3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 4 Congestion Avoidance3Com Corporation4-3incoming packetsqueue1 weight1queue2 weight2classifyoutgoing packetsqueueN-1 weightN-1queueN weightNtransmitqueueinterface……scheduler……WRED dropDiscardedpacketsFigure 4-1 Relation between WRED and Queue mechanismAssociating WRED with WFQ, the flow-based WRED can be realized. Becausedifferent flow has its own queue during packet classification, the flow with small trafficalways has a short queue length, so the packet dropping probability will be small. Theflow with high traffic will have the longer queue length and will drop more packets, sowe can protect the benefits of the flow with small traffic.4.2 WRED ConfigurationWRED configuration includes:z Enable WREDz Set WRED exponent for mean queue length calculationz Set WRED parameters for each precedence4.2.1 Enabling WREDPerform the following configuration in interface view.Table 4-1 Enable WREDOperation CommandEnable WRED qos wredRestore default undo qos wredWRED cannot be used independently or with the queuing methods but WFQ.By default, WRED is not used and the dropping method is tail drop.
