Congestion control for sudden bandwidth changes in TCP

In this paper, we propose a novel technique to deal with sudden bandwidth changes in transmission control protocol (TCP). In the current Internet, sudden bandwidth changes may occur because of vertical handovers between heterogeneous access networks, routing path changes, cognitive ratio, and multi-rate wireless local area network. The current implementation of TCP is designed and optimized for stable networks and does not adapt well upon sudden bandwidth changes. Consequently, it might suffer from packet losses in burst upon sudden bandwidth decrement and under-utilization upon sudden bandwidth increment. To resolve this problem, we propose to modify the current TCP algorithm to include a new phase, called fast adaptation (FA). The FA phase is triggered upon detecting sudden bandwidth changes, and a TCP sender in the FA phase attempts to recover lost packets quickly to avoid spurious timeouts upon sudden bandwidth decrement. Upon sudden bandwidth increment, it increases its window size drastically to realize full utilization. Through extensive simulations, experiments, and analysis, it is shown that the proposed scheme can effectively deal with sudden bandwidth changes. Copyright (c) 2011 John Wiley & Sons, Ltd.