1、 International Telecommunication Union ITU-T H.460.26TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2012) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Supplementary services for multimedia Using ITU-T H.225.0 call signalling connection as transport for medi
2、a Recommendation ITU-T H.460.26 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.259 Coding 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 an
4、d multimedia services H.360H.369 Supplementary services for multimedia H.450H.499MOBILITY 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 Ubiquitous sensor network applications and Internet of Things H.640H.649 IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV General aspec
7、ts H.700H.719 IPTV terminal devices H.720H.729 IPTV middleware H.730H.739 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 Digital Signage H.780H.789 For further details, please r
8、efer to the list of ITU-T Recommendations. Rec. ITU-T H.460.26 (06/2012) i Recommendation ITU-T H.460.26 Using ITU-T H.225.0 call signalling connection as transport for media Summary Recommendation ITU-T H.460.26 enables ITU-T H.323 devices under the condition where UDP transport is unavailable, to
9、transport media and control that otherwise would be transported over UDP to be tunnelled through the ITU H.225.0 signalling channel over TCP. This extension may be used in conjunction with Recommendation ITU-T H.460.17 “Using H.225.0 call signalling connection as transport for H.323 RAS messages“ to
10、 facilitate the transportation of RAS, signalling (Recommendation ITU-T H.225.0), control (Recommendation ITU-T H.245) and media packets (RTP/RTCP/SRTP/SRTCP) over a signal TCP channel. History Edition Recommendation Approval Study Group 1.0 ITU-T H.460.26 2012-06-29 16 ii Rec. ITU-T H.460.26 (06/20
11、12) FOREWORD The International Telecommunication 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
12、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 four years, establishes the topics for study by the ITU-T study
13、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, the necessary standards are prepared on a collaborative basis wi
14、th 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 voluntary. However, the Recommendation may contain certain mandatory prov
15、isions (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 negative equivalents are used to express requirements. The use of
16、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 use of a claimed Intellectual Property Right. ITU takes no posi
17、tion 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 Recommendation, ITU had not received notice of intellectual property, prote
18、cted by patents, which may be required 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 2013 All rights reserved. No part o
19、f this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T H.460.26 (06/2012) iii Table of Contents Page 1 Scope 1 2 References. 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation . 2 4 Abbreviations an
20、d acronyms 2 5 Feature description 2 6 Informative description . 2 7 Capability advertisement 3 8 ITU-T H.245 considerations . 3 9 Packaging of media. 3 9.1 Audio considerations 4 9.2 Video considerations 4 10 ITU-T H.225.0 message management 4 Annex A ASN.1 code for ITU-T H.460.26. 5 Rec. ITU-T H.4
21、60.26 (06/2012) 1 Recommendation ITU-T H.460.26 Using ITU-T H.225.0 call signalling connection as transport for media 1 Scope This Recommendation describes the procedures for the transportation of RTP/SRTP and RTCP/SRTCP messages over an existing ITU-T H.225.0 call signalling connection. Used in con
22、junction with ITU-T H.460.17 and utilizing ITU-T H.225.0 as transport for ITU-T H.245 messages, this proposed Recommendation allows call related messaging (signalling and media) to be transported over ITU-T H.225.0 signalling within a single TCP connection. 2 References The following ITU-T Recommend
23、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
24、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-
25、alone document, the status of a Recommendation. ITU-T H.225.0 Recommendation ITU-T H.225.0 (2009), Call signalling protocols and media stream packetization for packet-based multimedia communication systems. ITU-T H.235 Recommendation ITU-T H.235 (2003), Security and encryption for H-Series (H.323 an
26、d other H.245-based) multimedia terminals. ITU-T H.245 Recommendation ITU-T H.245 (2006), Control protocol for multimedia communication. ITU-T H.323 Recommendation ITU-T H.323 (2009), Packet-based multimedia communications systems. ITU-T H.460.1 Recommendation ITU-T H.460.1 (2002), Guidelines for th
27、e use of the generic extensible framework. ITU-T H.460.17 Recommendation ITU-T H.460.17 (2005), Using H.225.0 call signalling connection as transport for H.323 RAS messages. IETF RFC 3550 IETF RFC 3550 (2003), RTP: A Transport Protocol for Real-Time Applications. IETF RFC 3711 IETF RFC 3711 (2004),
28、The Secure Real-time Transport Protocol (SRTP). 3 Definitions 3.1 Terms defined elsewhere None. 2 Rec. ITU-T H.460.26 (06/2012) 3.2 Terms defined in this Recommendation This Recommendation defines the following term: 3.2.1 media over ITU-T H.225.0: The mechanism allowing the transportation of media
29、(RTP/SRTP/RTCP/SRTCP) over ITU-T H.225.0 signalling. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: ACF Admission Confirm ARQ Admission Request ASN.1 Abstract Syntax Notation No. 1 GEF Generic Extensible Framework LCF Location Confirm LRQ Location Req
30、uest PER Packed Encoding Rules RAS Registration, Admission and Status RCF Registration Confirm RRQ Registration Request RTCP Real Time Control Protocol RTP Real Time Protocol SRTCP Secure Real Time Control Protocol SRTP Secure Real Time Protocol TCP Transmission Control Protocol UDP User Datagram Pr
31、otocol 5 Feature description This Recommendation defines a procedure wherein media and media control may be transported over ITU-T H.225.0 signalling. This Recommendation is designed for use in secure and/or restricted networks where other ITU-T H.323 messaging may not be suitable, for instance in a
32、 network that restricts the number of available ports for either internal or external communication. 6 Informative description This Recommendation outlines the mechanism for using the ITU-T H.225.0 call signalling connection as a transport for media. This Recommendation may be used in conjunction wi
33、th ITU-T H.460.17 to allow the transportation of RAS, call signalling and media over a single TCP connection. This Recommendation should only be considered for the condition wherein the transport of media over UDP is unavailable. The detection/decision on whether transport over UDP is available is b
34、eyond the scope of this Recommendation. Rec. ITU-T H.460.26 (06/2012) 3 7 Capability advertisement Endpoints capable of supporting this Recommendation shall advertise this capability via the generic extensibility framework (GEF) defined in ITU-T H.323 and ITU-T H.460.1. When initiating a call and th
35、e endpoint is registered to a gatekeeper, the endpoint shall indicate its support of this Recommendation via the featureSet.supportedFeatures field in the ARQ message to the gatekeeper, and the gatekeeper shall acknowledge the requirement of this feature via the featureSet.neededFeatures field of th
36、e responding ACF message. The advertisement of this Recommendation may indicate to the gatekeeper that transport over UDP may not be available to the endpoint. When placing the call, this Recommendation shall advertise this feature in the featureSet.neededFeatures field of the ITU-T H.225.0 SETUP me
37、ssage and it shall be acknowledged in the ITU-T H.225.0 CALLPROCEEDING or ALERT or CONNECT message. Table 1 defines the media over ITU-T H.225.0 feature of this Recommendation. Table 1 Indication of media over ITU-T H.225.0 feature Feature name: Media over ITU-T H.225.0 Feature description: This fea
38、ture allows ITU-T H.225.0 to be used as a transport for media Feature identifier type: Standard Feature identifier value: 26 8 ITU-T H.245 considerations Transport addresses in the OpenLogicalChannel and OpenLogicalChannelAck have no meaning when tunnelling media. All optional mediaChannel and Media
39、ControlChannel elements contained in the H2250LogicalChannelParameters shall be omitted. The transportCapability element shall be present with an optional mediaChannelCapabilities field containing a SEQUENCE OF containing 1 element of MediaTransportType ip_TCP. 9 Packaging of media All media/control
40、 shall be packed as regular RTP/SRTP/RTCP/SRTP frames and shall be transmitted unaltered, and unpacked and processed as if they were regular media/control frames. Media shall be packed and transmitted over ITU-T H.225.0 via the Media Payload parameter contained within the genericData field of an ITU
41、-T H.225.0 INFORMATION message. Table 2 Media Payload parameter Parameter name: Media Payload Parameter description: Indicates the encoded payload Parameter identifier type: Standard Parameter identifier value: 1 Parameter type: Raw Parameter cardinality: One and only one The Media Payload parameter
42、 defined in Table 2 shall contain an encoded UDP_Frame element (refer to Annex A). 4 Rec. ITU-T H.460.26 (06/2012) The UDP frame element shall contain: sessionId: the unique session id of the RTP/SRTP/RTCP/SRTCP. dataframe: whether the frame field is RTP/SRTP (true) or RTCP/SRTCP (false). frame: seq
43、uence of complete RTP/SRTP/RTCP/SRTCP frames. The ITU-T H.225.0 INFORMATION message in this Recommendation is the designated transport media from the encoder device to the decoder device. If the call is then forwarded to another party, the ITU-T H.225.0 INFORMATION message shall be removed and not p
44、assed on. 9.1 Audio considerations To reduce message handling, it is recommended to bundle a small number of audio RTP/SRTP frames into one media payload element. 9.2 Video considerations To enable the efficient management of media, it is recommended to bundle video RTP/SRTP frames according to the
45、RTP/SRTP timestamp within the media payload element. In other words, all the elements of the media payload contain the same timestamp. 10 ITU-T H.225.0 message management To efficiently manage the ITU-T H.225.0 call signalling channel, it is recommended to prioritize the messages sent over the chann
46、el via a priority buffer. Preference shall be given to time-critical messages such as audio, delivery-critical messages such as call/media signalling, and discretionary/recoverable messages such as video. How the priority buffer is implemented is beyond the scope of this Recommendation. Furthermore,
47、 call signalling is transmitted over a reliable transport and may on occasion add long delays or block message transmission. It is recommended that the priority buffer times (time held in the buffer) be monitored and, once a limit is reached or the underlying transport is blocked, that the buffer be
48、 purged of video messages and that local bandwidth management policies be employed to reduce such delays or blockages. When purging video messages from the buffer, a fresh I frame shall be sent. Rec. ITU-T H.460.26 (06/2012) 5 Annex A ASN.1 code for ITU-T H.460.26 (This annex forms an integral part
49、of this Recommendation.) MEDIA-OVER-H2250 itu-t(0) recommendation(0) h(8) 460 26 version(0) 1 media-over-h2250(0) DEFINITIONS AUTOMATIC TAGS := BEGIN FrameData := CHOICE rtp OCTET STRING (SIZE(121500), rtcp OCTET STRING (SIZE(11500) UDPFrame := SEQUENCE sessionId INTEGER (0255), dataFrame BOOLEAN, frame SEQUENCE OF FrameData END Printed in Switzerland Geneva, 2013 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series D General tariff principles Series E Over
