Toward carbon-aware networking

Data transmission tends to be neglected when considering the carbon efficiency of systems, even though the electricity usage of data networks as a whole is as large, or larger, than that of data centers. Accounting for carbon cost of the movement of data is hard, and is often assumed to be the responsibility of the receiver or an intermediate provider. To be able to account for the carbon footprint of networks, mutually agreed metrics are required, covering the end-toend environmental cost of data transmission and up-the-stack network software costs of data processing, rather than merely the independent network devices. Beyond discussing the considerations for defining these metrics, this paper suggests building upon existing practices, such as network telemetry, programmable network elements and cost-aware routing to enable carbon-intelligent networking, a concept that goes beyond network energy efficiency and considers the impact of energy decarbonization on the routing and scheduling of data transmission.