CSNET

CSNET (the "Computer Science Network") was created by the US National Science Foundation in the early 1980s. Its purpose was to internetwork academic Computer Science departments nationwide. It was an alternative to ARPANET, to which many Computer Science departments didn't have the privilege of access. CSNET connected with ARPANET using TCP/IP, and ran TCP/IP over X.25, but it also supported departments without sophisticated network connections, using automated dial-up mail exchange.

see: http://www.cs.washington.edu/homes/lazowska/cra/networks.html