10GBase-T: overheated and out of spec?

Companies touting full TCP offload engines (TOEs) for 10Gig Ethernet are barking up the wrong tree - and worse than that, they do not comply with the specs for 10GBase-T, a chipset supplier has claimed.

"When Gigabit Ethernet came out, servers could only handle 300Mbit/s [of TCP processing], so people are worried about how to offload that into hardware," Solarflare Communications CTO Dr Steve Pope said, adding that processors are faster now, so no one much feels the need for Gigabit TOEs.

"Similarly, when 10Gig came out in 2001, servers could only do 3Gbit/s. Now you can do line-rate Ethernet with less than one core of a multicore CPU."

The big problem with 10Gig TOEs is power consumption. The current generation can consume in excess of 10W, and combined with the power drawn by the PHY - the chip that interfaces to the physical medium - they can push the NIC too close to the 25W limit of each PCIe slot in a server.

So some NIC developers have ratcheted down the range of their NICs to reduce power consumption. For example, Chelsio specs its TOE cards to around 35-50m.

Pope is distinctly unimpressed by that approach. "The spec mandates 100m. 30m may cover most data centres, but there's a whole ecosystem of architects, structured cabling companies and so on, all based around Ethernet going 100m."

He has an interest here, of course - his company has developed a 10Gig Ethernet controller called Solarstorm that only partially offloads the processor, but he claims that his "slim offload" approach can drive the signal 100m while still only consuming 2.2W.

"We have a second generation 10Gig Ethernet controller," he said. "We chose to implement only those features in silicon that will provide sustainable performance - in particular, we have avoided burdening the chip with heavy offload.

"We do the usual stateless offloads - IP, UDP and TCP checksums, iSCSI headers and data digest, and Windows receive-side scaling. And we have virtualisation, with a fully-protected hardware interface so you can plumb it directly into a guest operating system."

His company is the result of a transatlantic merger. The original Solarflare in the US developed a PHY for 10GBase-T, while UK-based Level5 Networks designed the 10Gig Ethernet controller.

Solarflare's aim, Pope said, is to deliver a 10GBase-T card at the same cost as a four-port Gigabit card - or rather, to sell silicon and reference designs to other companies which will then build the NICs.

"There will be products by mid-year," he said. "There are switch vendors working with us too, and we expect switches in the same timeframe." ®