Video-on-demand (VOD) servers have a limited amount of bandwidth with which to service client requests. Conventional VOD servers dedicate a unique stream 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 tapping that allows clients to "tap" into existing streams on the VOD server. By using existing streams as much as possible, clients can reduce the amount 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 servers. © 1999 Elsevier Science B.V. All rights reserved.

Broadcasting protocols can improve the efficiency of video on demand services by reducing the bandwidth required to transmit videos that are simultaneously watched by many viewers. It has been recently shown that broadcasting protocols using a very large number of very low bandwidth streams for each video required less total bandwidth than protocols using a few high-bandwidth streams shared by all videos. We present a hybrid broadcasting protocol that combines the advantages of these two classes of protocols. Our pagoda broadcasting protocol uses only a small number of high-bandwidth streams and requires only slightly more bandwidth than the best extant protocols to achieve a given maximum waiting time.