Strategies and Services for Energy Efficiency in Real-Time Ethernet Networks

The IEEE 802.3az amendment to the Ethernet standard, referred to as energy-efficient Ethernet (EEE), encompasses the new low power Idle operational mode that allows to strongly decrease the energy consumption of inactive links. The introduction of EEE in real-time industrial communications represents an interesting topic currently addressed by the scientific community, as well as by some standardization bodies. The outcomes of these activities are promising, since effective EEE strategies can be devised, and are able to cope with the very tight timing requirements of industrial communication. Unfortunately, the proposed analyses do not address implementation issues that, conversely, represent a crucial aspect in this scenario. Hence, in this paper, we specifically focus on practical issues concerned with the adoption of EEE strategies by real-time Ethernet (RTE) networks. At first, we address the use of commercially available network components and describe a measurement setup that can be adopted to achieve the adequate characterization of such components. Furthermore, we show that, in an RTE perspective, link activations/deactivations should be independently managed by suitably designed EEE strategies at the application level. Consequently, we defined a set of network services that have to be made available in the device drivers. Hence, we consider a generic RTE network and discuss methods for the practical implementation of those EEE strategies. A performance assessment carried out via theoretical models as well as numerical simulations shows that EEE strategies can be effectively implemented with considerable power savings at the expense of only minimal performance degradation.