Arpanet

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ARPANET - Wikipedia, the free encyclopedia
ARPAnet logic map, March 1977. The ARPAnet (Advanced ... 7 The ARPAnet and nuclear attacks. 8 Retrospective. 9 References in film and media. 10 See also ...
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ARPANET, Internet
ARPANET -- The First Internet ... The ARPANET was developed by the IPTO under the sponsorship of DARPA, and ... The ARPANET went into labor on August 30, 1969, ...
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ARPAnet - The First Internet
The model-T of the information highway - ARPANET was the first Internet. ... He claimed that ARPAnet was not created as a result of a military need, stating " ...
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What is ARPANET? - a definition from Whatis.com - see also: Advanced ...
ARPANET was the network that became the basis for the Internet. ... ARPANET took advantage of the new idea of sending ... Networking & ARPANET Solutions ...
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What is ARPANET? - A Word Definition From the Webopedia Computer Dictionary
This page describes the term ARPANET and lists other pages on the Web where you can find additional information. ... Established in 1969, ARPANET served as a ...
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History of the Internet - Wikipedia
Covers motivation, growth, applications, and standards. ... 5.2 ARPANET to Several Federal Wide Area Networks: MILNET, NSI, and NSFNet ...
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Internet Society (ISOC) All About The Internet: History of the Internet
An authoritative history, written by some of those who were most closely associated with its creation and ... The original ARPANET grew into the Internet. ...
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History of ARPANET - Part I: The history of ARPA leading up to the ARPANET
A climate of pure research surrounded the entire history of the ARPANET. ... ARPA assigned this duty to the initial designated ARPANET sites. ...
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ARPANET
When ARPANET connected UCLA to the Stanford Research Institute, UC Santa Barbara, ... During its first decade, ARPANET truly lived up to its billing as an " ...
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The ARPANET, developed by Defense Advanced Research Projects Agency of the United States Department of Defense, was the world's first operational packet switching network, and the predecessor of the global Internet.

Packet switching, now the dominant basis for both data and voice communication worldwide, was a new and important concept in data communications. Previously, data communication was based on the idea of circuit switching, as in the old typical telephone circuit, where a dedicated Derp circuit is tied up for the duration of the call and communication is only possible with the single party on the other end of the circuit.

With packet switching, a system could use one communication link to communicate with more than one machine by assembling data into Packet (information technology). Not only could the link be shared (much as a single post box can be used to post letters to different destinations), but each packet could be routed independently of other packets. This was a major advancement.

Background of the ARPANET The earliest ideas of a computer network intended to allow general communication between users of various computers were formulated by J.C.R. Licklider of Bolt, Beranek and Newman (BBN) in August 1962, in a series of memos discussing his "Galactic Network" concept. These ideas contained almost everything that the Internet is today.

In October 1963, Licklider was appointed head of the Behavioral Sciences and Command and Control programs at Defense Advanced Research Projects Agency (as it was then called), the United States Department of Defense Advanced Research Projects Agency. He then convinced Ivan Sutherland and Robert Taylor (computer scientist) that this was a very important concept, although he left ARPA before any actual work on his vision was performed.

ARPA and Poulsen continued to be interested in creating a computer communication network, in part to allow ARPA-sponsored researchers in various locations to use various computers which ARPA was providing, and in part to quickly make new software and other results widely available. Taylor had three different terminals in his office, connected to three different computers which ARPA was funding: one for the System Development Corporation Q32 in Santa Monica, one for Project Genie at the University of California, Berkeley, and one for Multics at Massachusetts Institute of Technology. Taylor later recalled:

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. .

Roughly contemporaneously, a number of people had (mostly independently) worked out various aspects of what later became known as "packet switching"; the people who created the ARPANET would eventually draw on all these different sources.

Origins of the ARPANET At the end of 1966, Taylor brought Larry Roberts to ARPA from MIT Lincoln Laboratory to head a project to create the networks. Roberts had some initial experience in this area: two years previously, in 1965, while at MIT Lincoln Laboratory, he had connected the TX-2 to System Development Corporation's Q32 over a telephone line, conducting some of the earliest experiments in which two computers communicated that way. Roberts's initial concept for the network for ARPA was to hook the various time-sharing machines directly to each other, through telephone.

At a meeting at the University of Michigan in Ann Arbor, Michigan in early 1967, many of the participants were unenthusiastic at having the load of managing this line put directly on their computers. One of the participants, Wesley A. Clark, came up with the idea of using separate smaller computers to manage the communication links; the small computers would then be connected to the large time-sharing Mainframe computer computers which were the typical machines to be connected to the ARPANET. This concept allowed most of the detailed work of running the network to be offloaded from the large mainframes; it also meant that correct operation of the network as a whole was not subject to the vagaries of individual host implementations, and that ARPA would have complete control over the network itself.

Initial planning for the ARPANET began on that basis, with a number of working groups on specific technical subjects meeting during the late spring and summer of 1967.

Roberts then proceeded to author a "plan for the ARPANET", which was presented at a symposium in Gatlinburg, Tennessee in October, 1967. Also presenting there was Roger Scantlebury, from Donald Davies' group at NPL. (Roberts had previously encountered Davies at a conference in Britain about time-sharing, in November, 1965.) He discussed Davies's packet switching ideas with Roberts, and introduced Roberts to Paul Baran's work.

The exact impact of all this is unclear, and somewhat controversial memoirs by different people involved in the process give sharply conflicting accounts, often in conflict with their earlier recorded statements. The general view of most historians is that all four (Baran, Kleinrock, Davies and Roberts) had important contributions:

Davies was instrumental in passing on the knowledge of packet switching that he and Baran had developed to Lawrence Roberts
Roberts's ideas for the network were modified by his discussions with Scantlebury. .. According to his later description, upon returning to Washington from the Gatlinburg meeting was influenced by Baran's reports
If anyone influenced Roberts in his earliest thinking about computer networks, it was Kleinrock. ... Baran's insights into data communications intrigued ... The Gatlinburg paper presented by Scantlebury on behalf of the British effort was clearly an influence, too.

Creation of the ARPANET By the summer of 1968, a complete plan had been prepared, and after approval at ARPA, a Request for Quotation (RFQ) was sent to 140 potential bidders. Most regarded the proposal as outlandish, and only 12 companies submitted bids, of which only four were regarded as in the top rank. By the end of the year, the field had been narrowed to two, and after negotiations, a final choice was made, and the contract was awarded to BBN Technologies on 7 April, 1969.

BBN's proposal followed Roberts's plan closely; it called for the network to be composed of small computers known as Interface Message Processors (more commonly known as IMPs). The IMPs at each site performed store-and-forward packet switching functions, and were connected to each other using modems connected to leased lines (initially running at 50 kbit/second). Host computers connected to the IMPs via custom bit serial interfaces to connect to ARPANET.

BBN initially chose a Rugged computer version of Honeywell's DDP-516 computer to build the first-generation IMP. The 516 was originally configured with 24 kbytes of core memory (expandable) and a 16 channel Direct Multiplex Control (DMC) direct memory access control unit. Custom interfaces were used to connect, via the DMC, to each of the hosts and modems. In addition to the lamps on the front panel of the 516 there was also a special set of 24 indicator lights to show 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 over leased lines.

The small team at BBN (initially only seven people), helped considerably by the detail they had gone into to produce their response to the RFQ, quickly produced the first working units. The entire system, including both hardware and the world's first packet switching software, was designed and installed in nine months.

Initial ARPA deployment

The initial ARPANET consisted of four IMPs. They were installed at:

UCLA, where Leonard Kleinrock had established a Network Measurement Center (with an SDS Sigma 7 being the first computer attached to it).
The Stanford Research Institute's Augmentation Research Center, where Douglas Engelbart had created the ground-breaking NLS (computer system) system, a very important early hypertext system (with the SDS 940 that ran NLS, named 'Genie', being the first host attached).
UC Santa Barbara (with the Culler-Fried Interactive Mathematics Centre's IBM System 360, running OS/MVT being the machine attached).
The University of Utah's Graphics Department, where Ivan Sutherland had moved (for a Digital Equipment Corporation PDP-10 running TOPS-20).

The first ARPANET link was established on january 14, 1969, between the IMP at UCLA and the IMP at SRI. By December 5, 1969, the entire 4-node network was connected .

The first message ever to be sent over the internet occurred at 10:30 PM on October 29, 1969. It was sent by UCLA student programmer Charley Kline and supervised by UCLA Professor Leonard Kleinrock. The message was sent from the UCLA SDS Sigma 7 Host computer to the SRI SDS 940 Host computer. The message itself was simply the word "login". The "l" and the "o" transmitted without problem but then the system crashed. Hence, the first message on the Internet was "Lo". They were able to do the full login about an hour later.

Software and protocol development The starting point for host-to-host communication on the ARPANET was the BBN Report 1822 which defined the way that a host sent messages to an ARPANET IMP. The message format was designed to work unambiguously with a broad range of computer architectures. Essentially, an 1822 message consisted of a message type, a numeric host address, and a data field. To send a data message to another host, the sending host would format a data message containing the destination host's address and the data to be sent, and transmit the message through the 1822 hardware interface. The IMP would see that the message was delivered to its destination, 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 IMP would send an acknowledgment message (called Ready for Next Message or RFNM) to the sending host.

Unlike modern Internet datagrams, the ARPANET was designed to transmit all 1822 messages reliably, or at least to be able to tell the host when a message was lost. Nonetheless, the 1822 protocol did not prove to be adequate by itself for juggling multiple connections between different applications residing on a single host. This problem was addressed with the Network Control Program or NCP, which provided a standard method to establish reliable, flow-controlled, bidirectional communications links between different processes on different hosts. The NCP interface allowed software application to connect across the ARPANET implementing higher-level communication protocols. This was an early example of the protocol layering concept incorporated into the OSI model.

In 1983, TCP/IP protocols replaced NCP as the principal protocol of the ARPANET, and the ARPANET became just one component of the fledgling Internet.

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. When the ARPANET migrated to the Internet protocols in 1983, the major application protocols migrated along with it.

E-mail: In 1971, Ray Tomlinson of Bolt, Beranek and Newman sent the first network email . By 1973, 75% of the ARPANET traffic was email.

File transfer: By 1973, the File Transfer Protocol (File Transfer Protocol) specification had been defined and implemented, enabling file transfers over the ARPANET.

Voice traffic: A Network Voice Protocol (NVP) specifications was also defined (RFC 741) and then implemented, but conference calls over the ARPANET never worked well, for technical reasons; voice over internet protocol would not become a workable reality for a few decades.

Growth of the network In March, 1970, the ARPANET reached the U.S. East Coast, when an IMP at BBN itself was joined up to the network. Thereafter, the network grew quickly: 9 IMPs by June of 1970, and 13 by December; 18 by September, 1971 (at which point twenty-three hosts, at universities and government research centers, were connected to the ARPANET); 29 by August, 1972, and 40 by September, 1973.

At that point, two satellite links, across the Pacific and Atlantic Oceans to Hawaii and Norway (NORSAR, see Norwegian Seismic Array) respectively, had been added to the network. From Norway, a terrestrial circuit added an IMP in London to the growing network.

By June 1974, there were 46 IMPs, and the network reached 57 in July, 1975. By 1981, the number of hosts had grown to 213, with a new host being added approximately every twenty days.

After the ARPANET had been up and running for several years, ARPA looked for another agency to hand off the network to; ARPA's primary business was funding cutting-edge research and development, not running a communications utility. Eventually, in July 1975, the network was turned over to the Defense Communications Agency, also part of the Department of Defense.

In 1983, the U.S. military portion of the ARPANet was broken off as a separate network, the MILNET. Prior to this there were 113 nodes on the ARPANet. After the split, that number was 68 nodes with the remainder moving to MILNET.

Later hardware developments 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 much used.

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 IMP (TIP), which added support for up to 63 ASCII 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 Kbytes of core memory for a TIP. The size of core memory was later increased, to 32 Kbytes for the IMPs, and 56Kbytes for TIPs, in 1973.

In 1975, BBN introduced IMP software running on the Pluribus multi-processor. These appeared in a small number of sites. In 1981, BBN introduced IMP software running on its own C/30 processor product.

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 1989.

The ARPANET and nuclear attacks A common semi-myth about the ARPANET states that it was designed to be resistant to nuclear weapon. The Internet Society writes about the merger of technical ideas that produced the ARPANET in A Brief History of the Internet, and states in a note:

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, only the unrelated (sic) RAND study on secure voice considered nuclear war. However, the later work on Internetting did emphasize robustness and survivability, including the capability to withstand losses of large portions of the underlying networks.

The ARPANET was designed to survive network losses, but the main reason was actually that the switching nodes and network links were not highly reliable, even without any nuclear attacks.Charles Herzfeld, ARPA director from 1965 to 1967, speaks about limited computer resources helping to spur ARPANET's creation:

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.

Retrospective Support and style of management by ARPA was crucial to the success of ARPANET. The ARPANET Completion Report, published jointly by BBN and ARPA, concludes by stating:

...it is somewhat fitting to end on the note that the ARPANET program has had a strong and direct feedback into the support and strength of computer science, from which the network itself sprung.

See also

History of the Internet
Computer Networks: The Heralds of Resource Sharing - 1972 documentary
AMPRNet
Project Cybersyn First Chilean national net in 1970

Notes

Abbate, Inventing the Internet, pp. 8
Norberg, O'Neill, Transforming Computer Technology, pp. 166
Hafner, Where Wizards Stay Up Late, pp. 69, 77
A History of the ARPANET, Chapter III, pg.132, Section 2.3.4