OSPF nonstop routing (NSR) synchronization reduction

摘要

A network element is configured to reduce the synchronization costs for implementing Open Shortest Path First (OSPF) Nonstop routing (NSR). The reduced synchronization costs are achieved by reducing the number of acknowledgement messages that are needed to be sent though reliable inter-process communication (IPC) between the active OSPF instance and the standby OSPF instance. The number of acknowledgement messages is reduced by tracking the link state advertisements (LSAs) that have been sent by the active OSPF instance to the standby OSPF instance and by the standby OSPF replying with an acknowledgement of only the last LSA in a group of LSAs received from the active OSPF instance, where the group can have a variety of boundaries such as a group of LSAs in an IPC message. This avoids having a significant number of acknowledgement messages sent through the IPC.

主权项

1. A method in a network element implementing Open Shortest Path First (OSPF) Nonstop Routing (NSR) for intradomain routing, wherein the network element is connected with a neighbor network element over a network connection, wherein the network element executes an active OSPF instance that maintains a link state data base (LSDB) of received links state advertisements (LSAs) and a standby OSPF instance that maintains a backup LSDB of received LSAs, the method to reduce resources utilized to synchronize the active OSPF instance with the standby OSPF instance executed by the network element, the method comprising the steps of:
receiving a new instance of a link state advertisement (LSA) from the neighbor network element over the network connection; adding the LSA to an on-hold LSA linked list or moving the LSA to a tail of the on-hold linked list by the active OSPF instance; sending the LSA to the standby OSPF instance via inter-process communication (IPC) by the active OSPF instance; receiving at the active OSPF instance an LSA acknowledgement for the LSA from the standby OSPF instance; looking up the acknowledged LSA in the on-hold LSA linked list by the active OSPF instance; and clearing the acknowledged LSA and all preceding LSAs in the on-hold LSA linked list, which reduces a number of LSA acknowledgements needed between the active OSPF instance and the standby OSPF instance to backup the LSDB.