1、 International Telecommunication Union ITU-T H.450.4TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2013) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Supplementary services for multimedia Call hold supplementary service for ITU-T H.323 systems Recommendatio
2、n ITU-T H.450.4 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 procedu
3、res 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 ser
4、vices 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 application
5、s 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, TRIPLE
6、-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 SERVICES AND APPLICATIONS FOR IPTV General aspects H.700H.719 IP
7、TV 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 Signage H.780H.789 For further details, please refer to the list
8、 of ITU-T Recommendations. Rec. ITU-T H.450.4 (03/2013) i Recommendation ITU-T H.450.4 Call hold supplementary service for ITU-T H.323 systems Summary This Supplementary Service describes the procedures and the signalling protocol for the Call Hold supplementary service in ITU-T H.323 (“Packet based
9、 multimedia communications systems“) networks. This revision introduces a number of corrections and clarifications by incorporating technical and editorial corrections from the ITU-T H.323-series Implementers Guide (03/2011). History Edition Recommendation Approval Study Group 1.0 ITU-T H.450.4 1999
10、-05-27 16 2.0 ITU-T H.450.4 2013-03-16 16 ii Rec. ITU-T H.450.4 (03/2013) 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
11、 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 telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets
12、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 procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts pur
13、view, 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 telecommunication administration and a recognized operating agency. Compliance with this Recommendation is vol
14、untary. However, the Recommendation may 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
15、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 RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may invol
16、ve 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 the Recommendation development process. As of the date of approval of this Recom
17、mendation, ITU had received notice of intellectual 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 htt
18、p:/www.itu.int/ITU-T/ipr/. ITU 2013 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 H.450.4 (03/2013) iii Table of Contents Page 1 Scope 1 2 References. 1 3 Definitions 1 3.1 Terms defined elsewhere
19、1 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Description 3 5.1 Near-end call hold 3 5.2 Remote-end call hold 4 6 Messages and information elements . 4 7 Actions at the holding endpoint 5 7.1 Normal procedures . 5 7.2 Exceptional procedures 5 8 Actions at the held e
20、ndpoint . 6 8.1 Normal procedures . 6 8.2 Exceptional procedures 6 8.3 Additional procedures 7 9 Interworking . 7 9.1 Interworking with SCN 7 9.2 Interworking with other supplementary services . 7 9.3 Interaction with ITU-T H.225.0 parameters . 8 10 Gatekeeper/proxy actions . 8 10.1 Remote-end call
21、hold 8 10.2 Near-end call hold 8 11 Dynamic description for call hold 9 11.1 Operational models and signalling flows . 9 11.2 Communication between holding signalling entity (HGSE) and holding signalling entity user (HGSE user) . 12 11.3 Communication between held signalling entity (HDSE) and held s
22、ignalling entity User (HDSE user) 13 11.4 Timers . 14 11.5 Counters 14 12 Operations in support of SS-call hold . 14 13 SDLs . 16 13.1 Near-end call hold SDLs 17 13.2 Remote-end call hold SDLs 18 Rec. ITU-T H.450.4 (03/2013) 1 Recommendation ITU-T H.450.4 Call hold supplementary service for ITU-T H.
23、323 systems 1 Scope This Recommendation specifies the Call Hold supplementary service (SS-HOLD), which is applicable to various basic services supported by ITU-T H.323 Multimedia Endpoints. SS-HOLD enables the Served (Holding) User A to put User B (with whom User A has an active call) into a hold co
24、ndition (Held User) and subsequently to retrieve that User again. During this hold condition, User B may be provided with music and/or video on hold. The Served (Holding) User A may perform other actions while User B is being held, e.g., consulting with another User C. The call between User A and Us
25、er B has to be in the active state before SS-HOLD may be invoked. This Recommendation makes use of the “Generic functional protocol for the support of supplementary services in ITU-T H.323 systems“ as defined in Recommendation ITU-T H.450.1. 2 References The following ITU-T Recommendations and other
26、 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 encouraged t
27、o 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. The reference to a document within this Recommendation does not give it, as a stand-alone document,
28、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.245 Recommendation ITU-T H.245 (2011), Control protocol for multimedia communication. ITU-T H.323 Rec
29、ommendation ITU-T H.323 (2009), Packet based multimedia 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 H.450.3 Recommendation ITU-T 450.3 (2011), Call diversion supplementa
30、ry service for ITU-T H.323 systems. 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 H.323 endpoints. The call begins with the call set-up procedure and ends with the
31、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 H.323 entities such as a Gatekeeper or MC. In case of interworking with some SCN endpoints via a Gateway, all t
32、he channels terminate at the Gateway where they are converted to the appropriate representation for 2 Rec. ITU-T H.450.4 (03/2013) 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 support
33、ing multiple simultaneous calls. 3.1.2 endpoint ITU-T H.323: An H.323 terminal, Gateway, or MCU. An endpoint can call and be called. It generates and/or terminates information streams. 3.1.3 terminal ITU-T H.323: An H.323 Terminal is an endpoint on the network which provides for real-time, two-way c
34、ommunications with another H.323 terminal, Gateway, or Multipoint Control Unit. This communication consists of control, indications, audio, moving colour video pictures, and/or data between the two terminals. A terminal may provide speech only, speech and data, speech and video, or speech, data and
35、video. 3.1.4 user ITU-T H.450.3: An application which uses one or more of the services defined in this Recommendation (activation, deactivation, interrogation, invocation) via an application programming interface. 3.2 Terms defined in this Recommendation This Recommendation defines the following ter
36、ms: 3.2.1 active state: The ITU-T H.225.0 call state U10 “Active“ (after CONNECT message). 3.2.2 consultation; consultation call: An ITU-T H.323 call established while having another call(s) on hold. 3.2.3 far-end call hold (Remote-end call hold): An SS-HOLD scenario in which the served user asks th
37、e held endpoint to provide MOH to the held User. 3.2.4 held user, User B: The user who has been put on hold by the remote User A. 3.2.5 media on hold (MOH): The media pattern which may be provided to the held user during hold condition. This may include music, announcements, video, freeze (blank) fr
38、ame, and other indications. 3.2.6 near-end call hold: An SS-HOLD scenario in which MOH is provided from the holding endpoint to the held user. 3.2.7 proxy: A proxy in conjunction with SS-HOLD is an entity on the call signalling path that intercepts messages for the remote-end call hold. This is in o
39、rder to act on behalf of User B for SS-HOLD. The proxy entity may be co-located with the gatekeeper or may be located in a separate transit entity. 3.2.8 served user, holding user, User A: The User who has put the remote User B on hold. 4 Abbreviations and acronyms This Recommendation uses the follo
40、wing abbreviations and acronyms: APDU Application Protocol Data Unit ASN.1 Abstract Syntax Notation One GK Gatekeeper HDSE (User) Held Signalling Entity (User) HGSE (User) Holding Signalling Entity (User) MOH Media on Hold NFE Network Facility Extension SCN Switched Circuit Network Rec. ITU-T H.450.
41、4 (03/2013) 3 SDL Specification and Description Language SS-HOLD Supplementary Service Hold 5 Description Call Hold (SS-HOLD) allows the served user, which may be the originally calling or the called user, to interrupt communications on an existing call and then subsequently, if desired, re-establis
42、h (i.e., retrieve) communications with the held user. SS-HOLD applies to the complete ITU-T H.323 call (audio and video media streams) for which the supplementary service is being invoked. Putting on hold only a subset of the media streams as well as putting on hold an ITU-T T.120 call is for furthe
43、r study. While having put the held user into a hold condition, the served user may perform other actions. Examples are: to communicate (consult) with another user, to have some private side talk, etc. Hold may only be invoked by the served user for a call in the active state. Communication on the me
44、dia channels is interrupted and the call is placed in the held state. The distant party is informed, and if appropriate, a specific MOH pattern (e.g., video and/or music on hold) may be provided to the held user. The served user may then originate or accept other calls, or use other services without
45、 impacting the call in the held state. NOTE 1 Contrary to muting, to just closing the audio logical channel or to just closing the video logical channel (which corresponds to a “video-off“ command in ITU-T H.221), SS-HOLD enables functional supplementary service control. An implementation may, for e
46、xample, depend/tie the invocation of other features to whether SS-HOLD is invoked or not. While a call is being held, the served user and/or the held user may be restricted from invoking other features depending on the implementation of those features. For example, a held user may be restricted from
47、 putting its call on hold (simultaneous hold). The served user invokes the Retrieve procedure to terminate the held state of a call. The held party is informed of the retrieval and communication on the media channels is re-established. Implementations may limit the time that a call can remain in the
48、 held state. A reminder may be provided to the served user to inform the served user that the distant user is still on hold (i.e., providing a hold time-out notification). Two scenarios are specified for SS-HOLD, “Near-end Call Hold“ and “Remote-end Call Hold“. The decision whether to invoke one or
49、the other of the methods is an implementation and application matter. NOTE 2 A reason for deciding to use Near-end Call Hold may, for example, be to provide a companys local announcement and thus use the opportunity to provide an advertisement to the held party. A reason for invoking Remote-end Call Hold may be to decrease network traffic. 5.1 Near-end call hold Hold is invoked at the holding endpoint as a local procedure. The holding endpoint informs the held endpoint of the hold condition by sending a hold n
