Traffic Mirroring; Traffic Counting; Red - Huawei Quidway S6500 Series Operation Manual

Operation Manual - QoS/ACL
Quidway S6500 Series Ethernet Switches
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) WRR
The round scheduling ensures every queue gets some time of service of the switch port.
Take 4 egress queues for each port as example, WRR gives every queue a weight (w3,
w2, w1, and w0 respectively) for resource obtaining. For example, you can configure
the weight value of the WRR algorithm for 100M port as 5, 3, 1, 1, 5, 3, 1, 1
(corresponding to the w7, w6, w5, w4, w3, w2, w1 and w0 respectively). Thus the
low-priority queue can be guaranteed to get the minimum bandwidth of 5Mbps,
avoiding the case in SP scheduling that the messages in the lower-priority queues may
not get any service for long time. Another advantage of WRR queue is that the service
time is assigned to each queue flexibly, although it is the round multiple queue
scheduling. When a queue is empty, it will switch to the next queue immediately,
thereby making good used of the bandwidth resource.

2.1.10 Traffic Mirroring

The traffic mirroring function is carried out by copying the specified data packets to the
monitoring port for network diagnosis and troubleshooting.

2.1.11 Traffic Counting

With the flow-based traffic counting, you can request a traffic count to count and
analyze the packets.

2.1.12 RED

When the congestion reaches a certain degree, S6506 Switch can select some frames
to drop, using RED algorithm. On one hand, it can alleviate the excessive congestion.
On the other hand, the global TCP synchronization caused by Tail-Drop algorithm can
be avoided.
In RED algorithm, every queue has a pair of high-low limits. It also regulates that:
If the queue length is smaller than the low limit, no packet will be discarded.
If the queue length is greater than the high limit, all the packets arrived later will be
discarded.
If the queue length is between the high-low limits, the packets arrived will be
discarded randomly. Every arrived packet will be given a random number.
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Chapter 2 QoS Configuration
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