Importance

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Abstract

Disclosed are methods and apparatus for facilitating recovery of a data connection that was established between an active router and a host. The data connection is a type of connection that tracks the sequence of data sent between the router and the host. This recovery may occur after a standby router takes over for the active router. For example, a Transmission Control Protocol (TCP) connection between the active router and a host may be recovered after a router switchover (e.g., when the standby router takes over for the active router in a hot standby router protocol system). To accomplish this, at least one sequence number that is associated with data sent from the active router (to the host) is sent to the standby router, and at least one sequence number from data sent from the host is also sent to the standby router. For example, the sequence numbers correspond to the initial SYN packet sent by the active router and the SYN packet sent by the host in response to the active router's SYN packet. These two sequence numbers are obtained for each connection in which the active router is an endpoint. When the standby takes over for the previously active router, the new active router may then recover the connection by sending these two sequence numbers within an acknowledgement packet to the host. The host then responds with the correct sequence numbers for the connection, and the standby router can then continue data transmission to the host using the correct sequence numbers.

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First Claim