Essential Concepts - Domain Name System (DNS)

In my previous tutorials, I have mentioned that each device connected to the internet has its own IP Address so that it can be uniquely identified. For devices connecting to internet, the IP address is provided by the ISPs. But here the question arise is -- Who is providing IP or range of IPs to the ISP?

Also a similar question arise is -- Who is providing specific IP to the Hosted Website? 

Let us take an example of facebook.com. We know that every server is identified by a unique IP. That means that facebook would also have its own IP. Who provided this IP to facebook?

You will get the answers to these questions in this tutorial.

Domain Name System (DNS) 

First, we will understand the term 'Domain Name'. Domain name is the name of the server hosting any number of websites. In example of facebook, facebook.com is a domain name as it is hosting a single website. In my case, i.e. libraryofhacks.blogspot.in , domain name is blogspot.com or blogger.com as it is hosting my website including many other websites too.

Domain names are used to identify one or more IP addresses. For example, the domain name microsoft.com represents about a dozen IP addresses. Domain names are used in URLs to identify particular Web pages.

The Domain Name System is a system which maps (translates) a host name into a particular IP Address.

Why to use DNS?

Since Internet is the mother of millions of computers each having a unique IP address, it becomes impossible for people to remember the IP address of each and every computer they want to access. So, in order to make this process simpler the concept of domain names was introduced. As a result users can easily access any website just by typing their domain names in the browser’s address bas such as “google.com” or “yahoo.com” without having to remember their actual IP addresses. 

However, since the network protocol understands only the IP address and not the domain names, it is necessary to translate the domain name back to its corresponding IP address before establishing a connection with the target server. This is where DNS comes in handy.

Your Internet Service Provider has a DNS server which maintains a huge record of existing domain names and their corresponding IP addresses. Each time you type the URL such as “http://www.google.com” on your browser’s address bar, your computer will use the DNS server from the ISP and translates the domain name “google.com” to its corresponding IP address to make a connection with the Google’s server. All this process will happen in a split second behind the scenes and hence goes unnoticed.

Concept Of Domain Name System (DNS) Server

The internet uses DNS (Domain Name System) records to translate host names into IP addresses (in this case 193.202.110.175) and in some cases vice versa too.

When you type the DNS of a website into your browser (which I would hope is Chrome, Firefox or Opera, and not IE) it begins looking up the host. This can be seen when your internet connection is slow. We know that when we surf on internet using any of the browsers mentioned above, we can see the status of connection at bottom-left/right corner. Now when your internet slows down, you will be able to see each and every status of the connection. The first one of it would be 'looking up the host'. This means that the browser is looking DNS servers for the host (Domain Name) you specified in the URL.

How DNS Works? 

 

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Whenever you type a URL such as “https://libraryofhacks.com” (doesn't exist now as I haven't bought my Professional Domain) on your browser’s address bar, your computer will send a request to the local name server (the ISP DNS server) to resolve the domain name to its corresponding IP address. This request is often referred to as a DNS query.

The local name server will receive the query to find out whether it contains the matching name and IP address in its database. If found, the corresponding IP address (response) is returned. If not, the query is automatically passed on to another DNS server that is in the next higher level of DNS hierarchy. This process continues until the query reaches the DNS server that contains the matching name and IP address. The IP address (response) then flows back the chain in the reverse order to your computer.