Service Manual

Queue
Conguration
Service-Pool
Conguration
WRED Threshold
Relationship
Q threshold = Q-T,
Service pool threshold
= SP-T
Expected Functionality
1 X Q-T < SP-T ECN marking to shared buer limits of the service-pool and
then packets are tail dropped.
SP-T < Q-T Same as above but ECN marking starts above SP-T.
Conguring WRED and ECN Attributes
The functionality to congure 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 congured threshold value to signify congestion. Explicit
Congestion Notication (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 congure 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 congure the weight factor for WRED and ECN capabilities, global buer pools for multiple queues, and associating a service
class with ECN marking, perform the following:
1. Congure 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
2. Congure a WRED prole, and specify the threshold and maximum drop rate.
WRED mode
Dell(conf-wred) #wred—profile thresh-1
Dell(conf-wred) #threshold min 100 max 200 max-drop-rate 40
3. Congure another WRED prole, and specify the threshold and maximum drop rate.
WRED mode
Dell(conf-wred) #wred—profile thresh-2
Dell(conf-wred) #threshold min 300 max 400 max-drop-rate 80
4. Create a global buer pool that is a shared buer pool accessed by multiple queues when the minimum guaranteed buers for
the queue are consumed.
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
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Quality of Service (QoS)