Agencies tap existing copper networks for gigabit-speed duty
Seldom does a network upgrade receive as warm a welcome as Gigabit Ethernet over copper has received recently. With its ease of use, attractive cost and high performance, it is a surefire bet for network managers who want to broaden bandwidth in their data centers without a major overhaul of their existing network infrastructures.
Gigabit-Ethernet-over-copper technology allows organizations to upgrade to new high-speed Ethernet services that travel on existing copper wires. This saves them the trouble and expense of installing new fiber-optic cabling, which was required with the first-generation Gigabit Ethernet products that started shipping a few years before Gigabit copper arrived on the scene.
Among the most grateful adopters of high-speed copper are those in the scientific and engineering communities, who are hungry for fatter, faster pipes that permit applications such as 3-D modeling collaboration among geographically dispersed teams.
While installing the Science and Engineering Network at NASA Goddard Space Flight Center recently, Pat Gary compared running Gigabit Ethernet over copper wires vs. over fiber lines. "There is no performance degradation at all. In fact, they are identical. The bits flow at a gigabit per second regardless of whether it's copper or fiber," said Gary, network project leader in the Earth and Space Data Computing Division in Greenbelt, Md.
Gary is expecting continued growth in the number of network users, so he'll need to add approximately 50 Gigabit Ethernet copper ports per year. "Since Gigabit copper is one-third the cost of fiber, the majority of the Gig E ports we are planning to buy in the future will be copper," he said.
Gary has already purchased 200 copper and 100 fiber Gigabit switches from an array of vendors, including Cisco Systems Inc., Extreme Networks Inc., Foundry Networks Inc., Netgear Inc., Marconi Corp. and Asanti. The switches are for the high-end users of the network, which spans 10 buildings at NASA Goddard.
Gary is linking the buildings with the more expensive fiber switches on the outside because they can support the greater physical distances between build.ings, while using less expensive copper switches inside the buildings, where the cable runs are shorter.
Gary's favorite cop.per switches are those that come with jumbo frames, a feature supported by Cisco, Extreme and Foundry. "At only 5 percent more cost, the technology improves network performance by a factor of six," Gary said.
Typically, Ethernet frames consist of 1,500 bytes each, so even with a Gigabit Ethernet line, you're only getting 400 megabits/sec of performance. "With jumbo frames, you get 9,000 bytes or 990 megabits/sec, almost one Gigabit," he said. He cautioned, however, that the end user's computer also must have drivers to support jumbo frames.
But Gary's high-end Gigabit users are not typical.
"There isn't a huge demand from the user side to have Gigabit Ethernet either over copper or fiber at the desktop," said Chris Kozup, a senior research analyst for the META Group Inc. in Stamford, Conn. "Where Gigabit Ethernet over copper makes sense today is in the data center."
Vendors in the federal arena have made the same observation. "The typical network design we see today is 100 megabit Ethernet to the desktop with a gigabit from the wiring closet to the data center," said Mike Rau, director of systems engineering for Cisco Federal in Herndon, Va.
That's exactly what the Army is doing in Fort Polk, La. "I'll only put this on servers, not on desktops," said Wilford Parker, Fort Polk's network manager. "It's easier and cheaper to install copper than fiber. You want to use fiber on the backbone because you've got greater distances there, but at your servers, where you have short distances, copper just makes sense." Parker uses Big Iron combination fiber/copper switches from Foundry.
The short distances typically found between servers or between servers and the wiring closet fall within the distance limitations of copper cabling. To achieve the top rates on copper, there must be no more than 100 meters of cabling before a switch is added to extend to another 100 meters.
Gigabit Ethernet requires a specific, though quite common, type of copper cabling called Category 5, which uses twisted pair cabling in which two copper wires in each pair are twisted together from one end to the other.
The prospects are bright for Gigabit copper market growth among federal agencies because most have already installed Category 5 cable, and Gigabit Ethernet copper uses accessible devices such as an RJ-45 jack, similar to the common RJ-11 telephone jack. As Thomas Ervin, a certified Cisco engineer at reseller GTSI Corp., points out, there are a lot more Category 5-compatible devices than fiber-compatible ones.
Intel Corp. has seen an ongoing increase in sales of Gigabit Ethernet copper Network Interface Cards since 2001. "Gig copper has continued to build momentum even though the economy has slowed down," said Tim Dunn, general manager of Intel's LAN Access Division in Hillsboro, Ore. "This growth, along with the upgrade to Gigabit copper accomplished on the server side, has set the stage for the transition of Gigabit copper to the desktop."
Gerber is a freelance writer based in Kingston, N.Y.
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