Fibre Channel Primer

39 Chapter 6: Topologies
is connection setup and tear-down, it is an efficient service for large
data exchanges. Fibre Channel Class 1 service provides an
acknowledgment of receipt for guaranteed delivery. Class 1 also
provides full-bandwidth, guaranteed delivery and bandwidth for
applications like image transfer and storage backup and recovery.
Some applications use the guaranteed delivery feature to move data
reliably and quickly without the overhead of a network protocol stack.
“Camp on” is a Class 1 feature that enables a switch to monitor
a busy port and queue that port for the next connection. As soon as
the port is free, the switch makes the connection. This switch service
speeds connect time, rather than sending a “Busy” back to the
originating N_Port and requiring the N_Port to retry to make the
connection.
“Stacked Connect” is a Class 1 feature that enables an originating
N_Port to queue sequential connection requests with the switch.
Again, this feature reduces overhead and makes the switch service
more efficient.
Class 1 has a variation called buffered service. It is used to
connect two Fibre Channel ports that are operating at different speeds.
Another form of Class 1 is called Dedicated Simplex Service.
Normally, Class 1 connections are bidirectional; however, in this
service, communication is in one direction only. It is used to separate
transmit and receive switching. It permits one node to transfer to
another node while simultaneously receiving from a third node.
Figure 6.2 Class 1 service provides dedicated bandwidth
Workstation
Switch
Server
RAID
Backup
Storage