How Internet Works?

What is Internet

The Internet is a global interconnected network of computers. Using the Internet you can look at documents and images even view videos or listen to sound files from anywhere in the world using your computer. You can also use the Internet to publish, so that others can look at your information in any of a number of standard file formats.

You can also use the Internet to send messages through e-mail, as long as you know the e-mail address of the recipient. The Internet can also be used to transfer files between any two people or computers. The Internet also creates new communities of individuals, belonging to newsgroups where information is shared between people with similar interests, even though individuals could be geographically dispersed. Letters and files can be posted to newsgroups, where others can share them.

Internet is the world's largest computer network, the network of networks, scattered all over the world. It was created nearly 25 years ago as a project for the U.S. Department of Defense. Its goal was to create a method for widely separated computers to transfer data efficiently even in the event of a nuclear attack. From a handful of computer and users in the 1960s, today the Internet has grown to thousands of regional networks that can connect millions of users. Any single individual, company, or country does not own this global network.

How Internet works

Now One of the greatest things about the Internet is that nobody really owns it. It is a global collection of networks, both big and small. These networks connect together in many different ways to form the single entity that we know as the Internet. In fact, the very name comes from this idea of interconnected networks.

The Internet backbone is made up of many large networks which interconnect with each other. These large networks are known as Network Service Providers or NSPs. Some of the large NSPs are UUNet, CerfNet, IBM, BBN Planet, SprintNet, PSINet, as well as others. These networks peer with each other to exchange packet traffic. Each NSP is required to connect to three Network Access Points or NAPs. At the NAPs, packet traffic may jump from one NSP's backbone to another NSP's backbone. NSPs also interconnect at Metropolitan Area Exchanges or MAEs. MAEs serve the same purpose as the NAPs but are privately owned. NAPs were the original Internet interconnect points. Both NAPs and MAEs are referred to as Internet Exchange Points or IXs. NSPs also sell bandwidth to smaller networks, such as ISPs and smaller bandwidth providers. Below is a picture showing this hierarchical infrastructure.

When you connect computers together, you get a "network" which allows computers to "talk" to each other. This communication was originally part of the "operating system" of a computer. The Internet originally arose as a bunch of UNIX-based (UNIX is an operating system) computers linked together, so a lot of the terms on the Internet have their origins in the UNIX world. This means a lot of weird cryptic terms or acronyms are used (words made up from initial letters of longer words). The standard for communicating on the Internet is called "TCP/IP" (pronounced as TCPIP without the '/') which is short for Transmission Control Protocol/Internet Protocol.

The key concept in TCP/IP is that every computer has to know or can figure out where all other computers are on the network, and can send data by the quickest route, even if part of the route is down. The reason the route is down might include a computer is shut down or a phone line disconnected or in repair. This is done by maintaining indexes of all IP addresses in a domain at multiple servers strategically spread around the country, so that messages are quickly routed along the fastest path.

TCP/IP transfers information in small chunks called "packets." Each packet includes the following information: the computer (or last few computers) the data came from, the computer to which it is headed, the data itself, and error-checking information (to ensure that the individual packet was accurately and completely sent and received). The elegance of TCP/IP is that a large file can be broken into multiple packets, each sent over different paths in the network. These packets then re-assembled at the other end into one file and saved on the destination computer.

To access the Internet you need an Internet Service Provider or "ISP". The ISP is connected to the Internet "backbone" which is the permanent cabling of the Internet. This backbone may consist of copper wire, fiber optic cable, microwave, and even satellite connections between any two points. To you it doesn't matter – the Internet's TCP/IP works this out for you. You can connect to the Internet in one of two basic ways, dialing into an Internet Service Provider's computer, or with a direct connection to an Internet Service Provider. The difference is mainly in the speed and cost.

The previous figure gives a pictorial representation of how Internet works. You want to access a web site that is hosted on a server somewhere in the world (say USA) and you want to access the information from India. You connect (using a computer and modem - Dial up access) to your local Internet Access Provider, then you type in the address of your site. Your request is sent form the local ISP's server through the different computers in the network (Internet backbone) till it reaches the server where you have hosted your site. It is like a letter traveling though the various postal networks and reaching the addressee’s place. Then the information stored on the web site that you are trying to access is sent back to your computer so that you can access it.