Eliminating data traffic jams. networks that steadily transfer data between computers at very high speeds - Ohio State Univ is developing asynchronous transfer mode ATM - Brief Article

USA Today (Society for the Advancement of Education), August, 1997

Technology developed at Ohio State University, Columbus, that lets data flow quickly and smoothly through a new kind of computer network will help improve interactive computer applications like telemedicine, videoconferencing, distance learning, and high-tech home entertainment. Asynchronous transfer mode (ATM) networks simultaneously can transport multimedia data -- the digital components of text, graphics, audio, and video that create an interactive on-line experience -- from one computer to another at very high speed. This keeps multimedia data flowing steadily in ATM networks.

In traditional networks, such as the Internet, computers bundle long streams of data into manageable packets for travel. The packets may be large or small. As the packets flow along wires to their destination across town, across the country, or across the world, they sometimes get separated.

Individual packets may follow different electronic paths and arrive at their destination in the wrong order. Or -- just like cars trying to cross a busy intersection -- some may get caught in the slow traffic of the more congested areas of the Internet. Such errors and delays spell disaster for multimedia transmission.

"Thats why not many people can watch video on the internet," points out Raj Jain, professor of computer and information science. What most people see is just a single frame of the picture, and after a delay, the next frame. For continuous video, data must flow continuously."

Even though each new generation of networking equipment offers faster connection speeds, the packets still travel according to the same old strategy. "Speed alone doesn't offer the guarantee of delivery that multimedia needs. In addition to speed, ATM gives an uninterrupted connection, like a telephone."

In ATM networks, data flows not in packets, but in cells of uniform size. All the cells for a single job travel along the same path from source to destination. Still, if too many cells try to enter a network at the same time, they cause a traffic jam. To ease the flow of data in ATM, Jain and his colleagues devised a new way for networks to regulate the amount of data that comes in.

To regulate traffic, traditional networks have only two options: They can drop the packets or tell the computers that send data to speed up or slow down, depending on how crowded the network is. What current networks can't do is tell the computers just how much to speed up or slow down.

With the Ohio State University traffic management technique, explicit rate indication for congestion avoidance (ERICA), an ATM network tells its computers exactly how much data to send. As a result, the ATM network never is overloaded or underloaded. For multimedia data, ERICA schedules the way text, graphics, voice, and video enter the network according to priority. Video, for example, must enter without delay for viewers to see a high-quality picture. Text, on the other hand, may wait for a short time without compromising the viewers' experience.