Traffic Shaping - HP 1910 User Manual

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 50, 30, 10, 10, 50,
30, 10, and 10 (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.
All the queues are scheduled by WRR. You can assign the output queues to WRR priority queue group
1 and WRR priority queue group 2. Round robin queue scheduling is performed for group 1 first. If group
1 is empty, round robin queue scheduling is performed for group 2.
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.

Traffic shaping

Traffic shaping shapes the outbound traffic.
Generic traffic shaping (GTS) limits the outbound traffic rate by buffering exceeding traffic. You can use
traffic shaping to adapt the traffic output rate on a device to the input traffic rate of its connected device
to avoid packet loss.
The difference between traffic policing and GTS is that packets to be dropped with traffic policing are
retained in a buffer or queue with GTS, as shown in Figure 477. When enough tokens are in the token
bucket, the buffered packets are sent at an even rate. Traffic shaping can result in additional delay and
traffic policing does not.
Figure 477 GTS
For example, in Figure 478, Device B performs traffic policing on packets from Device A and drops
packets exceeding the limit. To avoid packet loss, you can perform traffic shaping on the outgoing
interface of Device A so packets exceeding the limit are cached in Device A. Once resources are
released, traffic shaping takes out the cached packets and sends them out.
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