In much the same way that hot-rod idling wreaks havoc with your car's fuel economy, running your Ethernet links at full throttle can ruin your data center's energy efficiency -- that's the simple idea behind the Energy Efficient Ethernet initiative.The scheme described by Mike Bennett, senior network engineer at the Lawrence Berkeley National Laboratory in California, would adapt the speed of Ethernet links to match each device's needs within a data center. If you were checking e-mail, for instance, 100 Mb/s would be enough, but the network controller could ramp up to 1 Gb/s when downloading a large file. Bennett described the Energy Efficient Ethernet concept earlier this month at a Next Generation Data Center session at the LinuxWorld Expo in San Francisco.

Bennett chairs the IEEE 802.3az group that has settled on an approach for use on 100-Mbit and -Gbit chips called low-power idle. Under the Intel-led proposal, Ethernet chips with no data to send would be able to put the physical layer of an Ethernet network into a sleep mode. The Physical Layer, or PHY, is the first level in the seven-layer OSI model of computer networking. The PHY translates communications requests from the Data Link Layer into hardware-specific operations to affect transmission or reception of electronic signals.

Once the PHY is in sleep mode, technicians could decide whether they wanted to put other parts of their systems into a low-power state. Bennett said data centers would be able to establish control policies that will allow users to choose when to apply the energy-saving mode and how long to stay in energy-saving mode. "So, you can choose performance over energy savings, or vice versa."

Describing how the IEEE 802.3az proposal would work with virtualized systems, Bennett said that if the network is based on the PCI-E bus (the interface format introduced by Intel in 2004), even more savings are possible. An alternate IEEE proposal from startup Aquantia and Broadcom, called subset PHY, aims to scale 10-Gbit links down to 1-Gbit channels to save power.

The IEEE 802.3az work is part of a broader initiative at Lawrence Berkeley National Lab to lower energy consumption across a wide range of network and consumer systems that could potentially save $450 million in energy costs a year just in the U.S alone.

For more information:

See my previous blog entries-- Reducing Data Center Energy Consumption

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