Prefix Caching assisted Periodic Broadcast: Framework and Techniques to Support Streaming for Popular Videos1

The bandwidth-intensive and long-lived nature of high quality digital video make it a challenging problem to transmit such video over the Internet. In this paper, we consider the problem of streaming a set of popular videos from a remote server to a large number of asynchronous clients, while making efficient use of network bandwidth, and still allowing clients to start instantaneous playback. We propose a scalable and flexible framework which combines proxy-based prefix caching in conjunction with periodic broadcast of the suffix of a video from the server. We develop a methodology for (i) optimally allocating the proxy buffer space among a set of popular videos and (ii) choosing appropriate prefix and suffix transmission schemes based on the principle of decoupling the suffix and prefix transmissions from each other. A greedy proxy buffer allocation algorithm is presented that minimizes the aggregate bandwidth usage on the server-proxy path. Our studies show that this approach yields a buffer allocation close to global optimal for practical settings where proxy-client path bandwidth is much cheaper than long-haul path bandwidth. When the proxy buffer is allocated to a set of videos using our allocation scheme, a total buffer space of just 5 20% of the video repository is adequate to realize substantial reductions in the aggregate bandwidth usage on the server-proxy path. Finally, we present an integrated prefix and suffix transmission scheme such that the client only needs to listen to at most two channels simultaneously.