Modeling, design and performance evaluation of interactive distributed video-on-demand systems

A large scale, distributed video-on-demand (VOD) system allows geographically dispersed residential and business users to access video services, such as movies and other multimedia programs or documents on demand from video servers on a high speed network. In this paper we demonstrate through analysis and simulation the need for a hierarchical architecture for the video-on-demand distribution network. We assume a hierarchical architecture, which fits the existing tree topology used in today's cable TV (CATV) hybrid fiber/coaxial (HFC) distribution networks. We develop a model for the design, configuration, program placement and performance evaluation of such systems. The model takes into account the user behavior, the fact that the user re quests are transmitted over a shared channel before reaching the video server containing the requested program, the finite input/output (I/O) capacity of the video servers, the exponential storage cost of the multimedia programs imposed by the adopted architecture of the video-on-demand distribution network, and finally the communication cost. In addition, our model allows batching of user requests at the video server and we study the effect of batching on the performance of the video server and on the delivered to the user Quality of Service (QoS). The design and evaluation is based on an extensive analytical and simulation study. The results in this paper contribute to the understanding of the tradeoffs between quality of service, server I/O, storage required, program placement, and commu nication cost. They are helpful in configuring the VOD dis tribution network, optimally placing the programs across the hierarchy of the video servers, and maximizing the performance of the overall system.