Cisco Cisco Packet Data Gateway (PDG) Fehlerbehebungsanleitung
Interchassis Session Recovery
▀ Overview
▄ Cisco ASR 5000 Series Enhanced Feature Configuration Guide
OL-22982-01
Overview
The interchassis session recovery feature provides the highest possible availability for continuous call processing
without interrupting subscriber services. This is accomplished through the use of redundant chassis. The chassis are
configured as primary and backup with one being active and one standby. Both chassis are connected to the same AAA
server. A checkpoint duration timer is used to control when subscriber data is sent from the active chassis to the standby
chassis. If the active chassis handling the call traffic goes out of service, the standby chassis transitions to the active
state and continues processing the call traffic without interrupting the subscriber session. The chassis determines which
is active through a propriety TCP-based connection called a redundancy link. This link is used to exchange Hello
messages between the primary and backup chassis and must be maintained for proper system operation.
without interrupting subscriber services. This is accomplished through the use of redundant chassis. The chassis are
configured as primary and backup with one being active and one standby. Both chassis are connected to the same AAA
server. A checkpoint duration timer is used to control when subscriber data is sent from the active chassis to the standby
chassis. If the active chassis handling the call traffic goes out of service, the standby chassis transitions to the active
state and continues processing the call traffic without interrupting the subscriber session. The chassis determines which
is active through a propriety TCP-based connection called a redundancy link. This link is used to exchange Hello
messages between the primary and backup chassis and must be maintained for proper system operation.
Important:
ICSR is supported on chassis configured for GGSN or HA services only.
Interchassis Communication
Chassis configured to support interchassis session recovery communicate using periodic Hello messages. These
messages are sent by each chassis to notify the peer of its current state. The Hello message contains information about
the chassis such as its configuration and priority. A dead interval is used to set a time limit for a Hello message to be
received from the chassis‘ peer. If the standby chassis does not receive an Hello message from the active chassis within
the dead interval, the standby chassis transitions to the active state. In situations where the redundancy link goes out of
service, a priority scheme is used to determine which chassis processes the session. The following priority scheme is
used:
messages are sent by each chassis to notify the peer of its current state. The Hello message contains information about
the chassis such as its configuration and priority. A dead interval is used to set a time limit for a Hello message to be
received from the chassis‘ peer. If the standby chassis does not receive an Hello message from the active chassis within
the dead interval, the standby chassis transitions to the active state. In situations where the redundancy link goes out of
service, a priority scheme is used to determine which chassis processes the session. The following priority scheme is
used:
router identifier
chassis priority
SPIO MAC address
Checkpoint Messages
Checkpoint messages are sent from the active chassis to the standby chassis. Checkpoint messages are sent at specific
intervals and contain all the information needed to recreate the sessions on the standby chassis, if that chassis were to
become active. Once a session exceeds the checkpoint duration, checkpoint data is collected on the session. The
checkpoint parameter determines the amount of time a session must be active before it is included in the checkpoint
message.
intervals and contain all the information needed to recreate the sessions on the standby chassis, if that chassis were to
become active. Once a session exceeds the checkpoint duration, checkpoint data is collected on the session. The
checkpoint parameter determines the amount of time a session must be active before it is included in the checkpoint
message.