1、 International Telecommunication Union ITU-T H.248.4TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2009) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Gateway control protocol: Transport over Stream Control Transmission Protocol (SCT
2、P) Recommendation ITU-T H.248.4 ITU-T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS H.100H.199 INFRASTRUCTURE OF AUDIOVISUAL SERVICES General H.200H.219 Transmission multiplexing and synchronization H.220H.229 Systems aspects H.230H.239 Commu
3、nication procedures H.240H.259Coding of moving video H.260H.279 Related systems aspects H.280H.299 Systems and terminal equipment for audiovisual services H.300H.349 Directory services architecture for audiovisual and multimedia services H.350H.359 Quality of service architecture for audiovisual and
4、 multimedia services H.360H.369 Supplementary services for multimedia H.450H.499 MOBILITY AND COLLABORATION PROCEDURES Overview of Mobility and Collaboration, definitions, protocols and procedures H.500H.509 Mobility for H-Series multimedia systems and services H.510H.519 Mobile multimedia collabora
5、tion applications and services H.520H.529 Security for mobile multimedia systems and services H.530H.539 Security for mobile multimedia collaboration applications and services H.540H.549 Mobility interworking procedures H.550H.559 Mobile multimedia collaboration inter-working procedures H.560H.569 B
6、ROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 Advanced multimedia services and applications H.620H.629 IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV General aspects H.700H.719 IPTV terminal devices H.720H.729 IPTV middleware H.730H.739
7、 IPTV application event handling H.740H.749 IPTV metadata H.750H.759 IPTV multimedia application frameworks H.760H.769 IPTV service discovery up to consumption H.770H.779 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T H.248.4 (12/2009) i Recommendation ITU-T H.248
8、.4 Gateway control protocol: Transport over Stream Control Transmission Protocol (SCTP) Summary Recommendation ITU-T H.248.4 defines the transport of ITU-T H.248.1 Gateway Control Protocol messages over the Stream Control Transmission Protocol (SCTP). SCTP is an alternative to UDP or TCP. Transport
9、of ITU-T H.248.1 over UDP or TCP is defined in Annex D of Recommendation ITU-T H.248.1. This revision specifies the use of the LONG-TIMER to remove a Transaction Identity from the list of responses. History Edition Recommendation Approval Study Group 1.0 ITU-T H.248 Annex H 2000-11-17 16 1.0 ITU-T H
10、.248.4 2000-11-17 16 1.2 ITU-T H.248.4 (2000) Cor. 1 2004-03-15 16 2.0 ITU-T H.248.4 2009-12-14 16 ii Rec. ITU-T H.248.4 (12/2009) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication techn
11、ologies (ICTs). The ITU Telecommunication Standardization Sector (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 Teleco
12、mmunication Standardization Assembly (WTSA), which meets every 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 are
13、as of information technology which fall within ITU-Ts purview, 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 ope
14、rating agency. Compliance with this Recommendation is voluntary. 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 “shal
15、l“ or some other obligatory language such as “must“ and the negative 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 pra
16、ctice or implementation of this Recommendation may involve the 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 devel
17、opment process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are theref
18、ore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T H.248.4 (12/2009) iii CONTENTS Page 1 Scope 1 2 Referen
19、ces. 1 3 Definitions 1 4 Abbreviations and acronyms 1 5 Conventions 2 6 Providing the at-most-once functionality . 2 7 Transaction identifiers and three-way handshake . 2 7.1 Transaction identifiers 2 7.2 Three-way handshake . 2 8 Computing retransmission timers . 2 9 Provisional responses . 2 10 Or
20、dering of commands . 2 11 Stream independence 3 Rec. ITU-T H.248.4 (12/2009) 1 Recommendation ITU-T H.248.4 Gateway control protocol: Transport over Stream Control Transmission Protocol (SCTP) 1 Scope This Recommendation defines a package that extends the applicability of ITU-T H.248.1, Gateway cont
21、rol protocol. In particular, this Recommendation defines the transport of ITU-T H.248.1 Gateway Control Protocol messages over the Stream Control Transmission Protocol (SCTP) IETF RFC 2960. Protocol messages may be transmitted over the Stream Control Transmission Protocol (SCTP). In a transaction-or
22、iented protocol like H.248.1, there are still ways for transaction requests or responses to be lost, e.g., caused by entity/component failure. As such, it is recommended that entities using SCTP transport implement application level timers for each request. Commands should be sent to the default por
23、t number, 2944 for text-encoded operation, or 2945 for binary-encoded operation. Responses must be sent to the address and port from which the corresponding commands were sent, except if the response is to a handoff or failover, in which case the procedures of clause 11.5 of ITU-T H.248.1 apply. SCT
24、P payload protocol identifier shall be 7. To provide interworking between MTP3B and SCTP, and to allow for flexible implementations of gateways and controllers in order to offer efficient use of SCTP associations, the M3UA layer may be added on top of SCTP. 2 References The following ITU-T Recommend
25、ations and other references contain 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; users of this Recommendation are theref
26、ore encouraged to investigate 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. The reference to a document within this Recommendation does not give it, as a stand-
27、alone document, the status of a Recommendation. ITU-T H.248.1 Recommendation ITU-T H.248.1 (2005), Gateway control protocol: Version 3. IETF RFC 2960 IETF RFC 2960 (2000), Stream Control Transmission Protocol. 3 Definitions None. 4 Abbreviations and acronyms This Recommendation uses the following ab
28、breviations: MG Media Gateway MGC Media Gateway Controller MTP3B Message Transfer Part Layer 3 Broadband M3UA Message Transfer Part 3 (MTP3) User Adaptation layer 2 Rec. ITU-T H.248.4 (12/2009) SCTP Stream Control Transmission Protocol 5 Conventions None. 6 Providing the at-most-once functionality S
29、CTP is designed to recover from transport losses or duplications, but loss of a transaction request or its reply may nonetheless be noted in real implementations. In the absence of a timely response, ITU-T H.248.1 may repeat commands. Most ITU-T H.248.1 commands are not idempotent. The state of the
30、media gateway (MG) would become unpredictable if, for example, Add commands were executed several times. To guard against such losses, it is recommended that entities follow the procedures in Annex D.1.1 of ITU-T H.248.1 with one exception: the TransactionResponseAck parameter shall not be used. NOT
31、E The use of a received SCTP DATA acknowledge, instead of the LONG-TIMER, to remove a Transaction Identity from the list of responses is deprecated, as this method does not ensure the at-most-once functionality. A received SCTP DATA acknowledge indicates that the peer SCTP has received the message,
32、but does not indicate that it has been delivered to its user, i.e., the ITU-T H.248 layer. 7 Transaction identifiers and three-way handshake 7.1 Transaction identifiers It is recommended that clause D.1.2.1 of ITU-T H.248.1 be followed. 7.2 Three-way handshake Clause D.1.2.2 of ITU-T H.248.1 is not
33、applicable. 8 Computing retransmission timers With reliable non-duplicate delivery guaranteed by SCTP, application level timers are only used to guard against entity/component failure. Therefore, only simple timer mechanisms are required. The first retransmission of a request can occur after a short
34、 interval. If additional retransmissions are required, a longer time interval is recommended between the retransmissions. 9 Provisional responses The procedures in clause 8.2.3 of ITU-T H.248.1 apply. If an entity receives a repetition of a transaction that is still being executed, a TransactionPend
35、ing should be sent. 10 Ordering of commands SCTP provides both ordered and unordered reliable delivery, settable on a per-transaction basis. Therefore, ITU-T H.248.1 can take advantage of the ordered capability of SCTP. High priority transactions can get expedited treatment by properly using unorder
36、ed delivery. No special procedures are therefore required. Rec. ITU-T H.248.4 (12/2009) 3 11 Stream independence SCTP can provide up to 65535 unidirectional streams in each direction of an MGC-MG association. SCTP transmits messages and processes received messages in one stream, independent from the
37、 order or status of messages in any other streams. ITU-T H.248.1 may avoid head-of-line blocking by transmitting unrelated transactions on different streams. Reliability is still provided. Ordering of messages is available per-stream. It is recommended that transactions related to one context are tr
38、ansported over the same stream. Printed in Switzerland Geneva, 2010 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Series F Non-telephone telecomm
39、unication services Series G Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I Integrated services digital network Series J Cable networks and transmission of television, sound programme and other multimedia signals Series K Protection a
40、gainst interference Series L Construction, installation and protection of cables and other elements of outside plant Series M Telecommunication management, including TMN and network maintenance Series N Maintenance: international sound programme and television transmission circuits Series O Specific
41、ations of measuring equipment Series P Terminals and subjective and objective assessment methods Series Q Switching and signalling Series R Telegraph transmission Series S Telegraph services terminal equipment Series T Terminals for telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks, open system communications and security Series Y Global information infrastructure, Internet protocol aspects and next-generation networks Series Z Languages and general software aspects for telecommunication systems
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