Shortest path green routing and the importance of traffic matrix knowledge

Energy-efficient traffic engineering for wired network poses a number of difficulties due to equipment and protocols diversity and complexity. If emerging optimization are to be formulated exactly, they are intractable. This is why numerous heuristics for approximate solutions are proposed. They differ in assumptions on the routing scheme in the network, and also on the availability (and usefulness) of traffic-related or measurement-based power consumption data. Those most interesting w.r.t. authors' work are presented and classified. The authors propose a number of strategies for switching the links on or off, which are still worthy consideration - while the routing scheme stays in control of some shortest-distance mechanism, like OSPF. Operation of the algorithms is verified for two standard test cases, resulting in proposed further improvements and hints on implementation details.