1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD IZATI ON SECTOR OF ITU H.450.10 (031200 1 ) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Supplementary services for multimedia Call offering supplementary services for H.323 ITU-T Recommendation H.450.1 O (Formerly CCIlT Recomme
2、ndation) ITU-T H-SERTES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS INFRASTRUCTURE OF AUDIOVISUAL SERVICES General Transmission multiplexing and synchronization Systems aspects Communication procedures Coding of moving video Related systems aspects
3、UPPLEMEPfARY S SYSTEMS AND TERMINAL EQUIPMENT FOR AUDIOVISUAL SERVICES H.100-H.199 H.200-H.2 19 H.220-H.229 H.230-H.239 H.240-H.259 H.260-H.279 H.280-H.299 H.300-H.399 For further details, please rejr to the list of ITU-T Recommendations. ITU-T Recommendation H.450.10 Call offering supplementary ser
4、vices for H.323 Summary This Recommendation describes the procedures and the signalling protocol for the Call Offering supplementary service in H.323 (Packet Based Multimedia Communications Systems) networks. The Call Offer supplementary service (SS-CO) enables a calling user A, encountering a busy
5、destination user B, to “camp-on“ to the busy user. This means that the call is indicated to user B and kept in a waiting state until user B reacts to the indication, rather than being released due to the busy condi tion. This Recommendation makes use of the “Generic functional protocol for the suppo
6、rt of supplementary services in H.323“ as defined in ITU-T H.450.1. The support of ITU-T H.450.6 Call Waiting Supplementary Service for H.323 is required for ss-CO. This Recommendation requires H.323 version 2 (1998) or later. Version 2 products can be identified by H.225.0 messages containing a pro
7、tocolIdentifier = (itu-t (O) recommendation (O) h (8) 2250 version (O) 2) and H.245 messages containing a protocolIdentifer = itu-t (O) recommendation (O) h (8) 245 version (O) x, where “x“ is 3 or higher. The procedures and the signalling protocol of this Recommendation are derived from the Call Of
8、fering supplementary service specified in ISOAEC 14841 and ISOEC 14843. Source ITU-T Recommendation H.450.10 was prepared by ITU-T Study Group 16 (2001-2004) and approved under the WTSA Resolution 1 procedure on 1 March 2001. ITU-T H.450.10 (03/2001) 1 FOREWORD The International Telecommunication Un
9、ion (J33.J) 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 t
10、o standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the IT-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations
11、 is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within IT-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness t
12、o indicate both a telecommunication administration and a recognized operating agency. INTELLECTUfi PROPERTY RIGHTS IT 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 conc
13、erning 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 p
14、atents, which may be required to implement this Recommendation. However, Mplementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. o ITU 2001 All rights reserved. No part of this publication may be reproduced or
15、utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from IT. ITU-T H.450.10 (03/2001) 11 CONTENTS 1 2 3 4 5 5.1 5.2 5.3 6 7 7.1 Scope . References . Terms and Detions Abbreviations and Acronyms . SS-CO Service Descriptio
16、n Normal Procedures . 5.1 . 1 Activation/deactivation/registration/interrogation . 5.1.2 Invocation and operation . Exceptional Procedures . Interactions with other supplementary services 5.3.1 5.3.2 5.3.3 5.3.4 5.3.5 5.3.6 5.3.7 5.3.8 5.3.9 5.3.10 5.3.1 1 5.3.12 5.3.13 Call Transfer (SS-CT) . Call
17、Forwarding Busy (SS-CFB) . Call Hold Call Forwarding Unconditional (SS-CFU) Call Forwarding No Reply (SS-CFNR)/Call Deflection (SS-CD) Call ParkCall Pickup Message Waiting Indication Call Waiting (SS-CW) . Name Presentation . Completion of Calls to Busy Subscriber (SS-CCBS) Completion of Calls on No
18、 Reply (SS-CCNR) . Call Intrusion (SS-CI) Call Linkage Messages and information elements . Signalling Procedures . Actions at User As Endpoint 7.1.1 Normal procedures 7.1.2 Exceptional procedures Actions at User Bs Endpoint 7.2.1 Normal procedures 7.2.2 Exceptional procedures 7.2 8 Interworking and
19、Interactions . 8.1 Interworking with SCN . 8.2 Protocol interaction between SS-CO and other Supplementary Services ITU-T H.450.10 (03/2001) 1 1 1 2 3 3 3 3 4 4 4 4 5 5 5 5 5 5 5 5 5 5 6 6 iii 9 9.1 9.2 10 10.1 10.2 10.3 10.4 10.5 iv 8.2.1 8.2.2 8.2.3 8.2.4 8.2.5 8.2.6 8.2.7 8.2.8 8.2.9 8.2.10 8.2.11
20、 8.2.12 Call Transfer (SS-CT) . Call Forwarding Unconditional (SS-Cmr) Call Forwarding Busy (SS.CFB) . Call Forwarding on No Reply (SS-CFNR)/Call Deflection (SS-CD) . Call Hold Call ParkKall Pickup Call Waiting . Message Waiting Indication Name Presentation . Completion of Calls on Busy Subscriber (
21、SS-CCBS)/on No Reply (SS- CCNR) . Call Intrusion . Call Linkage GatekeeperFroxy Actions Gatekeeper passes on SS-CO operations to the endpoint . Gatekeepedproxy acts on behalf of si11 endpoint Gatekeepedproxy acts on behalf of endpoint A 9.2.1 9.2.2 Gatekeepedproxy acts on behalf of endpoint B Dynami
22、c Description Signalling Flows . Operational Model 10.2.1 Successful SS-CO 10.2.2 SS-CO invocation - unsuccessful 10.2.3 10.2.4 10.2.5 Successful SS-CO with GK acting on SS-CO . Communication between an endpoint A signalling entity (EASE) and its SS-CO invocation with user B not being busy Successfu
23、l SS-CO with GIS being transparent for SS-CO signalling . Signalling entity user (informative) 10.3.1 Table of pmtwes . 10.3.2 Primitive dehtion 10.3.3 Parameter Definition Communication between an endpoint B signalling entity (EBSE) and its signalling entity user (informative) . 10.4.1 Table of pmt
24、ives . 10.4.2 Primitive definition 10.4.3 Parameter Dehtion Call states 10.5.1 10.5.2 . . . Call States at endpoint A . Call States at endpoint B . ITU-T H.450.10 (03/2001) Page 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 9 10 10 10 10 11 11 12 13 13 14 15 15 15 15 16 16 16 16 16 16 Page 10.6 Timers . 16 11 Opera
25、tions in support of Call Offer supplementary service . 17 12 Specification and Description Language (SDL) Diagrams for SS-CO 18 12.1 Behaviour of user As endpoint. 19 12.2 Behaviour of user Bs endpoint . 19 ITU-T H.450.10 (03/2001) V ITU-T Recommendation H.450.10 Cali offering supplementary services
26、 for H.323 1 Scope This Recommendation specifies the Call Offer supplementary service (SS-CO), which is applicable to various basic services supported by H.323 multimedia endpoints. Ca1 Offer (SS-CO) is a supplementary service which, on request fkom the calling user (or on that users behalf), enable
27、s a call to be offered to a busy called user and to wait for that called user to accept this call. The service description, the procedures and the signalling protocol of this Recommendation are derived fiom the Call Offer supplementary service as specified in ISOIEC 14841 and 14843. The support of I
28、TU-T H.450.6, Call Waiting Supplementary Service for H.323 is required for SS-CO. 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 ind
29、icated 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
30、Recommendations is regularly published. - ITU-T H.225 .O (2000), Call signalling protocols and media stream packetization for packet-based multimedia communication systems. ITU-T H.245 (2000), Control protocol for multimedia communication. ITU-T H.248 (2000), Gateway control protocol. ITU-T H.323 (2
31、000), Packet-based multimedia communications systems. ITU-T H.450.1 (1 998), Generic functional protocol for the support of supplementary services in H.323. ITU-T H.450.2 (1998), Call transfer supplementary service for H.323. ITU-T H.450.3 (1998), Call diversion supplementary service for H.323. ITU-
32、T H.450.6 (1999), Call waiting supplementary service for H.323. ITU-T H.450.11(2001), Call intrusion supplementary services. - - - - - - - - 3 Terms and Definitions This Recommendation defines the following terms: 3.1 automatic Cali offer invocation timer: A timer governing the time after which SS-C
33、O is automatically invoked after the calling user has been informed that a call has failed because of busy at the destination. The duration of the timer is an implementation option. 3.2 busy, busy condition: A condition where a destination endpoint engaged in one or more calls cannot accept another
34、incoming call due to resource limitations. ITU-T H.450.10 (03/2001) 1 NOTE - In the absence of any supplementary services that might modia the behaviour, the endpoint will, in this situation, send a Release Complete message containing a ReleaseCompleteReason of inConf or a Cause IE with cause value
35、#17, “user busy“; an H.323 endpoint may be busy with one call or may be busy with more than one call depending on implementation. 3.3 3.4 opportunity to accept or reject the call. NOTE - Acceptance requires that resources will be freed first. 3.5 camp-on tone: A special tone or announcement provided
36、 to the calling user A while the call is offered to the busy user B. 3.6 consultation timer: A timer governing the time in which the calling user is allowed to request invocation of SS-CO after being informed that a call has failed because of busy at the destination. The duration of the timer is an
37、implementation option. 3.7 endpoint; gatekeeper; gateway; terminal; user: See ITU-T H.323. Designations “A“ or “BI refer to user As or user Bs side, respectively (see definitions of user Nuser B below). 3.8 free: A property of a user who can accept an attempt to present a call to that user (Le. allo
38、w the call to reach the alerting or answered state). 3.9 proxy: An entity that acts on behalf of an endpoint for the SS-CO procedures. The proxy may or may not be Co-located with the gatekeeper. 3.10 offered call: A call that is in a waiting condition as a result of invocation of SS-CO against a bus
39、y called user. 3.11 user A: The calling user, also the served user of SS-CO. 3.12 user B: The (busy) called user against whom SS-CO is invoked. call: Refer to Recommendation H.323. camp-on: The indication of an incoming call to a busy called user, giving this user the 4 Abbreviations and Acronyms Th
40、is Recommendation uses the following abbreviations: APDU Application Protocol Data Unit ASN. 1 Abstract Syntax Notation One EASE Endpoint A Signalling Entity EBSE Endpoint B Signalling Entity GK Gatekeeper IE Information Element MGC Media Gateway Controller NFE Network Facility Extension SCN Switche
41、d Circuit Network SDL Specification and Description Language SS-CO Supplementary Service - Call Offering 2 ITU-T H.450.10 (03/2001) 5 SS-CO Senice Description SS-CO is a supplementary service which, on request from the calling user (or on that users behalf), enables a call to be offered to a busy ca
42、lled user and to wait for that called user to accept the call, after the necessary resources have become available. The busy called user is given an indication of the offered call. During the time that the call is offered, the called user may either: - - ignore the offered call; or may attempt to ma
43、ke the necessary resources available (e.g. by releasing or placing on hold another call). After the necessary resources become available at the called user, the call shall be completed as a normal incoming call. 5.1 Normal Procedures 5.1.1 Activation/deactivation/registration/interrogation SS-CO is
44、permanently activated. Registration and interrogation are not applicable. 5.1.2 Invocation and operation There are four different methods of invoking SS-CO. An H.323 endpointlentity complying to this Recommendation shall offer one or more of these methods as follows: 1) Delayed user invocation: the
45、calling user, on being informed that a call has failed because of busy at the destination, shall be able, within a defined time period (consultation timer) to request invocation of SS-CO. If SS-CO is invoked, a call with the same characteristics as the failed call will be set up on behalf of the cal
46、ling user. Immediate user invocation: the calling user shaII be able to request invocation of SS-CO as part of the initial call Set-up. Delayed automatic invocation: the calling endpoint or a proxy acting on behalf of it, having informed the calling user that a call has failed because of busy at the
47、 destination, shall automatically invoke SS-CO unless the calling user initiates call clearing within a defined time period (automatic call offer invocation timer). If SS-CO is invoked, a call with the same characteristics as the failed call will be set up on behalf of the calling user. Immediate au
48、tomatic invocation: the calling endpoint or a proxy acting on behalf of it shall automatically invoke SS-CO whenever the calling user makes a call to a user that is busy, if required by the service profile of the calling user. NOTE 1 - If method 4 (immediate automatic invocation) is provided to a us
49、er, methods 1,2 and 3 will not be available to that user. If the calling user is provided with both methods 1 and 3 (delayed user invocation and delayed automatic invocation), the calling user shall be able to request SS-CO during the period of the automatic call offer invocation timer. If, at the time of expiry of the automatic call offer invocation timer, the calling user has not requested SS-CO and has not initiated call clearing, the calling endpoint or a proxy that acts on behalf of the calling endpoint shall automatically invoke SS-CO. On successful invocation of
