Editing ARPANET (section)

== Creation ==

In February 1966, Bob Taylor successfully lobbied ARPA's Director [[Charles M. Herzfeld]] to fund a network project. Herzfeld redirected funds in the amount of one million dollars from a ballistic missile defense program to Taylor's budget.<ref>Markoff, John, Innovator who helped create PC, Internet and the mouse, New York Times, 15 April 2017, p.A1</ref> Taylor hired [[Lawrence Roberts (scientist)|Larry Roberts]] as a program manager in the ARPA [[Information Processing Techniques Office]] in January 1967 to work on the ARPANET.<ref name=":24">{{cite web |last=Pelkey |first=James |title=4.7 Planning the ARPANET: 1967-1968 in Chapter 4 - Networking: Vision and Packet Switching 1959 - 1968 |url=https://historyofcomputercommunications.info/section/4.7/planning-the-arpanet-1967-1968/ |url-status=dead |archive-url=https://web.archive.org/web/20221223230647/https://historyofcomputercommunications.info/section/4.7/planning-the-arpanet-1967-1968/ |archive-date=December 23, 2022 |access-date=May 9, 2023 |work=The History of Computer Communications}}</ref> Roberts met Paul Baran in February 1967, but did not discuss networks.<ref name=":5c">{{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=285–6 |language=en |quote=Oops. Roberts knew Baran slightly and had in fact had lunch with him during a visit to RAND the previous February. But he certainly didn't remember any discussion of networks. How could he have missed something like that?}}</ref><ref>{{Cite web |last=O'Neill |first=Judy |date=5 March 1990 |title=An Interview with PAUL BARAN |url=https://conservancy.umn.edu/bitstream/handle/11299/107101/oh182pb.pdf?sequence=1&isAllowed=y |page=37 |quote=On Tuesday, 28 February 1967 I find a notation on my calendar for 12:00 noon Dr. L. Roberts.}}</ref>

Roberts asked [[Frank Westervelt]] to explore the questions of message size and contents for the network, and to write a position paper on the intercomputer communication protocol including “conventions for character and block transmission, error checking and re-transmission, and computer and user identification."<ref name=":24" /> In April 1967, ARPA held a design session on technical standards. The initial standards for identification and authentication of users, transmission of characters, and error checking and retransmission procedures were discussed.<ref>{{cite web|url=https://www.livinginternet.com/internet/i/ii_roberts.htm|title=Lawrence Roberts Manages The ARPANET Program|date=7 January 2000|website=Living Internet|access-date=2021-03-19}}</ref> Roberts' proposal was that all mainframe computers would connect to one another directly. The other investigators were reluctant to dedicate these computing resources to network administration. After the design session, [[Wesley A. Clark|Wesley Clark]] proposed minicomputers should be used as an interface to create a [[message switching]] network. Roberts modified the ARPANET plan to incorporate Clark's suggestion and named the minicomputers [[Interface Message Processor]]s (IMPs).<ref name=":24" /><ref>{{Cite web |url=https://www.forbes.com/sites/gilpress/2015/01/02/a-very-short-history-of-the-internet-and-the-web-2/|title=A Very Short History Of The Internet And The Web|last=Press|first=Gil|website=Forbes|access-date=2020-02-07}}</ref><ref>{{Cite web|url=https://web.stanford.edu/dept/SUL/library/extra4/sloan/mousesite/EngelbartPapers/B1_F20_CompuMtg.html|title=SRI Project 5890-1; Networking (Reports on Meetings).[1967]|website=web.stanford.edu|access-date=2020-02-15|quote=W. Clark's message switching proposal (appended to Taylor's letter of April 24, 1967 to Engelbart) were reviewed.|archive-date=2 February 2020|archive-url=https://web.archive.org/web/20200202062940/https://web.stanford.edu/dept/SUL/library/extra4/sloan/mousesite/EngelbartPapers/B1_F20_CompuMtg.html|url-status=dead}}</ref><ref name="LivingInternetIMP">{{cite web|url=https://www.livinginternet.com/internet/i/ii_imp.htm |title=IMP – Interface Message Processor|date=7 January 2000|website=Living Internet|access-date=2021-03-19}}</ref>

The plan was presented at the inaugural Symposium on Operating Systems Principles in October 1967.<ref>{{Cite book|last=Roberts|first=Lawrence|date=1967|title=Multiple Computer Networks and Intercomputer Communications|chapter=Multiple computer networks and intercomputer communication|chapter-url=https://people.mpi-sws.org/~gummadi/teaching/sp07/sys_seminar/arpanet.pdf|pages=3.1–3.6|doi=10.1145/800001.811680|s2cid=17409102|quote=Thus the set of IMP's, plus the telephone lines and data sets would constitute a message switching network}}</ref> Donald Davies' work on packet switching and the NPL network, presented by a colleague ([[Roger Scantlebury]]), and that of Paul Baran, came to the attention of the ARPA investigators at this conference.<ref name="Gillies2000">{{cite book|last1=Gillies|first1=James|last2=Cailliau|first2=Robert|title=How the Web was Born: The Story of the World Wide Web|date=2000|publisher=Oxford University Press|isbn=978-0-19-286207-5|page=25|url=https://books.google.com/books?id=pIH-JijUNS0C&pg=PA25}}</ref><ref name="Isaacson2014">{{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=978-1-4767-0869-0|page=237|url=https://books.google.com/books?id=4V9koAEACAAJ&pg=PA237}}</ref> Roberts applied Davies' concept of packet switching for the ARPANET,<ref>{{cite web|title=Inductee Details – Donald Watts Davies|url=http://www.invent.org/honor/inductees/inductee-detail/?IID=328|publisher=National Inventors Hall of Fame|access-date=6 September 2017|archive-url=https://web.archive.org/web/20170906091936/http://www.invent.org/honor/inductees/inductee-detail/?IID=328|archive-date=6 September 2017|url-status=dead}}</ref><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> and sought input from Paul Baran on dynamic routing.<ref name="Abbate20002">{{cite book|last1=Abbate|first1=Janet|author-link=Janet Abbate|url=https://books.google.com/books?id=9BfZxFZpElwC&pg=PA37|title=Inventing the Internet|date=2000|publisher=[[MIT Press]]|isbn=978-0-2625-1115-5 |location=Cambridge, MA|pages=37–38, 58–59}}</ref> The NPL network was using line speeds of 768&nbsp;kbit/s, and the proposed line speed for the ARPANET was upgraded from 2.4&nbsp;kbit/s to 50&nbsp;kbit/s.<ref name="brief">{{cite web|title=Brief History of the Internet|url=http://www.internetsociety.org/internet/what-internet/history-internet/brief-history-internet#f5|publisher=Internet Society|access-date=12 July 2017}}</ref>

By mid-1968, Roberts and Barry Wessler wrote a final version of the IMP specification based on a [[Stanford Research Institute]] (SRI) report that ARPA commissioned to write detailed specifications describing the ARPANET communications network.<ref name="LivingInternetIMP"/> Roberts gave a report to Taylor on 3 June, who approved it on 21 June. After approval by ARPA, a [[Request for Quotation]] (RFQ) was issued for 140 potential bidders. Most computer science companies regarded the ARPA proposal as outlandish, and only twelve submitted bids to build a network; of the twelve, ARPA regarded only four as top-rank contractors. At year's end, ARPA considered only two contractors and awarded the contract to build the network to BBN in January 1969.<ref name="Roberts1978"/>
[[File:1969 ARPANET BBN IMP.jpg|thumb|1969 ARPANET IMP]]
The initial, seven-person BBN team were much aided by the technical specificity of their response to the ARPA RFQ, and thus quickly produced the first working system. The "IMP guys" were led by [[Frank Heart]]; the theoretical design of the network was led by [[Bob Kahn]]; the team included [[David Walden|Dave Walden]], [[Severo Ornstein]], [[William Crowther (programmer)|William Crowther]] and several others.<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 |quote=Significant aspects of the network's internal operation, such as routing, flow control, software design, and network control were developed by a BBN team consisting of Frank Heart, Robert Kahn, Severo Omstein, William Crowther, and David Walden}}</ref><ref>{{Cite news|last=Hafner|first=Katie|url=https://www.nytimes.com/2018/06/25/technology/frank-heart-who-linked-computers-before-the-internet-dies-at-89.html|title=Frank Heart, Who Linked Computers Before the Internet, Dies at 89|date=2018-06-25|work=The New York Times|access-date=2020-04-03|language=en-US|issn=0362-4331}}</ref><ref name="Hafner1">{{harvnb|Hafner|Lyon|1996|pp=[https://archive.org/details/wherewizardsstay00haf_vgj/page/116/mode/2up?q=kahn 116, 149]}}</ref> The BBN-proposed network closely followed Roberts' ARPA plan: a network composed of small computers, the IMPs (similar to the later concept of [[Router (computing)|routers]]), that functioned as gateways interconnecting local resources. Routing, flow control, software design and network control were developed by the BBN team.<ref name=":23" /><ref name="F.E. Froehlich, A. Kent">{{cite book |author=F.E. Froehlich, A. Kent |url=https://books.google.com/books?id=gaRBTHdUKmgC&pg=PA344 |title=The Froehlich/Kent Encyclopedia of Telecommunications: Volume 1 - Access Charges in the U.S.A. to Basics of Digital Communications |date=1990 |publisher=CRC Press |isbn=0824729005 |page=344 |quote=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.}}</ref> At each site, the IMPs performed store-and-forward packet switching functions and were interconnected with [[leased line]]s via telecommunication data sets ([[modem]]s), with initial data rates of {{gaps|50|[[kilobit|kbit]]/s}}.<ref name="brief" /><ref>{{cite book |url=https://archive.org/details/DTIC_ADA096798 |title=ARPANET Information Brochure |date=May 1980 |page=12 |quote=The complete network is formed by interconnecting the nodes through wideband communication lines, normally 50,000 bits per second (50KBPS), supplied by common carriers}}</ref><ref>{{cite report | title=BBN Report No. 1928| date=January 1970| url=http://bärwolff.de/bbn-arpanet-reports-collection/BBN%20(1970)%20Interface%20Message%20Processors%20for%20the%20ARPA%20Computer%20Network%20(Report%201928,%20Quarterly%20Technical%20Report%204).pdf| quote=we designed and implemented a test program to obtain data on the performance of the fifty kilobit communication circuits}}</ref> The host computers were connected to the IMPs via custom [[serial communication]] interfaces. The system, including the hardware and the packet switching software, was designed and installed in nine months.<ref name="Roberts1978"/><ref name="LivingInternetIMP"/><ref>{{cite web|title=Looking back at the ARPANET effort, 34 years later|url=https://www.livinginternet.com/internet/i/ii_imp_walden.htm|access-date=2021-03-19|date=February 2003}}</ref> The BBN team continued to interact with the NPL team with meetings between them taking place in the U.S. and the U.K.<ref name="Abbate2000">{{cite book|last1=Abbate|first1=Janet|title=Inventing the Internet|date=2000|location=Cambridge, MA|publisher=[[MIT Press]]|isbn=978-0-2625-1115-5|page=38|url=https://books.google.com/books?id=9BfZxFZpElwC&pg=PA38}}</ref><ref>{{cite conference |first1=Frank |last1=Heart |author-link2=Bob Kahn |first2=Robert |last2=Kahn |first3=Severo |last3=Ornstein |author-link3=Severo Ornstein |first4=William |last4=Crowther |author-link4=William Crowther (programmer) |first5=David |last5=Walden |title=Proceedings of the May 5-7, 1970, spring joint computer conference on - AFIPS '70 (Spring) |chapter=The Interface Message Processor for the ARPA Computer Network |chapter-url=http://www.walden-family.com/public/1970-imp-afips.pdf |conference=1970 Spring Joint Computer Conference |page=565 |year=1970 |doi=10.1145/1476936.1477021|s2cid=9647377 }}</ref><ref>{{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>

As with the NPL network, the first-generation IMPs were built by BBN using a [[rugged computer]] version of the [[Honeywell]] [[DDP-516]] computer, configured with {{gaps|24|[[kibibyte|KB]]}} of expandable [[magnetic-core memory]], and a 16-channel Direct Multiplex Control (DMC) [[direct memory access]] unit.<ref>{{cite web|last=Wise|first=Adrian|url=https://www.old-computers.com/museum/computer.asp?c=551|title=Honeywell DDP-516|website=Old-Computers.com|access-date=6 June 2020|archive-url=https://web.archive.org/web/20200726104820/https://www.old-computers.com/museum/computer.asp?c=551|archive-date=26 July 2020|url-status=dead}}</ref> The DMC established custom interfaces with each of the host computers and modems. In addition to the front-panel lamps, the DDP-516 computer also features a special set of 24 indicator lamps showing the status of the IMP communication channels. Each IMP could support up to four local hosts and could communicate with up to six remote IMPs via early [[Digital Signal 0]] leased telephone lines. The network connected one computer in Utah with three in California. Later, the Department of Defense allowed the universities to join the network for sharing hardware and software resources.

According to Charles Herzfeld, ARPA Director (1965–1967):{{blockquote|The ARPANET was not started to create a Command and Control System that would survive a nuclear attack, as many now claim. To build such a system was, clearly, a major military need, but it was not ARPA's mission to do this; in fact, we would have been severely criticized had we tried. Rather, the ARPANET came out of our frustration that there were only a limited number of large, powerful research computers in the country, and that many research investigators, who should have access to them, were geographically separated from them.<ref>{{cite web|title=50 years ago today, the Internet was born. Sort of |website=[[ArsTechnica.com]] |date=29 October 2019 |url=https://arstechnica.com/information-technology/2019/10/50-years-ago-today-the-internet-was-born-sort-of/ |access-date=2022-06-21}}</ref>}}

The ARPANET used distributed computation and incorporated frequent re-computation of routing tables (automatic routing was technically challenging at the time). These features increased the survivability of the network in the event of significant interruption. Furthermore, the ARPANET was designed to survive subordinate network losses.<ref>{{cite book |first=Janet|last=Abbate|date=2000|title=Inventing the Internet|pages=194–195|location=Cambridge, MA|publisher=[[MIT Press]]|isbn=978-0-2625-1115-5}}</ref><ref>{{cite book|first = Vernon W.|last = Ruttan |date =2006 |url = https://books.google.com/books?id=Eopn-pYI1tsC&pg=PA125 |title =Is War Necessary for Economic Growth|page =125|publisher = Oxford University Press|isbn = 9780198040651}}</ref> However, the [[Internet Society]] agrees with Herzfeld in a footnote in their online article, ''A Brief History of the Internet'':

{{blockquote|It was from the RAND study that the false rumor started, claiming that the ARPANET was somehow related to building a network resistant to nuclear war. This was never true of the ARPANET, but was an aspect of the earlier RAND study of secure communication. The later work on internetworking did emphasize robustness and survivability, including the capability to withstand losses of large portions of the underlying networks.<ref name="brief-f5">{{cite web|title=Brief History of the Internet|url=http://www.internetsociety.org/internet/what-internet/history-internet/brief-history-internet#f5 |publisher=Internet Society|access-date=|first1 = Barry M. |last1=Leiner|first2= Vinton G.|last2= Cerf|first3= David D. |last3 =Clark|first4= Robert E. |last4= Kahn|first5= Leonard |last5=Kleinrock|first6= Daniel C.|last6 = Lynch|first7 = Jon|last7= Postel|first8= Larry G.|last8= Roberts|first9 = Stephen |last9 =Wolff|date = 1997}} (footnote&nbsp;5)</ref>|author=|title=|source=}}

[[Paul Baran]], the first to put forward a theoretical model for communication using packet switching, conducted the RAND study referenced above.<ref>{{Cite journal|last=Baran|first=Paul |date=2002|title=The beginnings of packet switching: some underlying concepts|journal=IEEE Communications Magazine |url=http://web.cs.ucla.edu/~lixia/papers/Baran2002.pdf|volume=40|issue=7|pages=42–48|issn=0163-6804|doi=10.1109/MCOM.2002.1018006 |quote= Essentially all the work was defined by 1961, and fleshed out and put into formal written form in 1962. The idea of hot potato routing dates from late 1960.}}</ref><ref name="RAND corporation" /> Though the ARPANET did not exactly share Baran's project's goal, he said his work did contribute to the development of the ARPANET.<ref>{{cite news |last=Brand |first=Stewart |url=https://www.wired.com/wired/archive/9.03/baran.html |title=Founding Father |volume= 9 |magazine=[[Wired (magazine)|Wired]] |date=March 2001|issue=3|access-date=31 December 2011}}</ref> Minutes taken by Elmer Shapiro of [[Stanford Research Institute]] at the ARPANET design meeting of 9–10 October 1967 indicate that a version of Baran's routing method ("hot potato") may be used,<ref>{{cite web|website=stanford.edu |url=https://web.stanford.edu/dept/SUL/library/extra4/sloan/mousesite/Archive/Post68/ARPANETMeeting1167.html |archive-url = https://web.archive.org/web/20150627133802/https://web.stanford.edu/dept/SUL/library/extra4/sloan/mousesite/Archive/Post68/ARPANETMeeting1167.html |archive-date = 27 June 2015 |url-status=dead |title= Shapiro: Computer Network Meeting of October 9–10, 1967}}</ref> consistent with the NPL team's proposal at the Symposium on Operating System Principles in Gatlinburg.<ref>{{Cite journal|last=Cambell-Kelly|first=Martin |date=1987|title=Data Communications at the National Physical Laboratory (1965-1975) |url=https://archive.org/details/DataCommunicationsAtTheNationalPhysicalLaboratory/page/n9/mode/2up |journal=Annals of the History of Computing |volume=9|issue=3/4|pages=239}}</ref>

Later, in the 1970s, ARPA did emphasize the goal of "command and control". According to [[Stephen J. Lukasik]], who was deputy director (1967–1970) and Director of DARPA (1970–1975):<ref>{{Cite web |title=DARPA DIRECTORS, 1958-PRESENT |url=https://www.darpa.mil/attachments/DARPA_Directors_Sheet_20201.pdf}}</ref>

{{blockquote|The goal was to exploit new computer technologies to meet the needs of military command and control against nuclear threats, achieve survivable control of US nuclear forces, and improve military tactical and management decision making.<ref>{{cite journal |last1=Lukasik |first1=Stephen J. |year=2011 |title=Why the Arpanet Was Built |doi=10.1109/MAHC.2010.11 |journal=IEEE Annals of the History of Computing |volume=33 |issue=3| pages=4–20 |s2cid=16076315}}</ref>}}