Understanding the environmental costs of fixed line networking

bit associated with real-world communication networking. We highlight the key real-world network deployment issues, particularly legacy systems and utilization, which can have a strong bearing on the level of energy efficiency. We show how and why the real-world metric values differ from prior models of network energy use. We show how including embodied energy leads to the overall environmental impact being minimized only when legacy systems are maintained. We capture the full end to end impact of networking including an understanding of the data centre and home equipment. An accurate understanding is needed if claims around the potential carbon benefit of communications technologies are to be substantiated.