1、STDOITU-T RECMN H.450.b-ENGL L999 m 48b2591 Obb508b 083 m INTERNAT IONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU H.450.6 (05/99) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Supplementary services for multimedia Call waiting supplementary service for H.323 ITU-T
2、 Recommendation H.450.6 (Previously CCITT Recommendation) ITU-T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS Characteristics of transmission channels used for other than telephone purposes Use of telephone-type circuits for voice-frequency telegraphy Telephone circuits or cables used
3、for various types of telegraph transmission or simultaneous transmission Telephone-type circuits used for facsimile telegraphy Characteristics of data signals CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS INFRASTRUCTURE OF AUDIOVISUAL SERVICES General Transmission multiplexing and synchronization Syst
4、ems aspects Communication procedures Coding of moving video Related systems aspects Systems and terminal equipment for audiovisual services H.10-H.19 H.20-H.29 H.30-H.39 H.40-H.49 H.50-H.99 H.100-H.199 H.200-H.219 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 de
5、tails, please refer to ITU-T List of Recommendations Summary This Supplementary Service describes the procedures and the signalling protocol for the Call Waiting supplementary service (SS-CW) in H.323 (Packet based multimedia communications systems) networks. SS-CW permits a served user while being
6、busy to be informed of an incoming call with an indication. The user then has the choice of accepting, rejecting or ignoring the waiting call. The user calling the busy party is informed about the call waiting condition. This Recommendation makes use of the “Generic functional protocol for the suppo
7、rt of supplementary services in H.323“ as defined in Recommendation H.450. l. Source ITU-T Recommendation H.450.6 was prepared by ITU-T Study Group 16 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on 27 May 1999. Recommendation H.450.6 (0999) 1 FOREWORD ITU (International Te
8、lecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on
9、 them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The appro
10、val of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. l. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation the
11、 term recognized operating agency (ROA) includes any individual, company, corporation or governmental organization that operates a public correspondence service. The terms Administration, ROA and public correspondence are defined in the Constitution of the ITU (Geneva, 1992). INTELLECTUAL PROPERTY R
12、IGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asse
13、rted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned
14、that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 2000 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 microfil
15、m, without permission in writing from the ITU. 1 2 3 4 5 6 7 7.1 7.2 7.3 8 8.1 8.2 9 9.1 9.2 9.3 9.4 CONTENTS Scope References Terms and definitions . Abbreviations and acronyms Description . Messages and information elements . Procedures Actions at the served endpoint B 7 . 1 . 1 Normal procedures
16、7.1.2 Exceptional procedures . Actions at the calling endpoint C . Gatekeeper actions . Intenvorking considerations . Intenvorking with other supplementary services 8.2.1 Call Diversion (H.450.3) . 8.2.3 Call Park and Call Pickup (H.450.5) . Intenvorking with SCN 8.2.2 Call Hold (H.450.4) Dynamic de
17、scrlptlon . Operational models and signalling flows for SS-CW Communication between Served endpoint and Served endpoint User 9.2.1 Table of primitives 9.2.2 Primitive definition . 9.2.3 Parameter definition 9.2.4 Call states Communication between Calling endpoint and Calling endpoint User . 9.3.1 Ta
18、ble of primitives 9.3.2 Primitive definition . 9.3.3 Parameter definition 9.3.4 Call states Timers . Recommendation H.450.6 (05/99) Page 1 1 1 2 2 3 4 4 4 4 4 4 5 5 6 6 6 6 6 6 6 7 7 7 7 . 111 Page 10 ASN.l Operations in support of SS-Call Waiting 7 11 Specification and Description Language (SDL) Di
19、agrams 8 1 1 . 1 Served endpoint SDLs 9 11.2 Calling endpoint SDLs . 10 iv Recommendation H.450.6 (05/99) Recommendation H.450.6 CALL WAITING SUPPLEMENTARY SERVICE FOR H.323 (Geneva, 1999) 1 Scope This Recommendation specifies the Call Waiting Supplementary Service (SS-CW), which is applicable to va
20、rious basic services supported by H.323 Multimedia Endpoints. 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. A
21、ll Recommendations and other references are subject to revision; all 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
22、is regularly published. - ITU-T Recommendation H.225.0 (1998), Call signalling protocols and media stream - ITU-T Recommendation H.245 (1 998), Control protocol for multimedia communication. - ITU-T Recommendation H.323 (1998), Packet based multimedia communication systems. - ITU-T Recommendation H.
23、450.1 (1998), Generic functional protocol for the support of packetization for packet-based multimedia communication systems. supplementary services in H. 323. 3 Terms and definitions This Recommendation defines the following terms: 3.1 Busy, busy condition: User B is engaged with one or more other
24、calls (“real-time busy“). In this busy condition, a further incoming call can only be accepted after freeing some resources, e.g. by releasing an existing call or by putting an existing call on hold. The maximum number of calls (active calls, held calls, alerting calls, etc.) an endpoint can handle
25、before a busy condition is encountered is implementation dependent and is therefore out of the scope of this Recommendation. As an option, a busy condition may be encountered if a user is engaged with other applications like writing email. This kind of busy condition is also known as “workflow-busy“
26、. 3.2 Camp-on: An incoming call while being busy is indicated to the served user. 3.3 Endpoint; terminal; user: See Recommendation H.323. 3.4 H.323 Call: Refer to Recommendation H.323. 3.5 User B, served user: User B is a user who has activated the Call Waiting supplementary service for his endpoint
27、. 3.6 User C, calling user: User C is the user who has originated a call to user B that causes the SS-CW to be invoked. 3.7 User A: User A is a user who is engaged in a call with user B. Recommendation H.450.6 (0999) 1 4 Abbreviations and acronyms This Recommendation uses the following abbreviations
28、: APDU Application Protocol Data Unit ASN. 1 Abstract Syntax Notation One GK Gatekeeper NFE Network Facility Extension PISN Private Integrated Services Network SCN Switched Circuit Network SDL Specification and Description Language SS-CFB Supplementary Service Call Forwarding Busy SS-cw Supplementar
29、y Service Call Waiting 5 Description The CW supplementary service (SS-CW) permits a busy user B to be informed of an incoming call while being engaged with one or more other calls. That is SS-CW operates in case of an incoming call when a busy condition within the endpoint is encountered. As an opti
30、on, a busy condition may also be encountered if the user is busy with workflow applications (e.g. writing emails). When a user C (calling user) attempts to call a busy user B, user B is given an appropriate indication of the waiting call. The calling user C may be informed about SS-CW being invoked
31、at the destination by being provided with an appropriate indication. After receiving the call waiting indication, user B has the choice of accepting, rejecting or ignoring the waiting call. During the call waiting condition, the calling user C has the option to release the call or to invoke other su
32、pplementary services, e.g. message waiting callback. The maximum number of calls that can be handled (e.g. active, held, alerting, waiting) for each endpoint is an implementation option. SS-CW occurs only when an attempt is made to exceed these limits. Provision and withdrawal SS-CW provision and wi
33、thdrawal is a local endpoint configuration matter. Call waiting may be offered with the following configuration options (see Table 1). Table 1lH.450.6 - Configuration options I Configuration option I Value I Calling user receives an indication that their call is waiting No; Yes due to SS-CW being in
34、voked at the served endpoint Maximum number of calls which can be waiting One, N, where N is more than one Optional Call Waiting timer (T-CW) (Note) NOTE - H.225.0 Timer T301 (min. 180 seconds) operates at the calling user side. min. 30 seconds 2 Recommendation H.450.6 (0999) SS-Call Waiting applies
35、 to the complete H.323 call for which the supplementary service is being invoked. SS-Call Waiting for a T. 120 call is for further study. 6 Messages and information elements The operations specified for SS-CW in clause 10 shall be sent within h4501 SupplementaryService APDUs contained within H.225.0
36、 ALERTING message. When conveying the Invoke APDU of operations defined in clause 10, the destinationEntity data element of the NFE shall contain the value “endpointtt. When conveying the Invoke APDU of operations defined in clause 10, the Interpretation APDU shall contain the value “discardAnyUnrec
37、ognizedInvokePdu“. 7 Procedures 7.1 Actions at the served endpoint B 7.1.1 Normal procedures When an incoming H.225.0 SETUP message from user C arrives, encounters a busy condition and SS-CW is provided for the served user, the served endpoint B shall return an ALERTING message towards the calling u
38、ser C and optionally start timer T-CW. Before sending ALERTING, a SETUP ACKNOWLEDGE or CALL PROCEEDING message (in accordance with H.225.0 basic call procedures) may be sent. Depending on the local configuration options of user B, a callwaiting Invoke APDU may be included within the ALERTING message
39、. The callwaiting Invoke APDU may be accompanied with argument nbOfAddWaitingCalls and with manufacturer specific information, The served endpoint shall locally provide a call waiting indication to the user B. The busy User B can free resources to accept a waiting call by: I a releasing an existing
40、call according to the procedures of Recommendation H.225.0; using the call hold supplementary service on an existing call according to the procedures of using the SS-PARK supplementary service on the existing call according to the procedures Recommendation H.450.4; of Recommendation H.450.5. If the
41、served user B accepts the waiting call, the served endpoint shall stop timer T-CW, if running, send CONNECT message to the calling user and proceed with normal call establishment procedures as described in Recommendation H.323 or H.225.0. 7.1.2 Exceptional procedures After the ALERTING message has b
42、een sent, this new incoming call may be rejected by user B by the sending of a RELEASE COMPLETE message with the ReleaseCompleteReason set to “destinationRejection“. I I l If the optional timer T-CW is running and T-CW expires, the call shall be cleared towards the calling user by the sending of a R
43、ELEASE COMPLETE message with ReleaseCompleteReason set to IdestinationRejection“. If the calling user C clears the call attempt before the call has been established, then call clearing of the waiting call. shall be performed in accordance with H.225.0 basic call clearing. Recommendation H.450.6 (05/
44、99) 3 7.2 Actions at the calling endpoint C On receipt of an ALERTING message fiom endpoint B containing a callwaiting Invoke APDU in response to a SETUP message, the calling endpoint may provide a call waiting indication to the calling user. The calling user in this situation has the following opti
45、ons: wait until the waiting call gets accepted (connected) by the served user B; o release the call; o invoke other supplementary services, e.g. message waiting callback (for further study); o perform other actions which are out of the scope of this Recommendation (e.g. sending email). 7.3 Gatekeepe
46、r actions In the case of a gatekeeper routed model, the gatekeeper shall pass on SS-CW operations transparently. A gatekeeper that has appropriate knowledge about the served endpoint B status may act on behalf of the served endpoint by means of inserting a callwaiting Invoke APDU into an ALERTING me
47、ssage received fiom endpoint B before sending on the ALERTING message towards the calling endpoint. 8 Interworking considerations 8.1 Interworking with SCN SS-CW may interwork with corresponding supplementary services as defined by other standards making use of gateway interworking functions. The sp
48、ecification of detailed gateway interworking procedures is out of the scope of this Recommendation and will be specified within other Recommendations. 8.2 Interworking with other supplementary services 8.2.1 Call Diversion (H.450.3) If the served user has subscribed to SS-CW and also has SS-CFB acti
49、ve, then SS-CFB shall take precedence. 8.2.2 Call Hold (H.450.4) The served user may invoke SS-HOLD on the existing call, in order to be able to accept the waiting call. 8.2.3 Call Park and Call Pickup (H.450.5) The served user may invoke SS-PARK on the existing call, in order to be able to accept the waiting call. A waiting call may be subject to SS-PICKUP. 4 Recommendation H.450.6 (0999) - STD-ITU-T RECMN H.450.b-ENGL L999 m 4862593 0665096 T22 W 9 Dynamic description 9.1 Operational models and signalling flows for SS-CW See Figures 1 and 2
