1、 International Telecommunication Union ITU-T H.248.46 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2007) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services Communication procedures Gateway control protocol: Connection capability control package ITU-T Recommend
2、ation H.248.46 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 aspects H.230H.239 Communication procedur
3、es 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 for audiovisual and multimedia serv
4、ices 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.519 Mobile multimedia collaboration application
5、s 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-working procedures H.560H.569 BROADBAND AND TRI
6、PLE-PLAY MULTIMEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. H.248.46 (01/2007) i ITU-T Recommendation H.248.46 Gateway control protocol: Connection capability control package Summary MGCs and MGs e
7、mploy different methods to control the MG internal connections. An MG may save transcoding resources by autonomously connecting the terminations in the same MG but different contexts directly to each other. However, in some special applications (e.g., test) this autonomous behaviour may not be desir
8、ed. Not all MGs support this autonomous behaviour, nor do they all support terminations being connected internally. Such a mix of behaviour leads to interoperability issues. This Recommendation contains a H.248 package to determine the MG internal connection capability and to set the appropriate MG
9、internal connection behaviour where necessary. Source ITU-T Recommendation H.248.46 was approved on 13 January 2007 by ITU-T Study Group 16 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. H.248.46 (01/2007) FOREWORD The International Telecommunication Union (ITU) is the Unite
10、d Nations specialized agency in the field of telecommunications. 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 telecomm
11、unications 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 covered by the proc
12、edure 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 indicate both a tele
13、communication 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 achieved when all of the
14、se 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. INTELLECTUAL PROPERTY RIGHTS ITU
15、 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 asserted by ITU membe
16、rs 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 cautioned that this may not
17、 represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. H.248.4
18、6 (01/2007) iii CONTENTS Page 1 Scope 1 2 References. 3 3 Definitions 3 3.1 Terms defined elsewhere 3 3.2 Terms defined in this Recommendation. 3 4 Abbreviations and acronyms 4 5 Convention 4 6 Termination connection model package. 4 6.1 Properties 4 6.2 Events. 5 6.3 Signals 5 6.4 Statistics 5 6.5
19、Error codes 5 6.6 Procedures 6 Bibliography. 9 ITU-T Rec. H.248.46 (01/2007) 1 ITU-T Recommendation H.248.46 Gateway control protocol: Connection capability control package 1 Scope This Recommendation defines a package that allows a MGC to determine and control whether the MG allows the application
20、of optimization mechanisms with regard to efficiency maximization of MG data-path resources, and/or optimization of QoS/performance metrics (e.g., MG transfer delay, speech quality, etc.), to the MG internal connection. Dedicated MGC implementations may not resolve cascaded contexts, therefore would
21、 benefit from using this package to determine if MGs are capable of this behaviour. MG may then simplify the internal connection of intentionally created and connected contexts in series under strict control of the MGC. The data path is the path that data flows from the ingress side to the egress si
22、de of the user plane which connects the two participants of a call. It is the MGs physical implementation of the abstract H.248 connection model. When the ingress and the egress are on the same MG, it is known as the “Internal connection“. This is illustrated in a 2-termination single context config
23、uration, where termination A is a TDM termination with G.711 encoded and termination B is an IP/RTP termination G.723.1 encoded; the data path may include the following steps: 1) E1/T1 decoding (media stream taken from correct timeslot); 2) Transport conversion (e.g., TDM to packet); 3) G.711 decodi
24、ng; 4) G.723.1 encoding; 5) RTP encoding; 6) IP packetization; 7) IP packet routing. Such a configuration results when a TDM call is received on a MGC/MG and the destination of the call is on another MGC/MG, and the connection between these is IP based. However, the data path in a MG is not constrai
25、ned to a single context/termination configuration. If for example the TDM call is received and the destination (also TDM) of the call is on the same MG (a separate MGC may control this), then the data path will be extended as such: 1) E1/T1 decoding (media stream taken from correct timeslot); 2) Tra
26、nsport conversion (e.g., TDM to packet); 3) G.711 decoding; 4) G.723.1 encoding; 5) RTP encoding; 6) IP packetization; 7) IP packet routing; 8) IP packet reception; 9) IP un-packetization; 10) RTP decoding; 11) G.723.1 decoding; 2 ITU-T Rec. H.248.46 (01/2007) 12) G.711 encoding; 13) Transport conve
27、rsion (e.g., packet to TDM); 14) E1/T1 encoding (media stream sent to correct timeslot). The additional steps (8-14) are largely the inverse of the previous steps (1-7) and as such cancel each other out. In order to optimize the data path, the MG could perform step (1) and (14) and successfully have
28、 media flow between the originator and the destination of the call. For each of these steps, the MG may have an internal means of addressing the function that performs the appropriate step. This is NOT the same address as any of those used by the H.248 connection model, but will be derived from the
29、model. The MG can use these internal addresses to perform optimizations. The MG-internal connection optimization may be based on connection information given by termination/context data and/or other internal resource usage data, but do not require call related information like call control informati
30、on from analog line signalling (Annex E.9 of ITU-T H.248.1) or channel associated signalling (ITU-T H.248.25, ITU-T H.248.28, ITU-T H.248.29) or DCME signalling (ITU-T H.248.42) or detected Digit strings (in case of enabled DigitMaps). That means for instance, MG-internal connection optimization is
31、not using address information from call/session control signalling. However, it is not in the scope of this Recommendation to describe how the MG-internal data path is addressed or how this is derived from the H.248 connection model as these are MG implementation/hardware specific. As the H.248 conn
32、ection model does not directly operate on the data path but by abstraction, the MG is responsible for determining the optimization mechanisms that may be applied to the data path. As such this package is also applicable for terminations with associated bearer control protocols (BCP) like Q.2630.x si
33、gnalling for AAL2 terminations or ITU-T Q.1970/ITU-T Q.1990 for IP terminations. (Termination-associated) BCPs could for instance delay internal connection optimizations, but this package may be in general also applied for such kind of terminations. In order to facilitate data-path optimization, thi
34、s Recommendation defines a H.248 package in order to determine the MG internal connection capability and to set the appropriate MG internal connection behaviour (Notes 1 and 2). Whilst the properties of the package may apply to all termination types, the optimizations that can be performed are data-
35、path dependent. NOTE 1 Only MG-internal connections are considered. That means that the only MG external connections loops that can be realized internally to the MG are optimized. Example of MG external connections loop: Context Cid1 with Tid1(type $) and Tid2(type IP) and 2nd context Cid2 with Tid3
36、(type IP) and Tid4(type $), and IP source/destinations addresses of Tid2 and Tid3 are so, that there would be an IP bearer connection between Tid2 and Tid3. NOTE 2 There are specific connection models with explicit internal terminations, e.g., cascaded context model according to clause 13.7.5 of b-E
37、TSI TS 123 205. There are consequently MG internal connections established (there are three in the Multi-Party supplementary service example of b-ETSI TS 123 205). Such specific context models could benefit from this package, i.e., are also in the scope of this Recommendation. This package may be us
38、ed by physical MGs (PMG) which utilize the VMG concept. According to H.248.1 procedures, there is one control association between a MGC and VMG; thus the use of the package is for a single VMG instance. However there may be multiple MGCs controlling VMGs in a single PMG. In case of multiple VMGs, th
39、ere may be a superior instance on the PMG level having knowledge about resource information and usage of all VMGs (instantiated on PMG). Such a function would be then associated with this package, but the function itself is out of scope of this Recommendation. In this case, data-path optimizations m
40、ay occur across VMGs according to the internal connection capability and internal connection behaviour properties associated with each of the VMGs. For example, if a PMG discovers that a data path occurs across two of its VMGs and their associated contexts and these contexts are allowed to be optimi
41、zed, then the PMG may optimize the path across both VMGs. However, if the contexts on one of the VMGs were marked that optimizations were not allowed then, only the path on the other VMG may be optimized. ITU-T Rec. H.248.46 (01/2007) 3 Parallel operation of multiple profiles per PMG or VMG, with di
42、fferent support of this package in each profile, is principally possible, but MAY affect the degree of application of this package. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommenda
43、tion. 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 applying the most recent edition of the Recommendations and other references
44、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 H.248.1 ITU-T Recommendation H.248.1 (2005), Gateway control protocol: V
45、ersion 3. ITU-T H.248.25 ITU-T Recommendation H.248.25 (2007), Gateway control protocol: Basic CAS packages. ITU-T H.248.28 ITU-T Recommendation H.248.28 (2007), Gateway control protocol: International CAS packages. ITU-T H.248.29 ITU-T Recommendation H.248.29 (2005), Gateway control protocol: Inter
46、national CAS compelled register signalling packages. ITU-T H.248.42 ITU-T Recommendation H.248.42 (2006), Gateway control protocol: DCME interworking package. ITU-T Q.1970 ITU-T Recommendation Q.1970 (2006), BICC IP bearer control protocol. ITU-T Q.1990 ITU-T Recommendation Q.1990 (2001), BICC beare
47、r control tunnelling protocol. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 ADD.req ITU-T H.248.1: H.248.1 Add command request 3.1.2 MOD.req ITU-T H.248.1: H.248.1 Modify command request 3.1.3 MOV.req ITU-T H.248.1: H.248.1 Move comm
48、and request 3.1.4 AuditCapability.req ITU-T H.248.1: H.248.1 AuditCapability command request 3.1.5 AuditCapability.rep ITU-T H.248.1: H.248.1 AuditCapability command reply 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 internal connection: The direct
49、collection/linkage of resources in a MG between the ingress and the egress of a user plane data which connects the two participants of a call. An “internal connection“ is there the intra-MG connection segment from an end-to-end (user plane) connection perspective. 3.2.2 autonomous behaviour: The ability of a MG to perform media/data path optimization for H.248 connections without the MGC performing optimizations of the media/data path through manipulation of the MG-internal H.248 connection configuration.
