H3C Technologies H3C S12500 Series Switches - Manual (Page 54)

45
SP queuing
SP queuing is designed for mission-critical applications, which require preferential service to reduce the
response delay when congestion occurs.
Figure 11 SP queuing
As shown in Figure 11 , 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. It 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 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.
WRR queuing
WRR queuing schedules all the queues in turn to make sure every queue is be served for a certain time,
as shown in Figure 12 .
Queue 7
Queue 6
Queue 1
Queue 0
……
Packets to be sent through
this port
Packet
classification
High priority
Low priority
Sent packets
Interface
Sending queue
Queue
scheduling