Performance Analysis of Proxy Caching for VOD Services With Heterogeneous Clients

Proxy-caching strategies, especially prefix caching and interval caching, are commonly used in video-on-demand (VOD) systems to improve both the system performance and the playback experience of users. However, because these caching strategies are designed for homogeneous clients, they do not perform well in the real world where clients are heterogeneous (i.e., different available network bandwidths and different sizes of client-side buffers). This paper investigates the problems caused by heterogeneous client-side buffers. We analyze the theoretical performance of these caching strategies, and then, derive cost functions to measure the corresponding performance gains. Based on these analytical results, we develop a caching strategy that employs both prefix caching and interval caching to minimize the input bandwidth of a proxy. The simulation results demonstrate that the bandwidth requirements of a proxy implementing our caching strategy are significantly lower compared to adopting prefix caching or interval caching alone.