Fibre Channel Primer

48 Fibre Channel: Connection to the Future
and a frame switch is not
required. Some switches
are dedicated circuit
switches and some are
dedicated frame switches.
In the frame-switch-
ing mode, the bandwidth is
dynamically allocated on a
link-by-link basis. Based
on adaptive routing within
the switch, individual
Figure 6.11 Fibre Channel switches use
circuit and frame switches
Circuit Switch
Frame Switch
INPUT SIDE OF PORTS
OUTPUT SIDE OF PORTS
1
2
3
N
N
1
2
3
frames between switch
ports are independently
switched. During frame
switching, buffering is re-
quired within the switch to
provide link level flow control between the switch and the connected
N_Port, NL_Port, or E_Port. Applications that need low latency for
short transfers will utilize frame switching.
In the future, E_Ports will also be connected to a WAN through
an Inter Working Unit (IWU). This is the result of a joint development
between the Fibre Channel industry in Japan and the U.S.
Installation
During initialization, address assignment and inter-switch paths
are automatically determined. At any time, nodes can be added or
deleted. When nodes are connected, they automatically login and
exchange operating parameters with the switch. During login, N_Ports
inherit the addresses of the corresponding switch ports. NL_Ports
inherit the top 16 bits of the switch FL_Port and assign up to 126
addresses using the bottom 8 bits for members of the loop.
SUMMARY
Point-to-point, loop, and switched Fibre Channel systems are
deployed in mission-critical applications, delivering reliable 7x24
operations with hundreds of gigabits per second of system bandwidth.