67
Figure 25 SP queuing
In
, 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 WRR queuing
Queue 0 Weight 1
……
Queue 1 Weight 2
Queue N-2 Weight N-1
Queue N-1 Weight N
Packets to be sent through
this port
Sent packets
Interface
Queue
scheduling
Sending queue
Packet
classification
