Communication is via IP addresses and ports over an IP network. There can be a varied IP network in between the FCIP endpoints. FCIP is best suited for asynchronous type replication because your not going to be dealing with the same latency and bandwidth as FCP, not to mention you have more overhead.
FCIP is not a server to storage protocol. Its a switch to switch protocol. Its used to extend your SAN over a WAN. If you wish to use server to storage IP technology, than that is iSCSI and/or FCoE. You really don't want to be doing iSCSI over the WAN however, and FCoE requires layer 2 adjacency, once again, not ideal for over the WAN. Storage is generally local to the servers. Over the WAN you might replicate storage to another storage, and FCIP or CWDM/DWDM/SONET technologies are good for this type of traffic (SAN Extension).
Brian
