期刊名称：International Journal of Computer Science and Information Technologies
电子版ISSN：0975-9646
出版年度：2014
卷号：5
期号：3
页码：3773-3776
出版社：TechScience Publications
摘要：The transmission control protocol (TCP) is a connection-oriented, end-to-end reliable protocol working between hosts in packet-switched network, and between interconnected systems of such networks. Though TCP has been greatly successful in the terrestrial Internet and provides a robust reliable service for the transfer of data from one part of the earth to the other using an unreliable network layer, it performs quite poorly in wireless and satellite based network which is one type of delay tolerant network. In a satellite based network, where the RTT is more than that of the terrestrial counterpart, the use of a proper Transport Protocol becomes very important. In the terrestrial internet the main problem faced by the congestion control protocols is the uncertainty of the traffic condition in the network and the fear of overloading the network with excessive traffic. For this whenever the TCP sender doesn’t receive any acknowledgement for the data it sent, it considers that the packet was dropped by the router because of congestion in the network and thereby reduce the congestion window. One of the major problems in a satellite-based network is the random packet errors, which are not common in the wired counterpart. TCP protocols react to the lack of arrival of acknowledgements or duplicate ACK as a sign of congestion. Therefore, the congestion window is reduced which leads to unnecessary throughput degradation. Moreover TCP injects a new packet into the network only after it receives an acknowledgement of the previously sent packets. This works fine as long as the RTT is moderate by keeping the network load within tolerable limits and maintaining the reliability of the data transmitted. But when the RTT increases, this mechanism creates the bottleneck in the performance of the protocol. The RTT is constrained by the speed of light and the total amount of data that needs to be sent in one RTT is given by the bandwidthdelay product of the link concerned and is not really achieved by the acknowledgement driven logic of TCP. Moreover there are problems because of bandwidth asymmetry and intermittency of the link.
