In 1950, United States Department of Defence (DoD) formed Advanced Research Project Agency under the guidance of the RAND Corportaion.ARPAnet aka ARPA Network was launched in 1969 by ARPA due to the potential threat of nuclear attack from the Soviet Union. The primary objective of ARPA to design such a robust network which would help United States Military forces to stay in touch during any case of disasters or war.
During that time, communication generally happened among the systems with the Network Control Protocol which had many limitations of communication. Due to the communication restrictions, NCP could not be deployed at larger scale. The main disadvantage of using NCP was that communication was restricted only with in few computers. But ARPA needed such language which could be used by any type of computer, any where in the world, robust by nature and easily fulfill all the requirements of mulitary forces.
1. No single point of failure.
2. Redundant paths to destination
3. Easily reroute the data in case of failure of one link.
4. Ability to connect different types of computers over any type of network.
To fulfill all the requirements and overcome the constraints of NCP, Transmission Control Protocol had given birth by Vint Cerf and Bob Kahn in 1974. This TCP was suite of protocols which eventually replaced NCP. By 1978, a new suite of protocols called TCP/IP came into existence and In 1982, finally it was decided by ARPAnet to replace NCP with TCP/IP. On January 1, 1983, ARPAnet migrated to TCP/IP. The full migration story from NCP to TCP is being described by RFC 801.