A stream tapping protocol with partial preloading

Stream tapping-also known as patching-can reduce the bandwidth requirements of video-on-demand services by allowing new customer requests to "tap" the data streams of other requests for the same video. Previous studies have shown that stream tapping works best when the request arrival rate does not exceed ten to twenty requests per hour for a two-hour video. At higher arrival rates, it performs much worse than broadcasting protocols. To overcome this limitation, we propose a stream tapping protocol that preloads in the customer set-top box the first few minutes of all popular videos. To offset the cost of the additional buffer space, our protocol never requires the set-top box to receive data from the video server at more than twice video consumption rate. Our simulations indicate that preloading the first eight minutes of a two-hour video was enough to achieve lower bandwidth requirements than the best broadcasting protocols at any request arrival rate