Low-Power Standards Watch: Ethernet

By Colleen Taylor
With a job that can legitimately count “the inherent constraints of quantum physics” as a major cause of workplace stress, engineers in the semiconductor industry have never exactly had it easy. But as policymakers focused on curbing emissions impose increasingly strict regulations on the power consumption of consumer electronic devices, a host of new challenges have emerged for chip designers.

In coming issues of Low-Power Engineering we’ll be taking a look at how some of the industry’s newly enacted standards and regulations—and others waiting in the pipeline—will continue to impact chip design in the years to come.

Ethernet
Low-power idle features are now required for most consumer electronic devices, but the Ethernet switches that deliver connectivity to those devices have remained woefully inefficient. According to an August report by the IEEE’s Juan Antonio Maestro and Pedro Reviriego, the hundreds of millions of Ethernet links installed throughout the world today consume a sizable amount of energy even when they are not transmitting data. With worldwide Internet usage showing no signs of slowing down, Ethernet has become one of the highest priority areas for today’s efficiency-minded technology standards boards.

A few years ago the IEEE set about tackling Ethernet’s power problem by forming an Energy-Efficient Ethernet (EEE) task force aimed specifically at reducing network energy usage by implementing low-power idle features in Ethernet devices. In early October the IEEE officially announced the ratification of 802.3az, the specification developed by the EEE task group, and last week the specification was formally published.

According to EEE task force chairman Mike Bennett, 802.3az was developed as an attempt to get in front of the Ethernet power consumption problem before government regulators began imposing their version of standards on the electronics industry. “The European code of conduct was starting to look at DSL and broadband-type links, and EnergyStar already had some incentives for computer systems and that sort of thing, so it’s only natural at some point to start looking at the network,” Bennett said. “I had a visionary colleague in the 802.3 group who said, ‘We need to do something before we’re told to do something. We can develop a solution that we want, or we can have regulators come in and tell us to do it.'”

Early feedback from chip designers working with the 802.3az has been positive, Bennett said. “Anecdotally, we’ve received very positive feedback. We did a panel on EEE at a conference earlier this year, and there was a system designer who commented on how he was able to get a prototype up and running fairly quickly.”

Designers working with the spec should experiment with taking advantage of 802.3az’s low power idle features and the layer 2 capability that comes with it, Bennett said. 802.3az includes the ability for widely-adopted BASE-T and BASE-K physical layer components to be able to be put into a low power idle while using the layer 2 link layer discovery protocol (LLDP) specified in IEEE 802.1ab and 802.3bc standards.

“The layer 2 capability that comes with EEE allows link partners to communicate how long it takes to go from asleep to awake,” he noted. “So if a designer would like to be aggressive in terms of power savings, if the PHY is asleep, he or she can also go turn off things in the system that don’t have to be running if the PHY is asleep and set parameters to make those things stay asleep longer.”

When 802.3az compliant-products have been fully deployed in new and existing Ethernet networks, the IEEE estimates that power savings in the United States alone can reach 5 terawatt-hours per year. That’s enough energy to power 6 million 100-watt light bulbs. Chip designers will set the pace for the timeline on which wide-scale deployment of EEE-compliant devices will take place. “We know that some network equipment vendors have already placed EEE on their roadmaps, so we know it’s coming. At this point, it’s just a matter of how quickly the chip designers can get products in the market,” Bennett said. “I’d be comfortable with guessing that within the next five to seven years, we’ll see a significant portion of the current Ethernet devices being replaced with low power ones.”

But while the challenges of working with 802.3az are sure to keep chip designers busy for the time being, engineers would do well to keep one eye on the horizon for new low-power Ethernet developments that are sure to come. For instance: While the new EEE specification will significantly improve the energy efficiency of 10Gbps copper transceivers, one study suggests that designers can achieve even better results if they look beyond the copper PHY status quo. According to a paper presented at the National Fiber Optic Engineers Conference in May 2010, optical Ethernet devices with fiber PHYs are more energy-efficient than 802.3az compliant copper PHY devices.

Bennett noted that the EEE task force chose to focus its first specification on devices with copper transceivers simply because most organizations are heavily invested in copper infrastructure. “We got the low-hanging fruit taken care of first,” he said. But the task force has been keeping abreast of the opportunities presented by optical Ethernet, and could well hold an informal discussion about the technology at the next 802.3 plenary session to be held in Dallas next week. “My personal opinion is [low-power optical Ethernet] ought to be studied,” Bennett said. “But generally, copper products are lower cost, and until the economics of that change, we won’t see a purely optical network for some time.”