1、 International Telecommunication Union ITU-T H.450.2TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2011) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Supplementary services for multimedia Call transfer supplementary service for ITU-T H.323 systems Recommend
2、ation ITU-T H.450.2 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 pro
3、cedures 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 for audiovisual and multimedia
4、 services H.360H.369 Supplementary services for multimedia H.450H.499MOBILITY 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 applica
5、tions 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, TR
6、IPLE-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 applic
7、ation 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.450.2 (05/2011) i Recommendation ITU-T H.450.2 Call tran
8、sfer supplementary service for ITU-T H.323 systems Summary Recommendation ITU-T H.450.2 describes the procedures and the signalling protocol for the call transfer supplementary service (SS-CT) in ITU-T H.323 (packet-based multimedia communications systems) networks. SS-CT is a supplementary service
9、which enables the served user A to transform an existing call (user A-user B) into a new call between user B and a user C selected by user A. User A may or may not have a call established with user C prior to call transfer. This Recommendation makes use of the “Generic functional protocol for the su
10、pport of supplementary services in ITU-T H.323 systems“ as defined in Recommendation ITU-T H.450.1 The procedures and the signalling protocol of this Recommendation are derived from the call transfer supplementary service specified in ISO/IEC 13865 and ISO/IEC 13869. This revision corrects errors di
11、scovered in the initial publication. History Edition Recommendation Approval Study Group 1.0 ITU-T H.450.2 1998-02-06 16 2.0 ITU-T H.450.2 2011-05-14 16 ii Rec. ITU-T H.450.2 (05/2011) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of t
12、elecommunications, 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 tel
13、ecommunications 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
14、 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 for conciseness to indicate both a
15、 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
16、 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 RIG
17、HTS 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 IT
18、U 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
19、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 2012 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T
20、H.450.2 (05/2011) 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 Recommendation . 2 4 Abbreviations and acronyms 2 5 Description 2 6 Messages and information elements . 3 7 Actions at the transferring endpoint (user A) . 3
21、 7.1 Normal procedures if only the primary call exists . 4 7.2 Normal procedures if also the secondary call exists 4 7.3 Exceptional procedures 4 8 Actions at the transferred endpoint (user B) . 4 8.1 Normal procedures . 4 8.2 Exceptional procedures 5 9 Actions at the transferred-to endpoint (user C
22、) 5 9.1 Normal procedures . 5 9.2 Exceptional procedures 6 10 Additional procedures . 6 10.1 Interworking with non-ITU-T H.323 terminals 6 10.2 Hold and consultation . 6 10.3 Transfer without rerouting (i.e., transfer by join) . 6 10.4 Further actions at transferred and transferred-to endpoints 7 10
23、.5 Interactions with ITU-T H.323 ad hoc conference . 7 10.6 Gatekeeper actions 7 10.7 Interactions with ITU-T H.225.0 parameters . 9 11 Dynamic description of transfer with rerouting 10 11.1 Transfer with rerouting without secondary call 10 11.2 Transfer with secondary call 12 11.3 Communication bet
24、ween transferring signalling entity TRGSE and TRGSE user 18 11.4 Communication between transferred signalling entity TRDSE and TRDSE user 19 11.5 Communication between transferred-to signalling entity TRTSE and TRTSE user 21 11.6 Peer-to-peer communication for transfer with rerouting 22 12 Operation
25、s in support of SS-CT . 28 iv Rec. ITU-T H.450.2 (05/2011) Page 13 Specification and description language (SDL) diagrams . 32 13.1 Call transfer block diagram 32 13.2 Call transfer substructure diagram 32 13.3 Transferring signalling entity SDLs . 34 13.4 Transferred signalling entity SDLs 37 13.5 T
26、ransferred-to signalling entity SDLs 40 Rec. ITU-T H.450.2 (05/2011) 1 Recommendation ITU-T H.450.2 Call transfer supplementary service for ITU-T H.323 systems 1 Scope This Recommendation describes the call transfer supplementary service (SS-CT), which is applicable to various basic services support
27、ed by ITU-T H.323 multimedia endpoints. SS-CT is based on the equivalent supplementary service for private integrated services networks (PISN) specified in ISO/IEC 13865 and ISO/IEC 13869. 2 References The following ITU-T Recommendations and other references contain provisions which, through referen
28、ce 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 re
29、cent 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.225.0 Recomme
30、ndation ITU-T H.225.0 (2009), Call signalling protocols and media stream packetization for packet-based multimedia communication systems. ITU-T H.245 Recommendation ITU-T H.245 (2009), Control protocol for multimedia communication. ITU-T H.323 Recommendation ITU-T H.323 (2009), Packet-based multimed
31、ia communications systems. ITU-T H.450.1 Recommendation ITU-T H.450.1 (2011), Generic functional protocol for the support of supplementary services in ITU-T H.323 systems. ITU-T I.112 Recommendation ITU-T I.112 (1993), Vocabulary of terms for ISDNs. ITU-T I.210 Recommendation ITU-T I.210 (1993), Pri
32、nciples of telecommunication services supported by an ISDN and the means to describe them. ITU-T Y.2201 Recommendation ITU-T Y.2201 (2009), Requirements and capabilities for ITU-T NGN. ISO/IEC 13865 ISO/IEC 13865:2003, Information technology Telecommunications and information exchange between system
33、s Private Integrated Services Network Specification, functional model and information flows Call Transfer supplementary service. ISO/IEC 13869 ISO/IEC 13869:2003, Information technology Telecommunications and information exchange between systems Private Integrated Services Network Inter-exchange sig
34、nalling protocol Call Transfer supplementary service. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 endpoint: ITU-T H.323. 3.1.2 terminal: ITU-T H.323. 2 Rec. ITU-T H.450.2 (05/2011) 3.1.3 user: ITU-T Y.2201. 3.2 Terms defined in this
35、 Recommendation This Recommendation defines the following terms: 3.2.1 primary call: Call between the transferring user A and the transferred user B. 3.2.2 secondary call: Call between the transferring user A and the transferred-to user C associated with the primary call (this association is an impl
36、ementation matter within endpoint A). 3.2.3 transferred call: Call between transferred user B and transferred-to user C which results from successful completion of call transfer. 3.2.4 transferring endpoint; user A: User/endpoint transferring a call with a terminal B, to a user C. 3.2.5 transferred
37、endpoint; user B: The remote endpoint/user of the call with user A which is transferred by user A to a user C. 3.2.6 transferred-to endpoint; user C: The endpoint/user, to which a user B, originally having a call to user A, is transferred. 4 Abbreviations and acronyms This Recommendation uses the fo
38、llowing abbreviations: APDU Application Protocol Data Unit ASN.1 Abstract Syntax Notation One CT Call Transfer GK/GKp/GKs Gatekeeper/Gatekeeper on primary call/Gatekeeper on secondary call MC Multipoint Controller MM MultiMedia NFE Network Facility Extension PISN Private Integrated Services Network
39、SCN Switched Circuit Network SDL Specification and Description Language SS-CT Supplementary Service Call Transfer TRDSE Transferred Signalling Entity TRGSE Transferring Signalling Entity TRTSE Transferred-to Signalling Entity 5 Description Call transfer (SS-CT) is a supplementary service which enabl
40、es the served user (user A or transferring user) to transform an existing call with user B (primary call) into a new call between user B and a user C (transferred-to user) selected by user A. User A may or may not have a call established with user C (secondary call) prior to transfer. Each call can
41、either be an incoming call to user A or an outgoing call from user A. On successful completion of SS-CT, user B and user C can communicate with each other and user A will no longer be able to communicate with user B or user C. Rec. ITU-T H.450.2 (05/2011) 3 The initial call between user A and user B
42、 (primary call) must be answered before transfer can be initiated. On invocation of call transfer, if a call between user A and user C exists (secondary call), the transferred-to endpoint is informed of the pending call transfer, and transfer only proceeds if this endpoint is able to participate. In
43、 this case, the transferred-to endpoint returns a temporary identifier to be used in the subsequent transfer procedure to identify the secondary call. The transferring endpoint (user A) requests the transferred endpoint (user B) to call the transferred-to endpoint (user C). The transferred endpoint
44、then establishes a call to the transferred-to endpoint (transfer by rerouting) and includes the temporary identifier for the secondary call if this call exists. User Bs gatekeeper may establish the call if it is handling the call transfer. The primary call is retained until the first acknowledgment
45、has been received from the transferred-to endpoint (user C), and is then released. This means that the primary call remains in place if call transfer fails before that stage. If the secondary call exists, it is retained until the new call request arrives at the transferred-to endpoint and is then re
46、leased. Upon answer from user C (if no secondary call exists) or successful association of user C with the new call (if user C was already involved in the secondary call), user B and user C can communicate with each other. The media exchange capabilities of the new call should be equal to those of t
47、he primary call as far as possible. If call transfer fails after the primary call was released, the action taken is for further study. NOTE Use of call transfer supplementary service for transferring only a subset of ITU-T H.323 media streams or for transferring ITU-T T.120 calls is for further stud
48、y. 6 Messages and information elements The APDUs of call transfer operations are transported within user-to-user information elements in call control and FACILITY messages as defined in ITU-T H.450.1. The call transfer operations are described in clause 12. When conveying the invoke APDU of the oper
49、ations defined in clause 12, the destinationEntity data element of the network facility extension (NFE) shall contain the value “endpoint“. When conveying the invoke APDU of operations callTransferAbandon, callTransferUpdate, callTransferComplete, callTransferActive and subaddressTransfer, the Interpretation APDU shall contain value discardAnyUnrecognizedInvokePdu. When conveying the invoke APDU of operation callTransferSetup, the Interpretation APDU shall contain value clearCallIfAnyInvoke
