Administrator Guide

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 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
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
Quality of Service (QoS) 1247