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700 CHAPTER 50: CONGESTION AVOIDANCE
exponent is the filtering coefficient for calculating the average queue length, and
the range of the value is 1 to 16, and the default value is 9.
When exponent=0 and the queue length exceeds the threshold, WRED will act
accordingly. When exponent is higher, WRED will act slowly to the change of
queue status.
This configuration should be performed after enabling WRED in the interface view.
Set the Priority
Parameters for WRED
You can set WRED drop lower threshold value, upper threshold value, and drip
probability denominator according to packet priority. The reciprocal value of the
denominator discard-prob will be taken as the maximum drop probability. The
system will handle the queues according to the length of the queues.
■ If the queue length is lower than the low-limit, no packet will be dropped.
■ If the queue length is between low-limit and high-limit, the drop probability
will increase with the queue length till it is almost equal to the reciprocal value
of discard-prob.
■ If the queue length is equal to or greater than high-limit, all the packets will be
dropped.
Please perform the following configurations in the interface view.
Table 740 Configure the Related Parameters for the Packets of Specific IP Priority
ip-precedence is the IP precedence, and the range of the value is 0 to 7.
low-limit and high-limit are the minimum and maximum thresholds respectively.
The default values are 10 and 30 respectively, and the range of the value is 1 to
1024.
discard-prob is the drop probability denominator and its default value is 10. The
reciprocal of discard-prob will be the maximum drop probability. The range of this
parameter is 1 to 255.
It should be noted that this configuration can only be performed after WRED is
enabled in interface view.
Configure the WRED weighted factor for
calculating the WRED average queue
length.
qos wred weighting-constant exponent
Recover the default value of the WRED
weighted factor for calculating the WRED
average queue length.
undo qos wred weighting-constant
Operation Command
Configure the related parameters for the
packets of specific IP priority
qos wred ip-precedence ip-precedence
low-limit low-limit high-limit
high-limit discard-probability
discard-prob
Recover the default values of the related
parameters for the packets of specific IP
priority
undo qos wred ip-precedence
ip-precedence