1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-1000643.1998(R2013) Integrated Services Digital Network (ISDN) Explicit Call Transfer Supplementary Service As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance the industr
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12、dwill in no circumstances give interpretation on any American NationalStandard. Moreover, no person shall have the right or authority to issue aninterpretation of an American National Standard in the name of the AmericanNational Standards Institute. Requests for interpretations should beaddressed to
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14、 this standard. Purchasers of American National Standards mayreceive current information on all standards by calling or writing the AmericanNational Standards Institute.American National StandardPublished byAmerican National Standards Institute, Inc.11 West 42nd Street, New York, NY 10036Copyright 1
15、998 by Alliance for Telecommunications Industry SolutionsAll rights reserved.No part of this publication may be reproduced in anyform, in an electronic retrieval system or otherwise,without prior written permission of the publisher.Printed in the United States of AmericaiContentsPageForewordii1Scope
16、, Purpose, and Application . 12Normative References 13Definitions and Acronyms. 24Definition of Explicit Call Transfer from the Users Perspective . 35Functional Capabilities and Information Flows. 116Switching and Signaling Specification at the User Network Interface 167Switching and Signaling Speci
17、fication for ECT at Interexchange Interface 278Specifications for Protocol Interworking . 32Tables1Subscription Options for ECT Service per Terminal Service Profile (TSP) or per ISDN Number/Bearer Service/TSP or per Interface. 32Allowable Conditions for Invocation of ECT . 43Allocation of Functions
18、to Equipment . 154DSS1 Messages for Support of ECT 165Valid Invocation States. 196Notification Indicator Subfield. 27Figures1Network Side SDL for ECT (AB Answered, AC Answered) 82Network Side SDL for ECT (AB Answered, AC Alerting) . 93Network Side SDL for ECT (Transferred Call Clearing) . 104Functio
19、nal Entity Model 115Information Flow Model for ECT (AB Answered, AC Answered) 136Information Flow Model for ECT (AB Answered, AC Alerting) . 147Information Flow Model for ECT (Transferred Call Clearing) . 158ECT Invocation with Both AB and AC Calls Answered 249ECT Invocation with AB Call Answered an
20、d AC Call Alerting 2510ECT Notification to Served User of Transferred Call Clearing . 2611ECT Invocation with Both Calls (AB and AC) Answered 3012ECT Invocation with Call AB Answered and Call AC Alerting 31AnnexABibliography 33iiForeword(This foreword is not part of American National Standard T1.643
21、-1998.)This is one of a series of standards on Integrated Services Digital Network (ISDN)supplementary services. This standard defines and describes the Explicit Call Trans-fer service capabilities in the context of the ISDN. This standard provides switchingand signaling specifications to allow a se
22、rved user having two independent voice-band information calls, 64-kbit/s data calls, or multi-rate (nx64 kbit/s) data calls, toconnect together the distant parties of the two calls, thereby releasing the serveduser from the call, in a single user-network interaction. The Explicit Call Transfer ser-v
23、ice allows the ISDN to notify the transferred parties of the transfer if the served usersubscribes to this capability. This standard includes the Digital Subscriber SignalingSystem No. 1 (DSS1) and the Signaling System No. 7 ISDN User Part (ISUP) proto-col and procedures to support these capabilitie
24、s.Service providers of Call Transfer services will find this standard to be useful in pro-viding a consistent suite of protocols and procedures to support the service capabili-ties in this standard. Manufacturers of user and network equipment that use theIntegrated Services Digital Network (ISDN) an
25、d Signaling System No. 7 can applythis standard to the design and development of their products.This standard was developed by Working Groups T1S1.1 and T1S1.3 of AccreditedStandards Committee T1 on Telecommunications.This standard contains one annex, which is for information only and is not conside
26、redpart of this standardSuggestions for improvement of this standard will be welcome. These should be sentto the Alliance for Telecommunications Industry Solutions, T1 Secretariat, 1200 GStreet, NW, Suite 500, Washington DC 20005.This standard was processed and approved for submittal to ANSI by Accr
27、editedStandards Committee on Telecommunications, T1. Committee approval of the stan-dard does not imply that all committee members voted for its approval. At the time itapproved this standard, Accredited Standards Committee T1 had the following mem-bers:G. H. Peterson, ChairmanE. R. Hapeman, Vice-Ch
28、airmanA. Lai, SecretaryR. Rossow, Senior EditorS. Sehgal, Technical EditorY. Pathak, Technical EditorOrganization Represented Name of RepresentativeEXCHANGE CARRIERSAmeritech L. Richard WoodLarry A. Young (Alt.)AT and must be answered if incoming to User A. At most one of the calls may be held by Us
29、er A using call hold function.ANSI T1.643-19984 The two calls are of the same bearer service or of compatible bearer services. For this service, thespeech and the 3.1 kHz audio bearer service are considered compatible.Table 2 lists the allowable combinations of the conditions of the two calls, i.e.,
30、 between Users A and B(AB) and between Users A and C (AC).Table 2 - Allowable Conditions for Invocation of ECTCase AB Call AC Call1 Incoming or Outgoing, Answered, not Held Incoming or Outgoing, Answered, not Held2 Incoming or Outgoing, Answered, Held Incoming or Outgoing, Answered, not Held3 Incomi
31、ng or Outgoing, Answered, not Held Incoming or Outgoing, Answered, Held4 Incoming or Outgoing, Answered, not Held Outgoing, Alerting, not Held5 Incoming or Outgoing, Answered, Held Outgoing, Alerting, not Held6 Incoming or Outgoing, Answered, not Held Outgoing, Alerting, HeldNOTES1 In this table, AB
32、 is assumed to be answered; however, the assignment of this condition is arbitraryand the allowable conditions for a given case could be reversed. For example, in case 5, the AC callcould be “Incoming or Outgoing, Answered, Held“ and the AB call could be “Outgoing, Alerting, not Held“.2 Incoming and
33、 outgoing are with respect to User A, i.e., calls received by and originated by User Arespectively.3 The service provider may, as an option, choose to disallow cases 4, 5, and 6.Upon receiving the request for ECT, the network shall check that the invocation is allowable in accordancewith the restric
34、tions above. If the request is accepted, the network shall connect Users B and C togetherand provide an indication of acceptance to User A. After providing this indication, the network shall removethe connections between User A and the other two users.If User C is being alerted at the time of transf
35、er invocation request as a result of the availability of the net-work option described above, it shall continue to be alerted, and on answer shall be connected to User B.If User A has subscribed to notification of transfer, the service provider shall notify Users B and C of thetransfer. If User C is
36、 alerting, the notification to User C will be provided after User C has answered thecall. The notification of transfer will indicate whether the other party (either User B or User C) has an-swered or is alerting at the time of transfer. Where a network supports the allowable conditions describedin T
37、able 2, Cases 4, 5, and 6, User B shall receive a second notification of transfer indicating that User Chas answered the call.If User A has subscribed to notification of transferred call clearing, the service provider shall notify User Awhen the transferred call is cleared.4.2.3 Exceptional Procedur
38、es4.2.3.1 Activation/DeactivationNone identified.4.2.3.2 Invocation and OperationAn ECT request shall be rejected either if the user invoking the service has not subscribed to the ECTservice, or if the allowable conditions defined in 4.2.2.2 are not met. User A shall be notified of the causefor reje
39、ction and the original calls AB and AC shall remain in the state they were in immediately before theECT request.ANSI T1.643-199854.2.4 Alternative ProceduresNone identified.4.3 Interworking ConsiderationsWhen interworking occurs on both calls (AB and AC) to be transferred and the calls were originat
40、ed byUser A, restrictions shall be placed on the ability of User A to invoke the transfer operations. This is re-quired to prevent the unsupervised connection of two non-ISDN parties who may be served from ex-changes that do not immediately forward disconnect for an incoming call.The ISDN shall not
41、allow User A to complete the transfer and disconnect from the calls unless at least oneof the calls meets one of the following conditions: an off-hook non-ISDN line on an access served by the controlling switch; an answered ISDN call on an access served by the controlling switch; an incoming trunk i
42、n the answered state served by the controlling switch; or, an outgoing trunk in the answered state which did not encounter interworking.If interworking with non-ISDN facilities had occurred on the original call to User B, to User C, or to both,then it may not be possible to deliver the optional noti
43、fication of the transfer to the remote users. This mayoccur due to the User Bs or User Cs terminal not being an ISDN terminal or due to interworking betweenUser As network and User Bs or User Cs network. In these cases, User As network may send the op-tional notification, although it may not actuall
44、y be delivered to User B or User C.4.4 Interactions with Other Supplementary Services4.4.1 Call WaitingThere is no interaction between ECT and ISDN Call Waiting. However, the following should be noted: A call waiting indication may be delivered to any party independently of the invocation of ECT by
45、thatparty, assuming that the party has subscribed to the Call Waiting service. Prior to invocation of ECT, the party may use normal Call Waiting procedures, including holding theestablished call to answer the waiting call. Following the invocation of ECT, Call Waiting indication remains and the wait
46、ing call may be handledvia normal procedures.4.4.2 Normal Call TransferIt shall be possible for User A who is subscribed to ECT and User B who is subscribed to Normal CallTransfer to transfer the call simultaneously. That is, if User A and User B are active in an established call,User A could transf
47、er the call to User C, and User B could transfer the call to User D. Call progress sig-nals and other notifications shall be delivered to the appropriate party at the time the signal is received.The result of these simultaneous transfers is that User C shall be connected to User D.1)Simultaneous tra
48、nsfers shall affect the delivery of the notifications of the transfers. For example, whenUser A transfers User B to User C, an optional notification of the transfer may be sent towards User B.Depending on the state of User Bs attempt to transfer User A, the notification shall be delivered: to User B
49、 if the AB call reference is still active, i.e., User B has not completed the transfer so the callreference for the AB call is still active;-1)The simultaneous use of Explicit Call Transfer by User A and Normal Call Transfer, Explicit Call Transfer or CallDeflection by User B or User C may lead to violation of the interworking restrictions described in 4.3, which may re-sult in connection of two users without sufficient network release supervision capabilities.ANSI T1.643-19986 to User D (the party to which User B transferred User A) if the call reference has bee
