QoS techniques
The QoS techniques include traffic classification, traffic policing, traffic shaping, line rate, congestion
management, and congestion avoidance. They address problems that arise at different positions of a
network.
Figure 4 Placement of the QoS techniques in a network
As shown in
congestion avoidance mainly implement the following functions:
Traffic classification—Uses certain match criteria to assign packets with the same characteristics to
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a class. Based on classes, you can provide differentiated services.
Traffic policing—Polices flows entering or leaving a device, and imposes penalties on traffic flows
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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.
Traffic shaping—Proactively adapts the output rate of traffic to the network resources available on
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the downstream device to eliminate packet drops. Traffic shaping usually applies to the outgoing
traffic of a port.
Congestion management—Provides a resource scheduling policy to determine the packet
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forwarding sequence when congestion occurs. Congestion management usually applies to the
outgoing traffic of a port.
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Congestion avoidance—Monitors the network resource usage, and is usually applied to the
outgoing traffic of a port. When congestion worsens, congestion avoidance reduces the queue
length by dropping packets.
Figure
4, traffic classification, traffic shaping, traffic policing, congestion management, and
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