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In-Order Delivery
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m .
Figure 21-6
Switch 1
In
Figure
delivered before Frame 1 and Frame 2.
When the in-order guarantee feature is enabled, the frames crossing a PortChannel are treated as follows:
•
•
•
Enabling In-Order Delivery
By default, in-order delivery is disabled on switches in the Cisco MDS 9000 Family.
You can enable the in-order delivery feature for a specific VSAN or for the entire switch.
We recommend that you only enable this feature when devices that cannot handle any out-of-order
Tip
frames are present in the switch. Load-balancing algorithms within the Cisco MDS 9000 Family ensure
that frames are delivered in order during normal fabric operation. The load-balancing algorithms based
on source FC ID, destination FC ID, and exchange ID are enforced in hardware without any performance
degradation. However, if the fabric encounters a failure and this feature is enabled, the recovery will be
delayed because of an intentional pausing of fabric forwarding to purge the fabric of resident frames that
could potentially be forwarded out-of-order.
Enabling IOD Globally
To verify that the IOD parameters are uniform across all VSANs, enable IOD globally before performing
a downgrade to a Cisco MDS SAN-OS Release1.3(3) or earlier.
To enable in-order delivery for the switch, follow these steps.
Command
Step 1
switch# config t
switch(config)#
Step 2
switch(config)# in-order-guarantee
switch(config)# no in-order-guarantee
Cisco MDS 9000 Family Configuration Guide
21-12
Link Congestion Delivery
Frame 2
Frame 4
21-6, the port of the old path (red dot) is congested. Hence Frame 3 and Frame 4 can be
Frames using the old path are delivered before new frames are accepted.
Frames that cannot be delivered in order through the old path within the switch latency drop period
are dropped.
The new frames are delivered through the new path after the switch latency drop period has elapsed.
Chapter 21
Configuring Fibre Channel Routing Services and Protocols
Switch 2
Frame 1
Frame 3
Old path
New path
Purpose
Enters configuration mode.
Enables in-order delivery in the switch.
Reverts the switch to the factory defaults
and disables the in-order delivery feature.
OL-6973-03, Cisco MDS SAN-OS Release 2.x
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