Patent ID: 8040795

Claim:
A method of shifting to a backup path in a Synchronous Optical Network (SONET) network including working links and backup links, each of said links being terminated at one end by a router, each router having a link state database and a routing table, the method comprising: in each router, initially populating the link state database with links that include both the working links extending from the router and the backup links extending from the router, and attaching a higher cost to the backup links so that the router selects the working links and none of the backup links for use in routes in the router's routing table; and in the SONET network, pre-establishing an Open Shortest Path First (OSPF) adjacency over the backup links, and when a failure of a working link is detected, switching to a backup link to bypass the working link, by notifying the routers terminating the working and backup links that they should change the costs of the backup link so that the routers change their routing tables to specify the backup link instead of the failed working link.