1、INTERNATIONAL TELECOMMUNICATION UNIONCCITT I.254.2THE INTERNATIONAL (08/92)TELEGRAPH AND TELEPHONECONSULTATIVE COMMITTEEINTEGRATED SERVICES DIGITALNETWORK (ISDN)GENERAL STRUCTURE AND SERVICECAPABILITIESTHREE-PARTY SUPPLEMENTARY SERVICERecommendation I.254.2Geneva, 1992FOREWORDThe CCITT (the Internat
2、ional Telegraph and Telephone Consultative Committee) is a permanent organ of theInternational Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariffquestions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwideb
3、asis.The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approvesRecommendations prepared by its Study Groups. The approval of Recommendations by the members of CCITT betweenPlenary Assemblies is covered by the procedure laid down in CCITT Resolution No.
4、2 (Melbourne, 1988).Recommendation I.254.2 was revised by Study Group I and was approved under the Resolution No. 2procedure on the 4th of August 1992._CCITT NOTES1) In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication Administration and
5、 a recognized private operating agency.2) A list of abbreviations used in this Recommendation can be found in Annex A. ITU 1992All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, wi
6、thout permission in writing from the ITU.Recommendation I.254.2 (08/92) 1Recommendation I.254.2Recommendation I.254.2THREE-PARTY SUPPLEMENTARY SERVICE(revised 1992)1 DefinitionThe Three-Party Service enables a user to establish a three-way conversation, i.e. a simultaneouscommunication between the s
7、erved user and two other parties.2 Description2.1 General description2.1.1 Beginning the Three-Party supplementary serviceThe served user, user A, who is involved in at least two calls (one active call and at least one call on hold),each of which may be an incoming or outgoing call, can join the act
8、ive and one held call together into a three-wayconversation by requesting the Three-Party Service (3 PTY). Both calls shall be answered prior to the invocation of theThree-Party supplementary service.2.1.2 Controlling the three-way conversationDuring an active three-way conversation the served user
9、shall be able to:i) disconnect one party;ii) disconnect the entire three-way conversation;iii) explicitly choose one party to have a private communication with that party.Note This last case will result in the served user having two calls available (one active and one held) similarto the situation b
10、efore the invocation of the Three-Party supplementary service.The Three-Party supplementary service shall be cancelled by the user actions listed above.2.2 Specific terminologyServed user: During the invocation and the active phase, the service is under the control of the “served user”,i.e. the one
11、by whom the service was invoked. This user is also referred to as user A.Remote parties (user B and user C): The parties involved in the two calls that are joined together into a three-way conversation (user A with user B, user A with user C).2.3 Qualifications on the applicability to telecommunicat
12、ion servicesThe Three-Party supplementary service shall be applicable to all telecommunication services carrying speech.2 Recommendation I.254.2 (08/92)3 Procedures3.1 Provision/withdrawalThe Three-Party supplementary service shall be provided by prior arrangement with the service provider.Withdrawa
13、l of the service shall be made by the service provider upon request by the subscriber or for serviceprovider reasons.3.2 Normal procedures3.2.1 Activation/deactivation/registrationNot applicable.3.2.2 ErasureNot applicable.3.2.3 Invocation and operation3.2.3.1 Beginning the Three-Party ServiceThe se
14、rved user, user A, who is involved in at least two calls (an active call with one party and at least one callon hold with another party) can request that the service provider joins the active call and one specified call on holdtogether into a three-way conversation. Both calls shall be answered prio
15、r to the invocation of the Three-Partysupplementary service.Note It shall be the responsibility of the served user to ensure that the two calls are compatible.3.2.3.2 Managing the three-way conversationServed user: During an active three-way conversation the served user shall be able to:i) disconnec
16、t one of the parties. This shall result in a single active call between the served user and the otherparty. The Three-Party supplementary service shall automatically be terminated;ii) disconnect the entire three-way conversation. Both calls shall be cleared;iii) Explicitly choose one party to have a
17、 private communication with that party. This shall result in thetermination of the Three-Party supplementary service (i.e. the release of the resources allocated for thethree-way conversation). The served user shall be able to explicitly indicate the party which shall remainactive afterwards. The ca
18、ll with the other party shall be placed on hold.Note If the served user again wants to join the two calls together into a three-way conversation, he has torequest the Three-Party supplementary service again.Other parties (B and C): Either of the remote parties (users B or C) shall be able to disconn
19、ect from thethree-way conversation which shall result in the Three-Party supplementary service being terminated. There shall remaina single active call between the served user and the other party.All participants of a three-way conversation shall receive a notification at the invocation and cancella
20、tion ofthis supplementary service.Note During an interim period of time some networks may not support the sending of notifications to theremote users.3.2.4 InterrogationNot applicable.Recommendation I.254.2 (08/92) 33.3 Exceptional procedures3.3.1 Activation/deactivation/registrationNot applicable.3
21、.3.2 ErasureNot applicable.3.3.3 Invocation and operationIf the served user attempts to invoke the Three-Party supplementary service and the service provider cannotaccept that request, the service provider shall reject the request with an appropriate cause.Possible reasons for rejection are: service
22、 is not subscribed to; resources cannot be allocated; subscriber restrictions are not met (e.g. Closed User Group); calls are not in an appropriate state (e.g. both calls are on hold).If the request is rejected, the calls shall remain in the same state as they were in before the attempt to invokethe
23、 Three-Party supplementary service.3.3.4 InterrogationNot applicable.4 Network capabilities for chargingThis Recommendation does not cover charging principles. Future Recommendations in the D-Series areexpected to contain that information.It shall be possible to charge the subscriber accurately for
24、the service.5 Intercommunication considerations5.1 Interworking with non-ISDN networksThe served user shall be an ISDN subscriber. The other parties may belong to any non-ISDN.In the case of interworking, users B and C may not be notified of changes occurring.5.2 Interworking with private ISDNsA pri
25、vate ISDN may transfer a users request for the Three-Party supplementary service to a public ISDN. Theresulting three-way conversation, as seen by the public ISDN, will be treated as the normal Three-Party supplementaryservice.The users B and C may belong to any private ISDN.Appropriate notification
26、s will be accepted from a private ISDN and transferred through the public ISDN, if theservice provider resides in a private ISDN.4 Recommendation I.254.2 (08/92)6 Interaction with other supplementary services6.1 Call WaitingNo impact, i.e. neither supplementary service affects the operation of the o
27、ther supplementary service.6.2 Call TransferThe served user who has invoked the Three-Party supplementary service shall not be able to invoke explicitCall Transfer in order to transfer either of the calls involved. The served user shall cancel the Three-Party supplementaryservice in order to be able
28、 to transfer either of the calls involved in the three-way conversation.6.3 Connected Line Identification PresentationNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.6.4 Connected Line Identification RestrictionNo impact, i.e. neither supplement
29、ary service affects the operation of the other supplementary service.6.5 Calling Line Identification PresentationNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.6.6 Calling Line Identification RestrictionNo impact, i.e. neither supplementary ser
30、vice affects the operation of the other supplementary service.6.7 Closed User GroupFor the successful invocation of the Three-Party supplementary service any CUG restrictions applied to onecall shall match with any Closed User Group (CUG) restrictions applied to the other call.6.8 Conference Calling
31、It shall be possible for each party of a three-way conversation to be involved alternatively in the three-wayconversation and an add-on conference.Served user: In order to convert a three-way conversation into an add-on conference the served user shallcancel the Three-Party supplementary service fir
32、st and then shall invoke the add-on conference from the active call asdescribed in Recommendation I.254.1. Subsequently, the held call can be added to the conference.Add-on conference controlled by another party: The network shall not be required to prevent that a leg to oneof the remote parties can
33、 be part of an add-on conference controlled by that party.6.9 Direct-Dialling-InNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.Recommendation I.254.2 (08/92) 56.10 Call diversion services6.10.1 Call Forwarding BusyNo impact, i.e. neither supple
34、mentary service affects the operation of the other supplementary service.6.10.2 Call Forwarding No ReplyNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.6.10.3 Call Forwarding UnconditionalNo impact, i.e. neither supplementary service affects the
35、 operation of the other supplementary service.6.10.4 Call DeflectionNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.6.11 Line HuntingNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.6.12 Thre
36、e-Party ServiceIt shall be possible for each party of a three-way conversation to be involved alternatively in another three-wayconversation.Served user: It shall not be possible to invoke the Three-Party supplementary service, if one or both callsinvolved are part of one or two other three-way conv
37、ersations.Three-way conversation controlled by one of the remote parties: The network shall not be required to preventthat a leg to one of the other parties can be part of another three-way conversation controlled by that party.6.13 User-to-User Signalling (UUS)6.13.1 UUS, Service 1No impact, i.e. n
38、either supplementary service affects the operation of the other supplementary service.6.13.2 UUS, Service 2UUS, Service 2 does not apply to calls that have been answered.6.13.3 UUS, Service 3Served user: No impact, i.e. neither supplementary service affects the operation of the other supplementaryse
39、rvice.Other parties: User-to-user information (UUI) can be sent to and received from the served user. UUI shall notbe transferred between users B and C.6.14 Multiple Subscriber NumberNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.6 Recommendati
40、on I.254.2 (08/92)6.15 Call HoldAny party involved in a three-way conversation can place the connection to the three-way conversation onhold and later retrieve it.While the connection of one party to the three-way conversation is held, the other parties can continue tocommunicate.6.16 Advice of Char
41、ge (AOC)6.16.1 AOC, Charging information at call set-up timeThe served user shall be informed about the charging rate for those calls which that user has established.Charges for the use of the Three-Party supplementary service: As a network option, the charging informationcan be sent to the served u
42、ser.Note However, in some networks no charging information can be given in this case, e.g. due to off-lineprocessing of the charges.6.16.2 AOC, Charging information during the callCharges for the different connections within the Three-Party supplementary service: charging informationshall be given f
43、or each call for which the AOC-D supplementary service has been activated.Charges for the use of the Three-Party supplementary service: As a network option, the charging informationcan be sent to the served user.Note However, in some networks no charging information can be given in this case, e.g. d
44、ue to off-lineprocessing of the charges.6.16.3 AOC, Charging information at the end of a callCharges for the different connections within the Three-Party supplementary service: At the end of each call forwhich the AOC-E supplementary service was activated, the served user shall be informed about the
45、 charges incurred.Charges for the use of the Three-Party supplementary service: As a network option, the charging informationcan be sent to the served user.Note However, in some networks no charging information can be given in this case, e.g. due to off-lineprocessing of the charges.6.17 Multi-level
46、 Precedence and PreemptionThe precedence levels of the calls are not changed by the use of the Three-Party supplementary service. In thethree-way conversation, when one of two original calls is preempted, the remaining parties of the three-wayconversation should be notified of the preemption. When t
47、he served user is preempted, all users are notified and theprocedure is followed as though the served user requested that the entire three-way conversation be disconnected.Note Calls that are originated by, or made to, non Multi-Level Precedence and Preemption (MLPP) userswill not be preempted.6.18
48、PriorityNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.Recommendation I.254.2 (08/92) 76.19 Malicious Call IdentificationNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.6.20 Outgoing Call B
49、arringNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.6.21 Reverse ChargingNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.Reverse Charging (REV) applies independently to each call.Note Charges for the use of the Three-Party supplementary service will not be subjected to reverse charging.6.22 Sub-addressingNo impact, i.e. neither supplementary service affects the operation of the other supplementary service.7 Dynamic description
