The instant invention improves the control of a low-power consumption state of network devices linked to a network switch by a suitable network such as an optical network. It allows for the sleep mode also to shut down the power supplies of the components of the network device necessary for the normal data link layer network communication according to the OSI model and the higher layers of the communication protocols. In the same way, the invention prevents that a disruption of the optical network leads to a sleep mode of the network device. Further, even in a freeze state, it is possible to activate the network device and bring it in a sleep mode. For this purpose, a special communication protocol is provided.