A Study Of Enhancing TCP Performance Over Heterogeneous Networks

With the development of the communication technology, computer network hasn't limited to wired,simplex and homogeneous network any more,but presents trend of heterogeneous highly. Next generation network can shied the characteristic of heterogeneous of low-level transmission equipment, and provide an open,steady and high-powed service platform to sustain quick exploitation,integration,customization and network distributed application.So far, the communication technology of adapting to heterogeneous networks would be TCP/IP which is the most successful technology in the Internet. This was largely attributed to the core design philosophy of end-to-end transparent.Traditional TCP has been designed and turned to perform well under the wired network which has small BDP (bandwidth delay product) and low channel BER (bit error rate). Therefore, traditional TCP is not ready for the heterogeneous networks like satellite,high-speed fiber,wireless and wired heterogeneous networks. TCP performance plays an important role in heterogeneous networks. When heterogeneous networks connect together, this complexity often leads to degraded performance owing to change of transmission bandwidth,difference of physical link quality,channel asymmetry,terminal remotion,large scale of delay variation and energy cost. So the study of enhancing TCP performance over heterogeneous networks has been becoming an important task in communication field.This paper will focus on TCP congestion control technology over heterogeneous networks; with hopefully could provide valuable reference to improve the TCP performance over heterogeneous networks.The main works are as follows:①The factors which affect the TCP performance and the problems of traditional TCP used in heterogeneous networks are discussed to further study laid a foundation.②Some representation results of TCP technology which suit for heterogenesous networks are analyzed and simulations over the heterogeneous environment are completed. Then, the problems which exist are presented.③An alternative scenario --TCP-selective,which may choose different TCP algorithms according to the different link types is proposed to solve the problems which the sole TCP enhancement plan can not solve. Through simulation results,the new TCP technology is available and feasible.④Relevant modified TCP mechanisms based on different current TCP algorithms are proposed and simulation results show that these algorithms also have good performance.The paper is organized as follows: research background,problems existed,works in the paper are introduced briefly in Chapter 1;TCP congestion control technology is outlined in Chapter 2; typical TCP algorithms in heterogeneous networks and performance analysis are explained briefly in Chapter 3. TCP whole performance improvement is discussed and a TCP congestion control mechanism based on link selection is analyzed in Chapter 4. TCP algorithms for different link types are discussed and 3 kinds of improved algorithms and simulation analyses are given in Chapter 5.