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The Advanced Research Projects Agency Network (ARPANET) was the first wide-area
packet-switched network In telecommunications, packet switching is a method of grouping data into '' packets'' that are transmitted over a digital network. Packets are made of a header and a payload. Data in the header is used by networking hardware to direct the pack ...
with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical foundation of the
Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
. The ARPANET was established by the
Advanced Research Projects Agency The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adv ...
(ARPA) of the
United States Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national sec ...
. Building on the ideas of J. C. R. Licklider, Bob Taylor initiated the ARPANET project in 1966 to enable access to remote computers. Taylor appointed Larry Roberts as program manager. Roberts made the key decisions about the network design. He incorporated
Donald Davies Donald Watts Davies, (7 June 1924 – 28 May 2000) was a Welsh computer scientist who was employed at the UK National Physical Laboratory (NPL). In 1965 he conceived of packet switching, which is today the dominant basis for data communic ...
' concepts and designs for packet switching, and sought input from
Paul Baran Paul Baran (born Pesach Baran ; April 29, 1926 – March 26, 2011) was a Polish-American engineer who was a pioneer in the development of computer networks. He was one of the two independent inventors of packet switching, which is today the dom ...
. ARPA awarded the contract to build the network to
Bolt Beranek & Newman Raytheon BBN (originally Bolt Beranek and Newman Inc.) is an American research and development company, based next to Fresh Pond in Cambridge, Massachusetts, United States. In 1966, the Franklin Institute awarded the firm the Frank P. Brown ...
who developed the first protocol for the network. Roberts engaged
Leonard Kleinrock Leonard Kleinrock (born June 13, 1934) is an American computer scientist and a long-tenured professor at UCLA's Henry Samueli School of Engineering and Applied Science. In the early 1960s, Kleinrock pioneered the application of queueing theor ...
at
UCLA The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California ...
to develop mathematical methods for analyzing the packet network technology. The first computers were connected in 1969 and the Network Control Protocol was implemented in 1970. The network was declared operational in 1971. Further software development enabled remote login, file transfer and
email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" mean ...
. The network expanded rapidly and operational control passed to the Defense Communications Agency in 1975.
Internetworking Internetworking is the practice of interconnecting multiple computer networks, such that any pair of hosts in the connected networks can exchange messages irrespective of their hardware-level networking technology. The resulting system of interc ...
research in the early 1970s led by
Bob Kahn Robert Elliot Kahn (born December 23, 1938) is an American electrical engineer who, along with Vint Cerf, first proposed the Transmission Control Protocol (TCP) and the Internet Protocol (IP), the fundamental communication protocols at the hea ...
at DARPA and
Vint Cerf Vinton Gray Cerf (; born June 23, 1943) is an American Internet pioneer and is recognized as one of " the fathers of the Internet", sharing this title with TCP/IP co-developer Bob Kahn. He has received honorary degrees and awards that include ...
at Stanford University and later DARPA formulated the Transmission Control Program, which incorporated concepts from the French
CYCLADES The Cyclades (; el, Κυκλάδες, ) are an island group in the Aegean Sea, southeast of mainland Greece and a former administrative prefecture of Greece. They are one of the island groups which constitute the Aegean archipelago. The name ...
project. As this work progressed, a protocol was developed by which multiple separate networks could be joined into a network of networks. Version 4 of TCP/IP was installed in the ARPANET for production use in January 1983 after the Department of Defense made it standard for all military computer networking. Access to the ARPANET was expanded in 1981, when the
National Science Foundation The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National ...
(NSF) funded the Computer Science Network (CSNET). In the early 1980s, the NSF funded the establishment of national supercomputing centers at several universities, and provided network access and network interconnectivity with the
NSFNET The National Science Foundation Network (NSFNET) was a program of coordinated, evolving projects sponsored by the National Science Foundation (NSF) from 1985 to 1995 to promote advanced research and education networking in the United States. The p ...
project in 1986. The ARPANET was formally decommissioned in 1990, after partnerships with the telecommunication and computer industry had assured private sector expansion and future commercialization of an expanded world-wide network, known as the Internet.


History


Inspiration

Historically, voice and data communications were based on methods of
circuit switching Circuit switching is a method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel ( circuit) through the network before the nodes may communicate. The circuit guarantees the full ...
, as exemplified in the traditional telephone network, wherein each telephone call is allocated a dedicated, end to end, electronic connection between the two communicating stations. The connection is established by switching systems that connected multiple intermediate call legs between these systems for the duration of the call. The traditional model of the circuit-switched telecommunication network was challenged in the early 1960s by
Paul Baran Paul Baran (born Pesach Baran ; April 29, 1926 – March 26, 2011) was a Polish-American engineer who was a pioneer in the development of computer networks. He was one of the two independent inventors of packet switching, which is today the dom ...
at the RAND Corporation, who had been researching systems that could sustain operation during partial destruction, such as by nuclear war. He developed the theoretical model of ''distributed adaptive message block switching''. However, the telecommunication establishment rejected the development in favor of existing models.
Donald Davies Donald Watts Davies, (7 June 1924 – 28 May 2000) was a Welsh computer scientist who was employed at the UK National Physical Laboratory (NPL). In 1965 he conceived of packet switching, which is today the dominant basis for data communic ...
at the United Kingdom's National Physical Laboratory (NPL) independently arrived at a similar concept in 1965. The earliest ideas for a
computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...
intended to allow general communications among computer users were formulated by computer scientist J. C. R. Licklider of
Bolt Beranek and Newman Raytheon BBN (originally Bolt Beranek and Newman Inc.) is an American research and development company, based next to Fresh Pond in Cambridge, Massachusetts, United States. In 1966, the Franklin Institute awarded the firm the Frank P. Brow ...
(BBN), in April 1963, in memoranda discussing the concept of the " Intergalactic Computer Network". Those ideas encompassed many of the features of the contemporary Internet. In October 1963, Licklider was appointed head of the Behavioral Sciences and Command and Control programs at the Defense Department's
Advanced Research Projects Agency The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adv ...
(ARPA). He convinced Ivan Sutherland and Bob Taylor that this network concept was very important and merited development, although Licklider left ARPA before any contracts were assigned for development. Sutherland and Taylor continued their interest in creating the network, in part, to allow ARPA-sponsored researchers at various corporate and academic locales to utilize computers provided by ARPA, and, in part, to quickly distribute new software and other
computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (includi ...
results. Taylor had three computer terminals in his office, each connected to separate computers, which ARPA was funding: one for the
System Development Corporation System Development Corporation (SDC) was a computer software company based in Santa Monica, California. Founded in 1955, it is considered the first company of its kind. History SDC began as the systems engineering group for the SAGE air-defens ...
(SDC) Q-32 in
Santa Monica Santa Monica (; Spanish: ''Santa Mónica'') is a city in Los Angeles County, situated along Santa Monica Bay on California's South Coast. Santa Monica's 2020 U.S. Census population was 93,076. Santa Monica is a popular resort town, owing to i ...
, one for
Project Genie Project Genie was a computer research project started in 1964 at the University of California, Berkeley. It produced an early time-sharing system including the Berkeley Timesharing System, which was then commercialized as the SDS 940. History P ...
at the
University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...
, and another for
Multics Multics ("Multiplexed Information and Computing Service") is an influential early time-sharing operating system based on the concept of a single-level memory.Dennis M. Ritchie, "The Evolution of the Unix Time-sharing System", Communications of ...
at the
Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...
. Taylor recalls the circumstance: "For each of these three terminals, I had three different sets of user commands. So, if I was talking online with someone at S.D.C., and I wanted to talk to someone I knew at Berkeley, or M.I.T., about this, I had to get up from the S.D.C. terminal, go over and log into the other terminal and get in touch with them. I said, 'Oh Man!', it's obvious what to do: If you have these three terminals, there ought to be one terminal that goes anywhere you want to go. That idea is the ARPANET". Donald Davies' work caught the attention of ARPANET developers at
Symposium on Operating Systems Principles In ancient Greece, the symposium ( grc-gre, συμπόσιον ''symposion'' or ''symposio'', from συμπίνειν ''sympinein'', "to drink together") was a part of a banquet that took place after the meal, when drinking for pleasure was acc ...
in October 1967. He gave the first public presentation, having coined the term ''
packet switching In telecommunications, packet switching is a method of grouping data into '' packets'' that are transmitted over a digital network. Packets are made of a header and a payload. Data in the header is used by networking hardware to direct the p ...
'', in August 1968 and incorporated it into the
NPL network The NPL network, or NPL Data Communications Network, was a local area computer network operated by a team from the National Physical Laboratory in London that pioneered the concept of packet switching. Based on designs first conceived by Donal ...
in England. The NPL network and ARPANET were the first two networks in the world to use packet switching.; (source: Gatlinburg, ... Association for Computing Machinery) Roberts said the ARPANET and other packet switching networks built in the 1970s were similar "in nearly all respects" to Davies' original 1965 design.


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. Taylor hired Larry Roberts as a program manager in the ARPA
Information Processing Techniques Office The Information Processing Techniques Office (IPTO), originally "Command and Control Research",Lyon, Matthew; Hafner, Katie (1999-08-19). ''Where Wizards Stay Up Late: The Origins Of The Internet'' (p. 39). Simon & Schuster. Kindle Edition. was par ...
in January 1967 to work on the ARPANET. Roberts asked Frank Westervelt to explore the initial design questions for a network."Planning the ARPANET: 1967-1968" in Chapter 2 on Networking: Vision and Packet Switching 1959-1968 Intergalactic Vision to Arpanet, ''Entrepreneurial Capitalism and Innovation: A History of Computer Communications 1968-1988''
James Pelkey, 2007
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. 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.
Wesley Clark Wesley Kanne Clark (born December 23, 1944) is a retired United States Army officer. He graduated as valedictorian of the class of 1966 at West Point and was awarded a Rhodes Scholarship to the University of Oxford, where he obtained a degree ...
proposed minicomputers should be used as an interface to create a
message switching In telecommunications, message switching involves messages routed in their entirety, one hop at a time. It evolved from circuit switching and was the precursor of packet switching. History Western Union operated a message switching system, Plan ...
network. Roberts modified the ARPANET plan to incorporate Clark's suggestion and named the minicomputers
Interface Message Processor The Interface Message Processor (IMP) was the packet switching node used to interconnect participant networks to the ARPANET from the late 1960s to 1989. It was the first generation of gateways, which are known today as routers. An IMP was a ...
s (IMPs). The plan was presented at the inaugural Symposium on Operating Systems Principles in October 1967. Donald Davies' work on packet switching and the NPL network, presented by a colleague (
Roger Scantlebury Roger Anthony Scantlebury (born August 1936) is a British computer scientist who worked at the National Physical Laboratory (NPL) and later at Logica. Scantlebury participated in pioneering work to develop packet switching and associated communi ...
), came to the attention of the ARPA investigators at this conference. Roberts applied Davies' concept of packet switching for the ARPANET, and sought input from Paul Baran. The NPL network was using line speeds of 768 kbit/s, and the proposed line speed for the ARPANET was upgraded from 2.4 kbit/s to 50 kbit/s. By mid-1968, Roberts and Barry Wessler wrote a final version of the IMP specification based on a
Stanford Research Institute SRI International (SRI) is an American nonprofit scientific research institute and organization headquartered in Menlo Park, California. The trustees of Stanford University established SRI in 1946 as a center of innovation to support economic ...
(SRI) report that ARPA commissioned to write detailed specifications describing the ARPANET communications network. Roberts gave a report to Taylor on 3 June, who approved it on 21 June. After approval by ARPA, a
Request for Quotation A request for quotation (RfQ) is a business process in which a company or public entity requests a quote from a supplier for the purchase of specific products or services. RfQ generally means the same thing as Call for bids (CfB) and Invitatio ...
(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. 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. This team was led by Frank Heart and included Robert Kahn and Dave Walden. The BBN-proposed network closely followed Roberts' ARPA plan: a network composed of small computers called
Interface Message Processor The Interface Message Processor (IMP) was the packet switching node used to interconnect participant networks to the ARPANET from the late 1960s to 1989. It was the first generation of gateways, which are known today as routers. An IMP was a ...
s (or IMPs), similar to the later concept of routers, that functioned as gateways interconnecting local resources. At each site, the IMPs performed store-and-forward packet switching functions, and were interconnected with leased lines via telecommunication data sets (
modem A modulator-demodulator or modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by Modulation#Digital modulati ...
s), with initial data rates of . 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. The BBN team continued to interact with the NPL team with meetings between them taking place in the U.S. and the U.K. The first-generation IMPs were built by BBN Technologies using a
rugged computer A rugged computer or ruggedized computer is a computer specifically designed to operate reliably in harsh usage environments and conditions, such as strong vibrations, extreme temperatures and wet or dusty conditions. They are designed from incepti ...
version of the
Honeywell Honeywell International Inc. is an American publicly traded, multinational conglomerate corporation headquartered in Charlotte, North Carolina. It primarily operates in four areas of business: aerospace, building technologies, performance ma ...
DDP-516 computer, configured with of expandable
magnetic-core memory Magnetic-core memory was the predominant form of random-access computer memory for 20 years between about 1955 and 1975. Such memory is often just called core memory, or, informally, core. Core memory uses toroids (rings) of a hard magneti ...
, and a 16-channel Direct Multiplex Control (DMC)
direct memory access Direct memory access (DMA) is a feature of computer systems and allows certain hardware subsystems to access main system memory independently of the central processing unit (CPU). Without DMA, when the CPU is using programmed input/output, it is ...
unit. 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.


Debate on design goals

According to Charles Herzfeld, ARPA Director (1965–1967): Nonetheless, according to Stephen J. Lukasik, who as deputy director (1967–1970) and Director of DARPA (1970–1975) was "the person who signed most of the checks for Arpanet's development": The ARPANET incorporated distributed computation, and frequent re-computation, of routing tables. This increased the survivability of the network in the face of significant interruption. Automatic routing was technically challenging at the time. The ARPANET was designed to survive subordinate-network losses, since the principal reason was that the switching nodes and network links were unreliable, even without any nuclear attacks. The
Internet Society The Internet Society (ISOC) is an American nonprofit advocacy organization founded in 1992 with local chapters around the world. Its mission is "to promote the open development, evolution, and use of the Internet for the benefit of all people ...
agrees with Herzfeld in a footnote in their online article, ''A Brief History of the Internet'':
Paul Baran Paul Baran (born Pesach Baran ; April 29, 1926 – March 26, 2011) was a Polish-American engineer who was a pioneer in the development of computer networks. He was one of the two independent inventors of packet switching, which is today the dom ...
, the first to put forward a theoretical model for communication using packet switching, conducted the RAND study referenced above. Though the ARPANET did not exactly share Baran's project's goal, he said his work did contribute to the development of the ARPANET. Minutes taken by Elmer Shapiro of
Stanford Research Institute SRI International (SRI) is an American nonprofit scientific research institute and organization headquartered in Menlo Park, California. The trustees of Stanford University established SRI in 1946 as a center of innovation to support economic ...
at the ARPANET design meeting of 9–10 October 1967 indicate that a version of Baran's routing method ("hot potato") may be used, consistent with the NPL team's proposal at the Symposium on Operating System Principles in Gatlinburg.


Implementation

The first four nodes were designated as a testbed for developing and debugging the
1822 protocol The Interface Message Processor (IMP) was the packet switching node used to interconnect participant networks to the ARPANET from the late 1960s to 1989. It was the first generation of gateways, which are known today as routers. An IMP was a r ...
, which was a major undertaking. While they were connected electronically in 1969, network applications were not possible until the Network Control Protocol was implemented in 1970 enabling the first two host-host protocols, remote login (
Telnet Telnet is an application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. User data is interspersed in-band with Telnet contr ...
) and file transfer ( FTP) which were specified and implemented between 1969 and 1973. The network was declared operational in 1971. Network traffic began to grow once
email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" mean ...
was established at the majority of sites by around 1973.


Initial four hosts

The first four IMPs were: *
University of California, Los Angeles The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California S ...
(UCLA), where
Leonard Kleinrock Leonard Kleinrock (born June 13, 1934) is an American computer scientist and a long-tenured professor at UCLA's Henry Samueli School of Engineering and Applied Science. In the early 1960s, Kleinrock pioneered the application of queueing theor ...
had established a Network Measurement Center, with an SDS Sigma 7 being the first computer attached to it; * The Augmentation Research Center at Stanford Research Institute (now
SRI International SRI International (SRI) is an American nonprofit scientific research institute and organization headquartered in Menlo Park, California. The trustees of Stanford University established SRI in 1946 as a center of innovation to support economic ...
), where Douglas Engelbart had created the new NLS system, an early hypertext system, and would run the Network Information Center (NIC), with the SDS 940 that ran NLS, named "Genie", being the first host attached; *
University of California, Santa Barbara The University of California, Santa Barbara (UC Santa Barbara or UCSB) is a public land-grant research university in Santa Barbara, California with 23,196 undergraduates and 2,983 graduate students enrolled in 2021–2022. It is part of the U ...
(UCSB), with the Culler-Fried Interactive Mathematics Center's IBM 360/75, running OS/MVT being the machine attached; * The University of Utah School of Computing, where Ivan Sutherland had moved, running a DEC
PDP-10 Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, espec ...
operating on TENEX. The first successful host-to-host connection on the ARPANET was made between Stanford Research Institute (SRI) and UCLA, by SRI programmer Bill Duvall and UCLA student programmer Charley Kline, at 10:30 pm PST on 29 October 1969 (6:30 UTC on 30 October 1969). Kline connected from UCLA's SDS Sigma 7 Host computer (in Boelter Hall room 3420) to the Stanford Research Institute's SDS 940 Host computer. Kline typed the command "login," but initially the SDS 940 crashed after he typed two characters. About an hour later, after Duvall adjusted parameters on the machine, Kline tried again and successfully logged in. Hence, the first two characters successfully transmitted over the ARPANET were "lo". The first permanent ARPANET link was established on 21 November 1969, between the IMP at UCLA and the IMP at the Stanford Research Institute. By 5 December 1969, the initial four-node network was established. Elizabeth Feinler created the first Resource Handbook for ARPANET in 1969 which led to the development of the ARPANET directory. The directory, built by Feinler and a team made it possible to navigate the ARPANET.


Growth and evolution

Roberts engaged Howard Frank to consult on the topological design of the network. Frank made recommendations to increase throughput and reduce costs in a scaled-up network. By March 1970, the ARPANET reached the East Coast of the United States, when an IMP at BBN in
Cambridge, Massachusetts Cambridge ( ) is a city in Middlesex County, Massachusetts, United States. As part of the Boston metropolitan area, the cities population of the 2020 U.S. census was 118,403, making it the fourth most populous city in the state, behind Boston ...
was connected to the network. Thereafter, the ARPANET grew: 9 IMPs by June 1970 and 13 IMPs by December 1970, then 18 by September 1971 (when the network included 23 university and government hosts); 29 IMPs by August 1972, and 40 by September 1973. By June 1974, there were 46 IMPs, and in July 1975, the network numbered 57 IMPs. By 1981, the number was 213 host computers, with another host connecting approximately every twenty days. Support for inter-IMP circuits of up to 230.4 kbit/s was added in 1970, although considerations of cost and IMP processing power meant this capability was not actively used. Larry Roberts saw the ARPANET and NPL projects as complementary and sought in 1970 to connect them via a satellite link. Peter Kirstein's research group at
University College London , mottoeng = Let all come who by merit deserve the most reward , established = , type = Public research university , endowment = £143 million (2020) , budget = ...
(UCL) was subsequently chosen in 1971 in place of NPL for the UK connection. In June 1973, a transatlantic satellite link connected ARPANET to the Norwegian Seismic Array (NORSAR), via the Tanum Earth Station in Sweden, and onward via a terrestrial circuit to a TIP at UCL. UCL provided a gateway for interconnection with British academic and research networks and a testbed for international internetworking. 1971 saw the start of the use of the non-ruggedized (and therefore significantly lighter) Honeywell 316 as an IMP. It could also be configured as a Terminal Interface Processor (TIP), which provided
terminal server A terminal server connects devices with a serial port to a local area network (LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as data encryption and user authentication ...
support for up to 63
ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because ...
serial terminals through a multi-line controller in place of one of the hosts. The 316 featured a greater degree of integration than the 516, which made it less expensive and easier to maintain. The 316 was configured with 40 kB of core memory for a TIP. The size of core memory was later increased, to 32 kB for the IMPs, and 56 kB for TIPs, in 1973. In 1975, BBN introduced IMP software running on the Pluribus multi-processor. These appeared in a few sites. In 1981, BBN introduced IMP software running on its own C/30 processor product.


Network performance

In 1968, Roberts contracted with Kleinrock to measure the performance of the network and find areas for improvement. Building on his earlier work on
queueing theory Queueing theory is the mathematical study of waiting lines, or queues. A queueing model is constructed so that queue lengths and waiting time can be predicted. Queueing theory is generally considered a branch of operations research because the ...
, Kleinrock specified mathematical models of the performance of packet-switched networks, which underpinned the development of the ARPANET as it expanded rapidly in the early 1970s.


Operation

ARPA was intended to fund advanced research. The ARPANET was a research project that was communications-oriented, rather than user-oriented in design. Nonetheless, in the summer of 1975, operational control of the ARPANET passed to the Defense Communications Agency. At about this time, the first ARPANET encryption devices were deployed to support classified traffic. The transatlantic connectivity with NORSAR and UCL later evolved into the SATNET. The ARPANET, SATNET and
PRNET The Packet Radio Network (PRNET) was a set of early, experimental mobile ad hoc networks whose technologies evolved over time. It was funded by the Advanced Research Projects Agency (ARPA). Major participants in the project included BBN Technol ...
were interconnected in 1977. The ''ARPANET Completion Report'', published in 1981 jointly by BBN and
DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Ad ...
, concludes that:


CSNET, expansion

Access to the ARPANET was expanded in 1981, when the
National Science Foundation The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National ...
(NSF) funded the Computer Science Network (CSNET).


Adoption of TCP/IP

The DoD made TCP/IP the standard
communication protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...
for all military computer networking in 1980. NORSAR and University College London left the ARPANET and began using TCP/IP over SATNET in early 1982. On January 1, 1983, known as flag day, TCP/IP protocols became the standard for the ARPANET, replacing the earlier Network Control Protocol.


MILNET, phasing out

In September 1984 work was completed on restructuring the ARPANET giving U.S. military sites their own Military Network (
MILNET In computer networking, MILNET (fully Military Network) was the name given to the part of the ARPANET internetwork designated for unclassified United States Department of Defense traffic.DEFENSE DATA NETWORK NEWSLETTEDDN-NEWS 26 6 May 1983 MILNE ...
) for unclassified defense department communications. Both networks carried unclassified information, and were connected at a small number of controlled gateways which would allow total separation in the event of an emergency. MILNET was part of the Defense Data Network (DDN). Separating the civil and military networks reduced the 113-node ARPANET by 68 nodes. After MILNET was split away, the ARPANET would continue be used as an Internet backbone for researchers, but be slowly phased out.


Decommissioning

In 1985, the NSF funded the establishment of national supercomputing centers at several universities, and provided network access and network interconnectivity with the
NSFNET The National Science Foundation Network (NSFNET) was a program of coordinated, evolving projects sponsored by the National Science Foundation (NSF) from 1985 to 1995 to promote advanced research and education networking in the United States. The p ...
project in 1986. NSFNET became the Internet backbone for government agencies and universities. The ARPANET project was formally decommissioned in 1990. The original IMPs and TIPs were phased out as the ARPANET was shut down after the introduction of the NSFNet, but some IMPs remained in service as late as July 1990. In the wake of the decommissioning of the ARPANET on 28 February 1990, Vinton Cerf wrote the following lamentation, entitled "Requiem of the ARPANET":


Legacy

The ARPANET was related to many other research projects, which either influenced the ARPANET design, or which were ancillary projects or spun out of the ARPANET. Senator
Al Gore Albert Arnold Gore Jr. (born March 31, 1948) is an American politician, businessman, and environmentalist who served as the 45th vice president of the United States from 1993 to 2001 under President Bill Clinton. Gore was the Democratic no ...
authored the
High Performance Computing and Communication Act of 1991 The High Performance Computing Act of 1991 (HPCA) is an Act of Congress promulgated in the 102nd United States Congress as (Pub.L. 102–194) on December 9, 1991. Often referred to as the Gore Bill, it was created and introduced by then Senator Al ...
, commonly referred to as "The Gore Bill", after hearing the 1988 concept for a National Research Network submitted to Congress by a group chaired by
Leonard Kleinrock Leonard Kleinrock (born June 13, 1934) is an American computer scientist and a long-tenured professor at UCLA's Henry Samueli School of Engineering and Applied Science. In the early 1960s, Kleinrock pioneered the application of queueing theor ...
. The bill was passed on 9 December 1991 and led to the
National Information Infrastructure The National Information Infrastructure (NII) was the product of the High Performance Computing Act of 1991. It was a telecommunications policy buzzword, which was popularized during the Clinton Administration under the leadership of Vice-President ...
(NII) which Gore called the '' information superhighway''. Inter-networking protocols developed by ARPA and implemented on the ARPANET paved the way for future commercialization of a new world-wide network, known as the
Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
. The ARPANET project was honored with two IEEE Milestones, both dedicated in 2009.


Software and protocols


IMP functionality

Because it was never a goal for the ARPANET to support IMPs from vendors other than BBN, the IMP-to-IMP protocol and message format were not standardized. However, the IMPs did nonetheless communicate amongst themselves to perform link-state routing, to do reliable forwarding of messages, and to provide remote monitoring and management functions to ARPANET's Network Control Center. Initially, each IMP had a 6-bit identifier, and supported up to 4 hosts, which were identified with a 2-bit index. An ARPANET host address, therefore, consisted of both the port index on its IMP and the identifier of the IMP, which was written with either port/IMP notation or as a single byte; for example, the address of MIT-DMG (notable for hosting development of
Zork ''Zork'' is a text-based adventure game first released in 1977 by developers Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling for the PDP-10 mainframe computer. The original developers and others, as the company Infocom, expanded a ...
) could be written as either 1/6 or 70. An upgrade in early 1976 extended the host and IMP numbering to 8-bit and 16-bit, respectively. In addition to primary routing and forwarding responsibilities, the IMP ran several background programs, titled TTY, DEBUG, PARAMETER-CHANGE, DISCARD, TRACE, and STATISTICS. These were given host numbers in order to be addressed directly and provided functions independently of any connected host. For example, "TTY" allowed an on-site operator to send ARPANET packets manually via the
teletype A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Init ...
connected directly to the IMP.


1822 protocol

The starting point for host-to-host communication on the ARPANET in 1969 was the
1822 protocol The Interface Message Processor (IMP) was the packet switching node used to interconnect participant networks to the ARPANET from the late 1960s to 1989. It was the first generation of gateways, which are known today as routers. An IMP was a r ...
, which defined the transmission of messages to an IMP. The message format was designed to work unambiguously with a broad range of computer architectures. An 1822 message essentially consisted of a message type, a numeric host address, and a data field. To send a data message to another host, the transmitting host formatted a data message containing the destination host's address and the data message being sent, and then transmitted the message through the 1822 hardware interface. The IMP then delivered the message to its destination address, either by delivering it to a locally connected host, or by delivering it to another IMP. When the message was ultimately delivered to the destination host, the receiving IMP would transmit a ''Ready for Next Message'' (RFNM) acknowledgement to the sending, host IMP.


Network Control Protocol

Unlike modern Internet datagrams, the ARPANET was designed to reliably transmit 1822 messages, and to inform the host computer when it loses a message; the contemporary IP is unreliable, whereas the TCP is reliable. Nonetheless, the 1822 protocol proved inadequate for handling multiple connections among different applications residing in a host computer. This problem was addressed with the Network Control Protocol (NCP), which provided a standard method to establish reliable, flow-controlled, bidirectional communications links among different processes in different host computers. The NCP interface allowed
application software Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a ...
to connect across the ARPANET by implementing higher-level communication protocols, an early example of the ''protocol layering'' concept later incorporated in the OSI model. NCP was developed under the leadership of Stephen D. Crocker, then a graduate student at UCLA. Crocker created and led the Network Working Group (NWG) which was made up of a collection of graduate students at universities and research laboratories sponsored by ARPA to carry out the development of the ARPANET and the software for the host computers that supported applications. The various application protocols such as TELNET for remote time-sharing access, File Transfer Protocol (FTP) and rudimentary electronic mail protocols were developed and eventually ported to run over the TCP/IP protocol suite or replaced in the case of email by the Simple Mail Transfer Protocol.


TCP/IP

Steve Crocker formed a "Networking Working Group" in 1969 with
Vint Cerf Vinton Gray Cerf (; born June 23, 1943) is an American Internet pioneer and is recognized as one of " the fathers of the Internet", sharing this title with TCP/IP co-developer Bob Kahn. He has received honorary degrees and awards that include ...
, who also joined an
International Networking Working Group The International Networking Working Group (INWG) was a group of prominent computer science researchers in the 1970s who studied and developed standards and protocols for computer networking. Set up in 1972 as an informal group to consider the tec ...
in 1972. These groups considered how to interconnect packet switching networks with different specifications, that is,
internetworking Internetworking is the practice of interconnecting multiple computer networks, such that any pair of hosts in the connected networks can exchange messages irrespective of their hardware-level networking technology. The resulting system of interc ...
. Stephen J. Lukasik directed DARPA to focus on internetworking research in the early 1970s. Research led by
Bob Kahn Robert Elliot Kahn (born December 23, 1938) is an American electrical engineer who, along with Vint Cerf, first proposed the Transmission Control Protocol (TCP) and the Internet Protocol (IP), the fundamental communication protocols at the hea ...
at DARPA and Vint Cerf at Stanford University and later DARPA resulted in the formulation of the Transmission Control Program, which incorporated concepts from the French
CYCLADES The Cyclades (; el, Κυκλάδες, ) are an island group in the Aegean Sea, southeast of mainland Greece and a former administrative prefecture of Greece. They are one of the island groups which constitute the Aegean archipelago. The name ...
project directed by
Louis Pouzin Louis Pouzin (April 20, 1931 in Chantenay-Saint-Imbert, Nièvre, France) is a French computer scientist. He designed an early packet communications network, CYCLADES. This network was the first actual implementation of the pure datagram model, ...
. Its specification was written by Cerf with
Yogen Dalal Instead of having a single "inventor", the Internet was developed by many people over many years. The following are some Internet pioneers who contributed to its early and ongoing development. These include early theoretical foundations, specifyi ...
and Carl Sunshine in December 1974 (). The following year, testing began through concurrent implementations at Stanford, BBN and
University College London , mottoeng = Let all come who by merit deserve the most reward , established = , type = Public research university , endowment = £143 million (2020) , budget = ...
. At first a monolithic design, the software was redesigned as a modular protocol stack in version 3 in 1978. Version 4 was installed in the ARPANET for production use in January 1983, replacing NCP. The development of the complete
Internet protocol suite The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the sui ...
by 1989, as outlined in and , and partnerships with the telecommunication and computer industry laid the foundation for the adoption of TCP/IP as a comprehensive protocol suite as the core component of the emerging
Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
.


Network applications

NCP provided a standard set of network services that could be shared by several applications running on a single host computer. This led to the evolution of ''application protocols'' that operated, more or less, independently of the underlying network service, and permitted independent advances in the underlying protocols.
Telnet Telnet is an application protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. User data is interspersed in-band with Telnet contr ...
was developed in 1969 beginning with RFC 15, extended in RFC 855. The original specification for the File Transfer Protocol was written by Abhay Bhushan and published as on 16 April 1971. By 1973, the
File Transfer Protocol The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and dat ...
(FTP) specification had been defined () and implemented, enabling file transfers over the ARPANET. In 1971,
Ray Tomlinson Raymond Samuel Tomlinson (April 23, 1941 – March 5, 2016) was an American computer programmer who implemented the first email program on the ARPANET system, the precursor to the Internet, in 1971; It was the first system able to send mail be ...
, of BBN sent the first network e-mail (, ). Within a few years, e-mail came to represent a very large part of the overall ARPANET traffic. The Network Voice Protocol (NVP) specifications were defined in 1977 (), and implemented. But, because of technical shortcomings, conference calls over the ARPANET never worked well; the contemporary Voice over Internet Protocol (packet voice) was decades away.


Password protection

The George B. Purdy#The Purdy Polynomial, Purdy Polynomial hash algorithm was developed for the ARPANET to protect passwords in 1971 at the request of Larry Roberts, head of ARPA at that time. It computed a polynomial of degree 224 + 17 modulo the 64-bit prime ''p'' = 264 − 59. The algorithm was later used by Digital Equipment Corporation (DEC) to hash passwords in the OpenVMS, VMS operating system and is still being used for this purpose.


Rules and etiquette

Because of its government funding, certain forms of traffic were discouraged or prohibited. Leonard Kleinrock claims to have committed the first illegal act on the Internet, having sent a request for return of his electric razor after a meeting in England in 1973. At the time, use of the ARPANET for personal reasons was unlawful. In 1978, against the rules of the network, Gary Thuerk of Digital Equipment Corporation (DEC) sent out the first mass email to approximately 400 potential clients via the ARPANET. He claims that this resulted in $13 million worth of sales in DEC products, and highlighted the potential of email marketing. A 1982 handbook on computing at MIT's AI Lab stated regarding network etiquette:


In popular culture

* ''Computer Networks: The Heralds of Resource Sharing'', a 30-minute documentary film featuring Fernando J. Corbató, J. C. R. Licklider, Lawrence G. Roberts, Bob Kahn, Robert Kahn, Frank Heart, William R. Sutherland, Richard W. Watson, John R. Pasta, Donald W. Davies, and economist, George W. Mitchell (economist), George W. Mitchell. * List of Benson episodes#Season 6 (1984–85), "Scenario", an episode of the U.S. television sitcom Benson (TV series), ''Benson'' (season 6, episode 20—dated February 1985), was the first incidence of a popular TV show directly referencing the Internet or its progenitors. The show includes a scene in which the ARPANET is accessed. * There is an electronic music artist known as "Arpanet", Gerald Donald, one of the members of Drexciya. The artist's 2002 album ''Wireless Internet'' features commentary on the expansion of the internet via wireless communication, with songs such as ''NTT DoCoMo'', dedicated to the mobile communications giant based in Japan. * Thomas Pynchon mentions the ARPANET in his 2009 novel ''Inherent Vice'', which is set in Los Angeles in 1970, and in his 2013 novel ''Bleeding Edge (novel), Bleeding Edge''. * The 1993 television series ''The X-Files'' featured the ARPANET in a season 5 episode, titled "Unusual Suspects (The X-Files), Unusual Suspects". John Fitzgerald Byers offers to help Susan Modeski (known as Holly ... "just like the sugar") by hacking into the ARPANET to obtain sensitive information. * In the spy-drama television series ''The Americans'', a Russian scientist defector offers access to ARPANET to the Russians in a plea to not be repatriated (Season 2 Episode 5 "The Deal"). Episode 7 of Season 2 is named 'ARPANET' and features Russian infiltration to bug the network. * In the television series ''Person of Interest (TV series), Person of Interest'', main character Harold Finch (Person of Interest), Harold Finch hacked the ARPANET in 1980 using a homemade computer during his first efforts to build a prototype of the Machine. This corresponds with the real life virus that occurred in October of that year that temporarily halted ARPANET functions. The ARPANET hack was first discussed in the episode List of Person of Interest episodes#ep34, ''2PiR'' (stylised ''2\piR'') where a computer science teacher called it the most famous hack in history and one that was never solved. Finch later mentioned it to Person of Interest Caleb Phipps and his role was first indicated when he showed knowledge that it was done by "a kid with a homemade computer" which Phipps, who had researched the hack, had never heard before. * In the third season of the television series ''Halt and Catch Fire (TV series), Halt and Catch Fire'', the character Joe MacMillan explores the potential commercialization of the ARPANET.


See also

* .arpa – top-level domain used exclusively for technical infrastructure purposes * * * * * Protocol Wars * , "A Poor Man's ARPAnet"


References


Sources

*


Further reading

* * * * * * * *


Oral histories

* Focuses on Kahn's role in the development of computer networking from 1967 through the early 1980s. Beginning with his work at BBN, Kahn discusses his involvement as the ARPANET proposal was being written and then implemented, and his role in the public demonstration of the ARPANET. The interview continues into Kahn's involvement with networking when he moves to IPTO in 1972, where he was responsible for the administrative and technical evolution of the ARPANET, including programs in packet radio, the development of a new network protocol (TCP/IP), and the switch to TCP/IP to connect multiple networks. * Cerf describes his involvement with the ARPA network, and his relationships with Bolt Beranek and Newman, Robert Kahn, Lawrence Roberts, and the Network Working Group. * Baran describes his work at RAND, and discusses his interaction with the group at ARPA who were responsible for the later development of the ARPANET. * Kleinrock discusses his work on the ARPANET. * * Lukasik discusses his tenure at the Advanced Research Projects Agency (ARPA), the development of computer networks and the ARPANET. * Frank describes his work on the ARPANET, including his interaction with Roberts and the IPT Office.


Detailed technical reference works

* * * * * * * * * * * * * * ** NTIS documents may be available from * *


External links

* * * Timeline. * * Personal anecdote of the first message ever sent over the ARPANET * * * {{Authority control ARPANET, American inventions History of the Internet Computer-related introductions in 1969 Internet properties established in 1969 Internet properties disestablished in 1990 1969 establishments in the United States Internet in the United States 1990 disestablishments in the United States