Internet Pioneers

Bob Metcalfe

As a graduate student, Bob Metcalfe worked on the ARAPNET at MIT. He later developed a new technology, called Ethernet, for connecting computers in a local network.

Work on the ARAPNET

Metcalfe was born in 1946, in Brooklyn, NY. He attended MIT where he earned degrees in electrical engineering and business management. He then earned a master's degree in applied mathematics from Harvard. While working on his Ph.D. in computer science at Harvard, he took a job at MIT building the hardware that would link MIT to the ARPANET. For a 1972 ARPANET conference he wrote an introductory pamphlet entitled Scenarios. The booklet included 19 scenarios for using the ARPANET, listed available resources at the various sites, and basic usage instructions.

Metcalfe had done a good job writing his informative booklet and was chosen to take ten AT&T officials on a virtual tour of the network. Unfortunately, the system crashed while Metcalfe was giving his demonstration. "I looked up in pain and I caught them smiling, delighted that packet-switching was flaky," said Metcalfe. "This I will never forget. It confirmed for them that circuit-switching technology was here to stay, and this packet-switching stuff was an unreliable toy that would never have much impact in the commercial world. It was clear to me they were tangled in the past." (Engelbart in Hafner & Lyon, 182).

Metcalfe's unpleasant experience with the AT&T officials made a lasting impression. "I saw that there are people who will connive against innovation," said Metcalfe. "They're hostile to it. And that has shaped my behavior ever since." (Engelbart in Kirsner)

Rejection and Hawaiian Inspiration

Metcalfe was excited about the ARAPNET and made it the topic of his doctoral dissertation. He was shocked when Harvard flunked him. His dissertation was "not theoretical enough." Metcalfe was angry. "They let me go into this thing and they gunned me. I'm even willing to stipulate that it wasn't very good. But I'd still justify my anger at those bastards for letting me fail. Had they been doing better jobs as professors, they would never have allowed that to happen. But I hated Harvard and Harvard hated me. It was a class thing from the start." (Engelbart in Kirsner)

Metcalfe had already accepted a job a Xerox's Palo Alto Research Center (PARC). He was told to come take his job anyway and finish his doctoral work later. His inspiration for a new dissertation came when he read a paper about the ALOHA network, or Alohanet at the university of Hawaii. The Alohanet used radio waves instead of telephone wire to transmit data. The main problem with using radio waves as a medium was that if two packets were sent out at the same time on the same broadcast channel they would interfere with each other and effectively cut off the transmission.

The Alohanet designers implemented a method called random access. Computers were allowed to transmit whenever they had data to send. They then waited to receive confirmation from the destination computer that the packets arrived. If packets collided and no confirmation was received, the sending computer would wait for a random (but very short) period of time and retransmit.

Metcalfe saw several problems in the design. He reworked the design and made it the topic of his new dissertation. His key improvement was to vary the random interval for re-transmission based on traffic load. If their was a lot of data traffic, the computer would wait longer periods before re-transmitting. This would greatly improve efficiency by limiting the number of repeat collisions. Metcalfe's new dissertation was accepted and he finally got his Ph.D.

Vint Cerf talks about the Alohanet.


Back at Xerox PARC, Metcalfe was given the task of designing a way to connect their new personal computers, the Altos, to each other. He modified his version of the Alohanet to use cables instead of radio and with several other adjustments created a new technology he called Ethernet. Ethernet worked well and Metcalfe started what would be years of selling his invention. In 1979, he started his own company, 3Com (which stands for computers, communication, compatibility) and continued to push Ethernet a the new standard for local area networks (LANs).

Throughout the 1980s LANs became very popular. They were especially popular at universities where many workstations were connected using Ethernet. Those LANs were in turn connected to the Internet to facilitate inter-institution communication. In this way, Ethernet was influential in the expansion of the Internet.

For Further Reading

Internet Collapses and Other Other InfoWorld Punditry
by Bob Metcalfe

Beyond Calculation: The Next Fifty Years of Computing



Home| Vannevar Bush | J.C.R. Licklider | Larry Roberts | Paul Baran |
Bob Metcalfe |
Doug Engelbart | Vint Cerf | Ted Nelson | Tim Berners-Lee |
Marc Andreesen
| Epilogue | References |