Ethernet Goes Metro

Metropolitan-area networks (MAN) built on Ethernet over fiber promise to deliver faster, cheaper and more flexible bandwidth than ATM/Sonet-based technologies. But IT professionals contemplating the deployment of a native metro Ethernet network for interconnecting corporate LANs have found limited options. That will change eventually, analysts say, but the transition could take years because the incumbent local exchange carriers (ILEC) have such a large investment in Asynchronous Transfer Mode (ATM) and Synchronous Optical Network (Sonet) infrastructures.

Ethernet MANs have several advantages. They can plug into enterprise-class Gigabit Ethernet switches or routers, eliminating the need for channel service units and other equipment required for traditional ATM/Sonet services. A native Ethernet design is easier to support, the equipment costs less than that of an ATM/Sonet network, bandwidth can be provisioned more quickly and efficiently (in increments as small as 1M bit/sec.), and the networks can scale to 10G bit/sec. But the biggest benefit is cost savings. "The Ethernet solution tends to be 50% cheaper than Sonet," says analyst Jay Pultz at Stamford, Conn.-based Gartner Inc.

The ILECs have, however, been hesitant to deploy native metro Ethernet services. "The carrier-class switches aren't mature enough to roll out services," says Doug Barnes, director of optical services at Atlanta-based BellSouth Corp., adding that the 50msec fail-over times Sonet offers are essential for the voice and data traffic it carries. The Metro Ethernet Forum is working on carrier-class standards, says Nan Chen, president of the Newport, Calif.-based industry consortium, and switch vendors say their products already offer such capabilities.

But that's an issue for carriers that must handle a mix of voice and data traffic types, not for IT, says David Passmore, an analyst at Burton Group in Sterling, Va. "Most people aren't running voice over metro networks, and the data running over them tends to be tolerant of the second or two of restoral times you find with IP networks," he says.

BellSouth, like many other ILECs, offers 10M bit/sec., 100M bit/sec. and Gigabit Ethernet transparent LAN (TLAN) services running over its ATM/Sonet service architecture. But users and analysts say that TLAN services are more expensive than native metro Ethernet offerings and don't scale in small increments. In addition, bandwidth upgrades require equipment changes that can take a week to several months to complete, users say. And these services aren't available everywhere.

Don Shackley, IT director at Steinberg Diagnostic Medical Imaging Centers in Las Vegas, says Sprint Corp. could offer him only ATM service over copper to connect three locations that needed high bandwidth. "Once they installed it, we were going to be stuck at 155M bit/sec," he says. "And it could take months—literally months—to do an upgrade."

That has left second-tier vendors, including cable companies, public utilities and start-ups, as the sole providers of native metro Ethernet services. Shackley, who went with Atlanta-based cable service company Cox Communications Inc., pays $10,000 per month for 100M bit/sec. service to three offices. ATM would have cost 50% more, he says, adding that upgrades can now be completed in a single day.

But provider coverage is spotty at best, users say, and many vendors are in dire financial straits. Yet corporations are still turning to these players. "It's the only way they can get the bandwidth they need," Passmore says.

Lighting Up

There is one other way. Some organizations have leased or laid their own "dark fiber" and built metro Ethernet networks. But this option isn't practical for most organizations.

"You're responsible for network reliability and availability. And Ethernet doesn't have a lot of testing tools if the link should fail," Passmore says. That's assuming you can get the fiber, which reaches only 10% of business offices, he says. And even when it's in place, the high cost of the last-mile connection to the street can sink the idea fast. Lighting dark fiber makes sense only for high-bandwidth applications in excess of T3 speeds, says Jim Slaby, an analyst at Giga Information Group Inc. in Cambridge, Mass., adding, "We don't think it makes sense for most large enterprises."

That leaves IT with few choices and many trade-offs. Gartner's Pultz suggests that organizations consider using a second-tier metro Ethernet service provider as the primary vendor, where available, and provisioning lower-bandwidth ATM or Integrated Services Digital Network services from an ILEC as a backup.

"You have less bandwidth for the backup, and the primary service is a lot cheaper," he says. "We're big on carrier redundancy."

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