5-3
Applying QoS Techniques in a Network
Figure 5-1 Positions of the QoS techniques in a network
As shown in
Figure 5-1, traffic classification, traffic shaping, traffic policing, congestion management,
and congestion avoidance mainly implement the following functions:
z Traffic classification uses certain match criteria to assign packets with the same characteristics to a
class. Based on classes, you can provide differentiated services.
z Traffic policing polices flows entering or leaving an AP, and imposes penalties on traffic flows that
exceed the pre-set threshold to prevent aggressive use of network resources. You can apply traffic
policing to both incoming and outgoing traffic of a port.
z Traffic shaping proactively adapts the output rate of traffic to the network resources available on
the downstream AP to eliminate packet drops. Traffic shaping usually applies to the outgoing traffic
of a port.
z Congestion management provides a resource scheduling policy to determine the packet
forwarding sequence when congestion occurs. Congestion management usually applies to the
outgoing traffic of a port.
z Congestion avoidance monitors the network resource usage and is usually applied to the outgoing
traffic of a port. When congestion worsens, congestion avoidance actively reduces the queue
length by dropping packets.
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