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ARPANET logical map, March 1977.
ARPANET logical map, March 1977.

The ARPANET (Advanced Research Projects Agency Network) developed by DARPA of the United States Department of Defense, was the world's first operational packet switching network, and the predecessor of the global Internet. The Defense Advanced Research Projects Agency (DARPA is an agency of the United States Department of Defense responsible for the development of new Technology The United States Department of Defense ( DOD or DoD) is the federal department charged with coordinating and supervising all agencies and functions of the government Packet switching is a network communications method that splits data traffic (digital representations of text sound or video data into chunks called packets, that are then The Internet is a global system of interconnected Computer networks

Packet switching, now the dominant basis for both data and voice communication worldwide, was a new and important concept in data communications. Packet switching is a network communications method that splits data traffic (digital representations of text sound or video data into chunks called packets, that are then Previously, data communication was based on the idea of circuit switching, as in the old typical telephone circuit, where a dedicated 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. In Telecommunications a circuit switching network is one that establishes a fixed bandwidth circuit (or channel) between nodes and terminals

With packet switching, a system could use one communication link to communicate with more than one machine by disassembling data into datagraphs, then gather these as packets. In Information technology, a packet is a formatted unit of Data carried by a Packet mode Computer network. 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. A post box ( British English and others also written postbox) (in the U

This idea was thought up by Paul Baran, of the RAND Corporation, for the U. Paul Baran (born April 29, 1926) was one of the three inventors of Packet-switched networks along with Donald Davies and Leonard Kleinrock The RAND Corporation ( R esearch AN d D evelopment is a Nonprofit global policy Think tank first formed to offer research and analysis S. Air Force to do a study on how it could maintain its command and control over its missiles and bombers, after a nuclear attack. This was to be a military research network that could survive a nuclear strike, decentralized so that if any locations (cities) in the U. S. were attacked, the military could still have control of nuclear arms for a counter-attack.

Quote from Paul Baran: "Packet switching is the breaking down of data into datagrams or packets that are labeled to indicate the origin and the destination of the information and the forwarding of these packets from one computer to another computer until the information arrives at its final destination computer. This was crucial to the realization of a computer network. If packets are lost at any given point, the message can be resent by the originator. "

Contents

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 "Intergalactic Computer Network" concept. Joseph Carl Robnett Licklider ( March 11, 1915  &ndash June 26, 1990) known simply as J Intergalactic Computer Network can be said to be the first conception of what would eventually become the Internet. These ideas contained almost everything that the Internet is today. The Internet is a global system of interconnected Computer networks

In October 1963, Licklider was appointed head of the Behavioral Sciences and Command and Control programs at ARPA (as it was then called), the United States Department of Defense Advanced Research Projects Agency. The Defense Advanced Research Projects Agency (DARPA is an agency of the United States Department of Defense responsible for the development of new Technology The United States Department of Defense ( DOD or DoD) is the federal department charged with coordinating and supervising all agencies and functions of the government He then convinced Ivan Sutherland and Bob Taylor that this was a very important concept, although he left ARPA before any actual work on his vision was performed. Ivan Edward Sutherland (born 1938 in Hastings, Nebraska) is an American Computer scientist and Internet pioneer Robert W Taylor (born 1932 was director of ARPA 's Information Processing Techniques Office (1965-69 founder and later manager of Xerox PARC 's Computer

ARPA and Taylor 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 SDC Q-32 in Santa Monica, one for Project Genie at the University of California, Berkeley, and one for Multics at MIT. System Development Corporation (SDC based in Santa Monica California, was arguably the world's first Computer software company Project Genie was a Computer research project started in 1964 at the University of California Berkeley by J The University of California Berkeley (also referred to as Cal, Berkeley and UC Berkeley) is a major research university located in Berkeley Multics ( Mult iplexed I nformation and C omputing S ervice was an extremely influential early Time-sharing Operating system 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. " [1].

Somewhat 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.

Creation of the ARPANET

By the mid-1968, a complete plan had been prepared, and after approval at ARPA, a Request For Quotation (RFQ) was sent to 140 potential bidders. A Request for Quotation (RFQ is a standard Business process whose purpose is to invite suppliers into a bidding process to bid on specific Products or services 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 on 7 April 1969. Events 529 - First draft of Corpus Juris Civilis (a fundamental work in Jurisprudence) is issued by Eastern Roman Emperor Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar.

BBN's proposal followed Roberts' plan closely; it called for the network to be composed of small computers known as Interface Message Processors (more commonly known as IMPs). The Interface Message Processor (IMP was the Packet-switching node used to connect computers to the original ARPANET in the late 1960s and 1970s 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). Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information A leased line is a symmetric Telecommunications line connecting two locations A kilobit is a unit of information abbreviated kbit (or kb) The standard definition is 1 kilobit = 103 bit = 1000 Bit. Host computers connected to the IMPs via custom bit-serial interfaces to connect to ARPANET. In Telecommunications serial transmission is the sequential transmission of Signal elements of a group representing a character or other entity

BBN initially chose a ruggedized version of Honeywell's DDP-516 computer to build the first-generation IMP. A rugged (or ruggedized, but also ruggedised) computer is a Computer specifically designed to reliably operate in harsh usage environments and Honeywell ( is a major American multinational conglomerate company that produces a variety of consumer products engineering services and aerospace systems The 516 was originally configured with 24 kB of core memory (expandable) and a 16 channel Direct Multiplex Control (DMC) direct memory access control unit. A kilobyte (derived from the SI prefix Kilo -, meaning 1000 is a unit of Information or Computer storage equal to either 1024 Direct memory access ( DMA) is a feature of modern Computers and Microprocessors that allows certain hardware subsystems within the computer to access system 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

First ARPANET IMP log - a record of the first message ever sent over the ARPANET; it took place at 10:30PM on October 29, 1969. This record is an excerpt from the "IMP Log" kept at UCLA, and describes setting up a message transmission to go from the UCLA SDS Sigma 7 Host computer to the SRI SDS 940 Host computer.
First ARPANET IMP log - a record of the first message ever sent over the ARPANET; it took place at 10:30PM on October 29, 1969. This record is an excerpt from the "IMP Log" kept at UCLA, and describes setting up a message transmission to go from the UCLA SDS Sigma 7 Host computer to the SRI SDS 940 Host computer.

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

The first permanent ARPANET link was established on November 21, 1969, between the IMP at UCLA and the IMP at SRI. Events 164 BC - Judas Maccabaeus, son of Mattathias of the Hasmonean family restores the Temple in Jerusalem. Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. By December 5, 1969, the entire 4-node network was connected [2]. Events 63 BC - Cicero reads the last of his Catiline Orations. Year 1969 ( MCMLXIX) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar.

The first message ever to be sent over the ARPANET (sent over the first host-to-host connection) 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 ARPANET 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 1822 protocol 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 ARPANET Network Control Program (NCP provided the middle layers of the Protocol stack running on an ARPANET host computer The NCP interface allowed application software to connect across the ARPANET implementing higher-level communication protocols. Application software is a subclass of Computer software that employs the capabilities of a computer directly and thoroughly to a task that the user wishes to perform In the field of Telecommunications, a communications protocol is the set of standard rules for data representation signaling authentication and error detection required to This was an early example of the protocol layering concept incorporated into the OSI model. The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model) is an abstract description for layered communications and computer Network protocol

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. The Internet Protocol Suite (commonly TCP/IP) is the set of Communications protocols used for the Internet and other similar networks

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.

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. The United States of America —commonly referred to as the 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. The State of Hawaii ( or həˈwaɪʔiː Hawaiian: Mokuāina o Hawaii) is a state in the United States located on an Archipelago in the Norway ( Norwegian: Norge ( Bokmål) or Noreg ( Nynorsk) officially the Kingdom of Norway, is a Constitutional NORSAR or Norwegian Seismic Array was established in 1968 as part of the Norwegian - US agreement for the detection of Earthquakes and 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. The Defense Information Systems Agency (DISA formerly known as the Defense Communications Agency) is a combat support agency of the United States Department of Defense

In 1983, the U. S. military portion of the ARPANet was broken off as a separate network, the MILNET. In computer networking MILNET was the name given to the part of the ARPANET Internetwork designated for unclassified United States Department of Defense 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. The Honeywell 316 was a popular 16-bit Minicomputer built by Honeywell starting in 1969 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. American Standard Code for Information Interchange ( ASCII) 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. The Pluribus Multiprocessor was an early multi-processor computer designed by BBN for use as a packet switch in the ARPANET. Multiprocessing is the use of two or more central processing units (CPUs within a single computer system 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 National Science Foundation Network ( NSFNET) was a major part of early 1990s Internet backbone.

The ARPANET and nuclear attacks

A common semi-myth about the ARPANET states that it was designed to be resistant to nuclear attack. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. 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. The Internet Society or ISOC is an international nonprofit organization founded in 1992 to provide leadership in Internet related standards education and policy This was never true of the ARPANET, only the unrelated 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. [4]

References in film and media

See also

Notes

Further reading

Detailed technical reference works

External links

Computer Networks The Heralds of Resource Sharing is a documentary film from 1972 produced by Steven King, about ARPANET. Google Video is a free video sharing website and also a video service from Google that allows anyone to upload Video Clips to Google's web
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