Configuration Procedure; Configuration Example - HP FlexFabric 5700 series Configuration Manual

Upper limit and lower limit—When the average queue size is smaller than the lower limit, packets
•
are not dropped. When the average queue size is between the lower limit and the upper limit, the
packets are dropped based on the user-configured drop probability. When the average queue size
exceeds the upper limit, subsequent packets are dropped.
• Drop precedence—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. Red packets
are dropped preferentially.
Exponent for average queue size calculation—The greater the exponent, the less sensitive the
•
average queue size is to real-time queue size changes. The formula for calculating the average
queue size is average queue size = (previous average queue size x (1 – 2
x 2 ), where n is the exponent.
–n
Drop probability in percentage—The larger the value is, the greater the drop probability is.
•

Configuration procedure

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 drop
parameters.
5. (Optional.) Enable ECN for
a queue.
6. Enter Ethernet interface view.
7. Apply the WRED table to the
interface.

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:
For the interface to preferentially forward higher-priority traffic, set a lower drop probability for a
•
queue with a greater queue ID. Set different drop parameters for queue 0, queue 3, and queue 7.
Drop packets according to their colors.
•
Command
system-view
qos wred queue table table-name
queue queue-id weighting-constant
exponent
queue queue-id [ drop-level drop-level ]
low-limit low-limit high-limit high-limit
[ discard-probability discard-prob ]
queue queue-id ecn
interface interface-type
interface-number
qos wred apply [ table-name ]
60
)) + (current queue size
–n
Remarks
N/A
N/A
The default setting is 9.
By default, the low limit is 100,
the high limit is 1000, and the
drop probability is 10%.
By default, ECN is not enabled
on any queue.
N/A
By default, no WRED table is
applied to an interface, and tail
drop is used on an interface.