TCP Implementation Enhancements for Improving Webserver Performance

This paper studies the performance of BSD-based TCP implementations in Web servers. We find that lack of scalability with respect to high TCP connection rates reduces the throughput of Web servers by up to 25% and imposes a memory overhead of up to 32 MB on the kernel. We also find that insufficient accuracy in TCP's timers results in overly conservative delays for retransmission timeouts, causing poor response time, low network utilization and throughput loss. The paper proposes enhancements to the TCP implementation that eliminate these problems, without requiring changes to the protocol or the API. We also find that conventional benchmark environments do not fully expose certain significant performance aspects of TCP implementations and propose techniques that allow these benchmarks to more accurately predict the performance of real servers