Frame Delivery Order - EMC Connectrix EC-1200 Planning Manual

Fibre Channel Switching Concepts
2

Frame Delivery Order

When switches calculate a new least-cost data transfer path through a
fabric, the switch routing tables immediately implement that path.
This can result in Fibre Channel frames being delivered to a
destination device out of order, because frames transmitted over the
new (shorter) path might arrive ahead of previously transmitted
frames that traverse the old (longer) path.
In order to guarantee correct frame delivery order, the Connectrix
Manager's Product Manager implements a Rerouting Delay
parameter. The delay period is equal to the E_D_TOV (Error Detect
Time Out Value) specified in the Product Manager application.
Class 2 frames transmitted into the fabric during this delay period are
rejected; Class 3 frames are discarded without notification.
The Rerouting Delay parameter can be enabled through the
Connectrix Manager's Product Manager.
By default, the Rerouting Delay is disabled. EMC tests with
Symmetrix and EMC-approved HBAs have shown no problems
when frames arrive out of order. By leaving the delay parameter
disabled, the servers and Symmetrix recovery much more quickly to
events in the fabric.
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Connectrix v6.02 Planning Guide