Scaling Ethernet to new heights - as much as 100Gbit/s - and developing 10Gig Ethernet for copper cabling and internal system backplanes, were both among the chief issues at the recent DesignCon conference.
Customers and producers of Ethernet say the need for 100Gig technology and a 100Gig Ethernet standard is approaching faster than expected. The use of Ethernet inside computers and switch chassis, and 10Gig Ethernet over copper, could result in performance gains and cost savings for customers of corporate LAN gear in the near future, industry insiders say.
"It's time to start a higher-speed study group in the IEEE," said Mike Bennett, senior network engineer at Lawrence Berkley National Lab (LBNL), who spoke on a 100Gig Ethernet panel at the Santa Clara event, which drew mostly members of the component and silicon design community.
Bennett said that the bandwidth needs among his peers at other US Department of Energy labs, as well as carrier networks, will soon call for a 100Gig standard. Current use of 10Gig Ethernet, and the need to aggregate 10Gig links, is driving this requirement.
There is some support in the design community for Ethernet to follow the progression of SONET to 40Gig - 10Gig Ethernet development stayed close to SONET OC-192 specifications, and OC-768, at around 40Gbit/s, is next highest speed of SONET available today. But Bennett thinks the bandwidth needs of high-end users and carriers will exceed 40Gbit/s by the time such a standards effort gets into motion, so moving to 100Gig is better planning for the future.
"We've always been an Ethernet shop," Bennett says. "And our whole upgrade plan is based on scaling by factors of 10, so it would just be a natural progression to go to 100Gig Ethernet."
LBNL uses several 10Gig links in its data centres to aggregate switch connections and links to supercomputer clusters, used for computer-intensive energy research.
"We're getting to the point where 10Gig Ethernet is taking off, and at some point you're going to need to aggregate those links," Bennett says.
Ethernet is also catching on as a backplane technology for a variety of gear, including bladeserver chassis, core LAN and MAN Ethernet switches and routers, and broadband wireless and DSL access equipment. The use of Ethernet in a device backplane involves the transmission of traffic in standard-sized Ethernet frames on a device backplane, which interconnects various modules and interface components of a machine. (In a blade server, the Ethernet backplane links blades with a shared interface; in switches, it’s the path traffic takes travelling among ports on different interface cards, or to a central packet processing module.) In 2004, the 802.3ap Task Force was formed in the IEEE to help standardise this implementation.
According to Adam Healey, a distinguished member of the technical staff at chip-maker Agere Systems, the physical interface standards for backplane Ethernet are approaching completion. Speaking at DesignCon, Healey said the 802.3ap Task Force is closing on the details of 1000Base-KX, 10GBase-KX4, and 10GBase-KR; these are specifications for running Gig or 10Gig Ethernet over distances of up to a metre, using a four-lane printed copper interconnect.
According to the standards crafters, the use of Ethernet in backplanes lets component makers create products at lower cost, because there is no need to reinvent the wheel.
Standardising the technology could pave the way for more interoperability among components, although observers say a level of component plug-and-play similar to the PC hardware market is unlikely. Official sanctioning of the 803.3ap standards by the IEEE is anticipated in about a year.
Closer to copper
More readily impacting users is the standards effort behind 10Gid Ethernet over unshielded twisted pair (UTP) cabling. IEEE ratification of the 10GBase-T standard is expected this summer.
With the technical standards pretty much set for the technology, the issues of powering 10GBase-T ports in large densities is among the challenges left for vendors bringing products to market, according to Paul Langner, director of systems & validation engineering for Aquantia, which makes 10Gig Ethernet chips. Speaking at DesignCon, Langer said that the greater electrical output 10GBase-T requires will be a challenge for switch vendors to meet. Also, controlling jitter on copper wires running 10Gig Ethernet will be a challenge for switch designers, as signal noise on UTP cabling is pushed to the theoretical limits of the medium with 10GBase-T.
LBLN's Bennett says most of his facility's high-speed links are fibre-based. But copper 10Gig Ethernet could be useful as more server and cluster nodes begin to support that speed of Ethernet.
"In one of our data centres we're looking to connect cluster elements at 10Gig soon," Bennett says. "By the time that's ready for production, 10GBase-T might" be the right technology.
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