1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T X.603TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (04/2004) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS OSI networking and system aspects Networking Information technology Relayed multicast protocol: Framework ITU-T Recommendation X.603 ITU-
2、T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS PUBLIC DATA NETWORKS Services and facilities X.1X.19 Interfaces X.20X.49 Transmission, signalling and switching X.50X.89 Network aspects X.90X.149 Maintenance X.150X.179 Administrative arrangements X.180X.199 OPEN SYSTEMS INTERC
3、ONNECTION Model and notation X.200X.209 Service definitions X.210X.219 Connection-mode protocol specifications X.220X.229 Connectionless-mode protocol specifications X.230X.239 PICS proformas X.240X.259 Protocol Identification X.260X.269 Security Protocols X.270X.279 Layer Managed Objects X.280X.289
4、 Conformance testing X.290X.299 INTERWORKING BETWEEN NETWORKS General X.300X.349 Satellite data transmission systems X.350X.369 IP-based networks X.370X.399 MESSAGE HANDLING SYSTEMS X.400X.499 DIRECTORY X.500X.599 OSI NETWORKING AND SYSTEM ASPECTS Networking X.600X.629 Efficiency X.630X.639 Quality
5、of service X.640X.649 Naming, Addressing and Registration X.650X.679 Abstract Syntax Notation One (ASN.1) X.680X.699 OSI MANAGEMENT Systems Management framework and architecture X.700X.709 Management Communication Service and Protocol X.710X.719 Structure of Management Information X.720X.729 Managem
6、ent functions and ODMA functions X.730X.799 SECURITY X.800X.849 OSI APPLICATIONS Commitment, Concurrency and Recovery X.850X.859 Transaction processing X.860X.879 Remote operations X.880X.899 OPEN DISTRIBUTED PROCESSING X.900X.999 TELECOMMUNICATION SECURITY X.1000 For further details, please refer t
7、o the list of ITU-T Recommendations. ITU-T Rec. X.603 (04/2004) i INTERNATIONAL STANDARD ISO/IEC 16512-1 ITU-T RECOMMENDATION X.603 Information technology Relayed multicast protocol: Framework Summary The Relayed Multicast Protocol (RMCP) is an application-layer protocol for providing end-to-end mul
8、ticast services over an IP-network environment. This Recommendation | International Standard specifies basic concepts of a relayed multicast scheme, data delivery models, service scenarios, required protocol functions for protocol operation, and basic message structures. This framework can be used t
9、o specify detailed relayed multicast protocols for various application requirements. Source ITU-T Recommendation X.603 was approved on 29 April 2004 by ITU-T Study Group 17 (2001-2004) under the ITU-T Recommendation A.8 procedure. An identical text is also published as ISO/IEC 16512-1. Keywords End-
10、to-end multicast service, Framework, Multicast Agent, Relayed multicast, Session Manager. ii ITU-T Rec. X.603 (04/2004) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sect
11、or (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 every
12、 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 purview,
13、 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 voluntar
14、y. 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 the neg
15、ative 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 involve the
16、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 Recommendati
17、on, 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 consult the TSB patent database. ITU 2005
18、 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. X.603 (04/2004) iii CONTENTS Page 1 Scope 1 2 Normative references . 1 3 Definitions 1 4 Abbreviations . 2 5 Framework of RMCP . 2 5.1 Introduction. 2
19、 5.2 Basic concept of RMCP 3 5.3 RMCP data delivery models . 5 5.3.1 Simplex delivery model for real-time services 5 5.3.2 Simplex delivery model for reliable services 5 5.3.3 N-plex delivery model for real-time services 6 5.3.4 N-plex delivery model for reliable services 6 6 RMCP service scenario 6
20、 7 RMCP functions. 8 7.1 Session initialization . 8 7.2 Session join . 8 7.3 Session leave. 8 7.4 Session release 8 7.5 Session maintenance . 8 7.6 Session monitoring 9 8 Message structure. 9 8.1 Basic message structure 9 8.2 Option format 9 8.2.1 Option types and values 10 Bibliography 11 iv ITU-T
21、Rec. X.603 (04/2004) Introduction This Recommendation | International Standard specifies the Relayed Multicast Protocol (RMCP) used for realizing relayed multicast. Relayed multicast, also known as overlay multicast or application-layer multicast, is a data-delivery scheme for group communications a
22、pplications over unicast. RMCP employs intermediate Multicast Agents for relaying application data from one or more senders to many receivers. The design of RMCP has been motivated from the following observations: In the marketplaces, diverse group applications and services have been provisioned com
23、mercially all over the world. Their examples include Internet TV, remote education, real-time streaming media applications, live broadcasting of special events such as the Victoria Show, stock-tickers, and so on. At present, most of the group applications mentioned above use a replicated IP unicast
24、method to realize multicast services. As a result, those applications have problems about degradation of service quality due to the limitation in the number of simultaneous service users. In the business model that means less revenue or profit. IP multicast has been known as an effective transport t
25、echnology for providing multicast services. Nevertheless, the IP multicast has not been deployed widely over the Internet due to several reasons, including the following: high deployment cost along with an uncertain Return-on-Investment model; IP multicast alone cannot support all kinds of group app
26、lications. Network services which offer, for example, group file transfer or network games, need a reliable multicast transport mechanism. However, even current reliable multicast transport mechanisms still have unresolved problems including that of scalability, flow control, congestion control, etc
27、. Until an appropriate multicast transport mechanism is laid down, group communications applications requiring reliable data transfer will continue to depend on the server-based replicated unicast method. Although IP multicast has not deployed globally, a lot of local networks have already been equi
28、pped with IP multicast transport. For example, Ethernet-based LANs and private networks such as corporate and campus networks substantially provide the multicast transport capability within their local subnet or administrative domains. Recognizing these observations, there is a crucial need to devel
29、op an alternative multicast delivery scheme. RMCP is one of such schemes to realize multicast delivery over the current Internet. It makes good use of existing unicast, multicast and/or multicast tunnelling schemes. In addition, RMCP is designed as several separate forms to support well any kind of
30、group service type. RMCP is expected to provide a substantial solution for group applications over the real-world Internet. ISO/IEC 16512-1:2005 (E) ITU-T Rec. X.603 (04/2004) 1 INTERNATIONAL STANDARD ITU-T RECOMMENDATION Information technology Relayed multicast protocol: Framework 1 Scope RMCP is a
31、 protocol which is used to realize a relayed multicast data transport scheme. Differently from the conventional IP multicast, RMCP can configure a relayed multicast path that multicast traffic flows by using intermediate end-hosts. RMCP can be applied to the current unicast based Internet where IP m
32、ulticast has not been deployed completely without any modifications. This Recommendation | International Standard addresses the basic concepts needed to specify RMCP for relayed multicast. It defines the related terminology and proposes a framework for the future development of RMCP. The framework c
33、overs network topology including network entities and the relationship between them, service scenarios, basic operations, and message encoding rules. 2 Normative references The following Recommendations and International Standards contain provisions which, through reference in this text, constitute
34、provisions of this Recommendation | International Standard. At the time of publication, the editions indicated were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this Recommendation | International Standard are encouraged to investigate the poss
35、ibility of applying the most recent edition of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently valid International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently valid ITU-T Recommendations. ITU-
36、T Recommendation X.601 (2000), Multi-peer communications framework. ITU-T Recommendation X.605 (1998) | ISO/IEC 13252:1999, Information technology Enhanced Communications Transport Service definition. ITU-T Recommendation X.606 (2001) | ISO/IEC 14476-1:2002, Information technology Enhanced Communica
37、tions Transport Protocol: Specification of simplex multicast transport. ITU-T Recommendation X.606.1 (2003) | ISO/IEC 14476-2:2003, Information technology Enhanced Communications Transport Protocol: Specification of QoS management for simplex multicast transport. 3 Definitions For the purposes of th
38、is Recommendation | International Standard, the following definitions apply: 3.1 multicast: A data delivery scheme where the same data unit is transmitted from a single source to multiple destinations in a single invocation of service. 3.2 IP multicast: Realizes a multicast scheme in the IP network
39、with the help of multiple multicast-enabled IP routers. 3.3 relayed multicast: A multicast data delivery scheme within unicast environments. 3.4 relayed multicast protocol (RMCP): A protocol to realize the relayed multicast scheme using end hosts. 3.5 RMCP session: A set of MAs which configures the
40、data delivery path using RMCP. 3.6 session ID (SID): Corresponds to group name and identifies RMCP session uniquely. 3.7 multicast agent (MA): An intermediate node which relays group application data. 3.8 sender multicast agent (SMA): An MA attached to a sender in the same system or local network. 3
41、.9 receiver multicast agent (RMA): An MA other than SMA. ISO/IEC 16512-1:2005 (E) 2 ITU-T Rec. X.603 (04/2004) 3.10 session manager: An RMCP entity that is responsible for the management of session membership and session tree. 3.11 parent multicast agent (PMA): A next upstream MA in the RMCP data de
42、livery path. 3.12 child multicast agent (CMA): A next downstream MA in the RMCP data delivery path. 3.13 simplex: Wherein only one sender is send only and all others are receive only. 3.14 N-plex: Wherein anyone can send something, and, if someone does so, all others may receive it. 4 Abbreviations
43、For the purposes of this Recommendation | International Standard, the following abbreviations apply: CMA Child Multicast Agent CP Contents Provider ID Identificator IP Internet Protocol IPC Inter-Process Communication IPIP IP in IP encapsulation MA Multicast Agent PMA Parent Multicast Agent RMA Rece
44、iver Multicast Agent RMCP Relayed Multicast Protocol RMT Reliable Multicast Transport SCTP Stream Control Transport Protocol SID Session ID SM Session Manager SMA Sender Multicast Agent T/TCP TCP extensions to Transactions TCP Transmission Control Protocol TP Transport Protocol UDP User Datagram Pro
45、tocol 5 Framework of RMCP 5.1 Introduction Relayed Multicast Protocol (RMCP) is an application-level control protocol. It constructs and manages a relayed multicast network to support Internet group application services over the current unicast-based Internet. After a series of RMCP control messages
46、 are exchanged, a multicast data delivery path is constructed by using multiple end hosts, such as even a personal desktop computer. Along the delivery path, real-time or reliable data transport channels are inter-connected between upstream and downstream MAs. Only after the data delivery path and d
47、ata channel are established can group applications work as if they were in a native IP multicast network. RMCP aims to support various kinds of Internet group applications. Table 1 categorizes the types of communications and the characteristics of data delivery. ISO/IEC 16512-1:2005 (E) ITU-T Rec. X
48、.603 (04/2004) 3 Table 1 Considerable Internet group application services Characteristics Type of communications Real-time data Reliable data Simplex Internet live TV, Internet live banner, etc. Stock-ticker, file dissemination, software live update, etc. N-plex Videoconference, inter-domain multica
49、st proxy, etc. Distributed virtual environment, network game, data mirroring and caching, etc. 5.2 Basic concept of RMCP Each RMCP session configures relayed multicast data delivery model with the following entities as shown in Figure 1: a) One session manager; b) SMA per sender application; c) One or more RMAs; d) Group applications sending or receiving group data. Figure 1 RMCP entities The SM (session manager) is just involved in session configuration and maintenance. A single SM can handle one or multiple sessions s
