DNS Lookup
Without DNS (domain name system) we would not be able to use our favourite websites such as Facebook and Twitter, nor would we be able to check out email accounts. The reason for this is because DNS enables the internet to work. So you may be wondering what DNS actually is and it is the process by which domain names are converted into an IP address that our machines can read. DNS lookup is the process by which you can find out what this IP address is.
You may be wondering what the IP address is and obviously you will need to know this before you can even begin to understand DNS lookup and how it works. An IP address is what computers use to communicate over the internet and it is a four block number and each block can range from 0 to 255. An example of an IP address would be 129.125.241.099. The IP address of a computer is what it uses in order to identify itself over the internet. A router cannot understand the name of a website or computer such as www.me.com but it can understand the IP address that DNS will convert the name to. DNS lookup is when you have the website name but need to find the IP address.
So what does DNS lookup actually do? Well every time that you type a URL into the browser, the computer will have to look up the IP address for the domain name that you have typed. The computer searches the primary DNS server to find the IP address for the domain name. Once it has found the IP address for the domain name that you have entered, it will be able to display the relevant website on your machine.
When a DNS lookup is performed, your machine will query its primary server but if your primary server cannot find the IP address then it will go through a chain of servers until it does find what it is looking for. The next server in the chain after the primary server is the ISP DNS server. This process will carry on with subsequent servers being queried until the root server is queried. The root server always has the IP address required because these servers hold the IP address for every single domain name.
In order to speed up the process, most DNS servers will hold a store of the most recent DNS records so that a further DNS lookup will not be required again if you want to search for the same website. This saves the root servers being queried again and again. DNS lookup is a complicated process made simply by technology. Most of us do not have a clue what goes on inside our computers in order to make a website visible on our screens.