Dealing with Sudden Bandwidth Changes in TCP

In this paper, we propose a novel technique to deal with sudden bandwidth changes in TCP. In the current Internet, sudden bandwidth changes may occur due to vertical handovers between heterogeneous access networks or routing path changes. 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 decrements of bandwidth and under-utilization upon sudden increments of bandwidth. 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 timeout upon sudden decrement of bandwidth. Upon sudden increment of bandwidth, it increases its window size drastically to realize full-utilization. Through extensive simulations and experiments, it is shown that the proposed scheme can effectively deal with sudden bandwidth changes.