1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T H.248.95 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2015) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services Communication procedures Gateway control protocol: ITU-T H.248 support f
2、or RTP multiplexing Recommendation ITU-T H.248.95 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 aspect
3、s H.230H.239 Communication 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
4、for audiovisual and multimedia services H.360H.369 Telepresence H.420H.429 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 serv
5、ices H.510H.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 collabor
6、ation inter-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 SERVI
7、CES 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.749 IPTV metadata H.750H.759 IPTV multimedia application frameworks H.760H.769 IPTV service discovery up to consumption H.770H.779 Digital Signa
8、ge H.780H.789 E-HEALTH MULTIMEDIA SERVICES AND APPLICATIONS Personal health systems H.810H.819 Interoperability compliance testing of personal health systems (HRN, PAN, LAN, TAN and WAN) H.820H.859 Multimedia e-health data exchange services H.860H.869 For further details, please refer to the list of
9、 ITU-T Recommendations. Rec. ITU-T H.248.95 (11/2015) i Recommendation ITU-T H.248.95 Gateway control protocol: ITU-T H.248 support for RTP multiplexing Summary Recommendation ITU-T H.248.95 provides an overview of the types of real-time transport protocol (RTP) multiplexing and discusses how these
10、may be implemented on ITU-T H.248 gateways. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T H.248.95 2015-11-29 16 11.1002/1000/12637 Keywords ITU-T H.248, GCP, RTCP, RTP. * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web bro
11、wser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T H.248.95 (11/2015) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communicati
12、on 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 view to standardizing telecommunications on a worldwide basis. The Worl
13、d 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 Recommendations is covered by the procedure laid down in WTSA Resolution 1. In
14、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 conciseness to indicate both a telecommunication administration and a recogn
15、ized 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 Recommendation is achieved when all of these mandatory provisions are met. The wo
16、rds “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. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that
17、 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, whether asserted by ITU members or others outside of the Recommendati
18、on 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 are cautioned that this may not represent the latest information and ar
19、e therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2016 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.248.95 (11/2015) iii Table of Contents Page 1
20、 Scope . 1 2 References . 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 3 4 Abbreviations and acronyms 4 5 Conventions 5 6 Overview of RTP multiplexing 5 6.1 Introduction 5 6.2 Protocol history: multiplexing framework defined for original RTP . 5 6.3 RTP
21、transport multiplexing 5 6.4 RTP media multiplexing . 6 6.5 UDP payload multiplexing . 6 7 Use cases with RTP multiplexing . 7 7.1 General note 7 7.2 Use case “multimedia call in NGN/IMS“ . 7 7.3 Use case “Web real-time communication“ . 7 8 ITU-T H.248 control of RTP multiplexing. 7 8.1 General prin
22、ciple 7 8.2 RTP media multiplexing . 7 8.3 RTP transport multiplexing 8 9 RTP multiplexing examples . 8 9.1 Video stream multiplexing . 8 9.2 Audio and video stream in separate multiplexes 11 Appendix I Existing ITU-T H.248 support for RTP multiplexing . 16 I.1 3GPP-defined multiplexing for IP beare
23、rs with 3GPP framing protocol . 16 Appendix II Functional processing model for RTP streams . 17 II.1 Reference 17 II.2 Purpose . 17 II.3 Functional processing model for RTP streams . 17 II.4 Functional processing model with scope on RTP multiplexing . 19 Bibliography. 20 Rec. ITU-T H.248.95 (11/2015
24、) 1 Recommendation ITU-T H.248.95 Gateway control protocol: ITU-T H.248 support for RTP multiplexing 1 Scope Communication services utilizing the real-time transport protocol (RTP) as the application level framing protocol normally use a native IP-based transport mechanism IETF RFC 3550, which resul
25、ts in using two separate user datagram protocol (UDP) ports for the RTP and RTP control protocol (RTCP) traffic components. ITU-T H.248 gateways provide a rich set of gateway services for such types of RTP traffic, as defined by ITU-T H.248.48, ITU-T H.248.58, ITU-T H.248.71, ITU-T H.248.77, ITU-T H
26、.248.87 and ITU-T H.248.88. In addition, multiple RTP-based traffic flow components could be multiplexed at multiple, different levels (from the perspective of a layered protocol architecture). The purpose of this Recommendation is to clarify how ITU-T H.248 gateways support such “multiplexing struc
27、tures“. The scope of this Recommendation addresses the following subjects: Terminology: clarification of RTP related terms and definitions; Multiplexing methods: summary of existing multiplexing schemes in context of RTP-based communication services; ITU-T H.248 support: provides information on how
28、dedicated multiplexing methods could be supported by ITU-T H.248 gateways inclusive of references to relevant signalling syntax; and Examples: provides some signalling examples as complementary information. This Recommendation does not define any new ITU-T H.248 protocol extensions. 2 References The
29、 following ITU-T Recommendations 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
30、 Recommendation are therefore 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 doe
31、s not give it, as a stand-alone document, the status of a Recommendation. ITU-T H.248.1 Recommendation ITU-T H.248.1 (2013), Gateway control protocol: Version 3. ITU-T H.248.48 Recommendation ITU-T H.248.48 (2012), Gateway control protocol: RTCP XR block reporting package. ITU-T H.248.50 Recommendat
32、ion 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 control protocol package. ITU-T H.248.58 Recommendation ITU-T H.248.58 (2008), Gateway control protocol: Packages for application le
33、vel H.248 statistics. ITU-T H.248.71 Recommendation ITU-T H.248.71 (2010), Gateway control protocol: RTCP support packages. 2 Rec. ITU-T H.248.95 (11/2015) ITU-T H.248.77 Recommendation ITU-T H.248.77 (2010), Gateway control protocol: Secure real-time transport protocol (SRTP) package and procedures
34、. ITU-T H.248.87 Recommendation ITU-T H.248.87 (2014), Gateway control protocol: Guidelines on the use of ITU-T H.248 capabilities for performance monitoring in RTP networks in ITU-T H.248 profiles. ITU-T H.248.88 Recommendation ITU-T H.248.88 (2014), Gateway control protocol: RTP topology dependent
35、 RTCP handling by ITU-T H.248 media gateways with IP terminations. ITU-T H.248.93 Recommendation ITU-T H.248.93 (2014), ITU-T H.248 support for control of transport security using the datagram transport layer security (DTLS) protocol. ITU-T H.248.96 Recommendation ITU-T H.248.96 (2015), Gateway cont
36、rol protocol: ITU-T H.248 Stream grouping and aggregation. IETF RFC 3550 IETF RFC 3550 (2003), RTP: A Transport Protocol for Real-Time Applications. IETF RFC 5761 IETF RFC 5761 (2010), Multiplexing RTP Data and Control Packets on a Single Port. IETF RFC 5764 IETF RFC 5764 (2010), Datagram Transport
37、Layer Security (DTLS) Extension to Establish Keys for the Secure Real-time Transport Protocol (SRTP). 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 media (section 2.1 of b-IETF RFC 7656): A sequence of synthetic or physical Stimuli (s
38、ound waves, photons, key-strokes), represented in digital form. Synthesized media is typically generated directly in the digital domain. 3.1.2 media sink (section 2.1.31 of b-IETF RFC 7656): The media sink receives a source stream that contains, usually periodically, sampled media data together with
39、 associated synchronization information. Depending on application, this source stream then needs to be transformed into a raw stream that is conveyed to the media render, synchronized with the output from other media sinks. 3.1.3 media source (section 2.1.4 of b-IETF RFC 7656): The logical source of
40、 a reference clock synchronized, time progressing, digital media stream, called a source stream. This transformation takes one or more raw streams and provides a source stream as output. The output is synchronized with a reference clock, which can be as simple as a system local wall clock or as comp
41、lex as NTP synchronized. 3.1.4 RTP endpoint (section 2.2.1 of b-IETF RFC 7656): A single addressable entity sending or receiving RTP packets. It may be decomposed into several functional blocks, but as long as it behaves as a single RTP stack entity it is classified as a single “endpoint“. NOTE The
42、self-contained notion of endpoint is consistent with b-ITU-T H-Sup.13. 3.1.5 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. An end system can act as one or more synchronization sources in a partic
43、ular RTP session, but typically only one. NOTE The term is used and is important in context of “RTP topologies“, see ITU-T H.248.88. The term is used as a synonym with “RTP endpoint“ in ITU-T H.248.88. Rec. ITU-T H.248.95 (11/2015) 3 3.1.6 RTP session (section 2.2.2 of b-IETF RFC 7656): An RTP sessi
44、on is an association among a group of Participants communicating with RTP. It is a group communications channel which can potentially carry a number of RTP streams. Within an RTP session, every Participant can find metadata and control information (over RTCP) about all the RTP streams in the RTP ses
45、sion. The bandwidth of the RTCP control channel is shared between all Participants within an RTP session. NOTE Clause 3.1.3 of ITU-T H.248.57 provides the following definition: RTP session: An RTP session comprises a single RTP flow and an optional RTCP flow. It could be concluded that the “H.248.57
46、 RTP session“ is a synonym to RTP stream in general. 3.1.7 RTP stream (section 2.1.10 of b-IETF RFC 7656): A stream of RTP packets containing media data, source or redundant. The RTP stream is identified by an SSRC belonging to a particular RTP session. 3.1.8 stream (H.248 media) (clause 3.2.9 of IT
47、U-T H.248.1): Bidirectional media or control flow received/sent by a media gateway as part of a call or conference. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 media gateway (MG) RTP topology: The configuration of RTP termination(s) (Note 1) for an
48、 individual RTP session with a single RTP stream within an RTP node. There are multiple RTP terminations in general besides the single case. The RTP terminations are meshed for the “multiple case“ and interconnected via an interworking function (IWF). There are a number of protocol layer related IWF
49、s, at the RTP layer itself and at lower or upper layers. A particular RTP topology is characterized by a specific IWF. Important MG RTP topologies are designated by a name. Figure 1 Illustration of “MG RTP topology“ NOTE 1 ITU-T H.248 terminology: an RTP-enabled ITU-T H.248 termination or stream endpoint. NOTE 2 Figure 1 illustrates the key aspects of the “MG RTP topology“ concept. The term “RTP leg“ is undefined but not decisive due to the relatio
