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Bob Metcalfe and Ethernet

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In the early days of networking there were a variety of LAN technologies such as DECNet, FDDI, Token Ring, and ARCNET. Often times a system would only run on one of these and that system was then isolated from systems running on other LAN technologies. When I started out in networking, it was on Token Ring. It was expensive, you had to know the ring speed before you plugged something in, and one bad station could take down the whole ring.

Then in 1974 along came Ethernet, which was developed at Xerox PARC. Ethernet was inspired by Robert Metcalfe and his ALOHAnet. The picture shown here is Bob Metcalfe's first sketch of Ethernet.

The concept was a network technology where all of the nodes shared a single segment of coax. These nodes used "Carrier Sense Media Access" CSMA technology to detect if anyone else was talking at the time that node wanted to talk. If no one was transmitting, the node could transmit. If two nodes transmitted at the same time, they would detect a "Collision" and backoff a random amount of time before attempting to retransmit.

Mr. Metcalfe went on to start 3Com make Ethernet a part of our lives today. Thank you Bob Metcalfe and those at Xerox PARC and 3Com for developing a technology that has become a cost effective way of interconnecting devices on the network!

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