1、INTERNATIONAL TELECOMMUN I CATI ON UN I ON ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU x.49 (1 0/96) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATION Public data networks - Interfaces Procedures for the provision of an extended multicast service for Data Terminal Equipments (DTEs) usi
2、ng Recommendation X.25 ITU-T Recommendation X.49 (Previously CCITT Recommendation) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATION UBLIC DATA NETWORKS X.1-X. 199
3、 Services and facilities x.1-x.19 Inte Transmission, signalling and switching X.50-X.89 Network aspects Maintenance Administrative arrangements 3PEN SYSTEM INTERCONNECTION Model and notation Service definitions Connection-mode protocol specifications Connectionless-mode protocol specifications PICS
4、profomas Protocol Identification Security Protocols Layer Managed Objects Conformance testing General Satellite data transmission systems MESSAGE HANDLING SYSTEMS DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS INTERWORKING BETWEEN NETWORKS Networking Efficiency Naming, Addressing and Registration Abstr
5、act Syntax Notation One (ASN. 1) Systems Management framework and architecture Management Communication Service and Protocol Structure of Management Information Management functions OS1 MANAGEMENT SECURITY OS1 APPLICATIONS Commitment, Concurrency and Recovery Transaction processing Remote operations
6、 OPEN DISTRIBUTED PROCESSING X.90-X.149 X.150-X.179 X. 180-X. 199 X.2O-X.299 x.200-x.209 X.210-X.219 X.22-X.229 X.230-X.239 X.240-X.259 X.260-X.269 X.270-X.279 X.280-X.289 X.290-X.299 X.300-X.399 X.300-X.349 X.350-X.399 X.400-X.499 X.500-X.599 X.600-X.699 X.600-X.629 X.630-X.649 X.650-X.679 X.680-X.
7、699 X.700-X.799 X.700-X.709 X.710-X.719 X.720-X.729 x.730-x.799 X.800-X.849 X.850-X.899 X.850-X.859 X.860-X.879 X. 8 80-X . 899 X.900-X.999 For further details, please refer to ITU-T List of Recommendations. COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Informati
8、on Handling ServicesSTD-ITU-T RECMN X-LiS-ENGL L77b 4Bb257L Ob27377 bbb U FOREWORD The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issuing
9、 Recommen- dations 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 IT-T Study Groups which, in their turn, produce Recommendations on the
10、se topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). ITU-T Recommendation X.49 was prepared by IT-T Study Group 7 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on t
11、he 5th of October 1996. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1997 All rights reserved. No part of this publication may be reproduced or utilized in any form or
12、 by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Recommendation X.49 (10/96) 1 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services1 2 3 4 5 6 7 8 9 10 11 12 13 CONTE
13、NTS Page Scope and field of application Normative references . 2.1 Identical Recommendations 1 Intemational Standards 2.2 Paired Recommendations I International Standards equivalent in technical content 2.3 Additional references Definitions 3.1 Reference Model definitions . 3.2 X.25 Packet Layer Pro
14、tocol definitions 3.3 Multicast service definitions . Abbreviations . Description of multicast service for members of a multicast group with interfaces operating in the extended mode . X.25 protocol element restrictions for DTEs operating in the extended mode Multicast group creation and membership
15、control . 7.1 General 7.2 Group attributes Multicast Call attributes . 8.1 Multicast Call Establishment attributes 8.2 Data Transfer attributes 8.3 Types of Data Transfer . Multicast service model . Multicast Service Sublayer . 10.1 Services Provided by the Multicast Service Sublayer 10.2 10.3 Multi
16、cast Service Sublayer Protocol Procedures 10.4 Mapping between X.6 messages and SMM primitives . Subnetwork Dependent Mapping Sublayer 11.1 Services provided by the Subnetwork Dependent Mapping Sublayer 11.2 Services assumed by the Subnetwork Dependent Mapping Sublayer 12.1 General 12.2 Parameter Ty
17、pe Encoding . Services assumed by the Multicast Service Sublayer . Encoding Principles for SNDME . 12.3 Parameter Value Encoding . X.25 PLP/8208 sublayer 13.1 Procedures for Flow Control 13.2 Procedure for Reset . 13.3 Other procedures . 13.4 Optional user facilities Annex A . Summary of Group and C
18、all attributes . A . 1 Group attributes A.2 Call Attributes . A.3 Data Transfer attributes . Annex B - Protocol Encoding of Multicast parameters in X.25 packets B.l Establishment of Multicast Call with Attribute values Different from Default values . B.2 Support of Recommendation X.6 Multicast servi
19、ces 1 1 1 1 2 2 2 2 2 3 4 5 6 6 6 7 7 9 9 10 12 12 12 13 24 24 24 24 35 35 35 36 41 41 42 42 42 44 44 45 47 48 48 53 11 Recommendation X.49 (10196) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSUMMARY This Recommendation which specif
20、ies the procedures for a Data Terminal Equipment (DTE) operating in accordance with Recommendation X.25 for the realization of the multicast service described in Recommendation X.6. The multicast service provided by this Recommendation requires additional protocol elements and other elements of proc
21、edures beyond that specified in X.25 Packet Layer Protocol (PLP). . Recommendation X.49 (10/96) 111 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSTD-ITU-T RECMN X.49-ENGL 197b 9Bb2591 062702 TBO m ,” .- I _. . r COPYRIGHT Internation
22、al Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSTD-ITU-T RECMN X.49-ENGL 199b W 48b257L b27403 917 Recommendation X.49 PROCEDURES FOR THE PROVISION OF AN EXTENDED MULTICAST SERVICE FOR DATA TERMINAL EQUIPMENTS (DTEs) USING RECOMMENDATION X.25 (Geneva, 1996
23、) 1 Scope and field of application Recommendation X.6 describes a connection-oriented multicast 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 d
24、efined in Recommendation X.6 is designed to work over a variety of transmission technologies. In a Packet Switched Public Data Network (PSPDN) environment, this Recommendation specifies the procedures for a Data Terminal Equipment (DTE) operating in accordance with Recommendation X.25 for the realiz
25、ation of the multicast service described in Recommendation X.6. The multicast service provided by this Recommendation requires additional protocol elements and other elements of procedures beyond those specified in the X.25 Packet Layer Protocol (PLP). The provision of a basic subset of the multicas
26、t service capabilities specified in Recommendation X.6 that does not require protocol elements or other elements of procedures in addition to the X.25 PLP procedures is specified in Recommendation X.48. Members of a multicast group with interfaces operating in the extended mode (i.e. in accordance w
27、ith this Recommendation) are able to participate in a multicast call with participants with interfaces operating in the basic mode (i.e. in accordance with Recommendation X.48). 2 Normative references The following Recommendations and other references contain provisions which, through reference in t
28、his 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: all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recen
29、t edition of the Recommendations and other references listed below. A list of currently valid ITU-T Recommendations is regularly published. 2.1 Identical Recommendations I International Standards - IT-T Recommendation X.200 (1994) I ISO/IEC 7498-1 :1994, Information technology - Open Systems Interco
30、nnection - Basic Reference Model: The Basic Model. ITU-T Recommendation X.213 (1995) I ISO/IEC 8348:1996, Information technology - Open Systems Interconnection - Network service definition. - 2.2 Paired Recommendations I International Standards equivalent in technical content - ITU-T Recommendation
31、X.25 (1996), Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE, for terminals operating in the packet mode and connected to public data networks by dedicated circuit. ISOiEC 8208:1995, Information technology - Data communications - X.25 Packet Layer Protocol
32、 for Data Terminal Equipment. ITU-T Recommendation X.223 (1993), Use of X.25 to provide the OSI connection-mode network service for ITU-T applications. ISOAEC 8878: 1992, Information technologv - Telecommunications and information exchange between systems - Use of X.25 to provide the OSI Connection-
33、mode Network Service. - Recommendation X.49 (10/96) 1 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services2.3 Additional references - ITU-T Recommendation X.6 (1993), Multicast service definition. - IS0 8648: 1988, Information processing sy
34、stems - Open Systems Interconnection - Internal organization of the Network Layer. - ISOIEC 10028: 1993, Information technology - Telecommunications and information exchange between systems - Definition of the relayingfunctions of a Network layer intermediate system. - ISOIEC 1 O 177: 1993, Informat
35、ion technology - Telecommunications and information exchange between systems - Provision of the connection-mode Network internal layer service by intermediate systems using ISOiIEC 8208, the X.25 Packet Layer Protocol. 3 Definitions 3.1 Reference Model definitions The following terms are defined in
36、IT-T Rec. X.200 1 ISOIEC 7498-1: - Protocol Data Unit (PDU); - Service Data Unit (SDU). 3.2 The following terms are defined in ITU-T Rec. X.25 and in ISOfiEC 8208: X.25 Packet Layer Protocol definitions - DTE/DCE Interface; - logical channel; - M-bit Sequence; - Qualifier bit (Q-bit); - virtual circ
37、uit. 3.3 Multicast service definitions The following terms are defined in Recommendation X.6: - multicast group; - multicast call; - active group; - call initiator; - one-way mode of communication; - two-way mode of communication; - N-way mode of communication; - multicast server; - participant; - c
38、apability; - ordering. In addition, the following terms are defined: 3.3.1 multicast service: A service to a specified group of service users such that when any one submits a Service Data Unit (SDU), it is delivered to ail members of the group. There may be no restrictions on how many users may subm
39、it SDUs at a given time. 3.3.2 basic multicast service: Packet multicast service provided to Data Terminal Equipments (DTEs) operating in accordance to the X.25 PLP specified in Recommendation X.25 with no additional protocol elements or other elements of procedures. A subset of the multicast servic
40、e capabilities specified in Recommendation X.6 is provided to DTEs operating in this mode. 2 Recommendation X.49 (10196) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSTDnITU-T RECMN X-qS-ENGL LSSb 48b259L Ob27L105 79T m 3.3.3 extende
41、d multicast service: Packet multicast service provided to DTEs operating protocol elements or other elements of procedures in addition to the X.25 PLP specified in Recommendation X.25. The multicast service capabilities specified in Recommendation X.6 are provided to DTEs operating in this mode. 3.3
42、.4 active group integrity (AGI): Set of conditions concerning the active group which must be true in order, for the participants in a multicast call, to transfer data. In principle if the AGI is not met, the multicast call may be either terminated or halted, i.e. the data transfer is ceased and the
43、multicast call enters the Pause state. The data transfer is resumed when the AGI is satisfied. The Pause and Resume services are not supported in this Recommendation, i.e. the multicast call is terminated if the AGI is not met. A set of conditions may also be defined concerning the policies for dete
44、ction of lost and duplicate PDUs and flow control during the data transfer phase. A special case of AGI which deals only with a single number is called Quorum. The AGI applies to a particular multicast call and relates to the characteristics of the active group. AGI is not an attribute of the indivi
45、dual active group members but is an attribute of the active group. 3.3.5 quorum: Minimum number of entities in the active group which meets the AGI when it is expressed in terms of a single condition which specifies a number for the execution of a certain function or policy (e.g. for a multicast cal
46、l to enter the data transfer phase, for a multicast call to remain in the data transfer phase, for a sender to detect lost andor duplicate PDUs, etc.). Note the following distinction between AGI and Quorum. AGI is the necessary and sufficient conditions for a multicast call to enter andor remain in
47、the data transfer phase. Quorum is the necessary condition to enter andor remain in the data transfer phase. Note that if an AGI is just a pure number (i.e. AGI is a single condition which is the Quorum requirement), then Quorum is necessary and sufficient. 3.3.6 dialogue control: Categorization of
48、an active group as either centralized or decentralized. 3.3.6.1 centralized active group: An active group in which a single (designated) member is permitted to originate multicast transmissions. The designation of a member as originator may be dynamic and change from one member to another as long as
49、 only a single member is allowed to originate multicast transmissions at any given time. 3.3.6.2 decentraized active group: An active group in which any member is permitted to originate multicast transmissions at the same time as other members. It is possible to place restrictions on individual members of the active group on whether they are permitted to originate multicast transmissions. An example of such restrictions is that only a subset of the active members may be permitted to originate multicast transmissions. 4 Abbreviations For the purposes of this Recommendation, t
