Inventor celebrates 30 years of Ethernet
Published: 21 May 2003 10:22 BST
Three decades ago, the medium that would one day earn the moniker "information superhighway" had such light traffic that there was little need for lanes, speed limits or highway patrols.
The odds were slim enough that electronic messages sent in a fraction of a second between a small pool of academic and military researchers would collide with one another. But scientists at Xerox's famed Palo Alto Research Centre knew that the situation was destined to change.
The task of devising a way to connect multiple computers to one another and to exchange messages over increasingly busy networks fell to Xerox PARC researcher Bob Metcalfe, who in a 1973 memo described the technology that would evolve into today's ubiquitous Ethernet protocol.
Metcalfe's Ethernet wasn't the first of such network protocols -- some preceded it, and many more followed. But it won out and became the dominant local area networking (LAN) technology for businesses, en route to its place in the Internet, besting a long series of what Metcalfe today calls networking "Godzillas".
Metcalfe, a 57-year-old native of Brooklyn, earned bachelor's degrees in both electrical engineering and management from MIT, and a master's degree in applied mathematics, before getting a doctorate in computer science from Harvard.
He completed his dissertation, "Packet Communication" -- a study, now available in hardcover, of the Arpanet and the Aloha Network -- the same year that he wrote the Ethernet memo. Now a resident of Boston with his wife and two teenage children, Metcalfe spoke to CNET News.com from Laguna Niguel, California, where he was attending IDG Forums' Vortex computer networking conference and preparing for Thursday's 30th birthday observances for Ethernet in Silicon Valley.
Tell me first of all how today's Ethernet has evolved from what you described 30 years ago.
It's evolved tremendously. Today's Ethernet bears very little resemblance to what David Boggs and I built in 1974, and it gives rise to the question, what is Ethernet exactly? I have a bunch of answers to that. It's gotten faster, it's been hubbed and switched unlike the original Ethernet. The original had packet collisions, but the latest versions have very few of those.
Today's Ethernet technology is extremely diverse and has very little in common with what appeared in '74. The good news is that they still call it Ethernet, and that's my word.
What did the word mean to you then?
My good fortune was to be given a problem that no one had ever had before -- how would you interconnect several computers with one at every desk? I was certainly early if not first in trying to solve that problem. We were building the first laser printer at that time. How could you connect the computers to each other and connect them to the printer and then to the early Internet, the Arpanet?
Ethernet was based on packets. Data was to be delivered in packets, and the Ethernet was to be decentralised so there could be nothing in the middle that could break or be unscalable. It lay within a hierarchy of protocols, so it only had to do what it needed to do, not things that would be handled elsewhere in the protocol stack, which was a relatively new idea at the time.
It was so simple, and that's one of its advantages. Another advantage was randomised retransmissions. That was based on the Aloha Network built at the University of Hawaii by Norm Abramson, a forerunner of 802.11 that had randomised retransmissions.
What's a randomised retransmission?
That means transmissions would be tried again later if they overlapped in time and interfered with each other, which we called a collision.
Arpanet introduced packet switching in about 1969, and the Aloha brought packet switching to radio in about 1970. So two big things happened in '73: One was the invention of the Ethernet, and the other was the beginning of the development of TCP/IP (Transmission Control Protocol/Internet Protocol), which started at Stanford in the summer of '73. The Internet and Ethernet have developed in lockstep since that time.
Today, most Internet packets, 99.99 percent of them, are carried on the Ethernet.
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