Improving bandwidth efficiency of video-on-demand servers

Video-on-demand (VOD) servers have a limited amount of bandwidth with which to service client requests. Conventional VOD servers dedicate a unique str eam of data for each client, and that strategy can quickly allocate all of the available bandwidth on the server. We describe a system called stream t apping that allows clients to "tap" into existing streams on the VOD server . By using existing streams as much as possible, clients can reduce the amo unt of new bandwidth they require, and that allows more clients to use the server at once, reducing client latency. Stream tapping uses less than 20% of the bandwidth required by a conventional VOD server for popular videos, and it performs better than many other strategies designed to improve VOD s ervers. (C) 1999 Elsevier Science B.V. All rights reserved.