H3C Technologies H3C S7500E Series Switches - Manual (Page 31)

2-3
Positions of the QoS Techniques in a Network
Figure 2-1 Positions of the QoS techniques in a network
As shown in Figure 2-1 , 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, differentiated services can be provided. Traffic classification uses
certain match criteria to organize packets with different characteristics into different classes.
Traffic classification is the basis for providing differentiated services.
z Traffic policing polices flows entering or leaving a device and can be applied in both inbound and
outbound directions of a port. When a flow exceeds the pre-set threshold, some restriction or
punishment measures can be taken to prevent overconsumption of network resources.
z Traffic shaping proactively adapts the output rate of traffic to the network resources available on
the downstream device to eliminate packet drop and delay. Traffic shaping is usually applied in
the outbound direction of a port.
z Congestion management provides a resource scheduling policy to arrange the forwarding
sequence of packets when congestion occurs. Congestion management is usually applied to the
outgoing traffic of a port.
z Congestion avoidance monitors the usage status of network resources and is usually applied to
the outgoing traffic of a port. As congestion becomes worse, it actively reduces the amount of
traffic by dropping packets.