Configuring Red - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - QUALITY OF SERVICE CONFIGURATION GUIDE 2010-09-22 Configuration Manual

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Configuring RED

Copyright © 2010, Juniper Networks, Inc.
WRED is an extension of RED that allows you to assign different RED drop thresholds to
each color of traffic. The router assigns a color to each packet. Committed means green,
conformed means yellow, and exceeded means red. When the queue fills above the
exceeded threshold, the router drops red packets, but still queues yellow and green
packets. When the queue fills above the conformed drop threshold, the router queues
only green packets.
Configuring RED on page 27
Configuring WRED on page 30
Each line module supports a default drop profile and 15 configurable drop profiles. You
can configure the default drop profile on all E Series line modules except for the ES2 10G
LM.
To configure RED:
Create a drop profile and enter Drop Profile Configuration mode.
1.
host1(config)#drop-profile internetDropProfile
host1(config-drop-profile)#
You can configure up to 16 drop profiles.
Set the average-length exponent, which specifies the exponent used to weight the
2.
average queue length over time, controlling WRED responsiveness.
host1(config-drop-profile)#average-length-exponent 9
Specifying an average-length exponent enables the RED average queue length
computation.
A higher value smooths out the average and slows WRED reaction to congestion
and decongestion, accommodating short bursts without dropping. Too large a value
can smooth the average to the point that WRED does not react at all.
A lower value speeds up WRED reaction. Too low a value can cause overreaction
to short bursts, dropping packets unnecessarily.
(Optional) Set the minimum and maximum threshold for committed traffic.
3.
host1(config-drop-profile)#committed-threshold percent 30 90 4
(Optional) Set the minimum and maximum threshold for conformed traffic.
4.
host1(config-drop-profile)#conformed-threshold percent 25 90 5
(Optional) Set the minimum and maximum threshold for exceeded traffic.
5.
host1(config-drop-profile)#exceeded-threshold percent 20 90 6
The thresholds specify a linear relationship between average queue length and drop
probability.
Chapter 4: Configuring Dropping Behavior with RED and WRED
27