HP StorageWorks XPath OS 7.4.X Administrator Guide (AA-RVHDD-TE, February 2006)

28 Performing basic configuration
For example:
Controlling routing within a fabric
There are two major aspects of Fibre Channel routing that you can control:
• Frame delivery order
• Use of dynamic load-sharing
Specifying frame delivery order
In a stable fabric, frames are always delivered in order, even when the traffic between switches is shared
among multiple paths. However, when topology changes occur in the fabric (for example, if a link goes
down), traffic is rerouted around the failure, and some frames can be delivered out of order. Most
destination devices tolerate out-of-order delivery, but some do not.
By default, out-of-order frame-based delivery is allowed to improve speed. You should force in-order frame
delivery across topology changes only if the fabric contains destination devices that cannot tolerate
occasional out-of-order frame delivery.
Forcing in-order frame delivery across topology changes
1. Connect to the switch and log in as admin.
2. Issue the iodSet command.
NOTE: This command can cause a delay in the establishment of a new path when a topology change
occurs; it should be used with care.
Restoring out-of-order frame delivery across topology changes
1. Connect to the switch and log in as admin.
2. Issue the iodReset command.
Using dynamic load sharing
Routing is generally based on the incoming port and the destination domain. This means that all the traffic
coming in from a port (either E_Port or Fx_Port) directed to the same remote domain is routed through the
same output E_Port.
To optimize fabric routing, when there are multiple equivalent paths to a remote switch, traffic is shared
among all the paths in a process called dynamic load sharing (DLS). DLS is recomputed when a switch is
booted up or every time a change in the fabric occurs. A change in the fabric is defined as an E_Port
going up or down or an Fx_Port going up or down.
router:admin> switchdisable
Switch is being disabled..
..............
router:admin> configure
Fabric parameter set. <cr> to skip a parameter
Domain: (1..239 or f(fabric_assign)) [100 unconfigured] 5
BB Credit: [1..32] [16]
R_A_TOV: (4000..120000) [10000]
E_D_TOV: (1000..5000) [2000]
Data field size: (256..2112 multiple of 4) [2112]
Switch PID Address Mode (1..2) [1]
WAN_TOV (0..R_A_TOV/4 ) [0]
MAX_HOP_COUNT (7..19 ) [7]
End-device RSCN Transmission Mode (0..2) [1]
Fabric configuration set
You must run 'switchenable' to put the switch back to running state
router:admin> switchenable