The Internet Published by Ali Hassan - On 00:35:00 - This post haved 0 comments

Browser: A program used on a computer connected to the Internet that provides access to the World Wide Web. The browser translates the documents stored on the World Wide Web into a format you can read on your screen.

Download: To transfer a file from a remote computer to your computer through a modem and a telephone line, cable, or wirelessly.

E-mail (Electronic Mail): Electronic mail messages you send over the Internet from one computer to another.

FAQ (Frequently Asked Questions): On a Web site, a list of questions commonly asked by users and the answers to those questions to assist people using the site.

Internet: A worldwide system of linked computers that allows users to send and receive e-mail and documents from one computer to another.

URL (Universal Resource Locator): The address of a Web page on the World Wide Web.

Web (World Wide Web or WWW): A subset of the Internet that allows people to view documents called Web pages using a browser. You can click items called links on a Web page to open another Web page anywhere on the Web identified by the link.

The most notable example of an internet is the Internet (note the uppercase I ), which originated from research projects going back to the early 1960s. The goal was to develop the ability to link a variety of computer networks so that they could function as a connected system that would not be disrupted by local disasters. Much of this work was sponsored by the U.S. government through the Defense Advanced Research Projects Agency (DARPA—pronounced “DAR–pa”). Over the years, the development of the Internet shifted from a government-sponsored project to an academic research project, and today it is largely a commercial undertaking that links a worldwide combination of LANs, MANs, and WANs

involving millions of computers.

Internet Architecture

As we have already mentioned, the Internet is a collection of connected networks. In general, these networks are constructed and maintained by organizations called Internet Service Providers (ISPs). It is also customary to use the term ISP in reference to the networks themselves. Thus, we will speak of connecting to an ISP, when what we really mean is connecting to the network provided by an ISP.

The system of networks operated by the ISPs can be classified in a hierarchy according to the role they play in the overall Internet structure. At the top of this hierarchy are relatively few tier-1 ISPs that consist of very high-speed, high-capacity, international WANs. These networks are thought of as the backbone of the Internet. They are typically operated by large companies that are in the communications business. An example would be a company that

originated as a traditional telephone company and has expanded its scope into providing other communication services.

Connecting to the tier-1 ISPs are the tier-2 ISPs that tend to be more regional in scope and less potent in their capabilities. (The distinction between the tier-1 and tier-2 ISPs is often a matter of opinion.) Again, these networks tend to be operated by companies in the communications business. Tier-1 and tier-2 ISPs are essentially networks of routers that collectivly provide the Internet’s communication infrastructure. As such, they can be thought of as the core of the Internet. Access to this core is usually provided by an intermediary called an access ISP. An access ISP is essentially an independent internet,

sometimes called an intranet, operated by a single authority that is in the business of supplying Internet access to individual users. Examples include companies such as AOL, Microsoft, and local cable and telephone companies that charge for their service as well as organizations such as universities or corporations that take it upon themselves to provide Internet access to individuals within their organizations.

The devices that individual users connect to the access ISPs are known as end systems or hosts. These end systems are not necessarily computers in the traditional sense. They range over a multitude of devices including telephones, video cameras, automobiles, and home appliances. After all, the Internet is essentially a communications system, and thus any device that would benefit from communicating with other devices is a potential end system.