1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-1000616.2014 Integrated Services Digital Network (ISDN) Call Hold Supplementary Service As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance the industrys most-pressing bus
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11、 retrieve, or connect to another call. The subscribed-to number of B-channels shall be kept available for the user as long as the user has at least that number of calls on hold with reservation. That is, the network should not reserve more than the subscribed-to number of B-channels for each ISDN Nu
12、mber/Bearer Service/TSP or TSP. If the network receives a Hold request from a user who is subscribed to B-channel reservation, and the network has already reserved all M B-channels for that user, then the network shall proceed with the Hold request in the normal manner, but no additional B-channel w
13、ill be reserved for the user. Table 1: Subscription options for the Call Hold service (per TSP, or number/bearer service/TSP) Subscription options Values Call Hold service assigned Notification of hold/retrieve sent to the held/retrieved party Limit of number of reserved channels B-channel reservati
14、on release allowed -No -Yes -No -Yes -M (where 0 M maximum number of channels available on the interface, M = 0 indicates no reservation) -No -Yes NOTE The number of calls that can be held is limited only by the limits on the number of calls on the interface as provided by the basic call description
15、. When the served user wishes to re-establish communications, the Retrieve operation is requested. The success of the Retrieve operation depends on whether or not a B-channel was reserved and whether a B-channel is currently available to the served user. The served user has the option at subscriptio
16、n to have the notification of hold/retrieve sent to the held party. Either no notifications will be sent or both hold and retrieve notifications will be sent. 3 ATIS-1000616.2014 In order to terminate calls that have been on hold for unreasonable amounts of time, a network optional guard timer may b
17、e set. The same length of the guard timer applies to all calls placed on hold by the service provider. The value of the optional guard timer ranges from 30 minutes to 48 hours, with 48 hours being the expected value. 4.2 Procedures 4.2.1 Provision/Withdrawal The Call Hold service can be provided on
18、a subscription basis, or can be provided to all users without subscription, as a service-provider option. The Call Hold service can be withdrawn for administrative reasons. As a network option, the Call Hold service can be offered with several subscription options. If the Call Hold service is provid
19、ed to all users without subscription, the service provider shall assign subscription option values. The service provider may provide the capability of combining 3.1-kHz Audio and Speech bearer services for the purpose of assigning subscription options. Options that apply separately to each terminal
20、service profile, or to each number/bearer service per TSP are listed in table 1. Withdrawal of the service is made by the service provider upon request by the subscriber or for service provider reasons. 4.2.2 Normal Procedures 4.2.2.1 Activation/deactivation The Call Hold service is active whenever
21、pro- vided on a subscription basis, or as a service provider option, whenever provided to a user without subscription. 4.2.2.2 Invocation on the called served users interface, by the called served user at any time after the call has been answered; and before call clearing has begun. The communicatio
22、n on the interface is then interrupted. The network acknowledges this action, and the associated channel is made available for other uses. Based on the subscription options, the network may send a notification to the held party indicating that the call has been placed on hold. This optional notifica
23、tion, for a call that has not yet become active end-to-end, shall be delayed by the net- work until the called party answers. If held call(s) are cleared for any reason, the network shall continue to reserve a B-channel for the specified terminal until there are no more held calls with reservation a
24、ssociated with the specified terminal. If at any time a call is in the held state, either party may clear the call. 4.2.2.2.2 Retrieve Request (see figure 2) 4 ATIS-1000616.2014 When the served user that invoked the Call Hold service indicates that a call is to be retrieved, the network shall re-est
25、ablish communications, provided that a B-channel is available, and notify the served user and optionally the held party. A call that is placed on hold and then retrieved before it is answered shall not have any notifications sent forward to the called party. The notifications of hold and retrieve sh
26、all cancel each other. The served user may optionally indicate a B- channel selection parameter in the retrieve request. The parameter may indicate: a) Any channel acceptable; b) Specified channel is preferred; or c) Specified channel is exclusively required. If the network can satisfy the request,
27、communications for the call on the interface shall be re-established; if it cannot, the request will be rejected with the appropriate cause returned to the served user. 4.2.2.2.3 Reservation Processing The following conditions concerning reservation against a B-channel apply: a) When a call is retri
28、eved, any reservation against a B-channel associated with that call shall be cleared, independent of which B- channel is used to retrieve the call; b) When a call is cleared, any reservation against a channel associated with the call shall be cleared; c) When all reservations are cleared, all B- cha
29、nnels become available for use by either the network or a user; d) When any reservation is outstanding for a given served user and that served user is associated with a held call, but is not using a channel for an active call, then the network shall consider a B-channel as “not free” for that user f
30、or subsequent incoming calls. (Interaction with the Call Waiting service when all channels are “not free” is described in 4.5.1.); e) When the Call Hold served user requests that reservation be released, the network shall release the reservation associated with this served user and immediately consi
31、der all reserved channels associated with this served user as “free” regardless of the number of outstanding calls on hold with reservation. 4.2.3 Exceptional Procedures 4.2.3.1 Activation/deactivation (None identified) 4.2.3.2 Invocation b) Only party B to have party A on hold; and c) Each party to
32、 have the other on hold. 5 Functional Capabilities b) Receives functional indications relating to requests from FE2 (i.e., hold confirmation/rejection, retrieve confirmation/rejection), then processes and relays them to the served user. 5.1.2 Description of Functional Entity 2 Functional Entity 2 pr
33、ovides the following functionality in support of Functional Entities 1 and 3: a) Receives service requests from FE1, verifies the invocations, and relays appropriate information through the network towards User B (e.g., receives a hold request from FE1 and relays an optional notification of the held
34、 call toward User B). In processing service requests, FE2 verifies that Call Hold services are invoked only by a subscribed user if subscription is required by the service provider; b) Performs the hold and retrieve functions; c) Provides the optional sending of hold/ retrieve notifications towards
35、User B; d) Sends functional indications relating to a held call to FE1 (e.g., hold confirmation, retrieve confirmation); e) Reserves a B-channel, if B-channel reservation is subscribed to; f) Supports B-channel release processing, if subscribed to. 5.1.3 Description of Functional Entity 3, 4, 5, 6 F
36、unctional Entity 3, and Functional Entities 4, 5, 6 if they exist, provide the following functionality in support of Functional Entities 2 and 7: receives optional notifications originating from FE2 (which may transit intermediate FEs, if they exist) that the served user User B call is being held or
37、 retrieved and relays them toward FE7. 5.1.4 Description of Functional Entity 7 Functional Entity 7 provides the following functionality in support of User B and Functional Entity 3, 4, 5, 6: receives optional notifications that the served user User B call is being held or retrieved and informs (rel
38、ays them to) User B. 7 ATIS-1000616.2014 5.2 Information Flow Model for Call Hold This subclause identifies the information that needs to be passed between functional entities, and identifies when this information needs to be passed in order to permit overall operation of the Call Hold service. Each
39、 information flow is an abstract representation that could be implemented as a new message or as an addition to an existing message in a call-control signaling system. See figures 4 and 5. Figures 6 and 7 show the explicit relation of the Call Hold information flows to the DSS1 and SS7 messages that
40、 implement them. 5.2.1 Definition of Individual Information flows 5.2.1.1 Hold Request Hold request is the information sent from FE1 to FE2 to request that a call be placed on hold by the network. It contains an identifier of the call to which the hold request applies. 5.2.1.2 Hold Confirmation Hold
41、 confirmation is the information sent from FE2 to FE1 that confirms that a call has been put on hold for the user by the network. It contains an identifier of the call to which the hold confirmation applies. 5.2.1.3 (Optional) Notification of Hold (Optional) notification of hold is the information s
42、ent from FE2 towards FE7 indicating that the call between FE1 and FE2 has been placed on hold. It contains an identifier of the call to which the (optional) notification of hold applies. 5.2.1.4 Retrieve Request Retrieve request is the information sent from FE1 to FE2 to request the reconnection of
43、a held call. It contains an identifier of the call to which the retrieve request applies. It also contains an optional indication that: a) Any channel is acceptable for retrieval; or b) A specified channel is preferred for retrieval; or c) A specified channel is exclusively required for retrieval. 5
44、.2.1.5 Retrieve Confirmation Retrieve confirmation is the information sent from FE2 to FE1 that confirms that communication was able to be re-established and that the held call is now reconnected. If an option- al indication concerning the B-channel over which communication was to have been re-estab
45、lished was included in the retrieve request, then the retrieve confirmation serves as an acknowledgment that retrieval was carried out as requested. The retrieve confirmation contains an identifier of the call to which the retrieve confirmation applies and an identifier of the channel over which the
46、 held call is reconnected. 5.2.1.6 (Optional) Notification of Retrieval (Optional) notification of retrieval is the information sent from FE2 towards FE7 indicating that the B-channel between FE1 and FE2 has been reconnected. It contains an identifier of the call to which the (optional) notification
47、 of retrieval applies. 8 ATIS-1000616.2014 5.3 Allocation of functions to equipment This subclause identifies a number of different plans, called scenarios, for allocating the functional subdivisions of Call Hold to specific network of user equipments (figure 8). Each scenario implicitly identifies
48、what protocol is impacted by the Call Hold information flows. Functional Entities 3, 4, 5, and 6 may not exist for the listed scenarios. 6 Switching b) HOLD ACKNOWLEDGE Message sent by the network to indicate that the Hold function has been successfully performed; c) HOLD REJECT Message sent by the
49、network to indicate denial of request to hold a call; d) RETRIEVE Message sent by the user to request retrieval of held call; e) RETRIEVE ACKNOWLEDGE Message sent by the network to indicate that the Retrieve function has been successfully per- formed; f) RETRIEVE REJECT Message sent by the network to indicate denial of request to retrieve the call. The NOTIFY message, as described in 3.1.7 of ATIS-1000607, is used for the notification of hold and retrieve. The INFORMATION message, as described in 3.1.6 of ATIS-1000607, is used for the B-channel reservation release p
