Transmission Control Protocol (TCP) carries the maximum Internet traffic, so performance of TCP largely affects the performance of Internet. However, end-to-end throughput in TCP degrades notably when operated in wireless networks, since random packet losses and packet reordering are considered as congestion. In wireless networks, due to high bit error rate and changing level of congestion, retransmission timeouts for packets lost in transmission is unavoidable. TCP misinterprets this loss to congestion and invokes congestion control by triggering fast retransmission and fast recovery, leading to under-utilization of the network resources. This paper presents various performance improvement mechanisms by which TCP does not consider every packet loss as congestion. These mechanisms help TCP to distinguish between congestion and packet loss and increase throughput performance.

Transmission Control Protocol (TCP) designed to deliver seamless and reliable end-to-end data transfer across unreliable networks works impeccably well in wired environment. In fact, TCP carries the around 90% of Internet traffic, so performance of Internet is largely based on the performance of TCP. However, end-to-end throughput in TCP degrades notably when operated in wireless networks. In wireless networks, due to high bit error rate and changing level of congestion, retransmission timeouts for packets lost in transmission is unavoidable. TCP misinterprets these random packet losses, due to the unpredictable nature of wireless environment, and the subsequent packet reordering as congestion and invokes congestion control by triggering fast retransmission and fast recovery, leading to under-utilization of the network resources and affecting TCP performance critically. This thesis reviews existing approaches, details two proposed systems for better handling in networks with random loss and delay. Evaluation of the proposed systems is conducted using OPNET simulator by comparing against standard TCP variants and with varying number of hops.iii Dedicated to my father.iv