The move ended up helping customers as well. "If you're doing ATM interworking, you can update remote sites to full T1 with no disruption at the host site," says Rick Malone, a principal with consulting firm Vertical Systems Group. "You can add applications like voice or video to a remote site through the existing data interface and not have any configuration changes at the data center site." But with frame, configuration changes would be required, Malone says.

Users running frame relay end-to-end eventually will need to step up to hybrid frame-ATM because of larger traffic flows and limitations on how frame relay products scale, Malone says. "Having an ATM interface at data center really does allow you to scale at the remote site," he says.

Hybrid networks also address the fact that not all remote sites have the same bandwidth needs. Enterprise resource planning applications and voice over frame, cell, or packet demand bandwidth, and quickly outstrip the 56-Kbps or 128-Kbps ports of most frame relay implementations. Frame-ATM hybrids let customers prioritize traffic accordingly.

Customers should recognize, however, that moving to hybrid networks means more money for new equipment. Hybrids typically require an integrated access device at the remote site to handle the frame-cell conversion. The cost of the device may be borne by the service provider. If not, customers must shell out $5,000 to $10,000 for them.

Southern Internet Services Inc., a nationwide Internet service provider in Palm Beach Gardens, Fla., uses Cabletron Systems Inc.'s Smartswitch 6500. But director of IT Rick Jones says users could deploy something as small as a media converter with an Ethernet uplink, or even a router/DSU combination.

Communications Supply Corp. in Carol Stream, Ill., uses a Cisco 3810 router to convert its frame relay traffic and access Sprint's ATM network.

Another important change also has altered the attractiveness of frame-ATM hybrids. Ten years ago, carriers such as AT&T, MCI, and Sprint didn't have local-access facilities, forcing customers to pay high leased-line rates to monopoly local providers. If they wanted to use ATM at all, customers were forced to spend $10,000 to $50,000 for a T3 access line.

Now, customers can buy lower-priced access lines directly from the long-distance carriers in many cities and connect locally to their ATM backbone. Because the frame relay and ATM networks are connected, they can buy T1-speed frame relay access for a few thousand dollars a month and use that to access the ATM backbone.

Southern Internet and its customers use various access methods, including frame relay, to attach locally to MCI WorldCom. The company, which operates metropolitan area networks across the Southeast, funnels traffic from its own customers across the MCI WorldCom ATM backbone to the Internet. "You can get a T1 locally for several hundred dollars, but a long-distance link from Atlanta to Savannah, for example, is several thousand dollars a month," Jones says.

The long-distance carriers not only want customers to buy local access from them, they want to make it functional. That's why the three biggest offer integrated access services: Sprint's Integrated On-Demand Network, MCI WorldCom's On-Net, and AT&T's Integrated Network Connection Service. They deploy integrated access devices that groom data, voice, and other kinds of traffic for transport across their ATM backbones. That conversion can take place at the customer's premises or at the carrier's point of presence inside its switching software.

MCI WorldCom says it has built various interworking gateways: frame to ATM, frame to IP, and ATM to IP. "Customers can run applications over frame, ATM, or the Internet," says Paul Blesse, MCI WorldCom's On-Net data product manager. Users are going to tap ATM for critical applications, while IP is more likely to be reserved for less time- or latency-sensitive applications, he adds.

Carriers scoff at the prospect that such interworking will lead to bandwidth commoditization. They say the value-added features they can lay atop such pipes--Web-based management, firewalls, service-level guarantees--will ensure their role and their margins.

"These integrated packages will be as big a change as frame relay was," says Communications Supply CIO Mason Rotelli. "If anybody's looking to install a network now, this is what they should consider."

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