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Energy-efficient Ethernet: A greener choice for 2010

By Sanjay Kasturia, CTO and chairman of Teranetics, and chief editor, IEEE 802.3az Standard, Network World
March 03, 2010 10:21 AM ET

Network World - Data center managers and equipment vendors looking for greener alternatives will begin to benefit this year from a major initiative aimed at reducing the power consumed by Ethernet equipment. IEEE 802.3az, or the Energy-Efficient Ethernet (EEE) standard, will implement low-power idle (LPI) modes for the full range of Ethernet BASE-T transceivers (100Mb, 1GbE and 10GbE) and the backplane physical layer standards (1GbE, 4-lane 1GbE and 10GbE).

Update: How to migrate to Energy Efficient Ethernet

Evolution of Ethernet

Computing and network hardware has traditionally been benchmarked on performance with no clear metrics for energy efficiency. And because the focus of development has been ever-higher performance, there has been a rapid increase in power consumption, particularly since the advent of multi-GHz processors. The EPA reports that energy usage in data centers doubled between 2000 and 2006 and is predicted to double again by 2011, hence the interest in energy efficiency.

Data centers are built to handle peak loads and often have excess capacity off peak. It's nice to have a lot of server cores available to tackle a big problem when you need them, but it costs a lot of money for power and cooling to keep those servers running constantly.

Clearly there are efficiencies to be gained by being able to operate the compute infrastructure in a manner that scales the power consumption down when the load is lower. Consider, for example, a data center built to provide stock quotes within seconds -- the servers are woefully underutilized when the market is closed. Making the power consumption proportional to the load would allow close to a ten-fold reduction in power consumption as the average utilization tends to be less than 10% of peak capacity.

Approaching the problem

While the EPA recently defined metrics for server energy efficiency, there had been no measure to rate the energy efficiency of network equipment, so the EPA sought input from the Energy ddepartment-supported Environmental Energy Technologies division of the Lawrence Berkeley National Laboratory (LBNL). Mike Bennett and Bruce Nordman of LBNL chose to bring this task to the IEEE LAN MAN Networking group, which initiated a standardization project (Project 802.3az).

When the energy efficiency standards activity started in the 802.3 working group, one of the options considered was stepping down the power consumption of Ethernet transceivers (PHYs) in stages when the data rate required was less than peak. That idea was abandoned, after much debate, in favor of defining LPI modes and mechanisms to switch rapidly between the full operating speed and the low-power idle mode. (How to migrate to Energy Efficient Ethernet.)

With this approach, the EEE standard will not only be able to improve the efficiency of data center network equipment, but also provide standardized signaling mechanisms that can enable rapid transitions between normal operation and LPI states in systems on either end of the physical layer link.

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