Energy consumption for data distribution in content delivery networks

A considerable percentage of worldwide electrical energy is consumed by information and communication technology. One significant element in this perspective are the data distribution systems via Content Delivery Networks (CDNs). We introduce a new model to compute the total energy consumption of CDNs which is based on a hierarchical Internet map and that takes into account the energy consumption needed to keep servers synchronized. The CDN is represented as a main server storing the whole data set and several surrogate servers, each caching a subset of the entire data set. Servers are located in a hierarchical three-tier network topology. We analyze the energy consumption trends as a function of the number of surrogate server. Results show that increasing the number of surrogate servers decreases the transmission delay but it does not always lead to decreasing energy consumption. Furthermore, the energy consumption profile as a function of the number of servers strongly depends on the ratio between the number of content requests and modifications. Finally, we show that the adoption of a hierarchical network model permits to highlight slightly different energy consumption trends with respect to those of standard “flat” network representation.