Flow-based traffic accounting, Burst, Traffic mirroring – H3C Technologies H3C S3600 Series Switches User Manual
Page 743: Qos configuration
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In WRED algorithm, an upper limit and a lower limit are set for each queue, and the packets in a queue
are processed as follows.
z
When the current queue length is smaller than the lower limit, no packet is dropped;
z
When the queue length exceeds the upper limit, all the newly received packets are dropped;
z
When the queue length is between the lower limit and the upper limit, the newly received packets
are dropped at random. The longer the queue, the more likely the newly received packets may be
dropped. However, a maximum drop probability exists.
In WRED, random numbers are generated to determine the packets to be dropped. As the dropping
policy is determined by IP precedence, packets with lower precedence are more likely to be dropped.
WRED prevents global TCP session synchronization. It enables other TCP sessions to be free of a TCP
session slowed down because of its packets being dropped. In this way, TCP sessions can operate in
different rates in any case and the link bandwidth can be fully utilized.
Flow-based Traffic Accounting
The function of flow-based traffic accounting is to use ACL rules in traffic classification and perform
traffic accounting on the packets matching the ACL rules. You can get the statistics of the packets you
are interested in through this function.
Burst
The Burst function can provide better packet cache function and traffic forwarding performance. It is
suitable for networks where
z
Large amount of broadcast/multicast packets and large burst traffic exist.
z
Packets of high-rate links are forwarded to low-rate links or packets of multiple links with the equal
rates are forwarded to a single link that is of the same rate as that of the incoming links.
Although the burst function helps reduce the packet loss ratio and improve packet processing capability
in the networks mentioned above, it may affect QoS performance. So, use this function with caution.
Traffic mirroring
Traffic mirroring identifies traffic using ACLs and duplicates the matched packets to the destination
mirroring port or CPU depending on your configuration. For information about port mirroring, refer to the
Mirroring module of this manual.
QoS Configuration
Complete the following tasks to configure QoS:
Task
Remarks
Configuring Priority Trust Mode
Optional
Configuring the Mapping between 802.1p
Priority and Local Precedence
Optional
Setting the Priority of Protocol Packets
Optional
Optional
Optional
Optional