12-06

The Effects of Wide-Area Conditions on WWW Server Performance

WWW workload generators are used to evaluate web server performance, and thus have a large impact on what performance optimizations are applied to servers. However, current benchmarks ignore a crucial component: how these servers perform in the the wide-area Internet.

This work shows how WAN conditions can affect WWW server performance. We examine these effects using an experimental testbed which emulates WAN characteristics in a live setting, by introducing factors such as delay and packet loss in a controlled and reproducible fashion. We demonstrate that when more realistic wide-area conditions are introduced, servers exhibit performance properties and scaling behaviors which are not exposed by existing benchmarks running on LANs. We find that packet losses can reduce server throughput by as much as 50 percent and increase response time as seen by the client. We show that using TCP SACK does not lower server throughput, and can reduce client response time.