Configuring Pause Drop Timeout For Fcoe - Cisco MDS 9000 Series Configuration Manual

Configuring Pause Drop Timeout for FCoE

(Optional) Depending on the Cisco MDS NX-OS release version you are using, use one of the following commands to
revert to the default FCoE congestion drop timeout value of 500 milliseconds:
• Cisco MDS NX-OS Release 8.1(1) and earlier releases
switch(config)# no system default interface congestion timeout milliseconds mode {core | edge}
• Cisco MDS NX-OS Release 8.2(1) and later releases
switch(config)# no system timeout fcoe congestion-drop {milliseconds | default} mode {core | edge}
Configuring Pause Drop Timeout for FCoE
When an FCoE port is in a state of continuous pause during the FCoE pause drop timeout period, all the frames
that are queued to that port are dropped immediately. As long as the port continues to remain in the pause
state, the newly arriving frames destined for the port are dropped immediately. These drops are counted as
egress discards on the egress port, and free up buffers in the upstream ingress ports of the switch, allowing
unrelated flows to continue moving through them.
To reduce the effect of a slow-drain device on unrelated traffic flows, configure a lower-pause drop timeout
value than the congestion frame timeout value, for edge ports. This causes the frames that are destined for a
slow port to be dropped immediately after the FCoE pause drop timeout period has occurred, rather than
waiting for the congestion timeout period to drop them.
By default, the FCoE pause drop timeout is enabled on all ports and the value is set to 500 ms. We recommend
that you retain the default timeout core ports and consider configuring a lower value for edge ports.
To configure the FCoE pause drop timeout value, perform these steps:
Step 1 Enter configuration mode:
switch# configure terminal
Step 2 Depending on the Cisco MDS NX-OS release version that you are using, use one of the following commands to configure
the system-wide FCoE pause drop timeout value, in milliseconds, for edge or core ports:
• Cisco MDS NX-OS Release 8.1(1) and earlier releases
switch(config)# system default interface pause timeout milliseconds mode {core | edge}
• Cisco MDS NX-OS Release 8.2(1) and later releases
switch(config)# system timeout fcoe pause-drop {milliseconds | default} mode {core | edge}
The range is from 100 to 500 milliseconds.
(Optional) Depending on the Cisco MDS NX-OS release version that you are using, use one of the following commands
to enable the FCoE pause drop timeout to the default value of 500 milliseconds for edge or core ports:
• Cisco MDS NX-OS Release 8.1(1) and earlier releases
switch(config)# system default interface pause mode {core | edge}
• Cisco MDS NX-OS Release 8.2(1) and later releases
switch(config)# system timeout fcoe pause-drop default mode {core | edge}
Cisco MDS 9000 Series Interfaces Configuration Guide, Release 8.x
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Congestion Detection, Avoidance, and Isolation