Class of Service Configuration 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 3-87

Queue Mode

CLI – The following sets the queue mode to strict priority service mode.

 

 

Console(config)#queue mode strict

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Console(config)#exit

 

Console#show queue mode

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Queue mode: strict

 

Console#

 

 

 

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 3-149,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 Table22 – 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)

22.CLI shows Queue ID.

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