APPENDIX D
ICSR Checkpointing
This appendix lists and describes macro- and micro-checkpoints employed by the Interchassis Session
Recovery framework. Checkpoints are exchanged between the active and standby ICSR chassis via the
Service Redundancy Protocol (SRP).
The following topics are discussed:
•
Overview of Checkpointing, page 363
•
Macro-checkpoints, page 363
•
Micro-checkpoints, page 365
Overview of Checkpointing
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.
Macro-checkpoints
This section lists and briefly describes ICSR macro-checkpoints.
ASR 5500 System Administration Guide, StarOS Release 21.5
363
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