1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T H.450.9 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2000) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Supplementary services for multimedia Call completion supplementary services for H.323 ITU-T Recommendation H.450.9 (Formerly CCITT Recommendati
2、on) 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 procedures H.240H.2
3、59 Coding of moving video H.260H.279 Related systems aspects H.280H.299 SYSTEMS AND TERMINAL EQUIPMENT FOR AUDIOVISUAL SERVICES H.300H.399 SUPPLEMENTARY SERVICES FOR MULTIMEDIA H.450H.499 For further details, please refer to the list of ITU-T Recommendations. ITU-T H.450.9 (11/2000) i ITU-T Recommen
4、dation H.450.9 Call completion supplementary services for H.323 Summary This new Recommendation describes the procedures and the signalling protocol for the Call Completion supplementary services in ITU-T H.323. The Call Completion supplementary services are Completion of Calls to Busy Subscribers (
5、SS-CCBS) and Completion of Calls on No Reply (SS-CCNR). SS-CCBS enables a calling User A, encountering a busy destination User B, to have the call completed when User B becomes not busy, without having to make a new call attempt. SS-CCNR enables a calling User A, encountering a destination User B th
6、at, though alerted, does not answer, to have the call completed when User B becomes not busy again after a period of activity, without having to make a new call attempt. This Recommendation makes use of the “Generic functional protocol for the support of supplementary services in H.323“ as defined i
7、n ITU-T H.450.1. This Recommendation requires H.323 version 2 (1998) or later. Version 2 products can 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) recommendatio
8、n (0) h (8) 245 version (0) x where “x“ is 3 or higher. The procedures and the signalling protocol of this Recommendation are derived from the Call Completion supplementary service specified in ISO/IEC 13866 and ISO/IEC 13870. Source ITU-T Recommendation H.450.9 was prepared by ITU-T Study Group 16
9、(2001-2004) and approved under the WTSA Resolution 1 procedure on 17 November 2000. ii ITU-T H.450.9 (11/2000) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T
10、) 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 telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four yea
11、rs, 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 procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the nece
12、ssary 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 telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the
13、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 ITU members or others outside of
14、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, implementors are cautioned that this may not represent the latest in
15、formation and are therefore strongly urged to consult the TSB patent database. ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU.
16、ITU-T H.450.9 (11/2000) iii CONTENTS Page 1 Scope. 1 2 References. 1 3 Terms and Definitions 1 4 Abbreviations and Acronyms . 2 5 SS-CCBS service description . 2 5.1 Normal procedures 3 5.1.1 Activation/deactivation/registration/interrogation. 3 5.1.2 Invocation and operation . 3 5.1.3 Cancellation.
17、 3 5.2 Exceptional procedures. 4 5.2.1 Invocation and operation . 4 5.2.2 Cancellation. 5 5.3 Interactions with other supplementary services 5 5.3.1 Completion of Calls on No Reply (SS-CCNR). 5 5.3.2 Call Transfer (SS-CT) . 5 5.3.3 Call Forwarding Unconditional (SS-CFU) 5 5.3.4 Call Forwarding Busy
18、(SS-CFB). 5 5.3.5 Call Forwarding on No Reply (SS-CFNR) 6 5.3.6 Call Hold 6 5.3.7 Call Park/Call Pickup 6 5.3.8 Call Waiting. 6 5.3.9 Message Waiting indication 6 5.3.10 Name Presentation. 6 5.3.11 Call Linkage 6 6 SS-CCNR service description. 7 6.1 Normal procedures 7 6.1.1 Activation/deactivation/
19、registration/interrogation. 7 6.1.2 Invocation and operation . 7 6.1.3 Cancellation. 8 6.2 Exceptional procedures. 8 6.2.1 Invocation and operation . 8 6.2.2 Cancellation. 8 6.3 Interactions with other supplementary services 9 6.3.1 Completion of Calls to Busy Subscribers (SS-CCBS) 9 6.3.2 Call Tran
20、sfer (SS-CT) . 9 6.3.3 Call Forwarding Unconditional (SS-CFU) 9 iv ITU-T H.450.9 (11/2000) Page 6.3.4 Call Forwarding Busy (SS-CFB). 9 6.3.5 Call Forwarding on No Reply (SS-CFNR) 9 6.3.6 Call Hold 10 6.3.7 Call Park/Call Pickup 10 6.3.8 Call Waiting. 10 6.3.9 Message Waiting Indication 10 6.3.10 Nam
21、e Presentation. 10 6.3.11 Call Linkage 10 7 Messages and information elements . 10 8 Procedures. 10 8.1 Actions at User As endpoint 11 8.1.1 Normal procedures 11 8.1.2 Exceptional procedures 13 8.2 Actions at User Bs endpoint. 15 8.2.1 Normal procedures 15 8.2.2 Exceptional procedures 17 9 Interwork
22、ing and interactions . 18 9.1 Interworking with SCN. 18 9.1.1 No functional call completion entity exists in SCN 18 9.1.2 Functional call completion entity exists in SCN . 18 9.2 Protocol interaction between SS-CCBS and other supplementary services . 19 9.2.1 Call Transfer (ITU-T H.450.2) 19 9.2.2 C
23、all Diversion (ITU-T H.450.3) 19 9.2.3 Call Hold (ITU-T H.450.4) 20 9.2.4 Call Park and Call Pickup (ITU-T H.450.5) 20 9.2.5 Call Waiting (ITU-T H.450.6). 20 9.2.6 Message Waiting (ITU-T H.450.7) . 20 9.2.7 Name Presentation (ITU-T H.450.8). 20 9.2.8 Call Linkage (ITU-T H.323, 1998) . 21 9.3 Protoco
24、l interaction between SS-CCNR and other supplementary services 21 9.3.1 Call Transfer (ITU-T H.450.2) 21 9.3.2 Call Diversion (ITU-T H.450.3) 21 9.3.3 Call Hold (ITU-T H.450.4) 22 9.3.4 Call Park and Call Pickup (ITU-T H.450.5) 22 9.3.5 Call Waiting (ITU-T H.450.6). 23 9.3.6 Message Waiting (ITU-T H
25、.450.7) . 23 9.3.7 Name Presentation (ITU-T H.450.8). 23 9.3.8 Call Linkage (ITU-T H.323, 1998) . 23 ITU-T H.450.9 (11/2000) v Page 10 Gatekeeper actions 23 10.1 Gatekeeper passes on SS-CC operations to the endpoint . 23 10.2 Gatekeeper/proxy acts on behalf of an endpoint 23 10.2.1 Gatekeeper/proxy
26、acts on behalf of endpoint B 23 10.2.2 Gatekeeper/proxy acts on behalf of endpoint A 24 11 Dynamic description. 24 11.1 Operational model and signal flows . 24 11.1.1 Successful CCBS. 25 11.1.2 Successful CCNR 29 11.1.3 User A busy . 30 11.1.4 User B busy again 32 11.2 Communication between an endpo
27、int A (EASE) Signalling entity and its Signalling entity user (informative) 35 11.2.1 Table of primitives. 35 11.2.2 Primitive definition 36 11.2.3 Parameter definition 36 11.2.4 Call States 37 11.3 Communication between an endpoint B (EBSE) signalling entity and its signalling entity user (informat
28、ive) . 38 11.3.1 Table of primitives. 38 11.3.2 Primitive definition 38 11.3.3 Parameter definition 38 11.3.4 Call States 39 11.4 Timers . 40 11.4.1 Timers at User As endpoint 40 11.4.2 Timers at User Bs endpoint 40 12 Operations in support of Call Completion supplementary service . 40 13 Specificat
29、ion and Description Language (SDL) diagrams for SS-CCBS. 43 13.1 Behaviour of User As endpoint 44 13.2 Behaviour of User Bs endpoint 52 ITU-T H.450.9 (11/2000) 1 ITU-T Recommendation H.450.9 Call completion supplementary services for H.323 1 Scope This Recommendation describes supplementary services
30、 Call Completion (SS-CC), which are applicable to various basic services supported by H.323 multimedia endpoints. SS-CC consists of two supplementary services: the Completion of Calls to Busy Subscribers supplementary service (SS-CCBS) and the Completion of Calls on No Reply supplementary service (S
31、S-CCNR). SS-CCBS allows completion of a call to a subscriber (i.e. user) that was unsuccessful because of a busy condition and SS-CCNR allows completion of a call to a user that was unsuccessful because the user, although alerted, did not answer. 2 References The following ITU-T Recommendations and
32、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 other references are subject to revision; users of this Recommendation are therefore encoura
33、ged 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. ITU-T H.225.0 (2000), Call signalling protocols and media stream packetization for packet-based
34、 multimedia communication systems. ITU-T H.245 (2000), Control protocol for multimedia communication. ITU-T H.323 (2000), Packet-based multimedia communications systems. ITU-T H.450.1 (1998), Generic functional protocol for the support of supplementary services in H.323. 3 Terms and Definitions This
35、 Recommendation defines the following terms. 3.1 call: Refer to ITU-T H.323. 3.2 call completion: The successful presentation of a previously unsuccessful call to a destination user (User B), which occurs when the call has entered an alerting phase or has been answered. 3.3 CC call: The re-initiatio
36、n, in the course of executing a CC Request, of the previously unsuccessful call from User As endpoint to User B on behalf of User A. 3.4 CC recall: An indication informing User A that User B is no longer busy (in the case of SS-CCBS) or has just completed a period of activity (in the case of SS-CCNR
37、). Acceptance of this indication by User A will cause the call to be completed. 3.5 CC request: An instance of SS-CCBS or SS-CCNR. 3.6 connection release/retain: The capability to release/retain the call independent signalling connection during the various phases of a CC Request. 3.7 endpoint; gatek
38、eeper; gateway; terminal; user: See ITU-T H.323. 2 ITU-T H.450.9 (11/2000) 3.8 free: A property of a user who can accept an attempt to present a call to that user (i.e. allow the call to reach the alerting or answered state). 3.9 proxy: An entity that acts on behalf of an endpoint for the SS-CC proc
39、edures. The proxy may or may not be co-located with the gatekeeper. 3.10 recall timer: This timer specifies the length of time that User As endpoint shall wait for a response from User A to a CC Recall. 3.11 service duration timer: This timer specifies the length of time that the SS-CC supplementary
40、 service shall be active within User As endpoint. 3.12 service retention: The optional capability to continue with a CC Request after the CC Call failed due to User B being busy again. 3.13 user A: Originating user that originated the call and requested the supplementary service. 3.14 user B: The re
41、mote user that was initially addressed in the original call set up. 4 Abbreviations and Acronyms This Recommendation uses the following abbreviations: APDU Application Protocol Data Unit ASN.1 Abstract Syntax Notation One CC Call Completion CCBS Completion of Calls to Busy Subscribers CCNR Completio
42、n of Calls on No Reply CT Call Transfer EASE Endpoint A Signalling Entity EBSE Endpoint B Signalling Entity ID Identification, Identifier IE Information Element NFE Network Facility Extension SCN Switched Circuit Network SDL Specification and Description Language SS-CC Supplementary Service Call Com
43、pletion (This is a generic term, used to describe aspects common to both SS-CCBS and SS-CCNR.) SS-CCBS Supplementary Service Completion of Calls to Busy Subscribers SS-CCNR Supplementary Service Completion of Calls on No Reply 5 SS-CCBS service description Completion of Calls to Busy Subscribers (SS
44、-CCBS) is a supplementary service that is offered to a calling User A. On encountering a busy called User B, it allows User A to request that User Bs endpoint monitor User B and notify User As endpoint when User B becomes free. On response by User A to that notification, User As endpoint shall attem
45、pt to complete the call to User B. ITU-T H.450.9 (11/2000) 3 5.1 Normal procedures 5.1.1 Activation/deactivation/registration/interrogation SS-CCBS is permanently activated. 5.1.2 Invocation and operation When a call from User A fails because the destination User, User B, is busy, User A shall be ab
46、le to request SS-CCBS. On receipt of a request for SS-CCBS, User Bs endpoint shall check whether it is possible to initiate the service and if so, shall send an acknowledgment to User As endpoint and start monitoring User B. On receipt of the acknowledgment, User As endpoint shall start the SS-CCBS
47、service duration timer. The acknowledgment means that User A can expect to receive a CC Recall if User B becomes free within the period of the SS-CCBS service duration timer. NOTE 1 The fact that User B is already being monitored, as a result of a call completion request from another user, need not
48、cause rejection of the request from User A. The handling of multiple requests against the same User B is an implementation matter; typically involving some sort of queue arranged in chronological or priority order. NOTE 2 The fact that User A has already invoked call completion against another user
49、need not cause rejection of any further requests for call completion from User A. Handling of multiple requests by the same User A is an implementation matter. NOTE 3 SS-CCBS can be invoked after notification that User B is busy. The recommended value of the SS-CCBS service duration timer is in the range of 1-60 minutes. A suitable default value could be 15 minutes. NOTE 4 The selective operation of SS-CCBS on calls associated with a specific basic service is for further study. After the SS-CCBS request has been acknowledged, User A shall be able
