Class of Service Configuration
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3
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. WRR uses a predefined relative weight for each queue that
determines the percentage of service time the switch services each queue before
moving on to the next queue. This prevents the head-of-line blocking that can occur
with strict priority queuing.
Command Attributes
•WRR - Weighted Round-Robin shares bandwidth at the egress ports by using
scheduling weights 1, 2, 4, 6, 8, 10, 12, 14 for queues 0 through 7 respectively.
(This is the default selection.)
•Strict - Services the egress queues in sequential order, transmitting all traffic in the
higher priority queues before servicing lower priority queues.
Web – Click Priority, Queue Mode. Select Strict or WRR, then click Apply.
Figure 3-74. 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 3-127, the traffic classes are mapped to one of
the eight egress queues provided for each port. You can assign a weight to each of
these queues (and thereby to the corresponding traffic priorities). This weight sets
the frequency at which each queue will be polled for service, and subsequently
affects the response time for software applications assigned a specific priority value.
Command Attributes
•WRR Setting Table* – Displays a list of weights for each traffic class (i.e., queue).
•Weight Value – Set a new weight for the selected traffic class. (Range: 1-15)
* CLI shows Queue ID.
Console(config)#queue mode strict 4-192
Console(config)#exit
Console#show queue mode 4-195
Queue mode: strict
Console#