For a term that has been bandied about for several years and adopted by virtually every carrier and vendor at some point, Next-Generation Networks, or NGNs, still have a surprisingly non-specific definition. And even in the current environment, where carriers are facing enormous competitive pressure from within — and outside — the traditional service provider group, most have differing descriptions of the ingredients that comprise the NGN.

As part of an effort to get the industry into some converged vision of NGN, the Alliance for Telecommunications Industry Solutions late last year published a North American framework of requirements for NGN. The document, called the ATIS NGN Framework, has been submitted to the International Telecommunication Union as part of an effort to develop a global definition and set of standards for NGN.

Among the major issues tackled in the framework is the basic definition of the high-level architecture that will be used by participating carriers in building out their own versions of NGN. Perhaps most important, though, is that virtually every large carrier in the U.S. participated and signed off on the framework. “The reason we're really interested in this is because it's such a large amalgamation of things, so we wanted to publish a document that helps us prioritize how that implementation should go,” said Balan Nair, vice president and chief technology officer for Qwest and chairman of ATIS' Technology and Operations (TOPS) Council, which developed the framework.

To be sure, the document comes about not simply from the desire to get the largest carriers in the industry thinking along the same lines, but also because of economic reasons. One of the first stated objectives in the document is to “focus on the variety of new, value-added, IP-centric services and applications.” Just as important is the reality that, regardless of how many legal battles incumbent carriers win in court or Congress, the future of telecommunications is likely to be significantly more competitive. To survive, carriers must be able to build networks that don't follow the same economic model as in the past, when incumbents could expect to command nearly 100% of the market for any given service.

“This is going to come more from a service creation standpoint,” Nair said. “This is something that has business rationalization behind it.”

Recognizing that the NGN won't exist in a vacuum and likely will take many years to develop, the TOPS Council built the new architecture by borrowing liberally from existing standards and other documents developed by organizations such as the Internet Engineering Task Force, the DSL Forum and the National Emergency Numbering Association. Perhaps none was more important, though, than the ETSI TISPAN extended IP multimedia system (IMS) session-based architecture. IMS, certainly one of the hottest buzzwords this year, came out of the Third-Generation Partnership Project (3GPP) and has been adopted by several carriers as a base to build services that cross the chasm between wireline and wireless worlds.

“I believe that the NGN work will build on the IMS work that's already been done,” said Chris Rice, chief technical officer of SBC Communications. “The intent wasn't to go out and build something that was brand new. 3GPP was more wireless-centric, though.

“The purpose [of the NGN document] really had to do with that fact that you had wireless going off with 3GPP, and as you looked at what was going on in the wireline side, there really was no single vision of what was going to be the next-generation network,” Rice continued. “That would drive a higher-cost network. Like the other TOPS work, it was really to go down and identify the set of requirements that need to be articulated for the NGN and identify who's working on it.”

Ultimately, the NGN is designed to blend the wireline and wireless worlds with private customer premises equipment networks into a single, cohesive and IP-based environment (see figure above). Among the most key elements of the NGN plan, at least initially, is to reflect the concerns of North American carriers and the unique challenges they face. Like much of the other work done by ATIS, the NGN plan will continue to evolve and become a significant part of the ITU definition of next-generation networks.

“Fundamentally, we see this as a North American view but with a global outlook,” said Brian McFadden, chief research officer for Nortel Networks. “We're trying to map this into the global bodies that will enable the service set.” And though one of the objectives of the NGN is to create a network that will require significantly less capital, traditional telecom vendors have an incentive to build toward that model if only because they have no other choice, McFadden added.

“In today's world, the network is bigger than any single vendor, and it's unlikely that any single vendor will be able to address all elements of a next-generation network,” he said. “Our view is that a common approach to building these networks around the world will not only be good for the industry but also be good for the consumers. We don't believe any one of us could have a more sustainable advantage without this kind of work.”

One aspect of the plan that is virtually irrefutable is its basis in IP. Without that basic agreement, virtually none of this could move forward, said Bill Smith, chief technology officer for BellSouth.

“Moving to IP is a common denominator for all forms of next-gen communications, whether its IPTV or voice calls over wireless network,” he said. “We think that gets people looking more broadly rather than people going off and solving whatever immediate problem they were facing.”

Beyond its packet-based foundation, the plan includes a number of other basic requirements, including a separation of access technology from application- and service-creation capabilities. The goal is to let carriers as well as application service providers (ASPs) offer converged service regardless of what device the end users may have. Rice cites the example of someone who establishes a broadband connection to watch streaming video on a wireless device in Dallas, then drives to Chicago while maintaining his connection the entire time. In that instance, the user likely passes through several carriers' networks but is able to not only keep the connection going but have his connection passed among different service providers while maintaining the same quality of service (QOS) and passing through various layers of security.

“This architecture is going to be pretty complex by the end just because of all the subsystems that go with it,” Rice said. “But the thing that's going to drive profitability is a push to mobility and portability. The real key to this is making all of the communications services — whether it be voice, data or video — truly mobile.”

Getting to that point, of course, will require an enormous effort on behalf of several carriers and participation from vendors. It also will take unprecedented cooperation among potential competitors. Vendors that participated in shaping the plan seem to understand the need to talk to each other on a number of different levels.

“Everybody knows that the NGN systems are no longer a monolithic approach,” said Harald Braun, president of the carrier networks division for Siemens. “It's a component issue. It consists of six, seven or eight components, and these components need to talk to each other.”

For carriers, though, the plan also requires a new openness, though not as much as some would like. Sketched out in the ATIS plan is a series of standardized interfaces that will allow ASPs to offer services over carriers NGN infrastructure. In addition, it includes standard interfaces between networks, as well as between networks and devices, regardless of their access technology (see story on page 9).

In some respects, that aspect of the NGN already is reflected in IMS for wireless carriers. “When I think of NGN, I always reference myself back to IMS,” Rice said. “You can be the infrastructure provider but not be the application service provider. I may be the service provider and may go out and buy applications from companies that I host on my IMS architecture.”

Operational aspects

From an operational perspective, however, implementing the NGN architecture — and separating access and applications — ultimately will benefit carriers. One of the biggest benefits will be in the way they deploy, monitor and support new services. For example, under most current network architectures, an application that is tied to a Class 5 switch needs to be deployed on a very distributed basis. In the NGN world, it can be deployed on a regional or national basis from one location. It also allows carriers to better leverage existing Layer 1 technology and provides an incentive to invest, according to BellSouth's Smith.

“You can centralize a lot of your capabilities. Instead of going out and deploying something in every one of our 1650 central offices, we can deploy capability on a more centralized basis,” he said. “At BellSouth, I would like to move to a much more logical network. I would like to use all the fiber we have in place today and extend it to the point where we have a mile or less of copper to customers.”

Many other parts of the network will undergo radical change. Billing and operations support systems, for example, will have to be able to track and monitor services across the architecture in ways that they don't currently. “From a subsystem standpoint, billing isn't something we look at as proprietary,” SBC's Rice said. “We look at it as having a standard interface. Regardless of who puts in that solution, you have to have standard interfaces.”

Under the NGN architecture, carriers also will have a common approach on implementing QOS, an attribute that currently is handled in multiple ways. That does not mean carriers will lose the ability to use QOS as a major attribute in differentiating services. Instead, the NGN design eventually will put standard attributes and definitions around QOS. It's also one of the more difficult issues to solve.

“On the signaling paradigms, we've all got to come to agreement,” Nair said. “In the next-gen network, we don't see so much as whether you recognize DiffServ, but agreeing that a specific bit means this or that.”

Smith added that the addition of QOS parameters is one of the areas where NGN would be a natural evolution of IMS. “IMS is a very important portion of the framework, but IMS is looking more at the control plane for lack of a better term,” he said. “We need to include thing such as QOS and also how inter-carrier QOS is delivered. IMS is an incredibly important ingredient, but it's not the entire NGN framework.”

Maintaining QOS in an environment where carriers are all using IP, a technology that is fundamentally designed for best-effort service, is one of the biggest challenges, Braun said. Given that the NGN is still in its early stages, though, he's confident the industry will be able to come up with a workable solution. “We can't say that IP networks have five-nines reliabilities,” Braun said. “You have to remember that the TDM network was developed over 25 or 30 years, and in the beginning, it wasn't five-nines reliable. We are working on the resilient telecommunications technology, but at the moment, we're not there.”

Securing the borders

In the world envisioned by those behind the NGN plan — where users freely jump across inter-carrier borders and ASPs have open interfaces to carrier networks — security also will be among the more difficult tasks. The NGN, in fact, includes a security focus group and lays out eight dimensions of security: access control, authentication, non-repudiation, confidentiality, communications security, data integrity, availability and privacy. While not endorsing any specific technologies for security, almost everyone involved in developing the plan agrees that the industry must take a multi-layered approach to security.

“All the different carriers are going to implement their security in different ways, and that's one of the reasons the standards are important,” Nair said. “The standard for NGN just enhances the overall security.”

However, the structure of the NGN also makes security that much more important, SBC's Rice added. In the previous network architecture transitions, such as moving from in-band signaling to SS7, the only entities connecting into the network were service providers that looked exactly alike, he said. “This [NGN] environment is very much like the Internet,” Rice said. “Why we have so many problems with worms and viruses is that there is no definition of who can be a service provider. The openness makes this [network transition] much more significant.”

But security must encompass more than just making sure rogue users don't have access to the network. It must include the ability to identify trusted users across networks and not open up user devices or the network itself to attacks.

“The points of attack will be there, and we need to answer the security questions from a point-of-entry level, from a device level and from a network level,” Braun said. “It could be that all the end points on this thing are attacked. You need to look at what you can do at the end point, what you can do at the application level and what you can do at the network level. You can't afford the downtime, and you can't afford the interruptions we have at the moment.”

Beyond securing the NGN, some elements of the security plan should be able to create additional revenue, Nair said.

Getting to the point where carriers can proclaim that they have implemented the NGN will take years, though. The next step for ATIS is developing a “gap analysis,” which will include input from several international organizations including the ITU. That should be completed by mid-year, according to Jim McEachern, head of carrier VoIP standards strategy for Nortel and the author of the vendor's contribution to the NGN plan.

After taking into account the gap analysis, the hope is to get a publishable standard in the next 12 months, Nair said. “The gap analysis is there so we don't reinvent the world,” he said.

Implementation of the plan, though, will vary significantly depending on the carrier. BellSouth, for instance, is looking at an implementation plan under which it will have about 50% of its traffic riding on top an NGN architecture in three to five years, Smith said.

SBC, meanwhile, anticipates a phased approach, according to Rice. “I'd like to think that [the NGN plan] will get finalized sometime in the 2006 time frame, with product being available in the 2007 time frame,” he said. “I see this as being more significant from the complexity of what was done in the past. It's [like] a phenomena that takes place once every 50 years.”