A join-the-shortest-queue prefetching protocol for VBR video on demand

We present a high-performance prefetching protocol for the delivery of prerecorded VBR video from a server across a packet-switched network to a large number of clients. Not only does the protocol give constant percept ual quality and almost 100% link utilization, but it also allows for immediate commencement of the video upon user request and near instantaneous response to pause/resume and temporal jumps. The protocol requires (1) that each client have a small amount of memory dedicated to the application (2) that there is one bottleneck shared link between the server and the clients. Our protocol is based on the observation that there are frequent periods of time during which the shared link's bandwidth is under utilized. During these periods the server can prefetch frames from any of the ongoing videos and send the frames to the buffers in the appropriate clients. The server chooses prefetched frames according to a join-the-shortest-queue policy. We present simulation results of our prefetch policy that are based on MPEG encoded traces.