-based networks bridged or routed to create one interconnected network. It shou
39、ld be emphasized that operation of H.323 terminals over the entire Internet, or even several connected packet-based networks may result in poor performance. The possible means by which quality of service might be assured on this packet-based network, or on the Internet in general is beyond the scope
40、 of this Recommendation. However, this Recommendation provides a means for the user of H.323 equipment to determine that quality problems are the result of packet-based network congestion, as well as procedures for corrective actions. It is also noted that the use of multiple H.323 gateways connecte
41、d over the public ISDN network is a straightforward method for increasing quality of service. ITU-T Rec. H.323 and this Recommendation are intended to extend H.320 and H.221 connections onto the non-guaranteed QoS packet-based network environment conferences. As such the primary conference model1is
42、one with size in the range of a few participants to a few thousand, as opposed to large-scale broadcast operations, with strong admission control, and tight conference control. This Recommendation makes use of (RTP/RTCP) Real-time Transport Protocol/Real-Time Transport Control Protocol for media str
43、eam packetization and synchronization for all underlying packet-based networks (see Annexes A, B and C). Please note that the usage of RTP/RTCP as specified in this Recommendation is not tied in any way to the usage of TCP/IP/UDP. This Recommendation assumes a call model where initial signalling on
44、a non-RTP transport address is used for call establishment and capability negotiation (see ITU-T Recs H.323 and H.245), followed by the establishment of one or more RTP/RTCP connections. This Recommendation contains details on the usage of RTP/RTCP. In ITU-T Rec. H.221, audio, video, data, and contr
45、ol are multiplexed into one or more synchronized physical SCN calls. On the packet-based network side of an H.323 call, none of these concepts apply. There is no need to carry from the SCN side the H.221 concept of a P 64 kbit/s call, e.g., 2 by 64 kbit/s, 3 by 64 kbit/s, etc. Thus, on the packet-ba
46、sed network side, for example, there are only single “connection“ calls with a maximum rate limited to 128 kbit/s, not 2 64 kbit/s fixed _ 1An optional broadcast-only conference model is under consideration; of necessity the broadcast model does not provide tight admissions or conference control. 2
47、Rec. ITU-T H.225.0 (12/2009) rate calls. Another example has single “connection“ packet-based network calls with a maximum rate limited to 384 kbit/s interworking with 6 64 kbit/s on the SCN side2. The primary rationale of this approach is to put complexity in the gateway rather than the terminal an
48、d to avoid extending onto the packet-based network features of H.320 that are tightly tied to ISDN unless this is necessary. In general, H.323 terminals are not aware directly of the H.320 transfer rate while interworking through an H.323 gateway; instead, the gateway uses H.245 FlowControlCommand m
49、essages to limit the media rate on each logical channel in use to that allowed by the H.221 multiplex. The gateway may allow the packet-based network side video rates to substantially underrun the SCN side rates (or the reverse) though the usage of a rate reducing function and H.261 fill frames; the details of such operations are beyond the scope of ITU-T Rec. H.323 and this Recommendation. Note that the H.323 terminal is indirectly aware of the H.320 transfe
