1、CCITT 1.253. I TH E INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COM M IlTEE INTEGRATED SERVICES DIGITAL NETWORK (ISDN) GENERAL STRUCTURE AND SERVICE CAPABILITIES CALL WAITING (CW) SUPPLEMENTARY SERVICE Recommendation 1.253.1 CCITT REMCN*I-253. 1 90 W 4862591 0561344 4 W INTERNATIONAL TELECOM
2、M U N CCITT CATION UNION 1.253.1 THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONS U LTATIVE COM M IlTE E INTEGRATED SERVICES DIGITAL NETWORK (ISDN) GENERAL STRUCTURE AND SERVICE CAPABILITIES CALL WAITING (CW) SUPPLEMENTARY SERVICE Recommendation 1.253.1 Geneva I990 CCITT REMCN*I.253. I 90 m 4862593 05
3、bLL45 b m FOREWORD The CCIIT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommunication Union (ITU). CCIIT is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to stan
4、dardizing telecommunications on a worldwide basis. The Plenary Assembly of CCIIT 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 CCIT between Plenary Assemblies is covered by t
5、he procedure laid down in CCIIT Resolution No. 2 (Melbourne, 1988). Recommendation 1.253.1 was prepared by Study Group I and was approved under the Resolution No. 2 procedure on the 2 July 1990. In this Recommendation, the expression “Administration“ is used for shortness to indicate both a telecomm
6、unication Administration and a recognized private operating agency. O ITU 1990 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 microfilm, without permission in writing from the ITU. CCITT
7、 REMCN*I.253. L 90 W 4Bb259L - 056LL4b - B W Recommendation 1.253.1 CALL WAITING (cw) SUPPLEMENTARY SERVICE) 1 Definition The Call Waiting service is a supplementary service which permits a subscriber to be notified of an incoming call (as per basic call procedures) with an indication that no interf
8、ace information channel is available. The user then has the choice of accepting, rejecting or ignoring the waiting call (as per basic call procedures). 2 Description 2.1 General description The ISDN Call Waiting service allows an out-of-band notification to subscriber B of the incoming call; this is
9、 the assumed case for this definition (for optional in-band indications, see Annex A). The maximum number of calls that can be handled (e.g. active, held, alerting, waiting) for each ISDN number on a given interface is specified at subscription time. Note - The situation where at least one B-channel
10、 is available may be, for a given terminal, a situation similar to the one where all B-channels are busy. A terminal receiving a call request and already having an active call, may process the new incoming call in the same way as it would have processed a call if no B-channel were available, i.e. re
11、act positively to the incoming cali request. Moreover, when at least one B-channel is free, any compatible busy terminal of subscriber B can react positively to an incoming call. 2.2 Specific terminology Throughout this Recommendation the following terminology will be used: Subscriber B: the subscri
12、ber who is provided by the network with the Call Waiting service on a particular User B: the user who reacts to the cali waiting at B. User C: the user who has originated a call to B which causes the Call Waiting service to be invoked. User A represents a user who is engaged in a call with user B (t
13、his call can be in any state). User Response timer T1: this timer specifies the period the network will wait for a positive response, from a No Answer timer T2 this optional timer specifies the period the network will wait for a response (answer), interface. terminal at B, to the offered call. It is
14、 part of the basic cal and has a value of a few seconds. from user B, to the offered call from user C. The value of this timer is between 0.5 and 2 minutes. i) This Recommendation replaces the text of Recommendation 1.253,s 1 of the CCI Blue Book. Recommendation 1.253.1 1 CCITT REMCN*I*253. 1 90 486
15、2591 0561147 T W 2.3 Qualcations on the applicability to telecommunication services This supplementary service is considered meaningful when applied to the Telephony teleservice and the speech and 3.1 kHz audio bearer services. Furthermore, it may also be meaningful when applied to other services. 3
16、 Procedures 3.1 Provisionlwithdrawal Call Waiting (CW) can be provided on a subscription basis or, as a network provider option, be generally available to all users without subscription. Call Waiting can be withdrawn for administrative reasons. As part of each applicable bearer service or teleservic
17、e, there is an option specifying the maximum number of information channels which can be used (occupied) on the interface for each ISDN number, ail ISDN numbers or subsets of ISDN numbers. Call Waiting for bearer services or teleservices occurs when an attempt is made to exceed these limits. As a ne
18、twork provider option, Call Waiting can be offered with several subscription options. The options apply separately to each ISDN number and service combination. For each subscription, only one value can be selected, Subscription options are summarized below: I Subscription options I Value I I Calls t
19、hat can wait - Others are for further study I Calling user receives notification call is - No waiting - Yes In addition, the following subscription options can be specified for each ISDN number, all ISDN numbers, or subsets of ISDN numbers on each interface: Subscription options Value I Maximum numb
20、er of caiis which can be waiting - 1,whereSlSn- m - One Note - The parameters m (maximum number of *ormation channel) and n (maximum number of total calls present) are defined in the relevant basic service description (refer to Recommendation 1.231 and 1.241. The use of T2 is a service provider opti
21、on. When used, the value of T2 shall be set by the service provider as a default value subject to change only by the service provider. 3.2 3.2. 2 Normal procedures Activationldeactivation The CW supplementary service is activated by the service provider at provision. The CW supplementary service is
22、deactivated by the service provider at withdrawal. Registration does not apply Recommendation 1.253.1 CCITT REflCN*I.253- 3 70 m 4862573 0563348 3 m Note - The introduction, as a network option, of the possibility for a user to activate and deactivate the CW supplementary service in the network may
23、be a long-term enhancement. 3.2.2 Invocation 3.2.2.1 When an incoming call from user C arrives at the access of subscriber B and encounters the channels busy condition, and a network determined user busy (NDUB) condition does not result, then the Call Waiting service will be invoked and the call sha
24、il be offered to subscriber B with an indication that the channels busy condition exists. 3.2.3 Operation 3.2.3.1 If a response is received from a terminal at the B access, within the normal basic call period, that the user) is (are) being informed about the incoming call, then user C will be given
25、an indication that the called user is (are) being informed of the incoming call. In some networks this indication may also indicate that call waiting is in operation. 3.2.3.2 If either user A or user B requests that the active call is terminated, then this call shall be terminated as for a basic cal
26、l. User B shall then be able to accept the waiting call from user C using normal information channel selection procedures before the expiry of T2. 3.2.3.3 User B can also free resources by using the Call Hold supplementary service. User B shall then be able to accept the waiting call from user C usi
27、ng normal information channel selection procedures before the expiry of T2. 3.2.4 Subscriber resources in use When an incoming call from user C arrives at the access of subscriber B and there is a B-channel available, the call shall be indicated to subscriber B. If a terminal at the access of subscr
28、iber B is busy because of another call but is able to accept the incoming call from user Cy it may indicate to the network that the called user is being informed about the incoming call. 3.3 Exceptional procedures 3.3.1 Activatonldeactvationlregistration Non identified. 3.3.2 Invocation Non identifi
29、ed. 3.3.3 Operation 3.3.3.1 Incoming callfrom user C ignored by subscriber B If the optional No Answer timer T2 exphes without any acceptance from subscriber B of the incoming call, then the network shall inform subscriber B that the call is no longer waiting and also inform user C that his call can
30、not be connected. Normal release applies to the call attempt from user C (the call is cleared indicating no response) with an appropriate indication given to user C. 3.3.3.2 Incorning call from user C rejected by user B A rejection of the waiting call by one of the terminals on the interface of subs
31、criber B will not stop the optional No Answer timer T2 as another terminal may subsequently accept the waiting call within the remainder of the specified period. Such a rejection may, however, cancel any indication provided to that terminal. Where rejections of a waiting call have been received from
32、 all those terminals that responded with an alerting indication before the expiry of the optional No Answer timer.T2, then the network shall inform user C that his call cannot be connected. Normal release applies to the cail attempt from user C with the call being cleared indicating user rejection.
33、Subscriber B is notified that the call is no longer waiting. 3.3.3.3 Release by user C within the specjed period If calling user C informs the network, before the.expiry of the optional No Answer timer T2, that he wishes to release his call attempt to subscriber By then the network shall inform subs
34、criber B of this situation and initiate release of the call attempt from user C. Recommendation 1.253.1 3 CCITT REMCN*I.253* I 90 4B6259L 05bL149 3 3.3.3.4 No positive response terminals at subscriber Bs interface If no positive response that user(s) are being informed of the waiting call is receive
35、d from a terminal at subscriber Bs interface during the normal call period (User Response timer Tl), then the call attempt from user C shall be released by the network with user C being given the reason for the release. 3.3.3.5 No reasons available If user B accepts a call and network resources do n
36、ot exist to complete the call (i.e. no information channels are available), the network will indicate an error to user B with cause “no B-channels available”. The network will not clear the call but will wait for another user B indication for acceptance, until user C clears the call or the optional
37、No Answer timer T2 expires. 3.3.3.6 Maximum number of waiting calls reached Subscriber B shall be considered as busy when the limit on the maximum number of calls which can be waiting has been reached. Any incoming call during this period shall be handled accordingly. 3.4 Alternative procedures 3.4.
38、1 Activationlakactivationlregistration None identified. 3.4.2 Invocation and operation None identified. 4 Network capabilities for charging expected to contain that information. This Recommendation does not cover charging principles. Future Recommendations in the D-Series are It shall be possible to
39、 charge the subscriber accurately for the service. 5 Interworking requirements impact on subscriber Bs service (see Annex A). normal alerting indication. Calls originating from outside the ISDN can undergo call waiting at the access of subscriber B with no As a service provider option, a special in-
40、band indication may be provided to the calling user instead of the 5.1 Interworking with private ISDNs When user C is on a different network from subscriber B (e.g. one user on a private ISDN and the other user on a public ISDN), then indications to user C, if applicable, shall be sent to the networ
41、k to which user C is attached for forwarding to user C. 6 Interaction with other supplementary services 6.1 Call Waiting Not relevan t. 6.2 Call Transfer from user C until he first establishes a connection to user C. User B, who has subscribed to both Call Waiting and Call Transfer services, cannot
42、transfer a waiting call 4 Recommendation 1.253.1 Assume that user B is on an active call with user A and has received an indication of a waiting call from user C. Users A and B have Call Waiting subscribed for their accesses and user B has subscribed to the Call Transfer service. User B intends to t
43、ransfer user A to user D. - User B may receive an indication of a waiting call from user C either before or during the transfer of user A to another party. The call waiting indication may be presented regardless of the type of transfer invoked by user B (Le. for Normal, Single Step, or Explicit tran
44、sfers). When user A has been transferred, a B-channel would normally become idle, enabling the waiting call to be answered by user B. - if user A has a call waiting indication before or during the transfer process, then upon successful completion of the mansfer of user A to user D, user A shall reta
45、in the waiting cail indication. User A could use normal call waiting procedures (if desired) to accept the waiting call. - If user D receives a call waiting indication during the transfer process, e.g. while being in a call with user B, then upon successful completion of the transfer of user A to us
46、er D, user D shall retain the waiting call indication. User D could use normal call waiting procedures (if desired) to accept the waiting call. In general, a call waiting indication may be delivered to users A or B (and to user D during the transfer process) when the called user has subscribed to th
47、e Call Waiting service. 6.3 Connected Line Identification Presentation (COLP) No impact, i.e. neither supplementary service affects the operation of the other supplementary service. When user B uses one of the call waiting procedures to accept a waiting call (within any time limits established by th
48、e service provider), user C will be informed of the connection. The confirmation that a connection has been established may provide the connected user Bs number. 6.4 Connected Line Identification Restriction (COLR) No impact, Le. neither supplementary service affects the operation of the other suppl
49、ementary service. 6.5 Calling Line Identification Presentation (CLIP) NO impact, i.e. neither supplementary service affects the operation of the other Supplementary service. If the user(s) at B is(are) given a call waiting indication, and has (have) subscribed to the CLIP service, then the calling user number shall be presented to the users at B at the time the call waiting indication is given. 6.6 Calling Line IdentBcation Restricion (CLIR) No impact, i.e. neither supplementary service affects the operation of the other supplement
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