INTEGRATION EQUATION

The integration of IP and optical is featured in almost every vendor's PowerPoint presentation these days, but as is so often the case with industry catch phrases, there's a big gulf between slideware and reality. And though some talk a good game, true integration between IP and optical appears to be a long way off. 

Sometimes separating fact from fiction isn't easy. Separating networking reality from blue sky predictions can be just as daunting. So it goes with the industry's ongoing integration of IP and optical.

Each technology has its own merits that would grow exponentially if the two were thoroughly integrated. But as with most technological evolutions, the process of combining IP and optical isn't as simple as it sounds. Bringing the two together involves the complex process of enabling two separate layers to work as one, a task that may be even more difficult in areas such as the metro.

By integrating IP and optical, providers can gain fast provisioning advantages and the associated lower operational costs, in addition to the ability to offer services such as advanced virtual private networking. But how demand, revenue potential and operating costs figure into the integrated IP/optical equation are huge factors to consider, and providers must first determine whether the benefits of a combined IP/optical network outweigh the costs.

In the end, much of the challenge lies in separating what carriers can accomplish today from what they should leave for tomorrow. And the answers, like the issues surrounding IP/optical integration, are as varied as the networks involved. At this point, it's mostly a matter of opinion.

As the service providers' appetite for more sophisticated services has expanded along with the size and strength of their networks, so, too, has network complexity. The task at hand is determining how, when and where to make alterations or improvements to their infrastructure in a way that will have long-term viability.

Most providers agree a great way to accomplish that is by collapsing the layers of a network rather than simply adding more on top. By integrating the IP and optical layers, service providers theoretically end up with a more simplistic network that enables routers to interoperate directly instead of the older approach in which IP was layered on top of optical transport.

And by integrating IP and optical, service providers are able to cut their provisioning times from days to minutes, said Rob Koslowsky, director of marketing and optical strategy for Cisco Systems. In addition, the constrain of not having the bandwidth necessary to deliver a service gets eliminated, he said.

Networks are made up of several critical layers, which include the physical fiber layer, the dense wave division multiplexing (DWDM) layer, the intelligent optical layer and, finally, the IP routing layer, which requires services from the other three (see figure).

PEELING BACK THE LAYERS

LAYER 1 The physical layer — Layer 1 is the most basic and defines what type of media is used (copper, fiber, wireless, etc.) It is over this layer that protocols such as Sonet are used. This layer takes frames from the data link layer and translates them into signals on the physical medium (copper, fiber, etc.)

LAYER 2 The data link layer — This is the layer where technologies such as DWDM come into play. It is responsible for end-to-end data transfer across a physical link and resolves problems caused by damaged, lost or duplicated frames

LAYER 3 The network (routing) layer — This layer is responsible for routing and restoration of traffic. It brings the “intelligence” into an optical network. This layer uses the transport layer above it and the data link layer below it. Layer 3 also addresses and resolves problems associated with data transmission between different networks

LAYER 4 The transport layer — Protocols in this layer enable networks to differentiate between types of applications and the device's route by content. This layer requires information from the other three and ensures that packets arrive complete and correct

IP/optical integration is certainly where networks are headed, said Dan Sheinbein, vice president of AT&T Labs network architecture and development.

It's worth noting that AT&T still uses the point-and-click method, or manual provisioning with a technician, but according to Sheinbein, “technological advances down the road might change that.”

AT&T recently turned up a new national intelligent optical network using Ciena's CoreDirector optical switches in the long-haul portion and Cisco System's ONS 15454 multiservice platforms for edge aggregation (see Telephony, Feb. 18, page 16). But while AT&T uses equipment from Cisco's highly touted IP+Optical portfolio, Sheinbein acknowledged a lack of vendor readiness to fully integrate the two.

“There is a big difference between what vendors supply and what 50,000 technicians are trained to do,” said Jayshree Ullal, group vice president of Cisco's optical networking division. “A lot still use more manual tools,” she said.

From a purist's perspective, the full benefits of an IP/optical integration will not be realized until those manual methods are removed.

Providers such as Genuity, which built out an extensive long-haul data network in 1999, and UUNet, WorldCom's data arm, are staunch supporters of IP and optical integration. In fact, Genuity has already achieved IP/optical integration, said Justin Aborn, associate chief technical officer for Genuity.

Genuity relies on IP, which has enough capacity to allow re-routes and lower cost. The provider used Juniper Networks and Cisco routers as well as Nortel Networks' OPTera gear for its infrastructure. Genuity runs IP over wavelengths, which feed into the optical switching gear, Aborn said.

Careful not to exclude Sonet, the old network standby, Genuity's architecture includes point-to-point links that run between routers with both Sonet and IP over wavelengths. The Sonet ring protection is redundant to the IP routing protection, Aborn said.

Yet even though Sonet leaves half of the capacity unused, Sonet and IP were obviously important enough to employ. “Both exist in our network. IP over wavelengths and IP over Sonet always exist together,” Aborn said. “But eventually, IP over wavelengths will predominate.” As the network or traffic grows more dependent upon IP and as the network grows, the gradual phase out and takeover will take place.

While IP is working its way deeper into service provider networks, many question where it's better positioned for pairing with the optical layer. And some networks simply may not be primed for network integration or have a particular demand for it.

“More is being written about [IP] services than is actually happening,” said Neil Flynn, president of FPL FiberNet, a Florida-based regional wholesale provider with utility roots. Instead, Flynn said, FPL FiberNet sees far more demand for DS-3 and OC-n services.

The lack of interest in IP and IP/optical integration is compounded by the fact that provisioning of IP services is severely constrained in the last mile. Ironically, though, where service providers are more apt to spend is in the metro and the last mile rather than in the long haul.

True integration of IP and optical simply hasn't happened yet in the metro landscape, said Doug McEuen, senior analyst for Pioneer Consulting. “In the long haul [IP and optical integration] will happen first because the optical network is built up and can take on more responsibility,” he said. That contrasts to the metro, which is really a “mishmash” of different technologies, he said.

Even though providers may not be spending in one particular area, Probe Research Vice President Maria Zeppetella views the entire process as cyclical. At this point, some providers have spent a lot on the long-haul space, but then they will shift to the metro space and vice versa, she said.

Service provider spending is concentrated in the metro, where ILECs are looking to evolve from legacy Sonet/TDM infrastructure to one that provides scalability, said Joe Padgett, director of marketing for Nortel. “They want to see a nice migration path and not tear up existing infrastructure,” Padgett said. “To do that, they need to get rid of as many overlays as possible and converge data into the optical domain.” Providers such as SBC Communications are currently using Nortel's OPTera equipment to accomplish that, Padgett added.

Even though service provider spending is directly tied to the integration of IP and optical, other technological issues surrounding provisioning have yet to be worked out. “Automatic signal provisioning [would] vastly ease the difficulty in bringing up services,” Aborn said.

Herein lies the holdup for IP and optical integration. And although Cisco's Ullal pointed to service provider implementation as the problem, she did concede that “we are not yet at total auto provisioning.”

Some service providers' hesitance to integrate the two and keep everything separate is tied directly to the standards process. “A lot of carriers want to hold off until standards are [set and met],” Zeppetella said. “And that relies heavily on [generalized multiprotocol label switching], which isn't done yet.” she said. Because of that, vendors are developing equipment that is GMPLS-ready once the standard has been completed.

Melding the IP and optical layers has obvious merits — including increased network simplicity, lower operational expenditures and easier network management solutions — but what integration proponents need to understand is that the process won't happen overnight. “[Service providers] don't have to take all the equipment out; it can be gradual and based on network demand,” Zeppetella said.

Considering the current constraints on service providers, that small-step upgrade process may be the only option for the integration of existing infrastructure. After all, the options available for building out a greenfield network may be more numerous and easier to implement, but these days, what company has that kind of capital?