Configuring the Switch
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Selecting the Queue Mode
You can set the switch to service the queues based on a strict rule that requires all
traffic in a higher priority queue to be processed before lower priority queues are
serviced, or use Weighted Round-Robin (WRR) queuing that specifies a relative
weight of each queue, or you can choose a hybrid of these two methods. WRR uses
a relative weighting for each queue which determines the amount of packets the
switch transmits every time it services each queue before moving on to the next
queue. Thus, a queue weighted 8 will be allowed to transmit up to 8 packets, after
which the next lower priority queue will be serviced according to it’s weighting. This
prevents the head-of-line blocking that can occur with strict priority queuing. When
configured for hybrid priority queuing mode, the switch will always employ strict
priority queuing for the highest priority queue (queue 3), before processing queues 2
through 0 according to their WRR weights.
Command Attributes
• WRR - Weighted Round-Robin shares bandwidth at the egress ports by using
scheduling weights with default values of 1, 2, 4, 8, for queues 0 through 3,
respectively. (Range: 1-15)
• Strict - Services the egress queues in sequential order, transmitting all traffic in the
higher priority queues before servicing lower priority queues.
• Hybrid - Services the highest priority queue (3) according to strict priority queuing,
after which the 3 lower priority queues (0, 1, 2) are processed according to their
WRR weightings.
Web – Click Priority, Queue Mode. Select Strict, WRR, or Hybrid, then click Apply.
Figure 3-114 Queue Mode
CLI – The following sets the queue mode to strict priority service mode.
Setting the Service Weight for Traffic Classes
This switch uses the Weighted Round Robin (WRR) algorithm to determine the
frequency at which it services each priority queue. As described in “Mapping CoS
Values to Egress Queues” on page 3-182, the traffic classes are mapped to one of
the eight egress queues provided for each port. You can assign a weight to each of
Console(config)#queue mode strict 4-247
Console(config)#exit
Console#show queue mode 4-251
Queue mode: strict
Console#
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