Performance Evaluation 58 (2004) 285–317 Time-domain analysis of Web cache filter effects Guangwei Bai, Carey Williamson ∗ Department of Computer Science, University of Calgary, 2500 University Drive NW, Calgary, Canada T2N 1N4 Available online 11 September 2004 Abstract This paper uses trace-driven simulation to study the traffic arrival process for Web workloads in a simple Web proxy caching hierarchy. Both empirical and synthetic Web proxy workloads are used in the study. The simulation results show that a Web cache reduces both the peak and the mean request arrival rate for Web traffic workloads, while the variance-to-mean ratio of the filtered traffic typically increases, depending on the input arrival process and the configuration of the cache. If the input traffic is self-similar, then the filtered request traffic remains self-similar, with the same Hurst parameter, though with reduced mean. Finally, we find that a Gamma distribution provides a flexible and robust means of modeling aggregate workloads in hierarchical Web caching architectures, for a broad range of workload characteristics and Web proxy cache sizes. To demonstrate the generality and effectiveness of the modeling approach, we present a detailed example of filter effects and traffic superposition in a two-level Web caching hierarchy with heterogenous input workloads. The Gamma modeling results match well with the results from trace-driven simulations. © 2004 Elsevier B.V. All rights reserved. Keywords: Internet and WWW technology; Web proxy caching; Web traffic simulation; Workload and traffic characterization 1. Introduction The World Wide Web (WWW, or the Web) continues to be a major driving force behind the growth in popularity of the Internet. The Web has become the preferred means for the timely dissemination of information in research, education, news, marketing, travel, business, and entertainment domains. The explosive growth of the Web, with its corresponding increase in Internet traffic volume, has led to user-perceivable network performance problems [3,23]. In some cases, the performance bottlenecks are ∗ Corresponding author. Tel.: +1 403 220 6780; fax: +1 403 284 4707. E-mail address: carey@cpsc.ucalgary.ca (C. Williamson). 0166-5316/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.peva.2004.07.009