Push or Pull?: Toward Optimal Content Delivery

Video-over-IP applications are experiencing a momentous popularity increase via crowd-acceleration. Content delivery using distributed caching can alleviate high bandwidth demands of such applications. However, existing content distribution networks (CDNs) are designed for relatively small web objects, and many prior efforts are mainly focused only on reducing user experienced latency. A few recent studies address the issue of bandwidth usage in CDNs. We argue that considering the bandwidth consumption together with delay performance is important for the emerging needs of videos of diverse object sizes and user perceived performance. We have formulated the joint optimization problem and proved it is NP-complete. We then develop an efficient light-weight approximation algorithm toward the optimization problem, and provide its theoretical complexity analysis. We also establish the performance bound of the proposed approximation algorithm that shows a much better worst case ratio than those in previous works. Simulation results exhibit that the performance is near optimal for most of the practical conditions.