3Com 8800 Configuration Manual page 402

3Com Switch 8800 Configuration Guide
1) Tail drop mode: Different queues (red, yellow and red) are allocated with different
drop thresholds. When these thresholds are exceeded respectively, excessive
packets will be dropped.
2) WRED drop mode: Drop precedence is taken into account in drop action. When
only min-thresholds of red, yellow and green packets are exceeded, excessive
packets are dropped randomly at given probability. But when max-thresholds of
red, yellow and green packets are exceeded, all excessive packets will be
dropped.
You must first configure WRED parameters for every outbound queue in defining drop
precedence.
I. Configuring WRED parameters
The switch provides four sets of default WRED parameters, respectively numbered as
0 to 3. Each set includes 80 parameters, 10 parameters for each of the eight queues.
The ten parameters are green-min-threshold, yellow-min-threshold, red-min-threshold,
green-max-threshold, yellow-max-threshold, red-max-threshold, green-max-prob,
yellow-max-prob, red-max-prob and exponent. Red, yellow and green packets
respectively refer to those with drop precedence levels 2, 1 and 0.
Perform the following configurations in the specified views.
Table 33-11 Configure WRED parameters
Enter WRED index view (system view)
Restore the default WRED parameters
(system view)
Configure WRED parameters (WRED
index view)
Restore the default WRED parameters
(WRED index)
Exit WRED index view (WRED index
view)
The command restores the parameters of the specified WRED index as the default
setting. The command restores the WRED parameters related to the queue as the
default setting.
The switch provides four sets of WRED parameters by default.
See the corresponding Command Manual for details of the commands.
Operation
33-18
Chapter 33 QoS Configuration
Command
wred wred-index
undo wred wred-index
queue queue-id green-min-threshold
green-max-threshold
yellow-min-threshold
yellow-max-threshold yellow-max-prob
red-min-threshold red-max-threshold
red-max-prob exponent
undo queue queue-id
quit
green-max-prob