The ARPANET computer network was a pioneering packet switching network that was launched in 1969. ARPANET was federally funded by the U.S. Department of Defense. ARPA was an agency of the U.S. Department of Defense who developed technological systems: mostly with a military application, but it did fund some scientific projects, like ARPANET, from 1958-1973.
ARPANET originally connected universities, research laboratories, and military installations. However, when the Defense Communication Agency (DCA) took control of ARPANET in 1975, it created MILNET, which separated ARPANET into a separate research network and MILNET became a separate federal military network. Both of these networks continued to use the same network architecture. MILNET was one of the first federal computer networks - more would follow - and each would use packet switching and TCP/IP.
By 1988, there was four notable U.S. federal computer networks:
The Federal Internet Exchange (FIX) was a physical location that provided a 'point' where federal computer networks could interconnect. The Federal Internet Exchange (FIX) was created in June 1989, and comprised two FIX locations:
The Federal Internet Exchange (FIX) connected together computer networks that used TCP/IP (Internet protocol suite), and heralded the creation of the modern Internet (network of networks). Present day, the Internet is comprised of hundreds of Internet Exchange Points (IXP) that fulfill an identical role to the FIX: interconnecting and exchanging data across global computer networks that use TCP/IP (Internet protocol suite).