Optimal Cache Deployment for Video-an-Demand Delivery in Optical Metro-Area Networks

Traffic demand in fixed and mobile networks is increasing rapidly, driven especially by the growing adoption of Video-on-Demand (VoD) services, which are responsible for roughly 70% of today's Internet's traffic. Network operators must continuously explore new architectural solutions to satisfy increasing traffic at minimum cost. A promising solution consists in deploying caches at the network edge such that VoD requests can be terminated locally. The dimensioning of edge network nodes in terms of storage capacity as well as their placement in the network must be optimized, to reduce costs, improve quality of service, and utilize network resources efficiently. In this paper, we aim to find the optimal deployment of caches, which minimizes overall network resource occupation for VoD service, across the various levels of a hierarchical optical metro network, in terms of the number of caches, their location and dimension (i.e., storage capacity). We develop a discrete-event simulator for dynamic VoD provisioning to measure the performance of different cache deployment strategies in terms of overall network resource occupation and blocking probability. We prove that deploying all the available storage capacity in nearest cache locations does not guarantee the minimal resource occupation. In fact, to minimize resource occupation given a fixed budget in terms of storage capacity, storage capacity must be distributed strategically among caches at different layers of the metro network based on the characteristics of the service, e.g., VoD content catalog popularity distribution.