Internet

A map graphically displaying interconnections on the Internet (known as routes)

The Internet is a "network of networks" best known as the global network on which a wide range of applications and networking experiments run, using technologies of the Internet Protocol Suite.

To the general public, the World Wide Web is the best-known application, but many other applications, such as electronic mail and large percentage of telephone calls run over Internet protocols. Web browsers are perhaps the most common user programs that access the Internet, but web browsers translate human requests to the Hypertext Transfer Protocol that actually runs from browser to Web server.

The Internet itself has no direct human interfaces; every user-visible function must go through a program resident on a client or server computer. There are literally hundreds of different protocols, applications and services that run over the Internet. Virtual Private Networks interconnecting the parts of individual enterprises, or sets of cooperating enterprises, overlay the Internet. A wide range of interconnected networks using the same protocols as the public Internet, but isolated from it, provide services ranging from passing orders to launch u, authorizing credit card purchases, collecting intelligence information, controlling the electric power grid, transferring medical images and even allowing remote surgery, etc.

To Internet operators, however, the public Internet is the set of interconnected, separately administered networks, which agree on conventions for addressing computers, and exchange information on reachability using the Border Gateway Protocol

Predecessors

The first functional networks between individual computers were created in the early 1970s. These networks, however, assumed the computers ran common software and protocols. Some of the networks were proprietary to computer vendors, such as IBM's Binary Synchronous Communications and the 1974 System Network Architecture, Xerox Network Services, Digital Equipment Corporation DECnet. X.25 was a nonproprietary standard, but used a different architecture than would the datagram networks such as the ARPANET and Internet.

Louis Pouzin first introduced the idea of a generalized method of interconnecting networks of computers rather than individual computers, which he termed a catenet, but the model needed refinement. Such refinement took place under the sponsorship of the United States Department of Defense's Advanced Research Project Agency (ARPA), later renamed the Defense Advanced Research Projects Agency (DARPA). ARPA was formed to meet a number of perceived Cold War technology challenges, and was established in 1958 as the first U.S. response to the Soviet launching of Sputnik.

Among ARPA's areas of interest was the interconnection of networks, under the management and inspiration of J.C.R. Licklider 1915-1990, one of the pioneers of cooperative research. Vint Cerf extended Pouzin's catenet model as the basis for what was to become the ARPANET:

The U.S.

DARPA research project on this subject has adopted the term to mean roughly "the collection of packet networks which are connected together." This is, however, not a sufficiently explicit definition to determine, for instance, whether a new network is in conformance with the rules for network interconnection which make the catenet function as confederation

of co-operating networks.

Cerf extended the concept of catenet to be usable in a specific research network, the ARPANET. ARPANET was the first large-scale "network of networks" using common mechanisms to interconnect disparate networks. It was funded through ARPA, and access was limited to selected universities, research organizations, and government agencies. Contrary to widespread legend, it was never intended to be a military network survivable under nuclear attack, although other, not necessarily packet-switching, networks, were intended for warfighting. starting as early as the 1963 SACCS, specific to the Strategic Air Command. Other warfighting networks included the even earlier Minimum Essential Emergency Command Network (MEECN), which was made up of multiple networks that were interconnected only through human intervention. Even today, the military warfighting networks, such as NIPRNET, SIPRNET, JWICS and Warfighter Information Network are separate from the Internet.

Many educational institutions and corporations began joining the network, and in 1983 all nodes on the ARPANET changed over at once to Internet Protocol version 4 (IPv4), which is still in use on the internet today. While this is often referred to as "TCP/IP", they are two distinct protocols: Transmission Control Protocol (TCP), and IPv4. In a literal sense the written term TCP/IP can be read aloud as "TCP over IP" and would be a correct description.

There were several intermediate steps between the ARPANET, to which access was strictly controlled, and today's ubiquitous Internet. See History

While IPv4 will be present indefinitely, it is limited in its capability for modern functions, and an evolution is in process to Internet Protocol version 6 (IPv6). Internally, the Internet is divided into Autonomous Systems, which exchange information about the destinations they can reach, using the Border Gateway Protocol (BGP).

History

1950s to 1970s

Among the first applications on the experimental networks was email, on the ARPANET as well as vendor-proprietary networks and early commercial packet-switching networks such as TELENET and TYMNET. The latter networks used the X.25 protocol that mimicked telephone calls, creating paths for each sender-receiver connection, as opposed to the connectionless Internet Protocol and its ancestors. Commercial email networks using X.25 were operational in 1972.

• DARPA
• BBN - Bolt, Barenek and Newman
• NCP (ARPANET)

Hypertext had been invented by Ted Nelson around 1960, and hyperdocuments could be transferred as files; Tim Berners-Lee later pioneered dynamic access to hyperdocuments on servers, which was the start of the World Wide Web.

1980 to 1985

The early, experimental ARPANET evolved to the NSFNET, originally a U.S. government funded network that linked five supercomputer centers. At these centers, authorized research and academic users could connect their networks and access both the supercomputers and other resources.

1985 to 1990

NSFNET did not allow commercial traffic, but there was a gradual creation of networks, often simple pairings, of various computers and networks over which traffic ineligible for the NSFNET passed. In the early nineties, an increasing number of IP networks were commercially available, which connected to one another, and to NSFNET, in many ways both official and unofficial.

Nevertheless, the Internet routed approximately same packets as today. The Internet of the time was not a public resource, and the research and academic users collaborated productively using electronic mail, file transfer, news, and other services.

Before AOL opened up USENET and other Internet resources in the late 80s, the Internet was first an environment for networking research, and second an environment to support other research and education. When anonymous access became common, the social environment changed radically. The environment was one of trust as well as collaboration; anonymous access was rare.

Malware such as worms and viruses were rare; the first well-known breakin happened in 1986, and the Morris worm hit in 1988.