How it Works
This section provides an overview of how this feature is implemented and the recovery process.
The Session Recovery feature provides seamless failover and reconstruction of subscriber session information in the event of a hardware or software fault within the system preventing a fully connected user session from being disconnected.
Session recovery is performed by mirroring key software processes (for example, session manager and AAA manager) within the system. These mirrored processes remain in an idle state (standby-mode) wherein they perform no processing, until they may be needed in the event of a software failure (for example, a session manager task aborts).
There are some situations wherein session recovery may not operate properly. More software or hardware failures occur during the session recovery operation. For example, an AAA manager fails while the state information it contained was being used to populate the newly activated session manager task.
Important | After a session recovery operation, some statistics, such as those collected and maintained on a per manager basis (AAA Manager, Session Manager, and so on) are in general not recovered, only accounting and billing related information is checkpointed and recovered. |