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Useful for:

  • People who are not concerned about the technicalities of internet addressing but want to know more at a non-technical level.

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  • People who want a detailed technical explanation of internet addressing

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There are billions of web pages on the internet, in order to access all of these there has to be some way of giving each one a unique address so your browser can find it.  Because of this computers need to be able to run calculations on addresses. We use text to recognise a web page, for example “” but computers can’t  run calculations on text, they need numbers.

So when you type a URL into the address bar of your browser and click go, the browser fires off a request to have this text translated into a number that is called an IP address, an example of one of these is Every publicly visible web server in the world has an IP address that is uniquely addressable. Many web servers host multiple web sites. The system that supplies the IP address is called the Domain Name System (DNS) which uses a chain of Name Servers that communicate with each other. Your Internet Connection Provider (ISP) maintains at least two name servers, often more. Your browser will contact one of these and based on the type of domain you are requesting (for example .com or will be able to find the name server that can list the correct IP address of the website, this is often called the authoritative name server. This then allows the browser to directly request the website from the correct web server and here you are!

It’s worth noting one problem that can arise with this process. In order to cut down on processing and Internet activity Name Servers cache results the first time they check out an address. This means that if the get the same request again they can provide the IP address without having to fire off another chain of requests to the authoritative name server. If the website has moved address once an address has been cached then of course your browser will be given the wrong address and you will get a message saying you can’t access the site. If this happens to you then first of a try clearing the history in your browser and the cache on your computers as they cache results too. If that doesn’t do any good then you will have to wait until your ISP‘s cache has cleared. Usually this is no more than 24 hour. If you need access urgently then use another computer that is connected to the internet using a different ISP to yours.

247 · June 16, 2009 · Everyday, Guides · Tags: , , , · [Print]

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