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Copper Tops 10 Gigabits

Posted on: Tuesday, 2 March 2004, 06:00 CST

OUTLOOK: Products that support 10 Gigabit Ethernet over twisted- pair cabling are still more than a year away, but an interim standard that runs over twin-axial copper cabling should be available for data center applications this year.

WHEN THE FIRST 1O CIGABIT Ethernet standard was released nearly two years ago, sky-high prices of more than $50,000 per port kept many IT organizations on the sidelines. Though prices have dropped since then, the technology remains expensive, in part because it runs only on fiber-optic cabling.

Two emerging standards could change that. Each will bring 10 Gigabit Ethernet speeds to copper cabling, enabling a new generation of switches and networking equipment that promise a less expensive entry point for 10 Gigabit networking. The first products could appear later this year - but there is a catch.

The more evolved of the two standards, the 10GBase-CX4 specification, created by the Institute of Electrical and Electronics Engineers Inc.'s 802.3ak Task Force, enables Ethernet to run over CX4, or four twin-axial copper cable pairs. Although switch vendors say equipment supporting this scheme of 10 Gigabit Ethernet on copper will cost perhaps half that of a fiber infrastructure, the range is limited to 15 meters. Nonetheless, that's enough to connect switches or servers inside a data center - the standard's intended purpose.

The other proposed IEEE standard, called 10GBase-T, will enable 10 Gigabit Ethernet speeds on twisted-pair cabling over a range of up to 100 meters. But the specification is still in an IEEE study group and remains in the early stages of development. Vendors say it might take another two years to develop and ratify the final specification. And even when products appear, the standard may face an uncertain future. One reason: the worry that 10GBase-T will end up running only on Category 6e (Cat 6) twisted-pair cable, rather than the Category 5e (Cat 5) cabling that exists in many sites today.

Several networking vendors that plan to offer networking products this year that support CX4 claim that the technology represents significant cost savings for customers planning data center connections with fiber. Final IEEE ratification of the CX4 standard is expected this month. In contrast, 10GBase-T is unlikely to be ratified until 2006, according to Bradley Booth, chairman of the IEEE's 10GBase-T Study Group.

If the final twisted-pair standard does require Cat 6, Tim Link, CIO at Ohio State University-Newark Campus, will be ready. The school has already begun installing Cat 6 cable to run 10 Gigabit Ethernet within some building locations across its 300-acre campus. The current campus backbone uses the established 10 Gigabit Ethernet standard: It runs over single-mode fiber and uses six Extreme Networks Inc. Black Diamond 10 Gigabit Ethernet switches.

But the university has also installed Cat 6 cable in a new conference building and will add it to a planned student center and library with an eye toward supporting 10 Gigabit Ethernet over copper. The new cabling system, from CommScope Properties LLC in Hickory, N.C., will support 10 Gigabit Ethernet to the desktop as a means of futureproofing the school for high-bandwidth needs such as distance learning and desktop video applications.

Ethernet Evolutions: AT A GLANCE

Link says he can "certainly see using copper in the backbone, because it is certainly cheaper." He notes that running fiber-optic cable costs twice as much as twisted-pair. But nobody is going to pull out fiber to put in copper, he adds, so it will be used only in new buildings or for expansions.

As for the 10GBase-CX4, the best fit may be for short distances between switches inside a data center, possibly within a single chassis or to another chassis nearby, vendors say. But Jay Adelson, chief technology officer at Equinix Inc. in Foster City, Calif., isn't sure that the standard will be all that useful even within the data center. He says the collocation facilities his company runs for hosting Web sites are so large that the 15-meter distance limitation won't be enough for many purposes. Like many organizations, Equinix is already using fiber for high-speed backbones - and fiber can support 10 Gigabit Ethernet over cabling runs of up to 300 meters.

"Our facilities are large, and it would be harder to do copper. I'm not a copper fan, because of the distance limits. Optical fiber is already easy to terminate," Adelson says.

Equinix uses San Jose-based Foundry Networks Inc.'s 10 Gigabit Ethernet switching gear. Adelson says he's sure Foundry will offer 10 Gigabit products that support the new copper standards, but given the extra cost, he wonders whether users will buy it.

Vendors Cautious

Some vendors are also unsure whether they will provide products supporting both copper standards, because they are uncertain how much interest customers will have. But Cisco Systems Inc. is already working with suppliers to get parts to support the CX4 standard. The cost for copper-switch modules should be half that of $4,000 fiberoptic modules used in Cisco's Catalyst 6500 series switches, says Bruce Tolley, senior manager for emerging technologies at Cisco.

Dan Dove, the chairman of the IEEE task force behind the 10GBase- CX4 twin-axial copper cable standard, says overall costs for copper in the data center should be 5% to 20% of the cost for fiber. He's hoping that CX4 can deliver 10 times the bandwidth of Gigabit Ethernet for two to three times the cost. "That was our guiding principle," Dove says.

As for the nascent twisted-pair standard, Tolley says Cisco will support it, but he adds that the company "can't do anything until people deliver the parts to us." He predicts that early installations of 10GBase-T will be expensive until volume sales bring down prices.

Tolley says that most installations of 10 Gigabit Ethernet have been at highend data centers, service providers and universities, "where they have been quite comfortable with fiber." But, he adds, "there has been demand for a lower-cost solution."

Several other vendors, including Extreme, Foundry, Nortel Networks Ltd. and Enterasys Networks Inc., say they expect customers to begin to ask for copper connections, although none has made formal product announcements.

Mark Hurley, senior product manager at Enterasys in Andover, Mass., says his company expects to release a CX4 product sometime in the third quarter. "There's very high interest in copper," he says, agreeing with Cisco that connection modules for CX4 could sell for half that of fiber units.

But analysts aren't enthusiastic about either standard catching on. "The demand for either copper standard is relatively small," says Mark Fabbi, an analyst at Gartner Inc. in Stamford, Conn. *44456

CX4: Standard on The Fast Track

Although the 100Base-T Study Group faces slow progress on a version of 10 Gigabit Ethernet over twisted-pair as vendors debate its suitability for use on Cat 5 cabling, Dan Dove, the chairman of the IEEE task force that developed the IOGBaseCX4 standard for twin- axial cable, says his study group's work went quickly. The process took about a year to complete, which is half the normal time, he says.

"It was a phenomenally smooth process, which was the most amazing experience I'd ever seen in 15 years of working with standards groups," says Dove, also the principal engineer for physical-layer technologies at HewlettPackard Co.

DAN DOVE

Dove says the big difference this time was that people agreed that the standard needed to be done quickly and that delay would ruin it. "10 Gig optical did not launch the way people wanted it to, and the realization became clear that they needed to do something."

As for the twisted-pair standard, Dove says the task force considering it is "obviously not making rocket-launch progress, but their objective is a much more difficult electrical challenge." The chairman of the 100Base-T Study Group, Bradley Booth, believes the standard will emerge in "early 2006." Members are still investigating the possibility of having the standard run on Cat 5 cabling, he says.

-Matt Hamblen

CABLE BY NUMBERS

Which cable types will best support 10Gbit Ethernet? Here's a look at the trade-offs:

QuickLink 44459

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A Twisted Plot For 10GBase-T

Richard Brand, director of advanced technology investment at Nortel Networks Ltd. and a member of the 106Base-T Study Group, is certain that users will see an implementation of 10 Gigabit Ethernet over twisted-pair cabling within the next two years.

The question is, Which twisted-pair cabling types will the final 10GBase-T specification support? Some in the group hope the specification will eventually run over both Cat 6 and Cat 5 cable types. Support for the more common Cat 5 would enable many companies to use existing cabling rather than running new wiring.

"Some on the study group are investigating Cat 5e for the specification," says Bradley Booth, the study group's chairman and an architect at Intel Corp. But Booth says that consideration isn't a major issue. "We've faced no major obstacles so far," he says.

Nonetheless, the study group is currently evaluating contradictory claims from Ethernet cabling and transmitter vendors as to whether Cat 5 can support 10 Gigabit Ethernet speeds and properly interoperate with other gear without causing interference. At this point in the process, Brand says, "the copper standard is 'wit\chplay,' actually."

"We're trying to determine who has the true story, so we're struggling in this committee," he says. And to complicate matters further, a new study group was formed in the midst of the 10GBase-T Study Group's January meeting to took at running 10 Gigabit Ethernet over the multimode fiber-optic cabling originally designed to support Fiber Distributed Data Interface networks. Such cabling was widely installed in the late 1990s. "We could have an FDDI standard in almost the same time frame as twistedpair," Brand says.

When will that be? It is possible a twisted-pair standard will be finalized by mid-2005, with ratification sometime after that, Brand says. Booth sees a final standard by early 2006.

Brand acknowledges that his time frame is optimistic - a view shared by many vendors. And the FDDI effort only adds confusion for corporate network planners, who must decide whether to install new Cat 6 or fiber cabling or use existing FDDI fiber or Cat 5 cabling for high-bandwidth networking, Brand adds. "In my opinion, there are too many choices, and too many choices stops the market. It makes it easier for customers not to do anything."

-Matt Hamblen

Copyright Computerworld Inc. Feb 23, 2004

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