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UBC Theses and Dissertations

End-to-end-acknowledged indirect TCP for wireless internetworked environments Chim, Victor

Abstract

TCP is a transport protocol developed for reliable end-to-end communications over the Internet, and is used by many popular Internet applications, including electronic mail, Telnet, FTP and WWW. TCP is designed to perform well over fixed internetworked environments, where packet losses occur primarily due to network congestion. It attempts to alleviate the congestion problem by initiating its congestion control mechanisms when a packet is believed to have lost. Perceived demand for mobile computing means that wireless links and mobile hosts will likely represent a large part of the next generation Internet. Wireless transmission errors and host mobility can introduce significant packet losses in wireless networks. TCP performance degrades on such wireless internetworked environments because the same congestion control mechanisms are invoked in response to these non-congestion related losses. In this thesis, an alternative transport protocol, known as end-to-end-acknowledged indirect TCP (EI-TCP), is proposed for the wireless internetworked environment. It is based on the indirect TCP (I-TCP) concept, but end-to-end semantics of TCP acknowledgments are maintained. Using computer simulations on a wireless internetworking model, throughput performance of EI-TCP is evaluated and compared against I-TCP and end-to-end TCP for bulk data transfer. Results indicate that by more effective error recovery over the wireless link, EITCP and I-TCP perform significantly better than end-to-end TCP. Also, EI-TCP performs slightly better than I-TCP with a more steady data flow as a result of end-to-end flow control. With link layer retransmissions over the wireless link, EI-TCP and I-TCP can boost end-toend throughput by avoiding competing retransmissions between transport and link layers.

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