by Jeff Caruso

From...

(IDG) -- Three Swedish start-ups equipped with a new technology for running voice, video and data over the same line are about to hit U.S. soil.

The technology, called Dynamic synchronous Transfer Mode (DTM), represents an alternative to more established technologies such as ATM switching. The timing of DTM's arrival is good; enterprises and service providers are struggling to find the best way to create multiservice networks for handling data and real-time voice and video traffic.

However, given the head start that ATM and high-speed IP routers have over DTM gear, backers of the new technology have much work ahead of them.

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It may be up to a few start-ups to get the word out.

One of the firms, Effnet, Inc., will put DTM interfaces on an upcoming router, one that fits on a card that can go in a Web server.

The two other Swedish start-ups are focusing more heavily on DTM itself. Dynarc, for example, last month introduced a DTM switch for enterprise networks into the U.S. market. This spring, the company plans to unveil a carrier-class version aimed at metropolitan-area networks (MAN).

And Net Insight this month will install its first U.S. DTM pilot network at ICG Telecom Group in Denver. Net Insight soon plans to introduce access devices for aggregating voice and data from enterprise networks onto citywide backbones.

DTM is a network architecture based on circuit switching, but with a twist. It can dynamically reallocate time slots, which means it can support real-time applications as well as bursty traffic such as IP.

Built on a fiber-optic ring in a corporate network or MAN, DTM can operate at very high speeds, with initial interfaces starting at about 1G bit/sec.

DTM, which has been in development since the early 1990s, also handles multicast traffic well.

ATM was designed to handle multiservice networks as well, but critics say it may not be the best-suited technology for all circumstances. "ATM is too complex to set up and tear down connections at a fast pace," says Olov Schagerlund, president and CEO of Dynarc. He also points out that ATM can't multicast easily because separate connections have to be established for every client receiving the multicast.

"We believe that IP/DTM could be implemented and maintained more cost-efficiently with the same or better functionality as the complex ATM/SONET stack," says Björn Pehrson, professor at the Swedish Royal Institute of Technology, where DTM was developed. The Royal Institute currently is working with Stanford University, experimenting with Dynarc DTM switches for videoconferencing and shared applications.

ATM, however, has a few advantages over DTM, says George Dobrowski, president of the ATM Forum.

DTM doesn't have access to intelligent network services like ATM does, he says. For instance, ATM can handle complex telephone call routing.

Dobrowski says that ATM is far ahead of DTM in implementation and availability.

"Is it justified to develop a new technology to replace what is already available?" Dobrowski asks.

ATM is also a standard, whereas DTM is a proprietary technology owned by Dynarc and Net Insight. Ericsson, which backed DTM's development, also owns several of the patents.

Getting the word out

DTM's biggest hurdle may be that few people have heard of it. The big-name internetwork companies contacted for this article, such as Cisco and Nortel Networks, couldn't even find representatives familiar with the technology.

On the other hand, many service providers are open to new technology, and the idea of changing horses in midstream may not be an issue. "Nobody's really on a horse right now," says Jennifer Pigg, senior vice president of data communications at Boston-based The Yankee Group.

The lack of DTM standards is probably not an issue in the short term, she adds. To avoid having the technology steered in a different direction by big network companies, the start-ups should keep DTM out of standards groups for as long as possible and focus on getting implementations in place, Pigg says.

Several high-speed routing firms in the U.S. are discussing the use of DTM technology within their routers as the internal architecture, Pigg says.

Dynarc's Schagerlund says the Swedish companies plan to take DTM to the International Telecommunication Union later this year for standardization, and will approach the Internet Engineering Task Force about standards for sending IP over DTM.

Jeff Caruso is a senior editor at Network World.