40 years ago, ARPANET moved to TCP/IP

40 years ago, ARPANET moved to TCP/IP

40 years ago, on January 1, 1983, the ARPANET network switched to the TCP/IP protocol, the basis of the Internet (the I in IP stands for Internet). Before this date, the network which connected universities but also military sites (until 1980) used the NCP protocol (Network Control Protocol).

A transition completed in 1983

The transition from NCP to TCP/IP dates from January 1, 1983, but this is the date of the effective abandonment of NCP: the RFC 801 dates from November 1981 and defines the main stages, including the abandonment of NCP. But in this document, it is explicitly stated that servers are already using TCP/IP at this time.

ARPANET in 1977

TCP (for Transmission Control Protocol) is a transport protocol still used today that will manage the transport of data. It cuts the data into segments on one side, to reconstruct them in the correct order on the other side and manages the data transfers between the two computers. IP, for Internet-Protocol, is placed under TCP in the OSI model and notably manages addressing in the network (yes, the IP address is linked to this protocol). In 1983, IPv4 was used: with just over 4 billion possible addresses, the limits seemed far away. In 2023, IPv6 (its successor) is increasingly widely used to support the very large number of devices connected to the Internet.

In 2022, the Internet is still largely based on TCP/IP, although other protocols exist and are used for different purposes. Finally, we can note that the DNS, which seems to be a fundamental part of our current experience, was not implemented until a few months later, in November 1983. Before this date, computers connected to ARPANET used a file hosts which contained the IP(v4) addresses of the various servers, with all the errors imaginable in this case.