The Internet's history can be traced back to ARPANET, which first went online in 1969. ARPA, the United States Department of Defense Advanced Research Projects Agency, created ARPANET as a research project for investigating new network technologies that could enable a military communications network to withstand a nuclear attack. This involved eliminating single points of failure and designing things to automatically and efficiently work around any failures.
ARPANET was the first major implementation of a packet switching network, a theory first published by Leonard Kleinrock at MIT in 1961. Packet switching was a new important concept in data communications. Previously, data communications were based on the idea of circuit switching, as in typical telephone circuits, where a dedicated circuit is tied up for the duration of the call, and communication is only possible with the party (machine) on the other end of the dedicated circuit. With packet switching, a system could use one communication link to communicate with more than one machine by assembling data into packets, and each packet could be routed independently of other packets. This was a big breakthrough.
There were four nodes on the initial ARPANET, known as Interface Message Processors or IMPs. The first four were installed at UCLA (where Kleinrock had established a Network Measurement Center), the Stanford Research Institute (where Doug Engelbart had worked on his "NLS" project, an early hypertext system), UCSB, and University of Utah.
The ARPANET was government-funded and therefore restricted to research use only. Commercial use was strictly forbidden. This initially restricted connections to military sites and universities. During the 1980s, as the TCP/IP protocols (developed by Vint Cerf and others) replaced earlier protocols like NCP, the connections expanded to more colleges and even to a growing number of companies such as Digital Equipment Corporation and Hewlett-Packard who were participating in research projects.
Regional TCP/IP-based networks such as NYSERNet (New York State Education and Research Network) and BARRNet (Bay Area Regional Research Network) grew up and started interconnecting with the ARPANET. This greatly expanded the reach of the growing network, and to a great extent was the point where the ARPANET turned into the Internet.
At the end of the 1980s, the US Department of Defense decided the network was developed enough for its initial purposes, and decided to stop further funding. The US National Science Foundation, another branch of the US government, took over responsibility for the core backbone. In 1989 the NSFNet backbone was established, the US military broke off as a separate MILNET network, and the ARPANET was shut down.
Commercialization and Privatization
Parallel to the ARPANET, other networks were growing. Some were educational and centrally-organized like BITNET and CSNET. Others were a grass-roots mix of school, commercial, and hobby like the UUCP network.
During the late 1980s the first Internet Service Provider companies were formed. Companies like PSINet, UUNet, Netcom, and Portal were formed to provide service to the regional research networks and provide alternate network access (like UUCP-based email and Usenet News) to the public.
The interest in commercial use of the Internet became a hotly-debated topic. Although commercial use was forbidden, the exact definition of commercial use could be unclear and subjective. Everyone agreed that one company sending an invoice to another company was clearly commercial use, but anything less was up for debate. The alternate networks, like UUCP, had no such restrictions, so many people were skirting grey areas in the interconnection of the various networks.
Many university users were outraged at the idea of non-educational use of their networks. Ironically it was the commercial Internet service providers who brought prices low enough that junior colleges and other schools could afford to participate in the new arenas of education and research.
By 1994, the NSFNet lost its standing as the backbone of the Internet. Other competing commercial providers created their own backbones and interconnections. Regional NAPs (network access points) became the primary interconnections between the many networks. The NSFNet was dropped as the main backbone, and commercial restrictions were gone.
E-mail had existed as a message exchanging service on early time sharing mainframe computers connected to a number of terminals. In 1971, Ray Tomlinson developed the first system of exchanging addressed messages between different, networked computers; he also introduced the "name@computer" notation that is still used today. E-mail turned into the internet "killer application" of the 1980s.
The second most popular application of the early internet was usenet, a system of distributed discussion groups which is still going strong today. Usenet had existed even before the internet, as an application of Unix computers connectid by telephone lines via the UUCP protocol.
It wasn't until the early to mid 1980s that the services we now use most on the Internet started appearing. The concept of "domain names" (like "wikipedia.com") requiring "Domain Name Servers" wasn't even introduced until 1984. Before that all the computers were just addressed by their IP addresses (numbers) or used a central "hosts" file maintained by the NIC. Most protocols used for email and other services were significantly enhanced after this.
Standards and Control
The Internet has developed a significant subculture dedicated to the idea that the Internet is not owned or controlled by any one person, company, group, or organization. Nevertheless, some standardization and control is necessary for anything to function.
Many people wanted to put their ideas into the standards for communication between the computers that made up this network, so a system was devised for putting forward ideas. Basically you wrote your ideas in a paper called a "Request for Comments" (RFC for short), and let everyone else read it. People commented on and improved your ideas in new RFCs. (With its basis as aneducational research project, much of the documentation was written by students or others who played significant roles in developing the network but did not have official responsibility for defining standards. Thus the very low-key name of "Request for Comments" rather than something like "Declaration of Official Standard".) The first RFC (RFC1) was written on April 7th, 1969. There are now well over 2000 RFCs, describing every aspect of how the internet functions.
The Internet standards process has been as innovative as the Internet itself. Prior to the Internet, standardization was a slow process run by committees with arguing vendor-driven factions and lengthy delays. In networking in particular, the results were monstrous patchworks of bloated specifications.
The fundamental requirement for a networking protocol to become an Internet standard is the existence of at least two working implementations that interoperate with each other. This makes sense looking back, but it was a new concept at the time. Other efforts built huge specifications with many optional parts and then expected people to go off and implement them, and only later did people find that they did not interoperate, or worse, the standard was not even implementable.
In the 1980s, the International Organization for Standardization (ISO) documented a new effort in networking called Open Systems Interconnect or OSI. Prior to OSI, networking was completely vendor-developed and proprietary. OSI was a new industry effort, attempting to get everyone to agree to common network standards to provide multi-vendor interoperability. The OSI model was the most important advance in teaching network concepts. However, the OSI protocols or "stack" that were specified as part of the project were a bloated mess. Standards like X.400 for e-mail took up several large books, while Internet e-mail took only a few dozen pages at most in RFC-822 and 823. Most protocols and specifications in the OSI stack are long-gone today, such as token-bus media, CLNP packet delivery, FTAM file transfer, and X.400 e-mail. Only one, X.500 directory service, still survives with significant usage, mainly because the original unwieldy protocol has been stripped away and effectively replaced with LDAP.
Some formal organization is necessary to make things operate. The first central authority was the NIC (Network Information Center) at SRI (Stanford Research Institute in Menlo Park, California).
World Wide Web
The part of the Internet most people are probably most familiar with is the World Wide Web.
As the Internet grew through the 1980s and early 1990s, many people realized the growing need to be able to find and organize files and related information. Projects such as Gopher, WAIS, and the Anonymous FTP Archive Site list attempted to create schemes to organize distributed data and present it to people in an easy-to-use form. Unfortunately, these projects fell short in being able to accommodate all the various existing file and data types, and in being able to grow without centralized bottlenecks.
One of the most promising ideas was hypertext, originated by Ted Nelson in his Project Xanadu. Small self-contained hypertext systems had been created before, such as Apple Computer's HyperCard, but nobody had figured out how to scale it up to be able to refer to another document anywhere in the world.
The solution was invented by Tim Berners-Lee in 1989. He was a physicist working at CERN, the European Particle Physics Laboratory, and wanted a way for physicists to share information about their research. His documentation project was the source of the two key inventions that made the World Wide Web possible.
The two key inventions were the uniform resource locator (URL) and hypertext markup language (HTML). The URL was a simple way to specify the location of a document anywhere on the Internet in one simple address that specified a machine domain name, a path on that machine, and a protocol to use. HTML was an easy way to embed codes into a text file that could define the structure of a document and also include links pointing to other URLs. An additional network protocol (HTTP: hypertext transfer protocol) was also invented for reduced overhead in transfers, but the true genius of the new system was that a new protocol was useful but not necessary; the URL and HTML system was backwards compatible with existing protocols like FTP and Gopher.
Later around 1992 people realized that the simple markup capabilities of HTML could allow graphics to be included in text documents. The first graphical web browsers were developed, Viola and Mosaic. Mosaic was developed by a team at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign (NCSA-UIUC), led by Marc Andreesen. Andreesen left NCSA-UIUC and joined Jim Clark, one of the founders of SGI (Silicon Graphics, Inc.). They started Mosaic Communications which became Netscape, making Netscape Navigator the first commercially successful browser. Microsoft acquired technology from SpyGlass (who got their technology from NCSA) to develop Internet Explorer.
The ease of creating new Web documents and linking to existing ones caused exponential growth. As the Web grew, search engines were created to track pages on the web and allow people to find things. The first search engine, Lycos, was created in 1993 as a university project. In 1993 it tracked 800,000 pages. In August 2001, the Google search engine tracked over 1,387,529,000 web pages and the growth continues.