Internet

The Internet is often described as a network of networks: universities, businesses, governments, providers and other organizations operate networks that connect to one another. Data is divided into packets, which are addressed and forwarded across links and routers toward their destinations. The Internet Protocol (IP) provides a common addressing and delivery layer; transport protocols such as TCP support communication between applications. Because the networks use interoperable protocols, equipment and software built by different organizations can exchange data without belonging to one centrally operated system.

Internet Protocol addresses help networks deliver data, but numerical addresses are not convenient for people to remember. The Domain Name System (DNS) lets people use names such as example.org and resolves them to the addresses needed for connections. The Internet is not the same as the World Wide Web. The Internet is the underlying infrastructure; the Web is one service that uses it, alongside email and other applications. Web pages and linked documents are accessed through web servers and browser software.

The Internet grew out of research into packet switching and ways to connect different computer networks. The ARPANET, developed with support from the U.S. Advanced Research Projects Agency, began with four nodes; its first computer-to-computer signal was sent in 1969. In the 1970s, DARPA-supported work developed protocols for linking unlike packet networks, giving rise to the TCP/IP protocol suite. The ARPANET's 1983 transition to TCP/IP was an important step in the Internet's evolution. Research, educational and commercial networks subsequently expanded the interconnected system. In a separate but related development, Tim Berners-Lee proposed the Web at CERN in 1989, and the first Web server and browser were running there by the end of 1990.

No single organization controls or operates the entire Internet. Network operators connect and manage their own infrastructure, while technical standards make communication across networks possible. The Internet Engineering Task Force (IETF) develops technical documents and standards through an open process; it does not govern or patrol the whole Internet. The Internet Corporation for Assigned Names and Numbers (ICANN) coordinates important parts of the domain-name system. These distinct roles help maintain shared identifiers and compatible protocols across a system that continues to grow and change.

The Internet supports a wide range of activities, including personal communication, access to information, scientific collaboration, public services and commerce. Its layered, interoperable design has allowed new applications to be built on shared infrastructure, rather than requiring a separate global network for each service. The system's scale also makes reliable operation, security and coordination continuing technical and organizational concerns.