Optimizing TCP parameters over GPRS and WLAN real networks

Internet based applications are mostly based on a reliable transport service. TCP (transmission control protocol) is one of the protocols responsible for applications performance. Mobile users access to Internet services through 2.5 and 3 Generation networks, which have a significant latency due to error mechanisms introduced at the link layer, as well as transmission delays in the radio access networks. High latency produces interaction with timers of upper protocols. Data rate is other limiting characteristic on these networks. Moreover, data rate changes during a TCP connection due to mobility. TCP can adapt its rate when slow data rate changes thanks to its self-clocking propriety. In case of a sudden change, TCP performance is degraded due to spurious retransmission, and the activation of its congestion control mechanisms. This paper will show the effects and optimization of some TCP parameters over GPRS (general packet radio service) and 802.11b real networks.