The Original NetworksARPANET is probably the network to which the origins of the Internet are most strongly tied, but it is not the only one. There were several networks, each of which brought a unique function that we now consider integral to the modern Internet. In this section, we’ll look at each network as well as its contribution to the whole. (For background reading, see A Timeline of the Development of the Internet and World Wide Web.)
ARPANETAlthough the work done by Paul Baran was prompted by the threat of nuclear attack, ARPA used Baran’s research to lay the foundation of a network designed to solve the issues it was having with limited computing resources.
ARPA had sponsored computers in different locations, each connected back to the ARPA offices. Unfortunately, to communicate with a particular location, the ARPA information processing director, Robert Taylor, would have to go to the terminal connected to that location. This meant switching terminals every time he wished to contact someone else.
The inconvenience of the setup prompted Taylor to search for a way to network the computers so that a single terminal could communicate with all the locations. To this end, he brought in Larry Roberts, who created a plan for a packet-switching network between the computers named ARPANET.
Armed with a plan, ARPA sent out a request for quotation (RFQ) for creating the necessary interface message processors (IMPs). This contract was won by Bolt Beranek and Newman (now BBN Technologies, a subsidiary of Raytheon). Other necessary components were brought together by teams at UCLA and the Network Analysis Corporation, among others.
By 1969, ARPANET was coming together using a system of requests for comment (RFCs) that helped the designers work out the issues as hosts were being connected to the network. The first host-to-host message was sent from UCLA to the Stanford Research Institute (SRI) and consisted of Kleinrock watching his student, Charley Kline, type while confirming over the phone that the letters were appearing on the screen in Stanford. The system crashed after the “g” in “login,” but the first Internet message had been sent.
Other Important NetworksAlthough ARPANET plays a central role up to this point in Internet history and going forward, there were other networks that brought something to the Internet in the form of alternative methods, or even just confirmation of important concepts. We’ll look at these briefly.
Mark IDonald Watts Davies was not idle after independently coming up with packet switching. He created proposals for a national data network that would span the U.K., but he didn’t have the support or the resources that ARPA had. Davies was, however, successful in creating a packet-switching network to serve the needs of the National Physical Laboratory. He created a small-scale network called Mark I in 1970, and then an improved version, Mark II, in 1973. The Mark II network was still operational in 1986, but its reach was limited by funding and resources.
Merit NetworkMerit Network was another network created in near parallel with the ARPANET timeline. It was formed in 1966 with the intention of linking together Michigan’s public university computers. It got off the ground in 1971 thanks to funding from the National Science Foundation (NSF). It evolved alongside ARPANET, and eventually became a cornerstone of the NSFNET, which served as a backbone for the modern Internet.
CycladesCyclades was a French-led packet-switching network that was inspired by ARPANET, but was designed to test out alternatives. Started in 1972, Cyclades pioneered several technical innovations that were later incorporated back into the ARPANET design. These innovations included layered architecture, adaptive routing, and making the host, rather than the network, responsible for the data (end to end). These innovations reappeared as part of TCP/IP on ARPANET.
Back to ARPANETARPANET evolved rapidly after the initial nodes were added, and its RFC system became fundamental to the creation of the Internet protocols we still depend on today. Network Control Protocol (NCP) served as the original host-to-host protocol as more and more hosts were added in the early ‘70s.
It is, however, dishonest to pretend that the history of the Internet was centered just on ARPANET. In truth, the innovations that took the concept of a few interconnected computers and transformed them into vast networks of networks came from many sources. There were the aforementioned networks as well as unmentioned organizations that played important roles. That said, the story is more easily told from an ARPANET-centric view - both for clarity and for two very important innovations that grew out of the project: TCP/IP and NSFNET.