Huawei Quidway S5000 Series Operation Manual page 15

Operation Manual - QoS/ACL
Quidway S5000 Series Ethernet Switches
of queue scheduling algorithms are Strict-Priority Queue (SP), Round Robin (RR) and
Weighted Round Robin (WRR).
1) SP
Packets sent via this
interface
Figure 2-1 SP
The SP is specially designed for the key service application. A significant feature of the
key service is requiring for priority to enjoy the service to reduce the responding delay
when congestion occurs. Take 8 egress queues for each port as example, SP divides
the queue of port into up to 8 kinds, from high-priority queue to low-priority queue
(which are shown as the Queue 7, 6, 5, 4, 3, 2, 1 and 0 in turn) with sequentially
reduced priority.
During the progress of queue dispatching, strictly following the priority order from high
to low, the SP gives preference to and sends the packets in the higher-priority queue
first. When the higher-priority queue is empty it will send the packets in the
lower-priority group. In this way, put the packets of higher priority service in the
higher-priority queue and put the packets of lower priority, like e-mail, in the
lower-priority queue, can guarantee the key service packets of higher priority are
transmitted first, while the packets of lower service priority are transmitted during the
idling gap between transmitting the packets of higher service priorities.
The SP also has the drawback that when congestion occurs, if there are many packets
queuing in the higher-priority queue, it will require a long time to transmit these packets
of higher service priority while the messages in the lower-priority queue
continuously set aside without service.
2) RR
high priority
Classify
Low priority
2-3
Chapter 2 QoS configuration
queue 7
queue 6
Packets sent
queue 5
queue 4
Dequeue Sending queue
queue 3
queue 2
queue 1
queue 0
are