Configuring Wred And Ecn Attributes - Dell S6000–ON Configuration Manual

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Table of Contents

Service-Pool

Configuration

Configuring WRED and ECN Attributes

The functionality to configure a weight factor for the WRED and ECN functionality for backplane ports is

supported on the Z9000 platform.

WRED drops packets when the average queue length exceeds the configured threshold value to signify

congestion. Explicit Congestion Notification (ECN) is a capability that enhances WRED by marking the

packets instead of causing WRED to drop them when the threshold value is exceeded. If you configure

ECN for WRED, devices employ this functionality of ECN to mark the packets and reduce the rate of

sending packets in a congested, heavily-loaded network.

To configure the weight factor for WRED and ECN capabilities, global buffer pools for multiple queues,

and associating a service class with ECN marking, perform the following:

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

front-end ports.

QOS-POLICY-OUT mode

Dell(conf-qos-policy-out)#wred—profile weight number

Configure a WRED profile, and specify the threshold and maximum drop rate.

Dell(conf-wred) #wred—profile thresh-1

Dell(conf-wred) #threshold min 100 max 200 max-drop-rate 40

Configure another WRED profile, and specify the threshold and maximum drop rate.

Dell(conf-wred) #wred—profile thresh-2

Dell(conf-wred) #threshold min 300 max 400 max-drop-rate 80

Create a global buffer pool that is a shared buffer pool accessed by multiple queues when the

minimum guaranteed buffers for the queue are consumed.

Dell(conf) #service-pool wred green pool0 thresh-1 pool1 thresh-2

Quality of Service (QoS)

WRED Threshold

Relationship

Q threshold = Q-

Service pool

threshold = SP-T

Expected Functionality

Queue-based ECN marking above queue

ECN marking to shared buffer limits of the

service-pool and then packets are tail dropped.

Same as above but ECN marking starts above