Cache on demand

Web caching is becoming increasingly important as rich content such as streaming media gains popularity on the Web. However, conventional Web caching lacks two essential functionalities for many services. First, Web caching is largely a "best effort" service, lacking the capability of guaranteeing application-level QoS such as content storage that many services (including streaming media) desire. Second, standard Web caching does not ensure strong content consistency. In this paper, we develop a cache on demand (CoD) system that addresses both problems. The key components of the CoD system are an admission control mechanism that guarantees the content storage, and the CoD protocol that ensures content consistency between the origin server and the cache. CoD also allows QoS to be switched between "guaranteed" and "best effort" as needed. CoD is a flexible and effective solution for providing application layer QoS and strong consistency, and provides a new model for revenue-generating services.