The Internet is a worldwide network of networks. This was the next step of ARPANET and NSFNET. It can be defined as a global network of over million of smaller heterogeneous computer networks consists of a set of national, regional and private. The internet is the common language whereby dissimilar computers with various operating systems, are able to communicate with each other, using a standard set of protocols.
There is nobody who owns Internet or no company called the “Internet”. Think of the Internet as the Universe and your computer as a planet, which is a part of that Universe.
The protocol used by the Internet for getting messages from one machine to another is called the Internet Protocol (IP). The Internet Protocol is a network protocol, and its job is to manage the logistics of getting a message from the sending machine to the receiving machine.
Messages delivered by the Internet protocol are called packets, and they are quite small, fifteen hundred or fewer bytes. Since this is much smaller than many of the messages and files that are transmitted over the Internet, it is common for a transmission to require multiple packets.
Collecting related packets, putting them in the proper order, and verifying that none are garbled are all tasks outside the scope of the Internet Protocol itself. The Internet has two transport protocols that deal with the integrity network transmissions (particularly those that span multiple packets), the Transmission Control Protocol (TCP) and the User Datagram Protocol.
If you're like most new Internet users, the first thing you probably want to know is what the Internet will enable you to do. There's a basic chicken-and-egg problem here: it's difficult to explain what you can do on the Internet without first explaining some things about how the internet works and how you get connected to it. On the other hand, if you don’t know what you can do with the internet, why should you bother to get connected to it in the first place?
Some people compare the internet to a highway system. To others the networks and connections that make up the Internet seem more like a cloud. Describing what you do on the Internet is no easier. To say that the Internet provides information access and communication does not begin to describe the breadth of what it offers.
The Internet is the world's largest computer network, a distinction it has earned by virtue of being a "network of networks." The Internet is an outgrowth of a network (ARPANET) established roughly a quarter-century ago to meet the needs of researchers working in the defense industry in the United States and a few of their colleagues in other countries.
The ARPANET grew slowly, from a handful of computers in 1971 to more than 1000 in 1984. Working with the ARPANET researchers came to regard high-speed computer networks as an indispensable tool for academic research in all fields, and in 1986 the US National Science Foundation established NSFNET to provide network connections to more research institutions and improve international network cooperation. in 1987, the Internet served more than 10,000 computers. By 1989 the network had grown to more than 100,000.
In 1990, the ARPANET ceased to exist, but the Internet continued to grow: 1 million computers in 1992, 2 million in 1993.The Internet has now spilled out of the academic world to offer both information access and a fast, inexpensive means of communication to the general public. It will be the next public utility; It is the reality behind the "Information Superhighway" buzzword.
The Internet most basic component is a physical network The Internet behaves as though all the computers in all the participating networks were joined by a giant cable. In fact, all the computers on the Internet are joined by connectors-not by one cable, but by thousands. All these connectors are coordinated to work like a single cable linking all the computers on the Internet. Many features of the Internet can be attributed directly to this physical network, the cabling that holds it all together.
Evolution of Internet
• The origin of Internet can be traced to a U.S. Department of Defense (DoD) organization called Advanced Research Projects Agency (ARPA).
• ARPA developed a four node packet switching. network called ARPANET in 1969. The network was intended to support the military research on fault tolerant computer networks. DoD wanted to ensure a reliable data transfer in the event of a nuclear war, even if parts of the network has been destroyed.
• As the years pass by, the network grew in size and by 1st January 1983, the ARPANET no longer remained an experimental network but its control was passed over to Defense Communications Agency (DCA).
• The network then became available for the academic research, government employee and contractors.
• .It was not until 1986, however that the dramatic growth of the Internet began. At this time, the National Science Foundation (NSF) which formed the National Science Foundation Network (NSFNET) linked five of its regional super-computer centers together to provide a national high speed backbone network across the United Sates.
• The world's fastest and most powerful computers were made available to a academic and scientific community.
• In 1990 the ARPANET was officially decommissioned. Some of the major networks contributing to the growth of the internet are as follows:
• USENET (User's network)
• CSNET (Computer science network)
• BITNET (Because it's time network)
• NSFNET (National science foundation network)
• WWW (World Wide Web)
• NREN (National research and education network)
• It is said that the Internet is growing at a rate of 20% per month. The data speeds have gone up considerably, which makes the access even faster.
• The event which started as a military assistance program is now largely a private enterprise.
• To understand how the Internet works, imagine complex network of roads. It consists of superhighways, highways, to the small roads on the countryside, all connected to each other in one way or the other. The nature of the internet is much similar to this.
• The high speed and powerful super computers connected to the Internet is the backbone of the system.
• The data that is being moved by these supercomputers is a few million bits per second.
• The regional networks are then connected to these supercomputers. The small computer network and individual users are then connected to this regional network.
• The data and information available on the Internet is increasing every day because every user can contribute it.
• Due to this the entire net will never crash down. Even if a part of it closes down the remaining network keeps working.
• There is no central computer to control the internet. There is no central body which governs the Internet structure, though volunteer groups of individuals have set some standards for Internet technologies. No particular person, group or organization owns the Internet.
Services on the Internet
The services that are available on the Internet can be classified into two categories:
• Communication services (electronic mail (e-mail))
• Information retrieval services ( Web (pages with links and multimedia content of its Web sites))
They can be further classified as shown in Fig.
• The person to person service includes E-MAIL. This is the most popular service and the most of the Internet traffic corresponds to the E-mail.
• The person to group service includes on line discussions between a user and many other participants from around the globe. A user can choose his topic of discussion from a list of more than 25, 000 topics.
• The fast spreading popularity of the Internet is basically due to the information retrieval services.
(i) The World Wide Web (www), which is world's largest and ever-growing data base.
(ii) FTP or file transfer protocol, which allows remote accessing to the tiles which contain programs, technical handouts, reports etc.
(iii) Telnet or remote login to commercial services.
Applications of Internet
• Traditionally the internet has the following applications.
3) Remote login
4) File transfer
5) World wide web (www).