Merging the networks and creating the Internet (ISP 3)

TCP/IP

With so many different network methods, something was needed to unify them. Robert E. Kahn of DARPA and ARPANET recruited Vinton Cerf of Stanford University to work with him on the problem. By 1973, they had soon worked out a fundamental reformulation, where the differences between network protocols were hidden by using a common internetwork protocol, and instead of the network being responsible for reliability, as in the ARPANET, the hosts became responsible. Cerf credits Hubert Zimmerman, Gerard LeLann and Louis Pouzin (designer of the CYCLADES network) with important work on this design. The specification of the resulting protocol, RFC 675 - Specification of Internet Transmission Control Program, by Vinton Cerf, Yogen Dalal and Carl Sunshine, Network Working Group, December, 1974, contains the first attested use of the term internet, as a shorthand for internetworking; later RFCs repeat this use, so the word started out as an adjective rather than the noun it is today.

With the role of the network reduced to the bare minimum, it became possible to join almost any networks together, no matter what their characteristics were, thereby solving Kahn's initial problem. DARPA agreed to fund development of prototype software, and after several years of work, the first somewhat crude demonstration of a gateway between the Packet Radio network in the SF Bay area and the ARPANET was conducted. On November 22, 1977 a three network demonstration was conducted including the ARPANET, the Packet Radio Network and the Atlantic Packet Satellite network—all sponsored by DARPA. Stemming from the first specifications of TCP in 1974, TCP/IP emerged in mid-late 1978 in nearly final form. By 1981, the associated standards were published as RFCs 791, 792 and 793 and adopted for use. DARPA sponsored or encouraged the development of TCP/IP implementations for many operating systems and then scheduled a migration of all hosts on all of its packet networks to TCP/IP. On January 1, 1983, TCP/IP protocols became the only approved protocol on the ARPANET, replacing the earlier NCP protocol.

ARPANET to several federal wide area networks: MILNET, NSI, and NSFNet

After the ARPANET had been up and running for several years, ARPA looked for another agency to hand off the network to; ARPA's primary mission was funding cutting edge research and development, not running a communications utility. Eventually, in July 1975, the network had been turned over to the Defense Communications Agency, also part of the Department of Defense. In 1983, the U.S. military portion of the ARPANET was broken off as a separate network, the MILNET. MILNET subsequently became the unclassified but military-only NIPRNET, in parallel with the SECRET-level SIPRNET and JWICS for TOP SECRET and above. NIPRNET does have controlled security gateways to the public Internet.

The networks based on the ARPANET were government funded and therefore restricted to noncommercial uses such as research; unrelated commercial use was strictly forbidden. This initially restricted connections to military sites and universities. During the 1980s, the connections expanded to more educational institutions, and even to a growing number of companies such as Digital Equipment Corporation and Hewlett-Packard, which were participating in research projects or providing services to those who were.

Several other branches of the U.S. government, the National Aeronautics and Space Agency (NASA), the National Science Foundation (NSF), and the Department of Energy (DOE) became heavily involved in Internet research and started development of a successor to ARPANET. In the mid 1980s, all three of these branches developed the first Wide Area Networks based on TCP/IP. NASA developed the NASA Science Network, NSF developed CSNET and DOE evolved the Energy Sciences Network or ESNet.

In 1984 NSF developed CSNET exclusively based on TCP/IP. CSNET connected with ARPANET using TCP/IP, and ran TCP/IP over X.25, but it also supported departments without sophisticated network connections, using automated dial-up mail exchange. This grew into the NSFNet backbone, established in 1986, and intended to connect and provide access to a number of supercomputing centers established by the NSF.

Transition towards the Internet

The term "internet" was adopted in the first RFC published on the TCP protocol (RFC 675: Internet Transmission Control Program, December 1974) as an abbreviation of the term internetworking and the two terms were used interchangeably. In general, an internet was any network using TCP/IP. It was around the time when ARPANET was interlinked with NSFNet in the late 1980s, that the term was used as the name of the network, Internet, being a large and global TCP/IP network.

As interest in wide spread networking grew and new applications for it were developed, the Internet's technologies spread throughout the rest of the world. The network-agnostic approach in TCP/IP meant that it was easy to use any existing network infrastructure, such as the IPSS X.25 network, to carry Internet traffic. In 1984, University College London replaced its transatlantic satellite links with TCP/IP over IPSS.

Many sites unable to link directly to the Internet started to create simple gateways to allow transfer of e-mail, at that time the most important application. Sites which only had intermittent connections used UUCP or FidoNet and relied on the gateways between these networks and the Internet. Some gateway services went beyond simple e-mail peering, such as allowing access to FTP sites via UUCP or e-mail.

Finally, the Internet's remaining centralized routing aspects were removed. The EGP routing protocol was replaced by a new protocol, the Border Gateway Protocol (BGP), in order to allow the removal of the NSFNet Internet backbone network. In 1994, Classless Inter-Domain Routing was introduced to support better conservation of address space which allowed use of route aggregation to decrease the size of routing tables. The picture on the right hand side shows a system made with the help of the high-tech company BBN. >>next>>