Energy Efficient Ethernet Now an IEEE Standard

Ethernet is becoming a whole lot more power efficient, thanks to a new standard from the IEEE.

The Energy Efficient Ethernet (EEE) standard has been ratified as IEEE 802.3az, and along with it has already come vendor support from silicon vendor Broadcom.

The EEE effort dates back to at least 2008, with the overall goal of reducing Ethernet power consumption by at least 50 percent by introducing a new low power state for idle periods and low utilization.

“If I think of a system as having two states, one when it is active and then a state when it is in lower-power mode, then the total amount of energy is the amount of power multiplied by the amount of time it spends in each state,” Wael Diab, vice-chair of the IEEE 802.3 Ethernet Working Group and a technical director with Broadcom, told

Power utilization states were not entirely unknown in the existing 802.3 Ethernet standards for physical layer devices (PHYs). Diab noted that current PHYs are either sending data or sending what is known as an active idle.

“What we did in 802.3az is put in an additional state called low-power idle that the PHYs can go into,” Diab said. “When you go in and out of that state, [it’s] outside of the scope of the standard and it depends on the actual traffic profile that is flowing.”

Diab added that it’s also desirable to spend more time in the lower-power state than the full-power active state without compromising performance. That’s where the concept of having a control policy to maximize power savings come into play, which is what Broadcom is delivering as part of its EEE implementation across multiple products in its portfolio.

“So what we’ve done at Broadcom is say, ‘okay, we build all the pieces including the PHY, the switch and the controllers, so we can make sure the glue between everything works really well,'” Diab said. “We want to make sure that the control policy can be acted on quickly in real time, otherwise you wouldn’t get any savings.”

The current EEE standard is defined for 100 Mbps and 1 Gbps Ethernet speeds over copper connections. In the future, Diab noted, other efforts might expand the applicability to the new 40 Gbps and 100 Gbps Ethernet standards. That said, the question of where it makes sense to implement EEE on a network is an easy one for Diab to answer.

“Where does it make sense to implement EEE? The answer is on as many links as you can,” Diab said. “Any link that has a copper interface where you put EEE, you can save energy, so the more the better.”

Sean Michael Kerner is a senior editor at, the news service of, the network for technology professionals.

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