HOW DOES INTERNET WORK

 

Internet is a global system of interconnected computer networks that use the standard Internet protocol suite (TCP/IP) to link several billion devices worldwide. It is a networks of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services.

 

Internet is a global network of computers each computer connected to the Internet must have a unique address. Internet addresses are in the form nnn.nnn.nnn.nnn where nnn must be a number from 0 - 255. This address is known as an IP address.

The picture below illustrates two computers connected to the Internet; our computer with IP address 1.2.3.4 and another computer with IP address 5.6.7.8. The Internet is represented as an abstract object in-between.

Diagram 1

 

If we connect to the Internet through an Internet Service Provider (ISP), we are usually assigned a temporary IP address for the duration of our dial-in session. If we connect to the Internet from a local area network (LAN) our computer might have a permanent IP address or it might obtain a temporary one from a DHCP (Dynamic Host Configuration Protocol) server. In any case, if we are connected to the Internet, our computer has a unique IP address.

Servers are where most of the information on the internet "lives". These are specialised computers which store information, share information with other servers, and make this information available to the general public.

Browsers are what people use to access the World Wide Web from any standard computer.

When we connect our computer to the internet, we are connecting to a special type of server which is provided and operated by our Internet Service Provider (ISP). The job of this "ISP Server" is to provide the link between our browser and the rest of the internet. A single ISP server handles the internet connections of many individual browsers - there may be thousands of other people connected to the same server that we are connected to right now.

 

The picture below show a slightly larger slice of the internet:

 

 

The ISP maintains a pool of modems for their dial-in customers. This is managed by some form of computer which controls data flow from the modem pool to a backbone or dedicated line router. This setup may be referred to as a port server, as it 'serves' access to the network. Billing and usage information is usually collected here as well.

After our packets traverse the phone network and  ISP's local equipment, they are routed onto the ISP's backbone or a backbone the ISP buys bandwidth from. From here the packets will usually journey through several routers and over several backbones, dedicated lines, and other networks until they find their destination.

 The information used to get packets to their destinations are contained in routing tables kept by each router connected to the Internet.

Routers are packet switches. A router is usually connected between networks to route packets between them. Each router knows about it's sub-networks and which IP addresses they use. 

INTERNET PROTOCOL

TCP/IP is the basic communication language or protocol of the Internet. It can also be used as a communications protocol in a private network (either an intranet or an extranet). When we are set up with direct access to the Internet, computer is provided with a copy of the TCP/IP program just as every other computer that we may send messages to or get information from also has a copy of TCP/IP.

TCP/IP is a two-layer program. The higher layer, Transmission Control Protocol, manages the assembling of a message or file into smaller packets that are transmitted over the Internet and received by a TCP layer that reassembles the packets into the original message. The lower layer, Internet Protocol, handles the address part of each packet so that it gets to the right destination. Each gateway computer on the network checks this address to see where to forward the message. Even though some packets from the same message are routed differently than others, they'll be reassembled at the destination.

 

 

 

 

http://www.mediacollege.com/internet/intro/thewww2.html

http://en.wikipedia.org/wiki/Internet

http://www.stanford.edu/class/msande91si/www-spr04/readings/week1/InternetWhitepaper.htm

http://searchnetworking.techtarget.com/definition/TCP-IP

Varun Singla 363/CO/11