Editing Donald Davies

{{Short description|Welsh computer scientist and Internet pioneer (1924–2000)}}
{{About|Donald Davies, the computer scientist}}
{{EngvarB|date=July 2017}}
{{Use dmy dates|date=July 2017}}
{{Infobox scientist
|name              = Donald Watts Davies
|honorific_suffix =  {{post-nominals|country=GBR|size=100%|CBE|FRS}}
|image             =  Donald-Davies Welsh computer scientist.jpg
|image_size        =
|caption           = 
|birth_date        = {{Birth date|df=yes|1924|6|7}}
|birth_place       = [[Treorchy]], [[Glamorgan]], Wales
|death_date        = {{Death date and age|df=yes|2000|5|28|1924|6|7}}
|death_place       = Esher, Surrey, England
|residence         = 
|ethnicity         = 
|fields            = [[Computer science]]
|workplaces        = [[National Physical Laboratory, UK|National Physical Laboratory]]
|alma_mater        = [[Imperial College London|Imperial College]]
|doctoral_advisor  = 
|academic_advisors = 
|doctoral_students = 
|notable_students  = 
|known_for         = [[Packet switching]]
|author_abbrev_bot = 
|author_abbrev_zoo = 
|influences        = 
|influenced        = 
|awards            = [[CBE]]<br>[[Fellow of the Royal Society|FRS]]<br>Distinguished Fellow, [[British Computer Society|BCS]]
|religion          =
|signature         = <!--(filename only)-->
|footnotes         = 
}}

'''Donald Watts Davies''', {{post-nominals|country=GBR|CBE|FRS}} (7 June 1924 – 28 May 2000) was a Welsh [[computer scientist]] and [[Internet pioneer]] who was employed at the UK [[National Physical Laboratory (United Kingdom)|National Physical Laboratory]] (NPL).

During 1965-67 he invented modern [[Data communication|data communications]], including [[packet switching]], high-speed [[Router (computing)|routers]], layered [[Communication protocol|communication protocols]], hierarchical [[Computer network|computer networks]] and the essence of the [[end-to-end principle]], concepts that are used today in computer networks worldwide. He envisioned, in 1966, that there would be a "single network" for data and telephone communications. Davies proposed and studied a commercial national data network in the United Kingdom and designed and built the first implementation of packet switching in the local-area [[NPL network]] in 1966-69 to demonstrate the technology. Many of the wide-area packet-switched networks built in the late 1960s and 1970s were similar "in nearly all respects" to his original 1965 design. Davies' work influenced the [[ARPANET]] in the United States and the [[CYCLADES]] project in France, and was key to the development of the data communications technology used in [[Internet]], which is a network of networks.

Davies' work was independent of the work of [[Paul Baran]] in the United States who had some similar ideas in the early 1960s, and who also provided input to the ARPANET project, after his work was highlighted by Davies' team.

==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.<ref name="thocp">[http://www.thocp.net/biographies/davies_donald.htm The History of Computing Project – Donald Davies Biography]</ref> He attended the [[Portsmouth College|Southern Grammar School for Boys]].<ref name="frs" />

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]]<ref name="thocp"/> on the nuclear weapons [[Tube Alloys]] project at Birmingham University.<ref name="MCK">{{cite journal|first=Martin|last=Cambell-Kelly|title=Pioneer Profiles: Donald Davies|journal=Computer Resurrection|number=44|date=Autumn 2008|issn=0958-7403|url=http://www.computerconservationsociety.org/resurrection/res44.htm}}</ref> 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.<ref name="frs" />

In 1955, he married Diane Burton; they had a daughter and two sons.<ref name="guardian">{{citation|title=Donald Davies Obituary|date=2 June 2000|url=https://www.theguardian.com/news/2000/jun/02/guardianobituaries2|work=The Guardian}}</ref>

==National Physical Laboratory==
From 1947, Davies worked at the [[National Physical Laboratory, UK|National Physical Laboratory (NPL)]] at [[Teddington]], just outside London, where [[Alan Turing]] was designing the [[Automatic Computing Engine]] (ACE) computer.<ref>{{Cite book |last=Copeland |first=B. Jack |url=https://www.google.co.uk/books/edition/Alan_Turing_s_Electronic_Brain/YhQZnczOS7kC?hl=en&gbpv=1&pg=PA349&printsec=frontcover |title=Alan Turing's Electronic Brain: The Struggle to Build the ACE, the World's Fastest Computer |date=2012-05-24 |publisher=OUP Oxford |isbn=978-0-19-960915-4 |language=en}}</ref> Davies spotted mistakes in Turing's seminal 1936 paper ''On Computable Numbers'', much to Turing's annoyance, which were perhaps some of the first "programming" [[Software bug|bugs]] in existence, even if they were for a theoretical computer, the [[universal Turing machine]].<ref>{{Cite book |last=Copeland |first=B. J. |url=https://www.google.co.uk/books/edition/The_Essential_Turing/7sEbjfnVWREC?hl=en&gbpv=1&pg=PR8-IA10&printsec=frontcover |title=The Essential Turing |date=2004-09-09 |publisher=Clarendon Press |isbn=978-0-19-160686-1 |language=en}}</ref> The ACE project was overambitious and floundered, leading to Turing's departure.<ref name="MCK"/> Davies took over the project and concentrated on delivering the less ambitious [[Pilot ACE]] computer, which first worked in May 1950. A commercial spin-off, [[English Electric DEUCE|DEUCE]] was manufactured by [[English Electric Computers]] and became one of the best-selling machines of the 1950s.<ref name="MCK"/>

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 switching===
{{Further|NPL network}}
In 1965, Davies became interested in [[Data communication|data communications]] following a seminar he gave at the [[Massachusetts Institute of Technology]].<ref name=":23" /><ref name=":6" /> 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.<ref name=":23">{{cite journal |last=Roberts |first=Lawrence G. |date=November 1978 |title=The evolution of packet switching |url=http://www.ece.ucf.edu/~yuksem/teaching/nae/reading/1978-roberts.pdf |journal=Proceedings of the IEEE |volume=66 |issue=11 |pages=1307–13 |doi=10.1109/PROC.1978.11141 |s2cid=26876676}}</ref> Davies' key insight came in the realisation that computer network traffic was inherently "bursty" in nature with periods of silence, compared with relatively constant telephone traffic.<ref>{{cite journal|last1=Dettmer|first1=R.|title=Almost an Accident|journal=IEE Review|date=16 July 1998|volume=44|issue=4|pages=169–172|url=https://ieeexplore.ieee.org/document/707839|issn=0953-5683|doi=10.1049/ir:19980411|doi-broken-date=7 December 2024 |url-access=subscription}}</ref><ref name="MCK" /> He applied the principle of time-sharing to the data communications line as well as the computer to invent the concept of what he called [[packet switching]].<ref name="MCK" /><ref name=":9">{{cite journal |last1=Barber |first1=Derek |date=Spring 1993 |title=The Origins of Packet Switching |url=http://www.cs.man.ac.uk/CCS/res/res05.htm#f |journal=The Bulletin of the Computer Conservation Society |issue=5 |issn=0958-7403 |access-date=6 September 2017}}</ref> Davies forecast today's [[Killer application|killer app]] for his new communication service:<ref>{{Cite journal |last=Edmondson-Yurkanan |first=Chris |date=2007 |title=SIGCOMM's archaeological journey into networking's past |url=https://dl.acm.org/doi/10.1145/1230819.1230840 |journal=Communications of the ACM |language=en |volume=50 |issue=5 |pages=63–68 |doi=10.1145/1230819.1230840 |issn=0001-0782|url-access=subscription }}</ref>

{{Quote|text=The greatest traffic could only come if the public used this means for everyday purposes such as shopping... People sending enquiries and placing orders for goods of all kinds will make up a large section of the traffic... Business use of the telephone may be reduced by the growth of the kind of service we contemplate.|author=Donald Davies (1965)}}

Davies proposed dividing computer messages into very "short messages in fixed format" that are routed independently across a network, with differing routes allowed for related packets, which are reassembled at the destination.<ref name=":8" /> Davies used the word "packet" after consulting with a linguist because it was capable of being translated into languages other than English without compromise.<ref>{{Harvnb|Harris|p=6}}</ref>

The following year, he returned to work at the NPL, where he became Superintendent of the Computer Science Division and transformed its computing activity.<ref name=":7">{{Cite conference |last1=Scantlebury |first1=Roger |last2=Wilkinson |first2=Peter |last3=Barber |first3=Derek |date=2001 |title=NPL, Packet Switching and the Internet |url=http://www.topquark.co.uk/conf/IAP2001.html |archive-url=https://web.archive.org/web/20030807200346/http://www.topquark.co.uk/conf/IAP2001.html |url-status=dead |archive-date=2003-08-07 |conference=Symposium of the Institution of Analysts & Programmers 2001 |access-date=2024-06-13 |quote=The system first went 'live' early in 1969 |website=}}</ref> He designed and proposed a commercial national data network based on packet switching in his 1966 ''Proposal for the Development of a National Communications Service for On-line Data Processing''.<ref name=":8">{{Citation | last = Davies | first = D. W. | author-link = Donald | title = Proposal for a Digital Communication Network | publisher = [[National Physical Laboratory (United Kingdom)|National Physical Laboratory]] | year = 1966 | url = http://www.dcs.gla.ac.uk/~wpc/grcs/Davies05.pdf }}</ref> This work was the first to describe the concept of high-speed "switching nodes", today known as [[Router (computing)|routers]] as well as "interface computers".<ref name=":6">{{cite web |last1=Roberts |first1=Dr. Lawrence G. |date=May 1995 |title=The ARPANET & Computer Networks |url=http://www.packet.cc/files/arpanet-computernet.html |url-status=dead |archive-url=https://web.archive.org/web/20160324032800/http://www.packet.cc/files/arpanet-computernet.html |archive-date=24 March 2016 |access-date=13 April 2016}}</ref><ref>{{Cite book |last=Pelkey |first=James |url=http://www.historyofcomputercommunications.info/Individuals/abstracts/donald-davies.html |title=Entrepreneurial Capitalism & Innovation: A History of Computer Communications 1968 - 1988 |date=2007 |quote=paper dated June 1966 ... introduced the concept of an “interface computer” to sit between the user equipment and the packet network. |access-date=2020-02-18}}</ref> Davies applied [[queueing theory]] to show that "there is an ample margin between the estimated performance of the [packet-switched] system and the stated requirement" in terms of a satisfactory [[Response time (telecommunications)|response time]] for a human user.<ref>{{Cite book |last=Roberts |first=Gareth Ffowc |url=https://www.google.co.uk/books/edition/For_the_Recorde/waCYEAAAQBAJ?hl=en&gbpv=1&pg=PA102&printsec=frontcover |title=For the Recorde: A History of Welsh Mathematical Greats |date=2022 |publisher=University of Wales Press |isbn=978-1-78683-917-6 |language=en |quote=Mathematicians had already developed methods of analysing traffic jams - 'queuing theory' ... - but it needed a new insight to solve the problem of how to avoid bottle-necks between computers. That insight was provided by Donald Davies, who established the principles that today enable computers to communicate easily and speedily with each other, allowing them to create computer networks that together form the 'Internet'}}</ref><ref name=":8" /> This addressed a key question about the viability of computer networking.<ref name=":92">{{cite tech report|last1=Heart|first1=F.|last2=McKenzie|first2=A.|last3=McQuillian|first3=J.|last4=Walden|first4=D.|url=https://web.archive.org/web/20230527095942/https://walden-family.com/bbn/arpanet-completion-report.pdf|title=Arpanet Completion Report|publisher=Bolt, Beranek and Newman|location=Burlington, MA|date=January 4, 1978}} pp. III-40-1</ref> In this paper, he predicted there would be a "single network" for data and telephone communications:<ref name=":8" />

{{Quote|text=Computer developments in the distant future might result in one type of network being able to carry speech and digital messages efficiently.|author=Donald Davies (1966)}}

Davies and his team were the first to write [[Communication protocol|communication protocols]] in a modern data-commutation context in an April 1967 memorandum ''A Protocol for Use in the NPL Data Communications Network'' written by [[Roger Scantlebury]] and Keith Bartlett.<ref>{{Cite book |last=Naughton |first=John |url=https://books.google.com/books?id=bbonCgAAQBAJ&pg=PT290 |title=A Brief History of the Future |date=2015-09-24 |publisher=Orion |isbn=978-1-4746-0277-8 |page=292 |language=en}}</ref><ref name=":3b2">{{Cite journal |last=Campbell-Kelly |first=Martin |date=1987 |title=Data Communications at the National Physical Laboratory (1965-1975) |url=https://archive.org/details/DataCommunicationsAtTheNationalPhysicalLaboratory |journal=Annals of the History of Computing |language=en |volume=9 |issue=3/4 |pages=221–247 |doi=10.1109/MAHC.1987.10023 |s2cid=8172150}}</ref>

His work on packet switching, presented by Scantlebury, initially caught the attention of the developers of the [[ARPANET]], a U.S. Department of Defense (DoD) network, at the [[Symposium on Operating Systems Principles]] in October 1967.<ref>{{cite book|last1=Isaacson|first1=Walter|title=The Innovators: How a Group of Hackers, Geniuses, and Geeks Created the Digital Revolution|date=2014|publisher=Simon & Schuster|isbn=9781476708690|page=237|url=https://books.google.com/books?id=4V9koAEACAAJ&pg=PA237}}</ref> The proposed network design was based on a hierarchical structure, with "local networks" communicating with a "high level network".<ref>{{cite report |url=https://apps.dtic.mil/sti/pdfs/ADA115440.pdf |title=A History of the ARPANET: The First Decade |date=1 April 1981 |publisher=Bolt, Beranek & Newman Inc. |pages=53 of 183 (III-11 on the printed copy) |archive-url=https://web.archive.org/web/20121201013642/http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA115440 |archive-date=1 December 2012 |url-status=live}}</ref> To deal with packet permutations (due to dynamically updated route preferences) and [[datagram]] losses (unavoidable when fast sources send to a slow destinations), he assumed that "all users of the network will provide themselves with some kind of error control",<ref name=":5">{{cite conference |last1=Davies |first1=Donald |last2=Bartlett |first2=Keith |last3=Scantlebury |first3=Roger |last4=Wilkinson |first4=Peter |date=October 1967 |title=A Digital Communication Network for Computers Giving Rapid Response at remote Terminals |url=https://people.mpi-sws.org/~gummadi/teaching/sp07/sys_seminar/how_did_erope_blow_this_vision.pdf |conference=ACM Symposium on Operating Systems Principles |archive-url=https://ghostarchive.org/archive/20221010/https://people.mpi-sws.org/~gummadi/teaching/sp07/sys_seminar/how_did_erope_blow_this_vision.pdf |archive-date=2022-10-10 |access-date=2020-09-15 |url-status=live}}</ref> thus inventing what came to be known as the [[end-to-end principle]]. 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".<ref name="J. Gillies, R. Cailliau">{{cite book |url=https://archive.org/details/howwebwasbornsto00gill|url-access=registration|author=J. Gillies, R. Cailliau|title=How the Web was Born: The Story of the World Wide Web|pages=[https://archive.org/details/howwebwasbornsto00gill/page/23 23]–25|publisher=Oxford University Press|date=2000|isbn= 0192862073}}</ref><ref>{{cite web|title=Oral-History:Donald Davies & Derek Barber|url=http://ethw.org/Oral-History:Donald_Davies_%26_Derek_Barber|access-date=13 April 2016}}</ref> [[Lawrence Roberts (scientist)|Larry Roberts]], of the [[Advanced Research Projects Agency]] (ARPA) of the [[United States Department of Defense]] (DoD), applied Davies' concepts of packet switching for the ARPANET, which went on to become a predecessor to the [[Internet]].<ref name="frs">{{Cite journal |last1=Needham |first1=R. M. |author-link=Roger Needham |year=2002 |title=Donald Watts Davies, C.B.E. 7 June 1924 – 28 May 2000 |journal=[[Biographical Memoirs of Fellows of the Royal Society]] |volume=48 |pages=87–96 |doi=10.1098/rsbm.2002.0006 |s2cid=72835589 |quote=The 1967 Gatlinburg paper was influential on the development of ARPAnet, which might otherwise have been built with less extensible technology. ... Davies was invited to Japan to lecture on packet switching.}}</ref><ref name=":0">{{Cite web |title=Computer Pioneers - Donald W. Davies |url=https://history.computer.org/pioneers/davies.html |access-date=2020-02-20 |website=IEEE Computer Society |quote=The design of the ARPA network (ArpaNet) was entirely changed to adopt this technique.}}</ref><ref>[http://www.internethalloffame.org/inductees/donald-davies "Pioneer: Donald Davies"], Internet Hall of Fame "America’s Advanced Research Project Agency (ARPA), and the ARPANET received his network design enthusiastically and the NPL local network became the first two computer networks in the world using the technique."</ref><ref>{{cite book|last1=Abbate|first1=Jane|author-link=Janet Abbate|title=Inventing the Internet|date=2000|publisher=MIT Press|isbn=0262261332|page=38|url=https://books.google.com/books?id=9BfZxFZpElwC&pg=PA38}}</ref> 

In July 1968, NPL put on a demonstration of real and simulated networks at an event organised by the [[Real Time Club]] at the [[Royal Festival Hall]] in London.<ref name=":9" /> Davies first presented his own ideas on packet switching at a conference in Edinburgh on 5 August 1968.<ref>Luke Collins, "Network pioneer remembered", ''Engineering & Technology'', IET, 6 September 2008</ref><ref>{{Citation| last1 = Davies| first1 = D. W.| author-link = Donald Davies| contribution = The Principles of a data Communication Network for Computers and Remote Peripherals| title = Information processing 68: proceedings of IFIP Congress 1968 | series = International Federation for Information Processing | date = August 1968 | publisher = North Holland | isbn = 0-7204-2032-6  }}</ref>  In 1969, Davies was invited to Japan to lecture on packet switching. He gave a series of nine three-hour lectures, concluding with an intense discussion with around 80 people.<ref name="frs" /> 

During 1968-9,<ref name=":3b2" /><ref>{{cite conference |last=Scantlebury |first=R. A. |author2=Wilkinson, P.T. |year=1974 |title=The National Physical Laboratory Data Communications Network |url=http://www.rogerdmoore.ca/PS/NPLPh/NPL1974A.html |pages=223–228 |book-title=Proceedings of the 2nd ICCC 74}}</ref> Davies directed the construction of the network, elements of which went live in early 1969,<ref name=":72">{{Cite conference |last1=Rayner |first1=David |last2=Barber |first2=Derek |last3=Scantlebury |first3=Roger |last4=Wilkinson |first4=Peter |date=2001 |title=NPL, Packet Switching and the Internet |url=http://www.topquark.co.uk/conf/IAP2001.html |archive-url=https://web.archive.org/web/20030807200346/http://www.topquark.co.uk/conf/IAP2001.html |url-status=dead |archive-date=2003-08-07 |conference=Symposium of the Institution of Analysts & Programmers 2001 |access-date=2024-06-13 |quote=The system first went 'live' early in 1969 |website=}}</ref><ref name="Hempstead20052" /> the first implementation of packet switching in the world.<ref name=":22">{{Cite journal |last1=John S |first1=Quarterman |last2=Josiah C |first2=Hoskins |date=1986 |title=Notable computer networks |journal=Communications of the ACM |language=EN |volume=29 |issue=10 |pages=932–971 |doi=10.1145/6617.6618 |s2cid=25341056 |quote=The first packet-switching network was implemented at the National Physical Laboratories in the United Kingdom. It was quickly followed by the ARPANET in 1969. |doi-access=free}}</ref><ref>{{Cite AV media |url=https://www.inc.com/computerfreaks |title=Computer Freaks |date=June 22, 2023 |last=Haughney Dare-Bryan |first=Christine |type=Podcast |publisher=Inc. Magazine |series=Chapter Two: In the Air |minutes=35:55 |quote=Leonard Kleinrock: Donald Davies ... did make a single node packet switch before ARPA did}}</ref> The local-area ''Mark I [[NPL network]]'', became fully operational in January 1970.<ref name="Hempstead20052">{{cite book |author1=C. Hempstead |url=https://books.google.com/books?id=2ZCNAgAAQBAJ&pg=PA574 |title=Encyclopedia of 20th-Century Technology |author2=W. Worthington |date=2005 |publisher=[[Routledge]] |isbn=9781135455514 |pages=573–5}}</ref> It was upgraded to the ''Mark II'' in 1973 with a layered protocol architecture, and remained in operation until 1986.<ref name=":3b2" /> The NPL team also carried out [[simulation]] work on packet networks, studying datagrams and [[network congestion]] in wide-area networks of a scale to facilitate data communications across the United Kingdom.<ref name="MCK" /><ref name="Hempstead20052" /><ref name=":82">{{Cite thesis |last=Clarke |first=Peter |title=Packet and circuit-switched data networks |date=1982 |degree=PhD |publisher=Department of Electrical Engineering, Imperial College of Science and Technology, University of London |url=https://spiral.imperial.ac.uk/bitstream/10044/1/35864/2/Clarke-PN-1982-PhD-Thesis.pdf}} "As well as the packet switched network actually built at NPL for communication between their local computing facilities, some simulation experiments have been performed on larger networks. A summary of this work is reported in [69]. The work was carried out to investigate networks of a size capable of providing data communications facilities to most of the U.K. ... Experiments were then carried out using a method of flow control devised by Davies [70] called 'isarithmic' flow control. ... The simulation work carried out at NPL has, in many respects, been more realistic than most of the ARPA network theoretical studies."</ref><ref name="Pelkey">{{cite book |last=Pelkey |first=James |title=Entrepreneurial Capitalism and Innovation: A History of Computer Communications 1968-1988 |chapter=6.3 CYCLADES Network and Louis Pouzin 1971-1972 |access-date=3 February 2020 |chapter-url=http://www.historyofcomputercommunications.info/Book/6/6.3-CYCLADESNetworkLouisPouzin1-72.html |archive-url=https://web.archive.org/web/20210617093154/https://www.historyofcomputercommunications.info/Book/6/6.3-CYCLADESNetworkLouisPouzin1-72.html |archive-date=17 June 2021 |url-status=dead}}</ref> These early years of computer [[Shared resource|resource sharing]] were documented in the 1972 film ''[[Computer Networks: The Heralds of Resource Sharing]]''. Davies' original ideas influenced other research around the world,<ref name="Hempstead20052" /><ref name=":2">{{cite journal |last1=Roberts |first1=Dr. Lawrence G. |date=November 1978 |title=The Evolution of Packet Switching |url=http://www.ismlab.usf.edu/dcom/Ch10_Roberts_EvolutionPacketSwitching_IEEE_1978.pdf |url-status=dead |journal=IEEE Invited Paper |archive-url=https://web.archive.org/web/20181231092936/http://www.ismlab.usf.edu/dcom/Ch10_Roberts_EvolutionPacketSwitching_IEEE_1978.pdf |archive-date=31 December 2018 |access-date=September 10, 2017 |quote=In nearly all respects, Davies’ original proposal, developed in late 1965, was similar to the actual networks being built today.}}</ref> including [[Louis Pouzin|Louis Pouzin's]] [[CYCLADES]] project in France.<ref name="Pelkey8.3">{{cite book |last=Pelkey |first=James |title=Entrepreneurial Capitalism and Innovation: A History of Computer Communications 1968–1988 |chapter=8.3 CYCLADES Network and Louis Pouzin 1971–1972 |chapter-url=https://historyofcomputercommunications.info/section/8.3/CYCLADES-Network-and-Louis-Pouzin-1971-1972/}}</ref> 

In a 1978 special edition of the [[Proceedings of the IEEE]] on packet switching, [[Robert Kahn (computer scientist)|Bob Kahn]], the guest editor, quoted Davies' reflections on ten years of experience with packet communication networks:<ref>{{Cite journal |last1=Kahn |first1=R.E. |last2=Uncapher |first2=K.W. |last3=van Trees |first3=H.L. |date=1978 |title=Scanning the issue |url=https://ieeexplore.ieee.org/document/1455409 |journal=Proceedings of the IEEE |volume=66 |issue=11 |pages=1303–1306 |doi=10.1109/PROC.1978.11140 |issn=0018-9219|url-access=subscription }}</ref>

{{Quote|text=... there are three factors, above all, which critically affect the quality of the network. The most critical factor is our ability to design man-machine interfaces which are convenient and natural for most people to use. A second factor of some importance is the high reliability and availability of the services. They cannot become an integral part of industry and commerce unless they can be utterly reliable in the way we have come to expect of the traditional telecommunication media. A third requirement is an overall system design which allows for adaptability to changes in the system as well as to new user requirements. |author=Donald Davies (1978)}}

=== Internetworking ===
Davies, along with Derek Barber, his deputy, and Roger Scantlebury, conducted research into protocols for [[internetworking]]. They participated in the [[International Network Working Group]] from 1972, initially chaired by [[Vint Cerf]] and later by Barber.<ref>{{Cite journal|last=McKenzie|first=Alexander|date=2011|title=INWG and the Conception of the Internet: An Eyewitness Account|journal=IEEE Annals of the History of Computing|volume=33|issue=1|pages=66–71|doi=10.1109/MAHC.2011.9|s2cid=206443072|issn=1934-1547|quote=Perhaps the only historical difference that would have occurred if DARPA had switched to the INWG 96 protocol is that rather than Cerf and Kahn being routinely cited as “fathers of the Internet,” maybe Cerf, Scantlebury, Zimmermann, and I would have been.}}</ref><ref name="ieee201703">{{cite magazine|author=Andrew L. Russell|date=30 July 2013|title=OSI: The Internet That Wasn't|url=https://spectrum.ieee.org/osi-the-internet-that-wasnt|magazine=[[IEEE Spectrum]]|volume=50|issue=8}}</ref><ref name=":18">{{cite web |date=24 April 1990 |title=Smithsonian Oral and Video Histories: Vinton Cerf |url=https://americanhistory.si.edu/comphist/vc1.html |access-date=23 September 2019 |website=[[National Museum of American History]] |publisher=[[Smithsonian Institution]] |quote=Roger Scantlebury was one of the major players. And Donald Davies who ran, at least he was superintendent of the information systems division or something like that. I absolutely had a lot of interaction with NPL at the time. They in fact came to the ICCC 72 and they had been coming to previous meetings of what is now called Datacomm. Its first incarnation was a long title having to do with the analysis and optimization of computer communication networks, or something like that. This started in late 1969, I think, was when the first meeting happened in Pine Hill, Georgia. I didn't go to that one, but I went to the next one that was at Stanford, I think. That's where I met Scantlebury, I believe, for the first time. Then I had a lot more interaction with him. I would come to the UK fairly regularly, partly for IFIP or INWG reasons}}</ref><ref>Davies, Shanks, Heart, Barker, Despres, Detwiler and Riml, "Report of Subgroup 1 on Communication System", INWG Note No. 1.</ref> Davies and Scantlebury were acknowledged by Cerf and [[Bob Kahn]] in their seminal 1974 paper on internetworking, ''A Protocol for Packet Network Intercommunication''.<ref name=":3">{{cite web |last=Scantlebury |first=Roger |date=25 June 2013 |title=''Internet pioneers airbrushed from history'' |url=https://www.theguardian.com/technology/2013/jun/25/internet-pioneers-airbrushed-from-history |access-date=1 August 2015 |work=The Guardian}}</ref><ref>{{Cite journal|last1=Cerf|first1=V.|last2=Kahn|first2=R.|date=1974|title=A Protocol for Packet Network Intercommunication|url=https://www.cs.princeton.edu/courses/archive/fall06/cos561/papers/cerf74.pdf|journal=IEEE Transactions on Communications|volume=22|issue=5|pages=637–648|doi=10.1109/TCOM.1974.1092259|issn=1558-0857|quote=The authors wish to thank a number of colleagues for helpful comments during early discussions of international network protocols, especially R. Metcalfe, R. Scantlebury, D. Walden, and H. Zimmerman; D. Davies and L. Pouzin who constructively commented on the fragmentation and accounting issues; and S. Crocker who commented on the creation and destruction of associations.}}</ref>

Davies and Barber published ''Communication networks for computers'' in 1973.<ref>{{Citation|last1=Davies|first1=Donald Watts|title=Communication networks for computers|year=1973|series=Computing and Information Processing|publisher=John Wiley & Sons|isbn=9780471198741|last2=Barber|first2=Derek L. A.}}</ref> They spoke at the Data Communications Symposium in 1975 about the "battle for access standards" between [[datagram]]s and [[virtual circuit]]s, with Barber saying the "lack of standard access interfaces for emerging public packet-switched communication networks is creating 'some kind of monster' for users".<ref name=":11">{{Cite journal|last=Frank|first=Ronald A.|date=1975-10-22|title=Battle for Access Standards Has Two Sides|url=https://books.google.com/books?id=wRo_E812FNcC&pg=PA17|journal=[[Computerworld]]|publisher=IDG Enterprise|pages=17–18}}</ref>

Internetworking experiments at NPL under Davies included connecting with the [[European Informatics Network]] (EIN) by translating between two different host protocols and connecting with the Post Office [[Packet switching#EPSS|Experimental Packet Switched Service]] (EPSS) using a common host protocol in both networks. Their research confirmed establishing a common host protocol would be more reliable and efficient than translating between different host protocols using a gateway.<ref>{{Cite book|last=Abbate|first=Janet|url=https://books.google.com/books?id=E2BdY6WQo4AC&pg=PA125|title=Inventing the Internet|date=2000|publisher=MIT Press|isbn=978-0-262-51115-5|pages=125|language=en}}</ref> Davies published ''Computer networks and their protocols'' in 1979, in which he notes:<ref name=":4">{{Cite book |last=Davies |first=Donald Watts |url=https://archive.org/details/computernetworks00davi |title=Computer networks and their protocols |date=1979 |publisher=Chichester, [Eng.]; New York : Wiley |others=Internet Archive |isbn=9780471997504 |pages=109, 150–1}}</ref>

{{Quote|text=The problems of routing in interconnected networks have received limited attention in the literature; notable papers are those by Cerf and Kahn and, more recently, Sunshine. ... The gateway nodes must be provided with an adequate packet buffer pool to cater for the likely level of inter-network traffic. Cerf and Kahn suggest that message reassembly should not take place at gateways; this implies that packet ordering need not be maintained if adaptive routing disrupts packet order. If fragmentation of packets is necessary because of different network packet size limits, Cerf and Kahn maintain that the only logical place to locate the reconstruction process is in the destination host (this is because the last network entered may have the least packet size limit, so that the last gateway has to fragment packets). This philosophy goes against the widely held view that packet networks should deliver a data stream exactly equivalent to the received data stream.|author=Donald Davies (1979)}}

For a long period of time, the network engineering community was polarized over the implementation of competing protocol suites, a debate commonly called the ''[[Protocol Wars]]''. It was unclear which type of protocol would result in the best and most robust computer networks.<ref>{{Cite book |last1=Davies |first1=Howard |url=https://books.google.com/books?id=DN-t8MpZ0-wC&q=%22protocol+wars%22&pg=PA106 |title=A History of International Research Networking: The People who Made it Happen |last2=Bressan |first2=Beatrice |date=2010-04-26 |publisher=John Wiley & Sons |isbn=978-3-527-32710-2 |language=en}}</ref>

===Computer network security===
Davies relinquished his management responsibilities in 1979 to return to research. He became particularly interested in [[Computer security|computer network security]] and his research on [[cryptography]] led to a number of patents, including methods for providing [[secure communication]] to enable the use of [[smart card]]s.<ref name="guardian" /><ref>{{Cite web |title=Donald Watts Davies Inventions, Patents and Patent Applications - Justia Patents Search |url=https://patents.justia.com/inventor/donald-watts-davies |access-date=2023-10-21 |website=patents.justia.com}}</ref>

He retired from NPL in 1984, becoming a leading consultant on data security to the banking industry and publishing a book on the topic that year.<ref name="MCK" /><ref name="guardian" /> Together with David O. Clayden, he designed the [[Message Authenticator Algorithm]] (MAA) in 1983, one of the first [[message authentication code]] algorithms to gain widespread acceptance. It was adopted as international standard ISO 8731-2 in 1987.<ref name="frs" />

== Later career ==
In 1987, Davies became a visiting professor at [[Royal Holloway and Bedford New College]].<ref name=":1">{{Cite news |last=Feder |first=Barnaby J. |date=2000-06-04 |title=Donald W. Davies, 75, Dies; Helped Refine Data Networks |url=https://www.nytimes.com/2000/06/04/business/donald-w-davies-75-dies-helped-refine-data-networks.html |access-date=2020-01-10 |work=The New York Times |language=en-US |issn=0362-4331 |quote=Donald W. Davies, who proposed a method for transmitting data that made the Internet possible}}</ref>

== Epilogue ==
Unbeknown to Davies at first, [[Paul Baran]] of the [[RAND Corporation]] in the United States had also worked on a similar concept in the early 1960s, although designed for voice communication using low-cost electronics without communication protocols.<ref name=":5a">{{Cite book |last=Waldrop |first=M. Mitchell |url=https://books.google.com/books?id=eRnBEAAAQBAJ&pg=PT285 |title=The Dream Machine |date=2018 |publisher=Stripe Press |isbn=978-1-953953-36-0 |pages=286 |language=en |quote=Baran had put more emphasis on digital voice communications than on computer communications.}}</ref><ref name="Pelkey6.1a">{{Cite book |last=Pelkey |first=James L. |title=Entrepreneurial Capitalism and Innovation: A History of Computer Communications 1968–1988 |chapter=6.1 The Communications Subnet: BBN 1969 |quote=As Kahn recalls: ... Paul Baran’s contributions ... I also think Paul was motivated almost entirely by voice considerations. If you look at what he wrote, he was talking about switches that were low-cost electronics. The idea of putting powerful computers in these locations hadn’t quite occurred to him as being cost effective. So the idea of computer switches was missing. The whole notion of protocols didn’t exist at that time. And the idea of computer-to-computer communications was really a secondary concern. |chapter-url=https://historyofcomputercommunications.info/section/6.1/The-Communications-Subnet-BBN-1969/}}</ref><ref>{{Cite journal |last=Kleinrock |first=L. |date=1978 |title=Principles and lessons in packet communications |url=https://ieeexplore.ieee.org/document/1455412 |journal=Proceedings of the IEEE |volume=66 |issue=11 |pages=1320–1329 |doi=10.1109/PROC.1978.11143 |issn=0018-9219 |quote=Paul Baran ... focused on the routing procedures and on the survivability of distributed communication systems in a hostile environment, but did not concentrate on the need for resource sharing in its form as we now understand it; indeed, the concept of a software switch was not present in his work.|url-access=subscription }}</ref> When Davies became aware of Baran's work in 1966 he acknowledged that they both had equally discovered the concept of packet switching and Davies and his team referenced Baran's earlier published work.<ref name="Harvnb|Harris|p=9">{{Harvnb|Harris|p=9}}</ref><ref>{{cite web |title=''Packets of data were the key...'' |url=http://www.npl.co.uk/news/packets-of-data |access-date=1 August 2015 |publisher=NPL}}</ref><ref>{{cite web |year=2010 |title=Donald Watts Davies |url=http://www.internet-guide.co.uk/DonaldWattsDavies.html |publisher=Internet Guide}}</ref><ref>[http://www.livinginternet.com/i/iw_packet.htm Packet Switching]</ref> 

Baran remained happy to acknowledge that Davies had come up with the same idea as him independently. Decades later, in an email to Davies, he wrote:<ref name="Harvnb|Harris|p=9" />

{{Quote|text=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. ... and [you were] the first to reduce it to practice.|author=Paul Baran (2000)}}

[[Leonard Kleinrock]], a contemporary working on analysing message delays using [[queueing theory]], developed a mathematical model for the operation of [[message switching]] networks in his PhD thesis during 1961-2, published as a book in 1964.<ref>{{Citation |last=Kleinrock |first=Leonard |title=Information flow in large communication nets |journal=RLE Quarterly Progress Report |issue=1 |year=1961 |author-link=Leonard Kleinrock}}</ref> However, Kleinrock's claim since the late 1990s to have developed the theoretical basis of packet switching networks is disputed by other [[Internet pioneers]],<ref>{{citation |author=Alex McKenzie |title=Comments on Dr. Leonard Kleinrock's claim to be "the Father of Modern Data Networking" |year=2009 |url=http://alexmckenzie.weebly.com/comments-on-kleinrocks-claims.html |access-date=23 April 2015}}
"...there is nothing in the entire 1964 book that suggests, analyzes, or alludes to the idea of packetization."</ref><ref>{{cite book |last1=Isaacson |first1=Walter |url=https://books.google.com/books?id=4V9koAEACAAJ&pg=PA245 |title=The Innovators: How a Group of Hackers, Geniuses, and Geeks Created the Digital Revolution |date=2014 |publisher=Simon & Schuster |isbn=9781476708690 |page=245 |quote=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}}</ref><ref>{{Harvnb|Harris}}</ref><ref>{{Cite AV media |url=https://www.inc.com/computerfreaks |title=Computer Freaks |date=June 22, 2023 |last=Haughney Dare-Bryan |first=Christine |type=Podcast |publisher=Inc. Magazine |series=Chapter Two: In the Air}}</ref> including by [[Robert Taylor (computer scientist)|Robert Taylor]],<ref>{{cite news |date=22 November 2001 |title=Birthing the Internet: Letters From the Delivery Room; Disputing a Claim |url=https://www.nytimes.com/2001/11/22/technology/l-birthing-the-internet-letters-from-the-delivery-room-disputing-a-claim-325210.html |access-date=10 September 2017 |work=New York Times |quote=Authors who have interviewed dozens of Arpanet pioneers know very well that the Kleinrock-Roberts claims are not believed.}}</ref> Baran<ref>{{citation |author=Katie Hefner |title=A Paternity Dispute Divides Net Pioneers |date=8 November 2001 |newspaper=The New York Times |url=https://www.nytimes.com/2001/11/08/technology/a-paternity-dispute-divides-net-pioneers.html?pagewanted=all |quote="The Internet is really the work of a thousand people," Mr. Baran said. "And of all the stories about what different people have done, all the pieces fit together. It's just this one little case that seems to be an aberration."}}</ref> and Davies.<ref>{{citation |author=Donald Davies |title=A Historical Study of the Beginnings of Packet Switching |journal=Computer Journal, British Computer Society |year=2001 |url=http://comjnl.oxfordjournals.org/content/44/3/152.extract |quote=I can find no evidence that he understood the principles of packet switching.}}{{dead link|date=May 2021|bot=medic}}{{cbignore|bot=medic}}
</ref><ref name=":3" />

== Legacy ==
Donald Davies and Paul Baran are recognized by historians and the U.S. [[National Inventors Hall of Fame]] for independently inventing the concept of digital packet switching used in modern computer networking including the Internet.<ref>{{Cite news |title=The real story of how the Internet became so vulnerable |url=http://www.washingtonpost.com/sf/business/2015/05/30/net-of-insecurity-part-1/ |access-date=2020-02-18 |newspaper=Washington Post |language=en-US |quote=Historians credit seminal insights to Welsh scientist Donald W. Davies and American engineer Paul Baran}}</ref><ref>{{cite web |title=Inductee Details - Paul Baran |url=http://www.invent.org/honor/inductees/inductee-detail/?IID=316 |url-status=dead |archive-url=https://web.archive.org/web/20170906091231/http://www.invent.org/honor/inductees/inductee-detail/?IID=316 |archive-date=6 September 2017 |access-date=6 September 2017 |publisher=National Inventors Hall of Fame |postscript=none}}; {{cite web |title=Inductee Details - Donald Watts Davies |url=http://www.invent.org/honor/inductees/inductee-detail/?IID=328 |url-status=dead |archive-url=https://web.archive.org/web/20170906091936/http://www.invent.org/honor/inductees/inductee-detail/?IID=328 |archive-date=6 September 2017 |access-date=6 September 2017 |publisher=National Inventors Hall of Fame}}</ref>

Larry Roberts said the computer networks built in the 1970s were similar "in nearly all respects" to Davies' original 1965 design.<ref name=":24">{{cite journal |last1=Roberts |first1=Lawrence G. |date=November 1978 |title=The Evolution of Packet Switching |url=http://www.ismlab.usf.edu/dcom/Ch10_Roberts_EvolutionPacketSwitching_IEEE_1978.pdf |url-status=dead |journal=IEEE Invited Paper |archive-url=https://web.archive.org/web/20181231092936/http://www.ismlab.usf.edu/dcom/Ch10_Roberts_EvolutionPacketSwitching_IEEE_1978.pdf |archive-date=31 December 2018 |access-date=September 10, 2017 |quote=In nearly all respects, Davies' original proposal, developed in late 1965, was similar to the actual networks being built today.}}</ref> Davies' work on data communications and computer network design has been described as the "cornerstone" technology used in the development of the [[Internet]], which is a global system of connected computer networks (a network of networks).<ref>{{Cite book |last=Yates |first=David M. |url=https://books.google.com/books?id=ToMfAQAAIAAJ&q=%22led+to+the+Internet%22 |title=Turing's Legacy: A History of Computing at the National Physical Laboratory 1945-1995 |date=1997 |publisher=National Museum of Science and Industry |isbn=978-0-901805-94-2 |pages=132–34 |language=en |quote=Davies's invention of packet switching and design of computer communication networks ... were a cornerstone of the development which led to the Internet}}</ref><ref name=":1" /><ref>{{Citation |last=Berners-Lee |first=Tim |title=Weaving the Web: The Past, Present and Future of the World Wide Web by its Inventor |page=[https://archive.org/details/weavingweb00timb/page/7 7] |year=1999 |url=https://archive.org/details/weavingweb00timb/page/7 |place=London |publisher=Orion |isbn=0-75282-090-7 |author-link=Tim Berners-Lee}} "The advances by Donald Davies, by Paul Baran, and by Vint Cerf, Bob Khan and colleagues had already happened in the 1970s but were only just becoming pervasive."</ref><ref>{{Cite journal |last=Harris |first=Trevor, University of Wales |date=2009 |editor-last=Pasadeos |editor-first=Yorgo |title=Who is the Father of the Internet? The Case for Donald Davies |url=https://www.academia.edu/378261 |url-status=dead |journal=Variety in Mass Communication Research |language=en |publisher=ATINER |pages=123–134 |isbn=978-960-6672-46-0 |archive-url=https://web.archive.org/web/20220502025941/https://www.academia.edu/378261/Who_is_the_Father_of_the_Internet_The_Case_for_Donald_Davies |archive-date=May 2, 2022}}</ref><ref>{{Cite web |last=Archives |first=L. A. Times |date=2000-06-03 |title=Donald W. Davies; Work Led to the Internet |url=https://www.latimes.com/archives/la-xpm-2000-jun-03-me-36923-story.html |access-date=2024-01-21 |website=Los Angeles Times |language=en-US}}</ref>

==Awards and honours==
Davies was appointed a Distinguished Fellow of the [[British Computer Society]] (BCS) in 1975 and was made a [[Order of the British Empire|CBE]] in 1983, and later a Fellow of the [[Royal Society]] in 1987.<ref name=":0" /><ref name="MCK" />

He received the John Player Award from the BCS in 1974.<ref>{{Cite web|title=Donald Davies|url=http://www.thocp.net/biographies/davies_donald.htm|access-date=2020-02-09|website=www.thocp.net}}</ref> and was awarded a medal by the John von Neumann Computer Society in Hungary in 1985.<ref>{{Cite web|title=Award - 1985 - Neumann-plakett és -oklevél - Donald W. Davies {{!}} Neumann János Számítógép-tudományi Társaság|url=https://njszt.hu/hu/node/2633|access-date=2020-04-10|website=njszt.hu|language=hu}}</ref>

In 2000, Davies shared the inaugural [[IEEE Internet Award]].<ref name="Harris">{{Citation |last=Harris |first=Trevor |title=Who is the Father of the Internet? The case for Donald Watts Davies |url=https://www.academia.edu/378261 |access-date=10 July 2013 |archive-date=10 October 2021 |archive-url=https://web.archive.org/web/20211010001438/https://www.academia.edu/378261 |url-status=dead }}</ref> In 2007, he was inducted into the [[National Inventors Hall of Fame]],<ref name="NIHF2007">{{cite web|url=http://www.invent.org/honor/inductees/inductee-detail/?IID=328|title=Inductee Details - Donald Watts Davies|publisher=National Inventors Hall of Fame|url-status=dead|archive-url=https://web.archive.org/web/20170906091936/http://www.invent.org/honor/inductees/inductee-detail/?IID=328|archive-date=6 September 2017|access-date=6 September 2017}}</ref> and in 2012 Davies was inducted into the [[Internet Hall of Fame]] by the [[Internet Society]].<ref>{{Cite web|url=https://www.internethalloffame.org/inductees/donald-davies|title=Donald Davies {{!}} Internet Hall of Fame|website=www.internethalloffame.org|access-date=2020-02-09}}</ref>

Davies received a lifetime achievement award in 2001 for his research into secure communications for smart cards.<ref>{{Cite journal |date=2001-03-31 |title=2001 Advanced Card Awards |url=https://www.sciencedirect.com/science/article/pii/S0965259001003139 |journal=Card Technology Today |volume=13 |issue=3 |pages=9–10 |doi=10.1016/S0965-2590(01)00313-9 |issn=0965-2590 |quote=Recognising excellence in smart cards, the programme — for which ... Donald Davies and Peter Hawkes, for their joint and individual contributions|url-access=subscription }}</ref><ref>{{Cite web |last=LIBRARY |first=NATIONAL PHYSICAL LABORATORY Â© CROWN COPYRIGHT/SCIENCE PHOTO |title=Smart card research, 1982 - Stock Image - C015/0453 |url=https://www.sciencephoto.com/media/492693/view/smart-card-research-1982 |access-date=2023-10-21 |website=Science Photo Library |language=en}}</ref>

NPL sponsors a gallery, opened in 2009, about the development of packet switching and "Technology of the Internet" at [[The National Museum of Computing]].<ref name=":02">{{cite web|title=Technology of the Internet|url=https://www.tnmoc.org/npl-gallery|access-date=3 October 2017|publisher=The National Museum of Computing}}</ref>

A [[blue plaque]] commemorating Davies was unveiled in Treorchy in July 2013.<ref name="blue plaque">{{cite news|author=Emily Gorton|url=https://www.independent.co.uk/life-style/gadgets-and-tech/news/blue-plaque-to-honour-welsh-computing-pioneer-donald-davies-8734451.html|title=Blue plaque to honour Welsh computing pioneer Donald Davies|date=26 July 2013|work=[[The Independent]]|access-date=26 January 2016}}</ref><ref>{{Cite news |date=2013-07-25 |title=Treorchy internet pioneer Donald Davies honoured |url=https://www.bbc.com/news/uk-wales-23446159 |access-date=2024-07-01 |work=BBC News |language=en-GB}}</ref>

== Family ==
Davies was survived by his wife Diane, a daughter, two sons and four grandchildren.<ref>{{cite web|url=http://www.isoc.org/internet/history/davies.shtml|title=Obituary: Data Pioneer Donald Davies Dies|website=[[Internet Society]] (ISOC)|date=31 May 2000|archive-url=https://web.archive.org/web/20100920230916/http://www.isoc.org/internet/history/davies.shtml|archive-date=20 September 2010}}</ref>

== See also ==
*[[History of the Internet]]
*[[Internet in the United Kingdom#History|Internet in the United Kingdom § History]]
* [[Internet pioneers]]
* [[Peter T. Kirstein]], pioneered internetworking at University College London in the early 1970s

==Books==
* {{Citation | last = Davies | first = Donald Watts | title = Digital Techniques | publisher = Blackie & Son | series = Electronic User Series | year = 1963 }}
* {{Citation | last1 = Davies | first1 = Donald Watts | last2 = Barber | first2 = Derek L. A. | title = Communication networks for computers | publisher = John Wiley & Sons | series = Computing and Information Processing | year = 1973 | isbn = 9780471198741 |ref=none }}
* {{Citation | last = Davies | first = Donald Watts | title = Computer networks and their protocols | publisher = John Wiley & Sons | series = Computing and Information Processing | year = 1979 | isbn = 9780471997504 | url = https://archive.org/details/computernetworks00davi | ref=none }} with W. Price, D. Barber, C. Solomonides
* {{Citation | last1 = Davies | first1 = D. W. | last2 = Price | first2 = W. L. | title = Security for computer networks: an introduction to data security in teleprocessing and electronic funds transfer | place = New York | publisher = John Wiley & Sons | year = 1984 | url = https://archive.org/details/securityforcompu0000davi | isbn = 978-0471921370 | url-access = registration |ref= none }}

==References==
{{reflist|30em}}

==External links==
{{Commons category}}
*[http://purl.umn.edu/107241 Oral history interview with Donald W. Davies], [[Charles Babbage Institute]], University of Minnesota. Davies describes computer projects at the UK [[National Physical Laboratory (United Kingdom)|National Physical Laboratory]], from the 1947 design work of [[Alan Turing]] to the development of the two [[Automatic Computing Engine|ACE computers]]. Davies discusses a much larger, second ACE, and the decision to contract with [[English Electric]] Company to build the [[English Electric DEUCE|DEUCE]]—one of the first commercially produced computers in Great Britain.
*[http://www.thocp.net/biographies/davies_donald.htm Biography] from the [http://www.thocp.net/ History of Computing Project]
*[http://www.npl.co.uk/people/donald-davies Donald Davies profile page at NPL]
*[http://thelinuxmaniac.users.sourceforge.net/docs/be/chc61/ A Tribute to Donald Davies (1924–2000)] {{Webarchive|url=https://web.archive.org/web/20170118054837/http://thelinuxmaniac.users.sourceforge.net/docs/be/chc61/ |date=18 January 2017 }}
*[http://www.livinginternet.com/i/ii_npl.htm UK National Physical Laboratory (NPL) & Donald Davies] from [http://www.livinginternet.com/ Living Internet]
*[http://video.google.com/videoplay?docid=4989933629762859961 Computer Networks: The Heralds of Resource Sharing], documentary ca. 1972 about the [[ARPANET]]. Includes footage of Donald W. Davies (at 19m20s).

{{Internet Hall of Fame|Pioneers}}
{{Telecommunications}}
{{Authority control}}

{{DEFAULTSORT:Davies, Donald Watts}}
[[Category:1924 births]]
[[Category:2000 deaths]]
[[Category:Alumni of Imperial College London]]
[[Category:Commanders of the Order of the British Empire]]
[[Category:Fellows of the British Computer Society]]
[[Category:Fellows of the Royal Society]]
[[Category:History of computing in the United Kingdom]]
[[Category:Internet pioneers]]
[[Category:Packets (information technology)]]
[[Category:People from Treorchy]]
[[Category:Recreational cryptographers]]
[[Category:Scientists of the National Physical Laboratory (United Kingdom)]]
[[Category:Welsh computer scientists]]
[[Category:Welsh inventors]]