1、 International Telecommunication Union ITU-T H.323TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2009) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Systems and terminal equipment for audiovisual services Packet-based multimedia communications systems Recomm
2、endation ITU-T H.323 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 H.220H.229 Systems aspects H.230H.239 Communication pr
3、ocedures 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.349Directory services architecture for audiovisual and multimedia services H.350H.359 Quality of service architecture for audiovisual and multimedia
4、 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 services H.510H.519 Mobile multimedia collaboration applic
5、ations 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 collaboration inter-working procedures H.560H.569 BROADBAND, T
6、RIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 Advanced multimedia services and applications H.620H.629 IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV General aspects H.700H.719 IPTV terminal devices H.720H.729 IPTV middleware H.730H.739 IPTV appli
7、cation 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.323 (12/2009) i Recommendation ITU-T H.323 Packet-based
8、 multimedia communications systems Summary Recommendation ITU-T H.323 describes terminals and other entities that provide multimedia communications services over Packet-Based Networks (PBN) which may not provide a guaranteed Quality of Service. H.323 entities may provide real-time audio, video and/o
9、r data communications. Support for audio is mandatory, while data and video are 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. The packet-based network over which H.323 entities communic
10、ate may be a point-to-point connection, a single network segment, or an internetwork having multiple segments with complex topologies. H.323 entities may be used in point-to-point, multipoint, or broadcast (as described in Rec. ITU-T H.332) configurations. They may interwork with H.310 terminals on
11、B-ISDN, H.320 terminals on N-ISDN, H.321 terminals on B-ISDN, H.322 terminals on Guaranteed Quality of Service LANs, H.324 terminals on GSTN and wireless networks, V.70 terminals on GSTN, and voice terminals on GSTN or ISDN through the use of Gateways. H.323 entities may be integrated into personal
12、computers or implemented in stand-alone devices such as videotelephones. Note that the title of H.323 (1996) was “Visual telephone systems and equipment for local area networks which provide a non-guaranteed quality of service“. The title changed in Version 2 to be consistent with its expanded scope
13、. Products claiming compliance with Version 1 of H.323 shall comply with all of the mandatory requirements of H.323 (1996) which references Rec. ITU-T H.225.0 (1996) and Rec. ITU-T H.245 (1997). Version 1 products shall be identified by H.225.0 messages containing a protocolIdentifier = itu-t(0) rec
14、ommendation(0) h(8) 2250 version(0) 1 and H.245 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 245 version(0) 2. Products claiming compliance with Version 2 of H.323 shall comply with all of the mandatory requirements of this Recommendation, H.323 (1998), which references
15、 Rec. ITU-T H.225.0 (1998) and Rec. ITU-T H.245 (1998 or later). Version 2 products shall be identified by H.225.0 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 2250 version(0) 2 and H.245 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 245 ver
16、sion(0) x, where “x“ is 3 or higher. Products claiming compliance with Version 3 of H.323 shall comply with all of the mandatory requirements of this Recommendation, H.323 (1999), which references Rec. ITU-T H.225.0 (1999) and Rec. ITU-T H.245 (1999 or later). Version 3 products shall be identified
17、by H.225.0 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 2250 version(0) 3 and H.245 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 245 version(0) x, where “x“ is 5 or higher. Products claiming compliance with Version 4 of H.323 shall comply w
18、ith all of the mandatory requirements of this Recommendation, H.323 (2000), which references Rec. ITU-T H.225.0 (2000) and Rec. ITU-T H.245 (2000 or later). Version 4 products shall be identified by H.225.0 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 2250 version(0) 4
19、and H.245 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 245 version(0) x, where “x“ is 7 or higher. ii Rec. ITU-T H.323 (12/2009) Products claiming compliance with Version 5 of H.323 shall comply with all of the mandatory requirements of this Recommendation, H.323 (2003)
20、, which references Rec. ITU-T H.225.0 (2003) and Rec. ITU-T H.245 (02/2003 or later). Version 5 products shall be identified by H.225.0 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 2250 version(0) 5 and H.245 messages containing a protocolIdentifier = itu-t(0) recommend
21、ation(0) h(8) 245 version(0) x, where “x“ is 9 or higher. Products claiming compliance with Version 6 of H.323 shall comply with all of the mandatory requirements of this Recommendation, H.323 (2006), which references Rec. ITU-T H.225.0 (2006) and Rec. ITU-T H.245 (05/2006 or later). Version 6 produ
22、cts shall be identified by H.225.0 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 2250 version(0) 6 and H.245 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 245 version(0) x, where “x“ is 13 or higher. Products claiming compliance with Version
23、7 of H.323 shall comply with all of the mandatory requirements of this Recommendation, H.323 (2009), which references Rec. ITU-T H.225.0 (2009) and Rec. ITU-T H.245 (2009 or later). Version 7 products shall be identified by H.225.0 messages containing a protocolIdentifier = itu-t(0) recommendation(0
24、) h(8) 2250 version(0) 7 and H.245 messages containing a protocolIdentifier = itu-t(0) recommendation(0) h(8) 245 version(0) x, where “x“ is 15 or higher. In addition to many minor corrections and clarifications, this version of Rec. ITU-T H.323 incorporates a new facility which signals support for
25、reception of multicast media from a single transmitter (clause 8.3.3), a new Annex M5 for the transport of ITU-T X.1303 common alerting protocol (CAP 1.1) messages, and a new clause 8.4.3.9 for the transmission of a conference list to an H.323 terminal for use in a subsequent call. Information secti
26、ons previously in Annex R have been moved to a new Appendix VII (informative notes on robustness methods for H.323 entities). History Edition Recommendation Approval Study Group 1.0 ITU-T H.323 1996-11-11 16 2.0 ITU-T H.323 1998-02-06 16 2.1 ITU-T H.323 Annex D 1998-09-25 16 2.2 ITU-T H.323 Annex E
27、1999-05-27 16 2.3 ITU-T H.323 Annex F 1999-05-27 16 3.0 ITU-T H.323 1999-09-30 16 3.1 ITU-T H.323 Annex G 2000-02-17 16 4.0 ITU-T H.323 2000-11-17 16 4.1 ITU-T H.323 Annex M3 2001-07-29 16 4.2 ITU-T H.323 Annex Q 2001-07-29 16 4.3 ITU-T H.323 Annex R 2001-07-29 16 4.4 ITU-T H.323 Annex P 2003-01-13
28、16 5.0 ITU-T H.323 2003-07-14 16 5.1 ITU-T H.323 (2003) Amend. 1 2005-01-08 16 5.2 ITU-T H.323 (2003) Amend. 2 2005-01-13 16 6.0 ITU-T H.323 2006-06-13 16 7.0 ITU-T H.323 v7 2009-12-14 16 Rec. ITU-T H.323 (12/2009) iii FOREWORD The International Telecommunication Union (ITU) is the United Nations sp
29、ecialized 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 the
30、m 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
31、 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 collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used
32、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 Re
33、commendation 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
34、 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 Proper
35、ty 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, implemen
36、ters 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 reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written p
37、ermission of ITU. iv Rec. ITU-T H.323 (12/2009) CONTENTS Page 1 Scope 1 2 References. 2 3 Definitions 5 4 Symbols and abbreviations . 10 5 Conventions 14 6 System description 14 6.1 Information streams 14 6.2 Terminal characteristics 15 6.3 Gateway characteristics 28 6.4 Gatekeeper characteristics 4
38、3 6.5 Multipoint controller characteristics . 45 6.6 Multipoint processor characteristics . 46 6.7 Multipoint control unit characteristics 47 6.8 Multipoint capability 47 6.9 Models for supplementary services 49 7 Call signalling . 50 7.1 Addresses 51 7.2 Registration, Admission and Status (RAS) cha
39、nnel . 52 7.3 Call signalling channel . 66 7.4 Call reference value 70 7.5 Call ID 71 7.6 Conference ID and conference goal . 71 7.7 Endpoint call capacity 71 7.8 Caller identification services 72 7.9 Generic extensible framework 78 8 Call signalling procedures 81 8.1 Phase A Call setup . 81 8.2 Pha
40、se B Initial communication and capability exchange 103 8.3 Phase C Establishment of audiovisual communication . 108 8.4 Phase D Call services 111 8.5 Phase E Call termination . 126 8.6 Protocol failure handling 129 9 Interoperation with other terminal types 130 9.1 Speech-only terminals 130 9.2 Visu
41、al telephone terminals over the ISDN (Rec. ITU-T H.320) 130 9.3 Visual telephone terminals over GSTN (Rec. ITU-T H.324) 131 Rec. ITU-T H.323 (12/2009) v Page 9.4 Visual telephone terminals over mobile radio (Annex C/H.324, a.k.a. “H.324/M“) . 131 9.5 Visual telephone terminals over ATM (H.321 and H.
42、310 RAST) . 131 9.6 Visual telephone terminals over guaranteed quality of service LANs (Rec. ITU-T H.322) 131 9.7 Simultaneous voice and data terminals over GSTN (Rec. ITU-T V.70) 132 9.8 T.120 terminals on the packet-based network 132 9.9 Gateway for H.323 media transport over ATM . 132 10 Optional
43、 enhancements . 132 10.1 Encryption 132 10.2 Multipoint operation . 132 10.3 Call Linkage in H.323 133 10.4 Tunnelling of non-H.323 signalling messages . 136 10.5 Use of RTP payload for DTMF digits, telephony tones and telephony signals . 138 11 Maintenance 139 11.1 Loopbacks for maintenance purpose
44、s 139 11.2 Monitoring methods . 140 Annex A H.245 messages used by H.323 endpoints 141 Annex B Procedures for layered video codecs . 146 B.1 Scope 146 B.2 Introduction 146 B.3 Scalability methods 146 B.4 Call establishment 146 B.5 Use of RTP sessions and codec layers . 146 B.6 Possible layering mode
45、ls 148 B.7 Impact on multipoint conferences 149 B.8 Use of network QoS for layered video streams 151 Annex C H.323 on ATM 152 C.1 Introduction 152 C.2 Scope 152 C.3 Architecture 152 C.4 Protocol section 157 Annex D Real-time facsimile over H.323 systems . 162 D.1 Introduction 162 D.2 Scope 163 D.3 P
46、rocedures for opening channels to send T.38 packets 163 D.4 Non-fast connect procedures 166 D.5 Replacing an existing audio stream with a T.38 fax stream . 168 vi Rec. ITU-T H.323 (12/2009) Page D.6 Usage of the maxBitRate/bandWidth in messages . 172 D.7 Interactions with gateways and T.38/Annex B d
47、evices 172 Annex E Framework and wire-protocol for multiplexed call signalling transport . 173 E.1 Scope 173 E.2 H.225.0 call signalling over UDP . 184 Annex F Simple endpoint types 188 F.1 Introduction 188 F.2 Specification conventions . 188 F.3 Scope 189 F.4 Normative references 190 F.5 Abbreviati
48、ons . 190 F.6 Simple (Audio) Endpoint Type System functionality overview . 190 F.7 Procedures for Simple Endpoint Types 191 F.8 Security extensions . 198 F.9 Interoperability considerations . 198 F.10 Implementation notes (Informative) . 198 Annex G Text conversation and Text SET . 202 G.1 Introduct
49、ion 202 G.2 Scope 202 G.3 References 203 G.4 Definitions 203 G.5 Capability Advertisement for Text in H.323 203 G.6 Procedures for opening channels for T.140 text conversation . 205 G.7 Framing and buffering of T.140 data . 206 G.8 Interaction with text conversation facilities in other devices . 207 G.9 Multipoint considerations . 208 G.10 Text SET: Text Conversation Simple Endpoint Type 209 Annex J Security for Annex F . 211 J.1 Introduction 2
