1、STD*ITU-T RECMN X-4B-ENGL L79b W LiBb257L Ob24bL9 374 INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU X.48 (I 0/96) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATION Data transmission - Interfaces Procedures for the provision of a basic multicast servi
2、ce for Data Terminal Equipments (DTEs) using Recommendation X.25 ITU-T Recommendation X.48 (Previously CCITT Recommendation) ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATION (1 PUBLK DATA NETWORKS X.1-X.199 I Services and facilities X.1-X.19 interfaces X20-X.49 Transmission
3、, signalling and switching Network aspects Maintenance Administrative arrangements Model and notation Service definitions Connection-mode protocol specifications Connectionless-mode protocol specification PICS proformas Protocol Identification Security Protocols Layer Managed Objects Conformance tes
4、ting General Satellite data transmission systems MESSAGE HANDLING SYSTEMS DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS Networking Efficiency Naming, Addressing and Registration Abstract Syntax Notation One (ASN.l) Systems Management framework and architecture Management Communication Service and Prot
5、ocol Structure of Management Information Management functions OPEN SYSTEM INTERCONNECTION INTERWORKING BETWEEN NETWORKS OS1 MANAGEMENT SECURITY OS1 APPLICATIONS Commitment, Concurrency and Recovery Transaction processing Remote operations OPEN DISTRIBUTED PROCESSING X.50-X. 89 X.90-X. 149 X. 150-X.
6、179 X.180-X.199 X.200-X.299 X.200-X.209 X.210-X.219 X.220-X.229 X.23 0-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.699 X.700-X.799 X.700-X.709 X.710-X.719 X.720-X
7、.729 X.730-X.799 X.800-X.849 X.850-X.899 X.850-X.859 X.860-X.879 X.880-X.899 X.900-X.999 Forjrther details, please refer to ZTU-T List of Recommendations. STD-ITU-T RECMN X-q-ENGL L7b m 4b257L b24b2L T22 FOREWORD The IT-T (Telecommunication Standardization Sector) is a permanent organ of the Interna
8、tional Telecommunication Union (ITU). The IT-T is responsible for studying technical, operating and tariff questions and issuing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets
9、every four years, establishes the topics for study by the IT-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 (Helsinki, March 1-12, 1993). IT-T Rec
10、ommendation X.48 was prepared by IT-T Study Group 7 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 5th of Octobre 1996. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recogn
11、ized operating agency. O ITU 1997 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. Recommendation X.48 (10196) 1 1 2 3 4 5 6 7 8 9 10
12、 11 12 13 STD-ITU-T RECMN X-LiB-ENGL 199b - 4Bb259L Ub24b22 969 W CONTENTS Scope and field of application Normative references . 2.1 Identical Recommendations I International Standards 2.2 Additional references Definitions 3.1 Reference Model definitions . 3.2 X.25 Packet Layer Protocol definitions
13、3.3 Multicast Service definitions Abbreviations . Description of multicast service for members of a multicast group with interfaces operating in the basic mode . X.25 protocol element restrictions for DES operating in the basic mode Multicast group creation and membership control . 7.1 General 7.2 G
14、roup attributes Multicast call attributes 8.1 Multicast call establishment attributes 8.2 Data transfer attributes 8.3 Type of data transfer . Multicast service model . Multicast service sublayer 10.1 Services provided by the multicast service sublayer 10.2 Services assumed by the multicast service
15、sublayer . 10.3 Multicast service sublayer protocol procedures 10.4 Subnetwork dependent mapping sublayer 11.1 Services provided by the subnetwork dependent mapping sublayer 11.2 Services assumed by the subnetwork dependent mapping sublayer . Mapping between X.6 messages and SMM primitives . X.25 PL
16、P 1 ISO/IEC 8208 Sublayer . Optional user facilities . Annex A . Summary of Group and Call attributes . Page 1 1 1 1 2 2 2 2 3 4 5 5 5 5 7 7 8 8 9 10 10 11 13 18 19 19 20 23 24 25 11 Recommendation X.48 (10/96) STD*ITU-T RECMN X-LiB-ENGL L99b W 48b259L Ob24b23 8T5 SUMMARY This Recommendation specifi
17、es the procedures for a Data Terminal Equipment (DTE) opereating in accordance with Recommendation X.25 to participate in a multicast data transmission service described in Recommendation X.6. The overriding god of this Recommendation is to make no changes to the DTE which wishes to participate in t
18、his service Recommendation X.48 (10196) . 111 Recommendation X.48 PROCEDURES FOR THE PROVISION OF A BASIC MULTICAST SERVICE FOR DATA TERMINAL EQUIPMENTS (DTEs) USING RECOMMENDATION X.25 (Geneva, 1996) 1 Recommendation X.6 describes a connection-oriented multicast service, in the sense that the multi
19、cast 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 defined in Recommendation X.6 is designed to work over a variety of transmission technologies. Scope and field of application In a Pa
20、cket Switched Public Data Network (PSPDN) environment, this Recommendation specifies the procedures for Data Terminal Equipment (DTE) operating in accordance with Recommendation X.25 for the realization of a basic subset of the multicast service described in Recommendation X.6. The basic multicast s
21、ervice provided by this Recommendation does not require additional protocol elements or other elements of procedures beyond those specified in X.25 Packet Layer Protocol (PLP). The provision of the multicast service capabilities specified in Recommendation X.6 that requires protocol elements or othe
22、r elements of procedures in addition to the X.25 PLP procedures is beyond the scope of this Recommendation. It is specified in Recommendation X.49. 2 Normative references The following Recommendations 1 International Standards contain provisions which, through reference in this text, constitute prov
23、isions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations 1 International Standards are subject to revision: all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent editions of the Re
24、commendations 1 International Standards listed below. Members of IEC, IS0 and IT maintain registers of currently valid Recommendations I International Standards. 2.1 Identical Recommendations I International Standards - IT-T Recommendation X.200 (1 994) I ISO/IEC 7498- 1 : 1994, Information technolo
25、gy - Open Systems Interconnection - Basic Reference Model: The Basic Model. IT-T Recommendation X.213 (1995) I ISO/IEC 8348:1996, Information technology - Open Systems Interconnection - Network service definition. - 2.2 Additional references - - ITU-T Recommendation X.6 (1993), Multicast service def
26、inition. ITU-T Recommendation X.25 (1996), Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for terminais operating in the packet mode and connected to public data networks by dedicated circuit. ISO/IEC 8208:1995, Information technology - Daia communicatio
27、ns - X.25 Packet Layer Protocol for Data Terminal Equipment. IS0 8648: 1988, Information processing systems - Open Systems Interconnection - Internal organization of the Network Layer. ISO/IEC 10028: 1993, Information technology - Telecommunications and information exchange between systems - Definit
28、ion of the relayingjimctions of a Network layer intermediate system. ISOIIEC 10 177: 1993, Information technology - Telecommunications and information exchange between systems - Provision of the connection-mode Network internal layer service by intermediate systems using ISO/IEC 8208, the X.25 Packe
29、t Layer Protocol. - - - - Recommendation X.48 (10196) 1 3 Definitions 3.1 Reference Model definitions The following terms are defined in ITU-T Rec. X.200 1 ISO/IEC 7498-1: - Protocol Data Unit (PDU). - Service Data Unit (SDU). 3.2 X.25 Packet Layer Protocol definitions The following terms are define
30、d in Recommendation X.25 and in ISODEC 8208: - DTE/DCE Interface. - Logical Channel. - M-bit Sequence. - Qualifier bit (Q-bit). - Virtual Circuit. 3.3 Multicast Service definitions The following terms are defined in Recommendation X.6: - Multicast group. - Multicast call. - Active group. - Call init
31、iator. - One-way mode of communication. - Two-way mode of communication. - N-way mode of communication. - Multicast server. - Participant. - Capability. - 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 a
32、ny one submits a Service Data Unit (SDU) it is delivered to all members of the group. There may be no restrictions on how many users may submit 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.2
33、5 PLP specified in Recommendation X.25 with no additional protocol elements or other elements of procedures. A subset of the multicast service capabilities specified in Recommendation X.6 is provided to DTEs operating in this mode. 3.3.3 extended multicast service: Packet multicast service provided
34、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. 3.3.4 active group integrity (AGI): Set of conditions conc
35、erning 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 multicast call enters the Pause state. The data transfer
36、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. 2 Recommendation X.48 (10/96) A set of conditions may also be defined concerning the policies for detection of lost and duplicate
37、 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 individual active group members b
38、ut 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 call to enter the data transfe
39、r phase, for a multicast call to remain in the data transfer phase, for a sender to detect lost and/or duplicate PDUs, etc.). Note the following distinction between AGI and Quorum. AGI is the necessary and sufficient conditions for a multicast call to enter and/or remain in the data transfer phase.
40、Quorum is the necessary condition to enter and/or remain in the data transfer phase. Note that if an AGI is just a pure number (Le. AGI is a single condition which is the Quorum requirement), then Quom is necessary and sufficient. 3.3.6 dialogue control: Categorization of an active group as either c
41、entralized or decentralized. 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 only a single member is allowed to
42、 originate multicast transmissions at any given time. decentralized 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 ar
43、e 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, the following abbreviations are used. AGI Active Group Integri
44、ty CUG Closed User Group D-bit Delivery confirmation bit DCE Data Circuit-terminating Equipment DTE Data Terminal Equipment IEC International Electrotechnical Commission IS0 International Organization for Standardization ITU-T M-bit More bit MSE Multicast Service Entity NI Network Internal NILS Netw
45、ork Internal Layer Service NISDU Network Internal Service Data Unit NPI Numbering Plan Identification NS Network Service NUI Network User Identification PCI Protocol Control Information PDU Protocol Data Unit PLP Packet Layer Protocol PSPDN Packet Switched Public Data Network International Telecommu
46、nication Union - Telecommunication Standardization Sector Recommendation X.48 (10/96) 3 STD-ITU-T RECMN X-qA-ENGL L77b i8b257L Ob24b28 387 Q-bit Qualifier bit QOS Quality of Service ROA Recognized Operating Agency SMM Subnetwork Multicast Mapping SNAcF Subnetwork Access Function SNAcP Subnetwork Acc
47、ess Protocol SNDME Subnetwork Dependent Mapping Entity TOA Type of Address 5 Description of multicast service for members of a multicast group with interfaces operating in the basic mode The burden of operation of the basic service is placed on the service provider. To eliminate changes to these int
48、erfaces, only out-of-band control mechanisms and group management mechanisms are used. NOTE 1 - In this Recommendation, the reference to out-of-band control mechanisms means the use of administrative mechanisms or protocol procedures that are outside the scope of this Recommendation. A member of a m
49、ulticast group with an interface operating in the basic mode can be included in the following lists of capabilities of the members of the group (see Recommendation X.6): - - - - Initiator Capability List: List of members who may initiate a multicast call. Send Capability List: List of members who may act as senders of data in a multicast call. Receive Capability List: List of members who may act as receivers of data in a multicast call. Terminate Capability List: List of members who may terminate a multicast call in progress. Members of a multicast group with interfaces o
