1、 International Telecommunication Union ITU-T H.460.17TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (09/2005) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Supplementary services for multimedia Using H.225.0 call signalling connection as transport for H.323 RAS
2、messages ITU-T Recommendation H.460.17 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.23
3、9 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 for audiovi
4、sual 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.519 Mobile multimedia c
5、ollaboration 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.559Mobile multimedia collaboration inter-working procedures H.560
6、H.569 BROADBAND AND TRIPLE-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.460.17 (09/2005) i ITU-T Recommendation H.460.17 Using H.225.0 call signalling connection as transport for H.323
7、 RAS messages Summary The current version of ITU-T Rec. H.323 requires two completely independent transports: one for RAS and another for H.225.0 call signalling. For several reasons, one of them is FW/NAT traversal; it would be advantageous to be able to use the same transport for both protocols. T
8、his Recommendation defines the mechanism of encapsulating RAS messages inside H.225.0 messages and the method for discovering the ability of a peer H.323 entity to support features defined in this Recommendation. Source ITU-T Recommendation H.460.17 was approved on 13 September 2005 by ITU-T Study G
9、roup 16 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. H.460.17 (09/2005) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a perma
10、nent 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), which meets every four years, establis
11、hes 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 within ITU-Ts purview, the necessary standa
12、rds 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 Recommendation is voluntary. However, the Recom
13、mendation 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 as “must“ and the negative equivalents are
14、 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 Recommendation may involve the use of a claimed Inte
15、llectual 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 approval of this Recommendation, ITU had not recei
16、ved notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2005 All rights reserved.
17、 No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. H.460.17 (09/2005) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Terms and Definitions 1 4 Abbreviations 2 5 Feature Description. 2 6 Discovering remote entitys support of
18、 RAS over H.225.0 2 7 Transport of RAS over H.225.0 2 7.1 Usage of H.225.0 2 7.2 Generic data usage 3 7.3 RAS over H.225.0 feature definition 3 7.4 RAS over H.225.0 parameters 4 8 Security considerations. 4 ITU-T Rec. H.460.17 (09/2005) 1 ITU-T Recommendation H.460.17 Using H.225.0 call signalling c
19、onnection as transport for H.323 RAS messages 1 Scope This Recommendation defines the mechanism of encapsulating RAS messages inside H.225.0 messages and the method for discovering the ability of a peer H.323 entity to support features defined in this Recommendation. 2 References The following ITU-T
20、 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 Recommendation
21、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 does not give it, a
22、s a stand-alone document, the status of a Recommendation. 1 ITU-T Recommendation H.323 (2003), Packet-based multimedia communications systems. 2 ITU-T Recommendation H.225.0 (2003), Call signalling protocols and media stream packetization for packet-based multimedia communication systems. 3 ITU-T Re
23、commendation H.460.1 (2002), Guidelines for the Use of the Generic Extensible Framework. 4 ITU-T Recommendation H.235.0 (2005), H.323 security: Framework for security in H-series (H.323 and other H.245-based) multimedia systems. 5 ITU-T Recommendation H.235.1 (2005), H.323 security: Baseline securit
24、y profile. 6 ITU-T Recommendation H.235.2 (2005), H.323 security: Signature security profile. 7 ITU-T Recommendation H.235.3 (2005), H.323 security: Hybrid security profile. 8 ITU-T Recommendation H.235.4 (2005), H.323 security: Direct and selective routed call security. 9 ITU-T Recommendation H.235
25、.5 (2005), H.323 security: Framework for secure authentication in RAS using weak shared secrets. 10 ITU-T Recommendation H.235.6 (2005), H.323 security: Voice encryption profile with native H.235/H.245 key management. 11 ITU-T Recommendation H.235.7 (2005), H.323 security: Usage of the MIKEY key man
26、agement protocol for the Secure Real Time Transport Protocol (SRTP) within H.235. 12 IETF RFC 2246 (1999), The TLS Protocol Version 1.0. 3 Terms and Definitions This Recommendation defines the following term: 3.1 RAS over H.225.0: The mechanism allowing transport of RAS messages inside the H.225.0 c
27、all signalling connection. 2 ITU-T Rec. H.460.17 (09/2005) 4 Abbreviations This Recommendation uses the following abbreviations: EP Endpoint GK Gatekeeper RAS Registration, Admission and Status RCF Registration Confirm RRQ Registration Request SCTP Stream Control Transmission Protocol TCP Transport
28、Control Protocol TLS Transport Level Security TSAP Transport Service Access Point 5 Feature Description This Recommendation defines two mechanisms: Discovery of the remote entitys support of RAS over H.225.0 Transport of RAS messages over the H.225.0 call signalling connection. 6 Discovering remote
29、entitys support of RAS over H.225.0 RAS messages are sent between EP and GK or between two GKs. In both cases the first RAS message between two particular H.323 entities is sent in the GK direction. The support of RAS over H.225.0 by a particular GK may be either known a priori (provisioned) or may
30、require discovery. H.460 feature negotiation mechanisms cannot be used in this case because the discovery should be performed before the first message between the H.323 entities is sent. Annex O/H.323 GK discovery mechanism should be used for discovery of support of RAS over H.225.0. The service for
31、 the discovery shall be either h323rs or h323ls. The H.225.0 transport will be discovered based on the following rules: In the case of H.225.0 signalling over TCP, the transport shall be tcp. In the case of H.225.0 signalling over Annex E/H.323, the transport shall be h323mux. In the case of H.225.0
32、 signalling over SCTP, the transport shall be sctp. If the IP address of the GK is known a priori and the port is unknown, the well-known H.225.0 call signalling port 1720 shall be used for RAS over H.225.0 procedure. 7 Transport of RAS over H.225.0 7.1 Usage of H.225.0 The entity which supports RAS
33、 over H.225.0 shall also support persistent H.225.0 transport connections as described in 7.3/H.323. An endpoint shall indicate such support by setting maintainConnection in RRQ to TRUE. If both the entity sending the RAS message, and the entity receiving it support RAS over H.225.0, then they shoul
34、d use it for RAS messages transport. In order to keep the transport connection open, the two entities should use lightweight RRQ, as described in 7.2.2.1/H.323. In the case of NAT traversal, the timeToLive value should be shorter ITU-T Rec. H.460.17 (09/2005) 3 than the NAT binding timeout. The enti
35、ties may use the IRR mechanism to support the same functionality. Alternatively, for the cases when transport is TCP, an entity which established the TCP connection may periodically send empty TPKT packets (packets containing bytes 03 00 00 04 only). A keep-alive interval in the range of 5 to 30 sec
36、onds should be used except in cases where it is known (for example, from the specifics of the network) that a longer interval will not result in the closure of pinholes. To send a RAS message between two H.323 entities supporting RAS over the H.225.0 feature, a persistent H.225.0 transport connectio
37、n shall be used between the entities. If such a connection is already established it may be re-used, or a new connection may be established. If no persistent connection is currently established, then it shall be established. Generally, the entity sending the first RAS message establishes the connect
38、ion to the entity receiving the RAS message. The H.225.0 signalling TSAP of the entity receiving the RAS message is used as the transport connection destination. The same transport connection should be used for RAS over H.225.0 signalling and regular H.225.0 signalling. If desired, more than one H.2
39、25.0 transport connection between the same two entities may be used for RAS messages transfer. No association is mandated between RAS messages and transport connections in such a case. To signal that the same GKs H.225.0 transport signalling TSAP shall be used for all RAS and H.225.0 communication,
40、the callSignalAddress and rasAddress fields of the RRQ and RCF shall contain a SEQUENCE OF containing zero elements. The H.225.0 FACILITY message shall be used to transfer RAS messages. The CRV field of the message shall have a value of 0 (including the flag bit). Such a message shall contain User-u
41、ser Information Element with the h323-message-body field of H323-UU-PDU set to empty. The genericData field of the H323-UU-PDU shall contain RAS messages as described in 7.2 and 7.4. An H.323 entity, which supports RAS over H.225.0, shall also support tunnelling of H.245 channel over H.225.0. 7.2 Ge
42、neric data usage RAS messages to be sent over H.225.0 call signalling shall be encapsulated in the genericData field of the H323-UU-PDU in the User-user Information Element of the H.225.0 FACILITY message. Each such genericData field has the id field specifying RAS over H.225.0 (as defined in Table
43、1) and one or more RAS message parameters (as defined in Table 2) containing binary encoding of one RAS message each. 7.3 RAS over H.225.0 feature definition Table 1 defines the RAS over the H.225.0 feature. Table 1/H.460.17 RAS over H.225.0 feature Feature name: RAS over H.225.0 Feature Description
44、: This feature allows transport of RAS messages over H.225.0 call signalling connection. Feature identifier type: Standard Feature identifier value: 17 4 ITU-T Rec. H.460.17 (09/2005) 7.4 RAS over H.225.0 parameters Table 2 defines the RAS over H.225.0 parameters. Table 2/H.460.17 RAS message parame
45、ter Parameter name: RAS message Parameter description: This parameter contains basic-aligned PER-encoded RAS message. Parameter identifier type: Standard Parameter identifier value: 1 Parameter type: raw Parameter cardinality: One or more 8 Security considerations The transport of RAS messages provi
46、ded by RAS over H.225.0 mechanism does not provide a means of security. It relies on the security mechanisms provided by underlying transport and security mechanisms defined for RAS messages. TLS may be used for the RAS over a TCP or SCTP channel. The procedure for supporting TLS is out of the scope
47、 of this Recommendation and needs to be addressed by H.235. Printed in Switzerland Geneva, 2005 SERIES OF ITU-T RECOMMENDATIONS Series A Organization of the work of ITU-T Series D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Ser
48、ies F Non-telephone telecommunication services Series G Transmission systems and media, digital systems and networks Series H Audiovisual and multimedia systems Series I Integrated services digital network Series J Cable networks and transmission of television, sound programme and other multimedia s
49、ignals Series K Protection against interference Series L Construction, installation and protection of cables and other elements of outside plant Series M Telecommunication management, including TMN and network maintenance Series N Maintenance: international sound programme and television transmission circuits Series O Specifications of measuring equipment Series P Telephone transmission quality, telephone installations, local line networks Series Q Switching and signalling Series R Telegraph transmission Series S Telegraph services te
