Performance Evaluation of TEAR, a TCP-friendly Flow Control Protocol, Over the Internet and Wireless Networks

Abstract

TCP Emulation at Receivers (TEAR) is a TCP-friendly protocol that has been proposed for real-time multimedia flow control. Most best-effort traffic on the Internet is well-served by TCP, the dominant transport protocol. However, many applications with real-time constraints, such as multimedia streaming find TCP's response to congestion quite severe and too drastic to deliver acceptable end-user quality. TEAR was designed in order to provide smoothly varying rate changes for such applications while being friendly to competing TCP flows. In this thesis, weevaluate and verify TEAR's performance over the Internet. We verify TEAR's fairness to TCP, the smoothness of its rate fluctuations and its stability in the presence of network perturbations. We then adapt TEAR to run over wireless networks and consider using round-trip delay instead of packet loss as a congestion indication for wireless networks. We present the results of our experiments with TEAR over commercially deployed wireless networks in South Korea. We recount our experiences with the loss-delay characteristics of these networks. We analyze how TEAR competes with TCP, which is known to suffer from severe degradations in environments where the underlying network is unreliable. We then study TEAR's rate variations and the increased longer-term predictability it provides over wireless networks. Finally, we compare the performance of a reliable protocol we built over TEAR with TCP.