Computer Network
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ARPANET was the network that became the basis for the Internet. Based on a concept first published in 1967, ARPANET was developed under the direction of the U.S. Advanced Research Projects Agency (ARPA). In 1969, the idea became a modest reality with the interconnection of four university computers. The initial purpose was to communicate with and share computer resources among mainly scientific users at the connected institutions. ARPANET took advantage of the new idea of sending information in small units called packets that could be routed on different paths and reconstructed at their destination. The development of the TCP/IP protocols in the 1970s made it possible to expand the size of the network, which now had become a network of networks, in an orderly way.

    • It is basically a WAN. It was developed by the ARPA (Advanced Research Project Agency) in 1968 which is the research arm of 000.
    • ARPANET was designed to service even a nuclear attack.
    • Before ARPANET, the networks were basically the telephone networks which operated on the circuit switching principle.
    • But this network was too vulnerable, because the loss of even one line or switch would terminate all the conversations.
    • ARPANET used the concept of packet switching network consisting of subnet and host computers.
    • The subnet was a datagram subnet and each subnet consists of minicomputers called IMPs (Interface Message Processors).
    • Each node of the network used to have an IMP and a host connected by a short wire.
    • The host could send messages of upto 8063 bits to its IMP which would break them into packets and forward them independently toward the destination.


    • The software for ARPANET was split into two parts namely subnet and host.
    • In 1974 the TCP/IP model and protocol were invented specifically to handle communication over internetwork because more and more networks were getting connected to ARPANET.
    • The TCP/IP made the connection of LANs to ARPANET easy.
    • During 1980s so many LANs were connected to ARPANET that finding hosts became increasingly difficult and expensive.
    • So DNS (Domain Naming System) was created for organizing machines into domains and map host names onto IP address.
    • In 1983 the management of ARPANET was handed over to the Defense Communications Agency (DCA) which separated the military portion into a separate MILNET.
    • By 1990 the ARPANET was shut down and dismantled, however MILNET continues to operate.