Usage Information If the average queue size is more than the maximum threshold of WRED, the packet isdropped. If the average queue size is between the minimum and maximum thresholdvalues, the decision to drop or queue the packet is taken based on the packet dropprobability. The probability that a packet is dropped depends on the minimumthreshold, maximum threshold, and mark probability denominator.Example Dell(conf-qos-policy-out)# wred weight 5wred ecnTo indicate network congestion without dropping packets, use explicit congestion notification (ECN).C9000 SeriesSyntax wred ecnTo stop marking packets, use the no wred ecn command.Defaults noneCommand Modes QOS-POLICY-OUT modeCommand History This guide is platform-specific. For command information about other platforms, referto the relevant Dell Networking OS Command Line Reference Guide.The following is a list of the Dell Networking OS version history for this command.Version Description9.9(0.0) Introduced on the C9010.9.2(1.0) Introduced on the Z9500.8.3.19.0 Introduced on the S4820t.8.3.11.1 Introduced on the Z9000.8.3.7.0 Introduced on the S4810.Usage Information When you enable wred ecn, and the number of packets in the queue is below theminimum threshold, packets are transmitted per the usual WRED treatment.When you enable wred ecn, and the number of packets in the queue is between theminimum threshold and the maximum threshold, one of the following scenarios canoccur:• If the transmission endpoints are ECN-capable and traffic is congested, and theWRED algorithm determines that the packet should have been dropped based onthe drop probability, the packet is transmitted and marked so the routers knowthe system is congested and can slow transmission rates.Quality of Service (QoS) 1841
