Session Based Admission Control: A Mechanism for Improving the Performance of an Overloaded Web Server

web servers, session-based workload, performance, simulation, overloaded server, admission control mechanism, web quality of service In this paper, we introduce a new, session-based workload for measuring a web server performance. We define a session as a sequence of client's individual requests. We then measure server throughput as a number of successfully completed sessions. Using a simulation model, we show that an overloaded web server can experience a severe loss of throughput measured as a number of completed sessions comparing against the server throughput measured in requests per second. Moreover, statistical analysis of completed sessions reveals that the overloaded web server discriminates against longer sessions. For e-commerce retail sites, longer sessions are typically the ones that would result in purchases, so they are precisely the ones for which the companies want to guarantee the completion.