Study On The Establishment And Emulation Of Network QoS ModelBased On The Fairness Of Diffserv

Message Switch is one of the best ways to guarantee the message fluency in order to offer high quality service in the air communication of the North Air Management Bureau (NTAMB). The congestion of network, however, is likely to occur when thousands of messages come into the Unit Message-Switching system. The safety problem caused by message jam and message underreport has been concerned by researchers in this field. Optimization of the existed network is used to solve the problem in the thesis, which can avoid the problem by changing the structure of the network on theory to reduce the message jam. At present, the congestion of network only can be solved in the field of Quality of Service (QoS) of computer network. In the field of Message Switch, the research is focused on the Fairness problem of the differentiated services in congestion control.Integrated services (IntServ), differentiated services (DiffServ) and Multiprotocol Label Switching (MPLS) are adopted to improve the QoS of IP networks. Differentiated Services is widely recognized since its scalability. Network congestion is an important issue of network QoS. With the development of multimedia application, Fairness among different flows emerges. Consequently, network congestion can not be solved only depending on TCP congestion control which is implemented in source node. Router should actively play an important role in congestion control, so congestion control based on the middle node gradually becomes the main direction in current research. For DiffServ, the fairness means that every micro-flow in the same aggregated flow can fairly share the resources. Queue management is a component in the congestion control mechanism. The distributed active queue management has a similar architecture toDiffServ and can assure fair bandwidth allocation among flows. Integrating distributed active queue management with DiffServ model to solve the fairness problem is proposed.Fairness problem in the DiffServ model is mainly discussed in this paper. Firstly the concept of network congestion and the causes of the problem are introduced;then the congestion control mechanisms based on source node and on middle nodes are briefly described as the solution of the problem. Four active queue management algorithms are presented and the structure of DiffServ and its characteristics are discussed in detail. Finally, a modified model merging SCALE-WFS algorithm with DiffServ model is proposed to achieve fairness in DiffServ model. Simulated results and the analysis show that this model can improve the fairness in DiffServ networks.