It’s not easy being green

Large-scale Internet applications, such as content distribution net-works, are deployed across multiple datacenters and consume mas-sive amounts of electricity. To provide uniformly low access laten-cies, these datacenters are geographically distributed and the de-ployment size at each location reflects the regional demand for the application. Consequently, an application’s environmental impact can vary significantly depending on the geographical distribution of end-users, as electricity cost and carbon footprint per watt is lo-cation specific. In this paper, we describe FORTE: Flow Optimiza-tion based framework for request-Routing and Traffic Engineering. FORTE dynamically controls the fraction of user traffic directed to each datacenter in response to changes in both request workload and carbon footprint. It allows an operator to navigate the three-way tradeoff between access latency, carbon footprint, and elec-tricity costs and to determine an optimal datacenter upgrade plan in response to increases in traffic load. We use FORTE to show that carbon taxes or credits are impractical in incentivizing carbon output reduction by providers of large-scale Internet applications. However, they can reduce carbon emissions by 10 % without in-creasing the mean latency nor the electricity bill