The Video-on-Demand (VoD) service is becoming one the most popular Internet services. Due to its bandwidth-consuming nature and thanks to the efforts made by telecom operators to provide the users with higher access rates, an huge amount of VoD traffic is expected to flood the core segment of the network, potentially leading to congestion and Quality of Experience degradation issues. A growing body of research is studying how to alleviate such traffic explosion. One of the most promising solutions consists in migrating the content in the metro and access segments of the network by deploying a system of Metro Servers (MSes) for VoD delivery. This way, the VoD traffic is kept as local as possible and the core network is traffic-offloaded. This paper investigates one of the most prominent risks by adopting this solution: in fact, if not carefully managed, a massive deployment of MSes in the network can lead to a significant increase of the overall energy consumption of the network. We first identify a consistent power model for the MSes and the network equipment in an integrated metro/access architecture scenario, then we define a strategy to switch on and off the network interfaces and the MSes depending on the VoD traffic load variation during the day. We show by means of simulations how our strategy always strikes the best trade-off between the energy consumption for content transport through the network and the energy consumption for processing and storage in the MSes.
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