1、CCITT RECMN*I-253. 2 92 m 4862593 0573920 593 m INTERNATIONAL TELECOMMUNICATION UNION CCITT THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE INTEGRATED SERVICES DIGITAL NETWORK (ISDN) GENERAL STRUCTURE AND SERVICE CAPABILITIES 1.253.2 (08/92) CALL HOLD Recommendation 1.253.2 - - - I
2、CCITT RECMN*Im253. 2 92 m 4862591 0573921 42T m FOREWORD The CCIn (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the Intemational Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariff questions and issuing Recomme
3、ndations on them with a view to standardizing telecommunications on a worldwide basis. The Plenary Assembly of CCIT which meets every four years, establishes the topics for study and approves Recommendations prepared by its Study Groups. The approval of Recommendations by the members of CCI” between
4、 Plenary Assemblies is covered by the procedure laid down in CCITI Resolution No. 2 (Melbourne, 1988). Recommendation 1.253.2 was revised by Study Group I and was approved under the Resolution No. 2 procedure on the 4th of August 1992. CCITT NOTE In this Recommendation, the expression “Administratio
5、n” is used for conciseness to indicate both a telecommunication Administration and a recognized private operating agency. O ITU 1992 All 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 microf
6、ilm, without permission in writing from the ITU. CCITT RECflN*I.253. 2 92 E V862591 0573922 366 Recommendation 1.253.2 CALL HOLD (revised 1992) 1 Definition The CaU Hold service allows a user to interrupt communications on an existing call and then subsequently, if desired, re-establish communicatio
7、ns. A B-channel (see Note) may or may not be reserved after the communication is interrupted to allow the origination or possible termination of other calls. Reservation must be provided by the service provider as a user option. The Call Hold service includes the retrieve operation which re-establis
8、hes communication on a B-channel between the served user and the held party. Note - Use of the Call Hold supplementary service to hold calls by a particular terminal simultaneously ushg more than one B-channel is outside the scope of this Recommendation. 2 Description 2.1 General description When th
9、e Call Hold (HOLD) service is invoked, communication on a B-channel is interrupted and the B-channel is released from use by the existing call. If reservation is subscribed to, a B-channel is reserved for use by the given terminal used to invoke the Call Hold supplementary service. When a user (as i
10、dentified by a terminal) places a call on hold and reservation applies, a B-channel should always be available on that users interface so that the user may retrieve that call from hold, or set up, retrieve or connect to another call. One B-channel should be kept available for the user as long as the
11、 user: i) has one or more calis on hold with reservation; and ii) is not currently connected to any other call. Hence, the network should not reserve more than one B-channel for the terminal used to invoke the Call Hold supplementary service. When the served user wishes to re-establish communication
12、s, the retrieve operation is requested. The success of the retrieve operation depends on whether a B-channel was reserved and whether a B-channel is currently available to the served user. 2.2 Specc terminology None identified. 2.3 Qaalcations on the applicability to telecommunication services The C
13、all Hold supplementary service is applicable to all circuit mode basic telecommunication services. Although it may not be meaningful for some services, the network will not otherwise restrict its applicability. 3 Procedures 3.1 Provsiodwthdrawal The Call Hold service is provided after prior arrangem
14、ent with the service provider or may be generally available. As the Call Hold service can often be used together with other supplementary services (e.g. the Call Waiting Recommendation 1.253.2 (08/92) 1 CCITT RECMN*I.253. 2 92 m 4862593 0573923 2T2 m and Three-Party Supplementary services) a service
15、 provider may choose to make the subscription to the Call Hold service implied by the subscription of these supplementary services. Withdrawal shall be at the request of the customer or for administrative reasons. 3.2 Normal procedures 3.2.1 Activaton/deactivationregistraton None identified. 3.2.2 I
16、nvocation and operation 3.2.2.1 Hold request The served user indicates to the service provider that the communication on the interface is to be interrupted. on the calling users interface, by the calling user at any time after the call has been answered but before the call is terminated or additiona
17、lly as a service provider option: after alerting has commenced, or after the calling user has provided all of the information necessary for processing the call; on the called users interface, by the called user at any time after the call has been answered and before call clearing has begun. The comm
18、unication on the interface is then interrupted. The service provider acknowledges this action, and the associated channel is made available for other uses, depending on the reservation option. As an option, the network may send a notification to the held party indicating that the call has been place
19、d on hold. When the call is held before the call has been answered, then as a service provider option: A call may be placed on hold: - - 1) the user shall be notified when the call is answered; or 2) the users that have responded shall be notified at any time. If at any time a cali is in the held st
20、ate, either party may clear the call. 3.2.2.2 Retrieve request When the user who invoked the Call Hold service indicates that the call is to be retrieved, the service provider will re-establish communications, provided that a B-channel is available, and acknowledge to the served user and optionally
21、to the held party that the call is now active. When the call is retrieved before the call has been answered, then as a service provider option: if the user was not notified that the call was held, the retrieval shall cancel any hold notification pending answer and the user shall not be notified; or
22、the users that have responded shall be notified at that time. - - The user may optionally indicate a B-channel selection parameter in the retrieve request. The parameter may i) any channel acceptable; 2) 3) If the service provider can satisfy the request, the call will be returned to the active phas
23、e; if it cannot, the indicate: specified channel is preferred; or specified channel is required exclusively. request will be rejected with the appropriate cause returned to the user. 3.2.2.3 Reservation processing The following conditions concerning reservations against a channel apply: 1) when the
24、call is retrieved, any reservation against a channel associated with that call should be cleared, regardless of which channel is used to retrieve the call; 2 Recommendation 1.253.2 (08192) CCITT RECMN*I*253- 2 92 4862591 0573924 139 2) when a call is cleared, any reservation against a channel associ
25、ated with this call should be cleared and the service provider should continue to reserve a B-channel for the terminal until there are no more held calls associated with the terminal; when all reservations are cleared normal channel allocaion procedures will apply; when any reservation is outstandin
26、g for a given user (as identified by a terminal) and that user is not using a channel for an active call, then the network must consider a channel as “not free” for that user for subsequent incoming calls. 3) 4) 3.3 Exceptional procedures 3.3.1 Activatioddeactivatiodregistration None identified. 3.3
27、.2 Invocution and operation 3.3.2.1 Hold request if the user tries to hold a call while not subscribed to the service or if, for some other reason, the service provider cannot hold the call, an indication will be provided to the user for the reason of failure. 3.3.2.2 Retrieve request If the service
28、 provider cannot retrieve a previously held call, the user will be informed of the reason for failure. (For example, there may not be any channel available, or the call may be in the process of being cleared.) 3.4 Alternative procediires None identified. 4 Network capabilities for charging This Reco
29、mmendation does not cover charging principles. Future Recommendations in the D-Series are expected to contain that information. It shall be possible to charge the subscriber accurately for the service. 5 interworking requirements 5.1 Interworking with non-ISDNs The operation of this feature is not a
30、ffected by the nature &e. integrated services digital network (ISDN) or non-ISDN) of the far end of the connection. If the distant user is a non-ISDN user, the notifications about the held and retrieved state of the call to that user may not be supported. In this interworking case it may also occur
31、that a call is held before alerting has commenced. 5.2 Intenvorking with private ISDN When a remote user is on a network different from that of the served user (e.g. one user on a private ISDN (and the other user on a public ISDN), indications to the remote user shall be sent to the remote users net
32、work for forwarding to the remote user. Recommendation 1.253.2 (08/92) 3 - - _._ _ - CCITT RECMN*I.253. 2 92 m 4862593 0573925 075 6 interactions with other supplementary services 6.1 Call Waiting No impact, i.e. neither supplementary service affects the operation of the other supplementary service.
33、 Note - If all channels are “not free” (busy or reserved) and a user has also subscribed to the Call Waiting service the network would be able to offer an incoming call with an indication that “no interface information channels are available”. The served user may accept that incoming call using a re
34、served channel. A user may use the hold feature to hold an active call and answer an incoming call that is being given call waiting treatment. 6.2 Call Transfer The invocation of the Call Transfer supplementary service should have no impact on any held calls not involved in the transfer. If either o
35、f the transferred users have put their call on hold prior to the transfer, the resulting transferred call should remain on hold by that user. The transferring user should be replaced as the held user in the resulting call by the other user. Note - The hold process is symmetric, i.e. both parties may
36、 place each other on hold. It is possible, therefore, for two parties that have subscribed to the Call Hold and Call Transfer services, to each place their active call on hold and to simultaneously transfer the other party. That is, if parties A and B have an active connection, party A may place the
37、 call on hold and transfer party B to another party C while at the same time party B puts his call to party A on hold and transfers party A to another party D. 6.3 6.4 6.5 6.6 6.7 6.8 Connected Line Identjcation Presentation No impact, i.e. neither supplementary service affects the operation of the
38、other supplementary service. Connected Line Identilfication Restriction No impact, i.e. neither supplementary service affects the operation of the other supplementary service. Calling Line Identjcation Presentation No impact, Le. neither supplementary service affects the operation of the other suppl
39、ementary service. Calling Line Identification Restriction No impact, i.e. neither supplementary service affects the operation of the other supplementary service. Closed User Group No impact, i.e. neither supplementary service affects the operation of the other supplementary service. Conference Calli
40、ng Any party involved in an active conference (Le. the conference controller or a conferee) may place the conference call on hold and later retrieve the connection to the conference. Any party placing the conference on hold may retrieve any other party it had previously placed on hold. See also the
41、Conference Calling service description Recommendation 1.254,s 1.6.15. 4 Recommendation 1.253.2 (08/92) CCITJ RECMN*I.253. 2 92 m 48b259L 057392b TO1 m 6.9 Direct-Dialling-In No impact, i.e. neither supplementary service affects the operation of the other supplementary service. 6.10 Cali diversion se
42、rvices 6.10.1 Call Fonvarding Busy No impact, i.e. neither supplementary service affects the operation of the other supplementary service. 6.10.2 Call Forwarding No Reply No impact, Le. neither supplementary service affects the operation of the other supplementary service. 6.10.3 Call Fonvarding Unc
43、onditional No impact, Le. neither supplementary service affects the operation of the other supplementary service. 6.10.4 Deflection No impact, i.e. neither supplementary service affects the operation of the other supplementary service. 6.11 Line Hunting No impact, i.e. neither supplementary service
44、affects the operation of the other supplementary service. 6.12 Three-Party service Any party involved in a three-way conversation can place the connection to the three-way conversation on hold and later rerieve it. While the connection of one party to the three-way conversation is held, the other pa
45、rties can continue to communicate. 6.13 User-to-User Signalling No impact, Le. neither supplementary service affects the operation of the other supplementary service. 6.14 Multiple Subscriber Number No impact, Le. neither supplementary service affects the operation of the other supplementafy service
46、. 6.15 Call Hold If the Call Hold supplementary service is provided to both users involved in one call, each of these users can hold and retrieve the call independently from these operations having been carried out by the other user. 6.16 Advice of Charge No impact, i.e. neither Supplementary servic
47、e affects the operation of the other supplementary service. Recommendation 1.253.2 (008192) 5 - - _ . CCITT RECMN*P.253. 2 92 = 4862593 0573927 948 6.17 Multi-level Precedence and Preemption A held call may be preempted due to lack of network resources or channels at the held partys interface. The c
48、all is cleared and the served user, who invoked the call hold service, will be notified of the preemption. For the case of multiple terminals on an interface, an idle channel that is reserved for a call held by another terminal may be seized in order to complete a higher precedence call. In addition
49、, an active channel that is reserved for a held call may be preempted and seized in order to complete a higher precedence call. In both cases, the held call is not preempted and may be retrieved when a channel becomes available. 6.18 6.19 6.20 6.21 6.22 7 6 Priority Sewice No impact, Le. neither supplementary service affects the operation of the other supplementary service. Malicious Call IdentGcation No impact, Le. neither supplementary service affects the operation of the other supplementary service. Outgoing Call Barring No impact, Le. neithe
