Editing History of the Internet (section)

==Foundations==
===Precursors===

==== Telegraphy ====
:The practice of transmitting messages between two different places through an electromagnetic medium dates back to the [[electrical telegraph]] in the late 19th century, which was the first fully digital communication system. [[Radiotelegraphy]] began to be used commercially in the early 20th century. [[Telex]] became an operational [[teleprinter]] service in the 1930s. Such systems were limited to [[Point-to-point (telecommunications)|point-to-point communication]] between two [[End system|end devices]].

==== Information theory ====
:Fundamental theoretical work in [[telecommunications]] technology was developed by [[Harry Nyquist]] and [[Ralph Hartley]] in the 1920s. [[Information theory]], as enunciated by [[Claude Shannon]] in 1948, provided a firm theoretical [[underpinning]] to understand the trade-offs between [[signal-to-noise ratio]], [[Bandwidth (computing)|bandwidth]], and error-free [[Transmission (telecommunications)|transmission]] in the presence of [[noise]].

==== Computers and modems ====
:Early fixed-program [[computer]]s in the 1940s were operated manually by entering small programs via [[Switch|switches]] in order to load and run a series of programs. As [[transistor]] technology evolved in the 1950s, [[central processing unit]]s and user [[Computer terminal|terminals]] came into use by 1955. The [[mainframe computer]] model was devised, and  [[modem]]s, such as the [[Bell 101 modem|Bell 101]], allowed [[digital data]] to be transmitted over regular unconditioned [[Telephone line|telephone lines]] at low speeds by the late 1950s. These technologies made it possible to exchange data between [[Remote desktop software|remote computers]]. However, a fixed-line link was still necessary; the point-to-point communication model did not allow for direct communication between any two arbitrary systems. In addition, the applications were specific and not general purpose. Examples included [[Semi-Automatic Ground Environment|SAGE]] (1958) and [[Sabre (travel reservation system)|SABRE]] (1960).

==== Time-sharing ====
:[[Christopher Strachey]], who became [[University of Oxford|Oxford University's]] first Professor of [[Computation]], filed a [[patent application]] in the United Kingdom for [[time-sharing]] in February 1959.<ref>{{Cite web|url=https://history.computer.org/pioneers/strachey.html|title=Computer Pioneers - Christopher Strachey|website=history.computer.org|access-date=2020-01-23}}</ref><ref name=":13">{{Cite web |title=Computer - Time-sharing, Minicomputers, Multitasking |url=https://www.britannica.com/technology/computer/Time-sharing-and-minicomputers |access-date=2023-07-23 |website=Britannica |language=en}}</ref> In June that year, he gave a paper "Time Sharing in Large Fast Computers" at the [[International Federation for Information Processing#History|UNESCO Information Processing Conference]] in Paris where he passed the concept on to [[J. C. R. Licklider]].<ref name="ctsspg">{{cite book|first=F. J. |last=Corbató |display-authors=etal |url=http://www.bitsavers.org/pdf/mit/ctss/CTSS_ProgrammersGuide.pdf |title=The Compatible Time-Sharing System: A Programmer's Guide |publisher=MIT Press |year=1963 |isbn=978-0-262-03008-3}}. "the first paper on time-shared computers by C. Strachey at the June 1959 UNESCO Information Processing conference".</ref><ref>{{harvnb|Gillies|Cailliau|2000|page=13}}</ref> Licklider, a vice president at [[BBN Technologies|Bolt Beranek and Newman, Inc.]] (BBN), promoted the idea of time-sharing as an alternative to [[batch processing]].<ref name=":13" /> [[John McCarthy (computer scientist)|John McCarthy]], at [[Massachusetts Institute of Technology|MIT]], wrote a memo in 1959 that broadened the concept of time sharing to encompass multiple interactive user sessions, which resulted in the [[Compatible Time-Sharing System]] (CTSS) implemented at MIT. Other multi-user mainframe systems developed, such as [[PLATO (computer system)|PLATO]] at the [[University of Illinois Chicago]].<ref>{{Cite web |title=Reminiscences on the Theory of Time-Sharing |url=http://jmc.stanford.edu/computing-science/timesharing.html |access-date=2020-01-23 |website=John McCarthy's Original Website |quote=in 1960 'time-sharing' as a phrase was much in the air. It was, however, generally used in my sense rather than in John McCarthy's sense of a CTSS-like object.}}</ref> In the early 1960, the [[Advanced Research Projects Agency]] (ARPA) of the [[United States Department of Defense]] funded further research into time-sharing at MIT through [[Project MAC]].

===Inspiration===
J. C. R. Licklider, while working at BBN, proposed a computer network in his March 1960 paper ''[[Man-Computer Symbiosis]]'':<ref>{{cite journal|author=J. C. R. Licklider|title=Man-Computer Symbiosis|journal=IRE Transactions on Human Factors in Electronics|volume=HFE-1|pages=4–11|date=March 1960|url=http://medg.lcs.mit.edu/people/psz/Licklider.html|doi=10.1109/thfe2.1960.4503259|access-date=January 25, 2014|archive-url=https://web.archive.org/web/20051103053540/http://medg.lcs.mit.edu/people/psz/Licklider.html|archive-date=November 3, 2005|author-link=J. C. R. Licklider|url-access=subscription}}</ref>

{{Blockquote|A network of such centers, connected to one another by wide-band communication lines [...] the functions of present-day libraries together with anticipated advances in information storage and retrieval and symbiotic functions suggested earlier in this paper}}

In August 1962, Licklider and Welden Clark published the paper "On-Line Man-Computer Communication"<ref>{{cite journal|author=[[J. C. R. Licklider]] and Welden Clark|title=On-Line Man-Computer Communication|journal=AIEE-IRE '62 (Spring)|pages=113–128|date=August 1962|url=http://cis.msjc.edu/courses/internet_authoring/CSIS103/resources/ON-LINE%20MAN-COMPUTER%20COMMUNICATION.pdf|access-date=October 31, 2014|archive-date=October 31, 2014|archive-url=https://web.archive.org/web/20141031214616/http://cis.msjc.edu/courses/internet_authoring/CSIS103/resources/ON-LINE%20MAN-COMPUTER%20COMMUNICATION.pdf}}</ref> which was one of the first descriptions of a networked future.

In October 1962, Licklider was hired by [[Jack Ruina]] as director of the newly established [[Information Processing Techniques Office]] (IPTO) within ARPA, with a mandate to interconnect the United States Department of Defense's main computers at [[Cheyenne Mountain]], the Pentagon, and SAC HQ. There he formed an informal group within DARPA to further computer research. He began by writing memos in 1963 describing a distributed network to the IPTO staff, whom he called "Members and Affiliates of the [[Intergalactic Computer Network]]".<ref>{{cite web|author=Licklider, J. C. R.|title=Topics for Discussion at the Forthcoming Meeting, Memorandum For: Members and Affiliates of the Intergalactic Computer Network|date=23 April 1963|location=Washington, D.C.|publisher=Advanced Research Projects Agency|url=http://www.kurzweilai.net/memorandum-for-members-and-affiliates-of-the-intergalactic-computer-network|access-date=2013-01-26}}</ref>

Although he left the IPTO in 1964, five years before the ARPANET went live, it was his vision of universal networking that provided the impetus for one of his successors, [[Robert Taylor (computer scientist)|Robert Taylor]], to initiate the ARPANET development. Licklider later returned to lead the IPTO in 1973 for two years.<ref>{{cite web|url=http://www.livinginternet.com/i/ii_licklider.htm|title=J.C.R. Licklider and the Universal Network|work=The Internet|year=2000|access-date=February 16, 2010|archive-date=October 17, 2019|archive-url=https://web.archive.org/web/20191017134454/https://www.livinginternet.com/i/ii_licklider.htm}}</ref>

===Packet switching===
[[File:The idea of the data packet (Baran, 1964)-en.svg|thumb|The "message block", designed by [[Paul Baran]] in 1962 and refined in 1964, is the first proposal of a [[data packet]].<ref name=":1">{{Cite web |last=Press |first=Gil |title=A Very Short History Of The Internet And The Web |url=https://www.forbes.com/sites/gilpress/2015/01/02/a-very-short-history-of-the-internet-and-the-web-2/ |access-date=2020-01-30 |website=Forbes |language=en}}</ref><ref name=":10" />]]
{{Main|Packet switching}}

The infrastructure for [[telephone]] systems at the time was based on [[circuit switching]], which requires pre-allocation of a dedicated communication line for the duration of the call. [[Telegram]] services had developed [[store and forward]] telecommunication techniques. [[Western Union]]'s Automatic Telegraph Switching System [[Plan 55-A]] was based on [[message switching]]. The U.S. military's [[AUTODIN]] network became operational in 1962. These systems, like SAGE and SBRE, still required rigid routing structures that were prone to [[single point of failure]].<ref>{{cite book |last1=Kim |first1=Byung-Keun |url=https://books.google.com/books?id=lESrw3neDokC&pg=PA52 |title=Internationalising the Internet the Co-evolution of Influence and Technology |date=2005 |publisher=Edward Elgar |isbn=978-1-84542-675-0 |pages=51–55}}</ref>

The technology was considered vulnerable for strategic and military use because there were no alternative paths for the communication in case of a broken link. In the early 1960s, [[Paul Baran]] of the [[RAND Corporation]] produced a study of survivable networks for the U.S. military in the event of nuclear war.<ref>{{Cite report |title=Reliable Digital Communications Using Unreliable Network Repeater Nodes |first=Paul |last=Baran |page=1 |date=May 27, 1960 |publisher=The RAND Corporation |url=http://www.rand.org/content/dam/rand/pubs/papers/2008/P1995.pdf |access-date=July 25, 2012}}</ref><ref>{{cite web |title=About Rand |url=http://www.rand.org/about/history/baran.html |access-date=July 25, 2012 |work=Paul Baran and the Origins of the Internet}}</ref> Information would be transmitted across a "distributed" network, divided into what he called "message blocks".<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 |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 |quote=There had been a paper written by [Paul Baran] from the Rand Corporation which, in a sense, foreshadowed packet switching in a way for speech networks and voice networks}}</ref><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>{{Cite web |title=On packet switching |url=https://www.nethistory.info/Archives/packets.html |access-date=2024-01-08 |website=Net History |quote=[Scantlebury said] Clearly Donald and Paul Baran had independently come to a similar idea albeit for different purposes. Paul for a survivable voice/telex network, ours for a high-speed computer network.}}</ref> Baran's design was not implemented.<ref>{{cite magazine |last=Metz |first=Cade |date=3 September 2012 |title=What Do the H-Bomb and the Internet Have in Common? Paul Baran |url=https://www.wired.com/2012/09/what-do-the-h-bomb-and-the-internet-have-in-common-paul-baran/ |magazine=WIRED |quote=He was very conscious of people mistaken belief that the work he did at RAND somehow led to the creation of the ARPAnet. It didn't, and he was very honest about that.}}</ref>

In addition to being prone to a single point of failure, existing telegraphic techniques were inefficient and inflexible. Beginning in 1965 [[Donald Davies]], at the [[National Physical Laboratory, UK|National Physical Laboratory]] in the United Kingdom, independently developed a more advanced proposal of the concept, designed for high-speed [[computer network]]ing, which he called [[packet switching]], the term that would ultimately be adopted.<ref name=":62">{{Cite book |last=Yates |first=David M. |url=https://books.google.com/books?id=ToMfAQAAIAAJ&q=packet+switch |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 |page=132-4 |language=en}}</ref><ref name="A Hey, G Pápay2">{{cite book |author=A Hey, G Pápay |url=https://books.google.com/books?id=NrMkBQAAQBAJ&pg=PA201 |title=The Computing Universe: A Journey through a Revolution |date=2014 |publisher=Cambridge University Press |isbn=978-0521766456 |pages=201 |access-date=2015-08-16}}</ref><ref>{{Cite book |last=Roberts |first=Gareth Ffowc |url=https://books.google.com/books?id=waCYEAAAQBAJ&pg=PA102 |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}}</ref><ref>{{Cite web |last=Dr. Ed Smith, FBCS, FITP, University of the Third Age; Mr Chris Miller BSc.; Prof Jim Norton OBE, FREng, University of Sheffield |title=Packet Switching: The first steps on the road to the information society |url=https://www.npl.co.uk/getattachment/about-us/History/Famous-faces/Donald-Davies/UK-role-in-Packet-Switching-(1).pdf |website=National Physical Laboratory}}</ref>

Packet switching is a technique for transmitting computer data by splitting it into very short, standardized chunks, attaching routing information to each of these chunks, and transmitting them independently through a [[computer network]]. It provides better bandwidth utilization than traditional circuit-switching used for telephony, and enables the connection of computers with different transmission and receive rates. It is a distinct concept to message switching.<ref>{{Cite news |last=Ruthfield |first=Scott |url=http://dl.acm.org/citation.cfm?id=332198.332202&coll=portal&dl=ACM |archive-url=https://web.archive.org/web/20071018045734/http://www.acm.org/crossroads/xrds2-1/inet-history.html |archive-date=October 18, 2007 |url-status=live |title=The Internet's History and Development From Wartime Tool to the Fish-Cam |periodical=Crossroads |volume=2 |issue=1 |pages=2–4 |date=September 1995 |access-date=April 1, 2016 |doi=10.1145/332198.332202}}</ref>