Analog and digital endpoints do not restart to fail over to an alternate server. However, the MGC of the analog and digital endpoint detects the registration failure and attempts the re-registration on behalf of these endpoints.

The MGC provides the services that allows the MGC to detect a Device Adapter failure. After the failure is detected, the MGC tries to re-register the endpoints to the primary server. The primary server is analogous to the S1 in case of UNIStim endpoints. If the primary server does not respond and if no alternate servers are programmed, the MGC waits briefly and retries the registration.

If the cluster is configured for N+1 along with geo-redundancy and if S1 does not respond, the MGC tries to register the endpoints to the first alternate server (Alt 1). If the Alt 1 server is unavailable and if a secondary alternate server (Alt 2) is programmed, the MGC tries to register the endpoints to the Alt 2, which is a local backup server. However, if Alt 2 is also not available, the MGC waits for a brief period and tries to register the endpoints to the primary server.

Regardless of whether geo-redundancy is configured, N+1 fail over occurs when the MGC attempts to find capacity in the primary server first.

If the primary cluster is sized to have enough capacity to support the endpoints within that cluster, the outage is usually short and may not be detected by an end user, unless the user tries to use the endpoint during the fail over.

Depending on factors such as network speed and Session Manager resiliency, the fail-over time for the endpoint to register to a Device Adapter node is typically five minutes or less after an endpoint detects a registration failure.

However, even a short interval for detecting the registration failure and failing over may be noticed by the users. Hence, even a very fast switch-over may be noticed by the users.