Administrator Guide

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.
wred-profile
Create a WRED profile and name the profile.
C9000 Series
Syntax
wred-profile wred-profile-name
To remove an existing WRED profile, use the no wred-profile command.
1340 Quality of Service (QoS)