While working on the SATNET satellite packet network project, he came up with the initial ideas for what later became the Transmission Control Protocol (TCP), which was intended as a replacement for an earlier network protocol, NCP, used in the ARPANET. TCP played a major role in forming the basis of open-architecture networking, which would allow computers and networks all over the world to communicate with each other, regardless of what hardware or software the computers on each network used. To reach this goal, TCP was designed to have the following features: