1、 International Telecommunication Union ITU-T H.248.5TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2009) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Gateway control protocol: Transport over ATM Recommendation ITU-T H.248.5 ITU-T H-
2、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 Communication procedures H.240H.259Coding of
3、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 multimedia services H.360H.369 Suppleme
4、ntary 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 collaboration applications and services H.520H.52
5、9 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 BROADBAND, TRIPLE-PLAY AND ADVANCED MULTI
6、MEDIA 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 IPTV application event handling H.740H.
7、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.248.5 (12/2009) i Recommendation ITU-T H.248.5 Gateway control protocol: Transport o
8、ver ATM Summary Recommendation ITU-T H.248.5 defines the transport of ITU-T H.248.1 gateway control protocol messages over ATM. ATM transport is an alternative to UDP or TCP. Transport 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
9、 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 I 2000-11-17 16 1.0 ITU-T H.248.5 2000-11-17 16 2.0 ITU-T H.248.5 2009-12-14 16 ii Rec. ITU-T H.248.5 (12/2009) FOREWORD The International Tel
10、ecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and
11、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 four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Rec
12、ommendations 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, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recom
13、mendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interopera
14、bility 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 negative equivalents are used to express requirements. The use of such words does not suggest that co
15、mpliance 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 use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, valid
16、ity 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 Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be requi
17、red to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore 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 reproduce
18、d, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T H.248.5 (12/2009) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations and acronyms 1 5 Conventions 2 6 Transport over MTP3b/NNI-SAAL/type 5 AAL . 2 6.1 Providing at-most-once functionality . 2
19、 6.2 Transaction identifiers and three-way handshake 2 6.3 Computing retransmission timers . 2 6.4 Provisional responses . 2 6.5 Ordering of commands . 3 7 Transport using SSCOP/type 5 AAL 3 7.1 Providing the at-most-once functionality . 3 7.2 Transaction identifiers and three-way handshake 3 7.3 Co
20、mputing retransmission timers . 3 7.4 Provisional responses . 3 7.5 Ordering of commands . 3 8 Transport using type 5 AAL with ALF 3 8.1 Providing the at-most-once functionality . 4 8.2 Transaction identifiers and three-way handshake 4 8.3 Computing retransmission timers . 4 8.4 Provisional response
21、s . 4 8.5 Ordering of commands . 4 Rec. ITU-T H.248.5 (12/2009) 1 Recommendation ITU-T H.248.5 Gateway control protocol: Transport over ATM 1 Scope This Recommendation defines a package that extends the applicability of the ITU-T H.248.1 gateway control protocol Recommendation. Specifically, this Re
22、commendation defines the transport of ITU-T H.248.1 gateway control protocol messages over ATM. ATM transport is an alternative to UDP or TCP. Transport of ITU-T H.248.1 over UDP or TCP is defined in Annex D of ITU-T H.248.1. 2 References The following ITU-T Recommendations and other references cont
23、ain 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 therefore encouraged to investigate th
24、e 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-alone document, the status of a
25、Recommendation. ITU-T H.248.1 Recommendation ITU-T H.248.1 (2005), Gateway control protocol: Version 3. ITU-T I.361 Recommendation ITU-T I.361 (1999), B-ISDN ATM layer specification. ITU-T I.363.5 Recommendation ITU-T I.363.5 (1996), B-ISDN ATM Adaptation Layer specification: Type S AAL. ITU-T Q.703
26、 Recommendation ITU-T Q.703 (1996), Signalling link. ITU-T Q.704 Recommendation ITU-T Q.704 (1996), Signalling network functions and messages. ITU-T Q.2110 Recommendation ITU-T Q.2110 (1994), B-ISDN ATM adaptation layer Service specific connection oriented protocol (SSCOP). ITU-T Q.2140 Recommendati
27、on ITU-T Q.2140 (1995), B-ISDN ATM adaptation layer Service specific coordination function for signalling at the network node interface (SSCF at NNI). ITU-T Q.2210 Recommendation ITU-T Q.2210 (1996), Message transfer part level 3 functions and messages using the services of ITU-T Recommendation Q.21
28、40. 3 Definitions None. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: AAL Asynchronous transfer mode Adaptation Layer ALF Application Level Framing ATM Asynchronous Transfer Mode MG Media Gateway 2 Rec. ITU-T H.248.5 (12/2009) MTP3b Message Transfer
29、Part level 3 using the services of ITU-T Q.2140 NNI-SAAL Network-to-Network Interface Signalling Asynchronous transfer mode Adaptation Layer SSCOP Service Specific Connection Oriented Protocol UDP User Datagram Protocol 5 Conventions None. 6 Transport over MTP3b/NNI-SAAL/type 5 AAL Protocol messages
30、 defined in this Recommendation may be transmitted over an SS7 network. Service indicator value 14, as defined in clause 14.2.1 of ITU-T Q.704, shall be used. The value corresponds to the bits DCBA equalling 1110. These protocol messages use the services of MTP3b as described in ITU-T Q.2210. In a t
31、ransaction-oriented protocol, there are still ways for transaction requests or responses to be lost. As such, it is recommended that entities using MTP3b transport implement application timers for each TransactionRequest. 6.1 Providing at-most-once functionality Messages being carried over MTP3b may
32、 be subject to losses. In the absence of a timely response, commands are repeated. Most commands are not idempotent. The state of the MG would become unpredictable if, for example, Add commands were executed several times. The transmission procedures shall thus provide an “at-most-once“ functionalit
33、y. The procedures in clause D.1.1 of ITU-T H.248.1 shall be followed with one exception: The TransactionResponseAck parameter shall not be used. NOTE The use of MTP3b information, instead of the LONG-TIMER, to remove a Transaction Identity from the list of responses is deprecated, as this method doe
34、s not ensure the at-most-once functionality. 6.2 Transaction identifiers and three-way handshake 6.2.1 Transaction identifiers Clause D.1.2.1 of ITU-T H.248.1 is recommended to be followed. 6.2.2 Three-way handshake Clause D.1.2.2 of ITU-T H.248.1 is not applicable. 6.3 Computing retransmission time
35、rs With reliable delivery, as MTP3b provides, the incidence of loss of a transaction request or reply is expected to be very low. Therefore, only simple timer mechanisms are required, e.g., the first retransmission of a request can occur after a short interval. If additional retransmissions are requ
36、ired, a longer time interval is recommended between the retransmissions. 6.4 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 TransactionPending should be sent. Rec. ITU-T H.248.5 (12/2009
37、) 3 6.5 Ordering of commands MTP3b provides ordered delivery of transactions, therefore no special procedures are required. 7 Transport using SSCOP/type 5 AAL Protocol messages described in this Recommendation may be transmitted via SSCOP links. These protocol messages use the services of SSCOP as d
38、escribed in ITU-T Q.2110. In a transaction-oriented protocol, there are still ways for transaction requests or responses to be lost. As such, it is recommended that entities using SSCOP transport implement application timers for each request and response. 7.1 Providing the at-most-once functionality
39、 Messages being carried over SSCOP are not subject to transport losses, but loss of a transaction request or its reply may nonetheless be noted in real implementations. In the absence of a timely response, commands are repeated. Most commands are not idempotent. The state of the MG would become unpr
40、edictable if, for example, Add commands were executed several times. To guard against such losses, it is recommended that entities follow the procedures in clause D.1.1 of ITU-T H.248.1. 7.2 Transaction identifiers and three-way handshake 7.2.1 Transaction identifiers Clause D.1.2.1 of ITU-T H.248.1
41、 applies. 7.2.2 Three-way handshake It is possible that transaction replies may be lost even with a reliable delivery protocol such as SSCOP. Entities using SSCOP shall follow the procedures in clause D.1.2.2 of ITU-T H.248.1. 7.3 Computing retransmission timers With reliable delivery, the incidence
42、 of loss of a transaction request or reply is expected to be very low. Therefore, only simple timer mechanisms are required. 7.4 Provisional responses The procedure of clause 8.2.3 of ITU-T H.248.1 applies. Entities that receive a TransactionPending shall switch to a longer repetition timer for that
43、 transaction. Entities shall retain transactions and replies until they are confirmed. The procedure of clause D.2.4 of ITU-T H.248.1 should be followed, but simple timer values should be sufficient. 7.5 Ordering of commands SSCOP provided ordered delivery of transactions. No special procedures are
44、required. 8 Transport using type 5 AAL with ALF Protocol messages defined in this Recommendation may be transmitted via type 5 AAL links. These messages use the services of type 5 AAL as described in ITU-T I.363.5. In a transaction-oriented protocol, there are still ways for transaction requests or
45、responses to be lost. As such, it is recommended that entities using type 5 AAL with ALF transport implement application level timers for each request and each response, similar to those specified for application level framing over UDP. 4 Rec. ITU-T H.248.5 (12/2009) 8.1 Providing the at-most-once f
46、unctionality Messages being carried over type 5 AAL with ALF may be subject to losses. In the absence of a timely response, commands are repeated. Most commands are not idempotent. The state of the MG would become unpredictable if, for example, Add commands were executed several times. The transmiss
47、ion procedures shall thus provide an “at-most-once“ functionality. To guard against such losses, it is recommended that entities follow the procedures in clause D.1.1 of ITU-T H.248.1. 8.2 Transaction identifiers and three-way handshake 8.2.1 Transaction identifiers Clause D.1.2.1 of ITU-T H.248.1 a
48、pplies. 8.2.2 Three-way handshake When type 5 AAL with ALF is used as transport, the entities shall follow the procedures in clause D.1.2.2 of ITU-T H.248.1. 8.3 Computing retransmission timers When type 5 AAL with ALF is used as transport, the entities shall provide the same type of calculation as
49、described in clause D.1.3 of ITU-T H.248.1. 8.4 Provisional responses When type 5 AAL with ALF is used as transport, the entities shall follow the procedures in clause D.1.4 of ITU-T H.248.1. 8.5 Ordering of commands When type 5 AAL with ALF is used as transport, the entities shall follow the procedures in clause 9.1 of ITU-T H.248.1. Printed in Switzerland Geneva, 2010 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series D General tariff principles Se
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