Administrator Guide

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 two 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 weight
Configure the weight factor for computation of average-queue size. This weight value applies to front-end ports. This mechanism to
configure a weight for WRED and ECN functionality for front-end ports is supported on the S6000 and Z9000 platforms.
S6000–ON
Syntax
[no] wred weight number
Parameters
weight Define the weight factor to be used for computation of the WRED average-queue size to
either enable WRED to discard packets or cause ECN to mark packets that exceed the
minimum threshold configured. This setting applies to front-end ports only.
number Enter the weight as a number to be used to calculate the average-queue size. The range
is 1 to 15. The default is 0.
Default The default weight is zero.
Command Modes QOS-POLICY-OUT mode
Command History
Version Description
9.10(0.1) Introduced on the S6010-ON and S4048T-ON.
9.10(0.0) Introduced on the S6100-ON.
9.8(1.0) Introduced on the Z9100-ON.
9.7(0.0) Introduced on the S6000-ON.
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
DellEMC(conf-qos-policy-out) # wred weight 5
wred-profile
Create a WRED profile and name the profile.
S6000–ON
Syntax
wred-profile wred-profile-name
1226 Quality of Service (QoS)