Donald Davies

This article is about Donald Davies, the computer scientist. For other uses, see Donald Davies (disambiguation).
Donald Watts Davies
Born (1924-06-07)7 June 1924
Treorchy, Glamorgan, Wales
Died 28 May 2000(2000-05-28) (aged 75)
Nationality Welsh
Fields Computer science
Institutions National Physical Laboratory
Alma mater Imperial College
Known for Packet switching

Donald Watts Davies, CBE, FRS[1] (7 June 1924 28 May 2000) was a Welsh computer scientist who was employed at the UK National Physical Laboratory (NPL). In 1965 he developed the concept of packet switching in computer networking,[2][3] and implemented it in the NPL network.[4][5] This was independent of the work of Paul Baran in the United States who had a similar idea in the early 1960s.[6] The ARPANET project credited Davies primarily for his influence.[7][8]

Early life

Davies was born in Treorchy in the Rhondda Valley, Wales. His father, a clerk at a coalmine, died a few months later, and his mother took Donald and his twin sister back to her home town of Portsmouth, where he went to school.[9]

He received a BSc degree in physics (1943) at Imperial College London, and then joined the war effort working as an assistant to Klaus Fuchs[9] on the nuclear weapons Tube Alloys project at Birmingham University.[10] He then returned to Imperial taking a first class degree in mathematics (1947); he was also awarded the Lubbock memorial Prize as the outstanding mathematician of his year.

In 1955, he married Diane Burton; they had a daughter and two sons.[11]

Career history

National Physical Laboratory

From 1947, he worked at the National Physical Laboratory (NPL) where Alan Turing was designing the Automatic Computing Engine (ACE) computer. It is said that Davies spotted mistakes in Turing's seminal 1936 paper On Computable Numbers, much to Turing's annoyance. These were perhaps some of the first "programming" errors in existence, even if they were for a theoretical computer, the universal Turing machine. The ACE project was overambitious and floundered, leading to Turing's departure.[10] Davies took the project over and concentrated on delivering the less ambitious Pilot ACE computer, which first worked in May 1950. A commercial spin-off, DEUCE was manufactured by English Electric Computers and became one of the best-selling machines of the 1950s.[10]

Davies also worked on applications of traffic simulation and machine translation. In the early 1960s, he worked on government technology initiatives designed to stimulate the British computer industry.

Packet switched network design

In 1966 he returned to the NPL at Teddington just outside London, where he headed and transformed its computing activity. He became interested in data communications following a visit to the Massachusetts Institute of Technology, where he saw that a significant problem with the new time-sharing computer systems was the cost of keeping a phone connection open for each user.[10]

Davies' key insight came in the realisation that computer network traffic was inherently "bursty" with periods of silence, compared with relatively constant telephone traffic. His work on packet switching, presented by his colleague Roger Scantlebury, initially caught the attention of the developers of ARPANET, a U.S. defence network, at a conference in Gatlinburg, Tennessee, in October 1967.[12] In Scantlebury's report following the conference, he noted "It would appear that the ideas in the NPL paper at the moment are more advanced than any proposed in the USA".[13][14] Davis first presented his own ideas on packet switching at a conference in Edinburgh on 5 August 1968.[15]

In 1965, Davies coined the term packet switching for the concept of dividing computer messages into packets that are routed independently, and possibly via differing routes, across a network and are reassembled at the destination, a concept previously known under a cryptic term distributed adaptive message block switching by Paul Baran.[16][17] He used the term "packets" as it was capable of being translated into languages other than English without compromise.[18] At NPL Davies helped build a packet-switched network (Mark I NPL network). It was replaced with the Mark II in 1973, and remained in operation until 1986, influencing other research in the UK and Europe.[19]

Larry Roberts of the Advanced Research Projects Agency in the United States applied Davies' concepts of packet switching in the late 1960s for the ARPANET, which went on to become a predecessor to the Internet.[10][20]

Baran was happy to acknowledge that Davies had come up with the same idea as him independently. In an e-mail to Davies he wrote

You and I share a common view of what packet switching is all about, since you and I independently came up with the same ingredients.[21]

Leonard Kleinrock, a contemporary working on analyzing data flow, also reached similar conclusions when he developed a theoretical basis for the operation of packet networks in his proposal for a Ph.D. thesis in 1961. He published his ideas in that year.[22] However, Kleinrock's contribution to packet switching is disputed by some,[23][24] including Baran[25] and Davies.[26]

Later work

Davies relinquished his management responsibilities in 1979 to return to research. He became particularly interested in computer network security. He retired from the NPL in 1984, becoming a security consultant to the banking industry.[10]

Awards and honours

Davies was appointed a Distinguished Fellow of the British Computer Society in 1975, a CBE in 1983 and a Fellow of the Royal Society in 1987. In 2012, Davies was inducted into the Internet Hall of Fame by the Internet Society.[27] A blue plaque commemorating Davies was unveiled in Treorchy in July 2013.[2]


Davies was survived by his wife Diane, a daughter and two sons.[28]



  1. Needham, R. M. (2002). "Donald Watts Davies, C.B.E. 7 June 1924 - 28 May 2000". Biographical Memoirs of Fellows of the Royal Society. 48: 87–10. doi:10.1098/rsbm.2002.0006.
  2. 1 2 Emily Gorton (26 July 2013). "Blue plaque to honour Welsh computing pioneer Donald Davies". The Independent. Retrieved 26 January 2016.
  3. Harris, Trevor, Who is the Father of the Internet? The case for Donald Watts Davies, retrieved 10 July 2013
  4. Scantlebury, Roger (25 June 2013). "Internet pioneers airbrushed from history". The Guardian. Retrieved 1 August 2015.
  5. "Packets of data were the key...". NPL. Retrieved 1 August 2015.
  6. "Donald Watts Davies". Internet Guide. 2010.
  7. "Pioneer: Donald Davies", Internet Hall of Fame
  8. Berners-Lee, Tim (1999), Weaving the Web: The Past, Present and Future of the World Wide Web by its Inventor, London: Orion, p. 7, ISBN 0 75282 090 7
  9. 1 2 The History of Computing Project - Donald Davies Biography
  10. 1 2 3 4 5 6 Cambell-Kelly, Martin (Autumn 2008). "Pioneer Profiles: Donald Davies". Computer Resurrection (44). ISSN 0958-7403.
  11. Obituary, The Guardian, 2 June 2000
  12. Isaacson, Walter (2014). The Innovators: How a Group of Hackers, Geniuses, and Geeks Created the Digital Revolution. Simon & Schuster. p. 237. ISBN 9781476708690.
  13. J. Gillies, R. Cailliau (2000). How the Web was Born: The Story of the World Wide Web. Oxford University Press. pp. 23–25. ISBN 0192862073.(source: head of the NPL Division of Computer Science)
  14. "Oral-History:Donald Davies & Derek Barber". Retrieved 13 April 2016.
  15. Luke Collins, "Network pioneer remembered", Engineering & Technology, IET, 6 September 2008
  16. Baran P. (April 1965) Distributed Adaptive Message Block Switching, Rand Corp. report No. P-3127.
  17. Packet Switching History
  18. Harris, p. 6
  19. Packet Switching
  20. Abbate, Jane (2000). Inventing the Internet. MIT Press. p. 38. ISBN 0262261332.
  21. Harris, p. 9
  22. Kleinrock, Leonard (1961), "Information flow in large communication nets", RLE Quarterly Progress Report (1)
  23. Alex McKenzie (2009), Comments on Dr. Leonard Kleinrock's claim to be "the Father of Modern Data Networking", retrieved April 23, 2015 "...there is nothing in the entire 1964 book that suggests, analyzes, or alludes to the idea of packetization."
  24. Isaacson, Walter (2014). The Innovators: How a Group of Hackers, Geniuses, and Geeks Created the Digital Revolution. Simon & Schuster. p. 245. ISBN 9781476708690. This led to an outcry among many of the other Internet pioneers, who publicly attacked Kleinrock and said that his brief mention of breaking messages into smaller pieces did not come close to being a proposal for packet switching
  25. Katie Hefner (November 8, 2001), "A Paternity Dispute Divides Net Pioneers", New York Times, Until Dr. Kleinrock began making his case prominently, two others -- Donald Davies, a British expert on computer security, and Paul Baran, formerly of the RAND Corporation -- were widely recognized as packet switching's inventors.
  26. Donald Davies (2001), "A Historical Study of the Beginnings of Packet Switching", Computer Journal, British Computer Society, I can find no evidence that he understood the principles of packet switching.
  27. 2012 Inductees, Internet Hall of Fame website. Last accessed April 24, 2012
  28. "Obituary: Data Pioneer Donald Davies Dies", Internet Society (ISOC), 31 May 2000

External links

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