Users Guide

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
– RST
– URG
In the existing software, ECE/CWR TCP flag qualifiers are not supported.
• Because this functionality forcibly marks all the packets matching the specific match criteria as ‘yellow’, Dell Networking OS
does not support Policer based coloring and this feature concurrently.
Quality of Service (QoS) 708