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Gig Ethernet challenges ATM for MAN

SONET-based networks retain reliability edge while Ethernet pushes price, bandwidth options.

By Michael Martin
The Edge, 12/11/00

igabit Ethernet is expanding into more metropolitan-area networks, but don't expect Ethernet to supplant ATM and SONET in the MAN anytime soon.

While Gigabit Ethernet offers application service providers, ISPs and companies cheap, scalable bandwidth, it doesn't yet offer the same carrier-class reliability that ATM and SONET provide.

Gigabit Ethernet in the MAN is definitely a growing business. Among metropolitan Ethernet providers, Yipes now serves 18 cities, Telson serves 17, and Cogent last month launched FiberCity, a unit serving the multitenant market.

The appeal of metropolitan Ethernet providers is obvious - lots of bandwidth at low prices. Cogent, for example, is serving up 100M bit/sec connections for $1,000 per month - about the price of a 1.5M bit/sec T-1 service from a traditional carrier.

But traditional carriers are still investing heavily in SONET and ATM equipment as they also move to fulfill their customers' insatiable appetite for bandwidth. "ATM and SONET are not going to go away," says Keith Mitchell, an analyst with Infonetics Research. "Because of bandwidth demands, shipments should actually increase over the next five years."

Why are ATM and SONET still selling in the MAN if Gigabit Ethernet is revolutionizing the bandwidth/price ratio?

One reason is that traditional carriers have a lot of money invested in existing SONET and ATM equipment and aren't going to toss away their equipment investments until they recoup their costs, says James Slaby, an analyst with Giga Information Group.

But perhaps more telling, Gigabit Ethernet doesn't provide the same reliability as the combination of SONET and ATM, so it may not be as suitable for delay-sensitive, mission-critical applications. SONET is able to recover from a loop cut in under 50 milliseconds, allowing even delay-sensitive traffic such as voice to survive.

"SONET was built for [time-division multiplex] voice, so there's no way Gigabit Ethernet is going to be as good for that," Mitchell says.

Metropolitan Ethernet providers are building some redundancy into their networks. Yipes, for example, brings fiber into customer sites from two directions, creating a redundant loop.

But even Yipes CEO Jerry Parrick notes that failover for Yipes takes several seconds as opposed to milliseconds. That's adequate for basic LAN connectivity, which is the market Yipes is going after, Parrick says.

While SONET-based providers set 99.999% uptime as their benchmark, Yipes can provide 99.99% uptime, Parrick says. He says that number should increase in 2001 as metropolitan Gigabit Ethernet equipment improves.

For emerging providers including Yipes, Gigabit Ethernet is a much better alternative to ATM and SONET, Slaby says. "If you're starting from scratch, you're going to use the ATM-less model," he explains. "It's much cheaper."

Another advantage of metropolitan Ethernet services is that they can be provisioned within hours from a remote console, Slaby says. Provisioning a new SONET circuit takes about 20 days and requires engineers to manually reconfigure cross-connects.

"SONET was not designed for automation," he says.

Finally, most metropolitan Ethernet providers can sell bandwidth in 1M bit/sec increments, which lets customers scale up their bandwidth gradually. In a SONET/ATM network customers often don't have many options between a T-1 and T-3. "That means you can be forced to buy a lot more bandwidth than you actually need," Slaby says.

The metropolitan Ethernet providers aren't causing the large ATM-based incumbent local exchange carriers (ILEC) a lot of pain yet, Slaby notes, because the metropolitan Ethernet providers haven't rolled out in many markets, and the service requires all-fiber transport.

"Once they get some ubiquity, they should start to take away some ILEC business in a big way," he says. "I think this is something the ILECs are going to have to address in 2001."

But Mitchell believes it may take longer for the metropolitan Ethernet providers to have a big impact on the established carriers.

"Price is something that grabs attention, but it's not the only factor," he says. "Security and name recognition will make a big difference. Someone's not going to drop their OC-3s to go with someone they've never heard of before."