TCP behavior of a busy Internet server: analysis and improvements

We analyze the way in which Web browsers use TCP connections based on extensive traffic traces obtained from a busy Web server (the official Web server of the 1996 Atlanta Olympic games). At the time of operation, this Web server was one of the busiest on the Internet. We first describe the techniques used to gather these traces and reconstruct the behavior of the TCP on the server. We then present a detailed analysis of the TCP's loss recovery and congestion control behavior from the recorded transfers. Our two most important results are: (1) short Web transfers lead to poor loss recovery performance for TCPs, and (2) concurrent connections are overly aggressive users of the network. We then discuss techniques designed to solve these problems. To improve the data-driven loss recovery performance of short transfers, we present a new enhancement to the TCP's loss recovery. To improve the congestion control and loss recovery performance of parallel TCP connections, we present a new integrated approach to congestion control and loss recovery that works across the set of concurrent connections. Simulations and trace analysis show that our enhanced loss recovery scheme could have eliminated 25% of all timeout events, and that our integrated approach provides greater fairness and improved startup performance for concurrent connections.