Research On Congestion Control Of SCPS-TP

With the rapid development of the Internet, the TCP/IP protocol has been adopted by the comminucation system on the ground, so it can support the application of various complex requirements, so as to realize the unification of ground communication protocol. If the satellite system which has complex task and dosen’t have unified standards uses the autonomous development of the situation,it will lead to badly combined with the ground network application,so we must use the internetwork protocol conversion agreement.SCPS protocol was presented at the end of the last century, the purpose of the study is not only compatible with terrestrial Internet and high-speed data transmission can support reliable, support multi node parallel tasks between network routing function selection, and has good interoperability and ground. The SCPS protocol solves many problems exist, For example: low signal intensity, strong channel noise, long transmission delay, bandwidth and delay product and link to interrupt.So SCPS protocol is widely used in the space communication networkFirstly,this thesis summarizes the SCPS-TP protocol’s application in many countries and the work to improve SCPS-TP protocol,and then make a detailed description of the SCPS-TP protocol to improve the traditional TCP congestion control algorithm. The simulation of NS2, points out that the Vegas protocol packet has burst phenomenon and premature enters the congestion avoidance phase to affect transmission performance, in the congestion avoidance phase, Vegas cwnd has linear growth, can not use all bandwidth as soon as possible. To solve the above problems, the third chapter of this thesis improves the Vegas algorithm in two aspects: in the slow start phase packet has burst phenomenon, so that the Vegas algorithm the premature ends the slow start phase, this section algorithm uses each RTT half of the increase. At the congestion avoidance phase, window growth does not as soon as possible to make full use of bandwidth, this section algorithm adopts adaptive window growth strategy. Through NS2 simulation,we can see, in a short period of time, the improved Vegas algorithm are significantly higher than the traditional Vegas algorithm in throughput. The fourth chapter, to solve the problem that Vegas protocol cannot use the bandwidth efficient in the slow start phase, we adopt the strategy of TCP Westwood algorithm. In view of the Vegas cannot distinguish the link congestion or route change, we use path monitoring strategy. And what we do reflect the state of the network more accurately, and also improve the use of satellite resource utilization. Simulation results shows that the new algorithm in system throughput improves obviously, and shows better fairness.Finally, this thesis design and implement an IP over CCSDS enhancement agentbased systems. Use of traditional TCP technology in the ground, satellite network terminal, use of improved Vegas algorithm in space link, in the face of High Delay, high BER environments, the new protocol show better performance.