R211x-HP Flexfabric 11900 ACL and QoS Configuration Guide

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• Upper threshold and lower threshold—When the average queue size is smaller than the lower
threshold, packets are not dropped. When the average queue size is between the lower threshold
and the upper threshold, the packets are dropped based on the user-configured drop probability.
When the average queue size exceeds the upper threshold, subsequent packets are dropped.
• Drop priority—A parameter used for packet drop. The value 0 corresponds to green packets, the
value 1 corresponds to yellow packets, and the value 2 corresponds to red packets.
• Exponent used for average queue size calculation—The bigger the exponent is, the less sensitive
the average queue size is to real-time queue size changes. The average queue size is calculated
using the formula: average queue size = previous average queue size × (1-2
-n
) + current queue size
× 2
-n
, where n can be configured with the qos wred weighting-constant command.
• Numerator for drop probability calculation in percentage—The larger the value is, the greater the
drop probability is.
To configure and apply a WRED table:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Create a WRED table
and enter its view.
qos wred queue table table-name N/A
3. (Optional.) Set the
WRED exponent for
average queue size
calculation.
queue queue-value weighting-constant
exponent
The default setting is 9.
4. (Optional.) Configure
the other WRED
parameters.
queue queue-value [ drop-level drop-level ]
low-limit low-limit high-limit high-limit
[ discard-probability discard-prob ]
By default, low-limit is 100,
high-limit is 1000, and
discard-prob is 10.
5. (Optional.) Enable ECN
for a queue.
queue queue-value ecn
By default, ECN is not enabled
on any queue.
6. Enter interface view.
interface interface-type interface-number N/A
7. Apply the WRED table
to the interface.
qos wred apply [ table-name ]
By default, no WRED table is
applied to an interface, and tail
drop is used.
A WRED table can be applied to
multiple interfaces. For a WRED
table already applied to an
interface, you can modify the
values of the WRED table, but
you cannot remove the WRED
table.
Displaying and maintaining WRED
Execute display commands in any view.
Task Command
Display the WRED configuration of a specified
interface or all interfaces.
display qos wred interface [ interface-type
interface-number ]