TCP/IP was designed by Vint Cerf and Bob Kahn to connect different packet-switched networks. Their work produced a system in which independent networks could exchange data using common protocols.
The Transmission Control Protocol originally handled reliable delivery and internet addressing together, but the functions were later separated. TCP provides transport features such as ordered, reliable delivery, while Internet Protocol handles addressing and routing packets between networks.
A major milestone came on 1 January 1983, when ARPANET officially adopted TCP/IP. That change allowed the network to interconnect with other packet-switched systems more flexibly than the earlier Network Control Protocol. TCP/IP is not one single protocol in practice; it is a suite that also includes protocols such as DNS, HTTP, and SMTP.