In the early 1970s, the term datagram was created by combining the words data and telegram by the CCITT rapporteur on packet switching,[1] Halvor Bothner-By.
In 1964, Paul Baran described, in a RAND Corporation report, a hypothetical military network having to resist a nuclear attack.
"[5] In 1970, Lawrence Roberts and Barry D. Wessler published an article about ARPANET, the first multi-node packet-switching network.
[9][10] A reliable message transfer service was thus offered to user computers, thus greatly simplifying the network design.
[11] Roberts presented the idea of packet switching to the communication professionals and faced anger and hostility.
[12] In 1973, Louis Pouzin presented his design for CYCLADES, the first large-scale network implementing the pure Davies datagram model.
[15] Although Pouzin's concern "in a first stage is not to make breakthrough [sic] in packet switching technology, but to build a reliable communications tool for Cyclades",[13] two members of his team, Hubert Zimmerman and Gérard Le Lann, made significant contributions to the design of Internet's TCP that Vint Cerf, its main designer, acknowledged.
[16] In 1981, the Defense Advanced Research Projects Agency (DARPA) issued the first specification the Internet Protocol (IP).
[19] The term datagram is defined as follows:[20] "A self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between this source and destination computer and the transporting network.
"A datagram needs to be self-contained without reliance on earlier exchanges because there is no connection of fixed duration between the two communicating points as there is, for example, in most voice telephone conversations.
TCP is a higher-level protocol running on top of IP that provides a reliable connection-oriented service.