Research On RTT-Based Network Congestion Control Of Transport Layer

Since the birth of the Internet,the increase of transmission demand and the limitation of network performance have always been a contradiction.We expect a higher transmission rate,but also do not want to have a network with high delay,or even collapse.Therefore,congestion control mechanism has always been an important guarantee to ensure the stable and efficient quality of the Internet.As long as this contradiction persists,congestion control will remain a hot issue in network research.Drawing lessons from traditional congestion control protocol,this paper proposes a congestion control method based on RTT(round-trip time).The main contents include:(1)The distribution model of RTT is analyzed.The RTT data obtained from the actual measurements on the Internet are used to observe the changes and distribution characteristics of RTT from multiple dimensions,and to make statistical analysis,It is concluded that the distribution of RTT is related to the network load.With the help of MATLAB test,it can be generally considered that RTT approximately obeys Gamma distribution,rather than discrete or step distribution.At the same time,MACD indicators are introduced to study the trend of RTT,construct specific strategies using MACD,and design relevant experiments by introducing data backtracking method.These experiments test the effectiveness of MACD strategy in judging RTT change trend in network congestion control scenarios,and determine the best parameter group of application of MACD index.(2)Motivates and describes a congestion control protocol TCP MACD based on RTT and MACD index.Bases on the basis of traditional Reno,aiming at the problem that Reno blindly enlarges the congestion window(cwnd)in the congestion avoidance phase,this protocol regards RTT as the feedback signal of network congestion change,judges the trend of RTT change by means of MACD index,then adjusts the size of congestion window(cwnd),and redesigns the algorithm of congestion avoidance phase as the core of congestion control mechanism.The TCP MACD protocol is simulated by NS2 simulation platform,and compared with the traditional TCP Reno and TCP Vegas protocols,it is analyzed from throughput>packet loss rate?fairness and friendliness.In view of the problem of insufficient competitiveness of TCP Vegas and TCP MACD when sharing bottleneck links with other TCP protocols,the TCP MACD+algorithm is improved by multi-cycle control method,and the improved effect is verified by NS2 simulation.