The average Internet surfer probably didn't notice, but an important shot in the battle over the future of the Internet was fired on Wednesday, Oct. 23, of this year when the Cells in Frames Alliance, chaired by Scott Brim of Cornell Information Technologies, announced the completion of version 1.0 of the Cells in Frames protocol specification.
The Cells in Frames Alliance is a consortium including hardware and software vendors, Internet service providers, user organizations and members of the trade press, along with Cornell. It was formed to develop a system that will allow the use of ATM (Asynchronous Transfer Mode) on existing Ethernet networks. Cornell plans to use ATM to provide telephone service over its data network, gradually phasing out the expensive PBX telephone system.
Completion of the specification is a big boost for those who are pushing the ATM protocol suite as the best way to provide reliable audio and video communication over both wide-area and local networks. (A "protocol" is a set of rules for transmitting data.)
Computer networks send data in short strings of 1s and 0s, with one string following another like bumper-to-bumper freeway traffic. ATM uses very short data strings called "cells," and moves them in ways that allow voice and video data to travel continuously. Ethernet uses much longer strings called "frames." Cells in Frames (CIF) allows up to 48 ATM cells to be strung together inside each Ethernet frame, which means a desktop computer can send and receive the data using the Ethernet card it already has installed. Without this system, the only way to use ATM here would be to install a new ATM card in every desktop computer on campus, at a total cost of several million dollars.
Brim has been working for several months to write the CIF specification, which tells hardware and software makers exactly how the ATM cells are arranged in an Ethernet frame and what information goes along with them. "Just writing a protocol is easy," said Brim, who is a member of CIT's Advanced Technologies and Planning group. "Making it efficient and flexible, leaving room for growth in the future, took seven drafts. We're quite pleased with it."
Computer applications that use voice have different needs from those that use video or text, Brim explained, and the trick was to create a system that satisfied each of those needs while not interfering with any of the others. "Vendors said 'that gets in my way' or 'that's too complicated,' and so on," Brim reported. "We have vendors doing strictly voice and strictly data and now they're all satisfied."
Brim and lots of others who do networking for a living hope ATM will become the future standard for local and campus area networks, but not everyone agrees. Other proposals are based on the belief that the currently dominant system, known as the TCP/IP protocol suite, is good enough, and that the only need is to provide "more bandwidth" -- that is, new hardware that can carry a lot more data in the same period of time.
Brim doesn't think we can solve all the problems just by building bigger pipes. ATM, he explained, will also offer different classes of service, some of which will have very little delay between when a piece of information is sent and when it is received. This means that interactive voice and video can flow without interruption, while lower-priority traffic like e-mail is shunted aside for a few seconds.
"My concern is voice," he explained. "Extremely low delays make all the difference in the world, and you could say the same thing about interactive video conferencing. When you're talking to someone face-to-face, you get instantaneous feedback when that person raises an eyebrow or makes a noise. There's no such thing as too little delay. We'll never get zero delay, but that's the goal."
ATM also offers other technical improvements that speed data transfer and conserve bandwidth.
Brim discussed ATM and Cells in Frames at two sessions during the Next Generation Network Conference in Washington, D.C., earlier this week. Version 1.0 of the Cells in Frames specification is posted on the CIF homepage at http://www.cif.cornell.edu .