Modelling and real-trace-based evaluation of static and dynamic coalescing for Energy Efficient Ethernet

The IEEE Standard 802.3az, namely Energy Efficient Ethernet (EEE), has been recently introduced to reduce the power consumed in LANs. Since then, researchers have proposed various traffic shaping techniques to leverage EEE in order to boost power saving. In particular, packet coalescing is a promising mechanism which can be used on top of EEE to tradeoff power saving and packet delay. In this paper, we analyze the interesting and special case of 1000Base-T EEE links, in which power saving operations are triggered only when links are inactive in both transmission directions. We are the first to provide an analytical model for EEE 1000Base-T which accounts for the bidirectional nature of LAN traffic. Our model allows to compute the power saving achieved by EEE, with and without packet coalescing, by using a few significant traffic descriptors. Furthermore, we use real traffic traces to investigate on the performance of static as well as dynamic coalescing schemes. Our results show that dynamic coalescing does not significantly outperform static coalescing in terms of power save and delay. © 2013 ACM.