Configuring No-Credit Timeout Value; Configuring Credit Loss Recovery Threshold And Action - Cisco MDS 9000 Series Configuration Manual

Chapter 2 Configuring Interfaces
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
To configure the stuck frame timeout value, follow these steps:
Command
Step 1
switch# config t
Step 2
switch(config)# system timeout
congestion-drop seconds mode E|F
switch(config)# system timeout
congestion-drop default mode E|F

Configuring No-Credit Timeout Value

When the port does not have the credits for the configured period, no-credit timeout can be enabled on
that port. This will result in all frames coming to that port getting dropped in the egress. This will free
the buffer space in the ISL link, which carries traffic for this port. This will help reduce fabric slow down
and congestion on other unrelated flows using the same link.
The frames that will be dropped would have just entered the switch or would have stayed in the switch
for the configured timeout value. These are preemptive drops and will clear the congestion completely
compared to the stuck frame timeout value.
No-credit timeout feature is disabled by default. We recommend that you retain the default configuration
for ISLs and configure a value not exceeding 500 ms (200 to 300 ms) for fabric F ports.
The no-credit timeout value and stuck frame timeout value are interlinked. The no-credit timeout value
Note
must always be greater than the stuck frame timeout value.
To configure the no-credit timeout value, follow these steps:
Command
Step 1
switch# config t
Step 2
switch(config)# system timeout
no-credit-drop seconds mode E|F
switch(config)# system timeout
no-credit-drop default mode E|F

Configuring Credit Loss Recovery Threshold and Action

When the port detects the credit loss condition and recovers, then the port can be error-disabled, a trap
can be sent with interface details, and a syslog can be generated with interface details. When the
configured threshold is exceeded, one or more of these actions can be combined together. These actions
can be turned on or off depending on situation. The port monitor feature provides the command line
interface to configure the thresholds and action.
The thresholds are that the credit loss recovery can be between 1 and 10 and the interval can be 1 second
to 1 hour. The default value is 3 in 10 minutes and generates a syslog.
When the port sees the credit loss condition and fails to recover, the port flaps. This function is already
part of port guard and so you can configure the supported actions using the Port Guard feature.
OL-19445-02, Cisco MDS NX-OS Release 4.2(x)
Configuring Slow Drain Device Detection and Congestion Avoidance
Purpose
Enters configuration mode.
Specifies the stuck frame timeout value in ms
and the port mode for the switch.
Specifies the default stuck frame timeout port
mode for the switch.
Purpose
Enters configuration mode.
Specifies the no-credit timeout value and port
mode for the switch.
Specifies the default no-credit timeout value port
mode for the switch.
Cisco MDS 9000 Family NX-OS Interfaces Configuration Guide
2-45