Storage Area Networks: Designing and Implementing a Mass Storage System

3.15. FC-AL Characteristics

There are three topologies supported by Fibre Channel: loop, point-to-point, and switched. FC-AL is the loop topology that will be discussed here. The Fibre Channel Arbitrated Loop (FC-AL) is a means by which to connect up to 126 devices in a serial loop configuration.

In the FC-AL, each port discovers when it has been attached to a loop. Addresses are assigned automatically on initialization. Access to the loop is arbitrated; there are no collisions and there is no single permanent loop master.

FC-AL permits fair access on a single arbitrated loop. Access fairness means every port wanting to initiate traffic will have the opportunity to own the loop and initiate traffic before any other port has the opportunity to ...