1、 International Telecommunication Union ITU-T H.248.71TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/2010) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Gateway control protocol: RTCP support packages Recommendation ITU-T H.248.71 ITU
2、-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 Communication procedures H.240H.259Codin
3、g 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 multimedia services H.360H.369 Sup
4、plementary 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.52
5、0H.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 BROADBAND, TRIPLE-PLAY AND ADVANCED
6、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 IPTV application event handling H.
7、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.248.71 (02/2010) i Recommendation ITU-T H.248.71 Gateway control protocol: RTCP
8、 support packages Summary Recommendation ITU-T H.248.71 defines three ITU-T H.248 packages that relate to the real-time control protocol (RTCP). The RTCP Source Description package, the Received RTCP package, and the RTCP Feedback Message package allow the media gateway controller (MGC) to monitor a
9、nd control RTCP flows that are terminated by (or that pass through) a media gateway (MG). History Edition Recommendation Approval Study Group 1.0 ITU-T H.248.71 2010-02-13 16 ii Rec. ITU-T H.248.71 (02/2010) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized a
10、gency 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 tariff questions and issuing Recommendations on them with a vi
11、ew 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 Recommendations on these topics. The approval of ITU-T Recommenda
12、tions 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 Recommendation, the expression “Administration“ is used for concise
13、ness 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., interoperability or applicability) and compliance with the Recommendatio
14、n 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 compliance with the Recommendation is required of any party. INT
15、ELLECTUAL 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, validity or applicability of claimed Intellectual Property Rights,
16、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 required to implement this Recommendation. However, implementers ar
17、e 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 reproduced, by any means whatsoever, without the prior written permissi
18、on of ITU. Rec. ITU-T H.248.71 (02/2010) iii 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 and acronyms 2 5 Conventions 3 6 RTCP source description package 3 6.1 Properties 3 6.2 Events . 3 6.3 Signa
19、ls 3 6.4 Statistics 3 6.5 Error codes 4 6.6 Procedures 5 7 Received RTCP package 6 7.1 Properties 6 7.2 Events . 6 7.3 Signals 6 7.4 Statistics 6 7.5 Error codes 8 7.6 Procedures 8 8 RTCP feedback message package 12 8.1 Properties 12 8.2 Events . 12 8.3 Signals 14 8.4 Statistics 15 8.5 Error codes 1
20、5 8.6 Procedures 15 Rec. ITU-T H.248.71 (02/2010) 1 Recommendation ITU-T H.248.71 Gateway control protocol: RTCP support packages 1 Scope This Recommendation defines several ITU-T H.248 packages that relate to RTCP flows that terminate at or pass though the MG. The RTCP Source Description package ma
21、ps information appearing in sent and received RTCP Source Description (SDES) packets into ITU-T H.248 statistics. Auditing these statistics allows the MGC to gain a better understanding of the RTP end-systems and intermediate systems that participate in an RTP session. The Received RTCP package maps
22、 information appearing in received RTCP Sender Report and Receiver Report packets into ITU-T H.248 statistics. By auditing these statistics, the MGC can collect performance and QoS metrics, measured by the remote participants of the RTP session. The RTCP Feedback Message package allows the MGC to be
23、 notified when the MG receives RTCP feedback messages, and to instruct the MG to send such messages. RTCP feedback messages are used by RTP Audio Visual Profiles with feedback extensions (see IETF RFC 4585). 2 References The following ITU-T Recommendations and other references contain provisions whi
24、ch, 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 the possibility of a
25、pplying 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 Recommendation. IT
26、U-T H.248.1 Recommendation ITU-T H.248.1 (2005), Gateway control protocol: Version 3, including its Amendment 2 (2009). ITU-T M.2301 Recommendation ITU-T M.2301 (2002), Performance objectives and procedures for provisioning and maintenance of IP-based networks. IETF RFC 3550 IETF RFC 3550 (2003), RT
27、P: A Transport Protocol for Real-Time Applications. IETF RFC 3629 IETF RFC 3629 (2003), UTF-8, a transformation format of ISO 10646. IETF RFC 4585 IETF RFC 4585 (2006), Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF). IETF RFC 5104 IETF RFC 5104 (2008),
28、 Codec Control Messages in the RTP Audio-Visual Profile with Feedback (AVPF). 3 Definitions 3.1 Terms defined elsewhere 3.1.1 RTP end-system IETF RFC 3550: An application that generates the content to be sent in RTP packets and/or consumes the content of received RTP packets. 2 Rec. ITU-T H.248.71 (
29、02/2010) 3.1.2 RTP mixer IETF RFC 3550: An intermediate system that receives RTP packets from one or more sources, possibly changes the data format, combines the packets in some manner and then forwards a new RTP packet. All RTP packets originating from a mixer are identified as having the mixer as
30、their synchronization source. 3.1.3 RTP translator IETF RFC 3550: An intermediate system that forwards RTP packets with their synchronization source identifier intact. Examples of translators include devices that convert encodings without mixing, replicators from multicast to unicast, and applicatio
31、n-level filters in firewalls. NOTE The RTP translator concept is further refined in b-IETF RFC 5117 into “RTP transport translator“ and “RTP media translator“. For the purposes of this Recommendation, there is no difference between the two. 3.2 Terms defined in this Recommendation 3.2.1 measurement
32、point (MP) (adapted from ITU-T M.2301): An MP is the physical or logical point at which measurements can be made and to which the data obtained is related. In the context of RTP and RTCP, any source of RTCP packets is a measurement point. Its measurement data is based on the RTP and RTCP traffic sen
33、t and received at that element. 3.2.2 reporting point (RP): This is the point at which the measurement data is reported to another network element. In the context of RTP and RTCP, any source of RTCP packets is a reporting point, where the measurement data is reported through RTCP. In addition, any I
34、TU-T H.248 MG is a reporting point, when reporting various measurement data through ITU-T H.248 statistics. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: ABNF Augmented Backus-Naur Form AVPF Audio Visual Profile with Feedback CNAME Canonical Name FB
35、Feedback FCI Feedback Control Information FMT Feedback Message Type IANA Internet Addressing and Numbers Authority IP Internet Protocol LSB Least Significant Bit MG Media Gateway MGC Media Gateway Controller MP Measurement Point NAT Network Address Translation PLI Picture Loss Indication PSFB Payloa
36、d Specific Feedback PT RTCP control Packet Type RP Reporting Point Rec. ITU-T H.248.71 (02/2010) 3 QoS Quality of Service RR RTCP Receiver Report RTP Real-time Transport Protocol RTCP RTP Control Protocol RTPFB Transport layer (RTP) Feedback SDES Source Description SDP Session Description Protocol S
37、R RTCP Sender Report SSRC Synchronization Source TMMBR Temporary Maximum Media stream Bit-rate Request 5 Conventions None. 6 RTCP source description package Package name: RTCP Source Description Package Package ID: rtcpsdes (0x0104) Description: This package defines statistics regarding the informat
38、ion appearing in source description (SDES) RTCP packets, as defined in IETF RFC 3550. The statistics detail both information generated locally at the MG and information learnt from remote systems participating in the RTP session. Version: 1 Extends: None. 6.1 Properties None. 6.2 Events None. 6.3 Si
39、gnals None. 6.4 Statistics 6.4.1 Local synchronization source Statistic name: Local Synchronization Source Statistic ID: lssrc (0x0001) Description: The RTP synchronization source (SSRC) used by the MG in the RTP and RTCP packets it sends. Type: Unsigned Integer 4 Rec. ITU-T H.248.71 (02/2010) Possi
40、ble values: Any Level: Stream 6.4.2 Remote synchronization source Statistic name: Remote Synchronization Source Statistic ID: rssrc (0x0002) Description: The RTP synchronization source (SSRC) appearing in RTCP packets received from remote RTP systems (end-systems, mixers or translators). Note that a
41、 single RTP session may have more than one remote system (e.g., in multicast sessions). Type: Sub-list of Unsigned Integer. Each element in the sub-list represents the SSRC of one remote system. Possible values: Any. If the MG does not yet know the SSRC of any remote system (e.g., because no RTCP pa
42、ckets were yet received), this statistic shall include a single element that is set to zero. Level: Stream 6.4.3 Local canonical name Statistic name: Local Canonical Name Statistic ID: lcname (0x0003) Description: The canonical name (CNAME) appearing in RTCP SDES packets generated by the MG. Type: S
43、tring Possible values: Any. See clause 6.6.4 for the text encoding of special octets. Level: Stream 6.4.4 Remote canonical name Statistic name: Remote Canonical Name Statistic ID: rcname (0x0004) Description: The canonical name (CNAME) appearing in SDES packets received from remote RTP systems (end-
44、systems, mixers or translators). Type: Sub-list of String. Each element in the Sub-list encodes the CNAME of one remote system. The order of the rcname elements shall match the order of the rssrc elements. Therefore the i-th elements of the rcname and rssrc statistics contain, respectively, the CNAM
45、E and SSRC of one remote system. Possible values: Any. If the CNAME of a certain system is not yet known, the appropriate sub-list element shall be encoded as a string containing a single minus character (i.e., “-“). See clause 6.6.4 for the text encoding of special octets. Level: Stream 6.5 Error c
46、odes None. Rec. ITU-T H.248.71 (02/2010) 5 6.6 Procedures 6.6.1 Locally generated values Some of the statistics of this package (lssrc and lcname) contain RTCP field values generated by the MG. These statistics shall be available even if the MG is not sending RTCP traffic (e.g., due to other ITU-T H
47、.248 parameters or local configuration). In such a case, the statistics shall include the values that would have been used had the MG sent RTCP traffic. 6.6.2 Received values If the rssrc and the rcname statistics are set on the MG, it populates the statistics relating to remote end-systems and tran
48、slators based on RTCP packets it receives. Specifically: 1) When the MG receives an RTCP packet, it shall ensure that the SSRC of the packets sender (i.e., the SSRC appearing in the RTCP header) appears in the rssrc statistic, adding it if necessary. 2) When the MG receives an SDES RTCP packet, it e
49、xamines each of that packets chunks. If the chunk relates to the system that sent the RTCP packet (i.e., if the SSRC appearing in the chunk is identical to the SSRC of the sender), the MG will use that chunks CNAME item to update the rcname statistic. This procedure ensures that, in the case of a mixer, the MG will record only the CNAME of the mixer itself, and not the CNAMEs of any of the contributing sources. NOTE It is possible for the MGC to set only one of these statistics on a str
