Using Energy Efficient Ethernet (802.3az) in Web Hosting Centers

Abstract

The contribution of this master thesis is twofold. First we present an analytical model of IEEE 802.3az and second we summarize the results of our measurement campaign conducted in collaboration between Institute IMDEA Networks and InterHost. The analytical model uses simple traffic parameters to estimate the power consumption of the newly released standard for Energy Efficient Ethernet (EEE), namely IEEE 802.3az. With our measurements, we have characterized the behavior of the aggregate traffic flowing through one of the InterHost company’s firewalls at one of their web hosting centers located in Madrid, Spain. We used the collected data in order to evaluate the potential for power saving that could be achieved by replacing the company’s gigabit wired links with EEE connections. In the thesis, we plot the daily load and the potential power saving computed by simulating the measured traffic with an EEE link simulator as well. Using the presented model for predicting the EEE power saving from few statistical traffic parameters, we show that the EEE power saving for 1000Base-T links can be estimated with good accuracy. Finally, to show the importance of precise measurements, we first collect high precision timestamps for packet arrivals by means of specialized high resolution hardware, then we post-process the collected traces and introduce uniformly distributed random noise to the original timestamps. Results show that (i) substantial power saving could be achieved, higher that 40% in the peak hour and as high as 90% overnight, and that (ii) EEE power saving predictions can be biased by timestamp errors and so, high precision hardware is needed. Last but not least, packet coalescing for EEE is discussed to further reduce the power consumption of links under medium to high load operation.