Abstract

The success of the Internet can be attributed directly to the large number of useful applications running on it. TCP/IP has been the underlying communication protocols enabling these applications. Despite the widespread deployment of the protocols, TCP/IP continues to be a hot research topic among R&D teams in the academia as well as the industry. Much of the recent work has been centered on adapting the protocols for use in wireless environments because of its ease of deployment, convenience to users, and high bandwidth brought about by maturing of advanced technologies (e.g., 3G and IEEE802.11 LAN). The next big wave -- mobile Internet, in which wireless will play a necessary part of the Internet infrastructure -- is around the corner. The original TCP design assumes packet loss is always induced by congestion. This assumption can lead to significant performance degradation in wireless networks where random loss due to environmental noise is rampant. The detrimental effect of random loss on TCP performance is a well-known outstanding problem that remains to be unsolved. This dissertation proposes and studies a novel end-to-end congestion control mechanism called TCP Veno that is able to deal with random loss effectively. Veno differs from the conventional TCP in a major way: it monitors the congestion level using an end-to-end estimation algorithm and uses that knowledge to refine the congestion control algorithm of TCP. Specifically, 1) it refines the multiplicative decrease algorithm of Reno by setting the congestion threshold -- a key control parameter in TCP - according to the perceived congestion level of the network instead of a fixed drop factor when packet loss is detected; 2) it vi refines the linear increase algorithm by attempting to stay longer in an op...

Citations