f your old networks are beginning to stagger under the combined load of more users, greedier software and the World Wide Web, get ready to hear the term "ATM." It stands for "asynchronous transfer mode," an advanced switching technology that can speed up delivery of your data, voice and video traffic.
Just a decade ago, ATM existed only on the drawing boards. The first commercial ATM switch hit the market in 1991. Today, ATM switching is becoming almost commonplace for some purposes, such as public telephone networks. As such, it's an unseen element of the communications infrastructure.
But its visibility is growing as ATM begins to make inroads into the domains of data- and communications-dependent organizations like federal agencies. Rapidly falling prices and the need for more communications capacity are behind a new willingness to install ATM backbones within organizational borders and ATM links to external networks. Organizations can replace several high-speed leased telephone circuits (so-called T1 and T3 lines) with a single ATM connection, for example, and save money.
Some users are interested more in ATM's capabilities than in cutting their costs. It can carry telephone calls and data and video transmissions simultaneously. This is not as easy as it might sound, because the transmission requirements are quite different. For example, voice requires a consistent but narrow transmission path, expressed as 64,000 bits of data per second. Data requires variable amounts of bandwidth, ranging from a few bits per second to billions.
The need for a lot of communications capability and flexibility was behind the Army's and the Air Force's decisions to install ATM networks on their bases. Each of the services will spend about $1 billion to upgrade old switches and cabling. Under its Information Technology for the 21st Century (IT21) program, the Navy will replace conventional local area networks (LANs) with ATM on all ships. In addition, the backbone Defense Information Systems Network-the information superhighway for future military operations-will be an ATM network running over synchronous optical network (Sonet) fiber cabling.
Next-Generation Warfare
ATM technology is a good fit with 21st century military needs. The Pentagon has concluded that in future wars, the side with better information will be the victor. The Defense Department is pouring billions into systems that will collect and process live video, maps and geographic data, voice, radar images and other digitized information for battlefield commanders and their staffs. The voluminous information will require a big, multimodal pipeline for its delivery.
ATM has other advantages, as well:
- It's scalable, which means you can use it in a range of situations.
- It can link a PC with a local network or connect long-distance network backbones.
- It's particularly well-suited for use with optical fiber cabling. Many federal communications decision-makers, whether military or civilian, prefer fiber on the grounds that it is more secure than copper wiring. Wiretaps, or break-ins, are readily detected with fiber. However, technologically savvy wiretappers now can capture the signals from a fiber cable without penetrating it, so that advantage has nearly disappeared.
- It lets users establish different classes of service or virtual circuits. They can segregate network traffic for security reasons, ease of administration or better network performance.
But ATM's use in internal networks-that is, campus and building LAN setups-is not inevitable. It's being challenged by beefed-up Ethernet, the basic local networking scheme. Most LANs began life as 10-megabit-per-second shared Ethernet networks. Many large and growing LANs have had switches installed for better performance and control over network traffic. Now these are being upgraded to 100-megabit-per-second Fast Ethernet channels.
Around the new year vendors are promising to deliver Gigabit Ethernet-transporting a billion bits per second, at least theoretically, over fiber-optic cable-with a much lower price tag than ATM. When Fast Ethernet arrived, buyers found they could get a tenfold increase in performance for little more than twice the cost of the older technology. Networking companies such as 3Com Corp. are hoping that with Gigabit Ethernet they can deliver boosts of the same magnitude in price and performance.
They say Gigabit Ethernet will supply all the raw power needed in today's offices, with little disruption because of its inherent compatibility with the LANs already in use. Traffic to individual computers on the network will not run at gigabit speeds, at least not at first, but the LAN backbone-the segments that connect servers and switches-will. The Gigabit Ethernet backbone will connect readily to an ATM network for external communications, the developers promise. For the network inside the building or campus, they say, Ethernet will be less expensive to acquire and much easier to administer because it's a simpler technology.
They are holding out a vision of a networking hierarchy in which users have Fast Ethernet connections to their PCs, a Gigabit Ethernet links LAN segments in a large building or on a campus, and something else-probably ATM-transports data to distant points over the Internet. "The whole idea of a bandwidth hierarchy is a good one," says Gregory P. Cline, director of network research for Business Research Group (BRG), a market research firm in Newton, Mass. "People are stepping up in the bandwidth hierarchy as prices go down."
A Complete Turnaround
Cline's research indicates that as the year 2000 begins, ATM, Fast Ethernet, conventional Ethernet and a fiber networking scheme, FDDI, will be neck-and-neck in the race for primacy in the internal backbone networks of large organizations such as federal agencies. This suggests Ethernet won't be readily displaced. But another finding by the research firm suggests that ATM may have an unforeseen edge. More than two-thirds of the network decision-makers the firm surveyed now say they agree with the statement that "consolidation of data, video and voice into a single network infrastructure is a key facet of my network strategy."
"This is an absolute, complete turnaround" from a comparable survey two years ago, Cline says. In 1995, a majority disagreed with the suggestion that they would seek to consolidate these different kinds of traffic on a common network. History is on their side. In federal agencies, as in other large organizations, telephone services customarily have been provided by staffs separate from computer and data processing staffs. The cultural gap between the two services is as big as the technological gap.
The divide between computing and telephony is looking more bridgeable these days, and that bodes well for ATM. But some analysts say ATM's growth is hampered by its neither-fish-nor-fowl character. It's not fully embraced by either the computing camp, which is emotionally attached to Ethernet, or the telecommunications camp, which distrusts ATM's roots in data communications.
Nevertheless, ATM is the first technology since plain old telephone service that may make sense for data communications at every level from the desktop to the intercity backbone. ATM transmissions can travel at different speeds in different segments of the same network. That's an unfamiliar concept to the network planners, but the need to beef up the entire communications infrastructure is forcing them at least to consider ATM.
"LAN backbones are being pushed to the brink of exhaustion due to new sources of traffic," says Brendan Hannigan, a senior analyst with Forrester Research Inc. in Cambridge, Mass. He says buyers are enthusiastic about ATM but predicts that Gigabit Ethernet will win out, mostly because of its price advantages. Unless an organization is using its ATM network for voice communications, it can't justify the extra expense, he says.
The price equation is changing rapidly, however. "The price points on ATM keep dropping 30 to 40 percent a year," says George Mather of Bell Atlantic Federal. An ATM connection for a single workstation once cost $5,000, he says. Now it's down to about $200 and becoming less expensive every month.
The Gartner Group, another respected market analysis firm, disagrees with Forrester's pessimistic view. "ATM is becoming the norm for campus backbones," a Gartner analysis says. In the long term, it adds, "multimedia applications will help drive the migration to a broader use of inherent ATM capabilities."
If you work for an intelligence agency where Cable News Network or a similar video feed is available on your desktop computer, you probably agree this future will arrive soon. If it seems distant, consider whether your agency should be planning for it today.
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