An energy management system for a data center network may include a central computer to establish an energy use policy for the computer data center network. The system may also include computer nodes in the computer data center network to receive a packet which is a query that obtains energy information from the nodes and/or a transmission reservation that provides instructions for the energy use policy to be implemented at the computer nodes. The computer nodes may reallocate data traffic on the computer data center network based on the energy use policy to improve energy consumption of the computer data center network.