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Internet

Internet:

Publicly accessible computer network connecting many smaller networks from around the world.

It grew out of a U.S. Defense Department program called ARPANET (Advanced Research Projects Agency Network), established in 1969 with connections between computers at the University of California at Los Angeles, Stanford Research Institute, the University of California-Santa Barbara, and the University of Utah. ARPANET's purpose was to conduct research into computer networking in order to provide a secure and survivable communications system in case of war. As the network quickly expanded, academics and researchers in other fields began to use it as well. In 1971 the first program for sending e-mail over a distributed network was developed; by 1973, the year international connections to ARPANET were made (from Britain and Norway), e-mail represented most of the traffic on ARPANET. The 1970s also saw the development of mailing lists, newsgroups and bulletin-board systems, and the TCP/IP communications protocols, which were adopted as standard protocols for ARPANET in 1982–83, leading to the widespread use of the term Internet. In 1984 the domain name addressing system was introduced. In 1986 the National Science Foundation established the NSFNET, a distributed network of networks capable of handling far greater traffic, and within a year more than 10,000 hosts were connected to the Internet. In 1988 real-time conversation over the network became possible with the development of Internet Relay Chat protocols . In 1990 ARPANET ceased to exist, leaving behind the NSFNET, and the first commercial dial-up access to the Internet became available. In 1991 the World Wide Web was released to the public (via FTP). The Mosaic browser was released in 1993, and its popularity led to the proliferation of World Wide Web sites and users. In 1995 the NSFNET reverted to the role of a research network, leaving Internet traffic to be routed through network providers rather than NSF supercomputers. That year the Web became the most popular part of the Internet, surpassing the FTP protocols in traffic volume. By 1997 there were more than 10 million hosts on the Internet and

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more than 1 million registered domain names. Internet access can now be gained via radio signals, cable-television lines, satellites, and fibre-optic connections, though most traffic still uses a part of the public telecommunications (telephone) network. The Internet is widely regarded as a development of vast significance that will affect nearly every aspect of human culture and commerce in ways still only dimly discernible.

Internet service provider (ISP)Company that provides Internet connections and services to individuals and organizations.

For a monthly fee, ISPs provide computer users with a connection to their site, as well as a log-in name and password. They may also provide software packages (such as browsers), e-mail accounts, and a personal Web site or home page. ISPs can host Web sites for businesses and can also build the Web sites themselves. ISPs are all connected to each other through network access points, public network facilities on the Internet backbone.

Data TransmissionSending and receiving data via cables (e.g., telephone lines or fibre optics) or wireless relay systems.

Because ordinary telephone circuits pass signals that fall within the frequency range of voice communication (about 300–3,500 hertz), the high frequencies associated with data transmission suffer a loss of amplitude and transmission speed. Data signals must therefore be translated into a format compatible with the signals used in telephone lines. Digital computers use a modem to transform outgoing digital electronic data; a similar system at the receiving end translates

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the incoming signal back to the original electronic data. Specialized data-transmission links carry signals at frequencies higher than those used by the public telephone network.

ProtocolIn computer science, a set of rules or procedures for transmitting data between electronic devices, such as computers.

In order for computers to exchange information, there must be a preexisting agreement as to how the information will be structured and how each side will send and receive it. Without a protocol, a transmitting computer, for example, could be sending its data in 8-bit packets while the receiving computer might expect the data in 16-bit packets. Protocols are established by international or industrywide organizations. Perhaps the most important computer protocol is OSI (Open Systems Interconnection), a set of guidelines for implementing networking communications between computers. The most important sets of Internet protocols are TCP/IP, HTTP, and FTP.

Types of Protocol

FTPIn full file transfer protocol

Internet protocol that allows a computer to send files to or receive files from another computer.

Like many Internet resources, FTP works by means of a client-server architecture; the user runs client software to connect to a server on the Internet. On the FTP server, a program called a daemon allows the user to download and upload files. Before the World Wide Web was introduced, FTP was one of the most popular methods of exchanging information over the Internet and many Web sites still use it to disseminate their larger files.

TCP/IP

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In full Transmission Control Protocol/Internet Protocol

Standard Internet communications protocols that allow digital computers to communicate over long distances.

The Internet is a packet-switched network, in which information is broken down into small packets, sent individually over many different routes at the same time, and then reassembled at the receiving end. TCP is the component that collects and reassembles the packets of data, while IP is responsible for making sure the packets are sent to the right destination. TCP/IP was developed in the 1970s and adopted as the protocol standard for ARPANET (the predecessor to the Internet) in 1983.

HTTPIn full HyperText Transfer Protocol

Standard application-level protocol used for exchanging files on the World Wide Web.

HTTP runs on top of the TCP/IP protocol. Web browsers are HTTP clients that send file requests to Web servers, which in turn handle the requests via an HTTP service. HTTP was originally proposed in 1989 by Tim Berners-Lee, who was a coauthor of the 1.0 specification. HTTP in its 1.0 version was “stateless”: each new request from a client established a new connection instead of handling all similar requests through the same connection between a specific client and server. Version 1.1 includes persistent connections, decompression of HTML files by client browsers, and multiple domain names sharing the same IP address.

IP AddressIn full Internet Protocol address

Number that uniquely identifies each computer on the Internet.

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A computer's IP address may be permanently assigned or supplied each time that it connects to the Internet by an Internet service provider. In order to accommodate the extraordinary growth in the number of devices connected to the Internet, a 32-bit protocol standard, known as IPv4, began to be replaced by a 128-bit protocol, IPv6, in 2000.

World Wide Web (WWW)Leading information-exchange service of the Internet.

It was created by Tim Berners-Lee and his colleagues at CERN and introduced to the world in 1991. The Web gives users access to a vast array of documents that are connected to each other by means of hypertext or hyperlinks. A hypertext document with its corresponding text and hyperlinks is written in HTML and is assigned an on-line address, or URL. The Web operates within the Internet's basic client-server architecture. Individual HTML files with unique electronic addresses are called Web pages, and a collection of Web pages and related files (such as graphics files, scripted programs, and other resources) sharing a set of similar addresses (see domain name) is called a Web site. The main or introductory page of a Web site is usually called the site's home page. Users may access any page by typing in the appropriate address, search for pages related to a topic of interest by using a search engine, or move quickly between pages by clicking on hyperlinks incorporated into them. Though introduced in 1991, the Web did not become truly popular until the introduction of Mosaic, a browser with a graphical interface, in 1993. Subsequently, browsers produced by Netscape and Microsoft have become predominant.

Internet ToolsThe following are the some popular internet tools.

1. FTP (File Transfer Protocol)2. Newsreader3. Telnet4. Videoconferencing

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URL :In full Uniform Resource Locator

Address of a resource on the Internet.

The resource can be any type of file stored on a server, such as a Web page, a text file, a graphics file, or an application program. The address contains three elements: the type of protocol used to access the file (e.g., HTTP for a Web page, ftp for an FTP site); the domain name or IP address of the server where the file resides; and, optionally, the pathname to the file (i.e., description of the file's location). For example, the URL .

Browser :Software that allows a computer user to find and view information on the Internet .

The first text-based browser for the World Wide Web became available in 1991; Web use expanded rapidly after the release in 1993 of a browser called Mosaic, which used “point-and-click” graphical manipulations. Such Web browsers interpret the HTML tags in downloaded documents and format the displayed data according to a set of standard style rules. Netscape Navigator became the dominant Web browser soon after its release in 1994; Microsoft's Internet Explorer was introduced a year later and has become widespread.

Domain Name :Address of a computer, organization, or other entity on a TCP/IP network such as the Internet.

Domain names are typically in a three-level “server.organization.type” format. The top level denotes the type of organization, such as “com” (for commercial sites) or “edu” (for educational sites); the second level is the top level plus the

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name of the organization (e.g., “britannica.com” for Encyclopædia Britannica); and the third level identifies a specific host server at the address, such as the “www” (World Wide Web) host server for “www.britannica.com”. A domain name is ultimately mapped to an IP address, but two or more domain names can be mapped to the same IP address. A domain name must be unique on the Internet, and must be assigned by a registrar accredited by the Internet Corporation for Assigned Names and Numbers (ICANN).