Owners Manual

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:
1. 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
2. Configure a WRED profile, 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. Configure another WRED profile, 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 buffer pool that is a shared buffer pool accessed by multiple queues when the
minimum guaranteed buffers for the queue are consumed. S4820T platform 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. Create a service class and associate the threshold weight of the shared buffer with each of the
queues per port in the egress direction.
INTERFACE mode
Dell(conf-if-te-0/8)#Service-class buffer shared-threshold-weight
Guidelines for Configuring ECN for Classifying and Color-
Marking Packets
Keep the following points in mind while configuring the marking and mapping of incoming packets using
ECN fields in IPv4 headers:
• Currently Dell Networking OS supports matching only the following TCP flags:
– ACK
– FIN
– SYN
– PSH
Quality of Service (QoS)
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