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How does the internet work?

I don’t actually get how the internet works? How are the signals/messages/data sent from one place to another? And where is all this information actually stored? So if you have a home page for any business, where is the information…. in some big computer in the sky?

Louisa Draper from London (age 25-34)

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2 Responses

  1. There are two parts for site on internet – a server which is just a fancy name for a computer where all the pages and data are stored and the client which is the browser on your computer.

    Between your browser and the server there is a lot of hardware (routers and switches) and wires that physically routing the requests to and from the server and your computer.

    Each server has a unique address – we know this as the URL for example http://bbc.co.uk and the http in that address tells the server to use the http protocol to communicate with the client/browser. The http protocol is just like an agreed language for the server and client to communicate via. It is what send the pages and images over the wires as binary data.

    Because the server address is unique your client can ask the server for a web page containing pictures. When it does so it also tacks on its unique address so that the server knows where to send the data back to – this address is known as an Internet Protocol or IP address – but it is useful to think of it like a phone number.

    Your browser says give me the home page the server gets the request – knows what the home page is and encodes it for sending and then sends all the data back to the client via the IP address.

    The client gets the data – decodes it because it knows the language http and then displays it as data on the screen.

    Every site has at least one server and big sites like Google can have thousands. These servers aren’t in the sky but in big warehouses known as data centres which have connections to the wires of the internet.

    The data is stored on these server computers just on a normal hard as on a home computer. So the internet is stored on millions of servers all over the world.

  2. The fundamental thing about the Internet is that it doesn’t exist as a single network, but was actually designed as a “network of networks” with an agreed set of standards for communication. As long as any company’s network conforms to these agreed standards and has somewhere they can “plug into”, their network can be part of the Internet.

    Today there are thousands of worldwide companies plugging into the “Internet”. Some of them plug in via satellite, others by undersea cables. Internet Service Providers (ISP’s) allow you to plug in to their networks (and hence the “Internet”) via telephone lines.

    Your computer will send and receive “packets” of data across the Internet. These are fixed-size bundles of data such as email, web pages and video, for example. If an email or web page transfer is too large for one “packet” of data, the information is split up into several and these are sent separately. Each “packet” is stored within a data “envelope” which has written on it what type of information it is, where it is going and where it came from.

    Using the agreed communication standards, the packets are sent from one computer network to another along the shortest routes possible. Computers along the way decide what these short routes are (they are called “routers”). As Tim Jones says, every computer or connected device on the Internet has a unique address, and these intermediate routers have a general idea of where all the millions of connected devices are (they are very complex and expensive computers!). It’s likely that each packet will take only a few milliseconds to travel from sender to receiver even if they are located across the world from each other, and have to travel over dozens of company networks!

    The computer receiving the data packets is able to “reconstruct” the original message or web page from the packets. Because of the agreed Internet standards, if any packet gets lost or has errors during transmission it is requested again. This all happens seamlessly and it’s unlikely you would ever know of this clever mechanism usually.

    We usually classify computers either as receivers of information or senders. The former are called “clients” in computer jargon and the latter “servers”. When you request a webpage you are simply contacting a computer somewhere asking for a particular piece of information. Just like in a library, this information is looked up and returned to you. Just like your own computer, the information is stored either in memory or on hard disk storage on the server. It’s likely the server will contain some sort of index or table of contents to allow it to retrieve and send this information to you quickly.

    As Tim Jones says, these server computers are often stored in big buildings called “data centres” run by companies with very fast communication mechanisms, but they don’t have to be. They could be stored in cupboards under the stairs or in weather stations at the south pole. The clever routers on the networks make the actual physical location of the computers less relevant to you: it might as well be a big computer in the sky!

    There are a few other things about the Internet worth investigating I haven’t mentioned here: for example, how internet domain names work in relation to the Internet standards. There is a book I have read which explains the origins of the modern Internet in an entertaining and informative manner called “Where the Wizards Stay Up Late” by Katie Hafner and Matthew Lyon. Although it’s a few years out-of-date now (which is ancient in Internet time!) it is a worthwhile read.

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