What it does
The MMTel Flexible Alerting (FA) service allows the creation of a group of member identities bound to a single number, called the Pilot Number.
When a call to the pilot number is identified, the service will alert all the members of the group and the caller is bound to the first member of the group that answers the call.
When a member answers the call with 200 (OK), the service cancels all other sessions towards the other members and finishes the call setup procedures between the calling party and the member that answered.
The service can be set to alert the group members:
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sequentially - sequentially alerts the group members in order, with each member sending a final response or timing out before the next is alerted.
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in parallel - alerts all the group members at once.
3GPP defines flexible alerting in TS 24.239 and the flexible alerting subscriber data schema is defined in TS 24.239 and TS 29.364.
Group members
The group of identities that may be contacted by the Flexible Alerting feature is called the FA Group.
There can be two types of FA Group:
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single-user - one user, who may have one or more devices.
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multiple-users - more than one user. An example would be the devices of more than person in the same office.
Interactions with other services
CAP charging
If CAP charging is in use, on inbound calls there will be a separate session between the Rhino VoLTE TAS and the service control point (SCP) providing the charging service for each forked PS and CS leg for each device. The leg that is answered by the called subscriber will be charged, and the other legs will be recorded as zero length calls with the SCP.
PSAP callback
Certain functions of the flexible alerting service that could interfere with emergency calls are disabled when an emergency call is detected:
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When a PSAP callback attempt is made to the undisclosed identity, the flexible alerting service will not block the call.
Communications Diversion (CDIV)
Communication Forwarding Unconditional (CFU)
If CFU is active for the Pilot Identity, the procedures will be applied and no group member will be alerted.
Communication Forwarding on Busy user (CFB)
If CFB is active for the Pilot Identity, the procedures will be applied if the pilot number is considered busy.
The definition of Busy for the pilot number depends on the group type:
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For single-user, when one member is busy the pilot number is busy.
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For multiple-uses all group members have to be busy for the pilot number to be considered busy.
Communication Forwarding on no Reply (CFNR) and Communication Forwarding on Subscriber Not Reachable (CFNRc)
If the FA Pilot Identity is considered in a state of CFNR or CFNRc, the procedures for those MMTel services will be applied.
The pilot number is considered in a state of:
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No Replywhen all group members are in a state of no reply. -
Not Reachablewhen all group members are in a state of not reachable.
Configuration
Currently, the declarative configuration for the flexible alerting service is only available through low-level overrides, which require the guidance of Metaswitch support.
To configure the service, contact your Metaswitch customer care representative.
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Full declarative configuration support for this service may become available in a later version. |
