DELL 9.7(0.0) User Manual

Queue

Configuration

Service-Pool

Configuration

WRED Threshold

Relationship

Q threshold = Q-T

Service-pool threshold =

SP-T

Expected Functionality

Enabled Enabled Disabled N/A

N/A

Queue-based ECN marking above

queue threshold.

ECN marking up to shared buffer

limits of the service-pool and then

packets are tail dropped.

Enabled

N/A

Q-T < SP-T

SP-T < Q-T

Same as above but ECN marking

starts above SP-T.

Configuring a Weight for WRED and ECN Operation

You can configure a WRED weight to customize WRED and ECN operation on a front-end or backplane

interface. In the configuration procedure, you must also configure the global service-pools of shared

buffer memory that can be accessed by multiple queues when the minimum guaranteed buffers for a

queue are consumed.

Configure the weight factor for computation of average-queue size. This weight value applies to

front-end and backplane ports.
QOS-POLICY-OUT mode

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 Z9500 supports four global service-
pools in the egress direction.

746

Quality of Service (QoS)