Research And Implementation Of Multipath Retransmission Technique In The New Internet Transmission Control Protocol

With the development of electronic information technology,smart devices equipped with multiple network interfaces become commonplace.As the traditional TCP/IP network structure supports only a single interface for communication,the multiple network interfaces capabilities have not been fully utilized.To change this situation,multipath transmission came into being.The conection-oriented transmission control protocol for the new Internet(COTCP)is an advanced protocol provides efficient transmission and dynamic service migration,as well as multipath transmission.Because senders's misjudgement about non-lost segment and receiver's buffer blocking may occur during multipath transmission,the thesis proposes the fast retransmission trigger algorithm and retransmission routing policy,so that the COTCP protocol can better support multipath transmission.Firstly,the thesis studies and compares the existing multipath transimission schemes in transport layer,analyzes the drawbacks of traditional retransmission scheme in supporting multipath transmission and proposes a path congestion aware fast retransmission trigger algorithm(PCAFRT).PCAFRT avoides unnecessary fast retransmission and inproves the effective throughput by analyzing the acknowlegement of segment and correctly identifying the cause of out-of-order segment at receiver.Then,by studying the existing multipath retransmission policies,the thesis analyzes the significance that path metric represents and limitations of one metric based retransmission policies,and proposes a retrasmission routing policy RTX-METRICS based on the mixed metrics of packet loss rate and transmission time.Based on this strategy,sender can select best path more accurately,thus speeding up the recovery from receiver's buffer blocking.At last,the verification experiments are carried out for each proposed scheme.The experiment is based on the new internet communication platform and carried out several times under different network conditions.The experiment results show that the proposed two schemes are feasible to COTCP and improve the performance of multipath transmission effectively.