HP FlexNetwork NJ5000, User Manual

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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 low-priority queues might fail to be served for a long time) is avoided.
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 user-defined parameters in
a round robin manner.
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 443 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 1-bit forwarding authority), the traffic conforms to
the specification, and the traffic is called "conforming traffic." Otherwise, the traffic does not conform
to the specification, and the traffic is called "excess traffic."
A token bucket has the following configurable parameters:
•
Mean rate
—Rate at which tokens are put into the bucket, or the permitted average rate of traffic.
It is usually set to the committed information rate (CIR).