Concept Guide
Queue Conguration Service-Pool
Conguration
WRED Threshold
Relationship
Q threshold = Q-T,
Service pool threshold =
SP-T
Expected Functionality
1 0 0 X X Queue based WRED,
No ECN marking
1 X Q-T < SP-T
SP-T < Q-T SP based WRED,
No ECN marking
1 1 0 X X Queue-based ECN marking above queue threshold.
ECN marking to shared buer limits of the service-pool and
then packets are tail dropped.
1 X Q-T < SP-T
SP-T < Q-T Same as above but ECN marking starts above SP-T.
Conguring WRED and ECN Attributes
The functionality to congure a weight factor for the WRED and ECN functionality for backplane ports is supported on the platform.
WRED drops packets when the average queue length exceeds the congured threshold value to signify congestion. Explicit Congestion
Notication (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 congure 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 congure the weight factor for WRED and ECN capabilities, global buer pools for multiple queues, and associating a service class with
ECN marking, perform the following:
1 Congure the weight factor for the computation of average-queue size. This weight value applies to front-end ports.
QOS-POLICY-OUT mode
DellEMC(conf-qos-policy-out)#wred—profile weight number
2 Congure a WRED prole, and specify the threshold and maximum drop rate.
WRED mode
DellEMC(conf-wred) #wred—profile thresh-1
DellEMC(conf-wred) #threshold min 100 max 200 max-drop-rate 40
3 Congure another WRED prole, and specify the threshold and maximum drop rate.
WRED mode
DellEMC(conf-wred) #wred—profile thresh-2
DellEMC(conf-wred) #threshold min 300 max 400 max-drop-rate 80
4 Create a global buer pool that is a shared buer pool accessed by multiple queues when the minimum guaranteed buers for the
queue are consumed.
mode
DellEMC(conf) #service-pool wred green pool0 thresh-1 pool1 thresh-2
DellEMC(conf) #service-pool wred yellow pool0 thresh-3 pool1 thresh-4
DellEMC(conf) #service-pool wred weight pool0 11 pool1 4
700
Quality of Service (QoS)