DNS Concept

The Domain Name System (DNS) is one of the most essential parts of the Internet’s infrastructure. Every website in the internet have their own unique domain names which are resisted in some authorized servers. We use these names to call for particular resource website through the internet. Actually every devices (or services) in the internet has a unique IP address (work with numbers).

If anyone want to get that service they have to uses those IP addresses which is bounded to the device
or service. But all the human beans are familiar with the words like English but not numbers and also it is hard task to remember those numbers.

For example consider the URL “www.mrt.ac.lk” University of Moratuwa website. We can remember this name because it includes English terms. But associated IP for that domain name is 192.248.8.88.This is harder to remember than its name. This is the most important advantage of domain name concept. But there are lot more advantages which does not see by looking the surface of the DNS concept. Therefore below describe how actually DNS works and important of DNS.
 

 Step1: Suppose we request mrt.ac.lk website from the web browser. Then the browser search this
domain name in its cash. If it can find that domain name, browser exactly knows website IP address.
Otherwise it goes to step 2.

Step2: Then the computer looks is its local DNS cache, which stores information that the computer has recently retrieved. We can manually tell our computer to IP addresses for our known website. In
windows there is a host file which stored in path: C:\Windows\System32\drivers\etc.It includes websites and its IP addresses. This is the way our computer knows “localhost” command when we type in the browser.

If the computer doesn’t already know the answer, it needs to perform a DNS query to find out.
 
Step 3: Ask from Recursive DNS serverIf our computer can’t find the IP address of mrt.ac.lk website, then it ask from our ISP’s recursive DNS servers. Recursive DNS name servers are responsible for providing the proper IP address of the intended domain name to the requesting host. Recursive name servers are like the phone operator looking up a phone number from multiple phone books on behalf of the requesting party. If it can’t find that particular domain name in its content, it will go to 4th step.

Step 4: Ask From Root Name serversIf ISP’s recursive name server can’t find that domain name ,it request a dns query to root name servers.There are 13 registered root name servers in all over the world. Those root name servers act as a kind of telephone switchboard for DNS. They don’t know the answer, but they direct a query to step 5.

Step 5: Ask From Top Level Domain Servers
Root name servers read the end part of the domain name (if type google.com, then end will be .com)
and send to TLD serve. These TDL guided to find the quarry in their own or otherwise send the query to authoritative DNS servers. It will exactly know the domain name and read the IP address of particular domain name and respond back. This works as a chain.

When the web browser knows the IP address, associated with the domain name, then it directly request resources from that website.

These are for your  further undemanding 

• Already know DNS helps to remember website name without remember its IP address.

• If there does not exist a concept like DNS, we have to store all the domain names and related IP address in our Browser cash or OS. Then there will be waste lot of money.

• And also we do not know websites which are newly hosted and therefore we cannot get those resources.

• In modern days ecommerce websites are more popular among the Sri Lankan people also. If there does not exist DNS concept, this ecommerce concept also never come to the world.
  Because without knowing proper IP address of particular ecommerce website, anyone cannot
  access it.

• If there does not exist DNS concept, most of the time Internet will never popular in the world and there may not improve communication mechanisms such as LinkedIn, Facebook,
  twitter..etc.

• We can configure alternate DNS servers (on behalf of ISP DNS) like Open DNS and can block unwanted websites.