Deployment Guide

Dell(conf-qos-policy-out)#wred weight number
2. Configure one or more WRED profiles, and specify the threshold and maximum drop rate
WRED mode
Dell(conf-wred)#wred thresh-1
Dell(conf-wred)#threshold min 100 max 200 max-drop-rate 40
Dell(conf-wred)#wred thresh-2
Dell(conf-wred)#threshold min 300 max 400 max-drop-rate 80
3. Associate a service class for each WRED profile, and assign the WRED profile to specific queues on backplane ports.
CONFIGURATION mode
Dell(conf)#service-class wred green queue5 thresh-1 queue7 thresh-2 backplane
Dell(conf)#service-class wred yellow queue1 thresh-2 queue3 thresh-1 backplane
Dell(conf)#service-class wred weight queue0 11 queue6 4 queue7 9 backplane
4. Create a global buffer pool that serves as a shared buffer accessed by multiple queues when the minimum guaranteed
buffers for a queue are consumed. The switch supports four global service-pools in the egress direction.
mode
Dell(conf)#service-pool wred green pool0 thresh-1 pool1 thresh-2
Dell(conf)#service-pool wred yellow pool0 thresh-3 pool1 thresh-4
Dell(conf)#service-pool wred weight pool0 11 pool1 4
5. Enable ECN marking on specific queues on backplane ports with a service class.
CONFIGURATION mode
Dell(conf)#service-class wred ecn 0, 3-5, 7 backplane
Pre-Calculating Available QoS CAM Space
Pre-calculating available QoS CAM space allows you to measure the number of CAM entries a policy-map consumes.
This feature allows you to avoid applying a policy-map on an interface that requires more CAM entries than are available
and receive a 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 (Te 12/20) entries on portpipe 1 for linecard 12
%EX2YD:12 %DIFFSERV-2-
DSA_QOS_CAM_INSTALL_FAILED: Not enough space in L3 Cam(PolicyQos) for class 5 (Te
12/
22) entries on portpipe 1 for linecard 12
Use the test cam-usage command 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 linecard {0–2} number port-set number
● test cam-usage service-policy input policy-map linecard {0–2} 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.
Specifically:
● Available CAM — the available number of CAM entries in the specified CAM partition for the specified line-card port pipe.
● Estimated CAM — the estimated number of CAM entries that the policy will consume when it is applied to an interface.
● Status — indicates whether the specified policy-map can be completely applied to an interface in the port-pipe.
Quality of Service (QoS)
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