What is a Domain Name System DNS ?

What is a Domain Name System DNS ?

What is a Domain Name System DNS ?

-In the world, networking computers don’t go by names like we do, they go by numbers because this is how computers and other similar devices communicate and identify with each other over a network which is by using numbers such as IP addresses,
in order to bridge the communication gap between computers and humans and make the communication a lot easier networking engineers developed  DNS,
DNS stands for a domain name system, and DNS resolve names to numbers to be more specific it translates domain names to IP addresses
For each IP address, there is a name of a network interface (computer)—or to be exact, a domain name. This domain name can be used in all commands where it is possible to use an IP address. A single IP addresses can have several domain names affiliated with it. The relationship between the name of a computer and an IP address is defined in the Domain Name System (DNS) database. The DNS database is distributed worldwide.

DNS Brief  History :

Thirty years ago when you were willing to visit a website you had to know the IP address of that site, because computers were and still only able to communicate using numbers:

Here is an example of an IP address

it is long and hard to remember, therefore we needed a way to translate computer-readable information into human-readable information

in 1983 Paul Mockapetris designed the Domain Name System and wrote first implementationthen mapped IP address to domain names, and voila A DNS was born, this system still serves as the mainstay of the modern internet; today

DNS structure

-The DNS  process domain names following their hierarchical structure a dm=omain name is composed of different  parts separated by “dots” and each part represents a hierarchy in the domain name structure and this hierarchy descent from the right to the left part of the domain name.

 -The drawing above shows a partial DNS hierarchy. At the top is what is called the root and it is the start of all other branches in the DNS tree.

- DNS is hierarchical in structure. A domain is a subtree of the domain namespace. From the root, the assigned top-level domains in the U.S. are:

     GOV – Government body.
      EDU – Educational body.
      INT – International organization
      NET – Networks
     COM – Commercial entity.
     MIL – U. S. Military.
     ORG –      Any other organization not previously listed.

How a DNS works

-The DNS directory that matches the names to numbers aren’t located all in one place in some dark corner of the internet. Like the internet itself, the directory is distributed around the world, stored on domain name servers that all communicate with each other on a very regular basis to provide updates and redundancies. with more than 337 million domain names and still going,
Every time a DNS query is made, the root servers are the first servers to be contacted. However, there is no need to contact the root servers every time a query is made since results can be obtained from the DNS cache which stores information for recent previous queries. If the DNS server does not find the results in the cached copies it asks a series of servers through a process called recursion until it reaches the authoritative name servers for that domain.

Each named site can correspond to more than one IP address. In fact, some sites have hundreds or more IP addresses that corresponds with a single domain name. For example, the server your computer reaches for www.google.com is likely completely different from the server that someone in another country would reach by typing the same site name into their browser
DNS information is shared among many servers, but is also cached locally on client computers. Chances are that you use google.com several times a day. Instead of your computer querying the DNS name server for the IP address of google.com every time, that information is saved on your computer so it doesn’t have to access a DNS server to resolve the name with its IP address.

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