1、 STDmITU-T RECMN T-LZZ-ENGL 1998 48b259L Ob47b47 807 INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU TA22 (02/98) SERIES T: TERMINALS FOR TELEMATIC SERVICES Multipoint communication service - Service definit ion ITU-T Recommendation T. 122 (Previously CCIT
2、T Recommendation) STD-ITU-T RECMN T.II22-ENGL I1998 m 48b259L ObV7b48 743 ITU-T T-SERIES RECOMMENDATIONS TERMINALS FOR TELEMATIC SERVICES Forjrther details, please refer to iTU-T List ofRecornmendationS. ITU-T RECOMMENDATION T.122 MULTIPOINT COMMUNICATION SERVICE - SERVICE DEFINITION Summary This Re
3、commendation defines a multipoint data delivery service for use in the audiographics and audiovisual conferencing service. It provides the mechanism for multipoint aware applications to send data to all or a subset of the group with a single send primitive and to force, if desired, a uniformly seque
4、nced reception of data at all users. It also provides a token mechanism to allow applications to control scarce resources or do multi-application signalling and synchronization. These services are provided in a manner that is independent of the underlying network connections. The following changes h
5、ave been incorporated into this Recommendation: - - Support for unreliable data transfer was added. Under certain conditions, MCS protocol version is allowed to differ between providers within a domain. The MCS-DOMAIN-PARAMETERS service primitive was added. Parameters were added to MCS-SEND-DATA and
6、 MCS-UNIFORM-SEND-DATA service primitives to facilitate data reassembly by the user application. Minor changes have been made to the Recommendation format. - - - Source ITU-T Recommendation T.122 was revised by ITU-T Study Group 16 (1997-2000) and was approved under the WTSC Resolution No. 1 procedu
7、re on the 6th of February 1998. - STD-ITU-T RECMN T-LZZ-ENGL 3998 = 4862593 0647b50 3T3 D FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of
8、 the IT. The 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 Conference (WTSC), which meets every four years, establishes
9、the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within IT-Ts pu
10、rview, the necessary standards are prepared on a collaborative basis with IS0 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 The ITU draw
11、s 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 Propem Rights, whether asserted by IT members o
12、r others outside of the Recommendation development process. As of the date of approval of this Recommendation, the 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
13、 represent the latest information and are therefore strongly urged to consult the TSB patent database. o ITU 1998 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 permis
14、sion in writing from the ITU. 11 Recommendation T.122 (02/98) . . STDmITU-T RECMN T.122-ENGL 1978 D 48b2591 Ob47b51 238 2 3 4 5 5.1 5.2 6 7 7.1 7.2 7.3 8 8.1 8.2 8.3 8.4 9 9.1 9.2 9.3 9.4 10 10.1 10.2 10.3 11 11.1 11.2 11.3 11.4 CONTENTS Scope References Definitions Abbreviations . Conventions Primi
15、tive parameters conventions Primitive notations . Model of MCS MCS connections and building the domain Establishing connections and binding them to the domain Attaching application users to a domain MCS-DOMAIN-PARAMETERS MCS channels . Multicast channels Single-member channels Private channels Chann
16、el Id numbering MCS data transfer . Simple Send Uniformly sequenced data transfer . Send data with responses (For further study) Unreliable data transfer Token management Exclusive event control and transfer Event coordination Token Id Numbering Introduction to MCS service primitives . MCS domain ma
17、nagement primitives MCS Channel Management primitives MCS data transfer primitives MCS token management primitives . . Page 1 1 2 3 3 3 3 3 4 4 6 6 7 -7 7 8 8 8 8 9 9 10 10 10 11 11 11 11 11 11 11 Recommendation T.122 (02198) iii 12 MCS domain management primitives 12.1 MCS-CONNECT-PROVIDER 12.1.1 F
18、unction . 12.1.2 Types of primitives and their parameters 12.1.3 Sequence of primitives 12.2 MCS-DISCONNECT-PROVIDER 12.2.1 Function . 12.2.2 Types of primitives and their parameters 12.2.3 Sequence of primitives 12.3 MCS-ATTACH-USER . 12.3.1 Function . 12.3.2 Types of primitives and their parameter
19、s 12.3.3 Sequence of primitives 12.4 MCS-DETACH-USER . 12.4.1 Function . 12.4.2 12.4.3 Sequence of primitives 12.5 MCS-DOMAIN-PARAMETERS Types of primitives and their parameters 12.5.1 Function . 12.5.2 Types of primitives and their parameters 12.5.3 Sequence of primitives 13 MCS channel management
20、primitives 13.1 MCS-CHANNEL-JOIN . 13.1.1 Function . 13.1.2 Types of primitives and their parameters 13.1.3 Sequence of primitives 13.2 MCS-CHANNEL-LEAVE . 13.2.1 Function . 13.2.2 Types of primitives and their parameters 13.2.3 Sequence of primitives 13.3 MCS-CHANNEL-CONVENE . 13.3.1 Function . 13.
21、3.2 Types of primitives and their parameters 1 3.3.3 Sequence of primitives 13.4 MCS-CHANNEL-DISBAND 13.4.1 Function . 13.4.2 Types of primitives and their parameters Page 12 12 12 12 13 14 14 14 14 15 15 15 15 15 15 16 16 16 16 17 17 18 18 18 18 18 18 18 19 19 19 19 20 20 20 20 20 iv Recommendation
22、 T.122 (02/98) STD-ITU-T RECMN T-LZZ-ENGL 1798 V86257L 0647b53 O00 m 13.5 13.6 14 14.1 14.2 15 15.1 15.2 15.3 15.4 15.5 13.4.3 Sequence of primitives MCS-CHANNEL-ADMIT . 13.5.1 Function . 13.5.2 Types of primitives and their parameters 13.5.3 Sequence of primitives MCS-CHANNEL-EXPEL . 13.6.1 Functio
23、n . 13.6.2 Types of primitives and their parameters 13.6.3 Sequence of primitives . MCS data transfer primitives MCS-SEND-DATA . 14.1.1 Function . 14,1.2 Types of primitives and their parameters 14.1.3 Sequence of primitives MCS-UNIFORMLY -SEQUENCED-SEND-DATA . 14.2.1 Function . 14.2.2 Types of prim
24、itives and their parameters 14.2.3 Sequence of primitives MCS token management primitives . MC S -TOKEN-GRAB 15.1.1 Function . 15.1.2 Types of primitives and their parameters 1 5.1.3 MCS.TOKEN.I“IBIT . 15.2.1 Function . 15.2.2 15.2.3 Sequence of primitives MCS-TOKEN-GIVE 15.3.1 Function . 15.3.2 15.
25、3.3 Sequence of primitives Sequence of primitives Types of primitives and their parameters Types of primitives and their parameters MCS-TOKEN-PLEASE . 15.4.1 Function . 1 5.4.2 Types of primitives and their parameters 15.4.3 Sequence of primitives MCS-TOKEN-RELEASE 15.5.1 Function . Recommendation T
26、.122 (02/98) Page 21 21 21 21 22 22 22 22 23 23 23 23 24 24 24 24 25 25 25 25 26 26 26 26 26 27 27 27 27 28 28 28 28 29 29 29 V STD=ITU-T RECMN T.122-ENGL 1996 m 48b2.591 0647654 T47 m 15.5.2 Types of primitives and their parameters 15.5.3 Sequence of primitives 15.6 MCS-TOKEN-TEST 15.6.1 Function .
27、 15.6.2 Types of primitives and their parameters 1 5.6.3 Sequence of primitives Annex A . Domain establishment. data transfer and release phases examples . MCS domain establishment phase MCS data transfer phase . MCS connection release phase . A . 1 A.2 A.3 Appendix I . Distributed token control . P
28、age 29 29 30 30 30 30 30 30 35 37 38 vi Recommendation T.122 (02/98) Recommendation T.122 MULTIPOINT COMMUNICATION SERVICE - SERVICE DEFINITION (revised in 1998) 1 Scope The Multipoint Communication Service (MCS) is a generic service designed to support highly interactive multimedia conferencing app
29、lications. It supports full-duplex multipoint communication among an arbitrary number of connected application entities over a variety of networks as specified in Recommendation T.123. This version of MCS utilizes only the basic mode of Recommendation T. 123. MCS provides efficient multicast message
30、 sequencing and token management features by means of an MCS provider, to which users are connected either directly or through other MCS providers. MCS offers the following features: Flexible modes of data transfer: - Broadcast, with flow control; - RequestResponse. Multipoint addressing: - One to a
31、ll; - One to sub-group; - Onetoone. Multipoint routing of data: - - Tokens are provided for resource contention resolution. Network independent: - Shortest path to each receiver; Uniform sequencing of data, where all users receive the same data in the same sequence. For fully reliable data transmiss
32、ion, MCS assumes the use of error-free transport connections that provide flow control (see Recommendation T. 123). MCS provides information to conference participants about other participants only in cases where this information cannot be provided by the participants themselves. For example, member
33、s of a domain are not informed when a new member joins (the new member can do so if it wishes), whereas they are informed by MCS when a member detaches, since the departing member may have no opportunity to inform the others. 2 References The following ITU-T Recommendations and other references cont
34、ain 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; ail users of this Recommendation are therefore encouraged to investigat
35、e 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. Recommendation T.122 (02/98) 1 STD-ITU-T RECMN ToL22-ENGL 1998 W 4862591 O647656 BIT - ITU-T Recommendation F.7
36、1 O (1 99 i), General principles for audiographic conference sewice. ITU-T Recommendation T. 123 (1 996), Network speciJic data protocol stacks for multimedia conferencing. - 3 Definitions This Recommendation defines the following terms: 3.1 MCS provider: An entity (Le. active element) of an MCS sub
37、system, interacting directly with application entities above and transport entities below. The services it provides and the services it uses are modelled in terms of abstract primitives. An MCS provider communicates with peer MCS providers. 3.2 MCS domain: A tree of MCS connections among MCS provide
38、rs or, in the degenerate case, part of a single MCS provider. The MCS providers involved are said to host the domain. A domain sets the boundary for data transfer among attached MCS users. 3.3 MCS domain selector: An octet string that distinguishes multiple domains hosted by the same MCS provider. T
39、he creation of MCS providers, their configuration to host one or more domains, and the internal structure of domain selectors are all local matters. 3.4 top MCS provider: In every domain a single MCS provider will become the Top MCS Provider and will be the exclusive manager of all the domains chann
40、el, user Ids and token resources. 3.5 MCS connection: A specified set of transport connections, managed as one unit, between a pair of MCS providers. Each end of an MCS Connection is bound to a respective MCS domain selector. One end of each MCS Connection is designated to be hierarchically superior
41、 to the other. 3.6 MCS user: An application entity obtaining services from an MCS provider. Once they have been attached to the same domain, MCS users can transfer data in point-to-point or multicast fashion. 3.7 MCS Service Access Point (MCSAP): A point through which an MCS user accesses an MCS pro
42、vider. 3.8 MCS attachment: A multi-connection end point within an MCSAP. Each MCS attachment is bound to an MCS domain selector. An MCS user may attach through an MCSAP to domains hosted by the MCS provider. 3.9 MCS user Id: A short identifier, unique within an MCS domain, that distinguishes between
43、 MCS attachments. A user with multiple attachments to the same domain, through the same or different SAPS, has equally many user Ids. 3.10 control-MCSAP: A unique MCSAP per MCS provider (distinguished by some local means) to which the MCS Connect and MCS Disconnect primitives are restricted. The MCS
44、 user of a Control-MCSAP does not have direct access to data transfer through the MCS Connection end points it contains; this is limited to the MCS provider. It is a local option whether a Control-MCSAP may also contain MCS attachments like ordinary MCSAPs and allow the MCS user to invoke other MCS
45、primitives. 3.11 MCS channel: A channel is a domain-wide address. Channels are used for MCS data unit distribution lists. All users who are members of the same channel will receive data sent to that channel. 3.12 MCS private channel: A channel with an authorized group of users. Only they may send an
46、d receive data over the channel. Attempts by unauthorized users to invoke an MCS primitive involving a private channel as parameter will fail. 2 Recommendation T.122 (02/98) STD-ITU-T RECMN T.322-ENGL 3998 4862593 0647657 756 3.13 regulates its authorized user group. If the manager detaches, the pri
47、vate channel is disbanded. 3.14 3 or greater and are either: MCS private channel manager: An MCS user who convenes a private channel and version 3 or V3 summit: The nodes in a domain hierarchy which use MCS protocol version e a Top Provider; or e have an upward connection path to a version 3 Top Pro
48、vider that flows only through other version 3 nodes. 4 Abbreviations This Recommendation uses the following abbreviations: MCS Multipoint Communication Service MCSAP MCS Service Access Point MCSPDU MCS Protocol Data Unit MCU SAP Service Access Point Multipoint Control Unit (see Recommendation F.710)
49、 5 Conventions 5.1 Primitive parameters conventions The primitive parameters defined in this Recommendation will use the following key: M Parameter is mandatory C Parameter is conditional U Blank Parameter is absent (=) Parameter is a user option Value of the parameter is identical to the value of the corresponding parameter of the preceding primitive. 5.2 Primitive notations The primitive services referred to in the text will be in italics. 6 Model of MCS MCS establishes a multipoint domain over point-to-point MCS connections. Within that multip
