Internet

The Internet is a vast international public communications network that interconnects thousands of small and large networks so that they work as a single network to permit communication between any two connected end points. A world-wide collection of computer networks, connecting government, military, educational and commercial institutions, as well as private citizens to a wide range of computer services, resources, data and information. A set of network conventions and common tools are employed to give the appearance of a single large network, even though the computers that are linked together use many different hardware and software platforms.

The Internet is a global network of networks connecting millions of users worldwide via many computer networks using a simple standard common addressing system and communications protocol called TCP/IP (Transmission Control Protocol/Internet Protocol). This includes federal networks, regional networks, educational and some foreign networks.

Types of Computer Network

A computer network comprises two or more computers connected together allowing the exchange of information and sharing of data and system resources.

A local area network (LAN) connects computers (each called a node) over dedicated, private communications links.

A wide area network (WAN) connects several nodes over long-distance communications links, such as common-carrier telephone lines.

An internet is a connection between networks. The Internet is a WAN that connects thousands of disparate networks in the U.S., Canada, Europe, and Asia, providing global communication between nodes on government, educational, and industrial networks.

For most of its existence the Internet was primarily a research and academic network. More recently, commercial enterprises and a vast number of consumers have come to recognize the Internet's potential. Today people and businesses around the world can use the Internet to retreive information, communicate and conduct business globally, and access a vast array of services and resources on-line.

Applications

A popular use of the Internet is electronic mail (commonly called e-mail). Millions of people use the Internet for electronic mail capabilities. Electronic mail however, is only a small part of what the Internet offers. There's also

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• chat groups
• the WWW
• bulletin boards and newsgroups
• remote computer access (telnet)
• file transfer (using ftp, or file transfer protocol)

In addition to file transfer, remote user login, e-mail, and access to the Web, the Internet now offers such enhancements as Web searching, "push" information services (which automatically send information according to interests expressed in advance by the user), multimedia e-mail, telephony and videotelephony, and multimedia teleconferencing.

Recent developments have made possible book and magazine publishing, video conferencing, and audio broadcasts. Amateur radio, cable television wires, spread spectrum radio, satellite, and fibre optics have all been used to deliver Internet services. Networked games, networked monetary transactions, and virtual museums are among applications being developed.

Users can join any of the thousands of Internet discussion groups, search for specific information in vast libraries, or transfer a variety of files to their computer. They can also explore the World Wide Web the Internet's multimedia service. Over just the last few years Internet-based resources and services have grown exponentially. Based on current projections this rapid growth will continue into the next decade as more businesses and consumers make the decision to move onto the Internet.

Email

The most widely used tool on the Internet is electronic mail, or e-mail. E-mail is used to send written messages between individuals or groups of individuals, often geographically separated by large distances.

Many computer systems are now connected to local or wide-area networks and users can communicate with other users anywhere on the network. Some services offer facilities that allow users to send and receive messages via a microcomputer, a telephone, and a modem.

E-mail messages are generally sent from and received by mail servers - computers that are dedicated to processing and directing e-mail. Once a server has received a message it directs it to the specific computer that the email is addressed to. The sender and receiver need not be on-line at the same time; the message is held in a computer mail-box, which the receiver is able to access.

A very convenient and inexpensive way to transmit messages, e-mail has dramatically affected scientific, personal, and business communications.

WWW

The World Wide Web, or 'web' is a service that allows computer users to quickly and easily navigate the Internet, giving them access to hundreds of millions of multimedia documents ('pages'), interlinked by hypertext -- references to other documents (on the same or another computer), that might also be of interest to the user. Hypertext allows users to select a linked word or image (typically by clicking a mouse), and obtain ('visit') another web document. These documents may comprise text, images, sounds, animations, or movies.

Accessing the Internet

Access to the Internet falls into two broad categories: dedicated access and dial-up access.

With dedicated access, the computer is directly connected to the Internet via a router, or the computer is part of a network linked to the Internet.

With dial-up access, a computer connects to the Internet with a temporary connection, generally over a telephone line using a modem a device that converts the electrical signals from a computer into tones which can be transmitted along a telephone line.

A modem is needed because computers are digital, meaning that their signals are made up of discrete units, while most telephone lines are analog, meaning that they carry signals that are continuous instead of discrete.

At the other end of the line, a similar modem operating in reverse converts the frequencies back into digital electrical signals.

Modems work to internationally agreed standards, the most important characteristic being the rate at which the data is transmitted, measured in bits per second.

Once a signal has traveled over the telephone line, a second modem is required at the other end of the line to reconvert the transmitted signals from analog to digital.

A great many companies, called Internet Service Providers (ISPs), provide dial-up access to the Internet for a modest fee. Examples of large ISPs are America Online (AOL), the Microsoft Network (MSN), and CompuServe.

Technology

When you send a message over the Internet, it is broken into small pieces, called packets, which travel over many different routes between your computer and the recipient's computer.

TCP/IP

The communications protocol used to route the packets across the Internet is TCP/IP (Transmission Control Protocol/Internet Protocol).

Use of this standard protocol enables computers using different operating systems to communicate with each other.

DOS-based PCs, PCs using the Microsoft Windows(R), Windows 95, or Windows NT(TM) operating system, Macintosh(R) computers, and UNIX(R)-based systems all use TCP/IP to connect to the Internet.

Client/Server

Once you connect to the Internet, you interact with other computers using a client/server model. The resources of the Internet -- information and services -- are provided through host computers, known as servers.

The server is the computer system that contains information such as electronic mail, database information, or text files.

As a customer, or "client," you access those resources via client programs (applications) which use TCP/IP to deliver the information to your screen in the appropriate format for your computer.

Browsers

A Browser is a client program (application) that is used to search through information provided by a specific type of server.

A browser helps you view and navigate through information on the Internet.

Today's most popular browsers, including Mosaic(R), Netscape(TM) Navigator, and the Microsoft Internet Explorer offer a graphical interface to the World Wide Web.

Organisations

The NSF continues to maintain the backbone of the network (which carries data at a rate of 45 million bits per second), but Internet protocol development is governed by the Internet Architecture Board (IAB), and the InterNIC (Internet Network Information Center) administers the naming of computers and networks.

The Internet Society (ISOC) is a voluntary membership organization whose purpose is to promote global information exchange through Internet technology. It appoints a council of elders, which is responsible for the technical management and direction of the Internet.

The council of elders is a group of invited volunteers called the Internet Architecture Board (IAB) .

The IAB meets regularly to agree upon standards, allocation of resources, and defines the rules of how to assign addresses. The final organization responsible for the Internet is the Internet Engineering Task Force (IETF). The IETF is another volunteer organization responsible for the operational and near term technical problems of the Internet.

There is no central authority or organization which collects fees for Internet use. Instead, everyone who uses the Internet pays for their part. Most networks get together and decide how to connect themselves and fund these interconnections. A educational facility, government agency, or corporation pays for their connection to some regional network which pays a national provider for its access. The process eventually filters down to you the end user, so everyone who uses the Internet has a hand in paying for it.

Standards

The Internet is made possible through creation, testing and implementation of Internet Standards. These standards are developed by the Internet Engineering Task Force.

The standards are then considered by the Internet Engineering Steering Group, with appeal to the

Internet Architecture Board, and promulgated by the Internet Society as international standards.

The RFC Editor is responsible for preparing and organizing the standards in their final form. The standards may be found at numerous sites distributed throughout the world. See, for example, the ds.internic.

At the applications level, the MIT World Wide Web Consortium plays the leading role in developing and promulgating WWW standards.

Vint Cerf has written a brief history of the relationship of the Internet Society with the Internet Engineering Task Force.