1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Q.2724.1 (07/96) SERIES Q: SWITCHING AND SIGNALLING Broadband ISDN - B-ISDN application protocols for the network signalling B-ISDN User Part - Look-ahead without state change for the Network Node Interface (
2、“I) ITU-T Recommendation Q.2724. I (Previously CCIlT Recommendation) ITU-T Q-SERIES RECOMMENDATIONS SWITCHING AND SIGNALLING STD-ITU-T RECMN Q-2724.1-ENGL 199b = 4862593 0b33+77 315 W For further details, please refer to ITU-T List of Recommendations. SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE I
3、NTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN SPECIFICATIONS OF SIGNALLING SYSTEMS No. 4 AND No. 5 SPECIFICATIONS OF SIGNALLING SYSTEM No. 6 SPECIFICATIONS OF SIGNALLING SYSTEM R1 SPECIFICATIONS OF SIGNALLING SYSTEM R2 DIGITAL EXCHANGES IN
4、TERWORKING OF SIGNALLING SYSTEMS SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 PUBLIC LAND MOBILE NETWORK INTERWORKING WITH SATELLITE MOBILE SYSTEMS CLAUSES APPLICABLE TO ITU-T STANDARD SYSTEMS INTELLIGENT NETWORK BROADBAND ISDN General aspects Signalling ATM a
5、daptation layer (SAAL) Signalling network protocols Common aspects of B-ISDN application protocols ,“r access signalling and network signalling and interworking (2.14.3 Q .4-Q. 59 Q.604.99 Q. 100-Q.119 Q.120-Q.249 Q.250-(2.309 (2.3 1 04.399 Q.400-(2.499 Q.500-Q.599 Q .600-Q. 699 Q .700-Q. 849 Q. 850
6、-Q. 999 Q. 1000-Q. 1 O99 (2.1 100-Q.1199 Q. 1200-Q.1999 Q.2000-(2.2999 Q.2000-Q.2099 Q.2 I 004.2 1 99 Q.2200-Q.2299 Q.2600-Q ,2699 B-ISDN application protocols for access signalling Q.2900-Q.2999 - STD-ITU-T RECMN Q.2724.1-ENGL L77b 48b257L Ob33478 051 = 1TU-T RECOMMENDATION 4.2724.1 B-ISDN USER PAR
7、T - LOOK-AHEAD WITHOUT STATE CHANGE FOR THE NETWORK NODE INTERFACE (“1) Summary This Recommendation specifies the extensions to the Broadband ISDN User Part for the support of look-ahead without state change. Source ITU-T Recommendation Q.2724.1 was prepared by ITU-T Study Group 11 (1993-1996) and w
8、as approved under the WTSC Resolution No. 1 procedure on the 9th of July 1996. FOREWORD IT (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the IT. The
9、 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 Conference (WTSC), which meets every four years, establishes the topics f
10、or study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the IT-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within IT-Ts purview, the ne
11、cessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention t
12、o the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by IT members or others ou
13、tside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU hadhad not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, impiementors are cautioned that this may not represe
14、nt the latest information and are therefore strongly urged to consult the TSB patent database. O ITU 1997 Ali rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in
15、writing from the ITU. II Recommendation 4.2724.1 (07/96) . STDeITU-T RECMN Q.2724.L-ENGL L99b LtBb259L Ob33480 70T CONTENTS Page 1 1.1 1.2 1.3 1.4 2 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 4 4.1 5 5.1 5.2 5.3 5.4 5.5 5.6 6 Overview Scope References Definitions Abbreviations . Specification model Look.Ahead. a
16、pplication process functions . Primitive interface AP/SACF . Procedures at initiating exchange . Normal procedures . .- 3.2.2 Exceptional procedures . Procedure at an intermediate national exchange Procedure at the outgoing screening point . Procedure at an intermediate international exchange . Proc
17、edure at the incoming screening point . Procedure at the destination local exchange . 3.7.1 Normal procedures 3.7.2 Exceptional procedures . 3.2.1 SACF Interface SCCP/SACF 4.1.1 Primitives 4.1.2 Use of SCCP LA-ASE Interface LA-ASEISACF Supported operation ASE procedures 5.3.1 Dialogue beginning . 5.
18、3.2 Normal dialogue end . 5.3.3 Abnormal dialogue end . Parameters Abstract syntax, general . ASN.l module TCAP 3 3 3 5 5 5 5 5 6 6 6 6 6 8 8 8 9 9 9 9 10 10 10 12 Recommendation Q.2724.1 (07/96) . 111 STD-ITU-T RECMN Q.2724-1-ENGL L77b 4862572 Ob33481 b4b W 6.1 Interface TCAPBACF 6.1.1 Primitives 6
19、.1.2 Use of TCAP . 7 Timers . Annex A . ASN.l module defining B-ISUP parameters applicable for LA-ASE Annex B . Network Look Ahead Indicator parameter B . 1 Network Look Ahead Indicator parameter . B.2 Forrnats . B.3 Procedures Appendix I . B-ISUP Parameters used in the Look-Ahead Procedure . Append
20、ix II . Guidelines on the use of Look-Ahead without state change Criteria for invocation II . 1.1 High-resource connections II . 1.2 Number analysis II . 1.3 Service indications II . 1.4 Calling party indications . Criteria for precluding use of Look-Ahead Management of Look-Ahead criteria Relations
21、hip between Look-Ahead and Multiparty service . II . 1 11.2 11.3 11.4 Appendix III . Look-Ahead message flow for the UNINNI intenvorking III . 1 First scenario 111.2 Second scenario 111.3 Third scenario . 111.4 Fourth scenario . 111.5 Fifth scenario Appendix IV . Primitive relationships Appendix V .
22、 Look-Ahead relationships involving Multiple Networks Appendix VI . Coding of instruction indicators for the Network Look Ahead Indicator . Page 12 12 12 13 13 16 16 17 17 18 18 18 18 19 19 19 19 19 20 20 20 21 21 22 23 24 25 27 iv Recommendation 4.2724.1 (07/96) STD-ITU-T RECMN Q*2724.1-ENGL 277b q
23、Bb2572 Ob33482 582 D Recommendation Q.2724.1 B-ISDN USER PART - LOOK-AHEAD WITHOUT STATE CHANGE FOR THE NETWORK NODE INTERFACE (“I) (Geneva, 1996) 1 Overview 1.1 Scope This Recommendation specifies the procedures for Look-Ahead without state change at the B-ISDN Network Node Interface. This Recommen
24、dation specifies the essential features, procedures and operations required for Look-Ahead. The Look-Ahead facility allows a network to perform called- terminal availability and compatibility checking without any commitment of network resources. The points-in-call at which this procedure may be invo
25、ked will be identified in the appropriate Basic Call, Additional Capability, or Supplementary Service Recommendations, i.e. in their Application Process procedures. However, guidelines for the selection of such points and how the procedure may be used are contained in Appendix II. Procedures and add
26、itional parameters for Look-Ahead on non-basic call will be identified in the appropriate service Recommendations. The action to be taken at six exchange types are described as: - initiating exchange; - intermediate national exchange; - - intermediate international exchange; - - destination local ex
27、change. Actions common for all exchange types are described only once. Different, or additional actions required in specific types are described in separate subclauses applicable to this type of exchange. Note that the incoming and outgoing screening points may be coincident with gateway exchanges,
28、transit exchanges, local exchanges, or as free-standing functions according to the specific national network architecture. outgoing screening point and/or gateway exchange; incoming screening point and/or gateway exchange; 1.2 References The following ITU-T Recommendations, and other references cont
29、ain provisions which, through reference in this text, constitute provision of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate
30、 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. i ITU-T Recommendation 4.2763 (199.51, Signalling Sstem No. 7 B-ISDN User Part (B-ISUP) - Formats and codes. 1 Re
31、commendation 4.2724.1 (07/96) 41 151 c91 ITU-T Recommendation 4.2764 (1995), Signalling System No. 7 B-ISDN User Part (B-ISUP) - Basic call procedures. ITU-T Recommendation 4.2610 (1995), Usage of cause and location in B-ISDN User Part and DSS 2. ITU-T Recommendation 4.2964.1 (1 996), Digital Subscr
32、iber Signalling System No. 2 - Basic Look-Ahead. ITU-T Recommendation 4.2725.1 (1 996), B-ISDN user part - Support of negotiation during connection setup. ITU-T Recommendation Q.77 1 (1 993), Functional description of transaction capabilities. ITU-T Recommendation Q.772 (1 993), Transaction capabili
33、ties information element definitions. ITU-T Recommendation 4.7 1 1 (1 996), Functional description of the signalling connection control part. ITU-T Recommendation 4.71 2 (1 996), Definition and function of signalling connection control part messages. ITU-T Recommendation Q.7 13 (1 996), Signalling c
34、onnection control part formats and codes. ITU-T Recommendation 4.7 14 (1 996), Signalling connection control part procedures. ITU-T Recommendation 4.71 5 (1 996), Signalling connection control part user guide. ITU-T Recommendation 4.293 1 (1 995), Digital Subscriber Signalling System No. 2 - User-Ne
35、twork Interface (UN4 layer 3 specijcation for basic call connection control. ITU-T Recommendation 4.93 1 (1 993), ISDN user-network interface layer 3 specification for basic call control. CCITT Recommendation X.209 (1988), Specfzcation of basic encoding rules for Abstract Syntax Notation One (ASN. 1
36、). ITU-T Recommendation 4.773 (1 993), Transaction capabilities formats and encoding. ITU-T Recommendation 4.774 (1 993), Transaction capabilities procedures. ITU-T Recommendation Q.775 (1 993), Guidelines for using transaction capabilities. 1.3 Definitions This Recommendation defines the following
37、terms. 1.3.1 screening function: This function is optionally provided within a network to support network-specific screening of Look-Ahead operations and parameters within the LA application. This screening may, for example, include checking of specific parameter values and field contents against bi
38、lateral agreements between originating and terminating network operators. 1.3.2 screening point: The location at which the screening function is deployed within a given network. This may be an exchange of any type, or it may be a free-standing node. 1.4 Abbreviations This Recommendation uses the fol
39、lowing abbreviations. AEI Application Entity Invocation 2 Recommendation Q.2724.1 (07196) - - STD-ITU-T RECNN Q.2724.1-ENGL 199b LIBb2591 Ob33484 355 ASE Application Service Element ASN. 1 B-ISDN B-ISUP Broadband ISDN User Part ISDN Integrated Services Digital Network LA Look-Ahead MTP-3 Message Tra
40、nsfer Part 3 SACF Single Association Control Function SA0 Single Association Object SCCP Signalling Connection Control Part TCAP Transaction Capabilities Application Part Abstract Syntax Notation No. 1 Broadband Integrated Services Digital Network 2 Specification model The description of the Look-Ah
41、ead procedures are structured according to the model described in Figure 1. AEI SA0 LA-ASE S A C F TCAP I EEI MTP-3 ri i 77840.95 Figure UQ.2724.1- Look-Ahead protocol architecture 3 Look-Ahead, application process functions 3.1 Primitive interface AP/SACF The Look-Ahead functions in the application
42、 process use the services provided by the SACF primitive interface. These are listed in Table 1. Recommendation Q.2724.1 (07/96) 3 Table UQ.2724.1- LA primitives between AP and SACF Primitive name LA-Invoke LA-Error TY Pes Req./Ind./Resp./Conf. Ind. Table 2 contains the list of parameters in the LA-
43、Invoke Req./ind./Resp./Conf. primitives that may be used for the Look-Ahead. NarrowbandHighLayerCompatibility (Note 1) NarrowbandLowLayerCompatibility (Note 1) OAMTrafficDescriptor Table 2/Q.2724.1- Contents of the LA-Invoke Req./Ind./Resp./Conf. primitive O O O Parameter Error-Type Table 3 contains
44、 the list of parameters, used for the Look-Ahead, in the LA Error Indication primitive. - Mandatory/Optional O Table 3/Q.2724.1- Contents of the LA-Error Indication primitive 4 Recommendation 4.2724.1 (07/96) 3.2 Procedures at initiating exchange Initiating exchange is the exchange initiating the LA
45、 procedure and it could be any of the types, originating, transit, gateway or destination (not a fi-ee-standing screening point). Actions where the initiating exchange is also the destination exchange are specified by DSS 2 protocol 4. 3.2.1 Normal procedures The LA-initiating exchange shall perform
46、 Look-Ahead based on service requirements, as indicated in Basic Call (Recommendation 4.2764) or other procedures (e.g. Point-to-multipoint, multiconnection, modification etc.). The criteria for this decision are outside the scope of this Recommendation, but some guidelines and suggestions are inclu
47、ded in Appendix II. The LA procedure is requested by the AP creating an instance of Look-Ahead AEI and sending an LA-1nvoke.req primitive to the SACF. If the LA-initiating exchange receives an LA-1nvoke.conf primitive: - which includes a satisfactory LookResult parameter, it shall start the normal s
48、etup procedure towards the addressed user, using the received alternatives; which includes an unsatisfactory LookResult parameter, or a Cause Indicators parameter, based on the received parameter values and possibly on the diagnostics field, it shall decide whether to clear the connection towards th
49、e calling party or to proceed with normal call setup. If the connection is to be cleared, the clearing message shall include the received cause value. - 3.2.2 Exceptional procedures If timer T-la expires, an LA-1nvoke.resp primitive will be received by the AP. The LA-initiating exchange shall decide, based on service requirements, whether to continue the call setup or to clear the call towards the calling party. An LA - Error.ind primitive will be received by the AP also when an error occurs at LA-ASE level. 3.3 The AP of an intermediate natio
