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Alteon Application Switch Operating System Application Guide
High Availability
Document ID: RDWR-ALOS-V2900_AG1302
575
Figure 89 - Service-Based Session Failover for Hot Standby Configurations, page 575 illustrates a
service-based session failover network topology:
Figure 89: Service-Based Session Failover for Hot Standby Configurations
When a new session is created on the master, the session entry is sent to the backup using NAAP.
The backup creates the session and sets the age to a maximum age. This prevents the session from
aging out on the backup and prevents frequent updates between the master and backup. When the
session is updated or deleted on the master, the session on the backup is also updated or deleted.
When the master becomes a backup due to reboot or link failure, it sends a session sync message to
the new master. The new master mirrors all the sessions that need to be mirrored to the backup. To
avoid performance impact, all sessions are not sent at the same time. A timer routine is used to
mirror the sessions. In each round, a maximum of 1024 sessions are sent to the backup.
Operations During Session Mirroring on Reboot
The following are the operations that take place during session mirroring on reboot:
• A session synchronize message is sent to the peer while booting.
• The timer routine sends the sync request based on following conditions:
— VRRP state is backup.
— The interswitch port is in forwarding or enable mode.