Connecting Two Computers Together

Bob Metcalfe was born in New York in a Norwegian ghetto! His mother was Norwegian and his father was Irish - not an easy combination back in the 1940s. His father was a technician working in the space industry building gyroscopic platforms. He encouraged Bob to build model trains in the basement including the electrical switching needed to control them. In high school he built a very simple, by today's standards, computer. It did nothing more than add binary numbers together but in 1959 there weren't even pocket calculators and so it was a real achievement.

With his particular interests in electronics it was natural for Metcalfe to enrol as an MIT student of electrical engineering. After graduating in 1969 he went to Harvard to study mathematics but still with a practical angle - the new subject of networking. While he was at Harvard he took a full time job with the Advanced Research Projects Agency (ARPA) on the big wide area network they were building - ARPAnet. Of course we now know that ARPAnet grew into the Internet but at the time it was just a way of connecting a small number of large computers. It did, however, introduce Metcalfe to the principles of packet switching. He wrote programs and helped with the design of the hardware.

It is important to know at this point that while ARPAnet was a packet switched network, i.e. one in which a data packet could be routed from one machine to another until it reached its final destination, there were hardwired long distance connections between pairs of machines. That is, the Wide Area Network (WAN) that was ARPAnet wasn't suitable as a model for building a Local Area Network (LAN) connecting many machines within the same building. You simply can't afford to run a cable between every machine in the building, the number of connections would be too great. You can't even afford to make individual connections between enough machines to make packet switching work.