What is an internet?

An internet is a series of connected computers ('hosts') and networks of computers. There are usually several hosts or networks that form the 'backbone' of the internet. These networks will transfer ('route') the majority of traffic that needs to reach a distant host, and can commonly process gigabits of data every second (1,000,000 kilobits of data compared to the 56 kilobits that most modems can transfer). As hosts and networks become further from this backbone, the less traffic they are required to process.

What is the Internet?
The Internet (note the capital I) is the largest connected network of computers in the world. When you connect to the Internet (like you are now!), your computer becomes part of it.

How does the Internet work?
Every computer that is connected to the Internet has its own unique IP (Internet Protocol) address. Data is transmitted through the Internet in fragments called 'packets', using a collection of 'protocols' called the TCP/IP (Transmission Control Protocol / Internet Protocol) protocols. Every packet that is sent and received is wrapped in one of these protocols and is given a header that contains essential information such as the source IP address, destination IP address and packet length, to name a few. The packet MUST contain a destination IP address to be sent to a remote computer.

These packets are sent over the Internet through what are called 'routers'. Each router has a list of every possible destination, grouped into large segments, and an associated address for the router that is the next step in the path to the destination address. These lists are updated by the routers frequently (using a 'routing protocol') to ensure that the path is as accurate and short as possible.

What is the World Wide Web?
The World Wide Web (WWW) is the name given to an incredibly large collection of documents that can be found residing on the Internet. These documents, called 'web pages', are stored on 'servers' that will send pages out when requested using another protocol called HTTP (HyperText Transfer Protocol). The pages are written in a special language called HTML (HyperText Markup Language) which is translated into a readable document by your web browser. The WWW also contains collections of other files that can be transferred from computer to computer using either the HTTP or FTP (File Transfer Protocol) protocols.

What is a URL?
URL is short for 'Universal Resource Locator'. It contains the name of the document, the name of the computer it resides on and the protocol used to transfer it. URLs have the following format :

protocol://hostname/path/filename

The protocol can be one of http, ftp or telnet. The hostname is the name of the computer in a format called 'fully qualified domain name'. The path and filename are the name and location of the document being requested.

For example: http://www.aph.gov.au/senate/main.htm

Breaking this down we see that the file will be transferred using the HTTP protocol, the hostname is www.aph.gov.au, and the file, called main.htm, is located in the senate directory. The hostname can be further broken down as follows:
www - the name of the computer
aph - the name of the remote network or site, or 'second level domain name'
gov - the 'top level domain name', usually states the type of network or site
au - country code, not always present

The top level domain name can be one of many codes such as .org (organisation), .com (commercial site), .net (network) and .gov (government). These codes can vary as more are being introduced to accommodate the growing number of computers connected to the Internet.

How does my computer know the IP address of remote computers?
What are these 'DNS' settings? As mentioned previously, for data to be transmitted over the Internet, a destination IP address must be specified. When a computer or domain name is supplied, in the form of a URL or otherwise, the name must be 'resolved' to an IP address before any data can be transmitted. This is done automatically by your computer by sending a request to a specially set up computer called a 'Domain Name Server' (DNS). These DNS servers contain listings of address resolutions for its own domain. DNS servers are connected in a hierarchical manner. If the name being resolved is outside the domain of the server, the request will be forwarded to a DNS server higher in the hierarchy.

contributed by: Dale Anderson