Displaying And Maintaining Wred; Wred Configuration Example; Network Requirements - HP 5920 Configuration Manual

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
× 2 , where n can be configured with the qos wred weighting-constant command.
-n
• Numerator for drop probability calculation in percentage—The larger the value is, the greater the
drop probability is.
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.
To configure and apply a WRED table:
Step
1. Enter system view.
2. Create a WRED table
and enter its view.
3. (Optional.) Set the
WRED exponent for
average queue size
calculation.
4. (Optional.) Configure
the other WRED
parameters.
5. (Optional.) Enable ECN
for a queue.
6. Enter interface view.
7. Apply the WRED table
to the interface.

Displaying and maintaining WRED

Execute display commands in any view.
Task
Display WRED configuration information on the
interface or all interfaces.
Display configuration information about a
WRED table or all WRED tables.

WRED configuration example

Network requirements

Apply a WRED table to interface Ten-GigabitEthernet 1/0/2, so that the packets are dropped as follows
when congestion occurs:
Command
system-view
qos wred queue table table-name
queue queue-value weighting-constant
exponent
queue queue-value [ drop-level drop-level ]
low-limit low-limit high-limit high-limit
[ discard-probability discard-prob ]
queue queue-value ecn
interface interface-type interface-number
qos wred apply [ table-name ]
Command
display qos wred interface [ interface-type
interface-number ]
display qos wred table [ name table-name ] [ slot
slot-number ]
54
) + current queue size
-n
Remarks
N/A
N/A
The default setting is 9.
By default, low-limit is 100,
high-limit is 1000, and
discard-prob is 10.
By default, ECN is not enabled
on any queue.
N/A
By default, no WRED table is
applied to an interface, and the
tail drop is used on an interface.