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Enterprise passive optical networks: a spanning-tree LAN alternative

Motorola, Ericsson and other telecom network equipment vendors are adapting their passive optical networking technology for enterprise use. Adoption of gigabit passive optical networks has been slow thus far, but some people see the appeal of the reduced operational and capital expenses. It's just a matter of whether enterprises want to rip and replace miles of copper cable.

Several vendors that have been selling fiber optic networks to telecoms for years are trying to convince enterprises that they can use the same technology to build corporate local area networks (LANs).

Gigabit passive optical networks (GPONs), or passive optical LAN (POL) as Motorola describes the technology, are the same point-to-multipoint technology that Verizon uses to deliver FiOS. Motorola, Ericsson and some other telecom network equipment vendors have adapted this technology for the enterprise.

"We're adapting technology that was founded in the carrier space," said Floyd Wagoner, director of product marketing for Motorola. "This is technology that comes to the enterprise space via fiber-to-the-home technology. We're not so rigid as to think that technology can only serve one use."

Motorola introduced its GPON products at Interop last May. The architecture of the technology is quite simple. A single Layer 2 AXS1800 aggregation switch can sit in the core of the network. It has 7,168 Gigabit Ethernet (GbE) ports that can connect to endpoints with no wiring closet or workgroup switches in between. Instead, Motorola places workgroup terminals throughout the LAN to provide Ethernet connectivity to end users. Similar to modems in fiber-to-the-home deployments, these small devices draw much less energy and require little to no cooling.

"Basically, if you go to the full configuration for passive optical LAN, you can get up to 7,000 users on a single chassis," Wagoner said.

In addition to the simpler architecture and the lower operational expenses associated with power and cooling, enterprise PON offers some other advantages. The transmission range of optical networks is measured in miles rather than feet, for instance, making it easier to connect multiple buildings via a LAN. Optical cabling is also more secure, since it's nearly impossible for a hacker to pull off inline interception of signals on such a network.

Despite the arguments for enterprise GPON, for most enterprises, adopting the technology is no small undertaking. It means ripping and replacing thousands of feet of copper cable and abandoning point-to-point, spanning tree networks with multiple layers of switches, a network architecture that has been the industry standard for nearly two decades.

Since announcing the technology in May, Motorola has just three customer deployments, according to Wagoner. All of them are government agencies. He knows of at least another dozen that Motorola's competitors such as Ericsson have pulled off.

But Wagoner insists that enterprise GPON is a disruptive technology that many enterprises will seriously consider. Motorola has signed one Tier 1 value-added reseller (VAR), SAIC, as an enterprise PON partner. Wagoner said his company is close to announcing a second Tier 1 VAR partner.

Notwithstanding enterprise PON's potential, other vendors with fiber optic product portfolios have declined to adapt the technology for the enterprise. Cisco Systems, which dominates the mainstream Ethernet switching market, is the most notable of the vendors that have decided not to test the waters.

"We did look at this," said Thomas Scheibe, director of product management for Cisco. "We have not seen the business need or the customer requests for such a solution in the enterprise."

We don't have any research on this, but I've got clients calling about it. And folks like Motorola want more information, so we're putting our thinking caps on right now.
Mark Fabbi
vice president, Gartner

There are two main reasons why enterprises will not go for enterprise PON, Scheibe said. First, they are very satisfied with the network architecture they already have in place. Also, enterprises are just not comfortable deploying optics out to every endpoint. "The majority of the last 100 meters in most enterprises is all copper," he said.

"There is no religion on the Cisco side," Scheibe added. "I don't want to say it makes no sense. Is it such a big benefit that you would change the way you architect your network today? Quite frankly, I can't see that. Deploying optics is just a different piece than deploying copper cable."

Scheibe pointed out that the vendor ecosystem in the networking world is built around mainstream point-to-point switching architecture. He questioned whether most network management tools would work with the technology. Also, pulling fiber is far more delicate than pulling copper cable, he said.

Mark Fabbi, vice president and distinguished analyst at Gartner, said Cisco is overstating the lack of interest in enterprise PON.

"When I first heard about it, I thought, 'Are they [Motorola] nuts?'" he said. "But we've heard from a few clients who are seriously interested in it, so Cisco's claim that there is no demand isn't quite on the mark."

Fabbi isn't 100% convinced that fiber to every endpoint is going to be the right solution, but he said enterprises and vendors see the appeal of collapsing network architecture and reducing the amount of intelligence written into each network tier.

"Think of the [Cisco] Nexus 2000, the port extender," he said. "Basically, it's a completely dumb edge forwarding product that has to connect to a Nexus 5000. That's not much different from the PON situation where they put really dumbed-down devices at the desktop and you aggregate everything back to a higher-order switch with features."

Fabbi said there are other examples in the copper-based network world where intelligence and features aren't pushed all the way to the edge but can aggregate it at least a half-step back.

"Well, what if I push it toward the extreme, like the PON guys are doing?" Fabbi asked. "Would I be giving up anything? You come up with a pretty comprehensive architecture without giving up a lot of features. What you give up is a lot of cost."

Fabbi said he likes the philosophy Motorola and other enterprise GPON vendors are offering, and he said some enterprises may be ready to consider it.

"I'm getting a lot of questions from clients," he said. "They say, 'I was a really early adopter of structured cabling, but it's run out of gas. Now what do I do?' They're in big trouble. Even the early CAT-5 installations from 1989 to 1992 are starting to look a little shady right now. So we have clients faced with multi-million-dollar cabling upgrades. I had one client with a fairly extensive campus who had a quote for upgrading his structured cabling system for $23 million. They'd forgotten about it. They had put it in the walls and in the ground and it had worked great. Twenty years later, it doesn't work anymore. It's time to upgrade, and it's not cheap. The price of copper is way up and the price of labor is way up. So people are starting to think about things."

"Would a PON system make more sense for them? Maybe PON supplemented with wireless for the last 50 feet might be the right solution here," Fabbi said. "We don't have any research on this, but I've got clients calling about it. And folks like Motorola want more information, so we're putting our thinking caps on right now."

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