rproxy paper proposal Caches are used to good effect on today's web to improve response times and reduce network usage. For any given resource, such as an HTML page or an image, the client remembers the last instance it retrieved, and it may use it to satisfy future requests. However, the current-system is all-or-nothing: the resource must either be exactly the same as the cached instance, or it is downloaded from scratch. The web is moving towards dynamic content: many pages are assembled from databases or are customized for each visitor. In the existing HTTP caching system, this means that many resources cannot be cached at all. A far better approach would be for the server to download a description of the changes from the old instance to the new one: a `diff' or `delta'. rproxy adds backwards-compatible extensions to HTTP that come into operation when two parties to a web request understand the `hsync' encoding. rproxy can be inserted as a stand-alone proxy so that neither the server nor client need be changed. We plan to integrate the rproxy into popular web software including Squid and Mozilla in the near future. Martin Pool, a lead developer of rproxy, will review the background and implementation of rproxy, present exciting experimental results, and discuss future plans. The session will be interesting to developers of Apache and of other web software, and to webmaster interested in reducing traffic volumes and improving response times. For more information, see