Video placement and configuration of distributed video servers on cable TVnetworks

A large-scale, distributed video-on-demand (VOD) system allows geographical ly dispersed residential and business users to access video services. such as movies and other multimedia programs or documents on demand from video s ervers on a high-speed network. In this paper. we first demonstrate through analysis and simulation the need for a hierarchical architecture for the V OD distribution network. We then assume a hierarchical architecture, which fits thr existing tree topology used in today's cable TV (CATV) hybrid fibe r/coaxial (HFC) distribution networks. We develop a model for the video pro gram placement. configuration, and performance evaluation of such systems. Our approach takes into account the user behavior. the fact that the user r equests are transmitted over a shared channel before reaching the video ser ver containing the requested program, the fact that the input/output (I/O) capacity of the video servers is the costlier resource, and finally the com munication cost. In addition, our model employs batching of user requests a t the video servers. We study the effect of batching on the performance of the video servers and on the quality of service (QoS) delivered to the user , and we contribute dynamic hatching policies which improve server utilizat ion, user QoS, and lower the servers' cost. The evaluation is based on an e xtensive analytical and simulation study.