Class of Service Configuration3-1293Selecting the Queue ModeYou can set the switch to service the queues based on a strict rule that requires alltraffic in a higher priority queue to be processed before lower priority queues areserviced, or use Weighted Round-Robin (WRR) queuing that specifies a relativeweight of each queue. WRR uses a predefined relative weight for each queue thatdetermines the percentage of service time the switch services each queue beforemoving on to the next queue. This prevents the head-of-line blocking that can occurwith strict priority queuing.Command Attributes• WRR - Weighted Round-Robin shares bandwidth at the egress ports by usingscheduling 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 thehigher priority queues before servicing lower priority queues.Web – Click Priority, Queue Mode. Select Strict or WRR, then click Apply.Figure 3-74. Queue ModeCLI – The following sets the queue mode to strict priority service mode.Setting the Service Weight for Traffic ClassesThis switch uses the Weighted Round Robin (WRR) algorithm to determine thefrequency at which it services each priority queue. As described in “Mapping CoSValues to Egress Queues” on page 3-127, the traffic classes are mapped to one ofthe eight egress queues provided for each port. You can assign a weight to each ofthese queues (and thereby to the corresponding traffic priorities). This weight setsthe frequency at which each queue will be polled for service, and subsequentlyaffects 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 4-192Console(config)#exitConsole#show queue mode 4-195Queue mode: strictConsole#
