Acronym for Advanced Research Projects Agency Network, ArpaNet was a pioneering WideAreaNetwork funded by the US Department of Defense.
It became operational in 1968 and served as the basis for early networking research, as well as a central backbone during the development of the InterNet. The ARPANET consisted of individual packet switching computers interconnected by leased lines. Protocols used include FTP and telnet. It has now been replaced (for DoD use) by NSFnet and is widely acknowledged as the parent of the InterNet.
Read about 
ARPANet's history.
3 pages link to ArpaNet:
