H.248 Link Loss Recovery is an automated way in which the gateway reacquires the H.248 link. H.248 Link Loss Recovery can occur when the link is lost from either a primary call controller or a survivable remote server. The H.248 link between a server running Communication Manager and a gateway, and the H.323 link between a gateway and an H.323-compliant IP endpoint, provide the signaling protocol for:

• Call setup

• Call control with user actions such as Hold, Conference, or Transfer, while the call is in progress

• Call tear-down

If the link is out of service, Link Recovery preserves any existing calls and attempts to reestablish the original link. If the gateway or endpoint cannot reconnect to the original server or gateway, Link Recovery automatically attempts to connect with alternate survivable processor.

Overlap with the Auto Fallback to Primary feature occurs when:

• Link Loss Recovery starts while the gateway tries to migrate back to the primary.

• Link Loss Recovery new registration message indicates that service is being obtained from elsewhere.

A rare condition can exist in which an outstanding gateway registration to the primary exists while the link to the survivable remote server is lost. The gateway awaits a denial or acceptance from the primary call controller. If the call controller accepts, then Link Loss Recovery is terminated, and the gateway is serviced by the primary call controller. If the call controller denies, then the gateway immediately sends a new registration to the primary call controller. The registration indicates no service, and the existing H.248 Link Loss Recovery feature takes over.

Both features try to return service to the primary call controller. However, Link Loss Recovery returns service based on a link failure, whereas auto fallback to primary returns service based on a working fragmented network.