We estimate potential energy savings in IP-over-WDM networks achieved by switching off
router line cards in low-demand hours. We compare three approaches to react on dynamics
in the IP traffic over time, Fufl, Dufl and Dudl. They provide different levels of freedom in
adjusting the routing of lightpaths in the WDM layer and the routing of demands in the IP
layer. Using MILP models based on three realistic network topologies as well as realistic
demands, power, and cost values, we show that already a simple monitoring of the lightpath …