Cooperative Web Caching

Abstract

Most clients are placed behind the proxy servers on the Internet. Proxy servers have the disk cache space, network bandwidth, and availability to cache part of the objects for clients. In addition, the number of proxy servers can be increased or decreased dynamically according to the anticipated server workload, making them good candidates to alleviate the bottleneck problem. We have described in the last two chapters how the caching methods provide better performance for continuous request streams in individual proxy servers. In this chapter, we show how the proxy servers may work together to improve the overall performance in delivering objects. At present, large multimedia objects are not cached or only partially cached in current proxy servers mainly for two reasons. First, the owner of the multimedia objects needs to ensure security and control of access of the objects before they are willing to let any proxy servers cache their objects. Thus, any new methods need to allow the content owner have complete control over the objects’ security. Second, the owner of the proxy server wishes to have full autonomy control over its own cache content so that the proxy server may maximize the cache efficiency for its own clients.