Web performance modeling issues

The Web has experienced phenomenal growth and has become an important eleme nt of the information infrastructure of many organizations. Web performance and around-the-clock availability are the major concerns of Webmasters of sites that support mission-critical applications, such as electronic commer ce, Web sites are complex computer systems consisting of many interconnecte d computers, networks, and routers. Some of the computers have specific fun ctions such as authorization or caching. Workloads on Web sites are often u npredictable in nature. Heavy-load spikes and a large variability of the ob jects requested over the Web are unique characteristics of Web workloads. T his paper reviews the important issues and challenges in modeling Web-based systems. Workload characterization, predictive models, and their use in va rious situations are discussed.