NPL network

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Short description: Historical network in England pioneering packet switching
NPL network schematic

The NPL network, or NPL Data Communications Network, was a local area computer network operated by a team from the National Physical Laboratory (NPL) in London that pioneered the concept of packet switching.

Based on designs first conceived by Donald Davies in 1965, development work began in 1968. Elements of the first version of the network, the Mark I, became operational during 1969 then fully operational in January 1970, and the Mark II version operated from 1973 until 1986. The NPL network followed by the ARPANET in the United States were the first two computer networks that implemented packet switching and the NPL network was the first to use high-speed links. It, along with the ARPANET and the CYCLADES project, laid down the technical foundations of modern Internet.

Origins

During 1965-66, Donald Davies, who was later appointed to head of the NPL Division of Computer Science, proposed a commercial national data network based on packet switching in Proposal for the Development of a National Communications Service for On-line Data Processing.[1] After the proposal was not taken up nationally, he headed a team which produced a design for a local network to serve the needs of NPL and prove the feasibility of packet switching.[2] The design was the first to describe the concept of an "interface computer", today known as a router.[3]

A written version of the proposal entitled A digital communications network for computers giving rapid response at remote terminals was presented by Roger Scantlebury at the Symposium on Operating Systems Principles in 1967. The design involved transmitting signals (packets) across a network with a hierarchical structure. It was proposed that "local networks" be constructed with interface computers which had responsibility for multiplexing among a number of user systems (time-sharing computers and other users) and for communicating with "high level network". The latter would be constructed with "switching nodes" connected together with megabit rate circuits (T1 links, which run with a 1.544 Mbit/s line rate).[4][5][6][7][8] 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".[9][10][11]

Larry Roberts incorporated these concepts into the design for the ARPANET.[12][13][14] The NPL network initially proposed a line speed of 768 kbit/s.[15] Influenced by this, the planned line speed for ARPANET was upgraded from 2.4 kbit/s to 50 kbit/s and a similar packet format adopted.[16][17]

Packet switching

NPL network packet

The first theoretical foundation of packet switching was the work of Paul Baran, in which data was transmitted in small chunks and routed independently by a method similar to store-and-forward techniques between intermediate networking nodes.[18] Davies independently arrived at the same model in 1965 and named it packet switching.[19] He chose the term "packet" after consulting with an NPL linguist because it was capable of being translated into languages other than English without compromise.[20] Davies gave the first public presentation of packet switching on 5 August 1968.[21] His original ideas influenced other research around the world, including Louis Pouzin's CYCLADES project in France.[22][6][23]

Network development

The NPL team used their packet switching concept to produce an experimental network using a Honeywell 516 node. Coincidentally, this was the same computer chosen by the ARPANET to serve as Interface Message Processors. Construction began in 1968.[24]

Elements of the first version of the network, Mark I NPL Network, became operational during 1969 (before the ARPANET installed its first node).[25][26] The network was fully operational in January 1970.[6] The local area NPL network followed by the wide area ARPANET in the United States were the first two computer networks that implemented packet switching.[27][28] The network later used high-speed links, the first computer network to do so.[29][30] The Mark II version operated from 1973.[6][31]

The NPL team also carried out simulation work on the performance of packet networks, studying datagrams and network congestion.[6][32][33]

The NPL network was later interconnected with other networks, including the Post Office Experimental Packet Switched Service and the European Informatics Network (EIN) in 1976.[6]

In 1976, 12 computers and 75 terminal devices were attached,[34] and more were added. The network remained in operation until 1986.[35]

Alongside Donald Davies, the NPL team included Derek Barber, Roger Scantlebury, Peter Wilkinson, Keith Bartlett, and Brian Aldous.[36][29][37]

Protocol development

NPL network model

The first use of the term protocol in a modern data-commutations context occurs in a memorandum entitled A Protocol for Use in the NPL Data Communications Network written by Roger Scantlebury and Keith Bartlett in April 1967.[29][38][39] A further publication by Bartlett in 1968 introduced the concept of an alternating bit protocol (later used by the ARPANET and the EIN)[40][41] and described the need for three levels of data transmission (roughly corresponding to the lower levels of the seven-layer OSI model that emerged a decade later). The Mark II version, which operated from 1973, used such a "layered" protocol architecture. The NPL team also introduced the idea of "protocol verification".[29]

The NPL network was a testbed for internetworking research throughout the 1970s. Davies, Scantlebury and Barber were active members of the International Networking Working Group (INWG) formed in 1972. Vint Cerf and Bob Kahn acknowledged Davies and Scantlebury in their 1974 paper A Protocol for Packet Network Intercommunication.[42] Derek Barber was appointed director of the European COST 11 project played a leading part in proposing the European Informatics Network (EIN) and led the project while Scantlebury led the UK technical contribution.[29][43][44][45] The EIN protocol helped to launch the INWG work,[41][46] which proposed an international end to end protocol in 1975.[47][48][49][50]

NPL investigated the "basic dilemma" involved in internetworking; that is, a common host protocol would require restructuring existing networks if they were not designed to use the same protocol. NPL connected with the European Informatics Network by translating between two different host protocols while the NPL connection to the Post Office Experimental Packet Switched Service used a common host protocol in both networks. This work confirmed establishing a common host protocol would be more reliable and efficient.[51]

Davies and Barber published Communication networks for computers in 1973 and Computer networks and their protocols in 1979.[52][53][54] They spoke at the Data Communications Symposium in 1975 about the "battle for access standards" between datagrams and virtual circuits, with Barber saying the "lack of standard access interfaces for emerging public packet-switched communication networks is creating 'some kind of monster' for users".[55] For a long period of time, the network engineering community was polarized over the implementation of competing protocol suites, commonly known as the Protocol Wars. It was unclear which type of protocol would result in the best and most robust computer networks.[56]

Davies' research at NPL later focused on data security for computer networks.[57]

Modern recognition

NPL sponsors a gallery, opened in 2009, about the development of packet switching and "Technology of the Internet" at The National Museum of Computing at Bletchley Park.[37]

See also

References

  1. ↑ Yates, David M. (1997) (in en). Turing's Legacy: A History of Computing at the National Physical Laboratory 1945-1995. National Museum of Science and Industry. p. 130. ISBN 978-0-901805-94-2. https://books.google.co.uk/books?redir_esc=y&id=ToMfAQAAIAAJ&focus=searchwithinvolume&q=%22proposed+national+packet-switched+network%22. 
  2. ↑ Pelkey, James (2007), "NPL Network and Donald Davies 1966 - 1971", Entrepreneurial Capitalism and Innovation: A History of Computer Communications 1968-1988, http://www.historyofcomputercommunications.info/Book/4/4.11-NPLNetworkDonaldDavies66-71.html, retrieved 13 April 2016 
  3. ↑ Roberts, Dr. Lawrence G. (May 1995). "The ARPANET & Computer Networks". http://www.packet.cc/files/arpanet-computernet.html. "Then in June 1966, Davies wrote a second internal paper, "Proposal for a Digital Communication Network" In which he coined the word packet,- a small sub part of the message the user wants to send, and also introduced the concept of an "Interface computer" to sit between the user equipment and the packet network." 
  4. ↑ Yates, David M. (1997) (in en). Turing's Legacy: A History of Computing at the National Physical Laboratory 1945-1995. National Museum of Science and Industry. p. 132-4. ISBN 978-0-901805-94-2. https://books.google.co.uk/books?redir_esc=y&id=ToMfAQAAIAAJ&focus=searchwithinvolume&q=packet+switch. 
  5. ↑ Roberts, Lawrence G. (November 1978). "The evolution of packet switching". Proceedings of the IEEE 66 (11): 1307–13. doi:10.1109/PROC.1978.11141. http://www.ece.ucf.edu/~yuksem/teaching/nae/reading/1978-roberts.pdf. "Both Paul Baran and Donald Davies in their original papers anticipated the use of T1 trunks". 
  6. ↑ 6.0 6.1 6.2 6.3 6.4 6.5 Hempstead, C.; Worthington, W., eds (2005). Encyclopedia of 20th-Century Technology. Routledge. pp. 573–5. ISBN 9781135455514. https://archive.org/details/EncyclopediaOf20thCenturyTechnologyAZMalestrom/page/n621/mode/2up?q=packet+switching. Retrieved 2015-08-15. 
  7. ↑ A History of the ARPANET: The First Decade (Report). Bolt, Beranek & Newman Inc.. 1 April 1981. pp. 53 of 183 (III-11 on the printed copy). https://apps.dtic.mil/sti/pdfs/ADA115440.pdf. 
  8. ↑ A Hey, G Pápay (2014). The Computing Universe: A Journey through a Revolution. Cambridge University Press. pp. 201. ISBN 978-0521766456. https://books.google.com/books?id=NrMkBQAAQBAJ&pg=PA201. Retrieved 2015-08-16. 
  9. ↑ "Oral-History:Donald Davies & Derek Barber". http://ethw.org/Oral-History:Donald_Davies_%26_Derek_Barber. "the ARPA network is being implemented using existing telegraphic techniques simply because the type of network we describe does not exist. It appears that the ideas in the NPL paper at this moment are more advanced than any proposed in the USA" 
  10. ↑ Naughton, John (2015). "8 Packet post". A Brief History of the Future: The origins of the Internet. Hachette UK. ISBN 978-1474602778. https://books.google.com/books?id=bbonCgAAQBAJ&q=English+outfit. "they lacked one vital ingredient. Since none of them had heard of Paul Baran they had no serious idea of how to make the system work. And it took an English outfit to tell them." 
  11. ↑ Barber, Derek (Spring 1993). "The Origins of Packet Switching". The Bulletin of the Computer Conservation Society (5). ISSN 0958-7403. http://www.cs.man.ac.uk/CCS/res/res05.htm#f. Retrieved 6 September 2017. "Roger actually convinced Larry that what he was talking about was all wrong and that the way that NPL were proposing to do it was right. I've got some notes that say that first Larry was sceptical but several of the others there sided with Roger and eventually Larry was overwhelmed by the numbers.". 
  12. ↑ "Computer Pioneers - Donald W. Davies". https://history.computer.org/pioneers/davies.html. "In 1965, Davies pioneered new concepts for computer communications in a form to which he gave the name "packet switching." ... The design of the ARPA network (ArpaNet) was entirely changed to adopt this technique." ; "A Flaw In The Design". The Washington Post. May 30, 2015. https://www.washingtonpost.com/sf/business/2015/05/30/net-of-insecurity-part-1/. "The Internet was born of a big idea: Messages could be chopped into chunks, sent through a network in a series of transmissions, then reassembled by destination computers quickly and efficiently. Historians credit seminal insights to Welsh scientist Donald W. Davies and American engineer Paul Baran. ... The most important institutional force ... was the Pentagon’s Advanced Research Projects Agency (ARPA) ... as ARPA began work on a groundbreaking computer network, the agency recruited scientists affiliated with the nation’s top universities." 
  13. ↑ Gillies, J.; Cailliau, R. (2000). How the Web was Born: The Story of the World Wide Web. Oxford University Press. pp. 23–26. ISBN 0192862073. https://archive.org/details/howwebwasbornsto00gill/page/23. 
  14. ↑ F.E. Froehlich, A. Kent (1990). The Froehlich/Kent Encyclopedia of Telecommunications: Volume 1 - Access Charges in the U.S.A. to Basics of Digital Communications. CRC Press. p. 344. ISBN 0824729005. https://books.google.com/books?id=gaRBTHdUKmgC&pg=PA344. "Although there was considerable technical interchange between the NPL group and those who designed and implemented the ARPANET, the NPL Data Network effort appears to have had little fundamental impact on the design of ARPANET. Such major aspects of the NPL Data Network design as the standard network interface, the routing algorithm, and the software structure of the switching node were largely ignored by the ARPANET designers. There is no doubt, however, that in many less fundamental ways the NPL Data Network had and effect on the design and evolution of the ARPANET." 
  15. ↑ Kaminow, Ivan; Li, Tingye (2002-05-22). Optical Fiber Telecommunications IV-B: Systems and Impairments. Elsevier. p. 29. ISBN 978-0-08-051319-5. https://books.google.com/books?id=TXhWJcsO134C&pg=PA29. 
  16. ↑ Abbate, Janet (2000). Inventing the Internet. MIT Press. p. 38. ISBN 0262261332. https://books.google.com/books?id=9BfZxFZpElwC&pg=PA38. 
  17. ↑ Roberts, Dr. Lawrence G. (May 1995). "The ARPANET & Computer Networks". http://packet.cc/files/arpanet-computernet.html. 
  18. ↑ Winston, Brian (2002). Media,Technology and Society: A History: From the Telegraph to the Internet. Routledge. pp. 323–327. ISBN 1134766327. https://books.google.com/books?id=T8YLfMsaAXAC&pg=PA327. 
  19. ↑ Scantlebury, Roger (25 June 2013). "Internet pioneers airbrushed from history". The Guardian. https://www.theguardian.com/technology/2013/jun/25/internet-pioneers-airbrushed-from-history. 
  20. ↑ Harris, Trevor, Who is the Father of the Internet? The case for Donald Watts Davies, p. 6, https://www.academia.edu/378261, retrieved 10 July 2013 
  21. ↑ "The accelerator of the modern age". BBC News. 5 August 2008. http://news.bbc.co.uk/1/hi/technology/7541123.stm. 
  22. ↑ Roberts, Dr. Lawrence G. (November 1978). "The Evolution of Packet Switching". IEEE Invited Paper. http://www.ismlab.usf.edu/dcom/Ch10_Roberts_EvolutionPacketSwitching_IEEE_1978.pdf. Retrieved September 10, 2017. "In nearly all respects, Davies’ original proposal, developed in late 1965, was similar to the actual networks being built today.". 
  23. ↑ Pelkey, James. "8.3 CYCLADES Network and Louis Pouzin 1971–1972". Entrepreneurial Capitalism and Innovation: A History of Computer Communications 1968–1988. https://historyofcomputercommunications.info/section/8.3/CYCLADES-Network-and-Louis-Pouzin-1971-1972/. 
  24. ↑ Scantlebury, R. A.; Wilkinson, P.T. (1974). "The National Physical Laboratory Data Communications Network". pp. 223–228. http://www.rogerdmoore.ca/PS/NPLPh/NPL1974A.html. 
  25. ↑ Haughney Dare-Bryan, Christine (June 22, 2023). Computer Freaks (Podcast). Chapter Two: In the Air. Inc. Magazine. 35:55 minutes in. Leonard Kleinrock: Donald Davies ... did make a single node packet switch before ARPA did
  26. ↑ John S, Quarterman; Josiah C, Hoskins (1986). "Notable computer networks" (in EN). Communications of the ACM 29 (10): 932–971. doi:10.1145/6617.6618. "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.". 
  27. ↑ "Donald Davies". internethalloffame.org. http://www.internethalloffame.org/inductees/donald-daviesnone ; "Donald Davies". thocp.net. http://www.thocp.net/biographies/davies_donald.htm. 
  28. ↑ Roberts, Lawrence G. (November 1978). "The Evolution of Packet Switching". http://www.packet.cc/files/ev-packet-sw.html. 
  29. ↑ 29.0 29.1 29.2 29.3 29.4 Campbell-Kelly, Martin (1987). "Data Communications at the National Physical Laboratory (1965-1975)" (in en). Annals of the History of Computing 9 (3/4): 221–247. doi:10.1109/MAHC.1987.10023. https://archive.org/details/DataCommunicationsAtTheNationalPhysicalLaboratory. "the first occurrence in print of the term protocol in a data communications context ... the next hardware tasks were the detailed design of the interface between the terminal devices and the switching computer, and the arrangements to secure reliable transmission of packets of data over the high-speed lines". 
  30. ↑ Guardian Staff (2013-06-25). "Internet pioneers airbrushed from history" (in en-GB). The Guardian. ISSN 0261-3077. https://www.theguardian.com/technology/2013/jun/25/internet-pioneers-airbrushed-from-history. "This was the first digital local network in the world to use packet switching and high-speed links." 
  31. ↑ A Hey, G Pápay (8 December 2014). The Computing Universe: A Journey through a Revolution. Cambridge University Press. ISBN 978-0521766456. https://books.google.com/books?id=NrMkBQAAQBAJ&pg=PA201. Retrieved 2015-08-16. (source: Roger Scantlebury - p.201)
  32. ↑ Cambell-Kelly, Martin (Autumn 2008). "Pioneer Profiles: Donald Davies". Computer Resurrection (44). ISSN 0958-7403. http://www.computerconservationsociety.org/resurrection/res44.htm. 
  33. ↑ Pelkey, James. "6.3 CYCLADES Network and Louis Pouzin 1971-1972". Entrepreneurial Capitalism and Innovation: A History of Computer Communications 1968-1988. http://www.historyofcomputercommunications.info/Book/6/6.3-CYCLADESNetworkLouisPouzin1-72.html. 
  34. ↑ "The National Physical Laboratory Data Communications Netowrk". 1974. http://rogerdmoore.ca/PS/NPLPh/NPL1974A.html. 
  35. ↑ Campbell-Kelly, Martin (1987). "Data Communications at the National Physical Laboratory (1965-1975)" (in en). Annals of the History of Computing 9 (3/4): 221–247. doi:10.1109/MAHC.1987.10023. https://archive.org/details/DataCommunicationsAtTheNationalPhysicalLaboratory. 
  36. ↑ Barber, Derek (Spring 1993). "The Origins of Packet Switching". The Bulletin of the Computer Conservation Society (5). ISSN 0958-7403. http://www.cs.man.ac.uk/CCS/res/res05.htm#f. Retrieved 6 September 2017. 
  37. ↑ 37.0 37.1 "Technology of the Internet". The National Museum of Computing. http://www.tnmoc.org/explore/npl-technology-internet-gallery. 
  38. ↑ Naughton, John (2015) (in en). A Brief History of the Future. Orion. ISBN 978-1-4746-0277-8. https://books.google.com/books?id=bbonCgAAQBAJ&q=%22first%20use%20of%20the%20term%20'protocol'%22. 
  39. ↑ Pelkey, James L.. "6.1 The Communications Subnet: BBN 1969". Entrepreneurial Capitalism and Innovation: A History of Computer Communications 1968–1988. https://historyofcomputercommunications.info/section/6.1/the-communications-subnet-bbn-1969/. "As Kahn recalls: ... Paul Baran’s contributions ... 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." 
  40. ↑ "ARPANET is now 50 years old | Inria" (in en). https://www.inria.fr/en/arpanet-now-50-years-old. 
  41. ↑ 41.0 41.1 Davies, Donald Watts (1979). Computer networks and their protocols. John Wiley & Sons. pp. 464. ISBN 9780471997504. https://archive.org/details/computernetworks00davi. 
  42. ↑ Cerf, V.; Kahn, R. (1974). "A Protocol for Packet Network Intercommunication". IEEE Transactions on Communications 22 (5): 637–648. doi:10.1109/TCOM.1974.1092259. ISSN 1558-0857. https://www.cs.princeton.edu/courses/archive/fall06/cos561/papers/cerf74.pdf. "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.". 
  43. ↑ Barber, D L. (1975). "Cost project 11" (in EN). ACM SIGCOMM Computer Communication Review 5 (3): 12–15. doi:10.1145/1015667.1015669. 
  44. ↑ Scantlebury, Roger (1986). "X.25 - past, present and future". in Stokes, A. V. (in en). Communications Standards: State of the Art Report. Pergamon. pp. 203–216. ISBN 978-1-4831-6093-1. https://books.google.com/books?id=3EaeBQAAQBAJ. 
  45. ↑ "EIN (European Informatics Network)". https://www.computerhistory.org/revolution/networking/19/375/2062. 
  46. ↑ Hardy, Daniel; Malleus, Guy (2002) (in en). Networks: Internet, Telephony, Multimedia: Convergences and Complementarities. Springer Science & Business Media. pp. 505. ISBN 978-3-540-00559-9. https://books.google.com/books?id=dRhHPINWo2AC&pg=PT526. 
  47. ↑ McKenzie, Alexander (2011). "INWG and the Conception of the Internet: An Eyewitness Account". IEEE Annals of the History of Computing 33 (1): 66–71. doi:10.1109/MAHC.2011.9. ISSN 1934-1547. 
  48. ↑ Cerf, V.; McKenzie, A; Scantlebury, R; Zimmermann, H (1976). "Proposal for an international end to end protocol" (in EN). ACM SIGCOMM Computer Communication Review 6: 63–89. doi:10.1145/1015828.1015832. 
  49. ↑ Scantlebury, Roger (25 June 2013). "Internet pioneers airbrushed from history". The Guardian. https://www.theguardian.com/technology/2013/jun/25/internet-pioneers-airbrushed-from-history. 
  50. ↑ Scantlebury, Roger (8 January 2010). "How we nearly invented the internet in the UK". https://www.newscientist.com/letter/mg24532640-100-how-we-nearly-invented-the-internet-in-the-uk/. 
  51. ↑ Abbate, Janet (2000) (in en). Inventing the Internet. MIT Press. pp. 125. ISBN 978-0-262-51115-5. https://books.google.com/books?id=E2BdY6WQo4AC&pg=PA125. 
  52. ↑ "Donald Davies". http://www.thocp.net/biographies/davies_donald.htmnone ; "Donald Davies". http://www.internethalloffame.org/inductees/donald-davies. 
  53. ↑ Davies, Donald Watts; Barber, Derek L. A. (1973), Communication networks for computers, Computing and Information Processing, John Wiley & Sons, ISBN 9780471198741 
  54. ↑ Davies, Donald Watts (1979). Computer networks and their protocols. Internet Archive. Chichester, [Eng.] ; New York : Wiley. pp. 456–477. ISBN 9780471997504. https://archive.org/details/computernetworks00davi. 
  55. ↑ Frank, Ronald A. (1975-10-22). "Battle for Access Standards Has Two Sides". Computerworld (IDG Enterprise): 17–18. https://books.google.com/books?id=wRo_E812FNcC&pg=PA17. 
  56. ↑ Davies, Howard; Bressan, Beatrice (2010-04-26) (in en). A History of International Research Networking: The People who Made it Happen. John Wiley & Sons. ISBN 978-3-527-32710-2. https://books.google.com/books?id=DN-t8MpZ0-wC&q=%22protocol+wars%22&pg=PA106. 
  57. ↑ Davies, D. W.; Price, W. L. (1984), Security for computer networks: an introduction to data security in teleprocessing and electronic funds transfer, New York: John Wiley & Sons, ISBN 978-0471921370, https://archive.org/details/securityforcompu0000davi 

Further reading

Primary sources

  • Davies, D. W. (10 November 1965), Remote On-line Data Processing and Its Communication Needs, Private papers .
  • Davies, D. W. (16 November 1965), Further Speculations on Data Transmission, Private papers .
  • Davies, D. W. (15 December 1965), Proposal for the Development of a National Communications Service for OnLine Data Processing, Private papers .
  • Davies, D. W. (June 1966), Proposal for a Digital Communication Network, Private papers, http://www.dcs.gla.ac.uk/~wpc/grcs/Davies05.pdf .
  • Davies, D.W. (February 1967), A Store-and-Forward Communication Network for Real-Time Computers and their Peripherals. PO Colloquium on Message Switching.
  • Scantlebury, R. A.; K. A. Bartlett (February 1967). An NPL Data Communications Network Based on the Plessey XL12 Computer. Private papers.
  • Scantlebury, R. A.; Bartlett, K. A. (April 1967), A Protocol for Use in the NPL Data Communications Network, Private papers .
  • Davies, D.W. (July 1967) Some Design Aspects of a Communication Network for Rapid-Response Computers. Computer Technology Conference.
  • Davies, D. W.; Bartlett, K. A.; Scantlebury, R. A.; Wilkinson, P. T. (October 1967). "A digital communications network for computers giving rapid response at remote terminals". ACM Symposium on Operating Systems Principles. https://dl.acm.org/citation.cfm?id=811669. 
  • Scantlebury, R. A.; Wilkinson, P.T. (1971). "The design of a switching system to allow remote access to computer services by other computers and terminal devices". Proceedings of the 2nd Symposium on Problems in the Optimization of Data Communications Systems. pp. 160–167. 
  • Barber, D. L. A. (1972). Winkler, S. ed. "The European computer network project". Computer Communications: Impacts and Implications (Washington , D.C.): 192–200. 
  • Scantlebury, R. A.; Wilkinson, P.T. (1974). "The National Physical Laboratory Data Communications Network". Proceedings of the 2nd ICCC 74. pp. 223–228. http://www.rogerdmoore.ca/PS/NPLPh/NPL1974A.html. 

External links



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