Wednesday, January 21, 2009

How Internet works?

Internet: How it works?

The Internet has created a revolution in the way in which people and businesses communicate. The Internet is a worldwide collection of computer networks that are connected by other computers and very powerful data transmission systems.

We can access the information on the Internet only when we are connected to the Internet. We talk about ‘surfing the Web’. What is meant here is that the user is using a software tool, known as a Web browser, to follow hypertext links (those you click around to navigate to different pages of a website) around various web sites, which have been created and set up by individuals and corporations all around the world. There are two main browsers that are currently popular. These are Mozilla FireFox and Microsoft Internet Explorer. You can use electronic mail (e-mail), file transfer (ftp), newsgroups (UseNet), World Wide Web (WWW), e-Commerce and many other facilities using Internet with the browser and some other application software.

In addition to the browsers, the success of the Web has been enhanced by the availability of ‘search engines’. These are software packages which search the entire World Wide Web (WWW) for the use of keywords and phrases, to enable the user to find information about a particular topic without knowing which Web site to begin looking at. The current most popular of these search engines are: Google and Yahoo Search Engines.

It might be interesting to know how this facilities and internet as a whole work for you all day night. Let’s try to explore it here.

The functional success of the Internet is due to the development of and adherence to a set of standards and protocols on a world wide basis. The standards are on Addressing of individual computers to enable identification of users and correct routing (passing message back/forth) of network messages, Communication protocols to enable the computers to communicate with each irrespective of their make and Programming & file standards to enable information to be readable by many different types or software.

IP Address
The computers which connect to the Internet are known as hosts (client). Each host has a unique address, known as an IP (Internet Protocol) address. These addresses have the form of a.b.c.d where a, b, c and d are numbers between 0 and 255. These addresses are used to label the packets that contain messages and the information that is being transported. By appending the target address (and some other data) to a packet, it is possible to determine which host should receive the packet.

Protocols
Protocols are set of rules. Protocols are needed to ensure that computers can communicate with each other irrespective of their make. They define the rules of the language that is used to enable this communication.

Internet Protocol (IP) – which defines the rules that determine how packets (data is sent/received through internet as packets) are transferred from one host to another. The Transmission Control Protocol (TCP) – operates on top of IP to produce a reliable transfer of these packets and guarantees that the packets will be delivered in a specific sequence. When IP and TCP are used in conjunction, they are referred to as TCP/IP. Other protocols include User Datagram Protocol (UDP) which operates on top of IP instead of TCP, Domain Name System (DNS) – resolves or translates textual names (eg. www.google.com) to the corresponding numerical IP address of the web server hosting the web site File Transfer Protocol, or FTP is an Internet protocol designed to make the copying of files from one computer to another convenient and efficient.

File Standards
The information is stored in files and for the purpose of the internet it should be able to provide information stored in files to the users. The files are transmitted over and above the protocols described above on internet. There are several file standards that have evolved to become crucial to the successful operation of the Internet

The general Information File Format in internet includes, HyperText Markup Language (HTML). A request to see the content of a web site (eg. www.google.com) is responded with the stream of HTML data. Which consists of text and tags and tells web browsers (like Mozilla FireFox) how to display the text. It can also include embedded graphics, audio and video to bring a Web page ‘to life’. Hypertext files are transmitted around the Internet using the Hypertext Transfer Protocol (HTTP). Another popular file format for sharing information on the World Wide Web, intranets, and elsewhere is eXtensible Markup(XML):

The graphical information is transferred in Graphics File Format like Graphics Interchange Format (GIF) and Joint Photographic Experts Group (JPEG: pronounced jay-peg ). The video and audio can be found over the internet in MPEG – Motion Picture Expert Group file format. When it is felt necessary to ‘fix’ the format of what is displayed the Adobe Acrobat PDF (Portable Document Format) is used. Macromedia Shockwave (SWF) is a proprietary format for multimedia content distribution over the Internet. It handles animation of various kinds, text and audio.

Programming Tools
There are several programming standards like Java (JSP), Php, MySQL, JavaScript, AJAX etc. which provide and easier way of developing internet (web) application and web sites.

Now following these standard sets of rules and addressing, whenever you type a address like http://www.google.com (the DNS converts it to the numerical IP which is of the server) the web browser sends HTTP request (Hyper Text Transfer Protocol) on the numerical address of the Google web server(at US) which has the information you requested and the server responds by sending you back the requested data, the data is in standard web format (HTML or XHTML) which is then displayed by the web browser in a formatted & readable form(managing the file formats) that you understand (eg. the search box and the buttons in case you typed Google’s web site in the address bar of the web browser.) The IP, TCP, FTP, DNS, HTTP, other protocols and network sub-systems all work for the inter-communication of the hosts (computers) in the networks of the internet. Every click on the links on web sites responds in the same manner.

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