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.248.39 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2014) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services Communication procedures Gateway control protocol: ITU-T H.248 SDP param
2、eter identification and wildcarding Recommendation ITU-T H.248.39 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.22
3、9 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 servi
4、ce 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 multimedia
5、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 Mobile mul
6、timedia 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 IPTV
7、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.770H.7
8、79 Digital Signage H.780H.789 E-HEALTH MULTIMEDIA SERVICES AND APPLICATIONS Interoperability compliance testing of personal health systems (HRN, PAN, LAN 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 Recommendations.
9、Rec. ITU-T H.248.39 (10/2014) i Recommendation ITU-T H.248.39 Gateway control protocol: ITU-T H.248 SDP parameter identification and wildcarding Summary Recommendation ITU-T H.248.39 describes the principles used to identify a single session description protocol (SDP) sub-field and how to apply wild
10、carding to that sub-field. The sub-field may be fully specified, wildcarded (CHOOSE “$“ or ALL “*“) or not significant “-“. Being able to identify a single sub-field is of use when requesting the media gateway (MG) to choose a parameter, specifying a range or for the purposes of auditing. Further sp
11、ecification of how SDP can be wildcarded will assist in interoperation between a media gateway controller (MGC) and an MG. This revision incorporates guidelines for the wildcarding of source-specific media attributes. It also includes a package to indicate MG support for advanced wildcarding procedu
12、res that allow a MGC to request multiple SDP parameter values and/or multiple SDP lines to be returned in response to a CHOOSE request. Additionally, it allows the linking of multiple CHOOSE wildcards so that they return the same value. Furthermore, a new maintain value wildcard is introduced to all
13、ow the retention of a previously set value to avoid repetition of redundant information. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T H.248.39 2006-05-29 16 11.1002/1000/8819 2.0 ITU-T H.248.39 2014-10-14 16 11.1002/1000/12236 _ * To access the Recommendation, type the UR
14、L 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.248.39 (10/2014) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in
15、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 view to sta
16、ndardizing 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 Recommendations is
17、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 conciseness to i
18、ndicate 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 Recommendation is ach
19、ieved 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. INTELLECTUA
20、L 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 of claimed Intellectual Property Rights, whether a
21、sserted 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 are caution
22、ed 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 2015 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU
23、. Rec. ITU-T H.248.39 (10/2014) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 3.1 Terms defined elsewhere 1 4 Abbreviations and acronyms 1 5 ITU-T H.248 wildcarding guiding principles . 2 5.1 General ITU-T H.248 wildcarding principles 2 5.2 Specific wildcarding principles f
24、or ITU-T H.248 embedded SDP 2 6 Identification of single parameters . 3 6.1 Protocol version 3 6.2 Owner/Creator 4 6.3 Session name 4 6.4 URI of description 5 6.5 Email address 5 6.6 Phone number . 6 6.7 Encryption key 6 6.8 Time description . 7 6.9 Repeat . 7 6.10 Time zone adjustments . 8 6.11 Med
25、ia description . 8 6.12 Media title and session information . 9 6.13 Connection information 10 6.14 Bandwidth information . 10 6.15 Attributes 11 7 Use for wildcarding (CHOOSE or ALL) 20 8 Use in auditing 21 8.1 Audit value . 21 8.2 Audit capability 22 9 Advanced SDP Wildcarding Package 22 9.1 Prope
26、rties 22 9.2 Events . 23 9.3 Signals 23 9.4 Statistics 23 9.5 Error codes 23 9.6 Procedures 23 Appendix I Example signalling scenarios for the maintain value wildcard “ . 28 I.1 Purpose . 28 iv Rec. ITU-T H.248.39 (10/2014) Page I.2 Signalling without the maintain value wildcard “ 28 I.3 Signalling
27、using the maintain value wildcard “ 31 I.4 Evaluation of the examples 33 Bibliography. 34 Rec. ITU-T H.248.39 (10/2014) 1 Recommendation ITU-T H.248.39 Gateway control protocol: ITU-T H.248 SDP parameter identification and wildcarding 1 Scope This Recommendation describes the principles to be used t
28、o identify a single session description protocol (SDP) sub-field and how to apply wildcarding to that sub-field. The sub-field may be fully specified, wildcarded (CHOOSE “$“ or ALL “*“) or not significant “-“ (see clause 5.2.2.2). Being able to identify a single sub-field is of use when requesting t
29、he MG to choose a parameter, specifying a range or for the purposes of auditing. This Recommendation contains a package that allows a media gateway controller (MGC) to request multiple SDP parameter values and/or multiple SDP lines to be returned in response to a CHOOSE request. It also allows the l
30、inking of multiple CHOOSE wildcards so that they return the same value. A new “maintain value“ wildcard, “, is introduced, which is a short notation syntax (versus the fully specified SDP information) that allows performance optimization as well as the reduction of syntax errors (by avoiding the rep
31、etition of redundant information). 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 Recommendations and othe
32、r 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 published. The ref
33、erence 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.248.15 Recommendation ITU-T H.248.15 (2013), Gateway control protocol: SDP H.24
34、8 package attribute. 3 Definitions 3.1 Terms defined elsewhere None. 3.2 Terms defined in this Recommendation None. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: ABNF Augmented BackusNaur Form ATM Asynchronous Transfer Mode DTLS Datagram Transport La
35、yer Security FFS For further study IP Internet Protocol 2 Rec. ITU-T H.248.39 (10/2014) LD Local Descriptor MG Media Gateway MGC Media Gateway Controller MIME Multipurpose Internet Mail Extensions RD Remote Descriptor RTCP RTP Control Protocol RTP Real-time Transport Protocol SDP Session Description
36、 Protocol SSRC Synchronization Source TLS Transport Layer Security UDP User Datagram Protocol VoATM Voice over ATM VoIP Voice over IP 5 ITU-T H.248 wildcarding guiding principles 5.1 General ITU-T H.248 wildcarding principles The overriding guidance provided by clause 7.1.8.1.1.1 of ITU-T H.248.1 on
37、 the use of CHOOSE in the session description protocol (SDP) is: “the use of CHOOSE is allowed in place of a single parameter value“. Subsequent principles are: 1) In any SDP scheme each mandatory element SHALL therefore be represented by a single CHOOSE “$“. 2) Any part that contain text tokens (e.
38、g., those in “ “) that are mandatory SHALL also be included in the wildcard command. 3) Optional parts of an SDP scheme should not be included unless the wildcard or value applies to them. 4) When an item specifies a wildcard for a single sub-field, this applies to the nested augmented BackusNaur fo
39、rm (ABNF) in that parameter. 5.2 Specific wildcarding principles for ITU-T H.248 embedded SDP 5.2.1 IETF SDP wildcards The core SDP b-IETF RFC 2327, as well as its successor b-IETF RFC 4566, does not specify any wildcards. SDP lines are therefore always fully specified. b-ITU-T H.248.49 provides, in
40、ter alia, complementary information concerning relationship and usage of ITU-T H.248 and the various IETF RFCs on SDP. 5.2.2 SDP wildcards introduced by specifications other than ITU-T H.248.1 Wildcards are used (by the MGC) for resource management and/or the indication of particular modes of operat
41、ion at the MG bearer level (aware versus agnostic). The scope of SDP wildcards in ITU-T H.248 messages is therefore limited to SDP media descriptions (see clause 7.1.8.1.1.2 of ITU-T H.248.1), within the Local Descriptor (LD) and the Remote Descriptor (RD). Rec. ITU-T H.248.39 (10/2014) 3 5.2.2.1 Wi
42、ldcard “-“ Wildcard “-“, meaning “not significant“ (or “agnostic“, “unaware“), was introduced (in 2005) by the so-called “H.248 Ia profile version 1“ (see clause 5.15 of b-ETSI ES 283 018), motivated by control needs in dedicated “IP-to-IP interworking modes“ in border gateways (see clause G.2.2 of
43、b-ETSI TR 183 068). 5.2.2.2 Wildcards “r“, “l“ and “0-F“ This Recommendation introduces the wildcarded value response “r“, line response “l“, interlinkage “0-F“ and the maintain value “ wildcards via the “Advanced SDP Wildcarding Package“ (see clause 9). 6 Identification of single parameters The cla
44、uses below define which parts of the SDP are classified as “single sub-fields (values)“ for the purposes of ITU-T H.248.1 wildcarding. Each of these sub-fields may be fully specified, designated as CHOOSE “$“, designated as ALL “*“ or designated as not significant “-“. The sub-fields should not be p
45、artially wildcarded. Each of the examples indicates what type of wildcarding is not valid. It also highlights some valid types of wildcarding and what should be returned. NOTE 1 For the purposes of the examples below, “?“ is used to denote the potential wildcards: “$“ CHOOSE, “*“ ALL, “ “not signifi
46、cant“. (See Note 2 below) NOTE 2 Not to be confused with clause B.2 of ITU-T H.248.1 encoding for NULL Context (see also clause 5.2.2.2). ABNF grammar, in subsequent clauses, is copied from Appendix A (SDP Grammar) of b-IETF RFC 2327 and other IETF RFCs concerning SDP extensions. NOTE 3 Even though
47、b-IETF RFC 2327 is replaced by clause 9 of b-IETF RFC 4566), references to b-IETF RFC 2327 have been used because ITU-T H.248.1 specifies the use of this RFC for SDP. 6.1 Protocol version Table 6-1 Protocol version SDP Specification: Definition: (Clause 6 of b-IETF RFC 2327) v= (protocol version) AB
48、NF: (Appendix A of b-IETF RFC 2327) proto-version = “v=“ 1*DIGIT CRLF ITU-T H.248/SDP encoding example with applied wildcarding: Result: v=? Is valid. It would give v= 1*DIGIT The only parameter that may be wildcarded is 1*DIGIT. 4 Rec. ITU-T H.248.39 (10/2014) 6.2 Owner/Creator Table 6-2 Owner/Crea
49、tor SDP Specification: Definition: (Clause 6 of b-IETF RFC 2327) o= (owner/creator and session identifier) ABNF: (Appendix A of b-IETF RFC 2327) origin-field = “o=“ username space sess-id space sess-version space nettype space addrtype space addr CRLF ITU-T H.248/SDP encoding examples with applied wildcarding: Results: o=? o=? ? o=? ? ? o=? ? ? ? o=? ? ? ? ? Are all invalid. There are six mandatory parameters: “username“, “sess-id“,
