Fiber Ethernet efforts progress gradually

technology

Getting your arms around all of the technology proposed for Ethernet transport in access networks could take a while. The access space, generally viewed as the portion of the network between the carriers' central office (CO) and the customers' demarcation point, is a highly segmented and differentiated market. When carriers and equipment vendors talk about Ethernet access, their discussions about the physical infrastructure alone could entail point-to-point Ethernet over short-reach copper; long-reach copper; or fiber, hybrid fiber/copper infrastructures, or point-to-multipoint Ethernet over fiber-based passive optical networks (PONs).

How did a solution touted as simple and low-cost get so complicated? While most agree that fiber is the end game, the economic reality in many markets today is that carriers need to leverage their existing legacy infrastructure, which is by and large voice-grade copper plant.

The arduous climb to the top of this mountain of architectural and technical issues is probably best understood by the people involved in "Ethernet in the first mile" (EFM) standards bodies, who are currently defining protocols and interfaces using different topologies over both copper and fiber media.

"It is really, really difficult to see clearly where the sweet spots are," concurs Bruce Tolley, senior manager, emerging technologies, at Cisco Systems (San Jose, CA) and a member of the IEEE 802.3ah Ethernet in the First Mile task force. "Overall, North America is a big part of the market. There is a capex [capital-expenditure] slowdown, but the recognition is that eventually capex spending will start again and people need to be ready.

"We are seeing customers in Europe and Asia building out greenfield-type applications, and we're also seeing some of the carriers in places like China and Asia, making sort of a long-term investment in fiber for the future. In places like China, there isn't that much copper in the local loop, so they seem quite eager to go directly to fiber."

The identification of clear market segments in the Ethernet access space remains a work-in-progress. Incumbent equipment companies and a host of emerging vendors are working with carriers worldwide to develop Ethernet transport and service solutions. For example, in December 2001, Cisco announced its Catalyst 4000 series of Ethernet switches for point-to-point optical Ethernet connections over fiber. The Catalyst 4000 family is a metro/access platform for carriers delivering broadband services to homes, business parks and multitenant units. Available products include a 48-port 1000Base-LX Gigabit Ethernet line card supporting point-to-point connections over singlemode fiber and a 48-port 100Base-FX line card supporting point-to-point Fast Ethernet connections over multimode fiber.

But carriers in North America, a sizable part of the worldwide Ethernet access market, today want copper-based equipment outside of new build-outs, which by some estimates represent less than 1% or 2% of the market. Fewer than 10% of commercial buildings in the United States currently have fiber access, according to market researcher RHK (San Francisco). The incumbent local-exchange carriers (ILECs) thus are primarily interested in migrating their enterprise customers from asymmetric DSL to the ITU-T's global standard high-bit-rate DSL (G.SHDSL), which would allow the delivery of symmetric business services over Ethernet connections using their existing copper access infrastructures.

"We've just started those architectural discussions now," says Cisco's Tolley. "The carriers are very sophisticated customers that have a long list of feature requirements, so you have to figure out exactly the right architecture and the right list of features before you tell the world that Cisco's got the perfect product." Cisco is also working on hybrid solutions.

Startup Hatteras Networks (Research Triangle Park, NC), formed in July 2000, is developing a first-mile offering that can deliver carrier-class Ethernet and TDM T1 (1.544-Mbit/sec) services over fiber (1 Gbit/sec) or existing copper (10 Mbits/sec) at distances of up to 12,000 ft. The products—described as modular with Ethernet switching and routing capabilities—were in beta trials in August and are in the initial stages of Telcordia Technologies' operations systems modification of intelligent network elements (OSMINE) process, according to Hatteras sources. The company's systems will not be formally announced until carriers deploy the technology in their networks.

"I think the metro/access space has yet to segment into the true pieces of the market," says Kevin Sheehan, vice president of marketing at Hatteras. "If you look at how the majority of business customers receive T1 services today, it is in a point-to-point fashion from a central office or from a remote terminal or a platform designed around the same concept. And that is the huge opportunity—the second wave of Ethernet services will be carriers up-selling T1 customers to greater bandwidth and a greater level of service over both copper and fiber."

"Some of Ethernet-in-the-first-mile initiatives, especially with respect to copper, are simply Ethernet framing over the DSL physical layer, so they are not pure Ethernet in the form that a lot of people think," says Ken Twist, program director, broadband access networks, at RHK. "On the fiber side, Ethernet in the first mile, when it is pure Ethernet not going through a SONET infrastructure, is a ways out. It really hinges on standards and how fast these standards bodies can do the work, because the technology is going to have to be more ubiquitous before service providers will deploy it. You're going to have to have vendors that interoperate with each other, vendors' [technologies] that can talk to CO deployments." Standardized equipment will in turn lower providers' equipment costs.

Service providers also need to figure out how they can tariff the service, notes Twist. "Right now, Ethernet in the first mile does have niche opportunities with some large corporate clients," he says, "but as you scale that to the rest of the network, you need to think about are you undermining your client services and cannibalizing your revenues?" Service issues and security concerns must also be resolved.

The EFM standards initiatives are well underway, but there is still a lot of work to be done. At its July meeting in Vancouver, British Columbia, the IEEE 802.3ah EFM task force voted in all of its proposals on point-to-point fiber, including Fast Ethernet over 10-km singlemode fiber and point-to-multipoint optics such as the baseline EPON protocol proposal. The task force also agreed on a proposal that will allow two wavelengths to offer bidirectional transport over a single fiber at 100 Mbits/sec and 1 Gbit/sec.

"We also moved forward on an OEM proposal to allow remote diagnostics at the customer premises," says Cisco's Tolley. Today, Ethernet networks are built with the assumption that the network operator has access to both ends of the link, which is true in the enterprise. The EFM proposal would allow carriers to manage the link asymmetrically from the CO to the customer premises or optical demarcation point.

The first draft of the EFM proposal was expected by the task force's meeting in September. Ratification of the standard is anticipated in September 2003.

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