Own in, Figure 5-3 – H3C Technologies H3C S5120 Series Switches User Manual

Page 365

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background image

5-3

Figure 5-3 Schematic diagram for WRR queuing

Queue 0 Weight 1

Queue 1 Weight 2

Queue 2 Weight 5

Queue 3 Weight 7

Packets to be sent through

this port

Sent packets

Interface

Queue

scheduling

Sending queue

Packet

classification

Assume there are four output queues on a port. WRR assigns each queue a weight value (represented

by w3, w2, w1, or w0) to decide the proportion of resources assigned to the queue. On a 100 Mbps port,

you can configure the weight values of WRR queuing to 50, 25, 25, and 25 (corresponding to w3, w2,

w1, and w0 respectively). In this way, the queue with the lowest priority is assured of 20 Mbps of

bandwidth at least, thus avoiding the disadvantage of SP queuing that packets in low-priority queues

may fail to be served for a long time.

Another advantage of WRR queuing is that while the queues are scheduled in turn, the service time for

each queue is not fixed, that is, if a queue is empty, the next queue will be scheduled immediately. This

improves bandwidth resource use efficiency.

The H3C S5120-SI Switch Series support group-based WRR queuing. You can assign output queues to

WRR queuing group 1 and WRR queuing group 2. The switch uses WRR queuing to schedule queues

in each group according to their weights, and then uses SP queuing to schedule the dequeued packets.

For example, assign queues 0 and 1 to WRR queuing group 1, with the weights 1 and 2 respectively,

and assign queues 2 and 3 to WRR queuing group 2, with the weights 1 and 3 respectively.

Figure 5-4

shows the scheduling process.

Figure 5-4 Scheduling process of WRR with two WRR queuing groups

Packets to be sent

through this interface

Queue 0 Weight 1

Queue 1 Weight 2

Queue 2 Weight 1

Queue 3 Weight 3

WRR Group1

WRR Group2

SP scheduling

Sending queue

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