Patent ID: 7808889

Claim:
A method comprising: establishing a network tunnel between a first device and a second device, wherein the first device includes a primary control unit and a backup control unit; mirroring sequence numbers at the primary control unit of the first device before a failover from the primary control unit to the backup control unit of the first device; failing over to the backup control unit in response to a failure of the primary control unit; directing packets received by a forwarding controller of an interface card of the first device to an interface controller of the interface card during the failover and prior to the backup control unit becoming active as a master control unit for the first device; with the interface controller, maintaining the network tunnel between the first device and the second device throughout the failover by acknowledging receipt of the packets received from the second device during the failover; when the failover is complete, sending a duplicate control plane packet from the backup control unit to the second device to elicit a response from the second device having current sequence numbers at the second device to allow the backup control unit to synchronize sequence numbers at the first device with sequence numbers at the second device, wherein the duplicate control plane packet is a duplicate of a control plane packet previously sent by the first network device; identifying one or more subscriber sessions associated with the network tunnel as not having been established at one of the first device and the second device when the failover is complete; and when the failover is complete, terminating with the backup control unit the identified one or more subscriber sessions associated with the network tunnel to synchronize subscriber sessions associated with the network tunnel at the first device with subscriber sessions associated with the network tunnel at the second device.