The Advanced Research Project Agency Network (ARPANET) was one of the world's first operational computer networks, and was the main precursor to what has become the modern Internet. Initially funded by the Advanced Research Projects Agency (ARPA) within the U.S. Department of Defense for use by its projects at universities and research laboratories in the US, many important computer and communications technologies were pioneered by the project. Packet switching, TCP/IP, and distributed computation were all vital technologies that would later form the backbone of how the Internet works.

 

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1. ARPA Initiative

    a. ARPA wanted an effective way to increase computing power as well as access and decentralize information

        i. Fear of a nuclear attack

        ii. Connecting the various powerful research computers spread around the country

    b. Wanted to improve existing communication infrastructure

    c. Inspired by J. C. R. Licklider, whose idea of an "Intergalactic Computer Network" contained almost everything that composes the contemporary Internet

2. Technical Hurdles

    a. Existing phone lines were made to transmit data via circuit switching, where each "call" has a dedicated end to end connection

        i. Worked very well for telephone connections

        ii. Resulted in very poor, lossy connections for connections between computers

    b. Every computer at each of the proposed connection points had vastly different hardware, software, and research staff

3. Technical Solutions

    a. The concept of packet switching developed by Paul Baran, Donald Davies, and Lawrence Roberts

    b. Smaller, simpler computers, known as Interface Message Processors (IMPs) connected each computer in the network to the physical infrastructure

        i. Eliminated the problem of every machine at each node in the network being different

        ii. Much easier to maintain, since each machine was the same

    c. A distributed telecommunications network ensured each packet of data always found a way to its destination

    d. TCP/IP offered a standard communication protocol that ensured compatibility between each node in the network

4. Connections and Applications

    a. Initial network comprised of UCLA, Stanford, UCSB, and the University of Utah, then expanded eastward, eventually including over 200 computers on the network

    b.E-mail, file transfer, and voice traffic were the main functions of the ARPANET while it was used

 

Sources:

The Dream Machine, M. Waldrop

Where Wizards Stay Up Late, Katie Hafner and Matthew Lyon

http://en.wikipedia.org/wiki/ARPANET