Shared Call Appearance in Business Continuity

Starting with SIP Server version 8.1.101.75, Shared Call Appearance (SCA) is supported in Business Continuity deployments.

In Business Continuity mode (when both BC/DR peers are running and connected to each other), one DR peer is considered a preferred site for SCA. The preferred site is configured by the sca-preferred-site option of the corresponding SCA DN. When an inbound call arrives at an SCA, SIP Server checks if the current site is the SCA-preferred site. If it is, the call is processed as usual and distributed to SCA members. If it is not, the call is redirected to the preferred site using the BC call forwarding procedure. So, the outgoing calls to SCA members are always distributed from the SCA-preferred site.

The DR call forwarding procedure is not used for calls distributed from the SCA. Instead, outgoing calls are distributed only to SCA members on a local DN, regardless of the agent presence on this DN.

If a DR peer fails, the remaining DR peer switches to the standalone HA mode and distributes all inbound SCA calls to SCA members; no preferred site check is performed. The same happens if a connection between DR peers is lost—each site tries to distribute all inbound SCA calls locally. This distribution can be successful if, on the site where an inbound call arrives, at least one DN belonging to an SCA member is in service.

Feature Configuration

1. On the Primary shared-line DN, specify the following configuration option in the [TServer] section:
   • sca-preferred-site
2. In the SIP Server Application, specify the following configuration option in the [TServer] section:
   • dr-peer-location

For Business Continuity deployments, see Basic Deployment for details.

sca-preferred-site

Default Value: No default value
Valid Values: Any string value
Changes Take Effect: For the next call

Specifies the name of the SIP Server DR Peer application corresponding to the preferred SCA site. If not set or set to an invalid application name, the preferred SCA site cannot be determined, and inbound SCA calls are processed at the site where they are received. The option can be configured only for the Primary shared line DN, where the shared-line option is set to true.

Feature Limitations

• Phones of SCA members must be SIP registered at the same preferred site.
• If a preferred site fails and an inbound call comes to SCA at a non-preferred site, calls will be delivered to those SCA members' phones which have already determined the preferred site failure and have SIP registered at the non-preferred site.
• If a preferred site recovers after failure and an inbound call comes to SCA at a preferred or non-preferred site, calls will be delivered to those SCA members' phones which have already determined the preferred site recovery and have SIP registered at the preferred site.
• If a connection between DR peers is lost, calls arriving at a non-preferred site will not be delivered to SCA members phones.