Failure scenarios

Last Updated : Nov 29, 2023 |

The failure scenarios explained in this topic are generic and are regardless of the Branch Session Manager survivability type, that is, Enterprise branch survivability and Edge friendly branch survivability.

However, in an Edge friendly branch survivability configuration, Avaya Session Border Controller (SBC) is required at the core edge for connectivity to the branch. The branch network is distinct from the enterprise network (core) and the connectivity between them is over the Internet rather than the VPN.

Generic diagram depicting branch survivability in a failure scenario

  • Branch users are provisioned with one core SM (SM-1) and the BSM. There is no secondary SM.

  • Branch SIP phones, after losing connectivity with SM-1, mark BSM as the active controller.

  • Media Gateways in the branch detect outage and connect with SRS as the controller.

  • SRS activates the link with BSM.

  • Branch loses connectivity with all the core networks.

The following example call scenarios illustrate the behavior of the feature. The scenarios listed are not intended to be a complete list of all possible configurations and call scenarios.

Case 1: Calls incoming from the SP branch SIP trunk to a branch SIP user

  1. Incoming request from the SIP SP arrives at BSM.

  2. BSM performs ingress adaptation.

  3. BSM detects the outage of the primary controller of the branch SIP user.

  4. BSM invokes SRS as the sequenced application and completes application sequencing.

  5. BSM terminates the call at the locally registered SIP endpoint.

Case 2: Calls going to the SP branch SIP trunk from a branch SIP user and entire core is unreachable

  1. A call originates from branch SIP user.

  2. BSM detects the outage of the primary controller of the branch SIP user.

  3. BSM invokes SRS as the sequenced application and completes application sequencing.

  4. BSM cannot connect with any core SM.

  5. BSM performs routing based on partial routing data.

  6. Before forwarding the request to SIP SP, BSM performs egress adaptation. No CAC is performed at this step.