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.248.78 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2015) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services Communication procedures Gateway control protocol: Bearer-level message
2、backhauling and application level gateway Recommendation ITU-T H.248.78 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.2
3、20H.229 Systems aspects 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
4、 service architecture 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 multi
5、media systems and services 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 Mobi
6、le multimedia collaboration 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
7、 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.749 IPTV metadata H.750H.759 IPTV multimedia application frameworks H.760H.769 IPTV service discovery up to consumption H.
8、770H.779 Digital Signage H.780H.789 E-HEALTH MULTIMEDIA SERVICES AND APPLICATIONS 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 ITU-T Recomm
9、endations. Rec. ITU-T H.248.78 (11/2015) i Recommendation ITU-T H.248.78 Gateway control protocol: Bearer-level message backhauling and application level gateway Summary Recommendation ITU-T H.248.78 defines a package that allows bearer-level application protocol (such as real-time streaming protoco
10、l (RTSP) or message session relay protocol (MSRP) messages received by a media gateway (MG) to be communicated to a media gateway controller (MGC). This allows the MGC to perform application-level gateway functionality such as network address translation on the messages and then forward the messages
11、 to the MG for sending to the destination. The 03/2013 revision incorporates an update to correctly refer to the “Message Session Relay Protocol“. The 04/2015 revision adds a further ITU-T H.248 package for support of: a) MG located application-level gateway functionality; and b) MG message backhaul
12、ing functionality. It also updates the title from “bearer-level application level gateway“ to “bearer-level message backhauling and application level gateway“. This 11/2015 revision adds Annex A that describes Extensible Messaging and Presence Protocol (XMPP) to MSRP interworking utilising mechanism
13、s defined in this Recommendation. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T H.248.78 2010-09-13 16 11.1002/1000/10988 2.0 ITU-T H.248.78 2013-03-16 16 11.1002/1000/11832 3.0 ITU-T H.248.78 2015-04-29 16 11.1002/1000/12453 4.0 ITU-T H.248.78 2015-11-29 16 11.1002/1000/1
14、2642 _ * 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. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii Rec. ITU-T H.248.78 (11/2015) FOREWORD The International Telecommunication Union
15、(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 tariff questions and
16、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 Recommendations on these
17、 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 Recommendation, the expres
18、sion “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., interoperability or applicabil
19、ity) 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 compliance with the Re
20、commendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU 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
21、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 received notice of intellectual property, protected by patents, which may be required to implement this Rec
22、ommendation. 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 2016 All rights reserved. No part of this publication may be reproduced, by any means whatsoeve
23、r, without the prior written permission of ITU. Rec. ITU-T H.248.78 (11/2015) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 2 5 Conventions 3 6 Application-level gateway
24、functionality . 3 6.1 MGC strictly controlled MG embedded bearer-level ALG . 5 6.2 MG autonomous embedded bearer-level ALG 6 7 MGC Controlled Bearer Level ALG package 6 7.1 Properties 7 7.2 Events . 7 7.3 Signals 11 7.4 Statistics 12 7.5 Error codes 12 7.6 Procedures 12 8 MG located Bearer Level ALG
25、 package 15 8.1 Properties 15 8.2 Events . 18 8.3 Signals 18 8.4 Statistics 18 8.5 Error codes 18 8.6 Procedures 18 Annex A XMPP to MSRP interworking utilising ITU-T H.248.78 . 20 A.1 Scope 20 A.2 Architectural assumptions 21 A.3 Procedures 21 A.4 Example 22 Appendix I MG located Bearer Level ALG se
26、rvice Illustration and signalling examples . 27 I.1 Illustration of concept . 27 I.2 Illustration of example use cases 28 Bibliography. 33 Rec. ITU-T H.248.78 (11/2015) 1 Recommendation ITU-T H.248.78 Gateway control protocol: Bearer-level message backhauling and application level gateway 1 Scope In
27、 a split media gateway controller (MGC) and media gateway (MG) environment, call-level application level gateways (ALGs) are common in order to translate address information (i.e., network address and port translation (NAPT) between two signalling domains. Typically, the application signalling trave
28、rses the MGC. ITU-T H.248 is therefore not involved in these translations other than to set the necessary media transport parameters on applicable Terminations. Increasingly bearer-level application control signalling is being used which instead traverses the MG. This bearer-level application signal
29、ling typically is used within a session that has been established by the MGC; thus, some coordination between the two levels is needed. This Recommendation provides functionality that allows the MGC and MG to coordinate bearer-level application level gateway functionality. By transporting bearer-lev
30、el application protocols between the MGC and MG using ITU-T H.248 signalling (a method known as “backhauling“), it allows the MGC access to the bearer-level application protocol. This Recommendation also supports the ability to use an alternative method to identify the bearer-level application proto
31、col on an ITU-T H.248 Stream. The “MG located Bearer Level ALG“ package allows an MG to autonomously act as an application level gateway and modify address information. This Recommendation also contains an annex that describes Extensible Messaging and Presence Protocol (XMPP) to MSRP interworking ut
32、ilising mechanisms defined in this Recommendation. 2 References The 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 Recommen
33、dations and other references are subject to revision; users of this 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 pu
34、blished. The reference to a document within this Recommendation does 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.248.69 Recommendation ITU-T H.248.69 (2009), Gateway control pr
35、otocol: Packages for interworking between MSRP and H.248. ETSI TS 123 228 ETSI TS 123 228 (2010), Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); LTE; IP Multimedia Subsystem (IMS); Stage 2 (3GPP TS 23.228 version 9.4.0 Release 9). IETF RFC 2
36、326 IETF RFC 2326 (1998), Real Time Streaming Protocol (RTSP). IETF RFC 6121 IETF RFC 6121 (2011), Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence. IETF RFC 6455 IETF RFC 6455 (2011), The WebSocket Protocol. 2 Rec. ITU-T H.248.78 (11/2015) IETF RFC 7247 IETF RFC 724
37、7 (2014), Interworking between the Session Initiation Protocol (SIP) and the Extensible Messaging and Presence Protocol (XMPP): Architecture, Addresses, and Error Handling. IETF RFC 7248 IETF RFC 7248 (2014), Interworking between the Session Initiation Protocol (SIP) and the Extensible Messaging and
38、 Presence Protocol (XMPP): Presence. IETF RFC 7572 IETF RFC 7572 (2015), Interworking between the Session Initiation Protocol (SIP) and the Extensible Messaging and Presence Protocol (XMPP): Instant Messaging. IETF RFC 7573 IETF RFC 7573 (2015), Interworking between the Session Initiation Protocol (
39、SIP) and the Extensible Messaging and Presence Protocol (XMPP): One-to-One Text Chat Sessions. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following term defined elsewhere: 3.1.1 application level gateway (ALG) ETSI TS 123 228: Is an application specific functional entity
40、that allows communication between disparate address realm or IP versions, e.g., an IPv6 node to communicate with an IPv4 node and vice versa, when certain applications carry network addresses in the payloads like SIP/SDP. NA(P)T-PT or NA(P)T is application unaware whereas ALGs are application specif
41、ic translation entities that allow a host running an application to communicate transparently with another host running the same application but in a different IP version or IP address realm. NOTE This definition originates from the first ALG description in clause 2.9 of b-IETF RFC 2663. 3.2 Terms d
42、efined in this Recommendation This Recommendation defines the following term: 3.2.1 backhauling: Refers to the transport of signalling information from the point of interface for the concerned protocol in the MG back to the point of call processing (i.e., the MGC) and vice versa. Hence, backhauling
43、implies the transport of a non-ITU-T H.248 related signalling protocol over the ITU-T H.248 gateway control protocol. NOTE 1 The definition is derived from b-IETF RFC 2719. NOTE 2 The primary scope of backhauling are signalling protocols, but the mechanism as such can be applied to bearer-level appl
44、ication protocols. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: ALG Application Level Gateway B2B Back to Back B-ALG Bearer level Application-Level Gateway DNS Domain Name System GW Gateway HTML Hypertext Mark-up Language HTTP Hypertext Transfer Pro
45、tocol Rec. ITU-T H.248.78 (11/2015) 3 IP Internet Protocol IPv4 Internet Protocol Version 4 IPv6 Internet Protocol Version 6 L3 Layer three L4 Layer four L4+ Above layer four LD Local Descriptor MG Media Gateway MGC Media Gateway Controller MSRP Message Session Relay Protocol NAPT Network Address an
46、d Port Translation OSI Open Systems Interconnection PDU Protocol Data Unit RD Remote Descriptor RTSP Real-Time Streaming Protocol S2X SIP to XMPP SCTP Stream Control Transport Protocol SDP Session Description Protocol SIP Session Initiation Protocol TCP Transmission Control Protocol UDP User Datagra
47、m Protocol WebRTC Web Real-Time Communication X2S XMPP to SIP XMPP Extensible Messaging and Presence Protocol 5 Conventions Elements of the ITU-T H.248 protocol model, e.g., Context, Termination, Stream, Event are represented using the first letter capitalized. Property, Event, Signal and Parameter
48、identities are given in italics. The suffix “.req“ added to an ITU-T H.248 command name stands for a command request, while the suffix “.rep“ stands for a command reply. For example “Notify.req“ represents a Notify request. 6 Application-level gateway functionality Address information carried at lay
49、er four (L4) or above (L4+) according to the ISO 7-layer model is primarily related to call/session control signalling (like the session initiation protocol (SIP). Such call-level application level gateways (ALGs) are consequently out of scope of ITU-T H.248-series Recommendations. However, there are IP applications with bearer-level transport of “L4+ address information“. These services may need a bearer-level ALG located in the ITU-T H.248 MG. 4 Rec. ITU-T H.248.78 (11
