The QoS techniques include traffic classification, traffic policing, traffic shaping, rate limit, congestion
management, and congestion avoidance. The following section briefly introduces these QoS techniques.
Figure 3 Position 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 a
class. You can provide differentiated services based on classes.
Traffic policing polices flows entering or leaving a device, and imposes penalties on traffic flows
that exceed the preset threshold to prevent aggressive use of network resources. You can apply
traffic policing to both incoming and outgoing traffic of a port.
To eliminate packet drops, traffic shaping proactively adapts the output rate of traffic to the network
resources available on the downstream device. Traffic shaping usually applies to the outgoing
traffic of a port.
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.
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
3, traffic classification, traffic shaping, traffic policing, congestion management, and