Removing TCP congestion control on the last hop in split TCP environments

Abstract

The poor performance of TCP in wireless networks is a well-known problem, and a large amount of research effort has been devoted to it. However, our own experiments show that existing solutions including split TCP and recently developed congestion control algorithms still suffer significant performance degradation in lossy environments, leaving considerable room for improvement. Rather than developing a more sophisticated congestion control algorithm, we explore a radically different approach: we instead propose to completely remove congestion control between the Wi-Fi access points and the wireless receivers. We introduce TCP Fixed, a TCP used in split TCP environments that eliminates congestion control for the last lossy hop, allowing TCP to send data as fast as the channel allows. Extensive evaluations in both lab and real-world settings demonstrate that our approach significantly improves TCP performance in the presence of packet losses. In addition, our results indicate that existing 802.11 rate adaptation schemes which strive to minimize frame loss unnecessarily decrease the data rate in the presence of TCP Fixed. These results offer new opportunities for future link-layer rate adaptation designs.