The History of TCP/IP When the history of the Internet is written, in a hundred years or so, what development will be remembered as the most important? A writer living now might say that the World Wide Web (WWW) is what put the Internet on the map. Although trying to ignore the WWW is like ignoring the proverbial elephant in the living room, there is a good chance that future historians will cite TCP/IP as the obvious winner. In 1969, the Defense Advanced Research Projects (DARPA), later renamed to ARPA, was searching for a way to facilitate communications between their agency and the contractors who bid on and fulfilled research contracts. An ARPA employee named Larry Roberts was pondering this question when he came on the idea of creating a network of computers that could use phone lines to communicate with each other across distances of hundreds of miles. This had never been done before, and there was no hardware available to interconnect the computers. Roberts created a specification for a special computer that would connect multiple other computers by taking information off a wire connected to one computer and placing it on a wire connected to another. This special computer was called an Interface Message Processor (IMP). A contract was signed with a company called Bolt, Baranek, and Newman, which delivered the first IMP in 1969. Four sites were chosen to install these IMPs: UCLA, University of California at Santa Barbara, the University of Utah, and the Stanford Research Institute. By the end of 1969, all four sites were connected and accessing each other's computers. At first, a Telnet application coordinated this access, but a program called the Network Control Protocol (NCP) soon replaced it. By 1971, 19 other sites had joined the network. In 1974, two engineers, Bob Kahn and Vinton Cerf, wrote a paper that described an improved protocol that they called the Transfer Control Protocol (TCP). It was later combined with another lower-level protocol called the Internet Protocol (IP) and renamed TCP/IP. Over the next several years, software written to this design began to replace NCP until 1983 when ARPA decreed that no other protocol would be allowed to connect to the ARPANET, as it had come to be called. After much weeping and gnashing of teeth, all the nodes on the ARPANET standardized on TCP/IP as their communication protocol. By 1983, the computers on the ARPANET were exchanging quite a bit of data that was not related to the U.S. Department of Defense. Because of this, the Defense Communications Agency split the ARPANET in two parts. They called one of them the Internet, and the other MILNET. MILNET was reserved for military-related sites, and the Internet was used for everything else. In the 1980s, TCP/IP was far from being the only, or even the dominant, protocol for interconnecting computers. It had an advantage over competing technologies in that day, however, because it was in the public domain. Before long, implementations of TCP/IP were written for every popular hardware platform. As a result, TCP/IP became the most common way to interconnect heterogeneous computers because it did not require hardware vendors to license each other's software. | 
