D. Core Networks
As we show in Fig. 4 the major share, about 90%, of the core network power consumption is concentrated in the nodes. The WDM links, by way of the optical amplifiers, make up only around 10% or less of the power consumption.
We used datasheets of Juniper T-series core routers to determine the power consumption distribution among the components. The line cards that provide input/output interfaces and that apply the packet forwarding logic are the major power consumers. The line cards’ layer 1 and 2 media interface provides framing, line speed signaling and physical connections to a specific network media type such as ATM, SONET (Synchronous Optical Networking), SDH or Ethernet. The purpose of core networks is to transfer traffic streams between different sites. Thus, power consumption in the core network is typically expressed in Watts per transferred bit. Fig. 5 plots the maximum power consumption of a number of Juniper routers against their aggregated capacity. As can be seen, high-end routers are more energy-efficient than low-end routers: while consuming more in absolute values, the power required to transfer a bit decreases with increasing router capacity. Current routers consume between 0.1 W/Mbps and 0.01 W/Mbps. On average, taking into account that near the edge of the core are a higher number of low-end routers, core routers consume about 0.05 W/Mbps. These values already include a correction for PUE.