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Cache On Demand Sadhna Ahuja, Tao Wu and Sudhir Dixit. Cache of Demand (Cod). Conventional web caching lacks two essential functionalities for many services
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Cache of Demand (Cod) • Conventional web caching lacks two essential functionalities for many services • Web caching is largely a “best effort” service, lacking the capability of guaranteeing application-level QoS such as content storage that many service (including streaming media) desire • Standard web caching does not ensure strong content consistency between the server and the cache
Because of “best effort” it may cache most recently requested content • Because a web cache does not guarantee storage for content and the content can be deleted from the web cache at any time. • This lack of service guarantee inhibits web caches from providing new value-added services • One of which would be providing content storage for resource-constrained terminals such as mobile phones and PDAs • There is no flexible mechanism for the server to notify the cache of the change
Key component of CoD system • Admission control mechanism for content storage guarantee and resource allocation storage • CoD protocol : strong content consistency mechanism between the origin server and the cache where the external entity has full control over the cached content CoD also allows QoS to be switched between the “guaranteed” and “best effort” service levels as needed CoD provides application layer QoS and strong consistency
The central idea of Cod is using enforceable resource allocation to provide application layer QoS
CoD enhances a web cache with the capability to allocate its local resources for external client