CHAPTER 24
Session Recovery
With robust hardware failover and redundancy protection, any hardware or software failures on the system
can quickly be corrected. However, software failures can occur for numerous reasons, often without prior
indication.
This chapter describes the Session Recovery feature that provides seamless failover and reconstruction of
subscriber session information in the event of a hardware or software fault.
Session Recovery is a licensed Cisco feature. A separate feature license may be required. Contact your
Cisco account representative for detailed information on specific licensing requirements. For information
on installing and verifying licenses, refer to the Managing License Keys section of Software Management
Operations.
Important
This chapter includes the following sections:
•
How Session Recovery Works, page 323
•
Additional ASR 5500 Hardware Requirements, page 326
•
Configuring the System to Support Session Recovery, page 326
•
Recovery Control Task Statistics, page 330
How Session Recovery 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).
The system spawns new instances of "standby mode" session and AAA managers for each active control
processor (CP) being used. These mirrored processes require both memory and processing resources, which
ASR 5500 System Administration Guide, StarOS Release 21.4
323
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