The connectivity path between the remote branch gateway and the Call Controller are direct to the server Processor Ethernet interface.
The connectivity path directly to the Processor Ethernet interface of the server is as follows:
branch gateway ⇔ IP network ⇔ PE interface of the server
Link connectivity between the main call controller and the branch gateway is monitored through the exchange of keep-alive messages between the two components. If the link between the active call controller and the branch gateway breaks, the branch gateway tries to reestablish the link using the alternate gatekeeper list. The alternate gatekeeper list is divided into primary and secondary addresses. The primary addresses receive priority over the secondary addresses.
In the event of a WAN failure, any IP endpoint or branch gateway that cannot reach the primary controlling server registers with a survivable remote server controller in survivable mode. In the duplex server/branch gateway configuration, up to 50 survivable remote servers are available and ready for the fail-over process. The survivable remote server is always ready to acknowledge service requests from IP telephones and branch gateways that can no longer communicate with their main controller. Once the telephones and the branch gateway are registered, end users at the remote site have full feature functionality. This failover process usually takes less than 3 minutes. After failover, the remote system is stable and autonomous.
