A client side WWW prefetching model

Network congestion remains one of the main barriers to the continuing success of the Internet. For web users, congestion manifests itself in unacceptably long response times. One possible remedy to the latency problem is to use caching at the client, the proxy server, or even within the Internet. However, WWW documents are becoming increasingly dynamic (i.e., have short, lifetimes), which limits the potential benefit of caching. The performance of a WWW caching system can be dramatically increased by integrating document prefetching (a.k.a., "proactive caching") into its design. While prefetching reduces the perceived user response time, it also increases network load, which in turn may increase the response time. In this study, we investigate this tradeoff through a mathematical model of a WWW caching/prefetching system. In our model, the client cache is divided into a "regular" cache for on-demand requests and a "prefetching cache" for prefetched requests. A set of such clients connect to a proxy server through bandwidth-limited dedicated lines (e.g., dialup phone lines). The proxy server implements its own caching system. Forecasting of future documents is performed at the client based on the client access profile and hints from the servers. Our analysis sheds light on the interesting tradeoff between aggressive and conservative prefetching, and can be used to optimize the parameters of a combined caching/prefetching system.