R3303-HP HSR6800 Routers ACL and QoS Configuration Guide

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SP queuing
SP queuing is designed for mission-critical applications that require preferential service to reduce the
response delay when congestion occurs.
Figure 25 SP queuing
In Figure 25, SP queuing classifies eight queues on a port into eight classes, numbered 7 to 0 in
descending priority order.
SP queuing schedules the eight queues in the descending order of priority. SP queuing sends packets in
the queue with the highest priority first. When the queue with the highest priority is empty, it sends
packets in the queue with the second highest priority, and so on. You can assign mission-critical packets
to the high priority queue to make sure that they are always served first and common service packets to
the low priority queues and transmitted when the high priority queues are empty.
The disadvantage of SP queuing is that packets in the lower priority queues cannot be transmitted if
packets exist in the higher priority queues. This might cause lower priority traffic to starve to death.
The router supports basic SP queuing, which contains multiple queues, with each queue corresponding
to a different priority. These queues are scheduled in descending order of priority.
WRR queuing
WRR queuing schedules all the queues in turn to ensure every queue is served for a certain time, as
shown in Figure 26.