Domain Name System is like a telephone directory for the Internet, which provides the IP addresses of all the registered computer hosts. Every computer has a unique number, called IP Address which is essential to establish a connection between the server and the client while sending an email or accessing a website.
Whenever an inquiry is to be made, you just type “www.google.com” on your browser’s address bar, and your computer will make use of the DNS server to fetch the IP address of Google’s server. As the IP address is obtained, your computer will establish a connection with the server and the home page of Google comes up on your screen, ready to search your inquiry.
As it is just not possible to remember the mobile number of every person you know, similarly, IP address of every website cannot be remembered, therefore, every website has been given a name. You type the name of the website on the address bar of your browser and the DNS server locates and makes a contact to bring the website in front of you.
Please note that you can even load a website by directly typing its IP address instead of its domain name in the browser’s address bar if you have it, however this would be a very cumbersome process.
The Domain Name System is a database that resides on multiple computers on the Internet in a hierarchical manner.
These servers have a complete database of higher level domain names and their corresponding IP addresses. Presently, there are 13 root servers distributed globally, that are named using the letters A, B, C and so on, up to M.
Local servers represent the most lower level DNS servers. These are owned and maintained by many business organizations and Internet Service providers. These local servers locate and update the frequently used domain names with their corresponding IP addresses. This job is done on a regular basis.
Whenever you type a URL in your browser’s address bar, your computer requests the local name server to locate the respective IP address. If found, then the response is returned and the home page of the website is loaded in front of you. Otherwise, the request goes to next higher server. This process continues until the corresponding domain name is located with its matching IP address. The response comes back in reverse order to your computer.
In a very rare case, the response reaches the root name servers.
Whenever a new domain name comes up or an existing one is updated, it is the responsibility of the domain registrar to publish its details and register it with the root name server. This information must get updated on all the major DNS servers so that the domain name can be located from all parts of the globe. This is called DNS propagation and the whole process takes about 24 to 72 hours to get completed.
There is no hard and fast rule of updating DNS servers. It normally depends on the organization that maintains the server. Some do it on an hourly basis while some do it daily.
DNS servers can cache the inquiries they receive for a set amount of time. This allows them to respond more quickly the next time a request for the same inquiry comes in. This lessens the load on the server and increases the efficiency of the website.