HP P4459A, Installation & Operation Manual

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HP P4459A 8-Port Fibre Loop Switch Installation & Operation Guide
Switching Operation
The fibre loop switch implements the Fibre Channel Arbitrated Loop protocol. It
provides concurrent connections to the storage area network (SAN) without
changing the FC-AL interface, which most SAN end-node devices normally
communicate.
The SAN operation changes dramatically when comparing a switch with a hub
environment. The normal operation, as seen by a single end-node device, does
not change, other than a rapid acceleration of responses in a switch environment.
Figure 3 illustrates how the fibre loop switch alters the response speed without
changing the nature of the responses seen by a participating node.
Figure 3: Switching Using Fibre Channel Protocol
The fibre loop switch maintains signal and data integrity by re-timing and
re-amplifying the signal at each port. The data-path routing, however, is
significantly different in the switch than with a hub.
As shown on the top of Figure 3, a Fibre Channel network has a physical loop
structure. All traffic must go through all nodes. Since the physical media is
shared by all nodes, the bandwidth must be partitioned between any nodes that