US Patent 7940650 Peer-agnostic TCP socket replication between primary and secondary routing engines

This application describes techniques for peer-agnostic socket replication to implement graceful failover. An exemplary method to enable non-stop routing includes receiving a packet with a first routing engine of a network device having the first routing engine and a second routing engine configured as a backup routing engine, replicating, before processing the packet at a transport layer, the packet to form a replicated packet, sending the replicated packet from the first routing engine to the second routing engine, receiving, at the first routing engine, an acknowledgement from the second routing engine acknowledging reception of the replicated packet, after receiving the acknowledgment, processing the packet at the transport layer of the first routing engine to extract application-layer data and assemble a routing message, and storing the application-layer data from the processed packet in a socket associated with a routing process of the first routing engine.