FC Switching Protocols

FSPF is the protocol used for routing within an FC-SAN. FSPF is a link-state protocol, but each vendor may choose which link-state algorithm to use. Dijkstra's algorithm is the most widely known link-state algorithm, but the ANSI T11 FC-SW-4 specification does not require the use of Dijkstra's algorithm. Well-defined interactions between switches ensure interoperability even if multiple link-state algorithms are used within a single FC-SAN. Additionally, the FC-SW-4 specification neither requires nor precludes the ability to load-balance, so FC switch vendors may choose whether and how to implement such functionality. In most other respects, FSPF is similar to other link-state protocols.

Routing between FC-SANs is currently accomplished via proprietary techniques. ANSI recently began work on standardization of inter-fabric routing, but no such standards currently exist. Each FC switch vendor currently takes a different approach to solving this problem. All these approaches fall into one of two categories: integrated or appliance-based. The integrated approach is conceptually similar to Layer 3 switching, wherein the ASICs that provide Layer 2 switching functionality also provide inter-fabric routing functionality as configured by administrative policy. The appliance-based approach requires the use of an external device that physically connects to each of the FC-SANs between which frames need to be routed. This approach is conceptually similar to the original techniques used for inter-VLAN IP routing (often called the router-on-a-stick model).