What was ARPANET?

One goal of ARPANET was to devise a network that would still be operational if part of the network failed. The research in this area resulted in a set of networking rules, or protocols, called TCP/IP (Transmission Control Protocol/Internet Protocol).

TCP/IP is a set of protocols that govern how data is transmitted across networks. It also enables different types of computer operating systems, such as DOS and UNIX, to share data across a network.