TCP Connection Management Mechanisms for Improving Internet Server Performance

This paper investigates TCP connection management mechanisms in order to understand the behaviour and improve the performance of Internet servers during overload conditions such as flash crowds. We study several alternatives for implementing TCP connection establishment, reviewing approaches taken by existing TCP stacks as well as proposing new mechanisms to improve server throughput and reduce client response times under overload. We implement some of these mechanisms in Linux and evaluate their performance. Our evaluation demonstrates that connection establishment mechanisms that eliminate the TCP-level retransmission of connection attempts by clients can increase server throughput by up to 40% and reduce client response times by two orders of magnitude. Additionally we evaluate the cost of supporting half-closed connections at the server and assess the impact of an abortive release of connections by clients on the throughput of an overloaded server. We observe that mechanisms that do not support half-closed connections additionally improve server throughput by more than 15%