Any organization that has a computer network is equipped with at least a central server that manages and organizes DNS queries. This server, called the Name Server, keeps a list of all the IP addresses assigned to the computers on that network. This server also holds the IP addresses of those computers that have been recently accessed outside of the network. Each computer in each network must know the location of only one name server.
When your computer requests an IP address, depending on whether the requested IP address is within your local area network, one of the following three situations occurs :
First state: If the requested IP address is locally registered (for example, this address belongs to one of your organization's network computers), you will receive a response directly from one of the Local Name Servers listed in your Workstation settings. In this case, it will take a very short time to answer, or it will happen in the instance.
Second state: If the requested IP address is not locally registered (for example, this address belongs to a computer outside the network of your organization), but someone in your organization recently visited the same IP address and connected to the site like that, then Name Server will retrieve the IP address from its cache storage system. Again, in this case, it will take a very short time to answer, or it will happen in the instance.
Third state: If the requested IP address is not registered locally and you are the first to request information about the system at a specific time interval (12 hours to a week ago), then the Local Name Server instead Your Workstation will perform a search. This search may include querying two or more other name servers at any other remote location. These queries may take from one second to more (depending on how well your connection to the remote network is and how to communicate with multiple Name servers).
Sometimes you may not receive an answer because of the lightweight protocol used in DNS. In such a situation, your Workstation or Client software may continue to receive an error message until it receives a response to your query.
When you use a program like Telnet to connect to another computer, you might enter the domain name to establish that connection instead of typing the desired computer address. The Telnet program receives the domain name that has been typed by the user and, using one of the methods described above, obtains the same IP address using the Name Server.
For example, DNS can be viewed as an electronic phone book for a computer network, so that if the computer name is known, the name server searches for and finds the IP address of the computer.