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Not using all of that GigE pipe? Save some energy

IEEE's Energy Efficient Ethernet looks at ways to throttle down connection speeds to save power
By Phil Hochmuth , Network World , 02/02/2007

The IEEE wants to make idle or underutilized Ethernet connections more energy efficient, which could mean huge electrical cost savings for large enterprises. The trick: finding a way to seamlessly throttle between 10Mbps and 10Gbps.

The standards outfit recently formed an Energy Efficient Ethernet (EEE) study group to explore how to do this. The idea is to save power in PCs and laptops (most of which ship with GigE cards now) when LAN links are idle, or not utilizing full bandwidth. Researchers estimate that U.S. companies could collectively save $450 million a year in power costs by using such a technology.

The study group is essentially refiguring the process of auto-negotiation — a link-detection technology in Ethernet, where a switch and NIC determine what speeds are supported (10/100/1000Mbps) and establish the link rate. EEE would make this a more real-time process on Ethernet networks. For instance, a GigE-enabled laptop would switch to 10Mbps when idle, maybe 100Mbps during low-bandwidth activities, such as e-mail or Web surfing, and burst to 1000Mbps when downloading large files or streaming video.

"There's lots to take on with this effort," says Mike Bennett, senior network engineer at Lawrence Berkeley National Lab, and chair of the EEE Study Group.

One challenge is finding a way to make a PC or laptop network interface card (NIC) change gears more quickly — "a couple orders of magnitude faster than auto-negotiation, to make the switch as seamless as possible," Bennett says. "Auto-negotiation runs at about 1.4 seconds and we're talking about — just to start the discussion — a millisecond of switching time."

EEE technology will have to work on both ends of a link to be successful, Bennett says. "When one device signals a speed change to another, the device would have to stop transmitting frames and tell the other end of the link, 'Hey, we're going to do a speed change here.'" The challenge with that is there are standard buffering sizes for Ethernet gear, he adds.

"Vendors build devices differently. Some have lots of buffers, some don't," he says.

If the IEEE and equipment vendors can figure all of this out, the savings could be huge for large organizations with thousands of Ethernet ports in PCs, servers and other devices, Bennett says.

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Comments (6)
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Re: Dubious savings calculationsBy Anonymous on December 20, 2007, 7:46 pm3) Disagree - What is being addressed here is the inactive non-bursty traffic times. Latency sensitive applications are transactional (DB record) vs. stream...

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Auto-Neg is dependent onBy Anonymous on December 20, 2007, 7:31 pmAuto-Neg is dependent on adapter vendor/type. I've see some adapters display link jitter for which an added driver delay is required to stabilize the line before...

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Dubious savings calculationsBy Geoff Strickler on February 5, 2007, 5:43 pmThose savings numbers might be valid in theory, but they fail to account for several critical factors: 1. While most new machines ship with 1Gb Ethernet ports,...

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Apples and grapesBy Mike in Michigan on February 5, 2007, 11:40 amAmazing. But I suspect that if large enterprises were to turn off some of the decorative lighting on their buildings or perhaps turn off every other light...

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Lower power?By Anonymous on February 4, 2007, 8:15 pmHow, exactly, does dropping the speed of ethernet drop the power consumption? Do ethernet NICs *really* use less power when running slower (or do they just idle...

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