3Com 3C13636 Configuration Manual page 1294

3Com Router 3000 Ethernet Family
Configuration Guide
Congestion avoidance: Exceeding congestion consumes network resources.
Congestion avoidance can monitor the usage status of network resources, and as
congestion becomes worse actively take the policy of dropping packets through
adjusting traffic, to resolve the overloading of the network.
Traffic shaping: A traffic control measure of actively adjusting the output speed of
traffics, generally it can enable the traffic to adapt to the network resources
supplied by the downstream router, to prevent the unwanted packet dropping and
congestion. Same as traffic policing, traffic shaping is implemented at the IP layer.
Physical-interface LR: Unlike traffic policing, which can handle only packets that
are processed at the IP layer, LR restricts all packets on physical interfaces and
thus is well suited to the situation where rate limiting on all packets is desired.
Among those traffic management technologies, traffic classification is the basis. It is a
prerequisite for differentiated service, which identifies the interested packet with certain
matching rule. As for traffic policing, traffic shaping, congestion management and
congestion avoidance, they implement management to network traffic and allocated
resources from different aspects respectively to realize the differentiated service.
Normally, QoS provides the following functions:
Traffic classification
Traffic policing and shaping
Congestion management
Congestion avoidance
3Com Corporation
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Chapter 1 QoS Overview