1-3A more effective solution is to provide differentiated services for different applications through trafficcontrol and resource allocation. In this way, resources can be used more properly. During resourcesallocation and traffic control, the direct or indirect factors that might cause network congestion should becontrolled to reduce the probability of congestion. Once congestion occurs, resource allocation shouldbe performed according to the characteristics and demands of applications to minimize the effects ofcongestion on QoS.Major Traffic Management TechniquesEnd-to-end QoS modelFigure 1-2 End-to-end QoS modelAs shown in Figure 1-2, traffic classification, traffic policing, traffic shaping, congestion management,and congestion avoidance are the foundations for a network to provide differentiated services. Mainlythey implement the following functions:z Traffic classification uses certain match criteria to organize packets with different characteristicsinto different classes, and is the prerequisite for providing differentiated services. Trafficclassification is usually applied in the inbound direction of a port.z Traffic policing polices particular flows entering a device according to configured specifications andis usually applied in the inbound direction of a port. When a flow exceeds the specification, somerestriction or punishment measures can be taken to prevent overconsumption of networkresources and protect the commercial benefits of the carrier.z Traffic shaping proactively adjusts the output rate of traffic to adapt traffic to the network resourcesof the downstream device and avoid unnecessary packet drop and congestion. Traffic shaping isusually applied in the outbound direction of a port.z Congestion management provides measures for handling resource competition during networkcongestion and is usually applied in the outbound direction of a port. Generally, it stores packets inqueues, and then uses a scheduling algorithm to arrange the forwarding sequence of the packets.z Congestion avoidance monitors the usage status of network resources and is usually applied in theoutbound direction of a port. As congestion becomes worse, it actively reduces the amount of trafficby dropping packets.Among these traffic management technologies, traffic classification is the basis for providingdifferentiated services by classifying packets with certain match criteria. Traffic policing, traffic shaping,congestion management, and congestion avoidance manage network traffic and resources in differentways to realize differentiated services.
