Energy Efficient Ethernet for Real-Time Industrial Networks

To increase the energy efficiency of Ethernet networks, in 2010, the IEEE published the IEEE 802.3az amendment, known as Energy Efficient Ethernet (EEE). The amendment introduces a new operational mode, defined as Low Power Idle (LPI), that allows to considerably reduce the power consumption of inactive Ethernet links. In this paper, we address the application of EEE to Real-Time Ethernet (RTE) networks, the popular communication systems typically employed in factory automation, characterized by tight timing requirements. We start with a description of the EEE basics and, subsequently, focus on the introduction of EEE in the industrial communication scenario. Then, we specifically address the implementation of effective EEE strategies for some popular RTE networks. The analysis is carried out on configurations commonly deployed at low levels of factory automation systems. The obtained results show that considerable power savings can be achieved with very limited impact on network performance. Note to Practitioners-This paper deals with the introduction of EEE in the industrial communication scenario, with specific attention to RTE networks. The work was motivated by the continuous need for efforts to increase energy efficiency at all levels of factory automation systems. Particularly, the IEEE 802.3az amendment represents a significant opportunity even if, unfortunately, it does not explicitly refer to industrial networks. The assessment carried out in this paper, besides confirming the possibility of a profitable adoption of EEE by RTE networks, raised up several aspects of interest for practitioners. Indeed, the cyclic traffic typical of industrial networks reveals suitable to support EEE strategies. Nonetheless, even in case a strict network synchronization is maintained, additional delays may possibly affect frame delivery due to the time overhead introduced by the LPI mode. The adoption of suitable strategies may, however, mitigate the impact of such delays. Also, it has been shown that acyclic traffic requests may reduce the effectiveness of EEE strategies, since they could introduce frequent undesired changes of the Ethernet links status. Finally, we would like to stress the importance of carrying out extensive measurement sessions on real testbeds, since outcomes from practical experiments definitely represent the best way to validate the theoretically designed EEE strategies.