Analysis And Design Of AQM Based On State-Space Models For Stabilizing TCP

In the past decades,the Internet has evolved from an academic network founded by the U.S. Government to a global commercial network. With the rapid development of computer networks,more restrictive demands are made on them.Nowadays more and more real time services such as voice, image and critical data are transmitted on networks,and all of them are sensitive to bandwidth,transmission delay and delay jitter.this situation enrichen the network resources,but at the same time puts forward the question of how to assure the quality of service in networks.In the case of most connections linked to a bottle-necked node at the same time,networks that attempt to deliver more data than their capacity will experience congestion,causing buffers to overflow and leading to undesirable data losses.So traffic and congestion control are vital to the successful operation of ATM networks.This paper presents the back ground of congestion control and active queue management scheme,and analysizes the existed AQM scheme first.Then, The paper introduces the general network simulation software NS,and specified the implementation of AQM scheme with PID controller.Based on static PID model,this paper also proposes an adaptive control mechanism to improve the system stability and performance under changing network conditions.In order to understand them in depth,a simulation under the same conditions are supplied using NS.Then,we study the AQM algorithm based on state space.we find almost all the existed algorithms neglect the impact on performance caused by large delay.In this study,firstly a fact through simulation experiments is verified,which is the queues controlled by several typical AQM algorithms,the dramatic oscillations in large delay networks are appeared,which deceases the utilization of bottleneck link and introduces the avoidable delayjilltter.After some appropriate model approximation ,we putforwards three algorithms based state space. The new algorithm restricts the negative impact on the queue stability caused by the large delay .The simulation experimental results show that the negative impact on the queue stability caused by the large delay.The simulation experimental results show that the integrated performance of the proposed algorithm is obviously superior to that of the existed schemes...