Data center network (DCN) is the core of cloud computing and accounts for 40% energy
spend when compared to cooling system, power distribution and conversion of the whole data center
(DC) facility. It is essential to reduce the energy consumption of DCN to esnure energy-efficient (green)
data center can be achieved. An analysis of DC performance and efficiency emphasizing the effect of
bandwidth provisioning and throughput on energy proportionality of two most common switch-centric
DCN topologies: three-tier (3T) and fat tree (FT) based on the amount of actual energy that is turned
into computing power are presented. Energy consumption of switch-centric DCNs by realistic
simulations is analyzed using GreenCloud simulator. Power related metrics were derived and adapted
for the information technology equipment (ITE) processes within the DCN. These metrics are
acknowledged as subset of the major metrics of power usage effectiveness (PUE) and data center
infrastructure efficiency (DCIE), known to DCs. This study suggests that despite in overall FT consumes
more energy, it spends less energy for transmission of a single bit of information, outperforming 3T
