10GBase-T power issues may slow 10GbE adoption

Ethernet adapters were announced in late January to support the 10 Gigabit Ethernet (GbE) over twisted pair (10GBase-T) standard ratified last summer. But it will be a year or two before products arrive to support them, say vendors and analysts, in part due to the power challenges posed by the new standard.

10GbE products have been available for some time, but 10GbE over CX4 co-axial cable can extend only to 15 meters and optical fiber options remain expensive. 10GBase-T over Category 6 or 7 twisted pair cabling can extend up to 100 meters, but power requirements hinder its cost-effectiveness.

Ethernet adapter vendor Chelsio Communications announced two single-port, dual-speed 10GbE cards, the S310e-BT storage adapter and the N310e-BT server adapter, in mid-January. At the same time, Tehuti Networks announced its TN7588-S single-port adapter and TN7588-D dual-port adapter. The products support 10GBase-T, but consume more power than the 1GbE cards currently available.

"Those are first-generation products [from Chelsio and Tehuti] that have very high power dissipation; they consume much more power than an optical module," said Bob Wheeler, senior analyst, networking silicon, The Linley Group, Mountain View, CA.

The 10GBase-T adapters from Chelsio and Tehuti require between 20 watts and 30 watts; their short-reach optical counterparts require between 14 watts and 21 watts, according to the two vendors' Web sites.

Even if later versions of network interface cards (NICs) dramatically lowered power consumption, it's unlikely they'll ever reach 1GbE levels, which could be problematic for switches with a high port density. Ed Chapman, VP, product management, data center and switching business unit at Cisco Systems, says that compared to a 48-port 10/100/1000 line card, which uses 700 milliwatts of energy, "we're talking roughly seven or eight times the power consumption to do a 10GbE over UTP [unshielded twisted pair] when they get down to 4 watts to 5 watts per interface."

Experts differ on what it will take to get power consumption rates down. Wheeler says 65 nanometer process technology is "a requirement to get to a reasonable power level." Mike Bennett is a senior network engineer at Lawrence Berkeley Laboratory's LBLnet Services Group and chair of the Energy Efficient Ethernet Study Group (EEESG), started by the Institute of Electrical and Electronics Engineers. Bennett says the EEESG is initially looking at ways to switch to a lower physical level during periods of low utilization.

The vendors and analysts we spoke with generally agree that 10GBase-T switches and lower power NICs won't be available until 2008. Still, there's interest in driving 10GBase-T power consumption down. Bennett says several 10GBase-T PHY (physical layer) vendors came to the EEESG's first meeting. "I think most people that are in tune with trying to save energy are at least looking at the study group," he says.

--Trina MacDonald

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