Cisco Cisco Packet Data Gateway (PDG)

 

▄  VPC-VSM System Administration Guide, StarOS Release 19 

Interchassis Session Recovery (ICSR) provides a framework for sessmgr instance-level checkpointing within an ICSR 
framework. A checkpoint is a snapshot of the status of an application. Checkpointing can be used by sessmgr to push 
instance level information to the peer chassis. 

Instance-level checkpointing sends messages to specific sessmgr instances. Each application, such as GGSN, PDSN, P-
GW, S-GW or SGSN, is responsibility for encoding and decoding the checkpoint message. The ICSR framework 
provides the APIs for transport of the instance-level checkpoint information and associated statistics.  

Macro-checkpoints contain full session information and micro-checkpoints contain only a few variables. Macro-
checkpoints are sent initially from the active chassis to the standby chassis on power up and reload, and periodically 
thereafter. When a standby chassis receives macro-checkpoints, it clears any existing CRR (Call Recovery Record) or 
CLP (Call Line Pointer) related to that session, and creates a new CRR or CLP. Macro-checkpoints are also known as 
full checkpoints (FCs). 

To conserve processing cycles and memory, dynamic and periodic updates from an active chassis to a standby chassis 
are done using micro-checkpoints. 

The output of the Exec mode show srp info command displays a complete list of SRP checkpoints.