1、 STD-ITU-T RECMN X=h-ENGL $997 “i 4862593 0643332 3/11 II INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU X.6 (08/97) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATION Public data networks - Services and facilities Multi cast service defini ti on ITU-T
2、 Recommendation X.6 (Previously CCITT Recommendation) ITU-T X-SERIES RECOMMENDATIONS Interfaces X.20-X.49 Transmission, signalling and switching X.50-X.89 Network aspects X.90-X. 149 Maintenance X.150-X.179 Administrative arrangements X.180-X.199 OPEN SYSTEM INTERCONNECTION X.200-X.299 Model and not
3、ation X.200-X.209 Service definitions X.210-X.2 19 Connection-mode protocol specifications X.220-X.229 Connectionless-mode protocol specifications X.230-X.239 PICS proformas X.240-X.259 Protocol Identification X.260-X.269 Security Protocols X.270-X.279 Layer Managed Objects X.280-X.289 Conformance t
4、esting X.290-X.299 INTERWORKING BETWEEN NETWORKS X.300-X.399 1 General X.300-X.349 Satellite data transmission systems x.350-x.399 MESSAGE HANDLING SYSTEMS X.400-X.499 DIRECTORY X.500-X.599 OS1 NETWORKING AND SYSTEM ASPECTS X.600-X.699 Networking X.600-X.629 DATA NETWORKS AND OPEN SYSTEM COMMUNICATI
5、ON For further details, please refer to ITU-T List of Recommendations. STD-ITU-T RECMN X.6-ENGL 3997 I 4Bb259L 0643314 197 I ITU-T RECOMMENDATION X.6 MULTICAST SERVICE DEFINITION Summary This Recommendation describes the service definitions and capabilities of a multicast service in Public Data Netw
6、orks. This Recommendation provides a common model for description of the service elements, defines the terminology and describes a set of capabilities which may be provided by such a multicast service. ITU-T Recommendations X.48 and X.49 define the procedures for provision of a basic and extended mu
7、lticast service for DTEs using Recommen- dation X.25, respectively. Source IT-T Recommendation X.6 was revised by ITU-T Study Group 7 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 9th of August 1997. Recommendation X.6 (08/97) 1 STDmITU-T RECMN Xnb-ENGL 3997 W q862591
8、1 06431115 023 FOREWORD IT (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommuni- cations. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The ITU-T is responsible for studying technical, operating and t
9、ariff 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 the topics for study by the ITU-T Study Groups which, in their turn, prod
10、uce 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 ITU-Ts purview, the necessary standards are prepared on a collaborative basis wit
11、h 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 draws attention to the possibility that the practice or implementation of th
12、is 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 asserted by ITU members or others outside of the Recommendation development process. As of the
13、 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 represent the latest information and are therefore strongly urged to
14、 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 permission in writing from the ITU. ii Recommendation X.6 (08/97) - STD=ITU
15、-T RECMN X-6-ENGL 1997 I 4b2591 0643336 TbT CONTENTS Introduction Scope and fieid of application Definitions Multicast service model . Service overview 5.1 Data transfer overview 5.2 Signalling and control overview . Service capabilities . 6.1 Multicast Group Creation and Membership Control 6.2 Mult
16、icast Call . 6.3 Data Transfer 6.4 Leave Call . 6.5 Join Call 6.6 Multicast Call Termination . 6.7 Multicast Status Data flow model . 7.1 Queue configurations in different communication modes 7.2 Data flow model and data transfer overview Appendix I . Summary of group and call attributes Appendix II
17、 - Mapping applications into multicast services II . 1 News service . 11.2 Weather service 11.3 Information service with back-up device 11.4 Examination 11.5 Name service 11.6 Distributed data base . 11.7 Time service 11.8 Interpersonal on-line conferencing . II.9 Lottery service 11.10 Product annou
18、ncements II . 11 Audio/Graphic Conferencing Appendix III - Provision of multicast service in PSPDN environments . Recommendation X.6 (08/97) Page 1 1 1 2 5 6 10 10 11 13 20 21 22 25 25 26 27 27 29 31 31 31 31 31 31 32 32 32 32 32 32 33 . 111 - - STD-ITU-T RECMN X-6-ENGL 1997 = 4862531 0643117 9Tb m
19、Recommendation X.6 MULTICAST SERVICE DEFINITION (revised in 1997) 1 Introduction The establishment in various countries of packet switched public data networks creates the need to produce Recommendations to facilitate the provision of point-to-multipoint (multicast) data services. NOTE - Whether mul
20、tipoint-to-point operation should be included as part of multicast services is for further study. This Recommendation describes the service definitions and capabilities of a multicast service. This Recommendation provides a common model for the description of the service elements, defines the termin
21、ology and describes a set of capabilities which may be provided by such a service. This Recommendation does not specify the interface specifications or the protocol elements that would be used to provide the service. 2 The multicast service described in this Recommendation is a connection-oriented m
22、ulticast service, in the sense that the multicast user must first establish a connection (virtual call or permanent virtual circuit) before it is able to send or receive any multicast data. The multicast service may be real time, that is, with predictable delay characteristics. The term connection a
23、s applied to the multicast service differs from point-to-point service in two ways: 1) 2) The multicast service described in this Recommendation may be used by a broad range of applications. Some typical examples are: 1) applications where a continuous stream of data, such as messages, status, event
24、s and process data, needs to be distributed to multiple destinations; 2) applications where data are produced with time constraints - data may have to be delivered to multiple destinations within a specified time, after which they may no longer be valid or useful; applications where a data base is d
25、istributed, for instance, to provide greater availability andor to spread the traffic loading. Scope and field of application the user connection terminates within the network, in an entity called the multicast server; from a users perspective, there are more than one remote users on this connection
26、. 3) The multicast service is designed to work over a variety of transmission technologies, such as packet switched data networks, local area networks, with multicast addressing, and satellite networks. 3 Definitions This Recommendation defines the following terms: 3.1 destinations; it is a one-in,
27、many-out service. multicast service: Is one in which a single data unit transmitted by a source is received by multiple A multicast service is intended to mean a service in the sense of services specified in Recommendations X. 1 and X.2. There is no intended relationship to an OS1 service. Recommend
28、ation X.6 (08/97) 1 3.2 multicast group: A set of members participating in the packet multicast service. The multicast group is defined by a rule (or set of rules) which identifies a collection of members implicitly or explicitly. This rule may associate members for the purpose of participating in a
29、 call, or may associate members who do not participate in data transfer but do participate in management, security, control, and accounting for the multicast group. 3.3 multicast call: The relationship that exists between the members of a multicast group for the purpose of transferring data. More th
30、an one multicast call may exist in a multicast group. A multicast call establishes an active group. 3.4 given instance of time. active group: Those members of the multicast group that are participating in a particular multicast call at a 3.5 multicast call. invoked group: Those members of the multic
31、ast group with which communication is attempted in a particular 3.6 participate in an open group. open group: A special multicast group which does not have pre-defined set of members. Any user may 3.7 control. group controller: The member (or third party) responsible for the multicast group creation
32、 and membership 3.8 initiate multicast calls. call initiator: The member (or third party) authorized to initiate a multicast call. More than one member may 3.9 one-way: Mode of communication (see 5.1.1). 3.10 two-way: Mode of communication (see 5.1.2). 3.11 n-way: Mode of communication (see 5.1.3).
33、3.12 multicast server: A logical entity which provides the packet multicast service to the members. 3.13 participant: A member of a multicast group participating in a particular multicast call at a given time. 3.14 participating in multicast data transmission. capability: Capabilities allow a partic
34、ipant or member to perform certain functions as part of managing or 3.15 concentrate: Transmissions from multiple sources are received by a single receiver. 3.16 senderlreceiver: A participant is defined as a “senderlreceiver“ when its primary function is sending. 3.17 receiverkender: A participant
35、is defined as a “receiver/sender“ when its primary function is receiving. The following terms are defined in Recommendation X.200: - protocol data unit; - service data unit. 4 Multicast service model The multicast service model (see Figure 1) shows a multicast group as consisting of members that par
36、ticipate in multicast communication using an immediate entity called the multicast server. The multicast server is a single logical entity which provides the multicast service to all members. The logical relationship between the members of a multicast group, for the purpose of transferring data, is
37、called a multicast call. In practice, a multicast call may be logically composed of n point-to-point connections, one between each member and the multicast server, as shown in Figure 1. 2 Recommendation X.6 (08/97) Multicast service Group member Multicast server TO71 664 if participant a leaves the
38、call at some later time, the active group of participants for multicast call 3 would then contain (c, ., g). Recommendation X.6 (08/97) 3 I I I I I I I I I I I I I I l I I I I I I I Server I Members Network Member Multicast service Indicates boundary of the multicast service as seen by the user a) S
39、ewer outside the network Membefi I I Indicates boundary of the multicast service as seen by the user b) Server inside the network Members T072669o-%/d02 c) Sewers in multiple networks and outside of networks Figure 2E.6 - Examples of server implementations 4 Recommendation X.6 (08197) - STDmITU-T RE
40、CMN X-b-ENGL 1997 E 4862593 Ob43121 327 E Multicast service Multicast call 1 cr Multicast call 3 Multicast call 2 Group 1 Members a b c . 9 h i . n TO7 16670-93603 Figure 3K.6 - Examples of call configurations Multicast communication to a subset of members of a multicast group may be accomplished by
41、 one of the following methods: I) creating a new multicast group containing the subset of members of the original group; 2) changing an existing multicast group rule set, which implies changing the membership of an existing group; or 3) using an inclusion list or exclusion list with the multicast ca
42、ll. The list specifies a set of members that are authorized (not authorized) to join the multicast call. Note that exclusion can occur at any time (i.e. during both call Set-up and data transfer). Figure 3 shows an example in which member b is not participating at that time in multicast call 3. 5 Se
43、rvice overview The multicast service, in general, provides the ability to establish a multicast relationship (i.e. multicast call) between the members of a group and allows them to participate in real-time data transfer. As shown in Figure 4, real-time implies that a data unit (x) received by the mu
44、lticast service at time t, will be delivered at least to those members of the multicast group that were participating in the multicast call at that time (Le. the active group); members that join the multicast call after time t may or may not receive this data unit. Recommendation X.6 (08/97) 5 Sende
45、r Service Receivers Time = t Begin transmission of data unit (x) to members who are participants at time (t) lme=t+e End transmission of data unit (x) to members who were participants at time t. Also, service may or may not have sent data unit (x) to members joining the multicast call before time (t
46、 + e) Service will send data unit (x) to appropriate active group members (Note 1) Service will not send data unit (x) to members joining the . multicast call here , c T07267C-S/d04 Time NOTE 1 - Appropriate active group members depend on the direction of transfer. NOTE 2 - The multicast service def
47、ined here determines the members of a particular group at “Time = t“ and transmits data unit (x) to ali members of the group the data unit (x) received from the sender. If a member of that group leaves the group after “Time = t“, it may receive the data unit (x). Figure 4R.6 - Real-time multicast 5.
48、1 Data transfer overview Several types of data transfer are possible. These types appear to be distinct, but actually can form a continuum of different multicast communications methods. Not every realization of a multicast service will provide all of these data transfer types, and may not support al
49、l of the options described. In general, it will not be useful for a participant sending data to receive a copy of its own transmission. However, specific realizations may wish to include this as an option to meet the needs of some applications. The use of the term “optionally“ to describe data transfer rules in the following three subclauses has two implications: 1) protocols which provide the multicast service may choose to support this data transfer rule; 2) protocols which support this data transfer rule may make it optional on per-call, per-packet,
