DNS - What is DNS ?

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 https://www.youtube.com/watch?v=JkEYOt08-rU

We have 4 Types of DNS servers  ?

• DNS Recursive Resolver /DNS Resolver
• Root Name Server
• Top Level Domain/TLD Name server
• Authoritative Name server

DNS Resolver is provided by the Internet service provider . It connects the web browser of our computer to the DNS name servers

Root Name Server :

There are 13 sets of root name servers logically named us 

• letter.root-servers.net  -- where "letter" ranges from "a" to "m"
• And are operated by 12 different organizations.
• Each set has a number of servers placed around the world and an information page exists in all root servers @ address letter.root-servers.org
• letter g - is the home page address : http://disa.mil/g-root
• Details of all root name servers can be found in www.root-servers.org
  

TLD Name servers :

TLD name servers stores the information about all the domains sharing a common domain extension .com, .net , .edu, .net , .in

• .com TLD name server stores the information of all websites ending with .com extensions.
• .net TLD name servers store the information of all website ending with .net extensions

 

Authoritative name server :

Last server in DNS . It stores the IP Address of the requested websites . Authoritative name server for a website can be found by the following commands. 

• nslookup
• set query-ns
• example.com(Domain name)
  

the marked in red -- one is master and the other is slave. Slave is the exact replica of master and is used to share the DNS server load. 

How a computer loads a Website ?

support you type facebook.com and since it needs it's ip address it forwards its request to the computer OS . OS are configured to forward it query to the DNS resolver . Operating systems then contacts the DNS resolver DNS resolver checks its cache whether it has the IP address that it is looking for

of the requested website if not - the DNS query is forwarded to "Root Name Servers" . Root name server checks the extension of the website whether it is .com , .net or any other . Based on the extension the "Root Name Server" provides the IP Address of the TLD name server to the DNS Resolver . In this case 

.com TLD name server's IP address is provided to the resolver . the DNS resolver then contacts the  > .com TLD Name server which then provides the IP Address of the authoritative name server which should necessarily store the IP address of the requested website. Finally the authoritative name server provides the exact IP Address of the www.facebook.com

DNS Resolver stores this information in it's cache for future use and provides and provides the IP Address to the computers OS . OS then forwards it to the web browser the the web browser is able to text the facebook server and loads the requested website that is www.facebook.com

But how does the TLD name server know IP Address of the requested website .

It all begins when we purchase a domain name from a registrar such as go daddy .In registrars website we can set the Authoritative name server that domain should use . We get the Authoritative name server name when we buy a web hosting plan companies like Hostgater

Once Authoritative name server details are entered in the registrars website . Registrar tells the TLD name server managing Authority Registry  to update the TLD name server with the details of the Authoritative name server the user has provided . Now the TLD name server know which Authoratitive name server can provide the IP Address of the requested website. 

Is DNS necessary 

As the number of website increases it is difficult to remember the IP Addresses there DNS becomes necessary