Huawei Quidway S3900 Series Operation Manual page 672

Operation Manual - QoS&QoS Profile
Quidway S3900 Series Ethernet Switches-Release 1510
Packets sent via this interface Packets sent via this interface Packets sent via this interface Packets sent via this interface
Figure 1-6 Diagram for WFQ
Before WFQ is introduced, you must understand fair queuing (FQ) first. FQ is designed
for the purpose of sharing network resources fairly and optimizing the delays and delay
jitters of all the flows. It takes the interests of all parties into account, such as:
Different queues are scheduled fairly, so the delay of each flow is balanced
globally.
Both short and long packets are scheduled fairly. When there are multiple long
packets and shorts packets to be sent among different queues, the short packets
must be scheduled preferentially, so that the delay jitters of packets of each flow is
reduced globally.
Compared with FQ, WFQ takes the priority into account when calculating the
scheduling sequence of packets. Statistically speaking, WFQ assigns more scheduling
chances to high priority packets than these to low priority packets. WFQ can classify
the traffic automatically according to the session information of traffic including the
protocol types, source and destination TCP or UDP port numbers, source and
destination IP addresses, and priority bits in the TOS area. WFQ also provide as many
queues as possible to accommodate each traffic evenly. Thus, the delay of each traffic
is balanced globally. When the packets dequeue, WFQ assigns the bandwidth for each
traffic on the egress according to the traffic precedence. The lower the traffic
precedence is, the less bandwidth the traffic gets. The higher the traffic precedence is,
the more bandwidth the traffic gets. Finally, each queue is polled and the corresponding
number of packets are taken out to be sent according to the proportion of bandwidth.
You can use the WFQ algorithm to assign bandwidth for queue 0 to queue 7, and then
decide which queue a traffic flows into according to the mapping between the COS
value of the traffic and the queue, and also deicide how much bandwidth is assigned to
each traffic.
3) WRR queue
queue1 weight1 queue1 weight1 queue1 weight1 queue1 weight1
queue2 weight2 queue2 weight2 queue2 weight2 queue2 weight2
...... ...... ...... ......
queueN- 1 weightN - 1 queueN- 1 weightN - 1 queueN -1 weightN - 1 queueN -1 weightN - 1
Classify Classify Classify Classify
queueN weightN queueN weightN queueN weightN queueN weightN
Huawei Technologies Proprietary
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Chapter 1 QoS Configuration
Packets sent Packets sent Packets sent Packets sent
Sending queue Sending queue Sending queue Sending queue
Dequeue Dequeue Dequeue Dequeue