Cisco Cisco Packet Data Interworking Function (PDIF)
Session Recovery
▀ Additional ASR 5x00 Hardware Requirements
▄ ASR 5500 System Administration Guide, StarOS Release 17
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When session recovery occurs, the system reconstructs the following subscriber information:
Data and control state information required to maintain correct call behavior.
A minimal set of subscriber data statistics; required to ensure that accounting information is maintained.
A best-effort attempt to recover various timer values such as call duration, absolute time, and others.
The idle time timer is reset to zero and the re-registration timer is reset to its maximum value for HA sessions to
provide a more conservative approach to session recovery.
Important:
Any partially connected calls (for example, a session where HA authentication was pending but has
not yet been acknowledged by the AAA server) are not recovered when a failure occurs.
Additional ASR 5x00 Hardware Requirements
Because session recovery requires numerous hardware resources, such as memory, control processors, NPU processing
capacity, some additional hardware may be required to ensure that enough resources are available to fully support this
feature.
capacity, some additional hardware may be required to ensure that enough resources are available to fully support this
feature.
Important:
A minimum of four packet processing cards (three active and one standby) per individual chassis is
required to use this feature.
To allow for complete session recovery in the event of a hardware failure during a packet processing card migration, a
minimum of three active packet processing cards and two standby packet processing cards should be deployed.
minimum of three active packet processing cards and two standby packet processing cards should be deployed.
To assist you in your network design and capacity planning, consider the following factors:
Subscriber capacity is decreased depending on the hardware configuration. A fully configured chassis would
experience a smaller decrease in subscriber capacity versus a minimally configured chassis.
The amount by which control transaction processing capacity is reduced.
The reduction in subscriber data throughput.
The recovery time for a failed software task.
The recovery time for a failed packet processing card.
A packet processing card migration may temporarily impact session recovery as hardware resources (memory,
processors, etc.) that may be needed are not available during the migration. To avoid this condition, a minimum of two
standby packet processing cards should be configured.
processors, etc.) that may be needed are not available during the migration. To avoid this condition, a minimum of two
standby packet processing cards should be configured.