IV. More proportional to load
one important feature of today network equipment is that they consume almost the same amount of energy no matter whether they are loaded or not, However more proportionality to load could bring an important reduction in all parts of the network, e.g. theoretical savings of 20-40% for sinusoidal traffic variations can be expected. Sleep mode is a way to introduce more proportionality as will be shown in this section. The load adaptation is then binary.putting a device into either working or sleep mode. Rate adaptation of equipment is also a solution that is particularly studied for elastic optical networks. rate adaptation provides a more gradual adaptation of available capacity to the actual traffic demands. Lastly,it is important to ensure that the power supply of equipments and cooling elements can efficiently support variable equipment power levels.