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What is the World Wide Web (WWW) ?
How does the World Wide Web work ?
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The Internet is a loose association of thousands of networks and millions of computers across the world that all work together to share information.
Like many complex systems, the internet is the easiest to explain through the use of metaphors, and the net has inspired its fair share. The one that has stuck is the ?Information superhighway?, and while it has become a clichè, the transportation analogy really does hold up pretty well. Think of the internet as a huge version of a mass transit system like the London underground, with a few main underground lines that intersect at certain points. Connecting to the underground lines are commuter rails, bus lines and ferry boats that spread out and crisscross the metropolitian area.
On the Net, the main lines carry the bulk traffic and are collectively known as the internet backbone. The backbone is formed by the biggest networks in the systems, owned by the biggest internet service providers(ISP?s) such as GTE, MCI, Sprint, UUNET, and America Onlines ANS.
By connecting to eachother these networks create a superfast pipeline that crisscross the united states ad extends to Europe, Japan, mainland Asia and the rest of the world. But that doesn?t mean that the network is equally well developed at every major point along the route. The U.S. backbone has so many intersecting points that if any point fails or slows down along the route that data can easily be rerouted quickly over another part, a feature called Redundancy. Overseas, the network may have
less redundancy and so be more vulnerable to slowdowns or breakdowns.
In the United States, there are five main access points, located in:
·San Francisco
·San Jose (California)
·Chicago
·New York
·Washington D.C.
Where the main lines intersect, kind of like how major U.S. airlines have hub cities. Confusingly enough, three of these are called network access points(NAP?s), while the other two are called metropolitian area exchanges (MAE?s), but they basically do the same thing: use high speed networking to connect the bqackbone to other networks.
These are networks owned by smaller regional and local ISP?s which in turn lease access to companies and individuals in the areas they serve.
Government agencies and universities are also actively involved in running the parts of the Internet that link supercomputer centers devoted to the research and education communities. While this used to be the main purpose of the Net, the explosion of private and corporate use has caused a huge traffic jam on the backbone. Academics now complain that they can't get their work done because the network is too packed with everybody else.
With help from theses communities, as well as financial support from the private sector, Congress has been actively plannin the Next Generation Internet. It aims to deliver on President Clinton?s pledge to build and promote a new faster network that will form a second backbone over the next five years. The internet II, as it?s sometimes referred to as, will not replace the existing Net, but will provide alternate routes for academics and government agencies to share information without getting caught in commercial traffic.
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No one person or organisation can claim the sole credit for the Internet.
But the first germ of the internet was a series of memos written in 1962 by MIT?s C.R. Licklider about what he called the ?Gallactic Network? concept. He envisioned a global network through which everyone could share and access data and programs. Only a few months later Licklider became the head of the computer research program at the United States Department of Defence?s Advanced Research Projects Agency (ARPA), the institute that largely spearheaded and funded the internet?s development.
In 1961, a series of independent research teams began developing packet switching and the beginnings of what would eventually become TCP/IP, the basic protocol that defines how information is exchanged over the Net. In 1967, ARPA's Lawrence Roberts published his "Plan for the ARPANet" computer network, which built on these new technologies to propose an architectural design for a worldwide network. By the end of 1968, the company that would become BBN Planet (a major backbone ISP recently bought GTE) was well into the development of the first hardware that could route data over the ARPA Net. In late, 1969, the first tests were made at UCLA and Stanford.Over the next several years, this test-tube Internet grew steadily but unremarkably as government agencies, universities, and corporations continued to develop and hammer out protocols and architectures. Email and the Internet made their first public appearances in 1972 at the Internet Computer Communication Conference. In 1973 and 1974, the protocol known as TCP/IP emerged in essentially its current form, although the same group of collaborators would continue to refine it through the early 1980s. Once the protocols were in place, the various developers formulated much of the software and services that make up the Internet. The basic services for connecting to files remotely (via Telnet), transfering files over the Internet (via FTP), and sending and recieving electronic mail appeared in the mid and late 1970?s. The Usenet news system first appeared in 1979 as an offshoot of the rise of Unix. The World Wide Web began in 1989.
In 1990, the U.S. government officially decomissioned ARPA Net, and the National Science Foundation (NSF) took over the role of managing the Internet backbone which was then called NSF Net. In 1995, the NSF inturn withdrew, turning the backbone over to a consortium of commercial providers.
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The seceret of the net is a network protocol called TCP/IP- that is, a kind of coding system that lets computers electronically describe data, like the contents of this story, to each other over the network. The term actually refers to two separate parts: the transmission control protocol (TCP) and the Internet protocol (IP). Together thry form the Esperanto of the Internet. Every computer that hooks to the Internet understands these two protocols and uses them to send and receive data from the next computer along the network. TCP/IP creates what is called a packet-switched network, a kind of network intended to minimize the chance of losing any data that is sent over the wires.
First, TCP breaks down every piece of data--such as an email message or instructions from a Java applet--into small chunks called packets, each of which is wrapped in an electronic envelope with Web addresses for both the sender and the recipient. The IP protocol then figures out how the data is supposed to get from point A to point B by passing through a series of routers sort of like regular mail passes through several post offices on its way to a remote location. Each router examines the destination addresses of the packets it receives and then passes the packets on to another router as they make their way to their final destination. If your email was broken into ten packets, then each of those may have traveled a completely separate route. But you'll never know it, because as the packets arrive, TCP takes over again, identifying each packet and checking to see if it's intact. Once it has received all the packets, TCP reassembles them into the original. TCP/IP is the most important of a long list of Internet protocols. It is sometimes used as a global term to describe additional protocals, including simple mail transfer protocol (SMTP), file transfer protocol (FTP) and Telnet protocol
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Although the terms Web and Internet are often used synonymously, they're actually two different things. The Internet is the global association of computers that carries data and makes the exchange of information possible. The World Wide Web is a subset of the Net--a collection of interlinked documents that work together using a specific Internet protocol call HTTP (Hyper Text Transfer Protocol). In other words, the Net exists independently of the Web, but the Web can't exist without the Net. The Web began in March 1989, when Tim Berners-Lee of the European Particle Physics Laboratory (a collective of European researchers better known by its original name CERN, or Conseil Européen pour la Recherche Nucleaire) proposed the project as a means to better communicate research ideas among members of the far-flung organization.
The Web uses a metaphor of individual pages, usually combined to make up sites. Web pages are written in HTML (Hyper Text Markup Language) which tells the browser how to display the page and its elements. The defining feature of the Web is its ability to connect pages to one another--as well as to audio, video, and image files--with hyperlinks. Just click a link, and suddenly you're at a Web site on the other side of the world. (Before the Web, you had to type in exact Net addresses or wade through a series of menus to get where you wanted to go.)
Despite its cool hyperlinking ability, the early Web labored for a while in obscurity, a little-known alternative to the less technically advanced Gopher protocol. But in february 1993, Marc Andreessen, then developing for the National Center for Supercomputing Applications, introduced the first graphical Web browser, called Mosaic. (Andreessen went on to cofound Netscape Communications in April 1994.) And the rest, as they say, is history
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The Web is based on a set of rules for exchanging text, images, sound, video, and other multimedia files, which is collectively known as HTTP. Web pages can be exchanged over the Net because browsers (which read the pages) and Web servers (which store the pages) both understand HTTP. But everything would still be chaos if the Web didn't have an addressing scheme that every computer on the network understands. An IP address is a 4- to 12-digit number that identifies a specific computer connected to the Internet. The digits are organized in four groups of numbers (which can range from 0 to 255) separated by periods. Depending on how your ISP assigns IP addresses, you may have one address all the time or a different address each time you connect. Web servers have the same kind of addresses: if you type http://204.162.80.183/ in your browser, you'll get the same result as if you had typed http://www.yahoo.com/.
Internet domain names are the next level of Internet addressing, just as the street name is followed by the city and state. Domain names create a single identity for a series of computers used by a company or an institution. So while there may be 38 servers at a given company, each with its own IP address, they all share a common domain name, such as YAHOO.COM. The domain name identifies all the computers in a group. But if you want to get to a specific page stored on any of those computers, you'll need an even more precise address. That's why every Web page on the Internet, and even the objects you see displayed on Web pages, has its own unique address, known as a Uniform Resource Locator (URL), which tells your browser exactly where to go on the server to find a page.