Explicit Loss Notification and Wireless Web Performance

This paper describes our experiences with improving TCP and Web performance over a WaveLAN-based wireless network. In previous work, we analyzed the problems to TCP performance in error-prone wireless networks and designed the Berkeley Snoop protocol to significantly improve performance over error-prone wireless links [7, 5]. Most efforts to date have focused on improving performance for transfers to a mobile host. We present a novel protocol based on Explicit Loss Notification (ELN) to improve performance when the mobile host is the TCP sender, a situation that is becoming increasingly common. Then, we use experimental packet traces of wireless errors from a production wireless network to derive an empirical model of channel errors. We use this to evaluate the performance of TCP Reno, TCP Selective Acknowledgments [17] and the Snoop protocol for Web workloads to mobile hosts. We also discuss the scaling behavior of the Snoop protocol and reflect on some general lessons we have learned about efficient protocol design for reliable wireless transport.