Satellite link speeds are now increasing in unison with those of terrestrial links. For example, the maximum link speed of WINDS (Wideband InterNetworking engineering test and Demonstration Satellite) which was launched on 2008 is 1.2Gbit/s. WINDS is expected to support applications in education, medicine including telemedicine, and disaster countermeasures. Therefore, such satellite communication service is one of the key technologies for network assurance. TCP-STAR was proposed to improve the throughput over satellite Internet. However, no experimental evaluation of TCP-STAR over satellite links such as WINDS has been published. Therefore, this paper evaluates the performance of TCP-STAR by comparing with TCP-NewReno and TCP-Hybla over a network consisting of WINDS, HDR-VSAT, and portable VSAT. As a result, it is found that TCP-STAR and TCP-Hybla achieve better throughput when segment losses do not occur, while TCP-STAR achieves the best throughput when segment losses occur.
Satellite Internet is one of the most important networks for emergency communications because of its tolerant of disasters such as earthquake. Therefore, satellite Internet has received considerable attention over recent years. However, most standard implementations of TCP congestion control method perform poorly in satellite Internet due to its high bit error rate and long propagation delay. This paper proposes a new TCP congestion control method called TCP-STAR to improve the throughput over satellite Internet. TCP-STAR has three new mechanisms, namely Congestion Window Setting (CWS) based on available bandwidth, Lift Window Control (LWC), and Acknowledgment Error Notification (AEN). CWS can resist the reduction of the transmission rate when data losses are caused by bit error. LWC is able to increase the congestion window quickly based on the estimated available bandwidth. AEN can avoid the reduction of the throughput by mis-retransmission of data. The mis-retransmission is caused by ack losses or delay. Simulations show that TCP-STAR can obtain the best throughput comparing with other TCP variants (TCP-J and TCP-WestwoodBR). Furthermore, we found that the fairness of TCP-STAR is a little lower than that of TCP-WestwoodBR. However, the fairness of TCP-STAR is equal to TCP-J.
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