Dell C9000 series, Reference Manual

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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.
Quality of Service (QoS) 1841