Multiple-server movie-retrieval strategies for distributed multimedia applications: a play-while-retrieve approach

In this paper, we present a generalized approach to retrieve a long-duration movie requested using a network-based video-on-demand service infrastructure employing multiple servers. We design and analyze a play-while-retrieve (PWR) playback strategy for this multiserver environment such that the access time (waiting time for the clients) is minimized. For this strategy, we use both the single-installment and multi-installment retrieval strategies to analyze the performance of the service system. For the above-mentioned retrieval strategies, we explicitly derive closed-form expressions for a minimum access time. For the case of multi-installment retrieval strategy, we conduct asymptotic performance analysis that quantifies the ultimate performance bounds of our strategy. We demonstrate analytically the impact of a large-scale network, as well as the impact of indefinitely increasing the number of installments, on the performance of such a multiserver service system. We then address the problem of buffer management at the client site, which is a closely related issue that has a significant influence on the performance of the strategy, and also serves as a key issue in making the service system attractive for clients. We derive relationships that quantify the minimum amount of buffer expected at the client site to have a smooth presentation with this multiserver service structure. Finally, we perform simulation experiments to verify all our theoretical findings. In the experiments, we compare the performance of PWR strategy with that of play-after-retrieve strategy, and discuss certain important points that are crucial for implementing a real-life working multiserver service system