For a survivable remote configuration, the following section shows the different branch connectivity scenarios and the associated call flows:
Normal Scenario: All provisioned entity link connections between the Branch Session Manager and the core are in service. The Media Gateway is in contact with the primary controller, that is, the core Communication Manager. No error is reported on any of the Branch Session Manager SM links.
Failure Scenarios: All provisioned entity link connections between the Branch Session Manager and the core are out of service. When the Media Gateway loses contact with the core Communication Manager, the Media Gateway attempts to re-register with the SRS. The Branch Session Manager is in complete survivable mode due to a full WAN outage of the branch. All the components in the branch such as phones, Media Gateway, and Branch Session Manager , have lost connectivity with all the components in the core, such as Session Manager and Communication Manager.
