In the world of Internet and the area of
computer networks, you will often come across the term Domain Name
System or Domain Name Service which is simply referred to as DNS. The
working of DNS forms one of the basic concepts of computer networks
whose understanding is very much essential especially if you are
planning to get into the field of ethical hacking or network security.
In this post, I will try to explain how Domain Name System works in a
very simple and easy to follow manner so that even the readers who do
not have any prior knowledge of computer networks should be able to
understand the conceptWhat is a Domain Name System?
A “Domain Name System” or “Domain Name Service”
is a computer network protocol whose job is to map a user friendly
domain name such as “Gohacking.com” to its corresponding IP address like
“173.245.61.120″.
Every computer on the Internet, be it a web server, home computer or
any other network device has a unique IP address allotted to it. This IP
address is used to establish connections between the server and the
client in order to initiate the transfer of data. Whether you are trying
to access a website or sending an email, the DNS plays a very important
role here.
For example, when you type “www.google.com” on your browser’s address bar, your computer will make use of the DNS server to
fetch the IP address of Google’s server that is “74.125.236.37″. After
obtaining the IP address, your computer will then establish a connection
with the server only after which you see the Google’s home page loading
on your browser. The whole process is called DNS Resolution.
With millions of websites on the Internet, it is impossible for people
to remember the IP address of every website in order to access it.
Therefore, the concept of domain name was introduced so that every
website can be identified by its unique name which makes it easy for
people to remember. However, the IP address is still used as the base
for internal communication by network devices. This is where the DNS
comes in to action that works by resolving the user friendly domain name
to its corresponding machine friendly IP address.
In simple words, domain names are for humans while IP addresses are for
network devices. The “Domain Name System” is a protocol to establish a
link between the two. Hence, it is not a surprise that you can even load
a website by directly typing its IP address instead of the domain name
in the browser’s address bar (give it a try)!
Types of DNS Servers and their Role:
The Domain Name System (DNS) is a distributed database that resides on
multiple computers on the Internet in a hierarchical manner. They
include the following types:
Root Name Servers:
The root servers represent
the top level of the DNS hierarchy. These are the DNS servers that
contain the complete database of domain names and their corresponding IP
addresses. Currently, there are 13 root servers distributed globally
which are named using the letters A,B,C and so on up to M.
Local Name Servers:
Local servers represent the most lower level DNS servers that are owned
and maintained by many business organizations and Internet Service
providers (ISPs). These local servers are able to resolve frequently
used domain names into their corresponding IP addresses by caching the
recent information. This cache is updated and refreshed on a regular
basis.
How DNS Server Works?
Whenever you type a URL such as “http://www.gohacking.com” on your
browser’s address bar, your computer will send a request to the local name server to resolve the domain name into 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 server that is in the next higher
level of DNS hierarchy. This process continues until the query reaches
the 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.
In rare cases where none of the lower level DNS servers contain the
record for a given domain name, the DNS query eventually reaches one of
the root name server to obtain the response.
FAQs about Domain Name System:
Here is a list of some of the FAQs about DNS:
How does a “root name server” obtain the information about new domains?
Whenever a new domain name is created or an existing one is updated, it
is the responsibility of the domain registrar to publish the details
and register it with the root name server. Only after this, the
information can move down the DNS hierarchy and get updated on the lower
level DNS servers.
What is DNS propagation?
Whenever a new domain name is registered or an existing one is updated,
the information about the domain must get updated on all the major DNS
servers so that the domain can be reached from all parts of the globe.
This is called DNS propagation and the whole process can take anywhere
from 24 to 72 hours to get completed.
How often the DNS servers are updated to refresh the cache?
There is no specific rule that defines the rate at which DNS servers
should be updated. It usually depends on the organization such as the
ISP that maintains the server. Most DNS servers are updated on an hourly
basis while some may update their databases on a daily basis.
I hope you have now understood the working of DNS in a very convincing manner. Pass your comments and share your opinion.
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