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Deciding the future of Ethernet

Deciding the future of Ethernet

Scaling Ethernet to new heights -- as much as 100Gbps -- as well developing 10G Ethernet for copper wiring and internal system backplanes were among the chief issues at last week's DesignCon conference.

Customers and producers of Ethernet say the need for scaling the technology to 100Gbps, and the need for a 100 Gigabit Ethernet standard, is approaching faster than expected. The use of Ethernet inside computers and switch chassis, and 10G Ethernet over copper, could result in performance gains and cost savings for customers of corporate LAN gear in the near future, industry insiders say.

Breaking 100

"It's time to start a higher-speed study group in the IEEE," says Mike Bennett, senior network engineer at Lawrence Berkley National Lab (LBNL), who spoke at a 100G Ethernet panel last week at the event in Santa Clara, which drew mostly members of the component and silicon design community.

Bennett says that the bandwidth needs among his peers at other U.S. Department of Energy labs, as well as carrier networks, will soon call for a 100Gbps standard. Current use of 10G Ethernet, and the need to aggregate 10G links, is driving this requirement.

There is some support in the design community for Ethernet to follow the progression of SONET technology's transmission speed, as 10G Ethernet development stayed close to SONET OC-192 specifications. OC-768, at around 40Gbps, is the rarified highest-level speed of SONET available today. But Bennett thinks bandwidth needs of high-end users and carriers will exceed 40Gbps by the time such a standards effort gets into motion; moving to 100G 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 100G Ethernet."

LBNL uses several 10G links in its data centers to aggregate switch connections and links to supercomputer clusters, used for computer-intensive energy research.

"We're getting to the point where 10G Ethernet is taking off, and at some point you're going to need to aggregate those links," Bennett says.

Ethernet inside

Ethernet also is catching on as a backplane technology for a variety of gear, including blade servers chassis, and core LAN and metropolitan-area network Ethernet switches and routers, as well as 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 traveling 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 standardize this implementation.

According to Adam Healey, distinguished member of the technical staff at chip-maker Agere Systems, development of physical interface standards for backplane Ethernet are getting closer. 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 Gigabit Ethernet, 10G Ethernet and 10G Ethernet specifications, respectively, for running Ethernet a distance up to 1 meter (around 3 feet), 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 reinventing of the wheel -- i.e., creating a new technology for moving data inside of a box, when Ethernet is already an established standard for moving data outside a device over wires.

Standardizing 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 10G 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 10G Ethernet chips.

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 10G 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 fiber-based. But copper 10G Ethernet could be useful as more server and cluster nodes begin to support that speed of Ethernet.

"In one of our data centers we're looking to connect cluster elements at 10G soon," Bennett says. "By the time that's ready for production, 10GBase-T might" be the right technology.


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