On Congestion Control Of Networks Based On Active Queue Management

With the development of computer Internet, the number of users and the network applications is increasing dramatically, which resulted in more and more serious network congestion. So the further development of the Internet is seriously hindered. Thus, the congestion control of the Internet is an important problem. Therefore, the network congestion control is the main way to improve the network performance and reform the service quality. The investigation of the network congestion control is important not only in the theory but also in the application.In the beginning of this paper, we give introduce the back grounds and causes of Internet congestion phenomenon, and also the problems of the congestion control algorithms nowadays. We expatiate the definition of congestion, congestion collapse and congestion control. This paper also describes and compares some significant TCP/IP congestion control algorisms in detail, and researches some novel research method and results in the Internet congestion control with the perspective of classic control system.Then we talk control theory about congestion control of networks based on active queue management. Because RED and its modified algorithm depend on the intuition, they are lack of systematical and theoretical, this paper refers the simplification model based on the fluid stream theory proposed by on Misra has been. Based on this model, the P controller, PI controller and PID controller is applied in the congestion control, and then comparing simulation results about the controller of RED, PI and PID. Through the simulation curves we can see, used the PID controller can improve the speed of response and the overshoot, but the queue curve has buffet.From the theory and experiment, we know that the PI controller has long time response and under the PID controller the system has over modulation. This paper make a new method improved GA-based PID active queue management control. We describe the details of the PID controller design. In the thesis, making comparing the performance of genetic algorithm with other algorithms. We can see its performance better than others. From the simulation we can see it has better control than others such as RED and PI. It has better performance.Finally, the conclusion and prospect which base on congestion control of networks based on active queue management are presented in this thesis.