After the group worked out the logistics of the proposed network, the first notable achievement of the ARPAnet project became the development of the IMP (Interface Message Processor). The IMP converted packets into a language that each of the host computers could understand and vice versa. This would allow for a tremendous growth in the network because it meant that the network was not machine specific. After connecting the first host computer at UCLA in 1969, four nodes were in operation within the initial ARPAnet (Leiner, et al). They began adding computers to the network, requiring a more efficient communications method. The first standard protocol for host-to-host communication, NCP (Network Control Protocol) was founded in 1970, which allowed for the development of network applications and fostered network growth.
The first public display of ARPAnet was in 1972. At the time of display, ARPAnet was a network consisting of 40 machines. It was at this same time that the first electronic mail application was developed. In a short period of time the use of e-mail became very popular among researchers. The initial vision of a network that could withstand a nuclear attack was crucial, because it would eventually allow a computer to tap in anywhere along the network. This was made possible by the packet switching technology, consisting of sliced packets sent different ways by the source. The packets would then eventually meet at the addressed destination. Because of these technologies, the ARPAnet grew rapidly. Many universities played a role in developing the network, and thus, were allowed to connect to it. In 1973 the first international connections were made to the ARPAnet: the University College of London, and the Royal Radar Establishment in Norway (Lecture).
Since NCP had no end to end host error control, and was not able to address LANs (Local Area Networks) connected to the network, a new network protocol would be needed. It was Robert Kahn's "internetting" research, teamed with Vincent Cerf's knowledge of interfacing to different operating systems, that would result in the protocol of TCP/IP (Transmission Control Protocol/Internet Protocol). Kahn and Cerf published their work on the TCP/IP protocol in 1974. The establishment of TCP/IP would become the communications basis of the Internet that we know today (Leiner, Cerf, et al, 1998).