Fabric Shortest Path First (FSPF) is a routing protocol used in Fibre Channel networks. It calculates the best path between switches, establishes routes across the fabric and calculates alternate routes in event of a failure or topology change. FSPF can guarantee in-sequence delivery of frames, even if the routing topology has changed during a failure, by enforcing a 'hold down' time before a new path is activated.
FSPF was created by Brocade Communications Systems, and has since been adopted as the industry standard for routing between Fibre Channel switches within a fabric.