Reference Guide

wred-ecn
To indicate network congestion, rather than dropping packets, use explicit congestion notification (ECN).
Z-Series
Syntax
wred-ecn
To stop marking packets, use the no wred-ecn command.
Defaults none
Command Modes CONFIGURATION (conf-qos-policy-out)
Command History
This guide is platform-specific. For command information about other platforms, refer to the
relevant FTOS Command Line Reference Guide .
The following is a list of the FTOS version history for this command.
Version 8.3.19.0 Introduced on the S4820t.
Version 8.3.11.1 Introduced on the Z9000.
Version 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 three 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.
• If the network is experiencing congestion, the packet is transmitted. No further
marking is required.
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.
Z9000
Syntax
wred-profile wred-profile-name
To remove an existing WRED profile, use the no wred-profile command.
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