Congestion Control Policy And Improvement Based On TCP

With the development of computer and communication technology, it is more and more indescribable that the people's demand in the Internet, so the more and the better control mechanisms which could smooth the network act very important actions, the congestion control is one of the crux, that is how avoid or eliminate the congestion in the network availability, so as to the network runs in the best and the low-grade congest state basically.Congestion stems from the disequilibrium about the resource and the flux in the network, it will not eliminate since the improvement of the network process ability. To this day, the congestion's problem hasn't a perfect solution scheme all the while. Face to the multifarious environment of the network, there are a certain difficulties not only in the design about the algorithm of the congestion control, but also in the function comparison of those protocols which need some centralized normals. According to the position of the algorithm achieve, they are falled into two algorithms: Source algorithm and Link algorithm, Source algorithm is performed at the mainframe and the end machines, it regulates the sending rate according the feedback information; Link algorithm is performed at the network equipments, such as the router and the switch, it examines the network congestion happen, and brings the feedback information. The crux is how brings the feedback information and responses them.TCP protocol is the most widely used in Source algorithm, and also the main popular transmission protocol, which consists of four epochs, that is Slow Start, Congestion Avoidance, Fast Transmission and Fast Discovery, the core algorithm of Congestion Avoidance uses a mechanism called AIMD (Additive Increase Multiplicative Decrease). Though TCP protocol has come through several improved versions, at this high speed wide network period, it obvious more and more localizations, especially its too slow response to the large windows, and too fast decrease when the congestion happened.Recently in these years, based on TCP protocol, some new improvement protocols have been put forward, such as HSTCP, STCP, H-TCP, Fast-TCP, BIC and CUBIC, these protocols have announced their improved algorithms, their properties'comparisons and estimations about the Scalability, Stability, TCP friendliness, RTT fairness and so on, they promote the network capability and the higher delicacy in the congestion epoch. Since they have their own advantages at the algorithms and implements, but none could solution all the problems in the network, come to a briefer and robuster congestion control protocol. The congestion control of Source algorithm needs go deeper into research, especially at the protocol parameters amendment. How to balance these properties still need our discussing.Therefore, my paper starts from the comparison and the analysis between STCP and CUBIC which show the good properties, through a large number simulation experiments, compares the movement of the cwnd (congestion window), throughput, Scalability, Stability, TCP friendliness and RTT fairness etc, to find the combine from these results, and proves CUBIC which is the better. From the experiments'results we find that...