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Camp Internet
How Does the Internet Work? The Internet is a worldwide network of computers connected together by anything from a single telephone wire to a huge bundle of fibre optic cables. When you connect to your Internet service provider (ISP) you become part of this network. Your computer can 'talk' - transmit and receive data - to any other computer on the network. This network - the inter'Net' - is made up of three types of computer: clients - your home or work computers, set up mainly to receive information servers - powerful computers you access to view webpages, retrieve email messages or retrieve data files routers - mapping computers that make sure the data finds its way to the right place What happens when you access a webpage? At the end of 2001, there were around 38.5 million active websites around the world. When you type in a website address or URL (Uniform Resource Locator) your 'client' computer contacts your ISP. Router computers then send your request over the network. They find the best available route to where the webpage is stored, or 'hosted' on a server computer. The information on the website is then sent back to your computer, over the Internet again, for you to read. The path taken to and from the site can often lead all over the world, even if the site you're looking at is hosted in the next road to you. What is narrowband? Accessing the Internet using a modem and a normal phone line is called 'narrowband'. Here, the data travels along a phone line. The amount of space or 'bandwidth' that's available on a line originally designed to carry voice signals is limited, hence the term 'narrow'. Broadband uses lines designed to carry much more information. Imagine water running through a pipe. A narrow pipe will deliver a slower stream than a broad pipe. Similarly, narrowband delivers information at a slower rate than broadband. How do modems work? Phone lines were originally meant to transmit voice information. So for webpages or emails to be sent down a phone line, the computer code has to be changed into sound. This is where the modem comes in. When dialling up the Net that strange screeching noise you hear is the sending modem. It alters the frequency of the computer data, or 'modulates' it, so it can be sent down the phone line as sound. The receiving modem changes the sound back, 'demodulates' it, into computer code. The name modem is a contraction of 'modulate-demodulate'. Once your computer has successfully connected to the Internet there is no need for you to hear what is going on so the speaker on your modem mutes itself. When the web starts to crawl Modems have been round since the 1960s. Now they've reached the limit to how fast they can stuff data down a phone line - 56,000,000 bits a second (56Kbps). A 'bit' is a unit of computer information. To give you an idea of how much this is, the letter 'A' takes up 8 bits. Unfortunately most phone lines aren't perfect. Add to this the slowing influence of: phone extensions multiple phone plugs Net congestion data-heavy downloads (such as pictures and animations) This is why web surfing can often turn into web crawling.