Overview of the World Wide Web or Internet                  

 
Internet, computer-based (computer-mediated) worldwide information network.

The Internet is composed of a large number of smaller interconnected networks called internets.

These internets may connect tens, hundreds, or thousands of computers, enabling them to share information with each other and to share various resources, such as powerful supercomputers and databases of information.

The Internet has made it possible for people all over the world to effectively and inexpensively communicate with each other.

 Unlike traditional broadcasting media, such as radio and television, the Internet is a decentralized system.

Each connected individual can communicate with anyone else on the Internet, can publish ideas, and can sell products with a minimum overhead cost.

 In the future, the Internet may have a dramatic impact on higher education and business as more universities offer courses and more companies offer goods and services online.

The internets from which the Internet is composed are usually public access networks, meaning that the resources of the network can be shared with anyone logging on to, or accessing, the network.

Other types of internets, called intranets, are closed to public use.

Intranets are the most common type of computer network used in companies and organizations where it is important to restrict access to the information contained on the network.

See also Local Area Network LAN.

During the 1990s the Internet has grown tremendously in the number of people using it and the amount of information contained on it.

According to the Internet Society, a non-profit society that studies and promotes the use of the Internet, 134 countries had full Internet connection and an additional 52 countries had limited access (for example, e-mail only) in 1996.

 Surveys performed by International Data Corporation and Matrix Information and Directory Services found that as of September 1997 there were between 53 and 57 million users of the Internet worldwide.

                        USES
From the late 1960s to the early 1990s, the Internet was a communication and research tool used almost exclusively for academic and military purposes.

This changed radically with the introduction of the World Wide Web (also called the WWW, or W3) in 1989.

The WWW is a set of programs, standards, and protocols governing the way in which multimedia files (documents that may contain text, photographs, graphics, video, and audio) are created and displayed on the Internet.

 The Internet contains the WWW and also includes all the hardware (computers, supercomputers, and connections) and non-WWW software and protocols on which the WWW runs.

 The difference between the Internet and the WWW is similar to the distinction between a computer and a multimedia program that runs on the computer.

The explosion in use and popularity of the Internet in the 1990s is most likely due to the graphics-intensive nature of the World Wide Web.

Individuals, companies, and institutions use the Internet in many ways.

Businesses use the Internet to provide access to complex databases, such as financial databases. Companies can carry out commerce online, including advertising, selling, buying, distributing products, and providing after-sales services.

Businesses and institutions can use the Internet for voice and video conferencing and other forms of communication that allow people to telecommute, or work from a distance.

The use of electronic mail (see e-mail) over the Internet has greatly speeded communication between companies, among coworkers, and between other individuals.

Media and entertainment companies use the Internet to broadcast audio and video, including live radio and television programs; to offer online chat, in which people carry on discussions using written text; and to offer online news and weather programs.

 Scientists and scholars use the Internet to communicate with colleagues, to perform research, to distribute lecture notes and course materials to students, and to publish papers and articles.

Individuals use the Internet for communication, entertainment, finding information, and to buy and sell goods and services.

HOW THE INTERNET WORKS  
The Internet is based on the concept of a client-server relationship between computers, also called a client/server architecture.

 In a client/server architecture, some computers act as servers, or information providers, while other computers act as clients, or information receivers.

The client/server architecture is not one-to-one—that is, a single client computer may access many different servers, and a single server may be accessed by a number of different client computers.

Prior to the mid-1990s, servers were usually very powerful computers such as mainframe or supercomputers, with extremely high processing speeds and large amounts of memory.

Personal computers and workstations, however, are now capable of acting as Internet servers due to advances in computing technology.

A client computer is any computer that receives information from a server and is often a personal computer.

To access information on the Internet, a user must first log on, or connect, to the client computer’s host network.

A host network is a network that the client computer is part of, and is usually a local area network (LAN). Once a connection has been established, the user may request information from a remote server.

If the information requested by the user resides on one of the computers on the host network, that information is quickly retrieved and sent to the user’s terminal.

 If the information requested by the user is on a server that does not belong to the host LAN, then the host network connects to other networks until it makes a connection with the network containing the requested server.

In the process of connecting to other networks, the host may need to access a router, a device that determines the best connection path between networks and helps networks to make connections.

Once the client computer makes a connection with the server containing the requested information, the server sends the information to the client in the form of a file.

A special computer program called a browser enables the user to view the file. Examples of Internet browsers are Mosaic, Netscape, and Internet Explorer.

Most Internet files are multimedia documents—-that is, text, graphics, photographs, audio, and video may be combined in a single document.

Non-multimedia documents do not need browsers to view their text-only contents and many multimedia documents provide access to text-only versions of their files.

The process of retrieving files from a remote server to the user’s terminal is called downloading.

One of the strengths of the Internet is that it is structured around the concept of hypertext. The term hypertext is used to describe an interlinked system of documents in which a user may jump from one document to another in a nonlinear, associative way.

 The ability to jump from one document to the next is made possible through the use of hyperlinks—portions of the hypertext document that are linked to other related documents on the Internet.

 By clicking on the hyperlink, the user is immediately connected to the document specified by the link. Multimedia files on the Internet are called hypermedia documents.

                        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 signals that can be transmitted over traditional telephone lines.

 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. 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 ISPs are America Online (AOL), the Microsoft Network (MSN), and CompuServe.

                        Packaging Information  
All data transmitted over the Internet is divided up into small units of information called packets, each of which is labeled with a unique number indicating its place in the data stream—the flow of information between computing devices.

When the various packets that make up a set of data arrive at their destination, they are re-assembled using the unique labels given them.

If part of the network over which the packets are sent is malfunctioning, or down, special automatic features of the Internet’s routing equipment re-route the packets so that they travel over functioning portions of the network.

Other features make sure that all the data packets arrive intact, automatically requesting that missing or incomplete packets be re-sent from the source. This system, called packet-switching, uses a series of protocols, or rules, known as TCP/IP (Transmission Control Protocol/Internet Protocol).

                        Network Addressing  
To be part of the Internet a computer must have a unique Internet Protocol (IP) network address so that messages can be correctly routed to and from the machine over the Internet.

 Internet addresses are called URLs (Uniform Resource Locators).

Some URLs are a string of numbers, but because long strings of numbers are difficult for people to remember, other addressing conventions are also used.

 An example of this convention is: http://encarta.msn.com/downloads/pryearbk.asp. The http indicates the protocol—in this instance the hypertext transfer protocol—used to access the particular location on the Internet. The name after the colon and double slash (encarta.msn.com) indicates the hostname, which is the name of a specific computer system connected to the Internet.

The remaining names after the hostname indicate various files to which the specific URL points. In the example URL, the file pryearbk is located within the directory downloads. Other files located in the same directory will have a similar URL, the only difference being the name of the file, or files, at the end of the address. Special name servers map IP numbers to domain names (msn.com in the above URL) and guarantee that the correct IP number of the source and the destination are provided for all packets. See also Domain Name System

            D         Electronic Mail  
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. 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. To send email, the process is reversed. A very convenient and inexpensive way to transmit messages, e-mail has dramatically affected scientific, personal, and business communications.

E-mail is the basis of much organized exchange between groups of individuals. List servers, for example, make it possible to address a list of subscribers either in one-way communication, as in keeping interested people up-to-date on a product, or two-way communication, as in online discussion groups.

Another use of e-mail is Usenet, in which discussions on a particular subject are grouped together into newsgroups. There are thousands of newsgroups covering an extremely wide range of subjects. Messages to a newsgroup are not posted directly to the user, but are accessible in the form of an ordered list on a dedicated local news server. The networking of these servers makes such discussions available worldwide. Associated software not only enables users to choose which messages they want to read, but also to reply to them by posting messages to the newsgroup.

                        Transmission Schemes  

Before the introduction of the World Wide Web, various standards and types of software existed for transmitting data over the Internet. Many of these are still in use, with Telnet, File Transfer Protocol (FTP), and Gopher among the most popular. Telnet allows an Internet user to connect to a distant computer and use that computer as if he or she were using it directly. FTP is a method of moving files from one computer to another over the Internet, even if each computer has a different operating system or storage format. Gopher is an improvement on FTP, making it easier to list and retrieve files remotely. While these transmission protocols and software are still in use, the WWW is much easier to use and is used much more often than earlier transmission protocols.

            Bandwidth  The amount of data that a computer network can transmit is called the bandwidth of the network and is usually measured in Kilobits per second (Kbps) or Megabits per second (Mbps). A bit—the smallest unit of information that computers can process—can have one of two values, either 0 or 1. A Kilobit is one thousand bits, while a Megabit is one million bits. The transportation of information between routers generally uses communication lines dedicated to this function, with capacities currently ranging from 64 Kbps up to as much as several hundred Mbps.

The speed at which information can be transmitted across the Internet depends on the lowest information transporting capacity along the route and the number of people using that route at any given time. A narrow bandwidth somewhere along the route acts as a bottleneck to data transport, and the more people using the line, the less information each of them can transport at any one time.

            HISTORY  The Internet is an extension of a computer network originally formed in the United States during the 1960s by the Advanced Research Projects Agency (ARPA). Working under contract to the U.S. Department of Defense, ARPA initially connected computers at the Stanford Research Institute in California, the University of California at Los Angeles (UCLA), the University of California at Santa Barbara (UCSB), and the University of Utah. This original network, the very first computer network, was called ARPANET (ARPA NETwork). Scientists built ARPANET with the intention of creating a network that would still be able to function efficiently if part of the network was damaged. This concept was important to military organizations, which were studying ways to maintain a working communications network in the event of nuclear war.

As ARPANET grew in the 1970s, with more and more universities and institutions connecting to it, users found it necessary to establish standards for the way that data was transmitted over the network. To meet the needs of data transmission standards, computer scientists developed the Transmission Control Protocol (TCP) and the Internet Protocol (IP). During the 1970s various government, scientific, and academic groups developed their own networks. Examples include the Department of Energy’s (DoE) Magnetic Fusion Energy Network (MFENet), the High Energy Physics NETwork (HEPNET), and the National Science Foundation NETwork (see NSFNET).

In 1989 English computer scientist Timothy Berners-Lee introduced the World Wide Web. Berners-Lee initially designed the WWW to aid communication between physicists who were working in different parts of the world for the European Laboratory for Particle Physics (CERN). As it grew, however, the WWW revolutionized the use of the Internet. During the early 1990s increasingly large numbers of users who were not part of the scientific or academic communities began to use the Internet, due in large part to the ability of the WWW to easily handle multimedia documents.

            THE FUTURE OF THE INTERNET  
A major challenge facing the continued growth of the Internet is the difficulty of providing enough bandwidth to sustain the network. As Internet applications become more sophisticated, and as more people around the world use the Internet, the amount of information transmitted across the Internet will demand very high bandwidth connections. While many communications companies are attempting to develop higher bandwidth technologies, it is not known whether the technology will be able to satisfactorily keep up with demand.

In order to accommodate the increasing number of users, the non-profit organization University Corporation for Advanced Internet Development (UCAID) is working on the construction of Internet 2. Internet 2 will add more bandwidth, or available communication lines, to the current information superhighway in order to accommodate larger packets of data. UCAID members include representatives from universities, the government, and the computer industry.

Another important question facing Internet growth is the issue of censorship. Because the Internet has grown so rapidly, governments have been slow to regulate its use and to pass laws regarding what content is acceptable. Many Internet users also see such laws as an infringement on their right to free speech. In 1996 the Congress of the United States passed the Communications Decency Act, which made it a crime to transmit indecent material over the Internet. This decision resulted in an immediate outcry from users, industry experts, and civil liberties groups opposed to such censorship. In 1997 the United States Supreme Court declared the act to be unconstitutional because it violated 1^st Amendment rights to free speech.

Commercial use of the Internet is sure to grow dramatically as more individuals gain access to it. It may be possible in the future to order nearly any goods from Internet sites and have them delivered using the postal service. Many companies are worried about security issues and the possibility of losing money through Internet commerce. They are therefore being very cautious about doing business on the Internet. Other businesses, however, are embracing the Internet, hoping to be first in what may be a rapidly expanding market.

The issue of business being conducted over the Internet raises important security issues. Companies doing business over the Internet must have very sophisticated security measures in place so that information such as credit card, bank account, and social security numbers cannot be accessed by unauthorized users. (see Computer Security) Similarly, government facilities, universities, and institutions must ensure that access to their computers over the Internet is strictly regulated.