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Dec 10

Explained DNS, Simple and Easy

DNS

What is DNS?

DNS stands for “Domain Name System” which converts human readable domain names into IP addresses. For example, the web page like www.google.com is translated to IP address 173.194.39.78. The DNS system in simple terms is the phone book of the internet where it lists the domain names with their corresponding IP addresses.

History of DNS

When the Internet was still in its infancy thirty years back, if you wanted to visit a website then you had to know the IP address associated with that website. It was because computers can only communicate using a series of numbers. The IP address is long and hard to remember for a human mind. So we needed a solution that could convert the computer readable info into human readable and also be fast, lightweight, and scalable.

Paul Mockapetris came with a system that automatically mapped the IP address to domain names and the system was named as DNS.

How does DNS work

We have an idea that the internet is a giant network of computers. Each computer is provided with a unique IP address which helps other devices to identify it. But when we want to search a website we have to enter the IP address in the browser which can be a lengthy process and also difficult to remember. So as discussed above the DNS makes it’s easy by using alphabets and by allowing users to select friendly names for their websites. The Domain Name System then converts those names into IP addresses and it guides the device in the right direction.

A domain name and its associated IP address are called a DNS record. In the following simple Four steps we can see how DNS works:

  1. When we open the browser and query a domain name, the computer system makes a quick check in the computer’s DNS cache. If the DNS record is found, then the rest of the DNS lookup is skipped and it directly takes to the website requested.
  2. If we are unsuccessful in finding the DNS record in step 1, then the query is sent to the local DNS server which is called a “Resolving Nameserver”. The resolving nameserver is the computer’s Internet service provider(ISP) who most likely has cached records for popular websites. However, these records are stored only for a short time but there is an option to specify the time limit called Time to Live(TTL). The time range may vary from 30 secs to 1 week.
  3. If the resolving name server does not have the required cached record, then it will ask the “root nameserver” to locate the DNS records. The root nameservers are scattered all around the world who store DNS data and maintain the smooth running of the DNS system. Once the record is found in the root nameserver, it is then cached by the computer.
  4. But if the record we are looking is not cached, then the resolving nameserver requests the root nameserver for the TLD (Top Level Domain) for that domain. The TLD then points to the Authorative nameserver that holds and is responsible for the resource DNS records. This server is at the bottom of the DNS lookup chain that will provide the IP address needed to access the website or other web resources.

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