A Connection Admission Control Method for Web Server Systems

Abstract

Most browsers establish multiple connections and download files in parallel to reduce the response time. On the other hand, a web server limits the total number of connections to prevent from being overloaded. That could decrease the response time, but would increase the loss probability, the probability of which a newly arriving client is rejected. This paper proposes a connection admission control method which accepts only one connection from a newly arriving client when the number of connections exceeds a threshold, but accepts new multiple connections when the number of connections is less than the threshold. Our method is aimed at reducing the response time by allowing as many clients as possible to establish multiple connections, and also reducing the loss probability. In order to reduce spending time to examine an adequate threshold for web server administrators, we introduce a procedure which approximately calculates the loss probability under a condition that the threshold is given. Via simulation, we validate the approximation and show effectiveness of the admission control.