Multicast with cache (Mcache): an adaptive zero-delay video-on-demand service

This paper presents a closed-loop (demand-driven) approach towards VoD services, called multicast with caching (Mcache). Servers use multicast to reduce bandwidth usage by serving multiple requests using a single data stream. However, this requires clients to delay receiving the movie until the multicast starts. Using regional cache servers, Mcache removes initial playout delays at the clients, because the clients can receive the prefix of a requested clip from regional caches while waiting for the multicast to start. In addition, the multicast containing the later portion of the movie can wait until the prefix is played out. While this use of caches has been proposed before, the novelty of our scheme lies in that the requests coming after the multicast starts can still be batched together to be served by multicast patches without any playout delays. The use of patches has been proposed to be used either with unicast or with playout delays. Mcache effectively hires the idea of a multicast patch with caches to provide a truly adaptive VoD service whose bandwidth usage is up to par with the best known open-loop schemes under high request rates while using only minimal bandwidth under low request rates. In addition, efficient use of multicast and caches removes the need for a priori knowledge of client request rates and client disk storage requirements which some of the existing schemes assume. This makes Mcache ideal for the current heterogeneous Internet environments where those parameters are hard to predict.