Domain Name & Domain Name System (DNS)

We discussed what is a domain name, and what purpose does it serve on the world wide web. So we have domain name that points to an IP Address of a web server, which is used for hosting a website. The key element that is used for domain name resolution from domain name to IP Address is Domain Name System (DNS) which we are going to read about now... (i.e. if you are interested - :))

What does Domain Name System (DNS) Do?
We all have used phone directory, or as you have in mobiles, or computers now - an address book. Imagine if you could only save telephone numbers without the ability to associate that number to any name, Scary thought isn't it!!! Well a domain name system does exactly the same thing that an address book does. So while you search for a name to place a call, internally your mobile is going to dial the mobile number associated with the name that has been stored by you. On the World Wide Web, this address book is the Domain Name System (DNS) that translates domain name like http://www.vu2.in to it's IP Address like eg. 209.51.196.242 for the browser and all associated networking components need to establish a connection, fetch information or deliver information from your machine to server and from the web server to your machine. Further to address book analogy for Domain Name System, just like you have the ability to store a contacts name, date of birth, anniversary information, Email Address etc, similarly a Domain Name System (DNS) stores list of mail exchange servers that would accept email for particular domain name apart from other entries for a particular domain.

How does Domain Name System (DNS) work?
In computers, files store information, and these files have a structure that is similar to trees, thus the data structure is called a tree, where each leaf of the tree represents information for a domain. The information thus stored for a domain name is called a resource record. The tree is further divided into zones. A zone is made up of such leaves, or normally called nodes which are served by an authoritative DNS nameserver. The Domain Name System consists of a set of DNS Servers. Each domain or sub domain would have one or more authoritative DNS server to provide relevant information about that domain, and the name servers of any domains beneath it. The starting point is the main nameserver - technically known as root nameserver. Root Nameserver is the server which handles the query to resolve a top level domain (TLD) name like http://www.vu2.in.

How do you find IP Address for a domain name?
If you wonder how to find an IP Address for a given domain name, all you have to do is to use command prompt and make use of any of the following command to get the actual IP being used.
1. PING
When you ping a domain name, you would instantly get IP Address of the Domain (after resolution by DNS) as shown below:
Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.
C:\>ping www.vu2.in

Pinging www.vu2.in [209.51.196.242] with 32 bytes of data:...

2. TRACERT
Like ping, tracert utility also allows you to fetch IP Address associated with a domain name as shown below

C:\>tracert www.vu2.in

Tracing route to www.vu2.in [209.51.196.242]
over a maximum of 30 hops:
1 One thing we must bear in mind is that while domain names are unique, multiple websites could share same hostname. Virtual hosting is used to host multiple websites on one machine or web server, and hence there is no one-to-one relationship between hostname and IP Address.

Finally a quick recap
a. DNS : Domain Name System (DNS)
b. Address Book for websites on the internet.
c. Stores mapping of domain name with IP Address / web server information.
d. Information for each domain name is stored in a tree like data structure on DNS Server.
e. Each leaf stores record for one domain name.
f. These leaves are called resource records.
g. Collection of leaves make up a zone.
h. Domain Name System (DNS) stores other information as well apart from name resolution.
i. You can get IP address for any domain using utilities like PING or TRACERT.

Next we would look at how things were before Domain Name System (DNS) came into existence ... Keep watching this space for more :)

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