INTERNET Sujata Rao

What is INTERNET? The Internet, sometimes called simply "the Net," is a worldwide system of computer networks. A network of networks in which users at any one computer can, if they have permission, get information from any other computer (and sometimes talk directly to users at other computers).

History It was conceived by the Advanced Research Projects Agency (ARPA) of the U.S. government in It was first known as the ARPANet.ARPANet The original aim was to create a network that would allow users of a research computer at one university to "talk to" research computers at other universities. A side benefit of ARPANet's design was that because messages could be routed or rerouted in more than one direction the network could continue to function even if parts of it were destroyed in the event of a military attack or other disaster.

Today’s Internet Today, the Internet is a public, cooperative and self- sustaining facility accessible to hundreds of millions of people worldwide. Physically, the Internet uses a portion of the total resources of the currently existing public telecommunication networks. Technically, what distinguishes the Internet is its use of a set of protocols called TCP/IP (for Transmission Control Protocol/Internet Protocol).TCP/IP Two recent adaptations of Internet technology, the intranet and the extranet, also make use of the TCP/IP protocol.intranetextranet

Internet Use For most Internet users, electronic mail ( ) practically replaced the postal service for short written transactions. People communicate over the Internet in a number of other ways including Internet Relay Chat (IRC), Internet telephony, instant messaging, video chat or social media. IRCInternet telephonyinstant messagingsocial media The most widely used part of the Internet is the World Wide Web (often abbreviated "WWW" or called "the Web").World Wide Web

Its outstanding feature is hypertext, a method of instant cross-referencing. In most Web sites, certain words or phrases appear in text of a different color than the rest; often this text is also underlined. When you select one of these words or phrases, you will be transferred to the site or page that is relevant to this word or phrase. Sometimes there are buttons, images, or portions of images that are "clickable." If you move the pointer over a spot on a Web site and the pointer changes into a hand, this indicates that you can click and be transferred to another site.hypertext

The Web BROWSER Web browsing is done with a Web browser, the most popular of which areChrome, Firefox and Internet Explorer.browserChromeFirefoxInternet Explorer The appearance of a particular Web site may vary slightly depending on the browser you use. Later versions of a particular browser are able to render more animation, virtual reality, sound, and music files, than earlier versions.virtual reality We have access to billions of pages of information.

The IP Address The Internet has continued to grow and evolve over the years of its existence. IPv6, for example, was designed to anticipate enormous future expansion in the number of available IP addresses. IPv6IP addresses In a related development, the Internet of Things (IoT) is the growing environment in which almost any entity or object can be provided with a unique identifier and the ability to transfer data automatically over the Internet.IoTunique identifier

What is an IP address  A way to identify machines on a network  A unique identifier  Used to connect to another computer  Allows transfers of files and Usage Structure  IP addresses consist of four sections  Each section can range from 0 to 255  Written, for example,

IP structure  Class A begins 1 to 126 for Government  Class B begins 128 to 191 for companies  Class C begins 192 to 223 for small companies  Class D are reserved for multicasting  Class E are reserved for future use

DNS A lookup mechanism for translating objects into other objects A globally distributed, loosely coherent, scalable, reliable, dynamic database Comprised of three components n A “name space” n Servers making that name space available n Resolvers (clients) which query the servers about the name space

February 2003slideset DNS Features: Global Distribution Data is maintained locally, but retrievable globally – No single computer has all DNS data DNS lookups can be performed by any device Remote DNS data is locally cachable to improve performance

Concept: Domains Domains are “namespaces” Everything below.com is in the com domain. Everything below ripe.net is in the ripe.net domain and in the net domain. net domain com domain ripe.net domain net com ripe www edu isi tislabs disi ws1 ws2 ftp sun moon google

Concept: Name Servers authoritative name server Give authoritative answers for one or more zones. The master server normally loads the data from a zone file A slave server normally replicates the data from the master via a zone transfer master slave

IP Address

How the Internet works: How the web gets connected & Works – works/index.php Ip Address & its working - For circuit switching for network packets working