The Study On Fairness Problem Of TCP Protocol In Satellite Network And Protocol Simulation

The next generation satellite communication network has the characteristics of large bandwidth-delay product. A lot of new problems will appear in transplanting existing TCP protocol to such a new-type networks directly, the fairness problem is an important respect among them. This thesis focus on the fairness problem of TCP protocol in the next generation satellite communication network . First the reason of fairness problem of TCP being produced and the impact on TCP fairness brought by the characteristic of the satellite network is analyzed. Then the resolution is brought out from the angle of end system congestion control. The improvement to TCP is validated by simulation finally. The Groundwork of this thesis is listed as follow.1) At first this thesis utilizes the relevant definition of fairness to analyze the origin of fairness problem and the factor influences fairness from TCP congestion control mechanism and the idea of " Best Effort " with which TCP/IP offer service, then the influence factor model of the fairness is presented.2) After analyze the characteristics of the satellite networks, with the aid of the influence factor model of the fairness, the factors which influences fairness and the control mechanisms which correlates with these factors in the satellite networks are found out. From the viewpoint of congestion control of the end system, against the quality of service requirements of the fairness and special type of service, this thesis research and analyze the mechanism of congestion control in the existing TCP protocol.3) Then bring the idea of DiffServ into congestion control mechanism of end system and the SB-AIMD(Service Based AIMD ) mechanism is presented.4) To validate the proposed mechanism. By combining the ON/OFF mechanism of NS and Pareto distribution ,a HTTP traffic model which has the characteristic of statistical similar is set up and realized..5) At last, the topology which can reflect to the characteristic of satellites channel in NS emulation platform is put up. And the simulation and analysis to AIMD , CR (constant rate) and SB-AIMD algorithm in this environment are performed.