technology & profits

Not Fade away?

BY ROBERT PEASE

Synchronous Optical Network (SONET) has served the communications industry well for more than 15 years, providing reliable voice transmission and enabling huge revenues for the likes of AT&T, Sprint, MCI WorldCom, and other incumbent network operators. But today, voice traffic no longer monopolizes the fiber-optic cables crisscrossing the land. Data traffic is skyrocketing, and more accommodating technologies, such as dense wavelength-division multiplexing (DWDM), Asynchronous Transfer Mode (ATM), and Internet protocol (IP), are primed to give SONET equipment the proverbial "boot" in long-haul networks because of its perceived incompatibility with data networking requirements.

On paper, the need for voice-friendly SONET gear certainly appears to have lessened. RHK Inc., a telecommunications industry analyst firm in south San Francisco, estimates most voice traffic is growing in the 8% to 15% range annually. That seems pretty substantial—until you compare that figure to data traffic's annual growth estimates of anywhere from 100% to 400%, depending on the carrier.

Yet SONET use continues to increase among long-haul carriers. RHK believes the 1999 SONET market will expand 62% in North America alone. That hardly looks like a wholesale switch to data networking, says Dana Cooperson, senior analyst for transport systems at RHK.

"A lot of the reliability, protection, and other features that people have gone to SONET for still aren't necessarily available in the data networking equipment," explains Cooperson. "So do we see a move to go right from an ATM switch or an IP router in to a DWDM system for long-haul transport? Absolutely. But it's not quite there yet. So SONET network elements still continue to have a very big role to play."

Carriers—and their customers—have become accustomed to a technology that, for lack of better terminology, "works." SONET delivers such attributes as reliability, timing and framing, add/drop multiplexing, protection, provisioning, robustness of transport, and bandwidth management capabilities. But even with the strong support of carriers and current traffic economics, a realistic look at the future makes it clear that the days are numbered for SONET as they know it.

A new role?

SONET's future is inextricably linked to emerging technologies such as DWDM, IP, and all-optical networking. New carriers are using these new technologies to build data-centric networks with all sorts of protocol combinations, while incumbent carriers are well aware they must eventually make a transition from their voice-centric networks into the world of data to keep pace.

In this context, there are several trends developing on which many carriers, new and old, agree. First, SONET will eventually make a migration of sorts to the edge of the network. In the core, DWDM is gradually taking over the transport role, with manufacturers already writing the specifications of SONET into their DWDM equipment. On the edge of the network, SONET will fulfill a need for multiplexing as part of next-generation equipment.

Global Crossing, in the form of the national U.S. network it recently acquired from Frontier Corp., illustrates this paradigm. "Our architecture certainly follows that," says Russ Shipley, vice president of network planning and development at Global Crossing. "If you look at the way we've designed our ATM and IP networks, they're directly on the optical layers, something you'll continue to see worldwide and not just in the United States."

Shipley prefers to think of voice as an application riding the core network, with SONET being the transport that works most efficiently for TDM voice networks. "They don't have SONET interfaces to switches, so you have to break it down into something the switch can handle when you're designing trunking networks around the world," says Shipley. "Without the interface, it needs to have the support of some type of DS-3 or DS-1 multiplexing, and SONET, by its nature, has that capability."

"One of the things SONET has provided, and provided well, is taking a lot of low speed signals and multiplexing them up to a higher speed signal that's more efficient for transport," agrees Cooperson. "There's an awful lot of activity to make access more efficient—not by abandoning SONET—but by adding functionality to what was a fairly single-purpose network element."

Access equipment manufacturers are developing products for the edge of the network that mix ATM switching, IP routing, and SONET add/drop functionality in single elements, providing more efficiency. A new generation of multifunction multiplexers, for example, is able to handle lower speed protocols that were difficult to handle previously.

"Eventually, the new carriers that appreciate the traditional SONET attributes will begin to incorporate equipment that will provide interoperability between one protocol and another," says Stephen Montgomery, president of ElectroniCast Corp., an industry forecasting company in San Jose, CA. "Basically, it's really important for vendors to manufacture multiprotocol systems and solutions. We're seeing data networks, using various protocols such as IP, ATM, SONET, Gigabit Ethernet, and others, leaving the building and going all the way to the central office. Vendors will have to have some kind of interfaces for access equipment that can deal with all these protocols and manage them intelligently."

G. Emory Anderson, an engineer in optical networking and SONET for Telcordia Technologies, agrees that SONET functionality will find its way into hybrid equipment. He believes that most of the SONET functions will be absorbed by the other protocols. Which pieces of equipment absorb what functions depends on where they reside in the network.

"We're seeing SONET creeping into the access area in various forms," says Anderson. "One reason is that SONET has evolved the capability to transport data, solving a lot of transport problems that haven't gone away. We're seeing a lot of different types of products coming out that make use of some of SONET's features. On one end of that scale, you're seeing some access products that simply offer data over large SONET frames, such as OC-3c and OC-12c. On the other end of the scale, companies are offering things like hybrid routers that offer protection switching."

SONET for legacy and new

While the future may indeed mirror these predictions, not everyone is rushing to embrace it. Several factors should ensure that SONET gear will hang on to its present position of prominence in many networks.

First, current bottom line realities support the continued use of SONET equipment. Even with data traffic approaching or surpassing 50% of the communications traffic today, data services don't yet provide 50% of the revenues on most networks. That, says Cooperson, is one more reason why there is still a lot of impetus for carriers to deal with their communications traffic in ways that are efficient for voice, and SONET does just that.

This factor even holds true for the emerging carriers. "Williams, for example, is focusing its network on data, but still buying SONET multiplexers because they have a need for private line and other data and data/voice mixes," says Cooperson. "Today, the most efficient and reliable way to transport that kind of traffic is to still use SONET." This reliance on SONET doesn't necessary diminish the company's value proposition as an economical alternative to incumbent carriers "Williams doesn't have to deal with the big legacy issue of what to do with management systems, from provisioning to installation, so they can potentially operate more efficiently,"

Yet even incumbent carriers with legacy networks can move into the data realm efficiently with SONET equipment. For example, a company such as AT&T is large enough that it can afford to have different networks running in parallel, each optimized for a different use, says Cooperson. "They have an IP backbone, for example, and are building that up to OC-192," she explains. "That's a big step for them. They're also doing their voice traffic in parallel. There's still a good life for SONET, particularly at the higher speeds of OC-48 and OC-192."

Meanwhile, incumbent carriers have existing customer bases they need to keep happy. Thus, carriers like Sprint are interested in reaping the benefits of the data explosion, but not by sacrificing the customer base they've built over the years. Sprint's national backbone is primarily made up of 4-fiber, bidirectional, line-switched SONET. Why? Because SONET has offered proven reliability. In fact, unlike some carrier companies that experienced as many as 15 to 20 reportable fiber cuts this year, Sprint says they have not contacted the Federal Communications Commission with a single fiber cut in 1999. Although it doesn't mean zero fiber cuts, it does mean service was never interrupted for customers.

"One thing you have to remember is that there are 250 million people in the United States," says Charles Fleckenstein, group manager for Sprint's business and technology division. "Most of those people are still connected to the old TDM [time division multiplexing] infrastructure. They're used to picking up the phone and having the dial tone work now. So one thing Sprint expresses to vendors is that we don't want to take a step backwards. We want this whole thing to evolve, but not at the expense of our customer base."

"There is going to be a migration as we move out of the SONET environment into more of the optical and direct IP-over-wavelengths on our DWDM systems," says Neil Grenfell, vice president of advanced research and technology at Sprint. "There are issues of making sure we maintain some of the same SONET attributes available, such as network management capabilities, within the optical environment. Most of the vendors are moving that way and their solution over the next few years will solve most of those problems."

Grenfell says there is still the lingering question of how to provide protection and service consistency. A gradual move to hybrid systems is likely, in which a considerable amount of SONET could still be used throughout the network, concentrating on the edges. What's the Sprint timeline look like?

"We're running IP over DWDM now," says Grenfell. "We'll have a significant amount of OC-48 IP-direct on wavelength by the end of this year. We'll be starting with the ATM OC-48 on the direct wavelength early next year."

RHK's Cooperson believes the incumbent carriers will likely spend at least five years making changes to enormous networks. Telcordia's Anderson says he recently heard it said there is about a trillion dollars worth of SONET equipment deployed today. So all the statements and predictions about SONET dropping out of sight in the near future have to be considered in light of a huge embedded base. Tomorrow's market for SONET equipment may not be a trillion dollars, but it's certainly not pocket change.