1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T H.460.12TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2004) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Supplementary services for multimedia Glare control indicator within H.323 systems ITU-T Recommendation H.
2、460.12 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 procedures H.240
3、H.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 services H.3
4、60H.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 applications and se
5、rvices 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 TRIPLE-PLAY
6、 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.460.12 (03/2004) i ITU-T Recommendation H.460.12 Glare control indicator within H.323 systems Summary Glare, also known as dual seizure, is a c
7、ondition in which two entities attempt to select the same circuit within the trunk group; in the context of this Recommendation, the two entities are a H.323 Gatekeeper and a PSTN switch. This Recommendation specifies a mechanism that allows an egress H.323-PSTN Gateway to resolve a glare condition
8、that is detected on the Gateway when circuit selection is done on the Gatekeeper. The Gatekeeper delivers a Glare Control Indicator to the Gateway to inform the Gateway on how to deal with the glare condition. Source ITU-T Recommendation H.460.12 was approved on 15 March 2004 by ITU-T Study Group 16
9、 (2001-2004) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. H.460.12 (03/2004) 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 permanent or
10、gan 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, establishes the
11、 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 standards are
12、 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 Recommendati
13、on 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 used t
14、o 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 Intellectua
15、l 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 received not
16、ice 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 2004 All rights reserved. No par
17、t of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. H.460.12 (03/2004) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Glare Control Indicator. 1 3.1 Delivery of Glare Control Indicator . 2 3.2 Glare resolution at Gateway . 2 3.3 Ge
18、neric Extensibility Framework. 2 4 Glare Control Indicator parameter 3 ITU-T Rec. H.460.12 (03/2004) 1 ITU-T Recommendation H.460.12 Glare control indicator within H.323 systems 1 Scope This Recommendation specifies a mechanism that allows an egress H.323-PSTN Gateway to resolve a glare condition (a
19、lso known as “dual seizure“) that is detected on the Gateway when circuit selection is done on the Gatekeeper. The Gatekeeper delivers a Glare Control Indicator to the Gateway to inform the Gateway on how to deal with the glare condition. For bidirectional (both-way) trunk groups between a H.323-PST
20、N Gateway and a PSTN switch, various circuit selection algorithms are defined in ITU-T Rec. Q.764 to minimize glare when both the Gateway and the PSTN switch attempt to select the same circuit within the trunk group. In addition, various algorithms may be used to specify the action to be taken to re
21、solve the glare condition. For example, if glare occurs on an even-numbered circuit within a trunk group, the outgoing call (from the H.323 network to the PSTN) may be allowed to proceed but the incoming call must be re-attempted on another available circuit. This glare resolution algorithm is norma
22、lly configured along with the circuit selection algorithm on each device. ITU-T Rec. H.323 provides the ability for a Gatekeeper to select the circuit within a trunk group to be used for a call from the H.323 network to a PSTN network through a H.323-PSTN Gateway. The group field in the H.323 destin
23、ationCircuitId structure may be used to transport the trunk group identifier and the member field in the same structure may be used to transport the circuit identifier from the Gatekeeper to the Gateway. This Recommendation provides a means for the Gatekeeper to also control how a glare condition ma
24、y be resolved on a Gateway. 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 other refer
25、ences 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 reference
26、to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T Recommendation H.225.0 (2003), Call signalling protocols and media stream packetization for packet-based multimedia communication systems. ITU-T Recommendation H.323 (2003), Pa
27、cket-based multimedia communications systems. ITU-T Recommendation H.460.8 (2002), Querying for alternate routes within H.323 systems. ITU-T Recommendation Q.764 (1999), Signalling system No. 7 ISDN user part signalling procedures. 3 Glare Control Indicator The Glare Control Indicator determines the
28、 action the Gateway should take if it detects glare for the circuit in question. The Glare Control Indicator has two values: 1) Outgoing call from the H.323 network to the PSTN has precedence. 2) Incoming call from the PSTN to the H.323 network has precedence. 2 ITU-T Rec. H.460.12 (03/2004) 3.1 Del
29、ivery of Glare Control Indicator The Gatekeeper includes a Glare Control Indicator along with the circuit selection information (destinationCircuitId) that it sends to the Gateway. In the case of direct routed call signalling, the Gatekeeper shall send the Glare Control Indicator with the destinatio
30、nCircuitId in the ACF message that it sends to the calling H.323 Endpoint which shall forward the Glare Control Indicator in the Setup message that it sends to the egress Gateway. In the case of Gatekeeper routed call signalling, the Gatekeeper shall send the Glare Control Indicator with the destina
31、tionCircuitId in the Setup that it sends to the H.323-PSTN Gateway. 3.2 Glare resolution at Gateway If the Glare Control Indicator indicates the outgoing call has precedence, then the Gateway will proceed with the outgoing call from the H.323 network to the PSTN and release the incoming call from th
32、e PSTN. If the Glare Control Indicator indicates the incoming call has precedence, the Gateway will allow the incoming call from the PSTN to proceed and send another ARQ to the Gatekeeper, so that it can select another available circuit for the outgoing call. The Gateway will use the ARQ ReQuery pro
33、cedures defined in ITU-T Rec. H.460.8 to inform the Gatekeeper that another circuit must be selected. The Gateway shall send a subsequent ARQ message with an incremented query count and a CallTerminationCause structure containing the cause IE set to Q.850 value requested circuit/channel not availabl
34、e. When the Gatekeeper receives a subsequent ARQ with an incremented query count and a CallTerminationCause structure containing the cause value set to Q.850 value requested circuit/channel not available, it shall select another circuit for the outgoing call and send an ACF back to the Gateway. 3.3
35、Generic Extensibility Framework A Gatekeeper includes the Glare Control Indicator with the destinationCircuitId in H.225.0 RAS and call signalling messages. The Glare Control Indicator parameter shall be transported using the generic extensibility framework as described below. When sending the Glare
36、 Control Indicator parameter in the call signalling messages, the Glare Control Indicator shall be coded in the genericData parameter in the H.225.0 H323-UU-PDU in the User-User Information Element. When sending the Glare Control Indicator parameter in the RAS messages, the Glare Control Indicator s
37、hall be coded in the genericData parameter in the request parameter of the H.225.0 RasMessage. The genericData parameter indicates the Glare Control Indicator feature and contains a Glare Control Indicator parameter. Table 1 defines the Glare Control Indicator feature. Table 1/H.460.12 Glare Control
38、 Indicator from a Gatekeeper to a Gateway Feature name: Glare Control Indicator Feature description: This feature allows an H.323 Gatekeeper to control glare resolution on a H.323-PSTN Gateway. Feature identifier type: Standard Feature identifier value: 12 ITU-T Rec. H.460.12 (03/2004) 3 4 Glare Con
39、trol Indicator parameter Table 2 defines the Glare Control Indicator parameter. Table 2/H.460.12 Glare Control Indicator parameter Parameter name: Glare Control Indicator Parameter Parameter description: This is the data sent in H.225.0 RAS and Call Signalling messages to control the glare condition
40、. Parameter identifier type: Standard Parameter identifier value: 1 Parameter type: number8, values: 1 = Outgoing call to PSTN has precedence. 2 = Incoming call from PSTN has precedence. Parameter cardinality: Once and only once Printed in Switzerland Geneva, 2004 SERIES OF ITU-T RECOMMENDATIONS Ser
41、ies A Organization of the work of ITU-T Series B Means of expression: definitions, symbols, classification Series C General telecommunication statistics Series D General tariff principles Series E Overall network operation, telephone service, service operation and human factors Series F Non-telephon
42、e 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 signals Series K Pr
43、otection against interference Series L Construction, installation and protection of cables and other elements of outside plant Series M TMN and network maintenance: international transmission systems, telephone circuits, telegraphy, facsimile and leased circuits Series N Maintenance: international s
44、ound 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 terminal equipment Se
45、ries T Terminals for telematic services Series U Telegraph switching Series V Data communication over the telephone network Series X Data networks and open system communications Series Y Global information infrastructure, Internet protocol aspects and Next Generation Networks Series Z Languages and general software aspects for telecommunication systems
