How an ISP works?

An Internet Service Provider (ISP), also called an Internet Access Provider, is a company that supplies individuals with access to the Internet. An ISP acts as an intermediary between a user's computer system and the Internet. The ISP feeds the small user's outbound information to the Internet, and also feeds inbound Internet traffic into the user's Internet connection. ISPs offer a wide variety of services. They generally charge their customers for Internet access depending on their usage needs and the level of service provided.

 Internet access is available from a wide range of companies, including telephone and cable companies, online services, large national ISPs, and small independent ISPs.

 

Types of ISPs:

1.Online services—such as America Online (AOL) and Microsoft Network (MSN)—are probably the easiest way for beginners to gain access to the Internet. It is usually very easy to set up an account with one of the major online services. In fact, many of these companies include access programs on new computers or offer free setup software in the mail. Computer users can establish an account and begin surfing the Internet with just a few clicks of a mouse. Unlike many other ISPs, the online services also offer a number of additional services to members, like discussion forums on various topics.

2.National ISPs,such as Earthlink and Mind Spring (USA) and BSNL ,Reliance and TATA (India) are large companies that offer Internet access in a broad geographical area. Compared to local ISPs, these companies tend to offer higher-speed connections and greater long-term stability. Many national providers also offer a broad range of services, including long-distance telephone service, web site hosting, and secure electronic transactions. They are generally a good choice for small businesses that want employees to be able to access the Internet while traveling. They may also be convenient for businesses that operate in several locations and wish to use the ISP for all locations.

3.Small, independent ISPs operate in many local or regional markets. These companies vary widely in size, stability, and quality of service. On the plus side, their access lines may be less busy than national ISPs. In addition, many smaller providers specialize in offering services to small businesses. Some of these ISPs may visit a small business customer's work site, evaluate the company's Internet access needs, and present different service packages. They may even assign a personal account representative to handle the small business's growing electronic needs.

How basically it all works?

You must remember that Internet is simply a network of networks. You must be familiar with these two terms to understand the whole thing..

1.Point of Presence (POP).- These are the points from where a given network can be accessed.

2. Network Access Points or NAPs.- These are the points through which different networks are interconnected.

When you connect to your ISP, you become part of their network. The ISP may then connect to a larger network and become part of their network.

Here's an example. Imagine that Company A is a large ISP. In each major city, Company A has a POP. The POP in each city is a rack full of modems that the ISP's customers dial into. Company A leases fibre optic lines from the phone company to connect the POPs together .

Imagine that Company B is a corporate ISP. Company B builds large buildings in major cities and corporations locate their Internet server machines in these buildings. Company B is such a large company that it runs its own fiber optic lines between its buildings so that they are all interconnected.In this arrangement, all of Company A's customers can talk to each other, and all of Company B's customers can talk to each other, but there is no way for Company A's customers and Company B's customers to intercommunicate. Therefore, Company A and Company B both agree to connect to NAPs in various cities, and traffic between the two companies flows between the networks at the NAPs.

In the real Internet, dozens of large Internet providers interconnect at NAPs in various cities, and trillions of bytes of data flow between the individual networks at these points.  

                                                                          The Internet is a collection of huge corporate networks that agree to all intercommunicate with each other at the NAPs. In this way, every computer on the Internet connects to every other. 

Routers:

The routers determine where to send information from one computer to another. Routers are specialized computers that send your messages and those of every other Internet user speeding to their destinations along thousands of pathways. A router has two separate, but related, jobs:

• It ensures that information doesn't go where it's not needed. This is crucial for keeping large volumes of data from clogging the connections of "innocent bystanders."
• It makes sure that information does make it to the intended destination.

In performing these two jobs, a router is extremely useful in dealing with two separate computer networks. It joins the two networks, passing information from one to the other. It also protects the networks from one another, preventing the traffic on one from unnecessarily spilling over to the other. Regardless of how many networks are attached, the basic operation and function of the router remains the same. Since the Internet is one huge network made up of tens of thousands of smaller networks, its use of routers is an absolute necessity

Internet Backbone:

The National Science Foundation (NSF) created the first high-speed backbone in 1987. Called NSFNET, it was a T1Line  that connected 170 smaller networks together and operated at 1.544 Mbps . IBM, MCI and Merit worked with NSF to create the backbone and developed a T3 (45 Mbps) backbone the following year. Backbones are typically fiber optic trunk lines. The trunk line has multiple fiber optic cables combined together to increase the capacity. Fiber optic cables are designated OC for optical carrier, such as OC-3, OC-12 or OC-48. An OC-3 line is capable of transmitting 155 Mbps while an OC-48 can transmit 2,488 Mbps (2.488 Gbps). Compare that to a typical 56K modem transmitting 56,000 bps and you see just how fast a modern backbone is.

Today there are many companies that operate their own high-capacity backbones, and all of them interconnect at various NAPs around the world. In this way, everyone on the Internet, no matter where they are and what company they use, is able to talk to everyone else on the planet. The entire Internet is a gigantic, sprawling agreement between companies to intercommunicate freely.

Difference between Internet and WWW: 

What is The Internet?
The internet is a massive network of networks, a networking infrastructure. It connects millions of computers together globally, forming a network in which any computer can communicate with any other computer as long as they are both connected to the Internet. Information that travels over the Internet does so via a variety of languages known as protocols.

What is The Web (World Wide Web)?
The World Wide Web or simply Web, is a way of accessing information over the medium of the Internet. It is an information-sharing model that is built on top of the Internet. The Web uses the HTTP protocol, only one of the languages spoken over the Internet, to transmit data. Web services, which use HTTP to allow applications to communicate in order to exchange business logic, use the the Web to share information. The Web also utilizes browsers, such as Internet Explorer or Firefox, to access Web documents called Web Pages that are linked to each other via hperlinks. Web documents also contain graphics, sounds, text and video. 

Who Owns the Internet? No one actually owns the Internet, and no single person or organization controls the Internet in its entirety. More of a concept than an actual tangible entity, the Internet relies on a physical infrastructure that connects networks to other networks. There are many organizations, corporations, governments, schools, private citizens and service providers that all own pieces of the infrastructure, but there is no one body that owns it all. There are, however, organizations that oversee and standardize what happens on the Internet and assign IP addresses and Domain names, such as the National Science Foundation, the Internet Engineering Task Force,ICANN, InterNIC and the Internet Architecture Board. 
 

What is an IP address?
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