A typical switch provides eight output queues per port. WRR assigns each queue a weight value (represented by w7, w6, w5, w4, w3, w2, w1, or w0) to decide the proportion of resources assigned to the queue. On a 100 Mbps port, you can set the weight values of WRR queuing to 25, 25, 15, 15, 5, 5, 5, and 5 (corresponding to w7, w6, w5, w4, w3, w2, w1, and w0, respectively). In this way, the queue with the lowest priority is assured of at least 5 Mbps of bandwidth, and the disadvantage of SP queuing (that packets in
Another advantage of WRR queuing is that while the queues are scheduled in turn, the service time for each queue is not fixed. If a queue is empty, the next queue will be scheduled immediately. This improves bandwidth resource use efficiency.
Basic WRR queuing contains multiple queues. You can configure the weight, percentage (or byte count) for each queue, and WRR schedules these queues based on the
You can implement SP+WRR queue scheduling on a port by assigning some queues on the port to the SP scheduling group when you configure WRR. Packets in the SP scheduling group are scheduled preferentially by SP. When the SP scheduling group is empty, the other queues are scheduled by WRR.
Rate limit
Rate limit is a traffic control method using token buckets. The rate limit of a physical interface specifies the maximum rate for forwarding packets (including critical packets). Rate limit can limit all the packets passing a physical interface.
Traffic evaluation and token bucket
A token bucket can be considered as a container holding a certain number of tokens. The system puts tokens into the bucket at a set rate. When the token bucket is full, the extra tokens will overflow.
Figure 460 Evaluate traffic with the token bucket
The evaluation for the traffic specification is based on whether the number of tokens in the bucket can meet the need of packet forwarding. If the number of tokens in the bucket is enough to forward the packets (usually, one token is associated with a
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