Administrator Guide

WRED mode
threshold
Applying a WRED Profile to Traffic
After you create a WRED profile, you must specify to which traffic Dell Networking OS should apply the profile.
Dell Networking OS assigns a color (also called drop precedence) — red, yellow, or green — to each packet based on it DSCP
value before queuing it.
DSCP is a 6–bit field. Dell Networking uses the first three bits (LSB) of this field (DP) to determine the drop precedence.
● DP values of 110 and 100, 101 map to yellow; all other values map to green.
● If you do not configure Dell Networking OS to honor DSCP values on ingress (refer to Honoring DSCP Values on Ingress
Packets), all traffic defaults to green drop precedence.
● Assign a WRED profile to either yellow or green traffic.
QOS-POLICY-OUT mode
wred
Displaying Default and Configured WRED Profiles
To display the default and configured WRED profiles, use the following command.
● Display default and configured WRED profiles and their threshold values.
EXEC mode
show qos wred-profile
Displaying WRED Drop Statistics
To display WRED drop statistics, use the following command.
● Display the number of packets Dell Networking OS the WRED profile drops.
EXEC Privilege mode
show qos statistics wred-profile
Pre-Calculating Available QoS CAM Space
Before Dell Networking OS version 7.3.1, there was no way to measure the number of CAM entries a policy-map would consume
(the number of CAM entries that a rule uses is not predictable; from 1 to 16 entries might be used per rule depending upon its
complexity). Therefore, it was possible to apply to an interface a policy-map that requires more entries than are available. In
this case, the system writes as many entries as possible, and then generates an CAM-full error message (shown in the following
example). The partial policy-map configuration might cause unintentional system behavior.
%EX2YD:12 %DIFFSERV-2-DSA_QOS_CAM_INSTALL_FAILED: Not enough space in L3
Cam(PolicyQos) for class 2 (TeGi 12/20) entries on portpipe 1
The test cam-usage command allows you to verify that there are enough available CAM entries before applying a policy-map
to an interface so that you avoid exceeding the QoS CAM space and partial configurations. This command measures the size of
the specified policy-map and compares it to the available CAM space in a partition for a specified port-pipe.
Test the policy-map size against the CAM space for a specific port-pipe or all port-pipes using these commands:
● test cam-usage service-policy input policy-map {stack-unit } number port-set number
● test cam-usage service-policy input policy-map {stack-unit } all
The output of this command, shown in the following example, displays:
● The estimated number of CAM entries the policy-map will consume.
● Whether or not the policy-map can be applied.
● The number of interfaces in a port-pipe to which the policy-map can be applied.
Quality of Service (QoS)
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