1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU 1.253.3 (07/96) SERIES I: INTEGRATED SERVICES DIGITAL NETWORK Service capabilities - Supplementary services in ISDN Call completion supplementary services: Completion of calls to busy subscribers ITU-T Recomm
2、endation 1.253.3 (Previously CCITT Recommendations) STD-ITU-T RECMN I-253-3-ENGL 177b 9 48b2571 Ob21352 1AL ITU-T - I SERIES RECOMMENDATIONS INTEGRATED SERVICES DIGITAL NETWORK ;ENERAL STRUCTURE Terminology Description of ISDNs General modelling methods Telecommunication network and service attribut
3、es General description of asynchronous transfer mode Scope General aspects of services in ISDN Common aspects of services in the ISDN Bearer services supported by an ISDN Teleservices supported by an ISDN SERVICE CAPABILITIES Supplementary services in ISDN OVERALL NETWORK ASPECTS AND FUNCTIONS Netwo
4、rk functional principles Reference models Numbering, addressing and routing Connection types Performance objectives Protocol layer requirements General network requirements and functions Application of I-series Recommendations to ISDN ucer-network interfaces Layer 1 Recommendations Layer 2 Recommend
5、ations Layer 3 Recommendations Multiplexing, rate adaption and support of existing interfaces Aspects of ISDN affecting terminal requirements ISDN USER-NETWORK INTERFACES INTERNETWORK INTERFACES MAINTENANCE PRINCIPLES B-ISDN EQUIPMENT ASPECTS ATM equipment Management of ATM equipment I. 1 00-1.1 99
6、1.1 10-1.1 19 I. 1 20-1.1 29 1.1 30-1.139 1.1 40-1.1 49 I. 1 50-1.1 99 1.200-1.299 1.200-1.209 1.210-1.219 I .220-1.229 I .230-1.239 1.240-1.249 1.25 I .300-1.399 1.31 0-1.31 9 I .32 - no B-channels available at user A; - CCBS recall pending on user A. 2.2.11 retention timer: This timer specifies th
7、e amount of time that the network retains all of the information supplied by the calling user when the call encounters busy. This timer is part of the basic call procedures. Although this timer is optional for the basic call procedures, it is needed for the operation of the CCBS supplementary servic
8、e. The minimum value of the timer shall be 15 seconds. 2.2.12 CCBS service duration timer: This timer specifies the maximum time the CCBS supplementary service will remain activated for user A within the network. The value of this timer is a network option, typically 15-45 minutes. 2.2.13 CCBS recal
9、l timer: This timer specifies the maximum time the network will wait for a response from user A to a CCBS recall. The value of this timer is between 1 O and 20 seconds. 2.2.14 destination B idle guard timer: This timer specifies the amount of time the network will wait after destination B has become
10、 free before informing user A. The value of this timer is between O and 15 seconds. 2.2.15 compatible terminal: A terminal which can support the bearer service or teleservice requested for the original call to destination B and which can accept calls to the ISDN number and sub-address identiQing the
11、 called user in the original call to destination B. 2.3 The CCBS supplementary service shall be applicable to all circuit mode bearer services defined in Recommendation 1.230, and all teleservices defined in Recommendation 1.240 with the following exceptions: a) b) Qualifications on the applicabilit
12、y to telecommunication services call 2 of the videotelephony service (see Recommendation F.721); all other circuit-switched telecommunications services requiring the use of more than one B- channel. 3 Procedures 3.1 Provision/withdrawal The CCBS supplementary service may be provided to user A after
13、prior arrangement with the service provider or may be generally available. The CCBS supplementary service shall be withdrawn by the service provider upon request of the subscriber or for service provider reasons. As a service provider option, the CCBS supplementary service can be offered with a subs
14、cription option which shall apply to the whole access of user A. The subscription option is detailed in Table 1. 2 Recommendation 1.253.3 (07/96) - TABLE 1fl.253.3 Subscription option Recall mode Values - CCBS recall offered to all terminals on the access - CCBS recall offered to the terminal that a
15、ctivated the CCBS supplementary service 3.2 Normal procedures 3.2.1 Activatioddeactivatiodregistration 3.2.1.1 Activation When user A encounters a busy destination B, the network shall retain the call information for the period defined by the retention timer, during which user A can activate the CCB
16、S supplementary service. An attempt to activate the CCBS supplementary service shall be accepted by the network only if a compatible terminal is present on the destination B access. The network assumes that all terminals can indicate their compatibility. NOTE 1 - Some service providers may not provi
17、de the compatibility check. If the network accepts the activation of the CCBS supplementary service, the network shall store the identification of the destination contained in the original call request, and user A shall be informed that the activation was successful. Multiple requests against destin
18、ation B shall be queued. When the activation of the CCBS supplementary service is accepted, the CCBS service duration timer is started. The network shall monitor for destination B becoming free. NOTE 2 - Some networks may not support the monitoring of destination B becoming free in the case where us
19、er A requests the CCBS supplementary service against a destination B, which is user determined user busy. In this case the CCBS request should be rejected with the reason “short-term denial“. User A can have a limited number of CCBS requests outstanding. This limit is a service provider option with
20、a maximum value of five. The requests can be to different destinations, or can be to the same destination B with different service requirements (e.g. bearer service and teleservice requirements), or as a service provider option, the same service requirements. Destination B can have a limited number
21、of incoming CCBS requests queued. This limit is a service provider option with a maximum value of five. Having activated the CCBS supplementary service, user A can originate calls and receive calls as normal. 3.2.1.2 Deactivation The following deactivation requests shall be made available to user A:
22、 1) 2) deactivate a specific CCBS request. This request shall contain enough information to correlate with the initial activation; or deactivate all outstanding CCBS requests. Recommendation 1.253.3 (07/96) 3 STD*ITU-T RECMN 1.253-3-ENGL Ob213bO 258 Upon successful deactivation the corresponding CCB
23、S request shall be discarded. User A shall be informed that the deactivation has been successful. If a specific CCBS request is deactivated, the network shall indicate which specific CCBS request has been deactivated. If the recall mode is “CCBS recall offered to all terminals“, then user A can deac
24、tivate any outstanding CCBS requests stored for that user from any of user As terminals. If the recall mode is “CCBS recall offered to the terminal which has activated the CCBS supplementary service“, then user A can deactivate only those outstanding CCBS requests made from that specific terminal. 3
25、.2.1.3 Registration Not applicable. 3.2.2 Erasure Not applicable. 3.2.3 Invocation and operation When destination B becomes free, or when destination B is free and either of the following occurs: - - then the destination B CCBS queue shall be processed, provided that an entry in the destination B CC
26、BS queue is not currently being processed. Entries shall not be processed in parallel. The first request which is not suspended shall be selected and the network shall reserve on destination Bs interface the resources (e.g. a B-channel) which are necessary to complete the CCBS call. Destination B ca
27、n use the reserved access resources or other free resources, in order to originate a call. An incoming call shall not use these reserved resources. A check for the existence of a compatible terminal which is free at destination B shall be performed. a CCBS request is received; or a CCBS request beco
28、mes not suspended, NOTE - Some service providers may not provide the compatibility check. If the compatibility check is performed and is unsuccessful, further requests which are not suspended shall be examined. Otherwise, the network shall start the destination B idle guard timer. When the destinati
29、on B idle guard timer expires, then, provided that interface resources are still available at destination B, and, provided that if a compatibility check has been done, a compatible terminal at destination B is still free, user A shall be informed. If user A is neither busy nor CCBS busy, user A shal
30、l be recalled with an indication that it is a CCBS recall, and with an indication to which CCBS request it applies. Then the CCBS recall timer shall be started. If user A accepts the recall before the CCBS recall timer expires, then user As network shall initiate the CCBS call to destination B. When
31、 the network receives an indication that the destination B is being informed of the CCBS call, the corresponding CCBS request shall be considered as completed. While the idle guard timer is running, and also while awaiting the CCBS call to destination B, a new incoming call shall not be offered to d
32、estination B if it has service requirements and destination selection information identical to the (not suspended) request which is currently being processed in the destination B CCBS queue. 4 Recommendation 1.253.3 (07/96) For such incoming calls, the called user shall be considered as being busy a
33、nd the calling user shall be informed as for basic call procedures. The CCBS requests in the destination B CCBS queue shall be processed in the order they are received. During the processing of the destination B CCBS queue, CCBS requests which are currently suspended shall be ignored. If, for any re
34、ason, no CCBS call results from the processing of a CCBS request, then provided that access resources are still available at destination B, the next request in the destination B CCBS queue shall be selected for processing. This procedure shall be repeated until the processing of the destination B CC
35、BS queue is complete. If, for any reason, no CCBS call results from the processing of a CCBS request and the access resources are no longer available at destination B, then the resources reserved for the CCBS supplementary service shall be released and the network shall monitor for destination B bec
36、oming free. If all of the destination B CCBS queue has been processed and no CCBS call results, then processing is complete and the resources reserved for the CCBS supplementary service shall be released. If requests which are not suspended exist in the destination B CCBS queue, then: - - if destina
37、tion B is busy, the network shall monitor for destination B becoming free; or if destination B is free, then the destination B CCBS queue shall be processed. 3.2.4 Interrogation User A can request the status of the CCBS supplementary service. In response to the request the following information may
38、be provided: 1) in response to a general request user A shall be given a list of the addresses against which CCBS requests are outstanding; or 2) in response to a specific request concerning one particular address, user A shall be informed whether or not user A has a CCBS request outstanding against
39、 that address. NOTE - In both cases, the network provides information relating to CCBS requests (Le. bearerservice and teleservice requirements, the destination selection information and calling user identity, if any). It is a matter for terminal implementation whether or not user A is given informa
40、tion about CCBS requests which are not compatible with the terminal. 3.3 Exceptional procedures 3.3.1 Activation/deactivation/registration 3.3.1.1 Activation The activation of the CCBS supplementary service shall be rejected if the user has not subscribed to the CCBS supplementary service. The activ
41、ation of the CCBS supplementary service shall be rejected if a compatibility check has been carried out and there is no compatible terminal at destination B. If the network cannot accept user As request to activate the CCBS supplementary service, the network shall inform user A and give one of the f
42、ollowing reasons: 1) Short-term denial: The network temporarily cannot accept user As request to activate the CCBS supplementary service. A later attempt to activate the CCBS supplementary service for the same destination B may succeed. This reason will be given e.g.: Recommendation 1.253.3 (07196)
43、5 STD-ITU-T RECMN 1-253.3-ENGL 177b LiBb2571 Ob213b2 O20 = - - - if user A has reached the limit of CCBS requests outstanding; or if there are already the maximum number of requests queued against destination B; or if there is an interaction with a supplementary service which temporarily prevents th
44、e activation of the CCBS supplementary service; or if no compatible terminal is found at destination B. - NOTE - If the network does not support the monitoring of destination B becoming free in the case, where user A requests the CCBS supplementary service against a destination By which is user dete
45、rmined user busy, then the network should inform user A with the reason “short-term denial“. 2) Long-term denial: The network cannot accept user As request to activate the CCBS supplementary service and a later attempt to activate the CCBS supplementary service for the same destination B will also b
46、e rejected. An example of long-term denial is where destination Bs network does not support the CCBS supplementary service. If destination B is free when the CCBS request arrives, then the CCBS request shall be accepted. Normal procedures shall apply, as described in 3.2.1.1. 3.3.1.2 Deactivation A
47、CCBS request shall be automatically deactivated by the network(s) and user A shall be informed if: 1) the CCBS service duration timer expires; or 2) user A does not accept the CCBS recall before the CCBS recall timer expires; or 3) destination B invokes a service that conflicts with the existing CCB
48、S request and deactivation becomes necessary. The user shall only be given information about deactivation of a CCBS request, if that user would have been given the CCBS recall associated with that CCBS request. 3.3.1.3 Registration Not applicable. 3.3.2 Erasure Not applicable. 3.3.3 Invocation and o
49、peration 3.3.3.1 The following situations can occur at the destination Bs side: a) Resources or compatible terminal at destination B no longer available, when the destination B idle guard timer expires: If no access resources are available at destination B when the idle guard timer expires, then processing the destination B CCBS queue shall cease. The network shall monitor for destination B becoming free and the procedures of 3.2.3 shall then apply. If a compatibility check is made and no compatible terminal(s) at destination B is free when the idle guard timer expires, then the n
