Domain Name System

DNS(DOMAIN NAME SYSTEM)

DNS abbreviated as Domain Name System . Primary goal of DNS is to make it easy for user to remember 

simply the domain names of the websites rather than the IP addresses of every site user wanted to visit. 

Without DNS it’s very difficult for user to remember IP address of every site. For example a user want to 

visit a site, it will harder to remember 17.254.3.183 instead of  just domain name of the site aaple.com.

Domain Name System used because Web sites are essentially positioned by their IP addresses. For 

instance, when a user want to access a site, computer sends a request for that site to adjacent DNS server, 

which find the IP address for that site.  Then user’s computer will connect to the server with that IP number.

DNS  Working

DNS Architecture:

In early days of internet when It was a small network, host names of the computers were achieved through a 

single server. As the number hosts increases load also increased. At that time new system was needed 

which reduce load on server also allow many data types. Domain Name Service presented in 1984 became 

this new system. Using DNS, to reduce the load on any one server, all the host names stored in database 

which can be scattered between the multiple servers. The potential size of DNS database is unlimited 

because its database is scattered also not decrease performance when multiple computers approach it. 

DNS Architecture

Domain Namespace:

DNS namespace define a hierarchical arrangement of domains that are combined to make a complete 

domain name. For instance, sub.secondary.com is a domain name where "com" is top-level domain, 

"secondary" is secondary domain name, and "sub" is a sub-domain. The names make a hierarchical tree in 

DNS database to form a complete domain name is called Domain namespace

Many organizations use their private domain namespace to create their own networks which are not visible 

on internet.

Recursive query:Iterative query/ non recursive query:

In recursive query , DNS server receive the user’s query then perform all the jobs to achieve the answer 

and give it back to the user. In this process, the DNS server can also query the other DNS server's in the 

internet on user’s behalf, for the answer.If DNS server does not have the information that is required it will 

query to other servers until it get the required information or until query fails.

Iterative query/ non recursive query:

In an iterative query, the DNS server gives the best answer which based on cache or zone data. If the DNS 

server does not have the required information of user then it will return a referral. DNS client send query to 

the referral DNS server until it met to a DNS server which will be authoritative for that query or until an 

error condition. All DNS servers must follow non recursive query.