1、 International Telecommunication Union ITU-T H.248.88TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2014) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Gateway control protocol: RTP topology dependent RTCP handling by ITU-T H.248 med
2、ia gateways with IP terminations Recommendation ITU-T H.248.88 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 S
3、ystems aspects H.230H.239 Communication 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 a
4、rchitecture for audiovisual and 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.
5、519 Mobile multimedia collaboration 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-
6、working procedures H.560H.569 BROADBAND, 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 APPL
7、ICATIONS FOR IPTV General aspects 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.78
8、9 E-HEALTH MULTIMEDIA SERVICES AND APPLICATIONS Interoperability compliance testing of personal health systems (HRN, PAN, LAN and WAN) H.820H.849 Multimedia e-health data exchange services H.860H.869 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T H.248.88 (01/2014
9、) i Recommendation ITU-T H.248.88 Gateway control protocol: RTP topology dependent RTCP handling by ITU-T H.248 media gateways with IP terminations Summary RTCP is the control protocol associated to RTP, which has various connection models called RTP topologies. The handling of RTCP information may
10、be RTP topology dependent. ITU-T H.248 media gateways may support various types of RTP topologies, driven by network application scenarios. Recommendation ITU-T H.248.88 provides both general and detailed information about this topic, as well as explicit control means to enforce dedicated RTP topolo
11、gies in such media gateways. History Edition Recommendation Approval Study Group Unique ID*1.0 ITU-T H.248.88 2014-01-13 16 11.1002/1000/12062-en _ *To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. F
12、or example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T H.248.88 (01/2014) 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
13、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 Telecommunication Standardization Assembly (WTSA
14、), 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 areas of information technology which fall wi
15、thin 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 operating agency. Compliance with this Recomm
16、endation 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 “shall“ or some other obligatory language such
17、 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 practice or implementation of this Recommend
18、ation 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 development process. As of the date of approva
19、l 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 therefore strongly urged to consult the TSB pat
20、ent database at http:/www.itu.int/ITU-T/ipr/. ITU 2014 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.248.88 (01/2014) iii Table of Contents Page 1 Scope 1 2 References. 1 3 Definitions 3 3.1 Term
21、s defined elsewhere 3 3.2 Terms defined in this Recommendation . 3 4 Abbreviations and acronyms 4 5 Conventions 6 6 Background to RTCP handling by ITU-T H.248 MGs 6 7 RTP topologies versus RTCP handling in ITU-T H.248 MGs . 7 7.1 Single ITU-T H.248 IP Termination per Context 8 7.2 Two ITU-T H.248 IP
22、 Terminations per Context 8 7.3 More than two ITU-T H.248 IP Terminations per Context 9 7.4 Other topologies . 10 7.5 Notes to the ITU-T H.248 Connection model 10 7.6 Classes of RTCP related functions . 10 7.7 Relation to modes of operations of IP-to-IP media gateways 11 7.8 Recommendations for ITU-
23、T H.248 profiles for IP-to-IP gateways 11 8 RTCP services 12 8.1 RTCP packet structure 12 8.2 Important RTCP information elements (from ITU-T H.248 MG perspective) . 12 8.3 RTCP service levels . 13 9 Scope of RTP topology control 13 10 RTP Topology Package 14 10.1 Properties 15 10.2 Events . 15 10.3
24、 Signals 15 10.4 Statistics 15 10.5 Error codes 15 10.6 Procedures 16 11 Package-independent procedures for RTP topology control 18 11.1 RTP source translator topology 18 Appendix I Examples of transparent forwarding 20 I.1 Introduction 20 I.2 Convention . 20 I.3 Examples for implicit signalling 21
25、Bibliography. 26 Rec. ITU-T H.248.88 (01/2014) 1 Recommendation ITU-T H.248.88 Gateway control protocol: RTP topology dependent RTCP handling by ITU-T H.248 media gateways with IP terminations 1 Scope The scope of this Recommendation is related to RTP control protocol (RTCP) handling by ITU-T H.248
26、media gateways (MGs) ITU-T H.248.1. The required MG behaviour is fairly clear for the majority of use cases. However, there are some scenarios which benefit from or even require explicit signalling indication for an unambiguous control of MG RTCP (but also RTP) traffic handling behaviour. This Recom
27、mendation covers: information on the history and motivation behind RTP topologies and RTCP handling and the available ITU-T H.248 tool landscape (clause 6); overview tables concerning RTP topology versus RTCP handling aspects and relevant ITU-T H.248 connection models (clause 7); RTCP service aspect
28、s (clause 8); scope and limitations of RTP topology control (clause 9); an ITU-T H.248 package for basic RTP topology control (clause 10); and package independent procedures for RTP topology control (clause 11). This Recommendation may be useful in scenarios where an MG supports multiple RTP topolog
29、ies and/or multiple RTP/RTCP services which may lead to ambiguous behaviour. In these scenarios an ITU-T H.248 profile specification may use the package in this Recommendation to alleviate this behaviour. 2 References The following ITU-T Recommendations and other references contain provisions which,
30、 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 appl
31、ying 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. ITU-T
32、 G.729.1 Recommendation ITU-T G.729.1 (2006), G.729-based embedded variable bit-rate coder: An 8-32 kbit/s scalable wideband coder bitstream interoperable with G.729. ITU-T G.799.3 Recommendation ITU-T G.799.3 (2011), Signal processing functionality and performance of an IP-to-IP voice gateway optim
33、ized for the transport of voice and voiceband data. ITU-T H.248.1 Recommendation ITU-T H.248.1 (2013), Gateway Control Protocol: Version 3. ITU-T H.248.30 Recommendation ITU-T H.248.30 (2008), Gateway control Protocol: RTCP extended performance metrics packages. 2 Rec. ITU-T H.248.88 (01/2014) ITU-T
34、 H.248.48 Recommendation ITU-T H.248.48 (2012), Gateway control Protocol: RTCP XR block reporting package. ITU-T H.248.50 Recommendation ITU-T H.248.50 (2010), Gateway control Protocol: NAT traversal toolkit packages. ITU-T H.248.57 Recommendation ITU-T H.248.57 (2013), Gateway control Protocol: RTP
35、 control protocol package. ITU-T H.248.58 Recommendation ITU-T H.248.58 (2008), Gateway control Protocol: Packages for application level H.248 statistics. ITU-T H.248.71 Recommendation ITU-T H.248.71 (2010), Gateway control Protocol: RTCP support packages. ITU-T H.264 Recommendation ITU-T H.264 (201
36、3), Advanced video coding for generic audiovisual services. ITU-T Q.9 Recommendation ITU-T Q.9 (1988), Vocabulary of switching and signalling terms. ITU-T T.411 Recommendation ITU-T T.411 (1993), Information technology Open Document Architecture (ODA) and interchange format: Introduction and general
37、 principles. ITU-T V.152 Recommendation ITU-T V.152 (2010), Procedures for supporting voice-band data over IP networks. ITU-T Y.1221 Recommendation ITU-T Y.1221 (2010), Traffic control and congestion control in IP-based networks. IETF RFC 3550 IETF RFC 3550 (2003), RTP: A Transport Protocol for Real
38、-Time Applications. IETF RFC 3551 IETF RFC 3551 (2003), RTP Profile for Audio and Video Conferences with Minimal Control. IETF RFC 3611 IETF RFC 3611 (2003), RTP Control Protocol Extended Reports (RTCP XR). IETF RFC 3711 IETF RFC 3711 (2004), The Secure Real-time Transport Protocol (SRTP). IETF RFC
39、4585 IETF RFC 4585 (2006), Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF). IETF RFC 4588 IETF RFC 4588 (2006), RTP Retransmission Payload Format. IETF RFC 5124 IETF RFC 5124 (2008), Extended Secure RTP Profile for Real-time Transport Control Protocol (
40、RTCP)-Based Feedback (RTP/SAVPF). IETF RFC 5576 IETF RFC 5576 (2009), Source-Specific Media Attributes in the Session Description Protocol (SDP). IETF RFC 5760 IETF RFC 5760 (2010), RTP Control Protocol (RTCP) Extensions for Single-Source Multicast Sessions with Unicast Feedback. IETF RFC 6051 IETF
41、RFC 6051 (2010), Rapid Synchronisation of RTP Flows. Rec. ITU-T H.248.88 (01/2014) 3 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 bit integrity ITU-T Q.9: Exists when the values of the bits in each octet of a digital bit stream at th
42、e output of a device or system are unchanged from those at the input. NOTE Digital processing devices such as A/law converters, echo suppressors and digital pads must be disabled to provide bit integrity. 3.1.2 data integrity ITU-T T.411: The property that data has not been altered or destroyed. 3.2
43、 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 basic RTCP service: RTCP services based on RTCP packet types SR (200), RR (201), SDES (202) and BYE (203). NOTE A minimum RTP implementation must support at least IETF RFC 3550. The resulting basic RTCP serv
44、ice is thus considered to be the absolute minimum of any RTP implementation (because IETF RFC 3550 delegates any service based on RTCP packet type APP (204) to other RT(C)P-related RFCs). 3.2.2 fully protocol unaware forwarding: This applies to transparent forwarding where the MG is unaware of the L
45、x protocol(s). The MG is thus not able to execute any kind of operation on the Lx-PDU. NOTE An example of “fully RTP protocol unaware forwarding“ is when the ITU-T H.248 descriptor(s) does not contain any kind of signalling information (such as ITU-T H.248 events, properties, signals, statistics or
46、SDP elements) related to the indication of RTP traffic. This would be a fully L4+ agnostic stream setting. 3.2.3 Lx-PDU integrity: In the context of packet processing, it is the basic property of data integrity. The MG must guarantee bit integrity for forwarded protocol data units (PDU) at layer Lx.
47、 Lower layer protocol control information (PCI) may be modified. 3.2.4 RTP domain: A network domain with RTP entities which share a common RTP/RTCP-related identifier space. An RTP domain is characterized therefore by a domain-wide (and temporal, see Note 2) uniqueness of such protocol identifiers,
48、which typically constitute unambiguous RTP traffic flows (e.g., protocol elements SSRC, CNAME, PT). NOTE 1 Temporal horizon of identifier values: b-IETF RFC 6222 differentiates the identifier lifetime in short-term persistent and long-term persistent identifier value assignments. NOTE 2 An end-to-en
49、d RTP traffic flow could traverse multiple RTP domains, leading to the following observations: The end-to-end communication association would be comprised of multiple, concatenated RTP sessions. The edge of RTP domains is given by RTP entities with RTP topologies of type RTP End system or Back-to-Back RTP End system. 3.2.5 RTP packet integrity: Lx-PDU integrity for RTP packet PDU type IETF RFC 3550. RTP packet integrit
