Performance Study of a Collaborative Method for Hierarchical Caching in Proxy Servers

With the increasing popularity of the World Wide Web, it is desirable to store copies of popular documents in client and proxy caches and thus reduce the network delay times for URL requests. In this paper we study the caching problem for Web documents in a hierarchy of collaborating proxy servers. Specifically, the focus of our work is to reduce duplicate caching between a proxy and its parent or higher level proxies in the hierarchy when making a caching decision. A collaboration protocol passes caching decision information along with the object to the next lower level proxy to facilitate its caching decision. We analyze the performance of the collaborative method and the conventional method by means of event driven simulation. The collaborative approach is found to provide a much more effective use of the caching resource. Various sensitivity analyses have been conducted. This result is found to be relatively insensitive to the nature of the workloads.