Internet protocol suite
TCP/IP is a layered framework for end-to-end data communication. It specifies how data should be packetised, addressed, transmitted, routed, and received. Its architecture rests on the end-to-end principle—placing intelligence at the edges—and uses encapsulation and the robustness principle (conservative sending, liberal receiving) to achieve interoperability across heterogeneous networks. Developed by Cerf and Kahn starting in 1973 under DARPA, it replaced the ARPANET's NCP with a modular, host-responsible reliability model. IPv4 was installed in the ARPANET in 1983, and TCP/IP was formally adopted as the US DoD standard in March 1982. The defining technical specifications are RFC 1122 and RFC 1123, which codify its four-layer abstraction model.