The Use of Multicast Delivery to Provide a Scalable and Interactive Video-on-Demand Service

In typical proposals for Video-On-Demand (VOD) systems, customers are serviced individually by allocating and dedicating a transmission channel and a set of server resources to each customer. This approach leads to an expensive-to-operate, non-scalable system. We consider a VOD system that uses multicast delivery to service multiple customers with a single set of resources. The use of multicast communication requires that part of the on-demand nature of the system be sacriiced to achieve scalability and cost-eeectiveness. One drawback to using multicast communication is that it complicates the provision of interactive VCR-style functions. Interactivity can be provided by either increasing the complexity of the customer set-top box or by modifying the semantics of the interactive functions to make them easier to provide. We describe a framework and mechanisms by which such interactive functions can be incorporated into a multicast delivery VOD system. Through the use of simulation, we evaluate and compare the performance of a unicast VOD system and multicast VOD systems ooering various levels of interactivity. A prototype Audio-on-Demand system incorporating the ideas in this paper and running in a Sun OS environment is available by contacting the authors.