What is DNS

The DNS system, more commonly known as Domain Name System is basically responsible for translating the complicated series of numbers that make up an IP address in words that the user can easily remember.

Each web page is accessed by an IP address. The problem is that there are so many that it is virtually impossible to remember the IP address of each. Imagine that instead of introducing “” would have to enter in the browser an address like “”. It would be a very complex task enter the IP of each of the pages, an almost impossible task.

What is DNS

To solve this problem the DNS is used. This allows the use of names (also called domains) instead of IP for access to websites. Basically, in the Internet, the DNS is a set of large distributed databases on servers around the world that indicate what IP is associated with a name (i.e., an address of type

How does it work the DNS system

Internet DNS services are a set of databases on servers scattered around the world. These databases have the function of indicating the IP that is associated with a name of a website. When you enter an address in the search, for example,, the computer asks the DNS servers of the ISP you find the IP address associated with If the servers do not have that information, starts a search with other servers that may have that data.

What is DNS

Root server

To better understand the DNS, go to the following example: Suppose you access the website For this, the server verifies and directed towards the completion .com server, which in turn redirects the server to register the domain, which reports what the IP, that is, the server where it is located the web.

DNS Cache

Suppose you access a website that has not been located by your DNS service provider, so you had to do a search on other DNS servers (through the hierarchical search).

To prevent that search to be performed again when another provider user tries to access the same web, DNS service stores information for the first consultation.

Thus, when another request arises, the server will have already stored the IP belonging to that site. This procedure is known as “DNS cache”.

What is DNS

The Cache information is stored for a certain period of time through a parameter known for TTL (Time-To-Live). This is used to prevent the stored information is updated. The period of time varies according to the server TTL and your manager.


The use of the DNS is not limited to Internet. That resource can (and is) also used in local networks. Its implementation can be made in virtually any operating system and is very common in the Unix and Windows systems.

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