The Internet and other networks are based on a fundamental idea developed by the computer scientist Donald Watts Davies, who died on May 28th aged 75. He is not always given full credit for his contribution because Paul Baran, an American working at the Rand Corporation in California, had independently come up with the same idea.
However, Baran was focusing on a way to restructure AT&T's telephone system. Donald Davies was creating a data network, and the design of the Arpanet, the precursor of the Internet, was changed completely to adopt his technique.
Also, his term for the idea, which he called "packet switching", was much catchier than Baran's "distributed adaptive message block switching". Donald Davies had considered many possibilities - block, unit, segment, etc., - before deciding on packet as a sort of small package. And as he later told Baran: "Well, you may have got there first, but I got the name."
Like all beautiful ideas, "packet switching" is fundamentally simple. The problem with long-distance communications is that it is difficult and expensive to maintain a connection that stretches a long way across many different telephone lines through many different exchanges, some run by different companies. Why not chop the message into small packets first, then shove them on to the network and let them make their own way to their destination by the easiest route available? The receiving system can shuffle them into the right order, and ask for any missing packets to be re-sent.
Donald Davies did not, of course, go on to found a megacorporation and try to dominate data networking. He wasn't that sort of person. A research scientist commented: "He was an ideas man, and didn't follow through. It wasn't that he couldn't have, it was just that he chose to move on to the next idea. But one of his key features was that he would pick things up well before other people realised they were going to be important."
Donald Davies was born in Treorchy, in the Rhondda Valley. He went on to get a first in physics at Imperial College, London, at the age of 19, then took another first in mathematics, graduating in 1947.
At Imperial College he attended a lecture about ACE, one of the first digital computers, which was being built at the National Physical Laboratory (NPL), and promptly applied to join the team. There he worked with Alan Turing, the computer pioneer best known for his wartime code-breaking work at Bletchley Park, and stayed for 37 years, a well-respected member of Britain's scientific civil service.
NPL gave him the opportunity to work in a wide range of fields and it was at NPL that he developed the packet switching idea in 1965. He was also the first project leader for the Ministry of Technology's advanced computer technology project.
He is survived by his wife, Diane, a daughter and two sons.
Jack Schofield Donald Watts Davies: born 1924; died, May 2000