US Patent 7978598 Connection replication

A standby content switch module maintains a connection after failure of the active CSM by maintaining a replicate connection state of the connection state of the active CSM. The active CSM transmits a replicate TCP SYN segment to the standby CSM to replicate a connection state on the standby CSM. The replicate SYN is constructed to appear to originate from the client originating the connection to the active CSM. The replicate SYN further includes encoded information enabling the standby CSM to distinguish the replicate SYN from an actual SYN. The replicate SYN frame contains information needed to create a connection state on the standby CSM that is a replica of the connection state on the active CSM.