Since the Internet was created and developed along with internetworking theory and technologies, its history perfectly illustrates the birth and evolution of the internetwork concept.
The first incarnation of the Internet was the ARPANET. It was funded by the Pentagon's Advanced Research Projects Agency both as a testing field and a means of communication for scientists working on packet switching technology across the country.
The Department of Defense was then trying to come up with a solution to communications in a post nuclear war situation. A packet switching network, which could keep running even after half its nodes had been blasted away, was that solution.
So in 1969, a first version of such a network, the ARPANET, was up and running with four switching nodes.
The protocols necessary to run such an internetwork were developed in the seventies, and the ARPANET grew with them, linking more and more sites, mostly research laboratories.
In 1979 the Internet Control and Configuration Board was created. Its goal was to loosely coordinate the ongoing research on internetworking technologies and to monitor the growth of the connected Internet, which had by that time begun to outgrow the ARPANET.
In 1980, the ARPANET switched from its original protocol, NCP, to the more sophisticated protocol suite called TCP/IP, and became the backbone of what had become the Internet.
In 1983, the ARPANET was split. One part, MILNET, reverted to the DOD and military communications. The other one, retaining the name ARPANET, was dedicated to the communication needs of the research community.
The protocol standards for TCP/IP were available to anybody, and the DARPA encouraged their linking to the popular BSD UNIX operating system, making them easier to use by application programmers. As a consequence, more and more organizations and universities were choosing TCP/IP as a network protocol suite, and hooking their existing networks to the Internet.
In 1984, the National Science Foundation joined the adventure. It began an ambitious program of expansion, in order to allow more scientists to get on the Internet.
In 1986, the NSFNET, the new long haul backbone linking the NSF supercomputers around the United States by the most advanced technologies available, was tied to the ARPANET.
The Internet began growing more and more quickly. To keep up with its growth, the NSFNET was upgraded and expanded in 1988, and again in 1990. The ARPANET officially expired in 1989, victim of its own success.
The ICCB, which had been reorganized and renamed as the Internet Activities Board in 1983, was again reorganized in 1989, to follow the changes brought by the evolution of the connected Internet. The IAB is now divided into two parts, the Internet Research Task Force and the Internet Engineering Task Force.
And it is mostly trying to keep up with the exploding growth of the Internet, by coming up with the technologies necessary to keep it running smoothly.