1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T H.460.27 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2015) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services Supplementary services for multimedia End-to-end session identifier for
2、ITU-T H.323 systems Recommendation ITU-T H.460.27 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 aspect
3、s 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 of service architecture
4、for audiovisual and multimedia services H.360H.369 Telepresence H.420H.429 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 VDSL H.610H.619 Advanced multimedia services and applications H.620H.629 Ubiquitous sensor network applications and Internet of Things H.640H.649 IPTV MULTIMEDIA SERVI
7、CES AND APPLICATIONS FOR IPTV General aspects H.700H.719 IPTV terminal devices H.720H.729 IPTV middleware H.730H.739 IPTV 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 Digital Signa
8、ge H.780H.789 E-HEALTH MULTIMEDIA SERVICES AND APPLICATIONS Personal health systems H.810H.819 Interoperability compliance testing of personal health systems (HRN, PAN, LAN, TAN and WAN) H.820H.859 Multimedia e-health data exchange services H.860H.869 For further details, please refer to the list of
9、 ITU-T Recommendations. Rec. ITU-T H.460.27 (11/2015) i Recommendation ITU-T H.460.27 End-to-end session identifier for ITU-T H.323 systems Summary Recommendation ITU-T H.460.27 describes an end-to-end session identifier for use in IP-based multimedia communication systems that enables endpoints, in
10、termediate devices and management systems to identify a session end-to-end, to associate multiple endpoints with a given multipoint conference, to track communication sessions when they are redirected and to associate one or more media flows with a given communication session. History Edition Recomm
11、endation Approval Study Group Unique ID* 1.0 ITU-T H.460.27 2015-11-29 16 11.1002/1000/12457 * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en
12、. ii Rec. ITU-T H.460.27 (11/2015) 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
13、 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 topic
14、s 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-Ts purview, the necessary standards are prepa
15、red 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
16、 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 ex
17、press requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Pro
18、perty 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 in
19、tellectual 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 2016 All
20、rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T H.460.27 (11/2015) iii 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 Recommen
21、dation . 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 Overview . 2 7 Identifying a communication session . 3 8 Session ID components . 3 9 Conveying the session ID . 3 10 Endpoint behaviour . 4 11 Processing by intermediaries 5 12 Multipoint control unit behaviour . 6 Bibliography. 8 Rec. ITU-
22、T H.460.27 (11/2015) 1 Recommendation ITU-T H.460.27 End-to-end session identifier for ITU-T H.323 systems 1 Scope This Recommendation defines the end-to-end session identifier (session ID), signalling syntax and procedures for using the identifier within ITU-T H.323 systems, including endpoints, mu
23、ltipoint control units and Gatekeepers. 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
24、 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. Th
25、e reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T H.225.0 Recommendation ITU-T H.225.0 (2009), Call signalling protocols and media stream packetization for packet-based multimedia communication systems. ITU-T H.323
26、 Recommendation ITU-T H.323 (2009), Packet-based multimedia communications systems. ITU-T H.460.1 Recommendation ITU-T H.460.1 (2013), Guidelines for the use of the generic extensible framework. IETF RFC 3261 IETF RFC 3261 (2002), SIP: Session Initiation Protocol. IETF RFC 4122 IETF RFC 4122 (2005),
27、 A Universally Unique IDentifier (UUID) URN Namespace. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 call ITU-T H.323: Point-to-point multimedia communication between two ITU-T H.323 endpoints. The call begins with the call set-up pro
28、cedure and ends with the call termination procedure. The call consists of the collection of reliable and unreliable channels between the endpoints. A call may be directly between two endpoints or may include other ITU-T H.323 entities such as a Gatekeeper or an MCU. In case of interworking with some
29、 SCN endpoints via a Gateway, all the channels terminate at the Gateway where they are converted to the appropriate representation for the SCN end system. Typically, a call is between two users for the purpose of communication, but may include signalling-only calls. An endpoint may be capable of sup
30、porting multiple simultaneous calls. 3.1.2 call identifier ITU-T H.323: A globally unique non-zero value created by the calling endpoint and passed in various ITU-T H.225.0 messages. 3.1.3 global call identification ITU-T H.323: A value assigned to an end-to-end call to uniquely identify that call f
31、rom end-to-end. 2 Rec. ITU-T H.460.27 (11/2015) 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 communication session: A communication session, or simply session, refers to a call or series of calls initiated or received by an endpoint for which the en
32、dpoint utilizes the same universally unique identifier (UUID) value in call signalling messages. From a calling users perspective, this would be all call signalling messages from the time the user initiates a call until the time the call is terminated. From the called users perspective, this would b
33、e all call signalling messages from first message received by the users terminal until the call is terminated. 3.2.2 Session Identifier: (Also referred to as a Session ID) A globally unique identifier used to identify a session from the point of origin, passing through any number of intermediaries,
34、to the ultimate point of termination. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: GEF Generic Extensible Framework IP Internet Protocol MAC Media Access Control MCU Multipoint Control Unit SCN Switched Circuit Network SIP Session Initiation Protoco
35、l UUID Universally Unique Identifier 5 Conventions None. 6 Overview The Session Identifier (Session ID) identifies a communication session from the point of origin, passing through any number of intermediaries, to the ultimate point of termination. The primary motivation for introducing the Session
36、ID into ITU-T H.323 ITU-T H.323 systems is to assist with troubleshooting network deployments. This includes the ability for network administrators to look at log files on a plurality of devices as well as to make use of a common or related set of identifiers conveyed in signalling messages. However
37、, the Session ID might be used for other purposes, including correlating participants in a multipoint conference, especially one that involves participants using a mixture of ITU-T H.323 and session initiation protocol (SIP) IETF RFC 3261 devices, or an association of call signalling messages and me
38、dia flows. This Recommendation does not prescribe how entities might use the Session ID. Rather, this Recommendation merely describes the syntax and signalling procedures. It should be appreciated that, while ITU-T H.323 defines the concept of a call, which begins with the call setup procedure and e
39、nds with the termination procedure, the users perception of a call and what ITU-T H.323 defines as a call are not the same. When a user initiates a call, a globally unique identifier, referred to as the call identifier, is assigned to that call. If the call is transferred or forwarded, the endpoint
40、will initiate a new call and assign a new identifier. While this is intended behaviour, from the users perspective this is a single call. Likewise, any network administrator trying to troubleshoot a network will also view the subsequent call as part of the same overall communication session. Rec. IT
41、U-T H.460.27 (11/2015) 3 As it is desirable to be able to associate related calls, ITU-T H.323 introduced the notion of call linkage (see clause 10.3 of ITU-T H.323). This concept is useful in allowing intermediaries, management systems, or other entities to know that a call is in some way related t
42、o a different call. However, due to complex service interaction, it is possible that the global call identifier is fully replaced, thus making it challenging to see a complete call history. The Session ID aims to solve the problem of identification of a session end-to-end. The syntax and procedures
43、are also defined so that they are compatible with SIP systems (see b-IETF RFC SIP). 7 Identifying a communication session A session is identified using two universally unique identifier (UUID) values, with each endpoint in a session allocating one of the UUID values. In the interest of brevity, the
44、set of values is written in a set notation such as A, B, where A refers to the UUID allocated by one endpoint and B refers to the UUID allocated by the second endpoint. While directionality information is associated with the conveyance of the Session ID in signalling messages, the Session ID itself
45、does not indicate whether A or B is the sender or recipient of a message. The reason for using two distinct UUID values to identify a communication session is to effectively deal with various complex service interactions and allow for associating one call with another call during such service intera
46、ctions. As a simple example, if endpoint Alice“ calls endpoint “Bob“, Alice will allocate a UUID “A“ for that call. Likewise, Bob will allocate a UUID “B“. The Session ID for the call between Alice and Bob is A, B. If Bob transfers that call to Carol, the call between Alice and Bob is terminated. Fr
47、om the users perspective, however, the call is merely transferred. Indeed, the “Alice“ endpoint will initiate a new call (using a new call ID) to Carol. However, the UUID allocated for the Session ID will remain the same. Carol will allocate a UUID for her contribution to the Session ID. The Session
48、 ID between Alice and Carol is, therefore, A, C. It is important to note that, while the Session ID will change during service interactions, the UUID contributed by an endpoint in a call will remain fixed. In the above example, the value “A“ is used in both the calls between Alice and Bob and betwee
49、n Alice and Carol. This property allows a network operator to immediately recognize that these two calls are part of the same communication session, with Alice and Bob being the first two endpoints in that session and Alice and Carol being the second two endpoints in that session. Observation of signalling messages would show that these calls ran serially. 8 Session ID components Each endpoint creates a UUID (see IETF RFC 4122) for insertion into signalling messages. The version
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