A survey of web caching schemes for the Internet <s> Between proxies and Web servers <s> Prefetching and caching are techniques commonly used in I/O systems to reduce latency. Many researchers have advocated the use of caching and prefetching to reduce latency in the Web. We derive several bounds on the performance improvements seen from these techniques, and then use traces of Web proxy activity taken at Digital Equipment Corporation to quantify these bounds. ::: ::: We found that for these traces, local proxy caching could reduce latency by at best 26%, prefetching could reduce latency by at best 57%, and a combined caching and prefetching proxy could provide at best a 60% latency reduction. Furthermore, we found that how far in advance a prefetching algorithmwas able to prefetch an object was a significant factor in its ability to reduce latency. We note that the latency reduction from caching is significantly limited by the rapid changes of objects in the Web. We conclude that for the workload studied caching offers moderate assistance in reducing latency. Prefetching can offer more than twice the improvement of caching but is still limited in its ability to reduce latency. <s> BIB001 </s> A survey of web caching schemes for the Internet <s> Between proxies and Web servers <s> The rapid growth of the World Wide Web has caused serious performance degradation on the Internet. This paper offers an end-to-end approach to improving Web performance by collectively examining the Web components --- clients, proxies, servers, and the network. Our goal is to reduce user-perceived latency and the number of TCP connections, improve cache coherency and cache replacement, and enable prefetching of resources that are likely to be accessed in the near future. In our scheme, server response messages include piggybacked information customized to the requesting proxy. Our enhancement to the existing request-response protocol does not require per-proxy state at a server, and a very small amount of transient per-server state at the proxy, and can be implemented without changes to HTTP 1.1. The server groups related resources into volumes (based on access patterns and the file system's directory structure) and applies a proxy-generated filter (indicating the type of information of interest to the proxy) to tailor the piggyback information. We present efficient data structures for constructing server volumes and applying proxy filters, and a transparent way to perform volume maintenance and piggyback generation at a router along the path between the proxy and the server. We demonstrate the effectiveness of our end-to-end approach by evaluating various volume construction and filtering techniques across a collection of large client and server logs. <s> BIB002
After proxies have been used to assist Web access, research interest has been shifted to investigating prefetching techniques between proxies and Web servers. Kroeger et al. BIB001 investigate the performance limits of prefetching between Web servers and proxies, and show that combining perfect caching and perfect prefetching at the proxies can at least reduce the client latency by 60 % for high bandwidth clients. Markatos and Chronaki  propose that Web servers regularly push their most popular documents to Web proxies, which then push those documents to the clients. They evaluate the performance of the strategy using several Web server traces and find that this technique can anticipate more than 40% of a client's request. The technique requires cooperation from the Web servers. The study does not evaluate client latency reduction from the technique. Cohen et al. BIB002 also investigate similar techniques. Wcol  is a proxy software that prefetches documents, links, and embedded images. The proxy, however, does not push the documents to the client. Gwertzman and Seltzer  discuss a technique called Geographical Push-Caching where a Web server selectively sends it documents to the caches that are closest to its clients. The focus of the study is on deriving reasonably accurate network topology information and using the information to select caches.