In access deployments, when users submit registration requests, the SBC stores details of each registration in data structures called registration control blocks (RCBs). After successful registration, the SBC uses information from the appropriate RCB when sending calls to registered users.
By default the SBC creates an RCB for each unique combination of address of record (AOR), source IP address/port, and zone ID. But, in a scenario where a user resides behind a PBX and sends registration requests from multiple devices (such as a phone and laptop), the registration requests share these values. In this case, the two requests do not lead to two separate registrations. However, the Contact headers in the two REGISTER requests provide distinguishing factors between the requests. Therefore, to allow separate RCBs for each device, you can configure an SBC zone with a Register Contact profile in which you specify Contact parameters (userpart, hostpart, or both) to use as additional parameters to uniquely define a registration.
After you assign a Register Contact Profile to a zone, the SBC considers the specified Contact header elements as additional keys for creating and retrieving RCBs for the users registering through that zone. In the previous scenario, this allows the SBC to forward two registration requests to the registering Application Server, one for each device. The Application Server then has the option to send multiple INVITE requests to the user, one for each device, so that both devices ring in the event of an incoming call.
Note
If you assign and enable a Register Contact profile on a zone, the SBC always considers the configured Contact header elements when creating or retrieving RCBs, irrespective of the setting of the multipleContactsperAOR flag.
For information on creating and assigning Register Contact profiles, refer to:
Overview
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