Administrator Guide

Command
History
Version Description
9.9(0.0) Introduced on the C9010.
9.2.1.0 Introduced on the Z9500 switch.
9.3.0.0 Introduced on the S6000 and Z9000 platforms
Usage
Information
If the average queue size is more than the maximum threshold of WRED, the packet is dropped. If the
average queue size is between the minimum and maximum threshold values, the decision to drop or queue
the packet is taken based on the packet drop probability. The probability that a packet is dropped
depends on the minimum threshold, maximum threshold, and mark probability denominator.
Example
Dell(conf-qos-policy-out)# wred weight 5
wred ecn
To indicate network congestion without dropping packets, use explicit congestion notification (ECN).
C9000 Series
Syntax
wred ecn
To stop marking packets, use the no wred ecn command.
Defaults none
Command Modes QOS-POLICY-OUT mode
Command
History
This guide is platform-specific. For command information about other platforms, refer to 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 Description
9.9(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 the minimum threshold,
packets are transmitted per the usual WRED treatment.
When you enable wred ecn, and the number of packets in the queue is between the minimum threshold
and the maximum threshold, one of the following scenarios can occur:
● If the transmission endpoints are ECN-capable and traffic is congested, and the WRED algorithm
determines that the packet should have been dropped based on the drop probability, the packet is
transmitted and marked so the routers know the system is congested and can slow transmission rates.
● If neither endpoint is ECN-capable, the packet may be dropped based on the WRED drop probability.
This behavior is the identical treatment that a packet receives when WRED is enabled without ECN
configured on the router.
When you enable wred ecn, and the number of packets in the queue is above the maximum threshold,
packets are dropped based on the drop probability. This behavior is the identical treatment a packet
receives when WRED is enabled without ECN configured on the router.
Related
Commands
wred-profile — creates a WRED profile and name that profile.
Quality of Service (QoS) 1449